Showing papers in "Welding in The World in 2021"
TL;DR: In this article, a new hybrid artificial intelligence approach is proposed to model the ultrasonic welding of a polymeric material blend, which is composed of an ensemble random vector functional link model (ERVFL) integrated with a gradient-based optimizer (GBO).
Abstract: In this study, a new hybrid artificial intelligence approach is proposed to model the ultrasonic welding of a polymeric material blend. The proposed approach is composed of an ensemble random vector functional link model (ERVFL) integrated with a gradient-based optimizer (GBO). First, welding experiments were conducted on acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) blends produced by the injection molding method. The experiments were designed according to the L27 orthogonal array considering three process factors (applied pressure, welding time, and vibration amplitude) and two responses (average temperature and joint strength). Then, the obtained experimental data were used to train the developed model. To verify the accuracy of the model, it was compared with standalone ERVFL in addition to two fine-tuned ERVFL models (ERVFL-SCA and ERVFL-MRFO) in which ERVFL is incorporated with sine cosine algorithm (SCA) or Manta ray foraging optimization (MRFO). The four models were evaluated using five statistical tools. ERVFL-GBO has the highest coefficient of determination and the lowest root mean square error, mean relative error mean absolute error, and coefficient of variance compared with other models which indicate its high accuracy over other tested models.
50 citations
TL;DR: In this article, the influence of Ar and N2 shielding gases was investigated in terms of nitrogen loss and in the microstructure and austenite content of different deposited geometries.
Abstract: This research work is the first step in evaluating the feasibility of producing industrial components by using Laser Metal Deposition with duplex stainless steel Wire (LMDw). The influence of Ar and N2 shielding gases was investigated in terms of nitrogen loss and in the microstructure and austenite content of different deposited geometries. The evolution of the microstructure in the build-up direction of the Ar and N2-shielded blocks was compared in the heat-treated and as-deposited conditions. The susceptibility for oxygen pick-up in the LMDw deposits was also analyzed, and oxygen was found to be in the range of conventional gas-shielded weldments. Nitrogen loss occurred when Ar-shielding was used; however, the use of N2-shielding prevented nitrogen loss. Austenite content was nearly doubled by using N2-shielding instead of Ar-shielding. The heat treatment resulted in an increase of the austenite content and of the homogeneity in the microstructure regardless of the shielding gas used. The similarity in microstructure and the low spread in the phase balance for the as-deposited geometries is a sign of having achieved a stable and consistent LMDw process in order to proceed with the build-up of more complex geometries closer to industrial full-size components.
21 citations
TL;DR: This work proposes a CNN-based weld defect recognition method, which includes an improved pooling strategy and an enhanced feature selection method integrating the ReliefF algorithm with the CNN.
Abstract: Weld defect recognition plays an important role in the manufacturing process of large-scale equipment. Traditional methods generally include several serial steps, such as image preprocessing, region segmentation, feature extraction, and type recognition. The results of each step have significant impact on the accuracy of the final defect identification. The convolutional neural network (CNN) has strong pattern recognition ability, which can overcome the above problem. However, there are two problems: one is that the pooling strategy has poor dynamic adaptability and the other is the insufficient feature selection ability. To overcome these problems, we propose a CNN-based weld defect recognition method, which includes an improved pooling strategy and an enhanced feature selection method. According to the characteristics of the weld defect image, an improved pooling strategy that considers the distribution of the pooling region and feature map is introduced. Additionally, in order to enhance the feature selection ability of the CNN, an enhanced feature selection method integrating the ReliefF algorithm with the CNN is proposed. A case study is presented for demonstrating the proposed techniques. The results show that the proposed method has higher accuracy than the traditional CNN method, and establish that the proposed CNN-based method is successfully applied for weld defect recognition.
21 citations
TL;DR: The weld metal and heat-affected zone in conventional alloys are characterized by non-equilibrium microstructural evolutions that most probably occur in high-entropy alloys and compositionally complex alloys as discussed by the authors.
