Low-Cycle Fatigue Prediction for Ramberg-Osgood Type Materialsby Faisal H. Al-Sugair, King Saud Univ, Riyadh, Saudi Arabia,
Abstract: The prediction of low-cycle fatigue crack growth is successfully made by an equation employing the J-integral range. This equation, originally proposed by Dowling and Begley, is analogous to the Paris law of linear elastic fracture mechanics, commonly used to predict high-cycle fatigue. The J-integral equation and the Paris equation are identical for high-cycle fatigue problems. The computation of the J-integral range, ΔJ, is based on measurements from load-deflection diagrams obtained during testing for crack growth. This makes the use of the equation difficult in practice. In this work, J-integral estimates for Ramberg-Osgood type materials loaded monotonically are extrapolated to cases of cyclic loading. Also, the estimates are fitted to existing data of ΔJ for A533B pressure vessel steel, and a correction term is established. The estimates are compared to the experimentally obtained values and prove to be quite accurate. The estimates are used as input in a stochastic model for low-cycle fatigue prediction previously developed. The model with the estimated ΔJ values predicts the crack growth curve quite well.
Subject Headings: Fatigue (material) | Cracking | Pressure vessels | Elastic analysis | Linear functions | Cyclic loads | Laws | Paris | France | Europe
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