• Title/Summary/Keyword: Waterjet

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Transition Mechanism from Brittle Fracture to Ductile Shear when Machining Brittle Materials with an Abrasive Waterjet

  • Huang, Chuanzhen;Zhu, Hongtao;Lu, Xinyu;Li, Quanlai;Che, Cuilian
    • International Journal of Precision Engineering and Manufacturing
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    • v.9 no.2
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    • pp.11-17
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    • 2008
  • Critical erosion kinetic energy models for radial/median cracks and lateral cracks in a workpiece are established in this study. We used experimental results to demonstrate that the fracture erosion resistance and erosion machining number could be used to evaluate the brittle fracture resistance and machinability of a workpiece. Erosion kinetic energy models were developed to predict brittle fracture and ductile shear, and a critical erosion kinetic energy model was developed to predict the transition from brittle fracture to ductile shear. These models were verified experimentally.

Removal of Hydrogen Fluoride from Waterjet Plasma Wastewater by Electrocoagulation (전해응집법에 의한 불화수소 함유 워터젯 플라즈마 폐수처리)

  • Lee, Chae Hong;Chun, Young Nam
    • Journal of Korean Society of Environmental Engineers
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    • v.34 no.10
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    • pp.702-708
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    • 2012
  • Tetrafluoromethane ($CF_4$) has been used as etching and Chemical Vapor Deposition (CVD) gases for semiconductor manufacturing processes. These gases need to be removed efficiently because of their strong absorption of infrared radiation and long atmospheric lifetimes which cause the global warming effect. Also, the wastewater including the fluorine is caused by of the ground water pollution. Long-term consumption of water containing excessive fluoride can lead to fluorosis of the teeth and bones. The wastewater including the fluorine among the by-product which is generated by using the waterjet plasma after destroying $CF_4$ by HF is generated. The system which can remove the hydrogen fluoride among the wastewater by using the electrocoagulation using this wastewater the aluminum electrode was developed. The operating condition such as initial pH, electrocoagulation time, wastewater flow rate, current density were investigated experimentally using a electrocoagulation. Through the parametric studies, the highest hydrogen fluoride destruction of 85% was achieved at 3.5 initial pH, 10 min electrocoagulation time, 10 mL/min wastewater flow rate and $159A/m^2$ current density.

Monitoring of waterjet cutting free surface using laser sensor (레이저 센서를 이용한 워터젯 절삭 자유면 모니터링)

  • Oh, Tae-Min;Hong, Chang-Ho;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.15 no.5
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    • pp.469-481
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    • 2013
  • The monitoring of a free surface generated by waterjet cutting technology is very important for an efficient construction process. In this study, experiments using a laser sensor were performed to provide a data processing method and to determine optimized parameters. The experimental parameters here are the angular resolution, measurement distance, and free surface cutting shape. The results show that the monitoring resolution increases with a decrease in the angular resolution and the horizontal measurement distance and with an increase in the cutting (free surface) width. This laser monitoring method can be applied during the measurement of free surface shapes and depths in situ.

A Study of PIV Analysis around 2-Dimensional Foil with Blowing (물분사장치를 이용한 2차원 익 주위의 PIV 해석에 관한 연구)

  • Oh, Kyoung-Gun;Cho, Dae-Hwan;Lee, Gyoung-Woo;Ko, Jae-Yong
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.1
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    • pp.45-49
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    • 2006
  • The flow around a foil with waterjet was investigated using the two-frame PIV(CACTUS 3.1) system. After separation, unsteady recirculation & reattachment region was shown as a result at reading edge. Separation area was decreased to 1/3 more by waterjet system with coanda effect. Angle of attack and waterjet velocity was a variable in the experiment. Each parameters was controlled to $0^{\circ}{\sim}35^{\circ}$ and 0[m/s]${\sim}$9.2[m/s]. The separation of flow appearanced at first when the angle of attack is $17^{\circ}{\sim}18^{\circ}$. However, according to grew up of velocity, beginning of the separation was delayed. In this experiment, vortex and separation region was disappeared by blown when each parameters are low level, and separation controlled more certainly.

