• 한국산학기술학회논문지
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• 제12권2호
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• pp.565-570
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• 2011

본 연구는 파인 블랭킹(fine blanking) 프레스로부터 기능면으로 사용되는 100% 매끄러운 전단면을 얻는 파인 블랭킹 공정에서 다이 롤(die roll) 크기를 최소화하기 위한 목적으로 실험을 통해 다이 챔퍼(die chamfer) 형상에 따라 성형되는 제품의 다이 롤 크기 변화를 검토한 것이다. 다이 챔퍼가 다른 여러 가지 다이 편(die insert)을 제작하여 파인 블랭킹 실험을 실시한 후 다이 챔퍼 형상에 따른 다이 롤 크기를 측정 분석하여 두께 방향 다이 롤 크기의 경향을 파악하였다. 이 연구 결과는 파인 블랭킹 판재 성형에서 두께 방향 다이 롤 크기를 최소화하기 위한 다이챔퍼 설계에 유용하게 적용될 것으로 판단된다.

• 소성∙가공
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• 제29권6호
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• pp.362-369
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• 2020

In this study, elastoplastic finite element analysis with multi-body treatment was used to elucidate the mechanical phenomena occurring from pre-stressing of die-system. A finite element analysis model with detailed conditions is proposed. The effects of die pre-stressing slope on the circumferential components of the pre-stressed die inserts were evaluated. The role of tight fitting between the supporter and die case was also emphasized because it has a significant effect on the undesirable change in the target slope of machined inner surface of the die case around the die insert. The two mechanical problems include the one between die-insert and die case and the other between supporter and die case, and their correlation is minimized to establish the optimum design in the die structural design stage because it cannot be quantitatively controlled owing to various factors affecting the die structural behavior during die pre-stressing.

• 한국정밀공학회지
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• 제16권3호통권96호
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• pp.62-71
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• 1999

Integrating micro-machined sensors and actuators on the conventional devices with the copper power lines was incompatible to fabricate the mass produced micro electromechanical system (MEMS) devices. To achieve the compatibility of the wiring method between MEMS parts and devices, we developed the three-dimensional sputter-evaporation system that coats micropatterned thin copper films on the surface of the MEMS element. The system consists of a process chamber, two branch chambers, the substrate holder, and a linear-rotary motion feedthrough. Thin copper film was sputtered and evaporated on the biocompatible polymer, Pellethane$^{circed{R}}$ and silicone, catheter that is 2 mm in diameter and 700 mm in length. The metal film coating technique with three-dimensional thin film sputter-evaporation system was developed to apply the power and signal lines on the micro active endoscope. In this paper, we developed the three-dimensional metal film sputter-evaporation system operated on the low temperature for the biopolymeric substrates used in the medical MEMS devices.

• 대한기계학회논문집A
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• 제21권6호
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• pp.918-924
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• 1997

A method for measuring the accuracy of rotating objects was studied. Rotating axis errors are significant; such as the spindle error of a manufacturing machine which results in the surface roughness of machined work pieces. Three capacitance type displacement sensors were used to measure the rotating master ball position. The sensors were mounted to the three orthogonal points on the spindle axis. The measurement data were analyzed and shown for rotating spindle accuracy, not only for average roundness error but also for spindle volumetric positional error during the revolutions. This method is simple and economical for industrial field use with regular inspection of rotating machines using portable equipment. Measuring and analyzing time using this method takes only a couple of hours. This method can also measure microscopic amplitude and 3-dimensional direction of vibrating objects.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.826-829
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• 2005

The State of the art of low noise fan design requires the consideration of optimal sound quality. The influential design parameters of the noise level by the centrifugal fan were selected that based on a preliminary test. The centrifugal fans were designed according from the experiment plan method by specify the selected design parameters. The experiments with the machined mock-up's of centrifugal impellers revealed the major design parameters having impacts upon the indices of sound quality (e.g. loudness, sharpness, roughness and fluctuation strength) at the same performance condition. With a response surface method. the major design parameters selected were analyzed to estimate their contributions upon the sound quality of the centrifugal fan and the optimal values were drawn for the consideration of the sound quality by using each level and its regression equation. In addition, the validity of the regression equations were numerically verified by means of the coefficient of determination. Furthermore, the mechanism of how the centrifugal fans influence the determinants of sound quality was suggested.

