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Weld bonding of stainless steel
Abstract
This paper presents a theoretical and experimental investigation of the weld bonding of stainless steels with the purpose of set-ting up the major technological parameters that are needed for its industrial implementation. Several commercial adhesives, with varying working times under different surface conditions are investigated for assembling standard test specimens. The numerical simulation of the process based on the commercial finite element program SORPAS is successfully utilized to help establish the most favourable welding parameters that allow spot-welding through the adhesives. The relative performance and quality of the resulting weld bonded joints is evaluated against alternative solutions based on adhesives or conventional spot-welding by means of macroetching observations, tension-shear tests and peel tests.
... [26] Many studies can be found in the open literature, where the superior static and fatigue properties are evident. [27][28][29][30][31][32][33][34][35][36][37] The structural adhesive must have good wetting and flow characteristics in order to obtain a good quality bond of the faying metal surfaces, and premature curing, during or prior to resistance spot welding, must be avoided, since it can significantly increase the resistance to electrical contact. [29] According to the same authors [29] , epoxy-based weld bonds performed better than conventional spot-welded joints in tension-shear tests, while methacrylate-based weld bonded joints showed the poorest performance. ...
... [27][28][29][30][31][32][33][34][35][36][37] The structural adhesive must have good wetting and flow characteristics in order to obtain a good quality bond of the faying metal surfaces, and premature curing, during or prior to resistance spot welding, must be avoided, since it can significantly increase the resistance to electrical contact. [29] According to the same authors [29] , epoxy-based weld bonds performed better than conventional spot-welded joints in tension-shear tests, while methacrylate-based weld bonded joints showed the poorest performance. Numerical studies developed by Chang et al. [27] reveal that the stresses in weldbonded joints and adhesive bonded joints have almost the same characteristics. ...
... [27][28][29][30][31][32][33][34][35][36][37] The structural adhesive must have good wetting and flow characteristics in order to obtain a good quality bond of the faying metal surfaces, and premature curing, during or prior to resistance spot welding, must be avoided, since it can significantly increase the resistance to electrical contact. [29] According to the same authors [29] , epoxy-based weld bonds performed better than conventional spot-welded joints in tension-shear tests, while methacrylate-based weld bonded joints showed the poorest performance. Numerical studies developed by Chang et al. [27] reveal that the stresses in weldbonded joints and adhesive bonded joints have almost the same characteristics. ...
This research compares the mechanical behaviour of adhesive bonded (AB), friction stir spot welded (FSSW) and hybrid joints (H). The H joints were performed using both AB and FSSW. The influence of tool geometry, tool rotational speed and tool penetration depth on the joint strength were examined. The analysis of the mechanical performance of the joints was done using metallographic, hardness and tensile testing. In order to determine the local strains an optical extensometer with digital image correlation was used. Adhesive bonded joints displayed higher strength than welded or weld-bonded joints. Penetration of the tool pin into the lower plate increases the strength of the welded joint, although it has an unfavourable influence on defect formation. The weld-bonded (hybrid) joints have lower strength than adhesive-bonded joints or welded joints, as the uncured adhesive makes welding difficult, and the heat generated in the welding harms the adhesive.
... The weld-through quickly became a viable alternative to permit higher viscosity adhesives to be used. By this technique, the components are primarily bonded, and the bonded region is then spot-welded before curing of the adhesive, i.e., within the working time (WT) of the adhesive [7,28]. This process was not fully understood until recently due to lack of systematic theoretical and experimental investigations, e.g., the experimental work of Charbonnet et al. [29] and the experimental/metallurgical and numerical studies of Darwish and Ghanya [7] and Darwish [25]. ...
... The work has also proved that conventional spot-welders can be used for weld-bonding. Regarding the strength of weld-bonded joints, different studies showed, either by testing or FEM stress analyses, the benefits of single-lap weld-bonded joints compared to spot-welded joints under static or fatigue loadings [28,[30][31][32]. Melander et al. [18] also testified the higher efficiency of weld-bonding compared to spot-welding on a peel test geometry. ...
... Melander et al. [18] also testified the higher efficiency of weld-bonding compared to spot-welding on a peel test geometry. Santos et al. [28] published a numerical/ experimental investigation of weld-bonded single-lap joints between steel adherends, for optimization of material and fabrication parameters. Three adhesives were tested (epoxy and methacrylate-based), considering varying time intervals between the bonding and welding operations. ...
... centrations due to stress raisers encountered in the conventional joints, such as bolted, riveted joints [2]. Adhesive weld bonding not only improves strength but also prevents sudden fracture (catastrophic) and leaking [3][4][5][6][7]. ...
... The structural adhesive must have good wetting and flow characteristics in order to obtain a good quality bond of the faying metal surfaces, and premature curing, during or prior to spot welding, must be avoided since it can significantly increase the electrical contact resistance. High values of the electrical contact resistance may result in excessive heat generation in the vicinity of the interface followed by subsequent metal expulsion, or it may simply impede the current running through [4]. It can thus be concluded that the weld bonding technology has great advantages compared to alternative processes such as spot-welding and adhesive bonding. ...
... However, despite such advantages, most of the industrial applications are still restricted to aerospace applications. Its utilization by other industries (e.g. automotive and train industry) is still in an early stage and will most likely be much more widespread when more knowledge based on systematic investigations of the process has been obtained [4]. So far, descriptions of the experimental load--displacement behaviour of the weld-bonded joints have been found only in a few studies for automotive materials, and for IF steel [2,4,8]. ...
In this study, the effect of adhesive bonding on strength and strength-ductility behaviour of welding joint in electrical resistance spot welding of 7315 grade IF steel sheets was investigated. 7315 grade (DIN EN 10130-1999) IF steels were adhesively bonded and different welding current and welding cycle conditions were performed in welding process. For adhesive bonding, Loctite Terostat 9120-Grey and Terostat 9220-Black grade adhesive bonders were used. Additionally, adhesively bonded joint samples were also performed without welding. Microstructure and tensile-shear tests of the adhesively bonded and welded materials were evaluated. Failure modes of the weld bonded tensile sheared samples were observed to be different from only welded samples. Experimental results have shown that with the increase in the weld time and weld current, the effect of the adhesive weld bonding on tensile performance also increases.
... In the first case, the parts are firstly welded, then the adhesive is applied followed by curing; in the second the adhesive is applied first with the consequent assembling, then parts are spot-welded and heated. Santos et al. [135] investigated numerically and experimentally the mechanical behaviour of welded joints with epoxy and methacrylate matrices. The authors demonstrate that, in general, weld-bonded joints with epoxy show better performance than simple spot-welded; however, it is not the case with methacrylate. ...
... According to their results, the weld-bonded joints considerably outperform adhesive joints. The requirements for a weld-bonded joint possessing good performance are cited in [132,134,135]. ...
