Mechanics Analysis In Structure Fracture Based On Unified Strength Theory

The brittle fracture of engineering structure has been attracting more and more attention, the previous brittle fracture judgment is used Fracture toughness K_IC is greater than the stress intensity factor K_I, Therefore stress intensity factor for containing crack structure becomes the most attention content in fracture mechanics. Analysis of structure with crack based on linear-elasticity and elasticity-plasticity in plastic zone at the crack tip will involve the material failure yield criterion.For small scale yielding crack tip of plastic zone correction and the stress intensity factor correction ever more uses a single Tresca,Mises,Mohr-Coulomb and Twin-Shear yield criterion. These criteria often doesn't consider that tension and compression performance ratioαand completely reflects the intermediate principal stress effects parameters b .The result makes this aspect of answer single,Thus analysis for engineering structure has certain constraints, Unified strength theory offsets this defect. The known existing strength theories are unified strength theory exceptions or linear approximation. This paper is based on a small scale yielding, the plastic zone under the unified strength theory that fixed the unified plastic zone linear-elastic fracture theory; application of plastic materials ideal applies to slip line theory based plane strain, getting the size of plastic zone and crack tip opening displacementδunder the unified strength theory and elasticity-plasticity fracture theory. Thus unified solutions of plastic-zone that using unified strength can be flexibly to the metal, geotechnical, engineering materials such as widely application scope. In the process for stress intensity factor correction, The unified solution of stress intensity factor correction is deduced under considering materials strengthening in small scope of yield, It makes the stress intensity factor correction under plane strain with larger scope of application,The strength of materials have great potential to improve, according to the different material nature, which can get different unified strength theory answer under different strength theory,and has necessary reference value for project application and material interrelated fracture research.The paper is based on finite element for precision analysis of the stress intensity factor, using different crack length a, considering whether the crack tip existing singular element and the grid division and around the crack tip radius of the stress intensity factor plays a significant influences for numerical solution. And through analytical solutions and boundary element solutions has been compared. Overall,The precision of unilateral throughout the crack is higher than bilateral throughout the crack for the answer of stress intensity factor.