The design optimisation control file was used to carry out the design optimisation process by varying the design variables, executing the model file, and evaluating the state variables and objective function. Typical design variables for Phase 1 were the width, depth and taper ratios of the shank, and the wall thickness of the small end. Typical design variables for Phase 2 were the radii of some of the big end features, the depth of the bolt hole, the radius and height of the cap web. For both phases the state variables were the maximum and minimum stresses, and the objective function was to minimise the total volume of the design. A number of random designs would be generated by varying the values of the design variables within the specified limits before the optimiser ‘homed’ in to the best design.
The macros were used to carry out single design stress analyses and also full design optimisation analyses for a number of connecting rod designs. The graphic above illustrates the von Mises stress for a design of shank and small end subjected to the compressive inertia loading. The graphic on the right illustrates the von Mises stress for the big end and cap of the same connecting rod design under the compressive inertia loading.
A bonded contact surface was described between the two halves of the bolt, such that, when they came into contact, the bolt became one solid component.
The second loading condition was the application of the "pull-out" load on the headlamp housing. This was modelled by applying a vertical displacement load to the outer diameter of the headlamp housing.
The figures show the component areas that were meshed for the model and a graphically enhanced contour plot of the (2-D axisymmetric) equivalent (or Von Mises) stress distribution at the final "pull-out" load, which far exceeded the normal service load. Even at this excessive "pull-out" load, the connector does not fail.