Calculation of Fit Tolerance with Clearance to Increase Relative Wear Resistance of Joints

Abstract

The total resource of the assembly unit, as well as the post-repair resource of the unit, depend on the specified resource for critical joints. The main problem of calculating the joint accuracy is to determine the margin of accuracy or the margin of material for wear since an increase in the estimated fit tolerance will lead to a decrease in durability, and its decrease will entail an increase in costs due to an increase in rejects or the need to introduce a technological operation. In this regard, a method for calculating the joint fit tolerance depending on the specified or design wear characteristics was developed based on the analysis of the parametric failure model. When modeling various wear rates, it is recommended to use the relative wear resistance of the joint in the obtained dependences only if the wear function is approximated in a linear form. An expression for calculating the relative wear resistance of a joint is obtained depending on the wear resistance of the surfaces of the parts that form it. Using the example of calculating the fit tolerance of a rolling bearing operating under hydrodynamic friction conditions, the resulting fits are analyzed at a certain resource of no-failure operation of the joint for cases of increasing the wear resistance of the joint by 10 and 20%. The scientific novelty of the research lies in obtaining a theoretical relation between the fit tolerance and the probabilistic characteristics of the wear process at a specified probability of failure-free operation. The practical significance of research is expressed in the possibility of calculating the accuracy parameters of a particular joint at a specified resource.