Study On Characterization Of Damage Evolution And Failure Law Of Engineering Materials

After the World Warâ…¡,as a result of the urgent needs for conventional weapons and strategic weapons, studies on the dynamic response of materials and structures, have been rapidly developed in those countries represented by the United States and Russia. With the research of dynamic mechanical properties of materials, the damage evolution and fracture criterion of materials under impact loading rise also. Material damage and failure not only in the fields of national defense and applied economics, such as weapons effects, protective engineering and safe and efficient construction, has a direct value, but also has important value in academic circles, because there are a variety of microscopic features of material damage and failure modes, which reflected to material damage constitutive, wave mechanics, transient computational mechanics and impact dynamics. In this paper, based on the idea of combining microscopic and macroscopic phenomenological theory, a variety of engineering materials of different types of damage models are presented to reveal the material damage model and the intrinsic link between the failure mode.This thesis comprehensively and systematically discussed the tensile damage for ductile metals. Presented two new damage models, which named Modified Tuler-Butcher model and micro-voids nucleated growth model. The former overcame Tuler-Butcher model's excluding early post-damage injury on the development impact of the defects, and the latter with "a nuclear grown up" new ideas to replace the so-called "nucleation and growth". The two models are more detailed characterize the tensile damage in ductile metals, and more in line with reality, more physical meaning, through simulations of D6AC steel and 45 steel spall experiments, one-dimensional contact explosion and a series of numerical simulation tests. The trial of damage evolution models are confirmed comprehensive and detailed. Given new damage evolution equation parameters, and discussed the influences of the material parameters and damage evolution equation parameters on the free surface velocity time history curves. Then, this paper modeled HESH(High Explosive Squash Head) as a one-dimensional model of engagement, using damage evolution parameters provided above, calculated a one-dimensional explosion caused spall. Types of explosives, material parameters and geometrical configuration of HESH were taken into account for its performance. Finally, this chapter proposed a new damage evolution equation embedded in HVP (high velocity penetration) finite element code, the two-dimensional numerical simulation code, calculating the blast load target spallation successful.This article pointed out that "adiabatic" in the "adiabatic shear" is only an approximation and not a shear band destruction of the nature of irreversible deformation heat and heat of the irreversible deformation of the material damage caused to accelerate the development of interaction is the shear band destruction of nature. This as a guide and energy conservation as the basis for the first time, the introduction of heat transfer elements which present a metal shear zone may reflect the development process of micro-damage evolution characteristics of a thermoplastic interaction damage evolution. The new fracture criterion was embedded in HVP finite element code to simulate the Arne tool-steel blunt nose projectile plugging Weldox 460 thin target. The thermoplastic interaction damage evolution and the thermoviscoplastic constitutive model predict completely the perforation process. The model is proved to be correct since the calculations are in good agreement with the experimental data, and is reasonable for further more detailed and more accurate to describe thermoplastic interaction damage criterion. In the shell structure under blast loading deformation, considered two damage models of ductile metals fracture, with the general explicit description of incremental strain thermal-plastic constitutive relations and the specific incremental thermal-plastic constitutive relations, combining the problem of sphere shell's fracture caused by the outside-explosive loading, we developed the self-contained equation group about the thermal-viscous constitutive sphere fracture problem. Numerical simulations were carried out with the presented constitutive relations for sphere shell fracture problem and the results were analyzed. In the last part of this article, damage and fracture in brittle materials under quasi-static and dynamic loadings were discussed. To micro-crack system, the "equivalent micro-void system" based on the concept, a new tensile damage model of brittle materials was presented. And a new pressure-shear coupled damage model was presented based on the stress-related yield of brittle materials. Based on the experimental data, numerical simulations of tungsten long rods penetration into 45# steel and confined AD95 ceramic targets were investigated, using Ansys/Lsdyna finite element analysis software. Since the computational results are in good agreement with the experimental results, the material constants of AD95 ceramic were obtained for the JH-2 model. The response of confined AD95 ceramic targets were also been investigated through finite element simulations. Then, using the newly proposed tensile damage model of brittle materials, the successful simulation of ceramic spall experiments showed that the proposed new tensile damage model of brittle materials is desirable. Finally, using brittle shear tensile damage and pressure-shear coupled damage presented in this chapter, spalling of concrete materials, and one-dimensional spherical explosion were simulated, given the simultaneous existence of tensile damage and pressure-shear coupled failure modes of concrete.