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激光作为一门新兴技术在刚产生就发挥了重要的作用。激光具有单色性好,亮度高,相干性好,方向性好的优点，这使得激光在很多方面的应用迅速开展起来。激光超声技术也应时而生。激光超声技术在无损检测领域有着广泛的应用。牙齿作为人类重要的器官组成,也容易患有一些疾病,然而早期的牙隐裂症状不明显，常规方法不容易检测，很难及时发现牙隐裂症状,而激光超声技术却可以很好的进行无损检测。
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人类牙齿容易发生龋齿,裂纹或者产生牙隐裂病症。牙隐裂是指未经治疗的牙齿表面由于某些因素的长期作用而出现的临床不易发现的细微裂纹，是牙裂综合征(CTS)中活髓牙发生牙裂的特殊病例。检测牙齿裂纹而又不对牙齿造成损害,就需要对牙齿特性进行模拟,利用激光超声技术检测牙齿裂纹时也就必须先对激光在牙齿中激发超声过程进行数值模拟。本课题将采用有限元方法进行数值模拟。关键字:激光 激光超声技术 牙隐裂 有限元方法
毕业设计说明书（论文）外文摘要5393
Title : The numerical simulation of laser exciting
ultrasound in human teeth
Abstract:
As a new technology , the laser was quickly used and played a important role in different fields. The laser has several advantages, for example: high brightness, coherence, good monochromaticity and directional, which make it quickly developed in different regions. Laser ultrasonic technology is just one of them .The laser ultrasonic technique has been widely applied in the field of nondestructive testing .As a important organ of human , the teeth also often suffer from some diseases, which is always hard to find out without causing some damage to our body. However ,the laser ultrasonic technique is just one of the best measurement.
Our teeth may cause dental caries ,crack .The teeth crack illness is some tiny cracks caused by the effects of some certain factors which effect on the long-term untreated teeth. It is a special cases of tooth crack syndrome in vital tooth crack(CTS).If we want to check it without any harm ,we had better to have a numerical simulation on the teeth. In this issue we use finite element method to have a numerical simulation.
Keywords: laser laser ultrasonics teeth cracks finite element method 目 次
1 绪论 4
1.1 研究背景和研究意义 4
1.2 激光激发超声技术的研究和进展 6
1.2.1 激光超声检测的研究发展 6
1.2.2 牙隐裂的病因和检测方法 7
1.2.3 有限元模拟激光超声的方法和历史 8
1.3 本文的主要工作 9
2 采用有限元方法研究激光超声问题的理论基础 11
2.1 声表面波的基本性质 11
2.1.1 声表面波的基本知识 11
2.1.2 声表面波的势函数和传播速度[29] 12
2.2 激光超声的热弹机制 15
2.3 有限元方法 17
2.3.1 有限元方法简介 17
2.3.2 热传导的有限元法分析 18
2.3.3 计算模型及理论 19
3 激光在牙齿上激发超声的数值模拟结果 21
3.1 不同波长激光在牙齿上激发超声的效率 21
3.2 激光对牙齿的热作用 22
3.3 激光超声对不同时期的牙隐裂检测 23