Showing papers on "Spot welding published in 2008"
15 May 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the relationship between failure mode and weld fusion zone characteristics (size and microstructure) was studied and it was found that spot weld strength in the pullout failure mode is controlled by the strength and fusion zone size of the galvanized steel side.
Abstract: Resistance spot welding was used to join austenitic stainless steel and galvanized low carbon steel. The relationship between failure mode and weld fusion zone characteristics (size and microstructure) was studied. It was found that spot weld strength in the pullout failure mode is controlled by the strength and fusion zone size of the galvanized steel side. The hardness of the fusion zone which is governed by the dilution between two base metals, and fusion zone size of galvanized carbon steel side are dominant factors in determining the failure mode.
176 citations
TL;DR: In this paper, a double-acting tool consisting of outer flat shoulder and inner retractable probe was used to re-fill probe hole of the joints, which increased effective cross sectional area of the nugget, resulting in higher tensile strength.
149 citations
TL;DR: In this article, the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds of advanced high strength steels (AHSS) under lap shear loading condition were examined.
147 citations
TL;DR: In this article, the authors investigated the failure modes of spot friction welds made by a flat tool in lap-shear specimens of aluminum 6111-T4 sheets based on the approach presented in Part 1.
140 citations
TL;DR: In this article, the fracture paths within the joint microstructure of spot welded AHSS, including dual phase (DP), transformation induced plasticity (TRIP), and ferritic-bainitic (FB), were compared to new high strength low alloy steels.
Abstract: Evaluating the impact performance of resistance spot welded joints in advanced high strength steels (AHSS) is critical for their continued integration into the automotive architecture. The effect of strain rate on the joint strength and failure mode is an important consideration in the design of welded structures. Recent results suggest that the failure mode is dependent upon the strength, chemistry, and processing of AHSS. Current literature, however, does not explain the effects of weld microstructure and a comprehensive comparison has yet to be conducted. The present study details the fracture paths within the joint microstructure of spot welded AHSS, including dual phase (DP), transformation induced plasticity (TRIP) and ferritic–bainitic (FB), in comparison to new high strength low alloy steels. Quasi-static and impact tests were conducted using a universal tensile tester and an instrumented drop tower respectively. Results for elongation, failure load and energy absorption for each material ...
138 citations
TL;DR: In this article, resistance spot welds were produced in dissimilar combinations of advanced high strength steels, and the microstructure and mechanical properties were characterised using metallurgical techniques and lap shear and cross-tension testing.
Abstract: Resistance spot welds were produced in dissimilar combinations of advanced high strength steels. A 600 MPa dual phase (DP) steel was welded to a high strength low alloy, a 780 MPa DP, and a 780 MPa transformation induced plasticity steel. The microstructure and mechanical properties were characterised using metallurgical techniques and lap shear and cross-tension testing. The results show that a pullout failure mode with improved mechanical properties is obtained when DP600 is paired with other advanced high strength steels, compared to the DP600 welded to itself, which is prone to interfacial failure and poor mechanical properties, given the same weld size. An in depth comparison of the interfacial to pullout failure transition in similar DP600 and DP780 and dissimilar DP600–DP780 welds was performed. The results show that the interfacial to pullout transition for the DP600–DP780 welds is significantly lower than with DP600 welded to itself. Increased fusion zone strength through dilution with th...
123 citations
TL;DR: In this paper, a 3D finite element-based model of the plunge phase was developed using the commercial code ABAQUS to study the thermomechanical processes involved during the plunge stage.
121 citations
TL;DR: In this paper, the influence of the primary welding parameters affecting the heat input such as, weld peak current, on the weld quality such as; surface appearances, weld nugget size, weld penetration, weld internal discontinuities, strength and ductility was determined for 304L resistance spot welded materials.
121 citations
TL;DR: In this paper, the authors examined resistance spot welding of advanced high strength steels (AHSS) including 590R, DP600, DP780 and TRIP780, and the mechanical properties and microstructure of these resistance welded steel alloys were detailed.
