Straightening of Relatively Flexible Cylindrical Parts. Part I. Establishing the Loading Conditions in Transverse Straightening

Abstract

Relatively flexible cylindrical parts (shafts and axles) may be straightened by loads produced by different stresses in different distributions. A promising method is straightening by flexure under a distributed load, with subsequent strengthening of the workpiece by surface plastic deformation based on transverse rolling between flat plates. The goal in the present work is to determine the stress state of the workpiece in transverse straightening so as to select the best type of load and treatment conditions. The mathematical analysis is based on the theory of an elastoplastic solid; ANSYS Workbench software is employed. Effective methods of loading in the transverse straightening of cylindrical parts are determined. Analytical calculations yield the residual stress corresponding to straightening of the cylindrical parts. The residual stress required for straightening depends on the initial flexure, the material in the workpiece, and its size. The stress state of cylindrical parts is determined for different types of transverse loading. The flexural stress for straightening of a shaft under a distributed load is less than the stress due to a transverse force. To straighten a rod (diameter 10 mm, length 200 mm) with initial flexure 0.5 mm, flexural stress of about 370 MPa must be created. In the transverse straightening of cylindrical parts, flexure under the action of a distributed load is an effective loading method. Limiting flexural coefficients of 5.3–5.5 are obtained for all values of the shaft rigidity in straightening by transverse flexure under a distributed load when l/L = 0.8. The proposed mathematical model correctly determines the residual stress corresponding to straightening of the cylindrical parts. The formula derived for calculating the total flexure and determining the effective load may be recommended for practical use in production conditions so as a ensure precise straightening of relatively flexible parts such as shafts.