PSI - Issue 54

Artur Kuchukov et al. / Procedia Structural Integrity 54 (2024) 369–375 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Three specimens were tested for each mode to determine the nominal values of destructive load and torque under uniaxial loads. Test modes are presented in Table 1. Table 1. Loading type of static tests Loading Loading rate Normal component, mm/min Shear component, deg/min Tension 2 0 Torsion 0 20 Tension-torsion (Proportional 1) 1 20 Tension-torsion (Proportional 2) 2 20

The results of quasi-static tests have been used to create loading diagrams (Fig. 1) using the data from the testing system.

Fig. 1. Loading curves: dependence of load on displacement, dependence of torque on angle The linear character of the curve in tension up to the maximum load value with transition to dynamic fracture was noted. This behavior corresponds to elastic-brittle fracture. When torsioned, the diagram was nonlinear. The presence of a plastic stage has been noted. In addition, after reaching the maximum value, a progressive decrease in torque was observed in some cases, which is characteristic of the post-critical deformation stage. For the Proportional 1 and Proportional 2 modes, a decrease in the maximum load and maximum torque values after the peak was detected. The sensitivity of the material to complex stress-strain state is demonstrated. Biaxial cyclic loading tests were performed to fatigue fracture at maximum cycle stress values half of the maximum stress values in quasi-static tests, with asymmetry coefficient R = 0.1 and frequency ν = 1 Hz. The fatigue test results are shown in Table 2.

Table 2. Fatigue test results

Loading Tension Torsion

Durability, cycles

29519 ± 9426 21456 ± 666

Tension-torsion (Proportional 1) Tension-torsion (Proportional 2)

2466 ± 440

13429 ± 4501

With equal ratios of the maximum values of the stress tensor components in the cycle to their values during static