• Title/Summary/Keyword: Composite numbers

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Crack Detection of Carbon Fiber Reinforced Composites by Electric Potential Method with Bridge Circuit Concept (브리지 회로 개념이 적용된 전기 전위법을 이용한 탄소섬유복합재료의 균열검출)

  • Hwang, Hui-Yun
    • Composites Research
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    • v.22 no.1
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    • pp.9-14
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    • 2009
  • This paper suggested the electric potential method with a bridge circuit concept for the detection of the location and crack growth of carbon fiber reinforced composites to reduce the measurement numbers. 2 pairs of electrodes were fabricated on the center cracked thin composite plates, and potential changes at one pair of adjacent electrodes were observed while external voltage input was applied to the other pair of adjacent electrodes. The effects of the size and interval of electrodes, location and propagating direction of center cracks were investigated by experiments and finite element analyses. Detectable crack size was influenced by the electrode interval rather than the electrode size, and crack detection was enhanced as the size and interval of electrodes were smaller. Besides, output potential changes were larger as the crack grew and was nearer the voltage input electrodes.

Free Vibrations and Buckling Loads of Axially Loaded Cross-Ply Laminated Composite Beam-Columns with Multiple Delaminations (다층간분리된 직교 적층 보-기둥의 자유진동과 좌굴하중)

  • 이성희;김형열;박기태;박대효
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.3
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    • pp.523-534
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    • 2002
  • Free vibration and buckling analysis of multi-delaminated composite beam-columns subjected to axial compressive load is performed in the present study In order to investigate the effects of multi-delaminations on the natural frequency and the elastic buckling load of multi-delaminated beam-columns, the general kinematic continuity conditions are derived from the assumption of constant slope and curvature at the multi-dclamination tip. The characteristic equation of multi-delaminated beam-column is obtained by dividing the global multi-delauunated beam-columns into segments and by imposing recurrence relation from the continuity conditions on each sub-beam-column. The natural frequency and the elastic buck)ing load of multi-delaminated beam-columns according to the incremental load of axial compression, which is limited to the maximum elastic buckling load of sound laminated beam-column, are obtained. It is found that the sizes, locations and numbers of multi-delaminations have significant effect on natural frequency and elastic buckling load, especially the latter ones.

Buckling of axially compressed composite cylinders with geometric imperfections

  • Taheri-Behrooz, Fathollah;Omidi, Milad
    • Steel and Composite Structures
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    • v.29 no.4
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    • pp.557-567
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    • 2018
  • Cylindrical shell structures buckle at service loads which are much lower than their associated theoretical buckling loads. The main source of this discrepancy is the presence of various imperfections which are created on the cylinder body during different processes as manufacturing, handling, assembling and machining. Many cylindrical shell structures are still designed against buckling based on the experimental data introduced by NASA SP-8007 as conservative lower bound curves. This study employed the numerical based Linear Buckling mode shape Imperfection (LBMI) method and modified it using a stochastic method to assess the effect of geometrical imperfections in more details on the buckling of cylindrical shells with and without the cutout. The comparison of results with those obtained from the numerical Simcple Perturbation Load Imperfection (SPLI) method for cylinders with and without cutout revealed a good correlation. The effect of two parameters of size and number of cutouts on the buckling load was investigated using the linear buckling and Modified LBMI methods. Results confirmed that in cylinders with a small cutout inserting geometrical imperfection using either SPLI or modified LBMI methods significantly reduced the value of the predicted buckling load. However, in cylinders with larger cutouts, the effect of the cutout is dominant, thus considering geometrical imperfection had a minor effect on the buckling loads predicted by both SPLI and modified LBMI methods. Furthermore, the modified LBMI method was employed to evaluate the combination effect of cutout numbers and size on the buckling load. It is shown that in small cutouts, an increasing in the cutout size up to a certain value resulted in a remarkable reduction of the buckling load, and beyond that limit, the buckling loads were constant against D/R ratios. In addition, the cutout number shows a more significant effect on decreasing the buckling load at small D/R ratios than large D/R ratios.

Effects of Temperature and Mechanical Deformation on the Microhardness of Lead free and Composite Solders (무연 복합 솔더의 미소경도에 미치는 기계적 변형과 온도의 영향)

  • Lee Joo Won;Kang Sung K.;Lee Hyuck Mo
    • Journal of the Microelectronics and Packaging Society
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    • v.12 no.2 s.35
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    • pp.121-128
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    • 2005
  • Solder joints in microelectronic devices are frequently operated at an elevated temperature in service. They also experience plastic deformation caused by temperature excursion and difference in thermal expansion coefficients. Deformed solders can go through a recovery and recrystallization process at an elevated temperature, which would alter their microstructure and mechanical properties. In this study, to predict the changes in mechanical properties of Pb-free solder joints at high temperatures, the high temperature microhardness of several Pb-free and composite solders was measured as a function of temperature, deformation, and annealing condition. Solder alleys investigated include pure Sn, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, Sn-2.8Ag-7.0Cu (composite), and Sn-2.7Ag-4.9Cu-2.9Ni (composite). Numbers are all in wt.$\%$ unless specified otherwise. Solder pellets were cast at two cooling rates (0.4 and $7^{\circ}C$/s). The pellets were compressively deformed by $30\%$ and $50\%$ and annealed at $150^{\circ}C$ for 2 days. The microhardness was measured as a function of indentation temperature from 25 to $130^{\circ}C$. Their microstructure was also evaluated to correlate with the changes in microhardness.

