PSI - Issue 68

Ibrahim T. Teke et al. / Procedia Structural Integrity 68 (2025) 365–371 I. T. Teke & A. H. Ertas/ Structural Integrity Procedia 00 (2025) 000–000

368

4

Table 1. 3D printing parameters for recycled-PLA. Parameters Values

Parameters

Values

Layer Thickness (mm) Nozzle Diameter (mm) Extrusion width (mm)

Nozzle Temperature ( o C) Bed Temperature ( o C) Printing Speed (mm/s) Infill Percentage (%)

213

0.2 0.4

63 55 30

1

Raster Angle ( o )

45

Density (gr/cm 3 )

1.23

Figures 2a and 2b show the fixed specimens on the fatigue testing machine for the S-D-S-ER and D-S-ER methods, respectively. The fixture was specifically designed for these tests, with a test span of 60 mm for the specimens.

Fig. 2. Fixed specimens on the machine, a) S-D-S-ER and b) D-S-ER model.

3. Results and Discussion The D-S-ER method has been theoretically proven to significantly enhance structural performance optimization (Teke et al. 2023). Building on this methodology, the S-D-S-ER approach was developed, incorporating an initial geometry design using a sub-modeling technique, followed by the application of the D-S-ER method. When evaluated through three-point bending tests, the S-D-S-ER and D-S-ER models exhibited notably different behaviors. The S-D S-ER model demonstrated an extended fatigue life, with the stages of crack initiation and propagation accounting for more than 50% of the total fatigue life, as illustrated in Figure 3. Conversely, the D-S-ER model showed a reduced lifespan, with complete failure occurring shortly after crack initiation, as also depicted in Figure 3 under loading conditions of 0–1 kN and 0–0.9 kN.