This work uses the molecular dynamics approach to study the effects of functionalization of carbon nanotubes(CNTs)on the mechanical properties of Cu64Zr36 metallic glass(MG).Three types of functional groups,carboxylic...This work uses the molecular dynamics approach to study the effects of functionalization of carbon nanotubes(CNTs)on the mechanical properties of Cu64Zr36 metallic glass(MG).Three types of functional groups,carboxylic,vinyl and ester were used.The effect of CNT volume fraction(Vf)and the number of functional groups attached to CNT,on the mechanical properties and thermal conductivity of CNT-MG composites was analysed using Biovia Materials Studio.At lower values of Vf(from 0 to 5%),the percentage increase in Young’s modulus was approximately 66%.As the value of Vf was increased further(from 5 to 12%),the rate of increase in Young’s modulus was reduced to 16%.The thermal conductivity was found to increase from 1.52 W/mK at Vf?0%to 5.88 W/mK at Vf?12%,thus giving an increase of approximately 286%.Functionalization of SWCNT reduced the thermal conductivity of the SWCNT-MG composites.展开更多
Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetime...Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetimes of these clusters are calculated according to their Lindemann index δ (t) using the criteria of δ≥0.07. For both the filled and empty clusters, we find the dynamics of bulk water determines the lifetimes of cage-like water clusters, and that the lifetime of 512 62 cage-like cluster is the same as that of 512 cage-like cluster. Although the methane molecule indeed makes the filled cage-like cluster more stable than the empty one, the empty cage-like cluster still has chance to be long-lived compared with the filled clusters. These observations support the labile cluster hypothesis on the formation mechanisms of gas hydrates.展开更多
When underground cavities are subjected to explosive stress waves,a uniquely damaged zone may appear due to the combined effect of dynamic loading and static pre-load stress.In this study,a rate-dependent two-dimensio...When underground cavities are subjected to explosive stress waves,a uniquely damaged zone may appear due to the combined effect of dynamic loading and static pre-load stress.In this study,a rate-dependent two-dimensional rock dynamic constitutive model was established to investigate the dynamic fractures of rocks under different static stress conditions.The effects of the loading rate and peak amplitude of the blasting wave under different confining pressures and the vertical compressive coefficient(K_(0))were considered.The numerical simulated results reproduced the initiation and further propagation of primary radial crack fractures,which were in agreement with the experimental results.The dynamic loading rate,peak amplitude,static vertical compressive coefficient(K_(0))and confining pressure affected the evolution of fractures around the borehole.The heterogeneity parameter(m)plays an important role in the evolution of fractures around the borehole.The crack propagation path became more discontinuous and rougher in a smallerheterogeneity parameter case.展开更多
The effects of tensile temperatures ranging from 100 K to 900 K on the phase transition of hexagonal close-packed(HCP)zirconium were investigated by molecular dynamics simulations,which were combined with experimental...The effects of tensile temperatures ranging from 100 K to 900 K on the phase transition of hexagonal close-packed(HCP)zirconium were investigated by molecular dynamics simulations,which were combined with experimental observation under high resolution transmission electron microscopy.The results show that externally applied loading first induced the HCP to body-centered cubic(BCC)phase transition in the Pitsch-Schrader(PS)orientation relationship(OR).Then,the face-centered cubic(FCC)structure transformed from the BCC phase in the Bain path.However,the HCP-to-BCC transition was incomplete at 100 K and 300 K,resulting in a prismatic-type OR between the FCC and original HCP phase.Additionally,at the temperature ranging from 100 K to 600 K,the inverse BCC-to-HCP transition occurred locally following other variants of the PS OR,resulting in a basal-type relation between the newly generated HCP and FCC phases.A higher tensile temperature promoted the amount of FCC phase transforming into the BCC phase when the strain exceeded 45%.Besides,the crystal stretched at lower temperatures exhibits relatively higher strength but by the compromise of plasticity.This study reveals the deformation mechanisms in HCP-Zr at different temperatures,which may provide a better understanding of the deformation mechanism of zirconium alloys under different application environments.展开更多
