Study On The Predision Cuttinh Ability Of Istropic Purolytic Graphite

Isotropic pyrolytic graphite is gradually used in aero-engine turbine shaft seals dues to its light weight, high thermal conductivity, low coefficient of friction, low liner expansible coefficient, high heat resistance, excellent thermal shock resistance and good chemical stability. But the isotropic pyrolytic graphite is a kind of typical brittle material. The fragmentary phenomena of the edge, low machining surface finish, low productivity and cutting tool wears seriously are occurred during the cutting process. It is the key for us to improve the productivity and surface quality to use the new methods for processing it.The nano-mechanical properties of isotropic pyrolytic graphite is the foundation of precision cutting. The nano-mechanical properties such as Young’s modulus E; the Plastic Property,Hardness H, are obtained by analyzing the load - displacement curve which is obtained through the indentation experiment. The three-dimensional finite element model of indentation process was developed based on the law of Saint-Venant Principle and the material properties which were obtained by the indentation experiments. The process of indentation was simulated by ABAQUS finite element analysis software. The plastic property of this material was obtained. During the loading and unloading processes the stress distributions was also obtained.Firstly this paper resorts to fracture mechanics and dislocation mechanics, interaction process of cracks and dislocation were simulated through the MATLAB software. The simulation results indicated that there existd optimal loading conditions under which the istropic pyrolytic graphite plastic deformation plastic deformation was involved more easily. Then using the simulation results to research the effect of rake angle on the istropic pyrolytic graphite’s brittle-ductile transition. The optimal rake angle was given. The results were validated through precision cutting experiments.Then the precision cutting experiments were studied. The laws of surface roughness and cutting force by changing cutting speed, feed rate, cutting depth, and the reasons were analyzed. The feed rate had the biggest effect on surface roughness. The cutting force and the surface roundness reduced with the feed rate decreased off.Finally tool wear not only affects surface quality but also influences the sealing performance of sealing rings. In order to study the mechanism of the diamond at the differernt period during the cutting process ,the single factor experiment was carried. It showed that the main wear mechanisms were typically mechanical wear, abrasive wear, micro grooves wear, cutting edge erosion wear and possible adhesive wear, oxidation wear.