• 한국정밀공학회지
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• 제16권12호
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• pp.168-173
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• 1999

It is investigated that internal defect of planetary gear which consists of two gears with different number of teeth on both side. The internal defect, central burst, begin to form at the place of adiabatic shear band which usually has maximum ductile fracture value during the forming operation, forward and backward extrusion. It makes the plastic forming of planetary gear difficult. The prediction of defect to minimize the cost to produce the planetary gear. The finite element simulation code DEFORM is applied to analyze the defects. In the analysis, the toothed gears are assumed as axisymmetric cylinders whose diameters are equal to those of pitch circles of the each gears. Experiments were carried out with the SCM415 alloy steel as billet material and AIDA 630-ton knuckle-joint press. The calculated results and experimental inspections are compared to design a die and blank without defects and the results are useful to predict the internal defect.

• 대한금속재료학회지
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• 제47권7호
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• pp.397-405
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• 2009

The high strain rate deformation behavior of ultra-fine grained 5083 aluminum alloys prepared via equal channel angular (ECA) extrusion was investigated in this study. The microstructure of ECA extruded specimens consisted of ultra-fine grains, and contained a considerable amount of second phase particles, which were fragmented and distributed homogeneously in the matrix. According to the dynamic torsion test results, the maximum shear stress and fracture shear strain of the route A (no rotation) specimen were lower than those of route C ($180^{\circ}$ rotation) specimen since that adiabatic shear bands of $100{\mu}m$ in width were formed in the route A specimen. The formation of adiabatic shear bands was addressed by concepts of critical shear strain, deformation energy required for void initiation, and microstructural homogeneity associated with ECA operations.

• Advances in materials Research
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• 제3권3호
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• pp.163-174
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• 2014

In this study, fatigue properties and crack growth characteristics of a polycarbonate (PC) were examined during cyclic loading at various mean stress (${\sigma}_{amp}$) and stress amplitude (${\sigma}_{mean}$) conditions. Different S vs. N and da/dN vs. ${\Delta}K$ relations were obtained depending on the loading condition. The higher fatigue strength and the higher resistance of crack growth are seen for the PC samples cyclically loaded at the higher mean stress and lower stress amplitude due to the low crack driving force. Non-linear S - N relationship was detected in the examination of the fatigue properties with changing the mean stress. This is attributed to the different crack growth rate (longer fatigue life): the sample loaded at the high mean stress with lower stress amplitude. Even if the higher stress amplitude, the low fatigue properties are obtained for the sample loaded at the higher mean stress. This was due to the accumulated strain energy to the sample, where severe plastic deformation occurs instead of crack growth (plasticity-induced crack closure). Shear bands and discontinuous crack growth band (DGB) are observed clearly on the fracture surfaces of the sample cyclically loaded at the high stress amplitude, where the lower the ${\sigma}_{mean}$, the narrower the shear band and DGB. On the other hand, final fracture occurred instantly immediately after the short crack growth occurs in the PC sample loaded at the high mean with the low ${\sigma}_{amp}$, i.e., tear fracture, in which the shear bands and DGB are not seen clearly.

• 한국전산구조공학회논문집
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• 제32권4호
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• pp.241-247
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• 2019

밴드갭은 기계적 파동의 전파가 금지되는 특정 주파수 범위를 의미한다. 본 연구는 경사도 기반의 설계 최적화 방법을 사용하여 낮은 가청 주파수 범위에서 밴드갭을 갖는 3차원 켈빈 격자를 설계하는 것을 목적으로 하고 있다. 블로흐 이론을 이용하여 무한주기 격자에서의 탄성파 전파를 해석하고, 기하학적으로 엄밀한 빔 이론에서 선형화를 통해 얻은 전단 변형 가능한 빔 모델을 사용하여 격자 구조 연결선을 모델링하였다. 주어진 격자 구성에서 중립 축 및 단면 두께를 B-spline 함수를 이용한 아이소-지오메트릭 매개화를 통해 설계 변수로 정의하고, 격자 구조의 밴드갭의 크기를 극대화하는 최적 설계를 수행하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1320-1325
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• 2006

When the train running on the high-speed track, there is a speed band which track distortion is unusually increased according to the condition of track and roadbed. This speed is called critical velocity and physical parameter values are increased greatly. These phenomenon happened as high-speed train were developed, studied regularly through TGV 100 running test in France. As research result until now, the main reason is soft roadbed's bearing capacity. Wave propagation and track support capacity is varied by the ground characteristics. This paper achieved theoretical examination about resonance band(speed and frequency) that occurred in roadbed on the base rock in point of geotechnical engineering. The examination of resonance divides with ground response analysis, critical band analysis by the shear wave velocity of roadbed and train critical speed through the ground stratum.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.443-447
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• 2005

When the high-speed train running on the track, there is a speed band which track distortion is unusually increased according to the condition of track and roadbed. This speed is called critical velocity and physical parameter value increased greatly. These phenomenon happened as high-speed train were developed, studied regularly through TGV 100 running test in France. As research result until now, the main reason is soft roadbed's capacity. Wave propagation and track support capacity is varied by the site characteristics. This paper achieved theoretical examination about resonance band(speed and frequency) that occurred in roadbed on the base rock in point of geotechnical engineering. The examination of resonance divides with ground response analysis, critical band analysis by the shear wave velocity of roadbed, train critical speed through the ground stratum.

