Showing papers on "Spot welding published in 2012"
30 Oct 2012-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the interfacial reaction between Al, AA6111, and Mg AZ31 alloys has been studied as a function of welding energy, and it was shown that the reaction layer thickness was already ∼5μm thick.
Abstract: High power ultrasonic spot welding (USW) is a low heat input solid-state joining process that may offer a solution for welding difficult dissimilar-material couples, like magnesium (Mg) to aluminium (Al) for automotive body applications. However, the high strain rate dynamic deformation in USW has been claimed to accelerate inter-diffusion rates in dissimilar joints. The interfacial reaction between Al, AA6111, and Mg AZ31 alloys has been studied as a function of welding energy. For the optimum welding condition of 600 J (0.4 s) the reaction layer thickness was already ∼5 μm thick. Intermetallic reaction centres were found to nucleate within microwelds at the interface at very short welding times and spread and grow rapidly to form a continuous layer, composed of two sub-layers of Al 12 Mg 17 and Al 3 Mg 2 . Interface liquation was also found for longer welding times at temperatures below the recognised lowest eutectic reaction temperature in the Al–Mg binary system. Modelling has been used to show that the solid state reaction kinetics were over twice the rate expected from parabolic growth predictions made using rate constants obtained under static test conditions. The reasons for this discrepancy and the depressed melting reaction are discussed.
153 citations
TL;DR: In this paper, the static and fatigue strength of mechanically clinched and self-pierce riveted joints in aluminium alloy sheets were compared with those of a resistance spot welded joint.
118 citations
TL;DR: In this paper, the effect of important welding parameters and tool properties that are effective on static strength in friction stir spot welds of polyethylene sheets were studied, including tool rotational speed, tool plunge depth and dwell time.
116 citations
TL;DR: In this article, the authors identify a number of critical weld attributes that determine the quality of welds by experimentally characterizing the weld formation over time, and a novel microstructural classification method for the weld region of an ultrasonic metal weld is introduced to complete the weld quality characterization.
Abstract: Manufacturing of lithium-ion battery packs for electric or hybrid electric vehicles requires a significant amount of joining such as welding to meet desired power and capacity needs. However, conventional fusion welding processes such as resistance spot welding and laser welding face difficulties in joining multiple sheets of highly conductive, dissimilar materials with large weld areas. Ultrasonic metal welding overcomes these difficulties by using its inherent advantages derived from its solid-state process characteristics. Although ultrasonic metal welding is well-qualified for battery manufacturing, there is a lack of scientific quality guidelines for implementing ultrasonic welding in volume production. In order to establish such quality guidelines, this paper first identifies a number of critical weld attributes that determine the quality of welds by experimentally characterizing the weld formation over time. Samples of different weld quality were cross-sectioned and characterized with optical microscopy, scanning electronic microscopy (SEM), and hardness measurements in order to identify the relationship between physical weld attributes and weld performance. A novel microstructural classification method for the weld region of an ultrasonic metal weld is introduced to complete the weld quality characterization. The methodology provided in this paper links process parameters to weld performance through physical weld attributes.Copyright © 2012 by ASME and General Motors
105 citations
TL;DR: In this paper, the experimental and numerical results of friction stir spot welding of high density polypropylene were presented, where the experimental tests, conducted according to combinations of process factors such as tool rotation speed, plunge depth and dwell time at beginning welding, were carried out according to the Taguchi orthogonal table L9 in randomized way.
97 citations
TL;DR: A 2D axisymmetric electro-thermo-mechanical finite element (FE) model was developed to study the effect of welding time and current intensity on nugget size in resistance spot welding process of AISI type 304L austenitic stainless steel sheets using ANSYS commercial software package.
94 citations
TL;DR: In this article, it has been shown that there is a clearly observable heat-affected zone (HAZ) when ultrasonic spot welding (USW) aluminium automotive alloys like AA6111-T4, the severity of which depends on the welding energy.
