Finite element analysis for impact tests on polycarbonate safety guards: Comparison with experimental data and statistical dispersion of ballistic limit

Design and testing of machine guards are provided by international standards in which the inadequacy/suitability of the tested materials for machine guards is obtained by the perforation/nonperforation of the guard in an experimental test at the maximum foreseeable speed of a standardized projectile. Uncertainties and limitations of this standardized test are known by researchers, but a better testing procedure is not already agreed on the standardization level. In this paper, finite element analysis of the impact of three different projectiles of a given mass on polycarbonate guards is presented and compared with experimental tests made using a standardized gas cannon. The good correlation found in terms of ballistic limit, energy absorbed, and residual velocity is presented trying to open the discussion to a "probability of perforation."Moreover, a statistical analysis of experimental results, based on a nonlinear regression model, is briefly introduced. The penetration behavior is described by the well-known Recht and Ipson equation, and an evaluation of the statistical dispersion of the ballistic limit for each type of projectile is presented through the calculation of confidence intervals.