PSI - Issue 20

Victor Petrov et al. / Procedia Structural Integrity 20 (2019) 87–92 Victor Petrov et al. / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 1. Magnet impulse test set «MIU-1» for material research.

Fig. 2. Specimen loading scheme: 1 – edge-notch tension specimen; 2 – striker of «MIU-1»

The tests used samples with one side incision (OBN) at fixed loads in the area of elastic proportionality of the model material polymethylmethacrylate (PMMA) at the following test temperatures: -90°, -40° and 20° C. The study of fractograms of fracture surfaces of samples showed the presence of three types of successive zones (1 – mirror; 2 – matte; 3 – feather). The first zone is characterized by traces in the form of grooves on a smooth surface, which are orthogonal to the crack propagation front. This zone corresponds to the initial, slow, stage of crack propagation. Experimental data showed that the length of this zone decreases with increasing impact energy of the striker. Justification and construction of the model Feature of polymers is a significant relaxation of dynamic processes due to processes of reorientation of macromolecules and times-disruption of amines in chains. So for the first the zones are characterized by a rupture of bonds due to high overvoltages, regardless of whether through which elements of the molecular or supramolecular structure passes the top of the crack. The probability of polymer rupture in this area more due to significant concentration stresses at the top of an accelerating crack as shown by Bartenev (1984). The achievement of the velocity, when the macromolecule rupture time is significantly less than the relaxation time of its bonds, corresponds to the beginning of brittle destruction of polymers described by Kireenko (1972). Second area (corresponds to the matte zone) is characterized by the achievement of the maximum crack velocity when inter cluster boundaries are being destroyed, which can lead to energy emissions in the form of secondary cracks and