Papers by Author: Jian Sun

Abstract: The purpose of the essay is to know the rock fragmentation mechanism of TBM and improve the efficiency of disc cutter. The method of simulation is applied. The cutter ring and cutter axis surface stress distribution are studied under different rocks and the change of them is analyzed under different penetrations. Under different rocks conditions, the cutter ring surface stress is affected due to the change of rock load; the same rock condition, it is changed along with the change of penetrations. But the cutter axis surface stress changes little. In different rocks conditions, the change of stress on the cutter ring surface is proportional to rock ultimate stress; the same rock condition, it is proportional to the penetration of the cutter ring. The results are significant in improving the working efficiency of disc cutter.

Abstract: In this paper, we studied the large deformation and the small deformation method based on the research of the existing system of straightening theory and considered the characteristics of copper-clad steel to find a proper straightening scheme for this new composite materials. the advantages and disadvantages of the method are also compared. the straightening scheme for straightening effect and parameters is a decisive role before all kinds of straightening parameter determination. But at present, there isnt a equipment for the straightening of this new material.

Abstract: Kinematics simulation study on Morse CVT input mechanism was established by using simulation software Adams, and it can get curves of displacement, velocity and acceleration of input mechanism of each bar to research its movement characteristics. This method is suit for kinematics simulation of connecting rod mechanism, meanwhile it can modify corresponding simulation parameter and is easy to do optimal design.

Abstract: Piezoelectric energy harvester with high output and low resonant frequency is required in wireless sensors and portable devices. It can be fabricated by bonding of the bulk PZT ceramics with excellent piezoelectric properties to the Si wafer. Firstly, the basic design principles of piezoelectric energy harvester were analyzed. Then, the novel process flow to manufacture piezoelectric energy harvester using bulk PZT was explored. Using 2µm Au layer as the bonding layer, the bulk PZT was bonded to Si wafer at the temperature of 5500C for 2 hours. With the lapping technique, the thickness of bulk PZT is reduced from 300µm to 60µm. KOH was used to etch the backside of Si from 500µm to 20µm as the supporting layer of the piezoelectric beam. The last procedure was to dice the wafer into many cantilevers with different length or width. One of PZT piezoelectric cantilevers was tested using a mechanical shaker, by applying a sinusoidal oscillation at different frequencies. The resonant frequency is 815 Hz, and the voltage output is around 632 mV at 0.5g. The result shows that the sample has excellent ability to harvest energy of vibration and the novel bonding technology is quite feasible.

Abstract: Piezoelectric sensor can produce voltage when deflected (function as an energy harvester) while piezoelectric actuator can deflect when a voltage is applied. Different device applications have different requirements on the thickness and in-plane geometry of the Lead Zirconate Titanate(PZT) piezoelectric layers and thus have their own processing difficulties. In this paper, PZT-Au-Si cantilever is fabricated by eutectic bonding and dicing process.The properties of lapped PZT ceramics and silicon cantilever is also evaluated. The PZT-Au-Si cantilever applications for both piezoelectric actuators and energy harvesters have been confirmed.

Abstract: As an energy conversion material, piezoelectric ceramic lead zirconate titanate (PZT) has been used in a wide range of areas. And a PZT wafer bonding with a silicon wafer technology is a promising method to fabricate micro-sensors and micro-actuators using well-established silicon machining techniques. In order to obtain the excellent piezoelectricity and suitable thickness from the bulk PZT, a method is presented. It is to bond a bulk PZT onto a silicon wafer via an intermediate layer. In this paper, two bonding methods are presented. One is to bond a bulk PZT with a silicon wafer by anodic bonding technique using a thin glass film as the intermediate layer. The other is to bond a bulk PZT with a silicon wafer by eutectic bonding using a thin gold film as the intermediate layer. The glass film is 2µm in thickness, deposited by sputtered method. Anodic bonding conditions are: 0.8MPa in pressure, 500 oC in temperature, 250V in voltage and different bonding time. The bonding strength test shows that the maximum bond strength is 13.93 MPa when the bonding time was 60 min. It is void-free structure in the interface of the PZT-Glass-Si structure. The gold film is 1.6µm in thickness, deposited by evaporation method. The eutectic bonding conditions are: 0.8MPa in pressure, 500 oC in temperature, and different bonding time. The bond strength of the PZT-Au-Si structure was tested and the maximum value was 13.19 MPa when the bonding time was 60 min.

Abstract: The precipitation behavior in the AL6XN austenitic stainless steel after creep deformation at temperatures 500~750 °C up to 3600 hours has been studied by electron microscope. The results showed that precipitates were hardly observed for the steel crept at 500~550 °C, and that the precipitates of carbides were mainly found at grain boundaries in samples crept at 600 °C. When the creep temperature was increased to 650~750 °C, a high density precipitates was found both at grain boundaries and within grains. The electron diffraction pattern and energy-dispersive X-ray spectroscopy analyses confirmed that these precipitates are  and Laves phases.

Abstract: The deformation microstructure of a metastable beta-Ti alloy with chemical composition of Ti-23Nb-0.7Ta-2Zr-1.2O at.% after cold swaging has been studied by electron backscattering diffraction and high-resolution transmission electron microscope. The results showed that the deformation structure of the cold-swaged alloy appears to be similar to the swirled structure that commonly found in bcc metals heavily deformed either by wire-drawing or by rotary swaging process, and <110> fiber texture is a typical texture component of bcc metals. HRTEM results further showed <111> dislocations in the deformed alloy. Additionally, {112}<111> mechanical twinning and stress-induced omega transition were further revealed.

Abstract: Site occupancies of ternary additions (Ti, V, and W) in the C15 ZrCr2 and NbCr2 Laves phases were predicted theoretically by first-principles calculations based on density functional theory. The results suggest that Ti preferentially occupies the Zr and Nb sites in ZrCr2 and NbCr2, respectively. V and W substitute the Cr sites in both ZrCr2 and NbCr2. The calculations of heats of formation also show that the occupancy of W on the Cr sites and of Ti on the Zr sites stabilize ZrCr2. For NbCr2, the occupancy of V on the Cr sites and of Ti on the Nb sites increases the phase stability.

Abstract: The bonding character of Laves phases TiCr2 and TiCo2 has been investigated by electron energy loss spectroscopy and ab-initio calculations. The results revealed the hybridization between the transition-metal atoms in Laves phases. The stronger Cr-Cr (Co-Co) bonding along the Kagome net forms a tetrahedral electronic network in the C15 TiCr2 (TiCo2) structure. This was discussed with the mechanical properties of Laves phases.