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Combined Fretting Fatigue Life Estimation Based on the Theory of Critical Distances

Salehi, Erfan | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53628 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farrahi, Gholamhossein
  7. Abstract:
  8. Theory of Critical Distances (TCD) is one of the methods that has attracted the scientists in life estimation of fretting fatigue problems in recent years. Less difficulty and less time consuming features of this method in comparison with other methods like fracture mechanics are the attracting aspects of this theory. In this research, the capability of the Theory of Critical Distances in life estimation of combined bending and tensile loading modes in fretting fatigue for the pads with sharp edges has been evaluated. This included the evaluation of this method in lifetime estimation of 316L stainless steel for fretting fatigue in two different types of heat treatments and the evaluation of its capability in identifying the variation of the stress field as a result of bending and tensile loading modes combinations. Three criteria that have been coupled with this method are Fatemi-Socie, Smith-Watson-Topper, and Stress-Life. The Critical Distance properties have been extracted from testing on notched specimens with three types of notches. After extracting the stress field by Finite Element Method, Point, Line, Area, and Volume Methods have been evaluated for life estimation. While the Stress-Life criterion was overestimating the results, Fatemi-Socie and Smith-Watson-Topper criteria were accurate in lifetime estimation of fretting fatigue. Whereas the Area and Volume Methods were not safe methods, Point and Line Methods are proper in lifetime estimation. Because of the higher ductility of 316L stainless steel after the heat treatment, at last, the TCD showed more conservative approach in lifetime estimation
  9. Keywords:
  10. Fretting Fatigue ; Ductility ; Combined Loading ; 316 Austenitic Stainless Steel ; Critical Distances Theory

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