Resistance Spot Welding Research Articles

Benchmark for welding gun fault prediction with multivariate time series data

In the automotive industry, machinery failures of the resistance spot welding (RSW) guns would interrupt the manufacturing lines and cause unplanned downtime, potentially resulting in a significant loss of production and reliability. Predicting the machinery failures of the RSW gun can provide more scientific strategies for predictive maintenance and decision-making. However, fault prediction of RSW guns has become increasingly challenging due to their complex behavior and data variability. In this paper, we created a benchmark dataset and proposed welding gun fault prediction benchmarks to aid in the development of machine learning approaches toward welding gun fault prediction. The dataset was collected at the Body-Shop (BS) of BMW Brilliance Automotive Ltd. from different components of hundreds of RSW guns to capture the patterns and trends before welding errors with historical data. Then we provide state-of-the-art machine learning (ML) benchmarks on time series forecasting methods in a welding gun fault prediction use case. This study will provide insights for time series forecasting while enabling ML researchers to contribute towards the fault prediction of the RSW guns.

Half-sectioned spot weld parameter optimisation for liquid metal embrittlement analysis in advanced high-strength steels

Half-section welding has been proposed as a method to observe nugget growth throughout the resistance spot welding process. Some past studies used this technique as an in-situ monitoring approach to analyse the cracking behaviour during welding. However, there is a lack of understanding regarding the half-sectioned welding parameters, which critically impacts the liquid metal embrittlement cracking index. This study optimised half-sectioned welding parameters for liquid metal embrittlement crack analysis by developing process maps that compare the half-sectioned and full-section processes. It was found that the liquid metal embrittlement crack located at the weld shoulder can correlate to the temperature gradient in the heat-affected zone. This study proposes half-sectioned welding as a viable technique for liquid metal embrittlement analysis.

Comparison of Weldability and Microstructure in Resistance Spot Welding of Aluminum 5052-H32 Alloy and Al 6014-T4 Alloy

This study was performed to compare the resistance spot weldability of Al 5052-H32 alloy and Al 6014-T4 alloy, and the cause of the differences in the weldability was investigated. In general, the surface of the aluminum alloy has an oxide film several nm thick, and local heat input is generated at the electrode-sheet interface and the sheet-sheet interface during resistance spot welding. XPS analysis proved that the Al 5052- H32 alloy has a relatively thick magnesium oxide film on the surface and contains a large amount of magnesium solute element. As a result, Al 5052-H32 has a higher resistance, in both the contact resistance of the electrodesheet interface and sheet-sheet interface, compared with the Al 6014-T4 alloy. Therefore, the Al 5052-H32 alloy has a larger nugget diameter at the same welding current as compared to the Al 6014-T4 alloy, but the surface contamination of the electrode is aggravated due to local heat input. The results indicated that a difference in oxide film type and thickness can significantly influence resistance heat generation and electrode cooling effects, as well as produce welds with different weld morphology and microstructure. In addition, the Al 5052-H32 alloy had more pores and shrinkage in the weld than Al 6014-T4 alloy, and longitudinal cracks were observed in the center of the nugget, but had relatively excellent mechanical properties.

Selected properties of single-sided resistance spot welded joints on 18650 battery tab

The aim of this study was to characterize selected properties of joints made by single-sided serial resistance spot welding of 0.15 mm thickness Hilumin connectors to the negative terminal of LGDBHG21865 lithium-ion cylindrical battery cell. Welding process was performed using production parameters to properly represent actual manufacturing conditions. Mechanical properties of the joints were examined by means of tensile stress test and microhardness measurements while additional studies include metallographic analysis of the joint cross sections by means of optical and scanning microscopy. Energy dispersive spectroscopy was performed in order to determine surface distribution of elements within the weld nugget. Studies confirmed suitable microstructure of welded joints, repeatability of the welding process and proper selection of the welding parameters.

On-line measurement of nugget diameter in automatic resistance spot welding based on embedded ultrasound probe

The inspection of resistance spot welding (RSW) quality is crucial in the sheet metal joining industries. This paper proposes an enhanced approach for the automated real-time measurement of weld nugget diameter in welded joints, utilizing an ultrasonic probe integrated within the electrode. The ultrasonic signals received by the probe are sequentially arranged to generate consecutive ultrasonic B-scan images, which effectively capture the entire weld nugget growth and solidification process. The corresponding maximum time of flight (TOF) for the liquid nugget is extracted from the B-scan image. In the condition of qualified welding quality, a mathematic equation between maximum TOF and weld nugget diameter is established, while the opposite is alarmed. The on-line quality inspection of RSW can autonomously determine the qualification of welding quality, as well as quantitatively evaluate the weld nugget diameter in qualified weld joints. The research is applicable to various processing and manufacturing fields.

