Issue 29

M. Romano et alii, Frattura ed Integrità Strutturale, 29 (2014) 385-398; DOI: 10.3221/IGF-ESIS.29.34 393 Figure 4 : CNC-manufactured plastic sabots with the mounted case containing precisely weighted propellant (left) and high-speed image of the bulking of the plastic sabot after having left the barrel whereas the bearing ball continues its undisturbed ballistic flight (right) . R ESULTS AND DISCUSSION n the following the evaluation of the experimental results is described. The obtained results are discussed and lead back to acting effects. Evaluation of experimental results For the evaluation of the experimental investigation each bearing ball is weighted to 0.1 mg precision. The mass of the impactors m lie in the range of 1.12 0.0005  g. Knowing the velocity of the impactor before the impact provided by the photoelectric barrier 1 v and the velocity of the impactor after penetration of the material provided by the double exposure and the high-speed camera 2 v the kinetic energy for both states can be calculated by 2 kin, 1 2 n n E mv  (6) where m is the mass, v is the velocity and n indicates the states, 1 before and 2 after the penetration of the material [21]. The mean value of the velocity of the impactor before the impact 1 v lies in the range of m 560.3 5.8 s  and the respective kinetic energy before the impact kin,1 E lies in the range of 175.8 3.7 J  . The difference between the kinetic energies before the impact kin,1 E and after the penetration of the material kin,2 E allows calculating the absolute value for the dissipated energy by penetrating the material by [21]   2 2 diss kin kin,1 kin,2 1 2 1 2 E E E E m v v       (7) In order to properly evaluate each single test and achieve nondimensional comparable results for the carried out experimental investigations it is reasonable to introduce the relative dissipated kinetic energy [21]   2 2 2 2 2 1 2 kin 1 2 2 diss,rel 2 2 2 kin,1 1 1 1 1 2 1 1 2 m v v E v v v E E v v mv         (8) where the dissipated kinetic energy due to penetration of the material kin E  is related to the initial kinetic energy of the Impactor kin,1 E . The introduction of the relative dissipated kinetic energy diss,rel E provides a specific value in percent. It I