High Temperature Fracture

his project has two objectives: develop and validate software to simulate high-velocity impact of preheated panels, and to advance the technology used in validation experiments. To meet the first objective requires addressing two levels: numerical methods and constitutive laws. Both levels will facilitate: coupled thermal-mechanical response; large deformations; large strains; large strain rates; and large variations from the reference temperature. The intended application results in the system, under certain circumstances, operating away from thermodynamic equilibrium. To ensure applicability to such cases, the constitutive laws will be developed to a priori satisfy the second law of thermodynamics. The numerical approach pursued couples two methods: mesh-free state based peridynamics (PD), and the extended finite element method (XFEM). In particular, PD representation is applied to model the subdomain most affected by the projectile-target impact and penetration. XFEM representation is applied to the remaining domain. This coupled approach leverages the advantages of both methods to deliver superior numerical accuracy and efficiency. Specifically, it facilitates representing discontinuities (e.g., cracks), which may develop throughout the domain, independent of the underlying mesh topology. It also leverages the insensitivity of the PD model to distortion (introduced by the excessive deformations in the vicinity of the impact zone). By contrast, the accuracy of mesh-based methods (e.g., finite elements) rapidly deteriorates with mesh distortion, necessitating costly remeshing. High-velocity impact engenders sharp shock waves in the bodies in contact. A goal of this project is to develop effective strategies to address shock waves. The development will emphasize smooth shock waves transition across the PD-XFEM interface. The material models will be constructed to enable representation of the operational environment expected: high-velocity impact at high-temperatures. Laboratory experiments will be conducted to obtain material properties, and to facilitate validating the model. The material properties obtained from the first set of tests will be used in simulations demonstrating the performance of the proposed model. The validation effort will include simulations of experiments where projectiles impact preheated panels. To verify reproducibility of the results, each of the material properties and ballistic impact tests will be repeated twice. Approved for Public Release | 25-MDA-12220 (23 Sep 25)