MDPI - Publisher of Open Access Journals

22 pages, 14643 KiB

Open AccessArticle

A Method for the Life Assessment of Aero-Engine Turbine Disks Based on a Time-Varying Load Spectrum

by Shunyu Yao, Xuming Niu, Zhigang Sun and Yingdong Song

Aerospace 2025, 12(5), 423; https://doi.org/10.3390/aerospace12050423 - 9 May 2025

Viewed by 543

The load spectrum serves as the foundation for the life analysis of aero-engine turbine disks. To enhance the accuracy of life assessments for turbine disks, this study compiles a time-varying load spectrum for turbine disks. Firstly, a surrogate model for transient processes at [...] Read more.

The load spectrum serves as the foundation for the life analysis of aero-engine turbine disks. To enhance the accuracy of life assessments for turbine disks, this study compiles a time-varying load spectrum for turbine disks. Firstly, a surrogate model for transient processes at the critical points of turbine disks is established, enabling the rapid evaluation of the transient temperature and thermal stress at these points under complex loading histories. Secondly, a performance degradation model is established based on real engine test data, explicitly describing the general trend of performance degradation characteristics with respect to the cycle number and engine power. Finally, a time-varying load spectrum for turbine disks is compiled, considering both short-term transient processes and long-term performance degradation. The life of turbine disks at the fir-tree slot root and disk bore is assessed using the Manson–Coffin equation, Wilshire equation, and linear damage accumulation rule. The results indicate that neglecting transient processes leads to conservative life assessment results while neglecting performance degradation leads to dangerous life assessment results. Compared with traditional methods, the time-varying load spectrum significantly improves the accuracy and scientific nature of turbine disk life assessment. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

45 pages, 11513 KiB

Open AccessArticle

Use of the Wilshire Equations to Correlate and Extrapolate Creep Data of Inconel 617 and Nimonic 105

by Vito Cedro III, Christian Garcia and Mark Render

Materials 2018, 11(12), 2534; https://doi.org/10.3390/ma11122534 - 13 Dec 2018

Cited by 9 | Viewed by 3765

Abstract

Advanced power plant alloys must endure high temperatures and pressures for durations at which creep data are often not available, necessitating the extrapolation of creep life. A recently developed creep life extrapolation method is the Wilshire equations, with which multiple approaches can be [...] Read more.

Advanced power plant alloys must endure high temperatures and pressures for durations at which creep data are often not available, necessitating the extrapolation of creep life. A recently developed creep life extrapolation method is the Wilshire equations, with which multiple approaches can be used to increase the goodness of fit of available experimental data and improve the confidence level of calculating long-term creep strength at times well beyond the available experimental data. In this article, the Wilshire equation is used to extrapolate the creep life of Inconel 617 and Nimonic 105 to 100,000 h. The use of (a) different methods to determine creep activation energy, (b) region splitting, (c) heat- and processing-specific tensile strength data, and (d) short-duration test data were investigated to determine their effects on correlation and extrapolation. For Inconel 617, using the activation energy of lattice self-diffusion as

Q_{C}^{*}

resulted in a poor fit with the experimental data. Additionally, the error of calculated rupture times worsened when splitting regions. For Nimonic 105, the error was reduced when heat- and processing-specific tensile strengths were used. Extrapolating Inconel 617 creep strength to 100,000 h life gave conservative results when compared to values calculated by the European Creep Collaborative Committee. Full article

► Show Figures

Figure 1

29 pages, 12518 KiB

Open AccessArticle

Use of the Wilshire Equations to Correlate and Extrapolate Creep Data of HR6W and Sanicro 25

by Vito Cedro, Christian Garcia and Mark Render

Materials 2018, 11(9), 1585; https://doi.org/10.3390/ma11091585 - 1 Sep 2018

Cited by 14 | Viewed by 4142

Abstract

Advanced power plant alloys must endure high temperatures and pressures for durations at which creep data are often not available, necessitating the extrapolation of creep life. Many methods have been proposed to extrapolate creep life, and one of recent significance is a set [...] Read more.

