Laser Induced Cavitation Micro Machining Experiment Research

Laser induced cavitation micro processing is a new kind of processing technology. Strong laser pulse focusing in the liquid and then induced cavitation, even when the cell level, can produce a ca vita ting shock wave, high speed micro jet, instantaneous high temperature and local vacuum negative pressure. Use of all kinds of physical phenomenon of cavitation can be achieved for micro/nano machining of various kinds of solid materials. Cavity produced by the pulsed laser in the blood rapid expansion, meet boundary block and then will produce a radius of 1μm micro jet, cause high voltage pulse peak of 1.6 GPa. The advantage of the cavitation effect into laser re canalization, is expected to develop a novel laser medical technology. Experiments using silica gel has good biocompatibility and elastic modulus close to blood clots, and was used to simulate the blood clots. So it is necessary for laser induced cavitation micro processing experiment and mechanism researchIn this paper, the laser induced cavitation micro processing experiment studied are summarized, the experiment of heating and cavitating jet impact are analyzed in theory. First, this paper introduces the laser induced cavitation micro machining and laser recanalization research significance. Secondly, this paper introduces the laser induced cavitation bubble numerical calculation and experimental study, laser vascular recanalization of the research status at home and abroad. Then, the experiment study the depth of the water layer and cavitation position these two factors influence on laser induced cavitation micro machining. Again, using high speed camera to observe bubble dynamic characteristics and plasma beam pattern, in the process of laser induced cavitation micro machining. Finally, the dynamic characteristics of cavitation above the surface of materials and flow field distribution and the pressure change has carried on the numerical simulation. The main research methods and conclusions are as follows.(1) Under the condition of different water depth change cavitation position to implement laser induced cavitation micro machining experiment, and then map pit width/depth trends, show typical cavitation location processing pit morphology. To study the law of cavitation micro machining and its mechanism. The results showed:The laser focus position below the surface and the lower the laser induced cavitation micro machining efficiency is higher, laser focus is located in near the surface of the material when machining precision is high. Laser energy heating effect and the phenomenon of cavitation are combined laser induced cavitation micro processing mechanism of material removal. Laser induced cavitation micro machining process, the phenomenon of water burial marks the energy shield, lost the cavitation in micro machining at this time. Optical fiber head in the initial stages of laser vascular recanalization should close to blood clots, and at the end of the thrombus ablation stages should be far away from blood clots.(2) Through high-speed camera observed cavitation bubble dynamics behavior and its surrounding flow field and the shape of the plasma beam when laser induced cavitation micro machining. Then analyse the mechanism of cavitation micro processing, mainly including laser energy heating and cavitating jet impact It turned out that:When the laser focus is lower than the material surface, bubble attached to the material surface, by cavitating shock waves and laser energy heating removing material. Was the bubble is located above the material surface, by shock waves and micro fluidic micro removing material, it can realize micro/nano machining, and cavitation melting thrombosis. Through the plasma shielding the laser energy heating to remove material, cavitating jet impact have the effect of the composite processing.(3) In the FLUENT software environment, using Volume of Fluid Method (VOF) to simulate bubble dynamics, the flow field distribution and the pressure change, different location near the surface of the material. The results showed:In the process of expansion-contraction, cavitation near the surface of materials can promote heat exchange and eliminate debris. Cavitation bubble expanding extrusion fluid formed water pressure and cavitation bubble breaking formed high speed micro jet have micro removal effects on materials. It is the main mechanism of laser induced cavitation micro machining, it is also the main mechanism of laser vascular recanalization cavitation ablation blood clots. Near the surface of the material the initial cavitation pressure and cavitation contraction to the minimum when the pressure is bigger. It is the key quantity of laser induced cavitation micro machining and cavitation ablation blood clots.