In order to study the dynamic characteristics of the missile erection system,it can be considered as a rigid-flexible coupling multi-body system.Firstly,the actual system is abstracted as an equal and simplified one a...In order to study the dynamic characteristics of the missile erection system,it can be considered as a rigid-flexible coupling multi-body system.Firstly,the actual system is abstracted as an equal and simplified one and then the forces applied to it are analyzed.Secondly,the rigid-flexible coupling dynamic simulation for erection system is accomplished by use of the system simulation software,for example Pro/E,ADAMS,ANSYS,MATLAB/Simulink,etc.Finally,having the aid of simulation results,the kinetic and dynamic characteristics of the flexible bodies in erection system are analyzed.The simulation considering the erection system as a rigid-flexible coupling system can provide valuable results to the research of its kinetic,dynamic and vibrational characteristics.展开更多
A multi-domain nonlinear dynamic model of a proportional solenoid valve was presented.The electro-magnetic,mechanical and fluid subsystems of the valve were investigated,including their interactions.Governing equation...A multi-domain nonlinear dynamic model of a proportional solenoid valve was presented.The electro-magnetic,mechanical and fluid subsystems of the valve were investigated,including their interactions.Governing equations of the valve were derived in the form of nonlinear state equations.By comparing the simulated and measured data,the simulation model is validated with a deviation less than 15%,which can be used for the structural design and control algorithm optimization of proportional solenoid valves.展开更多
The shock-induced reaction mechanism and characteristics of Ni/Al system,considering an Al nanoparticle-embedded Ni single crystal,are investigated through molecular dynamics simulation.For the shock melting of Al nan...The shock-induced reaction mechanism and characteristics of Ni/Al system,considering an Al nanoparticle-embedded Ni single crystal,are investigated through molecular dynamics simulation.For the shock melting of Al nanoparticle,interfacial crystallization and dissolution are the main characteristics.The reaction degree of Al particle first increases linearly and then logarithmically with time driven by rapid mechanical mixing and following dissolution.The reaction rate increases with the decrease of particle diameter,however,the reaction is seriously hindered by interfacial crystallization when the diameter is lower than 9 nm in our simulations.Meanwhile,we found a negative exponential growth in the fraction of crystallized Al atoms,and the crystallinity of B2-NiAl(up to 20%)is positively correlated with the specific surface area of Al particle.This can be attributed to the formation mechanism of B2-NiAl by structural evolution of finite mixing layer near the collapsed interface.For shock melting of both Al particle and Ni matrix,the liquid-liquid phase inter-diffusion is the main reaction mechanism that can be enhanced by the formation of internal jet.In addition,the enhanced diffusion is manifested in the logarithmic growth law of mean square displacement,which results in an almost constant reaction rate similar to the mechanical mixing process.展开更多
随着特高压输电技术的快速发展和大容量电力传输需求的不断增加,绝缘纸在极端环境下的电气性能、机械强度及热稳定性面临着更为严峻的挑战。该文提出纳米SiO_(2)粒子掺杂与等离子体氟化协同改性策略,系统研究协同改性前后绝缘纸的电气...随着特高压输电技术的快速发展和大容量电力传输需求的不断增加,绝缘纸在极端环境下的电气性能、机械强度及热稳定性面临着更为严峻的挑战。该文提出纳米SiO_(2)粒子掺杂与等离子体氟化协同改性策略,系统研究协同改性前后绝缘纸的电气性能、机械性能、疏水性能及热老化性能的演变规律,通过扫描电子显微镜(scanning electron microscope,SEM)和能量色散X射线光谱仪(energy dispersive spectrometer,EDS)表征氟化处理后绝缘纸表面形貌与元素分布变化。基于分子动力学模拟,揭示纳米粒子掺杂和含氟基团介质的协同增强机制。结果表明:纳米SiO_(2)粒子掺杂协同等离子体氟化改性可有效限制载流子的运动,显著提升了绝缘纸的绝缘性能。与未改性相比,绝缘纸的击穿场强和体积电阻率分别提高109.2%和134.9%。协同改性处理后,绝缘纸表面接枝了大量含氟基团,显著提升其表面疏水性;同时,含氟基团与纳米SiO_(2)间形成的氢键强化了纳米SiO_(2)与绝缘纸的桥接作用,进而可有效提升绝缘纸的热老化性能。展开更多
