Showing papers on "Welding published in 2016"
TL;DR: In this article, the authors developed a melt scan strategy for electron beam melting of nickel-base superalloy (Inconel 718) and also analyzed 3-D heat transfer conditions using a parallel numerical solidification code (Truchas) developed at Los Alamos National Laboratory.
367 citations
TL;DR: In this paper, approximated examples of the use of the electron beam are given by the welding, rapid prototyping, texturing surface, cladding with wire and powder as well as alloying.
257 citations
TL;DR: In this paper, the current state of understanding and development of RFW and LFW is presented, focusing on the process parameters, joint microstructure, residual stresses, mechanical properties and their relationships.
Abstract: Friction welding (FW) is a high quality, nominally solid-state joining process, which produces welds of high structural integrity. Rotary friction welding (RFW) is the most commonly used form of FW, while linear friction welding (LFW) is a relatively new method being used mainly for the production of integrally bladed disc (blisk) assemblies in the aircraft engine industry. Numerous similar and dissimilar joints of structural metallic materials have been welded with RFW and LFW. In this review, the current state of understanding and development of RFW and LFW is presented. Particular emphasis is placed on the process parameters, joint microstructure, residual stresses, mechanical properties and their relationships. Finally, opportunities for further research and development of the RFW and LFW processes are identified.
220 citations
TL;DR: In this paper, the temperature profiles of the printed layer (road) and sublayers of a model polymer during 3D printing were obtained from the infrared (IR) imaging, in conjunction with necessary reflection corrections and calibration procedures.
Abstract: In common thermoplastic additive manufacturing (AM) processes, a solid polymer filament is melted, extruded though a rastering nozzle, welded onto neighboring layers and solidified. The temperature of the polymer at each of these stages is the key parameter governing these non-equilibrium processes, but due to its strong spatial and temporal variations, it is difficult to measure accurately. Here we utilize infrared (IR) imaging – in conjunction with necessary reflection corrections and calibration procedures – to measure these temperature profiles of a model polymer during 3D printing. From the temperature profiles of the printed layer (road) and sublayers, the temporal profile of the crucially important weld temperatures can be obtained. Under typical printing conditions, the weld temperature decreases at a rate of approximately 100 °C/s and remains above the glass transition temperature for approximately 1 s. These measurement methods are a first step in the development of strategies to control and model the printing processes and in the ability to develop models that correlate critical part strength with material and processing parameters.
210 citations
TL;DR: Copper and aluminum materials are extensively used in different industries because of its great conductivities and corrosion resistant nature as discussed by the authors. And it is important to join dissimilar materials such as c....
Abstract: Copper and aluminum materials are extensively used in different industries because of its great conductivities and corrosion resistant nature. It is important to join dissimilar materials such as c...
206 citations
TL;DR: In this article, a theoretical approach for the formation of these process deviations and arising material defects is presented, and the impact of these deviations on building surface and part quality is investigated by 3D confocal microscopy, microsections and ultrasonic testing.
Abstract: Selective laser melting is a promising additive manufacturing technology for the production of complex metal components. The technique uses metallic powder as a starting material and a laser for melting and building-up parts layer by layer. One crucial factor influencing the process stability and therefore the part quality is the shielding gas flow. In addition to the shielding properties of the inert atmosphere the gas flow is responsible for the removal of process by-products like spatter and welding fumes originating from the process zone. Insufficient removal or inhomogeneous gas flow distribution may lead to increased interaction between laser and process by-products. Consequences are attenuation of the laser spot as well as redeposition of this by-products on surfaces which are exposed to the laser afterwards. Firstly, a conclusion on all known process by-products is drawn. Secondly, based on these considerations the uniformity of the gas flow is investigated by the width of single welds. Furthermore process deviations are provoked by unfavorable gas flow conditions. Thirdly, the impact of this deviations on building surface and part quality is investigated by 3D confocal microscopy, microsections and ultrasonic testing. Finally, theoretical approach for the formation of these process deviations and arising material defects is presented.
201 citations
TL;DR: In this article, three beam oscillating patterns that are transversal, longitudinal and circular were studied to join 4mm-thick AA6061-T6 aluminum alloy in butt configuration.
