• International Journal of Naval Architecture and Ocean Engineering
• /
• 제10권3호
• /
• pp.361-366
• /
• 2018

Ice crushing occurs in many situations that involve a sliding frictional component such as sports involving ice-contact, ice interaction with ship hulls, and ice-on-ice sliding/crushing within glaciers and between interacting sea ice floes. Ice crushing-friction tests were conducted in the lab at $-10^{\circ}C$ using a set of acrylic ice-crushing platens that included a flat smooth surface and a variety of high-roughness surfaces with regular arrays of small prominences. The experiments were part of Phase II tests of the Blade Runners technology for reducing ice-induced vibration. Ice was crushed against the platens where the ice movement had both a vertical and a horizontal component. High-speed imaging through the platens was used to observe the ice contact zone as it evolved during the tests. Vertical crushing rates were in the range 10-30 mm/s and the horizontal sliding rates were in the range 4.14-30 mm/s. Three types of freshwater ice were used. Friction coefficients were extraordinarily low and were proportional to the ratio of the tangential sliding rate and the normal crushing rate. For the rough surfaces all of the friction coefficient variation was determined by the fluid dynamics of a slurry that flowed through channels that developed between leeward-facing facets of the prominences and the moving ice. The slurry originated from a highly-lubricating self-generating squeeze film of ice particles and melt located between the encroaching intact ice and the surfaces.

• 대한조선학회지
• /
• 제27권1호
• /
• pp.17-23
• /
• 1990

세장비가 작은 구조부재는 충돌과 같은 상황하에서 압축을 받는 경우, 축방향으로 접혀지는 소성 변형에 의해서 충돌에너지의 대부분을 흡수한다. 이 경우, 관성을 무시한다 하더라도 연강 부재의 정적인 하중에 대한 압괴강도에 비해서 변형률에 의한 영향으로 인해 동적 압괴 강도가 높아진다는 것은 잘 알려진 사실이다. 본 논문에서는 부재의 정적 하중에 대한 압괴강도 추정법을 소성변형의 운동학적 방법을 이용하여 수행하였다. 종래의 항복하중에 변형률을 고려한 동적 압괴 하중 추정치가 동적 영향을 과대평가하게 되므로 평균 소성변형 응력의 변형률에 대한 영향을 고려하여 튜브부재의 동적 압괴 강도 추정을 유도하였고, 이를 발표된 실험결과와 비교 검토하였다. 본 연구에서 얻은 만족스러운 결과를 토대로 하여 앞으로 이 방법을 선박의 충돌시 선수구조의 충돌에너지 흡수의 추정에 적용시킬 것이다.

• 한국지반공학회논문집
• /
• 제29권11호
• /
• pp.61-72
• /
• 2013

Sabkha층 탄산질 모래의 입자파쇄발생시 이차압축특성을 파악하기 위하여 압밀시험을 수행하여 입자파쇄응력을 파악하였다. 입자파쇄 항복응력에서 순간적으로 발생한 입자파쇄 압축침하를 해석하기 위하여 이차압축률 대신 이차 파쇄압축률 $C_{{\alpha}{\epsilon}}{^*}$를 도입하였다. 입자파쇄 발생시의 간극비 $e_p{^*}$와 침하량 $H_p{^*}$가 이차압축거동의 기준점으로 사용되었다. 일차압축지수와 이차파쇄압축률을 비교한 결과 현장 Sabkha층의 경우 $C_{{\alpha}{\epsilon}}{^*}/C_c$ 값이 0.0105~0.0187로 나타났으며 일반적인 석영질 사질토에 비해 입자파쇄 발생으로 인한 이차압축거동이 매우 크게 나타났다. 동일한 재하응력에서는 Sabkha층의 심도가 깊을수록 입자파쇄침하량과 이차파쇄압축률이 증가함을 확인할 수 있었다.

• 산업기술연구
• /
• 제24권B호
• /
• pp.89-94
• /
• 2004

This Study is results of experimental works to investigate the characteristics of vibro-compaction of crushed stones having coarse grain sizes. For testing material, crushed stone, sieved within very narrow ranges of grain size distribution, was used. Cyclic loading apparatus was used to apply cyclic loading to the specimen prepared in the mold. Tests were performed by changing the ratio of the maximum to the minimum stress, frequency and the magnitude of the maximum and the minimum stresses. Settlement of specimen due to cyclic loading was measured to analyze the compaction efficiency and sieve analysis test after cyclic loading test was also carried out to find the crushing rate of the specimen. As results of cyclic loading test, normalized settlement in terms of specimen height tends to be converged around loading cycle number of 1500. The magnitude of normalized settlement is in the range of 3.11 ~ 8.57%. The crushing rate is in the range of 4.46 ~ 8.78%. Normalize settlement and the crushing rate tend to increase with decreasing the ratio of the maximum to the minimum stresses and they tend to increase with increasing the frequency and the magnitude of the maximum and the minimum stresses for the given ratio. In conclusions, compaction rate of crushed stone is controlled by the dynamic stress (difference between the maximum and the minimum stresses) and the crushing rate is dominated by applied energy to the specimen.

