W. Liu

Bio: W. Liu is an academic researcher. The author has contributed to research in topics: Weld access hole & Heat-affected zone. The author has an hindex of 1, co-authored 1 publications receiving 18 citations.

Preventing weld hot cracking by synchronous rolling during welding

Abstract: Based on the mechanical point of view of hot cracking in weldments, a new method, accomplished by synchronous rolling during welding (SRDW) along both sides of the weld at a suitable distance behind the welding arc, has been developed for preventing weld hot cracking. The theory behind this method was also examined. Three-dimensional simulative computations of displacement and strain fields produced by SRDW were carried out by means of the finite element method to reveal the mechanism of the new method and provide a theoretical basis for parameter choice. With a specially developed equipment for welding and synchronous rolling, experiments were performed to investigate the effectiveness and feasibility of this method in preventing weld hot cracking in high-strength aluminum alloy 2024-T4. Results show that weld hot cracking in 2024-Al alloy can be effectively prevented and the mechanical properties of welded joints can also be improved by the new method. It is an important new solution to weld hot cracking in welding of sheet metals.

A hot-cracking mitigation technique for welding high-strength aluminum alloy

Abstract: A hot-cracking mitigation technique for gas tungsten arc welding (GTAW) of high-strength aluminum alloy 2024 is presented. The proposed welding technique incorporates a trailing heat sink (an intense cooling source) with respect to the welding torch. The development of the mitigation technique was based on both detailed welding process simulation using advanced finite element techniques and systematic laboratory experiments. The finite element methods were used to investigate the detailed thermomechanical behavior of the weld metal that undergoes the brittle temperature range (BTR) during welding. As expected, a tensile deformation zone within the material BTR region was identified behind the weld pool under conventional GTA welding process conventional GTA welding process conditions for the aluminum alloy studied. To mitigate hot cracking, the tensile zone behind the weld pool must be eliminated or reduce to a satisfactory level if the weld metal hot ductility cannot be further improved. With detailed computational modeling, it was found that by the introduction of a trailing heat sink at some distance behind the welding arc, the tensile strain rate with respect to temperature in the zone encompassing the BTR region can be significantly reduced. A series of parametric studies were also conducted to derive optimal processmore » parameters for the trailing heat sink. The experimental results confirmed the effectiveness of the trailing heat sink technique. With a proper implementation of the trailing heat sink method, hot cracking can be completely eliminated in welding aluminum alloy 2024 (AA 2024).« less

Rolling to control residual stress and distortion in friction stir welds

Abstract: Considerable residual stress and distortion can be produced by friction stir welding, impeding industrial implementation. Finite element analysis has been used to develop three innovative rolling methods that reduce residual stress and distortion in friction stir welds. Of the three methods, post-weld direct rolling where a single roller is applied to roll the top surface of the weld after the weld metal has cooled to room temperature proved the most effective. The residual stress predictions from the model compared favourably with residual stress measurements reported in an accompanying paper. Finally, the effectiveness of using post-weld direct rolling is illustrated with an industrial example of a large integrally stiffened panel, where the distortion was virtually eliminated.

Finite element modelling and simulation of bulk material forming: A bibliography (1996‐2005)

Abstract: Purpose – To provide a selective bibliography for researchers working with bulk material forming (specifically the forging, rolling, extrusion and drawing processes) with sources which can help them to be up‐to‐date.Design/methodology/approach – A range of published (1996‐2005) works, which aims to provide theoretical as well as practical information on the material processing namely bulk material forming. Bulk deformation processes used in practice change the shape of the workpiece by plastic deformations under forces applied by tools and dies.Findings – Provides information about each source, indicating what can be found there. Listed references contain journal papers, conference proceedings and theses/dissertations on the subject.Research limitations/implications – It is an exhaustive list of papers (1,693 references are listed) but some papers may be omitted. The emphasis is to present papers written in English language. Sheet material forming processes are not included.Practical implications – A very...