Assessment of a Thermal Fatigue Test Using Open Source CAE and Elastic FEA-Based Simplified Method

Abstract

AbstractThe assessment of thermal fatigue is often required for high-temperature components such as those in thermal power and chemical plants. The procedures of thermal fatigue assessment are complicated, and in many cases, difficult to carry out. In addition, the verification and validation of thermal fatigue assessment using FEM are rarely carried out due to the high cost and long duration of the tests. In the fatigue-life assessment of high-temperature components, the strain range for thermal fatigue-life consumptions must be estimated using an inelastic analysis. Neuber’s rule has been used to estimate the strain range. The stress redistribution locus (SRL) approach is thought to lead to a more realistic behavior than Neuber’s rule. This paper describes the numerical confirmation of the SRL behavior under thermal loadings. In addition, this paper describes the fatigue assessment of components subjected to cyclic thermal loadings by the alternate injection hot and cold sodium flow, referring to a previously reported thermal fatigue test performed by Japan Atomic Energy Agency on a tapered cylindrical specimen. Finite element analysis (FEA) and non-steady-state thermal transient and stress analyses were performed to evaluate the thermal stress changes by using an open source FEA software (Salome-Meca, Code-Aster). The results of thermal fatigue assessments obtained by inelastic and elastic FEA route assessments using the SRL approach were compared with each other. The results of thermal fatigue assessments obtained by using the SRL approach were more realistic than those obtained by Neuber’s rule. In addition, the SRL can be used to carry out a more simplified evaluation procedure than the conventional evaluation procedure defined by ASME Section III Division 5.KeywordsThermal fatigueStress redistribution locusOpen-source CAEFinite element analysisVerification and validation