PSI - Issue 77

Fang Liu et al. / Procedia Structural Integrity 77 (2026) 215–220 F. Liu/ Structural Integrity Procedia 00 (2026) 000–000

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Computations were performed on a workstation equipped with an 11th Gen Intel® Core ™ i7 - 11700 processor, 16 GB RAM, running 64-bit Windows 10. 3. Results 3.1. Dependence of soft tissue stress and socket safety margin on interface friction The maximum Von Mises stress in the residual - limb soft tissues exhibited a U - shaped dependence on μ. Stress decreased sharply as μ increased from 0.3 to approximately 0.7, reached a minimum near 0.7, and then showed a slight rebound, stabilising for μ values above 0.9 (Fig. 1a). Across all values of μ , stresses were highest for HCFRPs, intermediate for PETG, and lowest for PE, indicating that lower-stiffness sockets attenuate peak tissue loading (Fig. 1 a). In contrast, the socket stress-to-yield ratio was largely insensitive to μ but displayed marked differences across materials, with the lowest values for HCFRPs, intermediate for PETG, and highest for PE (Fig. 1 b). These findings demonstrate an inherent trade-off between comfort and structural safety: sockets with lower stiffness reduce tissue stress at the expense of structural margins, whereas stiffer sockets increase safety margins while elevating tissue loading. The results suggest that a μ of approximately 0.7, in combination with a medium -to-high-stiffness material, provides a balanced configuration for socket performance (Figs. 1 a,b).

Fig. 1. Effect of interface friction on residual limb soft tissue loading and socket safety. (a) m aximum Von Mises stress in the residual limb soft tissue versus μ for sockets made from HCFRPs, PE, and PETG; (b) s ocket safety margin expressed as maximum Von Mises stress divided by the σ y of material , plotted against μ. Curves/columns correspond to HCFRPs (green), PE (blue), and PETG (red). When varying μ, the ν of each material was fixed at its reference value (see Section 2.2 for details). 3.2. Dependence of prosthetic socket stress and safety on Poisson’s ratio The maximum Von Mises stress in the socket decreased consistently with increasing ν across all three materials (Fig. 2 a). The steepest decline occurred between 0.30 and 0.40, with overall decreases of approximately 16 –18% from 0.10 to 0.50; a slight rebound was observed for PE at 0.50 relative to 0.40. At any ν , stresses were highest for HCFRPs, intermediate for PETG, and lowest for PE, reflecting the influence of material stiffness on internal stress distributions. The socket stress-to-yield ratio also exhibited clear material-dependent differences, with the same ordering observed in the μ analysis (HCFRPs < PETG < PE). Unlike the μ analysis, however, this ratio exhibited a slight but systematic dependence on ν, decreasing slightly as ν increased (Fig. 2 b), indicating that higher ν values not only reduce maximum socket stresses but also confer a modest improvement in the structural safety margin .