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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Fig. 2. Effect of Poisson’s ratio on socket stress and safety . (a) Maximum Von Mises stress in the socket versus ν for HCFRPs, PE, and PETG ; (b) socket safety margin expressed as maximum Von Mises stress divided by the σy of material, plotted against ν. Curves/colum ns correspond to HCFRPs (green), PE (blue), and PETG (red). When varying ν, μ was fixed at 0.3 (see Section 2.2 for details). 4. Discussion The U-shaped dependence of residual limb soft tissue stress on μ is consistent with contact -mechanics principles governing limb–socket interactions. At low-to- moderate μ, increased friction restricts interfacial slip and enlarges the effective stick zone, thereby redistributing shear stresses across a wider area and reducing local stress concentrations. Once slip is largely suppressed, further increases in μ primarily elevate interfacial shear without substantially altering load redistribution, resulting in a minimum stress response followed by a plateau (Dickinson et al., 2017b) . This trend aligns with finite-element analyses that simulate frictional stick–slip phenomena at the limb–socket interface (Linlin Zhang et al., 2013). In contrast, the socket stress-to- yield ratio exhibited limited sensitivity to μ , with variations across materials governed predominantly by their intrinsic mechanical strength. These findings suggest that a μ close to 0.7, combined with a medium-to-high stiffness material, provides an effective configuration that mitigates soft-tissue stresses while preserving sufficient structural safety margins. Variation in ν influences socket mechanics by modulating material compressibility and associated load transfer. Materials with higher ν exhibit reduced volumetric deformation, increased stick contact at the interface, and more uniform distribution of loads within the socket wall, resulting in lower peak Von Mises stresses (Greaves et al., 2011b). From a design perspective, the selection of socket materials with elevated ν = 0.40 –0.50 is advantageous, as it reduces maximum socket stress and simultaneously enhances the structural safety factor, thereby improving long -term reliability in transfemoral socket applications. 5. Conclusions This study systematically investigated the influence of μ and ν on the mechanical response of the socket –limb interface. These results indicate that configuring the limb–socket interface with an intermediate friction coefficient and employing materials with relatively high Poisson’s ratios can effectively attenuate soft -tissue loading while preserving an adequate structural safety margin of the socket. References Baum, B. S., Schnall, B. L., Tis, J. E., & Lipton, J. S. (2008). Correlation of residual limb length and gait parameters in amputees. Injury , 39 (7), 728 – 733. https://doi.org/10.1016/j.injury.2007.11.021 Berke, G. M., Fergason, J., Milani, J. R., Hattingh, J., McDowell, M., Nguyen, V., & Reiber, G. E. (2010). Comparison of satisfaction with current prosthetic care in veterans and servicemembers from Vietnam and OIF/OEF conflicts with major traumatic limb loss. The Journal of