Modelling Stress Relaxation in Bolt Loaded CT{Specimens

Abstract

Cracks in welds at higher temperature ranges (288 C) are prone to creep deformation and hence affect the crack tip stresses. Various creep models are presented. One of the models are used to describe the bolt load relaxation of modified CT-specimens analytically. The model is compared to numerical results using Ansys. The long term bolt load relaxation rate described by the model was similar to the three dimensional numerical analysis. It should be noted that a performed experimental bolt load relaxing experiment was performed, but due to lack of creep deformation data at the temperature of interest, fictive material data parameters were used instead. The CT-specimen was bolt loaded with 16:66 kN. After a 50 h heat treatment cycle at 288 C, the bolt had relaxed by approximately 30 %. A bolt load relaxation model for fictive materials were compared with numerical results using the numerical calculation tool Ansys. The shape of the model was consistent with the numerical results, although, some calibrations of the model is still required to reach a satisfying result.