The mesoscopic failure mechanism and the macro-mechanical characteristics of soil-rock mixture(S-RM) under external load are largely controlled by S-RM's meso-structural features. The objective of this work is to ...The mesoscopic failure mechanism and the macro-mechanical characteristics of soil-rock mixture(S-RM) under external load are largely controlled by S-RM's meso-structural features. The objective of this work is to improve the three-dimensional technology for the generation of the random meso-structural models of S-RM, for randomly generating irregular rock blocks in S-RM with different shapes, sizes, and distributions according to the characteristics of the rock blocks' size distribution. Based on the new improved technology, a software system named as R-SRM3 D for generation and visualization of S-RM is developed. Using R-SRM3 D, a three-dimensional meso-structural model of S-RM is generated and used to study the meso-mechanical behavior through a series of true-triaxial numerical tests. From the numerical tests, the following conclusions are obtained. The meso-stress field of S-RM is influenced by the distribution of the internal rock blocks, and the macro-mechanical characteristics of S-RM are anisotropic in 3D; the intermediate principal stress and the soil-rock interface properties have significant influence on the macro strength of S-RM.展开更多
Side loads and aeroelastic stability of rocket nozzle were studied by solving Navier-Stokes equation coupled with structural equation of motion.The computation was implemented at different total pressure inlet conditi...Side loads and aeroelastic stability of rocket nozzle were studied by solving Navier-Stokes equation coupled with structural equation of motion.The computation was implemented at different total pressure inlet conditions,and flow phenomena of free shock separation(FSS) and restricted shock separation(RSS) were captured.At certain total pressure inlet conditions,it was found that both kinds of separations existed in nozzle flow filed,while RSS exhibited combined space asymmetry and time unsteady characteristics.The corresponding asymmetric circumferential pressure distribution,strong pressure fluctuation in separation region and large range of displacement of shock wave all led to severe side loads.Besides,for flexible nozzles,the low pressure gradient in separation region might reduce structure stability at nozzle exit,resulting in large local deformation.It was also found that aeroelasticity exhibited buffeting characteristic due to the asymmetric separation,resulting in reduction of aeroelastic stability,even structure destruction.Moreover,aeroelasticity might amplify side loads and aggravate its growth rate.However,with increment of inlet pressure,nozzle aeroelastic stability was also increased when a full flow was nearly reached.展开更多
This paper reports on an experimental program of work which investigates the reliability, durability, and packaging of fiber Bragg gratings （FBGs） for application as distributed strain sensors during structural fati...This paper reports on an experimental program of work which investigates the reliability, durability, and packaging of fiber Bragg gratings （FBGs） for application as distributed strain sensors during structural fatigue testing of military platforms. The influence of the FBG fabrication process on sensor reliability is investigated. In addition, methodologies for broad-area packaging and surface-mounting of FBG sensing arrays to defense platforms are developed and tested.展开更多
基金Project(51109117)supported by the National Natural Science Foundation of ChinaProject(20111081125)supported by the Independent Research Plan of Tsinghua University,ChinaProject(2013-KY-4)supported by the State Key Laboratory of Hydroscience and Engineering Project,China
文摘The mesoscopic failure mechanism and the macro-mechanical characteristics of soil-rock mixture(S-RM) under external load are largely controlled by S-RM's meso-structural features. The objective of this work is to improve the three-dimensional technology for the generation of the random meso-structural models of S-RM, for randomly generating irregular rock blocks in S-RM with different shapes, sizes, and distributions according to the characteristics of the rock blocks' size distribution. Based on the new improved technology, a software system named as R-SRM3 D for generation and visualization of S-RM is developed. Using R-SRM3 D, a three-dimensional meso-structural model of S-RM is generated and used to study the meso-mechanical behavior through a series of true-triaxial numerical tests. From the numerical tests, the following conclusions are obtained. The meso-stress field of S-RM is influenced by the distribution of the internal rock blocks, and the macro-mechanical characteristics of S-RM are anisotropic in 3D; the intermediate principal stress and the soil-rock interface properties have significant influence on the macro strength of S-RM.
基金supported by the National Natural Science Foundation of China (Grant No. 11072199)
文摘Side loads and aeroelastic stability of rocket nozzle were studied by solving Navier-Stokes equation coupled with structural equation of motion.The computation was implemented at different total pressure inlet conditions,and flow phenomena of free shock separation(FSS) and restricted shock separation(RSS) were captured.At certain total pressure inlet conditions,it was found that both kinds of separations existed in nozzle flow filed,while RSS exhibited combined space asymmetry and time unsteady characteristics.The corresponding asymmetric circumferential pressure distribution,strong pressure fluctuation in separation region and large range of displacement of shock wave all led to severe side loads.Besides,for flexible nozzles,the low pressure gradient in separation region might reduce structure stability at nozzle exit,resulting in large local deformation.It was also found that aeroelasticity exhibited buffeting characteristic due to the asymmetric separation,resulting in reduction of aeroelastic stability,even structure destruction.Moreover,aeroelasticity might amplify side loads and aggravate its growth rate.However,with increment of inlet pressure,nozzle aeroelastic stability was also increased when a full flow was nearly reached.
文摘This paper reports on an experimental program of work which investigates the reliability, durability, and packaging of fiber Bragg gratings （FBGs） for application as distributed strain sensors during structural fatigue testing of military platforms. The influence of the FBG fabrication process on sensor reliability is investigated. In addition, methodologies for broad-area packaging and surface-mounting of FBG sensing arrays to defense platforms are developed and tested.