93 citations
TL;DR: In this paper, the effects of the welding parameters on static strength of friction stir spot welds of high density polyethylene sheets were investigated, and the plunge rate of the tool was determined to have a negligible effect on friction stir-spot welding.
90 citations
TL;DR: In this paper, a three-dimensional heat and mass transfer model is used to simulate the welding process, based on the solution of the equations of mass, momentum, energy conservation and solute transport in weld pool.
89 citations
TL;DR: In this article, the effects of laser mean power on the performance of dissimilar laser spot welds have been studied in terms of peak load and the fusion zone size in the weaker sheet.
88 citations
TL;DR: In this article, ultrasonic spot welds of magnesium-aluminium alloy were produced via a solid state welding process, and a sound joint was obtained under most of the welding conditions.
Abstract: Dissimilar spot welds of magnesium–aluminium alloy were produced via a solid state welding process, i.e. ultrasonic spot welding, and a sound joint was obtained under most of the welding conditions. It was observed that a layer of intermetallic compound (IMC) consisting of Al12M17 formed at the weld centre where the hardness became higher. The lap shear strength and failure energy of the welds first increased and then decreased with increasing welding energy, with the maximum lap shear strength and failure energy occurring at ∼1250 J. This was a consequence of the competition between the increasing diffusion bonding arising from higher temperatures and the deterioration effect of the intermetallic layer of increasing thicknesses. Failure predominantly occurred in between the aluminium alloy and the intermetallic layer, which normally stayed at the magnesium side or from the cracks of the IMCs in the reaction layer.
TL;DR: In this article, the preliminary investigation of joining parameter at various levels as well as the mechanical properties of friction spot joining of aluminium alloy (A5052) to polyethylene terephthalate (PET) was conducted.
Abstract: The weld strength of thermoplastics with aluminium alloy, such as high density polyethylene and polypropylene sheets, is influenced by friction stir welding parameters. This paper focuses on the preliminary investigation of joining parameter at various levels as well as the mechanical properties of friction spot joining (FSJ) of aluminium alloy (A5052) to polyethylene terephthalate (PET). A number of FSJ experiments were carried out to obtain optimum mechanical properties by adjusting the plunge speed and plunge depth in the ranges of 5–40 mm min−1 and 0·4–0·7 mm respectively, while spindle speed remains constant at 3000 rev min−1. The results indicated that A5052 and PET successfully joined with the aid of frictional heat energy originated from the friction spot welding process. The effect of plunge speed on the joined area and the effect of formation of bubbles at the interface of joints on the shear strength of joint are discussed.
TL;DR: In this article, a back propagation neural network model was developed to analyze RSW process and the interaction effects of the parameters, which was used as an optimization procedure for determining a set of process parameters; as a result, the maximum joint strength was obtained.
TL;DR: In this paper, a tin interlayer was inserted in between the faying surfaces during ultrasonic spot welding to improve the strength of dissimilar joints of AZ31B-H24 magnesium alloy to 5754-O aluminium alloy.
Abstract: Welding of magnesium to aluminium alloys is enormously challenging due to the formation of brittle Al12Mg17 intermetallic compounds (IMCs). This study was aimed at improving the strength of dissimilar joints of AZ31B-H24 magnesium alloy to 5754-O aluminium alloy by using a tin interlayer inserted in between the faying surfaces during ultrasonic spot welding. The addition of tin interlayer was observed to successfully eliminate the brittle Al12Mg17 IMCs, which were replaced by a layer of composite-like tin and Mg2Sn structure. Failure during the tensile lap shear tests occurred through the interior of the blended interlayer as revealed by X-ray diffraction and SEM observations. As a result, the addition of a tin interlayer resulted in a significant improvement in both joint strength and failure energy of magnesium to aluminium dissimilar joints and also led to an energy saving because the optimal welding energy required to achieve the highest strength decreased from ∼1250 to ∼1000 J.
