Abstract
Side and curtain shield air bags are becoming more popular occupant restraint
systems of passenger cars. Deployment timing of some air bags is dependent on accelerations
of sensors on the vehicle body structure. The mechanism of acceleration propagation during
side impact testing was hard to analyse by finite element method or by experimental method.
This paper describes a newly developed acceleration estimating method by using a finite
element model and this method can visualize the mechanism of acceleration propagation
during side impact testing.
Belytschko-Tsay shell element has been used for vehicle crash analysis since 1985, but this
element does not have warping stiffness. Acceleration propagation is not only a phenomenon
of plastic deformation but also phenomenon of transient vibration. The author focused on
improving transient vibration by taking account of warping stiffness. New type shell element
was introduced to finite element model instead of traditional Belytschko-Tsay shell element.
Body-in-white was supported on air tubes and hit by a hammer and accelerations were
measured at several points. Accelerations by finite element model were compared with test
results and correlation to the test was highly improved by using new shell elements. Also, the
correlation of acceleration of full vehicle finite element model to IIHS SUV side impact test
results was highly improved by taking account of precise stiffness of bracket of acceleration
sensors. Displacement of body structure of IIHS SUV side impact test during 0 to 10 ms was
visualized by this method. This method can be applied not only to IIHS SUV side impact test,
but also DOT and EU side impact testing.
Keywords: side impact, acceleration, finite element, body-in-white, crash analysis