Three-dimensional numerical analysis of twist extrusion process for annealed copper

Nowadays in order to achieve the materials with superior strength and appropriate formability, severe plastic deformation (SPD) methods are used in which the available coarsegrained materials are processed to produce substantial grain refinement and a nanostructure. A new SPD method based on direct extrusion process, proposed recently, is the «Twist Extrusion process». The process is capable of industrial usage and has the advantage of producing a finer structure as compared with other SPD methods. In this investigation, in order to help in determining the effective process variables and in understanding the die manufacturing process, the simulation of the twist extrusion process is presented by using explicit analysis procedure, and the von-Misses and equivalent plastic, strain distributions are considered. The effects of friction coefficient and speed of deformation on the maximum values of von-Misses stress and equivalent plastic strain for the annealed copper material are investigated, they are validated and compared with the corresponding theoretical and experimental values obtained from researchers. The simulation results show that the maximum and minimum equivalent plastic strains are produced at the corner and at the center of the billet, respectively. The maximum and minimum equivalent plastic strains predicted by the simulations are found to be 1.3 and 0.3, respectively. Serrated diagrams of instantaneous stress versus strain and applicable flow stress were observed and recalculated. Simulation results placed next to experimental results are indicative of an acceptable level of compatibility

Investigation of Nd:YAG pulsed laser dissimilar welding of AISI 4340 and AISI 316L stainless steels on weld geometry and mechanical properties

In this paper, laser welding of 316L and AISI 4340 steel is studied. Studies are focused on the effects of laser parameters on the depth and width of the welds. The results show that increasing in pulse energy and frequency will increase the weld depth and the weld width. The calculation of effective peak power density related to the welded joints results in optimum operating welding parameters with full penetration and proper dimensions and strengths. The tensile strength values of the full penetrated weldments are greater than the tensile strength values of AISI 316 base metal. The effects of laser parameters on weld grain size and HAZ size were investigated. The results show that the weld grain size and HAZ size increase with pulse energy and frequency