Abstract: High-entropy alloys (HEAs) and compositionally complex alloys (CCAs) represent new classes of materials containing five or more alloying elements (concentration of each element ranging from 5 to 35 at. %). In the present study, HEAs are defined as single-phase solid solutions; CCAs contain at least two phases. The alloy concept of HEAs/CCAs is fundamentally different from most conventional alloys and promises interesting properties for industrial applications (e.g., to overcome the strength-ductility trade-off). To date, little attention has been paid to the weldability of HEAs/CCAs encompassing effects on the welding metallurgy. It remains open whether welding of HEAs/CCAs may lead to the formation of brittle intermetallics and promote elemental segregation at crystalline defects. The effect on the weld joint properties (strength, corrosion resistance) must be investigated. The weld metal and heat-affected zone in conventional alloys are characterized by non-equilibrium microstructural evolutions that most probably occur in HEAs/CCAs. The corresponding weldability has not yet been studied in detail in the literature, and the existing information is not documented in a comprehensive way. Therefore, this study summarizes the most important results on the welding of HEAs/CCAs and their weld joint properties, classified by HEA/CCA type (focused on CoCrFeMnNi and AlxCoCrCuyFeNi system) and welding process.
20 citations
TL;DR: In this article, the effect of high-frequency axial magnetic field (HFAMF) on the shape of the welding arc and welding formation of tungsten inert gas (TIG) welding is analyzed theoretically and experimentally.
Abstract: The effect of high-frequency axial magnetic field (HFAMF) on the shape of the welding arc and welding formation of tungsten inert gas (TIG) welding is analyzed theoretically and experimentally. The 316L stainless steel plate was welded with HFAMF produced by the excitation coil installed on the welding torch. The influence of the HFAMF on the welding process is studied by changing the magnetic frequency from 0 to 2000 Hz. The experimental results show that when the magnetic field frequency reaches 1500 Hz, the arc rotation radius is decreased to the minimum; the arc shape changes from cone to compressed cylinder; and the arc temperature, the arc pressure, and the depth-width ratio of the weld beam reached the maximum. Otherwise, the effect of applied HFAMF on the stress of arc and weld pool is discussed, and the mechanism of arc contraction is analyzed.
16 citations
TL;DR: In this article, a review of the literature serves to provide an overview of the evolution of the laser and electron beam processes including the fundamental nature of the beam itself and how such a high-energy density beam has been applied for welding.
Abstract: High-energy density beam processes for welding, including laser beam welding and electron beam welding, are essential processes in many industries and provide unique characteristics that are not available with other processes used for welding. More recently, these high-energy density beams have been used to great advantage for additive manufacturing. This review of the literature serves to provide an overview of the evolution of the laser and electron beam processes including the fundamental nature of the beam itself and how such a high-energy density beam has been applied for welding. The unique nature of each process regarding weld bead formation and penetration, and metallurgical considerations are covered in detail. In addition, the evolution of monitoring systems for both characterization and control of these beam processes is reviewed. Over 500 references have been cited in this comprehensive review that will allow the reader to both understand the current state-of-the-art and explore in more detail the fundamental concepts and practical applications of these processes.
16 citations
TL;DR: In this article, low carbon steel sheets are joined together using FSB and FSVB while SiC nanoparticles are also incorporated in the joint and the microstructure and mechanical behavior of the joints developed under different conditions are analyzed.
Abstract: Friction stir vibration brazing (FSVB) by application of mechanical vibration was introduced in this investigation. In the current research, the adjoining samples are vibrated normally to the brazing line while FSB is performed. Low carbon steel sheets are joined together using FSB and FSVB while SiC nanoparticles are also incorporated in the joint. The microstructure and mechanical behavior of the joints developed under different conditions are analyzed. %67wt Sn-%33wt Pb alloy is used as braze metal. The results show that the strength of the friction stir vibration brazed specimens is higher than that of the friction stir brazed specimens. The vibration of adjoining specimens, during FSVB, enhances the eutectic reaction of the melt braze metal between the adjoining specimens and the melt fills the space between adjoining specimens thoroughly. By introducing vibration during the FSB process, both strain rate and temperature which have fundamental effects on the characteristics of the joints, increase. The results indicate that the strength and the hardness of FSVB-ed samples increase and the grain size decreases as vibration frequency increases from 30 to 60 Hz. In addition, the thickness of IMCs in the joint interface decreased to around 0.7 µm as the vibration frequency increased.
14 citations
TL;DR: In this paper, a three-dimensional finite element model of laser transmission welding of dissimilar plastics is presented, which takes into account all major thermal phenomena associated with the welding process, such as heat conduction, convection, and thermal radiation.
