Improvement Of Joint Strength Research Articles

Effect of joining temperature on the microstructure and strength of W–steel HIP joints with Ti/Cu composite interlayer

Cylinders of tungsten and P91 steel are successfully joined by using a hot isostatic pressing (HIP) method with the help of the combination of Ti and Cu as interlayer. The effect of joining temperature on the interfacial microstructure and tensile strength of the joints are investigated in this work. No intermetallic compound was observed at W/Ti and Cu/steel interfaces of the joints bonded at the temperature studied. However, the electron probe microanalysis and X–ray diffraction analysis reveal that Ti2Cu, TiCu, Ti3Cu4 and TiCu4 formed at Ti/Cu interface of the joint bonded at and below 950 °C. Further increase of the joining temperature caused the significant reduction in the intermetallic compounds at the Ti/Cu interface, and at 1050 °C the intermetallic compounds totally disappeared after joining due to the effect of liquid formation at Ti/Cu interface. The results indicate that the Ti/Cu liquid forming interlayer can be used to improve joint strength.

Review on underwater friction stir welding: A variant of friction stir welding with great potential of improving joint properties

Abstract Friction stir welding (FSW) is a solid-state welding process which is capable of joining materials which are relatively difficult to be welded by fusion welding process. Further, this process is highly energy-efficient and environmental-friendly as compared to the fusion welding. Despite several advantages of FSW over fusion welding, the thermal cycles involved in FSW cause softening in joints generally in heat-treatable aluminum alloys (AAs) due to the dissolution or coarsening of the strengthening precipitates leading to decrease in mechanical properties. Underwater friction stir welding (UFSW) can be a process of choice to overcome these limitations. This process is suitable for alloys that are sensitive to heating during the welding and is widely used for heat-treatable AAs. The purpose of this article is to provide comprehensive literature review on current status and development of UFSW and its importance in comparison to FSW with an aim to discuss and summarize different aspects of UFSW. Specific attention is given to basic principle including material flow, temperature generation, process parameters, microstructure and mechanical properties. From the review, it is concluded that UFSW is an improved method compared with FSW for improving joint strength. Academicians, researchers and practitioners would be benefitted from this article as it compiles significantly important knowledge pertaining to UFSW.

An innovative method to join two polymer rods through Y-shape extrusion channel

In everyday life polymer structures are widely used as advance structural material for several products due to low weight and high strength to weight ratio. Bonding of polymers are very difficult to achieve during heating (welding) process and hence present paper focussed on an eco-friendly deformation technique to join two round shape polymers parallel to each other. In this technique two similar nature of polymer rod joined when passed through preheated Y-shape extrusion channel maintaining a constant die temperature and constant reduction ratio. Universal testing machine (UTM) is used to extrude the polymer and joint strength of extruded samples are characterised by using numbers of destructive testing such as tensile, compression, peeling, lap shear, and micro hardness test. In peeling and lap-shear test, failure does not occur along the joint of extruded sample showing robustness of bonding. Base polymer which does not have any joint section failed early as compared to extruded sample during peeling and lap shear test. Hardness of joint section is higher than heat affected zone (HAZ) as well as base polymer as observed through micro hardness test. Concave shape of joint is an indication of better interlocking and hence improvement of joint strength as compared to other solid state joining. Polymers processed at 2/3rd of melting point have thin joint and void free interface as observed through its microstructure.

Challenges and advances in laser welding of dissimilar light alloys: Al/Mg, Al/Ti, and Mg/Ti alloys

With the growing demand for vehicle weight reduction and the increased application of multimaterial design, it is imperative to address the challenges of welding dissimilar light alloys. This paper presents a review on laser welding of Al/Mg, Al/Ti, and Mg/Ti alloys, with focus on the techniques used to suppress the formation of brittle intermetallic compounds (IMCs) and improve joining mechanism. For Al/Mg joints, studies have shown that the use of structural adhesives, the use of interlayers such as Ce, Ni, Ti, and Fe foils and Zn-Al filler metals, and hybrid adhesive-interlayers could suppress the formation of brittle IMCs and improve joint strength. The formation of brittle IMCs during laser welding of Al/Ti alloys could be minimized by offsetting the laser beam at an appropriate distance towards either the Al or Ti alloy, the use of split-beam laser with appropriate joint design, the use of high welding speed, improving the laser energy distribution, and the use of V-groove with Al-Si filler metals. For Mg/Ti alloys, offsetting the laser beam at an appropriate distance towards the Mg alloy, the use of AZ series Mg alloy-based filler wires, and coating the Ti alloy with Ni were found to facilitate the joint formation and improve the joint strength.

