• Elastomers and Composites
• /
• 제54권4호
• /
• pp.313-320
• /
• 2019

A typical wear pattern was reported to resemble the fatigue crack growth behavior considering its mechanism, especially for amorphous rubbers such as styrene-butadiene rubber (SBR). In this study, the wear and crack growth rates were correlated using two separate experiments for carbon black and silica-reinforced selected rubber compounds. The wear rate was determined using a blade-type abrasion tester, where the frictional energy input during wearing was measured. The crack propagation rate was determined under different tearing energy inputs using a home-made fatigue tester, with a pure-shear test specimen containing pre-cracks. The rates of abrasion and crack propagation were plotted on a log-log scale as a function of frictional and tearing energies, respectively. Reasonable agreement was observed, indicating that the major mechanism of the abrasion pattern involved repeated crack propagation.

• 대한기계학회논문집
• /
• 제11권2호
• /
• pp.243-252
• /
• 1987

본 논문에서는 작은 인공결함을 가진 표면균열의 진전거동을 밝히기 위하여 용접성이 좋고 강도도 적당하며 내식성이 좋아 해양구호무재 및 용접구호물재로서 널 리 사용되는 5083-H113 알루미늄합금을 준비하고 이재료의 피로표면균열 진전거동에 미치는 응력비의 영향을 균열닫힘과 함께 검토하였다.

• Journal of Welding and Joining
• /
• 제6권3호
• /
• pp.43-55
• /
• 1988

An experimental study was carried out to identify the fatigue fractue behavior of weld zone in generally rolled steel for marine structure. The bending an shear loads were applied simultaneously on the specimens to simulate real load condition for marine structure. The effect of the stress intensity factor under mode I with II loading condition on the initiation and the propagation of a crack were investigated, with particular emphaiss on mode II. When the $K_{II}$ stress intensiy factor in mode II was applied under mode I load condition, the growth behavior of a crack seems to be affected mainly by the anisotropic characteristic of materials. Especially, when the crack was located in and near the weld zone and parallel to th weld line, the propagation behaviour was turned out to be quite different from that of the base metal along the direction transverse to the weld line. In general, the propagation veiocity of the cracks in and near the weld zone was found to be slower that the velocity in base metal.

• 한국항공우주학회지
• /
• 제40권5호
• /
• pp.423-430
• /
• 2012

본 논문에서는 기하학적 비선형 후좌굴 유한요소 해석을 통하여 얇은 멤브레인에서 주름 발생이 컷의 진전방향에 미치는 영향을 연구하였다. 해석에는 양단에 인장을 받고 있고 중앙에 기울어진 컷을 가진 직사각형 멤브레인을 고려하였다. 주름이 발생한 경우와 주름이 발생하지 않은 경우에 대해 각각 해석을 수행하여 컷의 진전각도 및 $J$-적분값을 비교하였다. 컷의 진전각도는 에너지 방출률이 최대인 방향, $K_{II}$의 값이 0이 되는 방향을 구하는 방법 및 접선응력이 최대인 방향을 구하는 방법을 사용하여 계산하였다. 또한 다양한 컷의 초기방향각을 고려하여 각도에 따른 주름의 영향을 조사하였으며 가상의 미소크기의 컷을 반복적으로 진전시켜 컷이 전파되는 경향도 알아보았다.

• Journal of Welding and Joining
• /
• 제15권4호
• /
• pp.187-193
• /
• 1997

In the weldmentsm the crack propagation rate is changed due to the residual stress. The crack propagation rate is high in the region with the residual stress. However it shows rhw same behavior with the base metal in the region that does not include the residual stress. The fatigue crack growth rate for the material with residual stresses can be predicted more precisely by using the effective stress ratio. The difference between experimental results and prediction results in the initial stage seems to be due to the redistribution of residual stresses and microstructural change.

