Fitting impact fracture toughness data in the transition region

A method is proposed for fitting the variation of the mean absorbed energy during impact tests at different temperatures. The three distinct regions of the variation: upper shelf, lower shelf and transition zone are treated independently, which reflects the different fracture mechanisms associated with them. During impact tests, the amount of energy absorbed for fracture is controlled by the volume fraction of the regions fractured by a ductile mechanism. Accordingly, an equation has been derived to describe the variation of the mean impact energy in the transition region. The numerical procedure developed allows the model parameters to be determined with a high precision. No assumptions are made regarding the distribution of the impact values at a fixed test temperature, which makes the model appropriate for a wide variety of impact data sets.