Increase In Joint Strength Research Articles

Uniones adhesivas de traslape simple de compuestos

El siguiente artículo muestra un estudio de uniones de traslape simple de materiales compuestos, con y sin modificación. La falla de este tipo de uniones es causada por el alto esfuerzo de despegue en dirección perpendicular a la aplicación de la fuerza presentado en la singularidad geométrica. Se muestra que la resistencia de la unión es afectada por factores como la preparación de la superficie, el proceso de curado del adhesivo, y la limpieza. Ambas configuraciones, con y sin modificación, son comparadas. Se muestra que la unión de traslape simple modificada, tiene una mayor resistencia que sin modificación cuando se remueve el exceso de adhesivo en la singularidad geométrica. Sin embargo, el bajo incremento en la resistencia de la unión y la complejidad para manufactura, deja a consideración del fabricante la decisión respecto a qué tipo de unión usar.

The effect of modified fibrous fillers on the adhesive properties of polychloroprene-based adhesive compositions

A number of fibrous fillers modified with the product of interaction between phosphorus-boron oligomer and triethanolamine were used to assess their influence on the adhesive properties of polychloroprene-based adhesives. As a result, a significant increase in joint strength was observed.

Diffusion Brazing of Al6061/15 Vol. Pct Al2O3p Using a Cu-Sn Interlayer

Diffusion brazing of Al-6061 alloy containing 15 vol. pct Al2O3 particles was attempted using Cu-Sn interlayer. Joint formation was attributed to the solid-state interdiffusion of Cu and Sn followed by eutectic formation and subsequent isothermal solidification. Examination of the joint region using scanning electron microprobe analyzer (EPMA), wavelength dispersive spectroscopy (WDS) and X-ray diffraction (XRD) showed the formation of intermetallic phases such as Al7Cu3Mg3, Mg2Cu6Al5, Cu3Sn, and Mg2Sn. The results indicated an increase in joint strength with increasing bonding time giving the highest joint shear strength of 94 MPa at a bonding duration of 3 hours.

Cold-Metal-Transfer Arc Joining of Al 6K32 Alloy to Steel Sheets

In the arc joining of dissimilar metals, such as steel and Al alloys, a brittle intermetallic phase is formed at the interface. The thickness of this phase should be minimized because it causes solidification cracking. Cold metal transfer (CMT) arc welding technology is widely used throughout the automotive industry because of low spatter formation and heat input. A CMT arc was used to investigate arc joining between the Al 6K32 alloy and mild steel sheets. The behaviors of the interface layers were analyzed on the basis of filler wires and the coating type of the steel sheets. The thickness of the intermetallic phase was maintained under 10 μm and increased joint strength was achieved by selecting the appropriate filler wire and coating type.

Analysis for relative motion in ultrasonic welding of aluminium sheet

Ultrasonic welding of pure aluminium sheets was observed with a high speed video camera. The dynamic vibration behaviours of a welding tip and aluminium sheets were analysed using the digital image correlation method. The welding process consisted of the following three stages. First, the upper specimen in contact with the weld tip vibrated. The formation of partially welded regions was confirmed at this stage. Second, the vibration amplitude of the upper specimen decreased, while friction between the weld tip and the upper specimen increased. Growth of the partially bonded region was confirmed in the second stage. Third, the welding part began to plastically deform owing to the clamping force. The joint strength reached its maximum value at the third stage. The analysis demonstrated that the relative motion between the weld tip and the upper specimen predominantly affected the increase in joint strength.

Test Study on Effect of Joint on Rock Mass Mechanical Property

Strength, elastic modulus and failure modes of samples with different joint dip angle, joint continuity degree, joint set and joint width under uniaxial compressive load are studied by similar material tests. To the sample with single joint, its strength, elastic modulus and failure mode are controlled by joint dip angle to much extent, and it will shear and slip along or split across joint face to fail, in which sample’s strength and elastic modulus is minimum corresponding to the first failure mode. To the jointed sample with different joint continuity degree, its strength and elastic modulus decrease with joint continuity degree, and effect on sample’s strength is much more serious. With increase of joint set, sample’s strength and elastic modulus gradually decrease. With increase of joint width, strength and elastic modulus decreases, and effect on sample’s strength is much more serious.

