Search Results (612)

The use of weld bond (WB) joints in automotive manufacturing is gaining popularity for joining similar and dissimilar materials. This study investigated the effect of Sikaflex-252 (Sika Australia Pty Ltd, Perth, Australia) adhesive in DP600 similar steel joints and DP600 and AISI 316 stainless steel dissimilar steel joints. An increase in welding current from 7 kA to 10 kA increased the weld diameter and tensile shear strength in the RSW joints and the WB joints. WB joints had bigger weld diameters of 5.39 mm and 4.84 mm, higher tensile shear strengths of 12.3 kN and 6.85 kN, and higher energy absorption before failure of 32.6 J and 24.6 J at 10 kA compared to joints at 7 kA for similar and dissimilar joints, respectively. The use of adhesive increased heat generation at 10 kA welding current, due to the increase in dynamic resistance. At 7 kA welding current, the adhesive could not produce sufficient heat for spot weld development. The use of adhesive narrowed the weldability lobe in dissimilar RSW and WB joints and showed changes in failure mode. In similar RSW joints and WB joints, weldability lobe changes were not observed, and RSW and WB joints had the same fracture mode for the same welding current. WB welds have reduced stress distribution across the weld nugget compared to RSW welds because of the bigger weld diameter of 5.39 mm and lesser sheet bending of 1.13 mm. WB joint failure comprises the adhesive failure at the start and later the spot weld failure, while RSW joint failure is purely due to spot weld failure. Full article

The growing use of composites in automotive and aerospace fields highlights the need for effective joining of dissimilar materials. Adhesive bonding offers significant advantages over traditional methods. Therefore, comprehensively exploring the relationship between multiple design variables and joint strength, and subsequently achieving accurate prediction of joint strength based on this understanding, is essential for enhancing the effectiveness and efficiency of adhesive joint structural optimization. However, the joint—the critical yet weakest part—has strength governed by complex structural variables that are not fully understood, limiting optimization potential. Based on the effectiveness of finite element simulation in tensile fracture mechanics, this study developed a deep neural network (DNN). Combining the DNN model with a genetic algorithm (GA), both single-objective and multi-objective optimization were conducted. The single-objective optimization focused solely on maximizing joint strength, while the multi-objective GA further quantified the Pareto optimal trade-offs between joint strength and bond area, identifying compromise solutions. The effectiveness of the optimized parameters was validated, demonstrating higher efficiency and accuracy compared to traditional optimization methods such as response surface methodology (RSM). This integrated approach provides a robust framework for predicting joint strength and achieving effective optimization of bonded structures. Full article

To address the issue of interfacial shrinkage deformation in optical resin–cement-based composites, this study examined the effects of casting methods and coupling agent treatments on the interfacial deformation behavior and underlying mechanisms at the resin–cement interface. A self-developed interfacial shrinkage testing apparatus, combined with ABAQUS numerical simulations, was employed to facilitate this analysis. The results revealed that the interfacial shrinkage strain followed a characteristic distribution—higher at both ends and lower in the middle region—as the temperature increased. The experimental data showed a strong agreement with the simulation outcomes. A comparative analysis indicated that the pre-cast cement method reduced the interfacial shrinkage strain by 16% compared to the pre-cast resin method. Furthermore, treatment with a coupling agent resulted in a 31% reduction in the strain, while combining a serrated surface modification with a coupling agent treatment achieved a maximum reduction of 43.5%. Microscopic characterization confirmed that the synergy between the coupling agent and surface roughening significantly enhanced interfacial bonding by filling microcracks, improving adhesion, and increasing mechanical interlocking. This synergistic effect effectively suppressed the relative slippage caused by asynchronous shrinkage between dissimilar materials, thereby mitigating the interfacial cracking issue in optical resin–cement-based composites. These findings provide theoretical insights for optimizing the interface design in organic–inorganic composite systems. Full article

In engineering practice, liquid droplet impingement typically occurs at an oblique angle relative to the target surface, yet the influence of impact orientation on damage outcomes remains contentious and exhibits target-material dependency. In this paper, a typical single-waterjet-generating technique is applied to liquid impact tests on a unidirectional carbon fiber-reinforced polymer (CFRP) laminate, with special focus on the effects of the impingement angle and the fiber orientation. Finite-element simulation is employed to help reveal the failure mechanism of oblique impacts. The results show that, in most cases, the damage caused by a 15° oblique impact is slightly larger than that of a normal impact, while the increase amplitude varies with different impact speeds. Resin removal is more prone to occur when the projection of the waterjet velocity on the impact surface is perpendicular (marked as the fiber orientation PE) rather than parallel (marked as the fiber orientation PA) to the fiber direction of the top layer. A PE fiber orientation can lead to mass material peeling in comparison with PA, and the damage range is even much larger than for a normal impact. The underlying mechanism can be attributed to the increased lateral jet-particle velocity and resultant shear stress along the impact projection direction. The distinct damage modes observed on the CFRP laminate with the different fiber orientations PE and PA originate from the asymmetric tensile properties in the longitudinal/transverse directions of laminates coupled with dissimilar fiber–matrix interfacial characteristics. A theoretical model for the surface damage area under a single-jet impact was established through experimental data fitting based on a modified water-hammer pressure contact-radius formulation. The model quantitatively characterizes the influence of critical parameters, including the jet velocity, diameter, and impact angle, on the central area of the surface failure ring. Full article

