The effects of warm pre-stressing on cleavage fracture. Part 1: evaluation of experiments

An experimental programme has been performed to characterise the mechanical parameters and the fracture response of two steels, BS1501 and A533B. These are widely used in pressure vessel technology. The role of load history on improvements in cleavage fracture toughness has been investigated. Scatter within experimental cleavage toughness data has been described by using the model proposed by Wallin [Defect Assessment in Components, Fundamentals and Applications, ESIS/EGF 9, Mechanical Engineering Publications, London, 1991, p. 415] and combined with Chell [Int. J. Fract. 17 (1981) 61] model for warm pre-stressing (WPS) effect. The influence of parameters such as repeated cyclic pre-loading, sub-critical crack growth and specimen size on the WPS effect has also been noted. Finally the importance of the role of crack tip blunting and near tip residual stress field in describing the effect is discussed.