This letter solves an open question of origami paper spring risen by Yoneda et al.(Phys.Rev.E 2019).By using both dimensional analysis and data fitting,an universal scaling law of a paper spring is formulated.The scal...This letter solves an open question of origami paper spring risen by Yoneda et al.(Phys.Rev.E 2019).By using both dimensional analysis and data fitting,an universal scaling law of a paper spring is formulated.The scaling law shows that origami spring force obeys power square law of spring extension,however strong nonlinear to the total twist angle.The study has also successfully generalized the scaling law from the Poisson ratio 0.3 to an arbitrary Poisson's ratio with the help of dimensional analysis.展开更多
The Flapping Rotary Wing(FRW)is a micro air vehicle wing layout coupling flapping,pitching,and rotating motions.It can gain bencfits in high lift from a fast passive rotating motion,which is tightly related to the pas...The Flapping Rotary Wing(FRW)is a micro air vehicle wing layout coupling flapping,pitching,and rotating motions.It can gain bencfits in high lift from a fast passive rotating motion,which is tightly related to the passive pitching motion directly caused by wing flexible deformation.Therefore,flexible deformation is crucial for the wing kinematics and aerodynamic performance of an FRW.In this paper,we explored the effct of flexibility on wing kinematics and acrodynamics on the basis of a mechanical FRW model.A photogrammetric method was adopted to capture motion images according to which wing orientations and deformations were reconstructed.Corresponding acrodynamic force was computed using computational fluid dynamic method,and wing kinematics and deformations were used as simulation inputs.The experimental measurements presented the real orientation and deformation pattem of a real FRW.The wing passive deformation of a high-intensity FRW was found to be mainly caused by inertial force,and a linear positive spanwise twist was observed in the FRW.The effects of wing deformation on aerodynamic force production and the underlying mechanism were addressed.Results showed that lift augment,rotating moment enhancement,and power efficiency improvement can be achieved when a wing becomes flexible.Wing spanwise twist mainly accounts for these changes in aerodynamics,and increment in spanwise twist could further contributes to aerodynamic improvement.展开更多
Slender chiral filaments are ubiquitous in both artificial and biological materials.Due to their chiral microstructures,chiral filaments usually exhibit favorable properties such as superior elasticity and unusual str...Slender chiral filaments are ubiquitous in both artificial and biological materials.Due to their chiral microstructures,chiral filaments usually exhibit favorable properties such as superior elasticity and unusual stretch-twist coupling deformation.However,how these chiral microstructures affect the elastic behavior of filaments remains unclear.In this paper,a refined Cosserat rod model with misfit or mismatching of chirality induced by inhomogeneous arrangement of chiral microstructures incorporated is developed.Using the refined rod model,the force-displacement relationships and variation of structural chirality during the tensile processes of two typical helical structures,i.e.,single-strand helix and double-strand helix,are investigated.The results show that the misfit of chirality can lead to a bend-twist deformation with a high coupling degree,which makes the rod much“soft”when stretched.The chiral filaments undergo an unusual twist when stretched,corresponding to an obviously nonlinear variation of structural chirality.The work suggests that the misfit of chirality can be used to tune the elastic behavior of chiral filaments,which is helpful in guiding the design of flexible actuators and soft devices.展开更多
Real-time performance and accuracy are two most challenging requirements in virtual surgery training.These difficulties limit the promotion of advanced models in virtual surgery,including many geometric and physical m...Real-time performance and accuracy are two most challenging requirements in virtual surgery training.These difficulties limit the promotion of advanced models in virtual surgery,including many geometric and physical models.This paper proposes a physical model of virtual soft tissue,which is a twist model based on the Kriging interpolation and membrane analogy.The proposed model can quickly locate spatial position through Kriging interpolation method and accurately compute the force change on the soft tissue through membrane analogy method.The virtual surgery simulation system is built with a PHANTOM OMNI haptic interaction device to simulate the torsion of virtual stomach and arm,and further verifies the real-time performance and simulation accuracy of the proposed model.The experimental results show that the proposed soft tissue model has high speed and accuracy,realistic deformation,and reliable haptic feedback.展开更多
Twist leads to yarn torsion, which influences the physical and mechanical properties of yarn or fabric directly. In this paper, according to the basic principle of space geometry, the space geometric model of yarn was...Twist leads to yarn torsion, which influences the physical and mechanical properties of yarn or fabric directly. In this paper, according to the basic principle of space geometry, the space geometric model of yarn was established, then the linking number,twisting number, and writhing number of elastic rod model were defined. The reason of yarn snarling was analyzed based on the energy, and the relation between yarn snarling and yarn torsion was studied according to White formula. The results show when tow ends of yarn are fixed, the linking number is constant, which means the sum of twisting number and writhing number for yarn torsion deformation and bend deformation is constant.展开更多
基金the financial supports from Xi’an University of Architecture and Technology
文摘This letter solves an open question of origami paper spring risen by Yoneda et al.(Phys.Rev.E 2019).By using both dimensional analysis and data fitting,an universal scaling law of a paper spring is formulated.The scaling law shows that origami spring force obeys power square law of spring extension,however strong nonlinear to the total twist angle.The study has also successfully generalized the scaling law from the Poisson ratio 0.3 to an arbitrary Poisson's ratio with the help of dimensional analysis.
