The nonlinear vibration fundamental equation of circular sandwich plate under uniformed load and circumjacent load and the loosely clamped boundary condi- tion were established by von Karman plate theory, and then acc...The nonlinear vibration fundamental equation of circular sandwich plate under uniformed load and circumjacent load and the loosely clamped boundary condi- tion were established by von Karman plate theory, and then accordingly exact solution of static load and its numerical results were given. Based on time mode hypothesis and the variational method, the control equation of the space mode was derived, and then the amplitude frequency-load character relation of circular sandwich plate was obtained by the modified iteration method. Consequently the rule of the effect of the two kinds of load on the vibration character of the circular sandwich plate was investigated. When circumjacent load makes the lowest natural frequency zero, critical load is obtained.展开更多
The transient tribological phenomenon and premature lubricant breakdown have been widely observed in metal forming,leading to excessive friction at the contact interfaces.In this research,the transient tribological be...The transient tribological phenomenon and premature lubricant breakdown have been widely observed in metal forming,leading to excessive friction at the contact interfaces.In this research,the transient tribological behaviour of a two-phase lubricant were studied under complex loading conditions,featuring abrupt interfacial temperature,contact load,and sliding speed changes,thus representing the severe interfacial conditions observed in warm/hot metal forming applications.The strong experimental evidence indicates that the evolution of friction was attributed to the physical diminution and chemical decomposition effects.As such,a visco-mechanochemical interactive friction model was developed to accurately predict the transient tribological behaviour of the two-phase lubricant under complex loading conditions.The new friction model exhibited close agreements between the modelling and experimental results.展开更多
Two types of Mg-Cu composition system graded density impactors used for complex loading （shock loading and quasi-isentropic compression） are designed by the elastic-plastic hydrodynamic method in this paper. Mixture...Two types of Mg-Cu composition system graded density impactors used for complex loading （shock loading and quasi-isentropic compression） are designed by the elastic-plastic hydrodynamic method in this paper. Mixtures of metal powders in the Mg-Cu system are cast into a series of 17 and 25 uniform compositions ranging from 100% Mg to 100% Cu. The graded den- sity impactors are launched to the stationary 10 Ixm aluminum film and 12 mm LiF window targets by a two-stage light-gas gun in the National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, CAEP, and the resulting wave profiles are measured with the DISAR system. Hydrodynamic simulation results are perfectly consistent with the experiments. Our work in this paper will set up a foundation for further research of controllable loading/releasing routes and rate experiments in the future.展开更多
Classical strength criteria are developed based on some empirical assumptions and have been widely used in engineering to predict material strength owing to their simplicity. In some cases, however, considerable discr...Classical strength criteria are developed based on some empirical assumptions and have been widely used in engineering to predict material strength owing to their simplicity. In some cases, however, considerable discrepancies arise between classicalstrength-criteria-based theoretical predictions and experimental results. Recently, a global nonequilibrium thermodynamics model has made important progress over classical models without resorting to any empirical assumptions. A prominent advance of this rational energy model is that it straightforwardly determines the dissipation energy density function, which is pertinent to inherent material ductility, through simple uniaxial and equi-biaxial tensions. In this study, a brief introduction of the nonequilibrium energy model was followed by systematic experimental investigation to determine the dissipation energy function and predict the material strength of pristine 316 L stainless steel-commonly used in engineering-under complex loadings. The results indicated that the strength contours predicted by the nonequilibrium energy criterion for complex loadings are consistent with the experimental results obtained for biaxial tension, implying that the nonequilibrium thermodynamics model is both reasonable and reliable. The prediction error was presumed to be induced by the anisotropy of the 316 L stainless steel sheets.展开更多
Cascading failure can cause great damage to complex networks, so it is of great significance to improve the network robustness against cascading failure. Many previous existing works on load-redistribution strategies ...Cascading failure can cause great damage to complex networks, so it is of great significance to improve the network robustness against cascading failure. Many previous existing works on load-redistribution strategies require global information, which is not suitable for large scale networks, and some strategies based on local information assume that the load of a node is always its initial load before the network is attacked, and the load of the failure node is redistributed to its neighbors according to their initial load or initial residual capacity. This paper proposes a new load-redistribution strategy based on local information considering an ever-changing load. It redistributes the loads of the failure node to its nearest neighbors according to their current residual capacity, which makes full use of the residual capacity of the network. Experiments are conducted on two typical networks and two real networks, and the experimental results show that the new load-redistribution strategy can reduce the size of cascading failure efficiently.展开更多
The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas,such as oil and gas indus- try,power plant engineering and chemi...The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas,such as oil and gas indus- try,power plant engineering and chemical factories.An iterative algorithm is presented for the kinematic limit analysis of 3-D rigid-perfectly plastic bodies.A numerical path scheme for radial loading is adopted to deal with complex multi-loading systems.The numerical procedure has been applied to carry out the plastic collapse analysis of pipelines with part-through slot under internal pressure,bending moment and axial force.The effects of various shapes and sizes of part-through slots on the collapse loads of pipelines are systematically investigated and evaluated.Some typical failure modes corresponding to different configurations of slots and loading forms are studied.展开更多
