Analysis of hypersonic flow using three dimensional navier-stokes equations

2016
Özgün, Muharrem
Metallic materials in aerospace structures are exposed to impact type loads depending on their usage area. High strain rate material characterization of metallic materials is very crucial to properly prepare finite element models to be used in impact loading situations. Johnson-Cook material model is a suitable material model to represent the behaviour of metallic materials at high strain rates. In the present thesis study, parameters of the Johnson-Cook material model for Al 7075-T651 are determined utilizing the tensile test data in quasi-static loading condition and impact test data for impact loading condition. High strain rate material characterization of the metallic material is performed by the modified Taylor impact test and velocity interferometry. Modified Taylor impact test system and how the free surface velocity measurement by the velocity interferometry-VISAR is utilized for the determination of the strain rate constant of the Johnson-Cook material model are described in detail. Experimentally determined material constants are verified by simulating the modified Taylor impact test in Autodyn and comparing the experimentally and numerically determined free surface velocities.