PSI - Issue 77

Martin Matušů et al. / Procedia Structural Integrity 77 (2026) 127 –134 Martin Matušů / Structural Integrity Procedia 00 (2025) 000 – 000

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approach significantly. We analyzed a larger dataset, with samples positioned across a 5×5 grid covering the full platform area. Each zone contained multiple specimens, and for each, an individual S – N curve was constructed to assess fatigue behavior in detail. Fig. 4 b) presents a two- dimensional spatial map illustrating the influence of the specimen’s printing position on fatigue performance. The heatmap uses color intensity to indicate the proportion of specimens in each segment that exhibit fatigue strengths falling below the lower quartile threshold of the reference Weibull distribution, thereby classifying them as outliers. Each cell within the map corresponds to a discretized region of the build platform, with the percentage of outlier specimens shown numerically. Brighter regions indicate higher proportions of such fatigue outliers. Notably, several neighboring regions display elevated outlier concentrations — specifically within the x -axis interval of 0.2 to 0.4 and the y -axis interval of 0.2 to 0.4. These regions, highlighted with red font, exhibit outlier rates exceeding 25%, suggesting a statistically significant reduction in fatigue life that may be attributed to localized process-induced material or microstructural variability. In contrast, the central and peripheral regions, especially those with deep purple shading, demonstrate a lower incidence or complete absence of outliers, suggesting more consistent fatigue behaviour. It is important to note that cells in the corners of the building platform are based on limited data (e.g., fewer than 5 specimens), and therefore, these regions are excluded from definitive interpretations due to insufficient statistical robustness. This spatial trend strongly supports the hypothesis that the printing position within the build envelope significantly influences fatigue performance and must be considered in both experimental design and fatigue life prediction models. 3. Discussion The presented results confirm that build position significantly affects the fatigue performance of AlSi10Mg components produced via Laser Powder Bed Fusion (L-PBF). However, several aspects merit deeper discussion beyond the observed spatial variability. a. Discretization Limitations: The current 5×5 grid segmentation of the build platform, while practical, introduces a coarse spatial resolution. Specimens were assigned to zones based on their center coordinates, yet fatigue damage typically initiates at surface regions. These active fatigue zones may extend into neighboring grid cells, potentially distorting the spatial analysis. A more refined approach could involve weighted assignment based on the proportion of the fatigue-critical volume within each grid cell. b. Temporal and Operational Context: The study spans 22 experimental series, yet the temporal distribution of builds, platform usage, and powder history (virgin vs. reused) were not explicitly considered. Additionally, service interventions or recalibrations of the machine during this period could have influenced local process conditions. Future work should incorporate these variables to better isolate the effects of building position from other operational factors. c. Localized Anomalies and Critical Zones: The clustering of fatigue outliers in specific regions — particularly between 0.2 – 0.6 on the x-axis and 0.6 – 0.8 on the y-axis — suggests the presence of localized process anomalies. These may stem from optical misalignments, blind spots in laser scanning, or uneven powder spreading. The proximity of multiple extreme cases in this zone warrants targeted investigation, potentially using in-situ monitoring or post-build diagnostics. d. Root Cause Analysis: While the study proposes several plausible causes for spatial fatigue variability (e.g., laser angle, heat dissipation, powder dynamics), a systematic methodology is needed to identify dominant factors. Controlled experiments, machine logs, and high-resolution thermal or optical data could help distinguish between contributing mechanisms. e. Standardization and Transparency: To enhance reproducibility and facilitate comparative studies, we recommend that future publications include detailed build platform maps and precise specimen coordinates. Reviewers should encourage this practice to ensure spatial effects are properly documented and considered in fatigue assessments. 4. Conclusion The present study systematically quantifies the impact of build position on the fatigue behavior of AlSi10Mg specimens fabricated by Laser Powder Bed Fusion. Key conclusions include: