Finite Element Analysis Of Titanium Alloy Laser Selective Melting Technology

During the process of selective laser melting (SLM), rapid temperature cycles and steep temperature gradients occur in the scanned layers. Temperature gradients induce thermal stresses which remain in the part upon completion of the process (i.e. residual stresses). These residual stresses can be detrimental to the functionality and structural integrity of the built parts. Based on SLM temperature field on the forming effect, it is necessary to analyse the SLM process of titanium alloy from thermo dynamic point of view, so as to reveal the forming mechanism of the titanium alloy SLM. In this paper, the forming mechanism of titanium alloy SLM is studied by the combination of finite element simulation and experiment. Specific work is as follows:(1) Considering the influence of heat conduction and heat convection, the nonlinear relationship between temperature and thermal physical properties of materials, and the influence of latent heat of phase transformation, the finite element model of temperature field of titanium alloy SLM was established. Laser heat source is realized by parametric design language (APDL) is applied and a recursive call, using element birth and death technology to realize the simulation of multiple scan.(2)During the SLM temperature field research, analyzed the influence of process parameters on temperature distributions, molten pool dimensions, liquid times and molten pool overlap effect. The effects of different scanning strategies on the temperature field of single layer and multi-layer scanning are discussed. The temperature field analysis provides the theoretical guidance for the selection of the parameters in the later period of experiment.(3) In the study of thermal stress field of titanium alloy SLM, the reason of warping deformation of SLM titanium alloy was analyzed. Based on the temperature field analysis of the temperature field, the thermal stress of SLM was simulated by the method of ANSYS thermal structure coupling. The results showed that the distribution of thermal stress of SLM with different scanning strategies.(4)The SLM forming process test and finite element simulation truth combined, the test process and numerical simulation set a consistent process parameters and to verify the validity of the finite element simulation. By observing the evolution of titanium alloy melting characteristics and microstructure. It is found that the microstructure changes and macroscopic temperature field between have close relationship.