• Journal of Welding and Joining
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• v.28 no.5
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• pp.80-85
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• 2010

This study focused on laser assisted machining (LAM) of silicon nitride ceramic that efficiently removes the material through machining of the softened zone by local heating. The effects of laser-assisted machining parameters were studied for cost reduction, and active application in processing of silicon nitride ceramics in this study. Laser assisted machining of silicon nitride allows effective cutting using CBN tool by local heating of the cutting part to the softening temperature of YSiAlON using by the laser beam. When silicon nitride is sufficiently preheated, the surface is oxidized and decomposed and then forms bloating, micro crack and silicate layer, thereby making the cutting process more advantageous. HIPSN and SSN specimens were used to study the machining characteristics. Higher laser power makes severer oxidation and decomposition of both materials. Therefore, HIPSN and SSN specimens were machined more effectively at higher power.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.8
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• pp.18-24
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• 2021

Polymers, polymer compounds, are very moldable at low temperatures and have good strength against weight, and hence, are often used in the interior and exterior materials of cars. Owing to the increasing environmental problems, emission regulations have become stricter, which has increased the use of lightweight polymers as substitutes for metal materials. Therefore, as the use of polymer increases, extensive research is being conducted on the bonding technology of polymers, such as polyurethane and epoxy. However, the increased cost and environmental pollution by adhesives caused by the polymer manufacturing plant depend on the chemical composition or the manufacturer's mix ratio. To compensate for this issue, a laser beam is irradiated through a highly permeable polymer (PC) placed on top of an absorbent polymer (ABS) to transfer the laser output to the ABS polymer and fuse them at the interface. Moreover, enabling laser penetrating bonding by placing a stainless steel wire mesh between the two polymers can achieve improved bonding strength compared to conventional heterogeneous polymer bonding.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.1030-1033
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• 2002

In this study, it is important that we have an understanding of the metal flow for manufacturing condenser tube in porthole die extrusion, because this need to provide for household appliances market that is expected to grow into the major market of the cooling system hereafter. Condenser tube is mainly manufactured by conform exclusion. However, this method was not satisfied a series of the needs for manufacturing condenser tube as compared with porthole die extrusion. The deforming skill recently is required high-productivity, high-accuracy and reducing lead-time, thus it is essential to substitute conform exclusion by porthole die exclusion. Porthole die extrusion has many advantages such as improvement of productivity, reduction of production cost etc. In general, the porthole die extrusion process consists of three stages(dividing, welding and forming stages). In order to obtain the detailed mechanics, to assist in the design of proper die shapes and sizes, and to improve the quality of products, porthole die extrusion should be analyzed in as non-steady state as possible during the entire process to evaluate detailed metal flow, temperature distribution, welding pressure and extrusion lead, and therm stress analysis was practiced to obtain effective stress and elastic deformation value. A analytical results provide useful information the optimal design of the porthole die for condenser tube.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.57-57
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• 2010

For thin panel welded structure, the various welding distortions were found due to the low resistance against welding deformation. Especially, buckling distortion induced in the thin panel welded structure produce severe problems related to cost in production stage and safety in service life. So, many researches including mechanical and thermal tensioning method for preventing the occurrence of buckling distortion in the production stage have been performed. The purpose of this study is to identify the behavior of longitudinal residual stress at the SA butt weldment with thin plate of 6mm thickness under tension load by 3 dimensional FEA. For it, mesh design for 3D FEA was constructed with 20 nodes brick element for butt weldment and 8 nodes shell element for base metal. According to FEA results, the longitudinal compressive strain inducing tensile residual stress at the butt weldment decreased. It was because the compressive thermal strain in way of weldment was reduced by tension load. The control effect of residual stress increased with an increase in tension load. So, if the amount of tension load applied to the weldment exceeds 1.5 times of longitudinal shrinkage force, the amount of longitudinal residual stress decreased below the critical value inducing the buckling distortion at the SA butt weldment. Its validity was verified by experiment.

• Journal of Welding and Joining
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• v.19 no.2
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• pp.182-190
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• 2001

A marine structural material was well known to have high tensile strength, good weldability and proper corrosion resistance. Cu-containing high strength low alloy(HSLA) steel was recently developed for their purposes mentioned above. And the steel is free about preheating for welding, therefore it is reported that shipbuilding cost by using it can be saved more or less. However the marine structural materials like Cu-containing HSLA steel are being generally adopted with cathodic protection method in severe corrosive environment like natural sea water but the high strength steel may give rise to Hydrogen Embrittlement due to over protection at high cathodic current density for cathodic protection. In this study Cu-containing HSLA steel using well for marine atructure was investigated about the susceptibility of Hydrogen Embrittlement as functions of tensile strength, strain ratio, fracture time, and fracture mode, etc. and an optimum cathodic protection potential by slow strain rate test(SSRT) method as well as corrosion properties in natural sea water. And its corrosion resistance was superior to SS400 steel, but Hydrogen Embrittlement susceptibility of Cu-containing HSLA steel was higer than that of SS400 steel. However Hydrogen Embrittlement of its steel by SSRT method was showed with pheonomena such as decreasing of fracture time, strain ratio and fracture mode of QC(quasi-cleavage). Eventually it is suggested that an optimum cathodic protection potential not presenting Hydrogen Embrittlement of Cu-containing of HSLA steel by SSRT method was from-770mv(SCE) to - 900mV(SCE)under natural sea water.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.85-90
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• 2010

