Drop tower is an important ground based facility for microgravity science experiment. The technical performances of the drop tower NMLC are advanced compared with similar facilities in the US, Germany and Japan. The m...Drop tower is an important ground based facility for microgravity science experiment. The technical performances of the drop tower NMLC are advanced compared with similar facilities in the US, Germany and Japan. The main components such as drop capsule, deceleration devices, release mechanism present its advantages and creativities.展开更多
Despite numerous research investigations to understand the influences of various structural parameters,to the authors'knowledge,no research has been the effect of different angles of incidence on stab response and...Despite numerous research investigations to understand the influences of various structural parameters,to the authors'knowledge,no research has been the effect of different angles of incidence on stab response and performance of different types of protective textiles.Three distinct structures of 3D woven textiles and 2D plain weave fabric made with similar high-performance fiber and areal density were designed and manufactured to be tested.Two samples,one composed of a single and the other of 4-panel layers,from each fabric type structure,were prepared,and tested against stabbing at[0○],[22.5○],and[45○]angle of incidence.A new stabbing experimental setup that entertained testing of the specimens at various angles of incidence was engineered and utilized.The stabbing bench is also equipped with magnetic sensors and a UK Home Office Scientific Development Branch(HOSDB)/P1/B sharpness engineered knives to measure the impact velocity and exerted impact energy respectively.A silicon compound was utilized to imprint the Back Face Signature(BFS)on the backing material after every specimen test.Each silicon print was then scanned,digitized,and precisely measured to evaluate the stab response and performance of the specimen based on different performance variables,including Depth of Trauma(DOT),Depth of Penetration(DOP),and Length of Penetration(LOP).Besides,the post-impact surface failure modes of the fabrics were also measured using Image software and analyzed at the microscale level.The results show stab angle of incidence greatly influences the stab response and performance of protective textiles.The outcome of the study could provide not only valuable insights into understanding the stab response and capabilities of protective textiles under different angle of incidence,but also provide valuable information for protective textile manufacturer,armor developer and stab testing and standardizing organizations to consider the angle of incidence while developing,testing,optimizing,and using protective textiles in various applications.展开更多
In space,surface tension plays an important role and liquid behaviour is much different from that on the ground.The static capillary surfaces in the annular space between two coaxial cones under microgravity are studi...In space,surface tension plays an important role and liquid behaviour is much different from that on the ground.The static capillary surfaces in the annular space between two coaxial cones under microgravity are studied in this paper.Theoretical expressions of the capillary surfaces are derived and a procedure is developed to predict the capillary surfaces based on the expressions.By considering various liquid contact angles,liquid volumes,and container geometries,numerical simulation with the volume of fluid method is carried out and microgravity experiments in Beijing Drop Tower are performed.The numerical and experimental results are in good agreement with theoretical predictions.Furthermore,capillary surfaces in an annulus with constant cross-section and in a spherical tank with a central column are also discussed.z3 will decrease obviously with the increase of the liquid contact angle.The theoretical models and findings will be great helpful for liquid management in space and the evaluation of propellant residue.展开更多
文摘Drop tower is an important ground based facility for microgravity science experiment. The technical performances of the drop tower NMLC are advanced compared with similar facilities in the US, Germany and Japan. The main components such as drop capsule, deceleration devices, release mechanism present its advantages and creativities.
文摘Despite numerous research investigations to understand the influences of various structural parameters,to the authors'knowledge,no research has been the effect of different angles of incidence on stab response and performance of different types of protective textiles.Three distinct structures of 3D woven textiles and 2D plain weave fabric made with similar high-performance fiber and areal density were designed and manufactured to be tested.Two samples,one composed of a single and the other of 4-panel layers,from each fabric type structure,were prepared,and tested against stabbing at[0○],[22.5○],and[45○]angle of incidence.A new stabbing experimental setup that entertained testing of the specimens at various angles of incidence was engineered and utilized.The stabbing bench is also equipped with magnetic sensors and a UK Home Office Scientific Development Branch(HOSDB)/P1/B sharpness engineered knives to measure the impact velocity and exerted impact energy respectively.A silicon compound was utilized to imprint the Back Face Signature(BFS)on the backing material after every specimen test.Each silicon print was then scanned,digitized,and precisely measured to evaluate the stab response and performance of the specimen based on different performance variables,including Depth of Trauma(DOT),Depth of Penetration(DOP),and Length of Penetration(LOP).Besides,the post-impact surface failure modes of the fabrics were also measured using Image software and analyzed at the microscale level.The results show stab angle of incidence greatly influences the stab response and performance of protective textiles.The outcome of the study could provide not only valuable insights into understanding the stab response and capabilities of protective textiles under different angle of incidence,but also provide valuable information for protective textile manufacturer,armor developer and stab testing and standardizing organizations to consider the angle of incidence while developing,testing,optimizing,and using protective textiles in various applications.
基金supported by the China Manned Space Engineering Program(Fluid Physics Experimental Rack and the Priority Research Program of Space Station)the Natural Science Foundation Project(Grant No.12032020).
文摘In space,surface tension plays an important role and liquid behaviour is much different from that on the ground.The static capillary surfaces in the annular space between two coaxial cones under microgravity are studied in this paper.Theoretical expressions of the capillary surfaces are derived and a procedure is developed to predict the capillary surfaces based on the expressions.By considering various liquid contact angles,liquid volumes,and container geometries,numerical simulation with the volume of fluid method is carried out and microgravity experiments in Beijing Drop Tower are performed.The numerical and experimental results are in good agreement with theoretical predictions.Furthermore,capillary surfaces in an annulus with constant cross-section and in a spherical tank with a central column are also discussed.z3 will decrease obviously with the increase of the liquid contact angle.The theoretical models and findings will be great helpful for liquid management in space and the evaluation of propellant residue.
