• 한국강구조학회 논문집
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• 제12권6호
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• pp.749-758
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• 2000

본 연구는 지그재그모델에 근거하여 두꺼운 금속, 폴리머 복합재료 면재의 전단변형 효과를 고려해서 샌드위치평판의 휨해석 지배방정식을 유도하였으며, 판의 네 변은 단순지지 되어 있다고 가정하였다. 역대칭 적층면재의 화이버 각도와 면재의 적층수를 변화시켜가며 휨해석의 결과를 나타내었다. 해석방법의 정확성을 위해 일반 적층판이론의 값과 비교를 하여 검증을 하였다. 그 결과 적층판이론으로 구한 값보다 처짐에 있어서 더 큰 값을 나타냄을 알 수 있었는데, 그 이유로는 본 해석방법이 면재, 심재 모두 휨강성과 전단변형을 고려하였기 때문이라 사료된다. 강재, 폴리머 복합면재를 갖는 샌드위치평판을 설계할 때 제시된 정보를 유용하게 이용될 수 있을 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 전문대학교육위원
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• pp.150-154
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• 2005

This paper is presented for the development of the brushless DC(BLDC) spindle motors for hard disk drives. A new BLDC Motor has the use of insulated, compacted, iron powder for the armature core material of BLDC motors. Insulated iron powder in this paper is generally called soft magnet composite(SMC). The SMC is used for the stator of the motor instead of the laminated steel core. The motor used by SMC can have the good advantages in condition of the high frequency input power and small sized motor. It gets much more high efficiency than laminated steel core at same input power. The proposed motor has a technique of speed sensorless control. Experimental results show the performance of the proposed BLDC spindle motors for an HDD.

• Journal of Magnetics
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• 제19권2호
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• pp.146-150
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• 2014

The objective of this paper is to provide a comparison between two transverse flux rotary machines (TFRM) with different topologies of stator cores. Depending on how to make stator core with laminated steel sheets, the one topology is 'perpendicular stacking core' and the other is 'separated core'. Both of the two cores have been designed considering 3-dimensional (3-D) magnetic flux path with the same output power conditions, but the core losses are quite different and it causes different magnetic and thermal characteristics. For comparison of these two topologies of stator cores, therefore, core losses have been calculated and used as a heat source in no-load conditions, and the thermal stress has been also calculated. 3-D finite element method has been used for the magnetic field, thermal, and stress analysis to consider the 3-D flux path of the TFRM. After comparing the analysis results of the two topologies, experimental results are also presented and discussed.

• Journal of Magnetics
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• 제22권1호
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• pp.93-99
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• 2017

The effort attempts to investigate the influence of various non-oriented electrical steel sheets on the core loss of a switched reluctance motor (SRM). The core loss of the motor inherits a strong correlation with flux density and permeability of the material. The study involves the use of laminated 2.7 % high silicon steel suitable for the motor in view of its higher flux density and lower core loss. The accurate prediction of core loss leaves way to suggest measures for improving the performance of the SRM. The dynamic simulation measurements of a 1.5 kW, three-phase 12/8 SRM involve the finite element method (FEM) and use the data obtained experimentally from Epstein frame. The closeness of the simulated and hardware results obtained with laminations of M400-50A, DI MAX-M19 and DI MAX-M15 both for the stator and rotor, espouse a greater significance to the findings in terms of the core loss density and forge new dimensions for its use in the drive industry.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.275-278
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• 2005

The dynamic characteristics of rotor shafts for electric motors were investigated through the modal tests. The natural frequencies and modal dampings in each manufacturing stage of rotor core assembly were analyzed from the frequency response functions fer all 6 motors of a product model. The deviation of the each individual modal feature was found dependent on the mode shapes as well as the rotor assembly stage. The core stacking itself is known to widen the deviation of modal properties but fellowing processes of rotor bar insertion and swaging are confirmed to reduce the deviation. Finally the equivalent diameter of core part was estimated from the comparison of measured and calculated results to include the stiffness of core part.

• Smart Structures and Systems
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• 제16권6호
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• pp.1023-1047
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• 2015

In this study, the optimal location of the MR fluid segments in a partially treated laminated composite sandwich plate has been identified to maximize the natural frequencies and the loss factors. The finite element formulation is used to derive the governing differential equations of motion for a partially treated laminated composite sandwich plate embedded with MR fluid and rubber material as the core layer and laminated composite plate as the face layers. An optimization problem is formulated and solved by combining finite element analysis (FEA) and genetic algorithm (GA) to obtain the optimal locations to yield maximum natural frequency and loss factor corresponding to first five modes of flexural vibration of the sandwich plate with various combinations of weighting factors under various boundary conditions. The proposed methodology is validated by comparing the natural frequencies evaluated at optimal locations of MR fluid pockets identified through GA coupled with FEA and the experimental measurements. The converged results suggest that the optimal location of MR fluid pockets is strongly influenced not only by the boundary conditions and modes of vibrations but also by the objectives of maximization of natural frequency and loss factors either individually or combined. The optimal layout could be useful to apply the MR fluid pockets at critical components of large structure to realize more efficient and compact vibration control mechanism with variable damping.

