A simplified creep-reverse plasticity solution method for bodies subjected to cyclic loading (original) (raw)
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Creep deformation and failure under cyclic thermal loading
Nuclear Engineering and Design, 1989
The purpose of the present paper is to demonstrate how the results of limit load and shakedown analyses can be utilised in the prediction of the deformation characteristics and life of structures subjected to cyclic thermal loading. The structural response is described in terms of a material test conducted at a constant reference stress and a cyclic reference temperature history. Simple expressions for these quantities are given for deformation which require a knowledge of the limit load and shakedown boundary and the resulting mechanisms of collapse and incremental deformation beyond shakedown. A procedure is described for evaluating the time-to-failure, where the results depend on the shape of the isochronous surface in stress space. For an effective stress material the resulting reference quantities are the same as those for deformation.
International Journal of Fatigue, 2018
Creep-cyclic plasticity of a benchmarked holed plate subjected to thermo-mechanical loading is investigated by means of nonlinear finite element analysis. From the analyses, a structural creep recovery response is found within a dwell period, which has serious repercussions on structural integrity. The structural creep recovery can take place by reversing the creep stress in sign during the stress relaxation due to the creep stress redistribution, consequently enhancing unloading plasticity which causes a substantial increase of total strain range within a cycle. Based on this critical observation, further analyses and discussions are provided to investigate the root cause of this precautious structural response. Various cyclic loadings with a dwell at the peak thermal load are analysed to define factors influencing the structural creep recovery mechanism, and to investigate how the mechanism affects the lifetime of the structure. To show the effectiveness of the structural creep recovery mechanism under cyclic loading, Chaboche nonlinear kinematic hardening model is adopted. Limitations of applying elastic follow-up in predicting creep strains and appropriate creepfatigue damage calculation methods are discussed in the presence of this structural creep recovery mechanism. This research work confirms that when a structure experiences the structural creep recovery it can reduce creep damage, nevertheless the structure may experience significant fatigue damage due to creep enhanced plasticity.
European Journal of Mechanics - A/Solids, 2001
- A method for the evaluation of a ratchet limit and the amplitude of plastic strain for bodies subjected to cyclic loading. European Journal of Mechanics -A/Solids, 20 (4). pp. 555-571. ISSN 0997-7538 Strathprints is designed to allow users to access the research output of the University of Strathclyde. . (2001) A method for the evaluation of a ratchet limit and the amplitude of plastic strain for bodies subjected to cyclic loading. European Journal of Mechanics. A/Solids, 20 (4). pp. 555-571. ISSN 0997-7538 Abstract: By extending the elastic shakedown analysis, the plastic shakedown theory and basic relations to locate the ratchet limit of the structures subjected to variable load and temperature has been represented in paper [1]. Here numerical solutions of ratchet limit as well as shakedown and limit load for BREE problem and the 3-D holed plate are calculated. The maximums of the varying plastic strain magnitudes obtained by proposed method are compared with the Neuber approximate values. The positions of the ratchet boundary are confirmed by the analytical solutions or other numerical results via ABAQUS step-by-step analyses.
Numerical schemes based on the stress compensation method framework for creep rupture assessment
European Journal of Mechanics - A/Solids, 2020
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.
Constitutive modeling of cyclic plasticity and creep, using an internal time concept
International Journal of Plasticity, 1986
Using the concept of an internal time as related to plastic strains, a differential stressstrain relation for elastoplasticity is rederived, such that (i) the concept of a yield-surface is retained; (ii) the definitions ot~ elastic and plastic processes are analogous to those in classical plasticity theory; and (iii) its computational implementation, via a "tangent-stiffness" finite element method and a "generalized-midpoint-radial-return" stress-integration algorithm, is simple and efficient. Also, using the concept of an internal time, as related to both the inelastic strains as well as the Newtonian time, a constitutive model for creep-plasticity interaction, is discussed. The problem of modeling experimental data for plasticity and creep, by the present analytical relations, as accurately as desired, is discussed. Numerical examples which illustrate the validity of the present relations are presented for the cases of cyclic plasticity and creep.
Modelling of creep and plasticity deformation considering creep damage and kinematic hardening
Engineering Fracture Mechanics, 2019
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Study of creep relaxation under combined mechanical and residual stresses
Engineering Fracture Mechanics, 2012
In this work the elastic and elastic-plastic creep behaviour of cracked structures in the presence of residual stress has been studied numerically. The residual stress is introduced by prior mechanical loading and mechanical stress levels are varied to evaluate the transient crack tip parameter, C(t), in single edge notch bend, SEN (B), and tension, SEN (T), specimens, using the finite-element (FE) method. The near tip stress distributions are examined and the influence of residual stress on the evolution of the stress fields, quantified by C(t), is examined. The values of C(t) obtained from the FE analysis are compared to existing analytical solutions. It has been found that the transient C(t) value provides an accurate characterisation of the crack tip fields under combined primary and secondary stress. It has also been found that the level of conservatism of current C(t) estimation schemes, which account for primary and secondary stress, depends on material properties and the level of primary and secondary stress.
Creep-Fatigue Lifetime Assessment with Phenomenological and Constitutive Material Laws
Procedia Engineering, 2013
Variations in steam temperature due to start-up a thermomechanical stresses, which can lead to fatigu heated surface. With respect to component integrit mandatory. Lifetime assessment models have bee conducted. This paper presents a comparison and phenomenological approach, based on the generaliz account creep rupture damage at stress relaxation as as is an enhanced interaction method for the influenc viscoplastic constitutive material model of the type C of the types 1CrMoNiV (1Cr), 2CrMoNiWV (2Cr), The model allows the recalculation of the material be applicability and accuracy of the models is finally uniaxial and multiaxial experiments on notched speci