There has been increasing interest in numerical simulations of fragmentation of expanding warheads in 3D.Accordingly there is a pressure on developers of leading commercial codes,such as LS-DYNA.AUTODYN and IMPETUS Af...There has been increasing interest in numerical simulations of fragmentation of expanding warheads in 3D.Accordingly there is a pressure on developers of leading commercial codes,such as LS-DYNA.AUTODYN and IMPETUS Afea.to implement the reliable fracture models and the efficient solution techniques.The applicability of the Johnson—Cook strength and fracture model is evaluated by comparing the fracture behaviour of an expanding steel casing of a warhead with experiments.The numerical codes and different numerical solution techniques,such as Eulerian,Lagrangian.Smooth particle hydrodynamics(SPH).and the corpuscular models recently implemented in IMPETUS Afea are compared.For the same solution techniques and material models we find that the codes give similar results.The SPH technique and the corpuscular technique are superior to the Eulerian technique and the Lagrangian technique(with erosion) when it is applied to materials that have fluid like behaviour such as the explosive and the tracer.The Eulerian technique gives much larger calculation time and both the Lagrangian and Eulerian techniques seem to give less agreement with our measurements.To more correctly simulate the fracture behaviours of the expanding steel casing,we applied that ductility decreases with strain rate.The phenomena may be explained by the realization of adiabatic shear bands.An implemented node splitting algorithm in IMPETUS Afea seems very promising.展开更多
By utilizing the two numerical codes RFPA3 D and FLAC3 D, the effect of heterogeneity on failure mode and failure mechanism of rock around deep underground excavations under tri-axial stress is analyzed. It is found t...By utilizing the two numerical codes RFPA3 D and FLAC3 D, the effect of heterogeneity on failure mode and failure mechanism of rock around deep underground excavations under tri-axial stress is analyzed. It is found that zonal disintegration is a large scale shear-slip failure developed in deep surrounding rock mass under tri-axial stress, which is accompanied by a large amount of tensile failure. The distance between fractures and the number of fractures have a close correlation with the rock mass heterogeneity. With an increase of the homogeneity index of the rock mass, the distances between fractures decrease and the number of fractures increases. For an intact hard rock mass with relative high homogeneity, only failure mode characterized as v-shaped notches can be formed due to the intersection of intensively developed shear bands. None of the zonal disintegration can be formed due to the fact that with increasing homogeneity, the failure mechanism of rock mass is gradually dominated by shear failure rather than tensile failure.展开更多
with rapid achievement of current information technology and computing ability and applications,much more digital content such as films,cartoons,design drawings,office documents and software source codes are produced ...with rapid achievement of current information technology and computing ability and applications,much more digital content such as films,cartoons,design drawings,office documents and software source codes are produced in daily work,however to protect the content being copying,shared or deliberately stolen by inside or outside,digital rights management(DRM) became more and more important for digital content protection.In this paper,we studied various DRM model,technology and application,and first proposed DRM Security Infrastructure(DSI),in which we defined encryption,hash,signature algorithm,watermarking algorithms,authentication,usage control,trusted counter,conditional trace,secure payment,and based on the DSI we then proposed a whole classification approach and architecture of all kinds of DRMs,in which we proposed 6 typical classes of copyrights and content protection DRMs architecture:(1) Software-oriented DRM,(2) e Book-oriented DRM,(3) Video-oriented DRM,(4) Image-Oriented DRM(5) Unstructured data oriented DRM,(6) Text-oriented DRM.Based on the above DSI,we then proposed a dynamic DRM model selection method for various DRM application,which can be adapted dynamically for different technology of different applications,which can provide awhole solution for variant DRM development in a rapid and customized mode.The proposed DRM method,technology and application in this paper provided a common,flexible and extendable solution for variant DRM scenes,and can support rapid and customized development.Moreover,we proposed an opinion that the future life will enter into a new era that the content usage and consumption will not again adopt DRM technology rather than with law,liberty and morality.展开更多
文摘There has been increasing interest in numerical simulations of fragmentation of expanding warheads in 3D.Accordingly there is a pressure on developers of leading commercial codes,such as LS-DYNA.AUTODYN and IMPETUS Afea.to implement the reliable fracture models and the efficient solution techniques.The applicability of the Johnson—Cook strength and fracture model is evaluated by comparing the fracture behaviour of an expanding steel casing of a warhead with experiments.The numerical codes and different numerical solution techniques,such as Eulerian,Lagrangian.Smooth particle hydrodynamics(SPH).and the corpuscular models recently implemented in IMPETUS Afea are compared.For the same solution techniques and material models we find that the codes give similar results.The SPH technique and the corpuscular technique are superior to the Eulerian technique and the Lagrangian technique(with erosion) when it is applied to materials that have fluid like behaviour such as the explosive and the tracer.The Eulerian technique gives much larger calculation time and both the Lagrangian and Eulerian techniques seem to give less agreement with our measurements.To more correctly simulate the fracture behaviours of the expanding steel casing,we applied that ductility decreases with strain rate.The phenomena may be explained by the realization of adiabatic shear bands.An implemented node splitting algorithm in IMPETUS Afea seems very promising.
基金supported by the National Natural Science Foundation of China (Nos. 51304036, 51222401 and 51174045)the Fundamental Research Funds for the Central Universities of China(Nos. N120101001 and N120601002)+1 种基金the National Basic Research Program of China (No. 2013CB227900)the China-South Africa Joint Research Program (No. 2012DFG71060)
文摘By utilizing the two numerical codes RFPA3 D and FLAC3 D, the effect of heterogeneity on failure mode and failure mechanism of rock around deep underground excavations under tri-axial stress is analyzed. It is found that zonal disintegration is a large scale shear-slip failure developed in deep surrounding rock mass under tri-axial stress, which is accompanied by a large amount of tensile failure. The distance between fractures and the number of fractures have a close correlation with the rock mass heterogeneity. With an increase of the homogeneity index of the rock mass, the distances between fractures decrease and the number of fractures increases. For an intact hard rock mass with relative high homogeneity, only failure mode characterized as v-shaped notches can be formed due to the intersection of intensively developed shear bands. None of the zonal disintegration can be formed due to the fact that with increasing homogeneity, the failure mechanism of rock mass is gradually dominated by shear failure rather than tensile failure.
文摘with rapid achievement of current information technology and computing ability and applications,much more digital content such as films,cartoons,design drawings,office documents and software source codes are produced in daily work,however to protect the content being copying,shared or deliberately stolen by inside or outside,digital rights management(DRM) became more and more important for digital content protection.In this paper,we studied various DRM model,technology and application,and first proposed DRM Security Infrastructure(DSI),in which we defined encryption,hash,signature algorithm,watermarking algorithms,authentication,usage control,trusted counter,conditional trace,secure payment,and based on the DSI we then proposed a whole classification approach and architecture of all kinds of DRMs,in which we proposed 6 typical classes of copyrights and content protection DRMs architecture:(1) Software-oriented DRM,(2) e Book-oriented DRM,(3) Video-oriented DRM,(4) Image-Oriented DRM(5) Unstructured data oriented DRM,(6) Text-oriented DRM.Based on the above DSI,we then proposed a dynamic DRM model selection method for various DRM application,which can be adapted dynamically for different technology of different applications,which can provide awhole solution for variant DRM development in a rapid and customized mode.The proposed DRM method,technology and application in this paper provided a common,flexible and extendable solution for variant DRM scenes,and can support rapid and customized development.Moreover,we proposed an opinion that the future life will enter into a new era that the content usage and consumption will not again adopt DRM technology rather than with law,liberty and morality.
