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ALJOIN Final Technical Report - Transport Research & Innovation ...

CONTRACT N° : G3RD-CT-2002-00829

PROJECT N° : GRD2-2001-50065

ACRONYM : ALJOIN

FINAL TECHNICAL REPORT

TITLE : CRASHWORTHINESS OF JOINTS IN ALUMINIUM RAIL VEHICLES

PROJECT CO-ORDINATOR: D’APPOLONIA S.P.A.

PARTNERS :

D’APPOLONIA S.P.A.

ADVANCED RAILWAY RESEARCH CENTRE (ARRC) – The University of Sheffield (before 1

March 2004)

NEWRAIL – The University of Newcastle (from 1 March 2004 onwards)

ALCAN

BOMBARDIER TRANSPORTATION

DANSTIR

THE WELDING INSTITUTE (TWI)

REPORTING PERIOD : FROM 1 AUGUST 2002 TO 31 JULY 2005

PROJECT START DATE : 1 AUGUST 2002 DURATION : 36 MONTHS

Date of issue of this report : October 2005

Project funded by the European Community under

the ‘Competitive and Sustainable Growth’

Programme (1998-2002)


Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

1. TABLE OF CONTENTS

ALJOIN 1. TABLE OF CONTENTS ...................................................................................... 2

2. EXECUTIVE PUBLISHABLE SUMMARY .......................................................... 3

3. OBJECTIVES ...................................................................................................... 5

4. SCIENTIFIC AND TECHNICAL DESCRIPTION OF THE RESULTS ................. 6

4.1 Work Package 2: Performance Criteria ........................................................ 6

4.2 WORK PACKAGE 3: EXISTING JOINT ASSESSMENT ................................ 8

4.3 WORK PACKAGE 4A: STATIC MODELING OF JOINTS ............................ 11

4.4 WORK PACKAGE 4B: DYNAMIC MODELING OF COMPONENTS AND

STRUCTURES ...................................................................................................... 17

4.5 WORK PACKAGE 5: NEW JOINING TECHNIQUES AND JOINTS ............ 24

4.6 WORK PACKAGE 6: EXPLOITATION PRODUCTS AND STANDARDS .... 27

4.7 WORK PACKAGE 7: METHOD FOR ASSESSING CRASHWORTHINESS 29

4.8 WORK PACKAGE 8: DEMONSTRATORS ................................................... 30

4.9 WORK PACKAGE 9: VALIDATION .............................................................. 33

5. LIST OF DELIVERABLES ................................................................................ 38

6. COMPARISON OF INITIALLY PLANNED ACTIVITIES AND WORK ACTUALLY

ACCOMPLISHED ..................................................................................................... 40

7. MANAGEMENT AND CO-ORDINATION ASPECTS ........................................ 42

7.1 Project co-ordination ................................................................................... 42

7.2 Man Power and Progress Follow-up Table ................................................ 43

7.3 Work Plan ...................................................................................................... 48

7.4 Updated contact details for the consortium .............................................. 49

8. RESULTS AND CONCLUSIONS ...................................................................... 51

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Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

2. EXECUTIVE PUBLISHABLE SUMMARY

ALJOIN Aluminium alloys are now in widespread use in Europe and elsewhere for rail vehicle

construction from commuter to express trains. The main contributor to the success of

aluminium alloys as structural materials in rail transport, is the development of closed

cell aluminium extrusions that can easily be welded together to form lightweight rail

vehicles with high inherent rigidity that could not be achieved with older designs.

As rail transport is becoming more popular throughout Europe, there is an increased

need to improve passenger safety by improving the crashworthiness of rail vehicles to

minimise fatalities and injuries if an accident does occur.

The strength, integrity and performance of aluminium welds in rail vehicles contribute

greatly to the overall body shell strength and crashworthiness. In recent collisions

involving seam welded aluminium rail coaches, some of the longitudinal seam welds

fractured for some meters beyond the zone of severe damage, the panels themselves

generally being intact without significant distortion.

The experts on crashworthiness agree (in Cullen report recommendation 57) that

consideration should be given, in the case of new vehicles constructed of aluminium, to

the following:

• use of alternatives to fusion welding;

• use of improved grades of aluminium less susceptible to fusion weld

weakening;

• further development of analytical techniques to increase confidence in the

crashworthiness of rail vehicle structures, particularly those constructed of

aluminium.

The strategy that ALJOIN used to approach the problem can be described as follows:

• creation of performance criteria for the properties of aluminium welds in

the new generation of rail vehicles in terms of their stress/strain

performance;

• assessing the existing methods of joining techniques and joints;

• static and dynamic modelling of joints and structures;

• formulating new joining techniques and joints;

• definition of a method for assessing crashworthiness;

• demonstration and validation of the innovative technologies developed

against the performance criteria.

Real improvements in the safety of rail vehicles, introduction of innovative techniques for

aluminium welding and improvements in the crashworthiness of the new generation of

rail vehicles are among the main ALJOIN outputs.

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Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

ALJOIN The expected impact is a real improvement in the safety of the new generations of rail

vehicles, contributing to the safety of European citizens as well as to the EC policies in

safety issues and standardisation of the materials and aluminium welding methods used

in the rail industry.

The duration of the ALJOIN project was three years. In the first year ALJOIN was

dedicated to the research phase where a thorough investigation of existing joint designs

and joining techniques was carried out. This has revealed shortcomings in existing joint

designs.

First is the adverse effect of using partial penetration welds, which act as crack initiators

facilitating the process of dynamic tear of welds under impact loading and second, the

use of Al-Si filler wire (allowed by current manufacturing standards) which produces

welds with lower strength, ductility and fracture toughness compared to welds produced

with Al-Mg filler wires.

The second year of the work concentrated on the understanding of the fundamental

properties of aluminium weldments and an investigation of the performance of alternative

joining techniques such as adhesive bonding, bolted joints, laser welding and friction stir

welding. With the exception of adhesive bonding, which from an early stage proved

unsuitable for rail vehicle construction, the determined joint properties were used for the

development of analytical failure models and validated with component tests. The

modelling efforts have produced a very close agreement between experiment and

prediction. The modelling procedure was then used to examine solutions for improved

joint performance.

The final year of the project has concentrated on modelling efforts to simulate rail vehicle

impact with and without the implementation of the recommendations for improved joint,

as they arose from the previous work.

Furthermore an experimental methodology for assessing the dynamic loading

performance of joints was developed which can be used as a method of "ranking" the

impact performance of various joint designs. The experimental results were also used to

further validate model predictions.

The major outputs from this work can be summarised as follows:

• The stress levels at the weld region should be brought close to those of

the parent plate, through thickening of the aluminium plate at the weld

region. The precise amount of thickening would depend on alloy grade

and welding procedure.

• Friction stir welding (FSW) and MIG welding with Al-Mg filler wire are the

best performing joining methods in terms of crashworthiness as long as

the above recommendation is implemented.

• Aluminium alloys other than the 6005 alloy in the T6 temper have not

provided any appreciable improvement in joint strength.

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Final Technical Report – draft 1

3. OBJECTIVES

ALJOIN The aim of the project can be summarised to provide sufficient knowledge to design cost

effective aluminium rail vehicle bodies that will not fail by catastrophic joint failure under

extreme loading. To achieve such overall goal several specific objectives were

addressed:

• To determine the performance specifications required by critical

aluminium joints in rail vehicle cars to ensure the structural integrity;

• To provide physical evidence of the energy absorption capability of

aluminium alloy welds by testing;

• To investigate performance and failure criteria for aluminium welded and

bolted joints;

• To explain test results assessing the adequacy or inadequacy of current

design and construction practices of aluminium alloy welds in the context

of crashworthiness;

• Implementation and validation of material failure models for welds of

aluminium alloys;

• Definition of the main material and structural parameters which can

influence the mechanical behaviour of the joints;

• Development of the material constitutive modelling for the parent material

and the material in the welded volume;

• Numerical modelling of simple joints subjected to axial and transversal

forces;

• Numerical analysis of components and structures subjected to quasistatic

and impact (dynamic) loading conditions in order to evaluate the

structural response in terms of mean axial crushing force, total energy

absorption, load efficiency and uniformity, deformation mechanism.

• To investigate alternative welding techniques and/or joint designs for

improved joints of aluminium alloys.

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4. SCIENTIFIC AND TECHNICAL DESCRIPTION OF THE RESULTS

4.1 Work Package 2: Performance Criteria

Introduction

ALJOIN The future of aluminium in rail vehicles will depend on the performance of aluminium

joints. The objective of this Work Package was to determine the performance

specifications required by critical aluminium joints in rail vehicle cars to ensure the

structural integrity and the crashworthiness of the vehicles and to determine the

improved future performance required of the new crashworthy aluminium rail vehicles.

Aluminium is currently one of the preferred materials for rail vehicle manufacture.

Aluminium railway carbodies are manufactured from longitudinal extrusions which are

traditionally joined by automated metal inert gas (MIG) welding or bolting. The

advantages of using aluminium extrusions in the manufacture of rail vehicles are the

highly efficient assembly methods and the significant weight savings, whereas a

disadvantage is the potential crashworthy performance. There have been cases where

aluminium rail vehicles have been involved in accidents where, the energy absorption

devices appeared to have failed to operate effectively. The failure of these devices is

thought to be due to the breakdown of the supporting carbodies structural integrity.

Energy absorption devices can only operate effectively if the structural integrity of the

bodyshell is maintained. With current aluminium rail vehicles manufactured from full

length extruded sections, the structural integrity of the bodyshell is dependant on the

crashworthiness performance of the joints between the extrusions. There is an increased

effort to improve the crashworthy performance of aluminium rail vehicles and the

research is being concentrated to improve the joints and refine the analytical modelling

of these joints in crash scenarios.

Description of Results

The requirements for aluminium joints are directly related to the crashworthiness

performance of the vehicle, since they contribute to the structural integrity of the

bodyshell. In current designs of aluminium railway vehicles, the typical longitudinal joints

are either welded or bolted. Various techniques are available for welding and bolting

carbody structures to form a shell. Currently the most widely used welding techniques

are MIG, Twin Wire MIG and Friction Stir Welding (FSW). Typical bolted joints use Huck

Bolt connections. Figure 1 shows a typical bodyside/floor Huck Bolt connection being

assembled.

