The aerodynamics of 2-dimensional flexible wings in bees' normal hovering flight is studied. Four insect flapping flight coordinate systems, including a global system, a bodyfixed system, a rigid wing-fixed system an...The aerodynamics of 2-dimensional flexible wings in bees' normal hovering flight is studied. Four insect flapping flight coordinate systems, including a global system, a bodyfixed system, a rigid wing-fixed system and a flexible wingfixed system, are established to represent the insects' position, gesture, wing movement and wing deformation, respectively. Then the transformations among four coordinate systems are studied. It is found that the elliptic coordinate system can improve the computation accuracy and reduce the calculation complexity in a 2-dimensional rigid wing. The computation model of a 2-dimensional flexible wing is established, and the changes of the force, moment, and power are investigated. According to the computation results, the large lift and drag peaks at the beginning and end of the stroke can be explained by the superposition of the rapid translational acceleration, the fast pitching-up rotation and the Magnus effect; and the small force and drag peaks can be explained by the convex flow effect and the concave flow effect. Compared with the pressure force, pressure moment and translational power, the viscous force, viscous moment and rotational power are small and can be ignored.展开更多
Tensile stress-strain curves of five metallic alloys,i.e.,SKH51,STS316L,Ti-6Al-4V,Al6061and Inconel600were analyzed to investigate the working hardening behavior.The constitutive parameters of three constitutive equat...Tensile stress-strain curves of five metallic alloys,i.e.,SKH51,STS316L,Ti-6Al-4V,Al6061and Inconel600were analyzed to investigate the working hardening behavior.The constitutive parameters of three constitutive equations,i.e.,the Hollomon,Swift and Voce equations,were compared by using different methods.A new working hardening parameter was proposed to characterize the working hardening behavior in different deformation stages.It is found that Voce equation is suitable to describe stress-strain curves in large strain region.Meanwhile,the predicting accuracy of ultimate tensile strength by Voce equation is the best.The working hardening behavior of SKH51is different from the other four metallic alloys.展开更多
The velocity variable of a noise oscillator as an internal or external noise is proposed, the spectrum of which is quite different from that of the coordinate variable of the same noise oscillator. The former leads to...The velocity variable of a noise oscillator as an internal or external noise is proposed, the spectrum of which is quite different from that of the coordinate variable of the same noise oscillator. The former leads to ballistic diffusion for a free particle in long time limit and the asymptotical results of the system are sensitive to the initial condition. However, diffusion process induced by the coordinate of noise oscillator is a normal one and depends on the initial condition only in the transient time. This allows us to classify two kinds of non-Markovian processes: normal one and strong one, just like the processes induced by the coordinate and the velocity of noise oscillator, respectively.Applying to a correlation ratchet, we have found that the steady current of a particle subjected to the velocity of noise oscillator is opposite to that subjected to its coordinate, thus the former shows greenness and the latter redness.展开更多
基金The Fundamental Research Funds for the Central Universities(No.3202003905)Scientific Innovation Research of College Graduates in Jiangsu Province(No.CXLX12_0080)
文摘The aerodynamics of 2-dimensional flexible wings in bees' normal hovering flight is studied. Four insect flapping flight coordinate systems, including a global system, a bodyfixed system, a rigid wing-fixed system and a flexible wingfixed system, are established to represent the insects' position, gesture, wing movement and wing deformation, respectively. Then the transformations among four coordinate systems are studied. It is found that the elliptic coordinate system can improve the computation accuracy and reduce the calculation complexity in a 2-dimensional rigid wing. The computation model of a 2-dimensional flexible wing is established, and the changes of the force, moment, and power are investigated. According to the computation results, the large lift and drag peaks at the beginning and end of the stroke can be explained by the superposition of the rapid translational acceleration, the fast pitching-up rotation and the Magnus effect; and the small force and drag peaks can be explained by the convex flow effect and the concave flow effect. Compared with the pressure force, pressure moment and translational power, the viscous force, viscous moment and rotational power are small and can be ignored.
基金Project(51275414)supported by the National Natural Science Foundation of ChinaProject(3102015BJ(Ⅱ)ZS007)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(130-QP-2015)supported by the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),China
文摘Tensile stress-strain curves of five metallic alloys,i.e.,SKH51,STS316L,Ti-6Al-4V,Al6061and Inconel600were analyzed to investigate the working hardening behavior.The constitutive parameters of three constitutive equations,i.e.,the Hollomon,Swift and Voce equations,were compared by using different methods.A new working hardening parameter was proposed to characterize the working hardening behavior in different deformation stages.It is found that Voce equation is suitable to describe stress-strain curves in large strain region.Meanwhile,the predicting accuracy of ultimate tensile strength by Voce equation is the best.The working hardening behavior of SKH51is different from the other four metallic alloys.
文摘The velocity variable of a noise oscillator as an internal or external noise is proposed, the spectrum of which is quite different from that of the coordinate variable of the same noise oscillator. The former leads to ballistic diffusion for a free particle in long time limit and the asymptotical results of the system are sensitive to the initial condition. However, diffusion process induced by the coordinate of noise oscillator is a normal one and depends on the initial condition only in the transient time. This allows us to classify two kinds of non-Markovian processes: normal one and strong one, just like the processes induced by the coordinate and the velocity of noise oscillator, respectively.Applying to a correlation ratchet, we have found that the steady current of a particle subjected to the velocity of noise oscillator is opposite to that subjected to its coordinate, thus the former shows greenness and the latter redness.