Key Engineering Materials Vols. 375-376

Abstract: Based on loads analysis and failure analysis for high speed face milling cutter with indexable inserts, the failure criterion of cutter was propounded, and the finite element model of cutter was established. By means of modal analysis and stress field analysis, the law of influence of the structure and elements of cutter on the safety of cutter was acquired, high speed face milling cutter for machining aluminum alloy was developed. According to ISO15641 international standard, safety prediction of cutter and experiments were completed. The results indicate that rigidity failure rotational speed is higher strength failure rotational speed of high speed face milling cutter, connection strength between cutter body and screw bolt affects directly the safety rotational speed of cutter. High speed face milling cutter for machining aluminum alloy possesses higher safety and better dynamic milling performance as cutting speed is less than 2820m/min.

Abstract: A processing method based on wavelet transform for the monitoring signals of grinding wheel dull is presented. The noise-falling method based on wavelet transform is used to process AE signals, grinding force signals and the electric current signals of main axis motor produced in grinding process, and the processing results can be used to identify grinding wheel state. Test result indicates that the grinding wheel state can be identified exactly by these three kinds of signal characteristics, and have higher identified precision.

Abstract: The principle of laser peen forming (LPF) is introduced, the loading model of laser shock wave is established. This paper focuses on applying finite element analyses, instead of a complicated experimental procedure, to predict the development, magnitude and distribution of residual stresses induced by laser impacts on a metal plate, and dynamic process of laser continuous peen forming is realized with the FEM code ABAQUS. Based on the numerical analysis, the laser processing parameters can be optimized and the deformation contour of metal plate can be analyzed. The results calculated by the finite element method are correlated well with the available experimental results. The simulated results also reveal that adjusting the laser energy appropriately can result in an anticipated shape of plate in LPF process.

Abstract: A novel quantitative shadow testing equipment is presented based on the digital imageprocessing technique for characterizing local surface deformations on optical surface. Two magnetic stepping motors control the positions of the knife-edge for cutting the wave-front reflected back from the aspheric surface separately. At each position of the knife-edge blocking the image on the focal plane, it is recorded and analyzed by an image-processing set-up behind the knife-edge under computer control. Based on a group of images recorded, the analysis of local slopes is performed by picking up characteristics of illumination levels. Further the relationship between the changes of illumination level and deformations on surface is built on the principle of Fourier Optics. The results of tests approve that the method is effective on determining the characteristics of two parabolic surfaces using magnetorheological finishing.

Abstract: The balance precision of grinding wheel is a key technical parameter in ultra-high speed grinding process. The actual standard for the balance precision of rigid rotor is not fit for the thin ultra-high speed grinding system well. The unbalance factors affected on the ultra-high speed grinding wheel and its system were analyzed, and its effects on the machining quality in the process were also discussed. The theory and select principle of the balance precision for ultra-high speed grinding wheel system were studied. The test of dynamic performance was performed for the thin ultra-high speed CBN grinding wheel system whose structure was optimized. The groundwork to establish the standard of balance precision for thin ultra-high speed grinding system was offered.

Abstract: Multiple clamps are frequently used to serve the purpose of workholding in a fixture. So multiple clamping forces including their magnitudes, placements and application sequences, greatly influence contact forces and workpiece machining accuracy. In this paper, the impact of multiple clamping forces on workpiece location error is formulated analytically for a workpiece-fixture system. The proposed model takes into account the varying contact forces and friction force during entire clamping operation. It reveals that the historical accumulation of clamping steps influences heavily the final distribution of contact forces in the workpiece-fixture system. In addition, based on effect of contact forces from one step to another on workpiece location, a novel design model is presented to optimize the multiple clamping forces in order to minimize the workpiece location errors. Some numerical tests are finally demonstrated to validate the proposed model and approach.

Abstract: For detecting gradual tool wear state on line, the methods of Wavelet Fuzzy Neural Network, Regression Neural Network and Sample Classification Fuzzy Neural Network by detecting cutting force, motor power of machine tool and AE signal respectively are presented. Although these methods are not difficult to come true and processed accurately and rapidly, it is difficult to obtain comprehensive information of machining and exact value of tool wear when using single method of intelligent modeling and single signal detecting. For this purpose, fuzzy inference technique is adopted to fuse the recognized data. Emulation experiment is carried out by using Matlab software platform and this method is verified to be feasible. Experimental result indicates that by applying fuzzy data fusion, we can get an exact tool wear forecast rapidly.

Abstract: Static and dynamic characteristic of carbon nanotube is analyzed by molecular dynamic simulation. Static analysis show that maximum deflection of carbon nanotube appears at 0.033nm distance from free end of cantilever. When the value of driving voltage is less, the flexibility is more important, then the stiffness increase with the voltage increasing, and the collapse structure or hole appear on carbon nanobute. Under low pressure condition, deflection difference on equi-increase of pressure between no damping and damping simulation is larger than that on high pressure. The results of forced vibration indicate that system response consist of transient and steady-state response. With steps of molecular dynamic simulation increasing, transient response disappears gradually, so system response includes only steady-state response, which is simple harmonic vibration with the same frequency as excitation force. These results are in accord with the classical vibration theory. Moreover they will provide theoretic foundation for designing of nanostructure device.

Abstract: In order to meet the requirements of high speed turning, modern power operated jaw-chucks with centrifugal force compensation (CFC) were developed by some chuck producers. Based on the force and deformation analysis of the clamping system, a new analytic computation model of dynamic clamping force for modern chuck with CFC was developed, and verified by means of experimental investigations. The clamping behaviours during high speed turning, such as the loss of dynamic clamping force, centrifugal force compensation efficiency and clamping force hysteresis are investigated. Some problems of design and application of modern chuck with CFC are discussed. The study results provide reliable theoretic and technical supports to reasonably utilize the potential of modern chucks at higher rotational speed and guarantee a safe high speed turning process.

Abstract: To assure reliable locking and normal deployment of large space-born appendages, a type of lock-unlock mechanism driven by spring was proposed. The spiral spring was used as a retraction device to draw the clamp-band back due to its characteristics of storing much more energy in limited space. Centralized lock-unlock scheme was employed here to light down mass of the whole mechanism. Reliable retraction of the clamp band and no collision on the surface of satellite are inspection targets of retraction device. Effect on retraction track by varying the torque and mass of clamp band was presented in this paper. To some spaceborne flexible arm, simulation of retraction track was done under specified parameters. The result obtained from simulation reveals that clamp band can accomplish safely and reliably, and will not produce any spatial waste.