PSI - Issue 75

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

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By solving equation (2), it can be shown that the temperature rise follows a saturating exponential law, increasing during the loading phase and decreasing during the cooling phase. In the loading phase, the temperature rise reaches a stabilized value after a certain time (Figure 3). This stabilized mean steady state temperature ̅ 0 is determinated for each loading block and then plotted as a function of stress amplitude which is the so-called the self-heating curve (Figure 5).

Figure 5 : example of self-heating curve [6]

Since the temperature rise is not an intrinsic property of the material, the self-heating curve will be plotted using the volumetric energy dissipation which is an intrinsic property of the material. can be computed using the equation (5): = ̅ 0 ∗ ∗10 −3 (5) Where is the mass density and is the specific heat. However, since these two material properties are unknown, we used the normalized volumetric energy dissipation ̂ given by the equation (6): ̂ = ̅ 0 (6) Self-heating tests were carried out on the “ THEMA TTC ” hydraulic tension compression machine, capable of applying a maximum load of 100kN and loading frequency of 15 Hz. Cyclic load blocks ranged from 200MPa to 720MPa with a load ratio R=-1, at 15Hz, and with an application of 4500 cycles per block. Temperature was measured using type K thermocouples attached with adhesive tape on the specimen, the upper jaw and the lower jaw of the machine as shown in Figure 6.