Resistance Spot Welding Machine Research Articles

Joining of Dissimilar alloy Sheets (Al 6063&AISI 304) during Resistance Spot Welding Process: A Feasibility Study for Automotive industry

Present design trends in automotive manufacture have shifted emphasis to alternative lightweight materials in order to achieve higher fuel efficiency and to bring down vehicle emission. Although some other joining techniques are more and more being used, spot welding still remains the primary joining method in automobile manufacturing so far. Spot welds for automotive applications should have a sufficiently large diameter, so that nugget pullout mode is the dominant failure mode. Interfacial mode is unacceptable due to its low load carrying and energy absorption capability. Strength tests with different static loading were performed in, to reveal the failure mechanisms for the lap-shear geometry and the cross-tension geometry. Based on the literature survey performed, venture into this work was amply motivated by the fact that a little research work has been conducted to joining of dissimilar materials like non ferrous to ferrous. Most of the research works concentrated on joining of different materials like steel to steel or aluminium alloy to aluminium alloy by resistance spot welding. In this work, an experimental study on the resistance spot weldability of aluminium alloy (Al 6063) and austenitic stainless steel (AISI304) sheets, which are lap joined by using a pedestal type resistance spot welding machine. Welding was conducted using a 45-deg truncated cone copper electrode with 10-mm face diameter. The weld nugget diameter, force estimation under lap shear test and T – peel test were investigated using digital type tensometer attached with capacitive displacement transducer (Mikrotech, Bangalore, Model: METM2000ER1). The results shows that joining of Al 6063 and AISI 304 thin sheets by RSW method are feasible for automotive structural joints where the loads are below 1000N act on them, it is observed that by increasing the spots per unit length, then the joint with standing strength to oppose failure is also increased linearly incase of interfacial failure mode and non linear for pullout failure mode.

The Effect Of Nugget Sizes On Mechanical Properties In Resistance Spot Welding Of SPA-C Atmospheric Corrosion Resistant Steel Sheets Used In Rail Vehicles*

Abstract This publication presents an experimental study on the resistance spot welding of SPA-C steel sheets used in side wall and roof application of rail vehicles. SPA-C atmospheric corrosion resistant steel sheets with a thickness of 2.3 mm were joined by using resistance spot welding as lap joint. A timer and current controlled resistance spot welding machine with 120 kVA capacity and a pneumatic application mechanism with a single lever were used to join the specimens. Welding periods were chosen as 5, 10, 15, 20, 25 and 30 cycles (1 cycle = 0.02 s) and also welding currents were increased from 6 kA up to 14 kA by rising in steps of 0.5 kA. The electrode force was kept constant at 6 kN. The welding joints obtained were exposed to tensile peel and tensile shear tests and their nugget sizes were calculated by results of optical microscopy measurements. The effect of nugget sizes on tensile peel strength and tensile shear strength was researched by using related diagrams and the optimum welding currents and times were advised.

Study of safety operation of AC resistance spot welding system

This study deals with the safety operation of AC resistance spot welding (RSW) system. The input of the RSW system is the firing angle of the silicon-controlled rectifier (SCR) during each control cycle. Wrongly choosing a firing angle may induce disastrous consequence. The range of firing angle depends on the system's power factor angle; the relation between the firing angle, power factor angle and conduction angle is highly non-linear. After comparing three methods, a simple mathematical model is proposed in this study to facilitate the online calculation of the power factor angle and selection of the proper firing angle, so that the safety operation of RSW system can be guaranteed. In this condition, the RSW machine can work at the machine's the most capacity, the calculated value of power factor angle should be the lowest limit for actual selected firing angle of SCR. Finally, experimental results confirmed the effectiveness of the proposed mathematical model.

