【正文】 , curvature radius r = 0. 2 mm. We can see from the calculation, simulation and experimental value of the error as follows: μ = (137 129. 32) / 137 100% = 5. 6% As J IC corresponding to cracking force is actually crack initiation of the cracking strength, that is to meet the precrack slots crack initiation of the minimum force. In theory, crack after rapidly expanding until the fracture, depending on the flexibility of the release of crack growth can be the satisfaction of crack propagation on the surface energy requirements. If the elasticity of the release can be greater than the surface energy, crack can automatically expand。, curvature radius r = 0. 2 mm. Depending on the engine box bearing the process of the force characteristics of the model simplify the segmentation, due to fourcylinder engine box bearing process is the same time, five bearing fracture, all bearing the same characteristics as the force, to take one of them simulation analysis can be carried out. The model symmetry plane in the crackslot segmentation, due to bearing structure, symmetrical, they can be omitted Original half, so that the finite element simulation analysis of threedimensional part drawings on the original 1 / 2. As the box size is relatively large, fixed and therefore the lower box using a pletely fixed constraints, namely: U x = U y = U z = UR x = UR y = UR z = 0, the circular symmetry in the box surface, due to structural symmetry, load symmetry, the symmetry plane split points in X direction without displacement, namely: UR x = UR y = UR z = 0. Engine bearing cracker box, due to box at the bottom of fixed and expansion of the bearing sleeve off the second half of Arc has radial pressure, swelling and block the bearing seat and a half arc with the radial expansion force. And because it isI crack, and only the direction of radial force of the yponent of the crack work, x direction ponent of each other to balance the crack does not work, so when the applied load only the upper and lower semicircular surface crack y direction of applied load can, in the Marc / finite element simulation software, the load applied in different ways, such as the node load, line load, surface load and so on, according to processing technology bearing the characteristics of simulation analysis in this article, select the node load ( point load). The division of the grid is divided into cracks and nocrack zone, precrack in the model area set aside, and then Marc / software crack area of nonphysical modeling and meshing, using 8node tetrahedron element, No. 127 (See Figure 5 (a)). Then, generate crack zone entity model, using 21, 20 nodes in octahedral unit crack area due to the actual size of small, enlarge the crack area grid. Glue functions through the noncrack area and crack area grid stick together, the center symmetry plane and noncrack area contact connected with the Touching the mand and finally activated IDboundary conds mand, the plete finite element mesh model and boundary conditions shown in Figure 5 ( d) as shown. For the elasticplastic fracture mechanics, crack tip stress and strain fields generated 1 / r singularity, twodimensional case, this singularity can be overlapped with the three node triangular element simulation, while the analysis of this threedimensional model , can be used 20node degenerated block units constructed to simulate the crack front singular stress field. In this paper, namely, expansion of J integral method algorithm to calculate the Jintegral crack, and through topology discovery (Topology Search) automatically define the path integral. Topology search method refers to the program automatically selects the first point associated with the crack tip for all units outside the contour line as the first integral path, and then the further search and the first integral paths linked to the outer cell contour points as the second path, and so on, can be more easily determine the path points. Analysis of a 30stepstep loading, each step increment 4. 6. A total of 43 nodes in the crack tip, J integral path is defined as the number 6, the crack tip node tolerance set to 0. 001mm. The simula