The rheological properties of most liquid in nature are between liquids and solids, including both elastic changes and viscosity changes, that is socalled ＂viscoelastic＂. Dynamic oscillatory test was used to quantit...The rheological properties of most liquid in nature are between liquids and solids, including both elastic changes and viscosity changes, that is socalled ＂viscoelastic＂. Dynamic oscillatory test was used to quantitatively study the distinct viscoelastic behaviors of debris flow slurry in the shear stress conditions for the first time in this study. The debris flow slurry samples were from Jiangjiagou Ravine, Yunnan Province, China. The experimental results were found that at the low and middle stages of shearing, when the angular velocity 09〈72.46 s-1, the loss modulus （G was greater than the storage modulus （G3, i.e. G＂〉G＇. At the late stage of shearing, when the angular velocity co-72.46 s-x, the storage modulus was greater than or equal to the loss G = G, tan -〈 1 （where phase-shift modulus, i.e. ＇ 〉 ＂ angle 5=G＂,/G3, and the debris flow slurry was in a gel state. Therefore, the progress of this experimental study further reveals the mechanism of hyperconcentrated debris flows with a high velocity on low-gradient ravines.展开更多
To improve the machinability of optical glass and achieve optical parts with satisfied surface quality and dimensional accuracy, scratching experiments with increasing cutting depth were conducted on glass SF6 to eval...To improve the machinability of optical glass and achieve optical parts with satisfied surface quality and dimensional accuracy, scratching experiments with increasing cutting depth were conducted on glass SF6 to evaluate the influence of cutting fluid properties on the machinability of glass. The sodium carbonate solution of 10.5% concentration was chosen as cutting fluid. Then the critical depths in scratching experiments with and without cutting fluid were examined. Based on this, turning experiments were carried out, and the surface quality of SF6 was assessed. Compared with the process of dry cutting, the main indexes of surface roughness decrease by over 70% totally. Experimental results indicated that the machinability of glass SF6 can be improved by using the sodium carbonate solution as cutting fluid.展开更多
This paper is concerned with the global existence and exponential stability of solutions with large initial date in H^1 for real viscous heat-conducting flow with shear viscosity.
This paper investigates the bed shear stress based on the condition of the incipient motion of sediment in a uniform-flow flume covered with emergent rigid vegetation,which is represented by arrays of circular cylinde...This paper investigates the bed shear stress based on the condition of the incipient motion of sediment in a uniform-flow flume covered with emergent rigid vegetation,which is represented by arrays of circular cylinders arranged in a regular pattern.A total of 148 tests are performed to observe the influence of the vegetation density,bed slope,flow depth and sediment size on the bed shear stress.The tests reveal that when the sediment is in incipient motion,the resistances acting on the flow passing the rigid vegetation contain the vegetation resistance and the bed shear stress.This shear stress could be divided into two parts:the grain shear stress and the shear stress caused by sand dunes,which are the deformed bedform with the sediment incipient motion.An empirical relationship between the shear stress of the sand dune and vegetation density,the Froude number,the apparent vegetation layer velocity is developed.展开更多
Basing on a prototype of DCA airfoil and axial displacement overlap of 10% chord,seven kinds of tangential displacements are taken to simulate the flow conditions in tandem cascade with numerical methods to select a b...Basing on a prototype of DCA airfoil and axial displacement overlap of 10% chord,seven kinds of tangential displacements are taken to simulate the flow conditions in tandem cascade with numerical methods to select a better geometry with higher performance.The configuration with tangential displacement b/t=0.83 would gain better flow performance than the others.On this basis,two configurations with tangential displacement b/t=0.67 and 0.83 among several configurations are chosen to take into experimental investigations by using TR-PIV system to capture the flow velocity instantaneously.The configuration with b/t=0.83 is observed a better flow field performance than b/t=0.67.Its injection flow in the gap zone is much stronger,wake zone area of the front and rear blade is smaller and the stream flow is more improved.It shows that the flow performance in experimental investigation is quite in the same trend as the numerical results predict.展开更多
It is not uncommon to observe shear fractures in ductile rocks oriented at more than 45° with respect to the maximum compression direction. Since these orientations cannot be explained with the classic Mohr-Coulu...It is not uncommon to observe shear fractures in ductile rocks oriented at more than 45° with respect to the maximum compression direction. Since these orientations cannot be explained with the classic Mohr-Coulumb or Tresca yield criteria, Zheng et al.(Journal of Structural Geology, 35: 1394–1405, 2011) proposed the maximum effective moment(MEM) failure criterion. This rule suggests that shear fractures in ductile rocks form at ?55° with the maximum compression axis and that this orientation is material-independent and, therefore, universal. Zheng et al.(Science China: Earth Sciences, 57(11): 2819–2824, 2014) used data from our own experiments as supporting evidence of their failure criterion. In this contribution we discuss why shear fracture formation in ductile rocks indeed strongly depends on the mechanical properties of the deforming medium, and why experimental data should not be taken to prove the validity of the MEM criterion. The formation mechanisms and orientations of shear fractures in our experiments significantly vary depending on the material strength and degree and type of anisotropy(composite and intrinsic). We therefore demonstrate using experimental data that a universal failure angle in ductile and anisotropic rocks does not apply. Additionally, we highlight some inconsistencies of the MEM criterion.展开更多
基金supported by the Youth Talent Team Program of Institute of Mountain Hazards and Environment,CASthe National Natural Science Foundation of China (Grant No.406710260)
文摘The rheological properties of most liquid in nature are between liquids and solids, including both elastic changes and viscosity changes, that is socalled ＂viscoelastic＂. Dynamic oscillatory test was used to quantitatively study the distinct viscoelastic behaviors of debris flow slurry in the shear stress conditions for the first time in this study. The debris flow slurry samples were from Jiangjiagou Ravine, Yunnan Province, China. The experimental results were found that at the low and middle stages of shearing, when the angular velocity 09〈72.46 s-1, the loss modulus （G was greater than the storage modulus （G3, i.e. G＂〉G＇. At the late stage of shearing, when the angular velocity co-72.46 s-x, the storage modulus was greater than or equal to the loss G = G, tan -〈 1 （where phase-shift modulus, i.e. ＇ 〉 ＂ angle 5=G＂,/G3, and the debris flow slurry was in a gel state. Therefore, the progress of this experimental study further reveals the mechanism of hyperconcentrated debris flows with a high velocity on low-gradient ravines.
