• Title, Summary, Keyword: End effect

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Influence of end fixity on post-yield behaviors of a tubular member

  • Cho, Kyu Nam
    • Structural Engineering and Mechanics
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    • v.13 no.5
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    • pp.557-568
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    • 2002
  • For the evaluation of the capability of a tubular member of an offshore structure to absorb the collision energy, a simple method can be employed for the collision analysis without performing the detailed analysis. The most common simple method is the rigid-plastic method. However, in this method any characteristics for horizontal movement and rotation at the ends of the corresponding tubular member are not included. In a real structural system of an offshore structure, tubular members sustain a certain degree of elastic support from the adjacent structure. End fixity has influences in the behaviors of a tubular member. Three-dimensional FEM analysis can include the effect of end fixity fully, however in viewpoints of the inherent computational complexities of the 3-D approach, this is not the recommendable analysis at the initial design stage. In this paper, influence of end fixity on the behaviors of a tubular member is investigated, through a new approach and other approaches. A new analysis approach that includes the flexibility of the boundary points of the member is developed here. The flexibility at the ends of a tubular element is extracted using the rational reduction of the modeling characteristics. The property reduction is based on the static condensation of the related global stiffness matrix of a model to end nodal points of the tubular element. The load-displacement relation at the collision point of the tubular member with and without the end flexibility is obtained and compared. The new method lies between the rigid-plastic method and the 3-demensional analysis. It is self-evident that the rigid-plastic method gives high strengthening membrane effect of the member during global deformation, resulting in a steeper slope than the present method. On the while, full 3-D analysis gives less strengthening membrane effect on the member, resulting in a slow going load-displacement curve. Comparison of the load-displacement curves by the new approach with those by conventional methods gives the figures of the influence of end fixity on post-yielding behaviors of the relevant tubular member. One of the main contributions of this investigation is the development of an analytical rational procedure to figure out the post-yielding behaviors of a tubular member in offshore structures.

A Study on Regression Rate in End-Burning Hybrid rocket with Variation of Swirl Intensity (End-Burning 하이브리드 로켓의 스월 강도 변화에 따른 연료 후퇴율에 관한 연구)

  • Choi, Won-Jun;Woo, Kyoung-Jin;Moon, Hee-Jang;Sung, Hong-Gye;Kim, Jin-Kon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.70-75
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    • 2012
  • In this paper, the regression rate of the End-Burning Hybrid Rocket with variation of swirl intensity was investigated experimentally with the variation of fuel diameter, injector shape and angle. When fuel grain diameter is large, fuel mass flow rate increases. And the injector diameter increase, fuel regression rate decrease. The impinging effect of oxidizer flow on fuel surface for fuel combustion efficiency is stronger than swril effect in this End-burning propulsion system. The relation between the regression rate, oxidizer mass flux and swirl intensity was obtained.

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China's Brain Gain at the High End: An Assessment of Thousand Youth Talents Program

  • Sun, Yutao;Guo, Rongyu;Zhang, Shuai
    • Asian Journal of Innovation and Policy
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    • v.6 no.3
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    • pp.274-294
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    • 2017
  • While studies have viewed the effect of Chinese talent-attracting programs launched by government since reform and open door policy, little of them has assessed these programs empirically and pertinently. This article intends to assess an important program - the Thousand Youth Talents Program (TYTP). Frist, this paper proposed a transnational migration matrix of the academics to clarify the dynamic mechanism of academic brain gain at the high end. Then, the Kaplan-Meier analysis and Cox regression model are used to empirically analyze the policy effect of TYTP. The results show that, academic ability have double edged impacts on brain gain at the high end, some scholars whose last employer's academic ranking is world's Top100 have stronger willing to return, and the negative effect of academic ranking decreases with time passing; while scholars with a tenure-track position, a tenure position or a permanent position tend to stay overseas, and the hazard rate of staying increases with age. The older scholars have more intentions to go back China, while gender was not a significant factor influencing academic return at the high end. That is, the talent-attracting programs has partly succeeded in bringing back the academics at the high end.

Application of Statistical Analysis for Working Factors Effect of High Speed End-Milling for STD61 (열간금형용강의 고속 엔드밀 가공인자의 영향에 대한 통계적 분석의 적용)

  • Bae, Hyo-Jun;Lee, Sang-Jae;Woo, Kyu-Sung;Park, Heung-Sik
    • Proceedings of the KSME Conference
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    • pp.1148-1153
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    • 2004
  • Recently the high speed end-milling processing is demanded the high-precise technique with good surface rougj1ness and rapid time in aircraft, automobile part and molding industry. The working factors of high speed end-milling has an effect on surface roughness of cutting surface. Therefore this study was carried out to analyze the working factors to get the optimum surface roughness by design of experiment. From this study, surface roughness have an much effect according to priority on Spindle speed, feed rale, hardness and axial depth of cut By design of experiment, it is effectively represented shape characteristics of surface roughness in high speed end-milling And determination($R^2$) coefficient of regression equation had a satisfactory reliability of 89.7% and regression equation of surface roughness is made by regression analysis.

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Restrained Effect of End Plate on Plane Strain Test Evaluated by Digital Image Correlation Method (디지털 이미지 코릴레이션 기법으로 평가한 평면변형률 시험의 단부 구속 효과)

  • Jang, Eui-Ryong;Choo, Yoon-Sik;Lee, Won-Taeg;Chung, Choong-Ki
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.22-33
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    • 2008
  • The plane strain test has been used widely in order to examine the stress-strain relation and failure behavior. Its advantages are more realistic simulation of deformation and failure behaviors of soils. Most plane strain tests have been carried out with restrained end plates due to difficulties in manufacturing the equipment with free end condition and also performing it. In this study, plane strain tests with/without bottom plate restraint were performed on Jumunjin-sand. The measurement of overall and local deformation was accomplished by digital image correlation technique as well as external LVDT. By applying digital image correlation method using two consecutive images captured through the transparent wall, local deformation behavior of various parts inside the specimen was estimated. From digital image analysis result, the restrained effect of end plate was examined about formation and development of shear band, and deformation mechanism of sand under plane strain condition.

