Theoretical Aanlysis And Numerical Simulation Of Mechanical Behavior Of Bulk Metallic Glasses At Room Temperature

Due to the high strength, high elastic limit, high wear resistance and excellent magnetic properties, bulk metallic glass (BMG) has become one of the most promising classes of new materials in the field of military, aerospace, marine, electric power and mirco-electromechanical systems. However, because of the unique homogeneous structure of BMG, lacking of long-range ordering atomic packing and dislocation, the BMG has the different deformation mechanism and yield behavior from the traditional crystalline material. Meanwhile, the lack of plastic deformation at room temperature limits the engineering application of BMG. Thus, through the Meso-machining such as laser shock peening treatment to improve the plasticity of BMG and through the numerical simulation to study the mechanical behavior of BMG during the laser shock peening process have become the focus of the domestic and foreign scholars.In this paper, based on the free volume model, the lager deformation theory of nonlinear mechanics and Coulomb-Mohr yield criterion, a hydrostatic-pressure sensitive and rate-dependent constitutive model were established for the deformation behavior of BMG with the effects of hydrostatic-pressure sensitivity and plastically strain rate-dependence. Then the numerical simulation of bending process, laser shock peening process of BMG and the bending process after laser shock peening was investigated by ABAQUS/Explicit. In addition, an analytical study of stress, strain, moment and deflection in the process of sheet metal bending of BMG was accomplished. From the view of numerical simulation and theory analysis, this paper explores the laser shock peening process to enhance the plasticity of BMG at room temperature, which has great significance to extend the application of BMG.The simulation result of uniaxial compression process of Zr based amorphous alloys has a good agreement with the experiment, which has proved the rationality of our model. In the process of bending, With the increment of mesh density, the shear band width is decreased, but the shear band spacing nearly keeps constant. The shear band spacing is increased with the increase of the sample dimension. Thus, the density of shear bands in the sample are decreased, which results in the weakness of plastic forming ability of BMG. During the simulation of laser shock peening(LSP) on the surface of BMG, the micro-dimple is emerged on the laser peening zone, corresponding to the compressive residual stress. The compressive residual stress is increased and driven more deeply below the surface with the increase of shock pressure and pulse number. The compressive residual stress induced by LSP can improve the elastic limit and the yield strength during the next bending simulation.Based on the theory of elastic-plastic mechanics, the relationship of stress, strain, moment and deflection of metallic glass plate during bending process is preliminarily studied. Meanwhile, taking account of the influence of LSP, which can induce the residual stresses on the surface of BMG, the analytical formulations of stress, moment and deflection after the LSP process are obtained, and are compared with the previous formulations without the influence of LSP.