• 제목/요약/키워드: Mechanical Components

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Structural monitoring of movable bridge mechanical components for maintenance decision-making

  • Gul, Mustafa;Dumlupinar, Taha;Hattori, Hiroshi;Catbas, Necati
    • Structural Monitoring and Maintenance
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    • 제1권3호
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    • pp.249-271
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    • 2014
  • This paper presents a unique study of Structural Health Monitoring (SHM) for the maintenance decision making about a real life movable bridge. The mechanical components of movable bridges are maintained on a scheduled basis. However, it is desired to have a condition-based maintenance by taking advantage of SHM. The main objective is to track the operation of a gearbox and a rack-pinion/open gear assembly, which are critical parts of bascule type movable bridges. Maintenance needs that may lead to major damage to these components needs to be identified and diagnosed timely since an early detection of faults may help avoid unexpected bridge closures or costly repairs. The fault prediction of the gearbox and rack-pinion/open gear is carried out using two types of Artificial Neural Networks (ANNs): 1) Multi-Layer Perceptron Neural Networks (MLP-NNs) and 2) Fuzzy Neural Networks (FNNs). Monitoring data is collected during regular opening and closing of the bridge as well as during artificially induced reversible damage conditions. Several statistical parameters are extracted from the time-domain vibration signals as characteristic features to be fed to the ANNs for constructing the MLP-NNs and FNNs independently. The required training and testing sets are obtained by processing the acceleration data for both damaged and undamaged condition of the aforementioned mechanical components. The performances of the developed ANNs are first evaluated using unseen test sets. Second, the selected networks are used for long-term condition evaluation of the rack-pinion/open gear of the movable bridge. It is shown that the vibration monitoring data with selected statistical parameters and particular network architectures give successful results to predict the undamaged and damaged condition of the bridge. It is also observed that the MLP-NNs performed better than the FNNs in the presented case. The successful results indicate that ANNs are promising tools for maintenance monitoring of movable bridge components and it is also shown that the ANN results can be employed in simple approach for day-to-day operation and maintenance of movable bridges.

배관계 티에서 유동가속부식으로 인한 난류속도성분과 국부감육의 관계 규명 (Identification between Local Wall Thinning and Turbulent Velocity Components by Flow Acceleration Corrosion inside Tee of Pipe System)

  • 김경훈;이상규;조연수;황경모
    • 설비공학논문집
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    • 제23권7호
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    • pp.483-491
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    • 2011
  • When pipe components made of carbon steel in nuclear, fossil, and industry are exposed to flowing fluid, wall thinning caused by FAC(flow accelerated corrosion) can be generated and eventually ruptured at the portion of pressure boundary. A study to identify the locations generating local wall thinning and to disclose turbulence coefficient related to the local wall thinning was performed. Experiment and numerical analyses for tee of down scaled piping components were performed and the results were compared. In particular, flow visualization experiment which was used alkali metallic salt was performed to find actual location of local wall thinning inside tee components. To disclose the relationship between turbulence coefficients and local wall thinning, numerical analyses were performed for tee components. The turbulence coefficients based on the numerical analyses were compared with the local wall thinning based on the measured data. From the comparison of the results, the vertical flow velocity component(Vr) flowing to the wall after separating in the wall due to the geometrical configuration and colliding with the wall directly at an angle of some degree was analogous to the configuration of local wall thinning.

Microstructure and Mechanical Properties of Mg-Li Powder by Hot Rolling Process

  • Choi, Jeong-Won;Kim, Yong-Ho;Kim, Jung-Han;Yoo, Hyo-Sang;Woo, Kee-Do;Kim, Ki-Beom;Son, Hyeon-Taek
    • 한국재료학회지
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    • 제25권1호
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    • pp.32-36
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    • 2015
  • Hot rolling of Mg-6Zn-0.6Zr-0.4Ag-0.2Ca-(0, 8 wt%)Li powder was conducted at the temperature of $300^{\circ}C$ by putting the powder into the Cu pipe. The microstructure and mechanical properties of the samples were observed. Mg-6Zn-0.6Zr-0.4Ag-0.2Ca without Li element was consisted of ${\alpha}$ phase and precipitates. The microstructure of the 8 wt%Li containing alloy consisted of two phases (${\alpha}$-Mg phase and ${\beta}$-Li phase). In addition, $Mg_2Zn_3Li$ was formed in 8%Li added Mg-6Zn-0.6Zr-0.4Ag-0.2Ca alloy. By addition of the Li element, the non-basal planes were expanded to the rolling direction, which was different from the based Mg alloy without Li. The tensile strength was gradually decreased from 357.1 MPa to 264 MPa with increasing Li addition from 0% to 8%Li. However, the elongation of the alloys was remarkably increased from 10 % to 21% by addition of the Li element to 8%. It is clearly considered that the non-basal texture and ${\beta}$ phase contribute to the increase of elongation and formability.

