This work compares three aluminium sheet joining processes to determine their capability, efficiency and cost for mass production applications in automotive structures and closures. The joining processes investigated are Resistance Spot Welding (RSW), SelfPierce Riveting (SPR) and Spot Friction Joining (SFJ). Quantitative comparisons have been made on the basis of tensile strength (shear and peel), process time, equipment price and running cost. RSW is the most commonly employed joining method for steel sheet in the automotive industry. Its principle benefits are high speed and low cost operation, plus the ability to weld a wide range of joint configurations with the same gun. The main process limitations for aluminium are weld consistency and electrode-life, though recent work has shown that both of these can be largely overcome with regular electrode polishing

Comparison of Self-Pierce Riveting, Resistance Spot Welding and Spot Friction Joining for Aluminium Automotive Sheet

Overview of recent advances of process analysis and quality control in resistance spot welding

This paper presents a dynamical non linear model of the spatial time-dependant evolution of A 3 point during a particular sequence of resistance spot welding in steel material. The model is based on a solution to the heat equation, expressed in cylindrical coordinates inside the joint area, and when the source term is attributed to the electrical power. By the mean of the steel binary Fe–C diagram and the deduced t -dependant temperature rise profile, an estimation of the A 3 point spatial range date is given and compared to further results. The obtained temperature profile is yielded, taking into account main parameters variations, as a guide to non-destructive protocols and thermal characteristics investigation

A dynamical model for investigation of A 3 point maximal spatial evolution during resistance spot welding using Boubaker polynomials

In this study, we are concerned with the temperature distribution inside the central nugget during a particular sequence of resistance spot welding (RSW). Numerical calculations are issued from an attempt to solve heat transfer equation inside the heated device. Boubaker polynomial expansion scheme has been applied to the main system solution expressed in cylindrical coordinates and which is solved using the Householder-QR/QL algorithm. The melting point maximal front spatial evolution has been monitored in order to make comparison with precedent results.

Numerical Distribution of Temperature as a Guide to Investigation of Melting Point Maximal Front Spatial Evolution During Resistance Spot Welding Using Boubaker Polynomials

The aim of this paper is to provide an integrated real-time control system for resistance spot welding (RSW), which is capable of producing welds with predetermined nugget diameters. Nugget diameter is a commonly used criterion for estimating the weld quality; thus, the system can be used for online quality control of RSW. The proposed system consists of two parts: a constant current controller and an online nugget diameter estimator. The constant current controller is used to guarantee the consistency of the nugget formation and growth during the welding process, while the online nugget diameter estimator can be used as a sensor for online estimation of the nugget diameter. The proposed online nugget diameter estimator is a mathematical function of the heat energy absorbed by the weld, which is taken into account only after the time when the first melting point of a weld appears. This time can be obtained by means of the dynamic resistance curve with a high resolution. A mathematical model of the online nugget diameter estimator is proposed and realized based on the experiment results and mathematical analysis. The welding process would be terminated when the difference between the actual nugget diameter and the predetermined desired value is within a given tolerance. According to a series of experiments, the welds used in the experiments had nugget diameters, which were well within the limits and the errors were within the given tolerance.

Online nugget diameter control system for resistance spot welding

This paper presents a comparative study of the AC and MFDC resistance spot welding process. Both experiments and finite element simulation were conducted to compare the weld size and energy consumption. The experiments were performed on two identical spot welding machines, one with a single phase ac and the other with a mid-frequency DC weld control. The machines were instrumented such that both the primary and secondary voltage and current signals could be collected for energy calculation. The finite element simulation model was developed to understand the underlying mechanisms of the difference between the ac and MFDC processes. The effect of the current waveform was investigated by using the actual process measurements as an input to the simulation model. It is shown that the MFDC process generally produces larger welds than the AC process with the same root-mean-square welding current. However, this difference is more prominent when the welding current is relatively low. Overall, the AC welding process consumes more energy to make a same sized weld than the MFDC process. The larger the welding current is used, the less efficient the AC welding process will become. The differences between the two welding processes are caused by the contact resistance behavior and the electrical inductance in the AC welding process.

A comparative study of single-phase AC and multiphase DC resistance spot welding

This paper presents a comparative study of alternating current (AC) and direct current (DC) resistance spot welding (RSW) processes. Two identical weld guns were used, one with a single-phase AC and the other with a median-frequency DC (MFDC) weld control. The welders were instrumented such that the energy consumptions at both the primary and secondary side of the transformer could be calculated. A nugget growth experiment was conducted to compare the weld size and the energy consumption in the AC and MFDC welding processes. It has been found that given the same welding current, the weld sizes achieved in the AC and DC processes are different and the difference is more prominent when the welding current is low. When the welding current is high and close to the expulsion limit, the weld sizes are similar in the AC and DC processes. In general, it takes 10% more total energy to make a same size weld in the AC process than it does in the DC process. The differences in the AC and DC welding processes are explained with a finite-element simulation model. The energy efficiencies of the AC and DC welding processes are also discussed.

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Energy consumption in ac and mfdc resistance spot welding

A resistance spot welding monitoring system includes a plurality of sensors coupled to a resistance spot welding system to receive welding data produced during a welding operation. The monitoring system further includes a nugget prediction system. The welding data is indicative of welding parameters used to produce the weld nugget. The nugget prediction system retrieves the welding data and predicts a nugget size based upon the welding data received from the plurality of sensors. Additionally, the nugget prediction system generates a nugget size signal. The monitoring system also includes an indicator that receives the nugget size signal and notifies an operator of a predicted nugget size.

Resistance Spot Welding Monitoring System and Method

This paper presents a comparative study of the AC and MFDC resistance spot welding process. Two identical welders were used; one with a single phase AC and the other with a median frequency DC weld control. Both welders were instrumented such that the primary and secondary voltage and current could be collected. A nugget growth experiment was conducted to compare the weld size and energy consumption in the AC and MFDC welding processes. It is found that the MFDC process generally produces larger welds with the same welding current. However, this difference is more prominent when the welding current is low. Overall the AC welding process consumes more energy to make a same size weld. The larger the welding current is used, the less efficient the AC process becomes.Copyright © 2004 by ASME

A Comparative Study of AC and MFDC Resistance Spot Welding

Resistance spot welding is widely used for joining sheet metal materials in the automotive industry. Most of the existing resistance spot welding systems are single-phase AC-based, and with constant current control. The medium frequency DC (MFDC) system with constant heat control (CHC) is new technology in the resistance spot welding industry. This system promises dramatic improvement on the spot weld quality. However, many of the CHC features are still not known and need to be explored. This paper presents an experimental study on a new MFDC/CHC spot welding system. The goal is to characterize the MFDC/CHC welding process in terms of the process parameters, including the target energy level, force, and welding time. Real time process signals such as force, current, and tip voltage were also collected and analyzed to compare with the traditional spot welding process.Copyright © 2005 by ASME

Daniel Cerjanec

Papers

A comparative study of single-phase AC and multiphase DC resistance spot welding

Energy consumption in ac and mfdc resistance spot welding

Resistance Spot Welding Monitoring System and Method

A Comparative Study of AC and MFDC Resistance Spot Welding

Experimental Characterization of MFDC/CHC Resistance Spot Welding