PSI - Issue 5

Tretyakov M.P. et al. / Procedia Structural Integrity 5 (2017) 233–238 Tretyakov M.P / Structural Integrity Procedia 00 (2017) 000 – 000

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Fig. 6. Loading curves for various stiffness of the loading system: I – 12.5 kN/mm, II – 7.8 kN/mm, III – 6.3 kN/mm.

For all values the stiffness of the loading system were obtained the loading curves in conditions of stable crack growth process on the descending section of loading curves. With the aim of studying of kinetic of the crack growth processes were analyzed the rates of crack opening displacement on the linear sections of descending sections 1-1 ´ , 2-2 ´ and 3-3 ´ (Fig. 6). Changing of crack opening displacements u (mm) versus test time t (s) for stiffness of the loading system is 12.5 kN/mm ( I ), 7.8 kN/mm ( II ) and 6.3 kN/mm ( III ) are shown on Fig. 7.

Fig. 7. Changing of crack opening displacement u (mm) in test time t (s) for various stiffness of the loading system: I – 12.5 kN/mm, II – 7.8 kN/mm, III – 6.3 kN/mm.

On the linear sections of 1-1 ´ , 2-2 ´ and 3-3 ´ (Fig. 7), the rates of crack opening displacement were calculated. The Table 1 lists values of the stiffness of the loading systems ( kN/mm ) and crack opening displacement rates ( mm/s ) for specimens with different total length. It is shown, that the crack growth process depends on the loading conditions in particular on the stiffness of the loading system.