• Title/Summary/Keyword: free length

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Endwall Heat (Mass) Transfer in a Turbine Cascade Under Combustor-Level High Free-Stream Turbulence (연소기 출구 난류 상태에서의 터빈 익열 끝벽 열(물질)전달 특성)

  • Jun, Sang-Bae;Lee, Sang-Woo;Park, Byung-Kyu
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.759-764
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    • 2001
  • Heat (mass) transfer characteristics have been investigated on the endwall of a large-scale linear turbine cascade passage under a combustor-level high free-stream turbulence with a large length scale. Local heat (mass) transfer coefficients are measured by using the naphthalene sublimation technique. The result shows that local heat (mass) transfer on the endwall is greatly enhanced in the central region of the turbine passage, but there is no noticeable change in the local heat (mass) transfer in the region suffering severe heat load. Under the high free-stream turbulence, the local heat (mass) transfer coefficient shows more uniform distribution and its average value across the whole endwall region is increased by 26% of that at low turbulence condition. The heat (mass) transfer data on the endwall strongly supports that well-organized vortices near the endwall tends to suffer an suppression by the high free-stream turbulence.

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Analysis of Horizontal Behavior of a Single Column/Shaft by Horizontal Two-way Pile Load Test (반복수평재하시험을 통한 단일형현장타설말뚝의 거동분석)

  • Jeong, Sang-Seom;Song, Sung-Wook;Kim, Byung-Chul
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.1132-1143
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    • 2008
  • A single Column/Shaft which extended the pile to the column of the bridge with same diameter has better safety and economical profit, but it usually has larger lateral displacement due to lateral loads such as wind, earthquake, wave, etc. A series of horizontal pile load testing were performed to study the lateral behavior of single column/shaft with varying different free lengths and embedded pile lengths. Eight instrumented test piles were cast-in-placed by bonding strain gauges at certain locations on both faces of the pile to measure bending moment, from two-way loadings. Linear variable differential transformers(LVDTs) were installed to measure the lateral pile displacement. Based on this, it is found that the test single column/shaft with different free lengths shows different failure modes. If the test pile has a longer free length, the failure occurs at the near the ground surface, but the shorter one's failure occurs at the below the ground surface.

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Consistent couple-stress theory for free vibration analysis of Euler-Bernoulli nano-beams made of arbitrary bi-directional functionally graded materials

  • Nejad, Mohammad Zamani;Hadi, Amin;Farajpour, Ali
    • Structural Engineering and Mechanics
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    • v.63 no.2
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    • pp.161-169
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    • 2017
  • In this paper, using consistent couple stress theory and Hamilton's principle, the free vibration analysis of Euler-Bernoulli nano-beams made of bi-directional functionally graded materials (BDFGMs) with small scale effects are investigated. To the best of the researchers' knowledge, in the literature, there is no study carried out into consistent couple-stress theory for free vibration analysis of BDFGM nanostructures with arbitrary functions. In addition, in order to obtain small scale effects, the consistent couple-stress theory is also applied. These models can degenerate into the classical models if the material length scale parameter is taken to be zero. In this theory, the couple-tensor is skew-symmetric by adopting the skew-symmetric part of the rotation gradients as the curvature tensor. The material properties except Poisson's ratio are assumed to be graded in both axial and thickness directions, which it can vary according to an arbitrary function. The governing equations are obtained using the concept of Hamilton principle. Generalized differential quadrature method (GDQM) is used to solve the governing equations for various boundary conditions to obtain the natural frequencies of BDFG nano-beam. At the end, some numerical results are presented to study the effects of material length scale parameter, and inhomogeneity constant on natural frequency.

Rod Impact Test for the Determination of Dynamic Yield Stress of Metals (금속재료의 동적항복응력 결정을 위한 봉충격시험법)

  • 민옥기;이정민;남창훈;황재준
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.1
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    • pp.78-89
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    • 1993
  • A new theory based on the modified momentum and energy conservation has been proposed in order to overcome the drawbacks included in previous theories which are used for the determination of dynamic yield stresses and the investigation of dynamic behavior of metals. Then the improvements suggested by the new theory have been manifested through the analysis of the error included in the measurement of deformed length and through the comparison between the new theory, existing theories, and experimental results performed by previous workers. Meanwhile rod impact test has been performed which uses a compressed- air system for the acceleration of flat-ended cylindrical free-cutting brass rods. From the geomtrical measurements of deformed length, the dynamic yield stress of free-cutting brass has determined.

Free vibrations analysis of arbitrary three-dimensionally FGM nanoplates

  • Dehshahri, Kasra;Nejad, Mohammad Zamani;Ziaee, Sima;Niknejad, Abbas;Hadi, Amin
    • Advances in nano research
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    • v.8 no.2
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    • pp.115-134
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    • 2020
  • In this paper, the free vibrations analysis of the nanoplates made of three-directional functionally graded material (TDFGM) with small scale effects is presented. To study the small-scale effects on natural frequency, modified strain gradient theory (MSGT) has been used. Material properties of the nanoplate follow an arbitrary function that changes in three directions along the length, width and thickness of the plate. The equilibrium equations and boundary conditions of nanoplate are obtained using the Hamilton's principle. The generalized differential quadrature method (GDQM) is used to solve the governing equations and different boundary conditions for obtaining the natural frequency of nanoplate made of three-directional functionally graded material. The present model can be transformed into a couple stress plate model or a classic plate model if two or all parameters of the length scales set to zero. Finally, numerical results are presented to study the small-scale effect and heterogeneity constants and the aspect ratio with different boundary conditions on the free vibrations of nanoplates. To the best of the researchers' knowledge, in the literature, there is no study carried out into MSGT for free vibration analysis of FGM nanoplate with arbitrary functions.

