• 한국레이저가공학회지
• /
• 제2권1호
• /
• pp.22-29
• /
• 1999

This work was carried out as a fundamental experiment to fabricate a Graded-Boundary Ni/Steel material using a laser beam. A Ni sheet was placed on a steel substrate, and then a series of high power $CO_2$ laser beams were irradiated on the surface in order to produce a homogeneous alloyed layer. The processing parameters were : 4 ㎾ laser power, 2m/min traverse speeds, -2mm defocuing, 17 l/min sheiding gas flow rates. The sequential repetition of the laser surface alloying treatment up to 4 times, resulted in about 5mm thick of fair compositional gradient systems. In order to determine the microstructure, phase and compositional profiles in this material, optical microscopy, XRD and EDS were used. The compositions varied from 66% to 0% for Ni and 34% to 100% for Fe in this material The microstructures were typical morphologies of rapid solidification and solid-state cooling. Since compressive stress was formed in the heat affected region due to martensitic transformation, while relative tensile stress was developed in the alloyed region, cracks were formed between the alloyed region and the substrate region.

• Design & Manufacturing
• /
• 제10권3호
• /
• pp.34-38
• /
• 2016

Roll forming is a continuous production process that is mass-produced. The roll forming process is produced in various forms. The special feature of roll forming is a continuous production. Therefore, the process of cutting the material is essential. The troubles in a shearing process affects the low productivity. Accordingly, it is important to reduce the factors that inhibit the material flow. And it is difficult to apply the common shear angle. Because it is not a simple forms, such as a progressive die. This study shows how to select the angle of a shear punch and the shape of a cutting punch in the product with a specific shape. Conclusively through three different model, it is advantageous to apply the different shear angle and clearance along the forms.

• Journal of Advanced Marine Engineering and Technology
• /
• 제20권5호
• /
• pp.30-38
• /
• 1996

A PIV system consisting of an image board slit into personal computer and 2-D sheet light projector is developed and related techniques to improve its performance are discussed. A grey-level cross correlation method capable of overcoming particle seeding limitation is suggested. And a sub-pixed interpolation method in determining the vector terminal is preposed by considering 8-neighbours correlation distributing patterns. Furthermore, pressure estimation from the acquired velocity vectors by applying the Poisson equation is persented with reasonable feasibility. As a practical application of the present system, evaporator flows are analysed and attained instantaneous velocity vectors reveal that the flow phenomena maintain turbulent fluctuation.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2004년도 추계학술대회 논문집
• /
• pp.128-133
• /
• 2004

This study has been focused on the development of shear forming process of grid for lead-acid battery. The grid plays an important role in the flow of electricity because the grid is a skeleton of the pasted plate. Therefore, it must be of the highest quality to prevent plate failures and then, battery failure, and ensure the best battery performance possible. The finite element analysis of the shear forming process is carried out and the result is compared with the experimental data. The influence of the numerical parameters such as clearance, velocity of punch and critical damage value on the simulation results turns out to be very considerable.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 추계학술대회논문집
• /
• pp.192-195
• /
• 2004

Surface friction welding, SFW, is a newly developed solid state welding technology for joining of thin metal sheets. Workpieces are joined by frictional heat, shear deformation and plastic flow generated by friction between the rotating tool and surface of the workpiece. The SFW is an economical and environmentally conscious technology with high joining speed and excellent properties, and is expected to be used widely in various industries in the near future.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 추계학술대회논문집
• /
• pp.180-183
• /
• 2004

Superplastic formability depends on flow parameters such as temperature, strain rate, strain and stress, microstructures. Usually, superplastic properties of materials are characterized with using a uni-axial tension testing. However, superplastic sheet is formed under mutiaxial loading condition in most forming practices. In the present study, superplastic characteristics of A15083 alloys were determined with using both a uni-axial and biaxial bulging tests. Specially, cone-type die was used to achieve constant strain rate under constant pressure condition. Even though constant strain rate under a certain pressure was achieved only approximately, a cone-type bulging test was found to be quite beneficial to get a multiaxial formability of superplastic materials.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1991년도 춘계학술대회 논문집
• /
• pp.251-255
• /
• 1991

The primary objectives of the rolling process are to reduce the cross section of the incoming material while improving its properties and to obtain the desired section at the exit from the rolls. Many engineering metals, suchas aluminium alloys, copper alloys, and steels are often cast intoingots and are then further processed byhot rolling into blooms, slabs, and billets, which are subsequently rolled into other products such as plate, sheet, tube, rod, bar, and structural shapes. In shape rolling a round or square bar is rolled in several passes into various shapes. During eachpass, the bar elongates as well as spreads. Thus, a very complex three-dimensional metal flow takes place. In this paper TASKS results for the simulation of a 7 pass square-to-round shape rolling are presented. The results are verified by comparing it with experimental results from a previous study conducted at the Battelle Columbus Labs

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2003년도 학술대회지
• /
• pp.341-347
• /
• 2003

Single flighted screw extrusion is the most cost effective method for the production of film, sheet, pipe and the fundamental step in other processes including blow molding and injection molding The temperature and injection pressure in barrel play a very important role in quality of products. Because thermal distortion and displacement of barrel by temperature difference and injection pressure difference cause irregular resine melting and flow. In this paper thermal distortion and stress of barrel includes pressure and temperature distributions by finite element analysis to understand dynamic characteristics of barrel.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.344-347
• /
• 2006

Noise reduction and control is an important problem in the performance of underwater acoustic system and on the habitability of the passenger ship for crew and passenger. Furthermore, sound generated by a propeller is critical in underwater detection and is often related to the survivability of the vessel especially for military purpose. Generally propeller noise is often the dominant noise source of marine vehicle. The flow field is analyzed with potential-based panel method, and then the time dependent pressure and sheet cavity volume data are used as the input for Ffowcs Williams-Hawkings formulation to predict the far-field acoustics. Through this study, the dominant noise source of underwater propeller is analyzed, which will provide a basis for proper noise control strategies.

• 한국자동차공학회논문집
• /
• 제9권2호
• /
• pp.19-27
• /
• 2001

This paper is the first of 3 companion papers which investigate axial stratification process. In-cylinder fuel behavior has been investigated in the port injected SI engine by visualization for the purpose of understanding stratification. Planar laser light sheet from an Nd:YAG laser has been illuminated through the transparent quartz cylinder of the single cylinder optical engine and the Mie scattered light has been replaced with an air-ethanol mixture to utilize atomized fuel spray for the visualization purposes. This results have been compared with steady flow concentration measurement. For no swirl port, the axial penetration depends on the fuel injection timing. The fuel tends to remain in the upper region of the cylinder far from the spark plug and the distribution is not affected by the injection timing except 90 ATDC.