Structural integrity assessment of engineering components under cyclic loading at high temperature

  • Nak-Kyun CHO

Student thesis: Doctoral Thesis


Structural integrity assessment is essential for many industries, especially for industries which have machinery components and structures in operation at high temperature. Nuclear power plant industry is one of a good example, and they have planned to introduce the very high temperature reactor to increase efficiency. The high temperature operations may improve power productions but cause severe structural problems due to creep, fatigue, creep-fatigue failure mechanisms. Hence, performing structural integrity assessment accurately and developing effective assessment methods are vital tasks in these industries.;In order to contribute to the research field of the high temperature industries, this thesis have achieved the following three main objectives:;Firstly, this thesis provides insights into cyclic plasticity and creep-cyclic plasticity behaviours of high temperature engineering problems which have not been explored in the past. A numerical study investigates cyclic plasticity behaviours of 90° back-to-back pipe bends under cyclic thermo-mechanical load and constant pressure. Another numerical study investigates creep-cyclic plasticity behaviours of Particle Reinforced Titanium Matrix Composites (PRTMCs), which is a futuristic engineering material, subjected to a cyclic thermo-mechanical load. Both numerical studies are carried out using a novel direct method called The LMM Framework;Secondly, this thesis has enhanced the LMM Framework allowing to evaluate the structural response in non-isothermal condition and multiple dwell periods. In order to demonstrate this, the extended method is applied to analyse creep-cyclic plasticity behaviour of a superheater outlet tube plate subjected to a cyclic thermo-mechanical load, and to evaluate creep-fatigue damage endurance;Finally, this thesis introduces a critical high temperature failure mechanism, named as Structural Creep Recovery Mechanism (SCRM), utilising a numerical technique involving cyclic creep and plastic behaviours. This study identifies the cause of this critical failure mechanism and defines factors that have substantial influences on the structural integrity in the presence of SCRM. Chaboche nonlinear kinematic hardening model and temperature dependent material parameters are employed to demonstrate the effectiveness of SCRM in practical problems.
Date of Award29 Mar 2019
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorHaofeng Chen (Supervisor) & Robert Hamilton (Supervisor)

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