【作者】 盛晓军；

【导师】 胡俊；

【作者基本信息】 上海交通大学 ， 机械制造及其自动化， 2010， 硕士

【摘要】 激光切割是一项重要的激光加工应用技术,其中非金属材料的激光加工也已成了研究热点。激光热应力切割技术通过激光束切割材料表面时引起的温度场梯度变化产生热应力,诱导并控制裂纹扩展,从而分割材料,是对玻璃、陶瓷等脆性材料切割的有效方法。相对于传统的金刚刀切割和激光汽化切割方式,具有切割面光滑,材料没有损失,微裂纹小等优点。本文在自然科学基金项目的支持下,讨论了目前激光热应力切割陶瓷等脆性材料的研究现状及发展趋势,分析了激光热应力切割氧化铝陶瓷的机理,建立了激光切割的三维平面对称模型,研究了各切割参数对切割温度场和热应力场的影响分析,具体研究内容如下:首先从脆性材料断裂理论出发,研究激光热应力切割中的裂纹扩展机理。通过Ansys建立三维对称切割有限元仿真模型。采用APDL编程语言,引进表面效应单元surf152,实现对激光移动热源及换热模型的仿真。分析了激光热应力切割氧化铝陶瓷过程,研究了切割中的温度场和热应力场分布规律,揭示了温度场和应力场随激光功率、工件厚度和切割速度之间的关系。在激光切割路径上节点的正应力σy,在切割过程中经历“无应力‐拉应力‐压应力‐拉应力‐无应力”的变化过程,直至裂纹扩展。研究表明,激光功率和切割过程当中的最高温度成正比关系。功率增大,相同节点裂纹萌生越早,断裂时的拉应力σy更大。相同条件下切割速度增大,切割最高温度下降,越早发生断裂。在理论研究的基础上,利用50W连续CO2激光器对不同规格的氧化铝陶瓷片进行热应力切割实验。实验验证了切割质量与激光功率、工件厚度和切割速度关系的理论分析结果,为切割参数优化提供了理论和生产指导。最后,论文对所做的工作进行了总结,并对今后的进一步研究方向进行了展望。更多还原

【Abstract】 Laser cutting is one of the most important application technologies in laser machining industry, and the laser processing of non-metallic materials has become the study object of many scholars. The laser-controlled thermal stress cutting induces and controls the crack propagation by using the thermal stress which is caused by the surface temperature field gradient in the laser cutting. And it is an effective manner to split the glass, ceramics and other brittle materials. Compared with the traditional diamond knife cutting and laser vaporization cutting, laser-controlled thermal stress cutting has many advantages such as smooth cutting surface, no loss of materials, small micro-cracks and so on.Under the support of the project of natural science foundation, the paper discusses the present research status and development of laser-controlled thermal stress cutting, analyses the mechanism of laser cutting of alumina ceramic, establishes a three-dimensional symmetric model of laser cutting, and study the effect of various cutting parameters on temperature field and thermal stress field. The concrete research content is as follows:Firstly, the paper analysis the crack propagation mechanism of laser-controlled thermal stress cutting based on brittle fracture theory, and establishes the three-dimensional symmetrical finite element model by using Ansys software. APDL programming language is adopted, and surface effect element surf152 is introduced to simulate the moving laser heat source and heat transfer model.The laser-controlled thermal stress cutting process of alumina ceramics is studied, the law of the temperature field distribution and thermal stress distribution is analyzed, and the relationships between the temperature field and stress field with the laser power, workpiece thickness and cutting speed are revealed. The normal stressσy of nodes which are located in the laser cutting path is experienced in the cutting process of "no stress-tensile stress-compressive stress-tensile stress-no stress" until the crack propagation. The earlier the crack initiates with greater tensile stress when the laser power becomes greater. Under the same conditions, the sooner the fracture happens and the maximum temperature drops with cutting speed increased.Based on the theoretical study, alumina ceramic substrates offered by Xi’an Electronic Technology Co., Ltd are adopted to do the laser-controlled thermal stress cutting experiment. Laser cutting machine is 50W continuous carbon dioxide laser which is offered by Shanghai Institute of Laser Technology. Meanwhile, verify the theoretical relationship between the cutting quality and laser power, workpiece thickness as well as cutting speed to provide practical optimization of cutting parameters based on the cutting experiment.Finally, the paper summarizes all the done work and views the study direction in future.更多还原