At determination of the stretching tangential stress its pulsing value ( )t σ it was replaced average in the form of a rectangular impulse with an amplitude 0σ and duration equal to time from beginning of giving of current in coil until rupture of a ring ct : 0 0 0 0 ( ) ( ) , c c t t c c t dt t dt t t σ σ σ σ = = ∫ ∫ Time ct was measured in experiences. Characteristics of samples, conditions of experiments and results are provided in table 2, where: T - the period of fluctuations of current in the coil; h - ring thickness; c - ring width; ∅ - diameter of a ring; U - tension of a charge of the condenser; 0σ- the stretching stress of a ring rupture; τ - time before destruction; W - energy of the charged condenser; I - current amplitude via the coil. Table 2. Characteristics of samples, conditions of experiments and results Material Т, μs h, mm c , mm ∅, mm U, kv 0σ, MPa τ, μs W, J I, А Al 1 0,015 1,50 28,6 20 162 4,17 100 4200 Cu 1 0,015 1,00 28,6 20 577 4,68 100 5800 Cu notch 1 0,015 1,55 28,6 20 376 6,60 100 8400 3.1. Results of microstructural research Microstructural studying is carried out by the same technique that is presented in item 2.4. Microhardness measured on the PMT-3 device at loading 20g. Results of microstructural researches are given in photos (фиг.11) and in table 3, where: T - the period of fluctuations of current in the coil; S=hxb - sample section; D - grain size; n - quantity of a time on the area 400 μm2; HV – microhardness. Table 3. Results of microstructural researches Material Т, μs hxb, μm2 D, μm n, 1/400 μm2 HV, MPa Al 1 3 68,4 10 × 3,0 70 639,1 Al initial 120 х103 4,6 53 720,4 Cu 1 3 29,9 10 × 2,5 96 340,2 Cu notch 1 75,8 х103 0,8 380 103,3 Cu initial 15 х103 - 282 644,6 The copper sample before loading represented a monocrystal, and after loading as a result of dynamic recrystallization there are fine grains – the size – 0,8-2,5 μm. And dynamic recrystallization in a sample with a cut – here grains smaller is more developed. Quantity of a time in a sample with a cut too much more, than in a sample without a cut. Besides, in a sample with a cut a large number of strips of shift (fig.11d).
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