Experimental and numerical studies on erosion damage in damping holes on the valve plate of an axial piston pump

Shaogan Ye,Junhui Zhang,Bing Xu,Wei Song,Long Chen,Haiyong Shi,Shiqiang Zhu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.9

Erosion damage affects the reliability and durability of axial piston pumps. An axial piston pump was tested using endurance life testing method. The phenomenon of erosion damage on the valve plate was observed using a confocal laser scanning microscope, by comparing the surface on the valve plate before and after the endurance life testing. A CFD turbulence model inclusive of the cavitation effects was developed to predict the flow physics. The flow physics in the axial piston pump were presented and analyzed, including the fluid velocities, velocity fields, the total volume fraction fields of gas and vapor, and pressure fields. Two causes of erosion damage were found, the appearances of large amount of vapor, and directly hitting by the jetting flow. The first one is the cause of erosion damage on the surface near the transition region from the inlet port to the outlet port, and the second one is the cause of erosion damage on the surface near the transition region from the outlet port to the inlet port. Besides, the findings show that the fluid velocities closely relate to the area of erosion damage. The study provides insights into the occurrence of erosion damage in axial piston pumps.

Analysis of micro and nano particle erosion by analytical, numerical and experimental methods: A review

Suhas M. Shinde,Dayanand M. Kawadekar,Pradeep A. Patil,Virendra K. Bhojwani 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5

Erosion is one of the vital factors to consider for damage of solid-liquid, solid-gas multiphase flow system. The presence of solid particles in the fluid domain initiates the erosion. This paper focuses on the erosion analysis methods. Different erosion models for analytical and numerical investigation are discussed along with experimental test processes for erosion. Further, possible techniques used for analyzing the eroded surfaces are discussed. This study will be helpful for researchers working on erosion phenomena which can find erosion by analytical, numerical as well as experimental ways. Erosion prediction before implementation will save the system performance degradation. Lastly, consideration of the factors like temperature, impact angle variation during the flow and complex geometry is recommended for future study.

배관 침부식 손상 연속모사 장비 개발 및 실증

( Won Chang Nam ),( Kyung Ha Ryu ),( Jae Hyoung Kim ) 한국부식방식학회(구 한국부식학회) 2013 Corrosion Science and Technology Vol.12 No.4

Pipe wall thinning caused by erosion and corrosion can adversely affect the operation of aged nuclear power plants. Some injured workers owing to pipe rupture has been reported and power reduction caused by unexpected pipe damage has been occurred consistently. Therefore, it is important to develop erosion-corrosion damage prediction model and investigate its mechanisms. Especially, liquid droplet impingement erosion(LDIE) is regarded as the main issue of pipe wall thinning management. To investigate LDIE mechanism with corrosion environment, we developed erosion-corrosion damage simulation apparatus and its capability has been verified through the preliminary damage experiment of 6061-Al alloy. The apparatus design has been based on ASTM standard test method, G73-10, that use high-speed rotator and enable to simulate water hammering and droplet impingement. The preliminary test results showed mass loss of 3.2% in conditions of peripheral speed of 110m/s, droplet size of 1mm-diameter, and accumulated time of 3 hours. In this study, the apparatus design revealed feasibility of LDIE damage simulation and provided possibility of accelerated erosion-corrosion damage test by controlling water chemistry.

Al 6061-T6 합금의 해수 내 캐비테이션 진폭에 따른 캐비테이션-침식 조건하에서 전기화학적 특성

황현규 ( Hyun-kyu Hwang ),김성종 ( Seong-jong Kim ) 한국부식방식학회(구 한국부식학회) 2020 Corrosion Science and Technology Vol.19 No.6

Generally, Al alloys of 5000 and 6000 series show excellent weldability, workability, and specific strength, and are widely used in ship building. A combined experiment via cavitation erosion and corrosion damage involving 6061-T6 Al alloy was performed using potentiodynamic polarization under cavitation erosion (hybrid experiments) with amplitude (cavitation strength). The corrosion current density was approximately 52-fold higher at 30 μm than under static conditions, suggesting that the amplitude greatly affected the damage. The degree of damage increased with increasing cavitation amplitude. After the hybrid experiment, the corrosion rate was compared according to the weight loss and damage depth, and the relationship between the two values was expressed as alpha value. The alpha (α) values at amplitudes of 5 μm, 10 μm and 30 μm were 5.11, 12.81 and 8.74, respectively, suggesting that the α value at 10 μm was greater than at 5 μm, and indicating local corrosion damage. However, the α value at 30 μm was smaller than that of 10 μm, which is attributed to higher damage via uniform corrosion than damage induced by local corrosion.

