Straightening of Relatively Flexible Cylindrical Parts. Part II. Stress State of the Cylinder Workpiece in Transverse Rolling between Flat Plates

Resumo

The intended form of relatively flexible cylindrical parts (shafts and axles) may be restored by straightening by flexure under a distributed load, with subsequent strengthening of the workpiece by surface plastic deformation based on transverse rolling between flat plates. It is well known that the nonequilibrium stresses are generated in the whole workpiece after straightening by transverse flexure, and the part is eventually deformed again. Therefore, the workpieces should be additionally straightened with surface plastic deformation after straightening by flexure. We use transverse rolling by flat plates for that purpose. The aim in the present work is to determine the capture conditions and the stress state of the workpiece in transverse rolling of cylindrical parts between flat plates. The mathematical analysis is based on the theory of an elastoplastic solid; ANSYS Workbench software is employed. A new method is proposed for control of stress state in straightening of cylinderical workpieces. The limiting capture angle α ranging 2–8 degrees and the maximum absolute reduction depending on friction coefficient and on the diameter of workpiece are obtained. The optimum reduction varies ΔH = 0.07–0.15 mm. The calculation data show that the stress state of uniform extension occurs at the center in the workpiece cross section after transverse rolling, and the stress state of reduction is formed at the peripheral areas of the workpiece. The straightening method of transverse rolling between flat plates eliminates crack formation and destruction of the material in the central area of the cylindrical parts.