Constraint corrected cycle-by-cycle analysis of crack growth retardation under variable amplitude fatigue loading. (August 2019)

• Record Type: Journal Article
• Authors: Zhang, Jie; Muys, Louis; De Tender, Steven; Micone, Nahuel; Hertelé, Stijn; De Waele, Wim
• Is Part Of: International journal of fatigue. Volume 125(2019)
• Page Start: 199
• Page End: 209
• Publication Date: 2019-08
• Subjects: Fatigue crack growth -- Variable amplitude -- Retardation -- Crack tip plasticity models -- Wheeler model; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2019.03.046
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: An extended Wheeler model was proposed considering a variable shut-off load ratio. The out-of-plane constraint based on the strip yield mode was analyzed and included. The new model agrees better with experimental data than original/modified models. A method to calibrate the shape exponent of retardation factor was proposed. A cyclical crack growth algorithm was used with a quite limited computational cost. Abstract: Various models exist to predict load interaction effects on fatigue crack growth in variable amplitude loading conditions. Stress overloads have the potential to strongly retard or even arrest a propagating fatigue crack. Whereas global analysis methods (making use of equivalent quantities) allow to describe stochastic loading scenarios, describing the effects of deterministic overloads requires cycle-by-cycle analysis techniques. Within this category, plastic zone models have proven to be effective and pragmatic in terms of calibration. Current models, however, do not account for the effect of crack tip constraint on the plastic zone size, whose estimation is a requirement. This paper develops a novel ("extended") crack growth formulation based on the traditional plastic zone based Wheeler's model, taking into account the effect of out-of-plane constraint (plane stress versus plane strain). Calibration of the model requires characterization of shut-off overload ratios for different stress intensity factor levels. The "extended Wheeler" model gives better agreement with experimental tests results than the original and modified Wheeler model.