• Title/Summary/Keyword: Mechanical Characteristic

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Performance Analysis of a Geometrically Asymmetric Trapezoidal Fin for an Enhanced Heat Exchanger (향상된 열교환기를 위한 기하학적 비대칭 사다리꼴 핀의 성능 해석)

  • Song, Nyeon-Joo;Kang, Hyung-Suk
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.4
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    • pp.24-31
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    • 2011
  • Performance of the asymmetric trapezoidal fin with various upper lateral surface slopes is investigated by using the two-dimensional analytic method. For a fin base boundary condition, convection from the inner fluid to the inner wall, conduction from the inner wall to the fin base and conduction through the fin base are considered. Heat loss and fin efficiency are represented as a function of the fin base thickness, base height, inner fluid convection characteristic number, fin tip length and fin shape factor. One of the results shows that heat loss increases while fin efficiency decreases as the fin shape factor increases.

Measurement of Nonlinear Elastic Constants and Material Characterization by Using Nonlinear Elasto-acoustics (비선형 탄성-음향 효과를 이용한 비선형 탄성 계수의 계측과 금속재료의 특성평가)

  • ;;Sato, Takuso
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.8
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    • pp.1971-1979
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    • 1993
  • In this paper, a new method to estimate stress status in metal nondestructively by using nonlinear dependency of sound speed on stress is proposed. For the purpose, equivalent nonlinear elastic constants up to fourth-order are introduced and a new characteristic parameter given as a function of these constants is presented. And a concrete system to measure the characteristic parameter is constructed by electromagnetic pumping wave and ultrasonic probing wave system. Some experimental results for Al alloy showed that the estimation of stress status in metal is possible by the proposed method.

Dependency of Planarization Efficiency on Crystal Characteristic of Abrasives in Nano Ceria Slurry for Shallow Trench Isolation Chemical Mechanical Polishing (STI CMP용 나노 세리아 슬러리에서 연마입자의 결정특성에 따른 평탄화 효율의 의존성)

  • Kang, Hyun-Goo;Takeo Katoh;Kim, Sung-Jun;Ungyu Paik;Park, Jea-Gun
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2003.11a
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    • pp.65-65
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    • 2003
  • Chemical mechanical polishing (CMP) is one of the most important processes in recent ULSI (Ultra Large Scale Integrated Circuit) manufacturing technology. Recently, ceria slurries with surfactant have recently been used in STI-CMP,[1] became they have high oxide-to-nitride removal selectivity and widen the processing margin The role of the abrasives, however, on the effect of planarization on STI-CMP is not yet clear. In this study, we investigated how the crystal characteristic affects the planarization efficiency of wafer surface with controlling crystallite size and poly crystalline abrasive size independently.

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Combustion Characteristic of Non-esterified Bio-diesel Oil at Lower Common Rail Pressure (저 커먼레일 압력에서 비에스테르화 바이오 디젤유의 연소특성)

  • Lee, Sang-Deuk;Koh, Dae-Kwon;Jung, Suk-Ho
    • Journal of Power System Engineering
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    • v.17 no.6
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    • pp.11-17
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    • 2013
  • Esterified bio-diesel oil is normally used as blend oil of 3% that and 97% diesel fuel in Korea. Since specifics of it is similar to that of diesel fuel, availability of non-esterified bio-diesel oil that has a lower expenses of manufacturing is worthy of attention. However, bio-diesel oil has a demerit which it emits typically more NOx emission than diesel fuel. In this study, characteristic tests using blending oil with 95% gas oil and 5% bio-diesel oil were achieved at lower common rail pressure in order to improve this demerit. It was noticed that non-esterified bio-diesel oil has more similar characteristics to diesel fuel than esterified bio-diesel oil and it emits more NO emission by fuel NO mechanism.

Vibration of Elevator Rope with a Spring-mass System at the Tip (끝 단에 스프링-질량계가 연결된 엘리베이터 로프의 진동)

  • Kwak, Moon K.;Han, Sangbo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.4
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    • pp.317-323
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    • 2014
  • This study is concerned with the free vibration analysis of an inextensible uniform rope with a spring-mass system at the tip. The rope is hanged vertically in a gravitational field. This problem is related to the free vibration of an elevator rope connected to an elevator cage. The equation of motion and the corresponding boundary conditions are derived by using the Hamilton's principle. The general solution of the governing equation of motion is expressed in terms of Bessel functions. The characteristic equation was derived by applying the boundary conditions. The characteristic values which are in fact non-dimensionalized natural frequencies were obtained numerically. The effects of mass and spring constant were investigated. The numerical results show how the tip mass and spring affect the natural frequencies of the rope.

