Shape distortions, plastic strains and residual stresses after one-sided forging/rolling of the beam: application to additive manufacturing of the linear metal segment with layer-by-layer pressure treatment

A numerical model of the formation of a stress-strain state in a prismatic beam during its unilateral processing by plastic strains is developed. Such a model is required to select rational modes of layer-by-layer pressure treatment of additively accreted linear metal segments. Shape distortions, residual stresses and strength characteristics can be controlled through forging or rolling of the deposited metal layers. The process consisting of a stage of unilateral surface pressure treatment of a sample fixed on the opposite face on a flat surface by normal bonds, and a stage of releasing the sample from the fastenings is modeled. According to the experimental data, the impact of a pneumatic hammer is calibrated in the numerical model and the equivalent depth of the roller insertion is determined. The inhomogeneity of the distribution of plastic strains and longitudinal residual stresses along the cross section of the sample, the longitudinal and transverse curvature of the latter, the nature of deformations during unloading of the sample for AMg6 and VT6 alloys and 12X18N10T stainless steel, depending on the depth of the roller insertion, is investigated. For each of the materials, the existence of a critical roller insertion depth was found, after which the sign of the longitudinal curvature of the sample changes. Anticlastic curvature of samples of sufficiently large width was found. Methods of experimental determination of the state of a fixed sample (a linear segment of the frame) based on the state of the unloaded sample are discussed. The acceptability of measurements of the microhardness distribution over the height of the cross-section of the sample to estimate the localization zone size of plastic strains, as well as the acceptability of measurements of the longitudinal curvature of the sample to estimate residual stresses, are established. The questionable value of measurements of longitudinal residual stresses is demonstrated due to their significant heterogeneity, as well as redistribution during cutting layers.