A three-dimensional analysis of fracture mechanics test pieces of different geometries part 2 - Constraint and material variations

• Published in: The International journal of pressure vessels and piping 2012-05, Vol.93-94, p.51-56
• Main Authors: Tkach, Y., Burdekin, F.M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Compact tension; Constraint; Exact sciences and technology; Fracture mechanics; Fracture mechanics (crack, fatigue, damage...); Fracture toughness; Fundamental areas of phenomenology (including applications); Inelasticity (thermoplasticity, viscoplasticity...); Mathematical analysis; Mathematical models; Mechanical engineering. Machine design; Physics; Plain and side-grooved fracture specimens; Solid mechanics; Static elasticity (thermoelasticity...); Steel design; Steel tanks and pressure vessels; boiler manufacturing; Strain hardening; Stress strain curves; Stress triaxiality; Structural and continuum mechanics; Three dimensional
• ISSN: 0308-0161; 1879-3541
• DOI: 10.1016/j.ijpvp.2012.02.006

This paper reports the second stage of an extensive series of detailed three-dimensional elastic-plastic finite element analyses on the influence of fracture mechanics test specimen geometry and different material properties on constraint and triaxiality in the near crack tip region. The specimens studied were pre-cracked plain-sided and side-grooved Charpy sized specimens, plain-sided and side-grooved compact tension specimens of thickness B = 25 mm and plain-sided compact tension specimens of thickness B = 100 mm all with the ratio of the crack length to the specimen width a/W = 0.5. Stress–strain curves of materials of different yield strength and strain hardening behaviour spanning the range of practical interest for typical structural steels were implemented into the finite element models. The level of constraint in the specimens modelled has been characterised in terms of both the Q-stress parameter and the ratio of hydrostatic to the equivalent stress components. It has been established that in-plane constraint in the fracture toughness test pieces is significantly affected by the absolute ligament size of the specimen. It has also been shown that the strain hardening behaviour is one of the major material parameters defining constraint level in the fracture toughness specimen. ► 3D FE analyses on plain and side-grooved Charpy sized and CT specimens of two sizes. ► Crack tip constraint analysed for Q-stress and hydrostatic/equivalent stress ratio. ► In-plane constraint is significantly affected by the absolute ligament size. ► Constraint level is significantly affected by material strain hardening behaviour.