Numerical schemes based on the stress compensation method framework for creep rupture assessment

Abstract

Evaluation of creep rupture limit and prediction of creep rupture life are two significant issues for high-temperature devices under the action of cyclic thermo-mechanical loadings. In this paper, the shakedown solution procedure proposed recently by the authors, so-called stress compensation method (SCM), is extended for creep rupture assessment via an extended shakedown theory including creep.Two distinct numerical schemes based on the SCM framework are presented, where Scheme 1 is utilised for evaluation of creep rupture limit and Scheme 2 is utilised for prediction of creep rupture life. Instead of using the detailed creep constitutive equations, the present methods just need to know several material parameters including the creep rupture data. A holed plate is provided as a typical example to validate the reliability of two numerical schemes. Detailed cycle-by-cycle analyses are carried out to illustrate the good accuracy of these calculated creep rupture limits and reveal the failure mechanisms of the structure under different combinations of loads. A numerical study on a pipe junction is also conducted to show the engineering application of the methods. As a result, the two numerical schemes are proved to be effective and reliable for solving practical industrial problems.

Structural topology optimization of elastoplastic continuum under shakedown theory

“…After decades of development, shakedown analysis methods mainly include three types: (1) mathematical programming method, such as the nonlinear Newton-type iteration algorithm, 5,6 the second-order cone programming (SOCP), 7 and various interior-point methods(IPM), [8][9][10] which are directly used to solve mathematical programming problem; (2) basis reduction method [11][12][13][14] which is to reduce the number of bases of self-equilibrated stress field thereby stipulating the number of unknowns and combine some optimization algorithm; and (3) some methods based on mechanics mechanism, which do not depend on the mathematical programming, such as the elastic compensation method (ECM), 15,16 the linear matching method (LMM), 17,18 the residual stress decomposition method for shakedown (RSDM-S), [19][20][21] and the stress compensation method (SCM). [22][23][24] In addition, based on the classical shakedown theory of elastic-perfectly plastic systems, many extensions of shakedown theory are developed for covering various engineering concerns, such as geometric nonlinearities, [25][26][27] creeping effect, 28 frictional contact 6,29 and so forth. In this article, the recently developed PEM method 30 is applied for shakedown analysis of elastic-perfectly plastic continuum.…”