• Korean Journal of Optics and Photonics
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• v.29 no.6
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• pp.233-240
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• 2018

In this paper, a design method to reduce fabrication errors in reflector shape of a test lamp for a flame detector is carried out. Although the test lamp should be operated in parallel with a high-intensity light, it is difficult to fix the small reflector that controls the central light during fabrication. To solve these problems, a small spherical reflector is designed to minimize the performance degradation for a light loss factor of less than 5%, even during tilt and decenter, and a spherical shape is proposed for a small reflector with little effect on the error when designing the optical system.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.4
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• pp.463-468
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• 2015

High vibration of a low pressure (LP) turbine casing caused safety problems and life at the facility it was housed in. The main focus of this study was the cause of the high vibration in a low pressure turbine casing with manufacturing defects by frequency response analysis, compared with the results of experiments. Therefore, excited accelerations were obtained from the LP casing fundamental, and frequency responses were analyzed. The measurement and the modal analysis showed that the natural frequency of the LP turbine casing was 61.26 Hz and the excited frequency of the turbine rotor was 60.25 Hz. The manufacturing defect caused a decrease in the casing natural frequency and resulted in the high vibration of the casing because it moved close to the resonant frequency.

• Korean Journal of Optics and Photonics
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• v.16 no.1
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• pp.71-78
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• 2005

A null lens system of autostigmatic type, consisting of two mirrors, is designed for testing a large aspherical mirror. The system is theoretically analyzed to determine the limitation of measurement accuracy according to the manufacturing and alignment errors. We confirmed that irregularity of the null lens surface is the principal factor among tolerances in limiting measurement accuracy. Consequently, we can predict that measurement accuracy will be from 5λ/100 to 4λ/1000 according to the amount of this irregularity. That is, we can present the limitation of possible measurement accuracy with actual alignment and manufacturing errors.

• Journal of the KSME
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• v.22 no.1
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• pp.24-33
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• 1982

지계차는 1930 년대에 미국에서 개발되어 세계대전을 통하여 미군의 군수물자 운반에 크게 기 여하므로써 널리 알려진 물자취급(material handling)의 현대적 장비로 팰릿(pallet).컨테이너와 함께 일관수송에 있어서의 커다란 역할을 담당하고 있는 산업용 차량이다. 지계차는 크게 샤 시부분과 작업기 부분으로 구성되는데, 마스트레일은 주로 소형차에서는 생산량이 많기 때문에 압출의 제조공정으로 만들어지고 있으나 대형차는 수량이 적기 때문에 용접구조로 설계되고 있다. 마스트렝리의 중요한 특징을 말하면 (1) 폭에 비하여 길이가 긴 형강구조 (2) 레일 내폭의 공차가 비교적 엄격하다. (3) 용착량이 많아 변형되기 쉽고 일단 변형되면 교정이 어렵다. (4) 원가와 제조공정을 단축시키기 위하여 기계가공 공정을 뒤에 두지 않고 있다. 이상과 같은 특징을 가진 용접구조형 레일을 제작하는데 있어서 실제 적용된 CO2 용접 및 이의 간단한 부 착(attach)에 의한 저투자성 용접자동화 실현과정상의 제문제등을 중심으로 고찰해 보기로 한다.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.131-136
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• 2011

In commercial vehicle, sub-frame which equipped in main frame supporting dump deck and oil tanker. This is the main structure for all equipment which including joint function. Sub-frame is made by welding process, this susceptible to deform and crack by its longitudinal size. Also various kind of sub-frame make it difficult to standardization in manufacturing process and exclusive jig is not adapted yet. Frame size is over 6~8m and weight is more than 300kg this make re-work more difficult. If manufacturing company made precise sub-frame, this is not only convenient for customers but also save the company money by reducing the working time. In this study manufacture the sub-frame be suitable for its main function and develop exclusive welding jig for obtain checking fixture function as well.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.104-105
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• 2003

We have fabricated a side-illuminated p-i-n photodetectors with evanescently-coupled waveguides for surface hybrid integration in low-cost modules. We adopted WGPD of evanescently-coupled type to have high responsivity and coupling tolerance, and to avoid any reliability problem. This proposed photodetectors have a high responsivity of 1.10 A／W at a wavelength of 1.55 ${\mu}{\textrm}{m}$. The 1dB coupling tolerance to cleaved fiber and photodetectors is $\pm$3.5 ${\mu}{\textrm}{m}$ in the vertical direction and $\pm$11 ${\mu}{\textrm}{m}$ in the horizontal direction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.6
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• pp.475-484
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• 2012

Numerical investigation is performed to understand the effects of thickness uncertainty of a supporting airfoil due to manufacturing processes on the aerodynamic characteristics of an airfoil used for measuring data in a wind tunnel testing. This is done by comparing the coefficients of lift, drag and moment of the airfoils. In this work, the airfoil model consists of three parts, one located in the center for measuring and two outer parts used for supporting. The study is carried out with a NACA64-418 airfoil and the turbulence model of Transition SST. It is found that the effect of thickness uncertainty of the airfoils used for supporting is not significant to the performance of the test airfoil at various angles of attack and Reynolds numbers.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.412-419
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• 2006

We design and fabricate an autostigmatic null lens system assembled in a fixed tube mount in order to evaluate the shape of an aluminum hyperbolic mirror with the diameter of 300 mm and the f-number of 1.98, which is fabricated by a high precision aspherical DTM (diamond turning machine). Also, we evaluate the degree of shape of the aspherical mirror by this autostigmatic null lens testing method. The autostigmatic null lens system assembling in a fixed tube mount has several advantages of light weight, good mechanical stability, etc. The permissible fabricating limits of null lenses and a mount are determined by considering various tolerances to assure the measurement reliability.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.665-671
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• 2015

The performance of fault diagnostics for a planetary gearbox depends on vibration modulation characteristics, which can vary with manufacturing & assembly tolerance, and load condition. In this paper, a fault diagnostics technique that considers vibration modulation characteristics is proposed for the effective fault detection of planetary gearboxes in wind turbines. For identifying the vibration modulation characteristics in practice, re-sampled vibration signals are processed with narrow band-pass filters. Thereafter, the optimal position of the vibration extraction window is identified for effective detection of faulty signals under the varying vibration modulation characteristics. The proposed diagnostics technique makes it possible to perform robust diagnostics of the planetary gearbox with regard to the changeable vibration modulation effect. For demonstrating the proposed fault diagnostics technique, a 2-kW WT testbed is designed with two DC motors and gearboxes. A faulty gear with partial tooth breakage is machined and assembled into the gearbox.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.93-99
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• 2005

In this work, computer-aided process design is carried out to develop an optimal preform of a pressure vessel. Knowledge-based rules are employed to design the preform, and they are formulated using the handbooks of plasticity theories. In the FE-analysis, a commercial finite element code, ABAQUS was employed. Axisymmetric deep drawing of a hemisphere-bottomed cup has been analyzed fur various combinations of die design parameters. The length of the land of die, the clearance between punch and die and the clearance between the blank holder and die are optimized to minimize the forming load. The results of the simulations are verified with the experiments which are scaled down to one tenth of the actual size.