The present work , pursued in collaboration with CETIM , is focused on the mechanical performance of preloaded bolted composite joints for automotive and aeronautical fields. Owing to the controlled preload application , bolted joints occupy a significant segment in the industry. Working environmental conditions tend to vary over time, affecting sensitive to temperature and humidity thermoplastic composites. An estimation of out - of - plane elastic properties of composites is , therefore, essential for an accurate dimensioning of bolted joints. The objective of the t hesis is to take into consideration and analyse the environme ntal impact on woven thermoplastic composite materials in order to ameliorate an analytical model for bolted composite joints. Conditioning protocols are proposed for an accurate evaluation of m aterial state at several Relative Humidity levels. Effect of humid ageing is investigated through the performed mechanical characterisation of a neat thermoplastic matrix and two woven composite materials. Numerical simulations provide the out - of - plane environment - related properties enabling the material compliance estimation. Mechanical testing of bolted composite joints is proposed to determine the loss of preload over time and to relate composite mechanical properties to the durability of joints.
... A low viscosity adhesive is used which penetrates the overlap joint by capillary action; thereafter, curing is done. The 'Weld-Through' method which is shown in Fig. 1b follows the sequence of spot welding, adhesive application followed by curing [5][6][7][8]. The properties of weld-bond largely depend on surface characteristics of the substrate and the type of adhesive used besides factors affecting weld nugget of spot welding such as welding current, pressure and weld cycle time. ...
... For an optimum joint strength, the welding parameters for the preparation of weld-bond differ from those used in the case of spot welding alone [9]. Use of aluminium in automotive industries is encouraging researchers for weld-bonding of an aluminium alloy sheet mainly to reduce weight of the vehicle [6,7]. Literature survey revealed that almost no work has been done on weld-bonding of a 2-mm-thick sheet of aluminium alloys. ...
In this study, first various significant parameters of weld-bonding namely surface roughness, curing time, welding current, weld time and electrode pressure and their ranges were identified by conducting pilot experiments. The tensile shear resistance of the adhesive joints, resistance spot welds and weld-bond joints were evaluated and the results were obtained in the terms of ultimate shear tensile load (USTL). The USTL bearing capacity of the resistance spot weld and weld-bonded joints are compared and correlated with welding parameters. Further, fatigue properties of the adhesive joint, spot weld joint and weld-bonding joint were studied at the constant load ratio 0.5 by varying maximum and minimum load. The fracture surface of the adhesive, spot weld and weld-bond joints has studied under scanning electron microscope. Microstructure and hardness of the joints were studied under optical microscope and micro-hardness tester respectively. The correlation of the mechanical properties of the joint with their microstructure, nugget size and hardness has been discussed. Single and multiple effects of parameters (weld-bonding) by using response surface methodology have been studied and regression model for USTL of the weld-bonds were developed. The comparative results are useful for optimizing the processing parameters and improving the weld quality of weld-bonding.
... Charbonnet et al. [14] testaram ligações adesivas-soldadas com dois tipos dos adesivos (um adesivo epóxido e um selante de borracha), tendo-se observado uma melhoria significativa no desempenho das juntas, por comparação com juntas puramente soldadas. De facto, esta melhoria é conhecida para aplicações estáticas e de fadiga [15]. Melander et al. [16] também demonstraram a melhoria da eficiência das juntas adesivas-soldadas, através de juntas de arrancamento. ...
... Obtiveram-se os seguintes valores dos testes realizados: módulo de Young 204,32±2,40 GPa, tensão de cedência 279,11±0,82 MPa, tensão de rotura 347,51±0,93 MPa e deformação de rotura 3,36±2,45%. Para a selecção do adesivo, foram equacionadas a sua molhabilidade e o TT, para impedir a cura prematura e respectivo aumento do isolamento eléctrico, que poderia resultar na expulsão de metal e geração excessiva de calor durante o processo de soldadura [15]. O adesivo Araldite ® 2015, com um TT de 35 minutos, foi então seleccionado e caracterizado para a análise por MEF. ...
The proper design of joints for the union of components is highly important to prevent over-sized or defective structures. The traditional methods to join components include fastening, riveting, spot welding or adhesive bonding. Bonds with structural adhesives are currently one of the most widespread technical techniques in advanced structures (automotive, aerospace, aviation, sports equipment, among others). Adhesively bonded joints do not require holes and they distribute the load over a larger area than the mechanical methods. However, they tend to develop peak peel and shear stresses near the ends of the overlap, which can cause premature failures. The combination of adhesive bonding with spot welding allows some competitive advantages to the traditional adhesive bonds, such as higher strength (especially for brittle adhesives), weight reduction, increased stiffness, improved resistance to tearing and fatigue, and easier manufacture because a positioning device is not required during the curing of the adhesive. This paper presents an experimental and numerical study on hybrid joints (spot welded and adhesive), compared to the traditional welded and adhesive joints. Single-lap joints were considered in this study, which are widely used either for research or for practical purposes due to its simplicity. The numerical work is performed in Abaqus® using the Finite Element Method (FEM) and Cohesive Zone Models (CZM) for the simulation of damage growth. As a result of this work, this known numerical technique for predicting the structures strength is tested and validated for the simulation of hybrid joints. The parametric study presented, which considers some variables such as the overlap length (LO), allows the hybrid joints optimization.
... A low viscosity adhesive is used which penetrates the overlap joint by capillary action; thereafter, curing is done. The 'Weld-Through' method which is shown in Fig. 1b follows the sequence of spot welding, adhesive application followed by curing [5][6][7][8]. The properties of weld-bond largely depend on surface characteristics of the substrate and the type of adhesive used besides factors affecting weld nugget of spot welding such as welding current, pressure and weld cycle time. ...
... For an optimum joint strength, the welding parameters for the preparation of weld-bond differ from those used in the case of spot welding alone [9]. Use of aluminium in automotive industries is encouraging researchers for weld-bonding of an aluminium alloy sheet mainly to reduce weight of the vehicle [6,7]. Literature survey revealed that almost no work has been done on weld-bonding of a 2-mm-thick sheet of aluminium alloys. ...
This paper presents a comprehensive study on effect of surface roughness, curing time, welding current , weld time and electrode pressure on ultimate shear tensile load (USTL) on weld-bonds of a 2-mm-thick 6061T651 aluminium alloy sheet. Weld-bonding is a combination of adhesive bonding and resistance welding process in which adhesive is pre-placed in the joint and a spot weld is made through the adhesive. The tensile shear resistance of the adhesive joint and resistance spot welds were evaluated using uni-axial load on two ends of the lap joints and applying shear tensile load. A comparative study of ultimate shear tensile load of weld-bonds, resistance spot welds and adhesive bonds was carried out.
... Also, hybrid spot welded-bonded joints are easier to be manufactured with respect to adhesive ones, since the spot weld keeps in position the adherends, so handling time is shortened. Hybrid joints are usually obtained by merging any two-joining technology such as rivet-bonded, clinch-adhesive, bolted-bonded and weld-adhesive [18][19][20][21][22][23][24]. Hybrid joints improve the static and fatigue properties by significantly increasing load transfer in the inner overlap zones [25][26][27][28]. ...
