| 研究課題/領域番号 |
15H06320
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| 研究機関 | 京都大学 |
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研究代表者 |
ブカン アントニー 京都大学, 工学(系)研究科(研究院), 講師 (30756838)
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| 研究期間 (年度) |
2015-08-28 – 2017-03-31
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| キーワード | 精密研磨 / 材料加工 ・ 処理 / シミユレ一シヨン |
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| 研究実績の概要 |
This project aims to develop a novel process for rapid ultra-precision polishing of geometrically complex workpieces, by ultrasonic cavitation assisted fluid jet polishing.
The research first concentrated on producing a numerical model of the process. After an initial literature search, it was found that ultrasonic cavitation bubbles typically have a lifetime of few milliseconds (about 100 acoustic vibration cycles). For typical fluid jet outlet velocities, it was calculated that the onset of cavitation should occur a few millimetres away from the workpiece in order to affect the work surface. Using the multi-physics COMSOL software, a nozzle cavity was modelled consisting of a slurry inlet, conical chamber, outlet through a laser drilled sapphire insert, and an acoustic lens connected to a transducer. Using design optimization methodology, the dimensions of the cavity and lens were optimized to maximize acoustic resonance. Our final model predicted intense focusing of acoustic waves (amplitude up-to 40bar) near the cavity outlet, for frequencies in the range 28-127kHz and operating pressure in the range of 2-20bar (typical for fluid jet polishing).
Manufacturers of ultrasonic equipment were contacted in order to source the ultrasonic generator and acoustic lens. The equipment has been delivered to our laboratory and mounted on an vibration isolation table together with a nozzle cavity fabricated in the machine shop of our department. Experimental trials have now begun, and the generator has been successfully tuned to make the cavity resonate at the designed frequencies.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
Progress on the project during the year 27 has been in-line with expectations:
(1) The numerical modelling stage was completed, and has led to the design of an adequate nozzle cavity for the purpose of inducing and sustaining cavitation micro-bubbles near the work surface.
(2) Customized equipment (the ultrasonic generator, transducer, and acoustic lens) was ordered from industry together with a vibration isolation table. All other components (pressurized cavity, nozzle outlet insert, 3-axis jig, soft silicon tent for pressurized slurry containment) were fabricated by ourselves with the help of the machine shop at our university department.
(3) The prototype system has been fully assembled, and is now ready for the process experimentation and characterization phase.
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| 今後の研究の推進方策 |
Because of the small size of the nozzle cavity and intense focusing of the ultrasonic waves by the acoustic lens attached to the transducer, it has been observed that the temperature of the transducer quickly rises when operating the system. To avoid damaging the equipment, our first plan is to design and implement an adequate cooling system.
Once the thermal safety of the transducer is resolved, process experiments will be conducted: material removal tests will be carried out on metal alloys and ceramics to characterize the performance of the ultrasonic cavitation assisted system compared to conventional fluid jet polishing systems. In particular, the material removal rate (mm3/min) and surface roughness rms will be recorded, and used as a benchmark for quantifying the productivity of the new system.
Next, the stability of the system will be verified by performing removal trials over large surface areas with the aid of the 3-axis jig to which the prototype system is attached. Metrology equipment in the laboratory (profilometer and Fizeau interferometer) will be used to verify removal rate stability over time-scales ranging from minutes to hours.
Once the basic advantages and/or disadvantages of the prototype system have been ascertained, improvements to the original prototype system will be proposed and implemented.
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| 備考 |
The possibility of patenting this process is under consideration. Publication of the results will be on hold until a decision has been made.
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