The Research Of Impact Resistance Ability Of Bird Heads

Head injury has become a primary threat to our life in the accidents resulting from transportation, construction and sports. However, through observation, we find that some bird heads suffer a large impact during pecking on a hard surface, but their brain don't get injury. A good protective equipment can be designed through the study of the impact resistance characteristic of the bird heads. According to the characteristic of bird pecking, this article mainly discusses the impact resistance mechanism of woodpecker, pigeon and chicken's heads.The pecking frequency, pecking velocity and pecking force are measured when the three birds peck using a special design experiment device. The kinetic energy density, defined as the ratio of impact kinetic energy to whole body mass, is calculated to assess the shock resistance of the three birds. The result shows that the impact resistance abilities of woodpecker head is far better than pigeon and chicken.To obtain the accurate models of the three bird heads for numerical simulation, the three dimensional models are built using the reverse engineering method. First the bird heads are scanned by Micro-CT and the pictures of each section of the bird heads are obtained. Then the three dimensional models are extracted from the pictures and are meshed accurately. The pecking processes of the three bird heads are simulated using the finite element software.The stress wave propagation status of skull and brain is analyzed. The result shows that most of the stress propagates through the upper beak during woodpecker pecking, while the lower beaks of pigeon and chicken are used to propagate most of the stress. The high stress value in the bird heads is concentrated on beak area. The stress occurring in the bird brain location is very lower, which protects the brain from injury. During pecking, all the head structures are safe. As the impact is finished, the stresses of skull and brain tend to decline, but the decay time of brain's stress is longer than skull.The modal analysis of the bird heads indicates that the nature frequency of the three bird heads are larger than the pecking work frequency to avoid sympathetic vibration during pecking. It should be pointed out that the first vibration mode orientation of woodpecker head is perpendicular to the sagittal plane, while the orientation of pigeon and chicken head is along the direction of pecking. The more the skull volume in the head and the higher the ratio of the beak length to the head, the better the impact resistance ability of bird head.