Finite Element Method Research Of The Thermal Damage Of Material Induced By Intense Laser

Intense laser is usually divided into high energy laser and high power laser. In general, high energy laser is continuous wave laser and long pulse width laser, high power laser is short pulse laser and ultra-short pulse laser. The intense laser has important application in modern industry and military and so on. But under laser irradiation, materials are inevitably induced damage by the intense laser. Optical components of the intense laser system irradiated by high power laser may be damaged by intense field in shot time during process of the ICF (inertial confinement fusion), this should induce the quality of laser beam become worse, and then the system optimization function is influenced. If optical components are more severely damaged, laser devices may don't operate. The laser induced damage of the optical components limits the development of high-power and high- energy lasers. Moreover high energy laser applied to laser weapon and laser processing may lead to the emergence of temperature rise and thermal deformation and thermal stress inside material. Thus might cause laser thermal damage of material. So it is of great importance to study the physical mechanism of material damage induced by laser and impr ove the damage threshold of material.At present, the experimental method and the theoretical model analysis method and the numerical calculation analysis method are three main methods investigating the damage induced by laser. The numerical calculation analysis method mainly has the finite difference method and the finite element analysis method. The finite difference method is simple and high efficient and easy to program, whereas the finite element analysis method is more flexible and is able to deal with the more complicated problems. In this paper, based on the Fourier thermal conduction theory and the classical thermal-elastic theory, using finite element analysis method, the three-dimensional physical model of numerical calculation analysis method is established, the transient distributions of temperature and thermal stress in material are calculated, then the melting damage threshold and thermal stress damage threshold are obtained. Our central work and conclusions are obtained as follows:1. The research development of damage induced by high laser is reviewed. It is briefly discussed that the basic mechanisms of target materials' absorption, reflection and conversion to the laser energy in theory. The states and styles of material damage induced by laser are briefly depicted. Some kind of different mechanisms of damage induced by laser are introduced. Different factors influencing laser-induced damage of material are analyzed.2. The Fourier thermal conduction theory and the classical thermal-elastic theory are described using finite element analysis method. The three-dimensional numerical calculation model of finite element analysis method of material irradiated by laser is established. Appling this, model, respectively with K9 glass and Insb semiconductor and Insb (PV) photoelectric detector as example, the transient distributions of temperature and thermal stress in optical material and "semiconductor and photoelectric detector irradiated by laser are calculated, and the melting damage threshold and thermal stress damage threshold are gained. The types and mechanism of laser-induced damage are studied. The influence of laser parameter and material properties to damage threshold are discussed. The obtained qualitative conclusions match well with the correlative experiment. These indicate that the model in this paper is reasonable.The numerical calculation model of finite element analysis method of material irradiated by laser presented in this paper may provide the theoretical reference to the laser counterwork and laser reinforcement and laser processing efficiency.