Hybrid joints formed by combining two or more joining methods, including spot welding and adhesive bonding, are relatively new joints designed especially for use in the automotive industry. The aim of this work is to study numerically the static and fatigue behavior of ultrasonically spot-welded, adhesively bonded and hybrid spot welded – adhesive bonded joints. The Virtual Crack Closure Technique was used to model the experimental static and fatigue tests for single lap joints reported in the literature. By introducing a short fictitious initial crack, in static loading the simulations matched the experimental results, characterized by a higher stiffness and static strength of the bonded and hybrid joints compared to the just spot-welded ones, and by an approximately similar static strength of the bonded and the hybrid joints. By the same method, a good match between the numerical and the experimental fatigue strengths was found, with the hybrid joints providing higher strength compared to the just spot-welded joints at 0.1 load ratio. According to the numerical analyses, S–N curves of bonded joints are expected to be statistically similar to those of the hybrid joints. This indicates that the adhesive plays the major role in the fatigue behaviour of the hybrid joint. Finally, the fatigue strength of hybrid joints was simulated at 0.3 load ratio. It was found a reasonable agreement between the experimental and numerical observations at 0.3 load ratio. The VCCT proved to be capable of simulating the static and the fatigue behaviour of the hybrid joints, thus proving to be a tool useful for the interpretation of the results and for the design of other hybrid joint configurations.
... Weld-adhesive bond is also known as hybrid joining is a process where spot weld process is combined with adhesive layer applied on faying surfaces (Fig. 1) of the metal part [2]. Messler [3] stated that the process commonly acknowledged as hybrid joining consists of weld-brazing, rivet-bonding, and weld-bonding. ...
This paper presents an experimental investigation of the weld bonding of low carbon steel (JIS G3141) together with adhesive layers to increase the mechanical properties of weld bonding. Epoxy adhesive was used in this research applied on the sheet thickness of 1.2 mm. The weld-bonding was carried out by applying layer of adhesive followed by resistance spot welding on surface samples. The relative properties and characteristics of the resulting weld-bonded-adhesive joints are evaluated and compared with the conventional spot-welding through tensile-shear, peel, hardness tests and macro-etching observations. The strength of weld bond joints was calculated and compared with those in as-weld and adhesive-bond joints. Results showed that the strength of weld-bond adhesive is higher than as-weld specimen. The hardness distribution of weld bond adhesive joints was investigated, at three regions i.e. base metal (BM), the heat-affected zone (HAZ), and the fusion zone (FZ) using micro-hardness Vickers machine. It can conclude that the presence of adhesive does not affect the hardness of weld-bonded. From macro- etching observation, the layer adhesive influenced the weld bond via the size nugget of weld-bonded which is smaller than as-weld. The introduction of adhesive layer in spot welding improves the joint strength and quality of spot weld.
... BM. Weld-bonding joining techniques has the advantages of low manufacturing costs, higher static and fatigue performance, and improved corrosion resistance [106,107]. ...
Hybrid structures built using Mg/steel are expected to have an increasing impact on the future developments of the manufacturing sector, especially where lightweight structures are required in order to reduce fuel consumption, greenhouse gases and improve efficiency of energy-converting systems. To this end, there is a pressing need for a joining technology to produce effective and low-cost dissimilar Mg/steel joints. Joining of these materials has always been a challenging task for researchers, due to the wide discrepancies in physical properties and lack of metallurgical compatibilities that make the welding process difficult. Based on the existing literature, a successful joint between magnesium alloys and steel can be achieved by inserting an interlayer at the interface or mutual diffusion of alloying elements from the base metal (BM). Thus, intermetallic phases (IMCs) or solid solutions between Mg and the interlayer and also the interlayer and Fe formed at the interface. However, the interfacial bonding achieved and the joints performance depend significantly on the intermediate phase. This paper reviewed the research and progress in the area of joining of Mg alloys to various grades of steel by variety of welding processes, with focus on the techniques used to control the morphology and existence state of intermediate phase and improving the mechanical properties.
... However, resistance element welding gives rise to material protrusions above the upper SPS laminate surface, and to productivity losses due to the need of pre-punching. Possible use of adhesives on the adjoining structural part surfaces to improve durability and ensure leak tightness of the joint would transform the resistance welding stage into weld bonding [11,13]. ...
This paper presents a new resistance element welding process capable of producing invisible lap joints between steel-polymer-steel composite laminates. The process involves pre-drilling a flat-bottom hole in each laminate to remove the polymer core and one of the steel sheets, and positioning a cylindrical insert inside the two adjoining holes for subsequent resistance welding. Finite element modeling is utilized to construct the weldability lobe and to identify the parameters that lead to the formation of acceptable joints. Experimental results confirm the applicability of the process to produce invisible lap joints without signs of material protrusions or local indentations resulting from squeezing the polymer out to create contact between the steel sheets. Destructive peel and shear tests allow determining the maximum forces that the joints can safely withstand and comparing their performance against alternative joined by forming lap joints in which the mechanical interlocking is also hidden inside the laminates.
... Weld-bonding composes of four steps as follows: (1) spreading adhesive layer on the two metallic sheets, (2) assembling, (3) spot welding and (4) curing [191]. This method was used to prevent vibration and to reduce noise emission in automobile transmissions, railways carriage and aircraft due to their superior static and fatigue properties which result in lightweight structures [192][193][194][195]. In addition, weld-bonded joints avoid inner-surface corrosion of spot-welded joints and increase the durability of adhesive-bonded joints [196]. ...
This paper reviews the reported literature on dissimilar (non-matched adherend) adhesively bonded joints (ABJs), currently used bonding processes, and the mechanisms by which these types of joints fail when subjected to structural loading and environmental conditions. Additionally, approaches to improve the performance of dissimilar ABJs, through geometrical and material modifications, are also discussed. Many studies have reported on the strength and failure behaviours of adhesively bonded joints, but of those, few have reported on the performance of dissimilar ABJs. Unlike matched ABJs, the absence of accepted design approaches for dissimilar ABJs arises from their inherent inhomo-geneity, which introduces complexities in load transfer mechanisms , in the distribution of stresses through the joint, and in the mechanisms by which the joint ultimately fails. Several authors have proposed approaches to improve the performance of adhesively bonded joints, variously through geometrical or material modification means, but there remains unmet research needs to better understand novel dissimilar ABJ designs. ARTICLE HISTORY
... Similarly, some key physical (i.e., thermal conductivity, expansion coefficient, density, and specific heat) and electrical (i.e., resistivity) properties for the steel and copper are used in the coupled electrical-thermal-mechanical analysis model. The above-mentioned mechanical, electrical, and physical properties dependent on the elevated temperature assumed homogeneous and isotropic were determined from the available literature given in References [19,20]. ...
This study focused on the nugget formation in resistance welding of three dissimilar steel sheets influenced by different types and thicknesses of epoxy adhesive. An improved finite element model was employed to estimate the temperature distribution in three-sheet weld-bonding and was validated by the metallographic tests. Results showed that the weld initiation time and corresponding nugget size for weld-bonds would be earlier and larger than that of resistance spot welds in term of the same welding parameters. Compared to the adhesive Betamate Flex, the weld-bonding joint of three-sheets with adhesive Terokal 5089 would have a greater increment of the weld nugget sizes due to the increase of the static contact resistance brought by the interfaces between the steel sheets. However, the bond line thickness of the previously mentioned adhesive would take little effect on the weld sizes in weld-bonding of three dissimilar steel sheets.
