The paper contains experimental results on elastic-plastic deformation of steel under complex loading when the main directions of stress and strain tensors coincide. Particular attention has been given to experiments where unloading and active loading take place on different surface elements of externum tangential stresses. Basic hypotheses of plasticity theory are discussed
The velocity of ultrasound distribution V in metals and alloys is a structurally sensitive characteristics and can catch the changes, taking place in materials during a deformation and heat treatment. This makes it perspective for diagnostics of materials in time of fatigue loading. The dependence of V on a number of cycles of loading consists of three logical stages with different rate of quantity changes. We used 40, 40H, 70XGSA, X18N10T, 38X2MUA, 08G2S steels. The timely discovery of beginning the critical stage of fatigue on fall of dependence V(n) was used in work for recovery of articles resource on account of external energy action by powerful short one-pole current impulses, created by specially produced of thruster generator.