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Simulating Fatigue Cracks Growth in Spiral Bevel Gears Part 5

Tham khảo tài liệu 'simulating fatigue cracks growth in spiral bevel gears part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Figure 3.12 Least squares curve fit through new discrete crack front points. 3.3 Fracture Mechanics Software A suite of fracture mechanics software developed by the Cornell Fracture Group is used in this thesis FRANC3D 1999a 1999b . The codes were developed to handle the complexities of three dimensional crack trajectory predictions. OSM is used to define a three dimensional solid geometry model of an object. The program is based on defining the surfaces of the model explicitly in Cartesian space. The boundary of a solid is generated by adjacent surfaces or faces. Each face of the boundary element model has a three dimensional local coordinate system associated with it. In order to define a closed solid all of the local face normals must point away from the interior of the solid. The local coordinate system might also be of significance when defining boundary conditions. The geometry model is then read into FRANC3D. With FRANC3D a user can create a finite element or boundary element mesh based on the geometry model. Displacement or force traction boundary conditions must be defined for all the faces of the solid. The conditions must be specified in all three Cartesian dừections with respect to either the local or the global coordinate system. Material properties are also assigned to regions of the model using FRANC3D. Cracks are added to the solid by explicitly defining the vertices edges and faces that model the cracks. A crack has two distinct faces that must be meshed identically. As mentioned in Section 3.2.3 a crack front must be discretized prior to calculating SIFs and to propagating the crack. Within FRANC3D there are three options to discretize the crack front. The discrete points can be defined by the mesh nodes the midpoints of the elements sides along the crack or at a user defined number of equally spaced points along the crack front. The built in feature in FRANC3D to calculate SIFs uses the displacement correlation technique. The most accurate .