... High strength low-alloy steel, stainless steel, nickel, aluminum, titanium and copper alloys are also spot welded commercially [8]. After spot welding, important changes occur in mechanical and metallurgical properties of the spot welded areas and heat affected zones [9]. The investigation of these changes is very important for the safety strength of the welded joints. ...
Resistance spot welding is a comparatively clean and ef?cient weld-ing process that is
widely used in sheet metal joining. This process involves electrical, thermal and mechan-
ical interactions. Resistance spot welding primarily takes place by localized melting at
the inter-face of the sheets followed by its quick solidi?cation under sequential control of
water cooled electrode pressure and ?ow of required electric current for certain duration.
In this experimental work the tensile tests and the spot weld diameter were studied. The
objectives of this analysis is to understand the physics of the process and to show the
influence of the electrical current, weld time and the type material in resistance spot
welding process.
... In the field of hybrid joining, weld bonding is an innovative and useful technique for metal joining in aerospace and automobile industry [1,2]. The main advantage of weld bonding over the spot welding is that it reduces the stress concentration at the weld spot resulting in improved weld performance in terms of tensile, fatigue strength and stiffness [3][4][5][6][7][8]. ...
Tungsten inert gas (TIG) spot weld bonding is a hybrid joining process, which combines the conventional tungsten inert gas welding with adhesive bonding to achieve a better quality joint with superior joint performance than any single technique. The present research aims to study the effect of input process parameters i.e. welding current, weld time and gas flow rate on weld penetration, bead width and tensile shear strength of the weld bonds using design of experiment (DOE) approach. Further, some selected samples were characterized by optical microscopy and hardness testing. It was observed that weld time most significantly affect the weld performance followed by welding current and gas flow rate. The tensile results showed failure of weld bond in two ways namely interfacial failure and button pull out failure.
... Subsequent finite element modelling of weld-bonded joints by Al-Samhan and Darwish (2003) demonstrated how incorporating the RSW with the weld-bonded joint distributed the stresses over a wider area, increasing the overall strength. Santos et al. (2004) conducted a thorough study on weldbonded joints and used a finite element code, SORPAS to model the resistance spot welding process and understand the effect of the adhesive. Mechanical tests were undertaken to assess performance, demonstrating the synergistic effect of weld-bonding which provided a greater displacement to failure than either spot welding or adhesive bonding on their own. ...
This paper investigates a resistance spot welded reinforced adhesive (weld-bonded) joint between 304 stainless steel to carbon fibre reinforced plastic (CFRP), where welds are made both with and without the reinforcing carbon fibres present. Successful welds with the fibres present could only be produced with high electrode pinch forces, which helped reduce contamination of the weld nugget. Similar joint strengths were achieved in both cases, however the joints without fibres exhibited an increased strain to failure. Both joints were significantly stronger than either an adhesive joint or a comparable bolt reinforced adhesive joint. These techniques provide an alternative for joining thin metallic components to CFRP structures where increased strength and integrity is required.
... The technique is termed weld-bonding and is illustrated in Mechanical testing of this representative structural joint specimen demonstrated that the resistance spot-weld also acts as an alternative load path after adhesive joint failure (which could therefore be described as a fail-safe structural joint) and so extends the performance of the weld-bond joint (Shah et al., 2010). The performance benefits of weld-bonding is well documented in the literature (Darwish and Ghanya, 2000;Santos et al., 2004). ...
This thesis explores new methods for achieving load-carrying joints between the dissimilar materials of continuous fibre reinforced polymer matrix composites and structural metals. The new composite-to-metal joining methods investigated in this work exploit the metal-to-metal joining techniques of arc micro-welding, resistance spot welding, and metal filler brazing, to form novel micro-architectured metal adherends that can be used for enhanced composite-to-metal joining.
Through a combination of equipment instrumentation and metallographic inspection of fabricated prototype joints, understanding is gained of how materials respond when processed by manufacturing techniques that have not previously been exploited for dissimilar material joining. Mechanical testing of prototype joints; both to ultimate loading strength and partial failure states, with subsequent inspection of specimens and comparative performances evaluation enabled joining performance characterisation of the new joining methods.
Key results include: the identification of micropin reinforced adhesive joints to exhibit pseudo-ductile failure characteristics, resistance spot weld reinforcement of adhesive joints to boost bonding performance, and the use of a polymer infused metal foam to overcome difficulties of thermoplastic to metal adhesion.
Through this work knowledge of how novel micro-architectures reacted under mechanical loading enabled insights to be gained into how perceived manufacturing defects can benefit joining performance. Such examples include, localised material weakness that lead to global pseudo-ductile failure behaviour, and low-strength secondary joining mechanisms boosting primary load transfer systems.
By comparison of the diverse joining methods investigated in this work, trends were identified that suggest joining performance between the two dissimilar materials is improved by increasing the direct interaction between the composite reinforcement fibres and the metal structure. It is demonstrated that joining improvements are gained by forming mechanical connections between metals and composite precursory material before the final manufacturing process of the composite.
Full thesis available via Cranfield University CERES:
http://dspace.lib.cranfield.ac.uk/handle/1826/10009
... In his research, he found bad fluidity would make the welding process unsuccessful. And the weld bonded joints would have poor performance when the inappropriate adhesive was chosen [3,4] . ...
Laser spot weld bonding (LSWB) is a new joining process that combines laser welding with a layer of structural adhesive in a single joint, which has been put forward as low heat input, high robot performed, and insuring first time quality. The aim of this research is at the effect of adhesive properties on LSWB process, microstructure and mechanical properties. We found the viscosity of adhesive is the key factor during the welding process, due to good viscosity can reduce the impact of adhesive gas on the melting metal by providing a way to exhaust the adhesive gas. Carbon from the adhesive decomposing diffused into the welding joint, changing the microstructure of LSWB fusion zone from ferrite to pearlite, martensite and bainite. In tensile shear test, the result showed the fracture load of LSWB joint mainly depended on the mechanical properties of adhesive. The presence of adhesive will reduce the force distribution at welding joint and increase the bending angle. We found different fracture modes with different adhesives. The fracture mode of weld joint with better performance of adhesive is button-pullout mode, and the fracture mode will be interfacial fracture when the joint is made with worse performance adhesive.
... Usually, in the GTAW of stainless steels with argon shielding, full penetration welding is restricted to joints of a maximum thickness of 3 mm and to relatively low welding speed. Although the welding speed can be increased substantially (up to 160%) when helium or hydrogen is used as part of the shielding gas mixture, bead penetration can only be incre ased slightly (1-2 mm) [11,12]. The capacity to improve the penetration by the selection of the shielding mixture is further limited by the need to use inert or slightly reducing gases, restricting this selection basically to argon and helium mixtures [10]. ...
