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An Investigation into the Wear of an Eutectoid Steel Based on the Low-Cycle Fatigue Theory with the Finite Element Method

Abdi, Mohammad | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42426 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Karimi Taheri, Ali
  7. Abstract:
  8. In sliding wear, the process of making debris takes place with different mechanisms. Previous works estimating the wear rate have been carried out based on contact mechanics and material failure mechanisms. In present work, the possibility of existence of low-cycle fatigue as the dominant mechanism in the wear of an as-cast eutectoid steel is investigated. Moreover, wear coefficient and the the volume loss per distance of that steel was predicted. At first, wear tests were done in order to obtain the wear trend of the steel in different loads. Then, regarding the roughness of the disk surface, a finite element model was built to simulate the sliding of the pin surface over the asperities of the disk in different directions. After that, the possibility of existence of low-cycle fatigue as a dominant wear mechanism of this steel was investigated by considering the maximum equivalent plastic strain in surface layers of the pin and manson-coffin relation. Obtaining the D exponent in Manson-Coffin relation around 2, shows that the low-cycle fatigue is at least one of the main mechanisms in wear of this steel. Furthermore, regarding the plastic strain region and strain gradient from contact surface toward the center, the wear coefficient of this steel in steady state was predicted. The predicted and experimental results were compared to verify the validity of the model especially where D=2.5 in low forces. Finally, a new subroutine was written so as to predict the volume loss per distance in different loads. There were some efforts to involve the effect of plastic deformation which is taken place during wear and as a result of which, work hardening and increasing of yield stress occurs in surface layers. In this section, some results were obtained among which, the bests are those in which the D constant is considered equal to 2.7. The best consistency between model and experimental results was achieved in high loads
  9. Keywords:
  10. Low Cycle Fatigue ; Finite Element Model ; Cyclic Plastic Strain ; Manson-Coffin Relation

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