• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.34-35
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• 2003

고에너지적 Nd-Fe-B계 소결자석 제조를 위한 펄스자장 성형시, 금형 및 다양한 성형조건이 자석의 이방화율 향상에 미치는 영향에 대하여 조사하였다. 일반적으로 butterfly, disk or coin 형태의 자석을 제조하는 방법으로는, 종축자장성형법(Axial Die Press, ADP)을 이용하여 최종제품의 near-net shape으로 성형 및 소결하는 방법과, 횡축자장성형법(Transverse Die Press, TDP)을 이용하여 blick or cylinder 형태로 제조한 후 여러 단계의 가공공정을 거쳐 최종제품으로 제조하는 방법이 적용되고 있다. 그러나, ADP의 경우 분말의 자장정렬 후 성형단계에서 성형밀도가 증가함에 따라 배향의 틀어짐 현상이 증가하므로 이방화율 향상의 한계가 있어 (BH)$_{MAX}$+iHc=54 이상의 자석은 제조되기 어렵고, TDP의 경우 고이방화 자석의 제조가 가능하나 복잡한 형상의 제품을 직접 성형할 수 없어 성형/소결 후 복잡한 가공공정을 거쳐야 하므로 재료의 손실뿐만 아니라 고가의 가공비용이 소요되므로 경제적인 문제점을 갖게 된다. 반면에, 펄스자장 종축성형방법(PDP)은 3T~5T의 펄스자장을 이용하여 분말의 정렬 및 성형을 동시에 수행함으로써 TDP보다 향상된 배향율이 얻어질 수 있으며, ADP으로만 실현 가능한 복잡한 형성의 자석을 near-net shape으로 제조가 가능한 잇점이 있다.다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.312-318
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• 2001

This paper suggests the finite element method to analyze the dynamic characteristics of a rotating HDD system including the supporting structure with general shape. The flexible supporting structure was modeled by tetrahedra elements to produce a finite element model of disk-spindle-shaft-housing system and the dynamic characteristics of the HDD system was investigated due to the change of rotating speed. The validity of the presented method was verified by the modal testing. The supporting structure has an crucial effect on lower modes for HDD system, so that it is required to consider the supporting structure to accurately analyze the dynamic characteristics of HDD system.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.37-44
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• 2002

The dynamic behavior of rotor-bearing system has been investigated using finite element method. A procedure is presented for dynamic modeling of rotor-bearing system which consists of shaft elements, rigid disk, flexible bearing and support structure. A finite element model including the effects of rotary inertia, shear deformation, gyroscopic moments is developed. Linear stiffness and damping coefficients are calculated for 2 lobe sleeve bearing. The whirl frequency, mode shape, stability and unbalance response of rotor system including effects of bearing coefficient and support structures are calculated.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.285-290
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• 2000

This paper was undertaken to do morphological analysis of wear debris for slipper-pad of hydrauric rotary acuator. The lubricating wear test was performed under different experimental conditions using the wear test device and wear specimens of the pin on disk type was rubbed in paraffinic base oil by three kinds of lubricating materials. varying applied load, sliding distance. The four shape parameters(50% volumetric diameter, aspect, roundness and reflectivity) are used showed that the four shape parameters of wear debris depend on a kind of the lubricating condition. It was capable of presuming wear volume for slipper-pad of hydrauric rotary acuator on driving time.

• Electrical & Electronic Materials
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• v.10 no.9
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• pp.889-894
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• 1997

A miniaturized wind-mill type ultrasonic motor which has diameter in 12.7 mm and thickness in 2.0mm using PMN-PZT piezoelectric ceramics was fabricated. The wind-mill type ultrasonic motors has only three plate and of two wind-mill shape slotted metal endcaps a rotor whose end is hollowed out so that its periphery fits with the shape of the stator and a bearing to guide the rotor. A Finite Element Analysis was carried out to obtain the endcaps behavior under a radial displacement change of piezoelectric disk and to optimize the structure of the number of slots. Increasing the applied voltage the revolution speed of ultrasonic motors was increased. The maximum speed of 700 rpm and the maximum torque of 0.22 nN·m of the wind-mill type ultrasonic motors were obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.85-89
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• 1996

This paper was undertaken to analyze the morphology of wear debris for operating condition evaluatio of lubricated machine surfaces. The lubricating wear test was carried out under different experimental conditions using tile wear test device was made in our laboritory and wear testing spcimen of the pin on disk type was rubbed in paraffine series base oil, by varying specimen, applied load, sliding distance. The four shape parameters (50% volumetric diameter, aspect, roundness and reflectivity) to describe morphology of wear debris have been developed and are outlined in tile paper. A system using such techniques promises to obviate the need for subjective, human interpretation of particle morphology in machine condition monitoring

• Journal of the Korean Society for Precision Engineering
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• v.28 no.10
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• pp.1189-1195
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• 2011

For side airbag, the pipe type inflators have been wide used while the disk type inflators have been used for front airbag. For helping to prevent injury and death the airbag inflator system should be design with great care. The present study deal with optimizing the design of side airbag inflator by finite element analysis and design of experiment method. An optimization process was integrated to determine the optimum design variable values related to the side airbag inflator. Free shape optimization method has been carried out to find a optimal shape on an side airbag inflator model. Optimization of the air bag inflator was successfully developed using Sharpe optimization was carried out to find a new geometry. The improved results compared to the base design specification were achieved from design of experiment and optimization.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.94-103
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• 2002

Accurately controlling the shape of the read/write head structure is critical in the performance of a modern hard disk drive. The sliders investigated are composed of alumina and titanium carbide (AlTiC) and act as an air bearing when passing over the disks. Controlling the curvature of the slider is of primary importance. A laser scribing system that produces curvature by Inducing residual stress into the slider can be utilized. Predicting the curvature created by a pattern of scribes is of great importance to increase the control over the sliders' shape. Using finite element analysis a force system that produces stresses similar to the laser scribing is applied. The curvatures created by the force system are calibrated to experimental measurements.

• 한국기계연구소 소보
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• s.19
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• pp.149-154
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• 1989

Generally Cam-Follower systems consist of two elements: Cam is for rotating motion and follower for reciprocating motion. Depending on the shape of cam and type of follower, the motion of cam-follower system is determined. Thus design process and analysis process must be well defined. The design process means to find the coordinates of cam shape which can be defined the given motion of follower and the analysis process means to determine the motion curve of follower corresponding to the given cam based on the dimensions of a cam-follower system. This paper consists of two parts: One is development of a numerical method for design and analysis of cam-follower systems, the other is for development of a CAD program and its application. As the first part of the paper, an iterative contact method is proposed. This method can calculate the contact points between cam and roller and determine their contact angles iteratively. The second part of the paper presents the structure of a CAD program and its availability to the industrial applications.

• Transactions of Materials Processing
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• v.9 no.1
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• pp.52-58
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• 2000

Hot precision forging with a back pressure was investigated for manufacturing of compressor parts made of Al-Si alloy. Disk-shaped blank made of Al-Si alloy was hot forged, and ribs were formed by loading back pressure on their top. The influence of the back pressure and die temperature on forgeability and properties of parts made of Al-Si alloy were examined. Using the F.E.M. simulation, we found the optimum vallue of back-pressure. The prototypes of scroll parts were forged into the near-net shape and satisfied the required properties.