Design for creep

History-sensitive accumulation rules for life-time prediction under variable creep loading

“…in (Rabotnov, 1966;Penny & Marriott, 1971;Leckie & Hayhurst, 1974;Lokoshenko & Namestnikova, 1983). Note that the Monkman-Grant relationε mcr t * 0 = const also reduces to (32) if the power-type Norton relation is assumed between the applied stress and the minimum creep strain rateε mcr .…”

“…One of the most popular is the Robinson model (rule) of linear accumulation of partial life-times, (Robinson, 1938(Robinson, , 1952) (see also e.g. Rabotnov, 1969;Penny and Marriott, 1971), which allows to calculate the life-time t * = t * (σ) under a variable process σ(τ ) from the durability diagram under constant loads, t * 0 (σ), by equation ∫ t * 0 dτ t * 0 (σ(τ )) = 1.…”

3-D stochastic finite elements for thermal creep analysis of piping structures with spatial material inhomogeneities

“…However, with time, the effects of residual stresses due to the creep strains have contributions to the stress vector, and in turn, to the von Mises stress. The growth of the normal and shear creep strains with time is computed from the creep strain rate equations [15] and is highly nonlinear. This indicates that the creep damage growth as governed by Eq.…”

“…An inspection of Eqs. (12)(13)(14)(15) reveals that the spatial random variation of the elastic modulus implies a modification in the computation of the elemental load vector as well. Here, F t and F cr are seen to be dependent on elastic modulus and hence will have deterministic as well as stochastic components.…”

“…The deterministic components for thermal and creep loads are, respectively, denoted by F d t and F d cr and are identical to the expressions given in Eqs. (14) and (15)…”