• Title, Summary, Keyword: mass propagation

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Developing brittle transparent materials with 3D fractures and experimental study

  • Wang, Jing;Li, Shucai;Zhu, Weishen;Li, Liping
    • Steel and Composite Structures
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    • v.22 no.2
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    • pp.399-409
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    • 2016
  • The fracture propagation mechanism and fractured rock mass failure mechanism were important research in geotechnical engineering field. Many failures and instability in geotechnical engineering were related on fractures propagation, coalescence and interaction in rock mass under the external force. Most of the current research were limited to two-dimensional for the brittleness and transparency of three-dimensional fracture materials couldn't meet the requirements of the experiment. New materials with good transparent and brittleness were developed by authors. The making method of multi fracture specimens were established and made molds that could be reused. The tension-compression ratio of the material reached above 1/6 in normal temperature. Uniaxial and biaxial loading tests of single and double fracture specimens were carried out. Four new fractures were not found in the experiment of two-dimensional fractures such as the fin shaped crack, wrapping wing crack and petal crack and anti-wing crack. The relationship between stress and strain of the specimens were studied. The specimens with the load had experienced four stages of deformation and the process of the fracture propagation was clearly seen in each stage. The expansion characteristics of the fractured specimens were more obvious than the previous research.

Study on the propagation mechanism of stress wave in underground mining

  • Liu, Fei;Li, Lianghui
    • Computers and Concrete
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    • v.25 no.2
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    • pp.145-154
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    • 2020
  • For the influence of the propagation law of stress wave at the coal-rock interface during the pre-blasting of the top coal in top coal mining, the ANSYS-LS/DYNA fluid-solid coupling algorithm was used to numerical calculation and the life-death element method was used to simulate the propagation of explosion cracks. The equation of the crushing zone and the fracturing zone were derived. The results were calculated and showed that the crushing radius is 14.6 cm and the fracturing radius is 35.8 cm. With the increase of the angles between the borehole and the coal-rock interface, the vibration velocity of the coal particles and the rock particles at the interface decreases gradually, and the transmission coefficient of the stress wave from the coal mass into the rock mass decreases gradually. When the angle between the borehole and the coal-rock interface is 0°, the overall crushing degree is about 11% and up to the largest. With the increase of the distance from the charge to the coal-rock interface, the stress wave transmission coefficient and the crushing degree of the coal-rock are gradually decreased. At the distance of 50 cm, the crushing degree of the coal-rock reached the maximum of approximately 12.3%.

Computer modeling of crack propagation in concrete retaining walls: A case study

  • Azarafza, Mehdi;Feizi-Derakhshi, Mohammad-Reza;Azarafza, Mohammad
    • Computers and Concrete
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    • v.19 no.5
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    • pp.509-514
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    • 2017
  • Concrete retaining walls are the most common types of geotechnical structures for controlling instable slopes resulting from lateral pressure. In analytical stability, calculation of the concrete retaining walls is regarded as a rigid mass when its safety is required. When cracks in these structures are created, the stability may be enforced and causes to defeat. Therefore, identification, creation and propagation of cracks are among the important steps in control of lacks and stabilization. Using the numerical methods for simulation of crack propagation in concrete retaining walls bodies are among the new aspects of geotechnical analysis. Among the considered analytical methods in geotechnical appraisal, the boundary element method (BEM) for simulation of crack propagation in concrete retaining walls is very convenient. Considered concrete retaining wall of this paper is Pars Power Plant structured in south side in Assalouyeh, SW of Iran. This wall's type is RW6 with 11 m height and 440 m length and endurance of refinery construction lateral forces. To evaluate displacement and stress distributions (${\sigma}_{1,max}/{\sigma}_{3,min}$), the surrounding, especially in tip and its opening crack BEM, is considered an appropriate method. By considering the result of this study, with accurate simulation of crack propagation, it is possible to determine the final status of progressive failure in concrete retaining walls and anticipate the suitable stabilization method.

2 D Computer Simulation of Laser-Generated Ultrasonic Wave (레이저 여기 초음파의 2차원 컴퓨터 시뮬레이션)

  • Kim, Gyeong-Jo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.7
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    • pp.1847-1853
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    • 2000
  • A computer simulation technique for 2-dimensional laser generated ultrasonic waves was developed for visualization and investigation of ultrasonic propagation in solids. The technique is similar to a finite difference method (FDM) and a mass-particle model method, but uses a new nodal calculation method based on fundamental consideration of an elastic wave equation. By this method, the propagation behavior oflaser generated ultrasonic wave in thermoelastic and ablation mode is visualized and shows good agreement with previous experimental result or the numerical analysis result by Green function.

Friction-Based and Acoustically-Levitated Object Transport Using Ultrasonic Vibration (초음파 진동을 이용한 마찰 및 음향부상에 의한 물체의 수송)

  • Byoung-Gook Loh;Yong-Kuk Park
    • Journal of the Korean Society of Marine Engineering
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    • v.27 no.5
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    • pp.590-599
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    • 2003
  • In this study. object transport method based on ultrasonic flexural vibration is presented. Ultrasonic vibration generates ultrasonic traveling waves on the surface of elastic medium. Objects are transported through the interaction with traveling waves propagating in medium. Two types of transport methods are studied: frictional drive and acoustic levitation. With frictional drive, objects are transported in contact with the beam in the opposite direction of wave propagation whereas with acoustic levitation, objects are acoustically levitated above the beam surface and transported in the wave propagation direction. Transport characteristics are experimentally investigated using objects of different shapes and sizes. The transition from acoustic levitation mode to frictional drive mode is also examined. and it is found to occur when the ratio of mass to area of an object exceeds the threshold ratio of mass to area. It is envisaged that this feasibility study will serve as a stepping-stone for ultrasonic vibration to become an effective industrial material handling device in the future.

