The problem of geometric non-linearity simulation for spacial cable system was solved by introducing the truss element based on corotational coordinate (CR) system, cable structure materials and node coordinates and a...The problem of geometric non-linearity simulation for spacial cable system was solved by introducing the truss element based on corotational coordinate (CR) system, cable structure materials and node coordinates and automatic refreshing algorithms for element internal force. And the shape-finding problem for maneuvering profile was solved with the Newton-Raphson based on energy convergence criteria with search function. This has avoided the regular truss element assumption extensively used in traditional methods and catenary elements which have difficulties in practical application because of the complicated formulas. The use of CR formulation has taken into account the stiffness outside the cable plane via a geometric stiffness matrix, realizing the 3D space analysis of a cable bridge and improving the efficiency and precision for the space geometric non-linearity analysis and cable structure, and enabling more precised simulation of geometric form finding and internal force of the large span suspension bridge main cable under construction.展开更多
The rheological properties of cable insulation materials are critical to the long-term continuous extrusion performance of high-voltage cables,with the pre-cross-linking effect playing a key role in determining the rh...The rheological properties of cable insulation materials are critical to the long-term continuous extrusion performance of high-voltage cables,with the pre-cross-linking effect playing a key role in determining the rheological behaviour of the insulation material during extrusion.Considering the pre-cross-linking effect,this study investigates the influence of molecular structure on the extrusion temperature,viscosity and shear rate distribution of insulation materials through equivalence experiments and simulations.The results indicate that the maximum temperature of 143℃ occurs at the extrusion die land,where pressure and shear rate are highest.Furthermore,based on the optimised simulation model with experimental results,an empirical formula was established for predicting the maximum extrusion temperature of different insulation materials.This study reveals that although an increased terminal double-bond content in low-density polyethylene(LDPE)enhances the reactivity of insulation materials and reduces their shelf life,it also allows for a reduction in cross-linking agent content,thereby mitigating pre-cross-linking.Insulation materials with a higher long-chain branching degree and terminal double-bond content in LDPE,combined with a lower cross-linking agent content,are less susceptible to pre-cross-linking,which are more suitable for long-length submarine cables,whereas the reduced by-products also benefit the manufacture of DC cables;high-speed shear promotes the diffusion of the cross-linking agent dicumyl peroxide and enhances its interaction with the polyethylene chains.This research elucidates the influence of pre-cross-linking on the extrusion performance of insulation materials and develops an insulation material formulation more suitable for long-duration extrusion.展开更多
Future space missions demand operations on large flexible structures,for example,space webs,the lightweight cable nets deployable in space,which can serve as platforms for very large structures or be used to capture o...Future space missions demand operations on large flexible structures,for example,space webs,the lightweight cable nets deployable in space,which can serve as platforms for very large structures or be used to capture orbital objects.The interest in research on space webs is likely to increase in the future with the development of promising applications such as Furoshiki sat-ellite of JAXA,Robotic Geostationary Orbit Restorer (ROGER) of ESA and Grapple,Retrieve And Secure Payload (GRASP) of NASA.Unlike high-tensioned nets in civil engineering,space webs may be low-tensioned or tensionless,and extremely flexible,owing to the microgravity in the orbit and the lack of support components,which may cause computational difficulties.Mathematical models are necessary in the analysis of space webs,especially in the conceptual design and evaluation for prototypes.A full three-dimensional finite element (FE) model was developed in this work.Trivial truss elements were adopted to reduce the computational complexity.Considering cable is a compression-free material and its tensile stiffness is also variable,we introduced the cable material constitutive relationship to work out an accurate and feasible model for prototype analysis and design.In the static analysis,the stress distribution and global deformation of the webs were discussed to get access to the knowledge of strength of webs with different types of meshes.In the dynamic analysis,special attention was paid to the impact problem.The max stress and global deformation were investigated.The simulation results indicate the interesting phenomenon which may be worth further research.展开更多
基金National Science and Technology Support Program of China(No.2009BAG15B01)Key Programs for Science and Technology Development of Chinese Transportation Industry(No.2008-353-332-190)
文摘The problem of geometric non-linearity simulation for spacial cable system was solved by introducing the truss element based on corotational coordinate (CR) system, cable structure materials and node coordinates and automatic refreshing algorithms for element internal force. And the shape-finding problem for maneuvering profile was solved with the Newton-Raphson based on energy convergence criteria with search function. This has avoided the regular truss element assumption extensively used in traditional methods and catenary elements which have difficulties in practical application because of the complicated formulas. The use of CR formulation has taken into account the stiffness outside the cable plane via a geometric stiffness matrix, realizing the 3D space analysis of a cable bridge and improving the efficiency and precision for the space geometric non-linearity analysis and cable structure, and enabling more precised simulation of geometric form finding and internal force of the large span suspension bridge main cable under construction.
基金supported by the Programme of Beijing Huairou Laboratory(Grant No.ZD2022003A).
文摘The rheological properties of cable insulation materials are critical to the long-term continuous extrusion performance of high-voltage cables,with the pre-cross-linking effect playing a key role in determining the rheological behaviour of the insulation material during extrusion.Considering the pre-cross-linking effect,this study investigates the influence of molecular structure on the extrusion temperature,viscosity and shear rate distribution of insulation materials through equivalence experiments and simulations.The results indicate that the maximum temperature of 143℃ occurs at the extrusion die land,where pressure and shear rate are highest.Furthermore,based on the optimised simulation model with experimental results,an empirical formula was established for predicting the maximum extrusion temperature of different insulation materials.This study reveals that although an increased terminal double-bond content in low-density polyethylene(LDPE)enhances the reactivity of insulation materials and reduces their shelf life,it also allows for a reduction in cross-linking agent content,thereby mitigating pre-cross-linking.Insulation materials with a higher long-chain branching degree and terminal double-bond content in LDPE,combined with a lower cross-linking agent content,are less susceptible to pre-cross-linking,which are more suitable for long-length submarine cables,whereas the reduced by-products also benefit the manufacture of DC cables;high-speed shear promotes the diffusion of the cross-linking agent dicumyl peroxide and enhances its interaction with the polyethylene chains.This research elucidates the influence of pre-cross-linking on the extrusion performance of insulation materials and develops an insulation material formulation more suitable for long-duration extrusion.
文摘Future space missions demand operations on large flexible structures,for example,space webs,the lightweight cable nets deployable in space,which can serve as platforms for very large structures or be used to capture orbital objects.The interest in research on space webs is likely to increase in the future with the development of promising applications such as Furoshiki sat-ellite of JAXA,Robotic Geostationary Orbit Restorer (ROGER) of ESA and Grapple,Retrieve And Secure Payload (GRASP) of NASA.Unlike high-tensioned nets in civil engineering,space webs may be low-tensioned or tensionless,and extremely flexible,owing to the microgravity in the orbit and the lack of support components,which may cause computational difficulties.Mathematical models are necessary in the analysis of space webs,especially in the conceptual design and evaluation for prototypes.A full three-dimensional finite element (FE) model was developed in this work.Trivial truss elements were adopted to reduce the computational complexity.Considering cable is a compression-free material and its tensile stiffness is also variable,we introduced the cable material constitutive relationship to work out an accurate and feasible model for prototype analysis and design.In the static analysis,the stress distribution and global deformation of the webs were discussed to get access to the knowledge of strength of webs with different types of meshes.In the dynamic analysis,special attention was paid to the impact problem.The max stress and global deformation were investigated.The simulation results indicate the interesting phenomenon which may be worth further research.
