The Application Of The Constitutive Damage Model Of Rock And Soil In Problems Of Impact Dynamics

Dynamic constitutive and regularity of damage of rock and concrete,which is non-uniform and anisotropic,etc,is one of important scientific problems of impact dynamics at present. Research of the important scientific problem is real challenge to couple between nonlinear effect of deformation and damage for material and rate of straining.In this paper,progress and general research of the constitutive model of rock and concrete,ect. are critically reviewed.Various dynamic damage models are described and compared.At same time,the trends of damage constitutive models and researches needed for further development are discussed.Based on the above discussion,the key points of difficulty that may be met in the problem are clear and some new ideas to solve it are found.Under theory of generalized them-visco-plastic constitutive related with hydrostatic pressure, the universal form of the thermoplastic and thermo-visco-plastic incrernental constitutive relations related with hydrostatic pressure and the computational routine are established from the modified Drucker's postulate and theory of internal variables in the constitutive relations and yield function in stress space.This constitutive relation can cover various kinds of plastic hardening(softening) behaviors,thermo-softening behaviors,damage-softening behaviors and their coupling effects between each other.This constitutive is based on stress yield surface in stress space and has universality.At same time,it can be used in program or commercial software of dynamics and can be easily inserted in program of numerical calculation of impact dynamics.The practicability is obvious.Base on describing of fractal,fractal dimension and measuring of fractal in detail,relationship or comparison of fractal characteristics in damage of rock and concrete,ect is established by analysis.At same time,evidences for fractal distribution of micro-crack are given by documentation.Then variable of damage of material is defined related with fractal.Through describing damage of materials by fractal dimension,evolutionary equations of damage of rock and concrete,ect.under state of tension is are deduced in detail.Through introducing relationship between fractal dimension and dissipation of energy of damage in evolutionary equation,problem of excessive variables of damage model of rock or concrete,etc.is solved.The new model of fractal damage have advantages in influence of self-damage and in law of development of cracks in rock or concrete,ect.under stress waves.Fractal damage dynamic constitutive model is based on theory of model of equivalent modulus.Numerical simulations are carried out by existing program code of impact damage model.Numerical simulations is based on fractal damage constitutive of rock or concrete,ect.And evolutionary damage equations are established by relationship between fractal dimension and dissipation of energy of damage.Numerical simulations on impulse loads are carried out by implementing the constitutive model of fractal damage sandrock in one dimcnsional strain stress by finite difference code.The variables such as waveforms of stress,mean density of crack,fractal dimension,and damage ect.are obtained.The numerical results such as variation of fractal,mean density of crack,and damage,ect.with propagation of stress are show good agreement with documents.Penetration depth of projectiles into geo-medium,such as:rock and concrete etc.,is one of important problems of protective projects.In this article,nonlinear mapping relation between input of variables of l_p/d andσ_yt/σ_yp etc and output of penetration depth h is established by dimensional analysis and theory of artificial neural networks for problem of penetration depth of projectiles into geo-medium.Neural model of penetration depth of projectiles into geo-medium is got by nonlinear mapping relation.At same time,samples of neural network model is got from document data,which is treated according to need of modeling.Moreover,a satisfied output about penetration dcpth from modified BP neural networks and RBF neural network are gotten by a group of input sets and corresponding output sets,which comes from experimental data of document about concrete and granite.