Relaxation of residual stresses and precision of steel pipes
This paper describes a study of residual stress patterns characterizing cold plastic deformation of axisymmetric steel products. The authors propose a technique for calculating residual stresses created in axisymmetric steel pipes during plastic deformation, which accounts for the degree of plastic deformation, the key process parameters, as well as the mechanical properties of the processed material. The energy approach helped the authors determine the residual stresses in axisymmetric workpieces as a function of the key plastic deformation process parameters. Analytical solutions were obtained. The formulas for determining residual stresses include the key process parameters, the mechanical properties of the material and the product dimensions. With the help of the analytical relationships for determining residual stresses, one can predict the operational behaviour of steel products and prevent fractures. Operational stresses and deformations tend to change over time, even under constant loads. The authors analysed the effect of post-deformation relaxation of post-deformation residual stresses on the geometry of finished steel pipes. Knowing the actual residual stresses, one can predict the operational behaviour of steel products and prevent fractures. The importance of the problem of determining residual stresses lies in the fact that they can enhance the performance of steel products but they can also affect it. For theoretical definition of residual stresses, one would need to solve a rather complex thermoelastoplasticity problem, as well as a problem related to the mechanics of solid deformable bodies. One only finds scarce published sources - either domestic or foreign - that would describe such solutions with regard to production processes.