Tensile strength measurements of frangible bullets using the diametral compression test

Frangible bullets are designed to disintegrate on impact against rigid surfaces to avoid ricochet hazards in recreational shooting ranges or law enforcement training facilities. Their impact behavior against protective soft body armor is therefore quite different than conventional lead bullets, which are designed to expand on impact rather than shatter into fragments. Models to predict the impact of frangible bullets on soft body armor are currently sought to aid in the development of new performance standards for the law enforcement community against this unusual ballistic threat. Modeling success rests on the availability of constitutive data for frangible materials used in these bullets, such as tensile strength. To supply these critical data, the tensile strength of a Cu–Sn frangible bullet material is measured using the diametral compression test at quasi-static (1μm/s) and high (12.5m/s) displacement rates. The latter tests are conducted using a Kolsky bar. Finite element modeling is used to calculate the stress in the specimen at failure. Using a maximum tensile strain criterion, the effective tensile strength was found to be 104MPa±14MPa. Tensile strength was not strongly sensitive to the displacement rate.