• Title/Summary/Keyword: Solid vibrations

Search Result 45, Processing Time 0.037 seconds

Non-contact monitoring of 3-dimensional vibrations of bodies using a neural network

  • Ha, Sung Chul;Cho, Gyeong Rae;Doh, Deog-Hee
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.39 no.10
    • /
    • pp.1011-1016
    • /
    • 2015
  • Gas piping systems in power plants and factories are always influenced by the mechanical vibrations of rotational machines such as pumps, blowers, and compressors. Unusual vibrations in a gas piping system influence possible leakages of liquids or gases, which can lead to large explosive accidents. Real-time measurements of unusual vibrations in piping systems in situ prohibit them from being possible leakages owing to the repeated fatigue of vibrations. In this paper, a non-contact 3-dimensional measurement system that can detect the vibrations of a solid body and monitor its vibrational modes is introduced. To detect the displacements of a body, a stereoscopic camera system is used, through which the major vibration types of solid bodies (such as X-axis-major, Y-axis-major, and Z-axis-major vibrations) can be monitored. In order to judge the vibration types, an artificial neural network is used. The measurement system consists of a host computer, stereoscopic camera system (two-camera system, high-speed high-resolution camera), and a measurement target. Through practical application on a flat plate, the measured data from the non-contact measurement system showed good agreement with those from the original vibration mode produced by an accelerator.

Acoustic Enhancement of Solid-Liquid Phase Change Heat Transfer (음향 흐름에 의한 고-액 상변화 열 전달의 촉진)

  • 박설현;오율권
    • Journal of Energy Engineering
    • /
    • v.11 no.3
    • /
    • pp.262-268
    • /
    • 2002
  • The present paper investigated the effect of ultrasonic vibrations on the melting process of phase-change materials (PCM). Furthermore, the present study considered constant heat-flux boundary condition, whereas many of the previous researches had adopted constant wall-temperature condition. The results of the present study revealed that ultrasonic vibrations accompanied the effects like acoustic streaming, cavitation, and thermally-oscillating flow. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They speed up the melting process as much as 2.5 times, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, temperature and Nusselt numbers over time provided a conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.

Theoretical Studies of Surface Diffusion : Multidimensional TST and Effect of Surface Vibrations

  • 곽기정;신석민;이상엽;신국조
    • Bulletin of the Korean Chemical Society
    • /
    • v.17 no.2
    • /
    • pp.192-198
    • /
    • 1996
  • We present a theoretical formulation of diffusion process on solid surface based on multidimensional transition state theory (TST). Surface diffusion of single adatom results from hopping processes on corrugated potential surface and is affected by surface vibrations of surface atoms. The rate of rare events such as hopping between lattice sites can be calculated by transition state theory. In order to include the interactions of the adatom with surface vibrations, it is assumed that the coordinates of adatom are coupled to the bath of harmonic oscillators whose frequencies are those of surface phonon modes. When nearest neighbor surface atoms are considered, we can construct Hamiltonians which contain terms for interactions of adatom with surface vibrations for the well minimum and the saddle point configurations, respectively. The escape rate constants, thus the surface diffusion parameters, are obtained by normal mode analysis of the force constant matrix based on the Hamiltonian. The analysis is applied to the diffusion coefficients of W, Ir, Pt and Ta atoms on the bcc(110) plane of W in the zero-coverage limit. The results of the calculations are encouraging considering the limitations of the model considered in the study.

An Experimental Study of enhancing heat transfer by Ultrasonic Vibration (초음파 가진에 따른 열전달 향상에 관한 연구)

  • Youn, Joung-Hwan;Oh, Yool-Kwon;Cha, Kyung-Ok
    • Proceedings of the KSME Conference
    • /
    • 2001.11b
    • /
    • pp.235-240
    • /
    • 2001
  • This study presents experimental work on phase change heat transfer, in order to increase heat transfer rate, ultrasonic vibrations were introduced. Solid-liquid phase change occurs in a number of situations of practical interest. This study reveal that ultrasonic vibrations accompany the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. Some common examples include the melting of edible oil, metallurgical process such as casting and welding, and materials science applications such as crystal growth. Therefore, this study presented the effective way to enhance phase change heat transfer.

  • PDF

Free Vibrations of Tapered Circular Arches with Constant Volume (일정체적 변단면 원호형 아치의 자유진동)

  • Lee, Byoung-Koo;Lee, Tae-Eun;Yoon, Hee-Min;Choi, Jong-Min
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.20 no.2
    • /
    • pp.144-152
    • /
    • 2010
  • This paper deals with free vibrations of the tapered circular arches with constant volume, whose cross sectional shape is the solid regular polygon. Volumes of the objective arches are always held constant regardless shape functions of the cross-sectional depth. The shape functions are chosen as the linear, parabolic and sinusoidal ones. Ordinary differential equations governing free vibrations of such arches are derived and solved numerically for determining the natural frequencies. In the numerical examples, hinged-hinged, hinged-clamped and clamped-clamped end constraints are considered. As the numerical results, the relationships between non-dimensional frequency parameters and various arch parameters such as rise ratio, section ratio, side number, volume ratio and taper type are reported in tables and figures.

