Structural Model of Material Softening at Creep under Complex Stress Conditions

The process of softening and destructions of material is investigated at creep under complex tense state conditions on the basis of a structural model. Energy criterion of local element destruction is presented. Comparative analysis is performed of structural model calculation data and experimental data on the protracted durability for thin-shelled tubular steel standards 12X18H10T at $T=850\,^\circ \rm C$ for the followings types of tense state: tension, twisting and tension, intrinsic pressure and tension. Calculation results are compared with analogical data of the existing phenomenological creep and protracted durability models.