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Thermo mechanical analysis of a ceramic coated piston used in a diesel engine

  • Buyukkaya, Ekrem;Cerit, Muhammet;Coban, Mehmet
    • Steel and Composite Structures
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    • v.21 no.2
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    • pp.429-442
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    • 2016
  • The aim of this paper is to determine temperature and stress distributions in a ceramic based on Partially Stabilized Zirconia coated steel piston crown by using plasma spraying for improving performance of a marine diesel engine. Effects of coating constituent and thickness on temperature and stress distributions were investigated including comparisons with results from an uncoated piston by means of finite element method namely ANSYS. Temperature developed at the coated surface is significantly higher than that of the uncoated piston. The maximum stress components occur between bond coat and adjacent ceramic layer. Provided that coating thickness is constant as 0.5 mm, when numbers of layers increase, magnitude of the normal stress decrease about 34.1% on the base metal surface according to uncoated piston, but the base metal surface temperature of the steel piston increase about 13.1%.

PSO algorithm for fundamental frequency optimization of fiber metal laminated panels

  • Ghashochi-Bargh, H.;Sadr, M.H.
    • Structural Engineering and Mechanics
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    • v.47 no.5
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    • pp.713-727
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    • 2013
  • In current study, natural frequency response of fiber metal laminated (FML) fibrous composite panels is optimized under different combination of the three classical boundary conditions using particle swarm optimization (PSO) algorithm and finite strip method (FSM). The ply angles, numbers of layers, panel length/width ratios, edge conditions and thickness of metal sheets are chosen as design variables. The formulation of the panel is based on the classical laminated plate theory (CLPT), and numerical results are obtained by the semi-analytical finite strip method. The superiority of the PSO algorithm is demonstrated by comparing with the simple genetic algorithm.

A Parallel Multiplier By Mutidigit Numbers Over GF($P^{nm}$) (GF($P^{nm}$)상의 다항식 분할에 의한 병렬 승산기 설계)

  • 오진영;윤병희나기수김흥수
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.771-774
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    • 1998
  • In this paper proposes a new bit-parallel structure for a multiplier over GF((Pn)m), with k-nm. Mastrovito Multiplier, Karatsuba-ofman algorithm are applied to the multiplication of polynomials over GF(2n). This operation has a complexity of order O(k log p3) under certain constrains regardig k. A complete set of primitive field polynomials for composite fields is provided which perform modulo reduction with low complexity. As a result, multiplier for fields GF(Pk) with low gate counts and low delays are constructed. The architectures are highly modular and thus well suited for VLSI implementation.

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Interfacial Characteristics of $Al-2024/Al_2O_{3p}$ Composite Fabricated by Rheo-compocasting (Rheo-compocasting법으로 제조된 알루미나 입자강화 Al합금 복합재료의 계면반응)

  • Hyun, Suhk-Jong;Ye, Byung-Joon
    • Journal of Korea Foundry Society
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    • v.13 no.3
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    • pp.285-294
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    • 1993
  • Aluminum alloy 2024 matrix composites reinforced with $Al_2O_3$ particles, were prepared by rheo-compocasting, a process which consists of the incoporation distribution of reinforcement by stirring within a semi-solid alloy. The microstructures and characteristics of the interfaces have been studied using optical microscope and scanning electon microscope in 2024 aluminum alloy composites reinforced with $Al_2O_3$ particles. The main results are as follows: (1) $Al_2O_3$ particles were well distributed in composites by using rheo-compocasting. (2) As the addition of $Al_2O_3$ particle increases, the average dendrite numbers and the hardness were increased. (3) Interaction between $Al_2O_3$ particles and alloy 2024 resulted in the formation of Mg and Cu element rich region around the $Al_2O_3$ particles.

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Modeling free vibration analysis of osteon as bone unite

  • Ebrahimi, Farzad;Zokaee, Farin
    • Biomaterials and Biomechanics in Bioengineering
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    • v.5 no.1
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    • pp.1-10
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    • 2020
  • This paper investigated vibrational behavior of the osteon as bone unit in the different situations. This study can lead to increase our knowledge of our body. In this paper free vibration of the osteon with considering it as composite material has been studied. The effect of numbers of lamellae and radius of those on natural frequency of osteon are subtle; while thickness of lamellae have decreasing trend on natural frequency of osteon. The presence of nerve and blood in haversian canal change trend of natural frequency, absolutely. Using the nonlocal strain gradient theory(NSGT) leads to effectiveness of scale parameter on equations of motion and the obtained results. The governing equations are derived by Hamilton's principles. A parametric study is presented to examine the effect of various parameters on vibrational behaviour of osteon. The results can also be regarded as a benchmark in vibration analysis behavior of osteon as bone unite.

ON A COMPOSITE FUNCTIONAL EQUATION RELATED TO THE GOLAB-SCHINZEL EQUATION

  • Gordji, Madjid Eshaghi;Rassias, Themistocles M.;Tial, Mohamed;Zeglami, Driss
    • Bulletin of the Korean Mathematical Society
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    • v.53 no.2
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    • pp.387-398
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    • 2016
  • Let X be a vector space over a field K of real or complex numbers and $k{\in}{\mathbb{N}}$. We prove the superstability of the following generalized Golab-Schinzel type equation $f(x_1+{\limits\sum_{i=2}^p}x_if(x_1)^kf(x_2)^k{\cdots}f(x_{i-1})^k)={\limits\prod_{i=1}^pf(x_i),x_1,x_2,{\cdots},x_p{\in}X$, where $f:X{\rightarrow}K$ is an unknown function which is hemicontinuous at the origin.