The experimental phenomenon and theoretical analysis are given for the torsional buckling of elastic cylindrical shells. From the experiment, it is found that the postbuckling deformation doesn't occupy the whole ...The experimental phenomenon and theoretical analysis are given for the torsional buckling of elastic cylindrical shells. From the experiment, it is found that the postbuckling deformation doesn't occupy the whole length when the shell is longer. In the theoretical calculation, only the normal displacement boundary condition is taken into account. By comparing the present calculation results with the accurate result of Yamakis theory and the results of the present experiment, it is shown that the influence of the axial and circumference boundary condition is less important.展开更多
An experimental benchmark is proposed for piezoelectric,direct-torsion actuation using mono-morph piezoceramic d_(15)shear patches.This is reached by designing and assembling an adaptive plate having two identical com...An experimental benchmark is proposed for piezoelectric,direct-torsion actuation using mono-morph piezoceramic d_(15)shear patches.This is reached by designing and assembling an adaptive plate having two identical composite faces sandwiching a core made of connected six oppositely polarized(OP)piezoceramic d15 shear patches along the length.An electronic speckle pattern interferometry system was used to measure the static tip deflection of the adaptive sandwich composite plate that was mounted in a cantilever configuration and actuated in torsion by progressively applied voltages on the piezoceramic shear core electroded major surfaces.Then,the effective rate of twist was post-processed and proposed as an evaluation criterion for smart composites under piezoelectric torsion actuation.For verification of the experimental results,the proposed experimental benchmark was simulated using three-dimensional piezoelectric finite elements(FE)within ABAQUS®commercial software.The comparison of the obtained experimental and simulation results showed reasonable agreement,but the slight nonlinear experimental response was not confirmed by the linear FE analysis.The experimentally proved torsion actuation mechanism,produced by OP piezoceramic d15 shear patches,can be applied actively to prevent torsion in many applications,such as in wind turbines,helicopter blades,robot arms,flexible space structures,etc.展开更多
We consider there is a vacancy in the plasma in the solar system,and calculate the vector potential produced by the magnetic field frozen in the plasma.The result shows that,in the vacancy,the vector potential produce...We consider there is a vacancy in the plasma in the solar system,and calculate the vector potential produced by the magnetic field frozen in the plasma.The result shows that,in the vacancy,the vector potential produced by the magnetic field frozen in the plasma is much less than the large scale cosmic vector potential.This means if our earth is in such a vacancy,the total vector potential on the surface of the earth is dominated by the cosmic magnetic vector potential,which gives a further support of the reliability of the limit on photon mass given by rotating torsion balance experiment [Phys.Rev.Lett.90(2003) 081801].展开更多
文摘The experimental phenomenon and theoretical analysis are given for the torsional buckling of elastic cylindrical shells. From the experiment, it is found that the postbuckling deformation doesn't occupy the whole length when the shell is longer. In the theoretical calculation, only the normal displacement boundary condition is taken into account. By comparing the present calculation results with the accurate result of Yamakis theory and the results of the present experiment, it is shown that the influence of the axial and circumference boundary condition is less important.
基金the support of the Polymer Competence Center Leoben(Austria)for the support of the present work.
文摘An experimental benchmark is proposed for piezoelectric,direct-torsion actuation using mono-morph piezoceramic d_(15)shear patches.This is reached by designing and assembling an adaptive plate having two identical composite faces sandwiching a core made of connected six oppositely polarized(OP)piezoceramic d15 shear patches along the length.An electronic speckle pattern interferometry system was used to measure the static tip deflection of the adaptive sandwich composite plate that was mounted in a cantilever configuration and actuated in torsion by progressively applied voltages on the piezoceramic shear core electroded major surfaces.Then,the effective rate of twist was post-processed and proposed as an evaluation criterion for smart composites under piezoelectric torsion actuation.For verification of the experimental results,the proposed experimental benchmark was simulated using three-dimensional piezoelectric finite elements(FE)within ABAQUS®commercial software.The comparison of the obtained experimental and simulation results showed reasonable agreement,but the slight nonlinear experimental response was not confirmed by the linear FE analysis.The experimentally proved torsion actuation mechanism,produced by OP piezoceramic d15 shear patches,can be applied actively to prevent torsion in many applications,such as in wind turbines,helicopter blades,robot arms,flexible space structures,etc.
文摘We consider there is a vacancy in the plasma in the solar system,and calculate the vector potential produced by the magnetic field frozen in the plasma.The result shows that,in the vacancy,the vector potential produced by the magnetic field frozen in the plasma is much less than the large scale cosmic vector potential.This means if our earth is in such a vacancy,the total vector potential on the surface of the earth is dominated by the cosmic magnetic vector potential,which gives a further support of the reliability of the limit on photon mass given by rotating torsion balance experiment [Phys.Rev.Lett.90(2003) 081801].
