Journal of Advanced Joining Processes最新文献

Plastic/metal hybrid components made of amorphous thermoplastics such as polycarbonate and light metals such as aluminum offer potential to be used in modern automotive headlights to meet the high requirements for tolerances and surface quality. A microform-fit joining approach is used to join plastics and metals, which combines the advantages of material-fit and form-fit joining processes while at the same time avoiding some of the disadvantages of the respective joining approaches, such as stress peaks or the use of additional chemicals. For this purpose, the light metal component is microstructured through laser ablation. To ensure the functional safety of electrical components, the media tightness of the hybrid component is tested with a pressure drop test. An influence of the structure arrangement, the structure spacing and the molding compound on the media tightness can be determined. The highest media tightness can be achieved with a ring-shaped structural arrangement in which the microstructures are orientated orthogonally to the outlet direction of the test medium. The media permeability of a ring-shaped structure arrangement with a structure spacing of 500 µm is 0.42 cm³/s for test specimens made of aluminum and polycarbonate. As the value is below the threshold value of 12 cm³/s, watertightness up to an overpressure of at least 0.5 bar can be concluded.

Welding high-performance thermoplastics has gained popularity across various industries such as automotive, aerospace, and medical. Laser transmission welding (LTW) has emerged as an effective method for joining thermoplastic parts due to its precise control and high joint quality. PAEK (polyaryletherketone) are wide spreading over various industrial applications as a substitute to metals and thermosets when high durability and performance are required. Polyetherketoneketone (PEKK) is one of these PAEK and it has received less attention than PEEK until now. PEKK, being a semi-crystalline thermoplastic, requires additional care during processing due to its propensity to crystallize. This study presents both experimental and numerical investigations into LTW of PEKK molded parts, aiming to understand the influence of welding parameters and crystallinity on weld joint morphology and mechanical properties. PEKK plates, prepared in amorphous and semi-crystalline states, are subjected to LTW using a 975 nm diode laser. Material characterization confirms differences in crystallinity between the samples, which affect their thermal and optical properties, which are crucial for welding. Welding tests are conducted with varying laser power (between 75 and 95 W) and semi-transparent part thickness (2 and 4 mm). The morphology of joints is analysed. Assemblies undergo post-weld annealing treatment to examine its influence on weld crystallinity and consequent mechanical properties. Results reveal an anisotropic distribution of crystallinity within the heat-affected zone (HAZ). The depths of the molten layer (ML) and semi-crystalline layer (scL) vary with laser power and assembly type. A notable decrease in weld strength with laser power is highlighted, while annealing leads to enhanced crystallinity and improved weld strength. Despite variations, high weld strengths are achieved with annealing. Computational modelling elucidates the complex interplay between laser irradiation, temperature distribution, and crystallization kinetics observed experimentally. Overall, this comprehensive investigation provides valuable insights into optimizing LTW parameters for PEKK parts.

The escalation in electric vehicle (EV) adoption necessitates advanced laser joining techniques for critical battery pack components. However, using a standard Gaussian single-mode laser for joining similar and dissimilar material combinations e.g. aluminium/aluminium (Al/Al), aluminium/copper (Al/Cu) for tab-to-busbar connections often led to defects such as cracks and intermetallic compound (IMC) formation. This paper investigates using a dual-mode laser consisting of a core and ring to overcome these issues. In this research, 0.3 mm Al and Cu tabs were welded with 1.5 mm Al and Cu busbars using a 6 kW IPG dual-mode laser at a high welding speed of 1 m s^-1. The study focussed on the effects of dual-mode parameters (i.e. core and ring beam power) and welding speed on tab-to-busbar connections, analysing the interplay between electrical contact resistance, temperature and IMC formation through electrical resistance tests, elemental and strength analysis. The results show, that using the ring beam along with the core beam reduces excessive melting and evaporation of Al and minimises the intermixing of Al and Cu solid solutions in the joint. In the Cu tab-to-Al busbar joint, increasing the ring beam intensity effectively reduces the convexity defect found with single-mode beam attributed to improved keyhole stability. Overall, in dual-mode laser welding, the ring beam protects the keyhole and reduces the IMC formation, while the core beam, with its high peak intensities, controls the penetration depth. This necessitates balancing both core and ring beam intensities for optimal weld quality. Further, the joint resistance for Cu tab-to-Cu busbar (51.90 μΩ) joint was the lowest followed by Cu tab-to-Al busbar (68.38 μΩ) joint, Al tab-to-Cu busbar (84.44 μΩ) joint and Al tab-to-Al busbar (114.12 μΩ) joint.

