• 한국신뢰성학회지:신뢰성응용연구
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• 제15권4호
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• pp.241-247
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• 2015

Purpose : The demand for higher fuel economy vehicles has helped develop fuel-efficient vehicles such as a CVVL called continuous variable valve lift. Existing CVVL has been applying DC type motor to control intake valve, but recently some car parts manufacturers have been developing a BLDC type CVVL motor for improvements of endurance performance. The purpose of this study is to find the potential failure mechanism of the CVVL BLDC moto in early stage of development based on the design properties and design the accelerated life test model. Methods : CVVL BLDC is consist of brushs, coil, magnetic, PCB, bearing and so on. Each component has a latent failure mechanism caused by temperature, humidity, vibration. By analysis result of the failure mechanism, thermal fatigue is the most important factor of a durability of CVVL BLDC motor. So, we designed a new accelerated life test model for guarantee of the CVVL BLDC motor. Results : A crack occurred on via hole in test using the conditions we designed, so we did change the design to avoid this failure. The via hole dimension is changed a little larger, as a result we achieve improvements in reliability of the CVVL BLDC motor. By applying various kinds and extreme level of stresses, we can find the operating limits of products. Conclusion : In thesis, We analyzed the failure mechanism of CVVL BLDC and designed an accelerated life test method to give a guarantee for reliability. Based on the test results, we could improve the reliability of developments by change of design.

• 한국자동차공학회논문집
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• 제24권3호
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• pp.338-344
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• 2016

The study is actively being performed to increase fuel injection pressure of common rail system among countermeasures to meet the emission regulation strengthen of the Diesel engine. The common rail fuel injection tube in such ultra high pressure common rail system has the weakest structural characteristics against vibration that is generated by fuel injection pressure and pulsation during engine operation and driving. Thus the extreme durability is required for common rail fuel injection tube, and the drawing process is being magnified as the most important technical fact for strength of seamless pipe that is the raw material of common rail tube. In this respect, we analyzed the characteristic of dimension and stress variation of the ultra high pressure common rail fuel injection tube by variation of Die and Plug angle in drawing process. Based on the analysis, we tried to obtain the raw material strength of common rail fuel injection tube for applying to the ultra high pressure common rail system. As a result, Plug angle is more important than entry angle of Die and we could obtain the target dimension and strength of the ultra high pressure common rail fuel injection tube through optimization of Plug angle.

• Tribology and Lubricants
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• 제30권4호
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• pp.234-239
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• 2014

Magneto-rheological elastomer (MR elastomer) is a smart material, because it has mechanical properties that change under a magnetic field. An MR elastomer changes its stiffness characteristics when the inner particles (iron particles) align along the direction of a magnetic field. There has been much research to make use of this characteristic to control vibration issues in various mechanical systems, such as for mounting systems in the automotive field, home appliances, etc. Furthermore, the friction and wear properties of MR elastomer have been studied, as these relate to the durability of the material needed to meet engineering requirements. Rolling friction (or rolling resistance) is one of these friction properties, but has not yet been studied in the context of MR elastomers. In this study, an MR elastomer is fabricated in the shape of a hollow cylinder to evaluate the rolling friction characteristic under a magnetic field. The test apparatus is setup and a strain gauge is used to calculate the rolling resistance under test conditions. Permanent magnets are used to supply the magnetic field during tests. The load and rolling speed conditions are also considered for the tests. The test results show that rolling friction characteristic has a different trend under different magnetic field, load, and rolling speed conditions. It is assumed that the stiffness change of an MR elastomer under a magnetic field has an effect on the rolling friction characteristic of the MR elastomer. For the future work, the rolling friction characteristics of MR elastomers will be controlled by adjusting the strength of the magnetic field using electromagnets.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1267-1272
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• 2007

