PSI - Issue 42

7

D.I. Fedorenkov et al. / Procedia Structural Integrity 42 (2022) 537–544 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

543

Table 2. Properties and parameters of 25Cr1Mo1V at room temperature. E , MPa σ 0 , MPa r, MPa s nf , MPa  a, MPa b 211000 353 1.3 1.5 850 6.46 82877

ω c

428.81

0.29

5. Results and discussion To verify the found characteristics of the behaviour of steel, a numerical study was carried out using an ANSYS user material subroutine. The object of numerical studies was a smooth cylindrical specimen similar to that used in experimental studies. A low-cycle fatigue test under stress controlled was simulated. The computational scheme of the finite element method was formed from second order eight-node elements. The problem was modelled in the axisymmetric formulation with the application of cyclic load with an asymmetry factor of 1 R = − . The specimen was considered as broken when the critical damage parameter reached 0.299 c  = (Table 2). The Fig. 4 shows a comparison of calculated and experimental data when simulating low-cycle loading of standard cylindrical specimens made of 25Cr1Mo1V steel.

Fig. 4. Comparison of calculated and experimental data modeling the fatigue life of smooth cylindrical 25Cr1Mo1V steel specimens.

It is necessary to focus on the following point. In this work, a simplified representation of cyclic loading was used. Cyclic loading is represented through a set of repeated static loadings considering cyclic kinematic hardening. This makes it possible to reduce the required number of tests to determine the parameters of the generalized model and obtain acceptable accuracy in the required range of the fatigue curve. In this work an acceptable match in the range from 200 to 2000 loading cycles was obtained (Fig. 4). In cases where model accuracy proves insufficient, it is necessary to use exacting cyclic parameters of isotropic and kinematic hardening in the studied fatigue life range. However, this way will lead to the need for additional tests under cyclic loading. Moreover, the given material properties (Table 2) are valid within the specified limits of their definition. If the loading conditions change, it is recommended to check the obtained parameters and constants by other types of tests, for example, cyclic bend test. However, this may require the use of inverse methods for optimizing the experimental date.