• Journal of Welding and Joining
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• 제21권1호
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• pp.107-113
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• 2003

Joining of $Si_3N_4$ to $Si_3N_4$ with crystallized glass solder was studied. $SiO_2-Al_2O_3-MgO$ glass with $P_2O_5$ as a crystallizing reagent was used as a solder. To improve the hish temperature toughness of joined specimen, two stage heat treatment was applied to Joined sample for the crystallization of joined layer, Two factors, i.e. thickness of soldered layer and crystallization were taken and thier effects on joining strength were investigated by a SEM-EDX observation of joined interface and bending strength both at room and elevated temperatures. Obtained results are summarized as follows: (1) Nitrogen diffused from $Si_3N_4$ to solder during the Joining process. Average amount of nitrogen in soldered layer depended on the thickness of the soldered layer and increased with decrease of the thickness. (2) Joining strength of the specimen having a thinner soldered layer was stronger than that of thicker layer. This can be mainly attributed to the difference of the nitrogen content in the soldered layer. (3) Higher content of nitrogen in solder brought forth higher viscosity of the solder. Hence the crystallization of the solder become more difficult in thinner layer of the solder than thicker one. (4) Thus, the effect of crystallization was evaluated mostly by the thicker layer specimen. Crystallization of soldered layer improved markedly the fracure strength of joining at higher temperatures than the softening temperature of glass solder.

• 반도체디스플레이기술학회지
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• 제10권2호
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• pp.103-108
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• 2011

Ultrasonic welding is widely used in bonding of the same kind or dissimilar materials. The important variable of ultrasonic bonding is the bonding pressure, bonding time and applied amplitude energy. These variables have to be optimized in order to obtain the optimum bonding results. In this research, the important factor to optimal bonding between metal and glass were experimentally investigated by applying design of experiment.

• Journal of Welding and Joining
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• 제25권3호
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• pp.28-36
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• 2007

A bulk amorphous NiTiZrSiSn powder produced using an inert gas atomization was sprayed by kinetic spraying process that is basically a solid-state deposition process onto a mild steel substrate. They were successfully overlaid onto the mild steel substrate. In order to evaluate the tribological behavior of the kinetic sprayed NiTiZrSiSn BMG (Bulk Metallic Glass) coatings, a partially crystallized coating and a fully crystallized coating were prepared by the isothermal heat treatments. Tribological behaviors were investigated in view of friction coefficient, hardness and amorphous phase fraction of coating layer. Surface morphologies and depth in the wear tracks were observed and measured by scanning electron microscope and alpha-step. From the examination of the scratch wear track microstructure, transition from the ductile like deformation (micro cutting) to the brittle deformation (micro fracturing) in the scratch groove was observed with the increase of the crystallinity.

• 한국산학기술학회논문지
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• 제10권11호
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• pp.3074-3079
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• 2009

지속적인 경제 발전과 인구증가로 인하여 에너지 소비가 급증하게 되면서 에너지의 효율적인 사용이 필요하다. 특히 에너지 손실이 많은 건물의 창호에 단열성능이 좋은 고효율 진공유리 사용이 절실한데 아직 가격 및 성능등의 문제로 보급화가 이루어지지 않고 있다. 따라서, 본 연구에서는 저가의 진공유리 개발을 위한 유리 용접용 토치를 설계 및 제작하였다. 연료는 고밀도 열원인 수소-산소 혼합가스를 사용하였고 주로 토치 형상, 노즐 직경, 노즐 배치 등의 최적화를 수행하였다. 끝으로 개발된 토치를 이용하여 두 장의 유리용접을 성공적으로 수행함으로써 저가의 진공유리 개발 가능성을 확인하였다.

• Journal of Welding and Joining
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• 제27권6호
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• pp.43-48
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• 2009

In this study, Cu-based bulk metallic glass (BMG) coatings were deposited by atmospheric plasma spraying (APS) process with different process conditions (with- and without hydrogen gas). As adding the hydrogen gas, thermal energy in the plasma flame increased and induced difference in the melting state of the Cu-based BMG particles. The microstructure and mechanical properties of the coatings were analyzed using a scanning electron microscope (SEM) with an energy dispersive spectroscopy (EDS) and nano-indentation tester in the light of phase analysis. It was elucidated by the nano-indentation tests that un-melted region was a mainly amorphous phase which showed discrete plasticity observed as the flow serrations on the load.displacement (P - h) curves, and the curves of solidified region showed lower flow serrations as amorphous phase mingled with crystalline phase. Oxides produced during the spraying process had the highest hardness value among the phases and were well mixed with other phases resulted from the increase in melting degree.

