Papers by Keyword: Spot Welding

Abstract: An incremental and thermal electro-mechanical coupled finite element model has been presented in this study for predicting spot nugget size, gap between workpieces, and thermal expansion displacement during spot welding process. Approximate temperature dependent material properties, including physical and mechanical properties, have been considered. The spot nugget shape and the thermal expansion displacement were obtained by simulation. The solutions showed that the displacement of workpieces was directly related to the quality of solder joints and can be as a monitoring parameter of spot weld quality. These calculations provide a theoretical reference for nugget quality monitoring and forecasting by electrode expansion displacements.

Abstract: The magnetic pulse welding is a rapid process (takes place within few micro seconds) that joins both homogeneous and heterogeneous materials in the solid state. The process involves applying variable high current on an inductor to generate Lorentz forces on to the conductive primary part (flyer). To realize the weld it is necessary to accelerate the flyer to impact on to the secondary stationary part (base material) at a very high velocity attained over the distance, called air gap, between the parts. It is typically possible to perform welding of tubes and sheets provided there is an optimized air gap between the parts to be welded. As part of our work we have developed an innovative approach (Magnetic Pulse Spot Welding-MPSW) that eliminates the delicate task of maintaining the aforementioned air gap between the plates. The proposed method opens better viable perspectives for heterogeneous assembly of automotive structures or connecting batteries in a quasi-cold state. The developed approach has been validated on the heterogeneous assembly Al/Fe by tensile tests (quasi-static and dynamic) that attested the quality of welds.

Abstract: Ultrasonic spot welding of galvanized steel sheets has been conducted to investigate formation process of the weld microstructure, and effect of zinc coat on joint property. The joint strength showed a rapidly increase at the weld time of 0.8s, and it has the maximum value over 1.0 s. In the weld time range from 0.1s to 0.8s, fracture occurred in zinc coat/ steel interface. In contrast, the fracture partially occurred in the base steel in the weld time over 1.0s, and concaves in which the steel substrate of one specimen partially remains on the other specimen were observed. The formation process of weld microstructure of ultrasonic welding was proposed to be a two-steps process. First, zinc coat in the interface was mechanically removed by the vibration and clamping force, and some zinc particles dispersed in the weld interface. Second, the zinc particles melted due to the friction, and partially bonded regions were simultaneously formed around the zinc particles. The partially bonded regions were stirred with the steel substrate as the weld time increased. The joint strength increased by development of the stirred zone. At the weld time over 1.2s, the joint strength decreased due to growth of crack around the stirred zone.

Abstract: In the author’s opinion, Spot Welding Procedures Chart D.1 (hereafter referred to as Figure D.1) in Appendix D of International Standard ISO 15609-5 [1] is not accurate in principle. This figure is not suitable for materials need exerting forging force for spot welding such as aluminum alloy, especially hard aluminum alloy, for it does not correctively reflect loading moment of forging force. In the author’s opinion, the loading moment of forging force given by Figure D.1 is too late, which will lead to the generation of crack. In addition, two important reasons equally considered to advance loading moment of forging force are: (1) different spot welding equipments have different response time for welding pressure; (2) electric response speed is faster than that of mechanical or pneumatic mechanism, that is to say, response speed of current shall be faster than implementation speed of forging force. Is this paper, we discuss such above-mentioned kinds of different situations. We suggest advancing the forging force in Figure D.1 to the maintenance course of welding current. We propose an amended spot welding course schematic diagram and a simplified schematic diagram.

Abstract: In order to improve the welding efficiency of vehicle compartment side plate, the stability of welding parameter and control accuracy, the thesis applies advanced intelligent control theory (fuzzy and PID compound control) and multi-sensor fusion technology and combines with the automatic spot welding process, using the Mitsubishi FX2N-80MT-001 programmable controller and GT1155-QSBD-C touch screen, achieved the automatic spot welding control of the vehicle compartment side plate. Experimental results show that the system’s response speed, control accuracy and stability can meet the requirements of production.

Abstract: Single sided resistance spot welding (SSRSW) developed from RSW is a feasible plan to join vehicle structure to closed-form tube and is increasingly used in automobile manufacturing. During the process of SSSW, large deformation and complex contact status of the workpieces occur because there is no inside support. The complex contact status has directly influence on the size of the nugget which is critical to the quality of welding. In this study, the contact statuses during the current stage of sheet-to-tube spot welding were researched by numerical method. It was found that the widths of the contact regions of electrode to sheet and sheet and sheet to tube have dynamic change during welding process which decided the size and speed of the nugget formation. The results have direct guiding significance to the study on ring nugget formation during sheet-to-tube welding.

Abstract: The tungsten fiber reinforced titanium composite (W/Ti) was produced by the spot welding method. This manufacturing method used only a simple spot welding system, and it did not need a vacuum chamber and a high temperature furnace such as existing common methods. The arranged tungsten fibers were held between titanium plates (thickness 0.5mm) and fixed by spot welding. Therefore, this W/Ti composite produced by spot welding did not join at all positions between the tungsten fiber and the titanium matrix because of the partial welding in the spot welding point. The coverage, a rate of welding area to the whole plate area, became 150% for the sample in this study, because it should make up for the partial welding by this method. From the microscopic observation in the cross section of the W/Ti composite, it was conformed the good jointing in the whole position between the tungsten fiber and the titanium matrix. ON the other hand, the alteration of thermal residual stress under the thermal cycling was measured by the in-situ x-ray stress measurement technique. These results were discussed from the viewpoint of the thermal expansion coefficient between fiber and matrix.

Abstract: The design of multi-robot cells for spot welding strictly influences the feasibility and complexity of the multi-robot motion planning. In comparison to existing literature, the proposed approach simultaneously addresses: (i) the design of multi-robot cells for spot welding; (ii) the allocation of the welding points to the robots on the basis of required cell cycle time. First, the algorithm selects one robot model and one robot fixturing structure. Second, the approach identifies free trajectories among welding points for each couple gun/position of the robot in the fixturing structure through probabilistic roadmaps (PRMs). Third, on the basis of the previous results, an innovative mathematical model selects and allocates the resources taking into account cell investment costs. Finally, the solutions that differ on robot model and robot fixturing structure are compared and the best solution is selected. A test case is provided to show the applicability of the approach.

Abstract: The resistance spot welding of dissimilar materials is generally more challenging than that of similar materials due to differences in the physical, chemical and mechanical properties of the base metals. Advanced high strength steels and high strength low alloy steels are utilized in automotive industry to reduce weight of the vehicle body and consequently lowering the fuel consumption to achieve the lowest possible fuel consumption, high active and passive safety of passengers while decreasing the amount of emission. The influence of the primary welding parameters, especially welding current, microhardness and tensile shear load bearing capacity of dissimilar welds between TRIP 40/70 as an Advanced High Strength Steel and H220PD as a High-Strength Low-Alloy steel has been investigated in this paper.

Abstract: Tensile shear strength and ageing treatment of dissimilar 6063 aluminum alloy-316L stainless steel joint fabricated by spot welding were investigated. The results showed that tensile shear strength increased with the increasing of welding current. The enhancement of tensile shear strength of the joints was due to the enlargement of the nugget diameter. It was also found that the tensile shear strength values for heat treated joint almost similar to that of non-heat treated joint.