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Effect of Processing Parameters in Surface Machining of Plastic Materials (플라스틱 소재의 표면가공 중 공정조건의 영향)

  • Han, Chang Mo;Lee, Bong-Kee
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.15 no.5
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    • pp.1-7
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    • 2016
  • In the present study, a plastic surface end-milling was implemented to investigate the effects of processing parameters on surface quality. The end milling can be considered an efficient method for rapid prototyping of thermoplastic bio-systems since it exhibits several beneficial functions including short fabrication time and high dimensional accuracy. In this regard, putative biocompatible thermoplastic materials, such as PMMA, PET, and PC, were chosen as workpiece materials. Among the relevant processing parameters influencing the surface quality of the final product, depth of cut, feed rate, and spindle speed were considered in the present study. The roughness of surfaces machined under various conditions was measured to elucidate the effect of each parameter. We found that the cut depth was the most significant factor. Heat generation during machining also had a remarkable effect. From these investigations, an appropriate combination of processing conditions specific to each type of use and end-product could be found. This optimization can be useful in end-milling of thermoplastic bio-systems.

The Characteristic Analysis of Vector Control in a Linear Induction Motor Considering Static and Dynamic End Effects (정적 및 동적 단부효과를 고려한 선형 유도 전동기의 벡터제어 특성해석)

  • Kim, Dae-Gyeong;Gwon, Byeong-Il;U, Gyeong-Il
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.51 no.8
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    • pp.413-424
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    • 2002
  • Recently, in the linear motion system, high performances are required In dynamic characteristics. Vector control method is capable of instantaneous thrust control can meet these high performance requirements. Linear induction motor(LIM) have static and dynamic end effects due to its finite core length, so that per-phase impedances are asymmetric and an air gap flux distribution is distorted. These points of the d-q axis equivalent circuit model considering both end effects is more complicated. This paper proposes the d-q axis equivalent circuit and the vector control method considering both static and dynamic end effects of the LIM. As a result, it is shown that the results of the equivalent circuit method(ECM) have a good agreement with those of the finite element method(FEM).

Drained End Shield Effects on Heat Deposition Rate Distribution in CANDU 6 Reactor End Shield Structure

  • Jin, Yung-Kwon;Kim, Kyo-Youn;Hwang, Hae-Ryong
    • Nuclear Engineering and Technology
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    • v.26 no.4
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    • pp.570-577
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    • 1994
  • The loss of water in the carbon steel balls and water region of the end shield for CANDU 6 reactor could lead to significant temperature gradient through the end shield structure which amy result in the excessive deformation. With an assumed end shield drained scenario, the heat deposition rates were calculated through the end shield associated with the central fuel channel during full power operation as an initial step to thermal stress analysis. The drained case was compared with that of water present normal case in therms of heat deposition rater and the total heating throughout the end shield regions. The compared results show that the heat deposition and the total heating remain almost the same between the two cases. It was found that the change of volume integrated flux in the end shield regions due to the loss of water contribute a negligible effect on the heat deposition in this region.

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Relationships between Blossom-End Rot in Pepper and Calcium Fertilization during the First Fruit Setting Period

  • Byeon, Il-Su;Seo, Sun-Young;Chung, Jong-Bae
    • Korean Journal of Soil Science and Fertilizer
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    • v.45 no.1
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    • pp.79-82
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    • 2012
  • Blossom-end rot is probably the most recognizable Ca deficiency that affects fruit production including pepper. We investigated the induction of blossom-end rot during the period of rapid vegetative growth and fruit setting, and the effect of Ca fertilization on the suppression of blossom-end rot in pepper plants grown in a plastic-film house. During the first fruit setting period, more than 60% of pepper fruits larger than 8 cm showed the symptoms of blossom-end rot. Under the condition of transpiration occurring at a much faster rate, growing leaves of pepper plants could be the greater sinks for Ca than developing fruits. The incidence of blossom-end rot was significantly decreased after two weeks of Ca fertigation. Calcium application during the rapid vegetative growth and fruit setting period could be suggested as a preventive step to overcome the local Ca deficiency inducing blossom-end rot of pepper fruits.

End Bearing Capacity of a Pile in Cohesionless Soils (사질토에 있어서 말뚝의 선단부 지지력)

  • 이명환
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.71-123
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    • 1988
  • The aim of this paper is to examine the end bearing capacity of a pile in cohesionless soils. The ode of failure of soil due to pile installation is assumed from experimental observation of actual soil deformation. A new solution is proposed complying with the assumed mode of failure by employing the theory of cavity expansion. The effect of curvature of failure envelope is studied in relation to tile proposed solution. The influence of a curved failure envelope becomes larger with increasing degree of curvature and the level of confining stress. This effect in some cases or reduce the end bearing capacity by tore the 80 percent compared with that given by a straight failure envelope. For practical application of tile proposed solution, the method of determining the average volume change in the plastic zone is re-evaluated. The proposed solution is confirmed by comparing the theoretical values with experimental results obtained from model pile tests in a calibration chamber. The comparison shows that the proposed solution provides a reasonable prediction of end bearing capacity for both weak and strong grained soils.

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