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Final Technical Report – draft 1

ALJOIN Figure 1: Current vehicle floor structure (left) and bodyside/floor Huck Bolted

(Bombardier)

The European standards that target the design of rail vehicles and the welding

procedure for metallic materials do not detail the performance criteria of the joints in

aluminium rail vehicles. The standards and requirements of reference to be taken into

account comprise the following:

• BS 8118: Part 1 (1991) “Structural use of Aluminium”;

• BS 288-4 (1992) “Welding procedures for metallic materials”;

• Euronorm CEN 256 / BS-EN 12663 (2000) “Structural requirements of

railway vehicle bodies”

• TSI 96/48 – ST05 part 2 “Passive Safety Crashworthiness”

• Railtrack Safety & Standard GM/RT 2100: part 3 (October 2000),

“Structural requirements for railway vehicles”.

When a new weld is first designed it has to satisfy British/EN standard 288-4. One of the

major concerns about the current situation is that the mechanical properties and crash

performance of the weld and heat affected zones are not understood. Improvements in

knowledge of these properties would give numerical modellers more confidence in the

results from analytical models. From the standards examined there is no specific

requirement to generate detailed performance criteria for the joints in rail vehicles, but

there is a need to understand the properties of the joints to improve the crashworthiness.

To achieve this a comprehensive testing plan of current MIG welds is proposed which

involves static, quasi-static and dynamic testing, all will give valuable information and will

go towards addressing the lack of understanding of current joints. The results from

testing should characterise the parent metal, the weld and the heat affected zones and

this information will be used in two areas. Primarily the data will be used to establish a

benchmark for future work, where the use of new joining techniques and different

aluminium alloys will be investigated. Secondly the results will be used to refine the

current analysis techniques, so the elements representing the weld region in crash

scenarios are fully validated with experimental work. Once confidence has been

established in relating test results to element properties, similar procedures can be used

when changes are made to the joining process or the material.

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ALJOIN In an ideal situation the joint should not be the ‘weakest link’ in the bodyshell, put simply

‘Joint performance should be equal to that of the parent metal’.

4.2 WORK PACKAGE 3: EXISTING JOINT ASSESSMENT

Introduction

Carbodies of rail passenger vehicles have been manufactured using welded 6000 series

aluminium alloy extrusions for many years in the UK and Europe. Although welded joints

designed to conventional codes have performed satisfactorily under the normal

operational loads, it is less certain how welded joints would behave under extreme

loading conditions. In recent accidents involving welded aluminium rail vehicles,

observations showed that some of the longitudinal welds had fractured for some metres

beyond the zone of severe damage. There is a lack of knowledge in the design of

welded joints for high rate loading situations. The objective of this work package are

therefore:

• To provide physical evidence of energy absorption capability, or

incapability, of aluminium alloy welds by joint tests.

• To establish failure criteria of aluminium welded joints.

• To investigate performance and failure criteria of aluminium bolted joints.

• To explain structural performance observed in joint tests.

• To asses the adequacy on inadequacy of current design and construction

practices of aluminium alloy welds in the context of crashworthiness.

The MIG process is the main welding process employed by the industry today in the UK

and Europe. Either silicon or magnesium alloyed fillers are recommended for the welding

of 6000 series aluminium alloys, but this does not mean that the welds will perform as

well as the parent material. There is a need to investigate the effects of the filler material

on the structural behaviour of the welds.

Description of results

Materials and weld production

The aluminium alloy used in the present work was EN AW 6005A-T6. Extrusions of this

alloy are widely used for the construction of the carbody of rail passenger vehicles.

Some ten meters of welds were produced with the MIG process using either aluminiumsilicon

or aluminium-magnesium filler. These were butt welds in either 6mm thickness

extruded plates or rail vehicle floor extrusions.

Material characterisation testing

Material characterisation tests were conducted to investigate material behaviour in the

parent material, the weld metal and the HAZ of the MIG welds. These included hardness

surveys, tensile testing, Charpy impact testing and fracture resistance testing.

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ALJOIN The hardness of the parent material was about 100HV5. The reduction in hardness

values of the weld metal and the HAZ was confirmed in the hardness tests. The lowest

hardness value in the welds made using aluminium-silicon filler was about 45HV at the

weld centre line. The lowest hardness value in the welds made using aluminiummagnesium

filler was about 60HV at a distance of 5 to 10mm from the weld centre line in

the HAZ. The width of the zone of reduced hardness was about 30-40mm.

The parent material tensile properties as tested in transverse specimens were slightly

different from those in the longitudinal specimens, which suggested that the parent

material extrusion was slightly anisotropic. The specimen-to-specimen variation of the

tensile properties of the HAZ was relatively large. The lowest average 0.2% proof

strength, ultimate strength and area reduction were from the weld metal of weld made

using the aluminium-silicon filler. Although the weld metal 0.2% proof strength of the

weld made using aluminium-magnesium filler was about 55% of that of the parent

material, its ultimate strength was slightly higher than that of the parent material. The

elongation of the HAZ at the maximum load was relatively low, only 4 to 5%, and the

weld metals elongated a relatively small amount after the maximum load.

Tensile testing of notched cylindrical specimens was carried out for weldments made

using aluminium-silicon or aluminium-magnesium filler. Figure 2 shows the tensile

testing set-up at NEWRAIL. Fracture strains as a function of stress triaxiality were

obtained for the different zones in the welded joints.

Figure 2: Tensile testing set-up (NEWRAIL)

The average Charpy value of the base material was about 6 Joules. The lowest Charpy

energy, 5Joules, was from the aluminium-silicon filler weld metal. The highest average,

18Joules, was from the weld metal of the aluminium-magnesium filler weld. The variation

of the Charpy energy of the HAZ was relatively large, while the Charpy energy values of

the weld metals and the parent material varied little.

Some seventy single edge notch bend specimens were tested under either quasi-static

or dynamic loading. Different effects were found in the J R-curves of the three material

zones, i.e. the parent material, the weld metal and the fusion boundary. For the parent

material, the magnitudes of J under dynamic loading were higher than those under

quasi-static loading for the same amount of crack extension, but the slopes of the trend

lines of the J R-curves were quite similar. For the aluminium-silicon filler weld metal and

the associated fusion boundary, the J values under dynamic loading were generally

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Final Technical Report – draft 1

ALJOIN higher than those under quasi-static loading for crack extensions of less than 1.5mm.

They tended to be lower when the crack extension was greater than 1.5mm, and the

trend lines of the J values under the dynamic loading were flatter. For the aluminiummagnesium

filler weld metal and the associated fusion boundary, the J values under

dynamic loading were generally lower than those under quasi-static loading for crack

extensions of less than 1mm. They tended to be higher, when the crack extension was

greater than 1.5mm, and the trend lines of the J values under the dynamic loading were

steeper.

Joint and component testing

Cross weld tensile specimens were extracted from welded rail vehicle floor extrusion and

tested under quasi-static tensile loading. Plastic strain changes were monitored

continuously during the testing and fracture locations were recorded.

Welded joint components were extracted from the welded rail vehicle floor extrusions.

Component behaviour was investigated under axial quasi-static crush and drop weight

impact loading. The loading mode in these tests was predominately axial compression.

The welds in the rail vehicle floor extrusions did not fail catastrophically by fracture,

although severe plastic deformation occurred in the parent material. Local buckling

developed at the attainment of the maximum load. This was followed by tearing damage

in the local buckling area, particularly in the parent material at corners where the internal

web met the external skin.

Testing of bolted joints were developed with the aim of providing test data for finite

element simulation of failure in bolted joints. Tests have comprised testing of bolted

tubes subjected to axial impact (Figure 3 shows the example of damage joints after

testing done at TWI) and bolted joint tearing tests (Figure 4 shows the results of testing

and some details of the failure mode.

Figure 3: example of damage joints after testing (TWI)

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Final Technical Report – draft 1

Main Conclusions

Figure 4: Result of test and detail of bolt 1 failure (NEWRAIL)

ALJOIN Damage and final fracture will most likely be confined to the weld metal, the HAZ and /or

the interface between the two in MIG welded joints, which are designed for normal

operation loads, in a event of crash generating sufficient load normal to the weld, mainly

because strength undermatch. Al-Si weld metal is shown to have poor strength and poor

fracture toughness relative to the base material, the HAZ and the Al-Mg weld metal. The

present results have provided some explanation for the material aspect in real life weld

failures such as those in the Ladbroke Grove accident.

It is clear from the test results that the mechanical properties of the MIG welds made

with aluminium-magnesium filler metal in 6005A-T6 aluminium alloy extrusions were

superior in terms of strength, ductility and fracture toughness to those made with

aluminium-silicon filler metal. But there is limited scope for improvement of the

mechanical properties of the HAZ, particularly strength, as long as a fusion welding

process is employed.

4.3 WORK PACKAGE 4A: STATIC MODELING OF JOINTS

Introduction

The failure process of aluminium alloys involves void nucleation, growth and

coalescence. Failure mechanisms are investigated in WP3 by metallurgical and

microstructural examinations. Potential failure criteria are studied for implementation and

validation. The prediction of the fracture mechanism occurring in the welded regions is

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ALJOIN used to evaluate the progressive failure of the whole component that can occur without

significant yielding in the base material and in some cases under elastic stresses.

This work package aims to deliver:

• material failure models for aluminium alloy welds;

• constitutive model of the different welded joints;

• numerical results of simple joints subjected to axial and transverse forces.

Description of results

Material Failure Models

Dimpled rupture is a failure mode of aluminium alloys. It is strongly influenced by stress

triaxiality and by the volume fraction of inclusions and second phase particles.

There are two material failure models used widely for modelling of dimpled rupture,

namely the Hancook and Johnson & Cook model and the Gurson-Tvergaard model. In

the former, the fracture strain is expressed by the following equation:

σ

= D1

+ D2EXP(

D

σ

f

ε 3

where σm is the mean stress and σvM is the von Mises equivalent stress. σm/σvM is term

stress triaxiality in the literature. D1, D2 and D3 are material constants.