基金the National Natural Science Foundation of China(Nos.11902017 and 11672022).
文摘The Flapping Rotary Wing(FRW)is a micro air vehicle wing layout coupling flapping,pitching,and rotating motions.It can gain bencfits in high lift from a fast passive rotating motion,which is tightly related to the passive pitching motion directly caused by wing flexible deformation.Therefore,flexible deformation is crucial for the wing kinematics and aerodynamic performance of an FRW.In this paper,we explored the effct of flexibility on wing kinematics and acrodynamics on the basis of a mechanical FRW model.A photogrammetric method was adopted to capture motion images according to which wing orientations and deformations were reconstructed.Corresponding acrodynamic force was computed using computational fluid dynamic method,and wing kinematics and deformations were used as simulation inputs.The experimental measurements presented the real orientation and deformation pattem of a real FRW.The wing passive deformation of a high-intensity FRW was found to be mainly caused by inertial force,and a linear positive spanwise twist was observed in the FRW.The effects of wing deformation on aerodynamic force production and the underlying mechanism were addressed.Results showed that lift augment,rotating moment enhancement,and power efficiency improvement can be achieved when a wing becomes flexible.Wing spanwise twist mainly accounts for these changes in aerodynamics,and increment in spanwise twist could further contributes to aerodynamic improvement.
基金the National Natural Science Foundation of China(Grant Nos.12020101001,12021002,11872273,and 11890680)Tianjin Research Program of Application Foundation and Advanced Technology(Grant No.19JCYBJC19300).
文摘Slender chiral filaments are ubiquitous in both artificial and biological materials.Due to their chiral microstructures,chiral filaments usually exhibit favorable properties such as superior elasticity and unusual stretch-twist coupling deformation.However,how these chiral microstructures affect the elastic behavior of filaments remains unclear.In this paper,a refined Cosserat rod model with misfit or mismatching of chirality induced by inhomogeneous arrangement of chiral microstructures incorporated is developed.Using the refined rod model,the force-displacement relationships and variation of structural chirality during the tensile processes of two typical helical structures,i.e.,single-strand helix and double-strand helix,are investigated.The results show that the misfit of chirality can lead to a bend-twist deformation with a high coupling degree,which makes the rod much“soft”when stretched.The chiral filaments undergo an unusual twist when stretched,corresponding to an obviously nonlinear variation of structural chirality.The work suggests that the misfit of chirality can be used to tune the elastic behavior of chiral filaments,which is helpful in guiding the design of flexible actuators and soft devices.
基金This work was supported in part by the National Nature Science Foundation of China(No.61502240,61502096,61304205,61773219)Natural Science Foundation of Jiangsu Province(BK20150634,BK20141002).
文摘Real-time performance and accuracy are two most challenging requirements in virtual surgery training.These difficulties limit the promotion of advanced models in virtual surgery,including many geometric and physical models.This paper proposes a physical model of virtual soft tissue,which is a twist model based on the Kriging interpolation and membrane analogy.The proposed model can quickly locate spatial position through Kriging interpolation method and accurately compute the force change on the soft tissue through membrane analogy method.The virtual surgery simulation system is built with a PHANTOM OMNI haptic interaction device to simulate the torsion of virtual stomach and arm,and further verifies the real-time performance and simulation accuracy of the proposed model.The experimental results show that the proposed soft tissue model has high speed and accuracy,realistic deformation,and reliable haptic feedback.
基金the Fundamental Research Funds for the Central Universities,China
文摘Twist leads to yarn torsion, which influences the physical and mechanical properties of yarn or fabric directly. In this paper, according to the basic principle of space geometry, the space geometric model of yarn was established, then the linking number,twisting number, and writhing number of elastic rod model were defined. The reason of yarn snarling was analyzed based on the energy, and the relation between yarn snarling and yarn torsion was studied according to White formula. The results show when tow ends of yarn are fixed, the linking number is constant, which means the sum of twisting number and writhing number for yarn torsion deformation and bend deformation is constant.
