Designing Energy Absorbing Steering Wheels Through Finite Element Impact Simulation 931844

Light metal alloys based on magnesium and aluminum are increasingly being pursued for various vehicle interior applications because of distinct advantages such as weight savings and potential parts consolidation. One such application of light metal alloys is the steering wheel, which is an important component of a safety system that is comprised of the driver-side airbag, steering wheel, the steering column and its attachment bracketry to the instrument panel and the vehicle body structure. For the airbag to function effectively as a restraint during a frontal crash, the steering wheel has to provide adequate support. In addition to the steering column which is designed to absorb energy, the wheel can also function as an energy absorber if so designed. One way of achieving this energy absorption is through plastic deformation of the wheel. Adverse material characteristics, however, make the energy absorbing steering wheel design, using light metal alloys, a sizeable challenge. This is further aggravated by the various styling and packaging constraints imposed on a visible component of the vehicle such as the steering wheel.

In this study, an impact simulation methodology that guides the design of the steering wheels is demonstrated. The 15 mph body block impact on the steering wheel assembly (following the Federal Motor Vehicle Safety Standard 203 test) was simulated and used for the design evaluations. Nonlinear, transient finite elements were employed in this simulation to characterize the body block, the airbag module, the steering wheel and the steering column. Specialized and proprietary material models were utilized to simulate the die cast material behavior. Favorable comparison of the simulation results with test results demonstrates the usefulness of this simulation methodology in design. The study shows that steering wheels made of light metal alloys can be designed for energy absorption and compliance with other design requirements by using transient, nonlinear finite element methods.