188 citations
TL;DR: In this article, the microstructure evolution of the Al/Ti interface at 825 K and various annealing time was examined, and the growth kinetics showed four stages: incubation period (up to 1.5h), the growth govern by the chemical reaction (1.5-5 h), mixed mechanism of chemical reaction and volume diffusion and finally the volume diffusion growth (36-100 h).
146 citations
TL;DR: In this paper, the bond behavior between the steel tube and the concrete in concrete-filled steel tubes (CFST) is investigated, and a series of push-out tests on circular and square CFST specimens were conducted, and the main parameters considered in the test program were: (a) cross-sectional dimension (120-600mm); (b) steel type (carbon and stainless steels); (c) concrete type (normal, recycled aggregate and expansive concretes); (d) concrete age (31-1176 days); and (e) interface type (
144 citations
TL;DR: This study focuses on developing a fully automated system using robotic gas metal arc welding to additively manufacture metal components and demonstrates that the developed system is a significant contribution towards the ultimate goal of producing a practical and highly automated arc-welding-based additive manufacturing system for industrial application.
Abstract: Arc welding has been widely explored for additive manufacturing of large metal components over the last three decades due to its lower capital cost, an unlimited build envelope, and higher deposition rates. Although significant improvements have been made, an arc welding process has yet to be incorporated in a commercially available additive manufacturing system. The next step in exploiting "true" arc-welding-based additive manufacturing is to develop the automation software required to produce CAD-to-part capability. This study focuses on developing a fully automated system using robotic gas metal arc welding to additively manufacture metal components. The system contains several modules, including bead modelling, slicing, deposition path planning, weld setting, and post-process machining. Among these modules, bead modelling provides the essential database for process control, and an innovative path planning strategy fulfils the requirements of the automated system. A user friendly interface has been developed for non-experts to operate the developed system. Finally, a thin-walled aluminium structure has been fabricated automatically using only a CAD model as the informational input to the system. This exercise demonstrates that the developed system is a significant contribution towards the ultimate goal of producing a practical and highly automated arc-welding-based additive manufacturing system for industrial application. An automated arc-welding-based additive manufacturing system was reported.Integrated additive and subtractive manufacturing methodology was developed.Deposition paths and welding parameters were automatically generated.User interface using only CAD models as inputs was developed.The proposed automated system was verified experimentally.
144 citations
TL;DR: The proposed intelligent laser-welding architecture combines representation, prediction, and control learning: three of the main hallmarks of an intelligent system and promises to address several key requirements of modern industry.
TL;DR: In this article, a defect free dissimilar copper-aluminum friction stir welding was achieved by tilt angles 2°, 3°, and 4° with an interval of 1°, while other parameters such as rotational speed, welding speed, tool pin offset, and workpiece material position were kept constant.
Abstract: In the present investigation, dissimilar materials such as electrolytic tough pitch copper, and aluminum 6061-T651 were welded by friction stir welding technology. Effects of tool tilt angle on the mechanical and metallurgical properties were studied experimentally for dissimilar material systems. In the present study, the tool tilt angle was varied from 0° to 4° with an interval of 1°, while the other parameters such as rotational speed, welding speed, tool pin offset, and workpiece material position were kept constant. Macrostructure analysis, tensile test, macro hardness measurement, scanning electron microscopy, and energy dispersive x-ray spectrographic tests were performed to evaluate the weld properties of dissimilar copper–aluminum joints. The results revealed that a defect free dissimilar copper–aluminum friction stir welding was achieved by tilt angles 2°, 3°, and 4°. The maximum tensile strength was reported to be 117 MPa and the macro hardness was reported to be 181 VH (in the nugget zone) at ...
TL;DR: It is demonstrated that only epoxy vitrimer samples show substantial bond strength and the ability to be repeatedly welded thanks to the exchange reactions, which open the way towards joining composite parts without adhesives nor mechanical fasteners.
