PSI - Issue 52

Valery Shlyannikov et al. / Procedia Structural Integrity 52 (2024) 214–223 V.Shlyannikov, A.Sulamanidze, D.Kosov/ Structural Integrity Procedia 00 (2023) 000 – 000

218

5

node SOLID186 3D higher-order elements. The first five loading cycles were used for the continuous start-up, heating, and cooling sequences, which were fixed as the IP- and OOP TMF loading types . In our computations, a sequence of thermo-mechanical loading was simulated to reflect the loading implemented in experiments using an inductor coil and nozzles, as shown in Fig. 3a.Typical finite element meshes for the SENT specimen are illustrated in Fig. 3b.

a) b) Fig. 3. (a) Model for TMF multi-physics computations; (b) FE global model and sub-domain for crack front mesh.

The loading histories considered for the isothermal and thermo-mechanical processes are shown in Fig. 2. In the case of the TMF conditions (Fig.4) at the stress-controlled loading cycle simulations, the minimum temperature was 400°C, and the maximum temperature was 650°C. The temperature-dependent material properties used in the simulations are presented in Table 2. The thermal profile was combined with the loading profile using the ANSYS software package in order to obtain the desired key phase angles for the IP and 180° OOP TMF conditions.

a)

b)

Fig. 4. Loading histories for (a) IP and (b) OOP TMF processes.

The behaviour of elastic stresses at the crack tip in the test SENT specimen under isothermal fatigue conditions is conventional. Thermo-mechanical fatigue loading causes the coupled effect of time and temperature due to heat loss from the eddy currents of magnetic field and the forced convective air-cooling accounted for by the turbulence model response that leads to the necessity of a detailed analysis of stresses during a particular deformation cycle. The results of the loading history analysis at different time points of the IP and OOP TMF cycles are presented in Fig. 5; the figure shows the effective von Mises stress σ eqv distributions ahead of the crack tip at  = 0  as a function of the normalised crack tip distance r/a in the mid-plane ( z/B = 0.5) of the cracked SENT specimen. Time-dependent current temperature fields were applied with the same cyclic variations and magnitudes as those for