Abstract: This paper presents a three-dimensional finite element model (FEM) of laser transmission welding of dissimilar plastics. Welding of polycarbonate to ABS (acrylonitrile butadiene styrene) with a moving volumetric heat source is modeled using ANSYS® Parametric Design Language. In model development, consideration is given to all major thermal phenomena associated with the laser transmission welding process, such as heat conduction, convection, and thermal radiation. The model also incorporates the effects of dilution on temperature cycles. Welding experiments are conducted to validate the numerical model. The model predicted simulation results are in good agreement with the measurements. The results predicted by the model can further be used for the optimization of the process.
14 citations
TL;DR: In this article, an artificial neural network (ANN) is developed to predict the bead width, height, and contact angle, and a combined model is established to improve the ANN model.
Abstract: Cold metal transfer (CMT)–based wire-arc additive manufacturing (WAAM) is increasingly popular for the production of large and complex metallic components due to its high deposition rate, low heat input, and excellent material efficiency. The accurate prediction of the bead geometry is of great importance to enhance the stability of the process and its dimensional accuracy. Besides the wire feed speed (WFS) and travel speed (TS), the interlayer temperature is another key factor in determining the bead geometry because of the heat accumulation in the multilayer deposition. In this paper, considering the varying interlayer temperature, WFS, and TS as inputs, an artificial neural network (ANN) is developed to predict the bead width, height, and contact angle; then, by connecting the ANN model with a bead geometric model, a combined model is established to improve the ANN model. Based on experimental test data, with random combinations of input parameters, the combined model is demonstrated to be able to accurately predict the bead geometry (mean error < 5.1%). The general effect of interlayer temperature on the bead geometry was also investigated by experiment.
13 citations
TL;DR: In this article, the utilization of gas-metal-arc-welding additive manufacturing (GMAWAM) for the repurposing of components was explored, and the results reveal that the new features (i.e., thin walls) built by GMA-WAM possess different microstructure types.
Abstract: In this paper, the utilization of gas-metal-arc-welding additive manufacturing (GMAWAM) for the repurposing of components was explored. Herein, the GMAWAM process was used to build new low-carbon steel features on an existing low-carbon steel component to obtain a new part with new functionalities. To confirm the internal quality of the new part obtained by such a strategy that is adequate for real applications, its material properties were investigated. The obtained results reveal that the new features (i.e., thin walls) built by GMAWAM possess different microstructure types. The upper region of thin-walled features exhibits lamellar structures, whereas the middle region is characterized by granular structures, and mixed equiaxed and lamellar grains appear in the bottom region. Particularly, the new features have an excellent bonding strength with the existing part. The material properties of GMAWAM-repurposed parts also meet industrial requirements, confirming that the GMAWAM-repurposed parts are adequate with real applications.
13 citations
TL;DR: In this paper, a 3D transient mathematic model was developed to simulate the heat transfer, fluid flow, and geometry morphology in GMAW-based wire arc additive manufacturing (WAAM).
Abstract: In this study, we develop a 3D transient mathematic model to simulate the heat transfer, fluid flow, and geometry morphology in GMAW-based wire arc additive manufacturing (WAAM). The processes of droplet formation, growth, and detachment from the end of wire electrode, who travels dynamically along the scanning direction, are coupled with molten pool for the first time by considering their own mechanical conditions and solving the transport equations in the whole solution domain. By the developed model, the simulations of single-pass multi-layer of WAAM of Al-5%Mg are performed. The calculated results indicate that when the droplet falls into the molten pool, the maximum velocity inside the droplet reaches 0.9m/s, resulting in that liquid metal in the middle flows toward the bottom of the molten pool and a depressed region is formed. On the surface of molten pool, the liquid metal dominated by Marangoni force flows from center to periphery, and on the bottom of molten pool, a clockwise circulation is formed. In addition, the interlayer idle time contributes to the formation of deposit with higher height and narrow width. Finally, to validate the model, the deposit profiles are also compared between simulated and experimental results.
TL;DR: In this paper, a two-pass FSW implementation called parallel friction stir welding (P-FSW) is presented, which is classified into two categories: Advanced Parallel F Stir Washing (AP-FSW) and Retreating Parallel FSW (RP-SFW), and the effects of three parameters named the type of process, tool offset in first pass, and tool offloading in the second pass on tensile strength of AA6061-T6 and AA7075 -T6 joint have been investigated experimentally.
