Numerical Study On Multi Field Coupling Damage Effect Of Laser Irradiated Light Alloy Target

The target of laser weapon is mostly cylindrical shell structure.The working load of this structure mainly includes inertia overload,internal pressure of engine and high temperature load when engine working,and it also bears the aerodynamic load introduced by the surrounding flow field.Therefore,there is a complex multi-field coupling effect in the damage process of the laser weapon to the target.Accordingly,we divide it into two kinds of damage modes,which are thermal-mechanical coupling effect of target induced by laser irradiation and thermal-fluid-structure coupling effect of target induced by laser irradiation.For the two kinds of damage effect,typical targets are chosen and some research work is carried out:1.Thermal-mechanical coupling effect of target induced by laser irradiation.Firstly,the critical buckling load of cylindrical shells under axial compression is obtained through experiments,and the obtained results are compared with the buckling equations and analytical solutions of cylindrical shells under axial compression,and the experimental results are similar to those of large deflection nonlinear analytical solutions.The critical buckling load decreases rapidly as laser power density increases.Numerical investigation is presented to have an extensive analysis.Secondly,thermal-mechanical failure behavior of the internally pressurized cylinder shell under laser irradiation is investigated by using numerical approach.The dynamic bursting process are simulated,and the obtained failure mode is validated by experimental result.Three typical failure modes are found and corresponding parameter ranges are listed,and formation mechanisms of each failure mode are discussed.The effect of thermal softening on the threshold of internal pressure at different laser spot sizes and shell thicknesses are explored,and relation between internal pressure and failure time are discussed.Then,the types of thermal-mechanical failure modes of cylindrical shells subjected to combined action of axial compression and internal pressure under laser irradiation is investigated by using numerical approach and the reason for the transformation of failure modes under different calculation conditions are preliminarily explored.Finally,nondimensionalization processing is carried in heat conduction equation and thermal elastoplastic static equation,the similarity criterion is obtained for cylindrical shell subjected to coupling multiple loads or individual load.Attractive ability of finite element analysis(FEA)method is established to validate the similarity criteria and analyze the error,according to the load situations.2.Thermal-fluid-structure coupling effect of target induced by laser irradiation.A coupled thermal-fluid-structure model is presented to investigate the fracture of laser irradiated the thin aluminum sheet under tangential subsonic airflow.The results of failure modes,failure process and failure time are basically consistent with the experimental results.Results compared with the structural response of the aluminum plate under none-airflow show that a pressure decrease produced by tangential airflow not only accelerated deformation of the target but also affected the equivalent plastic strain.