J0310202 The Analysis of Micro Damage around Notch Tip under Stress- and Strain-Controlled Creep-Fatigue Conditions using Circular Notched Round Bar Specimen

Abstract

Recently, many heat resistant materials have been developed to establish more efficient thermal power plants. For practical use, it is necessary to establish a law of predicting the crack growth life and clarify the behavior of micro damage formation. Stress- and strain-controlled creep-fatigue tests have been conducted to investigate the crack growth life of the material in the thermal power plants. The fracture mechanism under high temperature, such as micro damage formation, is affected by vacancy diffusion. In this work, we conducted the numerical analysis of vacancy diffusion in order to clarify the behavior of vacancy diffusion caused by stress- and strain-controlled creep-fatigue conditions. In comparison with experimental results, the following results are obtained. Under stress-controlled condition, the concentration of vacancy around a notch tip increased with increasing loading cycles., which results in progression of creep damage. Under strain- controlled condition, the concentration of vacancy did not increase around a notch tip, which suggests fatigue damage becomes more dominant.