Abstract: This paper presents a new two-pass friction stir welding (FSW) implementation called parallel friction stir welding (P-FSW). This process is classified into two categories: Advanced parallel friction stir welding (AP-FSW) and retreating parallel friction stir welding (RP-FSW). The effects of three parameters named the type of process, tool offset in first pass, and tool offset in the second pass on tensile strength of AA6061-T6 and AA7075-T6 joint in FSW have been investigated experimentally. To design experiments, optimization, and analyzing the results, response surface methodology (RSM) has been used. Quantitative and qualitative variables have been considered in five and two levels, respectively. Based on obtained results, it has been observed that tool offset in the second pass, type of process, and tool offset in the first pass have the most effect on tensile strength of welded joint, respectively. In both AP-FSW and RP-FSW processes, the maximum tensile strength occurred at the maximum value of tool offset in the second pass and minimum value of tool offset in the first pass. The maximum joint efficiency of AP-FSW and RP-FSW processes with respect to AA6061-T6 were obtained 83.1% and 95.4%, respectively.
TL;DR: In this paper, the influence of arc energy and filler metal composition on the microstructure of additively welded thin-walled structures of duplex stainless steels was investigated using different commercially available standard and superduplex solid wire electrodes commonly used today.
Abstract: The influence of arc energy and filler metal composition on the microstructure of additively welded thin-walled structures of duplex stainless steels was investigated using different commercially available standard and superduplex solid wire electrodes commonly used today. As welding process, the cold metal transfer (CMT) process was used. The arc energy and cooling rate were varied by adjusting the wire feed and welding speed. Optical emission spectroscopy (OES) and carrier gas melt extraction (CGME) were used to determine the chemical composition of the specimens. The ferrite content was determined both by magnetic induction and by image analysis as a function of the wall height. In addition, the microsections were examined for intermetallic phases and precipitations. Moreover, corrosion tests were carried out according to ASTM G 48, Method A. The results indicate that an increase in arc energy leads to longer t12/8 cooling times. Depending on the filler metal composition, this leads to ferrite contents that are partially outside the values required according to ISO 17781. Furthermore, precipitates of secondary austenite are often found, which is attributed to the multiple reheating by the subsequent layers.
TL;DR: In this paper, a nickel-based alloy 625 and duplex stainless steel (DSS) UNS S32205 (2205) dissimilar pairs were welded with metal inert gas (MIG) welding process.
Abstract: In this study, nickel-based alloy 625 and duplex stainless steel (DSS) UNS S32205 (2205) dissimilar pairs were welded with metal inert gas (MIG) welding process. Weld metal, obtained with the utilization of ERNiCrMo-3 filler wire, was subjected to mechanical, microstructural, and corrosion investigations. V-notch impact tests and micro hardness measurements were realized on dissimilar weld metal. Microstructural changes in weld metal, fusion line, and heat-affected zone were examined using optical, scanning (SEM), and transmission electron microscopes (TEM) with energy-dispersive spectrometry (EDS). Phase precipitations rich of Nb and Mo were detected among dendritic austenite arms in the weld metal. It was observed that ERNiCrMo-3 filler metal had sufficient toughness because of high nickel content. Corrosion tests revealed that weld metal face pass is the least corrosion-resistant zone in weld metal unlike weld root. This is mainly because more intense intermetallics formed in weld metal face compared with the middle of the weld and the root.
TL;DR: In this article, a numerical scrutiny was performed to analyze the effect of driving forces on molten pool in gas metal arc welding, and a volume-of-fluid equation for free surface tracking and additional conservation equations for calculating the distribution of alloy elements were used.
Abstract: A numerical scrutiny was performed to analyze the effect of driving forces on molten pool in gas metal arc welding. In addition to the basic governing equations required for a general heat and mass transfer analysis by computational fluid dynamics, a volume-of-fluid equation for free surface tracking and additional conservation equations for calculating the distribution of alloy elements were used. Driving forces—buoyancy, drag force, arc pressure, electromagnetic force, Marangoni pressure, and droplet impingement—and the arc heat source were mathematically modeled and applied to the simulation. In order to examine the effect of driving forces, a two-dimensional axisymmetric simulation was performed, and the effect of each driving force was analyzed using the velocity components. In the radial velocity component, the effect of droplet impingement and the Marangoni force was large, and in the vertical velocity component, the droplet impingement effect was dominant. A three-dimensional simulation was also performed considering all the driving forces together, and the result was verified by comparison with experimental results. Relatively high alloying element contents were found at the bottom of the fusion zone, which was due to the droplet impingement generating a high vertical velocity.
TL;DR: In this article, the properties of stainless steel 316L (SS316L) sandwich structure built by combining PBF and DED process were investigated, where the external geometry of the SS316L samples built by PBF was extended by using DED technique.