• Steel and Composite Structures
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• 제28권5호
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• pp.629-639
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• 2018

In this paper, the vibroacoustic responses of baffled laminated composite sandwich flat panel structure under the influence of harmonic excitation are studied numerically using a novel higher-order coupled finite-boundary element model. A numerical scheme for the vibrating plate has been developed in the frame work of the higher-order mid-plane kinematics and the eigen frequencies are obtained by employing suitable finite element steps. The acoustic responses are then computed by solving the Helmholtz wave equation using boundary element method coupled with the structural finite elements. The proposed scheme has been implemented via an own MATLAB base code to compute the desired responses. The validity of the present model is established from the conformance of the current natural frequencies and the radiated sound power with the available benchmark solutions. The model is further utilized to scrutinize the influence of core-to-face thickness ratio, modular ratio, lamination scheme and the support condition on the sound radiation characteristics of the vibrating sandwich flats panel. It can be concluded that the present scheme is not only accurate but also efficient and simple in providing solutions of the coupled vibroacoustic response of laminated composite sandwich plates.

• Ocean and Polar Research
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• 제30권3호
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• pp.215-224
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• 2008

A piston core (MR06-04 PC23A) collected from the northern continental slope in the central Bering Sea has recorded the high-resolution millennial-scale variation of calcium carbonate ($CaCO3$) content during the last 65 kyr. An estimation of the age of the core sediments was carried out by using the lithologic correlation of the deglacial laminated layers with a neighboring core (HLY02023JPC), complementing the last appearance datum of both Lychnocanoma nipponica sakaii (54 kyr) and Amphimelissa setosa (85 kyr). The probable age of core MR06-04 PC23A was approximately younger than 65 kyr. Two distinct events of a significant increase of $CaCO3$ in the deglacial laminated sediments clearly correspond to MWP1A and MWP1B in the Bering Sea (Gorbarenko et al. 2005) and to T1ANP and T1BNP in the North Pacific (Gorbarenko 1996). These pronounced peaks of $CaCO3$ contents result from the elevated carbonate production in the surface water and the subsequent weakened dilution due to terrestrial input, along with an enhanced oxygen minimum zone. The $CaCO3$ contents are low (${\sim}2%$) during the last glacial period mainly because of a low carbonate production caused by an expanded sea-ice cover and an increased dilution by terrigenous particles due to their closer distance to the continent during the sea-level low stand. The occurrence of seven distinct $CaCO3$ peaks in core MR06-04 PC23A is remarkable during MIS 3 and MIS 4, and they most likely correlate to the short-term millennial Dansgaard-Oeschger events.

• 마이크로전자및패키징학회지
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• 제13권2호
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• pp.1-7
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• 2006

본 논문에서는 솔더 레지스트(solder resist)의 두께와 코어의 물성에 따른 인쇄회로기판의 철의 크기와 형상에 대하여 연구하였다. 인쇄회로기판의 굽힘 변형은 적층되는 재료의 열팽창계수의 차이에 의해 발생한다. 따라서 굽힘 변형의 감소를 위해서는 열팽창계수의 차이가 작은 적층 재료를 사용하는 것이 필요하며, 구조 형상에서도 상면과 하면의 불균일성을 완화시킬 필요가 있다. 또한, 적층 재료에서 코어의 강성을 높여 점의 발생을 억제할 수 있다. 코어를 이루는 복합재료는 적층 순서와 섬유 각에 따른 물성 특성의 방향성에 따라 굽힘과 비틀림이 연성되는 현상을 보이며, 이와 같은 성질을 이용하면 휨을 제어할 수 있다. 본 연구에서는 2층으로 구성된 chip scale package (CSP) 기판의 휨에 대한 연구로, 실험 및 유한 요소해석 툴을 이용하여 개선 결과를 도출하였다.

• Steel and Composite Structures
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• 제44권1호
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• pp.65-79
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• 2022

The main goal of this paper is to study the vibration of damaged core laminated annular plates with FG face sheets based on a three-dimensional theory of elasticity. The structures are made of a damaged isotropic core and two external face sheets. These skins are strengthened at the nanoscale level by randomly oriented Carbon nanotubes (CNTs) and are reinforced at the microscale stage by oriented straight fibers. These reinforcing phases are included in a polymer matrix and a three-phase approach based on the Eshelby-Mori-Tanaka scheme and on the Halpin-Tsai approach, which is developed to compute the overall mechanical properties of the composite material. In this study the effect of microcracks on the vibrational characteristic of the sandwich plate is considered. In particular, the structures are made by an isotropic core that undergoes a progressive uniform damage, which is modeled as a decay of the mechanical properties expressed in terms of engineering constants. These defects are uniformly distributed and affect the central layer of the plates independently from the direction, this phenomenon is known as "isotropic damage" and it is fully described by a scalar parameter. Three complicated equations of motion for the sectorial plates under consideration are semi-analytically solved by using 2-D differential quadrature method. Using the 2-D differential quadrature method in the r- and z-directions, allows one to deal with sandwich annular plate with arbitrary thickness distribution of material properties and also to implement the effects of different boundary conditions of the structure efficiently and in an exact manner. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. The sandwich annular plate is assumed to have any arbitrary boundary conditions at the circular edges including simply supported, clamped and, free. Several parametric analyses are carried out to investigate the mechanical behavior of these multi-layered structures depending on the damage features, through-the-thickness distribution, and boundary conditions.