Sheet Metal Joining Process Research Articles

Investigation on welding distortion in stainless steel sheet using gas tungsten arc welding process

TIG welding has found wide applications in various industries for sheet metal joining process due to its simple process with high quality welds. However, it still experiences various form of defects to the weld components such as incomplete fusion, undercut, cracks and distortion which might affect production accuracy, appearance and strength of weld components. It is obvious that various welding parameters can affect the welding distortion. The present study attempts to investigate the effect of welding parameters namely welding current and diameter of filler rod on the distortion angle, tensile strength and change in microstructures. The experiment was performed on a closed butt joint type of welding using a commercial TIG welding machine. A full factorial experiment was utilized in the present study. A higher welding current produced more heat input into the weld zone thus resulting in a higher angular distortion. Similarly, a bigger diameter of filler rod produced more angular distortion attributed to the bigger size of weld bead. While, the tensile strength increased with an increase of welding current whereas, the filler rod diameters showed no clear and direct effect. Based on the microstructures of weld area, there were full penetration joints with no obvious defects such as hot cracking and porosities.

Sheet metal joining process selector

Selecting the most suited manufacturing process for a specific product, as well as optimizing the design regarding manufacture and assembly, is actions that will directly impact on cost and quality, aiming at finding the best match between the product’s functional requirements and the attributes of the processes, and it should be carried out in the first stages of product development. In this context, the literature presents some sheet metal joining process selection methods, which can be classified as: mechanical (forming), metallurgical (welding) and chemical (adhesive) processes. However, such methods are complex and not specific for thin sheet metal. Therefore, our goal is to propose a joining process selector for overlapping sheet metal, which can correlate the product’s functional requirements with the technical characteristics of the processes (clinching, rivets and welding) in early stages of product development. Unlike what is found in the literature, this selector is subdivided into five different types of clinching processes. The selector design was based on the Quality Function Deployment (QFD) principle, which easily converts a product’s functional requirements into an ordered joining process list. The joining process data collection was carried out from two approaches: quantitative (joining sheet thickness, joint dimensions, production batch and joining strength) and qualitative (type of material, surface finish and accessibility to perform the joining). Three products were chosen to validate the selector. The results were compared against the literature and commonly commercially employed processes. The application of the selector in commercial products showed compatibility with the literature as well as the commercially used processes. However, depending on the product, other requirements might be considered, such as availability of equipment and production costs.

Optimization of Resistance Spotwelding Parameters Using Taguchi Method

Resistance spot welding (RSW) is a major sheet metal joining process in many industries, such as the automobile, domestic appliances, and space craft fabrication. It is one of the oldest of the electric welding processes in use by industry today. Furthermore, other metal-to-metal connections, such as wire-to-wire joints in the electronics industry, are accomplished by resistance spot welding. Application-specific measures, such as the diameter of the welding spot, define the quality of the joint. The weld is made by a combination of heat, pressure, and time parameters. As the name implies, it uses the resistance of the materials to the flow of electric current that causes a localized heating in the parts to be joined. Understanding of physical mechanisms for easily manipulating and controlling weld qualities in advance is extremely important. This paper represents the optimization of various parameters of resistance spot welding. The experimental studies have been conducted under varying pressure, welding current, pressure, and welding time parameters. In this investigation the quality characteristic (tensile strength and nugget diameter) parameters have been considered using Taguchi Method. The experimental studies have been carried out by varying welding currents, welding pressure and weld times for joining two sheets. The results of the investigation indicate the welding current to be the most significant parameter controlling the weld tensile strength as well as the nugget diameter. The contribution of welding current, holding time and pressure to tensile strength are 61%, 29%, 4% respectively and the contribution of these parameters to nugget diameter are 81%, 1.7%, 17% respectively. Relationship graphs have been plotted between tensile strength and nugget diameter with parametric variations according to orthogonal array.

