Surface fatigue wear, also called contact fatigue wear or rolling fatigue wear, is repeated rolling or sliding contact, in which the shear stresses bring about microcracks, particles and form wear pits that destroy the surface. It is a type of wear that occurs on the surface of materials due to repeated cyclic loading and unloading, especially under conditions involving rolling or sliding contact. It is a common phenomenon in mechanical systems where components like gears, bearings, and rolling elements experience repeated loading and motion.
Surface fatigue wear typically arises due to the accumulation of stress cycles that lead to the formation and propagation of cracks on the material's surface. This wear mechanism is particularly relevant in situations where the contact pressures are high and the materials are subjected to alternating stresses, as is the case in gears transmitting power, bearings supporting loads, and other mechanical systems involving rolling or sliding.
The process of surface fatigue wear can be explained as follows
- Crack Propagation - With each loading cycle, these micro cracks tend to grow and propagate further into the material due to the repetitive stress concentrations.
- Micro Cracking - As the cyclic loading continues, localized stresses at the contact points cause micro cracks to initiate on the material's surface.
- Spalling - As the cracks grow, they can eventually lead to material spalling, where small pieces of material break off from the surface. This results in pits, roughness, and degradation of the component's surface.
- Surface Deterioration - The continuous cycle of cracking, propagation, and spalling leads to a progressive deterioration of the material's surface, potentially affecting the performance and reliability of the mechanical system.
To mitigate surface fatigue wear, engineering strategies can include using materials with enhanced fatigue resistance, improving lubrication to reduce friction and wear, modifying the design of components to distribute stresses more evenly, and employing techniques like shot peening or surface hardening to enhance the material's resistance to crack initiation and propagation. Understanding and managing surface fatigue wear is essential in designing reliable and long lasting mechanical systems that are subjected to cyclic loading and rolling or sliding contact.