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Endoscopic submucosal dissection in colorectal neoplasia performed with a waterjet system-assisted knife: higher en-bloc resection rate than conventional technique

  • Paolo Cecinato;Matteo Lucarini;Francesco Azzolini;Mariachiara Campanale;Fabio Bassi;Annalisa Cippitelli;Romano Sassatelli
    • Clinical Endoscopy
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    • v.55 no.6
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    • pp.775-783
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    • 2022
  • Background/Aims: Colorectal endoscopic submucosal dissection (ESD) is burdened by its associated high risk of adverse events and long procedure time. Recently, a waterjet-assisted knife was introduced to simplify and speed up the procedure. The aim of this study was to evaluate the efficacy and safety of waterjet-assisted ESD (WESD) compared to that of the conventional ESD (CESD) technique. Methods: The charts of 254 consecutive patients who underwent colorectal ESD between January 2014 and February 2021 for colorectal neoplasms were analyzed. The primary outcome was the en-bloc resection rate. Secondary outcomes were complete and curative resection rates, the need to switch to a hybrid ESD, procedure speed, the adverse event rates, and the recurrence rates. Results: Approximately 174 neoplasias were considered, of which, 123 were removed by WESD and 51 by CESD. The en-bloc resection rate was higher in the WESD group (94.3% vs. 84.3%). Complete resection rates and curative resection rates were similar. The need to switch to a hybrid ESD was greater during CESD (39.2% vs. 13.8%). Procedure speed and adverse event rates were similar. During follow-up, one recurrence occurred after a WESD. Conclusions: WESD allows a high rate of en-bloc resections and less frequently requires a rescue switch to the hybrid ESD compared to CESD.

Effects of Mixing Chamber Shape on Cutting Performance in AWJ (AWJ에서 혼합챔버 형상이 절단성능에 미치는 영향)

  • Lee, Hyo-Ryeol;Kwak, Yong-Kil;Kim, Hwa-Young;Ahn, Jung-Hwan;Yeo, Myeong-Heon
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.5
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    • pp.535-540
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    • 2011
  • It is well known that abrasive waterjet (AWJ) was developed as a kind of high-density energy processing technologies. AWJ is used to obtain cutting quality of various materials such as metal, ceramics, glass and composite materials within a short manufacturing time because of the characteristics of heatless and noncontact processing. However, surface roughness and dimension error like round, burr, taper vary severely according to the processing conditions such as pressure, cutting speed, orifice diameter, stand off distance and abrasive flow rate. In this paper, the effect of the shape of mixing chamber on surface quality is studied. Three types of mixing chamber - round, parabolic, elliptical - are suggested and each performance is compared to that of cylindrical mixing chamber experimentally. From the result, is proved to be the optimal mixing chamber in the aspect of surface quality the parabolic one.

A Study on the Improvement of Hull-Form Design for Propulsion Type Change of Net Boat Mounted on Tuna Purse Seiner (다랑어 선망어선 탑재용 보조 작업선의 추진기 타입 변화에 의한 선형 개선 연구)

  • Lim, Jun-Taek;Jang, Ho-Yun;Lee, Kyoung-Woo;Seo, Kwang-Cheol
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.6
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    • pp.810-817
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    • 2018
  • In Korea, tuna purse seine fishery is the industry with the highest production volume in domestic deep-sea fishery. Research has been continuously carried out since the late 1980s, and research on modernization of technology has been actively conducted. However, while auxiliary works boats on the fishing vessels play an important role in the purse seine fishing, related research is not sufficient. In this study, we tried to rebuild the propulsion system of the Net-boat from the propeller to the waterjet type and to perform the hull form conversion to improve the resistance performance of the hull part and improve the motion performance. For this, we calculated the change of the fluid performance of the ship through computational numerical analysis. In addition, towing tank tests were carried out to verify the performance of the existing ship and the ship which changed the propulsion system. As a result, resistance performance of the waterjet type compared to the propeller type was improved by approximately 45 %. It was confirmed that this was due to reduction of the wetted surface area by removing net and improvements in hull form.