CF8M과 SA508 용접재의 열화거동과 기계적특성 평가 (Evaluation of Mechanical Properties with Thermal Aging in CF8M/SA508 Welds)

  • 우승완;최영환;권재도
    • 대한기계학회논문집A
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    • 제28권12호
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    • pp.1968-1973
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    • 2004
  • Structural degradations are often experienced on the components of nuclear power plants in reactor pressure vessels (RPV) and steam generators (SG) when these components are exposed to high temperature and high pressure for a long period of time. Such conditions result in the change of microstructures and of mechanical properties of materials, which requires an evaluation of the safeguards related to structural integrity. In a primary reactor cooling system (RCS), a dissimilar weld zone exists between cast stainless steel (CF8M) in a pipe and low-alloy steel (SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time under the operating temperature between 290 and 33$0^{\circ}C$. Under the same conditions, it is well known that degradation is not observed in low alloy steel. An investigation of the effect of thermal aging on the various mechanical properties of the dissimilar weld zone is required. The purpose of the present investigation is to find the effect of thermal aging on the dissimilar weld zone. The specimens are prepared by an artificially accelerated aging technique maintained for various times at 43$0^{\circ}C$, respectively. Then, The various mechanical test for the dissimilar welds are performed.

공작기계 시스템의 모델링과 동적특성 분석 (제2보) - 이송계의 모델링과 동적특성 분석 - (Modeling and Dynamic Analysis of Electro-mechanical System in Machine Tools(2$^{nd}$ Report) - Modeling and Dynamic Analysis of Feed Drive System -)

  • 박용환;신흥철;문희성;최종률
    • 한국정밀공학회지
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    • 제16권2호통권95호
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    • pp.218-224
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    • 1999
  • In the feed drive systems of machine tools that consist of many mechanical components such as motor, coupling, ballscrew, nut or table, a torsional vibration is often generated because of its elastic elements in torque transmission. Generally, the accuracy of motion control system is strongly influenced by the dynamic behavior of coupled transmission components. Especially, a torsional vibration caused by the elasticity of mechanical elements might deteriorate the quick movement of system and lead to shorten the life time of the mechanical transmission elements. So, it is necessary to analyze the electromechanical system mathematically to optimize the dynamic characteristics of the feed system. In this paper, the mathematical model of a feed drive system was developed and its mechanical characteristics were analyzed on the basis of the proposed model. The design concepts of speed control loop to stabilize a feed drive system were also proposed.

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경면가공을 위한 수퍼피니싱필름의 효율적인 적용조합에 관한 실험적 연구 (A Experimental Study on Efficient Applicable Combination of Super Finishing Films for Mirror Surface Machining)

  • 조강수;김상규;조영태;정윤교
    • 한국기계가공학회지
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    • 제13권1호
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    • pp.121-128
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    • 2014
  • Superfinishing is essential for mirror surfaces, because among mechanical components cylindrical workpieces such as spindles must maintain precision and reliability with respect to functional characteristics. However, research on standardization of polishing film application combination to obtain mirror surfaces is insufficient. Consequently, this has been a factor in rising costs of mechanical components. Therefore, in this study, experiments have been conducted to determine efficient polishing film application combination for mirror surfaces ranging from ductile materials such as SM45C, brass, aluminium 7075, and titanium to brittle materials such as $Al_20_3$, SiC, $Si_3N_4$, and $ZrO_2$. From the experimental results, efficient polishing film application combination for metallic materials and ceramic materials is confirmed.

