Papers by Author: Zhe Qin

Abstract: This paper regarded the sediments of Lake Baiyangdian as the object of study, researched and analyzed ammonia nitrogen adsorption characteristics of sediment samples. The results showed that: the sediments adsorption to ammonia nitrogen reached a state of equilibrium after 2.5h, The ammonia nitrogen adsorption rate was maximum in 0~10min. Sediment adsorption of ammonia nitrogen was higher as ammonia nitrogen liquid balance concentration increased. The adsorption isotherm curve of ammonia nitreogen can be fitted well by the Langmuir adsorption isotherm model. The total maximum adsorption quantity of ammonia nitrogen by the sediments of Lake Baiyangdian is between 54.12mg/kg to 240.12mg/kg.

Abstract: Drilling force and temperature of tibia at the high speed drilling for improving the design of surgical drills are very important. In this paper we describe experiments using pig tibia bones, measuring the drilling force and temperature of a new design of drill bit and compare the results against a twist drill. The result shows that the drilling force and temperature are affected by the feed rate and drilling speed, which vary with the drilling depth into the bone. The new surgical drill with three top cutting edges can achieve lower temperature below 47oC and lower drilling force than with the stainless steel twist drill and carbide twist drill.

Abstract: Cutting tools suffer severe abrasive friction and wear in high speed milling of graphite. Cutting forces were measured and analyzed using time-frequency analysis method to reveal the correlation between cutting force variations and tool wear evolution. The static and dynamic force components increased prominently with tool wear. The cutting force Fy was found the most sensitive to the tool wear evolution. The waveform of cutting force became periodic and irregular with the increase of tool wear. Good correlation was found between the first force harmonic and tool wear.

Abstract: When the pocket in die and mould is machined by high speed milling (HSM), the cutting forces increase and vibration fluctuates at the pocket corner because of the sudden change of cutting direction in general. It will cause serious wear and possible breakage of cutting tool, and poor quality of parts. By means of experiments, the cutting forces and vibration at the pocket corner with different HSM conditions are measured. The results show that the sharper pocket corner, higher cutting speeds, larger feed rate per tooth and radial depth of cut, will result in increasing of cutting forces and vibration amplitude. Thus, it will lead to be unstable during the process of high speed milling pocket corner.

Abstract: Micro carbide endmills suffer severe abrasive friction and impact wear in high speed milling of graphite. This paper focused on the study of the effect of Co content and WC grain size on the tool wear resistance of micro carbide endmills in high speed milling of graphite. The tool wear morphologies of cutting tools were examined at the initial wear stage and severe wear stage. The results showed that the abrasive resistance of micro carbide endmill increased with the decrease of Co content and WC grain size. The best impact resistance can be obtained with medium Co content and smaller WC grain size. The fine-grained carbide 0.2WC-8%Co is considered as the optimum tool material for high speed milling of graphite.

Abstract: High speed milling is widely employed in die and mold machining, and the attentions had been gradually paid on the details during the process. Based on the high-speed milling experiments of hardened steel with different extended length of tool, cutting force, cutting vibration, tool wear and surface roughness were measured and analyzed in this paper. It was founded that cutting force and vibration were not increasing straightly with the addition of extended length, but fell down when exceeded a certain value, and the surface quality improved at same time.