PSI - Issue 42

Theodoros Marinopoulos et al. / Procedia Structural Integrity 42 (2022) 903–910 T. Marinopoulos et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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create the new designs. It was observed that the added material resulted in similar stress distributions, but the maximum stress was decreased (Fig. 5).

Figure 5. Von Mises stress distribution in original and redesigned sockets for Condition I at 8000 N force

4. Discussion The use of FEA to reinforce the prosthetic sockets was successful, and the new designs showed improved mechanical performance in numerical simulations. Still, the mixed results were found in the experimental work. Although one would expect that the higher reinforcement of the socket would cause the higher load-bearing capacity, it was found that the biggest sockets did not perform equally well. An additional set of experiments was performed on sockets printed at maximum thickness of 4.5 mm. The sockets were printed in bPLA, and they outperformed both original and 6 mm redesigned sockets without failing at a maximum load of 8000 N (Fig. 7). The failure mode was common in all cases, meaning that the predicted load distribution was accurate. A closer look at the fracture surface of the sockets, though, showed that failure also occurred between the neighboring print paths (Fig. 6). This behavior is attributed to the effect of the printing methodology, demonstrating that different geometries require different printing parameters for a successful performance, instead of sharing them with the original design. The infill can also affect the obtained results (Fig. 8).

Fig. 6. Crack surface of 6 mm redesigned socket with visible failure of neighboring printing paths