PSI - Issue 40

M.V. Nadezhkin et al. / Procedia Structural Integrity 40 (2022) 321–324 M.V. Nadezhkin at al./ Structural Integrity Procedia 00 (2022) 000 – 000

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and deformation e D ), which can be taken as a criterion of permissible strength ensuring maximum performance of the metal in the studied temperature range. Fixing the destruction points allows one to calculate the destruction coefficient  =  D /  p , where  p and  D are the elasto-plastic and plastic-damage components in the total relative residual deformation (inset in Fig. 1a). Fig. 1b (curves 1 – 6) displays the ultrasound propagation velocity as a function of total deformation V ( e 1/2 ), where destruction points are marked as * in accordance with Fig. 1a. An increase in the dislocation density and in the martensitic phase volume with a decrease in temperature led to an increase in local internal stresses (stresses of second kind) and eventually to a decrease in the ultrasound velocity.

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Fig. 1. (a) Tension diagrams s ( е 1/2 ) at temperatures of 334 K (1), 318 K (2), 297 K (3), 270 K (4), 254 K (5), 227 K (6), 211 K (7), 180 K (8); (b) ultrasound sound as a function of strain V ( е 1/2 ) at temperatures of 318 K (1), 297 K (2), 270 K (3), 254 K (4), 211 K (5), 180 K (6).

The analysis of the ultrasound propagation velocity-temperature V ( T ) plots at each stage of total plastic strain revealed their linear behavior with a correlation coefficient R = 0.97. A decrease in the temperature from 297 to 180 K caused a change in the ultrasound velocity 0 0 ) / ( V V V  by 18% in the undeformed sample and by 16% in the deformed one (with a total deformation e = 0.3), where V 0 is the speed of sound in the undeformed material at room temperature.

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Fig. 2. (a) Temperature dependences of ultrasound attenuation coefficient (curve 1) and destruction coefficient (curve 2); (b) attenuation coefficient  and ultrasound speed V vs. yield strength σ B .