Work

Compared Influence of a Lubricant on Mode I and Mode II Fatigue Crack Growth Kinetics in a Gear Steel

Year: 2024

Type: article

Abstract: ABSTRACT The influence of a helicopter gearbox lubricant on Mode I or Mode II fatigue crack growth in 16NCD13 steel was characterized through tests performed on single‐edge notched tensile samples loaded in tension–compression and on cruciform samples submitted to reversed shear plus static biaxial compression, respectively. In Mode I, the lubricant reduced the growth rate at low ΔKI and increased the threshold , while in Mode II, it accelerated crack growth at low ΔKIIeffective, which was not only due to a reduction in crack face friction. The upward convective flow of lubricant carrying debris exuding from the crack, a modification in oil aspect and properties, and chemical analyses near the crack front suggest that a temperature‐induced degradation of the lubricant leads to a corrosive attack of the metal, which accelerates crack growth. A tribologically transformed structure is observed along the lips of cracks grown in Mode II with normal compression in oil.

Source: Fatigue & Fracture of Engineering Materials & Structures

DOI: 10.1111/ffe.14541

Authors: Véronique Doquet, Maël Zaid, Vincent Bonnand, Didier Pacou, Vincent Chiaruttini, Pierre Depouhon