RESUMO
This paper presents a longitudinal-torsional transducer for use during the ultrasonic vibration-assisted milling (UVAM) of honeycomb aramid material. The mechanism of longitudinal-torsional conversion was analyzed to guide the design of a vibration transducer. The transducer features five spiral grooves around the front cover plate, which function under the excitation of a group of longitudinal piezoelectric ceramics. A portion of the longitudinal vibration was successfully converted into torsional vibration. The resonant frequency, longitudinal vibration displacement and torsional amplitude at the top of the disk milling cutter were 24,609 Hz, 19 µm and 9 µm, respectively. In addition, the directivity of the longitudinal-torsional transducer was theoretically analyzed. Compared with conventional milling, UVAM with the longitudinal-torsional could significantly reduce the cutting force (40-50%) and improve the machining stability.
RESUMO
OBJECTIVE: To study the feasibility of treatment of aortic arch aneurysm with graftstent by intravascular surgery. METHODS: Animal model of aortic arch aneurysm was established using 10 piglets. An aortic arch-shaped graftstent was transferred and implanted to the site of aortic arch aneurysm through femoral artery under angiography. RESULTS: The aortic arch-shaped graftstent was successfully implanted in 8 piglets. Two piglets died from anaesthetic accident. Angiography showed disappearance of aneurysm, splendid development of the branches of aortic arch, and no blood leakage around the stent. CONCLUSION: Treatment of aortic arch aneurysm by implantation of graftstent by endovascular surgery is feasible.
