Fracture studies were carried out on bi-metallic pipe weld joints of 324 mm outer diameter having crack at different regions of weld in the circumferential direction. The bi-metallic pipe weld joints ...were made of low alloy steel (ferritic) and stainless steel (austenitic) materials. Welding consumable used was nickel-based alloy. The initial notch was located in the different regions of the weld joints such as base metals (ferritic and austenitic), centre of weld, buttering (nickel-based alloy on low alloy steel) and heat affected zones. Subsequent to fatigue pre-cracking, fracture tests were carried out under four-point bending under monotonic and cyclic loading. During the fracture tests, load, load-line displacement, deflections, circumferential deformations, surface crack growth, crack mouth opening displacement were recorded. In addition, number of cycles to failure were monitored for tests under cyclic loading. Under monotonic loading, collapse load of the bi-metallic pipe weld joint having initial crack in the centre of buttering reduced by 12% in comparison to the collapse load for crack in the centre of heat affected zone. Crack deviated towards austenitic region for the weld joints having crack in the centre of weld, centre of buttering and heat affected zone. The bi-metallic pipe weld joints subjected to cyclic loading failed at lower number of cycles even when the load amplitude was sufficiently below the collapse load under monotonic loading. Crack growth resistance of bimetallic pipe weld joints under cyclic loading was significantly lower compared to that under monotonic loading under displacement control.
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•Fracture studies were carried out on bi-metallic pipe weld joints under monotonic and cyclic loading.•Initial crack in the buttering layer reduced the collapse load by 12% when compared with initial crack in HAZ.•Irrespective of the location of initial crack in the weld, HAZ or buttering, crack growth was in the austenitic region.•Crack growth resistance under cyclic loading was significantly lower compared to that under monotonic loading.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This research work focused on different types of dissimilar weld joints commonly used in refineries and chemical industries to investigate the magnitude, type and distribution of welding residual ...stresses in weld metal and HAZ at both face and root sides. These joints were combined from mild steel, stainless steel types 304 and 316, and Incoloy 800. For comparison, similar weld joints for each material were also studied. Stress relaxation or sectioning technique was used for welding residual elastic strain measurements using electrical strain gauges. The results of this study have shown that measured elastic strains of both face and root sides were different and this difference increased with the increase in plate thickness. Welding residual stresses of HAZ did not depend on joint type, it depended only on properties of base metal. A considerable difference in the value of welding residual stresses between similar and dissimilar pipe weld joints was obtained. However, both have shown almost similar trend of stress distributions.
This work provide a model based on machine learning techniques in welds recognition, based on signals obtained through in-line inspection tool called "smart pig" in Oil and Gas pipelines. The model ...uses a signal noise reduction phase by means of pre-processing algorithms and attribute-selection techniques. The noise reduction techniques were selected after a literature review and testing with survey data. Subsequently, the model was trained using recognition and classification algorithms, specifically artificial neural networks and support vector machines. Finally, the trained model was validated with different data sets and the performance was measured with cross validation and ROC analysis. The results show that is possible to identify welding automatically with an efficiency between 90 and 98 percent.
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