Improve Joint Quality Research Articles

Application of Friction Riveting technique for the assembly of electronic components on printed circuit boards (PCB)

This study focuses on the effects of reducing the diameter of rivets used in Friction Riveting due to the need for downscaling when joining assemblies on a smaller scale. The Friction Riveting process has shown promising feasibility for a variety of material combinations and applications in the transportation industry. Recent research has explored the potential application of this technique in electronics, specifically for the assembly of printed circuit boards (PCBs), using AA-2024-T351 rivets on thin glass-fiber-reinforced epoxy substrates (FR4). The joint formation of joints produced with PCBs was investigated in terms of process temperature evolution, microstructural changes, and mechanical properties. Joints were obtained at process temperatures ranging from 285 ºC to 368 ºC. The use of 4 mm rivets resulted in extensive delamination, weak joint mechanisms, and cracking, impaired by the different coefficients of thermal expansion of the materials involved. Reducing the rivet diameter to 3 mm significantly improved joint quality. A further reduction to 2.5 mm minimized delamination but led to insufficient anchorage and cracking. Joints produced with a 3 mm rivet diameter achieved the highest ultimate tensile force of 276 N. This study sets the foundation for applying the Friction Riveting process to practical PCB assemblies, demonstrating that optimizing the process parameters to the diameter-to-thickness ratio can balance sufficient rivet anchoring, minimize delamination, and reduce cracking.

Effect of welding speed on mechanical properties of dissimilar friction stir lap-joint welding between AA6061 and C1100 copper

Nowadays, renewable energy such as wind and solar energy can be employed for marine application to enhance clean and green technology. So, using battery is necessary to apply power for ship activities. To contribute sustainable development, optimizing structure in electric transmission such as bimetal connector Cu-Al is necessary to improve joint quality. This study focused the influence of welding parameters on the quality of the lap-joint between AA6061 aluminum alloy and C1100 copper. Experimental results indicate that the welding interface was sensitive to welding speed. Some welding defect was found in the joint such as tunnel and hook defects. The highest tensile strength produced by the welding speed of 200 mm/min was approximately 1100 N. In all experimental regimes, the weld zone structure, hardness distribution, tensile strength, fracture location, and local deformation were analyzed and discussed in detail. Keywords: Friction stir welding, microstructure, mechanical properties, hardness

Effects of a nickel-based alloy interlayer on electrically assisted pressure joining of pure titanium and stainless steel 304

This study focuses on the solid-state joining of commercially pure titanium (CP-Ti) and stainless steel 304 (SUS304) using electrically assisted pressure joining. A nickel-based alloy foil acting as an intermediate layer (Ni interlayer) is inserted between two base materials during joining to avoid the formation of a detrimental TiFe intermetallic due to direct contact of the CP-Ti and SUS304. The solid-state joining process can be completed within 2 s. The effectiveness of incorporating the Ni interlayer on joint quality is systematically investigated by comparing joints made with and without the use of a Ni interlayer. Microstructure analysis reveals that the Ni interlayer plays a critical role in improving joint quality by forming a nanocrystal structure and preventing the formation of TiFe intermetallic. Furthermore, the joint with a Ni interlayer increases the joint shear strength by at least 50% more than a joint without a Ni interlayer in the same joining period and exhibits tensile ductile fracture at the heat-affected zone in the CP-Ti side during tension. The present study provides valuable insights into the benefits of Ni interlayers in the rapid and reliable creation of solid-state joints between CP-Ti and SUS304 using electrically assisted pressure joining.

Exploring a novel chamfered tool design for short duration refill friction stir spot welds of high strength aluminium

This work investigates refill friction stir spot welded joints of AA2024-T3 aluminium alloy, produced with short welding times between 3 s and 0.75 s. A novel tool geometry that incorporates a chamfer on the inner edge of the shoulder tip is investigated as a means of improving joint quality at short welding times by easing material flow during the refill stage. The influence of shoulder design on weld microstructure, defect formation, material flow, and mechanical properties was assessed. When compared with a standard shoulder geometry, it was found that the introduction of a chamfer on the inner tip edge improved material flow during the refill stage and led to improved material mixing at the weld periphery. The formation of voids in the region of the weld periphery was eliminated and tensile lap-shear strength of the welded joints was increased by 19% to 7.2 kN, and 27% to 8.16 kN, for 0.75 s and 1.5 s duration welds, respectively.

