• Corrosion Science and Technology
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• 제6권3호
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• pp.140-146
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• 2007

In the paper, with corrosion velocity measurement and metallographic observation on specimens after sulfuric acid/ferric sulfate boiling experiment, intergranular corrosion tendency of the new type ultra low carbon stainless steel developed by ourselves which experienced solution treatment at different temperatures was evaluated. A VHX 500 super depth field tridimensional microscope was used to observe corrosion patterns on the sample surfaces. The depth and width of grain boundary corrosion groove were measured by the tridimensional microscope, which indicated that the corrosion degrees of the samples which received solution treatment at different temperatures are quite different. Transgranular corrosion at different degree occurred along with forged glide lines. After comparison it was proved that the stainless steel treated at $1100^{\circ}C$ performs very well against intergranular corrosion.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1280-1287
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• 2002

The old technique of sandblasting which has been used for decoration of glass surface has recently been developed into a powder blasting technique for brittle materials such as glass, silicon and ceramics, capable of producing micro structures larger than $100{\mu}$ m. This paper describes the performance of powder blasting technique in micro-line grooving of glass and the effect of the number of nozzle scanning on the depth and width of line groove. Experimental results showed that increasing the no. of nozzle scanning resulted in the increase of depth and width in grooves. Increase of width which may cause several problems in the precision machining results from wear of mask film. Therefore, well-controlled masking process is the most important factor for micro machining of glass with accuracy.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.366-370
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• 1997

This paper descibes a micro groove machining process on the polyurethane biopolymer by KrF excimer laser. To investigate the etch charcteristics of polyurethane biopolymer quantitatively,laser system for ablation was installed with high precison moter and then polymer ablation experiment, in which paramteters were fluence,pulse repetition rate,numbers of pulses and assist gas, was carred out. In this experiment, we found out that the value of critical energy density for ablation is 30mJ/cmsup2/ and the etching rate is more dependent on the pulse number and fluence than any other pamameter. Finally, we machined micro grooves for fiexibility as width 300.mu.m depth 100.mu.m and port for micro-devices mounting as length 100.mu.m width 300.mu.m depth .mu.m on the outer wallof polyurethane biopolymer tube which is used as medical device.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1615-1622
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• 2003

Being contacted directly with. ground, the tire tread part is in shape of complex patterns of variable ASDs(anti-skid depth) to satisfy various tire performances. However, owing to the painstaking mesh generation job and the extremely long CPU-time, conventional 3-D tire analyses have been performed by either neglecting tread pattern or modeling circumferential grooves only. As a result, such simplified analysis models lead to considerably poor numerical expectations. This paper addresses the development of a 3-D tire mesh generation considering the detailed tread pattern and shows that the contact pressure and frictional energy distribution of tires considering the detailed pattern become better than those by the simplified tire model.

• 한국생산제조학회지
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• 제20권5호
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• pp.523-527
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• 2011

Polycarbonate (PC) polymer is an engineering plastic which has large tensile strength and impact resistance and is wildly used as functional parts like micro mold. Direct machining of PC materials produces lots of burrs and rough surface due to large ductility and weak heat resistance and hence it is very difficult to machine PC materials using cutting tool to make micro-parts. In this study, elliptical vibration cutting (EVC) or 2-dimensional vibration cutting was performed to minimize the size of micro V-grooves on PC material. From the experimental results, it was observed that as the cutting depth and pattern size become smaller, the better machining quality was obtained, which is attributed to the positive effect of EVC that is dependent on the ratio of vibration amplitude to cutting depth. As the height of V-groove becomes less than $1.8{\mu}m$, however, the machining quality becomes lower as the pattern size decreases.

• 한국정밀공학회지
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• 제18권11호
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• pp.101-106
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• 2001

In this work, an effort is made to investigate the behavior of a chip, from its initial flow to its final breaking stage. The expression for chip flow in grooved tools is verified analytically using FEM. Cutting parameters like velocity and depth of cut have a profound influence on chip flow behavior. Chip curling increases and, for a given tool geometry, effectiveness of the groove increases with increasing depth of cut. The feasibility of tool design using FEM simulations is also demonstrated. Optimization of tool geometry results in better chip control.

