MIT 3 A26 - Woodpecker pecking (9 pages)

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Woodpecker pecking



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Woodpecker pecking

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Pages:
9
School:
Massachusetts Institute of Technology
Course:
3 A26 - The Nature of Engineeering
The Nature of Engineeering Documents

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Woodpecker Pecking Drew Altschul Why it is that woodpeckers do not get brain injury from pecking People get brain injury if the brain decelerates at about 100g over about 5 millisecond the time of a typical impact in a car crash Measurements on woodpeckers indicate that they tolerate decelerations of up to 1500g over about 0 5 milliseconds during pecking g is the acceleration of gravity millisecond 1 1000 second May PRA Fuster JM Habe J and Hirschman A 1979 Woodpecker Drilling Behavior Arch Nerol 36 370 373 Woodpecker Pecking High speed video images taken at 2000 frames per second Get one image every 0 5 milliseconds Declerations of 600 1500g during impact May PRA Fuster JM Habe J and Hirschman A 1979 Arch Nerol 36 370 373 Scaling The stress on the brain in an impact is the force area The force is the brain mass times the deceleration force mass deceleration stress area area Scaling Assuming that the brain tissue of humans and woodpeckers can tolerate the same stress m h dh m w d w Ah Aw m mass d deceleration A area r2 h human w woodpecker Scaling Rearranging 2 w 2 h mh Aw mh r dw dh dh mw Ah mw r m mass d deceleration A area r2 h human w woodpecker Scaling Photos of human head and woodpecker head showing relative size removed for copyright reasons mh 1400 grams rh 60mm mw 2 grams rw 7mm giving dw 10 dh The woodpecker brain can withstand about 10 times the deceleration that a human brain can Scaling The deceleration that the human brain can tolerate depends on the duration of the deceleration Goldsmith W 2001 The state of head injury biomechanics past present and future Part 1 Critical Reviews in Biomedical Engineering 29 441 600 Scaling The duration of the woodpecker deceleration during pecking has been measured to be 0 5 milliseconds For this duration the human brain can withstand about 500g deceleration The woodpecker can withstand about 10 times this or 5000g Maximum measured decelerations of 1500g are well below this



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