The Feasibility of Static Shoulder Friction Stir Welding in Joining Dissimilar Metals of Al6061 and Ti6Al4V

In this study, static shoulder friction stir welding (SSFSW) is innovatively employed to join Al6061 and Ti6Al4V, aiming to minimize material mixing and intermetallic formation, significantly influencing the interfacial microstructure and joint strength. The results revealed that SSFSW reduced the intermetallic layer thickness at the interface, improving joint quality. The mutual interdiffusion of Al and Ti at the interface was influenced by an exothermic chemical reaction, forming an Al5Ti2–Al3Ti sequence due to the diffusion of Al into the Ti matrix. The microstructural analysis demonstrated better interfacial microstructural homogeneity in SSFSW joints than conventional FSW (CFSW), with finer titanium particle distribution. The larger particles resulted in coarser grains in CFSW, affecting the mobility of dislocations, which potentially led to the inhomogeneous concentration of dislocations at the interface. Recrystallization mechanisms varied between CFSW and SSFSW, with the Ti interface showing equiaxed and recrystallized grains due to the dynamic recovery driven by adiabatic shear bands. The tensile testing results of SSFSW exhibited a joint efficiency of 88%, demonstrating a 20.2% increase compared to CFSW, which can be attributed to differences in fracture modes. This study contributes to an understanding of dissimilar Al-Ti joining and provides insights for industries seeking to leverage the benefits of such combinations in lightweight and high-performance structures.

Investigation of Ultrasonically Welded Thermoplastic Composite Joints Using Netlike Energy Directors

Abstract This paper proposes a netlike energy director (ED) made of carbon fiber-reinforced thermoplastic (CFRP) composites for ultrasonic welding. To explore the benefits of using netlike EDs, the joint qualities with flat EDs and without EDs are included for references. The influence of the netlike ED geometry on weld attributes and joint quality are investigated in terms of joint cross-sectional microstructure, fracture morphology, and maximum shear load. It is found that for both netlike and flat EDs, the welding process can be accelerated compared with the one without EDs, caused by the concentration of welding energy into the expected welding region and the avoidance of welding edges introduced by surface curvature. Meanwhile, the maximum shear loads of the joints with netlike EDs are higher than those with flat EDs, because of the decrease of the contact area and consequent higher cyclic strain, resulting in more melted materials during the ultrasonic welding process. However, with the increasing of the netlike ED thickness, more porosities are generated in the welding layer leading to reduced bonded region and decrease of the maximum shear load. From the joint fracture morphology analysis, it is found that the netlike EDs introduce carbon fibers in the welding layer, and the fracture modes include fiber-matrix debonding and fiber pull-out in addition to polymer fracture, confirming the feasibility of improving joint quality by introducing CFRP netlike EDs.

Improving joint quality of hybrid friction stir welded Al/Mg dissimilar alloys by RBFNN-GWO system

Abstract Welding of Al/Mg dissimilar alloys faces many challenges. In this study, ultrasonic-stationary shoulder assisted friction stir welding (U-SSFSW) was employed to join the dissimilar alloys of AZ31B Mg and 6061-T6 Al. Radial basis function neural network (RBFNN) was used to model the relationships between the inputs of welding speed, rotating speed and ultrasonic power and the output of ultimate tensile strength (UTS) of U-SSFSW joint. After that, grey wolf optimization (GWO) algorithm was used to explore the maximum UTS and the corresponding optimal process parameters. The maximum UTS reached 158 MPa under the RBFNN-GWO system optimized process parameters. The microstructure and fracture behavior were analyzed to clarify the superiorities of the optimal process parameters and the enhancement mechanism of U-SSFSW technique under the optimized parameters.

Refill Friction Stir Spot Welding of Similar and Dissimilar Alloys: A Review

Refill friction stir spot welding, also known as friction spot welding (FSpW), is a solid-state welding process suitable for spot joining of lightweight materials. Through the efforts of improving joint quality for similar and dissimilar materials, for example, aluminum and magnesium, this joining technology is well developed. The joining mechanism and process characteristics of FSpW have been widely studied. However, the application of FSpW in industry has not been entirely successful. In this review article, the research of similar and dissimilar material joints, such as, Al/Cu, Al/Ti, Al/Mg and Al/Steel, is summarized. The microstructural features and mechanical properties of the joints, welding tool and the application development are discussed in detail.

