PSI - Issue 83

Niccolò Vilotta et al. / Procedia Structural Integrity 83 (2026) 246–255

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3.3. Infrared thermographic analysis Thermographic monitoring provides an additional perspective on the development of deformation. Figure 8 shows the temporal evolution of the temperature difference Δ T and true stress during the tensile test of the non-welded DMLS manufactured AISI 316L specimen. The initial phase (0–40 s) is characterized by slight non-linearity in both stress and temperature, attributed to mechanical settling and the stabilization of the specimen within the loading grips. Thermoelastic. A subsequent period of linear thermoelastic cooling is observed [16,19]. A slight deviation from thermal linearity is observed around 60 s, signalling the onset of micro-plasticity prior to macroscopic yielding. Following the yield point, the temperature trend reverses as mechanical work is irreversibly converted into heat [16–19]. This dissipative heating dominates the plastic region, with Δ T rising steadily despite the onset of necking and the subsequent drop in true stress. The temperature difference reaches its peak (about 2.25 °C) precisely at the point of fracture.

Figure 8: Temperature and true stress distribution over time.

Figure 9 shows the thermographic images of the welded specimen at the beginning of fracture (a) and after complete fracture (b). A clear thermal localization is observed in the upper part of the gauge section, where fracture initiates and subsequently develops. After rupture, the temperature field confirms that failure is associated with localized deformation and heat generation in the fracture region [17,18].

(a) (b) Figure 9: AM AISI 316L welded specimen at the beginning of fracture (a) and after fracture (b).