PSI - Issue 20

A.K. Kychkin et al. / Procedia Structural Integrity 20 (2019) 198–205 A.K.Kychkin et al / Structural Integrity Procedia 00 (2019) 000 – 000

201

4

errors, were accepted as the measurement result. The most significant indicator of the state of material under operation is a temperature of glass transition of binder. To define this indicator, the method of dynamic mechanical analysis using the DMA 861D installation of the NETZSCH company according to GOST 31938-2012 standard was used. To measure the temperature of glass transition, parallelepipeds with 2 x 50 mm size rods were cut out. 3. Results and discussion To define the strength limit σ of the BPA samples while being compressed in the reference state and after exposure, series of BPA samples were selected. In figure 1, typical charts of tests for buckling of BPA samples while being exposed and 28 months after the exposure are given.

Fig. 1. Diagram of tests for buckling of the BPA samples: а) - Ø6mm; b) - Ø8mm.

Comparison of values of compressive strength of the primary samples and the samples exposed in the open air shows an insignificant increase of this index by 4-8% (Table 1).

Table 1.Values of compressive strength for ABK samples.

compressive strength ВС, MPa

Regulation norms and documents for tests

Test conditions

Diameter, mm

354-474 410 418-519 466 297-509 428 426-550 504 248-490 405 410-520 485

6

Initial state

8

6

Exposure to natural environs (Yakutsk) during 28 months

GOST standard 31938-2012

8

6

Exposure to natural environs (Yakutsk) during 51 months

8

To define the ultimate bending strength of BPA samples in the reference state and after exposure in the open air in Yakutsk, six samples of each diameter were selected. Comparative data of tests for buckling are given in Table 2. Results of comparative testing of BPA samples for axial tension are presented in Table 3. Unequal changes of strength indicators of BPA after exposure are likely to be due to structuring of the polymer matrix. Such strengthening and insignificant alterations of properties are likely to be attributed to physical and