The Analysis For Crack Tip Plastic Zone Of Saturated Porous Media Under High-power Ultrasonic

One of most important of the technology of oil exploitation by high-power ultrasonic is to study the influence for the porous media of oil reservoir, and the key problem is to improve the permeability of the reservoir porous media. Reservoir porous media as a kind of natural rock mass, the mechanical performance is more complicated. Study the influence of high-power ultrasonic to saturated porous medium permeability. First of all need to understand the mechanical model of saturated porous media, and then on the basis of this to study high-power ultrasonic effect on pore of crack propagation. This paper adopts the research methods of theory and numerical simulation to study the influence of plastic zone of saturated porous media crack under high-power ultrasonic. The main research works included in the dissertation are as following:First of all, the paper analysis the saturated porous media of incremental elastic-plastic constitutive relation, given the general expression of incremental constitutive model, respectively derived the increment of stress space and strain space constitutive model and associated with elastic-plastic loading and unloading criterion. Then we choose the Von Mises as the yield surface of saturated porous media. Giving the stress and strain incremental expressions of plane stress condition.Next, in view of the small scale yielding fracture mechanics crack tip stress the theoretical value is inconformity with the engineering actual situation, and stress value of the plastic zone for the corresponding correction. At the same time based on the ideal elastic-plastic model to establish the reverse plastic zone of stress, according to the hardening characteristics of saturated porous media is to correct reverse plastic zone stress. Calculating the stress distribution conditions of pore on the crack extension under the condition of different ultrasonic sound pressure.Finally, using the ANSYS to calculate the stress distribution conditions of pore on the crack extension under the condition of different ultrasonic sound pressure. And compare with the theoretical calculation results, found that pore crack damage forms found is different:Under different ultrasonic sound pressure, the ultrasonic sound pressure is more greater and carrying of acoustic energy is more greater, the saturated porous media absorb the energy of ultrasonic is more and the pore crack crack propagation have more obvious effect.