In this paper, we demonstrate that thermal stress is the main mechanism in the process of paint removal by Q-switched Nd：YAG laser （λ = 1064 nm, τ = 10 ns）. A theoretical model ofpaint removal by short-pulse lase...In this paper, we demonstrate that thermal stress is the main mechanism in the process of paint removal by Q-switched Nd：YAG laser （λ = 1064 nm, τ = 10 ns）. A theoretical model ofpaint removal by short-pulse laser is established from the perspective of thermal stress. Thermal stress is generated by thermal expansion, and the temperatures of different samples are calculated according to the one-dimensional （1D） heat conduction equation. The theoretical cleaning threshold can be obtained by comparing thermal stress with the adhesion of paint, and the theoretical damage threshold is obtained by calculating the temperature. Moreover, the theoretical calculations are verified by experimental results. It is shown that the thermal stress model of the laser cleaning is very useful to choose the appropriate laser fluence in the practical applications of paint removal by Q-switched Nd： YAG laser because our model can validly balance the efficiency of laser cleaning and the safety of the substrate.展开更多
The surface morphological changes produced by Nd:YAG pulsed laser ablation of metal Al and semiconductor Si were carefully examined and analyzed by using scanning electron microscope. The formation mechanism of the dr...The surface morphological changes produced by Nd:YAG pulsed laser ablation of metal Al and semiconductor Si were carefully examined and analyzed by using scanning electron microscope. The formation mechanism of the droplets was discussed, and the reasons for formation of the microcracks on the laser irradiated area of the target surface were analyzed by calculating the thermal stress, the vapor pressure and the shock pressure induced by the laser supported detonation.展开更多
To reproduce the premature rupture process of metal sheet subjected to laser irradiation with subsonic airflow,which is an interesting phenomenon observed in the experiments given by Lawrence Livermore National Labora...To reproduce the premature rupture process of metal sheet subjected to laser irradiation with subsonic airflow,which is an interesting phenomenon observed in the experiments given by Lawrence Livermore National Laboratory,a coupled numerical model considering the interaction and evolution of metal elastoplastic deformation and aerodynamic pressure profile is presented.With the thermal elastoplastic constitutive relationship and failure criterion,the simulated failure modes and dynamic rupture process are basically consistent with the experimental results,indicating plastic flow and multiple fracturing is the main failure mechanism.Compared with the case of non-airflow,subsonic airflow not only accelerates deformation,but also turns the bugle deformation,plastic strain and rupture mode into asymmetric.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.61067002)the Foundation for Department of Education of Jiangxi Province,China(Grant No.GJJ12581)+1 种基金the Natural Science Foundation of Jiangxi Province,China(Grant No.20132BAB212008)the Foundation for GannanNormal University,China(Grant No.11kyz12)
文摘In this paper, we demonstrate that thermal stress is the main mechanism in the process of paint removal by Q-switched Nd：YAG laser （λ = 1064 nm, τ = 10 ns）. A theoretical model ofpaint removal by short-pulse laser is established from the perspective of thermal stress. Thermal stress is generated by thermal expansion, and the temperatures of different samples are calculated according to the one-dimensional （1D） heat conduction equation. The theoretical cleaning threshold can be obtained by comparing thermal stress with the adhesion of paint, and the theoretical damage threshold is obtained by calculating the temperature. Moreover, the theoretical calculations are verified by experimental results. It is shown that the thermal stress model of the laser cleaning is very useful to choose the appropriate laser fluence in the practical applications of paint removal by Q-switched Nd： YAG laser because our model can validly balance the efficiency of laser cleaning and the safety of the substrate.
文摘The surface morphological changes produced by Nd:YAG pulsed laser ablation of metal Al and semiconductor Si were carefully examined and analyzed by using scanning electron microscope. The formation mechanism of the droplets was discussed, and the reasons for formation of the microcracks on the laser irradiated area of the target surface were analyzed by calculating the thermal stress, the vapor pressure and the shock pressure induced by the laser supported detonation.
基金supported by the National Natural Science Foundation of China (11472276, 11332011, and 11502268)the National Defense Basic Scientific Research Program of China (JCKY2016130B009)
文摘To reproduce the premature rupture process of metal sheet subjected to laser irradiation with subsonic airflow,which is an interesting phenomenon observed in the experiments given by Lawrence Livermore National Laboratory,a coupled numerical model considering the interaction and evolution of metal elastoplastic deformation and aerodynamic pressure profile is presented.With the thermal elastoplastic constitutive relationship and failure criterion,the simulated failure modes and dynamic rupture process are basically consistent with the experimental results,indicating plastic flow and multiple fracturing is the main failure mechanism.Compared with the case of non-airflow,subsonic airflow not only accelerates deformation,but also turns the bugle deformation,plastic strain and rupture mode into asymmetric.
