PSI - Issue 59

Serhii Drobyshynets et al. / Procedia Structural Integrity 59 (2024) 601–608 Serhii Drobyshynets et al./ Structural Integrity Procedia 00 (2019) 000 – 000

607

7

deformations occurred up to the 42nd cycle, after which the deformations began to increase. At the 48th cycle, the deformation under load was  fb = 0.00001201, at the 50th cycle – 0.00001307, and at the 51st cycle – 0.00002083. The prism collapsed on the 51st cycle during unloading. The residual deformations increased similarly, from 0.0000242 on the third cycle to 0.00001424 on the 50th cycle. When loaded on the 51st cycle, the maximum deformations reached  fb = 0.00003505, which is almost twice as much as in the P-8 prism before fracture on the second cycle.

 fb , М P а

30

3 7 10 20

40

25

1

20

50

15

10

5

5

 fb *10

0

0

50

100

150

200

250

300

Fig. 4. Deformation diagram of the P-18 prism (numbers indicate the number of loading cycles).

The P-16 prism was subjected to cyclic tests at  fb /R fb = 0.63, it withstood 116 cycles, after which it was destroyed by reloading. The prism operated in a stable mode, and no signs of low-cycle fatigue were observed. Fig. 5 shows the experimental points and the low-cycle fatigue curve of the studied steel fibre-reinforced concrete. Some experimental points have deviations from the fatigue curve, which can be explained by the great complexity and labour intensity of the experiments when studying the low-cycle fatigue of materials under high loads. In most cases, the experimental and theoretical values have a satisfactory convergence. Dependence (7) will likely be refined by accumulating experimental data.

 fb,cyc

1

0,9

2

1

0,8

n cyc

0,7

0

20

40

60

80

100

Fig. 5. Dependence of the stress level on the number of cycles to failure:1 - experimental points; 2 - fatigue curve according to the formula (7).