철도교량의 경우 교면방수 시공 후 방진매트, 궤도자갈 및 침목부설, 레일 설치 등의 후속공정이 뒤따르고, 시공 및 경제적인 여건으로 인해 위의 공정이 연속적으로 시행되지 못하고 일정 구간 단위로 후속공정이 이루어지는 특수성을 갖고 있다. 이로 인해 교면방수 시공 이후 표면의 노출이 장기화 되는 것이 불가피한 실정으로, 시간 경과에 따른 열화현상으로 인해 발수재의 분해 및 용출이 발생하여 방수시공 초기의 침투깊이를 유지하지 못하고 있는 경우가 많다. 이처럼, 철도교량이 갖고 있는 시공적인 특수성과 궤도자갈이 부설되지 않고 영구적으로 표면이 노출되는 부분을 고려한다면 표면의 장기적인 노출에도 방수성능이 저하되지 않는 내구성을 갖고 있는 방수공법을 선택하는 것이 무엇보다 중요하다고 할 수 있다. 본 연구의 목적은 장기간 표면노출에 따른 열화현상을 방지하는 열화억제형 방수공법(DRA방수공법)에 대하여 시험시공을 통한 객관적인 분석 결과를 도출하고, DRA 방수 공법의 KNOW-HOW를 습득하는 것으로, 이를 통하여 철도교량의 교면방수 열화현상으로 인해 발생하는 하자를 방지하여 잦은 보수와 보강으로 인한 경제적 손실을 최소화하고 현장에서의 시공관계자들이 방수공법을 선정하는데 따른 합리적인 판단 기준을 제공하는데 있다.

• 한국융합학회논문지
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• 제6권5호
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• pp.85-90
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• 2015

본 논문은 ATV차량의 전면에 부착되는 범퍼의 구조적인 형상에 따른 수명평가를 피로해석을 토대로 연구하였다. 본 연구의 목적은 진동과 같이 반복적인 하중조건에 노출되는 범퍼의 특성의 파악하며, 여러 가지 피로 상황에서 발생되는 크랙의 위치를 사전에 파악하며 이를 보완하기 위함이다. 다목적 차량이 일반적인 포장도로가 아닌 비포장도로와 같은 험로를 주행하게끔 설계됨을 고려한다. 그리고 이러한 주행환경에 대한 수명평가 연구를 통해, 그 범퍼의 취약부위를 파악한다. 본 연구의 해석결과를 토대로 자동차 범퍼의 안전설계를 함으로서 내구성을 향상하고 설계에 있어 융합기술에 접목하여 그 미적인 감각을 나타낼 수 있다.

• 대한기계학회논문집A
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• 제34권3호
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• pp.353-359
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• 2010

최근 환경문제로 인한 차량의 연료절감이 중요해지면서 수송산업에서도 대형 수송기계의 경량설계에 대한 필요성이 지속적으로 커지고 있다. 본 연구에서는, 고강도강으로 대체된 대형 평판 트레일러 프레임의 경량모델을 개발하기 위하여 구조해석을 수행하였다. 이를 위하여, 트레일러 프레임의 주요 설계변수들을 선정하고 다구찌 기법을 적용하여 응력, 처짐량 그리고 비틀림 강성에 대하여 최적화된 결과를 도출하였다. 또한, 도출된 경량설계안의 타당성을 검토하기 위하여 시작품을 제작하여 실제 내구시험을 수행하였다.

• Elastomers and Composites
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• 제55권2호
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• pp.81-87
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• 2020