Application of hot forming quenching on patchwork blank using two-stage refilled friction stir spot welding

The purpose of this study is to apply Hot Forming Quenching (HFQ) on Patchwork Blank of AA6061 using Two-stage refilled Friction Stir Spot Welding (TFSSW). TFSSW is a developed joining method to improve joint strength of conventional Friction Stir Spot Welding (FSSW) and it consists of two stages. The first stage is a conventional FSSW process and second stage is a refilling process for refilling keyhole. The Design of Experiment (DOE) was used to optimize the TFSSW process parameters. A hat shape forming test was performed using a patchwork blank manufactured with the optimal process parameters to investigate validity of applying HFQ. Formed hat shape part was sequentially heat treated with artificial aging (T6) condition. The hardness of the weld zone was measured to confirm a drop of mechanical property in comparison with the conventional cold forming, which shows the validity of HFQ application to patchwork blank using TFSSW.

Optimization of welding parameters of hot plate welded PC/ABS blends by using the Taguchi experimental design method

This study aims to investigate the influence of welding parameters in hot plate welding (HPW) process of polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blends using Taguchi method. Three welding parameters, namely the plate temperature, heating time, and welding displacement, were optimized in terms of joint strength using the results of tensile tests. Taguchi experimental design method is implemented as a statistical design of experiment technique so as to set the optimum welding parameters and determine the optimal levels. For HPW of the specimens, the combination of process parameters based on three levels of L9 orthogonal array was utilized. The signal to noise ratio and the analysis of variance were employed to find the optimum levels and to indicate the impact of the welding parameters on joint strength after tensile tests of the welded joints were carried out. It was shown that it might achieve the improved joint strength using 290 °C of plate temperature, 1.25 mm of welding displacement,...

Fast responsive control of current and voltage waveforms for gas metal arc brazing of thin zinc-coated steel sheets

Thin zinc-coated steel sheets are brazed together using a copper-silicon filler alloy and employing a gas metal arc process with dynamic control of current and voltage transients. The actual heat inputs for different wire feed rates during brazing were estimated from the recorded current and voltage transients. Lowering of heat input was aimed at to reduce the thermal distortion and the thickness of the interface layer with intermetallic compounds while ensuring a sound, continuous bead profile. The influence of overall heat input on the thermal distortion, joint strength and interface layer thickness is examined using Fourier number that depicts a ratio of the rate of heat dissipation to accumulation. An increase in brazing speed and a decrease in the wire feed rate resulted in reduced heat input, higher Fourier number, thinner interfacial layer and improved joint strength. The brazing induced thermal distortion reduced with increase in Fourier number. Irrespective of the sheet thickness, a range of Fourier number in between 0.22–0.26 provided brazed joint strength up to 96 % of that of the base metals with minimum interface layer thickness and thermal distortion.

Microstructure and brazing mechanism of porous Si3N4/Invar joint brazed with Ag-Cu-Ti/Cu/Ag-Cu multi-layered filler

Porous Si3N4 was brazed to Invar alloy in this study, and Ag-Cu-Ti/Cu/Ag-Cu multi-layered filler was designed to inhibit the formation of Fe2Ti and Ni3Ti intermetallic compounds. The effects of the brazing temperature and the thickness of Cu interlayer on the microstructure and mechanical properties of brazed joints were investigated. The typical microstructure of the joint brazed with multi-layered filler was porous Si3N4/TiN+Ti5Si3/Ag-Cu eutectic/Cu/Ag-Cu eutectic/Cu-rich layer+diffusion layer/Invar. When the brazing temperature increased, the reaction layer at the ceramic/filler interface grew thicker and the Cu interlayer turned thinner. As the thickness of Cu interlayer increased from 50 to 150μm, the joint strength first increased and then decreased. In this research, the maximum shear strength (73MPa) was obtained when being brazed at 1173K with a 100μm Cu interlayer applied in the filler, which was 55% higher than that brazed with single Ag-Cu-Ti brazing alloy and had reached 86% of the ceramic. The release of residual stress and the barrier effect of Cu interlayer to inhibit the formation of Fe2Ti and Ni3Ti intermetallics played the major role in the improvement of joint strength.