수분 오염에 대한 그리스의 트라이볼로지적 특성 (Effect of Water Content on Tribological Characteristics of Grease)

  • 왕도영;유신성;김성수;김대은
    • 한국정밀공학회지
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    • 제33권1호
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    • pp.37-43
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    • 2016
  • Friction of mechanical components affects the life and reliability of various machines. In order to improve the wear resistance of mechanical components, grease has been used as a lubricant. However, depending on the operating condition of the machine, the grease may be contaminated with water, which lowers the its lubricating ability. In this work, the effect of the water content on the lubricating ability of grease was investigated. Friction tests using grease were performed between a stainless steel ball and an acrylic plate. Water content in the grease was varied (0, 5, 10 wt.%). It was found that the contact angle varied due to the addition of water in the grease. The friction and wear of the specimens were assessed with respect to amount of water content. Wear of the specimens was relatively severe when water was added. A water content of 10 wt.% resulted in significant lubricant degradation.

담배 주맥 바이오매스의 압착추출특성 연구 (Study on the Mechanical Extraction Properties of Tobacco Stem Biomass)

  • 성용주;한영림;이문수
    • 펄프종이기술
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    • 제40권2호
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    • pp.65-72
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    • 2008
  • This work evaluated the extractability of tobacco stem biomass for the papermaking type Reconstituted Tobacco Sheet(RTS). The effects of the soaking conditions on the hydration of stem biomass and the effects of the hydrated state on the mechanical extraction were investigated. In order to simulate the mechanical expression process of a papermaking type RTS mill, for example, the screw press process, the novel mechanical pressing analyzer was developed for this study. The hydration of stem biomass by soaking process was greatly affected by the soaking time and the soaking temperature. The longer soaking time and the higher soaking temperature resulted in the higher hydrated stem biomass. Since the higher hydrated stem had more combined water in the inner structure and resulted in the more flexible structure, the higher hydrated stem leaded to the more compressed filter cake and the higher water contents in the filter cake after the mechanical pressing. The pilot pulping experiments showed the difference in hydration and extractability between burley and bright tobacco stem. The bulkier structure of the burley stem resulted in the faster hydration by pilot pulping and leaded to the larger reduction in water soluble components. And the hydration process showed the major influence on the separation efficiency of water soluble components.

Preliminary Round Robin Test(RRT) for Program for the Inspection of Nickel Alloy Components(PINC) - Reactor Vessel Head Penetration (RVHP) -

  • Kim, Kyung-Cho;Kang, Sung-Sik;Shin, Ho-Sang;Song, Myung-Ho;Chung, Hae-Dong;Kim, Yong-Sik
    • 비파괴검사학회지
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    • 제29권3호
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    • pp.256-263
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    • 2009
  • After several PWSCCs were found in Bugey(France), Ringhals(Sweden), Tihange(Belgium), Oconee, Arkansas, Crystal Fever, Davis-Basse, VC Summer(U.S.A.), Thuruga(Japan), USNRC and PNNL started the research on PWSCC, that is, the PINC project. USNRC required KINS to participate in the PINC project in May 2005. KINS organized the Korean consortium at March 2006 and Pre-RRT for RVHP were performed for the preparation of PINC RRT. Through these preliminary RRT, Korea NDE teams can learn and develop the detection and sizing technique for RVHP dissimilar metal weld. These techniques are now being prepared in Korea and need to be utilized for the In-service inspection of the RVHP and BMI of Korea Nuclear Power Plants. PINC RRT mock-ups will be helpful to training.

Hydro-mechanical hole punching 공정의 유한요소 해석 (FE Analysis for hydro-mechanical Hole Punching Process)

  • 윤종헌;김승수;박훈재;최태훈;이혜진;허훈
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2005년도 춘계학술대회 논문집
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    • pp.159-162
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    • 2005
  • The milli-components for electronic and medical device etc. have been manufactured by conventional process. Forming and machining process for those milli-components need tremendous cost and time because products require higher dimensional accuracy than the conventional ones. For instance, conventional mechanical punching process has many drawbacks for applying to high accuracy products. The final radius of hole can be varied and burr which interrupting another procedure is generated. Hydro-mechanical punching process makes possible to reduce amount of burr and obtain the fine shearing surface using the operating fluid. Hydrostatic pressure retards occurrence of initial crack and induces to locate the fracture surface in the middle of sheet to thickness direction. In this paper, Hydro-mechanical punching process is analyzed using finite element method and the effect of hydrostatic pressure is evaluated during punching process. The prediction of fracture is performed adopting the various ductile fracture criteria such as Cockcroft, Brozzo and Oyane's criterion using a user subroutine in ABAQUS explicit.

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