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On the Plastic Strain Accumulation in Notched Bars During High-Temperature Creep Dwell

Published online by Cambridge University Press:  21 February 2020

Daniele Barbera  and
Haofeng Chen
Daniele Barbera
Affiliation:
School of Engineering, System, Power and Energy Division, University of Glasgow, Glasgow, UK
Haofeng Chen*
Affiliation:
Department of Mechanical & Aerospace Engineering, University of Strathclyde, Glasgow, UK
*
*Corresponding author (haofeng.chen@strath.ac.uk)
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Abstract

Structural integrity plays an important role in any industrial activity, due to its capability of assessing complex systems against sudden and unpredicted failures. The work here presented investigates an unexpected new mechanism occurring in structures subjected to monotonic and cyclic loading at high temperature creep condition. An unexpected accumulation of plastic strain is observed to occur, within the high-temperature creep dwell. This phenomenon has been observed during several full inelastic finite element analyses. In order to understand which parameters make possible such behaviour, an extensive numerical study has been undertaken on two different notched bars. The notched bar has been selected due to its capability of representing a multiaxial stress state, which is a practical situation in real components. Two numerical examples consisting of an axisymmetric v-notch bar and a semi-circular notched bar are considered, in order to investigate different notches severity. Two material models have been considered for the plastic response, which is modelled by both Elastic-Perfectly Plastic and Armstrong-Frederick kinematic hardening material models. The high-temperature creep behaviour is introduced using the time hardening law. To study the problem several results are presented, as the effect of the material model on the plastic strain accumulation, the effect of the notch severity and the mesh element type and sensitivity. All the findings further confirm that the phenomenon observed is not an artefact but a real mechanism, which needs to be considered when assessing off-design condition. Moreover, it might be extremely dangerous if the cyclic loading condition occurs at such a high loading level.

Keywords

PlasticityCreepStructural Integrity
Type
Research Article
Information
Journal of Mechanics , Volume 36 , Issue 2 , April 2020 , pp. 167 - 176
Copyright
Copyright © 2020 The Society of Theoretical and Applied Mechanics

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