Papers by Author: Yan Yan Yan

Abstract: According to the removal mechanism of ductile regime machining of nanoZrO2 ceramics and the dynamic characteristics of ultrasonic vibration assisted diamond flying cutting (UVADFC), the model of the material removal rate (MRR) of nanoZrO₂ ceramics under UVADFC and diamond flying cutting (DFC) have been proposed by infinitesimal method,. In this paper, the experiment of three factors and four levels was carried out to study the relationships between MRR and the machining parameters (cutting depth , spindle speed n and feed rate c). The results of the experiment shows that UVADFC is a cost-effective method which is applied to the machining of nanoZrO₂ ceramics, and the MRR of nanoZrO₂ ceramics under UVADFC is 1.3-2 times greater than that of DFC, and the degree of the factors significantly influence on the MRR of nanoZrO2 ceramics are feed rate, cutting depth, spindle speed in a sequence whether it is DFC or UVADFC. The results will shed more light on the material removal mechanism of UVADFC.

Abstract: Single crystal silicon has both important application value in the fields of micro-optics and MEMS, and it has been considered as one of the most difficult-to-cut materials because of its hardness and brittleness. Removal mechanism of the silicon was discussed, and the model of undeformed chip thickness was established in this article. According to the data of micro-groove surface roughness from the diamond fly-cutting experiment, the nonlinear relationship curve, between the largest undeformed chip thickness h_max and microgroove surface roughness R_a, were obtained using Gaussian-fitting principle, and the regression equation of the fitting curve was also got. Thus the prediction mathematical model of microgroove surface roughness was derived. The influence laws of the main working parameters on the R_a were obtained based on the result of this experiment and the response surface of the prediction model, and some conclusions were summarized: the surface roughness R_a of microgroove in the single crystal silicon decreases with the decrease of the cutting depth a_p, the feed f and the increase of the spindle speed n under the diamond fly-cutting; the experimental results also showed that feed f affects the value of R_a very much, cutting depth a_p less, and spindle speed n the least.

Abstract: Two dimensional ultrasonic vibration assisted grinding (TDUVG) is analyzed based on theoretical analysis of the cutting trace of a grain in the finished surface, and it gives the kinematical model of single grit during TDUVG, and the condition of the separate cutting is established, so two dimensional ultrasonic vibration are introduced into the system, which helps to form good machining way. Then TDUVG is applied in the ultra-precise machining of nanoZrO₂ ceramics, and grinding experiments on surface quality of nanoZrO₂ ceramics were carried out using diamond grinding both with and without ultrasonic vibration. Experimental results show that the surface quality after two dimensional ultrasonic assisted grinding is superior to that of diamond grinding. As a result, it is suitable for the ultra-precise machining of ceramics.

Abstract: By means of Adaptive Neural-Fuzzy Inference Systems(ANFIS), the prediction model of surface roughness of zirconia toughened alumina ceramics (ZTA ceramics) under ultrasonic assisted grinding is established, and the model may obtain the higher forecast precision (81.25%) by dealing with nonlinear problem among grinding parameters, and fuzzy rule curved face formed by prediction model showed four input factors have different influence on surface roughness Ra, and they are abrasive grain size, grinding method, grinding depth, axial feed and speed of worktable from top to bottom. So the prediction model provides a new and efficient method for intelligent information processing, and it could be applied in modeling and real-time control etc, and it is possible to be widely applied in engineering.

Abstract: Ultrasonic-vibration hard cutting (UVHC) is a advanced technology, where high- frequency vibration is superimposed on the movement of the cutting tool. Compared to conventional turning (CT), this technique allows significant improvements in processing hard-to-cut materials, by producing a noticeable decrease in cutting forces and a superior surface finish. The paper presents a finite-element model of both CT and UVHC. Stresses produced in workpiece and cutting forces acting on the cutting tool in UVHC are studied, and the influence of cutting parameters, such as cutting speed and cutting depth on cutting force are investigated.

Abstract: It discusses the reasons of the data transmission time delay and packets loss based on the theory of net data transmission. Aimed to the question of the time delay of data transmission and packets loss, the control system models are set up to analyze their influence to the performance of the control system. Based on the synchronous control model analysis with wireless data transmission, a method to control the system is reached with the state prediction when the communication error or data loss appears. It can control constantly when communication errors appear, and also it can get the most error period by numerical analysis.

Abstract: A study of the fracture phenomenon of zirconia-toughened alumina (ZTA) ceramics was carried. It analyzes the mechanisms of crack propagation of ZTA ceramics, and constructs fracture experiments of ZTA ceramics, so the propagation behavior on fracture in ZTA ceramics was investigated according to the experiment. By contrast, intercrystalline fracture happed in V-shaped groove of ceramic specimen under normal load without ultrasonic vibration during ceramic fracture, and transcrystalline fracture happed in V-shaped groove of ceramic specimen under normal load with ultrasonic vibration during ceramic fracture. Furthermore, the loading force of ceramic specimen under normal load with ultrasonic vibration is smaller than that under normal load without ultrasonic vibration all other conditions being equal. The results of fracture experiment prove that ultrasonic vibration assisted is good for the fracture of ceramic specimen, and it also proves that ultrasonic vibration assisted grinding may raise the working efficiency and improve surface integrity of ceramics from the standpoint of the fracture.

Abstract: The paper discusses the application of the wireless data transmission in the industrial control system and analyses the characteristics of the data transmission. It gives the different characteristics of data transmission in the four experiments with the Zigbee Protocol. By comparing the result of the wireless network-path loss model and experiments, it shows that the path loss, multiple-point jamming, communication barrier primarily affect the stability of data transmission.

Abstract: Based on good processing property of two-dimentional ultrasonic vibration assisted grinding (TUVAG), phase transformation in the grinding surface of nanozirconia toughened alumina ceramics (ZTA ceramics) is studied by XRD analysis. Experimental results show different processing method and grinding depth may lead to surface phase transformation of ZTA ceramics. Under the same grinding parameters, phase transformation ratio of grinding surface under TUVAG is higher than that under diamond grinding (DG), and its phase transformation ratio increases with the increasing of grinding depth. Phase transformation ratio can effectively inhibit generation and expansion of microcracks of grinding surface.

Abstract: Based on good processing property of two-dimentional ultrasonic vibration assisted grinding (TUVAG), the precision finishing of nano-zirconia toughened alumina ceramics (nano-ZTA) is carried out. According to theoretical analysis, TUVAG may obtain higher machining efficiency and better surface quality. Especially, experimental results show it may obtain the compressive stress in the finished surface of nano-ZTA that may restrain the expansion of surface microcrack, and surface residual stress of nano-ZTA under TUVAG differs from that under diamond grinding, and TUVAG may obtain the better surface quality of nano-ZTA than diamond grinding, as is characterized by scanning electronic microscope (SEM). As a result, it is good for TUVAG as a kind of processing method for nano-ZTA.