The role of grain boundaries in creep strain accumulation

Wilshire, B.; Whittaker, Mark

doi:10.1016/j.actamat.2009.05.009

Cited by 24 publications

(27 citation statements)

References 39 publications

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“…Therefore rather than seeking to identify 'steady-state' creep mechanisms, the focus of the Wilshire approach is directed at the deformation processes that define strain accumulation, and the damage mechanisms that accumulate and lead to eventual failure [9]. This allows a minimum creep rate to be defined as a decaying primary rate is offset by tertiary acceleration.…”

Section: An Alternative To Power-law Based Equationsmentioning

confidence: 99%

“…In an initial investigation of Al7010, Wilshire observed that power-law equations struggle to deal with precipitation strengthened materials [9] due to their inherit assumption of diffusional creep. As such a study was carried out on the nickel superalloy Waspaloy.…”

Section: Mechanisms Of Waspaloymentioning

confidence: 99%

“…However, detailed inspection of normal creep strain/time curves show that a minimum creep rate, έ m, not a steady-state value is usually reached where the decaying primary rate is offset by the tertiary acceleration as seen in Figure 1. Rather than seeking to identify 'steady-state' mechanisms, emphasis should therefore be directed to the deformation processes governing strain accumulation and the various damage mechanisms causing the creep rate to accelerate, leading to eventual fracture [9].…”

Section: Power-law Creep Mechanismsmentioning

confidence: 99%

“…To demonstrate the application of the Wilshire Equations with respect to the power-law, the example of polycrystalline pure copper is first considered [9,36].…”

Section: Yield Behaviour Of Polycrystalline Coppermentioning

confidence: 99%

“…For pure aluminium, pure copper and the precipitate hardened Al7010, Wilshire and Whittaker [9], examined the creep curve beyond the 'steady-state' to identify the dominant creep mechanisms.…”

Section: The Wilshire Approachmentioning

confidence: 99%

See 4 more Smart Citations

A Modern Philosophy for Creep Lifing in Engineering Alloys

Whittaker¹,

Gray²,

Harrison³

2018

Creep

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Lifing of components which are likely to be subject to high temperature creep deformation is a critical area to a range of industries, particularly power generation and aerospace. In particular, extrapolation of short term data to predict long-term allowable creep stresses is an area of significant importance, since no appropriate method of accelerating tests has been discovered. Traditional methods for extrapolation are mainly based around power law type equations that have historically formed the basis of creep mechanism understanding. The current chapter however, seeks to offer alternative approaches in the field, particularly emphasising the need to link lifing approaches to observable micro-mechanical behaviour.

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Section: An Alternative To Power-law Based Equationsmentioning

confidence: 99%

Section: Mechanisms Of Waspaloymentioning

confidence: 99%

Section: Power-law Creep Mechanismsmentioning

confidence: 99%

“…To demonstrate the application of the Wilshire Equations with respect to the power-law, the example of polycrystalline pure copper is first considered [9,36].…”

Section: Yield Behaviour Of Polycrystalline Coppermentioning

confidence: 99%

Section: The Wilshire Approachmentioning

confidence: 99%

See 3 more Smart Citations

A Modern Philosophy for Creep Lifing in Engineering Alloys

Whittaker¹,

Gray²,

Harrison³

2018

Creep

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Improved Tensile Strength and SCC Resistance via Nonisothermal Creep Aging under a High Stress Level

Yi,

Xu,

Tang

et al. 2024

Adv Eng Mater

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Compared with conventional isothermal creep aging, non‐isothermal creep aging does not involve a prolonged holding stage, but only has heating and cooling stages. During the non‐isothermal creep aging process, the precipitates nucleate and grow up in the early part of heating stage, resulting in fluctuations in creep rate and an increase in strength. The coarsening of precipitates in the later part of the heating stage, can lead to significantly increase of creep rate. Upon approaching the peak temperature, the dissolution of the precipitates occurs in conjunction with a partial coarsening of the remaining precipitates, causing a reduction in strength. However, the secondary precipitation during the cooling stage facilities a significant strength enhancement in a relatively shorter period. In contrast to the isothermal creep aging, the targeted non‐isothermal creep aging treatment gives an increase in ultimate strength while improves the stress corrosion cracking resistance. Moreover, the time required for non‐isothermal creep aging to obtain ultimate strength is only 13.9 % of that of the ICA treatment. A large amount of creep strain can be generated during the NICA process, which is equivalent to 630 % of that of creep age forming treatment.This article is protected by copyright. All rights reserved.

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Advanced Procedures for Long-Term Creep Data Prediction for 2.25 Chromium Steels

Whittaker

Wilshire

2012

Metall Mater Trans A

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A critical review of recent creep studies concludes that traditional approaches such as steady-state behaviour, power law equations and the view that diffusional creep mechanisms are dominant at low stresses should be seriously reconsidered.Specifically, creep strain rate against time curves show that a decaying primary rate leads into an accelerating tertiary stage, giving a minimum rather than a secondary period. Conventional steady state mechanisms should therefore be abandoned in favour of an understanding of the processes governing strain accumulation and the damage phenomena causing tertiary creep and fracture. Similarly, creep always takes place by dislocation processes, with no change to diffusional creep mechanisms with decreasing stress, negating the concept of deformation mechanism maps. Alternative descriptions are then provided by normalizing the applied stress through the ultimate tensile stress and yield stress at the creep temperature. In this way, the resulting Wilshire equations allow accurate prediction of 100,000h creep data using only property values from tests lasting 5000h for a series of 2.25 chromium steels, namely Grades 22, 23 and 24.

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The role of grain boundaries in creep strain accumulation

Cited by 24 publications

References 39 publications

A Modern Philosophy for Creep Lifing in Engineering Alloys

A Modern Philosophy for Creep Lifing in Engineering Alloys

Improved Tensile Strength and SCC Resistance via Nonisothermal Creep Aging under a High Stress Level

Advanced Procedures for Long-Term Creep Data Prediction for 2.25 Chromium Steels

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