Overlap Joints Research Articles

Prediction of interface width in overlap joint configuration for laser welding of aluminum alloy using sensors

We present a method that can predict the interface width in an overlapping joint configuration for laser welding of Al alloys using sensors and a convolutional neural network (CNN)-based deep-learning model. The inputs for multi-input CNN-based deep-learning prediction models are spectral signals, represented by the light intensity measured by a spectrometer and dynamic images of the molten pool filmed by a charge-coupled device (CCD) camera. The interface width, used as learning data for modeling, was constructed as a database along with the process signal by cross-sectional analysis. In this study, we present results showing high accuracy in predicting the interface width in the overlap joint configuration for Al alloy laser welding. For predicting the interface width, five models are created and compared: a single CCD and spectrometer sensor algorithm, a multi-sensor algorithm with two input variables (CCD, spectrometer), a multi-sensor algorithm excluding the processing beam in the spectrometer data on the combination of Al 6014-T4 (top)/Al 6014-T4 (bottom), and a multi-sensor algorithm applied to the combination of Al 6014-T4 (top)/Al 5052-H32 (bottom). The multi-sensor algorithm with two input variables (CCD and spectrometer) on the same material combination showed the highest accuracy among the models.

Comparison of Dimensional Accuracy of (Pmma) Denture Base Material Relined with Molloplast B Soft Liner by Different Curing Methods.

Background and objectives: The most common problem associated with the complete denture is the loss of retention after period of time therefore relining procedure is important in many cases, this study was done to compare the dimensional accuracy of PMMA before and after the application of Molloplast B Soft liner to the denture base material by different curing methods. Methods: A total of 80 PMMA samples were used in this study, 40 (SR Triplex hot) PMMA samples polymerized in water bath, 40 (Acron MC) PMMA samples polymerized in microwave, Molloplast B soft liner (Detax, Germany) were packed between each two PMMA strip as overlap joint and cured by water bath and microwave, the dimensional accuracy of PMMA samples were measured before and after the Molloplast B soft liner application using the (DOF scan app) software device. Results: The results showed that the dimensional accuracy of SR Triplex hot water bath polymerized PMMA samples experienced significant dimensional change after the application of Molloplast B soft liner, while in Acron MC microwave polymerized PMMA samples, non-significant dimensional changes were observed after Molloplast B soft liner application. Conclusion: Microwave polymerized PMMA samples showed better dimensional accuracy than the water bath polymerized PMMA samples after the addition of Molloplast B Softliner. Keywords; PMMA, Soft Liner, Microwave, Water Bath.

The investigation of laser beam interaction with aluminum/titanium overlap joint

In-situ analysis of dissimilar laser welding in overlap configuration, which finds the most frequent application in industry, attracts an increasing attention of the research community. In the present work, emission spectroscopy and high-speed imaging were used to investigate the vapor plume behavior during a Yb:YAG laser pulse on the overlap joint between pure titanium and aluminum alloy A5754. A 15 ms long laser pulse was applied to the overlap joints, where titanium and then A5754 were placed on the top. Correlation of the obtained results with post-mortem observation of the impact zones and with a finite-element model of the keyhole evolution was performed. The combination of these approaches facilitated the development of a comprehensive phenomenological timelines of the processes, along with an evaluation of the efficacy of the employed online methods to discern the involvement of the bottom material with the melted zone. The considered configurations showed very different behavior: with reflective A5754 placed on top, the use of high laser power produced an intense keyhole propagation in bottom titanium plate, inducing rapid mix between the elements, while with titanium on top, the use of lower laser power produced prolongated keyhole stagnation at the interface with reflective A5754. High-speed imaging showed very fluctuating behavior of the plume, where the involvement of the bottom material was traduced either by a drastic drop of thermal and atomic emission after the keyhole tip enters the bottom A5754 plate, or by strong periodic bursts of Ti-rich jet after the keyhole reaches the bottom titanium plate. The results of emission spectroscopy were found in adequation with the involvement of bottom material into the melted zone, however, they are affected by plume fluctuations and by the pollution of the top plate by volatile elements.

