PSI - Issue 77

Y. Bakir et al. / Procedia Structural Integrity 77 (2026) 639–648 Y.Bakir et al./ Structural Integrity Procedia 00 (2026) 000–000

643

5

As it can be seen in the Figure 5 gage length’s cross section is 1.3 x 2 mm. Minimum time for the exposure of a hatch vector was set to be approximately 10 milli-seconds. The idle time for each hatching line is calculated according to the length of the hatch vector length, shorter the vector shorter the exposure time thus longer idle time. 15 tensile specimens were printed vertically using each of the scanning strategies. There 3 parts printed inside of each prop support shell. The effect of these strategies on the tensile performance of the parts are investigated in relation with the evaluation of data gathered by a high-speed camera.

Figure 5 Cross section of gage length of specimens.

In addition, 12 parts in the shape of rectangular prisms were printed using two different strategies. 2 of the top surfaces of the parts were scanned by optical microscope Alicona IFM 4. And 10 of these parts were used for residual stress evaluation. Hole-Drilling strain gage method according to the ASTM E837 standard, was used for this purpose. And these parts had the cross section of 15 mm to 5 mm and the height of 15 mm.

Figure 6 Rectangular prism shaped parts that are printed for observing melting track formation.

3. Results and discussion 3.1. Melting Track Formation

Hatching lines are parallel with each other as explained before. At the end of exposure of each hatching lines, laser beam does a “U-turn” and continues with the exposure of the subsequent hatching line. According to the results of optical microscopy scans, there was drastic differences between the formation of melting tracks when idle time is introduced. Idle time between the exposure of melting tracks were approximately 4 micro-seconds. While default scanning strategy is used, ends of subsequent melting tracks seems to have conjoined. Conjoining of these, also influences the solidification behavior. Therefore, near the edges of the part, melting track width was measured to be 165 µm for default process, while idle time utilized the melting track width was 95 µm.