Service life prediction and evaluation of rubber components is the foundational technology necessary for securing the safety and reliability of the product and to ensure an optimum design. Even though the domestic industry has recognized the importance thereof, technology for a systematic design and analysis of the same has not yet been established. In order to develop this technology, identifying the fatigue damage parameters that affect service life is imperative. Most anti-vibration rubber components had been damaged by repeated load and aging. Hence, the evaluation of the fatigue characteristics is indispensable. Therefore, in this paper, we propose a method that can predict the service life of rubber components relatively accurately in a short period of time. This method works even in the initial designing stage. We followed the service life prediction procedure of the proposed rubber components. The weak part of the rubber and the maximum strain were analyzed using finite element analysis of the rubber bushing for the tracked vehicles. In order to predict the service life of the rubber components that were in storage for a certain period of time, the fatigue test was performed on the three-dimensional dumbbell specimen, based on the results obtained by the rubber material acceleration test. The service life formula of the rubber bushing for tracked vehicles was derived using both finite element analysis and the fatigue test. The service life of the rubber bushing for tracked vehicles was estimated to be about 1.7 million cycles at room temperature (initial stage) and about 400,000 cycles when kept in storage for 3 years. Through this paper, the service life for various rubber parts is expected be predicted and evaluated. This will contribute to improving the durability and reliability of rubber components.

• 한국유체기계학회 논문집
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• 제14권3호
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• pp.23-27
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• 2011

Due to a roots type medium vacuum pump is operated in condition of $1{\sim}10^{-3}$ torr vacuum, it could be applied for production and process of industrial parts, such as precise processing, vaporization, enrichment, separation, casting, metaling, welding, transportation. Therefore, the demand of this pump is increasing nowadays in our industrial markets of semiconductor, electric, electronic, automobile, material, environmental and transporting industries. However, the pumps are almost imported, because the domestic pumps are inferior in fields of vacuum range as under $10^{-1}$torr, relevant techniques(design, fabrication, casting, test, etc.) to the imported ones. In this study, essential parts of the development pump are designed with using of CFD and 3D decodes, FEM for analysing strength and deformation, generated heat, vibration and noise control, and are casted with using of mechanochemistry techniques for decreasing of weights, increasing of heat resistances and abrasion durability of materials for pump caing and impellers especially. Besides, in order to achieve ultimate vacuum around $10^{-3}$torr, this pump is composed of 6 stages, among which 1st stage is operated separately from remained stages. Additionally, a test rig for prototype pumps(300$m^3/h$ and 2,500$m^3/h$) is designed and procured as to apply for multi-staged rootz type vacuum pump, with modification of the test method recommended by KS B 6314 "Positive-displacement oil-sealed rotary vacuum pumps".

• 한국산학기술학회논문지
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• 제15권5호
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• pp.2617-2622
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• 2014

본 연구에서는 카메라 생산 시스템의 모터가 Z축 방향으로 작업할 때 시스템에 발생하는 위험진동수를 해석하였다. 모달해석을 통하여 얻어진 결과를 보면 두 가지 모델에 발생한 고유진동들에 있어서의 각 모드의 형상을 조사할 수 있다. 본 연구 시스템에서 고유진동수 범위는 100Hz부터 500Hz로 나왔다. 모터의 무게가 20kg인 경우에 모델의 최대 등가응력이 6.2335MPa로 발생하는 것을 확인할 수 있고 이 값은 모터가 10kg인 경우의 최대 등가응력 값보다 50배 큰 것으로 나타났다. 본 카메라 생산 시스템의 고유진동과 하모닉 응답해석을 통하여 시스템의 작업 안전성을 고찰할 수 있었다.

• 한국기계가공학회지
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• 제18권9호
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• pp.29-35
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• 2019

The structure of the machinery industry due to the 4th industrial revolution is changing from precision and durability to intelligent and smart machinery through sensing and interconnection(IoT). There is a growing need for research on prognostics and health management(PHM) that can prevent abnormalities in processing machines and accurately predict and diagnose conditions. PHM is a technology that monitors the condition of a mechanical system, diagnoses signs of failure, and predicts the remaining life of the object. In this study, the vibration generated during machining is measured and a classification algorithm for normal and fault signals is developed. Arbitrary fault signal is collected by changing the conditions of un stable supply cutting oil and fixing jig. The signal processing is performed to apply the measured signal to the learning model. The sampling rate is changed for high speed operation and performed machine learning using raw signal without FFT. The fault classification algorithm for 1D convolution neural network composed of 2 convolution layers is developed.