Microcosmic and macroscopic form of CFRP holes drilled by new PCD tool were observed in this paper. Location and distribution of burr and fiber direction of burr were analyzed, and formation mechanism of burr of CFRP hole exit is studied tentatively. The methods of inhibit the formation of burr formation were put forward from the design principles of the tool geometry parameters.
This paper puts forward a new method of pre-stress hard cutting which integrates pre-stress and hard cutting technology. A thermo-mechanical coupling model of Finite Element Analysis (FEA) for pre-stress hard cutting on material 42CrMo steel is established. In this model, chip-work separating is made by applying shear fracture failure criterion, element deletion and adaptive mesh technique based on arbitrary Lagrangian Eulerian (ALE) method. The key technology for FEA, such as intrinsic equation of workpiece material, chip separating criterion and friction model of tool-chip interface and thermal conduction equation are researched respectively. Then FE simulation of chip forming and cutting force in pre-stress hard cutting is made and relationship between pre-stress and residual stress on machined surface under various cutting conditions is got. Simulation result is compared with that of experiment and found they are good in accordance.
In this paper, modal analysis of ball end mills is modeled by finite element to work out natural frequency and chatter model in tooling system and to calculate the limit curve of stability in single degree freedom system. The effect of cutter flute length and cutter tooth number on limit curve of stability in single degree freedom system is also discussed. The research results show that steady critical cutting depth of milling system declines while the cutter flute length increases, but the trend is not linear, which shows increase partly. An engineering optimization design is made on milling cutter geometrical parameters based on this conclusion.
A cutting chatter forecast method based on continuous wavelet feature and multi-class spherical Support Vector Machines is studied in this paper. The method based on continuous wavelet transform extracts the cutting vibration signal feature and uses multi-class spherical Support Vector Machines to discern the chatter. In order to simplify computational complexity when binary classification SVM turn to multi-class classification, the algorithm makes every kind of samples have a spherical SVM. In the feature space identified the test sample and spherical SVM centre distance as a decision-making function. Experiments show that using combine spherical SVM with continuous wavelet feature Vector has good recognition effect in the milling chatter recognition system. Chatter inoculation forecast accuracy reaches 95%, and chatter outbreak forecast accuracy reaches 97.5%.
With the rapid development of static-press technique, multi-point constant oil supply system has been widely applied into bearing the work table of large CNC vertical turning machine. A group method has been proposed through the analysis of the operating principle, structural features and manufacturing method of multi-point gear flow dividers. Then the diversion characteristics of the twelve point gear flow dividers manufactured through this method are compared with those of the dividers alike both at home and abroad. The experimental results show that the multi-point gear flow dividers manufactured through this group method not only have good diversion accuracy , but reduce the manufacturing cost and assure workbench’s running stability as well as high quality and precision products.
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