The present publication deals with an energy-oriented approach to the statistical analysis of rotational friction welding processes. To illustrate the methodological approach, it is applied to investigate the effects of energy flow on material flow behavior and joint quality during friction welding of an AA6060 alloy with a low-alloy 16MnCr5 filler steel. The influences of the setting parameters on the energetic states are first analyzed by means of an initial screening. The evaluation using process simulation and statistical methods enables the generation of regressive response surfaces for the friction power, the friction time and the resulting induced friction energy. Based on these findings, a second experimental field is formed and evaluated, which considers the interaction between the energy input of the frictioning stage and the workpiece forging. This new approach results in the functional separation of the frictioning and forging stage, which eliminates the usual statistical interaction effects and thus facilitates analysis and optimization. The qualitative result variable required for the purpose of interpreting the results is the ultimate tensile strength of the friction-welded joint. Additionally determined hardness curves provide information about the properties of the thermally influenced zone and strength-relevant process sequences. The result is that, in addition to the amount of energy induced, the frictional power with which the former is induced also has a considerable influence on the joint strength, as it influences the material flow and the properties of the joining zone.

Achieving strong direct joining between steel and polymers through mechanical interlocking is crucial for developing multi-material structures, particularly in the automotive and aerospace industries. This study synthesized micro-scale structures on a pure Fe substrate (simulating interstitial-free (IF) steel) for mechanical interlocking with thermoplastic parts. Numerous submillimeter-scale Fe/TiB₂ composite particles were in-situ synthesized by laser scanning on the Fe-Ti-B powder mixture and well-bonded with the Fe substrate. The effects of powder composition (TiB₂ volume fraction) on the morphology, microstructure, and joint strength with PA6 were investigated. A TiB₂ volume fraction over 60 % was essential for the formation of the composite particles promoted by a TiB₂ skeletal structure. Higher TiB₂ volume fractions increased the area fraction of the composite particles and decreased the bonding ratio (adhesive) of the particles with the substrate due to poor adhesiveness at the edge of the laser-scanning line. A wider high-temperature region was generated at a higher TiB₂ volume fraction, suggesting that the reaction heat to form TiB₂ assisted the bonding of the particles with the substrate at the edge of the laser scanning line. The Fe/PA6 joint strength increased to approximately 30 MPa with increasing the TiB₂ volume fraction to 100 % and showed a linear correlation with the product of particle area fraction and bonding ratio. A higher TiB₂ volume fraction was preferable for enhancing the joint strength via the micro-scale structures synthesized by laser scanning on the Fe-Ti-B powder mixture. A combination of the micro-structuring process using a high fraction of TiB₂ with advanced joining technologies will contribute to manufacturing high-strength Fe/polymer hybrid parts.

This research investigates the inherent radial non-uniformity within the rotary friction welding process, particularly concerning microstructure attributes like grain size, grain boundaries, misorientation angles, and interlayer presence along the radial axis. SS321-AA2219 rotary friction welding was carried out with and without an AA6061 interlayer. The numerical thermal model suggests increase in temperatures from the center to the periphery, due to non-uniform heat generation. Also, dissimilar material across the interface resulted in an asymmetric temperature profile along axial direction. Plastic deformation on the Aluminum side suggests dynamic recrystallization and grain refinement, whereas pronounced low-angle grain boundary (LAGB) formation near the SS side interface validates dynamic recovery. A radial non-uniformity in microstructure is observed, with metrics such as average grain size, LAGB fraction, and misorientation showing an increase from the center towards the periphery. The insertion of an interlayer alters process dynamics, manifesting in reduced temperatures and heightened forces, resulting in a more consolidated joint by enhancing the strength by 31 %. Interdiffusion of elements across the interface formed Fe-Al intermetallic compounds (IMC) confirmed with X ray diffraction. Fractography analysis elucidates the presence of rubbing marks and facet surfaces in interlayer-less joints, while joints with interlayer display sticking and dimples.

