Papers by Author: Jun Li Liu

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: In order to solve the problem of shearer automation for the automated mining, analysis and processing by a plurality of sensors or observation information sources is the most promising solution to automatically control the shearer’s posture, while there is no vibration sensors with intrinsically safety that can be directly equipped on the shearers under coal mines. In the paper, study on a new intrinsic safe mode vibration sensor to solve the problem, it includes the hardware system designing and data collection programming. At the end, an experiment proves that the intrinsic safe wireless vibration sensor is able to collection the three-dimensional vibration data reliably and in time compared with the other vibration sensors.

Abstract: This paper is concerned with a synchronous control problem of distributed systems with wired and wireless hybrid communication network. A discrete tracking error mathematical model is established based on prediction model and non-memory state feedback controller. A sufficient condition for asymptotic stability of state tracking error between the master system and slave system is presented by constructing Lyapunov function, and a linear matrix inequality (LMI) approach has been employed to obtain the tracking controller gain matrix.

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: In this study, adding coal cinder to bottom of solar pond as a means of increasing temperature of the solar pond is presented. A series of small-scale tests are conducted in the simple mini solar ponds. These small-scale tests include the temperature evolution comparisons of this mode with other normal modes; the comparisons of the material added to LCZ and the comparisons of the different soaking times for coal cinder. In addition, a numerical calculation on predicting temperature evolution in large area of salt gradient solar pond is also given. Both of the experimental and numerical results suggest that adding porous media with low thermal diffusivity (e.g. coal cinder) could significantly increase the temperature in the vicinity of the bottom of the pond. From the view of long-term, this effect is supposed to enhance the average temperature of the solar pond.

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.

Abstract: ZTA ceramics is a kind of high performance structural ceramics, and its surface/subsurface damages after machining have great effect on reliability and long-service life of ceramic parts, so it introduces two-dimensional ultrasonic vibration assisted grinding (TUVAG) which is applied in the precision finishing of ZTA ceramic, mathematic motion model of abrasive grain during TUVAG is established, and the special machining path of abrasive grain during TUVAG is analyzed, and the surface/subsurface damages of ZTA ceramics after TUVAG are further discussed. Experimental results prove that TUVAG may make materials removed in a plastic state mostly, the probability of cracks formation and propagation becomes less, and obviously reduce surface damages of ZTA ceramics, and the grinding badness layer of ceramics after TUVAG is shallower than that after diamond grinding at the same grinding parameters.