Effect of Welding Current on Mechanical Properties of Welding Joints in S235JR(Cu) Steel Sheets in Resistance Spot Welding

This paper presents an experimental study on resistance spot welding of SPA-C steel sheets used in side wall and roof in rail vehicles. SPA-C steel sheets having 2.3 mm thicknesses were joined by using resistance spot welding as lap joint. A timer and current controlled resistance spot welding machine having 120 kVA capacity and a pneumatic application mechanism with a single lever was used to prepare the specimens. Welding periods were chosen as 5, 10, 15, 20, 25, and 30 cycles and also welding currents were increased from 6 kA up to 14 kA by rise of 0.5 kA. The electrode force was kept constant at 6 kN. The prepared welding specimens were exposed to tensile-shear and tensile-peel tests and the obtained results were supported by diagrams and, nally, appropriate welding parameters were advised to the users.

저항점 용접에서 전극팽창에 관한 동적모델

Abstract A lumped‐mass damped vibratory model was proposed for quantitative understanding of welding machinecharacteristics. An experimental setup was developed to determine the mechanical parameters (moving mass m, equivalent stiffness k and damping c) which govern the dynamic mechanical response of the resistance spot welding machine. During the test, acceleration of the electrodes for each level of applied load was measured by accelerometer, filtered and numerically integrated to find the corresponding velocity and displacement. The machine dynamic parameters were determined by finding the unknowns of the proposed model with experimental data. A Simulink model was proposed to investigate the influence of these mechanical parameters on the welding process. The electrode response was simulated by changing values of stiffness and damping. It was observed that both of the machine parameters(c, k) have significant effect on the response of electrode head. Key Words: Resistance spot welding, Electrode head movement, Accelerometer, Welding machine dynamics

Dissimilar Joining of Aluminum Alloy and Steel by Resistance Spot Welding

Recently, there are strong demands for light-weight, fuel efficient cars. An effective joining technique to join light metals, such as Al and Mg alloys, with steel is required. Mg alloy and steel are especially difficult pair of metals to join. Due to not only Mg alloy's surface oxide, but also their complete phase separation nature, Mg alloy and steel do not form an intermetallic at the joint interface. We aimed to join Mg alloy and steel by using Mg-Zn eutectic reaction, Zn layer was inserted between Mg alloy and steel as plating on steel. A conventional resistance spot welding machine was used, and joint strength was evaluated by tensile strength tests. It was found that Mg alloy surface oxide are removed along with eutectic melt at low temperature, and at the same time, thin and uniform intermetallic layer of Fe-Al and Al-Mg were formed at the joint interface.

Welding time effect on mechanical properties of automotive sheets in electrical resistance spot welding

In this study, the effects of welding time on the tensile-peel strength and tensile-shear strength of welding joints in electrical resistance spot welding of chromate micro-alloyed steel sheets having 1.2 mm thicknesses were investigated. A timer and current controlled electrical resistance spot welding machine having 120 kV A capacity and a pneumatic application mechanism with a single lever was used to prepare the specimens. Welding current periods of 5–10 kA and 12 kA were selected, and it was adjusted by increasing 5 cycle from 5 cycle to 15 cycle during the welding process. The electrode pressure was fixed at 6 kN. The welding joints were exposed to tensile-peel and tensile-shear tests, and the effect of welding time on tensile-peel strength and tensile-shear strength was researched by using related period diagrams. The optimum welding times were obtained.

Evaluation of welds of aluminum alloy AA6022-T4 welded using an electrode force changeable resistance spot welding machine

(2007). Evaluation of welds of aluminum alloy AA6022-T4 welded using an electrode force changeable resistance spot welding machine. Welding International: Vol. 21, No. 7, pp. 471-481.

A method for modelling the pneumatic drive and loadcarrying structure of resistance spot welding machines

A method for modelling the pneumatic drive and loadcarrying structure of resistance spot welding machines

Effect of welding current on mechanical properties of galvanized chromided steel sheets in electrical resistance spot welding

In this study, the effect of welding current on the quality of weld joint and obviously on tensile-shear and tensile-peel strengths of galvanized chromate steel sheets having 1.2 mm thickness in electrical resistance spot welding was investigated. A timer and current controlled electrical resistance spot welding machine having 120 kVA capacity and pneumatic application mechanism with a single lever was used to prepare the specimens. Welding periods were chosen as 5, 10, 12 and 15 cycles and also welding currents were increased from 4 kA up to 12 kA by rise of 1 kA. The electrode force was kept constant at 6 kN. The prepared welding specimens were exposed to tensile-shear and tensile-peel tests and the obtained results were supported by diagrams and, finally, appropriate welding parameters were advised to the users.

