PSI - Issue 6

A.M. Bragov et al. / Procedia Structural Integrity 6 (2017) 161–167 Author name / Structural Integrity Procedia 00 (2017) 000–000

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synchronous strain pulses in the measuring bars, demonstrating practical equality of the forces acting on the side surfaces of the specimen, which provides its equilibrium loading state. To decrease the effect of friction forces on the deformation process of the specimen, the ends of the measuring bars were oiled before testing. Besides, cracking or total disintegration of the specimens into halves took place along the diametric plane. The character of dynamic splitting failure, as well as compression failure, is qualitatively the same for all the brittle materials tested. Fig. 4 exemplifies averaged tensile stress as a function of time for the specimens of ceramic brick, obtained for different striker velocities.

Fig. 3. Strain pulses registered at cross-sections of the measuring bars in the splitting tests

The deformation diagrams obtained in compression tests were used to evaluate mechanical characteristics of the materials – maximal stress and time to failure corresponding to maximal stress, for different strain rates. Based on the results of the experiments, diagrams of the above mechanical characteristics as a function of strain rate were constructed for the tested materials. Keeping in mind that strain rate varies in the process of deformation, the experimental diagrams were constructed using the maximal value of strain rate before the beginning of failure in each test. The constructed diagrams show that, for the increasing strain rate, maximal stresses increase and time to failure decreases for all the materials tested.

Fig. 4. Time histories of tensile stresses of ceramic brick, obtained for different striker velocities