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Effects of cracks and other geometrical changes on the vibration of structures: with special application to turbine blades
KTH, Superseded Departments, Solid Mechanics.ORCID iD: 0000-0002-0307-8917
1982 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 1982. , 24 p.
Series
Rapport / Hållfasthetslära, KTH, ISSN 0281-1502 ; 37
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-196787OAI: oai:DiVA.org:kth-196787DiVA: diva2:1048461
Public defence
Kollegiesalen, KTH, Stockholm (English)
Opponent
Supervisors
Note

QC 20161122

Available from: 2016-11-22 Created: 2016-11-21 Last updated: 2016-11-22Bibliographically approved
List of papers
1. Tuning of turbine blades: a theoretical approach.
Open this publication in new window or tab >>Tuning of turbine blades: a theoretical approach.
1983 (English)In: Journal of engineering for power, ISSN 0022-0825, Vol. 105, no 2, 249-255 p.Article in journal (Refereed) Published
Abstract [en]

A perturbation method is described which predicts the changes in eigenfrequencies resulting from geometrical changes of a structure. This dependence is represented by dimensionless functions, one for each eigenfrequency, which vary over the surface of the structure. The functions are presented for each eigenfrequency as isoline plots. The method was applied to a turbine blade and a rectangular beam.

Keyword
MATHEMATICAL TECHNIQUES - Perturbation Techniques, Turbomachinery
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-25474 (URN)A1983RD17800005 ()
Note

QC 20101025

Available from: 2010-10-25 Created: 2010-10-25 Last updated: 2016-11-21Bibliographically approved
2. Eigenfrequency changes of structures due to cracks, notches or other geometrical changes
Open this publication in new window or tab >>Eigenfrequency changes of structures due to cracks, notches or other geometrical changes
1982 (English)In: Journal of the mechanics and physics of solids, ISSN 0022-5096, Vol. 30, no 5, 339-353 p.Article in journal (Refereed) Published
Abstract [en]

A first order perturbation method is presented which predicts the changes in resonance frequencies of a structure resulting from cracks, notches or other geometrical changes. The eigenfrequency changes due to a crack are shown to be dependent on the strain energy of a static solution which is easily obtainable for small cracks and other small cut-outs. The method has been tested for three different cases, and the predicted results correlate very closely to experimental and numerical results.

Keyword
STRUCTURAL ANALYSIS
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-25467 (URN)10.1016/0022-5096(82)90004-7 (DOI)A1982PP03100004 ()
Note
QC 20101025Available from: 2010-10-25 Created: 2010-10-25 Last updated: 2016-11-21Bibliographically approved
3. The dynamic behaviour of slender structures with cross-sectional cracks
Open this publication in new window or tab >>The dynamic behaviour of slender structures with cross-sectional cracks
1983 (English)In: Journal of the mechanics and physics of solids, ISSN 0022-5096, Vol. 31, no 4, 329-345 p.Article in journal (Refereed) Published
Abstract [en]

A dynamic model for beams with cross-sectional cracks is discussed. It is shown that a crack can be represented by a consistent, static flexibility matrix. Two different methods for the determination of the flexibility matrix are discussed. If the static stress intensity factors are known, the flexibility matrix can be determined from an integration of these stress intensity factors. Alternatively, static finite element calculations can be used for the determination of the flexibility matrix. Both methods are demonstrated in the present paper. The mathematical model was applied to an edge-cracked cantilevered beam and the eigenfrequencies were determined for different crack lengths and crack positions. These results were compared to experimentally obtained eigenfrequencies. In the experiments, the cracks were modelled by sawing cuts. The theoretical results were, for all crack lengths, in excellent agreement with the experimental data. The dynamic stress intensity factor for a longitudinally vibrating, centrally cracked bar was determined as well. The results compared very well with dynamic finite element calculations. The crack closure effect was experimentally investigated for an edge-cracked beam with a fatigue crack. It was found that the eigenfrequencies decreased, as functions of crack length, at a much slower rate than in the case of an open crack.

Keyword
BEAMS AND GIRDERS
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-25477 (URN)10.1016/0022-5096(83)90003-0 (DOI)
Note
QC 20101025Available from: 2010-10-25 Created: 2010-10-25 Last updated: 2016-11-21Bibliographically approved

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