Currently,the application of the Yellow River silt in subgrade,especially in expressway subgrade,has not been widely promoted.The main reason is that the research on the mechanical characteristics of the Yellow River ...Currently,the application of the Yellow River silt in subgrade,especially in expressway subgrade,has not been widely promoted.The main reason is that the research on the mechanical characteristics of the Yellow River silt used for subgrade filling is extremely limited.In this study,the static shear test of the Yellow River silt under drained condition was carried out using Global Digital Systems(GDS)triaxial apparatus,and the effects of confining pressure,relative density and shear rate on the strength and deformation behavior of the Yellow River silt were investigated.The cohesive force of the Yellow River silt is low,and the friction angle is the main factor determining the shear strength.Friction angle at phase transformation stateφpt,friction angle at peak stateφps,friction angle at critical stateφcs,were obtained via the observation on the evolution law of mobilized friction angle during the whole shearing process.The friction angles corresponding to three different characteristic states have the following magnitude relationship,namelyφps>φcs>φpt.The strength parameters for low-grade subgrade and highgrade subgrade were chosen to be 29.33°and 33.75°.The critical state line(CSL),envelop of phase transformation(EOP),and envelop of dilatancy(EOD)for three different characteristic states were determined.The critical stress ratio M,the phase transformation stress ratio Mptand the dilatancy stress ratio Mdof the Yellow River silt are 1.199,1.235,1.152,respectively.These results provide a basis for the mechanical analysis of the Yellow River silt subgrades and the subsequent establishment of dynamic constitutive model of the Yellow River silt.展开更多
The true stress-sWain relationships of Ti-5A1-2Sn-2Zr-4Mo-4Cr（TC17） alloy with a wide range of strain rates were investigated by tmiaxial quasi-static and dynamic compression tests, respectively. Quasi- static compr...The true stress-sWain relationships of Ti-5A1-2Sn-2Zr-4Mo-4Cr（TC17） alloy with a wide range of strain rates were investigated by tmiaxial quasi-static and dynamic compression tests, respectively. Quasi- static compression tests were carried out with Instron 8874 test machine, while dynamic compression tests were performed with the split Hopkinson pressure bar （SHPB） which was installed with heating device and synchro- assembly system. The dynamic mechanical behaviors tests of TC17 were carded out from room temperature to 800 ℃ at intervals of 200 ℃ and at high sWain rates （5 500-1 9200 s-l）. The stress-strain curves considering temperature-sWain rate coupling actions were obtained. The Johnson-Cook constitutive model was developed through data fitting of the stress-sWain curves. The material constants in the developed constitutive model can be determined using isothermal and adiabatic stress-strain curves at different strain rates. The Johnson-Cook constitutive model provided satisfied prediction of the plastic flow stress for TC17 alloy.展开更多
基金National Natural Science Foundation of China(Grant Nos.5217836952109140)+4 种基金Key Projects of High Schools of Henan province of China(20A560021)Natural Science Foundation of Henan Province of China(202300410424)Youth Talent Promotion Project of Henan Province of China(2021HYTP016)Key Specialized Research and Development Breakthrough in Henan Province of China(212102310977)China Postdoctoral Science Foundation(2019M662533)。
文摘Currently,the application of the Yellow River silt in subgrade,especially in expressway subgrade,has not been widely promoted.The main reason is that the research on the mechanical characteristics of the Yellow River silt used for subgrade filling is extremely limited.In this study,the static shear test of the Yellow River silt under drained condition was carried out using Global Digital Systems(GDS)triaxial apparatus,and the effects of confining pressure,relative density and shear rate on the strength and deformation behavior of the Yellow River silt were investigated.The cohesive force of the Yellow River silt is low,and the friction angle is the main factor determining the shear strength.Friction angle at phase transformation stateφpt,friction angle at peak stateφps,friction angle at critical stateφcs,were obtained via the observation on the evolution law of mobilized friction angle during the whole shearing process.The friction angles corresponding to three different characteristic states have the following magnitude relationship,namelyφps>φcs>φpt.The strength parameters for low-grade subgrade and highgrade subgrade were chosen to be 29.33°and 33.75°.The critical state line(CSL),envelop of phase transformation(EOP),and envelop of dilatancy(EOD)for three different characteristic states were determined.The critical stress ratio M,the phase transformation stress ratio Mptand the dilatancy stress ratio Mdof the Yellow River silt are 1.199,1.235,1.152,respectively.These results provide a basis for the mechanical analysis of the Yellow River silt subgrades and the subsequent establishment of dynamic constitutive model of the Yellow River silt.
基金Funded by the National Basic Research Program of China(No.2009CB724401)the Major Science and Technology Program of High-end CNC Machine Tools and Basic Manufacturing Equipment(No.2012ZX04003-041)
文摘The true stress-sWain relationships of Ti-5A1-2Sn-2Zr-4Mo-4Cr（TC17） alloy with a wide range of strain rates were investigated by tmiaxial quasi-static and dynamic compression tests, respectively. Quasi- static compression tests were carried out with Instron 8874 test machine, while dynamic compression tests were performed with the split Hopkinson pressure bar （SHPB） which was installed with heating device and synchro- assembly system. The dynamic mechanical behaviors tests of TC17 were carded out from room temperature to 800 ℃ at intervals of 200 ℃ and at high sWain rates （5 500-1 9200 s-l）. The stress-strain curves considering temperature-sWain rate coupling actions were obtained. The Johnson-Cook constitutive model was developed through data fitting of the stress-sWain curves. The material constants in the developed constitutive model can be determined using isothermal and adiabatic stress-strain curves at different strain rates. The Johnson-Cook constitutive model provided satisfied prediction of the plastic flow stress for TC17 alloy.