Abstract: Powder bed fusion (PBF) is an additive manufacturing (AM) technique commonly used to manufacture metallic components. External geometry of parts printed by PBF process can be extended by regular processes, namely, laser cladding and spraying powder metal. But these methods have disadvantages such as increased heat-affected zone (HAZ) and extended deficiencies like cracks and pores, whereas samples produced with directed energy deposition (DED) exhibited strong metallurgical bonding and has reduced HAZ due to least dilution. The present work investigates the properties of stainless steel 316L (SS316L) sandwich structure built by combining PBF and DED process. The external geometry of the SS316L samples built by PBF was extended by using DED technique. Metallurgical and mechanical characteristics of DED extended PBF samples were studied. Tensile properties such as percentage elongation and tensile strength were compared for PBF, DED, and SWS (DED extended PBF). It was found that the yield stress for the DED samples, PBF samples, and SWS samples is in the range of 486 MPa, 564 MPa, and 401 MPa. Moreover, the average hardness of the interface portion is found to be 220.5 HV and it is higher than the hardness observed in the PBF and DED regions.
TL;DR: In this article, the static and fatigue strength of single-lap joints incorporating nanoparticles were compared to those without nanoparticles, and the results revealed that average damage load increased significantly in nanoparticle-reinforced adhesive joints.
Abstract: Nano-technological developments, which have made significant progress in recent years, have significant impact on the science of adhesives. Therefore, in our study, the static and fatigue strengths of single-lap joints (SLJs) incorporating nanoparticles were compared to those without nanoparticles. Steel plates were used in the adhesive joints. The results revealed that average damage load increased significantly in nanoparticle-reinforced adhesive joints. The highest damage load was obtained with 4 wt% nano-Al2O3 in epoxy adhesive. As the average damage load increased, the locus of damage changed from interfacial to the mixture of interfacial and cohesive. Also, fatigue strengths of the joints increased when the adhesive joint had nano-Al2O3 and nano-SiO2, and decreased when the adhesive joint had nano-TiO2.
TL;DR: In this article, a comparative evaluation of the mechanical properties and failure behavior of QP980 steel with those of DP980 steel spot welds was performed, and it was found that the cross tension and tensile shear test samples all failed in a partial or full button pull-out mode, with an acceptable ductility ratio and cross tension strength.
Abstract: This study consisted of a comparative evaluation of the mechanical properties and failure behavior of QP980 steel with those of DP980 steel spot welds. Moreover, this paper contributes to the existing knowledge of the resistance spot welding behavior of QP steels by analyzing their microstructure, hardness profile, tensile shear strength, cross tension strength, and failure behavior. It was found that the cross tension and tensile shear test samples all failed in a partial or full button pull-out mode, with an acceptable ductility ratio and cross tension strength as per AWS. Fractography of the testing samples showed that the crack propagated along the fusion boundary, an occurrence previously reported in the literature for QP980, but with no comprehensive explanation regarding the mechanism behind the behavior. This work discusses the similarities between this behavior and welds exhibiting a possible softened region at the fusion boundary, a phenomenon known as the halo ring. The role of this softened region on the failure behavior of the welds is described.
TL;DR: In this article, a matrix phased array (MPA) ultrasonic imaging system was successfully integrated into a robot-assisted automated non-destructive testing (NDT) method for resistance spot weld applications.
Abstract: A commercially available matrix phased array (MPA) ultrasonic imaging system was successfully integrated into a robot-assisted automated non-destructive testing (NDT) method for resistance spot weld applications. The NDT system utilizes a dual-time gate feature, where optimized time gate positions and widths were determined for near-normal incidence inspections of spot welds in thin materials. The effects of probe contact pressure and ultrasonic beam incident angle were also studied using the robot arm. Based on the current robot-assisted automated NDT results, an optimized contact pressure of 0.5 lb, and an incidence angle of ± 0.5o relative to the normal direction were determined. Under these optimum probe contact conditions, it was found that a measurement uncertainty of less than 5% can be achieved when the gate position is set to be between one-half and two-third positions of the total part thickness, along with a gate width equals to one-third of the total stack thickness.
TL;DR: In this paper, the effects of shielding gas and laser reheating were investigated in welding of 1.5mm-thick FDX 27 (UNS S82031) DSS.