Experimental investigations were pedermed on the plastic deformation along bilinear strain paths with various values of corner-angle by subjecting thin-walled tubular specimens of type 302 stainless steel to combined ...Experimental investigations were pedermed on the plastic deformation along bilinear strain paths with various values of corner-angle by subjecting thin-walled tubular specimens of type 302 stainless steel to combined axial and torsional loads. Variations of scalar and vectorial behavior of the stress response are discnssed in the vector space of plastic strain. It is found that the intrinsic geometry of loading path, the plastic strain history and the coapled effect among strain components effect effectively the stress response of the material. The experimental results also show that these effects will disappear gradually with increasing strain.展开更多
Electroceuticals are medical devices that employ electric signals to alter the activity of specific nerve fibers to achieve therapeutic effects. The rapid growth of RF microelectronics has resulted in the development ...Electroceuticals are medical devices that employ electric signals to alter the activity of specific nerve fibers to achieve therapeutic effects. The rapid growth of RF microelectronics has resulted in the development of very small, portable, and inexpensive shortwave and microwave radio frequency (RF) amplifiers, raising the possibility of utilizing these new RF technologies to develop non-contact electroceutical devices. However, the bio-electromagnetics literature suggests that beyond 10 MHz, RF fields cannot influence biological tissue, beyond simple heating, because effective demodulation mechanisms at these frequencies do not exist in the body. However, RF amplifiers operating at or near saturation have non-linear interactions with complex loads, and if body tissue creates a complex loading condition, the opportunity exists for the coupled system to produce non-linear effects, that is, the equivalent of demodulation may occur. Correspondingly, exposure of tissue to pulsed RF energy could result in the creation of low frequency demodulation components capable of influencing tissue activity. Here, we develop a one-dimen- sional, numerical simulation to investigate the complex loading conditions under which such demodulation could arise. Applying these results in a physical prototype device, we show that up to7.5% demodulation can be obtained for a 40 MHz RF field pulsed at 1 KHz. Implications for this research include the possibility of developing wearable, electromagnetic electroceutical de- vices.展开更多
The load spectrum of the main bearing of tunnel boring machine( TBM) is difficult to establish because of the complex factors affecting the driving load of tunneling. In this paper, a simulation model of dynamic load ...The load spectrum of the main bearing of tunnel boring machine( TBM) is difficult to establish because of the complex factors affecting the driving load of tunneling. In this paper, a simulation model of dynamic load of cutterhead is established,with a view to structural features and special conditions, based on a complex combination stratum, the cutter layout model and cutterhead control parameters,and it is a dynamic load boundary of the main drive bearing. Combined with the load distribution calculation of the main bearing and Hertz contact theory, the prediction model of dynamic load spectrum of the main drive bearing is completed during tunneling,and in accordance with the predicted results,the static and dynamics characteristics of load spectrum for the main drive bearing on the thrust and tilting moment are analyzed. The results of cutterhead load show that,in the certain complex stratum, the fluctuations of load for thrust rollers can reflect formation interface information of complex stratum in current tunneling. The main drive bearing bear the thrust and overturning moment of cutterhead under the composite,the external load has a greater influence on the load-spectrum of reverse thrust roller than that of main thrust roller,and the maximum contact stress of the two row roller is almost the same. The load spectrum,obtained by this method,can provide a meaningful reference for the design and checking of the main drive bearing,and also can be the basis of its fatigue reliability.展开更多
In this paper, wave-body interactions under the effects of complex topography are investigated numerically by a two-phase incompressible Reynolds-Averaged Navier-Stokes(RANS) solver in OpenFOAM. A submerged bottom-sta...In this paper, wave-body interactions under the effects of complex topography are investigated numerically by a two-phase incompressible Reynolds-Averaged Navier-Stokes(RANS) solver in OpenFOAM. A submerged bottom-standing structure is distributed below the floating body, and the effects of the water depth and top width of the submerged structure on wave-body interactions are studied. The results show that the submerged structure can affect wave loads and roll motion. The vertical force can be amplified on the fixed body when the water depth of the submerged structure is smaller than half of the water depth of the body. The top width significantly affects the vertical force when the top width is smaller than the incident wave length and larger than the body width. For the free-rolling body, roll amplitude can be increased when the ratio of the incident wave length to the water depth of the submerged structure is large enough. On the resonance condition, roll amplitude is slightly reduced by the submerged structure. The effects of the top width on roll amplitude are remarkable when special conditions are fulfilled.展开更多
文摘The nonlinear vibration fundamental equation of circular sandwich plate under uniformed load and circumjacent load and the loosely clamped boundary condi- tion were established by von Karman plate theory, and then accordingly exact solution of static load and its numerical results were given. Based on time mode hypothesis and the variational method, the control equation of the space mode was derived, and then the amplitude frequency-load character relation of circular sandwich plate was obtained by the modified iteration method. Consequently the rule of the effect of the two kinds of load on the vibration character of the circular sandwich plate was investigated. When circumjacent load makes the lowest natural frequency zero, critical load is obtained.