Size-dependent free vibration and dynamic analyses of a sandwich microbeam based on higher-order sinusoidal shear deformation theory and strain gradient theory

  • Arefi, Mohammad;Bidgoli, Elyas Mohammad-Rezaei;Zenkour, Ashraf M.
    • Smart Structures and Systems
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    • v.22 no.1
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    • pp.27-40
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    • 2018
  • The governing equations of motion are derived for analysis of a sandwich microbeam in this paper. The sandwich microbeam is including an elastic micro-core and two piezoelectric micro-face-sheets. The microbeam is subjected to transverse loads and two-dimensional electric potential. Higher-order sinusoidal shear deformation beam theory is used for description of displacement field. To account size dependency in governing equations of motion, strain gradient theory is used to mention higher-order stress and strains. An analytical approach for simply-supported sandwich microbeam with short-circuited electric potential is proposed. The numerical results indicate that various types of parameters such as foundation and material length scales have significant effects on the free vibration responses and dynamic results. Investigation on the influence of material length scales indicates that increase of both dimensionless material length scale parameters leads to significant changes of vibration and dynamic responses of microbeam.

Analysis of Seismic Response of the Buried Pipeline with Pipe End Conditions (I) (단부 경계조건을 고려한 매설관의 동적응답 해석 (I))

  • Jeong, Jin-Ho;Lee, Byong-Gil;Park, Byung-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.1148-1158
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    • 2005
  • This work reports results of our study on the dynamic responses of the buried pipelines both along the axial and the transverse directions under various boundary end conditions. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends. We have studied the seismic responses of the buried pipelines with the various boundary end conditions both along the axial and the transverse direction. We have considered three cases, i.e., the free ends, the fixed ends, and the fixed-free ends for the axial direction, and three more cases including the guided ends, the simply supported ends, and the supported-guided ends for the transverse direction. The buried pipelines are modeled as beams on elastic foundation while the seismic waves as a ground displacement in the form of a sinusoidal wave. The natural frequency and its mode, and the effect of parameters have been interpreted in terms of free vibration. The natural frequency varies most significantly by the soil stiffness and the length of the buried pipelines in the case of free vibration, which increases with increasing soil stiffness and decreases with increasing length of the buried pipeline. Such a behavior appears most prominently along the axial rather than the transverse direction of the buried pipelines. The resulting frequencies and the mode shapes obtained from the free vibration for the various boundary end conditions of the pipelines have been utilized to derive the mathematical formulae for the displacements and the strains along the axial direction, and the displacements and the bending strains along the transverse direction in case of the forced vibration. The negligibly small difference of 6.2% between our result and that of Ogawa et. al. (2001) for the axial strain with a one second period confirms the accuracy of our approach in this study.

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Soft Tissue Reconstruction of Finger and Hand Using Arterialized Venous Free Flap (동맥화 정맥 유리 피판술을 이용한 수부와 수지 연부조직 결손의 재건)

  • Kong, Byeong-Seon;Kim, Yong-Jin;Cho, Kwang-Woo
    • Archives of Reconstructive Microsurgery
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    • v.13 no.2
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    • pp.107-116
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    • 2004
  • Flaps are necessary, when important structures such as bone, tendon, nerve and vessel are exposed. Arterialized venous free flap is suited to the coverage of finger and hand because the thickness of venous flap is thin. Authors performed 65 cases arterialized venous free flap for the soft tissue reconstruction of the hand and finger. The size of donor defect were from $1{\times}1cm\;to\;7{\times}12cm$. The mean flap area was $9.1cm^2$. The recipient sites were finger tip in 34 cases, finger shaft in 29 cases and hand in 2 cases. The donor sites were volar aspect of distal forearm in 40 cases, thenar area in 17 cases and foot dorsum in 6 cases. The types of arterialized venous free flap were A-A type in 4 cases and A-V type in 61 cases. The length of afferent vein was from 0.5 cm to 3 cm (mean 1.7 cm) and efferent vein was from 1 cm to 10 cm (mean 2.2 cm). 58 flaps(89.2%) survived eventually. 42 flaps(64.6%) survived totally without any complication. 8 flaps(12.3%) showed the partial necrosis but they were healed without any additional operations. 8 flaps (12.3%) showed the partial necrosis requiring the additional skin graft. We had a satisfactory result by using arterialized venous free flap for the soft tissue reconstruction of finger and hand. We believe that volar aspect of distal forearm, thenar area, foot dorsum are suited as a donor site and the short length of the flap pedicle, the strong arterail inflow affect the survival rate of arterialized venous free flaps.

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Free Vibration Analysis of Arches With General Boundary Condition (일반 경계조건 아치의 자유진동해석)

  • 이태은;이종국;이병구
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11b
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    • pp.995-999
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    • 2001
  • This paper deals with the free vibrations of arches with general boundary condition. Based on the dynamic equilibrium equations of a arch element acting the stress resultants and the inertia forces, the governing differential equation is derived for the in-plane free vibration of such arches. Differential equations are solved numerically to calculate natural frequencies. In numerical examples, the parabolic arch is considered. The effects of the arch rise to span length ratio, the slenderness ratio, the vertical spring coefficient and the rotational spring coefficient on the natural frequencies are analyzed.

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