A Thermodynamic Analyses Of Laser Engineered Net Shaping Process

Laser Engineering Net Shaping (LENS) technology is a new manufacturing technique, which using laser beam as the energy source, adopting advance or coaxial powder feeding mode, to melt material powder on the substrate. LENS can make complex metal parts directly, which is difficult for traditional industry, and the processing characteristics of quick heat transfer can change the physical properties of the work piece. Therefore, LENS is wildly used in aerospace field, automobile manufacturing field and model development field, etc.However, since this technique has not developed sufficiently, plenty of basic research is still unexplored. There are many problems existed during work piece forming process, such as edge embossment, crack and separation problems, which extremely influenced the forming accurate and the forming quality of work piece.Therefore, based on basic research, the temperature field, velocity field and stress field in a single-wall work piece was calculated by numerical simulation method in this study.Based on numerical heat transfer and fluid flow theory, the temperature-velocity coupling model was established in MATLAB by Finite Volume Method in this study.The temperature field and molten pool morphology during forming process were calculated by this model, and the molten pool morphology development in the work piece was analyzed emphatically. A height prediction of the work piece was given by calculating the effective amount of powder, which explained the reason of edge embossment problem. In the end, the numerical model was verified by a CCD tomography system, which was established to take pictures of molten pool morphology.The temperature-stress coupling model was established in ANSYS by indirect coupling method, to analyze transient stress field during LENS process. The equivalent stress distribution, the stress components distribution and the stress distribution on critical path were emphatically explored, which explained the reason of crack problem and separation problem of work piece.