Papers by Keyword: Joint Strength

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Authors: Omid Bahman Dehkordi, Ali Mohamad Hadian
Abstract: Bismuth oxide, due to its low melting point was selected as filler for joining alumina to alumina using Transient Liquid Phase (TLP) method. For this purpose a thin layer of bismuth oxide was placed as an interlayer between the ceramic bodies. To study the effect of time and temperature on the mechanical properties of the joined samples, the joining tests were carried out in 900, 1000 and 1100°C for various times. The mechanical properties of the joined samples were measured using shear testing method. To investigate the microstructure of the joining area, the cross section ofthe joints were studied using scanning electron microscope (SEM) and X-ray diffraction method. The results showed that longer joining times results in higher mechanical properties of the joints. The highest joint strength of about 80 MPa was obtained for the sample joined in 900°C for 10hour.
136
Authors: Naho Kaneko, Tomohiro Sasaki
Abstract: Ultrasonic spot welding of galvanized steel sheets has been conducted to investigate formation process of the weld microstructure, and effect of zinc coat on joint property. The joint strength showed a rapidly increase at the weld time of 0.8s, and it has the maximum value over 1.0 s. In the weld time range from 0.1s to 0.8s, fracture occurred in zinc coat/ steel interface. In contrast, the fracture partially occurred in the base steel in the weld time over 1.0s, and concaves in which the steel substrate of one specimen partially remains on the other specimen were observed. The formation process of weld microstructure of ultrasonic welding was proposed to be a two-steps process. First, zinc coat in the interface was mechanically removed by the vibration and clamping force, and some zinc particles dispersed in the weld interface. Second, the zinc particles melted due to the friction, and partially bonded regions were simultaneously formed around the zinc particles. The partially bonded regions were stirred with the steel substrate as the weld time increased. The joint strength increased by development of the stirred zone. At the weld time over 1.2s, the joint strength decreased due to growth of crack around the stirred zone.
332
Authors: Atsushi Watanabe, Takehiko Watanabe, Tomohiro Sasaki
Abstract: Ultrasonic welding between SS400 mild steel sheet and aluminum alloy A5052 sheet containing magnesium was conducted. In this study, authors investigated the influence of ultrasonic welding condition on the mechanical properties and the interface microstructure of a joint, and examined the effect of an insert metal to improve the joint strength. The main results obtained in this study are as follows. It was possible to ultrasonically weld SS400 mild steel sheet and A5052 sheet. When the clamping force was varied keeping the welding time constant for 1s, the joint strength showed the maximum at the clamping force of 588N and it decreased with increasing the clamping force because the frictional action at the interface decreased with it. When the clamping force was kept constant at 588N and the welding time was varied, the joint strength reached the maximum at the welding time of 2.5s, followed by decreasing in the joint strength welded at 3s welding time due to the formation of Fe2Al5 intermetallic compound at the interface. Using insert metal of commercially pure aluminum successfully improved the joint strength and the strength of the joint welded at 3s welding time was about three times larger than that without the insert metal.
627
Authors: Sandeep Kumar, Abhishek Upadhyay, Pal Dinesh Kumar, Arun Agarwal
Abstract: This paper explains the technique of vacuum brazing for joining Molybdenum and Kovar. Joining of Molybdenum and Kovar is difficult because of difference in their mechanical properties and Melting Points. Kovar is an alloy of Fe, Ni , Co (composition : Ni 29% , Co 17% , rest Iron) . Molybdenum is a refractory material and its joint with Kovar is used for high temperature applications. Various parameters affecting the vacuum brazing process , vacuum furnace and factors affecting joint strength are discussed.Vacuum brazing of Molybdenum and Kovar samples was carried out inside vacuum brazing furnace using Copper a filler material. Vacuum level of furnace hot zone was maintained better than 10-6 mbar. The joint-strength was evaluated in Universal testing machine with the help of fixtures as per AWS C 3.2 Standard for testing strength of brazed joints. Ram tensile test was conducted. Factors affecting the joint strength of brazed joints like external compressive weight, diffusion of filler material into the parent materials, surface roughness of parent materials, surface flatness have been discussed. Joint strength of 75 MPa is obtained. Failure was found at the brazed joint interface.
282
Authors: Takeshi Konno, Mitsuru Egashira, Mikihiko Kobayashi
Abstract: Gold particles several tens of micrometers in size were welded onto a gold substrate. High voltages of 4 kV or more were applied to a tungsten needle in contact with the particle on the substrate at a very low contact pressure. The particle was welded to the substrate in an instant with sparks. The needle was then retracted to 20 !m above the particle and a high voltage of about 2kV was applied to the needle. An electric discharge between the needle and the substrate enveloped the particle, and the joint was strengthened. The joint strength was measured, and the fractured surface was examined by scanning electron microscopy and scanning laser microscopy. The mechanism of joint strengthening is discussed. It is clear that an inert gas flow during the electric discharge is necessary to strengthen the joints.
1027
Authors: Mrunali Sona, K. Narayan Prabhu
Abstract: Solder plays a vital role in the interconnection of electronic devices in electronic assemblies. As an interconnection material, the solder joint executes electrical, mechanical and thermal functions. The use of lead bearing solders in electronic products is banned due to the toxicity and environmental risks coupled with lead. In the present study, wetting kinetics, interfacial reactions and the formation of intermetallic compounds (IMCs) during solidification of Sn-0.3Ag-0.7Cu solder alloy on Cu substrate and the corresponding joint strength were studied as a function of reflow time. Experiments were carried out at various reflow times of 10, 100, 300 and 500s. The reflow temperature was maintained at 270°C. The solder alloy showed enhanced wettability on the substrate at longer reflow times. The thickness of IMC layer formed during a reflow time of 10s was 1.67μm and the thickness increased to 2.20μm, 2.85μm, 2.91μm during 100s, 300s and 500s of reflow time respectively. The joint shear test was performed to assess the integrity of Sn-0.3Ag-0.7Cu solder solidified on Cu substrates using Nordson DAGE 4000 Plus bond tester. The joint strength increased with the increase in reflow time up to 300s and the maximum joint strength was observed for samples reflowed for 300s. Although the samples reflowed for 500s samples showed good wettability, they exhibited lowest joint strength.
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