Issue 42

D. V. Orlova et alii, Frattura ed Integrità Strutturale, 42 (2017) 293-302; DOI: 10.3221/IGF-ESIS.42.31 300 Figure 6 : Dependencies of ( ) aw V  : for 321H ( ); for G10080 ( ); for AISI 420 ( ); for silicon iron ( ). C ONCLUSIONS he deformation of metals and alloys is locally developed at all stages of a plastic flow, including elastic-plastic transition. During transition, dislocations actively move and spread in localization zones, and the density of dislocations is increased. This leads to a change in the characteristics for the propagation of acoustic waves. Thus, during the transition to the region of a plastic flow, there is the break of the curve for the velocity of ultrasonic Rayleigh waves versus the magnitude of deformation, and the increase is replaced with a drop. The break of the curve can serve as an acoustic criterion of irreversible deformation for the pressure treatment of metals, the operation and non-destructive testing of products and structures. For large deformation, at the pre-fracture stage of iron based alloys, the deformation process is gradually stopped in the entire volume of the material, except the part of the material that directly adjoins the place of necking and a ductile crack. In terms of self-organization, there is the autowave collapse of localized plastic deformation [21]. The kinetic characteristics of the autowave collapse at the pre-fracture stage, which can be found experimentally, allow the space-time coordinates of the object fracture to be predicted long before the occurrence of external signs. The work conducted contributes to the creation of a database on the mechanical and acoustic characteristics of alloys and steels both for elastic-plastic transition and large plastic deformations. This is necessary for the development of algorithms for predicting the resource of plasticity in the operation and manufacturing of parts and structures. A CKNOWLEDGMENTS he work was supported by the Russian Foundation for Basic Research (project No. 16-19-10025). R EFERENCES [1] Cottrell, A.H., Bilby, B.A., Dislocation theory of yielding and strain ageing in iron, Proc. Phys. Soc. A, 62 (1949) 1-40. [2] Kuhlmann-Wilsdorf, D., Dynamic effects in the mesh length theory of workhardening, Acta Metall., 37 (1989) 3217- 3223. -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 -0.025 0.000 0.025 0.050 0.075 0.100 mm V, mm/s  , T T