Numerical And Experimental Research Of Selective Laser Melting Additive Manufacturing For Metal Material

Selective laser melting technology(SLM)allows metal powder materials to be processed directly into complex metal parts without considering the complexity of the model,which is one of the most promising processes in the field of Additive Manufacturing(AM)technology.In the process of SLM forming,the rapid melting and solidification of metal powder will generate a large temperature gradient inside the part,which resulting in distortion of the part and affecting the precision of the part.The processing parameter is one of the most important factors affecting the temperature field and stress field in the forming process.In this paper,using the ABAQUS software to simulate the thermal-mechanical coupling field of the SLM multi-layer and multi-track forming process of 316L stainless steel material.Aiming at the existing problem of the present SLM model,the thermal physical parameters of metal materials that vary with temperature are obtained by the JMatPro software,and the corresponding thermal constitutive equations are established,considering the effects of thermal convection and thermal radiation of powder bed,and the Gaussian heat source model with longitudinal attenuation along the depth direction of powder bed is established by comparing with Gaussian heat source.The effects of different scanning speeds and laser power on temperature field distribution and molten pool morphology were studied.The result shows that when the laser power is 150W and the scanning speed is 500mm/s,the temperature,width and height of the molten pool are more suitable,which is conductive to the forming process of the SLM.Based on the research of temperature field,the influence of different process parameters on the distribution of thermal stress and residual stress in SLM forming process is further studied by using sequential finite element coupling method and considering the thermal elastoplastic properties of the material.The result shows that with the increase of laser power and the decrease of scanning speed,the residual stress in forming area increases gradually,and the influence of laser power on residual stress is more obvious than that of scanning speed.On the basis of finite element simulation,SLM samples of 316L stainless steel are prepared.During the process of the experiment,the temperature distribution of the molten pool is collected by infrared thermal imaging camera,and the surface morphology and longitudinal section of different samples are observed,and the experimental results are in good agreement with the numerical simulation results.According to the above research results,three kinds of porous structures are designed,and making a comprehensive analysis of forming complex porous structure from three aspects,which is the SLM process parameters,scanning strategy and mechanical properties.Because of the complication of porous structure,firstly,the stress-deformation simulation of different scanning strategies is carried out by ANSYS Additive software,the optimal scanning strategy is determined,the experimental preparation is carried out,and the results of compression mechanical properties test.The result shows that the elastic modulus and yield strength increase gradually with the increase of rod diameter/wall thickness;in addition,the quasi-static compression simulation of different structures is carried out,and the compression performance is analyzed with experimental data to determine the stress concentration areas of different structures.