Experimental Study and Finite Element Simulation of Residual Stress in Welded Sections of Steel P91 Pipes with Multi-pass Welding

Subject Areas : Mechanical Engineering

Davood Azadi ¹ , Nosratollah Solhjoei ² , SayedAli Mousavi ³

1 - Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
2 - Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
3 - Najafabad Branch, Islamic Azad University, Najafabad, Iran *Corresponding author

Received: 2015-12-20 Accepted : 2016-02-28 Published : 2017-01-14

Keywords: Arc welding, Finite Element Method, Goldak heat source model, Central hole drilling method, Residual stress,

Abstract :

All the producing and assembling processes exert residual stress on the pieces that may lead to structural failure. Therefore, calculating the residual stress in such structures has been common in recent years. In this article, distribution of temperature and residual stress resulting from arc welding in three-pass butt joint in P91 austenitic stainless steel pipes is calculated and estimated using the finite element method and experimental data. Simulating the welding process has been carried out three- dimensionally using Abaqus software. Distribution of the arc thermal flux has been identified based on the Goldak two-elliptical model using DFLUX subprogram in Abaqus software. The numerical method has been employed by doing thermoelastoplastic analysis and the technique of birth and death of the elements to model the welding passes and the melted elements. Then, using central hole drilling method, residual stress gradient of the thickness at distance 3mm from the welding line on the pipe is measured. Finally, the maximum percentage of error, through the results obtained from experimental measurements and finite element method, was reported 27% which is scientifically reasonable. The results show that the residual environmental stress in the internal surface of the pipe from the welding central line to 8.7mm varies with the gradient of 610MPa from 296MPa to -314MPa. Such a drastic stress distribution leads to genesising some cracks on the welded pipes.

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