摘要在毫秒激光打孔中，激光冲击到材料表面时会引起熔融和气化，从而产生气体和熔融物喷溅形式的物质迁移。然而随着孔深度的增加，反冲压力逐渐减小，熔融物没有足够动力离开小孔而影响小孔质量。提出利用纳秒激光作用产生的等离子体冲击波来促进熔融物离开小孔。通过毫秒激光打孔实验研究熔融物喷溅过程，分析激光能量与喷溅速率之间的关系。计算得出各激光能量对应的反冲压力值，如激光能量46.2J下反冲压力值为1.32×10-3N。而纳秒激光会产生等离子体爆轰波，经计算其产生的压力最高可达2250N。所以等离子体爆轰波引起的压力远大于毫秒激光下的反冲压力，证明纳秒激光更有利于熔融物喷溅。因此可采用毫秒和纳秒激光合束打孔，应当会获得较高的质量迁移率，提高小孔质量，这一技术将具有广阔的应用前景。67238

毕业论文关键词  激光打孔 毫秒激光 小孔质量 双脉冲

Title    Double pulse laser and plasma punch in the mechanical   effect of material migration studies                             

Abstract

Millisecond laser drilling, the laser impact the surface of the material will cause melting and vaporization, thereby generating gas and the molten material in the form of splashes migration. However, with the hole depth increases, the recoil pressure gradually decreases, the melt is not enough power left holes affect the quality of holes. Proposed use of nanosecond laser induced plasma shock wave produced to promote the melt leaving holes. Experimental studies by millisecond laser drilling process of melt splashes, splashing of the laser energy and the relationship between the rate. The laser energy calculated corresponding recoil pressure value, such as laser energy is 46.2J the recoil pressure of 1.32 × 10-3N. And nanosecond laser plasma detonation wave is generated, which pressure is generated by calculating up to 2250N. Therefore, the pressure caused by plasma detonation wave is much larger than the recoil pressure millisecond laser proved nanosecond laser is more conducive to melt splashing. Therefore can be combined millisecond and nanosecond laser beam drilling, should get a higher quality of mobility, improved hole quality, this technology will have broad application prospects.

Keywords  Laser drilling  Millisecond laser  Hole quality  Double pulse

目   次

1 引言1

1.1 研究背景1

1.2 研究现状1

1.3 本文的工作介绍5

2 理论基础5

2.1 激光参数5

2.2 激光熔融与气化6

2.3 激光引起的反冲压力7

2.4 靶表面激光等离子体的形成过程8

3 毫秒激光脉冲作用于铝靶时熔融物喷溅过程研究9

3.1 实验原理9

3.2 实验仪器9

3.3 实验步骤11

3.4 图像处理12

3.5 实验讨论20

4 纳秒激光与毫秒激光联合作用时的压力研究22

4.1 纳秒激光作用时等离子体对孔的压力研究22

4.2 双脉冲激光作用下孔底受到的压力24

结论25

致谢26

参考文献27

1  引言

1.1  研究背景

上个世纪是科学技术飞速发展的时代，出现了很多伟大的发明，激光就是其中之一。激光是一种高亮度的定向能束，如今已广泛应用于医学、工业、军事等多个领域[1]。激光应用的一个重要领域是激光与物质的相互作用。当高能量的激光冲击到材料表面时，材料会发生熔融和气化最后形成一个小孔。而在制造航空发动机的过程中常常需要加工大量精密的小孔，此时激光就起到了至关重要的作用。例如,一架高性能战斗机其喷气式发动机会含有大量的气膜冷却孔，可能会超过1.2×106个。这些采用激光工艺加工出来的孔具有良好的性能，如大深径比，高面密度等等。如表1所示。文献综述