FATIGUE FRACTURE PLANE UNDER MULTIAXIAL RANDOM LOADINGS - PREDICTION BY VARIANCE OF EQUIVALENT STRESS BASED ON THE MAXIMUM SHEAR AND NORMALSTRESSES

It is assumed that the plane in which the maximum variance of the equi valent stress appears is critical for a material and the fatigue fract ure should be expected in this plane. The equivalent stress is calcula ted according to the fatigue criterion of maximum shear and normal str esses in the fracture plane. It was demonstrated that for each station ary random stress state there is one or more critical planes where the fatigue fracture plane can be expected. The variance method together with the discussed fatigue criterion give good results for three analy sed types of carbon steels under multiaxial cyclic loadings.