Study of Local Fatigue Methods (TCD, N-SIF, and ESED) on Notches and Defects Related to Numerical Efficiency
The fatigue strength of structural components is strongly affected by notches and imperfections. Both can be treated similarly, as local notch fatigue strength methods can also be applied to interior defects. Even though Murakami’s √area approach is commonly used in the threshold-based fatigue desig...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2023-02-01
|
| Series: | Applied Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2076-3417/13/4/2247 |
| _version_ | 1797622669342932992 |
|---|---|
| author | Michael Stoschka Michael Horvath Stefan Fladischer Matthias Oberreiter |
| author_facet | Michael Stoschka Michael Horvath Stefan Fladischer Matthias Oberreiter |
| author_sort | Michael Stoschka |
| collection | DOAJ |
| description | The fatigue strength of structural components is strongly affected by notches and imperfections. Both can be treated similarly, as local notch fatigue strength methods can also be applied to interior defects. Even though Murakami’s √area approach is commonly used in the threshold-based fatigue design of single imperfections, advanced concepts such as the Theory of Critical Distances (TCD), Notch Stress Intensity Factors (N-SIF), or Elastic Strain Energy Density (ESED) methods provide additional insight into the local fatigue strength distribution of irregularly shaped defects under varying uniaxial load vectors. The latter methods are based on the evaluation of the elastic stress field in the vicinity of the notch for each single load vector. Thus, this work provides numerically efficient methods to assess the local fatigue strength by means of TCD, N-SIF, and ESED, targeting the minimization of the required load case count, optimization of stress field evaluation data points, and utilization of multi-processing. Furthermore, the Peak Stress Method (PSM) is adapted for large opening angles, as in the case of globular defects. In detail, two numerical strategies are devised and comprehensively evaluated, either using a sub-case-based stress evaluation of the defect vicinity with an unchanged mesh pattern and varying load vector on the exterior model region with optimized load angle stepping or by the invocation of stress and strain tensor transformation equations to derive load angle-dependent result superposition while leaving the initial mesh unaltered. Both methods provide numerically efficient fatigue post-processing, as the mesh in the evaluated defect region is retained for varying load vectors. The key functions of the fatigue strength assessment, such as the evaluation of appropriate planar notch radius and determination of notch opening angle for the discretized imperfections, are presented. Although the presented numerical methods apply to planar simulation studies, the basic methodology can be easily expanded toward spatial fatigue assessment. |
| first_indexed | 2024-03-11T09:13:33Z |
| format | Article |
| id | doaj.art-ee179a6da0d74659aa246a35b4bc9a01 |
| institution | Directory Open Access Journal |
| issn | 2076-3417 |
| language | English |
| last_indexed | 2024-03-11T09:13:33Z |
| publishDate | 2023-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Applied Sciences |
| spelling | doaj.art-ee179a6da0d74659aa246a35b4bc9a012023-11-16T18:52:54ZengMDPI AGApplied Sciences2076-34172023-02-01134224710.3390/app13042247Study of Local Fatigue Methods (TCD, N-SIF, and ESED) on Notches and Defects Related to Numerical EfficiencyMichael Stoschka0Michael Horvath1Stefan Fladischer2Matthias Oberreiter3Christian Doppler Laboratory for Manufacturing Process Based Component Design, Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Strasse 18, 8700 Leoben, AustriaChristian Doppler Laboratory for Manufacturing Process Based Component Design, Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Strasse 18, 8700 Leoben, AustriaChair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Strasse 18, 8700 Leoben, AustriaChristian Doppler Laboratory for Manufacturing Process Based Component Design, Chair of Mechanical Engineering, Montanuniversität Leoben, Franz-Josef-Strasse 18, 8700 Leoben, AustriaThe fatigue strength of structural components is strongly affected by notches and imperfections. Both can be treated similarly, as local notch fatigue strength methods can also be applied to interior defects. Even though Murakami’s √area approach is commonly used in the threshold-based fatigue design of single imperfections, advanced concepts such as the Theory of Critical Distances (TCD), Notch Stress Intensity Factors (N-SIF), or Elastic Strain Energy Density (ESED) methods provide additional insight into the local fatigue strength distribution of irregularly shaped defects under varying uniaxial load vectors. The latter methods are based on the evaluation of the elastic stress field in the vicinity of the notch for each single load vector. Thus, this work provides numerically efficient methods to assess the local fatigue strength by means of TCD, N-SIF, and ESED, targeting the minimization of the required load case count, optimization of stress field evaluation data points, and utilization of multi-processing. Furthermore, the Peak Stress Method (PSM) is adapted for large opening angles, as in the case of globular defects. In detail, two numerical strategies are devised and comprehensively evaluated, either using a sub-case-based stress evaluation of the defect vicinity with an unchanged mesh pattern and varying load vector on the exterior model region with optimized load angle stepping or by the invocation of stress and strain tensor transformation equations to derive load angle-dependent result superposition while leaving the initial mesh unaltered. Both methods provide numerically efficient fatigue post-processing, as the mesh in the evaluated defect region is retained for varying load vectors. The key functions of the fatigue strength assessment, such as the evaluation of appropriate planar notch radius and determination of notch opening angle for the discretized imperfections, are presented. Although the presented numerical methods apply to planar simulation studies, the basic methodology can be easily expanded toward spatial fatigue assessment.https://www.mdpi.com/2076-3417/13/4/2247theory of critical distancenotch stress intensity factorpeak stress methodelastic strain energy densityimperfectiondefect |
| spellingShingle | Michael Stoschka Michael Horvath Stefan Fladischer Matthias Oberreiter Study of Local Fatigue Methods (TCD, N-SIF, and ESED) on Notches and Defects Related to Numerical Efficiency Applied Sciences theory of critical distance notch stress intensity factor peak stress method elastic strain energy density imperfection defect |
| title | Study of Local Fatigue Methods (TCD, N-SIF, and ESED) on Notches and Defects Related to Numerical Efficiency |
| title_full | Study of Local Fatigue Methods (TCD, N-SIF, and ESED) on Notches and Defects Related to Numerical Efficiency |
| title_fullStr | Study of Local Fatigue Methods (TCD, N-SIF, and ESED) on Notches and Defects Related to Numerical Efficiency |
| title_full_unstemmed | Study of Local Fatigue Methods (TCD, N-SIF, and ESED) on Notches and Defects Related to Numerical Efficiency |
| title_short | Study of Local Fatigue Methods (TCD, N-SIF, and ESED) on Notches and Defects Related to Numerical Efficiency |
| title_sort | study of local fatigue methods tcd n sif and esed on notches and defects related to numerical efficiency |
| topic | theory of critical distance notch stress intensity factor peak stress method elastic strain energy density imperfection defect |
| url | https://www.mdpi.com/2076-3417/13/4/2247 |
| work_keys_str_mv | AT michaelstoschka studyoflocalfatiguemethodstcdnsifandesedonnotchesanddefectsrelatedtonumericalefficiency AT michaelhorvath studyoflocalfatiguemethodstcdnsifandesedonnotchesanddefectsrelatedtonumericalefficiency AT stefanfladischer studyoflocalfatiguemethodstcdnsifandesedonnotchesanddefectsrelatedtonumericalefficiency AT matthiasoberreiter studyoflocalfatiguemethodstcdnsifandesedonnotchesanddefectsrelatedtonumericalefficiency |