• Journal of Advanced Marine Engineering and Technology
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• 제26권3호
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• pp.328-336
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• 2002

decrease in efficiency due to cavity fluid fluctuation. The purpose of this study is to examine erosion aspect on the SS400 specimen by cavitation and the effect of impact pressure generated from the demolition of the cavity of ultrasonic vibrator horn in the marine sludge oil environment. The erosion damage of specimen was investigated mainly on weight loss, weight loss rate and maximum erosion rate with variation of the vibration amplitude of $50{\mu}m, 24{\mu}m$ as well as the change of space between transducer horn and specimen. The experimental results showed that as the space between ultrasonic vibrator horn and specimen disk increased, the weight loss and weight loss rate decreased and the values were larger in SFO than in SLO. These findings would help interpret the aspect of cavitation erosion damage in metallic materials of different operating environment and material characteristics.

• 수산해양기술연구
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• 제35권2호
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• pp.196-200
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• 1999

In the case that erosion and corrosion occurs in machinery and structure at the same time, the synergy effect by erosion-corrosion affects fatal effect to durability of machinery and structure. Therefore, in machinery and structure which use corrosion liquid, the study of the synergy effect of erosion-corrosion which affects metal material is requested. In this paper. the flow corrosion experiment about the effect of temperature change and liquid velocity change in sea water was carried out to study the characteristics of erosion-corrosion for tube material Cu heat exchanger The main results obtained are as follows. (1) Damage appearance of tube outside by erosion-corrosion becomes dull because electrode potentials of Cu tube is higher than electrode potential of STPG38 shell. (2) In the cooling system by sea water, the weight loss rate of Cu at tube outside liquid temperature of $70^{\circ}C$ is higher than that of temperature of $20^{\circ}C$. (3) In cooling system by sea water, the weight loss rate of Cu at liquid velocity of 5.1m/s is higher than that of velocity of 1.47m/s. But as the testing time passed, the weight loss rate of Cu at velocity of 5.1m/s is almost steady and becomes dull at velocity of 1.47m/s.

• Corrosion Science and Technology
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• 제13권4호
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• pp.130-138
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• 2014

Wall thinning can be classified into three types: flow-accelerated corrosion, cavitation erosion and solid particle erosion. This article presents a study of solid particle erosion, which frequently causes damages to power plants' pipe system. Unlike previous studies, this study uses a mechanism to make solid particles in a fluid flow collide with pipe materials in underwater condition. Experiment is conducted in three cases of velocity according to solid-water ratio using the three types of the materials of A106B, SS400, and A6061. The experiments were performed for 30 days, and the surface morphology and hardness of the materials were examined for every 7 days. Based on the velocity change of the solid particles in a fluid flow, the surface changes, the change in the amount of erosion, the erosion rate and the variation in the hardness of carbon steel and aluminum family pipe materials can all be determined. In addition, factor-based erosion rates are verified and a wall-thinning relation function is suggested for the pipe materials.

• 수산해양기술연구
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• 제28권2호
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• pp.171-183
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• 1992

In this paper, the behaviour of cavitation erosion, influence of corrosion and corrosion control on slide bearing metals for internal combustion engine were investigated, and this experiment was done by the vibratory cavitation erosion tester. The main results obtained are as follows: 1. With decreasing the space between horn and specimen, the weight loss and its rate increased step by step. But the weight loss and its rate of 0.2mm space decreased conversely more than that of 0.4mm space at early stage. 2. The weight loss and its rate with change of pH were appeared to the order of pH2>pH12>pH7>pH4. And the weight loss and its rate at pH 4 decreased at best. 3. The weight loss and its rate by cavitation erosion for bearing metals were shown to the order of W.M7>W.M1>K.M4. 4. There appeared mainly small pit hole at pH2, and appeared the pit of netting thread type at pH12 by the results of the damaged surfaces at pH2 and pH12 environments that were sensitive to cavitation erosion. 5. With increasing the viscosity of lubricating oil, the weight loss rate by cavitation erosion became dull at the space below 0.5mm. 6. The protective efficiency of cavitation erosion-corrosion is superior inhibitor of chormate(25 ppm) to cathodic protection.

• 해양환경안전학회지
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• 제7권3호
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• pp.75-84
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• 2001

Ultrasonic vibrator is an equipment which atomizes and homogenizes the oils by breaking the oil particles with ultrasonic vibration cavity, and possibly improves the properties. There are various parameters on the effect of ultrasonic irradiation. Especially, this study intended to investigate the matrix structure of sludge oils and the erosion damages for horn disc SS41 according to the variation of the oil temperature and the immersing depth of horn disc. Sludge oils were irradiated with ultrasonic vibration and then observed the aspects of the change of oil particles. From these, the recycling feasibility of sludge oil for useable oil to be burnt was determined. The erosion damages for horn disc SS41 were examined with weight loss, weight loss rate and the irradiation time to max. erosion rate. These data will be useful to the development of ultrasonic breaking systems to recycle sludge oil and to consider a countermeasure for the prevention of erosion damages.

