CTH is a family of codes developed at Sandia N_onal Laboratories for modelling complex " multi-dimensional, multi-material problems that are characterized by large de/Ormationsand/or strong shocks. A two-s_p, second-order accurateEulerian solution algorithm is used to solve themass, momen-_...._'_ C_[ mm, and energy conservation equations. CTH includes models for material strength, fracture, porous t_ "-_ materials, and high explosive detonation and initiation. [/ft.,' !.,., or rate-dependent models of material strength have been added recently. The formulations _U0 of Johno_3n-Cook,Vise°pla_c Zerilli-Annstrong, and Steinberg-Guina_|-Lundare standard options within CTI-LThese _ _ models rely on the use of an internal state variable (typically the equivalent plastic strain) to account for the histoq dependence of material response. The implementation of internal state variable models will be O _ T [ discussed and several sample calculations will be presented. Comparison with experimental data will be made among the various material strength models. The advancements made in modelling material response have signiticanfly improved the ability of CrH to model complex large-deformation, plasticflow dominated phenomena. The detonation of energetic material under shock loading conditions has been an area of great interest. A recently developed model of reactive burn for high explosives 0-lE) has been added to CTH. This model along with newly developed tabular equations-of-state for the HE reaction by-products has been compared to one-and two-dimensional explosive detonation experiments. These comparisons indicate excellent agreement of CTH predictions with experimental results. The new reactive bum model coupled _cg ___ g _ _ _ _ with the adw,pces in equation-of-state modeling make it possible to predict multi-dimensional bum phe-_. _-_ _ _ 8 _: _ _, _" nomena without modifying the model parameters for different dimensionality. Most current bum models 2. _o _, _ _ _ _., ,, = ct __g"g'_ _ o _ 8 _.__ do not accurately predict both one-dimensional plate acceleration experiments and two-dimensional cylin-_-_"._ _ _. _ _. :" b_" = der expansion experiments simultaneously. Our implementation is significant because it represents the _ _ o _ _ _ _ _ "first time a multi-dimensional model has been used to successfully predict multi-dimensional detonation _ o .., o ,_ _ _ _ z effects without requiringa modification of the model parameters.

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A nonequilibrium continuum mixture model has been incorporated into the CTH shock physics code to describe deflagration-to-detonation transition in granular energetic materials. This approach treats multiple thermodynamic and mechanics fields including the effects of relative material motion, rate-dependent compaction and interphase exchange of mass, momentum and energy. A finite volume description is formulated and internal state variables are solved using an operator-splitting method. Numerical simulations of low-velocity impact on a weakly-confiied porous propellant bed are presented which display lateral wall release leading to c&ed compaction and reaction wave behavior.

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