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Sterjovski Z.,Defence Science and Technology Organisation, Australia | Bayley C.,Dockyard Laboratory Pacific | Donato J.,Defence Science and Technology Organisation, Australia | Lane N.,University of Wollongong | Lang D.,Forgacs Engineering Pty Ltd.
Welding Journal | Year: 2014

Pulsed tandem gas metal arc welding (PT-GMAW) has the potential to increase productivity and minimize distortion in the fabrication of naval surface ship panels. In this study, the PT-GMAW process was used in pulse-pulse mode to butt joint weld 5-mm DH36,8-mm HSLA65, 9.5-mm 350WT, and 11-mm HSLA65 steel plate with ER70S-6 wire in order to assess its suitability as a replacement for submerged arc welding (SAW) and gas metal arc welding (GMAW) in panel lines of Australian naval shipyards. In the pulse-pulse mode, the wire feed rates for the leading and trailing welding wires are set independently and they alternately transfer metal into a single molten weld pool at deposition rates almost comparable with single-wire SAW. Radiographic inspection and subsequent analyses of the 8-, 9.5-, and 11-mm single-bead butt joint welds unexpectedly showed varying degrees of weld-end solidification cracking, which occurred within ∼30 mm from the run-off tab and was different than weld crater cracking. The percentage of plates with solidification cracking was greater at larger plate thicknesses due mainly to increases in both the weld bead depth:width ratio and joint restraint as plate thickness is increased. Also, relatively low levels of nickel in the weld metal resulted in less severe solidification cracks compared with weld metal with higher levels of nickel. There was no evidence of solidification cracks in the 5-mm welded plates. Potential strategies to overcome weld metal solidification cracking near the run-off tab in the PT-GMAW of steel are presented. Source


Asadi M.,University of Ottawa | Goldak J.A.,Carleton University | Bayley C.,Dockyard Laboratory Pacific
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2012

Welding distortion is usually controlled by clamping techniques that can be tack welds, pre-bending, and tension loading. Side heating or fast cooling can also mitigate the distortion in some applications. In addition to the clamping techniques, process parameters affect the distortion so that if one can control the welding process parameters, an optimized profile of such parameters could alleviate the distortion. It is shown in this paper that the distortion can be mitigated by using an optimized profile of welding current and travelling speed. These profiles keep the power per unit length of welding constant. It is shown that an increasing welding current at the beginning and the end of the welding path on an edge welded bar of Aluminum could result in a bar that is closer to flat compared to the constant welding current. Developing an optimized weld process parameter profile requires a trustable computational model to implement a control problem using a predictive model for distortion in front of the weld pool in order to adjust the welding current and speed. Unlike using a constant welding current for the full path of weld, the path length is divided into several sub-paths. For each of weld sub-path the control problem learns from the previous sub-path and tries to find the new value for the welding current and speed that minimize the distortion using predictive ComputationalWeld Mechanics (CWM). Final deflections of the bar are also com-pared between a constant welding current and optimized profile of welding current. Copyright © 2012 by ASME. Source


Asadi M.,Carleton University | Bayley C.,Dockyard Laboratory Pacific | Goldak J.,Carleton University
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2013

Temper bead welding is usually done by experiment, i.e., trial and error. This paper describes a computational weld mechanics model to compute the transient temperature and transient microstructure evolution in temper bead welds. The computed hardness from this model, is compared to measured hardness for validation. Furthermore, the effects of power per unit length, welding current, and welding speed on final hardness, are studied by designing and implementing three design-of-experiment matrices. © 2013 by ASME. Source


Bayley C.,Dockyard Laboratory Pacific | Goldak J.,Carleton University
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2012

Weld build-up or weld cladding is a welding process in which weld metal can be deposited in order to reclaim the material thickness. In certain applications, welding induced distortions must be controlled while simultaneously minimizing welding induced residual strains. In order to examine the relative effect of the weld build-up region on welding induced distortion and residual strains, two panels were fabricated with either a small 100 × 100 × 3 or large 200 × 200 × 3 mm depression that was subsequently filled by welding. During welding, the strains, displacements, and temperature were continuously monitored in order to compare the transient solution with companion finite element method (FEM) models of the same structures. The coupled thermo-mechanical problem was solved using Goldak Technology Inc., VRSUITE program, with the level of agreement of the measured distortions, strains, and temperature profiles dependent on their location and history. Both the numerical and experimental tests showed that despite the differences in the geometry, both panels developed the same strain state, although the large welded patch had greater peak value and larger distortions. © 2012 American Society of Mechanical Engineers. Source


Bayley C.,Dockyard Laboratory Pacific | Aucoin N.,Dockyard Laboratory Pacific
Engineering Fracture Mechanics | Year: 2013

The fracture behavior of welded single edge notched tension specimens was examined using constraints and loading conditions which approximated those of a flawed ship structural panel. The specimens were notched and fatigue pre-cracked in the microstructural region associated with a brittle coarse grained heat affected zone and dynamically fractured at the minimum design temperature. In all cases, the fracture event was preceded by some degree of plasticity. With the aid of validated finite element method companion models, a crack mouth to crack tip opening displacement transfer function was generated allowing the fracture toughness at failure to be determined. © 2013. Source

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