Papers by Keyword: Spot Welding

Abstract: Empirical relationships were developed between the resistance spot welding process parameters (i.e. power, time and electrode force) and quality characteristics (i.e., tensile shear failure load and nugget diameter) of resistance spot welded DP980 steel joints. Further, the process parameters were optimized to get maximum tensile shear failure load and optimum nugget diameter. It is observed that, the electrode force of 4.25 kg/cm², power of 70 kW and welding time of 3.5 sec yielded a maximum tensile shear failure load of 39 kN with an optimum weld nugget diameter of 4.58 mm.

Abstract: Corrugated web girders emerged in the past two decades. Their main advantages consists in the possibility to use slender webs avoiding the risk of premature local buckling. Consequently, higher moment capacity might be obtained increasing the beam depth with really thin webs, which are stiffened by the corrugations. Increased interest for this solution was observed for the main frames of single-storey steel buildings and steel bridges. A new solution was proposed at the Politehnica University of Timisoara, in which the beam is composed by a web of trapezoidal steel sheet and flanges of back-to-back lipped channel steel sections. This solution uses self-drilling screws for connecting flanges to the web and to ensure the continuity of the web as seam fasteners. Starting from this new technological solution the paper extends and investigates the use of spot welding as seam fastening to build the web, in order to increase the degree of automation of fabrication. Experimental work of specimens in shear having two or three layers of steel sheets connected by spot welding will be presented. The results will be implemented on a numerical model in order to study the behaviour of the beams presented above.

Abstract: The steel sheets used for the car body production are protected against corrosion by zinc coating. Resistance spot welding is used mainly for joining these sheets, because of its high speed and adaptability for automation in high-rate production. However, resistance spot welding has a negative influence on the corrosion resistance of joints. The paper focuses on the analysis of quality of welds on galvanized steel sheets and their corrosive properties. Tensile test and accelerated corrosion test in corrosive environment were used for evaluation of the welds’ quality. Protective efficiency of zinc coatings for automobile sheets was evaluated as well, based on the determination of their electrochemical characteristics in passivated and non-passivated state, as well as their corrosion resistance in simulated corrosion environments. Two types of DX54D+Z material were used for experiments: non-passivated and passivated with Cr3+.

Abstract: In this study, virtual and physical experimental investigations were performed on the resistance spot weldability of hot-formed ultra high strength steels (UHSS). The sheets were joined by the resistance spot welding as lap or cross joint. The mechanical properties were assessed in terms of cross tension strength (CTS) and tensile shear strength (TSS). The micro structural profile and weld nugget diameter were also investigated. Both virtual and physical methods yielding results are in good agreement. The results are discussed in the light of earlier work published in the literature and contribute to a better understanding on the evaluation of resistance spot weldability.

Abstract: During the resistance spot welding quality control process, the traditional quality control methods can’t compensate all the affecting factors effectively. By welding 316LVM stainless steel wire to the surface of sheet of the same material, three kinds of process parameters, including electrode voltage, dynamic resistance and electrode displacement which affected by many affecting factors during the spot welding process were measured and analyzed. The results show that, by comparing with the process parameters during the normal situation, the dynamic change of the these process parameters during different stage appears distinguishable characteristics, these characteristics would supply a research basis for recognizing whether the affecting factors exist.

Abstract: The heterogeneity of microstructure and mechanical performance of welding joints were affected by unique material properties such as high resistivity and low thermal conductivity, instantaneous high temperature of spot welding thermal cycle, and uneven local cooling rate. Because of ultra high strength of hot stamping parts, the welding joint is more inclined to fail as the failure mode of interfacial fracture, the traditional critical nugget formula fell down. Through designing orthogonal experiment, the effect of different welding parameters on joint performance was analyzed, the optimized welding process was obtained; on account of the quality evaluation of welding joint, nugget spherical mode was built to separately analyze the stress condition of welding joint in the failure modes of interfacial fracture and nugget pull-out, the new evaluation criterion aimed at high strength steel was established. Two kinds of 1.2 mm and 2.0 mm steels were used to validate the critical weld diameter. Results showed that the critical formula could accurately evaluate failure of the weld joints.

Abstract: The paper presents the experimental research into joining materials DX51D and DP600 by clinching. Analyses were performed for four sheet metal arrangement combinations in relation to the die and punch, and the resulting joints were shear tested. Based on the results obtained, changes occurring in the diameter of the joint and pressing force were examined for material DX51D. The analysis of welding current effect on maximum strength of joint was conducted. The strengths of pressed and spot welded joints (commonly used in car body assembly) were compared.

Abstract: The paper presents the optimization of spot welding parameters using offline simulation. The procedure of making simulation with SORPAS® is similar to the procedure of doing practical welding process, which can be divided into the following three steps:Data preparation - the materials and geometries of the workpieces and electrodes are defined, the type of welding machine is selected and the process parameters are specified.Running simulation of welding - the parts are welded in the selected welding machine with the specified process parameter settings. The simulations can be carried out in four ways: single simulations, batch simulations, automated optimizations and weld planning.Evaluation of results - the results of welding and quality of weld are evaluated thus the design and parameter settings are verified. With the optimization procedures the weld growth curve can be obtained.

Abstract: Control technology of pneumatic servo spot welding gun is studied, using the proportional flow valve as the control device. The mathematical model of the proportional valve-controlled cylinder system is established, and the experimental studies of position and force control for pneumatic servo spot welding gun have been done. The experimental results show that the servo gun opens smoothly and fast, the impact of electrode is greatly reduced, and the electrode force is controlled precisely and kept steadily, the quick changing of the electrode force is achieved in the welding process.

Abstract: In this paper, structural adhesive SikaPower-498 is associated with spot welds to produce weld bonded joint with KS2 specimens. The specimens are tested under tension, shear and peeling loading. Weld bonded joint ultimate strength and energy absorption are compared with single spot welded joints and adhesively bonded joints tests. In order to investigate the facture mechanism of weld bonded joint, optical microscopy and scanning electronic microscopy are used to check the material structure and the facture surfaces respectively. Weld bonded joints show the highest ultimate strength and energy absorption under tension and peeling test among the three tests while it has intermediate ultimate strength and the lowest energy absorption under shear. Fracture analysis shows that spot welds fail in ductile fracture. The results can be used to design weld bonded joint in car body-in-white and to calibrate modeling parameters for weld bonded joint modeling in finite element calculations.