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The Life of Materials at High Temperatures

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

Deadline for manuscript submissions: closed (15 May 2017) | Viewed by 42182

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Assoc. Prof. Dr. Mark Evans

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

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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:

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.
By quantifying the risks associated with extending the service life of existing power plants beyond their original design lives.
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

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Keywords

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

Published Papers (7 papers)

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Research

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2523 KiB

Open AccessArticle

Multiaxial Fatigue Damage Parameter and Life Prediction without Any Additional Material Constants

by Zheng-Yong Yu, Shun-Peng Zhu, Qiang Liu and Yunhan Liu

Materials 2017, 10(8), 923; https://doi.org/10.3390/ma10080923 - 09 Aug 2017

Cited by 76 | Viewed by 5574

Abstract

Based on the critical plane approach, a simple and efficient multiaxial fatigue damage parameter with no additional material constants is proposed for life prediction under uniaxial/multiaxial proportional and/or non-proportional loadings for titanium alloy TC4 and nickel-based superalloy GH4169. Moreover, two modified Ince-Glinka fatigue damage parameters are put forward and evaluated under different load paths. Results show that the generalized strain amplitude model provides less accurate life predictions in the high cycle life regime and is better for life prediction in the low cycle life regime; however, the generalized strain energy model is relatively better for high cycle life prediction and is conservative for low cycle life prediction under multiaxial loadings. In addition, the Fatemi–Socie model is introduced for model comparison and its additional material parameter k is found to not be a constant and its usage is discussed. Finally, model comparison and prediction error analysis are used to illustrate the superiority of the proposed damage parameter in multiaxial fatigue life prediction of the two aviation alloys under various loadings. Full article

(This article belongs to the Special Issue The Life of Materials at High Temperatures)

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4745 KiB

Open AccessArticle

A Combined High and Low Cycle Fatigue Model for Life Prediction of Turbine Blades

by Shun-Peng Zhu, Peng Yue, Zheng-Yong Yu and Qingyuan Wang

Materials 2017, 10(7), 698; https://doi.org/10.3390/ma10070698 - 26 Jun 2017

Cited by 97 | Viewed by 7670

Abstract

Combined high and low cycle fatigue (CCF) generally induces the failure of aircraft gas turbine attachments. Based on the aero-engine load spectrum, accurate assessment of fatigue damage due to the interaction of high cycle fatigue (HCF) resulting from high frequency vibrations and low cycle fatigue (LCF) from ground-air-ground engine cycles is of critical importance for ensuring structural integrity of engine components, like turbine blades. In this paper, the influence of combined damage accumulation on the expected CCF life are investigated for turbine blades. The CCF behavior of a turbine blade is usually studied by testing with four load-controlled parameters, including high cycle stress amplitude and frequency, and low cycle stress amplitude and frequency. According to this, a new damage accumulation model is proposed based on Miner’s rule to consider the coupled damage due to HCF-LCF interaction by introducing the four load parameters. Five experimental datasets of turbine blade alloys and turbine blades were introduced for model validation and comparison between the proposed Miner, Manson-Halford, and Trufyakov-Kovalchuk models. Results show that the proposed model provides more accurate predictions than others with lower mean and standard deviation values of model prediction errors. Full article

(This article belongs to the Special Issue The Life of Materials at High Temperatures)

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7234 KiB

Open AccessArticle

Fatigue Lifetime of Ceramic Matrix Composites at Intermediate Temperature by Acoustic Emission

by Elie Racle, Nathalie Godin, Pascal Reynaud and Gilbert Fantozzi

Materials 2017, 10(6), 658; https://doi.org/10.3390/ma10060658 - 16 Jun 2017

Cited by 29 | Viewed by 4928

Abstract

The fatigue behavior of a Ceramic Matrix Composite (CMC) at intermediate temperature under air is investigated. Because of the low density and the high tensile strength of CMC, they offer a good technical solution to design aeronautical structural components. The aim of the present study is to compare the behavior of this composite under static and cyclic loading. Comparison between incremental static and cyclic tests shows that cyclic loading with an amplitude higher than 30% of the ultimate tensile strength has significant effects on damage and material lifetimes. In order to evaluate the remaining lifetime, several damage indicators, mainly based on the investigation of the liberated energy, are introduced. These indicators highlight critical times or characteristic times, allowing an evaluation of the remaining lifetime. A link is established with the characteristic time around 25% of the total test duration and the beginning of the matrix cracking during cyclic fatigue. Full article

(This article belongs to the Special Issue The Life of Materials at High Temperatures)

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1838 KiB

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

by Mark Evans

Materials 2017, 10(6), 575; https://doi.org/10.3390/ma10060575 - 24 May 2017

Cited by 4 | Viewed by 3902

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 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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3074 KiB

Open AccessArticle

A New Energy-Critical Plane Damage Parameter for Multiaxial Fatigue Life Prediction of Turbine Blades

by Zheng-Yong Yu, Shun-Peng Zhu, Qiang Liu and Yunhan Liu

Materials 2017, 10(5), 513; https://doi.org/10.3390/ma10050513 - 08 May 2017

Cited by 85 | Viewed by 7696

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 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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10275 KiB

Open AccessArticle

Creep Deformation by Dislocation Movement in Waspaloy

by Mark Whittaker, Will Harrison, Christopher Deen, Cathie Rae and Steve Williams

Materials 2017, 10(1), 61; https://doi.org/10.3390/ma10010061 - 12 Jan 2017

Cited by 28 | Viewed by 8307

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 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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Review

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2453 KiB

Open AccessFeature PaperReview

A Review of Statistical Failure Time Models with Application of a Discrete Hazard Based Model to 1Cr1Mo-0.25V Steel for Turbine Rotors and Shafts

by Mark Evans

Materials 2017, 10(10), 1190; https://doi.org/10.3390/ma10101190 - 17 Oct 2017

Cited by 2 | Viewed by 3349

Abstract

Producing predictions of the probabilistic risks of operating materials for given lengths of time at stated operating conditions requires the assimilation of existing deterministic creep life prediction models (that only predict the average failure time) with statistical models that capture the random component of creep. To date, these approaches have rarely been combined to achieve this objective. The first half of this paper therefore provides a summary review of some statistical models to help bridge the gap between these two approaches. The second half of the paper illustrates one possible assimilation using 1Cr1Mo-0.25V steel. The Wilshire equation for creep life prediction is integrated into a discrete hazard based statistical model—the former being chosen because of its novelty and proven capability in accurately predicting average failure times and the latter being chosen because of its flexibility in modelling the failure time distribution. Using this model it was found that, for example, if this material had been in operation for around 15 years at 823 K and 130 MPa, the chances of failure in the next year is around 35%. However, if this material had been in operation for around 25 years, the chance of failure in the next year rises dramatically to around 80%. Full article

(This article belongs to the Special Issue The Life of Materials at High Temperatures)

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