The effect of anthropomorphic test device lower leg surrogate selection on impact mitigating system evaluation in low- and high-rate loading conditions

Quenneville, Cheryl E.; Fournier, Ed; Shewchenko, Nicholas

Affiliations

¹Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7

²School of Biomedical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7

³Biokinetics and Associates Ltd., 2470 Don Reid Drive, Ottawa, Ontario, Canada K1H 1E1

Abstract

Introduction: The lower legs are at risk of substantial injury during events such as frontal automotive crashes and antivehicular mine blasts. Loading to occupants can be assessed using an instrumented anthropomorphic test device (ATD), whose measurements can be compared to established injury criteria. NATO’s AEP-55 STANAG 4569 recognizes two surrogates for lower leg injury assessments from impacts with intruding floor pans resulting from underbelly blast loads; (1) the rigid Hybrid III instrumented lower leg, and; (2) the compliant MILitary Lower eXtremity (MIL-LX). The established injury criterion for the Hybrid III leg specifies a maximum lower tibia compressive load of 5.4 kN, whereas the MIL-LX limit is 2.6 kN measured at the upper tibia for similar injury severity levels. The difference in compliance between the two legs could affect the evaluation of protection levels, resulting in an over- or under-estimation of the force attenuation of energy attenuating (EA) floor mats. Materials and Methods: The responses of the two lower leg surrogates were evaluated at impact velocities up to 12 m/s, representing floor intrusions during antivehicle mine blasts. An air cannon was used to accelerate a rigid or padded floor plate into the sole of the surrogate lower legs, loading them axially, in order to assess the protective capability of commercial EA floor mats. The peak load from the lower and upper load cells in the Hybrid III and MIL-LX legs were compared to identify at what point their respective injury criteria would be exceeded in both the padded and unpadded conditions. Results: Comparisons of the surrogate legs’ responses resulted in different evaluations of risk, with the Hybrid III leg exceeding its limit at an impact speed of 6.0 m/s, and the MIL-LX exceeding its limit at 5.5 m/s (for tests including an EA product). Furthermore, the inclusion of an EA mat had a greater relative protective effect on the Hybrid III than the MIL-LX leg, with padding reducing the force to 17 to 34% of the unpadded condition for the Hybrid III, versus 67 to 89% of the unpadded condition for the MIL-LX. The load reduction was found to be velocity dependent for both surrogates. Conclusion: These results indicate that the two surrogates are not equivalent in their assessment of protective capability. Therefore, the selection of ATD leg for testing of EA mats (and other protective devices) will influence the evaluation of these systems, and more robust metrics are required to identify which is the most appropriate surrogate for evaluating injury to the lower limb.

Links

DOI: 10.7205/MILMED-D-16-00358

PubMed: 28885966

WoS: 000423306300038

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Cited By (4)

Year	Entry
2019	de Lange J, Quenneville CE. Evaluation of the distribution of forces on the foot under axial impact loading to assess variations among altered ankle postures between two ATD models. In: Proceedings of the 2019 International IRCOBI Conference on the Biomechanics of Injury. September 11-13, 2019; Florence, Italy.673-683.
2020	de Lange J, Quenneville CE. Investigation of the biofidelity of the MIL-Lx foot. In: Proceedings of the 2020 International IRCOBI Conference on the Biomechanics of Injury. 2020; Munich, Germany.647-658.
2019	Acharya I, Van Tuyl JT, de Lange J, Quenneville CE. A force-sensing insole to quantify impact loading to the foot. J Biomech Eng. February 2019;141(2):024501.
2019	de Lange J. Biomechanical Tools for Assessing Foot and Ankle Injury Risk in Frontal Automotive Collisions [Master's thesis]. Hamilton, ON: McMaster University; 2019.