Effect of annealing treatment on joint strength of aluminum/steel friction stir lap weld

In this work, the effects of the annealing temperature and duration on the joint strength of the steel/aluminum lap joints made by friction stir welding were investigated. The strength of the welded joints was evaluated by shear-tensile test. Formation of intermetallic layer at the joint interface and the fracture locations were studied using scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD). The results indicated that longer time of annealing treatment resulted in higher joint strength at 300 and 350°C and that the rate of the increase in joint strength with time was about 72% higher at the latter temperature than at the former one. In comparison with the atomic diffusion through the joint interface, the formation and development of a thin intermetallic layer in the joint after annealing at 300 and 350°C (with the thickness of less than 0.49μm) may have a higher impact on the improvement of the joint strength. However, the joint strength decreased with the increase in annealing duration at 400°C. In the samples annealed at 400°C for more than 90min, the joint strengths were degraded drastically. From the joint strength point of view, intermetallic layer thickness of ∼2.6μm was a critical thickness.

Kinetics and mechanism of formation of adhesive joints based on ethylene-vinyl acetate copolymers

The structure of transient zones in PVC-poly(ethylene-co-vinyl acetate), PET-poly(ethylene-co-vinyl acetate), and steel-poly(ethylene-co-vinyl acetate) adhesion systems is studied. It is shown that PET-poly(ethylene-co-vinyl acetate) and PVC-poly(ethylene-co-vinyl acetate) are related in incompatible and partially compatible systems, respectively. In the temperature range 100–180°C, diffusion coefficients and the activation energy of diffusion are determined. The depth of penetration of copolymer macromolecules into the PVC phase is calculated. The kinetics of adhesive-joint formation is studied. For all systems, the increase in joint strength has a common character; for each temperature, the steady state is attained. The results are analyzed in terms of wetting and diffusion theories. Both models satisfactorily describe the kinetics of joint formation in compatible and incompatible systems (including steel-poly(ethylene-co-vinyl acetate). The effective activation energy of the kinetics of adhesive-joint formation is determined and compared with the activation energies of diffusion, the viscous flow of copolymers, the β transition, and the rate of conformation rearrangements in the surface layers of ethylene-vinyl acetate copolymers. It is suggested that the data obtained can be generalized in terms of the Bikerman theory of a “weak boundary layer.”

Mechanical properties of A6082 welded joints with Nd–YAG laser

Weldability of A6082 with Nd–YAG laser was investigated to explain the advantages over the conventional MIG process. It is concluded that rapid cooling rate in heat-affected zone (HAZ) contributes to increasing joint strength and improvement durability against liquation cracking in HAZ during Nd–YAG laser welding. This is why rapid cooling rate is enough to prevent crossing the C-curve for precipitation of β′ and small volume of weld metal is enough to reduce shrinkage strain during solidification. And the joint strength increased with an increase of manganese content in the base metal, but by contraries the minimum hardness in HAZ where the fracture occurred in the tensile test decreased. This may be attributed to the prevention of intercrystalline embrittlement due to the addition of manganese in case of Al–Mg–Si series alloys with excessive Si content.

Small-scale projection lap-joint welding of KOVAR alloy and SPCC steel

The objective of this study was to investigate the effect of projection heights and operating conditions on projection collapse, nugget size, and joint strength of KOVAR alloy and steel plate cold-rolled commercial (SPCC) grade in small-scale projection welding of dissimilar metals. All welds were produced with a capacitor charging power supply. Three projection designs with different heights were used. Harris and Riley-type projection was embossed on the SPCC steel sheets. Nugget size was estimated using a peel test. Joint strength was evaluated using a tensile-shear test. The results indicated that a low-level projection has a positive effect, increasing the load-bearing capacity of projection. The nugget diameter and joint strength increase as the weld current and projection height increase. Increasing the electrode force will produce a small nugget. Nugget size is a good indicator of the strength of the welded joint. This study also found that a cold-collapse ratio of approximately 25% produces the highest tensile-shear strength of small-scale projection lap-joint welds.

