Investigation of heat accumulation effects during deep hole percussion drilling by high power ultrashort pulsed laser radiation
Investigation of heat accumulation effects during deep hole percussion drilling by high power ultrashort pulsed laser radiation
复制标题
DOI：
10.2351/1.5096084
复制
发表时间：
2019-05-01
影响因子：
2.1
通讯作者：
Finger, Johannes
中科院分区：
文献类型：
--
作者：
Haasler, Dennis;Finger, Johannes
在过去的几年里，商业上可用的超短脉冲(USP)激光系统的平均功率已经达到了100W，这使得它们在增强传统应用方面也很有意义。例如，激光打孔是一种传统的熔融为主的工艺，它将受益于USP烧蚀工艺的优势。由于激光打孔的加工面积很小，在几瓦的平均功率下就已经积累了大量的热量。这种热积累会产生熔融，但也会使平均烧蚀速率增加至少1个数量级，并可能导致高效的钻井过程。在这项研究中，研究了在高达300W的高平均功率和毫焦耳范围的脉冲能量范围内，不同金属和样品厚度的冲击钻削中由于热积累而导致的平均烧蚀率的增加。这些调查尚未进行到如此详细的程度。结果表明，在脉冲能量加倍的情况下，由于热积累，打孔时间可缩短2个数量级。这种行为适用于各种金属，如钢或铝，尽管它们的材料参数不同。通过分析不同重复频率和焦斑直径对热积累的影响，结果表明，表征热积累的主要参数是平均功率。如果通过较高的脉冲能量或重复频率设置从20W开始的平均功率，则没有显著差异。当脉冲持续时间从2 ps改变到20 ps时，不锈钢与其他被研究的金属相比具有不同的行为，这是由改进的等离子体产生引起的。对于不锈钢，钻探时间可以用一个经验公式来描述，整个测试的平均功率和样品厚度范围都是如此。
In the last few years, commercially available ultrashort pulsed (usp) laser systems have reached average powers of several 100 W, which makes them also interesting for enhancing traditional applications. For example, laser drilling, a conventionally melt-dominated process, would benefit from the advantages of an usp ablation process. Due to the small processing area in laser drilling, substantial heat accumulates already at a few Watts of average power. This heat accumulation creates melt but also increases the mean ablation rate at least 1 order of magnitude and could lead to a productive drilling process. In this study, the increase of the mean ablation rate in percussion drilling due to heat accumulation is examined for various metals and sample thicknesses for high average powers of up to 300 W and a pulse energy in the milliJoule range. Those investigations have not yet been performed in such detail. It is shown that by doubling the pulse energy the drilling time can be decreased by 2 orders of magnitude due to heat accumulation. This behavior is valid for various metals like steel or aluminum, despite their varying material parameters. By analyzing the influence of different repetition rates and focal diameters, it is shown that the predominant parameter to characterize the heat accumulation is the average power. No significant difference is observed if the average power starting from 20 W is set up by a high pulse energy or repetition rate. Stainless steel has a different behavior compared to the other investigated metals when the pulse duration is changed from 2 to 20 ps, which is caused by a modified plasma generation. For stainless steel, the drilling time is found to be describable with one empirical formula for the entire range of examined average power and sample thickness.