  A micromechanical model at the microscale within a crystal plasticity
self-consistent model, is used to analyse loading histories in Type 316H
stainless steel, common to structural components in high-temperature power
plants. The study compares the SCM predictions on changes in mechanical
behaviour and creep properties to analyses via the UK R5 structural assessment
code. Plant-relevant cyclic-creep histories in Type 316H stainless steel at
550C are examined with focus on the estimation of accumulated creep strain.
This aims to quantify how better understanding of creep deformation under
cyclic loading can inform R5 code life assessment methods, which are strain
based. The effect of cyclic plasticity on primary and secondary creep is
quantified. The levels of creep strain accumulated during different dwells,
following loading from different macroscopic stress states, is also evaluated
and link is made to experimental observations in explaining the response. The
impact of displacement- and load-controlled dwells on the evolution of the
cyclic hysteresis loop is examined which revealed how different assumptions for
creep strain accumulation could employ information from SCM results to reduce
uncertainty. It also provides guidance in the development of interpolation
frameworks for structural parameters, based on the SCM results which could be
used directly in structural assessment and design approaches to estimate the
accumulation of inelastic strain with a lower degree of conservatism.
