Resistance Spot Welding Quality Research Articles

Real time monitoring weld quality of small scale resistance spot welding for titanium alloy

Titanium and its alloys have been identified as one of the best engineering metals for application in industrial fields. Whereas, there is limited research work on monitoring and controlling the small scale resistance spot welding (SSRSW) of titanium alloy. This paper performed a systematic research on the voltage curve, which turned out to be an indication for weld quality of SSRSW. It was obtained through clipping two leads onto the electrodes during SSRSW process. As the common equipment in SSRSW, the high frequency (HF) power supply and constant current mode were employed in this study. First voltage curves at different welding parameters were analyzed and then a probabilistic neural network (PNN) model using three factors extracted from the voltage curve was employed in order to classify the weld quality, and satisfied experiment results were acquired. It was demonstrated that the dynamic voltage during a welding process could be identified as a good signature for weld quality monitoring purpose.

A Comprehensive Approach for Resistance Spot Welding Quality Estimation Using Dynamic Resistance Based Model

On-line quality assessment becomes one of the most critical requirements for improving the efficiency of automatic resistance spot welding (RSW) processes. Accurate and efficient model to perform non-destructive quality estimation is an essential part of the assessment. Besides the usual welding parameters, various measured variables have been considered for quality estimation in RSW. Among these variables, dynamic resistance gives a relative clear picture of the welding nugget formation and presents a significant correlation withseveral RSW quality indicators. This paper presents a structuredand comprehensiveapproach developed to design an effective dynamic resistancebased model for on-line quality estimation in RSW. The proposed approach examines welding parameters and conditions known to have an influence on weld quality, and builds a quality estimation model step by step. The modeling procedure begins by examining, through a structured experimental design, the relationships between welding parameters, typical characteristics of the dynamic resistance curves and multiple welding quality indicators. Using these results and various statistical tools, different integrated quality estimation models combining an assortment of dynamic resistance attributes are developed and evaluated. The results demonstrate that the proposed approach can lead to a consistentmodel able to accurately and reliably provide an appropriate estimationof the weld quality under variable welding conditions.

Dynamic Resistance Based Model for On-Line Resistance Spot Welding Quality Assessment

On-line quality assessment becomes one of the most critical requirements for improving the efficiency of automatic resistance spot welding (RSW) processes. Accurate and efficient model to perform non-destructive quality estimation is an essential part of the assessment. Besides the usual welding parameters, various measured variables have been considered for quality estimation in RSW. Among these variables, dynamic resistance (DR) gives a relative clear picture of the welding nugget formation and presents a significant correlation with the RSW quality indicators (QI). This paper presents a structured approach developed to design an effective DR-based model for on-line quality assessment in RSW. The proposed approach examines welding parameters and conditions known to have an influence on weld quality, and builds a quality assessment model step by step. The modeling procedure begins by examining, through a structured experimental design, the relationships between welding parameters, typical characteristics of the RD curves and multiple welding QI. Using these results and various statistical tools, different integrated quality assessment models combining an assortment of DR attributes are developed and evaluated. The results demonstrate that the proposed approach can lead to a general model able to accurately and reliably provide an appropriate assessment of the weld quality under variable welding conditions.

Quality monitoring of resistance spot welding based on process parameters

For on-line monitoring and controlling the quality of resistance spot welding, we design a high speed data acquisition and spot welding signal processing system. System hardware, which are made up of PLC 1800 high speed data acquisition card current sensor voltage sensor signal adjust circuit and IPC, is mainly responsible for A/D conversion and data acquisition; software system are mostly made up of data acquisition and memory module wavelet filtering of digit signal module U-I image and energy analyze module in electric signal of spot welding, which realize the data acquisition and processing base on welding current electrode voltage welding cycle. The experimental result showed that U-I image shape of different material are markedly dissimilar in spot welding, according to U-I image we can check if welding current and electrode voltage are normal in welding process or not, and through U-I image we can read the input energy of every U-I curve half-cycle and judge spot welding quality. Therefore, we can take U-I image monitoring method in spot welding quality monitoring of different material.

Influence of Corrosive Environment on the Surface Quality of Spot Welds

The paper deals with the evaluation of quality of resistance spot welds. Hot-dip galvanized steel sheets of DX54D+Z quality were used for experiments. Electrochemical properties of used materials were observed. Carrying capacities of spot resistance welds were measured before as well as after exposure in corrosive environment. The tensile test was used for evaluation of carrying capacities. The quality of spot welds was evaluated on the base of microhardness measurements results realized on the scratch patterns too.

