The Numerical Analysis And Experimental Research On The Thin-Walled Parts In Laser Metal Direct Manufacturing

Laser Metal Direct Manufacturing is an advanced technology which is developed from laser cladding technology and rapid prototyping technology in recent years. Because it can offer a number of advantages such as building a freeform complex three-dimensional part with high-performance and fully dense, and rapid, no dies and the near net shape manufacturing, it has a bright future in aviation, aerospace and automotive etc high-tech fields. So, this technology has become the hot research subject studied both at home and abroad in recent years.The influence rules of main process parameters such as laser power, scanning velocity and powder mass flow rate on the molten pool size can be obtained by numerical simulation in laser metal direct manufacturing, and they were verified by experimental research. The reasonable range of process parameters are also gained in meeting the setting conditions and the optimum process parameters can be determined according to the orthogonal test. The finite element analysis model of thin-walled parts was established in process. The processing procedure from point to line and then to surface in LMMD can be come true using the technology of "element birth and death" in the software of ANSYS for the characteristics of dynamic accumulation process. The temperature field of thin-walled parts in process was computed by numerical analysis. The variation of laser power can be obtained with the layer by layer when the molten pool temperature field is stable. Adopting the rule of laser power the thin-walled parts are fabricated by experiments. The experimental results show that the accuracy in thickness of the thin-walled part with the reducing the power layer by layer is better than that with the constant laser power.In addition, the stress field of the thin-walled part in LMDM process was also calculated by numerical analysis based the temperature field. The results show that the thermal stress is higher in ends and middle of the thin-walled part due to the energy accumulation. And it can generate that the thin-walled part occurs to crack and warp in the middle and ends.