Issue 42

T.V. Tetyakova et alii, Frattura ed Integrità Strutturale, 42 (2017) 303-314; DOI: 10.3221/IGF-ESIS.42.32 310 Figure 8 : Evolution of the inhomogeneous local strain rate and temperature fields on the surface of the flat specimens with two holes. The loading system is the set of deformable bodies, which deform due to the load transfer to the region under consideration. In tests the stiffness of the loading system ( LS R ) includes the elements of a testing machine (a frame, grips, a crosshead, a load cell) and deformable parts of a specimen, and is defined as: c M LS c M R R R R R   (1) where 0 c c c Eh b R l  ‒ is a stiffness of the additional deformable parts of a specimen (a control part), M R ‒ is a stiffness of a loading system, E ‒ elasticity modulus of the material under study. The Instron 5989 has the stiffness of 200 M R  MN/m at the load of 2 5 P   kN. By managing the length of the additional deformable part, or the control part, we obtained the loading system stiffness in range of 55.8 83.6 LS R   MN/m. The evolution of the inhomogeneous strain and temperature fields was analyzed, the patterns of the initiation and propagation of the Chernov-Lüder’s and the Portevin-Le Chatelier bands were registered and studied as well. The control part stay in the elastic state throughout the loading (Fig. 9). Analysis of the set of the ε yy y  profiles and the coefficient of the inhomogeneity of the plastic deformation showed that the loading system (in the investigated range of the stiffness) had no effect on the irregularity of the plastic flow. Furthermore, the effect of the quasi-periodic homogenization of the plastic strain observed during uniaxial tension tests in conditions of the jerky flow manifestation. The specimen with the complicated geometry as shown in Fig. 3 (d) has two ‘L-shaped’ crosscutting notches, which make the tie in the central area, consisting of two-tandem the gauge part 1 and the control part 2 , and two peripheral parts 3 and 4 . The parameters of the specimens with complicated configuration are shown in Table 5. Figure 9 : Inhomogeneous local strain rate fields on the surface of the flat specimen with additional deformable part.