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.