RESIDUAL STRESS RELAXATION IN A HARDENED CYLINDER UNDER CREEP, LOADED BY AN AXIAL FORCE, TORQUE, AND INTERNAL PRESSURE
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RESIDUAL STRESS RELAXATION IN A HARDENED CYLINDER UNDER CREEP, LOADED BY AN AXIAL FORCE, TORQUE, AND INTERNAL PRESSURE V. P. Radchenko∗ , V. V. Tsvetkov, and M. N. Saushkin
UDC 539.376:539.4.014.13
Abstract: A method is developed for solving a boundary-value problem of residual stress relaxation in a surface-hardened hollow cylinder under combined loading by an axial force, torque, and internal pressure. Methods for determining the stress–strain state after hardening and its kinetics during creep are proposed. The effect of internal pressure along with a tensile load or torque on a thickwalled cylindrical sample made of ZhS6KP alloy after air-shot peening is investigated. Computational diagrams for stress tensor components under instantaneous temperature-force loading during creep and after unloading are given and analyzed. The behavior of unhardened and hardened samples at the stage of steady creep after complete residual stress relaxation is compared. Keywords: residual stresses, surface plastic hardening, cylindrical sample, creep, relaxation, tension, torsion, internal pressure, boundary-value problem. DOI: 10.1134/S0021894420040124 INTRODUCTION Surface plastic hardening is a well-known method for increasing the reliability characteristics of structural elements, such as wear resistance, microhardness, ultimate fatigue strength, etc. It is believed that the formation of compressive residual stresses in the near-surface layer has a positive effect on these characteristics. There is a large number of studies on how residual stresses affect these reliability characteristics (see, e.g., earlier works [1–4] and more recent ones [5–10]). An important problem is to estimate the kinetics of induced residual stresses during the operation of a structure because creep strains occur in a material under high-temperature loading, thereby causing residual stress relaxation. In this case, it becomes necessary to use methods for predicting the stress–strain state kinetics in hardened structural elements under creep. In [11], a method for estimating the residual stress kinetics in a surface-hardened solid cylinder made of ZhS6UVI alloy under thermal exposure (exposure to high temperatures without external loads) at a temperature of 675◦ C was proposed and experimentally verified. In [12], a theoretical and experimental study of the residual stress relaxation in flat samples made of EP742 alloy after ultrasonic hardening, also under thermal exposure at 650◦C. The literature has virtually no experimental data on the combined effect of temperature and force loading on hardened parts. In [13, 14], direct methods for solving boundary-value creep problems for surface-hardened solid and hollow cylinders under axial tension, respectively, are presented for the first time. The applicability of these methods is confirmed for the case of tension of a solid cylinder made of ZhS6KP alloy at a temperature of 800◦ C
∗ Samara State Technical University, Samara, 443100 Russia; [email protected]; vi.v.tsvetkoff@gmail.com; [email protected]. Tran
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