ALBERT

Description: In the field of fracture mechanics, stress-intensity factors are important parameters for predicting fracture strengths and fatigue lives. BOFFO performs stress analysis of two-dimensional linear elastic orthotropic or composite bodies with or without cracks using the Boundary Force Method. The Boundary Force Method is versatile since complex geometries, crack configurations, and load distributions can be analyzed with ease. The BOFFO program is easy to use because only the boundaries of the region of interest are modeled using a built-in mesh generator. Stresses can be computed at any specified point in the body. Stress-intensity factor solutions and strain-energy release rates are computed for both mode I and mixed mode fracture problems. The Boundary Force Method is a numerical technique that uses the fundamental solutions for concentrated forces and moments in an infinite sheet to obtain the solution to the boundary value problem of interest. These fundamental solutions are used in the BOFFO program to exactly satisfy the stress-free conditions on the crack faces. The other boundary conditions are approximately satisfied by applying the appropriate sets of concentrated horizontal and vertical forces and moments along the boundary. The problem configuration is defined using two sets of axes. The global X- and Y-axes define the specimen boundaries, loads, and material properties. The local axes define the crack length and orientation. The user can specify four types of symmetry conditions: symmetry about the X-axis, symmetry about the Y-axis, symmetry about the X- and Y-axes, or no symmetry. The lines of symmetry are not modeled as boundaries. The accuracy of the solution depends on how well the boundary conditions are approximated, which in turn depends on the refinement of the boundary mesh. BOFFO uses the radial-line method for element mesh generation. BOFFO is written in FORTRAN V for execution on CDC CYBER 170 Series computers running NOS. The execution time and memory required depend on the number of boundary elements in the mesh. With twelve elements, the main memory requirement is 26K Cyber words. Input and output are tabular. BOFFO is available on a 9-track 1600 BPI ASCII Card Image format magnetic tape. This program was developed in 1990. CDC CYBER and NOS are trademarks of Control Data Corporation.