• Ocean and Polar Research
• /
• 제36권4호
• /
• pp.455-463
• /
• 2014

This paper presents data from performance tests carried out to assess a manganese nodule crusher. Manganese nodules should be crushed into smaller pieces in order to assure the slurry flow of the lifting system. Both artificial nodules and real manganese nodules are used to evaluate nodule breaking ability of the crusher. The crushing performance of the crusher depends on the flow rate and pressure of the power transmission device. The size of the crushed manganese nodules also depends on the shape of the crushing drum. In this paper, several comparative tests are carried out to evaluate and improve the crushing performance and find the optimal design point of the crusher.

• 한국철도학회논문집
• /
• 제11권4호
• /
• pp.384-389
• /
• 2008

궤도구성품 중 도상은 레일과 침목으로 전달되는 열차하중을 노반으로 전달하는 중간매개체 역할을 하며, 도상자갈의 열화는 궤도틀림 진전에 직접적으로 영향을 미친다. 본 연구에서는 대형 보선장비(멀티플 타이 탬퍼; MTT; Multiple Tie Tamper)를 사용한 도상다짐작업과 누적통과톤수가 자갈 세립화 및 도상열화의 주요 원인이다. 도상자갈의 열화특성을 파악하기 위하여 시험용 궤도 부설을 통한 현장실험(2장. 실외 실측시험)과 실제의 운행 환경을 모사한 모형실험(3장. 실내 모형실험)을 실시하였고 실제 운용중인 고속선에서 채취한 시료의 파쇄입자 비율과 비교분석하였다.

• 한국자동차공학회논문집
• /
• 제1권3호
• /
• pp.118-126
• /
• 1993

Static and dynamic crushing behaviors of composite box tube show the difference with those of metal tube. This paper investigates the characteristics of static and dynamic crushing test which were conducted to characterize the energy absorption and collapse mode of composite box tubes. Sixteen kinds of tube specimens were fabricated from[0/90] woven Glass/Epoxy fabric and autoclave cured. Axial crushing tests were performed using Instron and Dynatup Impact Tester. It is shown that collapse mode and energy absorption capacity can vary according to the aspect ratio, length, loading rate, lay-up direction of fabric, and trigger geometry of the composite box tube.

• Journal of Biosystems Engineering
• /
• 제20권4호
• /
• pp.323-332
• /
• 1995

The horizontal compression test of some selected corrugated fiberboards was performed to determine the cushioning properties of them. Creep behavior of the corrugated fiberboard boxes, which have been widely used in rural area for packaging fruits and vegetables, was tested. The flute crushing stress of the corrugated fiberboard depended upon mainly the basic weight of the corrugated medium, comparing with the combined basic weight of corrugated fiberboard. When moisture content of the corrugated fiberboards was increased about 8% (d.b.), the flute crushing stress of them was decreased at the rate of 44%~64%. The cushion factor of the sample fiberboards showed much higher value at the lower moisture content of them. These trends appeared to be more obvious at the lower applied stress levels. Also, the cushion factors of the double wall corrugated fiberboards(DW) were observed to be little higher than those of the single wall corrugated fiberboards(SW). The creep behavior of the sample boxes was found to be highly moisture and static load dependent. The creep behavior of the corrugated fiberboard boxes could be well analyzed by the asymptotic slope derived from the creep model.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2004년도 학술.기술논문발표회
• /
• pp.15-20
• /
• 2004

To the development on reusing method of the heat-source waste at Daegu Bisan dyeing-complex, this study is aimed to application of it's crushing material (hereafter waste sand) as concrete fine aggregate. The results are as follows; 1. Flow and unit weight of mortar using waste sand as concrete fine aggregate are decreased. 2. At the results of compressive strength test and bending strength test, mortar using waste sand superior to plain mortar within 80％ substitute ratio of waste sand. Because increasing rate of compressive strength is similar through increasing age, waste sand performs as filler's function of no-effect with cement only. 3. At the results of concrete application test, unit weight of concrete using waste sand is similar to plain concrete and compressive strength of concrete is superior to plain likewise the results of mortar test

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
• /
• pp.727-729
• /
• 2001

The air separation of PET (Polyethylene terephthalate) and PS(Polystyrene) was carried out by taking advantage of the different abrasive resistance of two plastics. PET bottles and PS packages were shredded to small square pieces $(5{\times}5mm)$. Both plastic shreds were treated by a shear-type crusher. The PET shreds were bent and twisted by the crush so that they were blown up easily, but the PS shreds were not. After the crush of mixture of both plastics, air separation experiments were carried out using four types of air separators. The number and location of the baffle attached to them are different. With the separator with a baffle attached at the upper part, PET recoveries for the crushing time of 30, 60 and 90sec were 67, 98 and 99% respectably at the air flow rate of 3.5m/s, whereas PS recoveries were null regardless of the crushing time.