This model predicts the fracture strain decreases exponentially with increasing stress

triaxiality, but the material damage before the final fracture is not modelled. The damage

is a result of the nucleation and growth of voids at inclusions and second phase

particles. Fracture is the final stage of this progressive damage process.

The Gurson-Tvergaard model provides a means of modelling the progressive damage.

The essence of the Gurson-Tvergaard model is contained in the yielding function below:


F ⎜

σ

=


⎝ σ

2


e ⎟

2

3f


y


m

vM

⎛ q2

3 ⎞

m

2 q1f

cosh⎜

σ

+

− ⎟ − ( 1+

q

⎜ 2 ⎟

⎝ σy


This yield function contains both the stress triaxiality and void volume fraction, which are

the two major factors in the dimpled rupture. Details of the two models will be discussed

in a final report for work package 4. Some of the numerical results using these two

failure models for fracture modelling are given below.

Numerical Simulation of Notched cylindrical specimen under tension

Fracture characterisation was carried out using a series of notched cylindrical

specimens. Results of load versus displacement were used to determine values of the

parameters in the Gurson-Tvergaard model through a calibration.

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ALJOIN There were three specimens in a series. The diameter at the minimum section was 3mm

and the three notch radii are 2, 6 and 10mm, respectively. Finite element meshes for the

three notched cylindrical specimens are shown in Figure 5. Each of the finite element

models with axi-symmetrical elements represents one half of the corresponding

cylindrical specimen. The plane at the minimum diameter is a symmetrical plane, where

displacements in the vertical direction were set zero in the finite element analyses.

(a) (a) (a)

Figure 5: Finite element mesh for notched cylindrical specimen with minimum neck

radius a=1.5mm: (a) R=2mm; (b) R=6mm; and (c) R=10mm

Values of Young’s modulus and Poisson’s ratio used in the analyses for the parent

material 6005A-T6 were equal to 60GPa and 0.3, respectively. The true stress versus

true plastic strain was described by the following equation:

σ = σ + αε / ε )

0. 2(

0.

2 1

where σ0.2=262MPa, ε0.2=σ0.2/E, α=0.15 and ß=0.135.

Best estimate values for the parameters in Gurson-Tvergaard model for the parent

material 6005A-T6 are summarised in Table 1.

Table 1 Best estimate values for the parameters in Gurson-Tvergaard model

q1 q2 q3 εN SN fN fc fN

1.5 1.0 2.25 0.10 0.01 0.04 0.08 0.2

The measured and computed results of load versus axial displacement in a gauge length

of 12.5mm are compared in Figure 6. The agreement between the measured and

computed curves is not excellent and needs to be improved. Nevertheless, the calibrated

Gurson-Tvergaard model provides a basis for modelling fracture of the parent material

6005A-T6.

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Axial load, kN

4.0

3.0

2.0

1.0

0.0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Axial displacement (12.5mm gauge length), mm

ALJOIN a1.5R2 - Test data (M11-39)

a1.5R6 - Test data (M11-40)

a1.5R10 - Test data (M11-41)

a1.5R2 FEA GT 19

a1.5R6 FEA GT19

a1.5R10 FEA GT 19

Figure 6: Comparison of measured and computed load versus displacement curves for

notch cylindrical specimen under tension

Numerical Simulation of single edge notched specimen under bending

Finite element analyses were carried out to predict crack propagation using the above

calibrated Gurson-Tvergaard model in a single edge notch bend (SENB) specimen of

the parent material 6005A-T6 under three point bending. Dimensions of the SENB

specimen are 5mm thickness, 15mm width and 60mm span. The ratio of initial crack

depth to specimen width is 0.35.

A three-dimensional finite element model for the SENB specimen is shown in Figure 7.

It is only necessary to model one quarter of the specimen geometry because of the

double symmetry. The linear strain brick elements are used.

Load Line

Figure 7: Finite element mesh for a quarter of a SENB specimen (B=5mm, W=15mm,

a/W=0.35, S=4W)

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ALJOIN The shape and position of the crack front are illustrated in Figure 8 for different amounts

of load line displacement. The initial crack advanced about 0.15mm at the mid-thickness

when the load line displacement was 0.86 ΔPmax, where ΔPmax is the load line

displacement at the maximum load sustained in the specimen. The crack continued to

advance as the load line displacement increased. The initially straight crack front

became a curved line with much smaller amounts of crack extension near the outside

surface than in the mid-thickness.

Current crack front

Initial crack front

(a) (b)

(c)

Mid-Thickness plane

Figure 8: Shape and position of current crack front: (a) D=0.87DPmax; (b) D=DPmax; (c)

D=1.4DPmax

Rail vehicle floor component under quasi-static crush

Quasi-static testing of the rail vehicle floor extrusion component is described in detail in

the report for work package 3. The testing was simulated using the general purpose

finite element ABAQUS. A deformed shape of the rail vehicle floor component at the

maximum applied load is shown in Figure 9. This is very similar to the deformed shape

of the tested specimens. A comparison of the measured and computed load versus

displacement curves is also given in Figure 9.

load (kN)

1200

1000

800

600

400

200

fine mesh - modes 1 to 10 imperfections

experimental data after machine stiffness and non-linearity correction

0

0 1 2 3 4 5 6 7 8 9

displacement (mm)

Figure 9: Deformed shape of rail vehicle floor component and Comparison of measured

and computed load versus displacement curve

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Rail vehicle floor component under drop weight impact

ALJOIN Drop weight impact testing of the rail vehicle floor extrusion component was simulated

using the general purpose finite element ABAQUS. A finite element model for the

simulation and a comparison of the measured and computed load versus time curves is

given in Figure 10.

Specimen

Drop mass

anvil

Ground concrete support

Load, kN

900

800

700

600

500

400

300

200

100

0

FEA

0 2 4 6 8

Time, ms

Test (W05-05)

Figure 10: Finite element model for drop weight impact testing (left) and Comparison of

measured and computed load versus time curves

Single bolt lap joint under tension

Finite element analyses were carried out for a single bolt lap joint of the parent material

6005A-T6 under tension. A finite element model is shown in Figure 11. The bolt pretension

was simulated with a temperature field. The friction forces between the mating

parts were modelled using contact modelling capability. Progressive damage in the joint

as loading increases was modelled using the Gurson-Tvergaard model. The fractured

joint is shown in Figure 11.

Figure 11: Finite element model for single bolt lap joint and fracture simulation

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ALJOIN 4.4 WORK PACKAGE 4B: DYNAMIC MODELING OF COMPONENTS AND

STRUCTURES

Introduction

Dynamic modelling of small- and full-scale structures and analysis of correlation between

design parameters and crashworthiness. The modelling work reflects the performance

criteria defined in WP2. Structures to be modelled comprise thin-walled members and

sandwich members with various types of cross sections in which the influence of the

welding is studied.

Objective of this work package is to design and model crashworthy structures which

deform under a controlled force and preserve sufficient survival space around the

occupants to limit body injury during an accident. To perform numerical analysis of

components and structures subjected to quasi-static and impact loading conditions in

order to evaluate the structural response in terms of mean axial crushing force, total

energy absorption, deformation mechanism. To review of load conditions, rates of strain

and modes of deformation of aluminium alloy welds of the rail vehicle under crash and

derailment scenarios.

The activities performed included:

• Plain and Notched Tensile Tests

• CTOA tearing tests

• Tearing tests of bolted joints

• Bolted Tubes subjected to axial impact

• Cleavage tests

Description of Results

Plain and Notched Tensile Tests

Simulations of plain and notched tensile tests have been carried out to analyse mesh

sensitivity and to verify the possibility of the Gurson model implemented in LS-DYNA to

take into account different mesh sizes. The procedure used for the determination of the

Gurson parameters was to start fixing most of the parameters (q1=1.5, q2=1, fN=0.01,

En=0.3, Sn=0.1) and using the experimental results of load vs. axial displacement to

determine the values of the remaining parameters (F0 and Fc) by best fit. An element

size dependent function for Ff (failure void volume fraction) was defined based on finite

element simulation of the tensile test results with 4 or 5 meshes of different sizes (see

Figure 12). Figure 13 shows the simulation of the failure of a notched specimen (notch

radius 2 millimetres) subjected to tensile loading.

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Figure 12: Meshes of 2 mm notched specimen

ALJOIN Figure 13: Simulation of failure of notched specimen subjected to tensile loading

CTOA tearing tests

Numerical analyses considered the Crack Tip Opening Angle (CTOA) tearing tests

carried out by ARRC. Testing was performed on 250 kN Mayes testing machine with a

strain rate of 0.02mm/second. Figure 14 shows testing equipment and the detail of the

crack growth along the weld and at the interface between the weld and the HAZ. Figure

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ALJOIN 15 shows the specimen geometry. Specimens were taken from the railway vehicle

double skinned extrusions so that a crack initiator could be centred in one of the relevant

zones: parent metal, HAZ and weld. The gauge section was machined to 2mm thick to

remove any evidence of variation in the extrusion process and ensure flatness. Samples

had a crack initiator machined in the centre of the gauge section to start the initial crack

in different zones: the parent metal, the weld and the HAZ.

Figure 14: CTOA testing set-up (left) and details of crack growth along the weld (up) and

at the interface between HAZ and weld

Figure 15 Crack Tip Opening Angle (CTOA) tearing tests (ARRC)

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ALJOIN The numerical analyses were carried out using the both the LS-DYNA explicit code and

the FRANC2D code. Figure 16 shows the results of the analysis, in terms of distribution

of the Von Mises equivalent stress, demonstrating the crack propagation along the

centreline of the specimen. Figure 17 shows the results of the simulations done using

the FRANC2D code 1 which allows to explicitly model the crack propagation in the mesh.

As the cracks propagate, automatic remeshing algorithms delete the mesh local to the

crack tip, extend the crack, and build a new mesh around the new tip. The constant

critical crack tip opening angle (CTOA) fracture criterion was used in the simulations.

