PSI - Issue 16

Eugene Kondryakov et al. / Procedia Structural Integrity 16 (2019) 43–50 Eugene Kondryakov et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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(Fig. 4) allow one to define the energy on the deformation and fracture of the specimen, as well as divide it into its constituents: energy of the crack initiation, energy of the ductile crack growth, energy of the brittle crack jump, and energy of the ductile rupture area. The high sensitivity of the system makes it possible to extend the signal scale in time within the region of the brittle crack propagation. Therefore, the energy of brittle fracture can be determined with sufficient accuracy.

Fig. 4. Characteristic diagram P(t) for steel 45 in the zone of ductile to brittle transition (b), macrofractogram of fracture in Charpy specimens with the specific zones of the crack propagation (a), variation of the signal during the brittle crack jump with a scaling-up in time (c).

A set of impact tests of three types of the specimens (standard Charpy specimens, sub-sized specimens, and side grooved specimens) was carried out in the wide range of temperatures with the registration of the complete diagram of deformation and fracture.

3. Experimental results

To determine the values of the total energy of deformation and fracture, as well as its components, the diagrams in the coordinates 'force-time' were converted into the diagrams of force-displacement P(s) by the method of double integration according to ISO (2005). The energy of fracture within each segment was determined as the area under the curve P(s). Knowing the area of the specific zone of fracture, which corresponds to the fracture segment on the curve P(s), allows one to calculate the specific energy of fracture within the given segment:

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