• 소성∙가공
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• 제16권3호
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• pp.157-162
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• 2007

The hydropiercing process gives a lot of advantages to the tube hydroforming such as cost reduction and high productivity. However it has a drawback, the amount of deflection around the hole is bigger than that of conventional die piercing process. The deflection can cause the problem at the assembly process of stamped parts and hydroformed part. Therefore the reduction of deflection is one of the most important issues for hydropiercing process. In this study, the deflection around hydropierced hole was investigated by experiment. As a result of investigation, the amount of deflection is influenced by the internal pressure, the material thickness' and the size of hole. Especially the hole size is most influencing factor on the deflection around the hydropierced hole.

• 한국정밀공학회지
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• 제23권9호
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• pp.76-83
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• 2006

Machining accuracy is closely related with tool deflection induced by cutting forces. In this research, cutting forces and tool deflection in end milling are expressed as a closed form of tool rotational angle and cutting conditions. The discrete cutting fores caused by periodic tool entry and exit are represented as a continuous function using the Fourier series expansion. Tool deflection is predicted by direct integration of the distributed loads on cutting edges. Cutting conditions, tool geometry, run-outs and the stiffness of tool clamping part are considered together far cutting forces and tool deflection estimation. Compared with numerical methods, the presented method has advantages in prediction time reduction and the effects of feeding and run-outs on cutting forces and tool deflection can be analyzed quantitatively. This research can be effectively used in real time machining error estimation and cutting condition selection for error minimization since the form accuracy is easily predicted from tool deflection curve.

• Restorative Dentistry and Endodontics
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• 제29권4호
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• pp.346-352
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• 2004

The purpose of present study was to evaluate the polymerization shrinkage stress and cuspal deflection in maxillary premolars resulting from polymerization shrinkage of composites and compomers. Composites and compomers which were used in this study were as follows: Dyract AP, Z100, Surefil. Pyramid, Synergy Compact, Heliomolar, Heliomolar HB, and Compoglass F. For measuring of polymerization shrinkage stress, Stress measuring machine (R&B, Daejon, Korea) was used. One-way ANOVA analysis with Duncan's multiple comparison test were used to determine significant differences between the materials. For measuring of cuspal deflection of tooth, MOD cavities were prepared in 10 extracted maxillary premolars. And reduction of intercuspal distance was measured by strain measuring machine (R&B, Daejon, Korea) One-way ANOVA analysis with Turkey test were used to determine significant differences between the materials. Polymerization shrinkage stress is $\mathbb{\ulcorner}$Heliomolar, Z100, Pyramid < Synergy Compact Compoglass F < Dyract AP < Heliomolr HB, surefil$\mathbb{\lrcorner}$ (P < 0.05). And cuspal delfelction is $\mathbb{\ulcorner}$Z100, Heliomolar, Heliomolar HB, Synergy Compact Surefil. < Compoglass F < Pyramid, Dyract AP$\mathbb{\lrcorner}$ (P < 0.05). Measurements of ploymerization shrinkage stress and those of cuspal deflection of the teeth was different. There is no correlation between polymerization shrinkage stress and cuspal deflection of the teeth(p > 0.05).

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권9호
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• pp.495-501
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• 2000

This paper presents a method to minimize the initial deflection of a multi-layer piezoelectric microactuator without loosing its piezoelectric deflection performance required for light modulating micromirror devices. The multi-layer piezoelectric actuator composed of PZT silicon nitride and platinum layers deflects or buckles due to the gradient of residual stress. Based on the structural analysis results and relationship between process conditions and mechanical properties we have modified the fabrication process and the thickness of thin film layers to reduce the initial residual stress deflection without decreasing its piezoelectric deflection performance. The modified designs fabricated by surface-micromachining process achieved the 77% reduction of the initial deflection compared with that of the conventional method based on the measured micromechanical material properties is applicable to the design refinement of multi-layer MEMS devices and micromechanical structures.

• 공학기술논문지
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• 제10권3호
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• pp.285-290
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• 2017

Molding of body with ribs is the most difficult during flow molding process. The rib area is easy to be deformed at the rear side due to wall thickness variation. In this study, relationships between molding condition and deflection of rib-shaped part is investigated during the compression molding of fiber reinforced plastic composites, and the following results are derived. Polypropylene(PP), Polystyrene(PS), and stampable sheet(SS 40wt%) show the increment of deflection along with releasing temperature. For the correlation between incremental holding pressure load and deflection, stampable sheet exhibits lower deflection along with higher holding pressure, while PS shows significant increase of deflection with higher holding pressure, PP shows completely different characteristic, significant reduction of deflection along with higher holding pressure. Regarding to mold temperature and deflection, deflection amount of SS is the biggest, and PS shows the smallest. In addition, all three kinds shows the highest amount of deflection at 173C. Deflection is reduced when mold closing speed is increased. Amount of deflection in SS is larger and is not highly dependent on molding conditions like holding pressure and cooling parameters, compared with single component material like PP. This can be elucidated by anisotropic and inhomogeneous characteristics of glass fiber during filling process of stampable sheet composite.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.565-573
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• 1999

