The shape of a strain-based failure assessment diagram

• Published in: The International journal of pressure vessels and piping 2012, Vol.89, p.59-66
• Main Authors: Budden, P.J., Ainsworth, R.A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Assessments; Defects; Exact sciences and technology; Failure assessment diagram; Failure assessment diagrams; Finite element method; Fracture; Fracture mechanics; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Mathematical analysis; Mechanical engineering. Machine design; Physics; Pressure vessels; Proposals; Solid mechanics; Steel design; Steel tanks and pressure vessels; boiler manufacturing; Strain hardening; Strain-based; Structural and continuum mechanics
• ISSN: 0308-0161; 1879-3541
• DOI: 10.1016/j.ijpvp.2011.09.004

There have been a number of recent developments of strain-based fracture assessment approaches, including proposals by Budden [Engng Frac Mech 2006;73:537–52] for a strain-based failure assessment diagram (FAD) related to the conventional stress-based FAD. However, recent comparisons with finite element (FE) data have shown that this proposed strain-based FAD can be non-conservative in some cases, particularly for deeper cracks and materials with little strain-hardening capacity. Therefore, this paper re-examines the shape of the strain-based FAD, guided by these FE analyses and some theoretical analysis. On this basis, modified proposals for the shape of the strain-based FAD are given, including simplified and more detailed options in line with the options available for stress-based FADs in existing fitness-for-service procedures. The proposals are then illustrated by a worked example and by comparison with FE data, which demonstrate that the new proposals are generally conservative. ► The strain-based failure assessment diagram approach to fracture is developed. ► The new approach modifies earlier proposals by Budden. ► A new generic Option 1 strain-based failure assessment diagram is proposed. ► Validation based on finite element J data for plates and cylinders is presented. ► The new approach is generally conservative compared with the finite element data.