• Title/Summary/Keyword: Dynamic condition

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Dynamic Process Capability Indices

  • Sun, Jing
    • International Journal of Quality Innovation
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    • v.3 no.2
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    • pp.74-83
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    • 2002
  • Process capability indices as an important kind of indices are intended to provide single-number assessments of the inherent process capability to meet specification limits on quality characteristic(5) of interest. In this paper the condition for the application of process capability indices is analyzed. On the basis of process capability indices, dynamic process capability indices as a new kind of indices to show the current process capability are discussed and the condition for the application of dynamic process capability indices is exhibited. Comparison between process capability index and dynamic process capability index and comparison between $D_p$ and $D_pk$ are made and the conclusions provide the approach for process control. According to the requirement of process capability indices provided by customer, quality control based on process capability indices dynamic process capability indices is discussed.

Experimental Study on Condition Evaluation for Railway Ballasted Track (자갈궤도의 상태평가를 위한 실험적 연구)

  • Choi, Jung-Youl;Bahng, Eun Young
    • Journal of the Korean Society of Safety
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    • v.33 no.2
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    • pp.152-157
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    • 2018
  • The degradation and damage of the components for ballasted track could be caused a serious problem for railway safety. Therefore, the integrity evaluation of ballasted track condition is important to ensure and predict that the track safety and track maintenance. Various track components such as rail pad, ballast, sleeper, and rail that are widely used in Republic of Korea and represent a range of physical properties have been selected for this research. In this study, the experimental modal analysis was performed by the non-destructive testing. Modal test results were obtained from the field test and used to assess the condition of the track components. From the field test, the system of ballasted track was found to be simplified as a two-degree-of-freedom(2DOF) dynamic system. The condition of track component was found to directly affect the dynamic response of ballasted tracks. As the results, the dynamic properties of the track component was depend on the track condition and was distributed more roughly and over a wider range than its initial design values. Further, the methodology presented in this study is possible to determine experimentally the fundamental track parameters which are required in the numerical analysis, and also are useful for the safety assessment of track condition.

EFFECT OF STRENGTH MISMATCH AND DYNAMIC LOADING ON THE DUCTILE CRACK INITIATION FROM NOTCH ROOT

  • An, Gyn-Baek;Yoshida, Satoshi;Ohata, Mitsuru;Toyoda, Masao
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.145-150
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    • 2002
  • It has been well known that ductile fracture of steels is accelerated by triaxial stresses. The characteristics of ductile crack initiation in steels are evaluated quantitatively using two-parameters criterion based on equivalent plastic strain and stress triaxiality. It has been demonstrated by authors using round-bar specimens with circumferential notch in single tension that the critical strain to initiate ductile crack from specimen center depends considerably on stress triaxiality, but surface cracking of notch root is in accordance with constant strain condition. In order to evaluate the stress/strain state in the specimens, especially under dynamic loading, a thermal, elastic-plastic, dynamic finite element (FE) analysis considering the temperature rise due to plastic deformation has been carried out. This study provides the fundamental clarification of the effect of strength mismatching, which can elevate plastic constraint due to heterogeneous plastic straining, loading mode and loading rate on critical condition to initiate ductile crack from notch root using equivalent plastic strain and stress triaxiality based on the two-parameter criterion obtained on homogeneous specimens under static tension. The critical condition to initiate ductile crack from notch root for strength mismatched bend specimens under both static and dynamic loading would be almost the same as that for homogeneous tensile specimens with circumferential sharp notch under static loading.

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Effect of Dynamic SGS Model in a Kerosene-LOx Swirl Injector under Supercritical Condition

  • Heo, Jun-Young;Hong, Ji-Seok;Sung, Hong-Gye
    • International Journal of Aeronautical and Space Sciences
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    • v.16 no.2
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    • pp.254-263
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    • 2015
  • In this study, numerical simulations are carried out to investigate the dynamic SGS model effects in a Kerosene-LOx coaxial swirl injector under high pressure conditions. The turbulent model is based on large-eddy simulation (LES) with real-fluid transport and thermodynamics. To assess the effect of the dynamic subgrid-scale (SGS) model, the dynamic SGS model is compared with that of the algebraic SGS model. In a swirl injector under supercritical pressure, the characteristics of temporal pressure fluctuation and power spectral density (PSD) present comparable discrepancies dependant on the SGS models, which affect the mixing characteristics. Mixing efficiency and the probability density (PDF) function are conducted for a statistical description of the turbulent flow fields according to the SGS models. The back-scattering of turbulent kinetic energy is estimated in terms of the film thickness of the swirl injector.

Kinematic Modeling and Inverse Dynamic Analysis of the IWR Biped Walking Robot (이족보행로봇 IWR의 기구학적 모델링과 역동역학 해석)

  • 김진석;박인규;김진걸
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.05a
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    • pp.561-565
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    • 2000
  • This paper deals with dynamic walking and inverse dynamic analysis of the IWR biped walking robot. The system has nine bodies of the multibody dynamics. and all of the .joints of them are made up of the revolute joints at first. The problem of redundant constraint in double support phase is solved by changing the type of the joints considering kinematic relation. To make sure of its dynamic walking, the movement of balancing weight is determined by which satisfies not only the condition of ZMP by applying the principle of D'Alembert but also the contact condition of the ground. The modeling of IWR and dynamic walking are realized using DADS.

