A buffer bag mechanism is designed,which can provide axial impact protection under small displacement.The stiffness characteristics of the structure under impact load are studied.The stiffness of the mechanism and the...A buffer bag mechanism is designed,which can provide axial impact protection under small displacement.The stiffness characteristics of the structure under impact load are studied.The stiffness of the mechanism and the internal pressure change of the buffer bag are compared and analyzed,when the filling materials are liquid and gas respectively.Finally,the influence of initial fluid bag pressure,bulk modulus and shell thickness on the stiffness of the mechanism and the change of bag pressure are studied.The results show that the stiffness of the liquid bag is better than that of the gas bag when the filler is liquid and gas;the liquid bag has obvious pressure rise after the mechanism is subjected to axial force by 300 kN,and the gas bag has almost no pressure rise;the change of bulk modulus,which is1000,1500,2000 and 2500 MPa,has an obvious effect on the liquid bag,and it is positively correlated with the stiffness of the mechanism.The change of gas modulus,which is 28 and 44,has little effect on the stiffness of the mechanism;the thickness of the buffer bag,which is 5,10 and 15 mm,also has an obvious effect on the stiffness.The stiffness of the liquid bag is greater,and the protection for flexible joint is better in the same condition.展开更多
The acoustic cloak can manipulate sound waves in surprising ways and enable us to guide the trajectories of waves at will.In contrast to the existing approaches for designing such devices that need exotic material par...The acoustic cloak can manipulate sound waves in surprising ways and enable us to guide the trajectories of waves at will.In contrast to the existing approaches for designing such devices that need exotic material parameters,here we demonstrate how to design a layered and isotropic acoustic cloak based on conformal transformation acoustics.A petal-shaped layered acoustic cloak is designed from the reduction of material parameters of an approximate rectangular cloak.The resultant material parameters span a narrow range,thus strongly facilitating the implementation.The invisibility performance of the cloak for different shapes of acoustic wavefront is verified using a full-wave finite-element analysis.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(No.NS2019003)。
文摘A buffer bag mechanism is designed,which can provide axial impact protection under small displacement.The stiffness characteristics of the structure under impact load are studied.The stiffness of the mechanism and the internal pressure change of the buffer bag are compared and analyzed,when the filling materials are liquid and gas respectively.Finally,the influence of initial fluid bag pressure,bulk modulus and shell thickness on the stiffness of the mechanism and the change of bag pressure are studied.The results show that the stiffness of the liquid bag is better than that of the gas bag when the filler is liquid and gas;the liquid bag has obvious pressure rise after the mechanism is subjected to axial force by 300 kN,and the gas bag has almost no pressure rise;the change of bulk modulus,which is1000,1500,2000 and 2500 MPa,has an obvious effect on the liquid bag,and it is positively correlated with the stiffness of the mechanism.The change of gas modulus,which is 28 and 44,has little effect on the stiffness of the mechanism;the thickness of the buffer bag,which is 5,10 and 15 mm,also has an obvious effect on the stiffness.The stiffness of the liquid bag is greater,and the protection for flexible joint is better in the same condition.
文摘The acoustic cloak can manipulate sound waves in surprising ways and enable us to guide the trajectories of waves at will.In contrast to the existing approaches for designing such devices that need exotic material parameters,here we demonstrate how to design a layered and isotropic acoustic cloak based on conformal transformation acoustics.A petal-shaped layered acoustic cloak is designed from the reduction of material parameters of an approximate rectangular cloak.The resultant material parameters span a narrow range,thus strongly facilitating the implementation.The invisibility performance of the cloak for different shapes of acoustic wavefront is verified using a full-wave finite-element analysis.
