• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1043-1050
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• 2005

Condenser tube is a component of the heat exchanger in automobile and air conditioning apparatus. It is generally made from the 1000 or 3000 series Al alloys that have good heat efficiency. In the case of 3000 series, these have high strength and hardness but have the disadvantage of low extruability. The development of extruding process in condenser tube with 3000 series Al alloys is studied in this paper. A study on extrusion process is performed through the 3D FE simulation in non-steady state and extrusion experimentation. Also, nano-indentation test is employed to estimate the weldability of tubes. Especially, An evaluation of the weldability using the nano-indentation is accomplished as compared with nano-hardness of welded part and the others in cross-section of tube.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.103-108
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• 2000

Since the ceramic/metal joint material is made at a high temperature, the residual stress development when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of $Si_3N_4/STS304$ joints quantitatively and to compare the strength of Joints. The difference of residual stress is measured when repeated thermal cycle is loaded under the conditions of the practical use of the ceramic/metal joint. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a residual it is known that the stress of joint decreases as the number of thermal cycle increases.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.534-540
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• 2001

One approach to testing the suitability of an adhesive joint for a particular application is to build and test to destruct ion a representative sample of the joint. The nondestructive test will not measure strength directly but will measure a parameter which can be correlated to strength. It is therefore, essential that a suitable nondestructive test is chosen and that its results are correctly interpreted. In this paper, typical defects found in adhesive joints are described together with their significance. The limits and likely success of current physical nondestructive tests are described, and future trends outlined.

• Journal of Welding and Joining
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• v.19 no.2
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• pp.98-103
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• 2001

Root gap out of standard by welding deformation is frequently produced at butt weld joints of steel bridge. For example although standard root gap is below 6mm at butt weld joints of plates under 15mm thickness. maximum 35mm root opening is produced at the weld field. At this case, the part out of standard is generally built up and the rest part is welded by WPS. Direct welding without built-up welding is preferred in weld field because built-up welding process bring about the cost-up at manufacturing. To apply this direct weld to root gap out of standard, the investigation about mechanical properties and fatigue at weldment is required. Inthisstudy, therefore the verification for direct weld without built up is performed at weldment as root gap. It includes tension, bending. hardness, impact and fatigue test for each welding specimen of 6mm, 25mm, 35mm root gap.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.139-147
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• 2005

The lubricant impregnated MC nylon has good frictional properties, but its mechanical strength is inferior to steel for the mechanical elements. For the tribological application Nylon as gears, sliding bearings, cam and etc, the steel shafts are fitted in pre-heated nylon cylinder by a process of interference expansion fit and bonded by induction heating method. The joint shear strength of the two materials was measured by a universal test machine. From the study, the adhesive shear strength between these two materials was affected by the factors of the interference between nylon and steel, the size of nylon cylinder, knurl of steel shaft and inducting heating conditions. The most effective jointing conditions were analyzed and decided for the practical application in the industry.

• Journal of Welding and Joining
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• v.28 no.5
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• pp.58-63
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• 2010

The purpose of this study is to develop improved boom structures with reliable fatigue strength of weldment and lower production cost. For that purpose, multibody dynamic analysis was performed to evaluate forces acting on arm & boom cylinders and joints of boom structure during operation of an excavator for three working postures, then stress analysis was made to investigate stress distribution around diaphragms at the bottom plate of boom structures which was known to be susceptible to fatigue failures of welded joints, and finally boom structure with optimum arrangement of diaphragms was proposed. This work basically consists of the following two parts: part 1 focuses on multibody dynamic analysis of excavators during operation and part 2 includes evaluations of fatigue strength of welded joints for modified boom structures.

• Journal of Welding and Joining
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• v.26 no.2
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• pp.69-74
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• 2008

590MPa grade weldable steels were gas metal arc welded with flux cored wires. Welding parameters such as current, voltage, and speed were varied independently. Effects of each parameter on the strength and chemical composition of weld metal were investigated. Increase of voltage caused decrease of weld metal tensile strength due to the low recovery of alloying elements such as carbon and manganese. On the contrary, increase of current and speed resulted in increase of weld metal strength because of higher recovery of the alloying elements.

• Journal of Welding and Joining
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• v.3 no.2
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• pp.64-73
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• 1985

X선응력측정법은 결정의 각자간 거리를 표점으로 하는 각자변형도를 X선회절현상을 이용하여 직접규정하여 응력을 구하는 것이다. 따라서 비교재의 교정곡선으로 부터 간접적으로 응력을 측 정하는 자기법이나 초음파법 등의 비파괴측정법에 비하여 X 선응력측정법은 잔류응력과 같은 내부응력의 비파괴측정법에 알맞고 지금까지 많은 연구자에 의하여 용접부에 적용시키기 위한 시도가 행해졌었다. 앞서 말한 국제회의에서도 X선응력측정법을 취급한 논문이 6편이고 그 가운 데서 3편이 용접구조물 또는 이음부에 이 방법을 적용한 것이다. 그래서 본고에서는 먼저 용접 잔류응력의 발생기구와 계산법, 측정법에 대하여 기술하겠다. 똔 잔류응력이 용접이음부의 파괴 강도 및 용접균열에 미치는 영향, 용접잔류응력의 대책과 이용법에 대하여 일본에서의 연구를 중심으로 소개하겠다.

• Journal of Welding and Joining
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• v.16 no.2
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• pp.48-56
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• 1998

This study was performed to find the best bonding conditions by comparing mechanical properties in thermoplastic resin of polyethylene (PE) and polyamide (PA) adhesion. Following results were obtained from the tests with varying welding time and welding pressure. Satisfactory adhesion was executed in ultrasonic welding for the same materials of PE and PA. The best welding conditions were found to be welding time of 1 second, welding pressure of 250kPa for PE-PE weding, 2 second and 350kPa for PA-PA welding. Welding time and welding pressure end to increase with the increase of materials strength. Dissimilar materials were adhered when adhesion and ultrasonc welding were performed simultaneously. The observation of the structure of ultrasonic welding area with microscope showed differenticated structures between well adhered region and badly adhered region.

• Journal of Welding and Joining
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• v.17 no.1
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• pp.77-81
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• 1999

Through-hole PCB(Printed Circuit Board) was soldered by flow soldering process using cleaning or noncleaning fluxes. Preheating temperature and conveyor speed were changed in the range of 323∼413K and 0.3∼2m/min respectively. The soldered joints were tensile tested in order to evaluated bonding strength. As experimental results, relatively high tensile fracture load, 120∼140N, were obtained in case of preheating temperature of 383K, and conveyor speed was 0.6∼1.0 m/min. Fractured surfaces of higher tensile strength show some dimple area, while those of lower tensile fracture load show brittle fracture.