Influence of FRP anchor fan configuration and dowel angle on anchoring FRP plates

To enhance the strain capacity of fibre-reinforced polymer (FRP) plates which have been bonded onto reinforced concrete (RC) members for strengthening purposes, FRP anchors can be utilised. Research on the characterisation of FRP anchors is still quite limited though despite the increasing use of FRP anchors in practice. In order to reduce such a knowledge gap, this paper reports the results of 30 single-shear FRP-to-concrete joint tests of which 26 joints were anchored with FRP anchors of differing geometric configurations and four joints were unanchored controls. More specifically for the anchored joints, the connection of the FRP anchor to the FRP plate via so called fan fibres was varied in addition to the angle of anchor insertion and these test parameters represent fundamentally important anchor components which have not been researched to date. Failure modes, joint strengths, load–slip responses as well as FRP plate strain distributions are reported and a relationship relating the influence of anchor insertion angle to joint strength is provided. A maximum increase in joint strength of 160% on average above the unanchored control joints was achieved. In addition, the maximum strain resisted by the FRP plate, relative to its elongation capacity, was increased on average from 25% for unanchored control joints to 67% for some anchored joints.

Study on Nugget Diameter and Joint Strength of Dissimilar Metals in Capacitor Charging Projection Welding

The purpose of this study was to investigate the effect of operating conditions on nugget diameter and joint strength of KOVAR alloy and SPCC steel in projection welding of dissimilar metals. All projection welds were produced with a capacitor charging power supply. Harris and Riley type projection was embossed on SPCC steel sheet. The nugget diameter was estimated using a peel test. The lap-joint strength of projection welds was evaluated using a tensile-shear test. The results indicated that the nugget diameter and joint strength increase as the weld current increase. Increasing the electrode force will produce a small nugget diameter. The nugget diameter of projection welds is a good indicator of the lap-joint strength.

SAC 305솔더와 ENIG 기판의 접합강도에 미치는 저주파 수소라디칼처리의 영향

Joint strength between a solder ball and a pad on a substrate is one of the major factors which have effects on electronic device reliability. The effort to improve solder joint strength via surface cleaning, heat treatment and solder composition change have been in progress. This paper will discuss the method of solder ball joint strength improvement using LF hydrogen radical cleaning treatment and focus on the effects of surface treatment condition on the solder ball shear strength and interfacial reactions. In the joint without radical cleaning, voids were observed at the interface. However, the specimens cleaned by hydrogen-radical didn`t have voids at the interface regardless of cleaning time. The shear strength between the solder ball and the pad was increased over 120%(about 800gf) when compared to that without the radical treatment (680gf) under the same reflow condition. Especially, at the specimen treated for 5minutes, ball shear strength was considerably increased over 150%(1150gf). Through the observation of fracture surface and cross-section microstructure, the increase of joint strength resulted from the change of fracture mode, that is, from the solder ball fracture to IMC/Ni(P) interfacial fracture. The other cases like radical treated specimen for 1, 3, 7, 9min. showed IMC/solder interfacial fracture rather than fracture in the solder ball.

Experimental evaluation of the effect of clamping force and hole clearance on carbon composites subjected to bearing versus bypass loading

Abstract A series of carbon fibre laminate bearing versus bypass load tests were carried out investigating the effect of hole clearance, laminate lay-up, washer contact size and clamping force value. Explanations of the underlying effects that influence the results are discussed. The results compare well with literature but hole clearance was shown to increase joint strength when bypass loads are dominant, which seems counter intuitive, and has not been reported in literature.

Effect of plasma treatment and electron beam radiations on the strength of nanofilled adhesive‐bonded joints

AbstractThis investigation highlights the adhesion performance of carbon fiber‐ and glass fiber‐reinforced polyphenylene sulfide when joined by high‐performance neat epoxy adhesive and nanofilled epoxy adhesive. A significant increase in the surface energy of these materials is observed after the surface modification with atmospheric plasma treatment. An increase in surface roughness is observed after exposing the surface to plasma. Lap shear testing of untreated and plasma‐treated joints is carried out to correlate the improvement in adhesion properties with the joint strength. A considerable increase in joint strength is observed when the surfaces of these materials are modified by atmospheric pressure plasma. There is a further increase in joint strength when the composites are joined by nanofilled epoxy adhesive, and subsequent exposure to electron beam radiations results in minor increase in the joint strength. Finally, the fractured surfaces of the joints are examined and the analysis is performed. POLYM. ENG. SCI., 50:1505–1511, 2010. © 2010 Society of Plastics Engineers

Influence of Nanoclay on the Morphology, Adhesive and Mechanical Properties of Polysulfide Modified Epoxy Resin

