The FEA project carried out by IDAC was split into three phases as follows:
Phase 1 - Shape
A topological optimisation was carried out in order to determine a preliminary design of the support frame. This part of the project was carried out using the Shape Optimiser in ANSYS Mechanical. The software approximated the initial structure as a large volume, which was then "eaten away" at locations with low stresses, leaving a "pixelated" representation of the optimised support structure. The graphics to the left (top) show the starting geometry as a large volume and below this, the initial design shape that was predicted by ANSYS can be seen. An envelope of the initial volume was defined to locate the soleplates for the support structure and to define the position of the side arms. The loading consisted of a static load (weight of the components and platform) and a dynamic load (reaction torque applied by the dynamometer and disc brake).
Phase 2 – Sizing & Dimensioning
Using the topologically optimised solution from Phase 1, a design optimisation was carried out in ANSYS Mechanical APDL. A parametric model of beam and shell elements was created and optimised. The sizes and thicknesses of the beams and shells respectively, were defined as design variables and the mass of the structure as the objective function. The natural frequency was defined as a state variable and the mass of the structure as the objective function to ensure that the natural frequencies of the steel support structure avoided the critical resonant frequencies of the concrete foundation block. One of the mode shape plots can be seen in the graphic to the right (top). The design optimisation allowed the design of the support structure to be refined, and the beams and plates to be sized; this was then forwarded to Whittaker Engineering, who would be manufacturing the support structure. Whittaker Engineering made some manufacturing modifications to the supporting structure design and provided IDAC with an Autodesk Inventor model of the structure for further analysis.