基金Supported by National Natural Science Foundation of China (No. 50775057)
文摘To improve the machinability of optical glass and achieve optical parts with satisfied surface quality and dimensional accuracy, scratching experiments with increasing cutting depth were conducted on glass SF6 to evaluate the influence of cutting fluid properties on the machinability of glass. The sodium carbonate solution of 10.5% concentration was chosen as cutting fluid. Then the critical depths in scratching experiments with and without cutting fluid were examined. Based on this, turning experiments were carried out, and the surface quality of SF6 was assessed. Compared with the process of dry cutting, the main indexes of surface roughness decrease by over 70% totally. Experimental results indicated that the machinability of glass SF6 can be improved by using the sodium carbonate solution as cutting fluid.
文摘This paper is concerned with the global existence and exponential stability of solutions with large initial date in H^1 for real viscous heat-conducting flow with shear viscosity.
基金supported by the National Basic Research Program of China ("973" Project) (Grant No. 2011CB403303)the China National Funds for Distinguished Young Scientists (Grant No. 51125034)the National Natural Science Foundation of China (Grant Nos. 50879019,51109065,51239003)
文摘This paper investigates the bed shear stress based on the condition of the incipient motion of sediment in a uniform-flow flume covered with emergent rigid vegetation,which is represented by arrays of circular cylinders arranged in a regular pattern.A total of 148 tests are performed to observe the influence of the vegetation density,bed slope,flow depth and sediment size on the bed shear stress.The tests reveal that when the sediment is in incipient motion,the resistances acting on the flow passing the rigid vegetation contain the vegetation resistance and the bed shear stress.This shear stress could be divided into two parts:the grain shear stress and the shear stress caused by sand dunes,which are the deformed bedform with the sediment incipient motion.An empirical relationship between the shear stress of the sand dune and vegetation density,the Froude number,the apparent vegetation layer velocity is developed.
文摘Basing on a prototype of DCA airfoil and axial displacement overlap of 10% chord,seven kinds of tangential displacements are taken to simulate the flow conditions in tandem cascade with numerical methods to select a better geometry with higher performance.The configuration with tangential displacement b/t=0.83 would gain better flow performance than the others.On this basis,two configurations with tangential displacement b/t=0.67 and 0.83 among several configurations are chosen to take into experimental investigations by using TR-PIV system to capture the flow velocity instantaneously.The configuration with b/t=0.83 is observed a better flow field performance than b/t=0.67.Its injection flow in the gap zone is much stronger,wake zone area of the front and rear blade is smaller and the stream flow is more improved.It shows that the flow performance in experimental investigation is quite in the same trend as the numerical results predict.
文摘It is not uncommon to observe shear fractures in ductile rocks oriented at more than 45° with respect to the maximum compression direction. Since these orientations cannot be explained with the classic Mohr-Coulumb or Tresca yield criteria, Zheng et al.(Journal of Structural Geology, 35: 1394–1405, 2011) proposed the maximum effective moment(MEM) failure criterion. This rule suggests that shear fractures in ductile rocks form at ?55° with the maximum compression axis and that this orientation is material-independent and, therefore, universal. Zheng et al.(Science China: Earth Sciences, 57(11): 2819–2824, 2014) used data from our own experiments as supporting evidence of their failure criterion. In this contribution we discuss why shear fracture formation in ductile rocks indeed strongly depends on the mechanical properties of the deforming medium, and why experimental data should not be taken to prove the validity of the MEM criterion. The formation mechanisms and orientations of shear fractures in our experiments significantly vary depending on the material strength and degree and type of anisotropy(composite and intrinsic). We therefore demonstrate using experimental data that a universal failure angle in ductile and anisotropic rocks does not apply. Additionally, we highlight some inconsistencies of the MEM criterion.
