Investigating Bomb Suit Blast Overpressure Test Methodologies

摘要

The U.S. National Institute of Justice (NIJ) released its NIJ 0117.01 standard for public safety bomb suits in April 2016. While this standard includes a wide array of protection and functionality requirements for bomb suits, it does not include quantitative requirements for blast overpressure attenuation, which is a primary threat from explosive devices that is unique to this application. Only a qualitative blast integrity requirement is currently included. NIJ's decision not to include quantitative blast overpressure requirements is attributed to the fact that scientists do not yet agree on the blast injury mechanisms and associated injury thresholds. Yet, there exist test protocols from the literature that can be used as benchmarks toward a standardized test methodology. To address this critical gap, given the importance of measuring how bomb suits and helmets attenuate this key threat, an ASTM working group was created in early 2017 with the objective to devise a standard for 'blast overpressure protection for bomb suits.' The present article investigates three main options to quantify the blast overpressure protection provided by bomb suits, all based on the use of a Hybrid III mannequin as a blast surrogate: (1) protected mannequin only, comparing with set thresholds for head acceleration, ear overpressure, and chest overpressure; (2) protected mannequin only but comparing with reference pressure values for the ear and chest; and (3) conducting both protected and unprotected mannequin tests to compute percentage reductions in all measurements. In line with the current NIJ 0117.01 standard, a single blast configuration (1.25 lb of C4 at a standoff of 2 ft) is proposed. For each of the three options, calculation methods are recommended and a minimum number of tests to be conducted is also proposed toward achieving some statistical significance.