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Special Issue "The Life of Materials at High Temperatures"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (15 May 2017)

Special Issue Editor

Guest Editor
Assoc. Prof. Dr. Mark Evans

College of Engineering, Swansea University, Singleton Park, Swansea, SA2 8PP, UK
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Special Issue Information

Dear Colleagues,

With many countries, such as the UK and the USA, currently facing a potential future mismatch between energy supply and demand, there is currently heightened interest in techniques that can accurately life critical components operating at high temperatures. Such techniques can help alleviate potential energy gaps in a number of different ways:

  1. By speeding up the time required for new experimental alloys to be considered as safe for use in new more efficient power plants designed to operate at higher temperatures.
  2. By quantifying the risks associated with extending the service life of existing power plants beyond their original design lives.
  3. By quantifying the tendency to under estimate safe life due to oxidation and other failure mechanisms and thereby extending the safe service life of existing power plants.

Whilst creep damage is temperature specific, other mechanisms, such a fatigue, surface oxidation and internal corrosion, interact with creep to have significant effects on high temperature damage accumulation and many different approaches are used to life materials at high temperature. At one end of the spectrum there are the fundamental mechanism based models that describe high temperature behaviour in terms of specific phenomenon and rely on microscopic parameters that are sometimes difficult to quantify. At the other end of the spectrum are the empirical models that can provide deterministic and probabilistic life assessments by extrapolation from short-term data sets on macroscopic properties such as strain and rupture time. In between these, are the models based on continuum damage mechanics (CDM) that relate strain to measurable external and internal variables. Often these approaches are combined, for example, when constitutive models are incorporated into finite element and other numerical models to predict the creep strain of complex components or the deformation of miniature disc specimens. Finally, there is increasing demand for non-destructive techniques and miniature specimen techniques (such as the small punch test) that can determine the remaining life of in service components.

It is my pleasure to invite you to submit a manuscript related to the lifeing of any material in any high temperature application for this Special Issue.

Assoc. Prof. Dr. Mark Evans
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Failure mechanisms (e.g. Creep)
  • Life Assessment techniques
  • High temperature materials
  • Damage/degradation

Published Papers (3 papers)

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Research

Open AccessFeature PaperArticle A Re-Evaluation of the Causes of Deformation in 1Cr-1Mo-0.25V Steel for Turbine Rotors and Shafts Based on iso-Thermal Plots of the Wilshire Equation and the Modelling of Batch to Batch Variation
Materials 2017, 10(6), 575; doi:10.3390/ma10060575
Received: 26 April 2017 / Revised: 18 May 2017 / Accepted: 20 May 2017 / Published: 24 May 2017
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Abstract
The aims of this paper were to: (a) demonstrate how iso-thermal plots of the Wilshire equation can be used to identify the correct structure of this equation (which in turn enables a meaningful description of the creep mechanism involved in deformation to be
[...] Read more.
The aims of this paper were to: (a) demonstrate how iso-thermal plots of the Wilshire equation can be used to identify the correct structure of this equation (which in turn enables a meaningful description of the creep mechanism involved in deformation to be made); and (b) show how a generalized specification of batch to batch variation could produce less conservative predictions of the time to failure associated with a given degree of risk. Such predictions were obtained using maximum likelihood estimation of the parameters of a generalised F distribution. It was found that the original Wilshire-Scharning assumption of a constant activation energy for this materials is incorrect. Consequently, their interpretation of deformation being due only to dislocation creep with deteriorating microstructure at long duration test times appears to be ill founded, with the varying activation energy suggesting instead that deformation is due to grain boundary sliding accommodated by either dislocation and diffusional creep with dominance changing from the lattice to the grain boundaries as the temperature changes. Modelling batch to batch variation as a function of stress also resulted in a 50% extended safe life prediction (corresponding to a 1% chance of failure) at 873 K and 47 MPa. Full article
(This article belongs to the Special Issue The Life of Materials at High Temperatures)
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Open AccessArticle A New Energy-Critical Plane Damage Parameter for Multiaxial Fatigue Life Prediction of Turbine Blades
Materials 2017, 10(5), 513; doi:10.3390/ma10050513
Received: 22 March 2017 / Revised: 2 May 2017 / Accepted: 4 May 2017 / Published: 8 May 2017
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Abstract
As one of fracture critical components of an aircraft engine, accurate life prediction of a turbine blade to disk attachment is significant for ensuring the engine structural integrity and reliability. Fatigue failure of a turbine blade is often caused under multiaxial cyclic loadings
[...] Read more.
As one of fracture critical components of an aircraft engine, accurate life prediction of a turbine blade to disk attachment is significant for ensuring the engine structural integrity and reliability. Fatigue failure of a turbine blade is often caused under multiaxial cyclic loadings at high temperatures. In this paper, considering different failure types, a new energy-critical plane damage parameter is proposed for multiaxial fatigue life prediction, and no extra fitted material constants will be needed for practical applications. Moreover, three multiaxial models with maximum damage parameters on the critical plane are evaluated under tension-compression and tension-torsion loadings. Experimental data of GH4169 under proportional and non-proportional fatigue loadings and a case study of a turbine disk-blade contact system are introduced for model validation. Results show that model predictions by Wang-Brown (WB) and Fatemi-Socie (FS) models with maximum damage parameters are conservative and acceptable. For the turbine disk-blade contact system, both of the proposed damage parameters and Smith-Watson-Topper (SWT) model show reasonably acceptable correlations with its field number of flight cycles. However, life estimations of the turbine blade reveal that the definition of the maximum damage parameter is not reasonable for the WB model but effective for both the FS and SWT models. Full article
(This article belongs to the Special Issue The Life of Materials at High Temperatures)
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Open AccessArticle Creep Deformation by Dislocation Movement in Waspaloy
Materials 2017, 10(1), 61; doi:10.3390/ma10010061
Received: 25 October 2016 / Revised: 5 January 2017 / Accepted: 5 January 2017 / Published: 12 January 2017
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Abstract
Creep tests of the polycrystalline nickel alloy Waspaloy have been conducted at Swansea University, for varying stress conditions at 700 °C. Investigation through use of Transmission Electron Microscopy at Cambridge University has examined the dislocation networks formed under these conditions, with particular attention
[...] Read more.
Creep tests of the polycrystalline nickel alloy Waspaloy have been conducted at Swansea University, for varying stress conditions at 700 °C. Investigation through use of Transmission Electron Microscopy at Cambridge University has examined the dislocation networks formed under these conditions, with particular attention paid to comparing tests performed above and below the yield stress. This paper highlights how the dislocation structures vary throughout creep and proposes a dislocation mechanism theory for creep in Waspaloy. Activation energies are calculated through approaches developed in the use of the recently formulated Wilshire Equations, and are found to differ above and below the yield stress. Low activation energies are found to be related to dislocation interaction with γ′ precipitates below the yield stress. However, significantly increased dislocation densities at stresses above yield cause an increase in the activation energy values as forest hardening becomes the primary mechanism controlling dislocation movement. It is proposed that the activation energy change is related to the stress increment provided by work hardening, as can be observed from Ti, Ni and steel results. Full article
(This article belongs to the Special Issue The Life of Materials at High Temperatures)
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