扫描路径对激光立体成形TC4构件热-力场的影响

In order to mitigate both residual stress and distortion induced by large thermal gradient in laser solid forming (LSF) process, the in-situ measurement first was used to monitor the thermal and distortion evolutions of the substrate during LSF and to calibrate the finite element model. Using the validated model, the effect of different scanning paths on the evolution of thermo-mechanical fields in LSF was analysed. The results show that good agreement is obtained between the numerical results and the experimental measurements. The maximum thermal gradient and the maximum tensile stress occur in the deposition of the first layer, and with the increasing of the layers, the temperature gradient is reduced gradually. The largest distortion is resulted from the long edge unidirectional scanning mode while the minimum residual stress and distortion is produced by short edge reciprocating scanning. The checkerboard scanning method can effectively reduce distortion of the substrate while hardly reduce the residual stress. In addition, the transverse bending of the substrate can notably curb the longitudinal bending of the substrate. Stress relaxation induced by the phase transformation has a significant effect on both residual stress and distortion of LSF part.