Topic
Spot welding
About: Spot welding is a research topic. Over the lifetime, 12491 publications have been published within this topic receiving 89845 citations. The topic is also known as: Spot_welding.
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TL;DR: In this paper, a combination of spot welding, a proper beam offset and special filler material is applied to eliminate brittle intermetallic phases in the welding structure of the welded joints.
Abstract: Aluminum combines comparably good thermal and electrical properties with a low price and a low material weight. These properties make aluminum a promising alternative to copper for a large number of electronic applications, especially when manufacturing high volume components. However, a main obstacle for a wide use of this material is the lack of a reliable joining process for the interconnection of copper and aluminum. The reasons for this are a large misalignment in the physical properties and even more a poor metallurgical affinity of both materials that cause high crack sensitivity and the formation of brittle intermetallic phases during fusion welding. This paper presents investigations on laser micro welding of copper and aluminum with the objective to eliminate brittle intermetallic phases in the welding structure. For these purposes a combination of spot welding, a proper beam offset and special filler material are applied. The effect of silver, nickel and tin filler materials in the form of thin foils and coatings in a thickness range 3-100 μm has been investigated. Use of silver and tin filler materials yields to a considerable improvement of the static and dynamic mechanical stability of welded joints. The analysis of the weld microstructure shows that an application even of small amounts of suitable filler materials helps to avoid critical, very brittle intermetallic phases on the interface between copper and solidified melt in the welded joints.
35 citations
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TL;DR: In this paper, the susceptibility of hot-dipped galvanized Q&P980 steel to LME cracking during resistance spot welding was systematically investigated by an orthogonal experiment, and cracks were detected by fluorescent magnetic particle testing and cross-sectional microscopic observation.
Abstract: Resistance spot-welded galvanized ultrahigh-strength steels are sensitive to liquid metal embrittlement (LME), which is manifested by surface cracks on the joints. LME occurs when a solid metal contacts a liquid metal under tensile stress, and the phenomenon has not been fully understood until now, especially for resistance spot welding. In this study, the susceptibility of hot-dipped galvanized Q&P980 steel to LME cracking during resistance spot welding was systematically investigated by an orthogonal experiment. Cracks were detected by fluorescent magnetic particle testing and cross-sectional microscopic observation. Cracks were mostly located at the indentation edge and slope, and a few cracks were also located at the indentation center and slope periphery. The severity of the cracking increased with the increasing welding current and welding time, and the decreasing electrode force. The sequence of influence degree from high to low was welding current > electrode force > welding time. Holding time had no obvious effect. Microstructural analysis revealed that the content of martensite in areas with cracking increased, indicating that a high temperature was experienced at these locations. Zinc accumulated inside the cracks, and the cracks were intergranular, which coincides with the characteristics of LME. The LME cracking was provoked by the simultaneous occurrence of a tensile stress, an appropriate temperature and liquid metal, and the cracks were influenced by the welding parameters. Under suitable conditions, Zn diffused along the grain boundaries and weakened them, resulting in LME cracking.
35 citations
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TL;DR: In this article, the authors investigated the underlying factors of the tensile shear strength of automotive steels' resistance spot welds during interfacial failure and found that the ratio of the fracture toughness to the hardness of the fusion zone is the critical factor governing the interfacer failure mechanism.
Abstract: The failure of advanced high-strength steels’ spot welds is a critical issue for automotive crashworthiness. This paper deals with understanding the underlying factors of the tensile-shear strength of automotive steels’ resistance spot welds during interfacial failure. It was found that the ratio of the fracture toughness to the hardness of the fusion zone is the critical factor governing the interfacial failure mechanism: ductile shear failure (controlled by the fusion zone hardness) vs. cleavage crack propagation (controlled by the fracture toughness). This clarification could pave the way for more accurate modelling of interfacial failure of advanced steel resistance spot welds and shed light on the design of proper post-weld heat treatment for improving the weld mechanical performance.
35 citations
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TL;DR: In this article, the deformation and failure of spot-welded joints have been successfully modelled using ac ohesive-zone model for fracture and failure by implementing a user defined, three-dimensional, cohesive-zone element within a commercial finite-element package.
Abstract: The deformation and failure of spot-welded joints have been successfully modelled using ac ohesive-zone model for fracture. This has been accomplished by implementing a user- defined, three-dimensional, cohesive-zone element within a commercial finite-element package. The model requires two material parameters for each mode of deformation. Results show that the material parameters from this type of approach are transferable for identical spot welds in different geometries where a single parameter (such as maximum stress) is not. The approach has been demonstrated using a model system consisting of spot-welded joints made from 5754 aluminium sheets. The techniques for determining the cohesive fracture parameters for both nugget fracture and nugget pullout are described in this paper. It has been demonstrated that once the appropriate cohesive parameters for a weld are determined, quantitative predictions can be developed for the strengths, deformations and failure mechanisms of different geometries with nominally identical welds.
35 citations
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TL;DR: In this paper, a methodology is proposed to find the optimum locations of spot welds and the optimum overlapping length of the joined plates for maximum fatigue life, where the total strain life equation is used to predict the fatigue life.
35 citations