Two Hindrances to More Accurate Automotive Crash Simulations

Automobile crashes cost the lives of 30,000 Americans in an average year. Some of these deaths might be prevented through the design of safer automobiles. Crashworthiness design relies heavily on computer simulations because reliable physical tests cannot be run until very late in the design of a vehicle. There are often discrepancies between simulations and the results of physical tests and these differences can lead to failures of critical tests late in the design cycle when correcting the problem is often costly and difficult. This paper discusses two hindrances to more accurate crash simulations: not being able to get accurate material data at impact speeds and the difficulty of modeling the contact between two colliding bodies during a crash. Getting accurate material properties at impact speeds is difficult because the testing often excites vibrations within the test device. The natural frequencies of the test device can lead to mechanical ringing that contaminates the impact response data. If the frequency of this ringing is not sufficiently high, it is very difficult to filter out this mechanical noise without affecting the material response data. Initial investigations have lead to the discovery of a test device whose internal resonances are well separated in frequency from the material response data, allowing material data to be filtered without adversely affecting the data. Two designs for an improved device are also being pursued. This paper also presents an open-source software module that is being developed for modeling impact and contact problems using the finite element method. The software is being written in Python and will be freely distributed. The open-source nature of the software will allow others to review, modify, and build on the algorithms for contact modeling. The software module and contact algorithms will be verified by comparison with experimental results.