Geometric Deviations and Stress Concentrations Along the Contact in the Flattened Brazilian Test: A Combined Numerical, Analytical, and Experimental Approach - Gutierrez Moizant, Ramon Alberto; Guerrero Miguel, D. J.; Ramirez Berasategui, Maria Beatriz; Prendes Gero, M. B. (ROCK MECHANICS AND ROCK ENGINEERING, 2026)