Numerical modeling of liquid metal embrittlement initiation during resistance spot welding of third generation advanced high strength steel – Effect of welding schedule and electrode alignment

Third generation (GEN3) advanced high-strength steels are increasingly used to reduce vehicle body structure weight for improved fuel economy. Zinc-induced liquid metal embrittlement (LME) has become a prevalent challenge when these steels are welded by resistance spot welding (RSW). In the literature, various numerical models have been developed to study LME during RSW of GEN3 steels. Those models tend to have a limited utility in predicting how various factors such as RSW parameters affect LME cracking. In this study, a novel LME calculation method has been developed by integrating an electro-thermo-mechanical finite element model of RSW process with an LME ratio for crack initiation established from hot tensile testing data. The onset of different types of LME cracking is tracked throughout the weld region over the entire course of RSW including the final cooling stage after electrode retraction. The model is validated using an existing set of literature data that involves different welding schedules, electrode geometries and electrode misalignments. The local temperature and stress conditions during RSW are calculated and used to understand how different welding parameters affect the severity of LME cracking. It is found that electrode misalignment exacerbates crack initiation on outer surfaces of the spot weld due to the tensile stress arisen from the off-centered squeeze force as well as the reduced surface cooling to electrodes. Initiation of cracks between the steel sheets, taking place mainly after electrode retraction, is not significantly affected by the welding schedule and the electrode tip diameter.

Joining thin galvanized low carbon steel sheet to AA6056-T4 by resistance spot welding and adhesive weld bounding

Multimaterial assemblies made by resistance spot welding (RSW) process offer a cost-efficient lightweight solution for automotive body-in-white production. However, joining different materials, such as steel (Fe) and aluminum (Al), brings issues due to their different physical properties and low weldability. The present work investigated the evolution of the weld between a thin galvanized low carbon steel sheet and an AA6056-T4 aluminum alloy from macroscopic observations to the evolution of the intermetallic compound layer (IMC) during RSW. Comparisons between homogeneous Al-Al RSW, Fe-Al RSW and Fe-Al adhesive weld bonding for different mechanical solicitations were also realized. Observations showed that the interface for short welding periods is composed of a thin and discontinuous IMC layer. The interface also presents defects that facilitate crack initiation and propagation, leading to an interfacial fracture mode. The different mechanical tests carried out demonstrated that the Al-Al and Fe-Al welds reached a similar maximum tensile load under the shear–tensile test. However, Fe-Al assemblies under cross-tensile test showed poor mechanical properties. The use of an adhesive layer with an Fe-Al spot weld seems to be a potential solution, as it is easily implementable on production lines and improves the mechanical properties of Fe-Al assemblies.

An Approach to Inline Monitoring of the Electrode State in Resistance Spot Welding

Resistance Spot Welding (RSW) is a key technology for joining car body parts. During the process, the upper and lower electrodes of the welding gun are subject to wear, which affects the electric current flow and thus, the quality of the spot weld. To counteract this effect, the electrode tip is dressed after a predefined number of spot welds. The frequency for tip dressing is based on experience and does currently not directly reflect the actual state of the electrode. This work provides an approach to inline electrode state monitoring to determine the ideal and demand-based point in time for electrode tip dressing based on process data. We avoid costly and time-intensive experimental labeling of electrode states and utilize changes in the dynamic electrical resistance between dressing cycles to represent the electrode wear state. To describe the changes in the dynamic electrical resistance curve, new features such as the peak time delay are calculated and visualized. We evaluate our approach with a real-world data set that stems from a dynamic and complex environment out of a series production line, which, in contrast to laboratory data, ensures a successful application of the proposed methods in an industrial setting.

Prospects for Numerical Simulation in Resistance Spot Welding

Prospects for Numerical Simulation in Resistance Spot Welding

Achieving excellent properties of resistance spot welded 2GPa-grade press hardened steel and galvanized DP980 steel via double-pulse

Obtaining the excellent resistance spot welding (RSW) properties of press hardened steel is a challenge due to the high strength with 2GPa-grade. In this study, the microstructure, mechanical properties of the RSW weld in 2GPa-grade PHS and galvanized DP980 steel were investigated. During the single pulse welding, the coarse columnar martensite is generated in the fusion zone (FZ). The low peak load is 13.2 kN for tensile-shear (TS) loading and 3.4 kN for cross-tension (CT) loading and the corresponding failure energy is 6.5 J and 16.7 J, respectively. The fracture mode under two loading conditions is partial thickness-partial pullout (PT-PP) mode. To enhance mechanical properties, the suitable double pulse welding was applied. Compared with that of the single pulse weld, double pulse weld has three special zones in FZ: the Re-melted FZ with columnar martensite, the recrystallization zone (RX-zone) with equiaxed martensite and the tempering zone (T-zone) with tempered columnar martensite. The peak load under the TS and CT loading is significantly improved by 39 pct and 44 pct and the failure energy for TS loading is enhanced by 38 pct and 186 pct for CT loading, respectively. The failure mode changes from the PT-PP mode to the pullout failure (PF) mode for CT loading in double pulse welds.

