THE EFFECT OF TEMPERATURE AND SPECIMEN GEOMETRY ON THE PARAMETERS OF THE LOCAL APPROACH TO CLEAVAGE FRACTURE

The present work investigates the temperature and specimen geometry de pendence of the Weibull parameters of a structural steel (BS 4360 Grad e 50D). Notched tensile, notched (Charpy-type) four point bend and fra cture mechanics specimens have been used to study the effect of specim en geometry. Axisymmetric and two and three-dimensional finite element analyses have been carried out to determine Weibull parameters for th e three specimen types at various temperatures. The results have shown that the parameters determined using notched tensile specimens can be regarded as temperature independent. However, the parameters determin ed using notched bend and fracture mechanics specimens exhibited some dependence on temperature. There were also differences between the Wei bull parameters determined from the different specimen geometries. The results show that there is a need to further develop the 'Local Appro ach' to cleavage fracture to incorporate effects of temperature and pl astic constraint. At present, it is recommended that fracture mechanic s specimens be used for the determination of Weibull parameters if the results are to be applied to cracked structures.