표토침식에 따른 내륙습지 훼손 가능성 평가

김성원,정안철,이대업,이기하 한국수자원학회 2020 한국수자원학회논문집 Vol.53 No.7

The purpose of this study is to suggest a quantitative assessment of wetland damage considering the effects of topsoil erosion and deposition from rainfall. In the Cheoncheon Basin located upstream of the Yongdam Dam, 16 wetlands are located, but the lacustrine and small palustrine wetland were analyzed for possible damage to erosion and deposition. As a result of applying typhoon events in 2002 and 2003, the sediment load from the upper basin was the highest at 2.30% (22,548 m3) of low water capacity. The average sediment load in the mountain areas was found to be 0.03% of the low water capacity, and it was analyzed to be less damaging than the lacustrine with relatively large watershed. as a result of the model, the lacustrine wetland, where a large area is used as agricultural land, shows a high probability of sediment yield, so it is highly likely to damage the wetland by topsoil erosion. 본 연구는 강우로부터 나타나는 표토침식과 퇴적의 영향을 고려하여 습지 훼손에 대한 정량적인 평가가 가능한 방안을 제시하고자 하였다. 용담댐 상류에 위치하고 있는 천천유역은 16개의 습지가 존재하며, 습지훼손 가능성에 대한 평가는 호수형습지와 소택지를 대상으로 이뤄졌다. 2002년, 2003년에 발생한 태풍사상을 적용한 결과, 벽남제습지의 경우 상류유역에서 유입되는 토사량은 저수용량의 2.30%(22,548 m3)로 가장 높았다. 산지영역에 위치하고 있는 소택지의 평균 유입토사량은 저수용량의 0.03%로 나타났으며 비교적 넓은 유역을 가지는 호수형습지보다 훼손가능성이 낮은 것으로 분석되었다. 넓은 면적이 농경지로 사용되고 있는 호수형습지는 모형의 결과에서 토사유입량이 높은 것으로 나타나 토양침식에 의한 습지훼손 가능성이 높을 것으로 판단된다.

Experimental studies of damage to aircraft skin under the influence of raindrops

Minggong Sha,Ying Sun,Li Yulong,Vladimir I. Goncharenko,Vladimir S. Oleshko,Anatoly V. Ryapukhin,Victor M. Yurov Techno-Press 2023 Advances in aircraft and spacecraft science Vol.10 No.6

Airplanes in flight collide with raindrops, and the leading edges of the airframe can be damaged when colliding with raindrops. A single waterjet testing platform was created to study rain erosion damage. Carbon fiber samples with three types of skins were studied and the mechanical properties were measured using a nanoindentation instrument. The research results show that the impact force on the sample increases with the continuous increase in the impact speed of raindrops, which leads to an increase in the damage area. Sheathing with low surface roughness is more damaged than other sheathings due to its rougher surface, and the result proves that surface roughness has a more significant effect on rain erosion damage to sheathings compared to their hardness.

Study on the Cavitation Damage of Cupronickel(70/30) Tube for Gas Absorption Refrigeration Machine

Lim, Uh-Joh,Jeong, Ki-Cheol,Yun, Byoung-Du The Korean Society of Marine Engineering 2004 한국마린엔지니어링학회지 Vol.28 No.2

The use of gas absorption refrigeration machine has considerably increased because of the shortage of the electric power in the summer and the regulation of freon refrigerant. Gas absorption refrigeration machine consists of a condenser, a heat exchanger. supplying pipes, a radiator etc, This system is likely to be corroded by acid. dissolved oxygen and gases, Cavitation erosion-corrosion by flow velocity of cooling water may happen in absorption refrigeration machine. In these cases. erosion and corrosion occur simultaneously. Then, it makes a serious damage with synergy effect. Therefore, this paper was studied on the cavitation damage of cupronickel(70/30) tube for gas absorption refrigeration machine, In the $30^{\circ}C$ tap water, linear polarization test and anodic polarization test were carried out for copper(C1220T-OL) and cupronickel(70/30) tube. Also, cavitation erosion-corrosion behavior of cupronickel (70/30) tube was considered, The main results are as following: (1) In the linear test, the corrosion current density of cupronickel(70/30) is higher than that of copper. (2) The erosion-corrosion rate of cupronickel(70/30) displayed later tendency than that of copper by vibratory cavitation in cooling water. (3) In cooling water, the progress mechanism of erosion-corrosion rate of copper and cupronickel(70/30) follows a pattern of incubation, acceleration, attenuation and a steady state period.

