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Implementation and Validation of the Johnson-Holmquist Ceramic Material Model in LS-Dyna

Dr. Cronin D. S., McIntosch G., Kaufmann C., Bui K., Dr. Berstad T. (University of Waterloo) Ceramic materials are commonly used in protective armour applications and may be subject to high-energy ballistic impacts in these situations. Under simple loading conditions, ceramics may be regarded as elastic-brittle materials. However, when considering ballistic impacts, the post-yield response of the ceramic becomes significant. One of the most widely used constitutive models for simulating the postyield response of ceramic materials is the JH-2 ceramic model. This constitutive equation was developed by Johnson and Holmquist and incorporates the effect of damage on residual material strength and the resulting bulking during the compressive failure of a ceramic material. The relevant equations describing the response of the material are described. In particular, the model parameters currently available for common ballistic ceramic materials are presented. The JH-2 constitutive model has been implemented in LS-Dyna as material 110 (*MAT_JOHNSON_HOLMQUIST_CERAMICS). Validation against the available test cases in the literature is discussed, and a sample calculation of a sphere impacting a ceramic material is presented. The JH-2 model in LS-Dyna has also been used by Kaufman et al. to successfully simulate the ballistic impact of 12.7 mm armourpiercing projectiles on supported alumina tiles.