文摘The transient tribological phenomenon and premature lubricant breakdown have been widely observed in metal forming,leading to excessive friction at the contact interfaces.In this research,the transient tribological behaviour of a two-phase lubricant were studied under complex loading conditions,featuring abrupt interfacial temperature,contact load,and sliding speed changes,thus representing the severe interfacial conditions observed in warm/hot metal forming applications.The strong experimental evidence indicates that the evolution of friction was attributed to the physical diminution and chemical decomposition effects.As such,a visco-mechanochemical interactive friction model was developed to accurately predict the transient tribological behaviour of the two-phase lubricant under complex loading conditions.The new friction model exhibited close agreements between the modelling and experimental results.
基金supported by the National Natural Science Foundation of China (Grant No. 11072228, 11002129)the Science Foundation of China Academy of Engineering Physics (Grant No. 2011B0202005)+1 种基金the Open Foundation of State Key Laboratory of Explosion Science and Technology(Grant No. KFJJ09-06)the Open Foundation of State Key Laboratory of Advanced Technology for Materials Synthesis and Process-ing, Wuhan University of Technology
文摘Two types of Mg-Cu composition system graded density impactors used for complex loading （shock loading and quasi-isentropic compression） are designed by the elastic-plastic hydrodynamic method in this paper. Mixtures of metal powders in the Mg-Cu system are cast into a series of 17 and 25 uniform compositions ranging from 100% Mg to 100% Cu. The graded den- sity impactors are launched to the stationary 10 Ixm aluminum film and 12 mm LiF window targets by a two-stage light-gas gun in the National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, CAEP, and the resulting wave profiles are measured with the DISAR system. Hydrodynamic simulation results are perfectly consistent with the experiments. Our work in this paper will set up a foundation for further research of controllable loading/releasing routes and rate experiments in the future.
基金supported by the National Natural Science Foundation of China(Grant Nos.11832019,and 12002401)the NSFC Original Exploration Project(Grant No.12150001)+1 种基金the Project of Nuclear Power Technology Innovation Center of Science Technology and Industry for National Defense(Grant No.HDLCXZX-2021-HD-035)the Guangdong International Science and Technology Cooperation Program(Grant No.2020A0505020005)。
文摘Classical strength criteria are developed based on some empirical assumptions and have been widely used in engineering to predict material strength owing to their simplicity. In some cases, however, considerable discrepancies arise between classicalstrength-criteria-based theoretical predictions and experimental results. Recently, a global nonequilibrium thermodynamics model has made important progress over classical models without resorting to any empirical assumptions. A prominent advance of this rational energy model is that it straightforwardly determines the dissipation energy density function, which is pertinent to inherent material ductility, through simple uniaxial and equi-biaxial tensions. In this study, a brief introduction of the nonequilibrium energy model was followed by systematic experimental investigation to determine the dissipation energy function and predict the material strength of pristine 316 L stainless steel-commonly used in engineering-under complex loadings. The results indicated that the strength contours predicted by the nonequilibrium energy criterion for complex loadings are consistent with the experimental results obtained for biaxial tension, implying that the nonequilibrium thermodynamics model is both reasonable and reliable. The prediction error was presumed to be induced by the anisotropy of the 316 L stainless steel sheets.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB328903)the Special Fund of 2011 Internet of Things Development of Ministry of Industry and Information Technology,China(Grant No.2011BAJ03B13-2)+1 种基金the National Natural Science Foundation of China(Grant No.61473050)the Key Science and Technology Program of Chongqing,China(Grant No.cstc2012gg-yyjs40008)
文摘Cascading failure can cause great damage to complex networks, so it is of great significance to improve the network robustness against cascading failure. Many previous existing works on load-redistribution strategies require global information, which is not suitable for large scale networks, and some strategies based on local information assume that the load of a node is always its initial load before the network is attacked, and the load of the failure node is redistributed to its neighbors according to their initial load or initial residual capacity. This paper proposes a new load-redistribution strategy based on local information considering an ever-changing load. It redistributes the loads of the failure node to its nearest neighbors according to their current residual capacity, which makes full use of the residual capacity of the network. Experiments are conducted on two typical networks and two real networks, and the experimental results show that the new load-redistribution strategy can reduce the size of cascading failure efficiently.
