Vehicle Crash and Steering Column Frequency Simulation of an Aluminum Instrument Panel Structure 2011-01-0765

Recent changes to the U.S. CAFÉ (Corporate Average Fuel Economy) requirements have caused increased focus on alternative vehicle component designs that offer mass savings while maintaining overall vehicle design and performance targets. The instrument panel components comprise approximately 6% of the total vehicle interior mass and are thus a key component of interest in mass optimization efforts. Typically, instrument panel structures are constructed of low carbon tubular steel cross car members with welded stamped steel component brackets. In some cases, instrument panel structures have incorporated high strength low alloy (HSLA) steels to reduce mass by reducing gage. In this study, aluminum low mass instrument panel structure concept designs are developed.

This paper illustrates the differences between a HSLA steel solution and four different aluminum instrument panel structure designs. The aluminum instrument panel structures are design optimized using computer-aided engineering (CAE) software to achieve specific performance requirements. Beam stiffness, Euro NCAP (European New Car Assessment Program) load case criteria measurements and steering column vibration measured by first response frequency modes in the vertical direction are conducted and evaluated.

The aluminum concept designs contain similar cross sections and packaging space compared to the HSLA steel design. The HSLA steel and aluminum designs display approximately the same vertical steering column resonant frequencies. However, the HSLA steel design and only one of the aluminum concept designs achieved low intrusion performance for Euro NCAP load cases. Analyzed as a standalone beam, the stiffness of the aluminum cross car beam is three times less than the HSLA steel beam. However, analyzed at a complete instrument panel structure to vehicle system level, the contribution of the body side attachment brackets and the floor pan tunnel braces enhance the overall performance and stiffness of the aluminum instrument panel structure. Thus, each design concept performs equally but the aluminum design concept is 42% lighter than the HSLA steel design.