Materials Science Forum Vol. 723

Abstract: A 3D finite element polycrystalline microstructure model of ceramic tool materials is presented. Quasi-static crack propagation is modeled using the cohesive finite element method (CFEM) and the microstructure is represented by 3D Voronoi tessellation. The influences of cohesive parameters, the ratios of maximum traction of grain boundary to maximum traction of grain on the crack patterns of Al2O3 have been discussed. This study has demonstrated the capability of modeling 3D crack propagation of ceramic microstructure with CFEM and Voronoi tessellation model. It is found that the fracture mode is changed from intergranular to transgranular as the maximum traction of grain boundary is increased.

Abstract: The thin-walled blade of aero engine has low stiffness, during machining, it easily generates deflection due to the milling force, but because high accuracy of such component is required, the prediction of the deflection exactly becomes extremely important. Therefore, this paper analyzes the milling process, and simplifies it reasonably. The deformation of the blade is predicted based on ABAQUS using FEM, and then the machining deflection curves of the blade is got. The result is analyzed soon afterwards, and deflection law is summarized. Finally, an experiment has been designed. The reliability of the method of predicting deflection is proved by comparing the measurement results and the simulation ones.

Abstract: Five-axis high speed machining can improve the efficiency and accuracy obviously, but the machining errors and tool interference are likely to happen due to the complexity of tool motion. So the collision detection and verification of tool path are very important and necessary before machining the part. Using a combination of process simulation and collision detection based on image analysis, a rapid detection approach is developed in this research. The geometric model provides the cut geometry for the collision detection and records a dynamic geometric information for in-process workpiece. For the precise collision detection, a strategy of image analysis method is developed in order to make the approach efficient and maintian a high detection precision. An example of five-axis machining propeller is studied to demonstrate the proposed approach.

Abstract: Material constitutive equation plays an important role in Finite Element Analysis (FEA) of metal cutting process. This paper proposes a method to obtain parameters for Power Law model of a Japanese type of alloy steel (SCM440H) for 3-D FEA of face milling process, involving pressure bar experiments and orthogonal metal cutting experiments. Since pressure bar test cannot reach the high strain rate occurred in cutting process, orthogonal cutting experiment was combined to obtain parameters for material model. By this method, the ideal parameters for FEA of the face milling process were finally determined. Face milling experiments were performed to verify the accuracy of the model built.

Abstract: Turbine blade plays an important role in aero engine and power generation equipment. As thin-walled and free-form surface component, deflection in spiral milling of turbine blade is common, which result in bad dimensional precision. In this paper, a five-axis milling experiment was firstly conducted to get the cutting force components. Then, deflections were studied at different positions. The results show that compensation can be made based on the FEM analysis.

Abstract: BP neural networks model which was used to predict the rang of breaking chip of 3D complex groove turning inserts was established, then training and testing of the network was realized with MATLAB, finally ,range of breaking chip of the insert which was designed by the author was predicted. Percentage of accuracy of predicting results reached 91.67% comparing with the chip breaking experiment. This indicates that neural networks can be used to predict rang of breaking chip of turning inserts, so, saving the inserts which is used for cutting experiments and work of experiments, reducing the periodic time of inserts designing and development, increasing the competitive strength of inserts.

Abstract: To solve the difficult problem of NC machining of closed blisk, the paper combines with the structure characteristics of processing surface and the characteristics of Channel processing, and at the same time to study the technology of processing impeller channel tool path planning. By planning different processing methods of tool axis control for different processing parts, take outer arc processing as an example, tool path planning method is analyzed. By the method to generate the ruled envelope surfaces in view of blade offset surfaces, to put forward new methods of dividing plunging region. The method of surface offset was applied to determine the safety space of tool axis movement. To determine the range of tool axis angle by the relationship between the boundary curves and division the processing area by the tangent method. Finally, The results of tool path planning were verified by using five-axis processing, which proved the reasonability and feasibility of the scheme.

Abstract: According to the principle of the experimental modal analysis, this study is based on tool system of the MIKRON UCP 710 numerical control machining center as test object for experimental modal analysis. Using the integral polynomial recognition method to identify the modal parameters (natural frequency, structural damping, and modal shape), and finally matching the results with the vector analysis method and the finite element simulation method. The results show that integral polynomial recognition method has higher precision than the vector analysis method to identify the multi-degree of freedom system; the experimental modal analysis can also obtain better modal parameters of the structure system, and a higher precision than the finite element simulation method. Obtained the MIKRON UCP 710 high-speed milling center tool system accurate modal parameters provides the necessary theoretical and experimental basis for the further study of the stability properties in the cutting processing of the high speed machining tool system.

Abstract: The finite element physical model of the high-manganese steel drilling has been established on Johnson-Cook (J-C) constitutive equation derived using experimental methods. Through simulation, the variation of drilling force and heat is given and stress and temperature nephograms in cutting zone is obtained. A comparative study of the experimental data and simulation values is carried out using drilling force measurement system self-designed and developed, which proves the accuracy and reliability of simulation results and the model.

Abstract: Surface machining has become a difficult problem in aviation manufacturing, we always using ball-end mills, it is easy to determine the tool position in five-axis machining, but because of the large program, low material remove rate, the processing cycle long, and the surface accuracy is also poor. The paper suggests using the flat-end mill to strip width machining. Using this way, the CNC program is shorter, surface quality is better, the most import is reducing the machining time obviously. Now this method only used in the simple surface, so it requires further research.