• 한국표면공학회지
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• 제53권6호
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• pp.293-299
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• 2020

The characteristics of the polycarbosilane (PCS)-based composite ceramic layer was studied by controlling the curing temperature. The stress at the interface of the graphite and SiOC composite layer was evaluated v ia finite element analysis. As a result, the tensile stress was released as the carbon ratio of the SiC decreases. In experiment, the SiOC layers were coated on the VDR graphite block by dip-coating process. It was revealed that the composition of Si and C was effectively adjusted depending on the curing temperature. As the solution-based process is employed, the surface roughness was reduced for the appropriate PCS curing temperature. Hence, it is expected that the cured SiOC layer can be utilized to reduce cracking and peeling of SiC ceramic composites on graphite mold by improving the interfacial stress and surface roughness.

• 한국산학기술학회논문지
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• 제13권10호
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• pp.4392-4397
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• 2012

본 연구에서는 우레탄레진(TSR-755)을 이용하여 레이저 조형으로 시작형 몰드를 가공하고, 상용패키지(Unigraphics)를 이용하여 자동차 단자함 케이블 케이스를 설계한 후 사출성형해석(Simpoe-Mold)을 사용하여 충전, 보압, 냉각, 변형해석을 수행하여 게이트 위치 선정 및 냉각 사이클 등을 검토 하였다. 해석결과, 세라믹소재 가공 후 사출금형에 인서트시켜 성형 시 열전도도 및 냉각시간을 줄여 줌을 확인할 수 있으며, 게이트 및 냉각라인 선정을 빠른 시간에 결정할 수 있어 생산성 향상을 가져올 것으로 나타났다.

• 한국기계가공학회지
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• 제12권4호
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• pp.87-92
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• 2013

In this study, we carried out the turning of plastic mold steel(STAVAX) with whisker reinforced ceramic tool(WA1) and analyzed ANOVA(Analysis of Variance) test. Multi-regression analysis was performed to find influential factors to surface roughness and to derive regression equation. Results are follows: From ANOVA test and confidence interval analysis of surface roughness, We found that influential factors to surface roughness was feed rate, cutting speed and depth of cut in order. From multi-regression analysis, we derived regression equation of STAVAX. it's coefficient of determination($R^2$) was 0.945 and It means that regression equation is significant. From experimental verification, we confirmed that surface roughness was predictable by regression equation. Compared with former research, we confirmed that increase of feed rate is the main cause of the growing of surface roughness and cutting force.

• 한국기계가공학회지
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• 제11권3호
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• pp.7-12
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• 2012

Ceramic core processing technology using 5-axis high-speed cutting machine is applied to make the glass molds for aspherical ophthalmic lenses. In the technology, optimum processing conditions for aspherical ceramic molds are based on minimal experimental data of surface roughness. Such surface roughness is influenced by fabricating tools, cutting speed, feed rate, and depth of cut, respectively. In this paper, we present that surface roughness and shape accuracy of aspheric ceramic mold obtained by optimum processing conditions are Pa $0.6184{\mu}m$ and Pt $5.0301{\mu}m$, respectively, and propose that these values are sufficiently possible to apply to making the glass molds for aspherical ophthalmic lenses.

• 한국정밀공학회지
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• 제13권12호
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• pp.151-157
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• 1996

The tool condition monitoring is one of the most important aspects to improve productivity and quality of workpiece. In this study, the wear of ceramic tool (A1$_{2}$0$_{3}$-TiC Series) cutting the hardened die material(SKD11) was investigated. Flank wear was more dominant than crater wear. Therefore the modeling of cutting force related to flank wear has been performed. The cutting force model was construct- ed by an assumption that the stress distribution on the tool face is affected by tool wear. The relationship between characteristics as cutting force and tool wear can be suggested by machining parameters depending on cutting conditions. Experiments were performed under the various cutting conditions to ensure the validity of force models. The theoretical predictions on the flank wear are approximately in good agreement with experimental results.

