• Journal of Welding and Joining
• /
• 제5권2호
• /
• pp.27-34
• /
• 1987

The characteristics of arc sprayed layer were studied with hardness test and microstructural observation. The erosion resistance of arc sprayed layer was also evaluated using a method of steel ball blasting test which was proposed in this study as a test method for measuring the erosion properties in the impact wear condition. By an impact of the molten droplets on the redeposited substrate, lamella structure was formed which contains laminated oxide layers, fissures, and porosities. As a result of mechanical tests, it was shown that the sprayed specimen showed higher hardness than the substrate, but it resulted in higher erosion rate than the substrate. The poor erosion property obtained with a sprayed coating was considered to be attributable to easy flaking off the the layers laminated with brittle oxide layers.

• 한국전산유체공학회지
• /
• 제18권3호
• /
• pp.94-101
• /
• 2013

In the present study, a practical method to predict cavitation erosion, which caused a critical damage on hydraulic machineries, was developed. Impact and critical velocities were defined to develop a practical method for the prediction of cavitation erosion. To develope the practical method, the computational fluid dynamics (CFD) was introduced. Cavitating flows with erosion in a converging-diverging nozzle and around a hydrofoil were simulated by developed and validated code. Based on the CFD results, the cavitation erosion coefficient was derived by a curve fitting method. The cavitation erosion coefficient was formulated as the function of the cavitation and Reynolds numbers. A cavitating flow in an axisymmetric nozzle followed by radial divergence was simulated to validate the developed practical method. For the application to a propeller, a cavitating flow around a propeller was simulated. Predicted damage extent showed similar with damaged full-scale propeller blade.

• Journal of Mechanical Science and Technology
• /
• 제17권1호
• /
• pp.114-121
• /
• 2003

Water droplet erosion is one of major concerns in the design of modern large fossil steam turbines because it causes serious operational problems such as performance degradation and reduction of service life. A new erosion model has been developed in the present study for the prediction of water droplet erosion of rotor blades operated in wet steam conditions. The major four erosion parameter : impact velocity, impacting droplet flow rate, droplet size and hardness of target are involved in the model so that it can also be used for engineering purpose at the design stage of rotor blades. Comparison of the predicted erosion rate with the measured data obtained from the practical steam turbine operated for more than 90,000 hours shows good agreement.

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

• Journal of Forest and Environmental Science
• /
• 제26권3호
• /
• pp.181-192
• /
• 2010

Water erosion is progressing in the Loess Plateau, especially in gullies, and the sediment runoff to the Yellow River amounts to 975 million tons every year. Natural factors for water erosion include climate, soil, geological feature, terrain and vegetation. Many development projects due to the increasing population reduced the forest coverage ratio to 10%, and 200 million people in the downstream area are suffering from the damage during intense rainfall. Accordingly, the Chinese government is continuously trying to efficiently prevent the erosion by establishing measures for water erosion, including fish-scale pits, terrace technique, and check dams.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2021년도 학술발표회
• /
• pp.316-316
• /
• 2021

Erosion in a watershed is one of the main sources of sediment inflow in dams. While sediment management practices can be performed to reduce and manage sedimentation in reservoirs, managing the sediment inflow before it reaches the reservoir should also be consider. The accurate location of areas with high erosion and deposition rates should be determined in order to propose an appropriate sediment management procedure such as the construction of check dams. In this study, the projected rainfall from HadGEMRA-3 for RCP 8.5, was used in C-SEM, a distributed rainfall-erosion model, to determine the projected spatial erosion patterns in Cheoncheon catchment, which is located in the upstream part of Yongdam Dam.

• 한국표면공학회지
• /
• 제23권2호
• /
• pp.11-17
• /
• 1990

The erosion characteristice of plasma-sprayed tungsten carbide chromium carbide coatings were investigated. Erosion tests were perfomed at room temperature by using Al2O3 and SiC particles accleerated in air stream. Weight losses of the coatings were measured over a range of paricle velocities and impingement angle. It was found that, for both of this coatings, the maximum erosion occurrd at a normal angle of impact, and the erosion rate at this impact angle was a power function of pparticle velocity. The values of the velocty emponent were between 3.07 and 3.50 Erosion value of chromium carbide coating was higher than that of tungsten carbide coating.

• 한국해안해양공학회지
• /
• 제14권4호
• /
• pp.247-256
• /
• 2002

동해안에 위치한 대부분의 중소어항은 주로 백사장 주위에 건설되어져 있으며, 이러한 어항 구조물은 인근 백사장의 침식에 중요한 영향을 끼쳐왔다. 이와 같은 문제를 해결하기 위해서는 우선, 사전예측 및 해안침식현상의 정확한 재현을 통해 그 원인을 파악하고검증할 필요가 있다. 아울러 대상해안에 적합한 침식 대책공법을 강구하여야 한다. 본 연구에서는 경제적인 측면을 고려하여 중소어항 주변해안에 실질적으로 적용할 수 있는 해안침식 대책을 도출하고, 그에 대한 방지효과를 수치시뮬레이션을 통해 검토하였다

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
• /
• pp.739-744
• /
• 2002

Recently we have discovered that sediments should be separated from lithosphere, and soil should be separated from biosphere, both sediment and soil will be mixed sediments-soil-sphere (Seso-sphere), which is using particulate mechanics to be solved. Erosion and sediment both are moving by particulate matter with water or wind. But ancient sediments will be erosion same to soil. Nowadays, real soil has already reduced much more. Many places have only remained sediments that have ploughed artificial farming layer. Thus it means sediments-soil-sphere. This paper discusses sediments-soil-sphere erosion modeling. In fact sediments-soil-sphere erosion is including water erosion, wind erosion, melt-water erosion, gravitational water erosion, and mixed erosion. We have established geographical remote sensing information modeling (RSIM) for different erosion that was using remote sensing digital images with geographical ground truth water stations and meteorological observatories data by remote sensing digital images processing and geographical information system (GIS). All of those RSIM will be a geographical multidimensional gray non-linear equation using mathematics equation (non-dimension analysis) and mathematics statistics. The mixed erosion equation is more complex that is a geographical polynomial gray non-linear equation that must use time-space fuzzy condition equations to be solved. RSIM is digital image modeling that has separated physical factors and geographical parameters. There are a lot of geographical analogous criterions that are non-dimensional factor groups. The geographical RSIM could be automatic to change them analogous criterions to be fixed difference scale maps. For example, if smaller scale maps (1:1000 000) that then will be one or two analogous criterions and if larger scale map (1:10 000) that then will be four or five analogous criterions. And the geographical parameters that are including coefficient and indexes will change too with images. The geographical RSIM has higher precision more than mathematics modeling even mathematical equation or mathematical statistics modeling.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 1998년도 제28회 추계학술대회
• /
• pp.67-74
• /
• 1998

Two kinds of polished and unpolished freestanding films prepared by DC plasma CVD method were impacted by SiC particles to understand erosion mechanism. Erosion damage caused by solid impact was characterized by surface profilometer, scanning electron microscopy and Raman spectroscopy. Gradually decrease of surface roughness and sharp reduction of crystallinity for unpolished CVD films were observed with increasing erosion time. It was found that smaller grains of the diamond were removed in early stage of erosion process and larger grains were eroded with further impingement. By introduction of re-growth method on polished diamond, further understanding of erosion mechanism was achieved. Most of the surface fractures were initiated at the grain boundary.