Effects of Process Parameters on Crack Inhibition and Mechanical Interlocking in Friction Self-Piercing Riveting of Aluminum Alloy and Magnesium Alloy

Friction self-piercing riveting (F-SPR) process has shown advantages over fusion welding, solid state welding, and traditional mechanical joining processes in joining dissimilar materials. Because of the thermo-mechanical nature of F-SPR process, formation of the joint is determined by both riveting force and softening degree of materials to be joined. However, it is still not clear that how exactly the riveting force and generated frictional heat jointly influence mechanical interlocking formation and crack inhibition during F-SPR process. To address these issues, F-SPR process was applied to join 2.2 mm-thick aluminum alloy AA6061-T6 to 2.0 mm-thick magnesium alloy AZ31B. The correlation of riveting force, torque responses, and energy input with joint quality was investigated systematically under a wide range of process parameter combinations. It was found that a relatively greater final peak force and higher energy input were favorable to produce sound joints. Based on that, a two-stage F-SPR method was proposed to better control the energy input and riveting force for improved joint quality. The joints produced by the two-stage method exhibited significantly improved lap-shear strength, i.e., 70% higher than traditional self-piercing riveting (SPR) joints and 30% higher than previous one-stage F-SPR joints. This research provides a valuable reference for further understanding the F-SPR joint formation mechanism and conducting process optimization.

A review on resistance spot welding of aluminum alloys

This paper presents a review on the resistance spot welding (RSW) of Al/Al alloys, Al alloys/steel, Al/Mg alloys, and Al/Ti alloys, with focus on structure, properties, and performance relationships. It also includes weld bonding, effect of welding parameters on joint quality, main metallurgical defects in Al spot welds, and electrode degradation. The high contact resistance, induced by the presence of oxide layer on the surface of Al alloys, and the need for application of high welding current during RSW of Al alloys result in rapid electrode tip wear and inconsistency in weld quality. Studies have shown that cleaning the oxide layer, sliding of a few microns between sheets, enhancing the electrode force, and the application of a low-current pre-heating can significantly reduce the contact resistance and improve joint quality. For Al/steel dissimilar RSW, the technique of resistance element welding, the use of optimized electrode morphology, the technique of RSW with cover plates, and the use of interlayers such as Al-Mg, AlSi12, and AlCu28 alloys were found to suppress the formation of brittle intermetallic compounds (IMC) and improve the joint quality. The employment of pure Ni foil, Au-coated Ni foil, Sn-coated steel, and Zn-coated steel interlayers was also found to restrict the formation of brittle IMCs during RSW of Al/Mg alloys. Furthermore, the techniques of RSW with cover plates and RSW under the influence of electromagnetic stirring effect were found to improve the weldability of Al/Ti dissimilar alloys.

Minimization of distortions during laser welding of ultra high strength steel

Ultra high strength steels are frequently used within the automotive industry for several components. Welding of these components is traditionally done by resistance spot welding, but to get further productivity and increased strength, laser welding has been introduced in the past decades. Fusion welding is known to cause distortions due to built in stresses in the material. The distortions result in geometrical issues during assembly which become the origin of low joint quality due to gaps and misfits. U-beam structures of boron steel simulating B-pillars have been welded with laser along the flanges. Welding parameters and clamping have been varied to create different welding sequences and heat input generating a range of distortion levels. The distortions have been recorded dynamically with an optical measurement system during welding. In addition, final distortions have been measured by a digital Vernier caliper. The combined measurements give the possibility to evaluate development, occurrence, and magnitude of distortions with high accuracy. Furthermore, section cuts have been analyzed to assess joint geometry and metallurgy. The results show that final distortions appear in the range of 0–8 mm. Distortions occur mainly transversely and vertically along the profile. Variations in heat input show clear correlation with the magnitude of distortions and level of joint quality. A higher heat input in general generates a higher level of distortion with the same clamping conditions. Section cuts show that weld width and penetration are significantly affected by welding heat input. The present study identifies parameters which significantly influence the magnitude and distribution of distortions. Also, effective measures to minimize distortions and maintain or improve joint quality have been proposed. Finally, transient finite element (FE) simulations have been presented which show the behavior of the profiles during the welding and unclamping process.

Review of Research Progress on Aluminum–Steel Dissimilar Welding

This paper presents a review of research progress on aluminum–steel dissimilar welding. Current issues and recent developments in improving the intermetallic compound layer of weld joint are critically assessed. Several welding factors that improve joint quality, such as welding method, weld and material preparations, as well as welding parameters, are also discussed. This study also examines recent developments in hybrid welding techniques and proposes a preheating method to enhance the weld joints of aluminum–steel dissimilar welding.