Six-week physical rehabilitation protocol for anterior shoulder dislocation in athletes.

Anterior shoulder dislocations are common in young athletes. The mechanism for the first or primary shoulder dislocation may involve a collision or a fall typically with the arm in an abducted and externally rotated position. The aim of this study was to design a physical rehabilitation program using the elastic band and resistive exercise to improve joint strength and range of motion in individuals diagnosed with a first-time shoulder dislocation. Twelve physically active males with a first-time acute shoulder dislocation were asked to volunteer. Participants began a physical rehabilitation program 2 weeks after the shoulder dislocation, which was confirmed by a referring physician. The rehabilitation program was 6 weeks in duration and required the participants to engage in progressive resistive loads/duration using elastic bands and weights 5 days per week. Pretest and posttest measures included shoulder strength and range of motion. All outcome measures were compared between the injured and uninjured shoulder, which served as the control condition in this study. There were statistically significant differences between the injured and uninjured shoulder for measures of strength and range of motion during pretests (P<0.01) but not post-tests (P<0.53). Finally, there were no differences between shoulders in regards to the volume measure suggesting that any changes in muscle atrophy or swelling were not detected. The physical rehabilitation program proposed in this study was effective at improving strength and range of motion in the injured shoulder as evidenced by the similarity in posttest values between the injured and uninjured shoulder.

Weld ability of dissimilar material of 304 stainless steel and polyethylene terephthalate

ABSTRACTGas tungsten arc welding was used to join dissimilar materials: 2-mm-thick plate of 304 stainless steel and 1.5-mm-thick polyethylene terephthalate (PET) plastic sheet. The joints of 30 mm in width possessed strong tensile shear loads of approximately 2.1 kN at the maximum and the tensile strength is 47.6 Mpa, which is almost the similar to shear load and tensile strength of the pure PET (the strength of PET is about 45 Mpa). The effect of main process parameters on the joint strength was investigated through experiments. It is found that appropriate amount of small bubbles is helpful to improve the strength of the joint. The infrared spectra analysis and energy-dispersive spectrometer results of the joints demonstrated that 304 and PET were bonded together through the reaction of carbonyl and metallic element in the joint, which lead to the, the chemical bond formation and the resulted in significantly improved joint strength.

Effect of modified flux on MIG arc brazing-fusion welding of aluminum alloy to steel butt joint

Pulsed MIG arc brazing-fusion welding process was applied to realize the butt joining of galvanized steel and 5052 aluminum alloy with no enclosed slot or groove adopted. A modified flux mixture was developed to improve the butt joint performance. After applying the modified flux, weld appearance became better and the spreadability of filler metal was also greatly improved. During brazing-fusion welding process, flux floating on the surface of welding pool weakened the surface tension between filler metal and Fe and reduced the evaporation of Zn, which both led to the greatly enhanced spreadability. The analysis of intermetallic compounds (IMCs) at brazed interface showed that Fe3Al was formed at upper side of steel plate, while Fe2Al5 was formed at other areas with the consideration of its lowest Gibbs free energy under certain temperature range. With modified flux, the tensile strength of the joint could reach up to 120MPa, which was about 60% of that of 5052 aluminum alloy base metal. From the fractured surface, two different fracture modes were identified, tear fracture and intergranular fracture, which confirmed that joint fractured in a brittle mode. The crack initiated at the front side of brazed interface due to the thicker IMCs layer, then propagated to the surface before the whole joint failed. The improved spreadability of filler metal on the top and back sides of steel plate due to the application of flux, contributed to the improvement of joint strength.

Joint properties of ultra thin 430M2 ferritic stainless steel sheets by friction stir welding using pinless tool

In this study, friction stir butt welding of ultra thin 430M2 ferritic stainless steel sheets with satisfactory joint properties has been achieved using a pinless WC-Co tool. Friction stir welding was carried out at a tool rotational speed of 900rpm and a travel speed of 96mm/min. FSW joints were welded completely without any unwelded zone resulting from smooth material flow, despite of being adopted pinless tool. It was revealed that the maximum tensile strength of FSW welds was 468MPa, equivalent to the tensile strength of base metal. Notably, it was found that sigma phase formation in FSW welds is suppressed compared with that of arc welds, resulting in improving joint strength. These results suggest that the low input process of FSW is an effective substitute for the conventional fusion welding GTAW in ultra thin ferritic stainless steel plate.

