Research On Static/Dynamic Damage Mechanics Behavior And Anti-penetrating Performance Of Concrete Materials

Concrete is a brittle material. It is widely used in construction, transportation, water conservancy, airport runway, municipal construction projects and military such as resistance to penetration and explosion of fortifications. As a kind of commonly used materials, the static and dynamic mechanical property of it is a hot topic for scholars. Based on the theoretical analysis, experimentation and numerical simulation, the thesis analysis the static and dynamic mechanical properties and yield criteria and damage evolution equation and equation of state of C40concrete. The main contents are as follows:1) The thesis studied on the mechanical property of C40concrete. The reliability of the data is also verified. Using the material testing machine (MTS809) and large size split Hopkinson pressure bar (SHPB) test device to study the concrete material under quasi-static and dynamic mechanical property under uniaxial compression. Using the MTS810device for direct tensile and Brazil disk split tests of concrete materials to studied the tensile mechanical property of concrete. Through the MTS815.03device the mechanical property of concrete material under confining pressure was studied. Different testing techniques, the experimental apparatus and data processing have influence on obtaining accurate experimental data. The thesis discusses and studies the effects of those.2) Based on the experimental study of SHPB, the strain rate effect of yield strength of concrete materials were studied, the corresponding dependence function and material parameters were given. Based on the experimental results under confining pressure, the stress related yield criterion of concrete was established. Some useful yield function can be gotten. Through the experimental data, three different forms of the state equation of concrete material was proposed, and the corresponding parameters also be given.3) The physical meaning of Murnagham equation of state is analyzed first from the view of thermodynamics, and the general mathematical form of Mumagham equation of state is derived and obtained. Then, the correlation between the linear D-u Hugoniot curves measured in shocks experiments, the approximation of weak shocks and Murnagham equation of state in pure mechanics case is discussed. The discussion indicates that for materials described by Murnagham equation of state, under the approximation of weak shocks the D～u Hugoniot relation must have the linear form, from which the transforming formulae of parameters in Murnagham equation of state and the linear D～u Hugoniot relation are obtained. The Murnagham equation of state of various material parameters are given by some reference test data fat home and abroad, has laid the foundation for the engineering application. It has laid the foundation for the engineering application.4) Combining "the concept of equivalent micro voids system" and "the model of existent damage-nucleation growing up",a damage evolution equation of brittle materials under the coupled compression-shear actions is presented by strict mathematical derivation based on some physical relations. And a tensile damage evolution equation is also established. Applying the damage evolution equation to the brittle-elastic damage constitutive model of concrete, and based on numerical simulations of the experimental stress-strain curve, the parameters in the damage evolution equation are gotten. From the damage constitutive relation and the damage evolution equation, the damage-time curve can also be obtained, which is consistent quite well with the pictures of internal micro voids evolution gotten from CT technology. Starting from the idea of energy conservation, the physical process of micro cracks is analysis, and a micro crack propagation of tensile damage evolution equation is proposed. Its corresponding material parameters are also determined.5) Hemispherical steel projectile penetrating concrete target experiments are carried out. Concrete target based on HJC constitutive model. The material parameters determined by experiments. Through simulation of penetration under different incident speed, the results show that the residual velocity of simulation is fit well with the experiment data. The results demonstrate that the anthology constitutive material parameters and experimental data model based on the scientific and reasonable.