Multi-Objective Design Optimization Using a Damage Material Model Applied to Light Weighting a Formula SAE Car Suspension Component 2009-01-0348

The Mississippi State University Formula SAE race car upright was optimized using radial basis function metamodels and an internal state variable (ISV) plasticity damage material model. The weight reduction of the upright was part of a goal to reduce the weight of the vehicle by 25 percent. Using an optimization routine provided an upright design that is lighter that helps to improve vehicle fuel economy, acceleration, and handling.

Finite element (FE) models of the upright were produced using quadratic tetrahedral elements. Using tetrahedral elements provided a quick way to produce the multiple FE models of the upright required for the multi-objective optimization. A design of experiments was used to determine how many simulations were required for the optimization. The loads for the simulations included braking, acceleration, and corning loads seen by the car under track conditions. The material model used is an ISV plasticity damage material model that includes microstructural content and considers void nucleation, growth, and coalescence. The multi-objective design optimization implemented metamodels to reduce the design time and number of simulations required compared with traditional simulation based design optimization. Radial Basis functions are used in the formulation of the metamodels because of their accuracy in nonlinear problems. The objective of the optimization was to reduce weight and maintain the stress levels and deflection in the upright. The multi-objective design optimization using the damage material model yielded a design that was 22 percent lighter and met the strength and stiffness requirements.