• Korea-Australia Rheology Journal
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• 제17권1호
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• pp.1-7
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• 2005

Acrylonitrile-Butadiene-Styrene (ABS), polycarbonate (PC) and their alloys are an important class of engineering thermoplastics that are widely used for automotive industry, computer and equipment housings. For the process of recycling mixtures of ABS and PC, it is desirable to know how sensitive the blend properties are to changes in compositions. It was for this reason that blends of virgin ABS and virgin PC at five different compositions, namely, $15\%,\;30\%,\;50\%,\;70%$ and $85\%$ by weight of ABS were prepared and characterised by rheological and mechanical measurements. Rheological properties of these blends in steady, oscillatory and transient step shear and mechanical properties, namely, tensile strength, elongation-at-break and Izod impact strength are reported. The results show that PC behaves in a relatively Newtonian manner, but ABS exhibits significant shear thinning. The ABS-rich blends show a trend that is similar to that of ABS, while PC-rich blends, namely $0\%$ and $15\%$, exhibit a nearly Newtonian behaviour. However, at a fixed shear rate or frequency, the steady shear or the dynamic viscosity varied respectively in a non-mono-tonic manner with composition. Except for $15\%$ blend, the viscosities of other blends fall into a narrow band indicating a wide-operation window of varying blend ratio. The blends exhibited a lower viscosity than either of the two pure components. The other noticeable feature was that the blends at $70\%$ and $85\%$ ABS content had a higher G' than pure ABS, indicating an enhancement of elastic effect. The tensile yield strength of the blends followed the 'rule of mixtures' showing a decreasing value with the increase of ABS content in PC. However, the elongation-at-break and the impact strength did not appear to obey this 'rule of mixtures,' which suggests that morphology of the blends also plays a significant role in determining the properties. Indeed, scanning electron micrographs of the fracture surfaces of the different blends validate this hypothesis, and the $15\%$ blend is seen to have the most distinct morphology and correspondingly different behaviour and properties.

• 콘크리트학회논문집
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• 제19권3호
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• pp.301-312
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• 2007

무량판 구조의 슬래브-기둥 접합부는 뚫림전단파괴에 취약하여 구조 성능을 향상시킬 필요가 있다. 본 연구에서는 새로운 슬래브-기둥 접합부 전단 보강 방법인 래티스 보강의 강도와 변형 능력을 평가하기 위한 실험 연구를 실시하였다. 주기 횡 하중을 받는 4개의 래티스 보강 접합부에 대한 실험을 실시하였으며, 비교를 위하여 전단 무보강 시험체, 스터드 레일, 전단 밴드, 스터럽 등 다양한 기존의 전단 보강 방법으로 보강된 실험체에 대하여 실험을 실시하였다. 실험 결과, 래티스 보강은 강도와 변형 능력면에서 모두 우수한 성능을 나타내었으며, 현행 기준의 예측 강도를 현저히 상회하는 강도를 나타내어 전단 보강에 매우 효율적인 보강 방법으로 평가되었다. 반면에 스터럽, 스터드 레일과 전단 밴드 실험체는 전단 무보강 실험체에 비하여 강도 증진 효과가 크지 않거나, 그 강도에 미치지 못하는 강도를 나타냈다.

• 동력기계공학회지
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• 제5권3호
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• pp.56-63
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• 2001

A slitter is a sort of machinery to cut sheet materials in rolls continuously in the longitudinal direction. Recently slitter line users have requiring higher quality and precision in products in addition to high productivity. A finite element analysis has been performed to investigate the effect of processing factors on shear planes in the slitting of Shrinkage Band(S,K.B.). For the analysis, Hot-dip 55% aluminum-zinc alloy-coated steel sheets and coils(SAZCC) is selected as a material. The results obtained are that deformation was concentrated along the very narrow zone and the maximum slitting load decreases by increasing the knife clearance. Also effective strain decreases according to the clearance increases.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.978-981
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• 2005

The vibration analysis of damped sandwich beam is conducted using finite element method. The equation of motion presented by Mead and Markus is used to formulate FEM. Also as the thickness of the core in the damped sandwich beam goes to zero, conventional beam theory based on the transformed-section method and the equation of Mead and Markus are compared. According to the change of thickness and loss factor of the core, the forced frequency response of beam is calculated and discussed. And then using the half-power band width method, the damping ratio of each mode is calculated and discussed about each case.