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Calculating Non-Linear Frontal Stiffness Coefficients
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 01, 2014 by SAE International in United States
This content contains downloadable datasetsAnnotation ability available
The analysis and modeling of vehicle crush in accident reconstruction has traditionally been based upon the use of linear crush-based, stiffness coefficients. Engineering Dynamics Corporation (EDC) created the accident reconstruction software Human-Vehicle-Environment (HVE) which contains the collision algorithm called DyMESH (DYnamic MEchanical SHell) which is capable of utilizing a non-linear stiffness coefficient model. The objective of this research was to develop an improved methodology for the calculation of non-linear stiffness coefficients.
Stiffness coefficients are used to represent the relationship between the impact force on a vehicle and the resulting vehicle crush. The method explored in the present research was focused on developing vehicle specific, non-linear stiffness coefficients (Pressure Model) based upon frontal crash tests into a fixed, rigid barrier equipped with load cells.
The load cell data from the barrier and the accelerometer data from the vehicles were used to establish a force per unit area (pressure) versus vehicle displacement (deflection) relationship. The area used in this calculation was based on the actual cross-sectional area of the vehicle for specific depths of crush. The pressure-deflection relationship was fitted using 3rd order polynomial equations. This methodology allowed these frontal stiffness coefficients to be used in the HVE-DyMESH collision algorithm.
The accuracy of the non-linear stiffness coefficients was evaluated by comparing output results from HVE-DyMESH for various parameters. These parameters included delta-V, peak force, peak acceleration, crush depth, force versus time graphs, as well as acceleration versus time graphs.
The greatest advantage of using a non-linear pressure model was a stronger correlation to the crash tests over a wide range of impact severities. Additionally, the length of the crash pulse increased substantially, providing improved correlation with the actual crash pulse. This is beneficial when trying to establish a crash pulse for use in occupant simulation.
CitationGilbert, B., Jadischke, R., and McCarthy, J., "Calculating Non-Linear Frontal Stiffness Coefficients," SAE Technical Paper 2014-01-0474, 2014, https://doi.org/10.4271/2014-01-0474.
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