Abstract: Integration of advanced high strength steels (AHSS) into the automotive architecture has brought renewed challenges for achieving acceptable welds. Resistance spot welding (RSW) is the primary method used in welding automotive structures, which has resulted in a demand to better understand RSW of AHSS. The varying alloy contents and processing techniques used in their production has further complicated this initiative. The current study examines resistance spot welding of AHSS including 590R, DP600, DP780 and TRIP780. HSLA material is also included to represent conventional high strength steels and benchmark AHSS performance. The mechanical properties and microstructure of these resistance welded steel alloys are detailed. Furthermore, a relationship between chemistries and fusion zone hardness is produced.
102 citations
TL;DR: In this article, the effects of weld nugget size and expulsion on the performance of low carbon steel resistance spot weld have been investigated in the presence of voids and porosity as well as electrode indentation associated with expulsion.
Abstract: The effects of weld nugget size and expulsion on the performance of low carbon steel resistance spot weld have been investigated in the present paper. Failure mode, peak load and failure energy obtained in tensile–shear test have been used to describe the performance of spot weld. The influence of voids and porosity as well as electrode indentation associated with expulsion on peak load and failure energy is discussed. The results showed that although expulsion does not reduce the load carrying capacity of spot welds, it decreases their energy absorption capability which was attributed to the change of failure location due to excessive electrode indentation associated with expulsion.
98 citations
TL;DR: In this article, material flow and intermixing during dissimilar friction stir spot welding and friction stir seam welding are investigated, and it is suggested that the onion ring structures observed in similar and dissimilar FSS welds mad...
Abstract: Material flow and intermixing during dissimilar friction stir spot welding and friction stir seam welding are investigated. During friction stir spot welding, a ribbon of contiguous dissimilar lamellae is produced during each rotation of the tool and the number of intermingled lamellae contained in the intermixed region is determined by the tool rotational speed setting and the dwell time applied. When the rotating tool moves across the component, the ribbon of dissimilar contiguous lamellae continues to be produced and the linear distance in the traversing direction between dissimilar lamellae corresponds with the pitch distance [the travel speed (mm s−1) divided by the tool rotational speed (Hz)]. The material flow pattern produced when a threaded tool moves across a component is therefore a variant of that produced during the touch down period when the rotating tool is held stationary. It is suggested that the onion ring structures observed in similar and dissimilar friction stir seam welds mad...
TL;DR: In this article, the effect of weld time, different weld atmospheres and weld cooling conditions on the resistance spot weld quality of 316L stainless steel was investigated and the microstructure of welded samples was evaluated and the tensile shear load bearing capacity of weldment was also determined.
TL;DR: In this article, an overview of the physical background of the resistance welding process is presented, followed by the main problems concerning the appurtenant control theory and solutions to these problems are presented primarily according to the measured signals used and to the type of control strategies.
Abstract: This paper presents an overview of resistance spot welding control. The presentation of the physical background of the resistance welding process is followed by the description of the main problems concerning the appurtenant control theory. Solutions to these problems are presented primarily according to the measured signals used and to the type of control strategies.
TL;DR: In this article, a neural network-based system was proposed to predict the quality and nugget size of each spot weld in real time, when operated at the borderline between acceptable and worn electrode tip conditions, to within ± 0.15mm.
TL;DR: In this paper, an electro-thermo-mechanical model is used to predict electrical potential, temperature and residual stress distributions during different stages of resistance spot welding, which is capable of considering the effects of welding parameters such as heat input and welding time on residual stress distribution.
TL;DR: In this article, the interfacial conditions encountered in electrodes and sheets assemblies used in resistance spot welding process are characterized, and the quick wear of the electrodes surfaces is also measured, depending on the type of sheets (coated or none coated).
TL;DR: Particle concentrations and elemental concentrations were compared with allowable concentrations as recommended by the Occupational Safety and Health Administration and the American Conference of Governmental Industrial Hygienists and in all cases, workplace levels were at least 11 times lower than recommended levels.
