PSI - Issue 37

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Theodoros Marinopoulos et al. / Procedia Structural Integrity 37 (2022) 139–144 T. Marinopoulos et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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Figure 4. Maximum sustained load for two different PLA designs and CFN sockets (The green dashed line shows the load-bearing capacity required by the standard.)

Another important observation from these initial tests was the stress-concentration area at the lateral-posterior distal end of the socket. It was evident in all the tested samples that this area contributed significantly to the load-bearing capacity of the product and was directly affected during failure. All the tested sockets exhibited brittle failure, with the crack spanning from the lateral-posterior distal end to the mid-top medial-anterior of the socket. On the PLA sockets segments of the crack were noticed to be parallel to the printing plane (Fig. 5C) while the crack of the CFN socket followed a straight path typical to reinforced homogeneous materials (Fig. 5D). 4. Conclusion This study successfully developed a testing methodology following the ISO standards guidelines, identifying new loading points and new load-level requirements specifically for paediatric prosthetic sockets. It was shown that silicone rubber can be successfully used to model a limb, transferring loads to the socket, thus loading the product as close to conditions of the real application as possible. The obtained results were in accordance with the literature signalling the importance of using a rubber residuum for the tests. It was also demonstrated that 3D printed sockets with the correct material choice and design are capable of meeting strict loading requirements. Despite the small number of specimens tested, it can be safely assumed that 3D-printing technology is suitable for prosthesis applications and manufacturing of prosthetic sockets, considering the design and the material choice as important factors for the structural compliance of the product. Further tests are in progress to better understand the complex behaviour of the 3D printed components and the effect of printing parameters on their

structural integrity. Acknowledgement

VVS gratefully acknowledges financial support from the Government of the Russian Federation under the mega-grant program, contract no. 075-15-2021-578, 31 May 2021, hosted by Perm National Research Polytechnic University.