Use of conventional stress-strain data to develop parameters for an advanced constitutive model

• Published in: Materials at high temperatures Vol. 19; no. 4; pp. 215 - 223
• Main Authors: O'Donnell, M P, Bate, S K, Bretherton, I, Gladwin, D N, Hayes, J P
• Format: Journal Article
• Language: English
• Published: Leeds Taylor & Francis Ltd 01.11.2002
• Subjects: Assessments; Austenitic stainless steels; Constants; Constitutive relationships; Evolutionary; Mathematical analysis; Mathematical models; Plasticity; Stress-strain relationships
• ISSN: 0960-3409; 1878-6413
• DOI: 10.3184/096034002783640350

For structural integrity assessment of power generating plant components it is becoming increasingly important to take advantage of inelastic constitutive models. This is particularly important for cases such as, severe loading conditions, postulated fault conditions, complex loading histories, complex geometries, and/or to reduce the conservatisms inherent in simplified assessment or design approaches. The inelastic model outlined in this paper has been developed within this framework and with a view to providing a robust representation of material behaviour with a practical approach to the number of material constants required. The model has the capability to capture the evolving nature of the materials being considered over a range of loading conditions and temperatures. Additionally, its incremental form is applicable for use under complex loading histories where simple process equations such as the power law are not capable of representing the path dependence of the load history, which results from the dissipation of energy during the plastic deformation process. This paper focuses on plasticity and provides details of a combined isotropic non-linear kinematic model, the fast reactor state variable (FRSV) model. The material parameters required to represent the evolutionary plasticity behaviour in Type 316 stainless steel from 400 to 650°C and total strain ranges from 0.4 to 2% have been determined. Details of the material testing requirements and the methodology used to derive the plasticity constants are outlined. Validation of the model against the experimental data is provided via finite element calculations.