• International Journal of Korean Welding Society
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• 제1권2호
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• pp.23-29
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• 2001

In this study, a preview-sensing visual sensor system is constructed far weld seam tracking in GMA welding. The visual sensor system consists of a CCD camera, a diode laser system with a cylindrical lens, and a band-pass-filter to overcome the degrading of image due to spatters and/or arc light. Among the image processing methods, Hough transform method is compared with the central difference method from a viewpoint of the capability for extracting the accurate feature position. As a result, it was revealed that Hough transform method can more accurately extract the feature positions and it can be applied to real time weld seam tracking. Image processing which includes Hough transform method is carried out to extract straight lines that express laser stripe. After extracting the lines, weld joint position and edge points are determined by intersecting the lines. Even though the image includes a spatter trace on it, it is possible to recognize the position of weld joint. Weld seam tracking was precisely implemented with adopting Hough transform method, and it is possible to track the weld seam in the case of offset angle is in the region of $\pm$ $15^{\circ}$.

• Journal of Welding and Joining
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• 제34권2호
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• pp.22-29
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• 2016

Recently, Application of composite materials are increased in transport area for weight reduction. Also, Related technical developments have been implemented actively at domestic and abroad. In particular, The carbon fiber has high strength and ultra light property higher than stainless steel, aluminum, GFRP as Eco-friendly material. Carbon fiber contribute to improving the environmental effect such as fuel saving, expansion of loadage, reducing the exhaustion of carbon dioxide through the weight reduction of transport area. In addition, The carbon fiber is applied to the ship in the area of race yacht, luxury cruise boat as weight reduction and high added-value materials, but there is limited application for general boat because price of carbon fiber is very expensive. For the weight reduction of general boat hull, being used as structure materials, glass fiber and carbon fiber are applied to hull with form of hybrid composite materials, but application of domestic and research for development are incomlete. In this study, An evaluations of mechanical strength property and fatigue strength are performed on composite materials by hybrid weaving of glass fiber and carbon fiber and composite materials forming method by hybrid forming.

• Journal of Welding and Joining
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• 제24권2호
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• pp.57-63
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• 2006

In this study, the curing kinetics and thermal degradation of underfill were investigated using differential scanning calorimetry (DSC) and thermo gravimetry analysis (TGA). The mechanical and thermal properties of underfill were characterized using dynamic mechanical analysis (DMA) and thermo-mechanical analysis (TMA). Also, we presented on underfill dispensing process using Prostar tool. The non-isothermal DSC scans at various heating rates, the exothermic reaction peak became narrower with increasing the heating rate. The thermal degradation of underfill was composed of two processes, which involved chemical reactions between the degrading polymer and oxygen from the air atmosphere. The results of fluidity phenomena were simulated using Star CD program, the fluidity of the underfills with lower viscosity was faster.

• Journal of Welding and Joining
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• 제26권4호
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• pp.44-49
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• 2008

Generally, wear plate is steel plate having improved surface contact strength and impact strength by surface hardening which is welded using materials with good corrosion resistance, wear resistance and thermal resistance property. CFP GMAW(Compound Filler Plate Gas Metal Arc Welding) is the cladding method using GMAW with the CFP, which is bound with waterglass, on the substrate. It has advantages of reducing compound powder loss, uniform penetration, and preventing hardness decrease. To develope mass production technique of CFP GMAW process for production of high quality wear plate, the method for controling shallow penetration and increasing productivity is required. In this study, twin torch method applied to CFP GMAW process for increasing productivity. And the method was developed by controling penetration control, CFP dry time, gas formation flux and water glass concentration. As a result, applying twin torch method to CFP GMAW process was possible and high quality wide bead could be made without overlap joint.

• Structural Engineering and Mechanics
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• 제90권5호
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• pp.481-492
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• 2024

This research examined the mechanical behavior of fiber-reinforced concrete at unstable environmental conditions. Concrete composites with varying percentages of steel and glass fibers were analyzed. Compressive, indirect tensile, and fracture toughness properties were evaluated using the Edge Notched Disc Bend (ENDB) test under freezing-thawing and acidic environments and the results were compared with normal conditions. Steel fibers decreased the strength in the specified cycles, while glass fibers showed a normal strength trend. The compressive, tensile and fracture toughness of the samples containing 1.5 vol.% fibers showed a 1.28-, 2.13- and 4.5-fold enhancement compared to samples without fibers, after 300 freezing-thawing cycles, respectively.