Microstructural Length-Scale Effects on Shaped-Charge Jet Formation and Critical Liner Thickness: An Anisotropic Thermoviscoplastic Modeling Study

This study develops a thermoviscoplastic model that incorporates an effective through-thickness microstructural length into the Hill48 yield criterion for shaped-charge liners. The model is implemented in the axisymmetric Hot Optimal Transportation Meshfree (HOTM) framework and verified through directional-yield and material-coordinate transformation tests. An isotropic bulk reference is adopted to isolate the thickness-dependent directional correction in comparisons with conventional J2 plasticity. Comparison with a published experiment supports the predicted global jet-formation response, while independent validation of the microstructural mechanism remains necessary. For the representative numerical case, the proposed model predicts higher jet-tip velocity, greater jet length, and modified deformation localization. A Walsh-type plastic-instability criterion is used to bracket the critical liner thickness for three charge calibers. The nominal critical thickness increases with caliber, whereas its normalized value decreases, indicating a departure from proportional scaling within the investigated range. These results demonstrate the sensitivity of the predicted jet response to the assumed thickness-dependent constitutive description. The findings remain limited to the adopted phenomenological parameters and investigated configurations and do not establish a general scaling law. The framework provides a basis for subsequent material calibration and experimental validation.