Sikahyflex-Epoxy Mixed Adhesive’s Effect on the Aluminum-Composite Joint’s Shear Tensile Strength for the Automotive Industry

The automotive industry sector encounters challenges in the construction of connections between different materials. Hence, a breakthrough is needed in the automotive industry in manufacturing connections between different wall panel materials. Mixed adhesive materials for different materials are required and represent an innovation in the manufacturing process for joints of different materials due to the need for stiff and slightly ductile adhesives. This research aims to analyze the effect of using a sikahyflex-epoxy mixture adhesive in aluminum-composite joints on the shear tensile strength of the joints for the automotive industry. This research serves as an innovation in dissimilar material connection systems by developing the use of mixed adhesives and cocofiber aluminum-composite adherend materials with environmentally friendly and corrosion-resistant properties. The research material used aluminum 5083-cocofiber composite. The adherend surface was roughened employing sandpaper of #60, #80, and #150. The adhesive used the addition of sikahyflex adhesive to the epoxy adhesive with additional variations of 10%, 20%, 30%, and 40% sikahyflex. Connections between different materials with the single lap joint type refer to ASTM D1002. The roughness test results yielded the best roughness grade #150 on the surface of the aluminum adherend and coco fiber composite. The shear tensile test results by adding 40% sikahyflex adhesive, 0.4 mm adhesive thickness, and #150 sandpapering resulted in a 20% increase in shear tensile strength in the single lap joint of 2.51 N/mm2. The surface roughness enhanced the adhesive bond strength between mechanical interlocking adhesives and adherend. Meanwhile, the failure modes observed in macro observations included thin-layer cohesive failure, cohesive failure, two-stage failure, and stock-break failure modes. The SEM observation revealed that in the initial propagation of microcracking and voids, which mark the initial onset of adhesive failure, tearing took place, leading to a failure mode in the aluminum-composite coco fiber single overlap joint.

Fatigue strength of single-sided fillet welds in overlapping ultra-high-strength steel sheets

From the manufacturing viewpoint, overlapping thin sheets can provide a substantial geometrical improvement in welded hollow sections compared to butt-welded cross-sectional details. However, the plate eccentricity and non-penetrating fillet welds make the joints susceptible to fatigue failures under transversal cyclic loads. This work experimentally investigates the fatigue strength of overlap joints prepared with gas metal arc welding in the single-sided fillet weld configuration. Fatigue tests were carried out on the lap joints made of S960 ultra-high-strength steel (UHSS) grade under uniaxial constant amplitude axial loading employing both pulsating tension (applied stress ratio of R ≈ 0) and pulsating compression (R ≈ -∞). In addition, the lap joints were prepared with both straight welds (the welds transverse to the loading direction) and inclined welds (the welds with a 30° inclement angle from the transversal direction) to investigate the shear stress effects on the joints’ fatigue performance. Plasma butt-welded samples were tested as a reference join type. For the plasma butt-welded joints, the recommended detail category of FAT71 in the nominal stress system for weld root failures in single-sided butt welds was observed clearly conservative—a mean fatigue strength of Δσc,50% = 130 MPa with a fixed slope parameter of m = 3 was obtained. Compared to the butt-welded joints, a significant decrease in fatigue strength capacity was found in the lap joint specimens with misalignment factors of km > 3.0. The failure locations were also different in joints subjected to the tension and compression loads. The shear load did not majorly contribute to the changes in the fatigue strength capacity compared to the joints subjected to the transversal normal stress.

Investigation of Tool Degradation during Friction Stir Welding of Hybrid Aluminum-Steel Sheets in a Combined Butt and Overlap Joint.

Friction stir welding, as a solid-state welding technique, is especially suitable for effectively joining high-strength aluminum alloys, as well as for multi-material welds. This research investigates the friction stir welding of thin aluminum and steel sheets, an essential process in the production of hybrid tailor-welded blanks employed in deep drawing applications. Despite its proven advantages, the welding process exhibits variable outcomes concerning formability and joint strength when utilizing an H13 welding tool. To better understand these inconsistencies, multiple welds were performed in this study, joining 1 mm thick steel to 2 mm thick aluminum sheets, with a cumulative length of 7.65 m. The accumulation of material on the welding tool was documented through 3D scanning and weighing. The integrity of the resulting weld seam was analyzed through metallographic sections and X-ray imaging. It was found that the adhering material built up continuously around the tool pin over several welds totaling between 1.5 m and 2.5 m before ultimately detaching. This accretion of material notably affected the welding process, resulting in increased intermixing of steel particles within the aluminum matrix. This research provides detailed insights into the dynamics of friction stir welding in multi-material welds, particularly in the context of tool material interaction and its impact on weld quality.