This study develops an optimized femtosecond laser welding process for joining quartz glass and TC4 titanium alloy (Ti-6Al-4V) under non-optical contact conditions, specifically addressing the manufacturing needs of specialized photoelectric effect research containers. The joint primarily consists of parallel laser-welded zones (WZ) interspersed with base material. The defocus distance of the femtosecond laser predominantly influences the depth and phase composition of the WZ, while the weld spacing influences the crack distribution in the joint region. The maximum shear strength of 14.4 MPa was achieved at a defocusing distance of +0.1 mm (below the interface) and a weld spacing of 40 μm. The XRD stress measurements indicate that the defocusing distance mainly affects the stress along the direction of laser impact (DLI), whereas the weld spacing primarily influences the stress along the direction of spacing (DS). GPA results demonstrate that when the spacing is less than 30 μm, the non-uniform shrinkage inside the WZ induces tensile stress in the joint, leading to significant fluctuations in DS residual stress and consequently affecting the joint’s shear strength. This study investigates the effects of process parameters on the mechanical properties of dissimilar joints and, for the first time, analyzes the relationship between joint residual strain and femtosecond laser weld spacing, providing valuable insights for optimizing femtosecond laser welding processes. Full article

The friction surfacing (FS) process has emerged over the past few years as a method for joining both similar and dissimilar materials, for volume damage repair of defective components, and for corrosion protection. The possibility to produce a metallic coating by FS, without melting the material, classifies this technique as distinct from other standard methods. This unconventional deposition method is based on the severe plastic deformation that appears on a rotating metallic rod (consumable material) pressed against the substrate under an axial load. The present study aims to investigate the tribological properties and corrosion resistance provided by the aluminum-based FS coatings deposited onto a structural S235 steel substrate and further modified by plasma electrolytic oxidation (PEO). During the PEO treatment, the formation of a ceramic film is enabled, while the hardness, chemical stability, corrosion, and wear resistance of the modified surfaces are considerably increased. The morpho-structural characteristics and chemical composition of the PEO-modified FS coatings are further investigated using scanning electron microscopy combined with energy dispersive spectroscopy analysis and X-ray diffraction. Dry sliding wear testing of the PEO-modified aluminum-based coatings was carried out using a ball-on-disc configuration, while the corrosion resistance was electrochemically evaluated in a 3.5 wt.% NaCl solution. The corrosion rates of the aluminum-based coatings decreased significantly when the PEO treatment was applied, while the wear rate was substantially reduced compared to the untreated aluminum-based coating and steel substrate, respectively. Full article

Electrocoagulation is rapidly gaining prominence in wastewater treatment due to its capabilities and less reliance on additional chemicals. While a lot of research efforts have been focused on the influence of the anode material, power supply, and reactor design, the contribution of the cathode to contaminant removal has been less explored. In this study, we investigated the performance of stainless steel (SS-304) and aluminium (Al-6061) electrodes in both similar and dissimilar configurations for a 120 min electrocoagulation treatment of spent machinery coolant. The anode–cathode configurations, including SS-SS, Al-Al, SS-Al and Al-SS, have been investigated. Additionally, we examined the effects of the initial pH and agitation methods on the process performance. Our findings indicated that the type of cathode could significantly affect the floc formation and contaminant removal. Notably, the combination of an Al anode and SS cathode (Al(A)-SS(C)) demonstrated a synergistic improvement in the Chemical Oxygen Demand (COD), with a removal of 84.3% within a short treatment time (<20 min). The final COD removal of 91.4% was achieved with a turbidity level close to 12 Nephelometric Turbidity Units (NTU). The Al anode readily released the Al ions and formed light flocs at the early stage of electrocoagulation, while the SS cathode generated heavy Fe hydroxides that mitigated the flotation effect. These results demonstrated the cathode’s significant contribution in electrocoagulation, leading to potential savings in the treatment time required. Full article

