Papers by Author: Pei Qi Ge

Abstract: A wire-saw cut KDP crystal geometrical model was founded and a mathematical model was established to calculate the grit average cut depth, based on indentation fracture mechanics theory(IFMT). The relationship between the grit cut depth and wire saw process parameter was analyzed theoretically. The research results indicate that there exists an approximate monotone increasing non-linear correlation between grit average cut depth and the ratio i value of crystal feed speed and wire speed. By increasing the wire speed and crystal feed speed accordantly, the value of i can be maintained invariable, however, this way can simultaneously bring higher machined surface quality and machining efficiency.

Abstract: The invariable heat flux is always loaded in temperature simulation for grind-hardening. The heat flux is time-variant in actual process. The paper uses experiment result of grinding force to calculate out the time variation heat flux. The grinding temperature is simulated based on time variation heat flux by ANSYS software. The variation tendencies for the grinding force and the simulated surface top temperature will be discussed.

Abstract: The characteristic of flow-induced vibration and heat transfer of a cylinder with elastic supporting in two-dimensional fluid flow was numerically investigated by Workbench and CFX software. The numerical results show that, in the same conditions, the greater elastic support stiffness of the cylinder is ,the greater the value and range of fluid speed where the vortex-induced vibration of a circular occurs; With the same elastic support stiffness, the frequency and amplitude of flow-induced cylinder vibrating along transverse direction are much greater than that of in in-line direction(longitudinal direction), and the value and range of fluid speed where the vortex-induced vibration along longitudinal direction of a cylinder occurs is much smaller than that of along transverse direction. When the max vibration velocity of cylinder is much less than the flow speed, the flow-induced cylinder vibration can not reach the effect of heat transfer enhancement.

Abstract: The grinding heat is utilized to induce martensitic phase transformation and strengthen the surface layer of alloy steel by raising surface temperature higher than austenitic temperature and cooling quickly. The surface residual stress is an important factor to evaluate the quality of surface hardening layer effectively. The experimental values of residual stress in the surface hardened layer are achieved by using X-ray diffraction method and corrosion stripping method. The numerical values of residual stress are simulated by using re-meshing and finite element method. The simulation values trend of residual stress in surface hardened layer is consistent with experimental results.

Abstract: A mathematical model to calculate the grit average cut depth in wire sawing single crystal silicon was founded. So the grit average cut depths were calculated theoretically by choosing different process parameters, and influences of process parameters on grit cut depths of slicing silicon crystal were analyzed. Analysis results indicate that the grit average cut depth relates to the silicon mechanical properties, grit shape and size, wire speed and ingot feed speed, etc. And there is a monotone increasing non-linear correlation between grit average cut depth and the ratio i value of ingot feed speed and wire speed, when the i value is lower, the average grit cut depth is lower.

Abstract: The purpose of this paper is to modify the resin binder for developing resin-bonded diamond wire saw. The optimization of components with different ratios in the resin binder was investigated using orthogonal design experiments. Besides, the resin-bonded diamond wire saw was developed using the piano wire (the diameter is 0.2mm), the modified resin and the diamond abrasive (the diameter is 20~30μm). Good surface quality and slicing performance were obtained when slicing silicon crystal using the resin-bonded diamond wire saw we made in the experiments.

Abstract: Grind-hardening is a new integrated machining technology which utilizes grinding heat to quench the non-quenched steel directly. In this paper, the technology is applied in the process of rack form grinding. A comprehensive numerical model is developed to simulate the temperature distributions of the rack under the dry grind-hardening conditions with finite element method(FEM). The temperature dependency of the thermal properties, the triangular heat distribution of the heat flux, latent heat and the air convection are taken into account. The simulated hardness penetration depth(HPD) is deduced from the local temperature distribution, time history of workpiece according to martensitic phase transformation theory. This provides a reliable method for the proper selection of process parameters in order to produce enough heat at the contact zone, enabling the treatment of the rack.

Abstract: Based on the method of the statistical probability, the theory forecasting model of grinding force is modified analytically. The calculated force is used as an input factor to calculate the heat flux. Then the transient grinding temperature field is simulated using the finite element analysis (FEA). An infrared imaging system for a full area temperature measurement is used to validate the numerical model. Additionally, the experimental results are synthesized with the simulation results to analyze the temperature field and the hardness penetration depth (HPD). The distribution of the temperature field and the stability of the grind-hardening process are discussed, which could provide a reliable forecasting method for optimizing the grind process and controlling the hardening effects forwardly.

Abstract: The heat partitioning to workpiece is an important parameter, which affects the grind-hardening technology. In this paper, the heat sources positions, which are around the grain, are analyzed. Ignoring the heat source produced in chip-grain interface, the heat partition model is established based on heat source position produced in grain-workpiece interface and the chip-workpiece interface. The heat partition is validated by using of finite element method and the experimental method. The results indicate the heat partition model can be used in grind-hardening temperature calculation.

Abstract: Based on reciprocating electroplated diamond wire saw (REDWS) slicing experiments, a study on REDWS machining brittle-ductile transition of single crystal silicon was introduced. The machined surfaces and chips were observed by using Scanning Electron Microscope (SEM), and some experimental evidences of the change of material removal mode had been obtained. The experimental results indicate there is a close relationship between material removal mode and the ratio r value of ingot feed speed and wire speed, through controlling and adjusting the r value, the material removal mode can be complete brittle, partial ductile and near-ductile removal.