Effects of Ar ion irradiation on the diffusion bonding joints of Zr55Cu30Ni5Al10 bulk metallic glass to aluminum alloy

1keV low energy argon ion beam was used to irradiate the surface of Zr55Cu30Ni5Al10 bulk metallic glass. Bulk metallic glass specimens irradiated for different times were used to join with Aluminum alloy by argon ion activated diffusion bonding. Compared with the joints using the as-cast bulk metallic glass, the tensile strength of the joints using irradiated specimens had a drastic improvement. Moreover, a crystalline layer was obtained in the BMG side of the joint interface using irradiated specimens. The improved joint quality was attributed to the local heating resulting from a crystallization behavior of irradiated surface layer which increases the probability of jumping the barrier to form the atom bonds, as well as the significant enhancement of the atomic diffusivity after crystallization.

Density, Permeability, Infiltration, and Absorption Used to Assess Quality of Hot-Mix Asphalt Longitudinal Joints

Longitudinal joint quality is critical to the successful performance of hot-mix asphalt pavements. The implementation of longitudinal joint quality specifications is gaining momentum in many states, with density being the most common quality parameter. However, distress at the joint is caused by the ability of air and water to enter the pavement structure, an ability that may be more compatible with a measure of permeability. The objective of this study was to provide guidance for the implementation of joint quality specifications by compiling information that more completely describes the relationships of density, absorption, permeability, and infiltration. On two resurfacing projects, eight joint construction techniques were used, and the ability of each to improve joint quality was assessed. In addition, joint quality was evaluated with regard to proximity to the joint. In general, the joint heater, joint stabilizer, and notched wedge construction methods were the best performers in regard to density and permeability. Traditional rolling methods exhibited lesser quality, indicating that additional measures may be necessary to generate acceptable levels of joint quality. For the most appropriate measure of quality, permeability and infiltration adequately discriminated between varying levels of joint quality, as did nuclear density. Reasonable relationships were developed between density, permeability, infiltration, and absorption. Thus, density measurements can be used for assessing joint quality and simultaneously protecting against excessive levels of permeability.

Evaluation of Longitudinal Joint Construction Techniques for Asphalt Pavements in Tennessee

Longitudinal joints between lanes of hot-mix asphalt (HMA) pavements are commonly susceptible to moisture damage and other failures. In 2006, the Tennessee Department of Transportation (TDOT) identified longitudinal joint failure as one of the major distresses for local HMA pavements. It was determined necessary to evaluate available practices and technologies to reduce longitudinal joint failure. This paper presents the results from a field project in Tennessee constructed with seven different longitudinal joint construction techniques. These techniques could be divided into three major categories: joint adhesives including an anionic emulsion and a polymerized emulsion commonly used by the TDOT, a hot-applied high-polymer rubber, and a high-polymer emulsion; joint sealers including a polymerized maltene emulsion and a polymerized agricultural oil; and infrared joint heater. Laboratory tests were conducted on the field cores taken from the test sections constructed with these techniques. Based on the different mechanisms of these techniques, the following laboratory tests were employed: air void content, permeability, indirect tensile (IDT) strength, and water absorption tests. Field cores were also scanned with the X-ray computed tomography to investigate the effect of infrared heating on air void distribution. The test results showed general consistency in the joint quality; i.e., the lower the air void content, the lower the permeability and the higher the IDT strength. The infrared heater exhibited the best effectiveness in improving joint quality among all the joint construction techniques used in this study.

Practical Application of High Efficiency Twin-Arc TIG Welding Method (Sedar-TIG) for Pclng Storage Tank

A high efficiency TIG welding method was developed, which employs two electrodes within a single torch. This system is shown to produce consistent penetration in the groove wall and high deposition rate, making it well suited for application to the construction of large capacity LNG storage tanks and thick walled pressure vessels. Authors have applied this new TIG welding method in the construction of an inner tank for PCLNG storage tank. The material of tank wall is 9% Ni steel. Proper welding condition for vertical and horizontal welding position (peripheral welding position) were selected, and sound joint properties were confirmed. For the practical application, stable welding procedures were developed. In result, it achieved greatly improving joint quality and reducing construction time.

Process modeling with neural networks for pulsed GMAW braze welds

In this work, an improved weld-bead geometry and reduced sheet metal distortion were desired in a weld-brazing process used to finish exterior sheet metal prior to painting. Numerical modeling techniques are widely used to model welding processes, but accurate methods for modeling pulsed-welding processes are lacking. Instead, a continuous empirical model of the welding process was developed using a statistically designed experiment and a neural network for data analysis. Graphical methods were used to simulate the process, and robust parameter design techniques were used to analyze response surfaces produced by the model. Using the response surfaces, possible welding procedures were generated and tested. A new process that resulted in improved joint quality was implemented in production.