Linear Impactor Calibration Procedure
This recommended practice provides a procedure for measuring quantitatively the physical characteristics of linear impactors that are believed to effect impact test accuracy, repeatability, and reproducibility. Suggested values and tolerance are also provided for specific applications of linear impactor testing (i.e. Ejection Mitigation tests, Head form Impact tests, Body Block tests). Two functional groups of linear impactors are considered, those whose function is related primarily to displacement and those related to measuring acceleration or force.
Linear impactor tests have been used for decades to create dynamic performance data of occupant protection materials and safety systems. This data is generally used for comparative purposes, to compute energy management capability, and as input to mathematical models and computer simulations. There are also examples of linear impact tests used for vehicle component certification such as the FMVSS 226 Ejection Mitigation test used by NHTSA.
Linear impactor test result variability is a problem that can be traced to many sources. One source of variability in the FMVSS 226 linear impactor test is associated with the characteristics of the impactor itself. A calibration procedure for the linear impactor is needed to reduce the variability associated with it.
This document establishes a standard for linear impactor performance that will ensure a level of test accuracy, repeatability, and reproducibility. No such standard exists today, resulting in a complete lack of these elements among the various laboratories and institutions that regularly utilize linear impact test methods.