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Residual stress distributions in multipass welded API 5L X70 steel plates were determined by numerical and experimental methods. SYSWELD finite element software was used for numerical simulations. Microstructure variations were also considered for calculation of residual stresses. The continuous cooling transformation diagram was obtained via JMatPro software. The results showed that residual stress distribution is sensitive to number of weld passes, and microstructure changes. The simulation results were compared with those obtained by Magnetic Barkhausen Noise measurements on the welded plates. Simulation and experimental results gave qualitatively similar tendencies for the variation of the residual stress state.

Variations of surface residual stresses as a function of weld runs in API 5L X70 steel plates were non-destructively monitored by Magnetic Barkhausen Noise (MBN) method. After each weld run, MBN signal and hardness distributions were recorded. MBN signals were converted into stress values by using a specific calibration procedure. The results were analyzed by considering microstructure investigations and hardness measurements, and then, they were compared with the results of X-ray diffraction measurements. MBN method seems to be a good candidate for monitoring the variation of surface residual stresses. It may also provide critical data for computer simulation and process design of welding processes.

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