• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.705-710
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• 2003

Many papers have studied computer simulations of elastic bodies undergoing large deflections and large deformations. But there have not been many attempts to check the validity of the numerical formulations because the simulation results could not be matched without correct input data such as material properties and damping effects. In this paper, these values are obtained from real experiment with a high-speed camera and a data acquisition system. The simulation results with the absolute nodal coordinate formulation (ANCF) are compared with the results of real experiments. Two examples, a thin cantilever beam and a thin plate, are studied to verify whether the simulation results are well matched to experimental results.

• Journal of Mechanical Science and Technology
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• 제18권5호
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• pp.742-752
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• 2004

Many papers have studied computer simulations of elastic bodies undergoing large deflections and large deformations. But there have not been many attempts to check the validity of the numerical formulations because the simulation results could not be matched without correct input data such as material properties and damping effects. In this paper, these values are obtained from real experiment with a high-speed camera and a data acquisition system. The simulation results with the absolute nodal coordinate formulation (ANCF) are compared with the results of real experiments. Two examples, a thin cantilevers beam and a thin plate, are studied to verify whether the simulation results are well matched to experimental results.

• 대한기계학회논문집A
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• 제32권4호
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• pp.327-332
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• 2008

The effectiveness of vehicle parts made through extrusion is in the limelight because of the advantages of high strength stiffness materials can be produced and the number of processes can be drastically reduced. Therefore, the parts should have sufficient stiffness and be lightweight enough to improve fuel efficiency. However, the application of extruded aluminum requires pre-bending technologies that can manufacture the complex designs profiles demanded by vehicle parts. The aim of this research is that the development of the variable curvature extrusion technology that can produce a variety of curvature. In order to produce a variable curvature, the guide transfer speed and transfer time should be controlled properly. The guide transfer speed and transfer time were examined by the theoretical analysis. A model was developed to simulate the deformation behaviors of extrusion and bending process from the symmetric bumper with range of radii from 1863mm to 2163mm. The theoretical analysis and FE analysis were verified through experimental method.

• 정보저장시스템학회논문집
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• 제2권4호
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• pp.245-250
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• 2006

Organizations such as broadcasting stations and libraries which deal with huge amount of information require high-capacity storage systems for archiving their materials and information. It is necessary and urgent for the storage people to develop a compact, high capacity, and low-cost data storage systems. Even though the Blue-ray technology is commercialized and now it is on the market, demand for the compact and low-cost system is still increasing. A flexible disk system has been introduced recently to satisfy above mentioned requirements. The system uses multiple of thin disks and is expected to achieve technical requirements. However, decreasing the disk thickness makes it difficult to read and write data because it decreases the disk rigidity so that the transverse vibration of the rotating disk increases easily due to both the interaction with surrounding air and the vibration characteristics of thin flexible disk itself. In this study, flat-type stabilizer is proposed to suppress the transverse vibration of a $95{\mu}m$-thick polycarbonate disk. Characteristics of disk vibration have been studied through the results of numerical analysis from the fluid mechanics point of view. Numerical simulation is verified through the experiment by measuring the gap between the rotating disk and the stationary flat stabilizer. The axial deflections of the disk are computed for various rotating speeds and reference gap sizes and then a method of regression is applied to those data. As a result, an empirical relation is proposed for the steady deformation shape of the rotating disk.

• 문화기술의 융합
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• 제9권5호
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• pp.529-534
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• 2023

고속 및 대면적 인쇄를 위한 라인 프린팅 기술은 늘어난 헤드 길이만큼 헤드 내부로 잉크를 공급하는 유로를 확보해야 하는 구조적 취약점과 제조 과정에서 발생하는 잔류응력에 의한 피드홀 변형으로 인해 노즐층이 파손되거나 잉크가 누출되는 결함이 있다. 따라서 본 논문에서는 견고하고 신뢰할 수 있으며 라인 프린팅 방식에 보다 적합한 열전사 방식의 잉크젯 프린트 헤드 형상을 제안하고자 한다. 먼저 실험을 통해 초기 라인 프린팅 헤드의 변형량을 측정한 후 이를 등가의 하중량으로 변환하였으며 FEA 해석을 통해 하중 추정 방법의 타당성을 검증하였다. 또한 헤드 크기를 증가시키지 않으면서 변형을 최소화할 수 있도록 기둥이나 지지벽으로 단위 노즐을 보강하거나 지지빔이나 건/습식각된 브릿지를 추가하여 내부 강성을 증가시킨 헤드 구조를 설계하였으며, 피드홀 변형이 최대 90% 감소하는 것을 확인하였다. 제안된 형상 중 공정 편의성과 제작비용을 고려하여 건식각된 피드홀 브릿지 형태의 헤드를 선정하였으며 실제 제작을 통해 노즐층 변형이나 잉크 누출 없이 정상 작동하는 것을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2170-2174
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• 2005