01 May 2012-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, material flow and local texture evolution during friction stir spot welding (FSSW) of AZ31 magnesium alloy was characterized by varying tool rotation rates and electron backscatter diffraction (EBSD) measurements at various locations of the welded region.
Abstract: Material flow and local texture evolution during friction stir spot welding (FSSW) of AZ31 magnesium alloy was characterized by varying tool rotation rates. Texture at various locations of the welded region was measured using electron backscatter diffraction (EBSD). Material flow is significantly influenced by tool rotation rate with a conical step spiral pin tool, and FSSW introduces a unique basal fiber texture in the welded region. Results indicate that local texture evolution is dominated by shear deformation through material flow. The tool shoulder applies both shear and compressive deformation to the upper region material; however, the rotating pin introduces only shear deformation to the adjacent material. As the tool rotation rate increases, the effect of both tool shoulder and pin becomes more prominent by introducing a higher degree of basal pole tilt with respect to the initial rolling texture at the periphery of the pin, but less tilt in the upper region beneath the tool shoulder undersurface. The equiaxed fine grain structure in the stir zone appears to result from the twinning-induced dynamic recrystallization and discontinuous dynamic recrystallization.
TL;DR: In this paper, the flat spot friction stir welding was applied to aluminum alloys and the results showed that sound joints can be successfully obtained with smooth surfaces and without any internal welding defects.
TL;DR: Aluminium alloy 6111-T4 and steel DC04 1mm sheets have been successfully welded with a cycle time of 1.5 hours as mentioned in this paper. But the cycle time was not specified.
TL;DR: In this paper, the effects of tool geometry and properties on friction stir spot welding properties of polypropylene sheets were studied and four different tool pin geometries, with varying pin angles, pin lengths, shoulder diameters and shoulder angles were used for friction stir-spot welding.
Abstract: The effects of tool geometry and properties on friction stir spot welding properties of polypropylene sheets were studied. Four different tool pin geometries, with varying pin angles, pin lengths, shoulder diameters and shoulder angles were used for friction stir spot welding. All the welding operations were done at the room temperature. Lap-shear tensile tests were carried out to find the weld static strength. Weld cross section appearance observations were also done. From the experiments the effect of tool geometry on friction stir spot weld formation and weld strength were determined. The opti- mum tool geometry for 4 mm thick polypropylene sheets were determined. The tapered cylindrical pin gave the biggest and the straight cylindrical pin gave the lowest lap-shear fracture load.
TL;DR: In this article, an alternative method to optimize process parameters of resistance spot welding (RSW) towards weld zone development is presented, where the optimization approach attempts to consider simultaneously the multiple quality characteristics, namely weld nugget and heat affected zone (HAZ), using multi-objective Taguchi method (MTM).
Abstract: This paper presents an alternative method to optimize process parameters of resistance spot welding (RSW) towards weld zone development. The optimization approach attempts to consider simultaneously the multiple quality characteristics, namely weld nugget and heat affected zone (HAZ), using multi-objective Taguchi method (MTM). The experimental study was conducted for plate thickness of 1.5 mm under different welding current, weld time and hold time. The optimum welding parameters were investigated using the Taguchi method with L9 orthogonal array. The optimum value was analyzed by means of MTM, which involved the calculation of total normalized quality loss (TNQL) and multi signal to noise ratio (MSNR). A significant level of the welding parameters was further obtained by using analysis of variance (ANOVA). Furthermore, the first order model for predicting the weld zone development is derived by using response surface methodology (RSM). Based on the experimental confirmation test, the proposed method can be effectively applied to estimate the size of weld zone, which can be used to enhance and optimized the welding performance in RSW or other application.
TL;DR: In this paper, the effect of process variables and energy input on joint formation between Al-6111 and Mg-AZ31 alloys was investigated and the optimum welding conditions, heat generation, and the formation of a significant intermetallic reaction layer were reported.
