Based on a dynamic analysis method and an explicit algorithm,a dynamic explicit finite element code was developed for modeling the fast upsetting process of block under drop hammer impact,in which the hammer velocity ...Based on a dynamic analysis method and an explicit algorithm,a dynamic explicit finite element code was developed for modeling the fast upsetting process of block under drop hammer impact,in which the hammer velocity during the deformation was calculated by energy conservation law according to the operating principle of hammer equipment.The stress wave propagation and its effect on the deformation were analyzed by the stress and strain distributions.Industrial pure lead,oxygen-free high-conductivity (OFHC) copper and 7039 aluminum alloy were chosen to investigate the effect of material parameters on the stress wave propagation.The results show that the stress wave propagates from top to bottom of block,and then reflects back when it reaches the bottom surface.After that,stress wave propagates and reflects repeatedly between the upper surface and bottom surface.The stress wave propagation has a significant effect on the deformation at the initial stage,and then becomes weak at the middle-final stage.When the ratio of elastic modulus or the slope of stress-strain curve to mass density becomes larger,the velocity of stress wave propagation increases,and the influence of stress wave on the deformation becomes small.展开更多
Mechanical analysis of cylinders being upset between spherical concave platen and concave supporting plate is conducted. Rigid-plastic mechanical models for cylinders are presented. When the ratio of height to diamete...Mechanical analysis of cylinders being upset between spherical concave platen and concave supporting plate is conducted. Rigid-plastic mechanical models for cylinders are presented. When the ratio of height to diameter, is larger than 1, there exists two-dimensional tensile stress in the deformed body, when the ratio is smaller than 1, there exists shear stress in static hydraulic zone. The former breaks through the theory that there is three-dimensional compressive stress irrespective of any ratio of height to diameter. The latter satisfactorily explains the mechanism of layer-like cracks in disk-shaped forgings and the flanges of forged gear axles. The representation of the two models makes the upsetting, theory into correct and perfect stage.展开更多
文摘Based on a dynamic analysis method and an explicit algorithm,a dynamic explicit finite element code was developed for modeling the fast upsetting process of block under drop hammer impact,in which the hammer velocity during the deformation was calculated by energy conservation law according to the operating principle of hammer equipment.The stress wave propagation and its effect on the deformation were analyzed by the stress and strain distributions.Industrial pure lead,oxygen-free high-conductivity (OFHC) copper and 7039 aluminum alloy were chosen to investigate the effect of material parameters on the stress wave propagation.The results show that the stress wave propagates from top to bottom of block,and then reflects back when it reaches the bottom surface.After that,stress wave propagates and reflects repeatedly between the upper surface and bottom surface.The stress wave propagation has a significant effect on the deformation at the initial stage,and then becomes weak at the middle-final stage.When the ratio of elastic modulus or the slope of stress-strain curve to mass density becomes larger,the velocity of stress wave propagation increases,and the influence of stress wave on the deformation becomes small.
基金National Natural Science Foundation of China(No.59235101)
文摘Mechanical analysis of cylinders being upset between spherical concave platen and concave supporting plate is conducted. Rigid-plastic mechanical models for cylinders are presented. When the ratio of height to diameter, is larger than 1, there exists two-dimensional tensile stress in the deformed body, when the ratio is smaller than 1, there exists shear stress in static hydraulic zone. The former breaks through the theory that there is three-dimensional compressive stress irrespective of any ratio of height to diameter. The latter satisfactorily explains the mechanism of layer-like cracks in disk-shaped forgings and the flanges of forged gear axles. The representation of the two models makes the upsetting, theory into correct and perfect stage.
