Veröffentlichungen und Präsentationen

Laser powder bed fusion (LPBF) is one of the most beneficial manufacturing methods for its precision and ability to create parts with complex geometry, although high thermal gradient due to the considerable temperature difference between ambient and peak temperature appeared during laser scanning causes high residual stress which can lead to serious damages during the process. Moreover, due to the unique application of Ti-6Al-4V, it is crucial to guarantee that the final product is precisely manufactured in its dimensions. Therefore, controlling the effective input parameters is necessary to tackle or minimize the issue[1]. An accurate simulation model can greatly enhance the ability to predict the residual stress and optimize the parameters aiming to achieve optimal mechanical properties while reducing costs and minimizing material usage[2][3]. In this study, the role of an appropriate heat source on simulation results was investigated with the help of developing a simulation model based on the finite element method (FEM) using COMSOL Multiphysics version 5.6. software. Moreover, the effect of important process parameters, including laser power and velocity on deposited pool geometry and residual stress along the scanning direction was studied. Simulation results showed that the prediction of melt pool dimensions in depth and width was improved in case of considering 3 dimensional heat source modeling with absorptivity decaying function. The results also showed that increasing the laser power and decreasing laser scanning velocity can result in higher maximum temperature and wider deposited area in both depth and width. However, the effect on residual stress is complex and depends on various factors. According to the results, reducing the laser velocity and increasing laser power generally led to higher residual stress as the area exposed to high temperature was wider, and consequently the volume of melt pool where expansion and contraction occur, increased. However, there is a critical point for the impact of laser velocity, where the role of the cooling rate overcomes the role of the melt-pool size. The simulation model was validated by comparing it with the experimental results obtained from previous literatures[4].