Reliable Joining Methods Research Articles

Friction stir welding and friction stir spot welding of acrylonitrile butadiene styrene: A review

In the past two decades, Friction stir welding (FSW) and Friction stir spot welding (FSSW) have expanded applications from similar/dissimilar metals and alloys to polymers pairs but also metal to polymers dissimilar joints The use of acrylonitrile butadiene styrene (ABS) is witnessing a significant rise in the transportation sector. The ability of FSW to weld polymers may be promising and unlocking its widespread use depends on the effective and reliable joining methods for ABS and its interface with different materials. This paper has attempted to present a structured review of literature on FSW and FSSW of (ABS) with a focus on similar and dissimilar polymers, -in different joint configurations. The work on FSW/FSSW of metals and alloys is enormous but the FSW of polymers has picked up lately and the status report on the factors affecting the quality of FSWed polymer joint is both important and useful for the industrial sectors employing this material. A status report on all aspects of research on the narrow and specific topic of FSW/FSSW of ABS shall provide a one-stop-ready reference for all the stakeholders who are working in this area. With this view, the latest literature on FSW/FSSW of ABS is studied and classified according to employed welding approaches, process parameters, and detailed findings are discussed in this review paper. An attempt is also made to present the classified summary of findings useful for future researchers working on joining ABS-to-ABS or ABS-to-other polymer by FSW and FSSW.

Ultrasonic-assisted soldering of Cu/Ti joints

Cu/Ti joints are expected to be used in various applications, while reliable joining method is still to be developed. It is commonly not possible to solder Ti alloys using Sn-based solder alloys because of their poor wettability. In this study, Sn-Ag-Cu soldering filler metal was used to joining TC4 titanium alloy and pure copper using ultrasonic-assisted soldering. The influence of different temperature and different ultrasonic time on the welded joint is studied and explored. Microstructure of the joints was investigated. Shear strength of the joints reached the maximum value, i.e. 38.2MPa. Relationship between the sonication parameters and the microstructure and strength of the joints was discussed. Thus, it is verified that dissimilar metal brazing of TC4 and copper is suitable for low temperature soldering.

Effect of Needle Punching Process on a Chopped Strand Mat Composite with an Open Hole

The easiest and most reliable joining method is the mechanical joint with a bolt and nut or rivet. However, in the case of composite laminates, mechanical joint properties decrease because of lower interlaminar properties compared to in-plane properties around hole. This study investigated needle punching process with the aim of improving the mechanical properties in the thickness direction of fiber-reinforced plastic composite laminates with an open hole. Needle punching process was applied to glass fiber chopped strand matused as the reinforcement for the composite laminates. Open-hole tensile tests and observations of end cross-sections after the tests were performed. The tensile properties and fracture mechanism of the specimens subjected to needle punching process were investigated. In addition, characteristic distance (a parameter for evaluating resistance to fracture in open-hole tensile test specimens) was also calculated to examine the effects of needle punching process conditions on fracture toughness. Tensile strength was improved by more than 15% by needle punching process. However, when a certain needle punching density was exceeded, the mechanical properties worsened. In addition, characteristic distance increased with increasing needle punching density. Thus, these results suggest that there is an optimal needle punching density with respect to strength and characteristic distance.

Evaluation of Molten Zone in Micro-welding of Glass by Picosecond Pulsed Laser

Glass materials have been widely used in optics, MEMS, electronics and biomedical applications because of their excellent optical, mechanical and chemical properties. Fusion welding by ultrashort pulsed laser has been proposed as a promising technique for glass joining, since joining can be accomplished without an intermediate layer and mechanical contact. However, to apply a fusion welding technique by ultrashort pulsed laser as a reliable joining method, it is important to understand the mechanical properties of the weld seam since glass materials are very sensitive to temperature gradients. Therefore, a method of evaluating the weld seam in the fusion welding of glass by picosecond pulsed laser was discussed, and its mechanical strength was investigated. A larger optical contact area had a great influence on the shear load of the weld seam, while a smaller optical contact area could reduce the influence of the contact area on the measurement of shear load. Therefore, it was important to reduce the optical contact area to accurately evaluate the shearing strength of weld seam. The mechanical strength of the weld seam reduced at a low pulse repetition rate. High bending strength and shear stress could be obtained at a proper pulse repetition rate.