Contact electrification (CE), or triboelectrification, is an electron transfer phenomenon occurring at the interface between dissimilar materials due to differences in polarity, holding significant research value in tribology. The microscopic mechanisms of CE remain unclear due to the complex coupling of multiple physical processes. Recently, with the rise of triboelectric nanogenerator (TENG) technology, solid–liquid contact electrification has demonstrated vast application potential, sparking considerable interest in its underlying mechanisms. Emerging experimental evidence indicates that at water–polymer CE interfaces, the process involves not only traditional ion adsorption but also electron transfer. Halogen-containing functional groups in the solid material significantly enhance the CE effect. To elucidate the microscopic mechanism of water–polymer CE, this study employed first-principles density functional theory (DFT) calculations, simulating the interfacial electrification process using unit cell models of water contacting polymers. We systematically and quantitatively investigated the charge transfer characteristics at interfaces between water and three representative polymers with similar backbones but different halogen-functionalized (F, Cl) side chains: fluorinated ethylene propylene (FEP), polyvinyl chloride (PVC), and polytetrafluoroethylene (PTFE), focusing on evaluating halogen’s influence and mechanism on interfacial electron transfer. The results reveal that electron transfer is primarily governed by the energy levels of the polymer’s lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO). Halogen functional groups modulate the material’s electron-donating/accepting capabilities by altering these frontier orbital energy levels. Consequently, we propose that the critical strategy for polymer chemical modification resides in lowering the LUMO energy level of electron-accepting materials. This study provides a novel theoretical insight into the charge transfer mechanism at solid–liquid interfaces, offers guidance for designing high-performance TENG interfacial materials, and holds significant importance for both the fundamental theory and the development of advanced energy devices. Full article

Conventional adhesively bonded joints, such as single-lap, curved-lap, wavy-lap, double-lap, stepped-lap, and scarf joints, are widely used for aerospace, automotive, and medical applications. These adhesively bonded joints exhibit different load transfer mechanisms and stress distributions within adhesive layers, which depend primarily on their geometries and mechanical properties of bonded materials. As such, joint geometry and material properties play a critical role in determining the capability of the joints to withstand high loads, resist fatigue, and absorb energy under impact loading. This paper investigates the effects of geometry and material dissimilarity on the performance of both conventional bonded and interlocking joints under tensile loading based on the information available in the literature. In addition, bonding and load transfer mechanisms were analysed in detail. It was found that stress concentration often occurs at free edges of the adhesive layer due to geometric discontinuities, while most of the load is carried by these regions rather than its centre. Sharp corners further intensify resulting stresses, thereby increasing the risk of joint failure. Adhesives typically resist shear loads better than peel loads, and stiffness mismatches between adherents induce an asymmetric stress distribution. Nonetheless, similar materials promote symmetric load sharing. Among conventional joints, scarf joints provide the most uniform load distribution. In interlocking joints such as dovetail, T-slot, gooseneck, and elliptical types, the outward bending of the female component under tension can lead to mechanical failure. Full article

The future of the automotive industry appears to hinge on the integration of dissimilar materials, such as aluminum alloys and carbon steel. However, this combination can lead to galvanic corrosion, compromising the structural integrity. In this study, laser-welded joints of 6013-T4 aluminum alloy and DP980 steel were evaluated for their morphology, microhardness, and corrosion resistance. Corrosion resistance was assessed using the electrochemical noise technique over time in 0.1 M Na₂SO₄ and 3.5% NaCl solutions. The wavelet function was applied to remove the DC trend, and energy diagrams were generated to identify the type of corrosive process occurring on the electrodes. Corrosion on the electrodes was also monitored using photomicrographic images. Analysis revealed an aluminum–steel mixture in the melting zone, along with the presence of AlFe, AlFe₃, and AlI₃Fe₄ intermetallic compounds. The highest Vickers microhardness was observed in the heat-affected zone, adjacent to the melt zone, where a martensitic microstructure was identified. The 6013-T4 aluminum alloy demonstrated the highest corrosion resistance in both media. Conversely, the electrochemical noise resistance was similar for the DP980 steel and the weld bead, indicating that the laser welding process does not significantly impact this property. The energy diagrams showed that localized pitting corrosion was the predominant form of corrosion. However, generalized and mixed corrosion were also observed, which corroborated the macroscopic analysis of the electrodes. Full article

This paper delves incto the tungsten inert gas (TIG) welding process, renowned for its efficacy in creating robust metal joints and widely employed in diverse industries for fusing similar or dissimilar materials. The focus of this study is the welding of mild steel with stainless steel, showcasing the method’s ability to amalgamate exceptionally sturdy metals and alloys. The resultant welded joints exhibit a meticulously refined microstructure and an impressive strength-to-weight ratio. The primary aim is to scrutinize TIG-welded joints, specifically those connecting mild steel with stainless steel, to elucidate their metallurgical and mechanical attributes. Notably, joints formed between distinct materials, such as mild steel and stainless steel, manifest commendable mechanical and metallurgical properties. This paper extensively investigates the metallurgical microstructures and tensile characteristics of both comparable and dissimilar metal junctions, contributing valuable insights to the field. Full article

