Issue 42

T.V. Tetyakova et alii, Frattura ed Integrità Strutturale, 42 (2017) 303-314; DOI: 10.3221/IGF-ESIS.42.32 311 Specimen c l c b 0 l 0 b a B 0 r 1 13.5 22 56.5 10 10 46 10 2 13.5 22 56.5 10 20 66 10 3 13.5 22 56.5 10 37 100 - 4 28.5 22 56.5 10 10 46 10 5 28.5 22 56.5 10 20 66 10 6 28.5 22 56.5 10 37 100 - 7 53.5 22 56.5 10 10 46 10 8 53.5 22 56.5 10 20 66 10 9 53.5 22 56.5 10 37 100 - Table 5 : The parameters of the specimens with complicated configuration. The stiffness of the gauge part 1 is equal 0 42.5 R  MN/m and defined as: 0 0 0 0 Eh b R l  (2) It follows thence, that the stiffness of the loading system can be defined as: 1 1 1 0 0 0 0 2 c LS c c M l L L h Ea R h Eb l l EB R                                  (3) Table 6 depicts a brief summary of the uniaxial tension tests for the stiffness of the loading system ranging from 58.3 to 177.9 MN/m. Table 6 : The obtained stiffness of the loading system for the specimens with complicated geometry . Fig. 10 shows load-displacement curves obtained for uniaxial tension tests (a nominal strain-rate of 1.67·10 −3 s −1 ) on the flat specimens with different widths of the peripheral parts: 1 ‒ 37 a  mm, 2 ‒ 20 a  mm, 3 ‒ 10 a  mm, the length of the control part is 13.5 mm. As can be seen from Fig. 10 (a), the ‘ P - u ’ curves exhibit the stage of the yield plateau forming and the jerky flow due to the Portevin-Le Chatelier. The stiffness of the loading system influences on the amplitude of the load serrations, that is, the increase of the stiffness causes the increase of ‘tooth’ amplitude. On the surface of the specimens with complicated geometry, the man parts. Fig. 7 presents profiles of the longitudinal strain calculated along the gauge length for the gauge part (a line 1 ) and peripheral parts (lines 2 , 3 ). Note, that the ε yy y  profiles are symmetric for the left and right peripheral parts. No. specimen LS R , MN/m No. specimen LS R , MN/m No. specimen LS R , MN/m 1 103.7 4 79.8 7 58.3 2 136.5 5 94.7 8 64.5 3 177.9 6 113.0 9 71.5