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Computational Study on Dynamic Characteristics of a Flapped Airfoil (전산해석을 이용한 고양력장치의 동특성 고찰)

  • Lee, Yung-Gyo;Kim, Cheol-Wan
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.206-209
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    • 2011
  • During landing approach, an airplane could experience dynamic unstable motion by the combination of a gust and elevator control to cancel the disturbances. This situation is dangerous and could lead to a loss of an airplane. In this paper, numerical analysis was used to study the effect of pitch oscillating 2-D high lift devices in a landing condition. Experimental data on a pitching naca0012 airfoil was used for code validation. Dynamic characteristics of an airfoil, single slotted flap for mid-class passenger aircraft were analyzed. Unsteady Navier-Stokes analysis was performed with Spalart-Allmaras turbulence model for separation dominant low speed flow. As a result, flow hysteresis of a flapped airfoil was more complex than that of an oscillating airfoil. So, dynamic analysis of a flap in a landing condition is very important for operational safety.

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Effect of Interphase Condition and Fiber Content on the Dynamic Properties of Short-fiber Reinforced Chloroprene Rubber (계면상 조건과 단섬유 함유량이 단섬유 강화CR의 동적특성에 미치는 영향)

  • Ryu, Sang-Ryeoul;Lee, Dong-Joo
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1151-1156
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    • 2003
  • The dynamic properties of short-fiber reinforced Chloroprene rubber for vibration isolators have been studied as functions of interphase conditions and fiber content. The loss factor showed the maximum at strain amplitude 2%, and increased 0.09 for matrix, 0.05 for reinforced rubber with increasing frequency respectively. The dynamic ratio rapidly decreased with increasing strain amplitude, and some increased with increasing frequency. The better interphase condition showed the lower dynamic ratio. Therefore, the short-fiber reinforced rubber could have the better isolation in frequency ratio(${\sqrt{2}}min$.) compared to frequency ratio(${\sqrt{2}}max$.). And we have investigate the possibility of applying short-fiber reinforced rubber to automotive engine mount.

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Variation of the dynamic coefficients of the plain journal bearing considering vapor pressure (증기압을 고려한 플레인 저널 베어링의 동특성 변화)

  • Seo, Jun-Ho;Park, Jae-Hong;Rhim, Yoon-Chul
    • Transactions of the Society of Information Storage Systems
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    • v.8 no.1
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    • pp.27-32
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    • 2012
  • Fluid dynamic bearings have several advantages that low noise, high rotational stability and low friction. So, early 2000s, the HDD spindle motors have been replaced ball bearings to fluid dynamic bearing. Most of studies apply inner boundary condition that is inside of bearing pressure larger than atmosphere pressure. Therefore, they used Half-Sommerfeld or Reynolds Boundary condition. This paper investigates the dynamic coefficients of the plain journal considered vapor pressure. As a result, it shows that the vapor pressure effect cannot ignore.

A Dynamic Output Feedback Variable Structure Controller for Uncertain Systems with Unmatched System Matrix Uncertainty (부정합 시스템 행렬 불확실성을 갖는 시스템을 위한 동적 출력 궤환 가변 구조 제어기)

  • Lee, Jung-Hoon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.11
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    • pp.2066-2072
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    • 2010
  • In this paper, a variable structure dynamic output feedback controller with an transformed sliding surface is designed for the improved robust control of a uncertain system under unmatched system uncertainty, matched input matrix uncertainty, and disturbance satisfying some conditions. This paper is extended from the results of the static output feedback VSS in [9]. To effectively remove the reaching phase problems, an initial condition of the dynamic output is determined. The previous some limitations on the dynamic output feedback variable structure controller is overcome in this systematic design. A stabilizing control is designed to generate the sliding mode on the predetermined sliding surface S=0 and as a results the closed loop exponential stability is obtained and proved together with the existence condition of the sliding mode on S=0 for all unmatched system matrix uncertainties. To show the usefulness of the algorithm, a design example and computer simulations are presented.

Study on the Transient EHL Fluid Film for the Dynamic Contact Behaviors between Cam and Follower with Multigrid Multilevel Method (다중격자 다중차원 기법을 응용한 캠과 종동물의 비정상 상태의 유막특성 연구)

  • 장시열
    • Tribology and Lubricants
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    • v.20 no.3
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    • pp.132-139
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    • 2004
  • Many researches about the contacts between cam and follower have investigated EHL film thickness either without dynamic loading effect or only with curve fitting formula such as Dowson-Hamrock's, because including squeeze film effect makes it hard to obtain convergence and stability of computation. Therefore, inaccurate information about minimum film thickness without dynamic loading condition causes inappropriate design of cam profiles and wrong selection of cam and follower materials. In this work, computation tools both for kinematics and dynamics of valve train system of push-rod type and for fluid film thickness with elastic deformation on the basis of dynamic loading condition with multigrid multi-level method is developed. The computational results of minimum film thickness with the respects of both static and dynamic loading conditions are compared for the contact of flat follower over the entire cycle.