A Study on the Normal Combustion and Abnormal Combustion in Automotive S.I.Engine (Knocking Phenomena in Quiscent or Swirl Flow Field) (자동차용 가솔린 기관의 정상연소 및 이상연소에 관한 연구)

  • Lee, K.W.;Fujimoto, H.;Park, K.S.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.3 no.6
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    • pp.250-261
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    • 1995
  • In this study, a rapid compression and expansion machine(RCEM) equipped with a swirl generator was designed and developed, in order to clarify normal and abnormal combustion(knocking phenomena). This RCEM is intended to simulate combustion process in actual automotive S.I.engines, having a high reproducibility in the compression stroke. Flame propagation and autoignition processes associated with normal and abnormal combustion were captured by the high speed schlieren photography. And swirl intensity. equivalence ratio and ignition position were varied to investigate the effect of turbulence, concentration in the unburnt gas region and flame propagation length. The knock intensity, knock mass fraction and knock mass fraction after autoignition were calculated by use of history of measured cylinder pressure.

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A Study on Structure-Borne Noise Reduction for Resiliently Mounted Pumps for Ship (탄성지지된 박용 펌프의 고체음저감에 관한 연구)

  • Kim, Hyun-Sil;Kang, Hyun-Ju;Kim, Bong-Ki;Kim, Sang-Ryul
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.5
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    • pp.488-495
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    • 2007
  • In this paper, SBN (Structure-Borne Noise) reduction of resiliently mounted machinery and effect of the foundation impedance on mount performance is studied. SBN reduction through the mount is analyzed by using two theoretical models; mass-spring model and wave model, in which longitudinal wave propagation is included. It is found that floor impedance greatly affects SBN reduction through lower mount, while it is almost negligible to SBN reduction through upper mount. Comparisons between measurement and predictions shows that the mass-spring model is valid only in low frequency range below few hundred Hz, while for high frequency ranges longitudinal wave propagation in the mount must be considered.

Mass Production of Sand Dune Plant, Vitex rotundifolia via Micropropagation

  • Park, Hye-Jeong;Min, Byeong-Mee;Cha, Hyeon-Cheol
    • Journal of Plant Biotechnology
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    • v.6 no.3
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    • pp.165-169
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    • 2004
  • The fruits of Vitex rotundifolia in Korea, known as 'Man Hyung Ja', occupy an important position as traditional oriental medicine in Asian countries. It is known that propagation of this plant by seed is difficult and time-consuming with little success. Attempts were made to develop a method by using nodal culture techniques. Explants of stem node without leaves cultured on Nitsch medium containing 1 ml/L BA, gave the best shoot induction ratio. Also, BA with IAA or TDZ treatment showed positive effect on shoot induction. Half-strength Nitsch medium was supplemented with 0.5 mg/L NAA produced better success than did the others on root formation. It showed that many of the regenerants grew successfully on growth chamber at $24^{\circ}c$.

Response of orthotropic Kelvin modeling for single-walled carbon nanotubes: Frequency analysis

  • Hussain, Muzamal;Naeem, Muhammad N.;Tounsi, Abdelouahed
    • Advances in nano research
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    • v.8 no.3
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    • pp.229-244
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    • 2020
  • In this paper, modified Kelvin's model has been used to analyze the orthotropic vibration frequencies of single walled carbon nanotubes with clamped-clamped and clamped-free boundary conditions. For this system the governing equation is developed with wave propagation approach. Armchair, zigzag and chiral structures are considered for the vibrational analysis to investigate the effect of different modes, in-plane rigidity and mass density per unit lateral area. Throughout the computations, on decreasing the length-to-diameter ratios, the frequencies of said structure increases. In addition, by increasing three different value of in-plane rigidity resulting frequencies also increase and frequencies decrease on increasing mass density per unit lateral area. The results generated using computer software MATLAB to furnish the evidence regarding applicability of present model and also verified by available published literature.

Are theoretically calculated periods of vibration for skeletal structures error-free?

  • Mehanny, Sameh S.F.
    • Earthquakes and Structures
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    • v.3 no.1
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    • pp.17-35
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    • 2012
  • Simplified equations for fundamental period of vibration of skeletal structures provided by most seismic design provisions suffer from the absence of any associated confidence levels and of any reference to their empirical basis. Therefore, such equations may typically give a sector of designers the false impression of yielding a fairly accurate value of the period of vibration. This paper, although not addressing simplified codes equations, introduces a set of mathematical equations utilizing the theory of error propagation and First-Order Second-Moment (FOSM) techniques to determine bounds on the relative error in theoretically calculated fundamental period of vibration of skeletal structures. In a complementary step, and for verification purposes, Monte Carlo simulation technique has been also applied. The latter, despite involving larger computational effort, is expected to provide more precise estimates than FOSM methods. Studies of parametric uncertainties applied to reinforced concrete frame bents - potentially idealized as SDOF systems - are conducted demonstrating the effect of randomness and uncertainty of various relevant properties, shaping both mass and stiffness, on the variance (i.e. relative error) in the estimated period of vibration. Correlation between mass and stiffness parameters - regarded as random variables - is also thoroughly discussed. According to achieved results, a relative error in the period of vibration in the order of 19% for new designs/constructions and of about 25% for existing structures for assessment purposes - and even climbing up to about 36% in some special applications and/or circumstances - is acknowledged when adopting estimates gathered from the literature for relative errors in the relevant random input variables.