• Current Optics and Photonics
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• 제4권4호
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• pp.293-301
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• 2020

In this paper we propose and theoretically analyze a monolithic multiparametric sensor consisting of a superstructure of surface-relief waveguide Bragg gratings (WBGs), a micro-machined diaphragm, and a cantilever beam. Diaphragms of two different configurations, namely circular and square, are designed and analyzed separately for pressure measurement. The square diaphragm is then selected for further study, since it shows relatively higher sensitivity compared to the circular one, as it incurs more induced stress when any pressure is applied. The cantilever beam with a proof mass is designed to enhance the sensitivity for acceleration measurement. A unique mathematical method using coupled-mode theory and the transfer-matrix method is developed to design and analyze the shift in the Bragg wavelength of the superstructure configuration of the gratings, due to simultaneously applied pressure and acceleration. The effect of temperature on the wavelength shift is compensated by introducing another Bragg grating in the superstructure configuration. The measured sensitivities for pressure and acceleration are found to be 0.21 pm/Pa and 6.49 nm/g respectively.

• 한국정밀공학회지
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• 제11권6호
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• pp.28-41
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• 1994

An efficient algorithm is proposed to select the proper tools and generate their paths for NC rough cutting of dies and molds with sculptured surfaces. Even though a milling process consists of roughing, semi-finishing, and finishing, most material is removed by a rough cutting process. Therfore it can be said that the rough cutting process occupy an important portion of the NC milling process, and accordingly, an efficient rough cutting method contributes to an efficient milling process. In order work, the following basic assumption is accepted for the efficient machining. That is, to machine a region bounded by a profile, larger tools should be used in the far inside and the region adjacent to relatively simple portion of the boundary while smaller tools are used in the regions adjacent to the relatively complex protion. Thus the tools are selected based on the complexity of the boundary profile adjacent to the region to be machined. An index called cutting path ratio is proposed in this work as a measure of the relative complexity of the profile with respect to a tool diameter. Once the tools are selected, their tool paths are calculated starting from the largest to the smallest tool.

• 비파괴검사학회지
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• 제24권3호
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• pp.259-267
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• 2004

탄성매질에서 레이저 여기에 의한 열탄성 영역에서의 초음파 발생 현상과 표면 균열과의 상호작용을 유한요소법으로 모델링하였다. 반무한 탄성체 표면에 집속된 레이저 선원을 전단 쌍극자(shear dipole)로 모델링하고, 2차원 평면 변형율 유한요소법을 사용하였다. 발생된 표면파의 변위와 종파 및 횡파의 지향성을 관찰함으로써 전단 쌍극자-유한요소 모델의 타당성을 조사하였다. 표면파와 균열(기계가공된 2차원 홈)과의 상호작용을 관찰하기 위하여 2가지 경우를 고려하였다 먼저 레이저 소스와 수신 위치가 균열에 대하여 모두 고정되어 있는 경우, 다음으로 수신자가 고정되어 있고 소스가 시험체 표면 위를 이동하는 주사형의 경우이다. 첫 번째 경우에 균열 깊이 $0.3-5.0mm ({\lambda}_R/d=0.21{\sim}3.45)$에 대하여 균열 상단과 하단에서 각각 반사된 파의 변위로부터 균열깊이를 측정할 수 있음을 보였고, 두 번째 경우에 레이저 소스가 결함 위를 주사할 때 발생하는 반사파의 큰 진폭 변화를 통하여 파장보다 한 차원 낮은 깊이의 균열을 탐지할 수 있음을 보였다.

