PSI - Issue 54

Ivana Zetková et al. / Procedia Structural Integrity 54 (2024) 256–263 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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or the used printing pattern with a checkerboard pattern. The manufacturer recommends setting this parameter when printing parts with different volumes and shapes in order to homogenize residual stresses in the structure. The results, shown in Figure 2, indicate that the setting of the minimum layer printing time delay function was not beneficial in the case of the selected samples. However, it is possible that this function will be beneficial for printing components with variable printing volume. Due to the disappointing results for the SW10 and MLT sets, a multifactor change with the designation T was proposed. In this set is modified both the process parameters and the subsequent heat treatment.The layer thickness was set to 50 µm with corresponding default parameters, which entailed a change in the Volume Energy Density parameter. The heat treatment was changed from 820°C for 1 hour to 940°C for 2 hours, as recommended by the manufacturer to reduce residual stresses. Figure 4 shows the residual stress profiles for samples printed with the T set of parameters. These profiles show a significant improvement over the previous results. While the profiles for the SP, SW10, and MLT sets started at higher values with a high scatter and gradually decreased, the profile for samples printed with the T parameters is very uniform, with only a very small scatter of tensile residual stresses (-120 MPa to -180 MPa) over the entire range of the monitored depth. These results suggest that the T set of parameters is effective in reducing residual stresses.

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Fig. 2. Profiles of suggested parameter sets SP, SW10, MLT, T.

For the last set of samples, labeled SP_P120, the building platform pre heating was changed from the default 40°C to 120°C, while the other parameters were kept the same as for the SP set. This setting had the greatest effect. There was a significant reduction in residual stresses. The graph in Figure 3 shows a significant difference in the profiles for the SP and SP_120 settings. Increasing the preheat temperature had a major impact on the stress profile and its polarity. The stress curves start at tensile values and reach compressive values at a depth of approximately 0.3-0.45 mm.