A generalisation of the Wilshire-Scharning methodology to creep life prediction with application to 1Cr-1Mo-0.25 V rotor steel

摘要

Wilshire-Scharning have recently developed a new methodology that has been demonstrated to deliver accurate longer term creep life predictions, and so offers the prospect of cost-effective acquisition of long-term creep design data. This methodology differs from existing approaches to creep life prediction by normalising the applied stress through the appropriate tensile strength. This article develops a generalisation of this Wilshire-Scharning model that has the potential to increase the predictive accuracy of this methodology-which will be so essential if it is to be adopted as a way of economising on the acquisition of creep design data. When applied to 1Cr-1Mo-0.25 V steel, it was found that this generalisation reduced the average error in prediction from 2.5 under the Wilshire-Scharning specification to 1.8 years when extrapolating from 5,000 out to over 100,000 h. Further, over this time scale the generalised model produces a mean absolute percentage error of 28%. This compares to 47% obtained using the traditional 4 Theta projection technique and 26% using a modification of this methodology as recently proposed by Evans.