• 대한치과보철학회지
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• 제43권1호
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• pp.78-94
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• 2005

Purpose. The purpose of this study was to compare the effects of various surface treatments by measuring resonance frequency and histomorphometric analyses. Material and methods. In 5 adult dogs, the mandibular premolar were extracted. Six months later, 30 screw titanium implants (Dentium Co., Seoul, Korea) 6mm in length and 3.4mm in diameter, were placed in the mandibles of 5 dogs. Implants were divided into five groups following to surface treatment methods ; Group 1 is machined controls, Group 2 is sandblasted with large grit and acid-etched (SLA), Group 3 is anodized (Autoelectric Co., Korea, 660Hz, Duty10), Group 4 is hydroxyapatite(HA) coated by ion beam assisted deposition(E-beam), Group 5 is hydroxyapatite(HA) coated with Sol-gel coating process. Resonance frequency was measured implant placement immediately, and 3, 6 weeks and 10 weeks of healing perods. With the animal subject's sacrifice 10 weeks after implantation, implants were removed on bloc and histologic and computer-based histomorphometric analyses were performed. Histomorphometric analysis involved quantification of the entire bone to metal contact around the implants. Statistical analyses were performed using the SPSS for Windows (ver. 9.0 SPSS Inc.) Statistical differences were considered significant at P<0.05. Results. The results were as follows : 1) In five groups, mean value of resonance frequency analysis(RFA) were highest in group 5 (Sol-gel implant) at implantation and those of group 4 (E-beam)was highest at 10 weeks . but there was no correlation between surface treatments and RFA. 2) In all surface treatment groups, the RFA values of implants decreased until 3 weeks and increased to 10 weeks. 3) The percentage of direct bone-to-implant contact (BIC) had statistical significance between five groups in cancellous bone, (P<0.05) the percentage of bone density inside the thread had no statistical significance between five groups. (P>0.05) 4) There was a significant difference between cortical bone and cancellous bone in BIC. (P<0.05) and bone density. (P<0.05) 5) There was a correlation between the RFA value of implants at 10 weeks and BIC in cancellous bone, and between the RFA value of implants at 10 weeks and bone density in cortical bone. (P<0.05). Conclusions. These results indicate that surface treatment does not affect the implant stability in case of good bone quality.

• 대한치과보철학회지
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• 제45권3호
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• pp.362-374
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• 2007

Statement of problem. The intial stability for osseointegration of implant has been an interesting factor. Especially, in the case of poor bone quality or immediately loaded implant, various strategies have been developed focusing on the surface of materials to improve implant fixation to bone. The microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. Purpose. The aims of this study are to perform a histologic and histomorphometric comparison of the healing characteristics of three different surfaces and the comparison of resonance frequency analysis (RFA) values measured by $Osstell^{TM}$ and perio-test values (PTV) measured by Periotest. Material and methods. A total of 24 screw titanium implants (Dentium Co., Seoul, Korea) with 6mm in length and 3.4mm in diameter, were placed in the mandible of 4 beagle dogs. Implants were divided into three groups following the surface treatment methods: Group I is machined(control group). Group II is anodically oxidized. Group III is coated 500nm in thickness with hydroxyapatite(HA) by ion beam assisted deposition(IBAD) on the anodized oxidization. Bone blocks from 2 dogs were caught after 3 weeks of covered healing and another blocks from 2 dogs after 6 weeks. RFA values and PTV were measured right after insertion and at 3 and 6weeks. Histomorphometric analysis was made with Kappa Image Base System to calculate bone-to-implant contact (BIC) and bone area inside the threads. Pearson's correlation analyses were performed to evaluate the correlation between RFA and PTV, BIC and bone area ratio of three different surfaces at 3 and 6 weeks. Results. 1) In all surface treatment methods, the RFA values decreased and the PTV values increased until 6 weeks in comparison to initial values. 2) At 3 weeks, no significant difference was found from bone-to-implant contact ratio and bone area ratio of three different surface treatment methods(P>0.05). However, at 6 weeks, different surface treatment methods showed significantly different bone-toimplant contact ratio and bone area ratio(P<0.05). 3) In the implants with the IBAD on the anodic oxidization, significant difference was found between the 3 weeks and the 6 weeks bone area ratio(P<0.05). 4) Correlation was found between the RFA values and the bone area ratio at 3 and 6 weeks with significant difference(P<0.05). Conclusions. These results indicate that the implants with the IBAD on the anodic oxidization may have a high influence on the initial stability of implant.