A simple method to estimate elastic follow-up factors for transient creep parameter C(t) under secondary stress

Abstract

In this article, a semi-analytical method to estimate elastic follow-up factor as input to estimate the transient creep C(t) parameter under secondary loading is presented and validated against finite element results for a cracked two-bar structure under constant displacement loading. Predicted values of C(t) agree well with the finite element results for both elastic-creep cases and for elastic-plastic cases with the same creep and plastic hardening exponents. For elastic-plasticcreep cases with different creep and plastic hardening exponents, the proposed method gives good predictions at long time but can under-or over-predict C(t) at short time.

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

“…Writing the expression for elastic follow-up in the form of the second part of Eq. ( 6) enables ) , as shown in [12][13][14][15] and here in Fig. 1.…”

“…Results for elastic follow-up factor have also been obtained by Je et al [15] for a cracked two-bar structure under displacement control. A range of crack sizes (a/t=0.1, 0.3, 0.5) and Ramberg-Osgood description of plastic properties, with stress exponents m=5 and 10, were considered.…”

“…. This expression for elastic follow-up factor has been used by Fujioka [12,13], for example, for relaxation of displacement controlled loading in uncracked structures, by Fujioka [14] for cracked structures and more recently by Je et al [15] for creep relaxation of crack-tip fields in cracked structures. Writing the expression for elastic follow-up in the form of the second part of Eq.…”

“…This has been examined by Je et al [15] and is set out more explicitly in Section 3.2. First, however, a discussion of the results of [12][13][14][15] is given in Section 3.1 to indicate the expected dependence of elastic follow-up on load magnitude. ) and the corresponding strain difference are small and hence it is unlikely that € Z s can be determined with accuracy.…”

“…From values of J, and hence V 0 from Eq. (5), Je et al [15] used the elastic-plastic definition of elastic follow-up factor given by Eq. (6) and shown in Figure 1 and evaluated € Z s .…”