Abstract: The ability to join dissimilar materials in the automotive industry will result in more efficient multimaterial structures. However, welding of aluminium (Al) to magnesium (Mg) alloys is problematic because of the rapid formation of brittle intermetallic phases at the weld interface. Ultrasonic welding (USW) is a solid-state joining technology that may offer a potential solution, but USW of Al to Mg is currently not well understood. Here, we have investigated the effect of process variables and energy input on joint formation between Al-6111 and Mg-AZ31 alloys, and we report on the optimum welding conditions, heat generation, and the formation of a significant intermetallic reaction layer. Furthermore, the factors influencing the interface reaction rate and the advantages of precoating the Mg with Al are discussed.
TL;DR: In this paper, the effects of local electrical contact resistance on transport variables, cooling rate, solute distribution, and nugget shape after solidification responsible for microstructure of the fusion zone during resistance spot welding are realistically and systematically investigated.
DOI•
07 Dec 2012
TL;DR: In this article, the authors developed a Computational Fluid Dynamics model to study steel weld pool hydrodynamics during conduction mode laser spot welding, and concluded that free surface deformations and instabilities have a strong impact on the fluid flow and heat transfer in weld pools, and should therefore be accounted for in weld pool simulations.
Abstract: Extending the weldability of novel materials, and improving the weld quality by tailoring weld microstructures are key factors to obtain the welding techniques demanded in the modern manufacturing industries. This can be done, for example, by feeding chemical elements from a consumable wire into the weld pool during welding. The mixing of chemical components in the weld pool and the resulting post-solidification weld microstructures are influenced by weld pool hydrodynamics. Weld pool hydrodynamics is known to be primarily driven by Marangoni forces acting at the free liquid surface, i.e by tangential gradients in surface tension along the liquid surface due to pronounced lateral gradients in temperature and surface active element concentration. In this research, we develop a Computational Fluid Dynamics model to study steel weld pool hydrodynamics during conduction mode laser spot welding. It is concluded that free surface deformations and instabilities have a strong impact on the fluid flow and heat transfer in weld pools, and should therefore be accounted for in weld pool simulations. With increasing the surface active element concentration and laser power, the weld pool flow becomes highly unstable and can no longer be accurately modeled with a flat surface assumption. More accurate predictions of weld pool physics can be made if the free surface, solidification stage, and three-dimensionality are taken into account. This reduces the need for the use of unphysical parameter fittings widely reported in literature.
TL;DR: In this paper, electron back scatter diffraction (EBSD) scanning, tensile testing, and laser beam profilometry (LBP) measurements along with optical microscopy (OM) images, failure loads and deformation of 6061-T6 aluminum alloy, RSW joints were experimentally investigated.
TL;DR: In this paper, an ultrasonic C-scan technique was evaluated for non-destructive testing (NDT) of resistance spot welding of aluminium, and it was established through fundamental trials that removal of surface indentation from the welding electrode is necessary in order to obtain credible nondestructive assessments of aluminium spot weld size and shape.
Abstract: An ultrasonic C-scan technique was evaluated for non-destructive testing (NDT) of resistance spot welding of aluminium. It was established through fundamental trials that removal of surface indentation from the welding electrode is necessary in order to obtain credible non-destructive assessments of aluminium spot weld size and shape. The non-destructive test results showed good correlation with peeled samples and metallographic cross sections. The technique also provided further fundamental understanding of aluminium resistance spot welding (RSW) process; especially with respect to the presence of an outer fused ring. The fundamental aspect of this study was underpinned using the NDT technique for a real assembly; challenging the technique with access issues, different material combinations, multiple joint stacks and independent measurements. The non-destructive test analyses obtained correlated well with actual tear down results and offered further encouragement that the C-scan technique is viable as a production tool if a suitably flattened surface can be provided.
