A model of evolution induced catastrophe(EIC)characterized by a nonlocal interaction is proposed.The general feature of the model is its two bias states:explosively catastrophic and globally stable,both consisting in ...A model of evolution induced catastrophe(EIC)characterized by a nonlocal interaction is proposed.The general feature of the model is its two bias states:explosively catastrophic and globally stable,both consisting in a cascade of locally unstable states.A one-dimensional analysis reveals a transition region from globally stable to catastrophe.A two-dimensional simulation gives a thin fractal fracture profile similar to that observed and also a possible spectrum of fracture fractal.All these are different from percolation.Hence,the EIC model may represent a prototype of natural processes.展开更多
地震是地壳中积累的大量弹性应变能突然释放的灾变破坏过程。对地震的预测(特别是短临预测)一直是地震学的一个巨大挑战,《Science》(2005)曾将其列为125个科学问题之一(Are there earthquake precursors that can lead to useful predi...地震是地壳中积累的大量弹性应变能突然释放的灾变破坏过程。对地震的预测(特别是短临预测)一直是地震学的一个巨大挑战,《Science》(2005)曾将其列为125个科学问题之一(Are there earthquake precursors that can lead to useful predictions?)。解决这一问题的关键点在于,是否存在与地震发生具有因果关联的、有物理基础的前兆现象?利用何种观测手段来探测并识别这种前兆现象?展开更多
This paper reports a comparative study of shear banding in BMGs resulting from thermal softening and free volume creation. Firstly,the effects of thermal softening and free volume creation on shear instability are dis...This paper reports a comparative study of shear banding in BMGs resulting from thermal softening and free volume creation. Firstly,the effects of thermal softening and free volume creation on shear instability are discussed. It is known that ther-mal softening governs thermal shear banding,hence it is essentially energy related. However,compound free volume creation is the key factor to the other instability,though void-induced softening seems to be the counterpart of thermal softening. So,the driving force for shear instability owing to free volume creation is very dif-ferent from the thermally assisted one. In particular,long wave perturbations are always unstable owing to compound free volume creation. Therefore,the shear instability resulting from coupled compound free volume creation and thermal softening may start more like that due to free volume creation. Also,the compound free volume creation implies a specific and intrinsic characteristic growth time of shear instability. Finally,the mature shear band width is governed by the corre-sponding diffusions (thermal or void diffusion) within the band. As a rough guide,the dimensionless numbers: Thermal softening related number B,Deborah number (denoting the relation of instability growth rate owing to compound free volume and loading time) and Lewis number (denoting the competition of different diffusions) show us their relative importance of thermal softening and free volume creation in shear banding. All these results are of particular significance in understanding the mechanism of shear banding in bulk metallic glasses (BMGs).展开更多
The note presents a method of constructing dynamic constitutive equations of material by means of Lagrange experiment and analysis. Tests were carried out by a light gas gun and the stress history profiles were record...The note presents a method of constructing dynamic constitutive equations of material by means of Lagrange experiment and analysis. Tests were carried out by a light gas gun and the stress history profiles were recorded on multiple Lagrange positions. The dynamic constitutive equations were deduced from the regression of a series of data which was obtained by Lagrange analysis based upon recorded multiple stress histories. Here constitutive equations of glass fibre reinforced phenolic resin composite(GFRP) in uniaxil strain state under dynamic loading are given. The proposed equations of the material agree well with experimental results.展开更多
基金Supported by the National Basic Research Project"Nonlinear Science"Chinese Academy of Sciences under special grant No.KM85-33.
文摘A model of evolution induced catastrophe(EIC)characterized by a nonlocal interaction is proposed.The general feature of the model is its two bias states:explosively catastrophic and globally stable,both consisting in a cascade of locally unstable states.A one-dimensional analysis reveals a transition region from globally stable to catastrophe.A two-dimensional simulation gives a thin fractal fracture profile similar to that observed and also a possible spectrum of fracture fractal.All these are different from percolation.Hence,the EIC model may represent a prototype of natural processes.
文摘地震是地壳中积累的大量弹性应变能突然释放的灾变破坏过程。对地震的预测(特别是短临预测)一直是地震学的一个巨大挑战,《Science》(2005)曾将其列为125个科学问题之一(Are there earthquake precursors that can lead to useful predictions?)。解决这一问题的关键点在于,是否存在与地震发生具有因果关联的、有物理基础的前兆现象?利用何种观测手段来探测并识别这种前兆现象?
基金the Chinese Academy of Sciences under the project "Multi-Scale Complex System" (Grant No KJCX-SW-L08)the National Natural Science Foundation of China (Grant Nos 10725211 and 10721202)the Doctorial Start-up Fund of Hunan University of Science and Technology (Grant No E50840)
文摘This paper reports a comparative study of shear banding in BMGs resulting from thermal softening and free volume creation. Firstly,the effects of thermal softening and free volume creation on shear instability are discussed. It is known that ther-mal softening governs thermal shear banding,hence it is essentially energy related. However,compound free volume creation is the key factor to the other instability,though void-induced softening seems to be the counterpart of thermal softening. So,the driving force for shear instability owing to free volume creation is very dif-ferent from the thermally assisted one. In particular,long wave perturbations are always unstable owing to compound free volume creation. Therefore,the shear instability resulting from coupled compound free volume creation and thermal softening may start more like that due to free volume creation. Also,the compound free volume creation implies a specific and intrinsic characteristic growth time of shear instability. Finally,the mature shear band width is governed by the corre-sponding diffusions (thermal or void diffusion) within the band. As a rough guide,the dimensionless numbers: Thermal softening related number B,Deborah number (denoting the relation of instability growth rate owing to compound free volume and loading time) and Lewis number (denoting the competition of different diffusions) show us their relative importance of thermal softening and free volume creation in shear banding. All these results are of particular significance in understanding the mechanism of shear banding in bulk metallic glasses (BMGs).
文摘The note presents a method of constructing dynamic constitutive equations of material by means of Lagrange experiment and analysis. Tests were carried out by a light gas gun and the stress history profiles were recorded on multiple Lagrange positions. The dynamic constitutive equations were deduced from the regression of a series of data which was obtained by Lagrange analysis based upon recorded multiple stress histories. Here constitutive equations of glass fibre reinforced phenolic resin composite(GFRP) in uniaxil strain state under dynamic loading are given. The proposed equations of the material agree well with experimental results.