The CTOD fracture criterion assumes that the crack growth will occur when the angle

made by the upper crack surface, the crack tip, and the lower crack surface reaches a

critical value. In a two-dimensional analysis, the displacement δ, perpendicular to the

crack, at a fixed distance d behind the crack tip are monitored during the analytical

loading of the model. When the displacements are such that the critical angle CTOA

(ψC) is attained (see equation 1), the crack is advanced by releasing the crack tip nodes

until a total distance d of crack growth is achieved.

−1⎛

δ ⎞

ψ C = 2 tan ⎜ ⎟

(1)

⎝ d ⎠

Then, the applied displacements are held constant while the internal forces are returned

to equilibrium. At each load increment, the CTOA was calculated and compared to a

critical value. When the CTOA exceeded this critical value, the crack-tip node was

released and the crack advanced.

t = 0.6 s

t = 2.0 s

Figure 16 Numerical Analysis of Crack Tip Opening (CTOA) tearing tests (Von Mises

Equivalent Stress)

1 Swenson D., James M., “FRANC2D/L: A Crack Propagation Simulator for Plane Layered Structures

Version 1.4 User's Guide”, Kansas State University •Manhattan, Kansas

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ALJOIN Figure 17 Numerical Analysis of CTOA tearing tests showing crack running along the

weld (left) and crack deviating towards the weld/HAZ interface

Tearing tests of bolted joints

The aim of these numerical analyses was to assess the existing criteria for the

simulation of bolted joints in dynamic loading conditions and validate the approach which

has been selected to model the bolted joints.

The activities performed include:

• numerical simulations of the tearing tests;

• validation of the material model;

• critical review and analysis of the results.

Several simulations have been performed, considering both shell and solid elements to

mesh the specimen. The bolts have been modelled using solid elements. The

numerical results are in good agreement with the experimental results. In particular

Figure 18 shows the results of the simulation in terms of global deformation and failure

mode, which correspond to the real behaviour (see Figure 4). Figure 19 reports the

comparison of the diagram of force versus displacements corresponding to three tests

and the numerical prediction. The numerical model is able to predict with a good

accuracy the peak force corresponding to the failure of the bolts. The difference in terms

of displacements is due to the pre-load in the bolts, not considered in the model.

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ALJOIN Figure 18 Results of the simulation of tearing tests of bolted joints – deformed structure

Figure 19: Tearing tests of bolted joints - comparison of measured and computed load

versus displacement curves

Bolted tubes subjected to axial impact

The work performed consisted mainly in:

• Selection of standard aluminium extrusions to be provided by ALCAN for the

preparation of the samples;

• Definition of small-scale sample geometry to obtain tubular bolted structures for

dynamic impact testing (see Figure 20);

• Design of the experiments: a fractional-factorial design of experiments using

orthogonal arrays was selected. The factors comprise: the material and temper

condition (AA 6005-T6 and 6008-T6), the number of bolts, and the impact

velocity

• Numerical analysis of the configurations selected.

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e

d

∅ = 6 mm bolt diameter

e = 28 mm edge distance

d = 24 mm

e

d

t = 2.4 - 6 mm thickness

thinnest outside ply

Figure 20 Definition of small-scale bolted samples

ALJOIN Figure 21 Numerical analysis of bolted joints subjected to axial impact – deformed

structure (above) and comparison of measured and computed load versus time curves

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WP4B Overall comments

ALJOIN • An extensive modelling work has been developed aiming at the definition

of proper material models and simulation approaches for structures and

joints under different loading conditions;

• Simulations of tensile tests have been carried out to analyse mesh

sensitivity and to verify the possibility of the Gurson model implemented in

LS-DYNA to take into account different mesh sizes

• Simulations of CTOA tearing tests, tearing tests of bolted samples, impact

tests of bolted structures are in good agreement with test results.

4.5 WORK PACKAGE 5: NEW JOINING TECHNIQUES AND JOINTS

Introduction

Conventional MIG welding processes and joint designs have been shown to be

inadequate for the increasing demand of crashworthiness performance of rail vehicles.

This has been highlighted by recent rail vehicle accidents. The need for alternative

joining techniques and joint designs is reinforced by the findings in the work package 3

(WP3) (existing joint assessment). The objectives of this work package (WP5) are:

• investigate alternative welding techniques and/or joint designs for

improved joints.

• compare adhesive bonding and fraction stir welding with traditional

methods.

A review of all the emerging joining techniques was carried out and the results were

discussed. Mechanical tests were carried out on the joints made using friction stir

welding and adhesive bonding techniques. A new design for butt welded joints was

proposed and is presented in the report, along with the use of finite element analyses to

assist joint design.

Description of Results

New joining techniques

A review of MIG welding as well as laser and hybrid laser-arc processes for the

fabrication of rail vehicle carbodies was carried out at TWI. For fusion welding

processes it will not be possible to eliminate entirely the HAZ associated with Al alloy

weldments. Hybrid laser-arc processes offer advantages over and above those of laser

and arc processes individually, including: higher welding speeds leading to increased

productivity and reduced distortion, improved weld quality (e.g. a reduced incidence of

welding defects such as pores and cracks), increased penetration, and increased

tolerance to fit-up, which is crucial in a production environment. For hybrid laser-arc

processes, an appropriate selection of process parameters and filler wire is anticipated

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ALJOIN to lead to as-welded ultimate tensile strengths above those reported for laser welds

(~60-80% of parent), with tensile failure occurring in the HAZ.

Extruded plates (6mm thick) of 6005A-T6, 6008-T6 and 6008-T7 have been welded by

friction stir welding (FSW) at DanStir (see Figure 22). The parent materials were

supplied by ALCAN. The samples were welded in a butt-joint configuration with a

backing bar to simulate the more common joint configuration in double-skin rail car

structures.

Figure 22 Welded extruded 6mm thick plate by friction stir welding at DanStir - overall

view (left) and close-up showing backing bar

Mechanical tests were performed to characterise material and joint mechanical

behaviour. These included hardness survey, Charpy impact, fracture mechanics and

cross weld tensile tests. Test results of FSW welds showed that:

• Strength and elongation of the FSW welded joints were similar to those of

the Al-Mg welded joints.

• Fracture toughness of the FSW weld nugget was much better than that of

the MIG weld metals.

Adhesive bonded full-scale rail vehicle carbody components were manufactured.

Preliminary tests were carried out under drop weight impact loading conditions. Peak

loads sustained by the specimens ranged from 16 to 28kN, which were much lower than

those sustained by the welded joints.

New joint design

The behaviour of partial penetration welds made by the MIG process was studied in the

“cleavage” tests by Bombardier. These tests demonstrated that the most likely failure

mode is weld fracture. Because of low fracture toughness of Al-Si weld metal as clearly

shown in the small scale fracture mechanics tests, partial penetration welds made using

Al-Si filler should not be used in safety critical components and structures. If there are no

other options, but partial penetration weld, Al-Mg filler metal is preferred. The size of the

weld should be such that the stresses in the weld metal should be similar to those in the

other zones immediately adjacent to the weld metal. This can be achieved by joint

geometry optimisation. An example of such a joint design is illustrated in Fig.11.

Basically, the local weld zone area is “over sized”.

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ALJOIN Figure 23 An example of new joint design showing local thickened area circled

Finite element analysis was employed to investigate the effect of weld over sizing on

joint behaviour. The stress-strain data and failure models established in work package 3

and 4 were used in the finite element analyses. It was shown that the minimum weld

over sizing factor was 1.4, corresponding to a situation where the critical section is not in

the joint (see Figure 24).

No weld oversizing: failure in the HAZ

Weld oversizing factor = 1.4: critical section not in

the joint

Weld oversizing factor = 1.2: failure in the HAZ

Weld oversizing factor = 1.6: critical section not in

the joint

Figure 24 Finite element analysis of effect of joint geometry on fracture failure

(D’Appolonia)

Main Conclusions

Many different joining/welding techniques, as an alternative to the conventional MIG

process, were investigated for rail vehicle carbody construction. This work included

reviews of AC-pulsed MIG, Tandem MIG, Low Stress No Distortion (LSND), Laser, and

Hybrid laser-arc process, mechanical tests of welds made using Tandem MIG, FSW,

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ALJOIN Laser, and Hybrid laser-arc process, and drop weight impact tests of adhesive bonded

joints.

The review of various fusion welding techniques has suggested that the hybrid laser arc

technique has potential in improving productivity and joint performance. Test results of

FSW welds showed that: strength and elongation of the FSW welded joints were similar

to those of the Al-Mg welded joints and that fracture toughness of the FSW weld nugget

was much better than that of the MIG weld metals.

For rupture due to over load transverse to the weld, localised failure will still occur in

FSW joints, and therefore energy absorption will still be limited by the joint failure.

Strength of the weld zone can be improved by increasing thickness in the weld zone

area. A new joint has been designed for the MIG process. Finite element analyses

conformed the improvement in strength of the new joints.

4.6 WORK PACKAGE 6: EXPLOITATION PRODUCTS AND STANDARDS

Introduction

It is envisaged that new joining technologies and materials will be used for further

development and, eventually, commercial exploitation in rail vehicle construction.

Additionally exploitation will be undertaken to develop other solutions in other transport

sectors and in different industries.

Description of Results

Exploitation Products

Current codes and standards allow an option to use Magnesium or Silicon based

aluminium alloy welding wire based on structural performance although this has not

been based on ‘Crashworthiness’ considerations. The comparison of partial penetration

welds with silicon and magnesium alloy filler wire subject to dynamic loading clearly

demonstrated the higher performance of magnesium welding in impact conditions (see .

This result clarifies the most suitable option for Rail applications with regard to crash

performance and also clarifies future design requirements for weld areas as being based

on the parent material properties for the rail industry and has potential benefits for other

transportation industries e.g. Automotive, Maritime.

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ALJOIN Figure 25 Silicon vs. Magnesium – partial penetration welds (Bombardier)

Current improvements within Bombardier as a direct exploitation of the available results

comprise:

• change to magnesium based filler wire;

• Friction Stir Welding of bodysides;

• increase in material thickness around HAZ;

• bolt together structures.