Torque Transmission Characteristics of the Press Fit Joint Between the Aluminum Shaft and Steel Ring with Small Teeth

Hybrid or aluminum tube structure requires reliable joining of the shaft to other components such as steel yoke and universal joint, which is often the most difficult task. Therefore, a reliable joining method between the aluminum tube and the steel yoke of a hybrid composite propeller shaft for automobile is required. In this work a press fitting method for joining of an aluminum tube to an aluminum yoke is devised by a steel ring with many small teeth to increase reliability as well as to reduce manufacturing cost of the hybrid propeller shaft rather than using other joining methods such as adhesively bonded or welded joints. The optimal shape and number of teeth of the steel ring were obtained experimentally for the maximum static torque capabilities and fatigue characteristics of the press fit joint, and was compared to the finite element analysis results. Finally, a design guideline for the press fit joint using a steel ring with many small teeth for joining the aluminum shaft to the steel ring was suggested. With the developed press fit joint, the static average shear strength of 70 MPa and fatigue strength of 21 MPa between the aluminum tube and the steel ring were realized, which were almost three times higher than that of the adhesively bonded joint.

Comparison of fatigue behaviour between resistance spot and friction stir spot welded aluminium alloy sheets

Tensile shear fatigue tests have been performed using resistance spot welded (RSW) joint and friction stir spot welded (FSSW) joint of aluminium alloy sheets. When fatigue strength was characterised in terms of applied load, RSW joint showed higher fatigue strength than FSSW joint in the entire load range, while the fatigue strength normalised with respect to the nugget area was higher in FSSW joint than in RSW joint. Friction stir spot welded joint exhibited a very small scatter of fatigue life compared with RSW joint, indicating that FSSW is a very stable and reliable joining method. Macroscopic fatigue fracture modes were similar in both joints: nugget shear fracture in high applied load region and parent sheet fracture in low applied load region. It was indicated that geometrical factors around the weld zone played a dominant role in determining the fatigue strength and fracture mechanism of the joints.

Analysis of circumferentially welded thin-walled cylinders to investigate the effects of varying clamping conditions

Arc fusion welding predominates in the welding industry as a reliable joining method and has been the subject of investigations by researchers for decades. To ensure in-service structural integrity, optimization of weld-induced imperfections such as welding deformations and residual stresses is critically desirable in circumferentially welded thin-walled cylinders owing to their wide applications in aerospace and aeronautical structures, pressure vessels, and nuclear engineering fields. In this research, computational methodologies for sequentially coupled non-linear transient thermomechanical analysis of the complex arc welding of thin-walled cylinders of stainless steel (AISI 304) are presented. Detailed three-dimensional finite element (FE) simulations with a single V butt-weld joint configuration of 150 mm outer diameter and 3 mm wall thickness cylinders are carried out to investigate the effects of varying structural boundary conditions (mechanical constraints) on weld-induced distortions and residual stress fields. Basic FE models are validated with carefully recorded and properly instrumented experimental data for temperature distribution, deformations, and residual stresses. Predicted and measured welding distortions and residual stresses are compared and discussed in detail. The results reveal that axial deformations are strongly dependent on the degree of restraints. Low-restraint structures exhibit high axial shrinkage, and vice versa. Diametral/radial shrinkage for different clamping conditions show no significant variation. Further, residual stresses show a weak dependence on the degree of restraints. Although the stress levels slightly vary in magnitude, a similar trend is observed for all the structural clamping conditions studied.

Adhesive joining of composite journal bearings to back-up metals

Composite journal bearings are becoming popular for marine applications because they eliminate the possibility of seizure to steel journals, which is a drawback of white metal bearings. However, a reliable joining method for composite bearings to steel housings is required. In this work, hybrid composite journal bearings composed of carbon/phenolic and glass/epoxy laminated composites were manufactured with different stacking sequences and adhesively bonded to steel housings. The effect of deformations of the composite bearings due to thermal residual stresses on the adhesive joint performance was estimated with respect to stacking sequence by finite element method, and compared to the experimental results. From the measured and experimental results, it was found that the outward radial deformation of the composite bearings was beneficial to the adhesively bonded joint strength of the hybrid composite journal bearing.