Free Vibrations of Circular Curved Beams with Constant Volume (일정체적 원호형 곡선보의 자유진동)

  • Lee, Byoung-Koo;Lee, Tae-Eun;Choi, Jong-Min;Park, Chang-Eun
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.21 no.6
    • /
    • pp.570-579
    • /
    • 2011
  • This paper deals with free vibrations of the circular curved beams with constant volume, whose cross sectional shapes are the circular solid cross-sections. Volumes of the objective beam are always held in constant regardless shape functions of the cross-sectional radius. The shape functions are chosen as the linear, parabolic and sinusoidal ones. Ordinary differential equations governing free vibrations of such beam are derived and solved numerically for determining the natural frequencies. In numerical examples, the hinged-hinged, hinged-clamped and clamped-clamped end constraints are considered. As the numerical results, relationships between frequency parameters and various beam parameters such as rise ratio, section ratio, elasticity ratio, volume ratio, slenderness ratio and taper type are reported in tables and figures.

Passive shape control of force-induced harmonic lateral vibrations for laminated piezoelastic Bernoulli-Euler beams-theory and practical relevance

  • Schoeftner, J.;Irschik, H.
    • Smart Structures and Systems
    • /
    • v.7 no.5
    • /
    • pp.417-432
    • /
    • 2011
  • The present paper is devoted to vibration canceling and shape control of piezoelastic slender beams. Taking into account the presence of electric networks, an extended electromechanically coupled Bernoulli-Euler beam theory for passive piezoelectric composite structures is shortly introduced in the first part of our contribution. The second part of the paper deals with the concept of passive shape control of beams using shaped piezoelectric layers and tuned inductive networks. It is shown that an impedance matching and a shaping condition must be fulfilled in order to perfectly cancel vibrations due to an arbitrary harmonic load for a specific frequency. As a main result of the present paper, the correctness of the theory of passive shape control is demonstrated for a harmonically excited piezoelelastic cantilever by a finite element calculation based on one-dimensional Bernoulli-Euler beam elements, as well as by the commercial finite element code of ANSYS using three-dimensional solid elements. Finally, an outlook for the practical importance of the passive shape control concept is given: It is shown that harmonic vibrations of a beam with properly shaped layers according to the presented passive shape control theory, which are attached to an resistor-inductive circuit (RL-circuit), can be significantly reduced over a large frequency range compared to a beam with uniformly distributed piezoelectric layers.

Systematic Study of Paper Breaks in Papermaking Process Using Fracture Mechanics - (1) Evaluation of Fracture Toughness in Wet State

  • Yung B. Seo;Roh, You-Sun
    • Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
    • /
    • 2002.05a
    • /
    • pp.76-84
    • /
    • 2002
  • Fracture toughness was considered as one of the good estimates of the paper break tendency of paper web in the press room. Paper break on the paper machine is caused by many factors such as paper machine irregular vibrations, impurities in the fiber furnish, shives, and so on. On the paper machine, the solid content of paper web is changing very rapidly from less than 1% to over 95%. We tried to measure the fracture toughness of paper web at different solid contents for providing the fundamental knowledge of paper break. Stretches of wet web were also measured and compared to the fracture toughness changes. Four different fiber furnishes (SwBKP, HwBKP, ONP, and OCC) were refined to different degrees, and at different solid contents (40%, 60%, 80%, and 95%), their fracture toughnesses were measured. Two fracture toughness measurement methods (essential work of fracture and Tryding's load-widening method) were used, and we found they gave identical results. The stretch curves of the wet webs against the axis of solid contents were very similar to the fracture toughness curves of those.

  • PDF

Systematic Study of Paper Breaks in Papermaking Process Using Fracture Mechanics - (1) Evaluation of fracture Toughness in Wet State

  • Seo, Yung-B;Roh, You-Sun
    • Journal of Korea Technical Association of The Pulp and Paper Industry
    • /
    • v.33 no.5
    • /
    • pp.37-44
    • /
    • 2001
  • Fracture toughness was considered as one of the good estimates of the paper break tendency of paper web in the press room. Paper break on the paper machine is caused by many factors such as paper machine irregular vibrations, impurities in the fiber furnish, shives, and so on. On the paper machine, the solid content of paper web is changing very rapidly from less than 1% to over 95%. We tried to measure the fracture toughness of paper web at different solid contents for providing the fundamental knowledge of paper break. Stretches of wet web were also measured and compared to the fracture toughness changes. Four different fiber furnishes (SwBKP, HwBKP, ONP, and OCC) were refined to different degrees, and at different solid contents (40%, 60%, 80% and 95%), their fracture toughnesses were measured. Two fracture toughness measurement methods (essential work of fracture and Tryding's load-widening method) were used, and we found they gave identical results. The stretch curves of the wet webs against the axis of solid contents were very similar to the fracture toughness curves of those.

  • PDF

Free Vibrations of Circular Uniform Strips Resting on Two Parameter Elastic Foundation (두 변수 탄성지반으로 지지된 원호형 등단면 띠기초의 자유진동)

  • Lee, Jong-Cheon
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.13 no.1 s.53
    • /
    • pp.125-134
    • /
    • 2009
  • This paper deals with the free vibrations of circular strip foundations which have uniform solid rectangular cross-section. The ground which supports circular strips was modeled as the two parameter elastic foundation. Differential equations governing the flexural-torsional free vibrations of circular strips supported by such foundation were derived, and solved numerically for obtaining the natural frequencies and mode shapes. Boundary condition of free-free ends was considered for numerical examples. Four lowest natural frequencies according to the variations of five system parameters i.e. subtended angle, depth ratio, contact ratio, elasticity ratio and soil parameter are reported in the non-dimensional forms. Also, typical mode shapes of both deformations and stress resultants are presented in the figures. Experiment was conducted for validating the theory developed in this study.