毕业论文移动版

摘要本文基于热传学理论、热弹性力学和弹塑性力学理论，建立毫秒激光辐照硅材料的二维轴对称有限元模型。并通过COMSOL软件对其过程进行了数值模拟，计算得到其温度场和热应力场。搭建了毫秒激光辐照单晶硅损伤实验平台，实验得到了不同晶面损伤形貌图。通过数值结果和实验结果，分析了毫秒激光对硅材料的塑性破坏的机理。结果表明：随着温度升高，吸收系数增大，热传导系数减小，使得激光沉积的深度越来越浅，在硅的表层形成巨大的温度梯度，进而导致了热膨胀的非均匀性，产生巨大的热应力。当温度升高到塑性屈服温度时，同时热应力超过屈服应力，将发生热软化效应，应力将迅速降低，造成硅材料的塑性损伤。在硅的前表面，激光光斑内由于热膨胀，应力为压应力。由于z轴不能像前表面那样自由凸起，因此在对称轴方向，相同时间点最大应力要比前表面大。结合硅表面损伤形貌图，讨论了不同晶面单晶硅在塑性损伤时，解理裂纹的产生机制。67127

毕业论文关键词  毫秒激光  热应力  塑性损伤  有限元方法

毕业设计说明书（论文）外文摘要

Title   The plastic damage in silicon induced by millisecond            laser

Abstract

Established axial symmetric finite element model based on the theory of heat transfer,thermal mechanical theory of elasticity and plastic.Laser irradiation of silicon material was simulated by COMSOL software,getting the temperature field and thermal stress field.Build a experiment platform to do the plastic damage in silicon induced by millisecond laser.Experiment get the different crystal faces damage morphology.According to the numerical and experimental results, analyze the plastic damage mechanism in silicon induced by millisecond laser.The results show that,with increasing temperature,increasing absorption coefficient,decreasing thermal conductivity,the more shallow depth of laser deposition, form a large temperature gradient in the silicon surface, Which led to non-uniformity of thermal expansion and an enormous thermal stress.When the temperature rises to the temperature of the plastic yield .Thermal softening will occur and the stress will reduce quickly causing plastic damage in silicon.The front surface of the silicon,because of thermal expansion,stress is compressive stress within the laser spot.The material of Z axis can’t be as free as the front surface of the protrusion.Maximum stress of z axis is larger than the front surface at the same time.Combined with silicon surface damage morphology,discuss mechanism of cleavage cracks when plastic damage in silicon happening on different crystal faces.

Keywords   millisecond laser  thermal stress  plastic damage

          finite element method

目次

1  绪论 1

1.1  课题背景及研究意义 1

1.2  激光与半导体材料相互作用的研究现状 1

1.3  本文的主要研究工作 3

2  毫秒激光与硅相互作用的数值研究 4

2.1  热传学基本理论及热传导方程的求解 4

2.2  热弹性力学和弹塑性力学的理论基础 6

2.3  温度场和热应力场的仿真模型  11

3  数值模拟结果  16

3.1  温度场结果与讨论  16

3.2  热应力场结果与讨论  19

3.3  小结  22

4  毫秒激光与硅相互作用的实验研究 22

4.1  实验装置  22

4.2  实验结果与讨论  23

4.3  小结  26

总结   27

致谢   28

参考文献   29 (责任编辑：qin)