We were honored to have Youssef Hammi from Mississippi State University present at the SIMULIA Americas Users Conference, May 1-2, 2024 in Novi, Michigan.

Abstract

Protective structures and other construction applications have been designed with Ultra-High Performance Concrete (UHPC) due to its exceptional strength, durability, and resistance to withstand high-velocity impacts of projectiles. Understanding the mechanical response of UHPC materials under high strain rate loadings is therefore important for these applications. This is conducted through both an experimentally and numerically based methodology. UHPC targets are impacted with a spherical projectile at velocities ranging from 432 to 1459 m/s and three target thicknesses ranging from 25.4 to 58.1 mm. The mechanical response of the concrete target was captured using an extended version of the Holmquist-Johnson-Cook (HJC) concrete model with its parameters calibrated to confined compressive experiments of the BBR9 concrete at low strain rate. The Holmquist-Johnson-Cook (HJC) concrete was implemented into the user material subroutine VUMAT of Abaqus/Explicit using a finite strain formulation. The simulations are compared to the kinetic experimental data to validate the HJC model for this concrete in these high strain rate loading applications.

Presenter Bio

Dr. Youssef Hammi is currently an Associate Professor at the Mechanical Engineering Department and held positions as an Associate Research Professor at the Center for Advanced Vehicular Systems at Mississippi State University and postdoctoral researcher at Sandia National Laboratories. Dr. Hammi’s research activities of particular interest encompass macromechanical/micromechanical constitutive modeling, user material subroutines (Umat/Vumat) inelastic behavior, damage, failure, fracture, fatigue, computational mechanics, discrete elements (DEM), user element subroutines (UEL), Coupled Eulerian Lagrangian (CEL), finite element analysis (FEA), and Fluid-Structure Interaction (FSI). He has served as PI/co-PI on several externally funded projects from NSF, NASA, ARL, DOE and DOD. He has over 25 years of experience in the use of computational mechanics and nonlinear finite element method. He has published over 50 refereed journal and conference papers on computational mechanical and nonlinear finite elements.