TL;DR: In this paper, a finite element method was applied for predicting the weld bead geometry i.e. bead length (BL), bead width (BW) and depth of penetration (DP) in laser spot welding of AISI 304 stainless steel sheet of thickness 2.5mm.
Patent•
16 Mar 2012
TL;DR: In this article, a tool drive unit of a friction stir spot welding device is configured to move a pin member (11) and a shoulder member (12) forward and backward, and is controlled by the tool drive control unit (21).
Abstract: In this invention, a tool drive unit (53) of a friction stir spot welding device is configured to move a pin member (11) and a shoulder member (12) forward and backward, and is controlled by a tool drive control unit (21). A press-fit reference point setting unit (22) sets the position of the pin member (11) or the shoulder member (12) when contacting an object to be welded (60) as the press-fit reference point. The tool drive control unit (21) controls the press-fit depth when a rotating tool (51) press-fits the object to be welded (60) starting at the surface thereof by controlling the relative location of the pin member (11) in relation to the shoulder member (12) based on the press-fit reference point. Thus, good welding quality with suitable precision in accordance with welding conditions can be achieved, especially with a double-acting type friction stir spot welding method.
TL;DR: In this article, an analysis of a joint connected by Friction Stir Spot Welds (FSSW) is performed from both a numerical and an experimental point of view, where the focus is to evaluate which structural parameters are strictly relevant to FSSW modeling in FE.
TL;DR: In this article, the fatigue strength of dissimilar welds was evaluated based on the effective nugget size, defined as the area where Al or Mg alloy remained on the steel side after static fracture.
Abstract: Aluminium alloy A6061-T6 or magnesium alloy AZ31 sheet was welded to steel sheet by a friction stir spot welding technique using a scroll grooved tool without a probe. The material flow in the nugget of the Mg/steel weld was less than that in the Al/steel one. The Al/steel weld exhibited higher static tensile–shear strength than the Al/Al weld, while the strengths of Mg/steel and Mg/Mg welds were comparable. Tensile–shear fatigue tests were performed using lap shear specimens of both dissimilar and similar welds. The dissimilar welds exhibited nearly the same fatigue strengths as the similar ones. The effective nugget size in the dissimilar welds was defined as the area where Al or Mg alloy remained on the steel side after static fracture. When the fatigue strengths of dissimilar welds were evaluated based on the effective nugget size, the normalised fatigue strengths of Al/steel and Mg/steel welds were comparable.
TL;DR: In this article, the authors investigated the resistance spot welding characteristics of martensitic steel (M130) having the thickness of 2 mm, utilising metallographic observation, microhardness and tensile-shear testing.
Abstract: Safety, emissions and fuel economy of vehicles have always been of great importance to automakers. Advanced high strength steels (AHSSs) have proved to be effective in fulfilling these needs of the industry, and this has led to great opportunities for increasing usage of AHSSs. The present work aimed to investigate the resistance spot welding characteristics of martensitic steel (M130) having the thickness of 2 mm, utilising metallographic observation, microhardness and tensile–shear testing. The results were compared for different combinations of martensitic steel and low carbon steel (LCS). In the study of interfacial to pull-out failure mode transition, dissimilar M130/LCS welds exhibited the lowest tendency to fail in the interfacial failure mode. Weld nugget diameter is proposed as a main variable controlling the peak load and energy absorption of the welds along with other factors such as electrode indentation and hardness/strength of the failure location.
Patent•
20 Dec 2012TL;DR: In this article, an apparatus consisting of at least one first sheet comprising a first material and at least two second sheets comprising a second material, where the first sheet is at least about 1.5 times the thickness of the second sheet.
Abstract: An apparatus is provided including: at least one first sheet comprising a first material; at least one second sheet comprising a second material, wherein the first material comprises at least one of: a thermal conductivity and an electrical conductivity that is at least 10% lower than that of the second material; and a joint comprising at least one resistance spot weld (RSW), wherein the first sheet is at least about 1.5 times the thickness of the second sheet. Methods are also provided.