CALCULATIONS OF THREE DIMENSIONAL J-INTEGRAL BY SURFACE INTEGRAL METHOD IN FINITE ELEMENT ANALYSIS

摘要

Calculating the values of three-dimensional J-integral is a very practical problem in engineeringrnand academic fields. There are several kinds of methods to compute the values of J-integral. In this paper, a surfacernintegral calculation method of three-dimensional J-integral in finite element analysis has been discussed.rnFirstly, after giving the surface definition of J-integral which can be easy to execute on micro-computer, a threerndimensional twenty-node-isoparametric incremental theory elastic-plastic finite element program containing thernsubroutine of J-integral according to its surface integral definition has been programmed and checked on personalrncomputers throughout. Secondly, through taking a thick wall cylindrical vessel subjected inner pressure load as anrnexample, the structure containing a semielliptical surface crack in inner surface of the cylinder has been calculatedrnand analyzed by using the 3D elastic-plastic J-integral finite element program. After the calculations and analyses,rnthe internal relationship between calculating precision and time with element meshing and nodal numbering hasrnbeen pointed out when 3D elastic-plastic J-integral calculation is carried out on a personal computer. And, anrneffective form of element meshing and numbering are also given in the same time. Thirdly, the value of J-integralrnat any point of the crack front can be predicted by taking the 3D J-integral as a vector. Finally, the value ofrnJ-integral evaluated by surface integral method is compared with the value evaluated by virtual crack extensionrnmethod given by Bloom.rnThe surface integral method has many advantages over the virtual crack extension method. The main advantage isrnthat the values at any point of crack front and any integral surface can be easily obtained in one time finite elementrnanalysis.