Papers by Author: C.Y. Gao

Abstract: The high-speed metal cutting process is analyzed by finite element (FE) method in order to understand the effects of the cutting speed on the thermomechanical responses of workpiece materials. The reliability of numerical simulation is firstly validated by comparing the simulated cutting force with experimental data. Then a series of FE simulations are carried out to reveal the effects of the cutting speed on three key cutting state variables. The cutting force varies with the cutting speed and shows a minimum inflexion at 10 m/s. The maximum temperature in the secondary deformation zone increases gradually with the cutting speed and finally tends to a steady value. The residual stress decreases with the cutting speed as a whole. Thus high speed cutting can improve surface machining precision of product. Besides, it is found that the high residual stress mainly concentrates in the topmost surface layer with a depth of 0.1 mm and sharply decreases to a low level beyond the layer.

Abstract: In this paper, a new approach to damage tolerance determination, which is related to the critical rupture strain, is proposed for cylindrical shells subjected to inner transient high-pressure loading. The relation of damage variable and circumferential plastic strain is deduced on the basis of a damage evolution equation as well as a simplified dynamic viscoplastic constitutive equation. The value of damage variable can be obtained then if the strain is known by strain measurement, and the damage tolerance just corresponds to the rupture strain of the structure. Further, the damage tolerance has been applied as the strain-based rupture criterion in the FE simulation of the dynamic fracture process for transient-pressurized cylindrical shells. Especially for the notched shells, the strain concentration effect of notches on the rupture criterion is analyzed quantitatively.

Abstract: Fourier transform profilometry in 3-D measurement based on wavelet digital filter is presented in this paper. Before phase demodulation, original modulated grating image is handled with wavelet transform in order to remove the background components and high frequency. This method resolves spectrum overlapping at some extent and reduces the requirement of low-pass filter.