Screening the critical locations of a fatigue-loaded welded structure using the energy-based approach
Yanchukovich, Alexei (2021-06-04)
Väitöskirja
Yanchukovich, Alexei
04.06.2021
Lappeenranta-Lahti University of Technology LUT
Acta Universitatis Lappeenrantaensis
School of Energy Systems
School of Energy Systems, Konetekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-335-667-2
https://urn.fi/URN:ISBN:978-952-335-667-2
Tiivistelmä
Fatigue analysis is a very important part of the design process of a welded structure. Several different methods are available, but the principal challenge is the very large number of potential critical points in a complex welded structure. Material development has led to a significant increase in the strength of steel and higher allowed static loading, which requires additional parameters to be considered and complicates the analysis of fatigue-loaded welded components. Reliable fatigue analysis requires an efficient screening procedure to define potential critical locations and limit the number of points for analysis.
A new method for the effective screening of critical locations of complex welded structures under fatigue loading is developed in this thesis. The method’s primary area of applicability is high cycle fatigue (HCF) under a combination of a few independent constant amplitude loads. The screening method utilizes energy-based damage criteria in combination with stress-based methods commonly used in the fatigue analysis of welded structures. The method includes the capability to consider multiaxial state, mean and residual stresses, local plasticity, and the yield strengths of materials. Flexible consideration of the different parameters enables the screening procedure to be adapted to ensure compatibility with common fatigue standards and rules for welded structures, and corresponding uniaxial fatigue strengths can be used to determine the required fatigue properties. The implemented fatigue tests demonstrate a good correlation between test results and the estimations of the developed screening method. The location of the site of failure was usually estimated successfully, and the mean fatigue life defined by the screening procedure was close to the results of the implemented fatigue tests. According to the test results obtained, the developed method has good potential as a tool to screen the critical locations of a welded structure.
The developed screening procedure limits the number of potential critical points requiring more detailed fatigue analysis and focuses resources on the accurate analysis of the most critical points. The results of systematic screening using the developed method give preliminary information about fatigue resistance of the structure, which improves efficiency and shortens the design process by avoiding unnecessary detailed analysis of unfinished concepts.
A new method for the effective screening of critical locations of complex welded structures under fatigue loading is developed in this thesis. The method’s primary area of applicability is high cycle fatigue (HCF) under a combination of a few independent constant amplitude loads. The screening method utilizes energy-based damage criteria in combination with stress-based methods commonly used in the fatigue analysis of welded structures. The method includes the capability to consider multiaxial state, mean and residual stresses, local plasticity, and the yield strengths of materials. Flexible consideration of the different parameters enables the screening procedure to be adapted to ensure compatibility with common fatigue standards and rules for welded structures, and corresponding uniaxial fatigue strengths can be used to determine the required fatigue properties. The implemented fatigue tests demonstrate a good correlation between test results and the estimations of the developed screening method. The location of the site of failure was usually estimated successfully, and the mean fatigue life defined by the screening procedure was close to the results of the implemented fatigue tests. According to the test results obtained, the developed method has good potential as a tool to screen the critical locations of a welded structure.
The developed screening procedure limits the number of potential critical points requiring more detailed fatigue analysis and focuses resources on the accurate analysis of the most critical points. The results of systematic screening using the developed method give preliminary information about fatigue resistance of the structure, which improves efficiency and shortens the design process by avoiding unnecessary detailed analysis of unfinished concepts.
Kokoelmat
- Väitöskirjat [1099]