A Study of Fuzzy Neural Networks Control for the Quality of Resistance Spot Welding

A fuzzy neural network based system was developed to control the quality of resistance spot welding. A fuzzy neural controller (FNC) was designed to realize the memory of the fuzzy neural control bases on a back propagation (BP) network, accordingly achieve the mapping of fuzzy input and output. The experiment results show that this method can compensate the multi-crossfire’s influence on the welding currency, keep a high control precision, and fulfill the demand of high precision quality monitoring to the resistance spot welding.

Effect of External Constant Magnetic Field on Weld Nugget of Resistance Spot Welded Dual-Phase Steel DP590

The applications of magnetic field in metal casting and welding processes have drawn much attention of researchers. However, the effect of external magnetic field on nugget formation of resistance spot welding (RSW) is still lack of understanding. In this paper, the effect of a radially oriented constant magnetic field generated by a pair of ring-shaped permanent magnets on the weld nugget of RSW was experimentally investigated. The nugget diameter, microhardness, and mechanical performance were compared between welds with and without the external magnetic field. Results showed that, under the action of the external magnetic field, the weld nugget got wider with an increase in diameter by nearly 10%. Besides, the Vickers hardness in fusion zone (FZ) of the welding joint was more uniform. As a result, the RSW joints welded under the constant magnetic field exhibited better mechanical performance in tensile-shear tests. Therefore, the application of the external constant magnetic field could be an effective way to control the weld quality of RSW by affecting its melting and crystallization process.

Impact of External Magnetic Field on Weld Quality of Resistance Spot Welding

Electromagnetic stirring (EMS) has been demonstrated to have significant effect on molten metal in terms of crystal orientation, grain refinement and macro appearance of solidified structures by making use of Lorentz force. In the present study, resistance spot welding (RSW) process of 1.25 mm thick dual-phase steel DP780 with and without the external magnetic field applied has been experimentally investigated. Impacts of the EMS method on nugget appearance, quasi-static performance, fatigue life, and fracture morphology have been systematically discussed. Results of the metallographic tests showed that, compared with the traditional resistance spot weld (RSW weld), the weld under the EMS effect (EMS-RSW weld) was wider and thinner with an obvious increase in nugget diameter. Besides, within the EMS-RSW weld, crystal orientation along the faying surface of workpieces was less directional and the grains were refined. Slightly higher uniformity in the fusion zone and more notable softening in the heat affected zone of the EMS-RSW weld were observed by microhardness tests. With regard to the mechanical properties, both tensile-shear and cross-tension samples of the EMS-RSW welds exhibited higher ultimate failure loads and longer elongations at the failure points than that of the traditional RSW welds. The EMS-RSW welds also showed longer fatigue life under dynamic tensile-shear loads, especially in high cycle conditions. Furthermore, the EMS-RSW welds exhibited a higher frequency of button-pullout fractures under the welding current close to the minimum current that the traditional RSW welds required to prevent weld interfacial fractures under quasi-static tensile-shear loads. Even if both types of the welds exhibited interfacial fractures under a relatively weak welding current, more dimples were found in the fracture surfaces of the EMS-RSW welds than that of the traditional RSW welds. It can be concluded that the external magnetic field during RSW process could improve weld performance of DP780 by enhancing weld strength and plasticity. EMS could be an effective method to improve the weldability in RSW of advanced high strength steel, ultra high strength steel, and even light metals.

Artificial neural network-based resistance spot welding quality assessment system

On-line quality assessment has become one of the most critical requirements for improving the efficiency and the autonomy of automatic resistance spot welding (RSW) processes. An accurate and efficient model to perform non-destructive quality estimation is an essential part of the assessment process. This paper presents a structured and systematic approach developed to design an effective ANN-based model for on-line quality assessment in RSW. The proposed approach examines welding parameters and conditions known to have an influence on weld quality, and builds a quality estimation model step by step. The modeling procedure begins by examining, through a structured experimental design, the effect of welding parameters (welding time, welding current, electrode force and sheet metal thickness) and welding conditions represented by typical characteristics of the dynamic resistance curves on multiple welding quality indicators (indentation depth, nugget diameter and nugget penetration) and by analyzing their interactions and their sensitivity to the variation of the dynamic process conditions. Using these results and by combining an efficient modeling planning method, neural network paradigm, multi-criteria optimization and various statistical tools, the identification of the model form and the variables to be included in the model is achieved by executing a systematic model optimization procedure. The results demonstrate that the proposed approach can lead to a general ANN-based model able to accurately and reliably provide an appropriate assessment of the weld quality under diverse and variable welding conditions.

