The Experts below are selected from a list of 1731 Experts worldwide ranked by ideXlab platform

S B Leen - One of the best experts on this subject based on the ideXlab platform.

  • thermomechanical fatigue in 9 12cr steels life prediction models and the effect of tensile dwell periods
    International Journal of Fatigue, 2019
    Co-Authors: Richard A Barrett, Christopher J Hyde, Padraic E Odonoghue, S B Leen
    Abstract:

    Abstract This paper is concerned with the assessment of life prediction models for thermomechanical fatigue (TMF), with specific application to P91 steel. A program of TMF tests, including dwell periods, are performed to determine the role of thermomechanical loading on fatigue life. As expected, fatigue life under conventional TMF testing (no dwells) is governed by maximum applied stress and Inelastic Strain-Range. However, with the introduction of dwell periods, at maximum tensile stress during TMF loading, in-phase loading becomes the life-limiting case. This is attributed here to increased microstructural degradation and oxidation, associated with the dwell at peak temperature. Analysis of commonly used TMF life prediction models shows that the effect of dwell periods currently cannot be predicted for in-phase loading. Thus, it is concluded that physically-motivated approaches are required to successfully predict fatigue life under more complex (service) thermomechanical loading histories.

Richard A Barrett - One of the best experts on this subject based on the ideXlab platform.

  • thermomechanical fatigue in 9 12cr steels life prediction models and the effect of tensile dwell periods
    International Journal of Fatigue, 2019
    Co-Authors: Richard A Barrett, Christopher J Hyde, Padraic E Odonoghue, S B Leen
    Abstract:

    Abstract This paper is concerned with the assessment of life prediction models for thermomechanical fatigue (TMF), with specific application to P91 steel. A program of TMF tests, including dwell periods, are performed to determine the role of thermomechanical loading on fatigue life. As expected, fatigue life under conventional TMF testing (no dwells) is governed by maximum applied stress and Inelastic Strain-Range. However, with the introduction of dwell periods, at maximum tensile stress during TMF loading, in-phase loading becomes the life-limiting case. This is attributed here to increased microstructural degradation and oxidation, associated with the dwell at peak temperature. Analysis of commonly used TMF life prediction models shows that the effect of dwell periods currently cannot be predicted for in-phase loading. Thus, it is concluded that physically-motivated approaches are required to successfully predict fatigue life under more complex (service) thermomechanical loading histories.

W Hardin - One of the best experts on this subject based on the ideXlab platform.

  • thermomechanical fatigue and bithermal thermomechanical fatigue of a nickel base single crystal superalloy
    International Journal of Fatigue, 2012
    Co-Authors: Robert L Amaro, R. W. Neu, Stephen D Antolovich, Patxi Fernandezzelaia, W Hardin
    Abstract:

    Abstract Thermomechanical fatigue (TMF) is a critical damage process incurred by turbine components. The most common methods for simulating the operating conditions of turbine components are either in-phase (IP) or out-of-phase (OP) TMF tests. However, due to the constantly changing temperature and applied load profile, it is challenging to decouple dominant damage mechanisms occurring in the material when relying solely on TMF test conditions. Further, the time to perform low(er) Inelastic Strain Range TMF tests to failure can be cumbersome. This work proposes implementation of bithermal fatigue (BiF) tests to address these issues. Out-of-phase BiF tests are Strain-controlled fatigue tests whereby a single cycle consists of an isothermal compressive half-cycle at the maximum temperature, followed by stress-free temperature change to the minimum temperature; the tensile half-cycle then occurs isothermally at the minimum temperature, followed by stress-free temperature change to the maximum temperature. Both conventional OP TMF and OP BiF tests were performed on nominally 〈0 0 1〉 oriented single crystal superalloy specimens. When plotting test results as Inelastic Strain Range versus cycles to crack initiation, the OP BiF results exhibit a clear demarcation from the TMF data at a particular value of Inelastic Strain Range; above which the results are primarily fatigue dominated and follow the trend of the OP TMF tests while below the results are environmentally dominated, creating a separate trend. Thermally-activated base material degradation supports the theory of damage driver segregation. A relationship is proposed relating the Inelastic Strain of BiF to that of TMF, for identical lives, within the environmentally dominated fatigue region. Finally, a life prediction model is proposed that includes fatigue and environmentally assisted damage mechanisms, which enables the life estimation of either test type. These relationships enable the use of BiF tests in place of, or in conjunction with, TMF tests, thereby providing insight into the dominant damage mechanisms present during testing and simplifying life prediction for more complex TMF cycles.

Y S Yoo - One of the best experts on this subject based on the ideXlab platform.

  • a comparative study on thermomechanical and low cycle fatigue failures of a single crystal nickel based superalloy
    International Journal of Fatigue, 2011
    Co-Authors: Hyunuk Hong, J G Kang, B G Choi, I S Kim, Y S Yoo
    Abstract:

    Abstract The cyclic deformation and lifetime behaviors of a single crystal nickel-based superalloy CMSX-4 have been investigated under out-of-phase thermomechanical fatigue (OP TMF) and isothermal low cycle fatigue (LCF) conditions. OP TMF life exhibited less than a half of LCF life although smaller Inelastic Strain Range and lower mean stress level during OP TMF were observed compared to those during LCF. During OP TMF cycling, the maximum tensile Strain at the minimum temperature was found to accelerate the surface crack initiation and propagation. Additionally, the multiple groups of parallel twin plates near crack provided a preferential path for crack propagation.

Christopher J Hyde - One of the best experts on this subject based on the ideXlab platform.

  • thermomechanical fatigue in 9 12cr steels life prediction models and the effect of tensile dwell periods
    International Journal of Fatigue, 2019
    Co-Authors: Richard A Barrett, Christopher J Hyde, Padraic E Odonoghue, S B Leen
    Abstract:

    Abstract This paper is concerned with the assessment of life prediction models for thermomechanical fatigue (TMF), with specific application to P91 steel. A program of TMF tests, including dwell periods, are performed to determine the role of thermomechanical loading on fatigue life. As expected, fatigue life under conventional TMF testing (no dwells) is governed by maximum applied stress and Inelastic Strain-Range. However, with the introduction of dwell periods, at maximum tensile stress during TMF loading, in-phase loading becomes the life-limiting case. This is attributed here to increased microstructural degradation and oxidation, associated with the dwell at peak temperature. Analysis of commonly used TMF life prediction models shows that the effect of dwell periods currently cannot be predicted for in-phase loading. Thus, it is concluded that physically-motivated approaches are required to successfully predict fatigue life under more complex (service) thermomechanical loading histories.