Improving the understanding of the long term rate dependent behaviour of materials is of critical
importance in many engineering applications. Without this understanding, it is potentially difficult
to ensure safe and effective plant operation while simultaneously satisfying requirements
for sustainability and responsible resource management. In the present work, a thermodynamically-
based constitutive model is proposed to capture the rate sensitivity, the stress relaxation
and the accelerated cyclic softening observed during cyclic deformation of a P91 steel at
an elevated temperature (600°C). The model is developed within the framework of
Thermodynamics of Irreversible Processes and Generalized Standard Materials formalism,
thereby offering a thermodynamically grounded coupling of both viscoelasticity (semi-recoverable
strain accumulation at vastly different time scales) and viscoplasticity (irreversible strain
observed above the stress threshold). The later part combines a hyperbolic sine-power flow rule
with non-linear isothermal cyclic evolution of isotropic and kinematic hardening. The applicability
of the model to various mechanical loadings (e.g., cyclic tensile-compression tests, fatiguerelaxation
tests, anhysteretic tests) is validated by designing a heuristic optimisation program
based on a nonlinear least-squares function coupled with the Levenberg-Marquardt algorithm.
The optimisation procedure is informed (through the estimation of initial material parameter
estimates and objective function evaluation) by anhysteretic type experiential data only (wherein
long

مقاله ISI انگلیسی اصلی
سال انتشار:2018
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