Mechanical properties and interface morphology of Mg/Al ultrasonic spot weld bonding welds

This paper investigates the mechanical properties and interface morphology of Mg/Al ultrasonic spot welding (USW) joint, adhesive bonding (AB) joint and ultrasonic spot weld bonding (USWB) joint. The peak load and fracture energy of USWB joint increased significantly compared to that of USW joint and AB joint. The USWB joint presented a hybrid fracture mode which was composed of the delamination failure at adhesive/Mg interface, cohesive failure within the adhesive and cleavage failure in the weld zone. The interface morphology suggested that USWB joint exhibited fewer defects in the cured adhesive matrix and elevated connection density of adhesive/metal interface, which improved joint strength and altered the fracture mode.

Improvement in Joint Strength of Spray-Deposited Al-Zn-Mg-Cu Alloy in Underwater Friction Stir Welding by Altered Temperature of Cooling Water

We improved the joint properties of spray-deposited Al-Zn-Mg-Cu alloy during underwater friction stir welding at cooling media temperatures of 8.6, 24.8 and 58.6 °C, respectively. The joint welded at high temperature (58.6 °C) showed a high tensile strength (467.18 MPa) and improved elongation. Its thermal cycle indicates preheating and slow cooling, which created a mild and uniform temperature gradient on both sides of the joint. DSC, SEM and EDS, and XRD analyses indicate that high-temperature cooling medium facilitated re-dissolution of the strengthening phases in the matrix, to strengthen the joint. Al32(Mg,Zn)49 exhibited a semi-coherent structure with matrix detected in the joint welded in a high-temperature medium. The high-temperature cooling medium is most efficient for joint optimization.

A new laser joining technology for direct-bonding of metals and plastics

A direct laser joining technique for bonding plastics to metals, namely laser-assisted metal and plastic (LAMP) joining was developed about eight years ago. Notwithstanding the successes that have been obtained for LAMP, the inherent features of laser-induced bubbles in the joint remains a major concern. In this research, a new laser joining technology with the aid of ultrasonic vibration has been developed to bond plastics to metals with improved joint strength. Experiments have been conducted to join polyethylene terephthalate and titanium using this new technology; preliminary results have been encouraging. With the aid of ultrasonic vibration, joint strength can be improved by as much as four times greater than that produced by the conventional LAMP process. This improvement is largely caused by the formation of a thicker chemically bonded metal-plastic interface, which was supported by the results of an XPS analysis conducted across the joint interface.

Transient Liquid Phase Diffusion Bonding of 6061Al-15 wt.% SiC p Composite Using Mixed Cu-Ag Powder Interlayer

Microstructure and shear strength of transient liquid phase diffusion bonded (560 °C, 0.2 MPa) 6061Al-15 wt.% SiCp extruded composite using a 50-µm-thick mixed Cu-Ag powder interlayer have been investigated. During isothermal solidification that took 2 h for completion, a ternary liquid phase formed due to diffusion of Cu and Ag in Al. Subsequent cooling formed a ternary phase mixture (α-Al + CuAl2 + Ag2Al) upon eutectic solidification. With mixed Cu-Ag powder interlayer, isothermal solidification was faster than for pure Al joints made using a 50-µm-thick Cu foil interlayer and for the composite joints made using a 50-µm-thick Cu foil/powder interlayer under similar conditions. The presence of brittle eutectic phase mixture (CuAl2 + Ag2Al) led to poor joint strength at short TLP bonding times. The mixture disappeared upon isothermal solidification with a 2-h hold yielding improved joint strength even with solidification shrinkage in the joint. Increased holding time (6 h) erased shrinkage via solid state diffusion and yielded the highest joint strength (87 MPa) and fair joint efficiency (83%).