Selective Laser Sintering (SLS) is a useful rapid prototyping technique for the manufacture of three dimensional (3D) solid objects directly from a scanning data. A new approach called a Selective Multi-Laser Sintering (SMLS) system has been developed at Korea Institute Machinery & Materials (KIMM) as an industrial type SFFS. This SMLS machine is built with a frame, heaters, nitrogen supply part, laser system. This system uses the dual laser and 3D scanner made in $Solutionix^{TM}$ to improve the precision and speed for large objects. The three-dimensional solid objects are made of polyamide powder. The investigation on each part of SMLS system is performed to determine the proper theirs design and the effect of experimental parameters on making the 3D objects. The temperature of the system has a great influence on sintering the polymer. Because the stability of the powder temperature prevents the deformation of each layer, the controls of the temperature in both the system and the powders are very important during the process. Therefore, we simulated the temperature distribution of build room using the temperature analysis with ANSYS program. Selected radiant heater is used to raise temperature of powder to melting point temperature. The laser parameters such as scan spacing, scan speed, laser power and laser delay time affect the production the 3D objects too. The combination of the slow scan speed and the high laser power shows the good results without the layer curling. The work is under way to evaluate the effect of experimental parameters on process and to produce the various objects. We are going to experiment continuously to improve the size accuracy and surface roughness.

• Structural Engineering and Mechanics
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• 제74권5호
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• pp.589-600
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• 2020

The bonding interface of the concrete slab track and cement-asphalt mortar layer plays an important role in transferring load and restraining the track slab's deformation for slab track structures without concrete bollards in high-speed railway. However, the interfacial bond-slip behavior is seldom considered in the structural analysis; no credible constitutive model has been presented until now. Elaborating the field tests of concrete to cement-asphalt mortar interface subjected to longitudinal and transverse shear loads, this paper revealed its bond capacity and failure characteristics. Interfacial fractures all happen on the contact surface of the concrete track slab and mortar-layer in the experiments. Aiming at this failure mechanism, an interfacial mechanical model that employed the bilinear local bond-slip law was established. Then, the interfacial shear stresses of different loading stages and the load-displacement response were derived. By ensuring that the theoretical load-displacement curve is consistent with the experiment result, an interfacial bond-slip constitutive model including its the corresponding parameters was proposed in this paper. Additionally, a finite element model was used to validate this constitutive model further. The constitutive model presented in this paper can be used to describe the real interfacial bonding effect of slab track structures with similar materials under shear loads.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.687-692
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• 2004

For the prediction of sloshing in the propellant tank of rocket vehicle utilized in RVT (reusable rocket vehicle testing) conducted by ISAS/JAXA, the flow field in the propellant tank during the ballistic flight was experimentally reproduced with the sub-scale model of it. The lateral acceleration as large as about 0.8 G was provided with a mechanical exciter and the deformation of liquid surface in the vessel was visualized with a high-speed camera. The several con-figurations of damping devices were installed and tested in the vessel, which should keep the ullage gas away from the outlet port. It was consequently suggested that the combination of a baffle plate and a perforated cylinder could be effective against the gas suction before the re-ignition of the engine. The sloshing phenomena were also simulated with the CFD code, called CIP-LSM. The numerical results showed good agreement with the corresponding data obtained in the experiment.

• International Journal of Automotive Technology
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• 제7권5호
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• pp.571-577
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• 2006

This paper deals with dynamic tensile characteristics for the polypropylene used in an IP(Instrument Panel). The polypropylene is adopted in the dash board of a car, especially PAB(Passenger Air Bag) module. Its dynamic tensile characteristics are important because the PAB module undergoes high speed deformation during the airbag expansion. Since the operating temperature of a car varies from $-40^{\circ}C$ to $90^{\circ}C$ according to the specification, the dynamic tensile tests are performed at a low temperature($-30^{\circ}C$), the room temperature($21^{\circ}C$) and a high temperature($85^{\circ}C$). The tensile tests are carried out at strain rates of six intervals ranged from 0.001/sec to 100/sec in order to obtain the strain rate sensitivity. The flow stress decreases at the high temperature while the strain rate sensitivity increases. Tensile tests of polymers are rather tricky since polymer does not elongate uniformly right after the onset of yielding unlike the conventional steel. A new method is suggested to obtain the stress-strain curve accurately. A true stress-strain curve was estimated from modification of the nominal stress-strain curves obtained from the experiment. The modification was carried out with the help of an optimization scheme accompanied with finite element analysis of the tensile test with a special specimen. The optimization method provided excellent true stress-strain curves by enforcing the load response coincident with the experimental result. The material properties obtained from this paper will be useful to simulate the airbag expansion at the normal and harsh operating conditions.

• 대한기계학회논문집A
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• 제34권9호
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• pp.1227-1233
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• 2010

가스터빈엔진 내의 블레이드에서는 표면에 외부의 찬 공기를 흘려주는 작은 냉각 홀들을 가공하고 열 차단 코팅시스템을 코팅하는 방법으로 기지금속을 고온에서 보호한다. 열 차단 코팅은 열피로 과정에서 산화막의 성장 및 접합층과 산화막의 열팽창계수의 불일치로 산화막내부에 잔류응력이 발생하며 궁극적으로 코팅층의 분리를 유발한다. 본 연구에서는 내열합금 시편 표면에 작은 홀을 가공하여 여러 가지 고온 유지 조건에서 열 및 기계적 피로 시험을 수행하여 홀 주위의 산화막의 변형을 관찰하였다. 실험결과 기계적 피로가 홀 주위의 산화막의 변형에 중요한 영향을 미치며, 동일한 산화막 두께에서 고온 유지 시간이 짧을수록 변형이 쉽게 발생 하였다. 또한 본 연구에서는 홀 주위 산화막의 응력해석을 위한 이론적인 연구도 시도되었다.