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A research investigation has been undertaken to identify the various stages and variation of welding parameters in friction taper plug welding (FTPW) process and to explore their effects on the performance and properties of the welds. According to the variation of axial force, the overall FTPW process is divided into feeding phase, pressing phase, welding phase, and forging phase. The rotating speed, welding force, and burn-off rate remain nearly constant in welding phase. However, the torque peaks in welding phase when after few seconds of welding force setting is reached. Rising the welding force would increase the peak torque, welding torque, and burn-off rate, but decrease the welding time. When improper welding parameter is used lack of bonding and incomplete filling defects would form within the weld. The microstructure of the weld metal is consist of retained austenite, pearlite, and various Widmanstätten ferrite. In heat affect zone, it is mainly of lathy upper bainite. Defect free welds exhibit favorable tensile properties of which 548.3MPa tensile strength and 27.5% elongation that equal to the base metal could be found. [ABSTRACT FROM AUTHOR]

The present work reports new results regarding developing the friction taper plug welding (FTPW) process in wet conditions for underwater welding and repairing solutions. In this study, the FTPW process, microstructures and mechanical properties of the weld are investigated. The main findings are as follows: defect-free FTP welds can be obtained with a 7000rpm rotational speed and an axial force of 30-50kN. In the heat-affected zone (HAZ) and the lower region of the weld metal (WM), a large volume of lath bainite and small amounts of acicular ferrite, polygonal ferrite, and martensite are observed. However, in the upper region of the WM, the microstructure mainly consists of lath martensite. The best results of ultimate tensile strength and V-notch impact energy are 500MPa and 39.5J, respectively, on the joint that was welded with a 45kN axial force. The impact failure is characterised by brittle fracture with a large area of cleavage and notably little quasi-cleavage and ductile. [ABSTRACT FROM AUTHOR]

Approximate J-estimation methods including the effects of weld mis-match, for a circumferentially surface-cracked pipe with an internal, constant-depth and finite-length surface flaw in pure bending are developed. The methods are based on principles described by Rahman and Brust. Closed-form J-solutions in terms of elementary functions are derived from classical beam theory combined with an equivalence criterion. Several numerical examples of welded joints are presented to verify the proposed methods. [Copyright &y& Elsevier]