The consequences of average curve generation: implications for biomechanics data.

One method of understanding the general mechanical response of a complex system such as a vehicle, a human surrogate, a bridge, a boat, a plane, etc., is to subject it to an input, such as an impact, and obtain the response time-histories. The responses can be accelerations, velocities, strains etc. In general, when experiments of this type are run the responses are contaminated by sample-to-sample variation, test-to-test variability, random noise, instrumentation noise, and noise from unknown sources. One common method of addressing the noise in the system to obtain the underlying response is to run multiple tests on different samples that represent the same system and add them together obtaining an average. This functionally reduces the random noise. However, if the fundamental response of each sample is not the same, then it is not altogether clear what the average represents. It may not capture the underlying physics. This paper evaluates the use of transducer time-histories for developing an underlying response when there is variation in the time-histories that is not due to random noise, but to a fundamental aspect of the response. Although the examples used are from NCAP tests, the analysis has direct application to the development of Anthropomorphic Test Devices (ATDs) when the underlying response to which the ATD is designed is obtained from impact tests on Post Mortem Human Surrogates.

Side Impact Response Corridors for the Rigid Flat-Wall and Offset-Wall Side Impact Tests of NHTSA Using the ISO Method of Corridor Development.

The purpose of this paper is to compare the biofidelity rating schemes of ISO/TR9790 and the NHTSA Bio Rank System. This paper describes the development of new impact response corridors being proposed for ISO/TR9790 from the results of a recent series of side-impact sled tests. The response data were analyzed by methods consistent with ISO/TR9790, including normalization by impulse-momentum analysis and the elimination of subjects that sustained six or more rib fractures. Unlike ISO/TR9790, this paper proposes the elimination of the data from tests in which the timing and the sequence of loading of the individual impact plates were inconsistent compared to other tests conducted with the same impact wall configuration. As a result of differences in the analysis methods, data selection criteria, and the method of corridor construction, the impact response corridors proposed here are different from those developed by NHTSA, despite the fact that both sets of corridors were developed from the same series of sled tests. Responses of the ES-2 and ES-2re side impact dummies are compared to both sets of corridors. The response corridors developed in this paper are proposed as an addition to and not a replacement for those given in the 1999 revision of ISO/TR9790.