Journal: Materials at High Temperatures

Abbreviation

Publisher

Maney

Journal Volumes

ISSN

0960-3409
1878-6413

Description

Filters

2014 - 20154
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Publications1 - 4 of 4
  • Temperature and stress-regime dependent primary-secondary-tertiary creep constitutive model
    Item type: Journal Article
    Hosseini, E.; Holdsworth, S. R.; Mazza, Edoardo (2015)
    Materials at High Temperatures
    High temperature deformation analysis of components such as steam turbine rotors requires a knowledge of the material deformation response for a wide range of stresses and temperatures. Deformation analysis of steam turbine rotors deals with stresses ranging above the material proof strength (shortly after plant start-up) down to those responsible for very long rupture durations (for the steady running phase of operation) at various temperatures. This study describes the construction of a temperature and stress-regime dependent (primary-secondary-tertiary) creep constitutive model to provide a more reliable representation for the material deformation response over wide ranges of stresses and temperatures. The adopted equation set is a refinement of the 'Characteristic Strain' model and depends in its formulation mainly upon creep rupture data. Successful application of the model for a 1CrMoV steel for a wide range of stresses over the temperature range of 450-675°C is demonstrated.
  • Modelling heat-to-heat variability in high temperature cyclic deformation behaviour
    Item type: Journal Article
    Hosseini, E.; Holdsworth, S. R.; Kuhn, I.; et al. (2015)
    Materials at High Temperatures
    In high temperature engineering design, representations of the cyclic deformation behaviour of the material of the component are required as analysis data input to determine the stress-strain state at critical locations and ultimately component lifetime. While description of the cyclic stress-strain properties for a single heat of an alloy is relatively straightforward, even using complex constitutive model formulations, the same is not necessarily true for the derivation of mean or minimum alloy property representations. A novel method has recently been developed for this purpose. The concept is demonstrated for a high temperature steel for temperatures between 22°C and its maximum application temperature using the non-linear kinematic strain hardening model of Chaboche applied to the mid-life cyclic/hold data for a number of heats of the alloy.
  • Temperature dependent representation for Chaboche kinematic hardening model
    Item type: Journal Article
    Hosseini, E.; Holdsworth, S.R.; Kühn, I.; et al. (2015)
    Materials at High Temperatures
    The assessment of high temperature components under cyclic deformation conditions increasingly relies on determinations of the stress-strain state at the critical location using nonlinear finite element analysis. An important consideration in such finite element simulations is the used constitutive model. The Chaboche model has been widely accepted as an advanced model for such applications. This study evaluates the variation of Chaboche model parameters with temperature for low cycle fatigue conditions and introduces an approach to systematically calibrate the model for a range of temperatures, rather than for single temperatures. Furthermore, mathematical representations have been proposed to consider the effect of superimposed creep deformation on the Chaboche model parameters. Successful application of the proposed approach/formulation for representing the behaviour of a 10%Cr steel under low cycle fatigue and cyclic/hold deformation conditions for the temperature range of 20-625°C is presented.
  • Creep-fatigue crack development from short crack starters
    Item type: Journal Article
    Yan, W.-T.; Holdsworth, S.; Kühn, I.; et al. (2014)
    Materials at High Temperatures
    A series of isothermal strain controlled creep-fatigue tests on fully instrumented cylindrical specimens with shallow chordal crack starters has been conducted for an advanced 9%Cr turbine rotor steel at 600 and 625 °C. Cyclic/hold wave shapes involving a dwell period at peak strain in tension or compression were also performed with crack development being monitored by means of electrical potential drop instrumentation. It is found that temperature, total strain range and hold period are the most influential factors on short creep-fatigue crack propagation rates and specimen life. In order to establish a reliable relationship to represent subcritical crack development for high temperature component integrity assessment, the effectiveness of candidate correlating parameters such as cyclic strain range, cyclic J integral and strain energy density factor have been evaluated. Their application to circumstances involving short crack development due to fatigue, and interacting and non-interacting creep loading are evaluated with reference to the evidence determined from post-test metallurgical examination.
Publications1 - 4 of 4