Petkovsek Rok, Panjan Igor, Babnik Ales, Mozina Janez
Faculty of Mechanical Engineering, University of Ljubljana, Askerceva 6, 1000 Ljubljana, Slovenia.
Ultrasonics. 2006 Dec 22;44 Suppl 1:e1191-4. doi: 10.1016/j.ultras.2006.05.069. Epub 2006 Jun 5.
This paper describes an analysis of pulsed lasers micro-drilling of different metals. Study focuses to an optodynamic phenomenon which appears as thermal effects induced by laser light pulses and leads to dynamic process manifested as ultrasonic shock waves propagating into the sample material. The shock waves are detected by a non-contact optical method by using arm compensated Michelson. Monitoring of the main parameters of the micro drilling such as material ablation rate and efficiency was realized by analysis of the optodynamic signals. The process is characterized by decreasing ablation rate that leads to the finite hole depth. The experimental part of study comprehends a comparison between various metals. In order to describe decreasing ablation rate a theoretical model based on the energy balance is proposed. It considers the energy/heat transfer from the laser beam to the material and predicts a decreasing drilling rate with an increasing number of successive laser pulses. According to the proposed model, the finite depth of the hole appears as a consequence of the increasing surface area through which the energy of the laser beam is conducted away to the material around the processed area. Decreasing ablation rate and the finite hole depth predicted by model were in good agreement with the experimental results.
本文描述了对不同金属进行脉冲激光微钻的分析。研究聚焦于一种光动力学现象，该现象表现为激光脉冲引起的热效应，并导致以超声波冲击波传播到样品材料中为特征的动态过程。通过使用臂补偿迈克尔逊干涉仪的非接触光学方法检测冲击波。通过对光动力学信号的分析实现了对微钻主要参数（如材料烧蚀率和效率）的监测。该过程的特点是烧蚀率降低，导致孔深有限。研究的实验部分包括对各种金属的比较。为了描述烧蚀率的降低，提出了一个基于能量平衡的理论模型。它考虑了从激光束到材料的能量/热传递，并预测随着连续激光脉冲数量的增加，钻孔速率会降低。根据所提出的模型，孔的有限深度是由于激光束能量传导到加工区域周围材料的表面积增加所致。模型预测的烧蚀率降低和孔深有限与实验结果吻合良好。
