Boundary element analysis of time-dependent material non-linearity
A two dimensional boundary element method (BEM) formulation and computer program for creep problems based on an initial strain approach has been successfully implemented using Fortran code. Two creep laws which can be used in this program are time hardening and strain hardening. The details of the numerical algorithm are presented using isoparametric quadratic elements to model the boundary with 3-node boundary elements, and to model the interior domain with 8-node quadrilateral cells. The BEM program also covers the variable stress load problems. The creep problems of a square plate, a plate with a circular hole and a plate with a semicircular notch are investigated. The boundary element formulation for creep problems has also been applied to creep damage mechanics problems. These types of problems have not been done by using the boundary element method before. A single damage variable is used in the program. The details of the numerical algorithm are presented. The two dimensional problems of creep damage in a rectangular plate and a square plate with a circular hole are tested and compared with the finite element solutions using ABAQUS UMAT. A BEM program for combined plasticity and creep problems has also been established. It is assumed that the plasticity and creep processes are separable. The details of the numerical algorithm are presented. The problems of a square plate, a plate with a circular hole and a plate with a semicircular notch are investigated. A BEM program for frictionless creep contact problems has been created. Similar to plasticity and creep problems, it is assumed that contact and creep processes are separable. In this program, it is assumed that the actual contact area is fixed during the creep procedure. The problems of a punch and a cylindrical punch on foundations are investigated. The results of all problems above are compared with the finite element solutions using ABAQUS and the analytical solutions where available and shown to be in good agreement.