Abstract: Airborne particles were characterized from six welding operations in three automotive plants, including resistance spot welding, metal inert gas (MIG) welding and tungsten inert gas (TIG) welding of aluminum and resistance spot welding, MIG welding and weld-through sealer of galvanized steel. Particle levels were measured throughout the process area to select a sampling location, followed by intensive particle sampling over one working shift. Temporal trends were measured, and particles were collected on filters to characterize their size and chemistry. In all cases, the particles fell into a bimodal size distribution with very large particles >20 μm in diameter, possibly emitted as spatter or metal expulsions, and very small particles about 1 μm in diameter, possibly formed from condensation of vaporized metal. The mass median aerodynamic diameter was about 1 μm, with only about 7% of the particle mass present as ultrafine particles <100 nm. About half the mass of aluminum welding particles could be acco...
TL;DR: In this paper, an inverse modeling methodology combining numerical modeling and indentation tests with a standard hardness test was used to characterise the detailed properties of different weld zones of spot-welded joints.
TL;DR: In this article, the effects of tool penetration depth and dwell time on joint strength were investigated, and the effect of these parameters on tensile failure load of the resulting joints was determined.
Abstract: Friction stir spot welding was used to make lap joints on strip specimens of polypropylene. The effects of tool penetration depth and dwell time on joint strength were investigated. The effect of these parameters on tensile failure load of the resulting joints was determined. An optimum combination of parameters that maximizes joint tensile failure load was identified.
TL;DR: In this article, local melting and tool slippage during friction stir spot welding of different Al-alloy base materials is examined using a combination of detailed microscopy and temperature measurement.
Abstract: Local melting and tool slippage during friction stir spot welding of different Al-alloy base materials is examined using a combination of detailed microscopy and temperature measurement. The stir zone peak temperature during welding is limited by either the solidus of the alloy in question or by spontaneous melting of intermetallic particles contained in the as-received base material. When spontaneous melting occurs this facilitates tool slippage at the contact interface. Accurate stir zone temperature and grain size measurements are essential elements when estimating the strain rate using the Zener–Hollomon relation. In Al 2024 and Al 7075 spot welds spontaneous melting of second-phase particles produces a drastic reduction in strain rate values. In Al 5754 and Al 6061 spot welds there is a strong correlation between tool rotational speed and estimated strain values. Local melted films dissolve rapidly in the high temperature stir zone and when the spot weld cools to room temperature following welding. Evidence of local melting is observed in Al 7075 friction stir spot welded joints made using a combination of rapid quenching, high plunge rates, and extremely short dwell time settings.
TL;DR: In this article, a tool path is given after the sinking phase nearby the initial penetration site; in this way a larger welding spot is obtained and more material is involved in the bonding process.
25 Sep 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a small-scale resistance spot welding (SSRSW) was carried out for austenitic stainless steels and a weld lobe that shows the process window for making sound joints was obtained for type 304 stainless steel thin sheets.
Abstract: Small-scale resistance spot welding (SSRSW) was carried out for austenitic stainless steels. A weld lobe that shows the process window for making sound joints was obtained for type 304 stainless steel thin sheets, and the effects of welding current, force and weld time on joint strength and nugget size were investigated. The cooling rate that was estimated from the solidification cell size was approximately 2.4 × 10 5 K/s which is almost similar to that produced by laser beam welding. The microstructures of weld zones were almost fully austenitic due to the rapid solidification rate. Despite the fully austenitic microstructure, no hot cracking was found in types 302, 304, 316L, 310S and 347 austenitic stainless steels by SSRSW. Rapid cooling rate in SSRSW made it difficult to predict the microstructures from the conventional Schaeffler diagram.
TL;DR: In this article, the characteristics of electrode radial wear and axial wear were compared with between DP600 and uncoated steels, and the results showed that when welding DP600, more alloy products and electrode deformation were produced to make electrode diameter increase at earlier wear stage.
Journal Article•
TL;DR: In this article, the quality of resistance spot welds in advanced high-strength steels was evaluated by considering the load-bearing ability of the weld rather than the fracture mode.
