Straightening of Shafts by Surface Plastic Deformation with Elastic Flexure of the Workpiece
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ightening of Shafts by Surface Plastic Deformation with Elastic Flexure of the Workpiece G. V. Muratkina and V. A. Sarafanovaa, * a
Togliatti State University, Togliatti, Russia *e-mail: [email protected]
Received June 28, 2019; revised August 16, 2019; accepted September 5, 2019
Abstract—A method is proposed for straightening nonrigid parts by surface plastic deformation. This method is based on the change in the stress–strain state of the workpiece in finishing. Keywords: nonrigid shaft, straightening, surface plastic deformation, residual strain, machining precision, stress DOI: 10.3103/S1068798X20080183
Improvements in machine tools focus on their reliability and the machining precision. Nonrigid components made of high-strength materials—for example, rotors, propellers, drive shafts, spindles, and hydraulic cylinder rods—are difficult to machine. These components largely determine the life and reliability of systems that must ensure high manufacturing precision, dimensional stability, and surface quality. However, it is difficult to ensure such high performance on account of the machining errors associated with elastic and residual deformation. The magnitude of such deformation largely depends on the rigidity of the components. Decrease in shaft rigidity always increases the deformation and considerably complicates the manufacture of such parts. Therefore, the machining of nonrigid shafts differs fundamentally from the manufacture of shafts of normal rigidity. The manufacturing technology for nonrigid shafts may differ significantly depending on which machining error is dominant [1, 2]. For example, in the manufacture of nonrigid shafts with L/D = 10–20, where L and D are the length and diameter of the shaft, respectively, errors in the shape and size due to elastic deformation are dominant. If L/D > 21, the spatial error due to the residual flexural strain is dominant [3]. This error consists of distortion of the part’s longitudinal axis. In contrast to errors in the shape and size, this is a complex vector error, which considerably hinders the use of many machining methods. The magnitude of this error depends not so much on the precision of the industrial equipment as on the level of manufacturing technology. Therefore, ensuring high machining precision of nonrigid shafts despite spatial error is a very complex problem. It calls for effective control of the workpiece’s stress–strain state in the course of machining.
The residual flexural strain is due to nonuniform changes in the part’s stress state associated with its manufacture, storage, transportation, and operation [4]. In manufacturing, the residual flexural strain arises in elastic unloading under the action of the flexural torque due to the asymmetric distribution of the initial stress in the cross section. The initial stress is understood to be the unbalanced stress in the part after machining but before deformation [5]. The residual flexural strain arising in operation is an order of magnitude less than the strain due to machining, as a rule. Ho
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