Dotoli Rosario - Consorzio CETMA, Centro di Progettazione, Design & Tecnologie dei Materiali
Lisi Daniela - Consorzio CETMA, Centro di Progettazione, Design & Tecnologie dei Materiali
Bardaro Danilo - Consorzio CETMA, Centro di Progettazione, Design & Tecnologie dei Materiali
|
The analysis of ceramics subject to impact is of significant interest due to their extensive use in protection applications. Ceramics are interesting materials due to their low density and high hardness, critical parameters in the performance of any protective system. These materials used in protective shield applications may be subject to high energy impacts; in these loading conditions ceramics may fail structurally, even by small particles, if kinetic energy of impacting objects exceeds certain limits.
Although experimental testing is always necessary, there is a considerable motivation for simulation and study in depth of numerical models.
The response of ballistic impacts on ceramics is related with: the projectile characteristics (size, velocity, material), the material supporting the specimen and, of course, the ceramic mechanical properties. The understanding of these dependencies through experimental testing can be very costly and time-consuming, because of the considerable degree of scatter in this type of data.
The aim of this paper is to evaluate Johnson-Holmquist (JH-2) constitutive model and analyze material model constant, damage and strength constants proposed.
Within this model, the crack initiation and propagation through material is tracked with a representative damage variable. The constitutive model expresses material strength as a function of pressure and damage, while incorporating material bulking due to damage.
Simulation of a steel sphere impacting a silicon nitride specimen is carried out to evaluate application of this constitutive model to FOD test. The specimen has a rectangular cross-section: 3 mm in thickness, 4 mm in width and 45 mm in length. Each target specimen is impacted in the middle of the wide side with a normal incidence angle.
Numerical simulation results are compared with experimental tests to observe damage evolution, fracture propagation, and damage resulting from compression waves reflected at a free surface. Finally it can be appreciated that the JH-2 material model (mat 110 in LS-Dyna) is suitable to simulate the ballistic impact of foreign object damage in order to support the understanding of the physical phenomenon. |