Advanced composites for the body and chassis of a production high performance car

Carbon fibre composites can offer a great deal of weight saving and manufacturing flexibility in the design of a high performance vehicle, while decades of research in metal science have produced manufacturing techniques that guarantee perfect surface finish, alloys that can withstand weathering agents during the lifetime of a vehicle and very reliable joining methods, these relatively new materials require constant evaluation in automotive applications to ensure equal if not greater performance than their metallic counterpart. This paper highlights the fundamental contributions of advanced composites in the production of the body panels and integrated chassis components for the Murcielago and Murcielago Roadster.

Joining of Aluminium Metal Matrix Composites

ABSTRACT Aluminium metal matrix composites (AlMMCs) offer several advantages relative to monolithic aluminium alloys such as high stiffness, strength, wear resistance, low thermal expansion coefficient, etc. However, despite considerable improvements in developing AlMMCs, the lack of reliable joining methods restrict their greater application. Fusion welding of AlMMCs has not proved successful because high temperature nature of the process normally causes unfavorable reactions between the reinforcement and the matrix, leading to the formation of a variety of defects. On the other hand, solid-state welding and diffusion bonding may not be suitable due to the presence of chemically stable surface layer of aluminium oxide, which, being insoluble in aluminium, inhibits metal-to-metal contact during diffusion bonding. Furthermore, diffusion bonding requires a very smooth and clean contact surface, which is difficult to obtain in industrial applications. As an alternative, transient liquid phase (TLP) diffusion bonding, which operates at a lower temperature, can be used to circumvent the problems associated with the oxide layer. The formation of liquid phase (eutectic) can assist the disruption of the oxide layer and promote metallic contact. The composite material used in the present study consisted of 6061 alloy containing 15 volume % of SiC particulates of 23 μm diameter. TLP bonding was carried out at 560 ˚C in argon atmosphere using copper as an interlayer with different pressures and holding times. TLP-bonded AlMMCs were characterized by optical and scanning electron microscopy, microhardness survey, and shear tests. The results indicated that adequate bond strength could be achieved with suitable bonding parameters such as holding time and initial pressure.

Development of carbon/epoxy structural components for a high performance vehicle

Development of the carbon/epoxy body panels and structural components of the Lamborghini Murcièlago is discussed, while use of aerospace grade technology and materials is justified for this particular application. The influence of fiber architecture on the strength of a composite panel for the same fiber/resin system is discussed, with a focus on the two failure modes usually considered the most critical in designing with polymer composites, delamination and flexural failure. Investigation covers four prepreg tapes and two fabrics, and the use of woven laminates over directional tape is motivated. Resin impregnated carbon fiber components can offer a great deal of weight saving with respect to their predecessors in high performance sport cars, high grade steel and aluminum, yet, while decades of research in metal science have produced manufacturing techniques that guarantee perfect surface finish, alloys that can withstand weathering agents during the vehicle lifetime, and very reliable joining methods, these relatively new materials require constant evaluation in automotive applications to ensure equal if not greater performance than their metallic counterpart. Engineering solutions for tooling operations in order to achieve class A surface certification are summarized. Design for environmental aging as well as accelerated degradation testing methods such as ASTM D2247 Cleveland and weatherometer ASTM G26 are described. Development and implementation of hybrid adhesive bonding as sole method of joining the composite body components to the tubular steel chassis is reviewed.