Assessment of the bending strength of mortise-tenon and dovetail joints in leg-and-rail construction using Klainedoxa gabonensis Pierre Ex Engl. and Entandrophragma cylindricum (Sprague) Sprague

ABSTRACTMortise-tenon joints for working chair construction fail under bending stresses. Dovetail joints could offer an alternative due to their resistance to bending. However, furniture joint strength depends on the design of the parts and appropriateness of the timber for the construction. Information on timber-joint design combination that would improve joint strength is lacking for most secondary timbers with prospects for joinery-making. This study assessed the bending strengths of two joint designs (dovetail and mortise-tenon) for leg-and-rail construction from Klainedoxa gabonensis (a secondary timber) and Entandrophragma cylindricum (popularly used for furniture). Dovetail joints were stronger than those of mortise-tenon. For both joints, the design with longer, wider and thicker tails and tenons [large-sized (Type LS)] was stronger than its counterpart [small-sized (Type SS)]. Joints manufactured from K. gabonensis were also stronger than those from E. cylindricum. Thus, K. gabonensis could be an appropriate material for joinery/furniture production. This would broaden the raw material base for the furniture sector. However, its working chairs designed with Type LS dovetail joints would resist bending forces better and ensure stronger furniture than mortise-tenon. To offset frequent furniture breakdown, this study provides designers with reliable information regarding joint strength from different timbers to guide selection.

Welding parameters and joint strength optimization during friction stir welding of high density polyethylene (HDPE) using the Taguchi method

Abstract The aim of this study is to investigate the effect of important process parameters and tool parameters on joint strength in fiction stir welding process of high density polyethylene (HDPE) using the Taguchi experimental design method. The tool rotation, feed rate and tool shoulder diameter were considered as varying parameter and used to fabricate the joints. The quality of the joint was evaluated by examining the characteristics of the joint as a result of ultimate tensile strength. For friction stir welding of the plates, the experiments were arranged by using Taguchi's L9 orthogonal array in randomized way. From the analysis of variance and the signal-to-noise response graphs, the significant parameters and the optimal combination level of the parameters were obtained. It was found that using a tool rotation of 1600 rpm, a feed rate of 20 mm·mm−1 and a shoulder diameter of 20 mm, an improved joint strength can be obtained. A confirmation run is also performed to prove the effectiveness of the Taguchi method. The results show that joint strength was improved by about 25% compared with the initial welding parameters.

Mechanical Behavior of Clinched Sheet Material Joints and Strength Design Procedure

Clinching is an effective joining technique for lightweight sheet materials that are difficult or impossible to weld. A theoretical model for clinched joints in metal sheets was established and a design method for improving joint strength by selecting different clinching tools was proposed. The analytic model is defined as a function of the neck-thickness and the undercut, which are the key parameters of joint geometry. Based on the analytic model, the design method of clinched joint strength that can satisfy required strength was proposed. Clinching experiments were conducted with 2.00 mm thick aluminium alloy 5052 sheets. Various conditions were used during the clinching process to validate the joint strength model. Tensile-shear strength of clinched joints was measured by a servo-hydraulic testing machine. The calculated joint strength was in good agreement with the experimental results.

Modifying a thermoplastic polyurethane for improving the bonding performance in an adhesive technical process

The present work describes pretreatment processes of thermoplastic polyurethane elastomer (TPU) material, used as an adhesive in powder form, that results in the increased peeling resistance of joints. The TPU in powder form is an environmentally-friendly adhesive and provides safer bonding conditions in the shoe manufacturing industry. TPU particles are soft and require an anti-blocking agent to prevent agglomeration. However, particles covered by such an anti-blocking agent may account for a low peeling resistance in the resulting joints. To overcome this disadvantage, two pretreatment processes for the TPU adhesive were evaluated. The results of a two-step wet washing process, representing a conventional solvent-based procedure that involves both the application of a solvent and a powder separation step, are compared to the performance of a one-step dry plasma treatment process. The process type did not affect the size and agglomeration behavior of the particles, and both processes were effective in improving joint strength according to peeling test results. Spectroscopic investigation of the particle surface after washing or plasma treatment indicated some zinc concentration, which is interpreted to result from the anti-blocking agent. The crystallinity of the TPU, investigated by thermal analysis, was higher after pretreatment. The obtained results indicate that TPU in powder form is a versatile adhesive for the shoe industry with a safer application compared to solvent based adhesive systems.