Figure 26 reports an example of the current improvements in Bombardier, corresponding

to new overmatched design of welded joints on the Electrostar Bodysides.

Figure 26 New Over-matched MIG Butt weld and FSW joint on Electrostar Bodysides

(Bombardier)

Standards

The two most relevant CEN standards are prEN 15085 “Railway applications – Welding

of railway vehicles and components” and prEN 15227, the draft standard for

Crashworthiness of Rail Vehicle Bodies. Comments have been sent for both standards

to include (amongst other text) the following or similar statements to the effect that:

• “Magnesium aluminium alloy (5000 series) weld fillers should be used for

welding of 6000 series aluminium alloys.”,

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ALJOIN • “It is recommended that in the main structural welds along the carbody

length, the geometry of the extrusion should ensure that weld and HAZ

strength is matched to the parent material strength. This will generally

require the weld and HAZ to be between 1.4 and 1.6 times thicker than

the adjacent parent material.”

Therefore Aljoin has produced results that will be made available for the review of the

future revisions of the relevant standards in the field of aluminium joint crashworthiness

and for the construction of the future aluminium railway carbodies. Moreover Aljoin

provided a significant contribution in relation to the report to the Cullen Enquiry, related

to the Ladbroke Grove crash (1999), that was prepared by Bombardier.

4.7 WORK PACKAGE 7: METHOD FOR ASSESSING CRASHWORTHINESS

Introduction

The behaviour of aluminium joints under highly dynamic conditions was largely unknown

before ALJOIN and also no reference testing of representative (railway) structures

existed. In order to address such issues the work has been addressed in a direction to

design a new method for assessing the crashworthiness of aluminium joints to be able to

represent the real critical loading conditions. In particular the problem of weld unzipping

needed to be studied and tested in more detail.

Description of Results

A demonstrator representative of full-scale rail vehicle sub-structure was designed by

Bombardier. The test pieces are constructed from a pair of extrusions joined using a

number of different welding processes. The extrusions contain representative weld

construction features and a robust ‘C’ slot for mounting in the test rig. A typical crosssection

is shown in Figure 27. The welded pairs will be in the order of 500mm long, the

‘C’ slot on the upper extrusion is used to support the test piece in the rig and the ‘C’ slot

in the lower extrusion is used to load the test piece.

Figure 27: Demonstrator Design for FSW (above) and MIG joints (Bombardier)

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ALJOIN The test piece is to be loaded dynamically and this has been done at Bombardier's test

facility in Crespin, France using an Air Cannon (see Figure 28). The test rig is shown in

Figure 29. One load cell each was installed in each of the four legs of the test rig for

obtaining transient forces. Transient displacements at the vicinity of the impact point

were measured with a Laser sensor.

Figure 28: Air gun facility at Bombardier Crespin

Figure 29: Test-Rig for the testing of demonstrators (Bombardier)

4.8 WORK PACKAGE 8: DEMONSTRATORS

Introduction

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ALJOIN The objective of this work package is the manufacturing and testing of the

demonstrators, in agreement of the findings of WP 7 where the methodology for the

assessment of their performance was defined. The challenge of this WP was mainly

related to the set up of the manufacturing processes for the manufacturing of

demonstrators characterised by constant and repetitive characteristics and the Design of

the testing Experiments. More in detail the objectives of the WP were:

• to apply the developed methods to the assessment of crashworthiness of

large-scale components.

• to demonstrate structural performance of welded joints of aluminium

alloys made by new technique and design.

• to perform large-scale tests of components of body shells under controlled

laboratory loading conditions reflecting those in vehicle collision

scenarios.

Description of Results

It is worth mention that more than 150 demonstrators were manufactured and tested.

There were two extrusion designs produced: one for MIG or hybrid Laser-MIG welds and

the other for friction stir welds. Double skin extrusions similar to those used for rail

vehicle floors were produced at Alcan, Switzerland, according to the sketch shown in

Figure 27. One of the FSW demonstrators being manufactured, and one MIG

demonstrator are shown in Figure 30.

Figure 30: FSW demonstrator (left) (Danstir) and MIG demonstrator (TWI)

The different configurations tested comprise a combination of the following parameters:

• 2 material grades:

o 6005

o 6008

• 2 material conditions:

o T6

o T7

• 3 weld thicknesses (weld oversizing) :

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ALJOIN o 3mm (no oversizing of the weld – normal skin thickness used on

the Ladbroke Grove vehicles)

o 4.2mm (oversizing factor 1.4)

o 4.8mm (oversizing factor 1.6)

• 3 Welding Processes

o MIG welded demonstrators with 5356 welding wire

o LASER welded demonstrators

o FSW demonstrators

• Initiator location:

o 1: no initiator

o 4: initiator located in correspondence of the parent material and

the HAZ

For the final test programme, three specimens each with or without initiator were

prepared for each combination of conditions. For each combination of aluminium grade

and welding process, test would stop when all six samples (3 each with or without

initiator) fractured in the parent material.

Test results show that fracture occurs mostly in the weld zone of the joint without weld

oversizing. The fracture runs through the entire length of the weld without arrest. There

is hardly global plasticity deformation in the specimen. An example of welded

specimens after being tested are shown in Figure 31.

Figure 31: example of welded specimens after testing.

The performance of the three parent materials in the impact tests is assessed in terms of

force and energy. Comparison of the performance of the three materials in terms of

absorbed energy in shown in Figure 32, from which it could be observed that 6005AT6 is

considered to be stronger and more crashworthy than 6008T6 or 6008T7.

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ALJOIN Figure 32: comparison of performance of the three materials with respect to the

absorbed energy.

Some tentative conclusions from the analysis of the test results are reported below:

• In the impact tests, 6005AT6 sustained higher fracture force and

absorbed more energy than 6008T6. With the initially available kinetic

energy of about 6.4kJ, 6005AT6 did not fracture completely through the

entire length of the specimen, while 6008T6 did. 6005AT6 was, therefore,

a more crashworthy material than 6008T6 under the loading conditions

similar to those prevailing in the tests.

• the weld zone stress levels can be reduced enough for fracture to occur in

the parent material by the increase of the weld zone thickness. The

minimum ratio of the thickness of the weld zone to that of the parent

material has been found to be between 1.4 to 1.6 for 3mm extrusion

skins. The precise ratio would depend on welding process and aluminium

grade. Increases in thickness above the optimum although they increase

the static failure load they have an adverse effect on the dynamic

response.

• from a crashworthiness viewpoint, fracture in the parent material appears

to be the best option. With this in mind, all the welding processes

considered in the present work can be used to produce good quality butt

welded joints, which should lead to fracture in the parent material when

the thickness of the weld zone is increased to the above mentioned

values.

4.9 WORK PACKAGE 9: VALIDATION

Introduction

The objectives of WP9 are to validate project results by testing and by modelling.

Validation by testing has comprised the detailed analysis of the tests results of the

demonstrators with the aim of understanding the effects of the main parameters (parent

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ALJOIN material, filler material, welding technology, joint design) on the performance of the joints

in terms of crashworthiness (adsorbed energy, and resistance to crack growth) and then

to transfer such findings to the design of the new joints of the full vehicle. Validation by

modelling has comprised the simulation of the testing of the demonstrators with the aim

of setting up the material models and the related parameters. Finally the validated

models have been used to the prediction of the performance of the joints of a full vehicle

under various collision scenarios.

Description of Results

Simulation of the demonstrator tests has been carried out with the aim of validating the

material models. Two materials models have been considered at this purpose: the

Gurson model and a model based on the maximum strain at failure. The two models are

able to simulate the crack initiation and growth in the material, as demonstrated in Figure

33. Figure on the left of Figure 33 shows a case (material 6005 T6, weld thickness 4.2

millimetres, magnesium filler wire, no crack initiator) in which failure was located in the

parent material and the material failure model was based on the maximum plastic strain.

Figure on the right of Figure 33 shows a case (material 6005 T6, weld thickness 3.0

millimetres, magnesium filler wire, no crack initiator) in which failure was located at the

interface between the HAZ and the weld, and the material model was the Gurson model.

The results shows the ability of the code and of the material model to represent the crack

growth in the structure. Different mesh densities have been considered in order to

assess the mesh sensitivity.

Figure 33: Results of the simulation of the demonstrators in case of failure located in the

parent material (left) and in the joint area

Simulations have been extended to the analysis of a full vehicle. Bombardier Vehicle

Class 165 was selected, being the type of vehicle involved in the Ladbroke Grove

disaster which originated ALJOIN. The computer model of the vehicle is shown in Figure

34. The goal was to demonstrate the progress made within ALJOIN with respect to the

state of the art concerning the ability to design crashworthy joints in aluminium rail

structures and to model their behaviour under impact conditions. The benchmark for

such analysis is represented by the vehicle which was involved in the Ladbroke Grove

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ALJOIN accident, shown in Figure 35. The pictures clearly show the catastrophic failure of the

longitudinal joints (partial penetration welds) without any plastic deformation.

Various impact scenarios have been investigated (different obstacle shapes) with the

aim of study the effect on the joints and their failure. Figure 36 shows the result of the

simulations considering an impact at 20 kilometres per hour against a flat obstacle and

with standard welded joints. The weld lines are highlighted in red. In the figure it is

clearly visible the simulation is able to predict the catastrophic failure of the longitudinal

joints ahead of the area of impact, a mechanism which is analogue to what occurred in

the Ladbroke Grove impact. The way forward to the current situation is represented by

the results of the simulations shown in Figure 37 and Figure 38. Figure 37 shows the

results of the simulations using the validated material model and considering a joint

oversising factor of 1.4. In this case we do not observe a dramatic failure of the joints

ahead of the area of impact and the entire section of the vehicle remain connected,

providing an improved protection to the passengers.

The analyses have been further extended to consider different shapes of the obstacles

with the aim of putting the joints in different loading conditions. Figure 38 shows the

results of the simulations obtained considering the Gurson material model, and

oversizing factor of 1.4 for the joints, and an obstacle of cylindrical and prismatic shape.

Also in this case the joints do not fail catastrophically, and the structure can exploit a

certain plastic deformation as a mechanism to increase impact energy absorption.

