What is the required hardness relationship between bearing liner material and the shaft?

The required hardness relationship between bearing liner material and the shaft is that the liner should be softer than the shaft. This is primarily due to the fact that a softer material can absorb the wear that occurs during operation, which is crucial for maintaining the integrity and lifespan of both the bearing and the shaft.

When the bearing liner is softer, it can yield slightly under pressure, allowing it to accommodate shaft misalignments and thermal expansions without causing damage to the harder shaft. This characteristic helps to prevent the creation of metal-to-metal contact that can lead to wear and failure. Additionally, the softer liner material is less likely to fracture or chip under stress, which can also contribute to a longer operational life and reduced maintenance needs.

In contrast, if the bearing liner were harder than the shaft, the result would likely be increased wear on the shaft itself. The harder material tends to resist deformation, which can lead to increased friction and ultimately result in catastrophic failures in high-load applications. The same hardness or using the same material as the shaft would not offer the necessary protection or wear characteristics required in most applications, which is why the softer liner is preferred.