Elasto-Plastic Cyclic Analysis of Structural Members

A two-dimensional elasto-plastic finite element analysis is developed herein which has the capability of analyzing structural members which are subjected to cyclic thermal-mechanical loadings. This analysis, therefore, is of great value in gas turbine applications. The analysis, which is based on an effective stress-strain formulation, employs a tangent modulus approach in its execution. Both principal and conventional stresses are computed in the body. Unloading procedures are established and subsequently employed in cyclic loading problems. Several examples are presented. A turbine blade shroud, which has been mechanically loaded due to interference with its adjacent member, is analyzed. Cyclic behavior is shown for a uniaxial tension specimen and then generalized to a multiaxial stress state. A “predictor-corrector” procedure, which calculates the most efficient loading increment, is developed. Analyses of stress concentration factors and thermal stress applications are also presented.