Research On The Mechanism Of Laser Interaction With 30CrMnSiA Steel And Other Typical Metals

The interaction between laser and materials forms the basis of laser applications with the development of laser technologies. It is a multidiscipline involving material science, mechanics, chemistry and physics, etc. The absorption coefficient of materials under laser irradiation, being representative of laser-material coupling efficiency, can be measured by means of reflectivity on material interface.When measuring the laser-material coupling efficiency using integrating sphere, we found that the thermal radiation of metals resulted from laser heating could significantly affect the detector in an integrating sphere, and therefore brought a large error to the measurement. Through an in-depth analysis on the measuring principle of integrating sphere, an approach is proposed in the thesis to eliminate the interference of thermal radiation of heated metal materials, so that the measurement accuracy is greatly improved. In addition, the measurement error of reflectivity using integrating sphere is analyzed systematically. This work has instructive significance in obtaining the true and reliable laser-material coupling efficiency data and improving the measurement accuracy.Based on the improved high-accuracy measurement of the interface reflectivity, the coupling power output efficiency between the 30CrMnSiA steel and the 1.06um CW laser of the order of～kW/cm2, is explored experimentally. By means of changing the intensity of laser irradiation, the mode of laser loading, and analyzing the variation of metal composition for those abrupt changes of material reflectivity, the mechanism of the coupling efficiency under laser irradiation is well revealed. Based on this work, the coupling rule between laser and Ly12 aluminum is also studied experimentally, and reliable data of reflectivity are obtained.Using the temperature distribution of rear surface which can be obtained experimentally, an inverse calculation, analogous to anti-integral method, is performed in the thesis to calculate the temperature variation on the front surface where laser irradiation is applied. The absorption coefficient obtained make up for the deficiency that experiment data are related to the absorption coefficient of a spot area in average. It is helpful to carry out the research on high-precision coupling rule between laser and materials in future. The one-dimensional calculations are given in the thesis. They are in good agreement with those of specially designed one-dimensional experiments.Finally, a reflectivity model is established by using the metal-film theory and the growth of oxide film theory. Also a one-dimensional program is composed and used to simulate the reflectivity variation in the process of laser irradiation. The trend of calculated results is in good agreement with that of experimental results. Through establishing the reflectivity model, we explain the variation of reflectivity in the experiments, and furthermore reveal the mechanism of the interaction between laser and 30CrMnSiA steel.