Hihg Tensile Steel enables to reduce the plate thickness comparing to the case when Mild Steel is used. From the economical view points this is very preferable since the reduction in the hull weight. however to use the High Tensile Steel effectively the plate thickness may become thin so that the occurrence of buckling is inevitable and design allowing plate buckling may be necessary. If the inplane stiffness of the plating decreases due to buckling the flexural rigidity of the cross sect6ion of a ship's hull also decreases. This may lead to excessive deflection of the hull girder under longitudinal bending. In these cases a precise estimation of plate's behavior after buckling is necessary and nonliner analysis of isolated and stiffened plates is required for structural sys-tem analysis. In this connection this paper discusses nonlinear behaviour of thin plate under thrust. Based on the analytical method elastic large deflection analysis of isolated plate is perform and simple expression are derived to evaluated the inplane rigidity of plates subjected to uniaxial compression.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 춘계 학술논문 발표대회
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• pp.107-108
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• 2019

The interlayer noise of the apartment house is a typical problem that reduces the quality of the residential environment. Therefore, many researchers have developed soundproofing materials that blocks noise between floors. However, most development technologies do not have the noise cut-off effect felt by residents, and may also have a defect in long-term deflection. In this respect, this study developed high-performance interlayer soundproofing material that can overcome existing problems. The developed technology has the noise reduction effect experienced by the residents and it has high durability without long-term deflection. Therefore, high-performance interlayer soundproofing material is expected to contribute to reducing disputes over noise between floors of apartment residents.

• 한국공작기계학회논문집
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• 제17권2호
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• pp.121-127
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• 2008

Micro end-milling has been becoming an important machining process to manufacture a number of small products such as micro-devices, bio-chips, micro-patterns and so on. Despite the importance of micro end-milling, many related researches have given grand efforts to micro end-milling phenomenon, for example, micro end-milling mechanism, cutting force modeling and machinability. This paper strongly concerned actual problem, micro tool deflection, which causes excessive machining errors on the workpiece. To solve this problem, machining error prediction method was proposed through a series of test micro cutting and analysis of their SEM images. An iterative algorithm was applied in order to obtain corrected tool path which allows reducing machining errors in spite of tool deflection. Experiments are carried out to validate the proposed approaches. In result, remarkable error reduction could be obtained.

• Journal of Biosystems Engineering
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• 제29권2호
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• pp.101-108
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• 2004

The objectives of this study were to determine the natural frequency of a walking-type cultivator's handle using a modal analysis, to determine whether or not the handle resonates with forcing frequency induced by its engine, and to determine a method to reduce the handle vibration using a technique of the operational deflection shapes(ODS). Results of the study are as follows: The natural frequencies of the handle up to third harmonics were found to be 20.4, 22.5 and 92.1 Hz in the vertical direction and 14.9, 93, and 132 Hz in the horizontal direction. It was found that the handle does not resonate with the forcing frequency of the engine, which is 52 Hz. The operational deflection shape analysis revealed the deflected shapes of the handle in the vertical and horizontal directions and suggested that the handle vibration can be reduced by adding some mass to the place where the largest deflection occurs. Attaching of 1.1 kg mass adjacent to the largely deflected area resulted in reductions of vibration from 9.45 to 8.03 m/s$^2$ in x-axis direction from 3.89 to 3.16 m/s$^2$ in y-axis direction and from 7.89 to 3.09 m/s$^2$ in z-axis direction, which are respectively 15, 19 and 61% reductions. The total vibration level was reduced by 29%, indicating that mass-adding method by the ODS is very effective for reducing the handle vibrations of the cultivators.

• 한국풍공학회지
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• 제22권4호
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• pp.155-161
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• 2018

현대 사회에서 도시화와 온난화로 인한 태풍 등 강풍에 의한 피해는 증가될 것으로 예상된다. 본 연구에서는 기 개발된 창호보호장치의 보강성능을 시험하기 위해 비 보강된 판유리와 보강된 판유리의 2점 가력실험과 등분포하중 실험을 수행하였다. 창호보호장치의 보강성능은 휨 성능평가를 토대로 평가하였다. 창호보호장치의 이론적 성능 산정은 탄성하중법과 처짐 곡선의 미분방정식을 이용한 수식해석과 Midas-Gen을 이용한 전산해석을 통해 수행하였다. 실험값과 이론 산정 값의 최대하중 가력시의 판유리 중앙부 최대 처짐 비교를 통해 산정방법의 유효성을 검토하였다. 창호보호장치 부착 시 실험조건하에서 40%까지의 응력감소효과와 동일 하중하에서 71.4%까지의 처짐 감소 효과가 있었다. 판유리를 보요소로 해석한 결과보다 판유리를 판 요소로 해석한 결과가 오차가 적으므로 성능 판단 시 가능하면 판 요소로 해석을 수행하는 것이 유리하다.