Advanced Materials Research Vol. 1027

Abstract: In order to study the states of oxide layer under different pre-dressing process conditions in ultrasonic vibration and electrolytic in-process dressing combined grinding. The effects of electrical parameters, wheel speed, ultrasonic vibration on the oxide layer are investigated with indicators of oxide layer surface morphology and thickness characteristics. The results indicate that the oxide layer thickness increases with the decrease of inter-electrode gap and the increase of duty ratio with pre-dressing time. The effect of ultrasonic vibration cause thinning of the oxide layer. Oxide layer surface morphology allowing processing requirements are obtained by duty cycle of 5μs: 5μs, electrode gap of 0.3mm, wheel speed of 3200 r/min.

Abstract: An investigation is reported of the relationships of the temperatures and grinding parameter for grinding of ceramics with a brazed diamond grinding tool. During the experiments, the temperature distributions along the workpiece surface were measured using a foil thermocouples and the energy partition to the workpiece estimated using a temperature matching method. The results show that the grinding temperature increased with the increasing of worktable feed rate or tool velocity and depth of grinding. The measured temperature responses were found to be in good relation with the analytical results of a moving heat source with a rectangular distribution at the grinding zone.The energy partition ε is about 23%.

Abstract: In grinding, high specific heat is generated and hence it is very important for the fluid to remove heat from the grinding contact zone to avoid thermal damage to the workpiece surface and/or sub-surface layers. In conventional grinding, a stiff air layer is generated due to the rotation of the porous grinding wheel at high speed. Hence, most of fluid isn’t penetrated into the grinding contact zone because of the stiff air layer around the grinding wheel. To improve grinding fluid cooling effection and avoid thermal damage, it is necessary to analyze the air flow and stiff air layer around the grinding wheel. Based on fluid dynamics and mathematical simulation method, the 3D finite element model of the air flow field around the grinding wheel is developed. The air flow pressure field and flow velocity near the grinding zone are analyzed. In results, the pressure and the velocity of the air flow near the grinding zone increase with the wheel speed increase, and the pressure and the velocity of the air flow near the grinding zone increase with the minimum gap between the grinding wheel and the workpiece reducing. After the air is drived by the grinding wheel into the high pressure area near the grinding zone, the air flows around both sides of the grinding wheel and there are no obvious returning air flow phenomena.

Abstract: In order to improve the positioning resolution of the tool adapter on ultra-precision machine tool for KDP crystals, this paper presents a new piezo tool actuator. First, a new flexible membrane structure is designed after considering the characteristics of the machine tool for KDP crystals. Then, its detailed structural dimension is determined by finite element method. Finally, the piezo tool actuator is machined based on designs and its performance data is obtained by experiments. Experimental results indicate that its positioning resolution is superior to 0.5μm and its stroke reaches 4.7μm, which can meet the requirements of ultra-precision machine tool for KDP crystals.

Abstract: Tool path generation is an important part of ultra-precision manufacturing, and spiral tool path is one typical driving path. For single point diamond turning (SPDT), two methods are commonly used to generate the driving points on the spiral tool path, which are equally spaced angles and equally spaced arcs for two adjacent cutting points. But these two methods both have the defects for machining radial sinusoidal surface with SPDT. In this paper, the theoretical analyses of the two different methods are conducted and compared respectively. Then, an optimal method of generating the spiral cutting tool path is proposed on the base of theoretical analyses, which can avoid disadvantages of two original methods. The proposed method can enhance the machining accuracy and fabricating efficiency for ultra-precision machining of the radial sinusoidal surface with SPDT.

Abstract: Form grinding is the most popular finishing process for large-size gear, so the design method of the machine based on QFD and AHP was proposed. First, researched the situation of home and abroad, then analyzed the quality of customer needs and the development of technical measures in order to establish a house of quality. To avoid the blindness of the development and design, really provides a systematic basis for decision making gear form grinding machine in a leading position in the domestic market in the future. Finally, an example is used to demonstrate the feasibility of this approach.

Abstract: Temperature variation of KDP crystal is an important reason for its cracking. A finite element model was constructed to analyze temperature and thermal stress distribution of KDP crystal during wire saw slicing. The results showed that the highest temperature of the crystal which was located on the sawing kerf remained stable during slicing. The temperature inside the crystal rose slowly at the start of the slicing, and then tended steady with the continued increase of sawing depth. Because of the good cooling condition during the sawing process, the overall rise in temperature was small, and the maximum thermal stress on the sawing kerf was less than the tensile strength of KDP crystal, so temperature variation during slicing had little effect on crystal cracking.

Abstract: For reducing diamond tool wear in ultra-precision cutting of ferrous metals, a process of combining ultrasonic elliptical vibration with graphite particle atmosphere was put forward. An experimental setup was built integrating an ultrasonic elliptical vibration mechanism with a jet lubrication device on a 4-axis ultra-precision lathe. The frequency of ultrasonic elliptical vibration is 38.36 kHz with a trajectory of 8.5×3.5μm. Graphite particles with sizes of 1.3~2μm were selected. Conventional cutting and the combined method were conducted on die steel. Compared with conventional cutting with a wear land width of about 300μm, diamond tool wear in the combined method was decreased to about 20 to 30μm. The combined method is feasible to further reduce the diamond tool wear when cutting die steel.

Abstract: The applicability of diamond cutting is greatly restricted due to the serious chemical wear for the machining of ferrous materials. The processes of diamond natural graphitization and graphitization in diamond/Fe interface were analysed by molecular dynamics (MD). Simulation proved that the graphitization temperature decreased from 5215 K of natural graphitization process to 1300 K at diamond/Fe interface, and diamond which near the Fe atoms was graphitized firstly. Diamond tool wear behavior during ordinary cutting and ultrasonic elliptical vibration cutting (UEVC) of NAK80, S136 was analysed. Results showed that the diamond tool wear decreased greatly in UEVC. MD Simulation and cutting experiments both demonstrated that lowering the temperature of the interface could effectively reduce the wear of diamond tool.