In order to investigate the springback rules, the variation characteristics of physical property and microstructure in bending creep age forming process, a series of creep forming tests of 2124 aluminum alloy were con...In order to investigate the springback rules, the variation characteristics of physical property and microstructure in bending creep age forming process, a series of creep forming tests of 2124 aluminum alloy were conducted based on three kinds of single and double curvature forming tools. The results show that the spingback rate would be the minimum under the optimal coupling conditions among the temperature, aging time and internal stress state of material. Difference exists in the two directions of the formed sample with double curvature, but the curvature variation keeps the same. Yield strength, ultimate tensile strength and fracture toughness of the double curvature formed sample appear to be higher than those of the single curvature formed sample under the same aging condition, but the elongation and the anisotropy are opposite.展开更多
The meandering river is an unstable system with the characteristic of nonlinearity,which results from the instability of the flow and boundary.Focusing on the hydrodynamic nonlinearity of the bend,we use the weakly no...The meandering river is an unstable system with the characteristic of nonlinearity,which results from the instability of the flow and boundary.Focusing on the hydrodynamic nonlinearity of the bend,we use the weakly nonlinear theory and perturbation method to construct the nonlinear evolution equations of the disturbance amplitude and disturbance phase of two-dimensional flow in meandering bend.The influence of the curvature,Re and the disturbance wave number on the evolution of disturbance amplitude and disturbance phase are analyzed.Then,the spatial and temporal evolution of the disturbance vorticity is expounded.The research results show:that the curvature makes the flow more stable;that in the evolution of the disturbance amplitude effected by curvature,Re and the disturbance wave number,exist nonlinear attenuation with damping disturbances,and nonlinear explosive growth with positive disturbances;that the asymmetry distribution of the disturbance velocities increases with the curvature;that the location of the disturbance vorticity’s core area changes periodically with disturbance phase,and the disturbance vorticity gradually attenuates/increases with the decrease of the disturbance phase in the evolution process of damping/positive disturbances.These results shed light on the construction of the interaction model of hydrodynamic nonlinearity and geometric nonlinearity of bed.展开更多
基金Project(2010CB731700)supported by the National Basic Research Program of China
文摘In order to investigate the springback rules, the variation characteristics of physical property and microstructure in bending creep age forming process, a series of creep forming tests of 2124 aluminum alloy were conducted based on three kinds of single and double curvature forming tools. The results show that the spingback rate would be the minimum under the optimal coupling conditions among the temperature, aging time and internal stress state of material. Difference exists in the two directions of the formed sample with double curvature, but the curvature variation keeps the same. Yield strength, ultimate tensile strength and fracture toughness of the double curvature formed sample appear to be higher than those of the single curvature formed sample under the same aging condition, but the elongation and the anisotropy are opposite.
基金supported by the National Natural Science Foundation of China(Grant Nos.51979185 and 51879182)。
文摘The meandering river is an unstable system with the characteristic of nonlinearity,which results from the instability of the flow and boundary.Focusing on the hydrodynamic nonlinearity of the bend,we use the weakly nonlinear theory and perturbation method to construct the nonlinear evolution equations of the disturbance amplitude and disturbance phase of two-dimensional flow in meandering bend.The influence of the curvature,Re and the disturbance wave number on the evolution of disturbance amplitude and disturbance phase are analyzed.Then,the spatial and temporal evolution of the disturbance vorticity is expounded.The research results show:that the curvature makes the flow more stable;that in the evolution of the disturbance amplitude effected by curvature,Re and the disturbance wave number,exist nonlinear attenuation with damping disturbances,and nonlinear explosive growth with positive disturbances;that the asymmetry distribution of the disturbance velocities increases with the curvature;that the location of the disturbance vorticity’s core area changes periodically with disturbance phase,and the disturbance vorticity gradually attenuates/increases with the decrease of the disturbance phase in the evolution process of damping/positive disturbances.These results shed light on the construction of the interaction model of hydrodynamic nonlinearity and geometric nonlinearity of bed.
