Laser Cutting of Functional Materials by Twin Laser Beam and Thermal Stress Analysis

1.根据激光切割实验，无论激光方向如何变化，裂纹的扩展方向都将偏离激光扫描线。2.采用最大切向应力理论对裂纹扩展方向进行了有限元分析。分析结果与实验结果吻合较好。3.根据有限元分析结果，可以通过控制激光扫描方向来控制裂纹扩展方向。然而，激光扫描方向的控制是复杂的，并且很难预测裂纹的扩展方向。4.根据有限元分析的结果，采用平行于激光扫描线的双激光束放置在裂纹尖端的前方和后方，可以有效地控制裂纹的扩展方向。通过改变两束激光的光强比和下一束激光的位置，可以改变裂纹的扩展方向。5.采用棱镜驱动激光束，研制了双光束激光头。该方法是一种简单易行的获得双光束的方法。通过在激光头中增加棱镜位置控制系统，可以根据有限元分析的结果切割复杂形状。6.研究了无起始切口试件的裂纹萌生行为。离焦量越小，裂纹越早萌生。7.有限元分析结果表明，离焦量越小，应力分布越陡。裂纹在此条件下不稳定扩展。

1.According to the laser cutting experiment, crack growth direction was going to out of the laser scanning line when the direction of the laser changed regardless of the angle.2.Crack growth direction was predicted by FEM analysis with the maximum tangential stress theory. Result of the analysis showed good agreement with that of the experiment.3.It could be possible to control crack growth direction by controlling laser scanning direction according to the result of FEM analysis. However, control of laser scanning direction is complicate and it is difficult to predict a crack growth direction.4.Appling a twin laser beam placed forward and following of the crack tip with in parallel to the laser scanning line is effective to control the crack growth direction according to the result of FEM analysis. Crack growth direction could change by the beam intensity ratio between two beams and the position of the following beam.5.Twin laser beam head was developed by using a prism to sprit a laser beam. This method is simple and easy way to obtain twin laser beam. By adding the control system for the position of a prism in the laser head, it could be possible to cut the complicated shape based on the result of FEM analysis.6.Crack initiation behavior was studied by using the specimen without a starter notch. Crack may earlier initiates when the defocusing distance is small.7.Stress distribution was steep in case of defocusing distance is small according to the results of FEM analysis. Crack unstably propagated with the condition.