A method for manufacturing a mechanically strong and durable hybrid structure of polyethylene–hydroxyapatite composite and titanium alloy

AbstractThe integration of polymer, metal, and ceramic materials in hybrid structures represents a potential but underexplored alternative for biomedical applications. Here, we present a methodology for manufacturing a mechanically strong and durable hybrid overlap structure from a composite of green high‐density polyethylene (HDPE) and hydroxyapatite (HA) compatibilized with HDPE‐g‐MAH joined to a substrate of Ti6Al4V alloy. This process involves laser structuring of micro‐scale grooves on the metal surface, followed by injection overmolding of the polymer composite. A hybrid overlap joint with strong interfacial anchoring was achieved, resulting in outstanding joining strength and fatigue life. This achievement holds significant promise for future biomedical applications.Highlights Joining of composite of HDPE–HA with Ti6Al4V alloy via injection overmolding Laser texturing was effective in improving mechanical interlocking A hybrid joint with high shear strength and fatigue life was developed The hybrid joint is promising for biomedical applications

Prediction of lap shear strength of GNP and TiO2/epoxy nanocomposite adhesives

Abstract In this study, graphene nanoplatelets (GNPs) and titanium dioxide nanofillers were added to epoxy resin P-5005 at five different weight percentages (wt%), viz., 1, 5, 10, 15, and 20 wt%. The tensile properties of the nanocomposites were experimentally tested following ASTM D638-14. Then, the above-mentioned nanocomposites were applied as adhesives for an overlap joint of two A5055 aluminum sheets. The apparent shear strength behavior of joints was tested following ASTM D1002-01. Moreover, experimentally obtained results were applied to train and test machine learning and deep learning models, i.e., adaptive neuro-fuzzy inference system, support vector machine, multiple linear regression, and artificial neural network (ANN). The peak tensile strength (TS) and joint failure load (FL) values were observed in epoxy/GNP samples. The ANN model exhibited the least error in predicting the TS and FL of the considered nanocomposites. The epoxy/GNP nanocomposites exhibited the highest TS of 28.49 MPa at 1 wt%, and the peak overlap joints exhibited an FL of 3.69 kN at 15 wt%.

Effect of Heat Input on Microstructure and Properties of Laser-Welded 316L/In601 Dissimilar Overlap Joints in High-Temperature Thermocouple.

Heat input, a crucial factor in the optimization of high-temperature thermocouple laser welding, has a significant impact on the appearance and mechanical properties of dissimilar welded joints involving stainless-steel- and nickel-based alloys. This study focuses on laser overlay welding of austenitic stainless steels and nickel-based alloys. The findings indicate that an increase in heat input has a more pronounced effect on the penetration depth and dilution rate. Under high heat input, the weld has cracks, spatter, and other defects. Additionally, considerable amounts of chromium (Cr) and nickel (Ni) elements are observed outside the grain near the crack, and their presence increases with higher heat input levels. Phase analysis reveals the presence of numerous Cr2Fe14C and Fe3Ni2 phases within the weld. The heat input increases to the range of 30-35 J/mm, and the weld changes from shear fracture to tensile fracture. In the center of the molten pool, the Vickers hardness is greater than that of the base metal, while in the fusion zone, the Vickers hardness is lower than that of the base metal. The overall hardness is in a downward trend with the increase of heat input, and the minimum hardness is only 159 HV0.3 at 40 J/mm. The heat input falls within the range of 28-30 J/mm, and the temperature shock resistance is at its peak.

Flexural behavior of wet panel-to-panel groove-and-tongue joints provided with lapped U-bars

A comprehensive experimental campaign was carried out to investigate the flexural behavior of wet joints provided with lapped U-bars connecting two precast concrete panels. Eleven assemblies were tested in 4-point bending. Nine assemblies had wet groove-and-tongue joints provided with U-bars, and different values for the overlap length, joint width, and concrete strength. As a reference, the remaining two assemblies had wet groove-and-tongue or flat joints reinforced with straight-through bars. All the assemblies but two were provided with water-stop strips. The test results show that a lap length of 15 times the bar diameter is sufficient to guarantee the same bending capacity as straight-through bars. Based on the deformations of the panels subjected to bending, a strut-and-tie model was developed to predict the flexural capacity of linear wet joints provided with lapped U-bars. The proposed model effectively predicts the flexural capacity of the assembly of two panels since the theoretical predictions and the test results differ by less than 10%.

