Experiments and predictions of the effects of load history on cleavage fracture in steel

A series of experiments conducted on two steels, A533B and A508, are summarised. Tests were conducted to explore the influence of different room temperature pre-loading cycles on subsequent low temperature (−150 °C and −170 °C) cleavage fracture. In all cases the low temperature fracture toughness was modified, with tensile pre-loading increasing the toughness and precompression reducing the toughness.
Results from finite element simulation of the pre-loading cycles are illustrated. Tensile pre-loading created compressive residual stresses and precompression generated tensile residual stresses. The residual stresses were adopted in a stress based local approach to fracture model using Weibull statistics and applied to the experimental results. The parameters in the Weibull model were calibrated for the virgin steels prior to its application to prior loading cases. The model is found to be successful in predicting the change in toughness relative to the virgin material for pre-loading in tension of A533B steel. The model underestimated the change in toughness for tensile pre-loading of A508 steel and overestimated the toughness change for precompression of both steels.