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CTM2D – Chemothermomechanical Cookoff Modeler

Chemothermomechanical calculations in two dimensions

chemmodel

The chemothermomechanical (CTM) behavior of heterogeneous energetic materials during cookoff is complex, and a single phenomenological constitutive law cannot accurately capture all the undergoing physical processes. The cookoff process can be split into three stages, as shown in the figure above. In the initial stage (a), a thermal flux is applied to the material leading to an increase in temperature, which triggers various physical phenomena including thermal expansion, chemical phase change, decohesion, damage, and other inelastic processes. During stage (b), the solid phase energetic materials produce gaseous intermediate products and trigger an ignition front leading into gas phase chemical reactions and one/more burning front(s), stage (c).

CTM2D is a multicore software framework that is capable of simulating stages (a) and (c) of the cookoff process in two-dimensional plane strain and axisymmetric configurations. Other Illinois Rocstar programs, such as Prop3D and Stat3D facilitate the characterization of the homogenized mechanical properties to be used by the macroscale CTM solver of CTM2D. In CTM2D a generalized finite element method (GFEM)-based finite strain formulation is used. To capture the elastic and inelastic mechanical behavior during cookoff, we use a Lagrangian formulation as opposed to an Eulerian formulation used in earlier studies addressing the combustion of solid propellants. Theoretical details of this solver can be found in the references listed below.

References

[1] K.R. Srinivasan, K. Matous, and P.H. Geubelle. “Generalized finite element method for modeling nearly incompressible bimaterial hyperelastic solids.” Comput. Method Appl. M., 197:4882–4893, 2008.

[2] K.R. Srinivasan, K. Matous, P.H. Geubelle, and T.L. Jackson. “Thermomechanical modeling of regressing heterogeneous solid propellants.” J. Comp. Phy., 228:7883–7901, 2009.