文摘This work uses the molecular dynamics approach to study the effects of functionalization of carbon nanotubes(CNTs)on the mechanical properties of Cu64Zr36 metallic glass(MG).Three types of functional groups,carboxylic,vinyl and ester were used.The effect of CNT volume fraction(Vf)and the number of functional groups attached to CNT,on the mechanical properties and thermal conductivity of CNT-MG composites was analysed using Biovia Materials Studio.At lower values of Vf(from 0 to 5%),the percentage increase in Young’s modulus was approximately 66%.As the value of Vf was increased further(from 5 to 12%),the rate of increase in Young’s modulus was reduced to 16%.The thermal conductivity was found to increase from 1.52 W/mK at Vf?0%to 5.88 W/mK at Vf?12%,thus giving an increase of approximately 286%.Functionalization of SWCNT reduced the thermal conductivity of the SWCNT-MG composites.
基金supported by the National Natural Science Foundation of China(Grant No.40102005 and No.49725205).
文摘Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetimes of these clusters are calculated according to their Lindemann index δ (t) using the criteria of δ≥0.07. For both the filled and empty clusters, we find the dynamics of bulk water determines the lifetimes of cage-like water clusters, and that the lifetime of 512 62 cage-like cluster is the same as that of 512 cage-like cluster. Although the methane molecule indeed makes the filled cage-like cluster more stable than the empty one, the empty cage-like cluster still has chance to be long-lived compared with the filled clusters. These observations support the labile cluster hypothesis on the formation mechanisms of gas hydrates.
基金Projects(51878190,51779031,51678170)supported by the National Natural Science Foundation of China。
文摘When underground cavities are subjected to explosive stress waves,a uniquely damaged zone may appear due to the combined effect of dynamic loading and static pre-load stress.In this study,a rate-dependent two-dimensional rock dynamic constitutive model was established to investigate the dynamic fractures of rocks under different static stress conditions.The effects of the loading rate and peak amplitude of the blasting wave under different confining pressures and the vertical compressive coefficient(K_(0))were considered.The numerical simulated results reproduced the initiation and further propagation of primary radial crack fractures,which were in agreement with the experimental results.The dynamic loading rate,peak amplitude,static vertical compressive coefficient(K_(0))and confining pressure affected the evolution of fractures around the borehole.The heterogeneity parameter(m)plays an important role in the evolution of fractures around the borehole.The crack propagation path became more discontinuous and rougher in a smallerheterogeneity parameter case.
基金Projects(51901248,51828102)supported by the National Natural Science Foundation of ChinaProject(2018JJ3649)supported by the Natural Science Foundation of Hunan Province,ChinaProject(2019CX026)supported by the Innovation-driven Plan in Central South University,China。
文摘The effects of tensile temperatures ranging from 100 K to 900 K on the phase transition of hexagonal close-packed(HCP)zirconium were investigated by molecular dynamics simulations,which were combined with experimental observation under high resolution transmission electron microscopy.The results show that externally applied loading first induced the HCP to body-centered cubic(BCC)phase transition in the Pitsch-Schrader(PS)orientation relationship(OR).Then,the face-centered cubic(FCC)structure transformed from the BCC phase in the Bain path.However,the HCP-to-BCC transition was incomplete at 100 K and 300 K,resulting in a prismatic-type OR between the FCC and original HCP phase.Additionally,at the temperature ranging from 100 K to 600 K,the inverse BCC-to-HCP transition occurred locally following other variants of the PS OR,resulting in a basal-type relation between the newly generated HCP and FCC phases.A higher tensile temperature promoted the amount of FCC phase transforming into the BCC phase when the strain exceeded 45%.Besides,the crystal stretched at lower temperatures exhibits relatively higher strength but by the compromise of plasticity.This study reveals the deformation mechanisms in HCP-Zr at different temperatures,which may provide a better understanding of the deformation mechanism of zirconium alloys under different application environments.