Effect of governing metal thickness and stack orientation on weld quality and mechanical behaviour of resistance spot welding of AA5754 aluminium

A study was carried out to investigate the effect of governing metal thickness (GMT) and stack orientation on weld quality and mechanical behaviour of resistance spot welded (RSW) AA5754 aluminium. Individual samples from 27 different joint stacks in three test geometries; lap-shear, coach-peel and cross-tension were evaluated for quasi-static and fatigue performance; micro examination was also conducted on some of the samples to assess weld quality. The results derived from over 1000 samples show that: the GMT has a significant effect on welding quality by controlling progression of weld nugget from under-developed to over penetrated. The GMT also determines the feasible quasi-static joint strength regardless of stacks in the three joint geometries tested, though the effect differs with respect to test geometry. The fatigue behaviour is dominated by the effect of GMT on attainable weld size, overall joint stiffness and stress concentration, providing good quality of weld nuggets is achieved. No notable effect of stack orientation on weld quality and joint strength was found with respect to the joint stack asymmetry and welding orientation to the electrodes. These fundamental relationships between weld qualities, joint strength, GMT and stack orientation for RSW of aluminium will have significant relevance to design and manufacturing communities.

Analysis of Electromagnetic Inverse Model of Resistance Spot Welding

Resistance spot welding (RSW) is an important welding process in modern industrial production, and the quality of welding nugget determines the strength of products to a large extent. Limited by the level of RSW quality monitor, however, RSW has rarely been applied to the fields with high welding quality requirements. Associated with the inversion theory, in this paper, an electromagnetic inverse model of RSW was established, and the analysis of influence factors, such as the layout of the probes, the discrete program and the regularization method, was implemented as well. The result shows that the layout of the probe and the regularization method has great influence on the model. When the probe is located at the y direction of x-axis or the x direction of y-axis and Conjugate Gradient method is selected, a much better outcome can be achieved.

Effect of aluminium sheet surface conditions on feasibility and quality of resistance spot welding

A study investigating the effect of sheet surface condition on resistance spot welding (RSW) of aluminium has been carried out. This concentrates on two automotive aluminium alloys; AA5754 and AA6111, used for structural and closure applications respectively. The results show the marked effect that surface condition can have on the RSW process. For AA5754 sheet incomplete removal of a ‘disrupted surface layer’ prior to surface pretreatment is shown to have a detrimental effect on the RSW process. The solid wax lubricant used to assist metal forming leads to unpredictable changes in contact resistance, and consequently affects the process stability. For AA6111 closures the final surface topography can influence the RSW process. Standard ‘mill’ and electro-discharge textured (EDT) finish sheet surfaces were examined and preliminary results suggest that both are suitable for welding. The successful application of RSW of aluminium sheet requires careful consideration of the sheet surface condition. This requires close collaboration between material suppliers and automotive manufacturers.

Input electrical impedance as quality monitoring signature for characterizing resistance spot welding

Poor quality of resistance spot welding (RSW) often causes quality issues like structural integrity and noise in the car body assembly. Research activities for reliable monitoring methods of RSW quality have therefore been extensive. So far, most of the monitoring methods found in literature are good for off-line utilization only and thus very expensive to apply. This paper introduces into a real-time and in-situ RSW quality monitoring method, which takes the input electrical impedance of the welding system as the monitoring signature. This signature is obtained by probing and processing the input voltage and current throughout the welding process. As input impedance characterizes a dynamic system, its variation with time reveals the conditions of the welding process which result in the final weld quality. By recognizing the pattern of the real part by an artificial neural network, we demonstrate that the weld quality could be classified non-destructively and automatically. Due to the fast signal collecting and processing, the quality monitoring is finished almost in real-time, i.e., classification can be completed before the next welding process is started. Another feature of the method is being in-situ because monitoring action does not jeopardize the welding operation or alter any of the welding parameters in general.

Resistance spot welding processing monitoring based on electrode displacement curve using moving range chart

Electrode displacement curve is an ideal monitoring parameter which can directly reflect spot weld nugget formation in resistance spot welding (RSW) process. The current RSW quality monitoring systems based on electrode displacement curve mainly focus on the low frequency information of the curve, such as the curve’s shape. Variation of the curve that represents process consistency is little studied. Based on on-line measured electrode displacement curve, statistical process control method is introduced to analyze the process consistency by employing moving range (MR) chart. The moving range method implemented the RSW process monitoring through providing the high frequency information of the curve. The results of this research will enhance the understanding of the electrode displacement curve, and help systematically design better on-line RSW quality monitoring systems. A case study demonstrates the validity and effectiveness of the methodology.

