Fracture assessments with elastic follow-up for combined primary and secondary loadings part 1: Predictive models

This paper reviews the definition of elastic follow-up starting with that used in creep assessments and seeking parallel definitions for the treatment of combined primary and secondary loadings in fracture assessments. Methods for estimating the elastic follow-up factor for secondary stresses acting alone in cracked structures are then presented. It is shown that elastic follow-up factors can be estimated from elastic-plastic estimates of J for high secondary stress and are weakly dependent on elastic-plastic material properties. Potential methods for estimating J under combined primary and secondary loadings, using the elastic follow-up factor evaluated for secondary stresses acting alone, are then presented. The applicability of these methods is examined in part 2 of this paper by comparison with detailed finite element calculations.