Abstract: Avoiding low austenite fractions and nitride formation are major challenges in laser welding of duplex stainless steels (DSS). The present research aims at investigating efficient means of promoting austenite formation during autogenous laser welding of DSS without sacrificing productivity. In this study, effects of shielding gas and laser reheating were investigated in welding of 1.5-mm-thick FDX 27 (UNS S82031) DSS. Four conditions were investigated: Ar-shielded welding, N2-shielded welding, Ar-shielded welding followed by Ar-shielded laser reheating, and N2-shielded welding followed by N2-shielded laser reheating. Optical microscopy, thermodynamic calculations, and Gleeble heat treatment were performed to study the evolution of microstructure and chemical composition. The austenite fraction was 22% for Ar-shielded and 39% for N2-shielded as-welded conditions. Interestingly, laser reheating did not significantly affect the austenite fraction for Ar shielding, while the austenite fraction increased to 57% for N2-shielding. The amount of nitrides was lower in N2-shielded samples compared to in Ar-shielded samples. The same trends were also observed in the heat-affected zone. The nitrogen content of weld metals, evaluated from calculated equilibrium phase diagrams and austenite fractions after Gleeble equilibrating heat treatments at 1100 °C, was 0.16% for N2-shielded and 0.11% for Ar-shielded welds, confirming the importance of nitrogen for promoting the austenite formation during welding and especially reheating. Finally, it is recommended that combining welding with pure nitrogen as shielding gas and a laser reheating pass can significantly improve austenite formation and reduce nitride formation in DSS laser welds.
TL;DR: In this paper, a two-pass friction stir welding (FSW) procedure was applied to limit mixing between the dissimilar materials to keep the corrosion resistance, and the welded specimens were evaluated by light microscopy, SEM equipped with EDS.
Abstract: This study investigates friction stir welding (FSW) in the dissimilar joining process of cladded plates. Samples of 4-mm thick ASTM 572 steel plate cladded with 3-mm thick Inconel®625 represent the base material. In order to limit mixing between the dissimilar materials to keep the corrosion resistance, a two-pass welding procedure was applied. Optimal welding parameters for each pass were identified. The welded specimens were evaluated by light microscopy, SEM equipped with EDS, and mechanical tests such as hardness, bending, and tensile testing. Defect-free joints with excellent surface finish have been obtained with a well-defined interfacial region between both materials. The FSW process changed the microstructure of both metals used in this study to a new refined grain region into the weld with complex microstructure inside the ASTM 572 steel, as well as change from a dendritic to an equiaxial microstructure in the Inconel®625. The breaking and the distribution of the intermetallic and secondary phases of the nickel alloy were promoted by the FSW process, moreover the second welding pass on the Inconel® tempered the steel which had previously been welded in the first FSW weld pass. The mechanical properties within the welding zone increased due to this microstructural rearrangement coupled with the Hall-Petch effect.
TL;DR: In this paper, a wavelet-based signal analysis has been performed to detect the defects in friction stir welding (FSW) process by analyzing the signal acquired during welding, and the results of defect identification have been validated by mapping the processed signal with the actual weld quality.
Abstract: The article attempts to detect the defects in friction stir welding (FSW) process by analyzing the signal acquired during welding. The said welding technique utilizes pressure and heat developed by the usage of a non-consumable tool. Thus, the axial force signal carries a lot of information about the physical process, and hence, it could be used to identify the weld defects. Signal analysis has been performed by using wavelet-based techniques. Before this analysis, a methodology has been followed to select the best mother wavelets suitable for the signal. The results of defect identification have been validated by mapping the processed signal with the actual weld quality.
TL;DR: In this paper, the authors explored the possibility of producing an improved interference-fit tubular joint between pure copper and stainless steel tube by electromagnetic crimping (EMC) and obtained with optimal parameters consisting of the outer surface profile of the inner tube and discharge energy Joints exceeding the strength of the parent tube are formed without any metallic bond formation.
