• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.101-101
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• 2016

DLC(Diamond Like Carbon)막은 그 물성의 다양함으로 인하여 산업기계, 금형, 공구, 광학 및 수송기기의 파워셀 부품등 많은 산업분야에 활용되고 있다. 일반적으로 DLC막은 증착에 사용되는 카본의 원료에 따라 크게 두 가지로 나눌 수 있는데, 이는 탄화 수소계 가스(CxHy)를 사용하여 증착된 a-C:H(amorphous Hydro-Carbon)과 고체 카본을 사용하는 a-C(amorphous Carbon)이다. 또한 a-C 중 진공 아크 공법으로 제작된 막(ta-C : tetrahedral amorphous-Carbon)은 다이아몬드 성분인 sp3의 분률이 높아, 그 경도는 40 - 85 GPa 이상이며, 무수소화로 500도 이상의 고온에서도 그 물성의 변화가 적어 그 활용도가 높아지고 있다. 하지만 높은 경도와 더불어 막의 잔류응력이 높아 3 um 이상 후막화하는 것은 어렵다. 이는 높은 잔류응력으로 인한 막의 증착시, 막 자체가 파손되거나, 기판과 막사이의 계면 밀착력이 약하여 박리되거나, 또는 높은 밀착력으로 인하여 모재가 파손되는 등 다양한 문제를 발생한다. 본 연구에서는 이 고경도 무수소 DLC막(ta-C)의 후막화하는 방안으로 주요 코팅 변수와 잔류응력과의 관계를 에너지 관점에서 파악하고 이를 활용 잔류응력을 제어하여 할 수 있는 방법을 제시하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.11
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• pp.1183-1189
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• 2015

This study focuses on the design of the tapered joints of a wind power turbine. The main variables of the tapered joint are the transmitted torque, shaft diameter, contact area of the tapered ring, and tightening torque of the bolts, which applies a compressive pressure from the hub to the shaft. The stress distribution of the taper fit was calculated under axisymmetric plane strain conditions because of the small taper angle. The axial displacement of the clamp can be calculated from the radial elastic deformation and the taper angle. The stress field of each ring is obtained from the cylinder stress equation. To verify the accuracy of the calculation, finite element (FE) analysis was performed, and the results of the calculation and FE analysis were compared. The hoop stress of the tapered surface showed a discrepancy of approximately 10, but the trends of the stress distributions of each component and the relative movement obtained by FE analysis were in good agreement with the analytical calculation results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.672-679
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• 2018

This paper describes a methodology for shape design using an optimal design system, whereas generally a three dimensional analysis is required for such designs. An automatic finite element mesh generation technique, which is based on fuzzy knowledge processing and computational geometry techniques, is incorporated into the system, together with a commercial FE analysis code and a commercial solid modeler. Also, with the aid of multilayer neural networks, the present system allows us to automatically obtain a design window, in which a number of satisfactory design solutions exist in a multi-dimensional design parameter space. The developed optimal design system is successfully applied to evaluate the structures that are used. This study used a stress gauge to measure the maximum stress affecting the parts of the side housing bracket which are most vulnerable to cracking. Thereafter, we used a tool to interpret the maximum stress value, while maintaining the same stress as that exerted on the spot. Furthermore, a stress analysis was performed with the typical shape maintained intact, SM490 used for the material and the minimizing weight safety coefficient set to 3, while keeping the maximum stress the same as or smaller than the allowable stress. In this paper, a side housing bracket with a comparably simple structure for 36 tons was optimized, however if the method developed in this study were applied to side housing brackets of different classes (tons), their quality would be greatly improved.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.18-21
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• 2009

The life of components under high thermal load is typically shorter than other components. The turbopump turbine of liquid rocket is operated under these environments like high temperature and high centrifugal dorce due to high rotating velocity during operating time. These conditions may often cause low-cycle fatigue problem in the turbopump turbine. First of all, to analyze heat stress, ABAQUS/CAE is used and Coffin-manson's equation is used to consider elasticity and plasticity strain. S.W.T's method is used to consider the mean stress effect, using strain history, low-cycle fatigue analysis is done for turbopump turbine which may have FCL(fracture critical location). In this paper, strain life method is applied to analyze low-cycle fatigue.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.481-486
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• 2010

Recently, carbon fiber reinforced plastic (CFRP) have been used in various fields because of its high specific modulus, and chemical properties. Most products in which CFRP composites are used are manufactured by joining the product components by bolts or pins. Holes for bolts and pins decrease the strength of the components because these holes act as notches in the structures. In this study, the fracture strength of CFRP plain-weave composite plates containing holes is experimentally investigated to examine the effects of hole-size and specimen width on notched tensile strength. The results show that the characteristic length considered in the point stress criterion depends on the hole size and specimen width. There exists a certain relation between notched tensile strength and characteristic length. Fracture criterion is redefined on basis of this relation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.5
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• pp.575-582
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• 2011