• 한국전자파학회논문지
• /
• 제9권3호
• /
• pp.410-418
• /
• 1998

밀리미터파대역의 강우감쇄와 교차편파를 여러 나라의 측정치와 비교하였다. 그리고 국내환경에 적용할 수 있도록 $\tau$분 강우율을 1분 가우율롤 변환할 수 있는 변환모델을 제시하였다. 변환한 국내의 가웅율 데이타를 이요하여, 강우감쇄와 교차편파의 확률분포를 다양한 모델을 이용하여 계산하고, 그 결과를 서로 비교하였다.

• 한국해양공학회지
• /
• 제8권2호
• /
• pp.115-123
• /
• 1994

Under variable amplitude loading conditions, retardation or accelerated condition of fatigue crack growth occurs with every cycle, Because fatigue crack growth behavior varied depend on load time history. The modeling of stress amplitude with storm loading acted to ships and offshore structures applied this paper. The crack closure behavior examine by recording the variation in load-strain relationship. By taking process mentioned above, fatigue crack growth rate, crack length, stress intensity factor, and crack closure stress intensity factor were obtained from the stress cycles of each type of storm ; A(6m), B(7m), C(8m), D(9m), E(11m) and F(15m) which was wave height. It showed that the good agreement with between the experiment results and simulation of storm loads. So this estimated method of crack propagtion rate gives a good criterion for the safe design of vessels and marine structure.

• 한국조경학회지
• /
• 제25권2호
• /
• pp.9-19
• /
• 1997

These studies were carried out to investigate seed propagation method and conducted using stem cuttings of Styrax japonicus for using as a woody landscape plant. The results are obtained as follows. After the H\sub2\SO\sub 4\ and GA\sub 3\ treatment to the seeds of Styrax japonicus, three months of warm treatment followed by cold stratification for four months increased seed germination rate. The rooting rate of Styrax japonicus was increased by the treatment with concentrated IBA, especially highest at 7,000ppm. Rooting percentages were highest for cuttings taken on July 15, 1995. Therefore, the most effective method for rooting of Styrax japonicus was treatment with 7,000ppm IBA on July 15 cuttings, which showed rooting rate of over 90%. Half-leaf-remained cuttings were more effective than those with two leaves on rooting of Styrax japonicus. Dipping for 10 seconds in IBA solution resulted in rooting rate of over 70%. The longer the treatment time the worse the rooting.

• 한국안전학회지
• /
• 제16권1호
• /
• pp.18-24
• /
• 2001

The fatigue crack growth behavior of the SA516/70 steel which is used for pressure vessels was examined experimentally at room temperature, $-60^{\circ}C$,$-80^{\circ}C$ and $-100^{\circ}C$ with stress ratio of R=0.05, 0.1 and 0.3. Fatigue crack propagation rate da/dN related with stress intensity factor range ${\Delta}K$ was influenced by stress ratio in stable of fatigue crack growth (Region II) with an increase in ${\Delta}K$. The resistance of fatigue crack growth at low temperature is higher compared with that at room temperature, which is attributed to the extent of plasticity-induced by compressive residual stress according to the cyclic loads. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and low temperatures are mainly explained by the crack closure and the strengthening due to the plasticity induced and roughness induced.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2001년도 추계학술대회 논문집(Proceeding of the KOSME 2001 Autumn Annual Meeting)
• /
• pp.80-87
• /
• 2001

The fatigue crack growth behavior of the SA516/60 steel which is used for pressure vessels was examined experimentally at room temperature $25^{\circ}C, -30^{\circ}C, -60^{\circ}C, -80^{\circ}C, -100^{\circ}C$ and -l2$0^{\circ}C$ with stress ratio of R=0.05, 0.1 and 0.3. Fatigue crack propagation rate da/dN related with stress intensity factor range ΔK was influenced by stress ratio in stable of fatigue crack growth (Region II) with an increase in ΔK. The resistance of fatigue crack growth at low temperature is higher compared with that at room temperature, which is attributed to the extent of plasticity-induced by compressive residual stress according to the cyclic loads. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and low temperatures are mainly explained by the crack closure and the strengthening due to the plasticity induced and roughness induced.