Abstract: This paper explores the possibility of producing an improved interference-fit tubular joint between pure copper and stainless steel tube by electromagnetic crimping (EMC) Successful joints are obtained with optimal parameters consisting of the outer surface profile of the inner tube and discharge energy Joints exceeding the strength of the parent tube are formed without any metallic bond formation Three destructive testings, namely, pull-out, compression and torsion tests, have confirmed the successful joint formation as the failure occurs in the copper base tube Analysis of failure mechanisms has revealed joint behaviour at various discharge energies and surface profiles Among smooth, knurled and threaded surface profiles with different discharge energy levels, knurled surface provides best joint strength at 62 kJ, which has shown a failure in the parent Cu tube during all three destructive testings Radial deformation of the tubes is measured and compared for different discharge energy and surface profile No metallic bond formation and the wavy interface are observed between the joining partners during microstructural analysis Furthermore, no elemental overlapping is observed during energy dispersive spectroscopy mapping analysis indicating an absence of diffusion Higher micro-hardness is observed near the Cu-SS tubular joint interface due to strain hardening caused by high-velocity impact
TL;DR: In this paper, the joining zone between semi-crystalline polyamide 6 and aluminum EN AW 6082 was examined in laser-based joining and the mechanical properties of the joint were examined to the point of cohesive failure.
Abstract: This paper examined the joining zone between semi-crystalline polyamide 6 and aluminum EN AW 6082 in laser-based joining and evaluated the mechanical properties of the joint. The joint tests were carried out in overlap configuration and a characterized in terms of energy per unit length. The mechanical properties were examined to the point of cohesive failure. An increasing energy per unit length resulted in a reduced crosshead displacement in short-term testing and a decreased fatigue strength. Further material testing was carried out locally at various positions within the joining zone. The mechanical properties were correlated with results of a hardness test, thermoplastic morphology, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). By combining the findings with heat-treated samples at elevated temperatures, secondary crystallization was identified and evidenced as a primary effect among the changes in mechanical properties due to the heat treatment of the thermoplastic material.
TL;DR: In this paper, a Ni-based superalloy, Inconel 625, is widely used for aerospace, petrochemical and marine applications due to its excellent corrosion and elevated temperature mechanical properties.
Abstract: A Ni-based superalloy, Inconel 625, is widely used for aerospace, petrochemical and marine applications due to its excellent corrosion and elevated temperature mechanical properties. In this study, efforts were made to identify optimum deposition parameters to produce directionally solidified Inconel 625 components using wire arc additive manufacturing (WAAM). Components were deposited by short-circuiting and short-circuiting with pulse mode of droplet transfers using a commercial cold metal transfer gas metal arc welding (CMT-GMAW) power source. For a given arc energy, metal droplet transfer behaviour was studied using a high-speed camera. Microstructural analysis and corrosion resistance of Inconel 625 samples produced by WAAM and samples made by conventional casting process were compared by advanced characterisation methods. Inconel 625 samples produced using a combination of short-circuiting with pulsing free flight transfers showed improved mechanical properties than as-cast samples and samples made only by short-circuiting transfer due to the formation of directionally solidified coarse-grained columnar microstructure. Moreover, corrosion resistance of WAAM samples was found to better than that of as-cast samples. Based on the results, an optimised current-voltage waveform and droplet transfer modes were identified to produce defect-free Inconel 625 deposits with desired microstructure, and mechanical and corrosion-resistance properties.
TL;DR: In this paper, the authors investigated the influence mechanism of single physical field parameters of electromagnetic-ultrasonic compound field-assisted laser cladding on the cladding layer as well as the parameter optimization of compound field assisted laser claddings.
Abstract: Compound field–assisted laser cladding is an advanced laser processing technology. In this paper, the influence mechanism of single physical field parameters of electromagnetic-ultrasonic compound field–assisted laser cladding on the cladding layer as well as the parameter optimization of compound field–assisted laser cladding are investigated. The Box-Behnken design response surface methodology method is used for experimental design. Through the response surface modeling analysis, it is found that the ultrasonic power has the greatest influence on the microhardness of the cladding layer. For the wear volume of the cladding layer, as the ultrasonic power increases, the wear volume increases and the wear resistance of the cladding layer decreases. Besides, a smaller ultrasonic power and a larger DC current value can obtain a cladding layer with a smaller wear volume. The optimal combination of physical field parameters was obtained through response surface methodology parameter analysis and experimental verification.
TL;DR: In this paper, the authors focused on flange gusset welded joint; lateral connection plates were welded to the base plate from both sides, and the specimens were painted by either fluorine resin paint or epoxy resin paint.
