Response of Woodpecker's Head during Pecking Process Simulated by Material Point Method.

Prevention of brain injury in woodpeckers under high deceleration during the pecking process has been an intriguing biomechanical problem for a long time. Several studies have provided different explanations, but the function of the hyoid bone, one of the more interesting skeletal features of a woodpecker, still has not been fully explored. This paper studies the relationship between a woodpecker head's response to impact and the hyoid bone. Based on micro-CT scanning images, the material point method (MPM) is employed to simulate woodpecker's pecking process. The maximum shear stress in the brainstem (SSS) is adopted as an indicator of brain injury. The motion and deformation of the first cervical vertebra is found to be the main reason of the shear stress of the brain. Our study found that the existence of the hyoid bone reduces the SSS level, enhances the rigidity of the head, and suppresses the oscillation of the endoskeleton after impact. The mechanism is explained by a brief mechanical analysis while the influence of the material properties of the muscle is also discussed.