Mechanism and formability of micro-heading of metal rod by laser dynamic loading

Abstract

Heading forming can produce special-shaped micro-shafts and serve as the basis of complex parts. This paper proposes a new method of micro-heading of metal rod by laser dynamic loading (MHLDL). The forming process, stress wave propagation and metal flow law of MHLDL, the characteristics of forming section, and the influence of laser energy and grain size on forming size are studied combined with numerical simulation and experiment. Results confirm the feasibility of using MHLDL to prepare micro-heading forming parts. The plastic deformation of the metal inside the workpiece is related to stress wave propagation and its own inertia. The metal on the top of the workpiece can flow freely to the surroundings. When the deformation of the heading is small, the heading shows a mushroom shape with thick top and thin bottom due to the stress wave and inertia effects on high-speed forming. When the heading deformation gradually increases, the friction effect becomes dominant, and the heading assumes a drum shape with equal up and down diameters. These two regular appearances prove that MHLDL can produce a uniform metal flow and improve the forming performance of the material. The forming size of the heading increases with the laser energy, but at a slow rate. The forming size of the heading increases with the increase of the workpiece grain size, which can be explained by the dislocation packing theory and the surface layer model.