Influence of tool pin profile on the mechanical strength and surface roughness of AA6061-T6 overlap joint friction stir welding

This study presents the tensile strength and surface roughness resulting from friction stir welding (FSW) on the lap joint method using AA 6061 –T6. FSW is conducted by comparing three different tool pin shapes: hexagon, thread, and square. Overlap welding using the FSW method is challenging if machine parameters, such as spindle speed and feed rate, are incompatible. The experiment was conducted using a conventional milling machine with a spindle speed of 1400 -1750 rpm and a feed rate of 20 – 30 mm/min. The results show that a spindle speed of 1750 rpm and a feed rate of 30 mm/min using a square tool pin results in 83.5088 MPa ultimate tensile strength and 0.85 µm surface roughness (Ra), which is much better than hexagon and thread type tool pins. In addition, the overall results on all three tool pin shapes show that higher processing parameters increase tensile strength and surface roughness. This study revealed the effect of parameters on AA6061 –T6 and the resulting implications of mechanical strength and surface roughness.

Effect of overlap joint position on strength of composite interlaminar reinforcement for fused filament fabrication 3D printer

Fused filament fabrication (FFF) 3D printers have the advantages of being able to build complex structures automatically and at low cost. On the other hand, the tensile strength in the thickness direction is lower than that in the horizontal direction for objects fabricated by using fused filament fabrication 3D printers. In this study, we conducted mechanical evaluations by using an automatic strengthening method in which carbon-fiber-reinforced plastic (CFRPs) were embedded in the vertical direction in the form of joints, through 3D finite element method (FEM) simulations and experiments. We performed 3D FEM simulations on an analytical model with epoxy resin and two CFRP joints embedded inside polylactic acid, and confirmed that fracture occurred at the ends of the CFRP. The simulations showed that longer joint lengths and shorter distances between CFRPs increased the strength. Tensile testing of the specimens with CFRP embedded in the form of two CFRP joints showed that the maximum CFRP spacing affected the strength. This is consistent with the analysis results, which showed that the strength decreased with increasing CFRP spacing.

Topological Optimization of Interconnection of Multilayer Composite Structures

This study focuses on the topological optimization of adhesive overlap joints for structures subjected to longitudinal mechanical loads. The aim is to reduce peak stresses at the joint interface of the elements. Peak stresses in such joints can lead to failure of both the joint and the structure itself. A new approach based on Rational Approximation of Material Properties (RAMP) and the Finite Element Method (FEM) has been proposed to minimize peak stresses in multi-layer composite joints. Using this approach, the Mises peak stresses of the optimal structural joint have been significantly reduced by up to 50% under mechanical loading in the longitudinal direction. The paper includes numerical examples of different types of structural element connections.

Interfacial microstructure and mechanical properties of AZ31B/AA7075 joints using non-equilibrium thermal compensation resistance welding

In this study, a novel non-equilibrium thermal compensation resistance welding method was proposed for the welding of Al–Mg dissimilar metal overlap joints. The aim was to control the heat distribution of Al–Mg joints by applying the difference of Joule heat generated by different specifications of graphite electrodes on both sides of joints. The interface structure and joining mechanism of the joint were analyzed by adding zinc interlayer. The results show that the tensile strength of Al–Mg direct welded joint is as high as 99 MPa under this process, while the strength of Al–Mg joint with zinc interlayer is only 12 MPa. The reason for the above results is that the interface of Al–Mg direct welded joint is mainly composed of Al–Mg diffusion layer and a small amount of compounds, while a large number of brittle hardening compounds are formed at the interface of Al/Zn/Mg joint. This study provides a new idea and method for the design and manufacture of aluminum-magnesium high quality welded joint.

