Papers by Author: De Yuan Zhang

Abstract: In this paper the reason of chromium coating seepage on piston rods is analyzed. The results show that the chromium coating seepage is mainly caused by the net structure of micro-cracks produced in electroplating process. According to this special structure of chromium coating, experiments are made to study the feasibility that the chromium coating is burnished by using the ultrasonic elliptical vibration burnishing (UEVB) process to prevent seepage. The results of study demonstrate that the UEVB process make the micro-cracks on the surface of chromium coating closed or eliminated because the UEVB process could make the chromium coating plastic-forming. Thereby airtightness of piston rods is increased and seepage is prevented approximately. Compressive stress within the material of chromium coating will produce so that the micro-cracks propagation would be restrained and the life of parts is extended.

Abstract: The vibration tapping technology has been employed with success on some difficult-to-machine material such as titanium alloy, hardened steel and so on. However, there are very few studies on the application of the torsion vibration tapping in particle reinforced aluminum. The tapping performance of small size thread holes in particle reinforced aluminum matrix composites Al₂O₃p/Al and SiCp/Al during common tapping and low-frequency vibration tapping using high speed steal(HSS) machine-used taps is researched experimentally in this work. The influence of vibration parameters, e.g. cutting speed V, net forward angle of each stroke LT and times of repeat cutting Q on tapping torque, tool wear, tool life and quality of thread holes is investigated during the experimentation. The results show that the common vibration tapping with small amplitude, relatively high frequency and a lot of repeat cutting times suit to tap the Al₂O₃p/Al, whereas the step vibration tapping with large amplitude, relatively low frequency and a few repeat cutting times suit to tap the SiCp/Al due to difference performance of the two kinds of material. The influence of Q and LT on the quality of thread holes, tapping torque and tool life is sensitive on the Al₂O₃p/Al, whereas the influence of V and Q on the quality of thread holes, tool wear and tool life is sensitive on the SiCp/Al. Furthermore, the optimum vibration parameter in the Al₂O₃p/Al by dry cutting is cutting speed of 400r/min, net forward angle of each stroke of 1.5°, backward angle of each stroke of 45°. The optimum vibration parameter in SiCp/Al by dry cutting is cutting speed of 220r/min, net forward angle of each stroke of 420°, backward angle of each stroke of 430°. From the test results and micrographs, it was observed that the particle could be fractured on the surface finish on tapping processing. The proper vibration tapping parameter can void the adhesion in the tap flute, decrease the tapping torque, improve the quality of thread hole and prolong the tap life.

Abstract: Vibration drilling with internal spray-cooling method was proposed for the poor thermal conductivity characteristics of superalloys. Cutting temperature and tool wear in vibration drilling, conventional drilling and step drilling were compared by experimental study. The results show that: the cutting temperature in vibration drilling does not change significantly with the hole depth and slowly increased with the increase in the number of drilling; the tool wear rate is reduce, tool life is extened and the processing efficiency is improved.