Evaluation Of Laser Target Damage Effectiveness

As high-energy laser weapons gradually move to the practical application stage,their advantages in attack speed,energy concentration and low cost become more and more prominent,and they are gradually receiving attention from various countries.The laser damage assessment module is a very important part of the laser weapon system.The laser damage effectiveness assessment can predict the target damage threshold before combat and simulate the damage effect.At the same time,it can promote the improvement and design of laser weapons.In industrial applications,the exploration of laser damage mechanisms can accelerate the development of laser processing and other industries.However,there are still some shortcomings in the research on the damage performance of laser to target.Therefore,it is necessary to continuously explore the mechanism of laser damage.In this thesis,the damage mechanism of laser to target is explored by two different materials,metal target and carbon fiber composite target.The temperature field of the target under laser irradiation is solved,and the damage simulation of carbon fiber composite is carried out by using the life and death unit method.The thermal stress destruction effect of the metal target was carried out,and the damage experiments of two types of targets irradiated by laser were carried out.The main research contents and achievements of the thesis are as follows:(1)The finite element solution of the temperature field of the laser damage target was studied.Starting from Fourier’s law,the finite element equation of the temperature field is derived by combining with the finite element theory.The problem of solving the phase change temperature of the target is solved by the enthalpy method.The thermal properties of the material are updated by the continuous iteration of the thermal conductivity matrix and the specific thermal matrix,and the obtained temperature field is closer to the actual situation.(2)Temperature field modeling of metal targets and carbon fibers was performed.The model of laser absorption rate of metal target was established.Considering the factors of thermal property change with temperature and melting phase transition,the temperature rise characteristics of aluminum target under different power densities were studied.Aiming at the thermal ablation phenomenon of carbon fiber target,the life and death unit method is solved to solve the problem of carbon fiber surface layer peeling,and the temperature field of laser irradiated carbon fiber composite target is more accurately simulated.(3)The finite element solution of the thermal stress field and the thermal stress distribution characteristics of the metal target are studied.Because the temperature distribution is not uniform,the degree of thermal expansion inside the target is different,and the area outside the spot and the area inside the spot are mutually restricted to form thermal stress,and the increase in temperature causes the mechanical properties of the target to decrease,thereby aggravating the damage of the laser to the target.During the irradiation of metal targets,the thermal softening effect is intensified,and the central region is most susceptible to plastic deformation.(4)Experiments on laser damage to metal targets and carbon fiber composites were carried out.The metal target will reflect the glare of the light at the initial stage of irradiation.After the laser ablation penetrates the metal target,there is residue around the pore of the target,which is a material that is re-solidified after melting.The residue under the pore is the most under gravity.When the laser damages the carbon fiber target,the ablation is dominant,and the carbon fiber in the spot area on the front surface of the target is more easily blown,and the separation between the layers of the material around the spot is serious,mainly due to the thermal stress damage and the mass loss of pyrolysis.