Investigation of the role of residual stresses in the warm prestressing (WPS) effect part II: analysis

Reed, P.A.S. and Knott, J.F. (1996) Investigation of the role of residual stresses in the warm prestressing (WPS) effect part II: analysis. Fatigue & Fracture of Engineering Materials & Structures, 19 (4), 501-513.

Abstract

Curry’s model [1] of the WPS effect has been applied to the results of the preceding paper, and is extended to treat warm prestressing in blunt notched test-pieces. The effect of more complex prestress cycles is also predicted by an extrapolation of the model. The effects of the LCF cycle can be reasonably predicted for both sharply precracked and blunt notched specimens. For the sharply precracked specimens the effects of the LUCF cycle at -196?C are consistently overpredicted and this may be due to a decrease in the cleavage fracture stress at -196?C of the material at the crack tip which has been subjected to repeated plastic straining by the combination of loading cycles. Modifications to the model are suggested which reduce the overprediction but a wide degree of scatter is observed in the experimental observations. Blunt notched specimens show a reasonable correlation between prediction and theory for the tensile LUCF cycle. Problems have been found in predicting the effect of various prestress cycles in different specimens due to the inherent variability in baseline fracture behaviour of the weld metal. It is concluded that the general trend of results is adequately explained by superposition models but that a greater understanding of local flow properties at a crack tip is required to achieve reasonable predictive success for weld metals such as A533BW.

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Contributors

Author: P.A.S. Reed

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