Determination of the stress state in the deformation zone when rolling rotation of a carbon steel workpiece at a local site

A new method for straightening and strengthening non-rigid cylindrical parts based on rolling on flat wedge plates has been developed. The first stage of this process involves straightening and rolling rotation of a local section of the workpiece on a narrow lead-in section of the plates. The main geometric parameters of the lead-in section of the wedge plates are the length l, the width b and the lift angle α, which ensures the condition for gripping the workpiece. The results of theoretical calculation and computer modeling of the influence of the main geometric parameters of the entry section on the stress state of a workpiece made of structural elastic-plastic steel 3 are presented based on the Ansys Workbench software package. The calculation showed that the value of the relative reduction of the workpiece is directly dependent on the lift angle α and the angle of rotation of the workpiece φ at the lead-in section. The ranges of the lead-in section lift angle (0 < α < 5.7°) and the maximum permissible value of the absolute reduction (Q = 4.4 %) have been theoretically determined. To meet the condition of gripping the workpiece during one turn at the entry section, the angle α must not exceed 4°. During the workpiece rolling, the intensity of temporary stresses increases with an increase in the entry section elevation angle α and exceeds the ultimate strength of the material after a full turn at α ≥ 4°. In the center of the workpiece cross-section, the radial stress has a positive value, which is characterized by tensile stresses, and compressive stresses are formed in the contact zones of the workpiece with the plates. The results of computer modeling of the stress state confirm the theoretical calculation of the ultimate value of the relative compression. Rational geometric dimensions of the entry section of wedge plates for straightening a cylindrical workpiece in a local section are established. To ensure the strength condition of the part, it is necessary to make one full turn of the workpiece (φ = 360°) at the entry section elevation angle α = 2°.