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Fatigue Analysis of Welded Joint Considering Residual Stresses and Stress Relaxation Using Different Models of Material Hardening

Heiran, Malihe | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44204 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farrahi, Gholamhossein
  7. Abstract:
  8. Welded joints are the most used joints in industrial applications. Fatigue analysis of welded joints is of great importance. Residual stresses produced during welding process play an important role in fatigue failure of welded joints. Residual stresses’ effect on fatigue life of the structures is similar to mean stresses and can be accounted for like mean stress effect. However residual stresses are not constant and do change in service. In this thesis, welding process has been modeled using FE software ABAQUS in order to predict residual stress distribution due to welding. The predictions show good agreement with measurements especially for longitudinal residual stresses. Then cyclic load has been applied to the welded structure and an elastic-plastic finite element (FE) analysis has been done .Two material hardening models have been used in the FE analysis: linear kinematic hardening and multilinear kinematic hardening. The results show that residual stress relaxation occurs rapidly and most of the residual stresses relax in the first loading cycle for both hardening models .This result is in agreement with other researches in literature. The difference between these two hardening models has been observed in stability of stress amplitude. Stress amplitude stabilizes more rapidly when simple linear hardening model has been used and stability occurrs much later when multilinear kinematic hardening model has been used. This is because of better modeling of material behavior by multilinear hardening model
  9. Keywords:
  10. Residual Stress ; Fatigue ; Stress Relaxation ; Hardening ; Weld Modeling

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