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According to Bahai (2001) calculation of the stress concentration factor (SCF) is an essential initial step in the fatigue life estimation of a threaded connection using a particular finite element (ABAQUS) sub-modelling technique. The data obtained can form the basis for obtaining parametric equations describing SCFs in terms of drill string thread geometric parameters. Hence thread design optimisations based on minimum axial and bending SCFs can be established. Rinehart (2003) used the finite element method by using ABAQUS Viewer to study the effects of localised geometric imperfections that cause the dent stress concentration behaviour of pressurised cylindrical shells. Khazhinskii (2005) agrees that more accurate estimates of stress concentration are obtained by the finite element method or experimentally by strain measurement (Xue et al., 2005; Alexander, 2008a). However, Xue et al. (2005) used different software for the finite element method using ANSYS in their study of cylindrical shell intersection stress concentration and flexibility factor before the structure experiences plastic behaviour. They determine limit load and burst pressure when an elastic – plastic analysis method is employed. Kosai et al. (1999) also mention that a numerical procedure is able to help them predict the crack trajectories in full-scale fuselage rupture tests. All numerical results agree well with their measured counterparts regardless of size. By using this ABAQUS software, Kim et al. (2007) manage to present plastic limit loads and approximate J estimates for axial through-wall cracked pipe bends under internal pressure and in-plane bending successfully. In order to avoid problems associated with incompressibility, they use reduced integration elements (i.e. element type C3D20R within ABAQUS). Shin (1986) makes a comparison study, based on the elastic stress distributions in single and double edge notched geometries in a finite plate, that have been estimated from Creager and Paris (1967), and Neuber‘s expressions. He demonstrates the stress concentration factor expressed by Creager and Paris as as 44 and Neuber which are very close to the FEM result just ahead of the notch. The error increases with distance from the notch root. Shin (1986) concludes that both the Creager and Paris expressions are more accurate for the notch root of sharper
notches and Neuber‘s is better for the blunter notches. However, these predictions are not applicable for the external notched pipe which is subjected to internal pressure and, therefore, other expressions are needed. Other example of finite element application is the use of a Non Destructive Examination (NDE) field, especially in the detection of gas pipe wall thickness based on Electromagnetic Flux Leakage as presented by Zhang and Yan (2007). Their numerical calculation of the FEA, using ANSYS, provides a good solution in revealing the relation between the wall thickness and the magnetic flux density at the same position in a magnetic leakage field. Parvin and Wu (2008) demonstrate that the finite element analysis is able to show that Carbon Fibre Reinforced Polymer (CFRP) wrapping is effective in retrofitting the existing beam-column joints. The wrap ply angle stacking sequence of -45°/ +45°/ -45°/ +45° appears to offer prevention against the brittle shear failure of the joint under combined axial and cyclic loads. 2.7.1 Stress Concentration Factor (SCF) and Stress Intensity Factor (SIF) Measurement in Pipeline The stress concentration factor (SCF), 45 Kt max can be used for fatigue assessment of pipelines whenever they are subjected to variations of internal pressure. For a fatigue assessment to be carried out, a rather detailed analytical expression for stress concentration factors in pipes that are derived for a number of design cases based on classical shell theory has been presented by Lotsberg (2008). In another study carried out by Radaj and Zhang (1996), they point out that with the presence of a stress concentration notch in pipelines, the initiation of a surface crack is often provoked. Carpinteri et al. (2004) numerically demonstrate that the SCF parameter is very important especially in presence of cracks since it heavily affects the SIF results. Therefore, Radaj and Zhang (1996) emphasise that local notch stress concentration is the basis for the assessment of the fatigue strength and life of structural components. nom
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CRANFIELD UNIVERSITY MAHADI ABD MUR
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ABSTRACT One of the most common pro
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TABLE OF CONTENTS ABSTRACT ........
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3.7.1 Introduction ................
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5.6 Summary and Conclusions .......
