Dynamic fracture characteristics of brass foil subjected to laser shock loading

Abstract

Micro scale laser shock punching is a high strain rate micro forming method which uses the high-amplitude shock wave pressure induced by pulsed laser irradiation. The process can serve as a rapidly established and high precision technique to impress micro features on thin sheet metals. The response of brass foil under different ratio of laser beam diameter (<i>d</i>) to die hole diameter (<i>D</i>) in micro scale laser shock punching was investigated. The typical fracture surface morphologies were observed using scanning electron microscope. The influence of the ratio <i>d/D</i> on dynamic deformation and fracture of the brass foil was characterized. The results show that the dynamic fracture behavior of the brass foil is sensitive to the ratio <i>d/D</i>. According to the general mechanical analysis, the specimen fails in a shear fracture mode at <i>d/D</i>=1.75 due to the existence of shear stresses, while the fracture occurs in a tensile fracture mode at <i>d/D</i>=0.47 under the effect of bidirectional tensile stresses. In the case of <i>d/D</i>=0.70, the specimen fails in a mixed fracture mode under the co-action of tensile and shear stresses.