In this study, AISI 304, AISI 316L and AISI 431 stainless steels which are widely used as base materials in implant instruments were utilized, and were joined by GTAW method using AISI 431 and X 318 Si welding wires. Prepared samples were subjected to X Ray, corrosion, tensile, charphy notched impact and Brinell hardness test. Moreover, the microstructure of weld region and base metal were investigated using SEM or optical microscope. Materials used in implant instrumentation should have a brittle structure. AISI 431 and AISI 431 materials welded by AISI 431 welding wire showed the best corrosive, mechanical and metallurgical properties.
Keywords: Implant Instrument, Stainless Steel, GTAW.
... Electric welding by resistance [1,2,3,4] is a process of assembly which is significantly used in several industrial fields of manufacture and maintenance (car industry, aerospace and nuclear sectors, electronics and electric industries). Resistance welding or spot welding is the generic term for electric welding processes in which the heat for welding is generated by the passage of welding current through a point of locally high electrical resistance created by pressure from electrode (spot and seam welding), or projections (projection welding), or by pressure applied across the whole area of the members being joined (resistance butt welding) [5]. ...
... The weldbonding offers advantages relatively to the other conventional joining processes, namely, acoustic isolation, vibration attenuation, reduction of corrosion, and more uniform stress distribution. Chang et al. [4], Ghosh and Vivek [5] and Santos et al. [6] conducted studies to characterize and compare the performance of resistance spot welding, adhesive bonding and weldbonding joining processes under static loading. Several experimental studies have been reported on the mechanical behaviour of welbonding joints, particularly in steel adherends. ...
The increasing restrictions in terms of safety and energy consumptions imposed in the transport vehicles construction promotes the use of new materials and new processes searching weight reduction. Lighter materials and better joining processes, like adhesive bonding can contribute to obtain some weight gain. Present work studies the shear strength obtained with weldbonding technique and compares it with the traditional resistance spot welding. The single lap joints were obtained with thin plates of 6082T6 alloy and a high strength epoxy adhesive of two components (araldite 420 A/B). The strength of weldbonded joints was found to be significantly higher than equivalent spot welded joints. Numerical models were developed replicating experimental work. Nugget diameter was found to have a major influence in stiffness and stress level, while thickness reduction showed a much lower influence. The adhesive reduced significantly the stress level at the nugget root.
... This technology has the advantages of resistance spot welding and adhesive bonding combined [2]. At present, due to the excellent mechanical properties of weldbonded joints, the weld bonding process has been widely used in automobile transmissions, railway carriages and aircraft [3][4][5]. ...
... Evaluated against bonded joints, weld-bonded unions result in a more uniform stress distribution than bonded joints, justifying for both situations the improved characteristics of these hybrid joints [9,10]. Weld-bonded joints were initially developed for aircraft applications [11], and the flow-in method was firstly employed, in which the components were spotwelded, and a low-viscosity adhesive subsequently filled the bonding regions by capillarity, followed by heating for curing. The weld-through quickly became a viable alternative to permit higher viscosity adhesives to be used. ...
A variety of methods to join structural components is available nowadays. Joining with high-strength adhesives is presently widespread for advanced structures such as aerospace or aeronautical, on account of a few distinctive advantages over traditional methods (elimination of drilling operations and distribution of loads over a larger area than mechanical joints). Nonetheless, stress concentrations emerge at the overlap ends because of the adherends straining and load asymmetry, which can result on premature fractures. Structural joints can equally be severely affected by the surface treatment of the bonding surfaces, extreme environmental conditions and ageing. Weld-bonded joints (combination of adhesive bonding with spot-welding) can surpass these disadvantages, adding a superior static strength and stiffness, and higher peeling and fatigue strength. This work presents and experimental and numerical study comparing hybrid spot-welded/bonded single-lap joints with purely spot-welded and bonded joints. The Finite Element Method (FEM) and Cohesive Zone Models (CZM's) for damage growth were tested in Abaqus ® to evaluate this technique for strength prediction. Strength improvements up to 58% compared to spot-welded joints and 24% over bonded joints were achieved by this hybrid method, with accurate FEM estimations.
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Joining similar and dissimilar materials using polymer bonds is common practice being followed in various sectors. The strength of these polymer bonded joints depends on process parameters like adherend thickness; adhesive layer thickness, overlap, geometric configuration of joints, materials used and surface roughness of the sheet metal. The main aim of present experimental work is to optimize process parameters of Aluminium 2024-T3 joints bonded using Epoxy resin modified with rubber powder. Three variability levels were considered for each factor selected for the present experimental work. Bondline thickness was the most significant parameter followed by surface roughness, adherend thickness and the overlap.
Hybrid weld-adhesive bonding (AB) was used as an approach to improve the mechanical properties of martensitic stainless steel resistance spot welds. The weld fusion zone in both techniques was composed of predominantly martensite and δ-ferrite. It was found that the presence of adhesive does not induce excess hardening effect in the fusion zone. It was shown that hybrid AB/resistance spot welding) i.e. weld-bonding) technique can double the peak load and energy absorption of the joints compared to those of the resistance spot welds. To obtain high performance weld-bonded joints, heat generation during welding should be controlled to produce weld bonds with large fusion zone size, but without detrimental effect on the adhesive strength.
Electrical resistance spot welding (ERSW) is an ideal process for joining sheet metal assemblies. Nowadays, aluminum alloys are increasingly being used in automotive industries in order to minimize the inertia. It is known that the process parameters play a vital role to determine the desired weld strength. In this study, an empirical relationship was established to predict the tensile shear fracture load (TSFL) of electrical resistance spot welded AA2024-T3 aluminum alloy joints with sheet thickness of 2.7 mm. A central composite rotatable design with four factors and five levels was chosen to minimize the number of experiments. Response surface methodology was used to optimize the process parameters. And TSFL of optimized electrical resistance spot welded joint was compared with TSFL of optimized friction stir spot welded AA2024-T3 aluminum alloy joint. However, ERSW could be used for joining of aluminum alloys; FSSW exhibited the maximum TSFL at the optimized condition.
This paper investigates the mechanical properties and interface morphology of Mg/Al ultrasonic spot welding (USW) joint, adhesive bonding (AB) joint and ultrasonic spot weld bonding (USWB) joint. The peak load and fracture energy of USWB joint increased significantly compared to that of USW joint and AB joint. The USWB joint presented a hybrid fracture mode which was composed of the delamination failure at adhesive/Mg interface, cohesive failure within the adhesive and cleavage failure in the weld zone. The interface morphology suggested that USWB joint exhibited fewer defects in the cured adhesive matrix and elevated connection density of adhesive/metal interface, which improved joint strength and altered the fracture mode.
Weld-bonding technology has been widely used in vehicle manufacturing to improve structural crashworthiness, fatigue performance, and corrosion resistance. This study focused on the weld quality in weld-bonding multiple stacks of steel sheets composed of 0.8-mm-thick SAE1004,1.4-mm-thick DP600, and 1.8-mm-thick DP780 with various adhesive placements. To investigate the effect of the adhesive placement on the weld-bonding process, the static contact and dynamic resistances between the steel sheets with adhesive were measured. Then, the weld formation, weld size, and hardness of weld-bonded joints with various adhesive placements were studied by metallographic tests. Results showed that the static contact and dynamic resistances between the steel sheets increased significantly due to the presence of the adhesive. The weld initiation time and weld size for weld-bonded joints were about 40 ms earlier and 10% larger than that without adhesive under the same welding parameters. Weld qualities of weld-bonded joints with two adhesive layers at both faying interfaces between multiple stacks of steel sheets produced the best. This study provides the guidelines to the application of adhesive in weld-bonding multiple stacks of steel sheets for vehicle manufacturing.