Fracture Resistance Characteristics of SA516-Gr.70 Steel Plate for RCS Piping Elbow and Support Skirt (원자로 냉각재배관 엘보우 및 서포트 스컷트용)

  • Son, Jong-Dong;Lim, Man-Bae
    • Journal of the Korean Society of Safety
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    • v.21 no.4 s.76
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    • pp.49-54
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    • 2006
  • The evaluation of elastic-plastic fracture characteristic was investigated in ferrite steel SA 516- Gr70 used for reactor coolant piping elbow and support skirt of pressure vessels. This paper describes the effect of temperature on J-R curve characteristic of this material. The elastic-plastic fracture mechanics parameter J is obtained with unloading compliance method. The test method were analyzed according to ASTM E 813-89 and E 1152-89. Unloading compliance $J_{IC}$ tests were performed on 1 CT specimens at varied temperatures from $25^{\circ}C$ to about $400^{\circ}C$ using a high temperature extensometer. At all temperature, valid $J_{IC}$ measurements could be made and $J_{IC}$ decreased with increasing temperature. SEM fractography schematically illustrates microvoid initiation, growth and coalescence at the tip of a preexisting crack.

Leakage Characteristic of Angled-Circumferential-Groove-Pump Seal with CFD Analysis (각이 진 평행 홈 펌프 실의 누설량 특성 해석)

  • Choi, Bok-Sung;Ha, Tae-Woong
    • Tribology and Lubricants
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    • v.25 no.2
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    • pp.96-101
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    • 2009
  • In order to improve leakage characteristic, angled-circumferential-groove pump seal is suggested. CFD analysis using FLUENT has been performed to predict leakage and determine an optimum slanted-groove angle $\alpha$ which yields the best leakage reduction. The optimum value of $\alpha$ ranges from $45^{\circ}$ to $60^{\circ}$ and depends on the pressure difference of seal and number of grooves for the same groove geometry. The maximum leakage reduction ratio increases as increasing the pressure difference of angled-circumferential-groove pump seal with the optimum value of $\alpha$.

Transient Response of Head Slider with the Head Geometry Change in Magnetic Storage Devices

  • Mongkolwongrojn, M.
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.906-909
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    • 2005
  • In this study, the dynamic flying characteristics of the worn head sliders are investigated theoretically due to the change in head geometry caused by head and disk contact. The film shapes can be approximated as taper- truncated cycloidal-flat film. Two-dimensional time dependent modified Reynolds equation included molecular slip effect are formulated with neglected the roughness effect. The motion of head slider was assumed to have two degree of freedom in this work. Finite difference approximation with Newton Raphson iterative technique and the fourth order Runge-Kutta method were implemented to obtain the transient response of the slider head with various change in head geometry numerically and compared with the transient response of the IBM3380 type head slider. The simulation results show the film shape has affects significantly on the static and dynamic characteristic of slider head in magnetic storage systems.

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Reignition of Methanol Droplet Flames Under Acoustic Pressure Oscillation (메탄올 액적 화염의 음향파 가진에 의한 재점화)

  • Kim, Hong Jip;Sohn, Chae Hoon;Chung, Suk Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.1
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    • pp.114-122
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    • 1999
  • Reignition as special cases of acoustic pressure responses of flame are numerically studied by employing methanol droplet flame as a laminar flamelet. Quasi-steady flame responses occur in the range of small amplitude, low frequency oscillation. Reignition phenomena can occur when, by increasing the frequency of large amplitude acoustic pressure, the magnitude of characteristic acoustic time is the same order of that of characteristic reaction time of flames. And more increasing of amplitude of acoustic pressure induces the direct extinction of flame. Flame can sustain its own intensity even under the steady extinction temperature in case of high frequency acoustic oscillation, and this tendency is remarkable with increasing frequency. Reignition regime with respect to amplitude and frequency of acoustic pressure doesn't exist in low frequency($10^2$ Hz, in this study), but broadens with frequency of acoustic pressure.