Several Problems Of Mechanical Responses And Failure Of Plates Subjected To Thermal Energy Deposit

High power laser tends to cause elevated temperature and rapid rising of temperature of the irradiated objects. Under the pull of interaction between high power laser and materials and structures in optical and target systems, this thesis experimentally and theoretically researches on the mechanical responses and failure of two metals and several thin-formed structures subjected to both mechanical loads and irradiation of power laser beams. The main contents and results are as follows: (1) By using the Gleeeble- 1500 thermal-mechanical material testing system, the effects of heating speed on mechanical properties of two structural metals (LY12 aluminum and 1-162 brass) are studied through two systematic experiments of tension under a certain temperature and heating under a certain pre-Ioad. The results of the tension experiments show that, when the test temperature is lower than the recrystallization temperature, the mechanical properties of the materials do hardly change with heating speed, when the test temperature is higher than the recrystallization temperature, the effects of heating speed on mechanical properties of the materials are significant, and higher the heating speed is, lower the yielding and strength limits of the materials are. The results of heating experiments indicate that under a same level of pre-load, higher the heating speed is, higher the temperatures at which the metals are caused to yield or fracture are. The near-tip metallurgraphics of the LY 12 aluminum and H62 brass are also observed and analyzed. It shows that both temperature and heating-rate play significant roles in the mechanical behavior of the material and the inconsistence of local heat induced by high heating-rate accounts for the severe defect in the materials and the failure of the materials. (2) By using finite Hankel transform, the second chapter derives the thermo- mechanically coupled solution of an axisymmetric circular plate which is subjected to irradiation of a laser beam on one of its surfaces and has boundary conditions of a constant temperature and a special displacement-force confinement on its circumference. Two plates of different materials are calculated. The present analytical and FEM results are in accordance with each other and indicate that the effects of thermomechanical coupling on the thennoelastic vibrations of a plate are pertinent to the material properties. For some materials, the effects of thermomechanical coupling are of significance, and for others, they are of insignificance. Meanwhile, the relationships between the transverse mass inertial effect and the thickness-to-radius III ratio are calculated, which implies that the dynamic effect is of importance when the thickness-to-radius ratio is small enough. A theorem of solving a system of non-homogeneous linear differential equations through integrating its basic solutions is put forward and proved. In order to demonstrate the mathematical and physical significance, the theorem is applied to solving the problem of thermo-force bending of a thick plate and the formulas of deflections and rotary angles are deduced. This application example indicates that the solving process is concise and canonical. The obtained formulas are available in further related studies. Based on the Maximum shear stress theory, theoretical models are developed for the spallation of a thin film and for the reverse...