Cyclic Void Growth Model to Assess Ductile Fracture Initiation in Structural Steels due to Ultra Low Cycle Fatigue

• Published in: Journal of engineering mechanics Vol. 133; no. 6; pp. 701 - 712
• Main Authors: Kanvinde, A. M, Deierlein, G. G
• Format: Journal Article
• Language: English
• Published: Reston, VA American Society of Civil Engineers 01-06-2007
• Subjects: Exact sciences and technology; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Inelasticity (thermoplasticity, viscoplasticity...); Physics; Solid mechanics; Structural and continuum mechanics; TECHNICAL PAPERS; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...); Metallic structure; High strain; Brittle fracture; Metal; Steel structures; Test bar; Modeling; Low cycle fatigue; Finite element method; Voids; Inelasticity; Cavity; Earthquakes; Ductile material; Crack initiation; Collapse; Notched test piece; Fatigue; Steel; Cavitation; Monotonic load; Ductile fracture; Structural steel; Porosity; Fractography
• ISSN: 0733-9399; 1943-7889
• DOI: 10.1061/(ASCE)0733-9399(2007)133:6(701)

A new model is proposed to simulate ductile fracture initiation due to large amplitude cyclic straining in structural steels, which is often the governing limit state in steel structures subjected to earthquakes. Termed the cyclic void growth model (CVGM), the proposed technique is an extension to previously published models that simulate ductile fracture caused by void growth and coalescence under monotonic loading. The CVGM aims to capture ultra low cycle fatigue (ductile fracture) behavior, which is characterized by a few (generally, less than 20) reverse loading cycles to large inelastic strain amplitudes (several times the yield strain). The underlying mechanisms of low-cycle fracture involve cyclic void growth, collapse, and distortion, which are distinct from those associated with more conventional fatigue. The CVGM represents these underlying fracture mechanisms through plastic strain and stress triaxiality histories that can be modeled at the material continuum level by finite-element analyses. Development and validation of the CVGM is substantiated by about 100 notched bar tests, with accompanying finite-element analyses, metallurgical tests, and fractographic examinations of seven varieties of structural steels.