The laser beam with pre-gasification pulse is used in titanium Ti6Al4V laser spot weld bonding test. The influence of residual carbon from adhesive pyrolysis on microstructure and properties of titanium laser spot weld-bonded joint is studied. The results show that lots of TiC appear in the titanium weld-bonded joint because of residual carbon from adhesive pyrolysis, and interface reaction zone compose mainly by TiC appear in the interface between spot-welded joint and adhesive layer. The residual carbon that affects the microstructure of titanium laser spot weld-bonded joint is mainly from the pyrolysis in the pre-gasification pulse, and the residual carbon which composes interface reaction zone is from the back flow of adhesive after the joining process. The advent of TiC increase the hardness of titanium weld-bonded joint, but also has an adverse effect on the tensile-shear load of titanium weld-bonded joint.
High strength steels have been continually being developed to improve in fuel economy in automotive and ensure safety of passengers. New bonding and welding methods have been required for improving weldability on high strength steels. In this study, resistance spot welding and Weld-bond with nugget diameters of 4.0mm, 5.0mm, 6.0mm and 7.0mm were produced and tested, respectively. In order to confirm the effect of nugget diameters on tensile shear characteristic of the Weld-bond, tensile shear characteristics of Weld-bond were compared with those of resistance spot welding and adhesive bonding. Peak load of Weld-bond were increased as the nugget diameter increases. After appearing maximum peak load continuous fracture followed with second peak owing to load being carried by resistance spot weldment. Fracture modes of the adhesive layer in Weld-bond fractures were represented by mixed fracture mode, which are cohesive failure on adhesive part and button failure at resistance spot welds. The results showed that the tensile shear properties can be improved by applying Weld-bond on TRIP steel, and more apparent with nugget diameter higher than 5{\surd}t.
Weld bonding, which is a combination of resistance spot welding and adhesive bonding, is finding application in vehicle structures that involve advanced high-strength steels. The strength of weld-bonded specimens is attributed to the strength of the weld nugget and adhesive strength. The existence of an insulating epoxy adhesive layer causes a rise in contact resistance and current density during the welding stage, and thus enhances the heat input. The aim of the present study is to explore the mechanical properties and microstructure of the weld nugget in weld-bonded dual-phase steel by means of comparison with a spot-welded nugget. Tensile-shear tests, weld lobe determination, microstructural characterization, and microhardness tests of weld-bonded and spot-welded specimens were conducted. The results of tensile-shear tests show that the weld nuggets of weld-bonded specimens have a higher tensile-shear force and energy absorption, and exhibit button-pullout fracture more easily at lower welding current. The weld lobe of weld-bonded dual-phase steel is too narrow. The results of microstructural characterization and microhardness tests indicate that, compared with resistance spot welding specimens, weld-bonded specimens have a larger nugget size at lower current; finer martensite and lower hardness in the heat-affected zone; and slightly more ferrite and lower hardness in the fusion zone. The comparative results are useful for optimizing the processing parameters and improving the weld quality of weld bonding.
Nowadays, most car manufactures have tried to improve fuel efficiency and corrosion resistance of car body. Therefore, use of high strength steels and coated steel becomes more and more increased. In this study, spot weld characteristics according to lap sequence of sheets were analyzed using simulation method for three different steel sheet of car body which were EDDQ class coated steel with 0.7t, high strength steel 440R with 1.2t and advanced high strength steel DP 590 with 1.0t. Using simulation, weldability was evaluated by nugget size of welded zone according to nugget growth curve and welding current with respect to lap sequence of sheets. Contact resistance of each sheets contact point was used to analyze formation of nugget and optimal lap sequence was suggested.
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.
The study focused mainly on one of the parameters of mount technology - tolerance for fitting the rivet in the hole in riveted and hybrid (riveted adhesive) joints. The research included numerical simulations of double lap joints with four rivets arranged in two rows and subjected to uniaxial tension. Simulations were carried out in Abaqus both for the purely mechanical and the hybrid joints. The connections without clearance (neat-fit) and with clearance of 0.2 mm, as well as with interference of-0.2 mm. The presence of clearance in one of the holes in the hybrid joint causes a decrease in the capacity of the hybrid connection by about 15% in configuration 1 (Fig. 2). This decrease can be even higher (21%) in the worse clearance placement, i.e. in configuration 2 (Fig. 2). The study shows that the occurrence of clearance in the holes can lead to dangerous consequences, so it is recommended to use holes calibration or develop a special type of rivet.
A single-sided spot welding technique is investigated by numerical analysis using a commercial CAE package to estimate the weldability. The reliability of the method is verified by the welding experiment performed under conditions similar to those of a real product. Several conditions are analyzed to find an optimal condition set, including the boundary condition for the ground location and the electrical contact resistance. The resulting Lobe curve with respect to welding time and current is obtained. The weldability of the single-sided spot welding specimen is estimated through the tensile strength test. A certain level of tensile strength can be obtained at the range of welding variables for the optimal nugget sizes, which supports the reliability of the single-sided RSW.
The CO2 pulse laser is used in laser spot weld bonding test using Q195 mild steel and adhesive J-11. The fracture process of laser spot weld bonded (LWSB) joints with different spot arrangements is studied. The results show that the adhesive bonded area in LWSB joint firstly fractures, and then the spot fractures, when there is only one spot in LSWB joint. When the spot arrangement in LSWB joint is parallel to the load direction, the fracture sequence is the adhesive bonded area outside of the spot, and the adhesive bonded area inside of the spot. When the spot arrangement in LSWB joint is vertical to the load direction, the adhesive bonded area of the LWSB first fractures, then the adhesive bonded area and the spot fracture together. Besides, the finite element modeling is used to analyze the influence of spot arrangement in LSWB joint on stress distribution under some tensile-shear condition. The calculated results are in good agreement with the experimental results.
The resistance spot welding procedure is one of the most important joining techniques in lightweight car body shell mass production. Especially for newly developed high strength multiphase steels, also called advanced high strength steels (AHSS), and ultra high strength steels (UHSS), this joining technique has more advantages than other thermal and mechanical joining procedures for thin steel sheets. Additionally, the technique of adhesive bonding and its combination with the technique of resistance spot welding called weldbonding becomes more and more important. One of the targets of the contribution is to show the influence of joined advanced high strength steels on the process reliability for both the resistance spot welding process and the weldbonding process. Based on welding current ranges and on results of electrode wear tests, statements concerning the resistance spot weldability of some special AHSS will be given. The mechanical behaviour of spot welded and weldbonded joints for different AHSS will be studied. Furthermore, some statements regarding the fracture behaviour, the hardness and the fatigue behaviour of both spot welded and weldbonded joints for different AHSS will be given. Finally, some results on the mechanical properties of spot welded and weldbounded joints under corrosive attacks with be discused.
