A three-dimensional analysis of fracture mechanics test pieces of different geometries – Part 1 Stress-state ahead of the crack tip

• Published in: The International journal of pressure vessels and piping 2012-05, Vol.93-94, p.42-50
• Main Authors: Tkach, Y., Burdekin, F.M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Compact tension; Crack tip stress fields; Exact sciences and technology; Finite element method; Fracture mechanics; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Inelasticity (thermoplasticity, viscoplasticity...); Mathematical analysis; Mechanical engineering. Machine design; Physics; Plain sided and side grooved fracture specimens; Solid mechanics; Static elasticity (thermoelasticity...); Steel design; Steel tanks and pressure vessels; boiler manufacturing; Stress strain curves; Stress-strain relationships; Stresses; Structural and continuum mechanics; Three dimensional
• ISSN: 0308-0161; 1879-3541
• DOI: 10.1016/j.ijpvp.2012.02.005

An extensive series of detailed three-dimensional elastic–plastic finite element analyses has been carried out to investigate the influence of fracture mechanics test specimen geometry on the near-tip stress fields. The specimens studied were pre-cracked plain-sided and side grooved bend specimens of Charpy specimen size, plain-sided and side-grooved compact tension specimens of thickness B = 25 mm and plain-sided compact tension specimens of thickness B = 100 mm. The standard ratio of the crack length to the specimen width a/W = 0.5 was employed in all the cases considered. 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. Variations of the local crack tip driving forces in terms of the J-integral and crack tip opening displacement (CTOD) over the crack front have been investigated. The near-tip stress fields in the fracture toughness specimens were analysed in detail with the emphasis on the opening mode stress. Further studies on the constraint parameter Q and hydrostatic and equivalent stress components are reported in a separate paper, Part 2 of this work. ► 3D FE analyses on plain and side grooved Charpy sized and CT specimens of two sizes. ► Near crack tip stress fields analysed to give opening mode stress distributions. ► Peak opening mode stresses are higher in CT (tension) than Charpy (bend) specimens. ► The local tip and global bending stress fields interact in the Charpy specimen. ► Volumes of material subject to a given peak stress differ in different specimens.