Shock tubes create simulated blast waves which can be directed and measured lo study blast wave effects under laboratory conditions.It is desirable to increase available peak pressure from ~1 MPa to ~5 MPa to simulate...Shock tubes create simulated blast waves which can be directed and measured lo study blast wave effects under laboratory conditions.It is desirable to increase available peak pressure from ~1 MPa to ~5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors.Three methods are experimentally investigated to increase peak simulated blast pressure produced by an oxyacetylene driven shock tube while maintaining suitability for laboratory studies.The first method is the addition of a Shchelkin spiral priming section which supports a deflagration to detonation transition.This approach increases the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve(near Friedlander waveform).The second method is a bottleneck between the driving and driven sections.Coupling a 79 mm diameter driving section to a 53 mm driven section increases the peak pressure from 1.17 MPa to 2.25 MPa.A 103 mm driving section is used to increase peak pressure to 2.64 MPa.The third method,adding solid fuel to the driving section with the oxyacetylene,results in a peak pressure increasing to 1.70 MPa.展开更多
Among the intrinsic properties of some materials,e.g.,foams,porous materials,and granular materials,are their ability to mitigate shock waves.This paper investigated shock wave mitigation by a sandwich panel with a gr...Among the intrinsic properties of some materials,e.g.,foams,porous materials,and granular materials,are their ability to mitigate shock waves.This paper investigated shock wave mitigation by a sandwich panel with a granular core.Numerical simulations and experimental tests were performed using Autodyn hydro-code software and a shock tube,respectively.The smoothed particle hydrodynamics(SPH)method was used to model granular materials.Sawdust and pumice,whose properties were determined by several compression tests,were used as granular materials in the sandwich panel core.These granular materials possess many mechanisms,including compacting(e.g.,sawdust)and crushing(e.g.,pumice)that mitigate shock/blast wave.The results indicated the ineffectiveness of using a core with low thickness,yet it was demonstrated to be effective with high thickness.Low-thickness pumice yielded better results for wave mitigation.The use of these materials with a core with appropriate core reduces up to 88%of the shock wave.The results of the experiments and numerical simulations were compared,suggesting a good agreement between the two.This indicates the accuracy of simulation and the ability of the SPH method to modeling granular material under shock loading.The effects of grain size and the coefficient of friction between grains have also been investigated using simulation,implying that increasing the grain size and coefficient of friction between grains both reduce overpressure.展开更多
A newly designed shock-tube for biological testing has been built in our labo-ratory.This tube is 39.34 m long.It consists of several sections:high pressure section,divergent section,transitional section,test section ...A newly designed shock-tube for biological testing has been built in our labo-ratory.This tube is 39.34 m long.It consists of several sections:high pressure section,divergent section,transitional section,test section and wave-dissipated section.In theopen condition,the maximal overpressure is about 214,3 kPa,while in the closed condi-tion,the maximal overpressure may go up to 630.3 kPa.The energy source is compres-sed air.Using this equipment,we are able to inflict blast injuries with various degreesof severity in rabbits,dogs and sheep.展开更多
文摘Shock tubes create simulated blast waves which can be directed and measured lo study blast wave effects under laboratory conditions.It is desirable to increase available peak pressure from ~1 MPa to ~5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors.Three methods are experimentally investigated to increase peak simulated blast pressure produced by an oxyacetylene driven shock tube while maintaining suitability for laboratory studies.The first method is the addition of a Shchelkin spiral priming section which supports a deflagration to detonation transition.This approach increases the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve(near Friedlander waveform).The second method is a bottleneck between the driving and driven sections.Coupling a 79 mm diameter driving section to a 53 mm driven section increases the peak pressure from 1.17 MPa to 2.25 MPa.A 103 mm driving section is used to increase peak pressure to 2.64 MPa.The third method,adding solid fuel to the driving section with the oxyacetylene,results in a peak pressure increasing to 1.70 MPa.
文摘Among the intrinsic properties of some materials,e.g.,foams,porous materials,and granular materials,are their ability to mitigate shock waves.This paper investigated shock wave mitigation by a sandwich panel with a granular core.Numerical simulations and experimental tests were performed using Autodyn hydro-code software and a shock tube,respectively.The smoothed particle hydrodynamics(SPH)method was used to model granular materials.Sawdust and pumice,whose properties were determined by several compression tests,were used as granular materials in the sandwich panel core.These granular materials possess many mechanisms,including compacting(e.g.,sawdust)and crushing(e.g.,pumice)that mitigate shock/blast wave.The results indicated the ineffectiveness of using a core with low thickness,yet it was demonstrated to be effective with high thickness.Low-thickness pumice yielded better results for wave mitigation.The use of these materials with a core with appropriate core reduces up to 88%of the shock wave.The results of the experiments and numerical simulations were compared,suggesting a good agreement between the two.This indicates the accuracy of simulation and the ability of the SPH method to modeling granular material under shock loading.The effects of grain size and the coefficient of friction between grains have also been investigated using simulation,implying that increasing the grain size and coefficient of friction between grains both reduce overpressure.
文摘A newly designed shock-tube for biological testing has been built in our labo-ratory.This tube is 39.34 m long.It consists of several sections:high pressure section,divergent section,transitional section,test section and wave-dissipated section.In theopen condition,the maximal overpressure is about 214,3 kPa,while in the closed condi-tion,the maximal overpressure may go up to 630.3 kPa.The energy source is compres-sed air.Using this equipment,we are able to inflict blast injuries with various degreesof severity in rabbits,dogs and sheep.
