Influence of design parameters on the penetration resistance of machine guards

In the last years, different research on ballistic penetration of machine tools guards, as defined in EU Directive 2006/42/EC, were conducted in different worldwide laboratories. Even if the design of machine safety guards using the material/thickness are defined in annexes of ISO standardization, a revision of those annexes is expected in next years. Standardized tests have some limitations because they are performed using a given penetrator that impacts perpendicularly the surface of flat plates of about 500 mm x 500 mm. In this paper the influence of some design parameters will be investigated by polycarbonate sheets of 4mm thickness. The evaluation of ballistic limit for 4 mm sheets of 300 mm x 300 mm and 500 mm x 500 mm size will be presented. Moreover, the influence of constraint on ballistic limit of standardized 500 mm x 500 mm sheets will be also presented by two different constraint devices: one similar to a border hinge constraint, one to a border rigid clamping. Discussion of results will be presented with a view to review the ISO standardization annexes on ballistic penetration.