טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShpitzer Moran
SubjectHigh Velocity Spherical Copper Fragment Penetration into
a Ceramic Tile
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Daniel Rittel
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

After several severe accidents that took place on large munitions deposits and on a few war ships (including aircraft carriers), the US army decided on a new approach and standardization in munitions design. The IM (Insensitive Munitions) standards were founded. In order to be an IM, munitions should go through several tests, in which they are fired upon (bullet impact and fragment impact), going through different heat fluxes: fast cook off, slow cook off and being dropped from few meters. The munitions reaction (explosion or debris scattering) should not exceed a defined amount of energy. The present research deals with the fragment impact test and the industrial motivation is to define an armor that can be implemented in the munitions packaging. The armor should be capable of dealing with the particular needs of the threat (fragment mass and velocity), in order to receive a non energetic reaction from the munition (as defined in the standard).

The objectives of the research are:

Establish a calibrated numeric simulation, supported by a couple of tests, to a penetration problem of copper fragment into a ceramic tile, in a velocity of 1.83 [km/s].

Achieve DOP (Depth of Penetration) data and X-Ray flashes from the firing tests.

Compare the DOP and X-Ray test data to the similar simulation data, given different material models and choose the best model.

Fine calibration of the different material parameters in order to achieve full agreement with tests data.

The armor that was examined, consists of a ceramic tile (98% Al2O3) with a dimensions of 17x50x50 [mm] (thick x wide x length).

The simulations were carried out using a commercial finite element code (AUTODYN V6.1) with a 2D axis symmetry Lagrangian solver. The quantitative values that were compared between the simulation and the tests and were used to calibrate the simulation are: The residual DOP to the semi- infinite backing (i.e. SS304) and the fragment deformation and position during the penetration process (flash X-Ray).  

Two Alumina strength models were examined: Drucker-Prager (DP) and Johnson- Holmquist (JH). An array of values for the models parameters were examined systematically and their DOP results were compared to the DOP tests data. The outcome of this research is an experiment based update suggestion to the brittle material JH strength model.