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Use of Experiments, Computations and Models for HCF Design
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).ORCID iD: 0000-0003-0275-5557
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , 27 p.
Series
TRITA HFL, ISSN 1104-6813 ; 0569
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-160354ISBN: 978-91-7595-438-7 (print)OAI: oai:DiVA.org:kth-160354DiVA: diva2:789475
Presentation
2015-02-20, Semminarierummet Hållfasthetslära, Teknikringen 8D, KTH, Stockholm, 13:15 (English)
Opponent
Supervisors
Note

QC 20150219

Available from: 2015-02-19 Created: 2015-02-19 Last updated: 2015-03-02Bibliographically approved
List of papers
1. FE-mesh effect of the volume based weakest-link fatigue probability applied to a compressor blade
Open this publication in new window or tab >>FE-mesh effect of the volume based weakest-link fatigue probability applied to a compressor blade
2012 (English)In: Proceedings of the ASME Turbo Expo: Volume 7, Issue PARTS A AND B, 2012, ASME Press, 2012, no PARTS A AND B, 427-438 p.Conference paper, Published paper (Refereed)
Abstract [en]

When dealing with design process of compressor blades, predominantly deterministic models are used for High Cycle Fatigue (HCF) investigations. The existing scatter in factors such as material inhomogeneity of the blade material and loading condition is accounted for by safety factors that often end up in conservative designs. An alternative way to account for these uncertainties is the application of probabilistic models. More information about the scatter in different sources together with probabilistic models can lead to a more robust design process. In order to compute the stresses acting in a compressor blade, the Finite Element (FE) method is widely used as standard tool. This method may show mesh dependence. Therefore, mesh requirements always exist in FE computations. In this work, a probabilistic HCF investigation is carried out for a transonic compressor rotor blade. The sensitivity of the volume based weakest-link probabilistic model (WL) due to different mesh properties of the blade is investigated. The goal is to provide advice for better finite element meshing of the blades based on linear type solid elements for the computation of stress history. The mesh types of the blade are the input parameters for the probabilistic HCF investigation. A stress invariant based HCF local criterion, Sines, and a critical plane criterion, Findley, are used in weakest-link to describe the failure probability for the 12% Cr-steel material used for the compressor blade. The estimation of the weakestlink and the local HCF criteria material parameters are performed using HCF experimental data based on 2 million load cycles obtained for smooth and notched specimens. The study shows that the choice of the mesh property through the thickness of the compressor blade has much more effect on the failure probability predictions compared to the in-plane mesh property of the blade.

Place, publisher, year, edition, pages
ASME Press, 2012
Series
Proceedings of the ASME Turbo Expo, 7
Keyword
Conservative designs, Deterministic models, Experimental datum, Failure Probability, Finite element meshing, Material inhomogeneity, Probabilistic models, Transonic compressor rotor, Compressors, Exhibitions, Gas turbines, Loading, Product design, Safety factor, Finite element method
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-128976 (URN)10.1115/GT2012-69852 (DOI)000335868800048 ()2-s2.0-84881183212 (Scopus ID)978-079184473-1 (ISBN)
Conference
ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, GT 2012; Copenhagen; Denmark; 11 June 2012 through 15 June 2012
Note

QC 20130918

Available from: 2013-09-18 Created: 2013-09-17 Last updated: 2016-02-22Bibliographically approved
2. On the optimal choice of experiments for determination of parameters in multiaxial HCF-criteria
Open this publication in new window or tab >>On the optimal choice of experiments for determination of parameters in multiaxial HCF-criteria
2014 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 61, 315-324 p.Article in journal (Refereed) Published
Abstract [en]

Material parameters in multiaxial HCF-criteria must be estimated from experiments, which always are affected by scatter from several sources. A higher number of tests provides a more reliable parameter estimation, but the cost for the testing increases. In this paper, by starting from a known fatigue limit distribution for the titanium alloy Ti-6-4, test series are simulated according to different predefined test strategies. In Monte Carlo simulations, scatter in the material properties and in specimen alignment in the testing machine is taken into account. Based on the results obtained from the simulations, it is determined which one of the defined strategies that is most beneficial for HCF-criteria material parameter estimation, and also how many tests that should be performed in order to maximize the benefit of the information obtained from the fatigue testing.

Keyword
Experiments, Fatigue criteria, HCF, Monte Carlo
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-142321 (URN)10.1016/j.ijfatigue.2013.08.024 (DOI)000331919900032 ()2-s2.0-84893736361 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20140305

Available from: 2014-03-05 Created: 2014-02-28 Last updated: 2017-12-05Bibliographically approved
3. An investigation of the prediction accuracy for volume based HCF models using scaled geometries and scaled loading
Open this publication in new window or tab >>An investigation of the prediction accuracy for volume based HCF models using scaled geometries and scaled loading
2015 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 82, no 2, 317-324 p.Article in journal (Refereed) Published
Abstract [en]

he prediction accuracy for the volume based Weibull- and V* high cycle fatigue models is investigated and compared to the point method. A high number of fatigue tests are performed in rotating bending for single notched cylindrical specimens manufactured in a 12% Cr-steel, a high quality structural steel. The specimens are designed with different highly stressed volume and stress gradient by scaling the geometry, but with the same stresses at the corresponding scaled points. Thus, the maximum stress in the notch is the same. Experiments are performed for three specimen sizes at several stress levels. The volume based Weibull- and V*-models, as well as the point stress method are fitted to the experimental results. Based on the results, the V*-model is favored for design purposes.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
HCF, Size effect, Scaled geometries, Weakest-link, Failure probability
National Category
Materials Engineering
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:kth:diva-160353 (URN)10.1016/j.ijfatigue.2015.04.024 (DOI)000365365900021 ()2-s2.0-84959557264 (Scopus ID)
Note

QC 20150219

Available from: 2015-02-19 Created: 2015-02-19 Last updated: 2017-12-04Bibliographically approved

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Licentiate Thesis(986 kB)165 downloads
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