• 동력기계공학회지
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• 제7권2호
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• pp.29-35
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• 2003

The monitoring and diagnostics of the rotating machinery have been received considerable attention for many years. The objectives are to classify the machinery condition and to find out the cause of abnormal condition. This paper describes a classification method of diagnosing the small reciprocating compressor for refrigerators using the artificial neural network and the wavelet transform. In order to extract salient features, the wavelet transform are used from primary noise signals. Since the wavelet transform decomposes raw time-waveform signals into two respective parts in the time space and frequency domain, more and better features can be obtained easier than time-waveform analysis. In the training phase for classification, self-organizing feature map(SOFM) and learning vector quantization(LVQ) are applied, and the accuracies of them ate compared with each other. This paper is focused on the development of an advanced signal classifier to automatize the vibration signal pattern recognition. This method is verified by small reciprocating compressors, for refrigerator and normal and abnormal conditions are classified with high flexibility and reliability.

• 한국정밀공학회지
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• 제33권10호
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• pp.797-804
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• 2016

The vehicle-mounted radar system (VMRS) including its electronic parts must be designed so that its performance is maintained under varying environmental conditions. The important aspects are typically weight and safety. Since many rotating VMRSs have been developed, discussion about the vibration and shock requirements for the transportation conditions has occurred: in addition, the dynamic unpaved, paved, and off-road effects have been emphasized with respect to lightweight designs. A lightweight-design VMRS should be capable of operating stably under the wind condition with the support of the vehicle structure. In this paper, a structural analysis regarding the support of the VMRS is performed, whereby the real-load conditions for three types of road and pressure were employed in terms of the wind condition. The structural analysis for the safety of the VMRS is performed, and the structural-integrity analytical processes of the VMRS are presented for different load conditions.

• 한국기계가공학회지
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• 제9권2호
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• pp.60-65
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• 2010

Injection molding process is one of the popular manufacturing methods to produce plastic parts with high efficiency and low cost. The tub-drum for drum type washer is made by an insert injection molding process with aluminum alloy insert of windmill type and has a big and complex structure consisted of many ribs to sustain the strength. In this paper, the volumetric shrinkages of rib part and bottom part surrounded by a windmill type insert are analyzed according to the vertical and circumferential direction of tub-drum. Volumetric shrinkage and its difference according to the height or radius of tub drum inform the designer to reduce the warpage of tub drum, and the optimal design of tub drum can be done from the those results. The change of volumetric shrinkage according to packing pressure is also analyzed. It is very important to analyze the volumetric shrinkage of tub drum because it generates the wearing phenomena at the rotating part connected to an aluminum alloy insert due to the warpage of tub drum.

• 한국정밀공학회지
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• 제14권3호
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• pp.66-74
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• 1997

In a high speed and high precision vertical machining center, chatter vibration is easily generated due to unbalanced masses in rotating parts and changtes of cutting forces. In this paper, modal test is performed to obtain modal parameters of the vertical machining center. In order to predit the cutting force of endmilling process for various cutting conditions, a mathematical model is given and this model is based on chip load, cutting geometry, and relationship between cutting forces and the chip load. Specific cutting constants of the model are obtained by averaging forces of cutting tests. The interactions between the dy- namic characteristics and cutting dynamics of the vertical machining center make the primary and the secondary feedback loops, and we make use of the equations of system to predict the chatter vibration. The chatter prediction is formulated as linear differential-differene equations, and simulated for several cases. Trends of vibration as radial and axial depths of cut are changed are shown and compared.

• 한국항공우주학회지
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• 제33권6호
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• pp.92-99
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• 2005

30톤 추력급 터보펌프에 대한 회전체 동역학 해석이 수행되었다. 연료펌프와 터빈에 의해서 유발되는 공력 및 수력 하중이 볼 베어링과 비접촉식 실의 강성 및 감쇠 예측을 위하여 고려되었다. 임계 속도의 분리 안전 여유와 회전체 부품의 팁 변위를 예측하기 위하여 임계 속도 해석과 질량 불평형 응답 해석이 수행되었다. 정확한 해석을 위하여 3차원 유한요소법을 사용하였고 1차원 전달함수 행렬법의 결과와 비교하였다. 탄성 링을 추가적으로 장착함으로써 베어링 지지부의 강성 제어를 통하여 충분한 공진 분리 여유의 확보가 가능함을 확인하였다.

