Probabilistic LCF Risk Evaluation of a Turbine Vane by Combined Size Effect and Notch Support Modeling

Mäde, Lucas; Gottschalk, Hanno; Schmitz, Sebastian; Beck, Tilmann; Rollmann, Georg

doi:10.1115/gt2017-64408

Cited by 20 publications

(14 citation statements)

References 5 publications

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“…Although notches may promote crack initiation, there is also a tendency for conventional lifing methods to underestimate the fatigue life of the component if the lifing method is applied using the notch root stress. The phenomenon is sometimes referred to as notch support [2,3] and arises from the fact that (typically) a very small material volume is exposed to the high notch root stress; ahead of the notch, stresses typically drop significantly.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Notches on the Fatigue Life of a Nickel-Base Gas Turbine Disk Material

Eriksson¹,

Moverare²,

Chen³

et al. 2018

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Gas turbine disks carry significant load under high temperatures and may be subject to fatigue failure. Disks contain several notches in the form of the fir tree blade attachments. Low cycle fatigue tests were performed on blunt notch compact tension specimens made from alloy 718. The results indicated that notch support needed to be incorporated not to cause an overly conservative life prediction. The notch support diminished as the plastic strain range decreased, indicating that notch support is only present in the low cycle fatigue regime. A critical distance approach was applied to account for the notch support. An equation relating the critical distance to the notch root stress was derived. The chosen life model was formulated in terms of a variation on the Smith–Watson–Topper (SWT) parameter. The modified SWT parameter taken at the critical distance was used in a life model calibrated for smooth specimens to successfully predict the fatigue life of notched specimens.

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Section: Introductionmentioning

confidence: 99%

The Effect of Notches on the Fatigue Life of a Nickel-Base Gas Turbine Disk Material

Eriksson¹,

Moverare²,

Chen³

et al. 2018

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“…Low cycle fatigue (LCF)-driven surface crack initiation is particularly important for the reliability of highly loaded engineering parts as turbine components [38,46]. The design of such engineering parts therefore requires a model that is capable of accurately quantify risk levels for LCF crack initiation, crack growth and ultimate failure.…”

Section: Optimal Reliability and Efficiencymentioning

confidence: 99%

“…As this work is focused on the existence and the mathematical properties of the Pareto front in shape optimization, it does not contain any numerical and algorithmic contributions. However, numerical implementations for the computation of the reliability of failure can be found in [39,46]. The adjoint method for computing the shape derivatives for such objective functionals has been applied in [12,29,30].…”

Section: Introductionmentioning

confidence: 99%

An Analytical Study in Multi-physics and Multi-criteria Shape Optimization

Gottschalk

Reese

2021

J Optim Theory Appl

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A simple multi-physical system for the potential flow of a fluid through a shroud, in which a mechanical component, like a turbine vane, is placed, is modeled mathematically. We then consider a multi-criteria shape optimization problem, where the shape of the component is allowed to vary under a certain set of second-order Hölder continuous differentiable transformations of a baseline shape with boundary of the same continuity class. As objective functions, we consider a simple loss model for the fluid dynamical efficiency and the probability of failure of the component due to repeated application of loads that stem from the fluid’s static pressure. For this multi-physical system, it is shown that, under certain conditions, the Pareto front is maximal in the sense that the Pareto front of the feasible set coincides with the Pareto front of its closure. We also show that the set of all optimal forms with respect to scalarization techniques deforms continuously (in the Hausdorff metric) with respect to preference parameters.

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“…Recently, Mäde et al coupled the Coffin‐Manson‐Basquin (CMB) equation and Seibel's empirical formula into probabilistic low cycle fatigue (LCF) risk evaluation of turbine vanes. Specifically, the notch support factor n χ is utilized directly in the form of

1 + A_{χ} \times χ^{k_{χ}}

, where A χ and k χ are material‐dependent notch support parameters.…”

Section: Introductionmentioning

confidence: 99%

Recent advances on notch effects in metal fatigue: A review

Liao

Zhu

Correia

et al. 2020

Fatigue Fract Eng Mat Struct

161

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Notch features including holes, fillets, shoulders, and grooves commonly exist in engineering components. When subjected to external loads, these geometrical discontinuities generally act as stress raisers and thus present significant influences on the component strength and life, which are more remarkable under complex loading paths. Accordingly, numerous theories and approaches have been developed to address notch effects in metal fatigue as well as damage modelling and life predictions, which aim to provide theoretical support for structural optimal design and integrity evaluation. However, most of them are self‐styled or focus on specific objects, which limits their engineering applicability. This review recalls recent developments and achievements in notch fatigue modelling and analysis of metals. In particular, four commonly used methods for fatigue evaluation of metallic notched components/structures are summarized and elaborated, namely, nominal stress approaches, local stress‐strain approaches, and critical distance theories and weighting control parameters‐based approaches, which intend to provide a reference for further research on notch fatigue analysis and promote the integration and/or development among different approaches for practice.

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Probabilistic LCF Risk Evaluation of a Turbine Vane by Combined Size Effect and Notch Support Modeling

Cited by 20 publications

References 5 publications

The Effect of Notches on the Fatigue Life of a Nickel-Base Gas Turbine Disk Material

The Effect of Notches on the Fatigue Life of a Nickel-Base Gas Turbine Disk Material

An Analytical Study in Multi-physics and Multi-criteria Shape Optimization

Recent advances on notch effects in metal fatigue: A review

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