BLAST MITIGATION SEAT ANALYSIS - EVALUATION OF LUMBAR COMPRESSION DATA TRENDS IN 5th PERCENTILE FEMALE ANTHROPOMORPHIC TEST DEVICE PERFORMANCE COMPARED TO 50? PERCENTILE MALE ANTHROPOMORPHIC TEST DEVICE IN DROP TOWER TESTING

摘要

Although blast mitigation seats are historically designed to protect the 50th percentile male occupant based on mass, the scope of the occupant centric platform (OCP) Technology Enabled Capability Demonstration (TEC-D) within the U.S. Army Tank Automotive Research Development Engineering Center (TARDEC) Ground System Survivability has been expanded to encompass lighter and heavier occupants which represents the central 90th percentile of the military population. A series of drop tower tests were conducted on twelve models of blast energy-attenuating (EA) seats to determine the effects of vertical accelerative loading on ground vehicle occupants. Two previous technical publications evaluated specific aspects of the results of these drop tower tests on EA seats containing the three sizes of anthropomorphic test devices (ATDs) including the Hybrid Ⅲ 5th percentile female, the Hybrid Ⅲ 50th percentile male, and the Hybrid Ⅲ 95th percentile male. The first publication addressed the overall trends of the forces, moments, and accelerations recorded by the ATDs when compared to Injury Assessment Reference Values (IARVs), as well as validating the methodology used in the drop tower evaluations. Review of ATD data determined that the lumbar spine compression in the vertical direction could be used as the "go/no-go" indicator of seat performance. The second publication assessed the quantitative effects of Personal Protective Equipment (PPE) on the small occupant, as the addition of a helmet and Improved Outer Tactical Vest (IOTV) with additional gear increased the weight of the 5 th percentile female ATD more than 50%. Comparison of the loading data with and without PPE determined that the additional weight of PPE increased the overall risk of compressive injury to the lumbar and upper neck of the small occupant during an underbody blast event. Using the same data set, this technical paper aimed to evaluate overall accelerative loading trends of the 5th percentile female ATD when compared to those of the 50th percentile male ATD in the same seat and PPE configuration. This data trend comparison was conducted to gain an understanding of how seat loading may differ with a smaller occupant. The focus of the data analysis centered around the lumbar spine compression, as this channel was the most likely to exceed the IARV limit for the 5th percentile female ATD. Based on the previous analysis of this data set, the lightest occupant trends showed difficulty in protecting against lumbar compression injuries with respect to the 5th percentile female's IARV, whereas the larger occupants experienced fewer issues in complying with their respective IARVs for lumbar compression. A review of pelvis acceleration was also conducted for additional kinetic insight into the motion of the ATDs as the seat strokes. This analysis included a review of how the weight and size of the occupant may affect the transmission of forces through a stroking seat during the vertical accelerative loading impulse. Pelvis velocity data for the 5th percentile female ATD was always higher than that of the 50th percentile male ATD, demonstrating a distinct difference in the energy absorption properties of the tested seats and their inability to provide equivalent protection for both small female and mid-size male occupants. Data trends for peak lumbar compression and peak pelvis acceleration were more varied between tested seats for the 5th percentile female and 50th percentile male ATDs, confirming the sensitivity of the seat design to occupant size and weight. A cursory review of lumbar compression loading rates revealed that some seats were able to maintain the same initial loading profiles regardless of occupant size and weight, while other seats showed marked differences. All of the seats tested showed sensitivity to occupant weight in the ability to provide equivalent protection. In conclusion, continued research and engineering development is needed to improve seat energ