DETERMINATION OF THE DEPTH OF HARDENED LAYER AFTER CENTRIFUGAL ROLLING OF LOW-RIGID SHAFTS

Abstract

The issues regarding improving the quality of low-rigid shafts are considered through studying the stressed state of their surface layer. The depth of hardening, value and distribution of the residual stresses in the surface layer have a direct impact on the geometrical stability of low-rigid shafts. The main goal of hardening consists in providing the uniformity of the stressed state in the bulk. A novel design of a centrifugal roller is proposed to ensure effective hardening of low-rigid shafts. A notion of a mutual impact zone is introduced. Theoretical dependences providing determination of the optimal depth of the hardened layer of low-rigid shafts are presented. The experimental results regarding determination of the hardening depth as a function of the rotational frequency of a centrifugal roller are presented. The experimental data show that the quality of treating low-rigid shafts with a centrifugal roller depends on the characteristics and thickness of the mutual impact zone, which is determined by the average grain size of the microstructure. The developed design of a centrifugal roller provides an unchanged value of the working force, stability of deformation and stresses along the workpiece length. The optimal depth of hardening of the surface layer of low-rigid shafts attained upon finishing-hardening by surface plastic deformation (SPD), which is proved both theoretically and experimentally, should not exceed the size of the mutual impact zone.