The article deals with determining of fatigue lifetime of structural materials during by multiaxial cyclic loading. The theoretical part focuses on fatigue and criterions for evaluation of the multiaxial fatigue lifetime. The experimental part deals with modeling of combined bending -torsion loading and determining the number of cycles to fracture in region low-cycle fatigue and also during of the loading with the sinusoidal wave form under in phase φ = 0°. Based on the experimental results the fatigue design curves are compared to fatigue data from base metal and weldments