Міцність та структура стикових, напускових і кутових з’єднань сплаву АМг6М, отриманих зварюванням тертям з перемішуванням

Міцність та структура стикових, напускових і кутових з’єднань сплаву АМг6М, отриманих зварюванням тертям з перемішуванням

Strength and structure of butt, overlap and fillet joints of AMg6M alloy produced by friction stir welding

Strength and structure of butt, overlap and fillet joints of AMg6M alloy produced by friction stir welding

Damping Properties of Large-Scale Overlap Joints Bonded with Epoxy Hybrid Resin or Polyurethanes: Experimental Characterisation and Analytical Description

Structures in various industries are exposed to dynamic loads. The dissipative properties of adhesively bonded joints can contribute to the damping of dynamically stressed structures. Dynamic hysteresis tests are carried out to determine the damping properties of adhesively bonded overlap joints by varying the geometry and test boundary conditions. The dimensions of the overlap joints are full-scale and thus relevant for steel construction. Based on the results of experimental investigations, a methodology is developed for the analytic determination of the damping properties of adhesively bonded overlap joints for various specimen geometries and stress boundary conditions. For this purpose, dimensional analysis is carried out using the Buckingham Pi Theorem. In summary, it can be stated that the loss factor of adhesively bonded overlap joints investigated within this study is in the range between 0.16 and 0.41. The damping properties can particularly be increased by increasing the adhesive layer thickness and reducing the overlap length. The functional relationships of all the test results shown can be determined by dimensional analysis. An analytical determination of the loss factor considering all identified influencing factors is enabled by derived regression functions with a high coefficient of determination.

Interface microstructure and mechanical properties of copper-steel joints with nickel transition layer prepared by ultrasonic additive manufacturing

In order to suppress the problems of intergranular copper infiltration, liquid phase separation and thermal cracks in the process of fusion welding between copper and 304 stainless steel, UAM technology was used to consolidate the nickel transition layer on the surface of stainless steel to achieve surface modification, and then obtained copper-304 stainless steel overlap joints by pulse TIG process. Through the study of the joint interface configuration, microstructure, microhardness distribution and room temperature tensile strength of the control group, it was found that the introduction of the nickel interlayer can realize the metallurgical isolation between copper and steel and relieve the interfacial stress. Stainless steel and copper form the high-quality brazed joint with a nickel interlayer of 0.1 mm thickness, and the ultimate tensile strength of the joint at room temperature reaches 165 MPa. The joint fracture occurred near the fusion line near the copper side, and the fracture showed a ductile fracture mode.

Weld-penetration-depth estimation using deep learning models and multisensor signals in Al/Cu laser overlap welding

Al/Cu laser-welded overlap joints, in which weld-penetration depth significantly influences both joint strength and electrical conductivity, are widely applied in automotive battery cells. In this study, a unisensor convolutional neural network (CNN) model that predicts penetration depth using coaxial weld-pool images as input and multisensor CNN models that utilize additional photodiode signals are proposed. The penetration depth was estimated using an optical coherence tomography sensor. The coefficient of determination values for the unisensor and multisensor CNN models were between 0.982 and 0.985, and their mean absolute errors were between 0.0278 and 0.0302 mm. The short-term Fourier transform multisensor model presented the best performance in terms of prediction of penetration depth when applied to the photodiode signal. The proposed prediction models were validated using a gradually varying laser power experiment, which demonstrated the efficacy of this approach and its potential use in automotive applications. Keywords: Laser welding, Al/Cu overlap joint, Penetration-depth estimation, Image sensor, Photodiode, CNN, Deep learning.

Study on MIG-TIG hybrid brazing of galvanised thin sheet

To increase productivity when joining galvanised sheet metal, metal inert gas (MIG) and tungsten inert gas (TIG) arc brazing are combined in a hybrid process. This coupling of two arc processes increases brazing speed and reduces weld reinforcement and the tendency to spatter. Because the arcs are 6 mm apart, they influence each other. Therefore, the blowing action is a major challenge in hybrid arc brazing. A current modulation and the optimal relative position of the arcs to each other are compulsory conditions. Selected brazing parameters are tested in order to verify the hybrid arc brazing. Overlap joints are brazed on galvanised sheets. The mechanical-technological properties of the brazed joints are determined. It has been shown that hybrid brazing can achieve significantly higher brazing speed with the same or better brazing quality compared to standard arc brazing. For the realisation of the hybrid arc brazing process, software-controlled welding machines are used, which will replace conventional power sources in the future.