Abstract: Vitrimers appear as a new class of polymers that exhibit mechanical strength and are insoluble even at high temperatures, like thermosets, and yet, like thermoplastics, they are heat processable, recyclable and weldable. The question arises whether this welding property is maintained in composite materials made of more than 50 vol% of reinforcing fibers. In this paper, we quantitatively analyze the bond strength of epoxy vitrimer-based composite plates made by resin transfer molding and compare them to their non-vitrimer counterparts made of a standard thermoset epoxy. It is demonstrated that only epoxy vitrimer samples show substantial bond strength and the ability to be repeatedly welded thanks to the exchange reactions, which promote improved surface conformity and chemical bonding between the adherands at the joint interface. This opens the way towards joining composite parts without adhesives nor mechanical fasteners.
TL;DR: The effects of heat input from the welding process and post-weld-heat-treatment (PWHT) are shown to give uniform NAB alloys with superior mechanical properties revealing potential marine applications of the WAAM technique in NAB production.
Abstract: Cast nickel aluminum bronze (NAB) alloy is widely used for large engineering components in marine applications due to its excellent mechanical properties and corrosion resistance. Casting porosity, as well as coarse microstructure, however, are accompanied by a decrease in mechanical properties of cast NAB components. Although heat treatment, friction stir processing, and fusion welding were implemented to eliminate porosity, improve mechanical properties, and refine the microstructure of as-cast metal, their applications are limited to either surface modification or component repair. Instead of traditional casting techniques, this study focuses on developing NAB components using recently expanded wire arc additive manufacturing (WAAM). Consumable welding wire is melted and deposited layer-by-layer on substrates producing near-net shaped NAB components. Additively-manufactured NAB components without post-processing are fully dense, and exhibit fine microstructure, as well as comparable mechanical properties, to as-cast NAB alloy. The effects of heat input from the welding process and post-weld-heat-treatment (PWHT) are shown to give uniform NAB alloys with superior mechanical properties revealing potential marine applications of the WAAM technique in NAB production.
TL;DR: In this paper, two mechanisms for macrosegregation were proposed based on the liquidus temperature of the bulk weld metal, T LW, relative to metal 1, T L 1, and metal 2, T L 2, to verify the mechanisms, a pure Cu sheet was butt welded to a low carbon steel sheet without a filler metal.
TL;DR: In this paper, a dissimilar friction stir welding between aluminium and copper was investigated and the experimental results indicate that high quality joints can be obtained by placing the Cu plate on the advancing side of the tool rotation.
TL;DR: In this paper, the authors describe the application of modeling approaches used in Computational Welding Mechanics (CWM) applicable for simulating additive manufacturing (AM), focusing on the approximation of the behavior in the process zone and the behavior of the solid material.
Abstract: The paper describes the application of modeling approaches used in Computational Welding Mechanics (CWM) applicable for simulating Additive Manufacturing (AM). It focuses on the approximation of the behavior in the process zone and the behavior of the solid material, particularly in the context of changing microstructure. Two examples are shown, one for the precipitation hardening Alloy 718 and one for Ti-6Al-4V. The latter alloy is subject to phase changes due to the thermal cycling.
TL;DR: In this paper, the quality of dissimilar weld joints between copper and stainless steel (SS) plates using electron beam welding with and without beam oscillation was evaluated through microstructural analysis, hardness, tensile, bend and impact tests.
TL;DR: Different forms of laser beam welding including single beam laser welding, dual-beam laser welding and laser arc hybrid fusion-brazing welding are reviewed in this paper, where the main problems are how to control the thickness of the intermetallic compound layer and reduce or avoid the generation of pores, cracks, and thermal stresses which severely limit the mechanical properties of welded joints.
Abstract: Joining aluminum to steel can lighten the weight of components in the automobile and other industries, which can reduce fuel consumption and harmful gas emissions to protect the environment. However, the differences of thermal, physical, and chemical properties between aluminum and steel bring a series of problems in laser welding. The main problems are how to control the thickness of the intermetallic compound layer and reduce or avoid the generation of pores, cracks, and thermal stresses which severely limit the mechanical properties of welded joints. Laser fusion-brazing technology utilizes the precise control of heat input with or without filler to partially melt the low melting temperature aluminum base material and promote wetting on the high melting temperature steel base material in order to achieve sound metallurgical by combining the advantages of fusion welding and brazing. Different forms of laser beam welding including single beam laser welding, dual-beam laser welding, and laser arc hybrid fusion-brazing welding are reviewed.
