Papers by Author: Zhe He Yao

Paper TitlePage

Authors: X.Y. Gang, Zhe He Yao, Zi Chen Chen
Abstract: Horizontal vibration has critical influence upon elevators’ ride quality. Based on the wave theory of one-dimensional string vibration, a horizontal vibration wave model is built to simulate the dynamic performance of a high speed elevator system. Through coordinate transformation, Galerkin’s method is used to discretize the governing partial differential equations into a dumped-mass system, which can be solved effectively with classic methods. Numerical results show that the horizontal vibration behaviors are closely interconnected with the location, velocity and acceleration of elevator cab.
Authors: X.Y. Gang, Zhe He Yao, Zi Chen Chen
Authors: Xin Li, Zhe He Yao, Zi Chen Chen
Abstract: Chatter often occurs during precision hole boring, it results in low quality of finished surface and even damages the cutting tool. In order to identify chatter rapidly and gain the precious time for chatter suppression, a chatter monitoring system was established and an effective feature extraction method for boring chatter recognition was presented. According to the characteristic of chatter signal, empirical mode decomposition (EMD) was introduced into chatter feature extraction, and its basic theories were investigated. The vibration signal was decomposed by EMD, then the intrinsic mode functions (IMF) was got. Finally, the feature of chatter symptom was extracted by analyzing the energy spectrum of each IMF. The results show that feature extracted from vibration of boring bar by EMD can indicate chatter outbreak symptom, and it can be used as feature vectors for rapidly recognizing chatter.
Authors: Hong Hua Zhou, Zhe He Yao, Zi Chen Chen
Abstract: Processing parameters of micro thixoforming, such as height-diameter ratio, die/punch temperature, billet temperature, and punch speed, have direct and complex impact on final quality of the workpiece, which is to be applied as the reaction plate of a microreactor for hydrogen production from methanol steam reforming. The micro/meso features of the workpiece, which is for catalyst loading, are micro-pin-fin arrays. Size of the surface area and uniformity of the pin-fins are quantified by average height (Ha) and relative standard deviation (RSD). An orthogonal experiment design is adopted to investigate the influence of the parameters on the semi-solid forming process. The results of the orthogonal experiment show that the optimum parameters are 150 °C for die/punch temperature, 576 °C for billet temperature, 0.14 for height-diameter ratio and 8.33 mm/s for punch speed. The experimental results validate that the optimized processing parameters can improve the quality of the reaction plate with micro-pin-fin arrays.
Authors: Pei Tang, Zhe He Yao, Hong Hua Zhou, Zhuo Xiong Sun
Abstract: The induction heating of the billets is a critical step in the thixoforming process. To improve the quality of thixoforming, the induction heating strategy should be investigated. In this study, by using an induction heating system of 50 kHz, multi-step reheating schemes were adopted to reheat the nondendritic A356 alloy to the temperature between the solidus and liquidus line. To obtain uniform temperature distribution and fine globular microstructure, the effects of the reheating parameters, such as reheating time, reheating temperature, holding time and holding temperature, were investigated. Then the analysis of the final temperature difference and the optical microstructure of the reheated billets were conducted, the results showed that two-step reheating process is suitable for A356 alloy with the size of 45 mm × 25 mm, and the suitable time for the final holding process is 2 min.
Authors: Chun Liang Zhang, Zhe He Yao, Zi Chen Chen
Authors: Chun Liang Zhang, Zhe He Yao, Zi Chen Chen
Authors: Biao Jin, Zhe He Yao, Miao Qian
Abstract: In order to carry out reaction smoothly, a measure and control system of an onboard micro-channel reactor for hydrogen production via methanol steam reforming is developed. A subsystem of temperature control is designed to measure and control the temperatures of reactor and evaporator. Flow control subsystem, including liquid flow control of reactant and mass flow control of reducing gas, is also developed. Virtual instrument technology and graphical programming language LabVIEW are applied to integrate all the control functions in a single program, which makes it convenient for operation and further development. The experimental results validate that the reaction can be carried out successfully under the control of this measure and control system.
Authors: Hao Yan Wang, Zhe He Yao, De Qing Mei
Abstract: Micro/meso forming, as an emerging manufacturing process for miniature metallic workpieces, has attracted great attention since the 1990s due to its high production efficiency, low material waste and high precision. Due to the so-called size effects in the scaling down, many traditional theories in metal forming cannot be simply applied to the micro/meso forming. In this study, the micro/meso upsetting experiments of Brass H62 were conducted at various temperatures. The stress−strain curves in the experiments were measured and compared. The effects of the temperature and the sample size on the flow stress were discussed. It is found that the flow stress of the material decreased with the decrease of the sample size at room temperature. However, the flow stress of the material may increase with the decrease of the sample size at elevated temperatures. The results indicate that the size effects in the micro/meso forming are significantly affected by the processing temperature.
Authors: Zhe He Yao, Xin Li, Zi Chen Chen
Abstract: Self-chatter is a serious problem in cutting process. This paper aims to solve the problem by establishing time series model of vibration acceleration signal in cutting process based on Hidden Markov Model (HMM) technology and achieve the purpose of chatter recognition and prediction. Features which can indicate cutting state are extracted from the acceleration signal. HMM parameters are obtained by model training, and the reference models database is built. Then cutting state recognition is performed according to the feature matching level. Simulations and experiments are conducted, and the results show that the proposed method is feasible and it could get high recognition
Showing 1 to 10 of 13 Paper Titles