Elastic-plastic fracture analysis of stiffened plate under bending load

摘要

Compared with plane fracture problem, elastic-plastic fracture problem of stiffened plate under bending has its particularity and inevitability for research, and its essence is a three-dimensional fracture mechanics problem. The aim of this paper is to develop a method to analyze bending elastic-plastic fracture of stiffened plates with crack in plate based on Dugdale model, combined with the Paris displacement formula and generalized variational principle, and the three-dimensional fracture problem is transformed into a two-dimensional problem. The Paris displacement formula and generalized variational principle are applied to calculate the displacement of a stiffened plate with central-through crack under uniaxial moment and yield strength in plastic zone. By discretizing stiffened plate into stiffener and plate, the generalized variational principle is combined with deformation compatibility equation to define the node shearing effect of the stiffener. Numerical simulation is carried out by finite element software ANSYS, a procedure for determination of crack-tip plastic zone and crack tip opening displacement (CTOD) has been proposed for stiffened plates with different stiffness, allowing for the existence of a central through crack in the plate, the results from the theoretical model are compared with those of the finite element results. The validity of the developed method is demonstrated by comparing with the FEM results in an illustrative example. It is found that the results from the method agree well with those from the FEM. It is shown that the theoretical model results are reliable compared with those from FEM. The model well reflects the fracture behavior of stiffened plate and the anti-crack property of stiffener; the results have important significance in the low cycle fatigue research on hull structures.