Addition of nanoclay particles to a typical tertiary amine cured polysulfide modified epoxy adhesive leads to large increase in the single-lap shear strength of aluminum-aluminum joint. The nanoclay particles are very well dispersed (near fully exfoliated) in the polymer matrix even at 8 wt.% of nanoclay concentration. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies provide evidences for the excellent dispersion of the nanoclay platelets in the polymer matrix. The addition of nanoclay particle results in a significant increase in the elongation at break values along with the marginal increase in the tensile strength. The nanoclay provides good ductility to the epoxy-polysulfide adhesive by forming very flexible interface, which leads to less brittle composite having good strength. The increase in work to break (Wb) values by the addition of nanoclay represents the potential for dissipating a greater amount of energy during the bond rupture process of the lap shear test, and hence the adhesive strength increases. In addition, the increase in joint strength by the addition of nanoclay can also be attributed to the good interaction between the epoxy-polysulfide adhesive and the aluminum substrate in the presence of nanoclay.

Joining of Polycarbonate Ring/Disk to Metal Sheet/Shaft and its Easy Disassembly

For the possibility of easy disassembly of a joint assisted by strain recovery, the joint is fabricated with a cold rolled circular polycarbonate (PC) disk embedded in the center of an aluminium or a PC disk. Also, a shaft and a hollow circular disk are assembled by compressing or press fitting a cold rolled PC ring into the gap between them. First, the cold rolled polycarbonate disk is heat treated and the change in geometry is examined. Secondly, in order to evaluate joint strength, shear force and torque of the assembled joints are discussed with regard to reduction in thickness, tool clearance and interference. Lastly, joints are heat treated and the disassembly is checked. The cold rolled disk is recovered with the temperature 190°C for 20min. In embedding, disk compression in addition to rolling reduction is effective in increasing joint strength. In fabricating the shaft/disk joint, deformation of polycarbonate was not effective due to the recovery in room temperature after joining, while press fitting of the polycarbonate ring could fabricate the assembly. Heat treatment helped the joint to be automatically disassembled. The directly joined parts became completely apart, but the shaft/disk joint was disassembled only between the ring and the disk.

Fatigue performance of metallic reverse‐bent joints

ABSTRACTAdhesively bonded lap shear joints have been investigated widely and several ideas have been proposed for improving joint strength by reducing bondline stress concentrations. These include application of adhesive fillets at the overlap ends and use of adhesive with graded properties in the overlap area. Another, less common, approach is to deform the substrates in the overlap area in order to obtain a more desirable bondline stress distribution.Previous work carried out by the authors on a number of different substrate materials indicated that a reverse‐bent joint geometry is useful for increasing joint strength. Results from static stress analysis and experimental testing demonstrated that significant improvements could be achieved. This paper presents results of further work carried out to assess the fatigue performance of reverse‐bent joints. Substrates with different yield and plastic deformation characteristics were used and the effects of different overlap lengths on strength were examined. The results of this research show that the improvements obtained under static tests conditions translate to even higher benefits in fatigue. The paper also explains the failure mechanism of the joints under fatigue loading.

Dissimilar friction stir spot welding of low carbon steel and Al–Mg alloy by formation of IMCs

Dissimilar lap joints of low carbon steel and Al–Mg alloy were obtained by friction stir spot welding. Mechanically mixed layer between top and bottom plates was not formed at the weld nugget due to the limited tool penetration and the pin height of welding tool lower than the thickness of Al plate laid in top side. These welding conditions made it possible to weld steel plate using welding tools made out of a general tool steel. With increasing tool penetration depth (TPD), tensile shear force of joint increased and maximum value of 3·0 kN was obtained at the TPD of 0·5 mm, but excessive tool penetration beyond 0·5 mm was caused in a deformation of Al plate of top side. In the result of interface observation, interaction layer was formed between Fe and Al alloy, which was constituted by various intermetallic compounds (IMCs). Consequently, the size of strongly bonded area containing Fe3Al and Fe4Al13 IMCs increased with TPD, which resulted in the increase in joint strength under the limited TPD.

Influence of Wood Welding Frequency on Wood Constituents Chemical Modifications

Interesting chemical differences betwen weldlines obtained at 100 Hz and 150 Hz frequencies in linear vibration wood welding were observed by FT-IR and 13C NMR. An increase in the proportion of unoxidized phenolic groups in the lignin is observed by FT-IR and the increased joint strength observed is ascribed to the improved adhesion derived from this. The much decreased level of oxidation due to the much shorter welding time possible at 150 Hz was clearly observed by 13C NMR by a marked decrease, even disappearance, of the presence of dark coloured quinones in the weldline at 150 Hz. This yielded colourless weldlines.