Mechanical Properties and Microstructure of Resistance Spot Welded Joints of AISI 409M Ferritic Stainless Steel

Resistance spot welding is widely used as a sheet metal joining process, especially in automotive and rail coach manufacturing industries. Ferritic stainless steel (FSS) is used for structural applications in these areas, owing to its superior corrosion resistance compared to conventional carbon steels. In this paper, mechanical properties and microstructure of resistance spot welded FSS joints to grade AISI 409M was investigated. Tensile shear test and micro hardness test were carried out to assess the mechanical properties and failure characteristics of weld joints. Microstructure was evaluated with optical microscopy. The effect of welding current on nugget growth, peak load, fusion zone (FZ) hardness, failure energy and failure mode were analyzed at various current ratings, keeping electrode force, weld cycle time and electrode tip diameter as constants. The results showed that, with the increment in welding current, tensile shear strength increased. Nugget diameter was found to be increasing with increase in current, in expulsion free welds. At low currents, failure mode was found to be interfacial and the pull out mode of failure occurred, at relatively higher current values. Average FZ hardness was found to be more than that of base metal (BM) but less than that of maximum hardness at heat affected zone. Grain enlargement was noticed at high temperature heat affected zone. FZ microstructure consists of predominantly columnar ferrite. Failure occurred at the BM region in all the samples welded above 10 KA current.

Control-Oriented Modeling and Simulation of a Low Carbon Steel A.C. Resistance Spot Welding Process

Resistance spot welding (RSW) has been extensively used as a sheet metal joining process, and the welding process identification is the essential issue for the design of high performance control strategy and set-up of a new welding schedule. However the RSW is a nonlinear time-varying uncertain process which couples the thermal, electrical, mechanical and metallurgical dynamics. To understand this complicated physical phenomenon an M-series pseudo-random electrical pattern is adopted to excite the RSW electrical-thermal dynamics and the thermal response is recorded according to the welding power outputs. Based on the experimental information the transfer function of an RSW electrical-thermal mechanism is identified, and the optimum model order and parameters are determined. Subsequently a control-oriented RSW model is established to explore the welding power control algorithm. The simulated results from the control model show their agreement with the experimental data, which validates its feasibility for corresponding welding control.

Effect of Localized Metal Matrix Composite Formation on Spot Friction Welding Joint Strength

In this study, metal particles were added during the spot friction welding (SFW) process, a solid state sheet metal joining process, to create a localized metal matrix composite (MMC) for the improvement of lap shear strength in AISI 6111-T4 aluminum alloy sheets. The Ancorsteel® 1000 particles were compressed between the upper and lower sheets and distributed concentrically around the tool axis perpendicular to the plate surface, which formed a localized MMC and were effective as the reinforcement particles in aluminum 6111-T4 alloy sheets. Results revealed that the MMC reinforcement improved the lap shear strength of SFW joints by about 25%. An aluminum-ferrous solid solution was formed around the steel particles along the aluminum matrix interface. The load-deflection curve shows that the steel particle MMC increased both the strength and ductility of SFW joint. This is attributed to two phenomena observed on the failed lap shear tensile specimens with SFW MMC. One is the longer and more torturous crack path, and the other is the secondary crack on steel particle MMC reinforced SFW joints.

The analysis of lock forming mechanism in the clinching joint

In this study, the effect of the process parameters of the clinching process on the joinability of advanced high-strength steel was investigated using finite element analysis (FEA). The effect of die geometrical parameters on the achieved joint lock size and maximum forming force has been determined. It has been determined that the die groove width is the most important parameter affecting the material flow effect and energy consumption of the joining process. From the result, the die radius, die depth, and die groove shape were mainly affected by the joinability of advanced high-strength steel H320LA. The results of experiments and numerical tests enable determining the effective process parameters of H320LA sheet metal joining process.

A Study on Fatigue Strength Improvement of Aluminum Alloy Resistant Spot Welds by Cold Working

Resistance spot welds (RSW) have been widely used in the sheet metal joining process due to high productivity, low cost and convenience. The application of aluminum alloys in automobile manufacturing has resulted in the reduction of weight in vehicle, fuel economy and improvement of drivability and driving performance. Therefore, the resistance spot weld (RSW) process has attracted attention to fabrication of aluminum structures. However, applications of Al RSW are limited due to the unreliable durability of the weld-bonded joints. This study presents an experimental investigation on the use of a post-weld cold working process to improve the fatigue strength of Al RSW. The post-weld cold working process includes a pair of uniquely shaped indenters that are pressed or driven into the structure in order to induce the compressive residual stresses around the RSW. The mechanical properties of the post-weld cold worked Al RSW were investigated, including the experimental results of fatigue. The effect of the post-weld cold working process parameters on the fatigue strength of the Al RSW was also investigated. Comparisons of the mechanical properties and qualitative results between the as-welded RSW specimens and the post-weld cold worked RSW specimens of each post-cold working parameter have been carried out. Also, discussions on the experimental results using the finite element method (FEM) for the post-weld cold working parameters are performed.