Abstract: To judge the quality of resistance spot welds in advanced high-strength steels, the load-bearing ability of the weld should be considered more important than the fracture mode.
SIDI1
TL;DR: In this paper, a dynamical non-linear model of the spatial time-dependant evolution of A 3 point during a particular sequence of resistance spot welding in steel material is presented.
Abstract: This paper presents a dynamical non linear model of the spatial time-dependant evolution of A 3 point during a particular sequence of resistance spot welding in steel material. The model is based on a solution to the heat equation, expressed in cylindrical coordinates inside the joint area, and when the source term is attributed to the electrical power. By the mean of the steel binary Fe–C diagram and the deduced t -dependant temperature rise profile, an estimation of the A 3 point spatial range date is given and compared to further results. The obtained temperature profile is yielded, taking into account main parameters variations, as a guide to non-destructive protocols and thermal characteristics investigation
TL;DR: Friction stir spot welding (FSSW) was applied to a lap joint of Al alloy 6061 sheets, 1 mm in thickness, to clarify its micro-mechanical properties as discussed by the authors.
Abstract: Friction stir spot welding (FSSW), which was recently developed as a spot joining technique, has been applied to a lap joint of Al alloy 6061 sheets, 1 mm in thickness, to clarify its micro...
TL;DR: In this paper, a linear vector quantization (LVQ) neural network was proposed for estimating the button size class based on a small number of dynamic resistance patterns for cold, normal and expulsion welds that are collected during the stabilization process.
Abstract: Real-time estimation of weld quality from process data is one of the key objectives in current weld control systems for resistance spot-welding processes. This task can be alleviated if the weld controller is equipped with a voltage sensor in the secondary circuit. Replacing the goal of quantifying the weld quality in terms of button size by the more modest objective of indirect estimation of the class of the weld, e.g., satisfactory (acceptable, “normal” button size), unsatisfactory (undersized, “cold” welds), and defects (“expulsion”), further improves the feasibility of the mission of indirect estimation of the weld quality. This paper proposes an algorithmic framework based on a linear vector quantization (LVQ) neural network for estimation of the button size class based on a small number of dynamic resistance patterns for cold, normal, and expulsion welds that are collected during the stabilization process. Nugget quality classification by using an LVQ network was tested on two types of controllers; medium-frequency direct current (MFDC) with constant current controller and alternating current (AC) with constant heat controller. In order to reduce the dimensionality of the input data vector, different sets of features are extracted from the dynamic resistance profile and are compared by using power of the test criteria. The results from all of these investigations are very promising and are reported here in detail.
TL;DR: In this paper, the structural stress and stress intensity factor solutions for spot welds in lap-shear, square-cup, U-shape, cross-tension and coach-peel specimens are obtained based on elasticity theories and fracture mechanics.
TL;DR: In this paper, the relationship between weld fusion zone attributes and failure behavior was studied. But, it was observed that increasing fusion zone size is accompanied by an increase in load carrying capacity and energy absorption capability.
Abstract: Resistance spot welding was used to join austenitic stainless steel sheets. Mechanical properties of the spot welds were evaluated using tensile shear test. Mechanical behaviour was described by peak load, failure energy and failure mode. The relationship between weld fusion zone attributes and failure behaviour was studied. Generally, it was observed that increasing fusion zone size is accompanied by an increase in load carrying capacity and energy absorption capability. However, when expulsion occurs, despite almost constant weld fusion zone size, energy absorption capability reduces significantly due to increase in electrode indentation depth. Considering the failure location and failure mechanism in the tensile shear test, minimum required fusion zone size to ensure the pull-out failure mode was estimated using an analytical model. According to this model, in addition to sheet thickness, ratio of fusion zone hardness to failure location hardness is the key metallurgical factor governing failur...
TL;DR: In this paper, a 3D finite element simulation is used to simulate the water jet spot welding process and the results are validated using the experimental data obtained previously by one of the authors and others.