Modeling small-scale resistance spot welding machine dynamics for process control

Electrode displacement is generally regarded as a variable that can provide real-time information useful for monitoring and controlling resistance spot welding (RSW) process quality. However, in small-scale RSW production, it is difficult to measure the displacement because its magnitude is very small. By contrast, force signals are relatively large and thus are less susceptible to measurement noise. In this article, an empirical model is proposed to simulate the dynamics of an SSRSW head with the objective of calculating electrode displacement from the variation of electrode clamping force measured during welding. The parameters in the model were determined by fitting experimental force and displacement signals with polynomials and then performing an optimization search for parameters of first-order dynamic models. To verify the models’ accuracy, they were subsequently applied to simulate the electrode displacement curves of welds with expulsion and without expulsion. The calculated displacement curves agreed well with experimental measurements, and the occurrence of expulsion was clearly indicated by the model predictions. A more comprehensive model is under construction with an objective to eliminate displacement sensor in the monitoring and control of SSRSW process.

The effect of nucleus size on mechanical properties in electrical resistance spot welding of sheets used in automotive industry

In this study, the effects of welding current and time on the tensile-peel strength and tensile-shear strength of welding joint in electrical resistance spot welding of chromided micro-alloyed steel sheets having 0.8 mm thickness and galvanized chromided micro-alloyed steel sheets having 1.0 mm thickness were investigated. A timer and current controlled electrical resistance spot welding machine having 120 kVA capacity and pneumatic application mechanism with a single lever was used to prepare the specimens. Welding current periods of 5, 10, 15, 20 and 25 were selected and it was adjusted by increasing 1 kA from 3.5 to 10 kA during welding process. The electrode pressure was fixed at 6 kN. The obtained welding joints were exposed to tensile-peel and tensile-shear tests and their core sizes, heights and nucleus size ratios were calculated by means of an optical microscope. The effect of nucleus size ratios on tensile-peel strength and tensile-shear strength were researched by using related diagrams and the optimum welding currents and times were advised.

A prototype fuzzy resistance spot welding system

In assembly automation, the need to perform on-line quality monitoring and to provide near real-lime inspection of resistance spot welds, has attained unsurpassed importance in industries. This paper describes the development of a prototype fuzzy control system for a two-stage resistance spot welding machine with potential of being incorporated into an automation line. It encompasses a new approach aimed at providing simultaneous control of more than two major welding parameters for achieving consistent quality spot welds by assessing the condition of the heat affected zone created. The prototype system, developed in C language, comes with a decision making mechanism and a quick search mechanism. Its rule-base contains a total of 125 heuristic control rules derived from literature reviews and interviews with experts and through experiments. The various factors affecting the quality of spot welds are outlined in the paper. The correlation between spot weld quality and welding parameters were examined using...

Determining the constitutive properties of the heat-affected zone in a resistance spot weld

A methodology is described for determining the mechanical properties of the heat-affected zone (HAZ) in a resistance spot weld. To perform detailed finite-element analyses of spot weld overload failures, it is necessary to have the mechanical properties of the various HAZ subzones. To this end, simulated HAZ material samples were fabricated in a process that utilized a resistance spot welding machine fitted with specially modified electrodes. Tensile tests at several loading rates were performed on miniature notched-bar specimens machined from the simulated HAZ material. These tests provided the empirical data from which the strain hardening capacities and strain rate sensitivities of the weld HAZ were determined through detailed finite-element analyses of the notched-bar tensile tests.

Mechanical properties of resistance spot and projection welding machines

Mechanical properties of resistance spot and projection welding machines