Prediction of cleavage failure probabilities using the Weibull stress

In this work, the use of the Weibull stress as a measure of the failure pro bability of a cracked body is examined. Closed form expressions for the Wei bull stress are presented for linear elastic and power law materials. These expressions allow Weibull stress values and failure probabilities to be es timated without the need for finite element analyses and provide insight in to the use of the Weibull stress as a parameter for the prediction of cleav age failure of cracked bodies. Application of the Weibull stress to the prediction of transition region an d upper shelf cleavage failure probabilities of Ferritic steel welds is als o discussed. The effect of ductile tearing, described by a Gurson-type mate rial model, is examined. Numerical analyses of compact tension fracture tes ts are carried out and used to interpret experimental fracture toughness da ta for ferritic steel welds. A comparison between the finite element result s and the experimental data indicates that the scatter in the cleavage frac ture toughness values in the transition region are quite well captured by t he Weibull stress. However, cleavage failure probabilities close to the upp er shelf using: the two parameter Weibull model are considerably higher tha n those observed in practice. A number of reasons for this discrepancy and suggestions to improve the predictions are proposed. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.