Berlin 2018 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 45: Topical Session (Symposium MM): Fundamentals of Fracture
MM 45.3: Vortrag
Mittwoch, 14. März 2018, 17:45–18:00, TC 006
Extraction of Information about Fracture at High Imposed Strain Rates from Ballistic Indentation Experiments — •Max Burley1, Bill Clyne1, Jimmy Campbell1, and James Dean2 — 1University of Cambridge, UK — 2Double Precision Consultancy, Cambridge, UK
Ballistic indentation experiments have been carried out, using high-speed photography to monitor projectile motion and stylus profilometry to record residual indent shapes. In addition, X-ray computed tomography has been used to capture the 3-D architecture of crack patterns in impacted samples. This experimental work has been coupled with iterative FE modeling of projectile penetration and rebound. Cermet spheres of 5 mm diameter were incident on cylindrical samples of pure Mg, with velocities in the range 50-200 m s-1. The strain rates operative during these experiments were ~104 - 106 s-1. In addition, quasi-static uniaxial compression tests were carried out, at several temperatures, to obtain the values of parameters characterizing the plastic deformation and its sensitivity to temperature. The Johnson-Cook formulation was then employed and ABAQUS software used for iterative simulation of the impact event. A Nelder-Mead convergence algorithm was then used to obtain best-fit values for the coefficient of friction and the J-C strain rate sensitivity parameter. Correlation was then established between the crack pattern and the stress field during the period of crack growth. It is concluded that the cracks are likely to have propagated largely under mode II conditions, with critical strain energy release rates that were considerably lower than those under quasi-static loading.