Friction welding is a common practice to join axially symmetrical parts for automobile industry applications. The shaft for automobile reverse idle gear is generally produced by forging steel, SF 45. This method is not so good because of high cost of material and production. In this study, in order to investigate the possibility of application of SM 45C to SF 45 dissimilar friction welding, the dissimilar friction welded joints were performed using 20 mm diameter solid bar in forging steel(SF 45) to carbon steel(SM 45C). The optimal friction welding parameters were selected to ensure reliable quality welds on the basis of visual examination, tensile test, micro-Virkers hardness surveys of the bond of area and optical microstructure investigations for welded joint parts. Finally, post weld heat treatment(PWHT) of the high-frequency induction hardening was performed for the friction welded specimens under the optimal welding conditions. And then, the mechanical properties were compared for as-welded and PWHT in SM 45C to SF 45.

• Journal of Adhesion and Interface
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• v.12 no.3
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• pp.99-104
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• 2011

Currently, automotive pre-primed coatings has been developed to overcome environmental regulations and to reduce manufacturing cost in automotive industry. By these reasons, an automotive pre-primed system has been investigated to remove the wash and pre-treatment process using a roll coating application. It is required to develop non-weldable pre-primed system for automotive structural adhesives, because pre-primed sheet coated with organic compounds is hard to be assembled by welding process. Primer 1 (polyester type) and primer 2 (urethane type) were designed to satisfy flexibility and formability for non-weldable pre-primed system. According to the results of physical property test of the primers, adhesion test such as single-lap shear test and T-peel test, primer 1 (polyester type) had better physical properties such as pencil hardness, solvent resistance, flexibility and adhesion with automotive adhesive than that of primer 2 (polyurethane type). In addition, the possibility of the non-weldable pre-primed system was applicable to automotive assembly process in place of welding process.

• Journal of Korea Society of Industrial Information Systems
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• v.27 no.2
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• pp.71-82
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• 2022

In order to replace the sampling tensile test of products produced in the tab welding process, which is one of the automotive battery manufacturing processes, vision inspectors are currently being developed and used. However, the vision inspection has the problem of inspection position error and the cost of improving it. In order to solve these problems, there are recent cases of applying deep learning technology. As one such case, this paper tries to examine the usefulness of applying Faster R-CNN, one of the deep learning technologies, to existing product inspection. The images acquired through the existing vision inspection machine are used as training data and trained using the Faster R-CNN ResNet101 V1 1024x1024 model. The results of the conventional vision test and Faster R-CNN test are compared and analyzed based on the test standards of 0% non-detection and 10% over-detection. The non-detection rate is 34.5% in the conventional vision test and 0% in the Faster R-CNN test. The over-detection rate is 100% in the conventional vision test and 6.9% in Faster R-CNN. From these results, it is confirmed that deep learning technology is very useful for detecting welding error of lead tabs in automobile batteries.

• Design & Manufacturing
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• v.14 no.2
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• pp.49-55
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• 2020

Recently, when a new component of construction equipment is designed, a stamping process capable of producing parts having high appearance quality and precision has been gaining attention. However, in general, as it is developed based on existing parts made by welding metal sheets and tubes, frequent to die modification occurs, which increases the time and cost of developing new parts. Thus, it is necessary to reduce the cost by shortening the die development period. In this study, a stamping process was designed for the urea tank cover, which is a part for excavators, to reduce the die development period through sheet metal forming analysis. The stamping process was designed by determining the blank holding force after selecting the initial blank shape and size. The round value at the corner was modified such that formability is ensured. After selecting process parameters, the thickness reduction rate and spring-back effect were reviewed.

• 한국기계연구소 소보
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• s.16
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• pp.127-136
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• 1986

Recently deck crane of multi purpose cargo vessel (MPCV) is designed to posi¬tion in side instead of in the center line of the upper deck with a view to reduce the transportation cost and shipbuilding cost by shortening the length of ship. In this paper, the crane post was at first designed according to the crane maker’s specification and parent ship and the structure is analysed with Finite Ele¬ment Method. Through the careful reviews on the result of analysis, the final design of crane post was modified. The crane post is designed as a cylindrical in upper part and hexagonal in lower part instead of cylindrical on the whole as before. The connecting part of crane post is designed with the form of mixture of the cylinderical and hexagonal. Since the center of cylindrical and hexagonal section are not on the same line, it is expected to have the stress concentration. So, in order to attenuate the concentrated stress on the connecting part, the upper and lower parts was stiffened by inserting plate to enlarge the area of welding. The structure of deck part includes the tank side floor which is depend on the lower structure of the crane post that would support the force of the crane post by placing with 1.5 frame interval of the vertical plate.