Advanced power plant alloys must endure high temperatures and pressures for durations at which creep data are often not available, necessitating the extrapolation of creep life. Many methods have been proposed to extrapolate creep life, and one of recent significance is a set of equations known as the Wilshire equations. With this method, multiple approaches can be used to determine creep activation energy, increase the goodness of fit of available experimental data, and improve the confidence level of calculating long-term creep strength at times well beyond the available experimental data. In this article, the Wilshire equation is used to extrapolate the creep life of HR6W and Sanicro 25, and different methods to determine creep activation energy, region splitting, the use of short-duration test data, and the omission of very-short-term data are investigated to determine their effect on correlation and calculations. It was found that using a known value of the activation energy of lattice self-diffusion, rather than calculating

Q_{C}^{*}

from each data set, is both the simplest and most viable method to determine

Q_{C}^{*}

. Region-splitting improved rupture time calculations for both alloys. Extrapolating creep life from short-term data for these alloys was found to be reasonable. Full article

► Show Figures

Figure 1

30 pages, 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 3 | Viewed by 4019

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 [...] Read more.

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)

► Show Figures

Figure 1

16 pages, 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 5 | Viewed by 4523

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)

► Show Figures

Figure 1

14 pages, 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 34 | Viewed by 9433

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)

► Show Figures

Figure 1

28 pages, 1033 KiB

Open AccessArticle

A Critical Analysis of the Conventionally Employed Creep Lifing Methods

by Zakaria Abdallah, Veronica Gray, Mark Whittaker and Karen Perkins

Materials 2014, 7(5), 3371-3398; https://doi.org/10.3390/ma7053371 - 29 Apr 2014

Cited by 59 | Viewed by 9705

Abstract

The deformation of structural alloys presents problems for power plants and aerospace applications due to the demand for elevated temperatures for higher efficiencies and reductions in greenhouse gas emissions. The materials used in such applications experience harsh environments which may lead to deformation [...] Read more.

The deformation of structural alloys presents problems for power plants and aerospace applications due to the demand for elevated temperatures for higher efficiencies and reductions in greenhouse gas emissions. The materials used in such applications experience harsh environments which may lead to deformation and failure of critical components. To avoid such catastrophic failures and also increase efficiency, future designs must utilise novel/improved alloy systems with enhanced temperature capability. In recognising this issue, a detailed understanding of creep is essential for the success of these designs by ensuring components do not experience excessive deformation which may ultimately lead to failure. To achieve this, a variety of parametric methods have been developed to quantify creep and creep fracture in high temperature applications. This study reviews a number of well-known traditionally employed creep lifing methods with some more recent approaches also included. The first section of this paper focuses on predicting the long-term creep rupture properties which is an area of interest for the power generation sector. The second section looks at pre-defined strains and the re-production of full creep curves based on available data which is pertinent to the aerospace industry where components are replaced before failure. Full article

(This article belongs to the Section Energy Materials)

► Show Figures

20 pages, 2487 KiB

Open AccessArticle

Recent Advances in Creep Modelling of the Nickel Base Superalloy, Alloy 720Li

by William Harrison, Mark Whittaker and Steve Williams

Materials 2013, 6(3), 1118-1137; https://doi.org/10.3390/ma6031118 - 20 Mar 2013

Cited by 31 | Viewed by 9287

Abstract

Recent work in the creep field has indicated that the traditional methodologies involving power law equations are not sufficient to describe wide ranging creep behaviour. More recent approaches such as the Wilshire equations however, have shown promise in a wide range of materials, [...] Read more.

Recent work in the creep field has indicated that the traditional methodologies involving power law equations are not sufficient to describe wide ranging creep behaviour. More recent approaches such as the Wilshire equations however, have shown promise in a wide range of materials, particularly in extrapolation of short term results to long term predictions. In the aerospace industry however, long term creep behaviour is not critical and more focus is required on the prediction of times to specific creep strains. The current paper illustrates the capability of the Wilshire equations to recreate full creep curves in a modern nickel superalloy. Furthermore, a finite-element model based on this method has been shown to accurately predict stress relaxation behaviour allowing more accurate component lifing. Full article

(This article belongs to the Special Issue Superalloys)

► Show Figures

Figure 1

Search Results (8)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (8)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI