PSI - Issue 6

Y.V. Petrov et al. / Procedia Structural Integrity 6 (2017) 134–139 Author name / Structural Integrity Procedia 00 (2017) 000 – 000

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static strength was c  =3.7 MPa. The source of the dynamic load was a water filled pipe placed between the explosive and a cylindrical sample. To obtain different load intensities, the length of the tube (30, 50, 70, 100, 150, 200 and 300 mm) was varied. With increasing tube length, the intensity of the effect decreased. For each length of the pipe, a series of experiments was carried out. Measurement of the velocity of the free surface of the sample made it possible to obtain a loading history. A good reproducibility of the velocity profiles at the free end in each series was found. Also, a high-speed camera was used to monitor the position of the spall fracture. It was found that in each series the coordinates of the spall sections change from experience to experiment. In addition, with a pipe length of 30, 50 and 70 mm, two spall sections were observed. Thus, it was established that there is practically no single connection between the level of the applied load and the spall cross-section coordinate. The observed effects can be explained by the above method on the basis of the structural-temporal approach. Let the velocity of the free surface measured in the experiment be   v t . Time is counted from the moment at which   v t it becomes different from zero, i.e. from the moment of the beginning of reflection. The coordinate of the free surface is assumed to be zero. Then the stresses in the material can be determined from the formula 1 ( , ) 2 x x t x c v t v t c c                         (7) Substituting (7) into (1) it is possible to determine for each particular section x whether the criterion condition is violated. In the event that the condition is violated for a given section, one can find the minimum time at which this happened. The corresponding dependencies for the experiments described in Kubota et al. 2008 for different pipe lengths are shown in Fig. 2 a-d. The length of the pipe is 50, 70, 100 and 200 mm, respectively. As can be seen on the graphs, in all the cases considered, there is an area in which the destruction condition is realized almost

Fig. 2. Dependence of the fracture time on the coordinate in the experiments Kubota et al. 2008