A Parametric Failure Model for the Calculation of the Fit Tolerance of Joints with Clearance

Abstract

Using an analysis of the relationship between the elements that characterize the initial scattering of the fit clearances, the wear rate, and its scattering, a dependence for the calculation of the design fit tolerance was obtained by modeling the parametric failure of a joint. The dependence allows for an accurate determination of the requirements for the initial scattering of the clearances in the joint to ensure a specified lifetime at a fixed probability of failure-free operation. It is shown by using a real example that the reduction in the fit tolerance from 20 to 1 µm can result in an increase in the lifetime by only 5%. A further increase in the durability of the joint can be achieved by the creation of the parts’ surfaces with higher wear resistance maintaining the accuracy of the machining within the specified cost-effective design limits.