Observations on fatigue crack paths in the corners of cold-formed high-strength steel tubes

• Published in: Engineering fracture mechanics Vol. 75; no. 3; pp. 833 - 844
• Main Authors: Heinilä, Sami, Marquis, Gary B., Björk, Timo
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Tarrytown, NY Elsevier Ltd 01.02.2008; Oxford Elsevier
• Subjects: Cold forming; Crack path; Exact sciences and technology; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Multi-axial fatigue; Physics; Residual stresses; Solid mechanics; Static elasticity (thermoelasticity...); Structural and continuum mechanics; Crack path; Cold forming; Residual stresses; Multi-axial fatigue; Axial stress; Stress analysis; Mean field approximation; Small dimension; Tube; Surface crack; High strength steel; Bending stress; Wedge; Test bar; Modeling; Fatigue crack; Edge crack; Plate; Crack propagation; S shape; Shear stress; Residual stress; Strength of materials
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2007.01.010

Fatigue crack propagation in cold-formed corners of high-strength structural steel plate-type structures has been investigated. Large- and small-scale test specimens having complex residual stress states and subject to multi-axial cyclic local stresses have been investigated using both laboratory tests and numerical simulations. The combinations of alternating bending stress, alternating shear stress and static mean stress producing complex multi-axial stress states have been found to influence the fatigue crack path behaviour. Straight, zig-zag and “S” shaped cracks were observed depending on the material strength, range of cyclic loading, residual stress field and multi-axiality of the local stresses. Numerical simulations of residual stresses and linear elastic fracture mechanics were used to help understand the alternate crack paths. Mode I cracks propagating into a static compressive stress field did not arrest, but, due to the multi-axial stresses, combinations of mixed mode I, II and III crack growth with distinct paths were observed. The crack paths depend on the type and range of cyclic loading, material properties and residual stress conditions of the specimens.