• 대한기계학회논문집A
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• 제30권11호
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• pp.1376-1383
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• 2006

Densification behavior of various metal and ceramic powders was investigated under cold compaction. The Cap model was proposed by using the parameters involved in the yield function for sintered metal powder and volumetric strain evolution under cold isostatic pressing. The parameters for ceramic powder can also be obtained from experimental data under triaxial compression. The Cap model was implemented into a finite element program (ABAQUS) to compare with experimental data for densification behavior of various metal and ceramic powders under cold compaction. The agreement between finite element calculations from the Cap model and experimental data is very good for metal and ceramic powder under cold compaction.

• E2M - 전기 전자와 첨단 소재
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• 제9권4호
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• pp.410-414
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• 1996

기존의 초고압 옥외절연물은 세라믹을 소재로한 porcelain이었지만 최근 신소재기술의 발달로 내열성, 내후성, 내트래킹성 등이 우수한 고분자 재료들이 개발됨에 따라 구미 선진국을 중심으로 이들의 전기절연물분야 적용이 크게 증가하고 있다. 인발(pultrusion)공법으로 glass fiber와 수지를 결합시켜 고강도 무결점의 FRP절연봉이나 tube를 만들 수가 있다. 절연물에서 요구되는 구조재로서의 기계적 특성은 FRP복합재료가 충족시킬 수 있는데 이러한 봉을 core재로 하여 절연물의 표면전기특성을 만족하도록 고무로 된 shed를 씌우고 양쪽 끝에 금구류를 부착하여 composite insulator를 만들 수가 있다. composite insulator는 여러개의 shed를 한번에 진공사출하거나 shed를 금형에서 찍어 조립하여 제작할 수가 있는데 지금까지 검토되어 온 어떤 고분자 절연물보다 특성이 우수하고 장점이 많기 때문에 상업적 가치를 인정받고 있다. 본 고에서는 옥외용 절연물의 절연성능과 섬락사고기구를 요약하고 고분자신소재 절연물인 composite insulator의 장점, 국내외 개발현황, 평가방법등을 정리하였다.

• 한국정밀공학회지
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• 제23권8호
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• pp.203-210
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• 2006

This paper focuses on the development of RT technology suitable for manufacturing a small quantity of metal prototype of a precise part from an RP master. Dimensional accuracy and surface roughness are evaluated from Thermojet part of a 3D printer, and effective post-processing method is introduced. Investment casting is done using a prototype built from 3D printer as a wax pattern. Ceramic shell investment casting technique is developed to build a prototype with materials mostly wanted. Also, experimental result shows this research is very useful in manufacturing of a small quantity of functional part or a test part of a specific material.

• 한국정밀공학회지
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• 제16권11호
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• pp.62-67
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• 1999

The RP&M(Rapid Prototyping and Manufacturing) is the most appropriate technology for the small-lot production system, in which the production cycle is getting shorter owing to various needs from consumers. Recently RP products which are made of plastics, wax, and paper are used to verify the design of samples. But these products cannot be applied to the real mold because the strength enough to be a mold cannot be given by soft materials such as plastics. So RP products are copied to AFR(Al powder Filled Resin) molds or metal molds, which is called the RP&M. In this paper, RP&M is applied to a casting process. A porous casting mold, which is made from ceramic powder and binder, is used for rapid tooling of aluminum shoes molds.

• 한국생산제조학회지
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• 제9권3호
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• pp.9-17
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• 2000

The use of ceramic inserts in steel forging tools offers significant technical and economic advantages over other materi-als of manufacture. These potential benefits can however only be realised by optimal design of the tools so that the ceramic insert are not subjected to stresses that led to their premature failure. In this paper the data on loading of the tools is determined from a commercial forging simulation package as the contact stress distribution on the die-workpiece interface and as temperature distributions in the die. This data can be processed as load input data for a finite-element die-stress analysis. Process simulation and stress analysis are thus combined during the design and a data exchange program has been developed that enables optimal design of the dies taking into account the elastic detections generated in shrink fitting the die inserts and that caused by the stresses generated in the forging process. The stress analysis of the dies is used to determine the stress conditions on the ceramic insert by considering contact and interference effects under both mechanical and thermal loads. Simulation results have been validated as a result of experimental investigation. Laboratory tests on ceramic insert dies have verified the superior performance of the Zirconia and Silicon Nitride ceramic insert in order to prolong maintenance life.