Effects of strain rate and temperature on fracture strength of ceramic/metal joint brazed with Ti-Ag-Cu alloy

Ceramics are significantly used in many industrial applications due to their excellent mechanical and thermal properties such as high temperature strength, low density, high hardness, low thermal expansion, and good corrosion resistive properties, while their disadvantages are brittleness, poor formability and high manufacturing cost. To combine advantages of ceramics with those of metals, they are often used together as one composite component, which necessiates reliable joining methods between metal and ceramic. Direct brazing using an active filler metal has been found to be a reliable and simple technique, producing strong and reliable joints. In this study, the fracture characteristics of Si3N4 ceramic joined to ANSI 304L stainless steel with a Ti-Ag-Cu filler and a Cu (0.25–0.3 mm) interlayer are investigated as a function of strain rate and temperature. In order to evaluate a local strain a couple of strain gages are pasted at the ceramic and metal sides near joint interface. As a result the 4-point bending strength and the deflection of interlayer increased at room temperature with increasing strain rate. However bending strength decreased with temperature while deflection of interlayer was almost same. The fracture shapes were classified into three groups ; cracks grow into the metal-brazing filler line, the ceramic-brazing filler line or the ceramic inside.

Rührreibschweißen - Wärmearmes Verbinden von Aluminiumlegierungen

Der vielfältige Einsatz von Aluminiumlegierungen in unterschiedlichen Industriebereichen ist in den Werkstoffeigenschaften begründet. So sind Aluminiumkonstruktionen aus Luft- und Raumfahrt, Tieftemperaturbehälterbau, Fahrzeugindustrie, Schiffbau, Elektrik und Elektronik nicht wegzudenken. Der globale Wettbewerb übt auf die Produktionsmethoden und hier natürlich auf die eingesetzten Schweißverfahren einen erheblichen Kostendruck aus. Die Nachfrage nach einem einfach anzuwendenden und qualitativ hochwertigen Schweißverfahren für Aluminiumlegierungen besteht daher seit langem. Das Rührreibschweißen (Friction Stir Welding), vom TWI in England entwickelt, verbindet viele Vorteile des Reibschweißens mit der einfachen Anwendung beim Verbinden von Strangpressprofilen, Platten und Gußkonstruktionen. Inzwischen wird dieses Verfahren nicht nur im Schiffbau sondern auch in der Fahrzeugindustrie, in der Raumfahrt und in anderen Segmenten praktisch eingesetzt. Die gegenüber den konventionellen Lichtbogenschweißverfahren wesentlich geringere Wärmeeinbringung beim Friction Stir Welding stellt sich immer mehr als einer der Hauptvorteile des neuen Verfahrens heraus. Dieser Beitrag ist der Beschreibung des Verfahrens, seiner Anwendung sowie seiner Vorteile und Begrenzungen gewidmet. Friction Stir Welding – Joining of Aluminium with Low Heat Input Since several years Aluminium consumption worldwide shows increasing figures. Space-, aircraft- as well as automotive industry and besides shipjards a lot of other segments are on the way to use Aluminium more extensive or try to minimize costs in production. Requests for cost effective, simple to use but reliable joining methods are on the table. A new welding method, called Friction Stir Welding (FSW) combines a lot of advantages for Welding of extrusion-, plate- and cast Aluminium in practice. One of the most important advantages of FSW is the low heat input resulting in lower distortion compared to fusion welding. Friction Stir Welding is already in use for segments in ships, cooling blocks, chassis for electromotors, waggon parts and soon also in rocket tanks. The welding method FSW and its advantages, limitations and use is described.

Thermal Analysis for Resistance Welding of Large-Scale Thermoplastic Composite Joints

The need for effective and reliable joining methods continues to grow as the use of thermoplastic composites becomes widespread. It is now possible to join large- scale components with the development of an automated sequential resistance welding process. The thermal history generated by the heating element placed at the interface be tween adherends determines the quality and performance of the welded joint. This article presents a thermal analysis for the resistance welding of large-scale components that over comes the limitations of previous models. To simulate welding of the interface, a heat gen eration term was incorporated that accounts for the Joule heating of graphite fibers in the heating element. A parametric study was conducted to investigate the influence of welding parameters and assess the uniformity of interface temperatures. Components were joined by the resistance welding process to obtain experimental verification. Regions of localized overheating where potential current leakage may occur were identified as a function of process parameters. Insights on promoting more uniform heating for the resistance weld ing process are discussed.