Page 14 and 15: Figure 3.1: Schematic diagram of th
Page 16 and 17: Figure 5.4: The average temperature
Page 18 and 19: NOMENCLATURES ACFM Alternating Curr
Page 21 and 22: 1 INTRODUCTION One of the most comm
Page 23 and 24: 1.1 Objectives Knowing this backgro
Page 25 and 26: The methodology of this integrated
Page 27 and 28: Chapter 6 contains the summary and
Page 29 and 30: period of the major part of the exi
Page 31 and 32: Figure 2.2: Reported interest in de
Page 33 and 34: Figure 2.4: Dent damage caused by v
Page 35 and 36: presented current practices, recent
Page 37 and 38: Energy Workforce Sdn Bhd (2011) cla
Page 39 and 40: available provides real time detect
Page 41 and 42: 2.3.3 Reliability Analysis of Infor
Page 43 and 44: Figure 2.9: Pipeline failure probab
Page 45 and 46: 2.3.3.1 NDT Reliability and POD cur
Page 47 and 48: increase in the yield limit of stee
Page 49 and 50: the SCC assessment in their integri
Page 51 and 52: Manufacturers such as Walkers Techn
Page 53 and 54: Company L.P, 2005); Aquawrap ® pro
Page 55 and 56: monitoring, inspection, and damage
Page 57 and 58: 2.6.2 Aims of Structural Health Mon
Page 59 and 60: Figure 2.16: Application fields and
Page 61 and 62: egistered by the piezoelectric sens
Page 63: discretization error. Round-off err
Page 67 and 68: maximum local stress at discontinui
Page 69 and 70: De Carvalho (2005) concludes that t
Page 71 and 72: accurate simulation of loading espe
Page 73 and 74: Based on the above facts, the opera
Page 75 and 76: 3 FINITE ELEMENT ANALYSIS (FEA) IN
Page 77 and 78: Figure 3.2: Schematic diagram of th
Page 79 and 80: In this modelling work (i.e. compos
Page 81 and 82: This partition toolset also helps u
Page 83 and 84: Figure 3.6: Mesh control using Swee
Page 85 and 86: Figure 3.7: Schematic representatio
Page 87 and 88: discretization. Therefore, in this
Page 89 and 90: According to Staten et al. (2010b),
Page 91 and 92: 3.5 The influence of pressure on th
Page 93 and 94: each pressure value remains constan
Page 95 and 96: Axial Stress, σa (S22) was referre
Page 97 and 98: Figure 3.14 shows a graph of analyt
Page 99 and 100: the notch defect is found to be in
Page 101 and 102: One of the contributions of this st
Page 103 and 104: Table 3.4: Convergence tests on var
Page 105 and 106: Figures 3.16 and 3.17 show that the
Page 107 and 108: Figure 3.20 shows that as the relat
Page 109 and 110: 3.7.4 Concluding Remarks A biaxial
Page 111 and 112: yarns change and lateral contact be
Page 113 and 114: For predicting E2 and Gl2, a number
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Where: Ar = weight of one sheet of
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Where; The Stiffness matrix is trad
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simulations for the hoop strain at
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Figure 3.24: Finding the hoop stres
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Table 3.8: The effect of repair len
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four up to 18 layers. In this study
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hoop and axial stress concentration
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Table 3.11: Predicted Elastic Const
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Table 3.13: Axial Stress v/s L/W ra
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Hoop Stress (MPa) Figure 3.3: Hoop
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However, Frost (2008) and Alexander
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Table 3.17: Ratio of Axial Stress N
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axial load (e.g. buried pipelines t
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3.10 Numerical Strain Analysis of C
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Figure 3.36 shows the contours befo
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Stress Concentration Factor 2 1.8 1
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In fact, for Notch 40 with 18 plies
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this second approach (i.e. the expe
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4.2.2 Strain Gauge Selection and Cr
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Finally, a method used to calculate
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Where, and are the maximum and mini
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should be between 20 and 28 bar and
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welded weld neck flange at both end
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Figure 4.7: Sensor and heating elem
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Figure 4.9: A summary of data acqui
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One of the objectives of doing this
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Figure 4.14: A schematic diagram of
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Table 4.1: Strain gauge readings at
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microstrain 3.00E-04 2.50E-04 2.00E
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However, the axial load transfer is
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Mircostrain 500 450 400 350 300 250
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Since the defect is not a flat notc
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Again, the epoxy resin plays a sign
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Table 4.4: Study at the defect area
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Mircostrain 300 250 200 150 100 50
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Mircostrain 600 500 400 300 200 100
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14.25% in hoop strain and 23.5% in
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consideration for the selection of
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5.4 Methodology of Thermal Expansio
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Figure 5.1: Some preventive measure
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5.4.1 The Fundamentals of the Therm
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5.5 Analysis of Results 5.5.1 The t
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Thermal Output (strain ) 0.0002 0.0
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(Strain ,ε) Figure 5.12: Coefficie
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(Strain ,ε) 0.0002 0.00018 0.00016
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Table 5.1: The strain readings afte
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maximum shear strain increase as th
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The above results show that shear s
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shear strains becomes more stable a
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for future safe design and operatio
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has been fully cured. Poor surface
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6.3 Primary PhD Achievements The ea
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In Chapter 5, the CTE was determine
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ASM International (2002), "Thermal
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Bucinell, R. B. (2001), Calculating
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Proceedings of OMAE'01 20th Interna
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Greenwood, R. (2002), UKOPA Pipelin
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Kotrechko, S. A., Krasovskii, A. Y.
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Mousavi, S. E., Xiao, H. and Sukuma
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Raju, I. S. and Newman, J. C. (1986
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Tennyson, R. C. and Mufti, A. A. (2
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Xue, L., Widera, G. E. O. and Sang,
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General Technical Specifications: T
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Photos of the Design and Build of t
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Composite Installation Process usin
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APPENDIX 3 - STRAIN GAUGE INSTALLAT
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Figure 7: Mylar tape was stuck onto
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Figure 19: Repeating the above proc
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2) Electrical Insulation Test Resul
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