Flow-through and forming mechanism of laser shock micro-coining

Abstract

Sheet-bulk metal forming (SBMF) is an advanced technology to efficiently produce high-quality parts based on high resource utilization. Coining, a kind of SBMF, can be used to fabricate functional and decorative microstructures. In this paper, a new method called laser shock micro-coining (LSMC) is proposed based on the unique advantages of intense pulsed laser of high strain rate dynamic loading characteristics and suitable for micro-forming. However, smaller sheet thickness will lead to the emergence of flow-through. In this paper, ALE model and SPH-FEM model are established for numerical simulation to study LSMC. Through numerical simulation and experiment, the forming mechanism and improvement methods of flow-through are studied, and the appropriate research parameters are determined. The material flow, forming mechanism, stress wave propagation mechanism and forming uniformity are studied. Results show that the lack of material near the projections and the unique inverse plastic deformation in dynamic forming are the important factors leading to flow-through. Suitable laser energy and large sheet thickness as well as the existence of the punch can inhibit the formation of flow-through from one or two aspects. Under dynamic forming, the material has high forming rate and good filling properties. Material deformation is related to the propagation of stress wave. The propagation of stress wave and the height of sheet metal result in a unique short rod mechanism. The process has good forming uniformity, and a more uniform forming effect can be obtained by appropriately increasing the laser energy.