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Finite Element Analysis of Repair Welding Residual Stress in Pressure Vessels and Piping System

Ehsani, Mohammad | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48222 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farrahi, Gholamhossein
  7. Abstract:
  8. Repair welding is one of the most prevalent processes in repair and maintenance part of all industries. Amongst the issues of welding processes are residual stresses and distortions. Thus prediction of residual stresses and their distribution are important for designing welding procedure specifications. Circumferential butt weld is often used for joining steam and hot water lines in plants. Due to the intense concentration of heat in the welding, the regions near the weld line undergo severe thermal cycles. The thermal cycles cause non-uniform heating and cooling in the material, thus generating inhomogeneous plastic deformation and residual stresses in the weldment. The presence of residual stresses can be detrimental to the performance of the welded product. Tensile residual stresses are generally detrimental, increasing the susceptibility of a weld to fatigue damage, stress corrosion cracking and fracture. When assessing the risk for growth of defects such as surface flaws in piping systems, the welding residual stress may give a large contribution to the total stress field than stress caused by design loads. In the present study, based on the SYSWELD software, a three-dimensional (3-D) model is developed to simulate the temperature fields and the welding residual stress fields in steel pipe considering phase transformation including dilatation and transformation plasticity. Moreover, post weld heat treatment (PWHT) is also simulated to assess its contribution to stress relief
  9. Keywords:
  10. Finite Element Analysis ; Phase Transformation ; Repair Welding ; Post Weld Mechanical Treatment ; Stress Relieving ; Multipass Welding

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