Papers by Keyword: Stability Prediction

Abstract: To classify quantitatively the topological structure of all carbon fullerene molecules (fullerene graphs) we suggest a novel two-step method based on the following concept: As a first step, the duals of the fullerene graphs are generated, and as a second step, by using two molecular descriptors called Zagreb indices, we construct appropriately defined topological indices for structural characterization of fullerene isomers. Performing comparative tests on the set of C40 fullerene isomers, it will be demonstrated that the method suggested can be efficiently applicable to the stability prediction of fullerene-like materials.

Abstract: The flutter in the hard cutting has a significant impact on the efficiency of production, the quality processed, the environment in processing, the cost, and the life of the machines and tools . However, the application of the method named numerical simulation in MatLab predicted the stability limitation of the hard cutting system, analyzed the influence of cutting system dynamics parameters on the stability limitation of system, at the same time, an experimental verification of hard cutting had been carried out. And the results of analysis showed that improving the system stiffness K and cutting system damping ratio ζ, cutting the stiffness coefficient K_c and the direction coefficient , adjusting the cutting speed to the correct, reducing the amount of turning a_p, decreasing the tip radius of circular arc , increasing the feeding f can be used as the methods of vibration reducing in the system. So the results of the research provide reference for the reasonable choice of cutting parameters.

Abstract: In order to forecast the stability of deep roadway and optimize the parameters of bolts, the complex stress environment and the multivariate surrounding rocks characteristics of deep roadway were analyzed. Then the classification prediction method and the numerical simulation method were simultaneously used to analysis the stability of surrounding rocks. Furthermore, the supporting parameters of bolts were also designed optimally. It was shown that the characteristics of stress distribution, deformation and failure zone of surrounding rocks are not ideal. So it is necessary to optimize the supporting parameters of deep roadway. All these research findings will provide the theory basis for bolts of deep roadway and will ensure the optimization of bolts and the stability of deep roadway in the long run.

Abstract: A common problem in the aeronautical industry is the chatter vibration due to the lack of dynamic stiffness in the milling of thin walls and thin floors. The present work proposes a method for chatter avoidance in the milling of flexible thin floors with a bull nose end mill. It allows the calculation of the thickness previous to finish milling or the minimum dynamic stiffness that the floor must have to avoid the chatter vibration appearance. To obtain these values, the stability model algorithm has been inverted to estimate the thickness or the dynamic stiffness required in a floor to allow a stable milling. This methodology has been validated satisfactorily in several experimental tests.

Abstract: . A method for the structural classification of fullerenes via graph invariants is presented. These graph invariants (called edge-parameters) represent the 9 different types of bonds existing in fullerenes between two neighbouring carbon atoms and they are also applicable to classify the fullerene isomers into equivalence classes. Discriminating performance of edge-parameters has been tested on the sets of C40 and C66 fullerene isomers. It is shown that the stability of C40 and C66 isomers can be efficiently predicted using a novel topological descriptor (Ω) defined as a function of four appropriately selected edge parameters.

Abstract: Chatter problems occurring during high speed milling affect the quality of the finished workpiece and, to a lesser extent, the tool life and the spindle life. Therefore, the prediction of stable milling regions is a critical requirement for high speed milling operations. In this paper, a dynamic model of a high speed spindle system considering the multi-mode dynamics is elaborated for the purposed of stability prediction. A stability lobes diagram (SLD) shows the boundary between chatter-free machining operations and unstable processes, in terms of axial depth of cut as a function of spindle speed. These diagrams are used to select chatter-free combinations of machining parameters. The proposed method enables a new stability lobes diagram to be established that takes into account the effect of spindle speed on multi-mode dynamic behavior.

Abstract: High-speed milling (HSM) which is characterized as high productivity and low power consumption can be widely used in the manufacture industry. However, while the speed of spindle-tool reach the high speed range, the prediction of its stable milling faces more difficulties, as the gyroscopic effects become prominent. In this paper, a dynamics model of HSM system was set up considering the influence of gyroscopic moment due to high rotating speed of spindle-tool. Then a method was proposed by transforming time-varying stiffness system into fixed-step time invariant one. Finally the stability lobes diagrams (SLD) was elaborated. The results shows that the gyroscopic effects due to high rotating speed have non-negligible impact on the stability limitation, which must be considered for the predicting of stability limit in the high speed milling.