• Journal of Biosystems Engineering
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• 제32권5호
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• pp.301-308
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• 2007

Sesame has usually been harvested manually in korea. The conventional sesame harvest procedures consists of cutting, binding, drying and pod shattering. The procedures of drying and shattering are repeated $2{\sim}3$ times. By manual works of this conventional shattering, it was found that some extent of pods were has always remained unopened. Therefore, this study was conducted to find a way to save the labor of sesame shattering by use of a drying device; a prototype of shattering machine was developed and tested the performance. The developed prototype consists of several parts: a continuous horizontal inlet using a chain conveyer, a shattering by a shocking agitator, a rotating cone for shattering of remaining closed pods, and a winnow. The shattering ratio measured by this prototype was 90.3%, 6.4% and 3.3% at the first, second and third shattering step, respectively. We found that in contrast to the conventional method which required at least 3 times operations for complete shattering, this shattering prototype with the condition of sufficient dried sesame pod offered more than 90% of shattering ratio in the first operation.

• Tribology and Lubricants
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• 제25권6호
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• pp.421-426
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• 2009

The brake system is important part of automobile safety system. The disc brake system is divided two parts: the rotating axisymmetrical disc and the stationary pads. During braking, the kinetic energy and potential energy of moving vehicle were converted into the thermal energy through frictional heat between the brake disc and the pads. The frictional heat, which is generated on the interface of the disc and pads, can cause high temperature during the braking process. The object of present work is to determine temperature and thermal stress, to compare to simulation results and experimental results in the disc by partial 3D model of ventilated disc brake with appropriate boundary conditions. In the simulation process, the mechanical loads were applied to the thermo-mechanical coupling analysis in order to simulate the process of heat produced by friction.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.55-61
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• 2000

Tungsten heavy metal is characterized bi a high density and novel combination of strength and ductility. Among them, 90W-7Ni-3Fe is used for applications, where the high specific weight of the material plays an important role. They are used as counterweights, rotating inertia members, as well as for defense purposes(kinetic energy penetrators, etc.). Because of these applications, it is essential to detemine the dynamic characteristics of tungsten alloy. In this paper, Explicit FEM(finite element method) is employed to investigate the dynamic characteristics of tungsten heavy metal under base of stress wave propagation theory for SHPB, and the model of specimen is divided into two parts to understand the phenomenon that stress wave penetrates through each tungsten base and matrix. This simulation results were compared to experimental one and through this program the dynamic stress-strain curve of tungsten heavy metal can be obtained using quasi static stress-strain curve of pure tungsten and matrix.

• 드라이브 ㆍ 컨트롤
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• 제16권4호
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• pp.87-92
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• 2019

Rotary dampers are damping devices which provide high resistance to shaft rotation. Rotary dampers are being used in various areas to enable the gentle opening and closing of the rotation motion relative to home furniture, industry machinery and automotive parts. Rotary dampers can be installed directly at the rotating point of a various part and can achieve uniform, gentle movement which increases quality and value of products. And generally, the silicone fluid is used as the damping medium because of its stable viscous properties. The movement of these little decelerators can be achieved with a high viscosity of working fluid and throttles installed in the body of the rotary damper. The damping force can be achieved clockwise, anti-clockwise or in both directions according to the structure of the orifices or throttles. In this paper, the torque performances of the rotary damper containing air in the working fluid were studied. For this purpose, the torque characteristic of the rotary damper according to the variation of various operating conditions such as clearance of leakage, dimensions of groove orifice, content ratio of air, etc., were simulated with AMEsim software.

• 한국정밀공학회지
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• 제22권8호
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• pp.92-99
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• 2005

Tungsten heavy metal is characterized by a high density and novel combination of strength and ductility. Among them, 90W-7Ni-3Fe is used for applications, where the high specific weight of the material plays an important role. They are used as counterweights, rotating inertia members, as well as fur defense purposes(kinetic energy Penetrators, etc.). Because of these applications, it is essential to detemine the dynamic characteristics of tungsten alloy. In this paper, Explicit FEM(finite element method) is employed to investigate the dynamic characteristics of tungsten heavy metal under base of stress wave propagation theory for SHPB, and the model of specimen is divided into two parts to understand the phenomenon that stress wave penetrates through each tungsten base and matrix. This simulation results were compared to experimental one and through this program, the dynamic stress-strain curve of tungsten heavy metal can be obtained using quasi static stress-strain curve of pure tungsten and matrix.