Lathe turning mode optimisation for parts working under conditions of cyclic loading

Abstract

This work is devoted to questions of technological cyclic durability maintenance, of the material for parts working under cyclic loading conditions, by lathe processing optimization. The analysis of the impact of the surface layer quality on fatigue characteristics is described for parts operating under cyclic loads. Survey of methods for evaluating cyclic durability is completed, which showed lack of information about the mathematical relation between the cyclic durability of the part’s material and technological conditions of its production. A fatigue experimental study was carried out, the results of which allowed to create a mathematical model of cyclic durability of the material from lathe processing mode and tension cycle. The complex objective function that takes into account the dependence of cyclic durability of turning from technological conditions of handling and processing was developed. It is proposed to determine tension cycle for the most unsafe parts of a constructive element with consideration of conditions of service using the finite element method. The mathematical model of lathe processing of parts working under conditions of variable cyclic loads is developed and represented by total complex target function and system of constraints, including set of constrains on: feed, speed, strength and power of cutting, cutting precision, tool life and roughness of the workpiece. In addition, this mathematical model takes into account the actual characteristics of the material and expands its use to other materials of alloyed chromium steel. Submitted multi-criteria task is solved by using the method of sliding clearance. Steel 40Х GOST 4543-71 was used as an example for the proposed mathematical model of the part turning process, part operates under cyclic loading, and best values for feed and cutting speed are calculated.