Future-proof welding simulation tools to improve vehicle operational reliability

The article discusses technologies for modeling welding operations using modern design tools, which will improve the quality of repairs with the existing resource base, as well as the operational reliability of vehicles after repairs. Keywords resistance Spot Welding (RSW), welding simulation, transport system safety, operational reliability

Features and Challenges of Single-sided Resistance Spot Welding

Features and Challenges of Single-sided Resistance Spot Welding

The effect of current on the resistance spot welding of dual phase steels

The effect of current on the resistance spot welding of dual phase steels

An Investigation of the Effects of Parameters on the Development of Nuggets and the Tensile Properties of IN-625 During Resistance Spot Welding

An Investigation of the Effects of Parameters on the Development of Nuggets and the Tensile Properties of IN-625 During Resistance Spot Welding

Electrode lifetime in resistance spot welding of coated sheets: Experiments and modeling

One of the most important challenges associated with resistance spot welding of coated sheets is short electrode life time. It has been established that the two factors-electrode tip growth and surface alloy formation-each affect negatively on electrode life when considered separately. This study's objectives were to examine the combined effects of these factors and ascertain how they relate to electrode life. Due to this, two electrodes were used to investigate the electrode life when resistance welding galvanized steel: a conventional Cu-Cr electrode with a compressive strength of 800 MPa and a dispersion strengthened copper electrode with a high volume percentage of alumina particles (3.5 %) with a compressive strength of 500 MPa. Electrode life time tests showed that the life of composite electrode (700 weld number) was reduced by about 20 % compared to Cu-Cr electrode (900 weld number). Electrode tip features showed that cracking in Cu-Cr electrode formed at about 200 weld number while in composite electrode this occurred at 600 weld number. The electrode tip cross section revealed the formation of four separate alloy layers at the tips of both electrodes, however the Cu-Cr electrode had significantly higher crack densities and a lower average thickness during life test (45 µm) than the composite electrode (55 µm). It was caused by the higher rate of electrode tip growth in Cu-Cr electrodes, which increased welding current and extended electrode life. A simple model was purposed for electrode life based on Joule heating effect that takes the effects of both electrode tip growth and electrode tip alloy formation in to account. According to the model and experiments when significant interaction occurs at the electrode tip, the some tip growth rate not only isn’t detrimental but also increases the electrode lifetime.

Advanced process characterization and machine learning-based correlations between interdiffusion layer and expulsion in spot welding

Over the past decades, substantial endeavors have been dedicated to unraveling the intricacies inherent to Resistance Spot Welding (RSW). However, a comprehensive and consensual understanding of the RSW process physics is still lacking, including the exact number of physical phases behind the RSW process. For example, a widely accepted model indicates that metal only starts melting after the peak of dynamic resistance, while the latest research on welding uncoated materials challenges this by suggesting that melting begins around the resistance peak. Furthermore, most of existing physical models only consider welding materials without coatings in a controlled lab setting, whereas coated sheet metal is the norm in real production. Addressing these challenges, this paper introduces an enhanced model for RSW that considers the melting phase of the coating's InterDiffusion Layer (IDL) in Press Hardening Steels (PHS). This phase is believed to influence both welding quality and the occurrence of expulsions. Additionally, the timing at which each phase starts has been determined by analyzing real-time, multi-variable sensing data from various welding scenarios, and a signal processing technique has been devised to automatically identify when these phases begin. Leveraging this refined process understanding and characterization, meaningful explainable features are extracted, and a data-driven multilayer perceptron model is constructed for 1) predicting IDL thickness and 2) detecting expulsions upon predicted IDL thickness. The experimental results validate that the proposed IDL-inclusive model advances existing physical models for RSW and the IDL prediction improves the RSW defect detection and process monitoring.

