Penske gets on fast form with FEA systems

Motor sport team Penske used finite element analysis (FEA) software from Ansys to speed its new car design for the 2003 Indy Racing League (IRL), which entered last year for the first time. Team Penske, which has 115 Indy car wins under its belt and a record 12 Indy 500 wins, embarked on a considerable challenge when it entered the IRL. Not only did its race team need to compete with different race track equipment on 15 different tracks, but the designers had to take on board the IRL regulations – and get done in a five-month off season. “The IRL is a technology-restricted formula,” says design engineer Chris Kirk. “We have to work within very tight body design criteria and are limited in what we can change. Competing cars have to use chassis from one of three manufacturers, for example, and have to use the same gearbox. So major alterations are impossible. “Cars have to be ready by January for testing, so we cannot analyse every single part of the car each season. We have no time for back-up plans or mistakes; we have to get it right first time to give the team optimum performance.” The design team uses Pro/Engineer as its primary system, running on HP C3700 hardware, with Ansys FEA for testing changes. The tool significantly shortens time-to-market by allowing engineers to use analysis capabilities during the design phase – thus enabling them to make early intelligent decisions about design, materials and manufacturing. Kirk: “We are basically limited to changes on the suspension and the aerodynamic area in front of the rear wheels. A number of minor changes can each give tiny benefits, which together can make all the difference to the car’s performance. “The cars race for several hours and often cross the finishing line within hundredths of a second of each other, so tiny speed advantages can make big differences to race results. For example, we designed a new upright that has to be both light and stiff and can significantly affect performance. “Over a week we built an Ansys model using solid and shell elements, and the testing highlighted an area of the upright that was over-flexing. We were able to redesign the upright which, when it was re-tested was 25% stiffer for the same weight. This dramatically improves the feedback that the driver gets from the steering wheel and provides the information to help him drive more effectively.” Penske also uses Ansys for composite analysis. A considerable problem from a composite FEA point of view is the increased amount of data involved, due to the ply lay-ups, versus normal homogeneous material models. Ansys provides a number of tools for first checking the validity of the composite material modelling used, and second helping the user to evaluate the results. Non-linear material behaviour and material failure models can also be used to evaluate problems. “The way we lay-up composites can be a powerful way of effecting performance, and we find that Ansys handles them all and, using IGES, we can transfer the data between Ansys and Pro/Engineer faultlessly,” confirms Kirk. “Once the Ansys model is constructed we can quickly alter the ply layups to find the optimum… We can quantify the effects and recommend the best layup for a given part. For aerodynamic pieces we can find the loads that the part will experience from our wind tunnel testing, and we also must abide by the rules which prevent excessively flexible parts being used to gain an advantage.”