FEM analysis in excellent cushion characteristic of ostrich (Struthio camelus) toe pads

Abstract

African ostrich ( Struthio camelus ) is the largest and fastest extent bipedal animal. The ostrich mainly relies on the 3rd toe to support the entire body under high-speed motion. The short and severe impact concentrated on the limited area would produce tremendous momentary internal stress and strain, which may contribute to the phalanges disloaction, soft tissue damage and the like. The vibration and excessive negative acceleration caused by the ground reaction force also affect the stability of the touching process. Therefore, ostrich toe pads are required to have excellent cushion characteristics. However, current studies often explains the cushion properties by analyzing the macro-microscopic structure of the pad organism, and there is a paucity of research on its biomechanical behaviour. Consequently, from the perspective of multi-layer structure and biomaterial assembly, this study aims to explain the biomechanical characteristics of the ostrich toe pads by FEM (Finite Element Method) analysis. Based on results, we deem that the ostrich toe pad could absorb energy and reduce vibration effectively. Firstly, the multi-layer structure of the pads make the stress and strain decay from outside to inside. Secondly, the minimal response frequency of the pad is 164.22 Hz, making it effectively avoid resonance phenomenon. Finally, the composite material model has the best performance in decreasing the negative acceleration peak value, the impact force peak value and the maximal equivalent stress value at velocities of 0.669 m/s and 1.339 m/s. These results help to further understand the buffer mechanism of the ostrich toe pad, and also have important inter-species reference value for the pathogenesis of human foot soft tissue injury.

Study on bio-inspired feet based on the cushioning and shock absorption characteristics of the ostrich foot

“…The hardness levels, elastic moduli, and densities of different soft tissues, including skin, fascia and digital cushions, were measured and published [24]. Here, test details were not repetitively described and related parameters were directly cited.…”

“…skin, fascia and digital cushions) have been measured, and excellent cushion characteristic of ostrich toe pad has been analyzed using the finite element method (FEM). The toe pad can disperse the load effectively and without excessive deformation [24]. If the internal material is too soft, the maximum impact force and stress of the external structure will be significantly improved, and the stability will be deteriorated.…”

“…If the internal material is too soft, the maximum impact force and stress of the external structure will be significantly improved, and the stability will be deteriorated. Therefore, the foot pad should have a moderate hardness to maintain the stability of the touchdown process [24]. An ostrich foot locomotion system composite model showed the von Mises stress maximized in bones, followed by articular cartilages and plantar soft tissues [25].…”