Study Pecks Into Ability of Woodpeckers to Absorb Shock

Photo: Woodpeckers were studied by researchers.
Sang-Hee Yoon/Courtesy
Woodpeckers were studied by researchers.

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There has been new information concerning woodpeckers and their relation to shock absorbency.

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Woodpeckers can drum the trunk of a tree at a rate of 18 to 22 times per second at a high force of 1200g, and yet they completely evade brain damage or loss of consciousness, a phenomenon former UC Berkeley graduate students investigated in a study.

The study - currently available online and to be published in the March issue of IOPscience - contains evidence that the head and beaks of woodpeckers may lead to improvements in shock absorption technology, potentially improving the quality of military ammunition, football helmets, Formula 1 cars and further protection for black boxes on airplanes.

Sang-Hee Yoon and Sungmin Park began "pecking" at the study in 2008 as UC Berkeley mechanical engineering graduate students. Yoon is now a postdoctoral researcher in biomechanics at Harvard University and said Park is a postdoc at the University of Maryland.

"Based on X-ray, CT images, movie clips and material properties of a woodpecker, the hidden secrets of a woodpecker were unveiled," Yoon said in an e-mail.

According to Yoon, they initially analyzed the shock absorbing capability of the Golden-fronted Woodpecker, but soon came to discover that all woodpeckers have very similar qualities when it came to shock absorption.

He attributes this ability to avoid brain damage to the composition of the strong beaks and the makeup of their skulls. Woodpeckers have a unique tissue that encompasses their heads and nostrils, which evenly distributes impact caused from drumming - an ability not seen in many other birds.

"In terms of shock absorption, the head of the woodpecker is composed of two bones: a spongy bone and a skull bone," Yoon said in the e-mail. "The bones are relatively dense but spongy compared to the other bones, thus filtering incident mechanical excitations."

Professor of mechanical engineering and avid feeder of woodpeckers that reside in his backyard, Benson Tongue, said in an e-mail the study is akin to the idea of "egg drop" contests when trying to protect the egg from abrupt decelerations.

Based on the experiments' results, the researchers modeled a new shock-absorbing device - similar to that of the mechanics of the woodpecker - consisting of a steel-encased aluminum cylinder filled with glass beads.

Yoon said they tested the device by firing a 60-millimeter air gun to introduce a high-force mechanical shock. The results showed the device protected against forces up to 60,000g.

While the study was initially aimed to protect electronic devices from high force impact such as gunfire shock, it has also inspired experiments in advanced head-protection gear such as for football or U.S. Army helmets. Its aim is to reduce pressure to the brain upon impact during incidences that commonly result in head injuries, like football tackles or car accidents.

Tongue said though this approach may be a useful way to protect micromechanical devices, it may pose a challenge to creating efficient products that are as large as headgear like helmets.

"The most important thing is that a large reduction in loads was observed and now the question is how one could optimize the approach with regard to size and complexity," he said in the e-mail.


Contact Dominic Amara and Jasmine Mausner at [email protected]

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