Vyacheslav Em

High residual stresses (RS) in laser powder bed fusion (PBF-LB) components present significant structural challenges, yet traditional characterization techniques are cost- and time-intensive. This study introduces three rapid mechanical testing methodologies to estimate longitudinal RS in PBF-LB 316 L stainless steel by using the premature micro-yielding of pre-tensioned near-surface regions in cylindrical geometries. The proposed methods evaluate RS through: (I) plastic work density calculated from cyclic loading-unloading, (II) virtual unloading mathematically projected from standard monotonic tensile data, which also allows the analysis of existing tensile test results, and (III) the detection of a macroscopic micro-yielding threshold (0.01% strain). The estimates were benchmarked against neutron diffraction (ND) measurements across multiple heat-treatment conditions (as-built to 1000 °C). The energy-based approaches (Proposed Methods I and II) demonstrated linear correlations with relative ND stress reductions (R ² = 0.75 and 0.71, respectively). Furthermore, by subtracting the empirical micro-yielding threshold from condition-specific macroscopic yield strengths, Proposed Method III captured the relative RS relaxation trend. Electron backscatter diffraction (EBSD) analysis supported the proposed mechanistic interpretation by showing localized geometrically necessary dislocation (GND) accumulation prior to bulk yielding. These findings show that the proposed mechanical methods can serve as accessible tools for evaluating stress mitigation strategies in additive manufacturing.

High residual stresses (RS) in laser powder bed fusion (PBF-LB) components present significant structural challenges, yet traditional characterization techniques are cost- and time-intensive. This study introduces three rapid mechanical testing methodologies to estimate longitudinal RS in PBF-LB 316L stainless steel by using the premature micro-yielding of pre-tensioned near-surface regions in cylindrical geometries. The proposed methods evaluate RS through: (I) plastic work density calculated from cyclic loading-unloading, (II) virtual unloading mathematically projected from standard monotonic tensile data, and (III) the detection of a macroscopic micro-yielding threshold (0.01% strain). Estimations were quantitatively validated against neutron diffraction (ND) measurements across multiple heat treatment conditions (as-built to 1000 °C). The energy-based approaches (Proposed Methods I and II) demonstrated linear proportionality with relative ND stress reductions (R2= 0.82 and 0.77, respectively). Furthermore, by subtracting the empirical micro-yielding threshold from condition-specific macroscopic yield strengths, Proposed Method III tracked absolute RS relaxation. Electron backscatter diffraction (EBSD) analysis physically validated these techniques, confirming that the initial non-linear macroscopic mechanical response is governed by localized geometrically necessary dislocation (GND) accumulation prior to bulk yielding. These findings establish the proposed mechanical methods as highly accessible alternatives for evaluating stress mitigation strategies in additive manufacturing.