文摘In order to study the dynamic characteristics of the missile erection system,it can be considered as a rigid-flexible coupling multi-body system.Firstly,the actual system is abstracted as an equal and simplified one and then the forces applied to it are analyzed.Secondly,the rigid-flexible coupling dynamic simulation for erection system is accomplished by use of the system simulation software,for example Pro/E,ADAMS,ANSYS,MATLAB/Simulink,etc.Finally,having the aid of simulation results,the kinetic and dynamic characteristics of the flexible bodies in erection system are analyzed.The simulation considering the erection system as a rigid-flexible coupling system can provide valuable results to the research of its kinetic,dynamic and vibrational characteristics.
基金Project(2008ZHZX1A0502) supported by the Independence Innovation Achievements Transformation Crucial Special Program of Shandong Province,China
文摘A multi-domain nonlinear dynamic model of a proportional solenoid valve was presented.The electro-magnetic,mechanical and fluid subsystems of the valve were investigated,including their interactions.Governing equations of the valve were derived in the form of nonlinear state equations.By comparing the simulated and measured data,the simulation model is validated with a deviation less than 15%,which can be used for the structural design and control algorithm optimization of proportional solenoid valves.
基金supported by the State Key Program of National Natural Science Foundation of China(Grant No.12132003)State Key Laboratory of Explosion Science and Technology(Grant No.QNKT20-07)。
文摘The shock-induced reaction mechanism and characteristics of Ni/Al system,considering an Al nanoparticle-embedded Ni single crystal,are investigated through molecular dynamics simulation.For the shock melting of Al nanoparticle,interfacial crystallization and dissolution are the main characteristics.The reaction degree of Al particle first increases linearly and then logarithmically with time driven by rapid mechanical mixing and following dissolution.The reaction rate increases with the decrease of particle diameter,however,the reaction is seriously hindered by interfacial crystallization when the diameter is lower than 9 nm in our simulations.Meanwhile,we found a negative exponential growth in the fraction of crystallized Al atoms,and the crystallinity of B2-NiAl(up to 20%)is positively correlated with the specific surface area of Al particle.This can be attributed to the formation mechanism of B2-NiAl by structural evolution of finite mixing layer near the collapsed interface.For shock melting of both Al particle and Ni matrix,the liquid-liquid phase inter-diffusion is the main reaction mechanism that can be enhanced by the formation of internal jet.In addition,the enhanced diffusion is manifested in the logarithmic growth law of mean square displacement,which results in an almost constant reaction rate similar to the mechanical mixing process.
文摘随着特高压输电技术的快速发展和大容量电力传输需求的不断增加,绝缘纸在极端环境下的电气性能、机械强度及热稳定性面临着更为严峻的挑战。该文提出纳米SiO_(2)粒子掺杂与等离子体氟化协同改性策略,系统研究协同改性前后绝缘纸的电气性能、机械性能、疏水性能及热老化性能的演变规律,通过扫描电子显微镜(scanning electron microscope,SEM)和能量色散X射线光谱仪(energy dispersive spectrometer,EDS)表征氟化处理后绝缘纸表面形貌与元素分布变化。基于分子动力学模拟,揭示纳米粒子掺杂和含氟基团介质的协同增强机制。结果表明:纳米SiO_(2)粒子掺杂协同等离子体氟化改性可有效限制载流子的运动,显著提升了绝缘纸的绝缘性能。与未改性相比,绝缘纸的击穿场强和体积电阻率分别提高109.2%和134.9%。协同改性处理后,绝缘纸表面接枝了大量含氟基团,显著提升其表面疏水性;同时,含氟基团与纳米SiO_(2)间形成的氢键强化了纳米SiO_(2)与绝缘纸的桥接作用,进而可有效提升绝缘纸的热老化性能。