Nowadays, car manufacturers tried to improve automotive fuel efficiency, and applied many high strength steels such as AHSS or UHSS to car bodies. Therefore, the number of steel combinations for the resistance spot welding are dramatically increased and the need for weldability evaluation of these combinations are also required. In this study, we suggest the lobe curve using FEM simulations for DP780 steel with 1.0t, 1.4t. The lobe curves which could expressed weldablity and optimal welding condition were obtained according to 6 steel combinations. There were two combinations for same steel sheet which were DP780 1.0t, DP780 1.4t. Dissimilar steel sheet combination with different thickness was 1.0t and 1.4t of DP780. Different steel combinations were DP780 1.0t and SPRC440 1.0t, and DP780 1.0t and DP590 1.0t. Finally dissimilar combinations was and DP780 1.0t and DP590 1.4t. The trend of low boundary and high boundary variation of lobe curve were analyzed with a viewpoint of the contact resistance and the heat input.
Modelling and testing of hybrid joints obtained by combination of two simple techniques, i.e., by application of spot welding and adhesive, is reported. The joints were subjected to uniaxial tension. The experiments were performed for: 1) a pure joining of the parts by spot welding and 2) spot welding–adhesive joining of the structural elements. A new experimental method was elaborated with application of two digital image correlation (DIC) systems. The method allowed for online monitoring of the deformation process of the joined elements with complex shapes. Modelling of the hybrid joints response to mechanical loading was performed by ABAQUS code. Damage process in the adhesive layer was taken into account. The obtained results lead to the conclusion that the strengthening of joints by the application of adhesive significantly improves static strength and energy absorption. The visible degradation process of the adhesive layer which started prior to the maximum value of force carrying the hybrid joint was obtained.
Hybrid joints obtained by a combination of two simple techniques, e.g. by spot welding and adhesive, are relatively modern joints developed especially for application in aerospace industry. This contribution describes the modelling and testing of structural elements by application of an angle bar and spot welding techniques with the introduction of adhesive layers between adherends.
Numerical modelling of the mechanical response using the Finite Element Analysis requires a description of 3 different damage processes: (1) plastic degradation of the spot welded points, (2) plastic deterioration of the joined parts around the regions of spot points and (3) degradation of the adhesive layer.
The whole uniaxial deformation process of samples was experimentally investigated with the application of 2 Digital Image Correlation systems to monitor the development of deformation up to the final failure. The first damage process starts within the adhesive layer, much below the maximum force that can be carried by the specimen. The second damage process activated in the joined adherends surrounding the spot welded points – near the maximum of the carrying force. The failure of the specimens took place when the adhesive layer was almost totally degraded and the welded spots were subjected to intensive plastic degradation.
Zinc coated dual phase 600 steel (DP 600 grade) was investigated, utilisation of which has gradually increased with each passing day in the automotive industry. The adhesive bonding (AB), resistance spot welding (RSW), and adhesive weld bonding (AWB) joints of the zinc coated DP 600 steel were investigated. Additionally, the zinc coating was removed using HCL acid in order to investigate the effect of the coating. The microstructure, tensile shear strengths, and fracture properties of adhesive bonding (AB), resistance spot welding (RSW), and adhesive weld bonding (AWB) joints of the coated and uncoated DP 600 steel were compared. In addition, a mechanical-electrical-thermal coupled model in a finite element analysis environment was utilised. The thermal profile phenomenon was calculated by simulating this process. The results of the tensile shear test indicated that the tensile load bearing capacity (TLBC) values of the coated specimens among the three welding methods were higher than those of the uncoated specimens. Additionally, the tensile strength of the AWB joints of the coated and uncoated specimens was higher than that of the AB and RSW joints. It was determined that the fracture behaviours and the deformation caused were different for the three welding methods.
The microstructures, tensile and fatigue properties of weld-bonded (WB) AZ31B-H24 Mg/Mg joints with different sizes of bonding area were evaluated and compared with the adhesive-bonded (AB) Mg/Mg joints. Typical equiaxed dendritic structures containing divorced eutectic Mg17Al12 particles formed in the fusion zone of both WB-1 (with a bonding area of 35 mm×35 mm) and WB-0.5 (with a bonding area of 17.5 mm×35 mm) joints. Less solidification shrinkage cracking was observed in the WB-0.5 joints than WB-1 joints. While the WB-0.5 joints exhibited a slightly lower maximum tensile shear stress than the AB-0.5 joints (with a bonding area of 17.5 mm×35 mm), the energy absorption was equivalent. Although the AB-0.5 joints exhibited a higher fatigue resistance at higher cyclic stress levels, both the AB-0.5 and WB-0.5 joints showed an equivalent fatigue resistance at lower cyclic stress levels. A higher fatigue limit was observed in the WB-0.5 joints than in the WB-1 joints owing to the presence of fewer shrinkage pores. Cohesive failure mode along the adhesive layer in conjunction with partial nugget pull-out from the weld was observed at the higher cyclic loads, and fatigue failure occurred in the base metal at the lower cyclic loads.
This paper presents the research on weldability of magnesium alloy AZ61 sheets by overlap laser welding, adhesive bonding, and laser seam weld bonding processes. Microstructures and mechanical properties of the joints are investigated. In overlap laser welding, the joint fractures at the interface between the sheets and maximum shear strength can reach 85% of that of the base metal. Off-center moment during tensile shear test can lead to the strength loss, while the weld edge can also influence the strength as a cracking source. Adhesive bonded joint can offer high tensile shear failure force but low peel strength. Laser weld bonded joint offers higher tensile shear failure force than either laser welded joint or adhesive bonded joint does, and the improved failure load is due to combined contribution of the weld seam and the adhesive. The weld seam can block the adhesive crack propagation, and the adhesive improves the stress distribution, so they can offer a synergistic effect.
The aim of this study was to evaluate microstructures, tensile and fatigue properties of weld-bonded (WB) magnesium-to-magnesium (Mg/Mg) similar joints and magnesium-to-steel (Mg/steel) dissimilar joints, in comparison with resistance spot welded (RSW) Mg/steel dissimilar joints. In the WB Mg/Mg joints, equiaxed dendritic and divorced eutectic structures formed in the fusion zone (FZ). In the dissimilar joints of RSW and WB Mg/steel, FZ appeared only at Mg side with equiaxed and columnar dendrites. At steel side no microstructure changed in the WB Mg/steel joints, while the microstructure in the RSW Mg/steel joints consisted of lath martensite, bainite, pearlite and retained austenite leading to an increased microhardness. The relatively low cooling rate suppressed the formation of shrinkage porosity but promoted the formation of MgZn2 and Mg7Zn3 in the WB Mg/steel joints. The added adhesive layer diminished stress concentration around the weld nugget. Both WB Mg/Mg and Mg/steel joints were significantly stronger than RSW Mg/steel joints in terms of the maximum tensile shear load and energy absorption, which also increased with increasing strain rate. Fatigue strength was three-fold higher for WB Mg/Mg and Mg/steel joints than for RSW Mg/steel joints. Fatigue failure in the RSW Mg/steel joints occurred from the heat-affected zone near the notch root at lower load levels, and in the mode of interfacial fracture at higher load levels, while it occurred in the Mg base metal at a maximum cyclic load up to ∼10 kN in both WB Mg/Mg and Mg/steel joints.