In this study, the new loosening behavior was discovered and investigated when offset loads were repeatedly applied to both ends of a bolted joint initially tightened to a thin plate made of high-tensile steel. In the experiments, the impact of offset distance on reduction of clamp force was investigated through multiple applications of symmetric offset axial load to the bolted joint assembly. The experimental results showed that even a slight offset load reduced the clamp force, and the larger the offset distance, the greater the reduction of the clamp force. It was also found that the decrease in clamp force depends not on the number of times the offset load is applied but on the magnitude of the offset load. Until now even if the thin plate bolted joint was subjected to an offset load, as long the plates do not deform significantly due to plastic deformation, it has been generally recognized that the clamp force is not reduced. This loosening phenomenon is new and its mechanism has not been elucidated yet. In order to clarify the mechanism that may lower the clamp force, this study conducted FE analysis using a simplified model of a bolted joint. In the FE model, the bolt and nut are considered as a single unit and the effect of slippage between the thread surfaces and the effect of plastic deformation is ignored by using elastic analysis. The results of the FE analysis showed that the main factor causing the reduction in clamp force was slippage between the thin plates to be joined, which was caused by offset load, and that the slippage didn't return to the original position resulting in the reduction in clamp force.

The paper presents the results of an experimental study of the friction weldability of Titanium Grade 2 with ultrafine-grained (UFG) microstructure obtained by hydrostatic extrusion and rotary swaging (HE+RS). High-speed friction welding with different rotational speed (n) values was used as a joining method. The best properties were obtained for n=7000 rpm. Metallographic observations confirmed the formation of a continuous friction joint with a changed microstructure of the base material in the thermal-mechanical affected zone (TMAZ) and a friction weld (FW). The results of the mechanical properties showed the greatest decrease in hardness in the TMAZ. The friction welded joint had an 18 % lower tensile strength value than initial state UFG Titanium Grade 2 after the HE+RS process (with UTS=1050 MPa).

Two-component room temperature vulcanizing silicone adhesive RTV566 with a lower elastic modulus has been widely used in precision optomechanical products such as remote sensors and aerospace infrared cameras. However, the silicone adhesive is of poor manufacturability due to its extremely high viscosity, and the bonded joint usually exhibits low bonding strength and requires a long curing time. This paper investigates a way to improve both the adhesion strength and curing efficiency of Invar alloy and optical glass with RTV566 through single-lap experiments. It is found that adding small amounts of acetone and water can significantly reduce the viscosity, enhance the bonding strength, and shorten the curing time. The viscosity can be reduced by 63.4 % and the bonding strength can be improved by 136.4 % with the weight ratio of adhesive to acetone being 20:2. Moreover, a little amount of water in the weight ratio of 100:10:0.1 (adhesive: acetone: water) can shorten the curing time from 7 days to 4 days without harms to the bonding strength and elastic modulus. As to the mechanism, the silicone adhesive can be dissolved by acetone and its sulfuration reaction can be enhanced by water, resulting in good manufacturability and high curing efficiency. This work contributes a novel and easy-to-use method to greatly improve the performances of the bonding process of precision optical structures.

Dissimilar metal welding is seeing growing adoption across industries to enhance structural functionality and efficiency. Achieving high-quality, defect-free dissimilar weld joints requires a comprehensive understanding of the interrelationships between the welding-induced microstructural changes and the material's performance characteristics, particularly its fracture-related properties. This study investigates the impact of microstructural changes on the fracture toughness of dissimilar welds between structural low-carbon steel (S355J2) and austenitic stainless steel (SS316L) prepared using the Rotary Friction Welding (RFW) technique. Welding preforms were created from respective pipe pup pieces. The evaluation involves microstructural analysis, tensile testing, hardness testing, and fracture toughness testing using compact tension specimens derived from various zones of the weld joints. Results revealed significant microstructural differences across the weld joint. The weld region exhibited stable hardness with a maximum of 208 HV1 in S355J2′s thermo-mechanically affected zone (TMAZ). High tensile strength (Ultimate Tensile Strength 540 MPa, Yield Strength 367 MPa) with failures mainly on the S355J2 side. The fracture toughness (K_Q) matched parent metal values, with the RFW weld centre line (WCL) showing superior crack tip opening displacement (CTOD) of 0.35 mm. Fractography generally indicates ductile failure.