Fatigue and Notch Mechanics

Linear Elastic Notch Mechanics (LENM) extends the concepts of the well known Linear Elastic Fracture Mechanics (LEFM) to notches having root radius different from zero and arbitrary notch opening angle. LENM is based on fundamental analytical results and definitions introduced by Williams and Gross and Mendelson . From the experimental point of view, it has been applied for the first time by Haibach on pure phenomenological basis to analyse the fatigue strength of welded joints using the strain gauge technique. Subsequently, LENM was developed thanks to the progressively increasing use of the Finite Element Method (FEM). Nowadays, NM has been formalised and applied to structural strength assessment of components. Different application techniques exist, but the theoretical frame remains unchanged. The present paper, after recalling the classic notch fatigue design criterion and the LEFM, aims at illustrating the link between Notch Mechanics and those classic approaches. In particular the aim is two-fold: on one side the use of Notch Mechanics in notch fatigue design will be illustrated, on the other side it will be shown how it can be used to better analyse and explain in deep the fundamentals of the classic approaches mentioned previously.