Real Time Monitoring Weld Quality of Resistance Spot Welding for Stainless Steel

Resistance spot welding (RSW) is one of the most widely used processes in sheet metal fabrication. Although used in mass production for several decades, RSW has a major problem of inconsistent quality from weld to weld, which results from both the complexity of basic process as well as from various process conditions, noise and errors. There have been a number of investigations on monitoring and controlling the resistance spot welding of low carbon steel by using dynamic resistance, but those for stainless steel are limited because the dynamic resistance has descent property. Dynamic resistance curve in spot welding for low carbon steel has a typical shape: the resistance drops sharply at the beginning, and then rises; before the current is terminated, the resistance starts to drop, which results in a peak. Unlike low carbon steel, dynamic resistance for stainless steel decreases rapidly at the beginning and then decreases at a reducing rate.The objective of this research is to explore the effects of various process conditions in spot welded stainless steel on quality by using dynamic resistance. The process conditions studied in this research are chosen to be the most often observed in production, such as variations of welding parameters, edge weld, small weld spacing, poor fitup and axial misalignment. A series of experiments will be conducted to research how process conditions affect the dynamic resistance. The results show that dynamic resistance responds well to the variations of process conditions and can serve as an important indicator of weld quality.

인장전단시험을 이용한 TRIP1180강의 계면파단특성 평가

The weldability of resistance spot welding of TRIP1180 steels for automobile components investigated enhance in order to achieve understanding of weld fracture during tensile-shear strength (TSS) test. The main failure modes for spot welds of TRIP1180 steels were nugget pullout and interfacial fracture. The peak load to cause a weld interfacial failure was found to be related to fracture toughness of the weld and the weld diameter. Although interfacial fracture occurred in the spot welded samples, the load-carrying capacity of the weld was high and not significantly affected by the fracture mode. Substantial part of the weld exhibits the characteristic dimple (or elongated dimple) fractures on interfacial fractured surface also, dimple fracture areas were drawmatically increased with heat input which is propotional to the applied weld current. In spite of the high hardness values associated with the martensite microstructures due to high cooling rate. The high load-carrying ability of the weld is directly associated with the area of ductile fracture occurred in weld. Therefore, the judgment of the quality of resistance spot welds in TRIP1180 steels, the load-carrying capacity of the weld should be considered as an important factor than fracture mode.

OPTIMIZING THE PROCESS OF RESISTANCE SPOT WELDING FOR 2014 – O ALUMINUM ALLOY SHEET

There is a strong interest in the use of aluminum alloy sheet for vehicle applications, particularly the body, where resistance spot welding is the principle joining method. The resistance spot welding (R.S.W) quality has a great effected by the process variable such as, welding current, welding time, and electrode pressure beside other variable such as material thickness and type and electrode diameter.
 In this work the effect of process variable on welding quality was investigated. Trials were conducted on 1.2 mm thick 2014 – O aluminum alloy sheet. The tensile shear strength was used as primary index of welds quality. Experimental investigation show that the best current is 45 KA, best time is 10 cycle, and electrode pressure of 3 KN .

Controlling the quality of resistance spot welding by stabilising secondary current during wear of welding electrodes

(2008). Controlling the quality of resistance spot welding by stabilising secondary current during wear of welding electrodes. Welding International: Vol. 22, No. 2, pp. 110-112.

Multiple information fusion and quality classification of aluminum alloy resistance spot welding

Resistance spot welding quality real-time monitoring of aluminum alloy is realized by distributed multiple-sensor synchronous collection system and the related data processing software is also developed by using LABVIEW graphical language.The results show that the endo-expulsion in spot welding is related to the notching curve of voltage and electrode displacement signal.Moreover,there is a correlation between the high frequency impulse amplitude and duration of the electrode pressure signal and the expulsion strength index,and three characteristics simultaneously or separately occur according to the expulsion strength index in spot welding. Resistance spot welding quality can be reflected by nine characteristics of high signal-to-noise ratio,and they become the base of on-line quality classification of aluminum alloy spot welding in future.Furthermore,using principal component analysis may implement the information fusion and data compression.The percentage of spot welding quality classification accuracy can reach 98%.

Improving the quality of resistance spot and butt welding using electrodes made from dispersion-hardened composite materials

Improving the quality of resistance spot and butt welding using electrodes made from dispersion-hardened composite materials