A Physics-Informed Framework for Force-to-Stress Conversion in Small Punch Creep Tests of Creep-Resistant Alloys at High Temperatures

The small punch creep test (SPCT) requires only a small amount of material, but converting the applied force into an equivalent uniaxial creep stress remains difficult. This study presents a physics-informed framework that uses transfer learning for this conversion in creep-resistant alloys at high temperatures. A Teacher Model is trained on uniaxial creep rupture data to relate rupture life to stress, temperature, and chemical composition. A Mapper Network then estimates the equivalent uniaxial stress from the SPCT force, temperature, and composition, so that the Teacher Model reproduces the measured SPCT rupture life. The physical constraints are this rupture life equivalence and an empirical force-to-stress anchor; the network does not solve a creep constitutive equation. The conversion was examined for P91 steel, 2.25Cr1MoV steel, 1CrMoV steel, and Incoloy 800H, using specimens of 0.5 mm thickness. For these alloys, the converted stresses are compared with uniaxial Larson–Miller curves. The resulting force-to-stress ratio varies with temperature, force, and material within the tested range.