PSI - Issue 75

KADIRI Mounir et al. / Procedia Structural Integrity 75 (2025) 633–641 KADIRI Mounir/ Structural Integrity Procedia (2025)

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Each loading block comprises two stages:

• Loading stage between times 0 and 1 (Figure 3) during which the specimen is subjected to the specified number of cycles under sinusoidal load control • Cooling stage between times 1 and 2 (Figure 3) during which the cyclic loading is interrupted so as to cool down the specimen to the initial temperature 0

Figure 3 : temperature and stress evolution versus time during one loading block [6]

This protocol is repeated for each loading block, and the temperature evolution associated with each stress amplitude is recorded. Since a zero-dimensional (0D) approach has been adopted, the temperature field is assumed homogeneous. The temperature at the specimen’s center is measured using a thermocouple. Temperature changes in the jaws during cyclic loading may generate additional heating in the specimen. Consequently, to obtain the specimen’s true temperature evolution, the jaws ’ average temperature ((T_(upper jaw) +T_(lower jaw))/2) must be subtracted from the specimen temperature, leading to the temperature rise: 0 = − + 2 (4) The temperature rise of each loading block can be plotted in a single graph to track its evolution as a function of time during the test (Figure 4b)

Figure 4 : (a) example of loading block (b) example of temperature rise curve on each loading block [6]