A cleaning blade is an attachment installed in the toner cartridge of a laser printer for removing the residual toner from an organic photo-conductive drum. There have been many studies on the performance and life of the rubber blade. We focus on optimally designing the blade shape parameters to minimize the maximum stress of the blade while satisfying design constraints on the cleaning performance and part interference. The blade is optimally designed using a design of experiments, meta-models and an optimization algorithm implemented in PIAnO (process integration, automation, and optimization), a commercial PIDO (process integration and design optimization) tool. We integrate the CAE tools necessary for the structural analysis of the cleaning blade, automate the analysis procedure, and optimize the solution using PIAnO. We decreased the maximum stress by 32.6% in comparison with that of the initial design.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.4
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• pp.223-231
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• 2022

Residual stress that can occur during the metal additive manufacturing process is an important factor that must be properly controlled for the precise production of metal parts through 3D printing. Therefore, in this study, the factors affecting these residual stresses were investigated using an experimental method. For the experiment, a specimen was manufactured through an additive manufacturing process, and the amount of deformation was measured by cutting it. By appropriately calibrating the measured data using methods such as curve fitting, it was possible to quantitatively analyze the effect of process parameters and metal powder reuse on deformation due to residual stress. From this result, it was confirmed that the factor that has the greatest influence on the magnitude of deformation due to residual stress in the metal additive manufacturing process is whether the metal powder is reused. In addition, it was confirmed that process parameters such as laser pattern and laser scan angle can also affect the deformation.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.4
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• pp.7-15
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• 2008

In manufacturing aircraft, safety and lightness of structure are important factors. Utilizing autofrettage technique, these benefits can be obtained. This technique is most frequently applied to a single cylinder. However, the Bauschinger effect reduces the benefits of autofrettage process Therefore, there is increasing interest in the use of compound cylinder that combine shrink fit and autofrettage. In this paper, single and compound cylinders that has same geometry were considered. It was found that compound cylinder which was autofrettaged has lower tangential hoop stress and plastic strain than single cylinder at bore. This means a reduction in the impact of the Bauschinger effect after shrink-fitting which produces the beneficial bore hoop stress.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.20-20
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• 2012

최근, 수송기기 분야는 국제 환경규제 강화에 따른 CO2 절감, 연비향상, 경량화를 위한 기술적 수요가 증대되고 있으며, 그린카, 그린선박 등 친환경 수송기기에 대한 연구가 활발히 진행되고 있다. 하지만, 기존의 금속소재가 가지는 경량화의 한계를 극복하기 위해서는 CFRP, GFRP 등 금속대체 복합소재를 적용한 수송용 경량부품 개발에 대한 필요성이 요구되고 있다. 복합소재는 섬유사이에서 응력을 전달하는 기지(Matrix)와 하중을 전달하는 섬유(Fiber)의 종류와 양 및 적층 각도에 따라 수송용 부품에 적합한 기계적 특성을 얻을 수 있고, 높은 비강도와 비강성의 값을 갖게 되어 경량화가 용이한 장점이 있다. 반면, 섬유재의 종류, 성형방법, 경화온도 등에 따라 물리적 특성에 큰 변화가 발생하며, 수지의 경화조건에 따라 성형시간이 많이 소요되는 단점을 가지고 있다. 따라서, 본 연구에서는 자동차, 선박, 항공기, 철도차량 등 각종 수송기기의 경량화를 목적으로 생산성 향상 및 성형시간 절감을 위해 열가소성 수지, 저온속경화 수지를 적용하여, 경화 시간을 단축시키고, 3D-fabric 및 다층구조 직물을 Vacuum Infusion 공법으로 성형하여, 기존의 섬유재 적층시 소요되는 작업 공정을 간소화 할 수 있도록, 고속성형 복합소재를 적용한 수송용 경량부품 개발에 관한 연구를 수행하였다.

• Journal of the Korean Society for Precision Engineering
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• v.4 no.4
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• pp.13-21
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• 1987

4-4 품질관리 품질관리에는 세가지의 중요한 스텝이 있다. 첫째는 소요자재의 관리, 두째는 공장에서 조립할때의 관리, 세째는 출고관리이다. 특수 파괴설계방법론을 이 모든 과정들에 적용시켜야 할 것이다. 4-4-1 수입자재의 품질 자재들을 매입 혹은 수입할 경우에 검사하여야 할 여러가지 가 있다. 1 재료를 매입할 때 성질들이 얼마나 균일한가\ulcorner 2 최소 인성치는 얼마로 보증되어 있는가\ulcorner 3 재료들을 선별하여 거절하느나, 수락하느냐를 결정하기 위하여 어떠한 비파괴 검사법을 사용하느나\ulcorner 수입재료들에 대해서 파괴측정 시험을 해보면 실험방법이나 재료종류들에 관련되어서 실험데이타들에 전형적인 산포현상이 나타나게 마련이다. 예를들어보면 항복응력이 1400Mpa인 퀘칭하여 켐퍼링한 강의 공칭 파괴인성치는 $_{4}$는 90Mpa .root. m 일 수도 있고 60Mpa .root. m일 수도 있다. 아래 그림에 이 현상을 예시하였다. 파괴문제가 중요시 되는 부품에 대해서는 특수하게 파괴인성치를 규정하여 재료를 구입하여야 한다.