Papers by Author: Pei Qi Ge

Abstract: The single-asperity friction of polished single crystal silicon using a cone with a spherical apex tip was quantitatively studied concerning the influence of normal load and scratching cycles. Specific friction equations were presented and the interfacial friction equations were determined by fitting the experiment data obtained in the scratching tests. The influence of different scratch conditions to both the interfacial fiction and the plowing friction was analyzed. This paper aims to understand the mechanisms of friction and material removal of single crystal silicon in micro and nanocutting or polishing.

Abstract: KDP (KH₂PO₄) crystal is a kind of excellent nonlinear optical crystals, which has been widely used in nonlinear optical and Inertial Confinement Fusion (ICF) engineering. KDP crystal with the characteristics of low hardness, high brittleness, easy deliquescence and temperature-sensitive is easy to crack during the crystal growth, taken out from crystallizer, and the process of slicing. Stress concentration caused by the initial internal stress redistribution and the growth defect in KDP crystal is an important reason of KDP crystal cracking during sawing process. The numerical simulation model of the KDP crystal containing spherical cavity defect and sawing with fixed abrasive wire saw is established by finite element method in this paper. The effects of initial internal stress, spherical cavity defect on sawing stress are investigated. The maximum tensile stress near the defect during the sawing process is simulated and analyzed. The results show that sawing stress changes smoothly during sawing process, and the fixed abrasive wire saw slicing belongs to low stress cutting way. The sawing stress at sawing kerf is increased obviously. The crystal defect leads to local stress concentration during sawing process. The coupling effect of sawing stress with initial internal stress and the effect of stress concentration are enhanced when the sawing kerf approaches to the defect.

Abstract: Temperature variation of KDP crystal is an important reason for its cracking. A finite element model was constructed to analyze temperature and thermal stress distribution of KDP crystal during wire saw slicing. The results showed that the highest temperature of the crystal which was located on the sawing kerf remained stable during slicing. The temperature inside the crystal rose slowly at the start of the slicing, and then tended steady with the continued increase of sawing depth. Because of the good cooling condition during the sawing process, the overall rise in temperature was small, and the maximum thermal stress on the sawing kerf was less than the tensile strength of KDP crystal, so temperature variation during slicing had little effect on crystal cracking.

Abstract: The machining quality of rolling bearing raceway has an important impact on bearing life. In this paper, the finishing experiment equipment of rolling bearing raceway is built and the mechanical and electrochemical mechanical experiments are conducted. The impact of clearance between cathode and workpiece, the rotation speed and the abrasive grain size on electrochemical mechanical machining quality is analyzed. The surface roughness decreases from Ra0.20μm to Ra0.04μm through electrochemical mechanical machining. The surface morphology of workpiece after finishing is observed. Contrast with the surface morphology after conventional mechanical polishing, the surface after electrochemical mechanical finishing is more suitable to the bearing raceway.

Abstract: For the purpose of obtaining mathematical force model in grinding process, the contacting grain numbers and the single grain forces should be taken into considered. In this paper, a mathematical model was established for single grain forces calculation. A Matlab program is edited and the calculation results were obtained and discussed. In the work of this paper, only plowing and cutting forces were take into considered because that the sliding forces were proved to be neglected based on Hertz contact theory. Because of different micro-interacting mechanisms of plowing and cutting grains with workpiece material, different force models were developed separately.

Abstract: Sliding and plowing are discriminated based on Hertz contact, and the grain number statistics model is established considering that grain size and abrasive protrusion height fit normal distribution. The analysis shows that less than 5% of grains are contacting with workpiece in the grinding arc, about 96% of contacting grains plow and about 4% cut. Sliding grains accounting for contacting grains is about 0.2%, which is almost negligible.

Abstract: This paper introduces the structure of the resin bonded abrasive wire saw manufacture equipment. The equipment can complete the process of the wire saw production, including uncoiling wire, cleaning wire, binder coating, Pre-curving and coiling wire. Wire saw are manufactured successfully by this equipment in the manufacture experiment. The quality of the wire saw was examined by SEM. The average slicing ability of the wire saw is 205 mm2 per meter in the experiment of KDP crystal slicing.

Abstract: The high temperature in grinding hardening induces workpiece thermal deformation. The thermal deformation causes a concavity on the ground profile and affects the grinding hardening depth. The paper uses ANSYS thermo-mechanical coupling module to simulate the thermal deformation in grinding hardening. The workpiece profile by simulated is compared with the test result.

Abstract: Elastic tube bundles are universally used in heat transfer enhancement by flow-induced vibration in heat exchangers, and the study of the heat transfer performance is of importance. The structure of conical spiral tube bundle heat exchanger was introduced first, and the structure of pulsation flow generator was also introduced. The frequency of pulsation flow was discussed. Finally, in condition of same shell side diameter, the heat transfer and natural frequency of the conical spiral tube bundle were compared with the planar elastic tube bundle. The results show that the natural frequency of conical spiral tube bundle was smaller, the heat transfer performance of conical spiral tube bundle was better than the planar elastic tube bundle.

Abstract: Elastic tube bundles are universally used in heat transfer enhancement via the flow-induced vibration in heat exchangers, and the study of the tube vibration characteristic is essential. The natural vibration of multiple conical spiral tube bundles was discussed in this paper based on numerical simulation. The substructures of ten conical spiral tubes, the inlet and the outlet branch were set up individually. Then the mass matrix and the stiffness matrix of these substructures were calculated. The general matrices were obtained and the vibration equation of the overall structure was founded. The results show that the natural frequencies of the multiple conical spiral tube bundles are smaller than the traditional planar elastic tube bundles and each natural vibration mode has a frequency band, which contains several natural frequencies.