Papers by Author: De Yuan Zhang

Abstract: Service life of tap is shorter when low frequency torsional vibration tapping is used to tap on superalloy GH4169. The analysis of experimental data show that excessive repeated cutting times and high friction speed result in rapid wear of tap. In order to avoid above unfavorable factors, step type vibration tapping is proposed, which has larger cutting angle, such as 90°, and lower spindle speed. It was proved by experiments on superalloy GH4169 that service life of tap of step type vibration tapping is about twice of that of common low frequency torsional vibration tapping .

Abstract: To investigate the effective permittivity of composites composed of ellipsoidal inclusions, three-dimension numerical models for ellipsoidal inclusions distributed randomly are built with the finite-element modeling software Comsol Multiphysics. After calculating the effective permittivity for different cases and comparing the results with analytical results from the Maxwell-Garnett mixing rule, we find that the finite-element method has an advantage in detecting details of the interaction among inclusions, which have some impacts on the effective permittivity and could not be accurately taken into account in the analytical model. The finite-element method is expected to solve more complex problems on electromagnetic computation.

Abstract: Graphite-FeSi absorbents were fabricated by mechanical milling method. The complex permittivity and permeability were measured in frequency 1-4 GHz, and then reflection loss (RL) and shielding effectiveness (SE) were calculated. It was obtained that the graphite was bonded to the surface of FeSi by X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images. The permittivity and permeability could be enlarged as graphite added in the milling process. It was attributed to the excellent conductivity of graphite and interactions of the two particles. The graphite-FeSi composites had a better shielding property (maximum 25.93 dB) in 1-4 GHz as well as the absorbing property at 1GHz than FeSi composites.

Abstract: In order to provide references for the application of low frequency torsional vibration tapping, three typical difficult to cut materials 30CrMnSi, GH4169 and TC4 were selected to carry out experiments. Experiment results show that net cutting angle L_T and backoff angle L_G have great influence on tapping torque, and the process parameters should be selected reasonably according to material characteristics and combining with tapping efficiency. Larger L_G and smaller L_T should be selected for materials with small elastic modulus such as TC4. Smaller L_G and larger L_T can be selected for materials similar to 30CrMnSi. For materials similar to GH4169, parameters should be selected between that of TC4 and 30CrMnSi.

Abstract: The thin-walled components of aero industries in general have complex structures whose machining accuracy is very difficult to be guaranteed because of the weak rigidness. To resolve the problem of the thin-walled disc clamping deformation, one novel clamping approach with flexible clamping capability is proposed in this paper. The surface morphology measuring systems (SMMS) and fast servo cutting system (FSCS) are developed, and its microstructure morphology duplicating accuracy is experimentally proved to be about 1μm under working environment. The clamping deformation is clarified weaker via flexible clamping approach which makes thin-walled disc morphology uniformly adaptive to the clamp.

Abstract: A kind of single inlet swirl atomizer is set to adjust the inlet location and the length of the outlet for an optimization spray angle and uniformity in this literature.Stationary wave theory is used to describe the results of spray quality.Experimental and theoretical analysis show that using property machining process size, single inlet swirl nozzles can achieve the optimized quality of atomization (spray cone angle of 55 °and more, skewness of spray cone center below 5 ° ).

Abstract: In this paper a method of ultrasonic elliptical vibration cutting has been applied to precision boring of micro hole due to its superior performances such as low cutting force, high quality surface finish and long tool life. A transducer with the longitudinal excitation is carried out to machining(boring) micro hole of 1Cr18Ni9Ti workpiece. The cutting force and surface quality are studied in detail.The workpiece with surface roughness of Rz 0.4μm is achieved.The results showed that the ultrasonic elliptical vibration transducer can be applied rationally in micro hole precision boring.

Abstract: Low frequency torsional vibration tapping is an effective method to solve the problem of tapping in difficult to cut materials. Tapping parameters affect tapping torque and service life of tap, and cutting angle is the key parameter. Experiments were conducted to study the lubrication mechanism and the influence of cutting angle on lubrication effect. Experimental results indicate that the separate type boundary lubrication mode greatly enhances the lubrication effect of cutting fluid and the lubrication effect decreases with the increase of cutting angle. To obtain good technological effect, the smaller cutting angle should be selected.

Abstract: Hardened stainless steels are materials widely used in the field of aviation and spaceflight. Machining of this materials with conventional cutting (CC) method is a real challenge compared to other difficult-to-cut materials. Ultrasonic elliptical vibration cutting (UEVC) method is a novel and non-conventional cutting technique which has been successfully applied to machine such intractable materials for the last decade. However, few studies have been conducted on the cutting force in ultrasonic elliptical vibration cutting of hardened materials. This paper presents an experimental study on cutting force in UEVC of hardened stainless steels using cemented carbide tools. Experiments have been carried out to investigate the effect of cutting parameters in the UEVC method in terms of cutting force, while cutting hardened stainless steels. The tests have revealed that the average thrust force,principal force and feed force drop to 3%,10% and 90% of CC value for UEVC of hardened stainless steels. The ratio between the CC force and the UEVC force decrease with the increase of DOC and cutting speed.

Abstract: Super alloys is the ideal material for high temperature components although it has a great difficulty to cut, especially drilling. Minimum Quantity Lubrication (MQL) has a good advantage of green, lubricating and cooling effect. Comparison experiments of MQL cooling drilling and pouring cooling drilling were done with coolant holes in drill. The results show that: the maximum measure temperature is less than 100°C and the amount of wear is very small. Internal Minimum Quantity Lubrication drilling is an effective process to solve problems of high temperature and wear fast for super alloys drilling.