Analysis of Stress and Strain of Fatigue Specimens Localised in the Cross-sectional Area of the Gauge Section Testing on Bi-axial Fatigue Machine Loaded in the High-cycle Fatigue Region

Fatigue is a progressive, localized, permanent structural change that occurs in materials subjected to fluctuating stresses and strains that may result in cracks or fracture after a sufficient number of fluctuations. Fatigue fractures are caused by the simultaneous action of cyclic stress, tensile stress and plastic strain. If one of these three acting phenomena is not present, fatigue cracking will not initiate and propagate. Small geometrical changes in the specimens, or specifically, test conditions by invariable angular displacement cannot significantly allow analytical calculation of stresses and strains. Therefore a numerical analysis of stresses generated through bending and torsion fatigue specimens has been performed using available FEM-program ADINA. Computer simulation has been performed on fatigue specimens made of high-strength steel DOMEX 700 MC D.