Repeatability of Full - Scale Crash Tests and Criteria for Validating Simulation Results

A method of comparing two acceleration time histories to determine whether they describe similar physical events is described. The method can be used to assess the repeatability of full-scale crash tests and it can also be used as a criterion for assessing how well a finite-element analysis of a collision event simulates a corresponding full-scale crash test. The method is used to compare a series of six identical crash tests and then is used to compare several finite-element analyses with full-scale crash test results. Historically, roadside hardware has been evaluated by performing full-scale crash tests representing practical worst-case scenarios. Crash tests are relatively expensive and require specialized facilities and personnel to perform, therefore, researchers generally try to minimize the amount of full-scale testing required to evaluate the performance of a roadside safety appurtenance. The result is that often important policy and design decisions are based on the results of just one or two full-scale tests. Crash tests, like all other physical phenomena, are subject to small variations in impact conditions, vehicle characteristics, construction materials, and imprecise construction methods. Recommendations for performing full-scale crash tests, such as NCHRP Report 350 and SAE J211, are designed in part to minimize experimental variations, although experimental error can never be eliminated (1,2). Even using these test and data collection procedures to minimize experimental variation, if several essentially identical tests were performed it is reasonable to expect that the resulting acceleration and velocity histories of the vehicle would exhibit some variability as a result of random experimental error. The purpose of this paper is to use several highly repeatable crash tests to quantify the variability that can be expected in crash test results and finite-element analyses used to predict crash test results. The issue of the repeatability of crash tests has several important practical applications. First, an appreciation for the variability in crash testing will help researchers and policy makers make decisions about performing crash tests and evaluating the significance of any one crash test experiment. At times it may be prudent to run identical tests when the outcome of the test will have broad policy implications. Second, if finite-element analyses are used to either predict or explain crash test behavior, it is essential to be able to quantify how well the analytical predication compares with the actual crash test event. Although subjective comparisons are useful, more quan-tifable criteria for judging the validity of a …