Relatively simple fatigue tests have been performed on two common engineering materials, cast ductile iron and low‐carbon steel, using two stress states, cyclic torsion and cyclic torsion with static axial and hoop stresses. Tests were designed to discriminate between normal stress and hydrostatic stress as the most suitable mean stress correction term for high cycle fatigue analysis. Microscopy shows that cracks in low‐carbon steel nucleate and grow on maximum shear planes, while for cast iron pre‐existing flaws grow on maximum normal stress planes. The data illustrate that tensile normal stress acting on a shear plane significantly reduced fatigue life and is an appropriate input for fatigue analysis of ductile materials. Static normal stresses did not significantly affect the fatigue life for the cast iron because the net mean stress on the maximum normal stress plane was zero. Mean torsion significantly reduced the fatigue strength of the cast iron. A critical plane long‐life parameter for nodular iron which accounts for both stress state and mean stress is proposed, and is found to accurately correlate experimental data.
|Journal||Fatigue & Fracture of Engineering Materials & Structures|
|Publication status||Published - 2000|
|MoE publication type||A1 Journal article-refereed|