In lightweight car body shell mass production, due to requirements on vehicle weight reduction and carbon dioxide emissions, joining of advanced high strength steels (AHSS) with different joining procedures and especially hybrid bonding techniques is becoming more and more important. One of these hybrid bonding techniques is the combination of resistance spot welding and adhesive bonding called weldbonding. One of the important advantages of weldbonded joints in comparison to resistance spot welded joints are the enhanced mechanical properties. To guarantee sufficiently high quality conditions regarding the strength of the weldbonded joints, the influences of the applied adhesive systems and of different base metal combinations are studied. This is carried out for both non-corrosive and corrosive environments and for the choice of different joining parameters settings. In particular, the mechanical behaviour of the weldbonded joints is investigated under quasi-static, impact and fatigue loads. Furthermore, the energy absorption of the weldbonded joints for both non-corrosive and corrosive environments is studied. It is shown that the weldbonded joints possess higher mechanical strengths in all load cases (quasi-static, impact and fatigue). Corrosive attack affects weldbonded joints, and the quasi-static strength is reduced. Resistance spot welded joints are not affected by the corrosive attack, but even after several weeks of corrosive attack, the quasi-static strength of weldbonded joints remains higher than that of resistance spot welded joints.
A research study on the fatigue behaviour of aluminium alloy adhesive lap joints was carried out to understand the effect of surface pre-treatment and adherends thickness on the fatigue strength of adhesive joints. The adherend material used for the experimental tests was an aluminium alloy 6082-T6 in the form of thin sheets, and the adhesive used was a high strength epoxy (Araldite 420 A/B). The surface preparation included an abrasive preparation (AP joints) and sodium dichromate–sulphuric acid etch (CSA joints).A maximum fatigue strength was obtained for the CSA surface treatment with a 1.0mm adherends’ thickness. The fastest fatigue damage was related with a high surface roughness and a high stress perpendicular to adhesive surface, which helps to promote the adhesive failure. A numerical analysis was also performed to understand the effect of the adherends thickness on the stress level. Results showed an increase of the out-of-plane peak stresses with the increase of adherends thickness.
To develop an effective modeling technique for weld-bonded structures, fundamental experimental studies, including adherend and adhesive tests, and static tests with spot-welded, adhesive-bonded and weld-bonded coupons, were carried out. These studies reveal the brittle nature of the epoxy-adhesive-bond and the ductile rupture characteristic of the spot-weld pull-out. In the failure process of a weld-bonded structure, the adhesive-bond and the spot-weld fail at different stages and have little coupling effect, but they supplement each other.A modeling strategy was devised and implemented based on the static experimental findings and an assessment of available modeling approaches in a finite-element analysis program. As a result, a combination of the constrained spot-weld (CSW) model and the mesh-independent spot-weld (MISW) model is recommended for modeling the deformation and failure of weld-bonded vehicle structures. An approach for calibrating the failure parameters in the failure criteria is also developed. The recommended modeling method renders satisfactory correlation between simulations and tests at the static coupon test level and acceptable time-step for full-vehicle crash simulations.
Based on long time engineering research and dedicated collaborations with industry, a new welding software, SORPAS, has been developed for simulation of resistance projection and spot welding processes applying the powerful finite element method (FEM). In order to make the software d irectly usable by engineers and technicians in industry, all of the important parameters in resistance welding are considered and automatically implemented into the software. With the specially designed graphic user interface for Windows, engineers (even w ithout prior knowledge of FEM) can quickly learn and easily operate and utilize the software. All industrial users, including welding engineers from DaimlerChrysler, Volkswangen, PSA Peugeot Citroen, VOLVO, Siemens, ABB and so on, have started using the software just after taking a one-day training course. With the user-friendly facilities for flexible geometric design of work pieces and electrodes as well as process parameter settings similar to real machine settings, the software has been readily applied in industry for supporting product development and process optimization. After simulation, the dynamic process parameters are graphically displayed. The distributions of temperature, current, stress and deformation in the materials are displayed in color, which can be animated like slow-motion video. The software has been extensively verified and today applied in various industries including automotive, electronics and other metal processing industries as well as welding equipment manufacturers.
The association of spot welding and adhesive bonding, named weldbonding, is a steel joining technique which increasingly interests car manufacturers. Nevertheless, weldbonding is not at present used extensively by them due to a lack of data related to the performance of this technique. Studies carried out by Usinor have succeeded in demonstrating that weldbonding is a very well adapted joining technique to decrease the weight of steel structures.
Often in spot welding, the metals to be joined are similar or the thicknesses of the sheets to be joined are similar or both. The aim of the present work is to analyze spot-welded dissimilar thickness joints. The finite element technique was used for the analysis of the present work. The present work gives that the stresses are more concentrated towards the thinner part of a spot-welded dissimilar thickness joint, however, the introduction of an adhesive layer in conjunction with the spot weld nugget, resulted in strengthening and balancing the stresses on both members of the joint.
It is well established that weld-bonded joints enhance the fatigue as well as the corrosion resistance of resistance welded joints. In the present work, both techniques of weld-bonding, namely, weld-through and flow-in, have been evaluated. Metallic fillers at optimum percentages were also tried in order to enhance the electrical conductivity of the adhesive material. The present work demonstrated that the flow-in technique is far better when compared with the weld-through technique, both from economical as well as technological points of view.
Metals Joining Manual Book
- M M Schwartz
M.M. Schwartz, Metals Joining Manual Book, McGraw-Hill,
New York, 1979.
Design and Implementation of Software for Resist-ance Welding Process Simulations Fig. 11. Load-displacement curves in peel testing of weld bonds with three different adhesives. Test specimens (1.5 mm thickness) were applied without surface cleaning, immediately after the appli-cation of adhesive
- W Zhang
W. Zhang, Design and Implementation of Software for Resist-ance Welding Process Simulations. SAE 2003 World Congress, Detroit, USA, 2003. Fig. 11. Load-displacement curves in peel testing of weld bonds with three different adhesives. Test specimens (1.5 mm thickness) were applied without surface cleaning, immediately after the appli-cation of adhesive (t 0 ).
Load-displacement curves in peel testing of weld bonds with three different adhesives Test specimens (1.5 mm thickness) were applied without surface cleaning, immediately after the application of adhesive
- Fig
Fig. 11. Load-displacement curves in peel testing of weld bonds
with three different adhesives. Test specimens (1.5 mm thickness)
were applied without surface cleaning, immediately after the application of adhesive (t 0 ).
Test specimens (1.5 mm thickness) were applied without surface cleaning, immediately after the application of adhesive
- Fig
Fig. 11. Load-displacement curves in peel testing of weld bonds
with three different adhesives. Test specimens (1.5 mm thickness)
were applied without surface cleaning, immediately after the application of adhesive (t 0 ).