Abstract: According to the periodical inspection manual for civil infrastructures in Japan, the visual inspection plays a very important role to detect deterioration such as fatigue cracking. Since the steel bridges are covered with paint coating, a fatigue crack is often detected as a crack of the paint. Conventionally, when a paint crack is detected, the paint coating is removed and magnetic particle test is applied. However, it is not always true that there is a fatigue crack under the paint crack. This process is time-consuming, especially when no fatigue crack is detected. The objective of this study is to detect fatigue crack without removing the paint coating by nondestructive technique. Among nondestructive techniques, ultrasonic test was applied, because an internal crack can be detected. This study focused on flange gusset welded joint; lateral connection plates were welded to the base plate from both sides. After being welded, the specimens were painted by either fluorine resin paint or epoxy resin paint. Fluorine and epoxy paints are mainly applied for highway road and railway bridge, respectively. Fatigue tests were carried out for the specimens. During the fatigue test, when strain to monitor crack initiation was changed, ultrasonic test by creeping wave was conducted. The creeping wave is a longitudinal wave that travels very close to the test surface. A fatigue crack of 1.1 by 1.6 mm could be detected by the ultrasonic test.
TL;DR: In this article, a real-time X-ray direct observation method and volume of fluid method (VOF) were performed to study the flow in molten pool and liquid flow in the molten pool.
Abstract: In the wire arc additive manufacturing (WAAM) process, the flow behavior of the molten pool determines the formation accuracy and formation defects. Therefore, it is significant to understand the complex physical process of the molten pool behavior in the WAAM. A real-time X-ray direct observation method and volume of fluid method (VOF) were performed to study the flow in molten pool and liquid flow in the molten pool. X-ray was used to observe the liquid flow in the molten pool and the droplet transfer from the WAAM. A three-dimensional model of the molten pool and droplet was established based on the VOF method, and the temperature distribution and flow status of the molten pool were calculated. By controlling different wire feeding speeds, two different droplet transfer modes were observed by X-ray, which include globular transfer and bridging transfer. Compared with globular transfer, bridging transition has little effect on molten pool flow. The flow model during the deposition process is established; the x–z plane is divided into four regions according to the flow characteristics of different positions in the molten pool. The maximum velocity in the molten pool appears in the action area of plasma arc force, which is 0.277 m/s, which leads to the increase in melting depth and promotes the flow of molten metal.
TL;DR: In this article, a novel auxiliary wire feeding gas metal arc-based additive manufacturing (A-GMA-AM) approach is proposed to achieve high deposition rate at low deposition current, and the influence of the feeding speed of auxiliary wire on the bead geometries and the heat-affected zone area was analyzed.
Abstract: Traditional gas metal arc-based additive manufacturing (GMA-AM), also referred to as wire arc additive manufacture (WAAM), improves deposition rate via increasing deposition current, but it is easy to affect the shape-forming and microstructure of the deposited part due to the increased heat input. To avoid such problems, a novel auxiliary wire feeding GMA-AM (A-GMA-AM) approach is proposed to achieve high deposition rate at low deposition current. This paper investigates the effects of A-GMA-AM when the deposition current ranges from 100 to 180 A. The process window was explored, and the influence of the feeding speed of auxiliary wire on the bead geometries and the heat-affected zone area was analyzed. It was observed that the increase in the feeding speed of the auxiliary wire can increase the bead height and remain the bead width unchanged. When the feeding speed of the auxiliary wire reaches the upper limit at the corresponding deposition current, the deposition rate of A-GMA-AM is at least 1.65 times than that of traditional GMA-AM at the same deposition current, and the heat-affected zone area is reduced by at least 28.6%. The results showed that the A-GMA-AM method is more efficient in increasing deposition rate and reducing the heat in AM components.
TL;DR: In this article, the heat-affected zone (HAZ) behavior in an API 5L X70 steel welded by the gas metal arc welding process (GMAW) was investigated.
Abstract: This study aimed to investigate the heat-affected zone (HAZ) behavior in an API 5L X70 steel welded by the gas metal arc welding process (GMAW). In the steel welding processes, this region is very critical due to microstructural and allotropic transformations that affect the mechanical properties. Three samples were welded using a robotic arm with different welding speeds, thus obtaining three different heat inputs, which were 2.0 kJ/mm, 2.5 kJ/mm, and 3.0 kJ/mm. For all heat inputs, the microstructures of the HAZ showed the Widmanstatten ferrite, Acicular ferrite, bainite, and martensite and retained austenite, which influenced the mechanical properties of this region. The electron backscattering diffraction analysis showed that the presence of low-angle grain boundaries (2–15°) increases the fracture toughness. The kernel average misorientation map and the results of the Charpy impact test showed that the heat input of 3.0 kJ/mm lead to characteristics of the HAZ that are remarkably similar to the base metal (BM).