TL;DR: In this paper, a double global optimum genetic algorithm and particle swarm optimization (GA-PSO) based approach is proposed to solve the welding robot path planning problem, where the shortest collision-free paths are used as the criteria to optimize the welding path.
Abstract: Spot-welding robots have a wide range of applications in manufacturing industries. There are usually many weld joints in a welding task, and a reasonable welding path to traverse these weld joints has a significant impact on welding efficiency. Traditional manual path planning techniques can handle a few weld joints effectively, but when the number of weld joints is large, it is difficult to obtain the optimal path. The traditional manual path planning method is also time consuming and inefficient, and cannot guarantee optimality. Double global optimum genetic algorithm–particle swarm optimization (GA-PSO) based on the GA and PSO algorithms is proposed to solve the welding robot path planning problem, where the shortest collision-free paths are used as the criteria to optimize the welding path. Besides algorithm effectiveness analysis and verification, the simulation results indicate that the algorithm has strong searching ability and practicality, and is suitable for welding robot path planning.
TL;DR: In this article, the major part of equations and assumptions needed to simulate laser welding are discussed and their effects on simulation results are illustrated for each simulation type, and sufficient knowledge and tools to allow a simulation of laser welding is presented.
Abstract: The work presented in this paper deals with the laser welding simulation. Due to the rise of laser processing in industry, its simulation takes also more and more place. Nevertheless, the physical phenomena occurring are quite complex and, above all, very coupled. Thus, a state of art is necessary to summarize phenomena that have to be considered. Indeed, the electro-magnetic wave interacts with the material surface, heating the piece until the fusion and the vaporization. The vaporization induces a recoil pressure and deforms the liquid/vapor interface creating a vapor capillary. The heat diffused in the material produces thermal dilatation leading to mechanical stress and strain. As a complete simulation is too large to be computed with one model, the literature is composed by two kinds of models, the thermo-mechanical simulations and the multi-physical simulations. The first aims to find the mechanical stress and strain due to the welding. The model is usually simplified in order to reduce the simulation size. The second, compute the more accurately the thermal and the velocity fields. In that case authors usually search also the size of the weld bead and want to be totally self consistent. In this review, the major part of equations and assumptions needed to simulate laser welding are shown. Their effects on simulation results are illustrated for each simulation type. The paper aims to give sufficient knowledge and tools to allow a simulation of laser welding.
TL;DR: In this paper, microstructural and chemical analyses of clad plates obtained by the explosive method are presented, which are made of titanium grade 1 explosively bonded with a thin layer of st52-3N low alloy steel.
TL;DR: In this paper, the effect of tool traverse speed, offset and rotation direction during dissimilar butt friction stir welding of Al 5083-H321 and 316L stainless steel plates was studied at constant rotational speed of 280.
TL;DR: A proof of principle study is presented on the utilization of thermophoretic Janus particles and capsules employed as dyes for infrared laser‐assisted tissue welding that proves to be efficient in sealing the wound on the mouse in vivo.
Abstract: Current wound sealing systems such as nanoparticle-based gluing of tissues allow almost immediate wound sealing. The assistance of a laser beam allows the wound sealing with higher controllability due to the collagen fiber melting which is defined by loss of tertiary protein structure and restoration upon cooling. Usually one employs dyes to paint onto the wound, if water absorption bands are absent. In case of strong bleeding or internal wounds such applications are not feasible due to low welding depth in case of water absorption bands, dyes washing off, or the dyes becoming diluted within the wound. One possible solution of these drawbacks is to use autonomously movable particles composing of biocompatible gold and magnetite nanoparticles and biocompatible polyelectrolyte complexes. In this paper a proof of principle study is presented on the utilization of thermophoretic Janus particles and capsules employed as dyes for infrared laser-assisted tissue welding. This approach proves to be efficient in sealing the wound on the mouse in vivo. The temperature measurement of single particle level proves successful photothermal heating, while the mechanical characterizations of welded liver, skin, and meat confirm mechanical restoration of the welded biological samples.
