Numerical investigation of Powder Metallurgy manufactured gear wheels subjected to fatigue loading

A 2D numerical study of the damage accumulation at the root of a Powder Metallurgy (PM) manufactured gear wheel subjected to frequent overloads, i.e. low cycle fatigue loading, has been performed. The initial porosity distribution of the gear was obtained from a 3D simulation of double action compaction of the gear. The porosity distributions over the centre plane and at the surface were transferred into 2D, and the damage accumulation was followed using the Gurson material model. The initial damage within the gear is here interpreted as the porosity distribution resulting from the manufacturing compaction process. It was found that an accurate description of initial damage distribution only has a small narrow influence on the resulting damage. The damage accumulation is a highly local phenomenon, and that the damage development is highly dependent on the local initial damage at the gear root. Based on this, a simple life estimate model, relating the number of cycles to accumulate a pre-described amount of damage to applied load and initial damage, is also presented.