Figure 34: FEM model of Bombardier Vehicle Class 165 (Bombadier)

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ALJOIN Figure 35: vehicle involved in the Ladbroke Grove accident (Bombadier)

Figure 36: Simulation of full-vehicle impact at speed of 20 km/h with standard welded

joints

Figure 37: Simulation of full-vehicle impact with improved joint design

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ALJOIN Figure 38: Simulation of full-vehicle impact with improved joint design and different

obstacle shape

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Contract N° G3RD-CT-2002-00829

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ALJOIN 5. LIST OF DELIVERABLES

The list of deliverables, according to the Work Programme, is presented in the table

below.

Table 2 Deliverables produced in the first 18 Month period

TASK DELIVERABLE Date Partner TYPE & CONTENT

WP 2

WP 3

WP 3

WP 3

WP 3

WP 3

WP3

Performance Criteria

Report

Progress Report on

ALJOIN WP3 – material

and structural behaviour

of MIG butt welds in

6005A-T6 aluminium

alloy extrusions under

quasi-static and impact

loading

WP3 Testing

Material and structural

behaviour of MIG butt

welds in 6005A-T6

aluminium alloy

extrusions under quasistatic

and impact loading

Plain and notched tensile

tests and analysis on

welded 6005A-T6

specimens for ALJOIN

WP 3

Laser and hybrid laserarc

welding of aluminium

alloys – Principles and

potential for application to

rail vehicle body

structures

Mechanical and Material

Analysis of Welded

Aluminium 6005A-T6

Specimens for ALJOIN

Work Package 3

WP3 Bolted Tearing Tests

WP3

Adhesive and Silicon

Welded Tensile test

February 2003

ARRC,

Bombardier

October 2003 TWI

September

2003

ARRC

February 2004 TWI

January 2002 ARRC

January 2004 TWI

May 2004 NEWRAIL

November

2004

November

2004

NEWRAIL

NEWRAIL

WP 4A Static Modelling of Joints March 2004 TWI

38

Report

Formulation of performance criteria

Future requirements for crashworthy

aluminium rail vehicles.

Report containing the findings on

testing of 6005A-T6 aluminium alloy

extrusions under different test

conditions

Report containing ARRC results on

hardness tests, notched tensile, and

Crack Tip Opening Angle (CTOA)

tearing tests. FEA of tests was also

performed.

Report containing the findings on

testing of 6005A-T6 aluminium alloy

extrusions under different test

conditions

Report containing results of a set of

plain and notched tensile tests for the

evaluation of the tri-axiality and true

strain values required by the selected

failure model.

Report containing a review of current

application of laser and hybrid laserarc

welding of aluminium alloys in

transportation and feasibility for

application to rail vehicle body

structures

Report detailing the development and

the results of uniaxial tests, TOA tests,

hardness tests developed by

NEWRAIL. Also microscopy images

of the materials are reported and

commented.

Description of results of bolted tearing

tests performed by NEWRAIL

Report describing tensile tests on

adhesive and silicon welded joints

performed by NEWRAIL

Report delivering: material failure

models for aluminium alloy welds,

constitutive model of the different

welded joints, and numerical results of


Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

ALJOIN TASK DELIVERABLE Date Partner TYPE & CONTENT

WP4B

WP5

WP6

WP7

WP8

WP8

WP9

WP4B-Dynamic

Modelling of Components

and Structures

WP5 Report - New

Joining Techniques and

Joints

Technological

Implementation Plan

Design of Cleavage test

and test specifications

Analysis of large scale

impact tests of welded rail

vehicle components of

aluminium alloys

Demonstrator Test

Results

Validation of the

modelling activities and

new joints design

performance evaluation

March 2004 D’Appolonia

March 2004 TWI

March 2004

Bombardier +

all

May 2004 Bombardier

July 2005 TWI

July 2005 Bombardier

September

2005

D’Appolonia

simple joints subjected to axial and

transverse forces

Report detailing the results of the

simulations of CTOA tearing tests,

tearing tests of bolted joints, bolted

Tubes subjected to axial impact, and

cleavage tests

Report providing the results of WP5

concerning new joining techniques

and joints

Draft of TIP for the mid term of project

containing the plans for the

exploitation of the project results by all

partners

Drawings of the MIG and FSW

demonstrators to be tested

dynamically and test specifications

Report describing the methodology

used for the testing of the ALJOIN

demonstrators and the analysis of the

results

Test results of demonstrators,

containing the values of the forces

and impact energy

measured/calculated from the tests

and the pictures of the tested samples

Presentation of the validation activities

at the Final ALJOIN Workshop held in

York

The list of milestones, according to the Work Programme, is presented in the table

below.

Table 3 Overview of Milestones

O V E R V I E W O F M I L E S T O N E S

Milestone Due Brief description of Decision criteria for

No. date M milestone objectives

assessment

M1.1 6 Consortium agreement.

Approved and signed by all the

partners.

M2.1 6

Completion of WP2

Performance Criteria report

Criteria assessed, future

performance investigated

M3.1 12 Completion of WP3 report

Method of assessing Joints in

Aluminum created.

M1.2 18 MID-TERM REVIEW

Successful evaluation of the

innovative solutions

39


Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

ALJOIN 6. COMPARISON OF INITIALLY PLANNED ACTIVITIES AND WORK ACTUALLY

ACCOMPLISHED

The work has been carried out according to the original Work Programme.

The table below summarises the status of each project task with respect to the

planned progress.

Table 1: Status of Project Tasks

WORK PACKAGE ACTUAL vs. PLANNED PROGRESS STATUS

WP 2 –

Performance

Criteria

WP 3 – Existing

Joint Assessment

WP 4A – Static

Modelling of Joints

WP 4B - Dynamic

Modeling of

Components and

Structures

WP 5: New

Joining

Techniques and

Joints

WP 6: Exploitation

Products and

Standards

WP 7: Method for

Assessing

Crashworthiness

WP 8:

Demonstrators

Performance criteria for critical aluminium joints in

railway vehicles have been defined.

No deviation from the planning.

An extensive testing activity has been carried out on

different materials.

An extension of this WP was required to perform tests

originally not planned.

Material failure models suitable for the simulation of the

aluminium extrusions and the ALJOIN materials have

been analysed.

Numerical results on simple joints have been carried

out using such material models.

No deviation from the planning.

Numerical analysis of bolted structures, Crack Tip

Opening Angle (CTOA) tearing tests, numerical

analysis of “cleavage” test, tearing tests of bolted joints.

No deviation from the planning.

New Joining techniques and Joints have been

analysed, comprising Hybrid laser-arc process,

adhesive bonded joints, and friction stir joints.

No deviation from the planning.

The innovations produced within ALJOIN, in particular

concerning the new joining techniques, have been

already used by Bombardier in their production.

Comments to the main standards relevant to ALJOIN

have been issued.

No deviation from the planning.

Test planning completed for the tests to be developed

on small specimens and full-scale components.

No deviation from the planning.

A prototype dynamic cleavage demonstrator

component test methodology has been developed and

40

Completed

Completed

Completed

Completed

Completed

Completed

Completed

Completed


Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

ALJOIN WORK PACKAGE ACTUAL vs. PLANNED PROGRESS STATUS

WP 9: Validation

prototype demonstrators have been tested. The test

has the potential to become a new standard for the

evaluation of resistance to crack growth of welded

structures.

No deviation from the planning.

Validation by modelling of rail vehicle in crash

scenarios and of full-scale cleavage tests

41

Completed


Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

7. MANAGEMENT AND CO-ORDINATION ASPECTS

ALJOIN 7.1 Project co-ordination

A number of technical meetings were held during the project development to address the

main technical aspects of the work. The list of the main project meetings is shown in the

following Table.

Description

Table 4 List of Main Meetings

Location

Date

ALJOIN kick-off meeting D’appolonia

Genova

06-09-02

A general Kick-off meeting, with introduction presentations and discussions

about the ALJOIN project

WP2 Meeting Bombardier Transport, Derby 17-10-02

Discussed design standards. Different joining techniques. Alternative materials

and WP3 kick-off meeting

FSW workshop TWI – Cambridge 06-11-02

A Friction Stir Welding workshop, Chaired by Torben Lorentzen (DANSTIR)

presentations on technical benefits, current and potential applications and

demonstrations

WP2 Review Meeting TWI – Cambridge 13-11-02

Discuss the work needed to complete WP2

WP2 Review Meeting ARRC – University of

Sheffield

20-11-02

ARRC and D’Appolonia discussed the work needed to complete WP2

WP3 Kick off meeting ARRC – University of

Sheffield

28-11-02

WP3 kick-off meeting, presentations from all represented parties, development

of a matrix for the testing to be carried out in WP3

WP2 Report Preparation

Discussion Meeting

Bombardier Transport, Derby 14-01-03

To discuss the performance criteria report for WP2 and further work necessary

for WP2 deliverables

WP2 Report Preparation ARRC – University of 05-02-03

Discussion Meeting

Sheffield

ARRC and D’Appolonia to discuss the current version of the report for WP2

6 Month Management

Meeting

D’Appolonia S.p.A., Genova 24-02-03

Six Month Meeting to discuss the accomplished activities

12 Month Management

Meeting

TWI The Welding Institute 30-07-03

12 Month Meeting to discuss the accomplished activities

WP5 Kick Off Meeting TWI The Welding Institute 27-08-03

To discuss the work needed on WP5

WP3 Tear Test

ARRC – University of September 03

Discussion Meeting

Sheffield

Discussed results from WP3 testing

42


Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

Description

43

Location

ALJOIN Date

Pre-18 Month Review

Meeting

Bombardier Transport, Derby January 04

Review of project development in preparation to the Mid Term Review and

discussion on RSSB participation and demonstrator testing

18 Month Review Meeting NEWRAIL, Newcastle

University, UK

March 04

21 Month Meeting

Mid Term Assessment Meeting

TWI, Cambridge April 04

Technical Meeting to review the progress of work and discuss the testing

activities

24 Month Review Meeting D’Appolonia S.p.A., Genova August 04

30 Month Meeting

24 Month Review Meeting

Bombardier Transport,

Bruxelles

30 Month Meeting

February 05

Demonstrator Testing Bombardier Transport,

Crespin (France)

April 05

Attendance to the demonstrator testing

Technical Meeting Newrail, Newcastle (UK) June 05

Discussion on overall project development in preparation to the Final Review

Final Meeting D’Appolonia S.p.A., Rome

Final Review Meeting

July 05

7.2 Man Power and Progress Follow-up Table

The Man Power and Progress Follow-up Table is reported in the next pages.

