UWE Bristol Engineering showcase 2015

William Lovell
Mechanical engineering BEng
Project Supervisor: Jason Mathews
Design and structural analysis of an agricultural trailer chassis
Aims
The aim of this project is to establish a suitable design specification for a medium distance road haulage semi-trailer, design an appropriate chassis using CAD
and to verify the model using finite element analysis.
This model should be capable of further work allowing the designer to go on to optimise the design to save cost and weight.
Top-Down Design
The design approach that will be used for this project is a Top-down
modelling approach, this is due to the chassis itself being designed from
scratch and as yet no standard components being added, once the axles and
other standard parts are added to the assembly a combination of Top-down
modelling and bottom up modelling will be used.
Bottom-up modelling is a good technique for integrating commercial
components into an assembly, where only a few parts linking already existing
parts are unique, for example design brackets to hold a number of
components, where most of the parts are purchased components and
therefore will not change in the design.
The Top-down technique, also known in SolidWorks ad “in-context”, it is used
by designers and engineers when designing from scratch with multiple
unique parts. Also when designing an assembly with the need to make
multiple changes to the a Top-down is preferred. Using the Top-down
approach it is possible to relate parts and parameters. In the case of the
trailer design, basic dimensions will be set out from the design specification
and then from there the parts will be added, this adds flexibility to make any
design changes necessary with ease.
Finite Element analysis
The analysis being carried out on the trailer is to verify the levels of stress
through the part under standard loading conditions, as the trailer is expected
to remain in the elastic domain a linear stress analysis will be used.
If the analysis were undertaken to predict how the part would fail in a nonelastic
range then a non-linear analysis would be used.
The goal for this set of analysis will be to achieve a factor of safety of 4
throughout the trailer. Where this cannot be achieved the strain energy will
be double checked to ensure that the part will not deform elastically.
The visualization above shows stress concentrations in the drawbar area,
during the project this area was reduced using stiffening plates to achieve a
lower value of stress and a more robust design.
Final Design
Below is an image of the final design with trailer bed and axles for
visualization. To fully complete the design axles will need to be specified and
mounting established onto the chassis.
Project summary
This study outlines the body of work
undertaken by the author when designing
and validating the design of a new agricultural
trailer chassis, relevant and applicable to JCB.
It presents a step by step process of design
from determining the design specification to
development and improvements of the
model.
Project Objectives
To achieve the above aim, the following
objectives need to be investigated
• Understand the basic laws governing trailer
design
• Understand the typical application for the
trailer
• Produce a full design specification for the
trailer
• Design the trailer chassis in Solid Works
• Complete a comprehensive structural
analysis of the chassis using dynamic loading
conditions with FEA
• Make the necessary changes and
improvements to the chassis
Project Conclusion
The project achieved Its key objectives and
has resulted in a good basic chassis design,
from here axles must be selected and then
mounting and more stress analysis must be
carried out. Also Weld stresses should be
analysed and verified further .