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Lab-to-lab differences have become a very important consideration in the verification testing of Hybrid III 5th Female necks in user labs. It has been observed that a neck certified by one laboratory does not always pass the same certification test in a different lab. This has led the Anthropomorphic test device Certification Research group (ACR) to investigate the precision of the test procedure in relation to the test specification corridors. This study adapts an industry recognized ASTM procedure to measure the precision of the SAE neck calibration laboratory test procedure in Engineering Aid 25 [1]. The ASTM procedure is ASTM E 691-99 “Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method” [2]. This paper details how the ASTM procedure was adapted and presents the results of the ASTM E 691 statistical analysis procedures.

Lab-to-lab differences are an important consideration in the verification testing of Hybrid III dummy necks in user labs. The authors, the Anthropomorphic test device Certification Research group (ACR), conducted and presented two previous studies investigating lab to lab differences in Hybrid III 5th female dummy neck certification results [1, 2]. The results of both studies underscored the need to have better controls on the test procedure. The complex procedure for dummy neck certification has many setup factors that can contribute to test variation and unacceptable precision. Two steps within this protocol - two aspects of the neck's physical setup - were identified by the ACR group as potential sources for variation: 1) setting the pre-test D-plane angle by neck bracket adjustment, and 2) setting the torque on the neck cable. Fifth female neck flexion tests were conducted with variations in these factors to determine their effect on neck test results.

Lab to lab differences in the testing of the Hybrid III 5th female dummy neck have led to the same neck passing in one lab and failing in another. Several indicators led to the hypothesis that the neck rotation measurement system is a critical factor in the differences observed. The Transportation Research Center Inc. and Denton ATD Inc. collaboratively conducted tests to understand the nature and importance of any differences obtained when different measurement devices are used. Dummy testing laboratories today use a neck rotation measurement system consisting of two rotary potentiometers, one attached to the neck/pendulum interface and one attached to the pivot pin which moves with the head of the dummy, plus a linkage between the two potentiometers (pots). The data from the two pots is summed for a total rotation. Neck testing was performed on two necks (of different manufacture) to investigate the effect of three rotation measurement assemblies' designs and masses.