The effort globally spent by the partners in the project shows no major deviation from

what planned.


44

Task/Subtask

(N°/title)

WP1 Project

Management and

Dissemination

WP2 Performance

Criteria

WP3 Existing Joint

Assessment

Partner

(Name/

abbrev.)

Planned efforts - at start of period

(MM)

Month 1-

18

Month

18-24

Table 5 Man Power and Progress Follow-up Table

Actual

Devia-

Planned

Assessed* Devia-tion

effort

tion

(%)

(%)

(%)

(MM)

Comments on major

(MM)

Contract

deviations and/or

Month 1- Month

Month 1- Month

Month 1- Month

Year 3 Total Totals Year 3 Year 3 Month 36

modifications of planned

18 18-24

18 18-24

18 18-24

efforts.

(a1+b1+c1

(a+b+c)

(a1+b1)/

a1/d1

) (d1-d)/d

/d

d1

/d1

Number G3RD-CT-2002-00829

Year 3 Total

a b c d a1 b1 c1 d1 d1-d a/d (a+b)/d

DAPP 6 2 3 11 7,1 3,75 2,4 13,25 2,25 55% 73% 100% 54% 82% 100% 20%

NEWR 4,5 1,5 3 9 3,75 1,5 4,5 9,75 0,75 50% 67% 100% 38% 54% 100% 8%

ALCAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

BOM 0 0 0 0% 0% 0% 0% 0% 0% 0%

DAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

TWI 0 0 0 0% 0% 0% 0% 0% 0% 0%

Total 10,5 3,5 6 20 10,85 5,25 6,9 23 3 53% 70% 100% 47% 70% 100% 15%

DAPP 0 0 0 0% 0% 0% 0% 0% 0% 0%

NEWR 3 3 3 3 0 100% 100% 100% 100% 100% 100% 0%

ALCAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

BOM 2 2 2,5 2,5 0,5 100% 100% 100% 100% 100% 100% 25%

DAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

TWI 0 0 0 0% 0% 0% 0% 0% 0% 0%

Total 5 0 0 5 5,5 0 0 5,5 0,5 100% 100% 100% 100% 100% 100% 10%

DAPP 0 0 0 0% 0% 0% 0% 0% 0% 0%

NEWR 5 1 6 5 1 6 0 83% 100% 100% 83% 100% 100% 0%

ALCAN 1 1 1 1 0 100% 100% 100% 100% 100% 100% 0%

BOM 5 5 5 5 0 100% 100% 100% 100% 100% 100% 0%

DAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

TWI 6 6 6 6 0 100% 100% 100% 100% 100% 100% 0%

Total 17 1 0 18 17 1 0 18 0 94% 100% 100% 94% 100% 100% 0%

Final Technical Report – draft 1

ALJOIN


45

Task/Subtask

(N°/title)

WP4 Dynamic

Modelling of

Components and

Structures

WP5 New Joining

Techniques and

Joints

WP6 Exploitation

Products and

Standards

Partner

(Name/

abbrev.)

Table 5 Man Power and Progress Follow-up Table (continue from previous page)

Planned efforts - at start of period

Actual

Devia-

Planned

Assessed* Devia-tion

(MM)

effort

tion

(%)

(%)

(%)

(MM)

(MM)

Comments on major

Contract

deviations and/or

Month

Month 1- Month

Month 1- Month

Month 1- Month

Year 3 Total Year 3 Total Totals Year 3 Year 3 Month 36 modifications of planned

18-24

18 18-24

18 18-24

18 18-24

efforts.

(a1+b1+c1

(a+b+c)

(a1+b1)/

a b c d a1 b1 c1 d1 d1-d a/d (a+b)/d

a1/d1

) (d1-d)/d

/d

d1

/d1

Number G3RD-CT-2002-00829

Month 1-

18

DAPP 19 19 0 38 21,6 24 0 45,6 7,6 50% 100% 100% 47% 100% 100% 20%

NEWR 6 6 12 0 12 12 0 50% 100% 100% 0% 100% 100% 0%

ALCAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

BOM 0 0,5 0,5 0,5 0% 0% 0% 0% 0% 0% 0%

DAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

TWI 8,5 6,5 15 8,8 6,2 2,5 17,5 2,5 57% 100% 100% 50% 86% 100% 17%

Total 33,5 31,5 0 65 30,9 42,2 2,5 75,6 10,6 52% 100% 100% 41% 97% 100% 16%

DAPP 0 0 0 0% 0% 0% 0% 0% 0% 0%

NEWR 0 0 0 0% 0% 0% 0% 0% 0% 0%

ALCAN 1,9 1,1 3 1,9 1,1 3 0 63% 100% 100% 63% 100% 100% 0%

BOM 0 0,5 0,5 1 1 0% 0% 0% 0% 0% 0% 0%

DAN 0,7 0,3 1 0,7 0,3 1 0 70% 100% 100% 70% 100% 100% 0%

TWI 2,5 2,5 5 2,5 2,5 2,5 7,5 2,5 50% 100% 100% 33% 67% 100% 50%

Total 5,1 3,9 0 9 5,6 4,4 2,5 12,5 3,5 57% 100% 100% 45% 80% 100% 39%

DAPP 0 0 0 0% 0% 0% 0% 0% 0% 0%

NEWR 3 3 6 0,5 5,5 6 0 0% 50% 100% 0% 8% 100% 0%

ALCAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

BOM 1,5 1,5 3 6 1,5 1 3,5 6 0 25% 50% 100% 25% 42% 100% 0%

DAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

TWI 0,5 0,5 1 2 0,5 0,5 2,5 3,5 1,5 25% 50% 100% 14% 29% 100% 75%

Total 2 5 7 14 2 2 11,5 15,5 1,5 14% 50% 100% 13% 26% 100% 11%

Final Technical Report – draft 1

ALJOIN


46

Task/Subtask

(N°/title)

WP7 Method for

assessing

crashworthiness

WP8 Demonstrators

WP9 Validation

Partner

(Name/

abbrev.)

Table 5 Man Power and Progress Follow-up Table (continue from previous page)

Planned efforts - at start of period

Actual

Devia-

Planned

Assessed* Devia-tion

(MM)

effort

tion

(%)

(%)

(%)

(MM)

(MM)

Comments on major

Contract

deviations and/or

Month

Month 1- Month

Month 1- Month

Month 1- Month

Year 3 Total Year 3 Total Totals Year 3 Year 3 Month 36 modifications of planned

18-24

18 18-24

18 18-24

18 18-24

efforts.

(a1+b1+c1

(a+b+c)

(a1+b1)/

a b c d a1 b1 c1 d1 d1-d a/d (a+b)/d

a1/d1

) (d1-d)/d

/d

d1

/d1

Number G3RD-CT-2002-00829

Month 1-

18

DAPP 0 0 0 0% 0% 0% 0% 0% 0% 0%

NEWR 3 3 6 0,5 5,5 6 0 0% 50% 100% 0% 8% 100% 0%

ALCAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

BOM 3 3 6 4 3 7 1 0% 50% 100% 0% 57% 100% 17%

DAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

TWI 0 0 0 0% 0% 0% 0% 0% 0% 0%

Total 0 6 6 12 0 4,5 8,5 13 1 0% 50% 100% 0% 35% 100% 8%

DAPP 0 0 0 0% 0% 0% 0% 0% 0% 0%

NEWR 0 0 0 0% 0% 0% 0% 0% 0% 0%

ALCAN 3,3 3 6,3 1,8 4,5 6,3 0 0% 52% 100% 0% 29% 100% 0%

BOM 10 10 20 2 4 14 20 0 0% 50% 100% 10% 30% 100% 0%

DAN 1 2 3 0,5 3,9 4,4 1,4 0% 33% 100% 0% 11% 100% 47%

TWI 1 1 2 1 2 3 1 0% 50% 100% 0% 33% 100% 50%

Total 0 15,3 16 31,3 2 7,3 24,4 33,7 2,4 0% 49% 100% 6% 28% 100% 8%

DAPP 6 6 1 6 7 1 0% 0% 100% 0% 14% 100% 17%

NEWR 6 6 6 6 0 0% 0% 100% 0% 0% 100% 0%

ALCAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

BOM 3 3 3 3 0 0% 0% 100% 0% 0% 100% 0%

DAN 0 0 0 0% 0% 0% 0% 0% 0% 0%

TWI 0 0 0 0% 0% 0% 0% 0% 0% 0%

Total 0 0 15 15 0 1 15 16 1 0% 0% 100% 0% 6% 100% 7%

Final Technical Report – draft 1

ALJOIN


47

Task/Subtask

(N°/title)

TOTALS

Partner

(Name/

abbrev.)

Table 5 Man Power and Progress Follow-up Table (continue from previous page)

Planned efforts - at start of period

(MM)

Month 1-

18

Month

18-24

Year 3 Total

Month 1-

18

Actual

effort

(MM)

Month

18-24

Deviation

(MM)

Year 3 Total Totals

Month 1-

18

Month

18-24

a b c d a1 b1 c1 d1 d1-d a/d (a+b)/d

Year 3

Month 1-

18

(a+b+c)

/d

a1/d1

Month

18-24

(a1+b1)/

d1

Devia-tion

(%)

Year 3 Month 36

(a1+b1+c1

) (d1-d)/d

/d1

DAPP 25 21 9 55 28,7 28,75 8,4 65,85 10,85 45% 84% 100% 44% 87% 100% 20%

NEWR 18,5 14,5 15 48 11,75 15,5 21,5 48,75 0,75 39% 69% 100% 24% 56% 100% 2%

ALCAN 2,9 4,4 3 10,3 2,9 2,9 4,5 10,3 0 28% 71% 100% 28% 56% 100% 0%

BOM 8,5 14,5 19 42 12 9,5 23,5 45 3 20% 55% 100% 27% 48% 100% 7%

DAN 0,7 1,3 2 4 0,7 0,8 3,9 5,4 1,4 18% 50% 100% 13% 28% 100% 35%

TWI 17,5 10,5 2 30 17,8 10,2 9,5 37,5 7,5 58% 93% 100% 47% 75% 100% 25%

TOTAL 73,1 66,2 50 189,3 73,85 67,65 71,3 212,8 23,5 39% 74% 100% 35% 66% 100% 12%

*) Please note that the actual technical progress percentage and the updated remaining efforts must reflect the physically assessed status of the work.