TL;DR: In this paper, the maximum |dT/d(fS)1/2| (T is temperature and fS fraction solid) was calculated, whose validity as the crack susceptibility index was verified.
Abstract: Joining of commercially pure Ti to 304 stainless steel by fusion welding processes possesses problems due to the formation of brittle intermetallic compounds in the weld metal, which degrade the mechanical properties of the joints. Solid-state welding processes are contemplated to overcome these problems. However, intermetallic compounds are likely to form even in Ti-SS joints produced with solid-state welding processes such as friction welding process. Therefore, interlayers are employed to prevent the direct contact between two base metals and thereby mainly to suppress the formation of brittle Ti-Fe intermetallic compounds. In the present study, friction-welded joints between commercially pure titanium and 304 stainless steel were obtained using a thin nickel interlayer. Then, the joints were characterized by optical microscopy, scanning electron microscopy, energy dispersive spectrometry, and X-ray diffractometry. The mechanical properties of the joints were evaluated by microhardness survey and tensile tests. Although the results showed that the tensile strength of the joints is even lower than titanium base metal, it is higher than that of the joints which were produced without nickel interlayer. The highest hardness value was observed at the interface between titanium and nickel interlayers indicating the formation of Ni-Ti intermetallic compounds. Formation these compounds was validated by XRD patterns. Moreover, in tensile tests, fracture of the joints occurred along this interface which is related to its brittle nature.
TL;DR: In this article, an attempt has been made to perform friction welding of dissimilar plastic based materials by controlling the melt flow index (MFI) after reinforcement with metal powders.
Abstract: Friction welding is one of the established processes for joining of similar as well as dissimilar polymer/plastics and metals. In past 20 years numbers of application in different areas using this process have been highlighted, but very limited contributions have been reported on properties of friction welded joints of dissimilar polymer/plastic materials after reinforcement with metal powder. In the present work an attempt has been made to perform friction welding of dissimilar plastic based materials by controlling the melt flow index (MFI) after reinforcement with metal powders. The present studies of friction welding for dissimilar plastic were performed on Lathe by considering three input parameters (namely: rotational speed, feed rate, and time taken to perform welding). Investigations were made to check the influence of process parameters on mechanical and metallurgical properties (like: tensile strength, Shore D hardness and porosity at joint). The process parameters were optimized using Minitab software based on Taguchi L9 orthogonal array and results are supported by photomicrographs.
TL;DR: In this paper, a 40-layered Ti-Al composites were fabricated in a single-shot explosive welding process and the structure of the composites was thoroughly investigated using scanning and transmission electron microscopy.
TL;DR: In this article, sound Al Zn-steel "sandwich" joints were achieved with the tool pin inserted into zinc foil, vast zinc was stirred into aluminum fabricating AlZn mixing layer structure in the upper part of aluminum side and no intermetallic compound interlayer was discovered at the interface.
10 Jan 2016-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the mechanical, microstructural and fracture properties of dissimilar FSW welds obtained by evolving the tool rotation and translation speeds are evaluated and correlated with the FSW parameters to obtain the optimum weld conditions.
Abstract: Friction stir welding (FSW) has been used for joining AZ31B magnesium alloy and Al 6061-T6 aluminum alloy sheets. In this regard, the current work aims to study the mechanical, microstructural and fracture properties of dissimilar FSW welds obtained by evolving the tool rotation and translation speeds. The dissimilar welds microstructure and mechanical properties are evaluated and correlated with the FSW parameters to obtain the optimum weld conditions. The results showed that placing aluminum on the advancing side of the weld resulted in better quality welds. The evaluation of the microhardness along the joint section showed values evolving between the microhardness values of the base metals (Al and Mg). A discontinuity in the microhardness values, attributed to the intermetallic compounds (IMC) present, was observed at the weld interface between Mg and Al sheets. The room temperature tensile testing of the weld showed weld joint efficiency between 18% and 55% and at higher temperatures (200 °C) joint efficiency was observed to be between 58% and 78%. The specimen showed brittle behavior under tensile testing, and the specimen fracture occurred along the weld joint. The specimen fracture seems to have initiated in the brittle Mg2Al3 and Mg17Al12 IMCs formed between the welded sheets.