Jamel E. Belwafa

Analysis of crash test and computer aided engineering pulses for airbag sensor development

The concept of frequency analysis to extract a representative signal that is experienced by a vehicle during a crash for sensor development is described. The method of Fourier series is used, as an illustration, for characterising crash sensor signal to derive a base crash curve for developing sensing algorithms in airbag fire/no-fire decision making. Based on the signals from various crash test data, a cut-off frequency of 300 Hz is found to give accurate representation of signals. Results indicate that low frequency band in signals dominates the crash behaviour. This desired cut-off frequency can be used in sensor studies for sensing algorithm development as well as for assessing current computer aided engineering capability in predicting sensor crash pulses in the frequency domain. Crash signal predictions from finite element analysis (FEA) models correlate fairly well at low frequency range up to this cut-off frequency. In addition, improvements of FEA methods for sensor development are proposed.

Design of a Frontal Rail Structure With Thickness Variation That Performs Under Axial and Oblique Loading

Progressive crushing of the frontal part of the frame in any collision (frontal, offset and oblique) is one of the factors that determine the safety level that a car or a truck can provide to the occupant. A new approach in frontal rail design will be covered in this paper. The rail thickness will vary along the length of the rail in such away that the compressive strength of a rear section on the compression side of the rail will be greater than or equal to the section in front of it. This design will enable the front rail to collapse in a progressive manner such that the collapse will be transmitted from the front to the rear. Preventing early global bending in the rail will enhance the efficiency of energy absorbed during a crash. Starting with the section with the lowest compressive strength (most forward section of the rail), in a controlled way, the section strength is designed to increase with length. This will help meet the federal regulations such as FMVSS 208 by collapsing the least strong front sections at lower speeds and the strong rear sections at higher speeds. Also, collapsing of the weak frontal sections in a crash can help in compatibility between different vehicles on the road.Copyright