• Tribology and Lubricants
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• 제22권4호
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• pp.218-224
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• 2006

The sludge oils were produced necessarily in the ships operation, so that it will be the best way to manage the sludge oils inside ship itself from a viewpoint of the prevention of marine oil pollution. The ultra-sonic breaking system which recycle the sludge oil from ship into usable oil to be brunt is recognized as a most possible recycling device. In this regards, the purpose of this study is to examine erosion damage,on the SS400 specimen by cavitation and the effect of impact pressure generated from the demolition of the cavity of ultrasonic vibration in the marine sludge oil environment.. The erosion damage of specimen was investigated mainly on weight loss, weight loss rate and maximum erosion rate with variation of the oil temperature as well as the change of space between transducer hem and specimen. The experimental results showed that as the space between ultrasonic vibrator horn and specimen disk increased, the weight loss and weight loss rate decreased and the values were larger in SFO than in SLO. The experimental results can be useful to the development of sludge oil disposing systems and to consider a countermeasure for the prevention of erosion damages by cavitation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.403-408
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• 2003

The erosion behavior of :artificially aged HK40 steel was investigated. Erosion tests were conducted at room temperature, $200^{\circ}C$ and $400^{\circ}C$ using $Al_2O_3$ particles. Erosion rates increased with increment of temperature. The maximum erosion rate increased with the impingement angle of 30 degree. The erosion rate increased, reached the maximum at 1000 hours, and after that, decreased with heat treatment time. The mechanism of erosion seems to be the cutting wear which is very much associated with the strength of material. As results, the erosion rates were rather affected by the tensile strength and the strain hardening coefficient than the hardness and the yield strength. Such changes of material properties would be caused by the change of micro-structure due to the precipitation of carbide and the dissolution of solid element within matrix during the heat treatment.

• 한국해양공학회지
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• 제31권1호
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• pp.60-68
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• 2017

In this study, we analyzed the real time video image obtained from the video monitoring system to grasp the shoreline, beach width, and area change of Haeundae beach. The video monitoring techniques enabled continuous monitoring for a long period at a much lower cost than general survey methods. It was possible to grasp quantitative beach variation characteristics of Haeundae beach through image acquisition, rectification, and image processing of video images. According to the monitoring results, the erosion rate of Haeundae beach in spring and summer was -19.8% in 2014 and -6.7% in 2015. The erosion rate in 2016 was -6.4%, which showed that the erosion rate in spring and summer continued to decrease. In particular, the influence of the erosion at the time of typhoon CHABA was revealed to be smaller than in the past. It can be concluded that these variations were due to beach width expansion by beach nourishment and the installation of submerged breakwaters.

• 한국제4기학회지
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• 제20권2호
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• pp.1-10
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• 2006

자연환경과 인위적 환경변화에 의한 홍수재해는 하상변동과 밀접한 관계를 갖는다. 본 연구는 금강유역을 대상으로 지리정보시스템(GIS)과 원격탐사(RS)를 이용하여 유역에서의 토양침식과 하상변동의 관계를 규명하고자 하였다. 지리정보시스템에서 범용토양유실공식 (USLE)을 이용하여 토양침식율을 계산하였다. 공주에서 이포까지 하상지형을 측량하였고, 3차원의 하상변화도를 작성하였다. 1982년에서 2000년까지 Landsat TM 영상을 이용하여 금강유역의 하상변동을 추적하였다. 연구결과, 강경일대의 토양침식율은 $1.8\;kg/m^2/$년이며, 하상증가율은 $+5\;cm/m^2/$년으로 산정되었다. 따라서 금강하류의 하상변화는 일정한 비율로 토양침식에 의하여 영향을 받는 것으로 해석된다. 또한 하상변동은 주로 금강의 지류와 본류의 접합부 하류일대에서 발생하였다. 금강하류에서 하상변동은 하성 세골재 채취가 하나의 원인으로 해석될 수 있으며, 골재채취로 인하여 1991년도에서 1995년도 사이 금강하상 위에 노출된 하상면적의 감소를 초래했던 것으로 추정된다. 한편, 금강유역 하상을 따라 교량건설, 경작지 조성을 위한 사주개간, 제방과 같은 수중 구조물들 설치는 퇴적물 집적과 퇴적하상의 노출면적 증가를 초래하였던 것으로 추정된다.

• Tribology and Lubricants
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• 제9권1호
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• pp.55-61
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• 1993

Recently, due to the erosion damage that were generated increasingly at alloy metals of slide bearing by cavity of lubricating oil with tendency of high speed and high output of reciprocating engine, there is a need to study the process on the formation of cavitation erosion, and the characteristic of cavitation erosion at lubricating oil environments under various condition for marine ship. Therefore, the apparatus of cavitation erosion experiment used 20 KHz, $24 \mu m$ piezoelectric vibrator. The main results obtained through this test method are as follows: 1. The max. erosion rate at lubricating oil environments was related to the change of space, oil film thickness, and shown to tendency of gear oil>system oil>turbine oil>mixed oil environments with different viscosity. 2. The pitted hole by cavitation erosion at high viscosity oil environments became small and deep, and in addition to, they appeared to be wide and shallow at low viscosity.