Planned

(%)

Assessed*

(%)

Comments on major

deviations and/or

modifications of planned

efforts.

Contract Number G3RD-CT-2002-00829

Final Technical Report – draft 1

ALJOIN


GROWTH PROJECT ALJOIN Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

7.3 Work Plan

48

ALJOIN The Work Plan diagram is reported on next page. The only modification agreed with the

partners was the extension of WP3, in order to complete the testing plan.


CONTACT

PERSON

GROWTH PROJECT ALJOIN Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

COORDINATOR

Andrea Barbagelata

Maura Primavori

Donato Zangani

CONTRACTORS

Mark Robinson

George Kotsikos

Denis Hofmann

Christian Leppin

Mick Roe

Martin Wilson

Mick Wood

7.4 Updated contact details for the consortium

PARTNER

NAME

D'Appolonia S.p.A. Via S. Nazaro 19

16145 Genova

Italy

NEWRAIL

ALCAN Fabrication

Europe

Bombardier

Transportation

Torben Lorentzen DanStir ApS

Danish Stir Welding

Technology

John Davenport

Weiguang Xu

OTHER MEMBERS

Aqeel Janjua Rail Safety &

Standards Board

EUROPEAN COMMISSION

Dennis Schut European

Commission Officer

ADDRESS TEL./FAX/E-MAIL

University of

Newcastle

Department of

Mechanical & Systems

Engineering

Stephenson Building

Newcastle upon Tyne

NE1 7RU

Alcan Technology &

Management Ltd.

Badische

Bahnhofstrasse 16

CH-8212 Neuhausen

Switzerland

Litchurch Lane

Derby, DE24 8AD

United Kingdom

Park Allé 345

Box 124

DK-2605 Brondby

Denmark

TWI Limited Granta Park,

Great Abington

Cambridge CB1 6AL

United Kingdom

Floor 1 Evergreen

House

160 Euston Road

London

NW1 2DX

United Kingdom

European Commission

DG RTD H2, Office-B7

02/111, B-1049

Rue Belliard 7,

49

ALJOIN tel. +39-010-3628148

fax +39-010-3621078

andrea.barbagelata@dappolonia.it

maura.primavori@dappolonia.it

donato.zangani@dappolonia.it

Tel: +44 (0)191 222 5889

Fax: +44 (0)191 2227679

newrail@ncl.ac.uk

George.Kotsikos@newcastle.ac.uk

tel. +41-(0)-52 674 9523

fax +41-(0)-52 674 9216

mobile: +41 (0) 79 432 4841

denis.hofmann@alcan.com

tel. +41-(0)-52 674 9527

christian.leppin@alcan.com

tel. +44 (0)1332 266056

fax +44 (0)1332 251840

mobile +44 (0)7789 08779

mick.roe@uk.transport.bombardier.com

martin.j.wilson@uk.transport.bombardier.com

mick.wood@uk.transport.bombardier.com

tel: +45 4326 7035

fax: +45 4326 7040

mobile: +45 2330 3383

tlo@danstir.com

tel. +44-(0)-1223 891162

fax +44-(0)-1223 892588

john.davenport@twi.co.uk

fax +44-(0)-1223 890689

guang.xu@twi.co.uk

tel. +44 (0) 20 7904 7966

aqeel.janjua@rssb.co.uk

Tel. +32 2 295 09 27

fax: +32 2 296 33 07

Dennis.SCHUT@cec.eu.int


GROWTH PROJECT ALJOIN Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

Sandro Maluta Project External

Assessor

Brussels

Belgium

Via M. Lutero, 8

20126 Milano,

Italy

50

Tel. +30-333 9076104

samaluta@tin.it

ALJOIN


GROWTH PROJECT ALJOIN Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

8. RESULTS AND CONCLUSIONS

51

ALJOIN The introduction of double skinned construction, through the use of aluminium

closed cell extrusions, has greatly improved the crash resistance of rail vehicles.

On the other hand, the impact resistance of fusion welds that have traditionally

been the joining technique of the extruded sections, had not received adequate

consideration, in terms of the contribution of they make on the crash resistance

of a rail vehicle.

The ALJOIN project arose from the need to improve the crashworthiness design

of aluminium rail vehicles and establish guidelines for the future build of such

vehicles.

Aluminium alloys derive their physical properties (i.e. strength, stress corrosion

cracking resistance etc) through a range of elaborate heat treatments. The

additional heat input introduced by the fusion welding process alters the

microstructure at the weld region resulting in a reduction of strength there of up

to 50% of that of the parent plate. This can have detrimental effects in the

behaviour of such joints in high velocity impact situations. This effect has been

demonstrated by the failure of the rail coaches in the Ladbroke Grove accident in

the UK.

ALJOIN has carried out a detailed investigation of the joining of components in

rail vehicles by initially reviewing the current state of the art and assessing

alternative joining techniques.

It has been found that the use of Al-Mg filler wires in MIG welding results in

superior performance welds in terms of strength, ductility and fracture toughness

compared to Al-Si filler wires. Other joining techniques such as Laser Welding

(LW) and Friction Stir Welding (FSW) have also been investigated with the

former technique appearing attractive in terms of increased productivity and the

latter in terms of a moderate increase in fracture toughness and improved

surface finish, when they were compared to the traditional automated MIG

welding process.

ALJOIN has shown that the use of MIG welding with Al-Mg filler and FSW are

both good candidates for future built of train vehicles. It has also been

demonstrated that the design of the joint is equally important in the impact

performance of the joint.

Under-matching in an aluminium weldment is unavoidable due to the reduction in

strength at that region even after moderate heat inputs (as in the case of FSW).

After extensive testing both on small specimens and large demonstrators a

significant output of the ALJOIN project has been the recommendation for the


GROWTH PROJECT ALJOIN Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

52

ALJOIN aluminium sheet thickness at the weld region to be increased, so that the

resultant stress levels there are equivalent to those of the parent plate. The

amount of thickening of the plate is a factor of the aluminium grade and welding

process.

Another joint design improvement realised by this project is the avoidance of

partial penetration welds through appropriate shaping of the extrusions at the

joint region.

The validity of the design recommendations described above has been proved

through large scale demonstrator tests which have shown that dynamic failure

always takes place in the parent plate (that inherently possesses much higher

toughness) rather than the weldments.

Adhesive bonding of aluminium sections has also been investigated but has not

proved attractive neither in terms of productivity nor strength or impact

resistance. Furthermore, other issues such as the ease of carrying out NDE

inspections for both quality control or to establish levels of damage and need for

repair after minor impacts have proved impractical.

A methodology to assess experimentally the performance of welded aluminium

extruded sections was also developed during the ALJOIN project.

The methodology measures the energy absorbed by the specimen and the

displacement of the free end as it "tears away" from the clamped part of the

specimen and provide a measure of the tearing resistance of the material when

subjected to high loading rates.

The term "tearing resistance" in this test is not to be confused with the fracture

mechanics derived term. Since there is no sharp crack to initiate the failure the

test can be considered as dynamic tensile test where the peak load describes the

energy required to yield the cross-section and tear the material. The subsequent

rate of load drop is a measure of how easily the tear propagates through the

material. The results of this work have shown that the parent material (6005-T6)

possesses substantial tearing resistance and have also demonstrated the

benefits of increasing the cross-section thickness at the weld region in diverting

failure (i.e. crack initiation and propagation) away from the weld and into the

parent material.

The tests also demonstrated that increasing this increase in the section thickness

is a function of alloy grade and welding process. It is important here to note that

there is an optimum increase in the section thickness at the weld region. Any

further increase, although it improved the static strength of the joint, it reduced

the dynamic loading response, resulting in a lower initiation load and tearing


GROWTH PROJECT ALJOIN Contract N° G3RD-CT-2002-00829

Final Technical Report – draft 1

53

ALJOIN resistance. This was attributed to the increased thickness moving the failure

mode from plain stress to plain strain failure.

The ability to accurately model the collision behaviour of a rail vehicle has also

been a major output of the ALJOIN project. The modelling efforts have been

aided by detailed static and quasi-static mechanical property tests in order to

derive the material parameters that can best describe failure. In addition to

mechanical property and fracture mechanics tests, component tests were carried

out to validate the resultant models. The Gurson-Tvergaard model used within

the LS-DYNA finite element analysis code has provided very good predictions of

failure under static, quasi-static and dynamic loading conditions.

A model of a rail vehicle (class 165 by Bombardier, involved in the Ladbroke

Grove accident) was constructed and subjected to a number of head on collision

scenarios. The modelling exercise has demonstrated a notable improvement in

the failure mode when the joint design recommendations developed through this

project were implemented, (use of Al-Mg filler wire, increase of the sheet

thickness at the weld region and full penetration welds throughout).

ALJOIN has provided a number of results that have demonstrably improved the

structural integrity of rail vehicles and their crashworthiness. It is important to

note though that a collision between two rail vehicles or derailment cannot be

accurately modelled as there is an infinite number of loading configurations that a

rail vehicle and its individual structural components could be subjected to. Offaxis

loads as well as extreme loading rates are possible and it is clear that there

could still be a risk of fast fracture of weldments. The pipeline industry that for

many years has encountered fast fractures that can run for kilometres

understand the limitation in predicting this material behaviour.

This project is nevertheless a major step forward in understanding the role of

weldments in the crashwothiness of rail vehicles and produced recommendations

to improve the performance of weldments subjected to dynamic loading.

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