Experimental and numerical investigations on limit strains using an enhanced Rousselier model. (1st March 2020)

• Record Type: Journal Article
• Authors: Fehringer, Florian; Seidenfuß, Michael
• Is Part Of: Engineering fracture mechanics. Volume 226(2020)
• Publication Date: 2020-03-01
• Subjects: Damage mechanics -- Rousselier model -- Limit strain concept -- Stress triaxiality -- Lode angle; Fracture mechanics -- Periodicals; Rupture, Mécanique de la -- Périodiques; Fracture mechanics; Periodicals; 620.112605
• DOI: 10.1016/j.engfracmech.2020.106868
• Languages: English
• ISSNs: 0013-7944

Abstract

Highlights: Ductile failure is simulated with an enhanced Rousselier model. Extensions of the Rousselier model based on large experimental program. Strain based structural integrity assessment concept using damage mechanics. Validation of the concept with a pipe branch under pressure and bending load. Abstract: The permanent risk of environmentally caused accidents, which exceed the design limits of power plant components, makes the evaluation of safety margins against failure a crucial task. The evaluation concepts proposed in technical standards are mostly stress-based. These concepts are usually unable to fully utilize the high ductility of common materials used for power plant components. To overcome this disadvantage, a proposal for a strain-based structural integrity assessment (SIA) concept is given in this paper. The SIA concept is based on damage mechanics simulations using the Rousselier model. To cover the influences of stress triaxiality, component size, non-proportional loading and multiple loadings, the standard Rousselier model is enhanced by three extensions. First, the von Mises plasticity law is replaced by a Hosford-like yield criterion to introduce the influence of the Lode angle on the plastic deformation behavior. Second, for the prediction of failure under shear stress conditions, the description of damage evolution is enhanced by an approach developed by Nahshon and Hutchinson. Last, back-stress tensors are added to describe the very low cyclic loading behavior. All theoretical extensions are verified on the basis of an extensive experimental program using ferritic steel 20MnMoNi5-5. At the end, the proposed SIA concept is successfully validated using a combined pressure and in-plane bending test of a pipe branch.