Behaviour of aluminium/steel hybrid RSW joints under high cycle fatigue loading

The lightweight construction of automotive car bodies is the more important to reduce the fuel consumption and costs. High-strength steels and aluminium alloys are suitable for achieving these aims. Recent car bodies contain both materials, therefore necessary to make reliable joints between them. The resistance spot welding (RSW) can be used for joining of car bodies and it is applicable for aluminium/steel hybrid joints, too. High cycle fatigue (HCF) test results can be rarely found in the literature while HCF loading basically determines the lifetime of hybrid joints. 5754-H22, 6082-T6, and DP600 base materials were used for similar and hybrid RSW joints and HCF tests were performed. Number of cycles to failure values, failure modes, furthermore brittle intermetallic compound (IMC) layers were studied and analysed. In both aluminium/steel hybrid joints, the HCF test results showed better endurance limit like concerning aluminium/aluminium similar joints, but worse than steel/steel joints. For 5754-H22 alloy the endurance limit values are 648 N, 939 N, and 1285.5 N, for similar aluminium, hybrid, and similar steel joints, respectively. For 6082-T6 alloy these values are 513 N, 625.5 N, and 1285.5 N, respectively. In case of similar joints only base material fracture happens, but hybrid joint specimens show different failure modes. Base material fracture and shearing after partial base material fracture were typical failure modes in case of 5754-H22/DP600 and 6082-T6/DP600 hybrid joints, respectively. The full and partial plugging as a failure modes appeared for hybrid joints, too. The IMC layer characteristics showed opposite results in cases of hybrid joints, both the layer thicknesses of the shared and plugged joints and the thickness differences between the inner and outer parts of the joints were different.

Effect of coating type on electrode degradation and its life in resistance spot welding of a low carbon steel

In this study, the degradation occurring on the surface of the electrodes used in resistance spot welding of hot dip galvanized and galvannealed low carbon steels are examined and the life of the electrodes are tested. Several characterization studies are carried out on the surface and cross-sections of CuCrZr-based electrodes, following the life tests that are carried out according to SEP 1220 standard, and it is observed that a more convex degradation surface is formed on the electrode surface used in the welding of galvannealed steel compared to the galvanized one. This geometry indicates that the induced current is more stable. Depending on the increase in the number of spots, coating type and the amount of convexity, it is determined that the phases formed on the electrode surface also differ. Although the coating type has no significant effect on the welding strength value and no significant difference is observed in the maximum current values, a longer life is determined in the electrode used for the welding of galvannealed steel. It has been identified that the dominant mechanism affecting electrode life is the coating type, which is directly related to electrode degradation.

Effects of Sheared Edge and Overlap Length on Reduction in Tensile Fatigue Limit before and after Hydrogen Embrittlement of Resistance Spot-Welded Ultra-High-Strength Steel Sheets

The effects of a sheared edge and overlap length on the reduction in the tensile fatigue limit before and after hydrogen embrittlement of resistance spot-welded ultra-high-strength steel sheets were investigated. Ultra-high-strength steel sheets with sheared and laser-cut edges were subjected to resistance spot welding followed by hydrogen embrittlement via cathodic hydrogen charging and subjected to static tensile shear and fatigue tests. The distance between the resistance spot weld and the sheared and laser-cut edges was changed by changing the overlap length, and the influence of the weld position was investigated. In the tensile shear test, the maximum load decreased with decreasing overlap length and the maximum load decreased with hydrogen embrittlement, but the effect of hydrogen embrittlement was smaller than that in the fatigue test. In the fatigue test, the fatigue mode changed from the width direction to the sheared edge direction with the increase in the repeated load. Even if the overlap length was reduced, the fracture changed to the sheared edge direction. In the specimens with sheared edges, the effect of fatigue limit reduction due to hydrogen embrittlement was greater than in the specimens with laser surfaces. In particular, the effect was greatest when the fatigue mode was changed via hydrogen embrittlement.

Coaxial one-side resistance spot welding for cross-lap joints of Al5052 and CFRP: Thermal process and strength evaluation

Coaxial one-side resistance welding (COS-RSW) is an advanced joining technology for the metal-plastic hybrid structure, which has great application potential in the lightweight design of body-in-white. In the present research, the Al5052-CFRP cross-lap joints were fabricated by COS-RSW with different welding conditions. The author-developed finite element (FE) code JWRIAN-RSW was employed to reproduce the multi-physics coupled phenomena of COS-RSW and predict thermal history. The influence of welding current and welding time on molten zone generation and joining strength was discussed in detail. The results showed that the developed FE model can predict temperature distribution and variation effectively, which were verified by the bonding zone observation and infrared thermal image measurement. Both welding current and welding time had a significant contribution to the Joule heat generation. While their influence on the molten zone growth during heating and cooling stage was distinct. The maximum joining strength of COS-RSW cross-lap joints can reach about 1380 N. The static tensile strength was improved significantly when the maximum interface temperature exceeded 340 °C and the failure mode altered into staged fracture. The strength degradation induced by significant CFRP decomposition was appeared when the predicted interface temperature reached 410 °C. For the COS-RSW joint of Al5052 and CFRP, it was better to improve the joining strength using longer welding time rather than higher welding current, which led to sufficient heat generation, persistent thermal conduction and elongated melting duration for sound joining.