미국 특허법상 시장점유율에 기한 손해배상액 산정 -경제적 분석을 중심으로-

배대헌 ( Bae Dae Heon ) 한국상사판례학회 2003 상사판례연구 Vol.15 No.-

In considering whether to award lost profits, cases have turned attention to whether there are acceptable non-infringing substitutes for the patentee`s product. Without significant non-infringing substitutes, courts infer that the infringer divert sales from the patentee and award lost profits for that sales. It is a general test based on `but-for rule` causation in Panduit case. From an economic perspective, however, when there would be acceptable non-infringing substitutes in relevant market, the but-for rule should be clarified for calculating the lost profits damages in reality. It is `market share rule` that initiated with State Industries case in 1980s for calculating lost profits in patent infringement. This decision relied on the portion of the patentee`s relevant market that has been captured by the infringer. Before the market share rule is applied to the calculation of lost profits, the market has to include the non-infringing substitutes besides the patent infringer(s). Based on the market share rule derived from the sales proportion among the patentee and the non-infringer in the relevant market, it has increased awareness of the need for an economically consistent calculation of lost profits. Also, the method with the `price erosion` on the economic framework is to accept for calculating damages from patent infringement cases. A sufficient analysis of lost profits, which would include the market share rule and the methodology of price erosion damages, should be to compensate the patentee for economic loss caused by competing, infringing sales.

해수 유속 변화에 따른 Al5052-O와 Al6061-T6 알루미늄 합금의 침식부식 특성

김성종,김영복 한국부식방식학회 2019 Corrosion Science and Technology Vol.18 No.6

The hull material of a high-speed ship may cause erosion damage from fluid impact. When physical erosion and electrochemical corrosion combine, erosion corrosion damage occurs. The aluminum ship is vulnerable to erosion corrosion because it can be operated at high speed. Thus, in this study, Al5052-O and Al6061-T6 aluminum alloys for the marine environment were selected as experimental materials. The erosion corrosion resistance of Al5052-O and Al6061-T6 aluminum alloys in seawater was investigated by an erosion test and potentiodynamic polarization test at the various flow rate (0 m/s, 5 m/s, 10 m/s, 15 m/s, 20 m/s). Erosion corrosion characteristics were evaluated by surface analysis, 3D analysis, SEM analysis, and the Tafel extrapolation method. The results of surface damage analysis after the erosion test showed that Al6061-T6 presented better erosion resistance than Al5052-O. The results of the potentiodynamic polarization test at the various flow rate, corrosion current density by Tafel extrapolation presented lower values of Al6061-T6 than Al5052-O. Al5052-O showed more surface damage than Al6061-T6 at all flow rates. Consequently, Al6061-T6 presented better erosion corrosion resistance than Al5052-O. The results of this study are valuable data for selecting hull material for an aluminum alloy vessel.

Impact Damage on Brittle Materials with Small Spheres (I)

Woo, Su-Chang,Kim, Moon-Saeng,Shin, Hyung-Seop,Lee, Hyeon-Chul Korean Society for Precision Engineering 2003 International Journal of the Korean Society of Pre Vol.4 No.1

Brittle materials such as glasses and ceramics, which are very weak under impact loading, show fragile failure mode due to their low fracture toughness and crack sensitivity. When brittle materials are subjected to impact by small spheres, high contact pressure occurs at the impacted surface causing local damage on the specimen. This damage is a dangerous factor in causing the final fracture of structures. In this research, the crack propagation process of soda-lime glass by the impact of small spheres is explained and the effects of several constraint conditions for impact damage were studied by using soda-lime glass; that is, the effects for the materials and sizes of impact ball, thickness of specimen and residual strength were evaluated. Especially, this research has focused on the damage behavior of ring cracks, cone cracks and several other kinds of cracks.