Collision welding represents a promising solid-state joining technique for combining both similar and dissimilar metals without the thermal degradation of mechanical properties typically associated with fusion-based methods. This makes it particularly attractive for lightweight structural applications. In the context of collision welding, it is typically assumed that ideally smooth and defect-free surface conditions exist prior to welding. However, this does not consistently reflect industrial realities, where surface imperfections such as scratches are often unavoidable. Despite this, the influence of such surface irregularities on weld integrity and quality has not been comprehensively investigated to date. In this study, collision welding is applied to the material combination of AA6110A-T6 and AA6060-T6. Initially, the process window for this material combination is determined by systematically varying the collision velocity and collision angle—the two primary process parameters—using a special model test rig. Subsequently, the effect of surface imperfections in the form of defined scratch geometries on the resulting weld quality is investigated. In addition to evaluating the welding ratio and tensile shear strength, weld quality is assessed through scanning electron microscopy (SEM) of the bonding interface and high-speed imaging of jet formation during the collision process. Full article

Friction stir spot welding (FSSW) is a solid-state joining technique increasingly favored in industries requiring high-quality, defect-free welds in lightweight and durable structures, such as the automotive, aerospace, and marine industries. This review examines the current advancements in FSSW, focusing on the relationships between microstructure, properties, and performance under load. FSSW offers numerous benefits over traditional welding, particularly for joining both similar and dissimilar materials. Key process parameters, including tool design, rotational speed, axial force, and dwell time, are discussed for their impact on weld quality. Innovations in robotics are enhancing FSSW’s accuracy and efficiency, while numerical simulations aid in optimizing process parameters and predicting material behavior. The addition of nano/microparticles, such as carbon nanotubes and graphene, has further improved weld strength and thermal stability. This review identifies areas for future research, including refining robotic programming, using artificial intelligence for autonomous welding, and exploring nano/microparticle reinforcement in FSSW composites. FSSW continues to advance solid-state joining technologies, providing critical insights for optimizing weld quality in sheet material applications. Full article

Adhesive bonding has emerged as a transformative joining method across multiple industries, offering lightweight, durable, and versatile alternatives to traditional fastening techniques. This review provides a comprehensive exploration of adhesive bonding, from fundamental adhesion mechanisms, mechanical and molecular, to application-specific criteria and the characteristics of common adhesive types. Emphasis is placed on challenges affecting bond quality and longevity, including defects such as kissing bonds, porosity, voids, poor cure, and substrate failures. Critical aspects of surface preparation, bond line thickness, and adhesive ageing under environmental stressors are analysed. Furthermore, this paper highlights the pressing need for sustainable solutions, including the disassembly and recyclability of bonded joints, particularly within the automotive and aerospace sectors. A key insight from this review is the lack of a unified framework to assess defect interaction, stochastic variability, and failure prediction, which is mainly due complexity of multi-defect interactions, the compositional expense of digital simulations, or the difficulty in obtaining sufficient statistical data needed for the stochastic models. This study underscores the necessity for multi-method detection approaches, advanced modelling techniques (i.e., debond-on-demand and bio-based formulations), and future research into defect correlation and sustainable adhesive technologies to improve reliability and support a circular materials economy. Full article

S1100QL and S1300QL steels are classified as fine-grained steels with a low-carbon martensitic structure. Tandem welding is a method of creating a joint by melting two electrode wires in a one-behind-the-other configuration. This article presents the effects of creating dissimilar joints, elements of varying thicknesses made from S1100QL and S1300QL steels. The analysis focused on temperature changes in the heat-affected zone (HAZ) during welding, as well as the macro and microstructure, and the properties of the joints created at welding speeds of 80, 90, and 100 cm/min. The shortest cooling time (t8/5) in the HAZ for S1300QL steel was 9.4 s, while the longest was 12.4 s. Thermal cycle simulations were performed for the analyzed materials, with a cooling time of 5 s. The test results demonstrated that TWIN welding was stable, and an optimum welding speed is 80 cm/min. The HAZ microstructure for the highest cooling speed (t8/5 = 5 s) of S1100QL steel contains, in addition to martensite, lower bainite, while S1300QL steel consists of martensite. Tempered martensite was also detected at slower cooling rates. For all speed variants, the impact energy is above 27 J at a test temperature of −40 °C. In turn, hardness tests showed that the base material for both steels has the highest hardness. However, the lowest hardness was found for the weld. Full article