1 Scope
This document specifies a method for the determination of the strength of finished ceramic balls for ball bearings, preferably made of silicon nitride (Si3N4), with ball diameters from 3 mm to 50 mm.
NOTE 1 ISO 26602 specifies the requirements for preprocessed silicon nitride materials for rolling bearing balls. ISO 3290‑2specifies requirements for finished silicon nitride balls for rolling bearings.
NOTE 2 Other test methods to determine ceramic ball strength can be found in Reference [7].
The results of the strength tests slightly depend on the Poisson's ratio. For this reason, all calculations are restricted to a Poisson's ratio ranging from 0,15 to 0,35. This includes the Poisson's ratio of a typical silicon nitride ceramic used as rolling element in ball bearings.
The method can also be used for rolling bearing balls made of other ceramic materials, but the reported prefactors may not be valid.
NOTE 3 Poisson’s ratio of isotropic materials can be determined by one of the methods given in ISO 17561.
Because of the (defect controlled) brittle fracture behaviour of ceramic materials, a significant scatter of individual results in the characterization of a series of nominally identical samples can occur.
NOTE 4 A further statistical analysis according to ISO 20501 can be carried out.