Hourglass is remarkably aroused in ring rolling simulation with reduced integration element because of violent ring vibration and small contact area of ring with forming rollers. Hourglass energy can be reduced by imp...Hourglass is remarkably aroused in ring rolling simulation with reduced integration element because of violent ring vibration and small contact area of ring with forming rollers. Hourglass energy can be reduced by improving mesh density. Combined approach of artificial damping and artificial stiffness can control the hourglass. A ring with rectangular section is simulated with the weight factor of artificial stiffness resistance set to 0.2. The artificial damping hourglass control coefficient is set to 0.1, and the artificial stiffness hourglass control coefficient is set to 0.001. The ratio of hourglass energy to internal energy is reduced to 2.5 percent. Compared with axial spread width test, the effectiveness of hourglass control in ring rolling simulation is verified.展开更多
In this paper one-point quadrature'assumed strain'mixed element formulation based on the Hu-Washizu variational principle is presented.Special care is taken to avoid hourglass modes and volumetric locking as w...In this paper one-point quadrature'assumed strain'mixed element formulation based on the Hu-Washizu variational principle is presented.Special care is taken to avoid hourglass modes and volumetric locking as well as shear locking.The assumed strain fields are constructed so that those portions of the fields which lead to volumetric and shear locking phenomena are eliminated by projection,while the implementation of the proposed URI scheme is straightforward to suppress hour- glass modes.In order to treat geometric nonlinearities simply and efficiently,a corotational coordinate system is used.Several numerical examples are given to demonstrate the performance of the suggested formulation,including nonlinear static/dynamic mechanical problems.展开更多
This paper presents a detection method for hourglass worm based on follow-up pre-positioning technolo-gy, by establishing theoretical model of the corresponding relation between the movements of the worm and theprobe....This paper presents a detection method for hourglass worm based on follow-up pre-positioning technolo-gy, by establishing theoretical model of the corresponding relation between the movements of the worm and theprobe. The probe coordinate of next sample point is mapped through the actual motion coordinate measured ateach sample point. And then the probe is located to the next sample point in advance by using the precision mo-tion control based on time subdivision. This detection method can realize online servo measurement for machiningerror of hourglass worm and actual space spiral measurement under specific throat radius. The actual surface con-tour of hourglass worm is constructed by helixes in different throat radiuses, then the machining error can be ob-tained by comparing the contour with theoretical model. The detection system, which includes host and slave sub-systems, is designed according to this method.展开更多
基金Supported by National Natural Science Foundation of China Key Project (50335060)
文摘Hourglass is remarkably aroused in ring rolling simulation with reduced integration element because of violent ring vibration and small contact area of ring with forming rollers. Hourglass energy can be reduced by improving mesh density. Combined approach of artificial damping and artificial stiffness can control the hourglass. A ring with rectangular section is simulated with the weight factor of artificial stiffness resistance set to 0.2. The artificial damping hourglass control coefficient is set to 0.1, and the artificial stiffness hourglass control coefficient is set to 0.001. The ratio of hourglass energy to internal energy is reduced to 2.5 percent. Compared with axial spread width test, the effectiveness of hourglass control in ring rolling simulation is verified.
文摘In this paper one-point quadrature'assumed strain'mixed element formulation based on the Hu-Washizu variational principle is presented.Special care is taken to avoid hourglass modes and volumetric locking as well as shear locking.The assumed strain fields are constructed so that those portions of the fields which lead to volumetric and shear locking phenomena are eliminated by projection,while the implementation of the proposed URI scheme is straightforward to suppress hour- glass modes.In order to treat geometric nonlinearities simply and efficiently,a corotational coordinate system is used.Several numerical examples are given to demonstrate the performance of the suggested formulation,including nonlinear static/dynamic mechanical problems.
基金supported by National Natural Science Foundation of China ( No. 51127001)the Chongqing Postgraduate students research and innovation project ( No. CYS15218)
文摘This paper presents a detection method for hourglass worm based on follow-up pre-positioning technolo-gy, by establishing theoretical model of the corresponding relation between the movements of the worm and theprobe. The probe coordinate of next sample point is mapped through the actual motion coordinate measured ateach sample point. And then the probe is located to the next sample point in advance by using the precision mo-tion control based on time subdivision. This detection method can realize online servo measurement for machiningerror of hourglass worm and actual space spiral measurement under specific throat radius. The actual surface con-tour of hourglass worm is constructed by helixes in different throat radiuses, then the machining error can be ob-tained by comparing the contour with theoretical model. The detection system, which includes host and slave sub-systems, is designed according to this method.