基金Project supported by the Ministry of Science and Technology of China (No.2001BA803B03-05).
文摘The integrity assessment of defective pipelines represents a practically important task of structural analysis and design in various technological areas,such as oil and gas indus- try,power plant engineering and chemical factories.An iterative algorithm is presented for the kinematic limit analysis of 3-D rigid-perfectly plastic bodies.A numerical path scheme for radial loading is adopted to deal with complex multi-loading systems.The numerical procedure has been applied to carry out the plastic collapse analysis of pipelines with part-through slot under internal pressure,bending moment and axial force.The effects of various shapes and sizes of part-through slots on the collapse loads of pipelines are systematically investigated and evaluated.Some typical failure modes corresponding to different configurations of slots and loading forms are studied.
文摘Experimental investigations were pedermed on the plastic deformation along bilinear strain paths with various values of corner-angle by subjecting thin-walled tubular specimens of type 302 stainless steel to combined axial and torsional loads. Variations of scalar and vectorial behavior of the stress response are discnssed in the vector space of plastic strain. It is found that the intrinsic geometry of loading path, the plastic strain history and the coapled effect among strain components effect effectively the stress response of the material. The experimental results also show that these effects will disappear gradually with increasing strain.
文摘Electroceuticals are medical devices that employ electric signals to alter the activity of specific nerve fibers to achieve therapeutic effects. The rapid growth of RF microelectronics has resulted in the development of very small, portable, and inexpensive shortwave and microwave radio frequency (RF) amplifiers, raising the possibility of utilizing these new RF technologies to develop non-contact electroceutical devices. However, the bio-electromagnetics literature suggests that beyond 10 MHz, RF fields cannot influence biological tissue, beyond simple heating, because effective demodulation mechanisms at these frequencies do not exist in the body. However, RF amplifiers operating at or near saturation have non-linear interactions with complex loads, and if body tissue creates a complex loading condition, the opportunity exists for the coupled system to produce non-linear effects, that is, the equivalent of demodulation may occur. Correspondingly, exposure of tissue to pulsed RF energy could result in the creation of low frequency demodulation components capable of influencing tissue activity. Here, we develop a one-dimen- sional, numerical simulation to investigate the complex loading conditions under which such demodulation could arise. Applying these results in a physical prototype device, we show that up to7.5% demodulation can be obtained for a 40 MHz RF field pulsed at 1 KHz. Implications for this research include the possibility of developing wearable, electromagnetic electroceutical de- vices.
基金Scientific Research Project of Department of Education of Liaoning Province,China(No.L2014228)
文摘The load spectrum of the main bearing of tunnel boring machine( TBM) is difficult to establish because of the complex factors affecting the driving load of tunneling. In this paper, a simulation model of dynamic load of cutterhead is established,with a view to structural features and special conditions, based on a complex combination stratum, the cutter layout model and cutterhead control parameters,and it is a dynamic load boundary of the main drive bearing. Combined with the load distribution calculation of the main bearing and Hertz contact theory, the prediction model of dynamic load spectrum of the main drive bearing is completed during tunneling,and in accordance with the predicted results,the static and dynamics characteristics of load spectrum for the main drive bearing on the thrust and tilting moment are analyzed. The results of cutterhead load show that,in the certain complex stratum, the fluctuations of load for thrust rollers can reflect formation interface information of complex stratum in current tunneling. The main drive bearing bear the thrust and overturning moment of cutterhead under the composite,the external load has a greater influence on the load-spectrum of reverse thrust roller than that of main thrust roller,and the maximum contact stress of the two row roller is almost the same. The load spectrum,obtained by this method,can provide a meaningful reference for the design and checking of the main drive bearing,and also can be the basis of its fatigue reliability.
基金supported by the National Key Research and Development Program of China under Grand No.2016YFB0200902supported by the Program for Guangdong Introducing Innovative and Entrepreneurial Teams under Grant No.2016ZT06D211
文摘In this paper, wave-body interactions under the effects of complex topography are investigated numerically by a two-phase incompressible Reynolds-Averaged Navier-Stokes(RANS) solver in OpenFOAM. A submerged bottom-standing structure is distributed below the floating body, and the effects of the water depth and top width of the submerged structure on wave-body interactions are studied. The results show that the submerged structure can affect wave loads and roll motion. The vertical force can be amplified on the fixed body when the water depth of the submerged structure is smaller than half of the water depth of the body. The top width significantly affects the vertical force when the top width is smaller than the incident wave length and larger than the body width. For the free-rolling body, roll amplitude can be increased when the ratio of the incident wave length to the water depth of the submerged structure is large enough. On the resonance condition, roll amplitude is slightly reduced by the submerged structure. The effects of the top width on roll amplitude are remarkable when special conditions are fulfilled.