• 소성∙가공
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• 제16권8호
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• pp.603-613
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• 2007

This paper is concerned with joining of thin metal sheets by single stroke clinching process. This method has been used in sheet metal work as it is a simple process and offers the possibility of joining similar-dissimilar thin sheet metals. Clinching generates a joint by overlapping metal sheets deforming plastically by punching and squeezing sequence. AA 5754 aluminum alloy of 0.5 mm thick sheets have been selected as a modal material and the process has been simulated under different process conditions and the results have been analyzed in terms of the quality of clinch joints which are influenced mainly by tool geometries. The rigid-plastic finite element method is applied to analyses in this paper. Analysis is focused mainly on investigation of deformation and material flow patterns influenced by major geometrical parameters such as die diameter, die depth, groove width, and groove corner radius, respectively. To evaluate the quality of clinch joints, four controlling or evaluation parameters have been chosen and they are bottom, neck thickness of bottom and top sheets, and undercut thickness, respectively. It has been concluded from the simulation results that the die geometries such as die depth and diameters are the most decisive process parameters influencing on the quality of clinch joints, and the bottom thickness is the most important evaluation parameter to determine if the quality of clinch joints satisfies the demand for industrial application.

• 한국정밀공학회지
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• 제14권9호
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• pp.146-154
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• 1997

Ion implantation has been used successfully as a surface treatment technology to improve the wear. fatigue and corrosion resistances of materials. A modified surface layer by ion implantation is very thin(under 1 m), but it has different mechanical properties from the substrate. It has also different wear characteristics. Since wear is a dynamic phenomenon on interacting surfaces with relative motion, an effective method for investigtating the wear of a thin layer is the observation of wear process in microscopic detail using in-situ system. The change of wear properties produces the transition of wear mode. To know the microscopic wear mechanism of this thin layer, it is very important to clarify its microscopic wear mode. In this paper, using the SEM and AFM Rribosystems as in-situ system, the microscopic wear of Ti ion-implanted 1C-3Cr steel, a material for roller in the cold working process, was investigated in repeated sliding. The depth of wear groove and the speciffc wear amount were changed with transition of microscopic wear mode. The depth of wear groove with friction cycles in AFM tribosystem and specific wear amount of Ti ion-implanted 1C-3Cr steel were less about 2-3 times than those of non-implanted 1C-3Cr steel. The microscopic wear mechansim of Ti ion-implanted 1C-3Cr steel was also clarified. The microscopic wear property was quantitatively evaluated in terms of microscopic wear mode and specific wear amount.

• Steel and Composite Structures
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• 제27권3호
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• pp.337-353
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• 2018

In previous weak-axis moment connection tests, brittle fracture always initiated near the edge of the beam flange groove weld due to force flow towards the stiffer column flanges, which is the opposite pattern as strong-axis moment connections. As part of the China NSFC (51278061) study, this paper tested two full-scale novel weak-axis reduced beam section moment connections, including one exterior frame connection specimen SJ-1 under beam end monotonic loading and one interior frame joint specimen SJ-2 under column top cyclic loading. Test results showed that these two specimens were able to satisfy the demands of FEMA-267 (1995) or ANSI/AISC 341-10 (2010) without experiencing brittle fracture. A parametric analysis using the finite element software ABAQUS was carried out to better understand the cyclic performance of the novel weak-axis reduced beam section moment connections, and the influence of the distance between skin plate and reduced beam section, a, the length of the reduced beam section, b, and the cutting depth of the reduced beam section, c, on the cyclic performance was analyzed. It was found that increasing three parametric values reasonably is beneficial to forming beam plastic hinges, and increasing the parameter a is conducive to reducing stress concentration of beam flange groove welds while increasing the parameters b and c can only reduce the peak stress of beam flange groove welds. The rules recommended by FEMA350 (2000) are suitable for designing the proposed weak-axis RBS moment connection, and a proven calculation formulation is given to determine the thickness of skin plate, the key components in the proposed weak-axis connections. Based on the experimental and numerical results, a design procedure for the proposed weak-axis RBS moment connections was developed.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.68-74
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• 1999

One of the recent changes in machining technology is rapid application of micro- and high precision grinding processes. A fine groove generation is necessary for the fabrication of optic, electronic and semiconductor parts, and achieved by chemical or mechanical processes. Slot grinding is very efficient for the generation of micro ordered groove with hard and brittle materials. As slot grinding is continuous, the ground depth become gradually shallow because of wheel wear. The form accuracy become worse from the increase of ground slot width by the loading phenomena at wheel side, results on chipping damage of the workpiece. The experiments achieve to the enhancement of the form accuracy and chipping free of the brittle materials using V shaped cast iron bonded diamond wheels. In this study we focused on the investigation of the effect of the high pressure air jet on the grinding characteristics. As a results, we found that the high pressure air jet is very effective on the reductions of the wheel wear, enhancement of the form accuracy.