Talking to Trees for Better Lumber

“Mathematics is the language in which God has written the universe,” stated astronomer and physicist Galileo Galilei.

And just like everything in nature and the cosmos, trees have a mathematical language too.

A scientist at the Forest Products Laboratory (FPL) and his colleagues are tapping into the language of trees to produce more reliably classed wood products—from evaluating and grading structural timber to wood-based composite materials (veneer, laminated veneer lumber, and glued laminated timber).

Acoustic wave technology is a nondestructive, effective testing tool for trees and logs employed since the 1970’s in order to evaluate raw wood materials. Acoustic wave measurements in trees gauge their Modulus of Elasticity (MOE). MOE is basically the stiffness of a material and how much pressure that material can withstand before failing under applied stress.

Decades of utilizing this technology have proven that there is a strong correlation between the MOE in a standing tree to that of its logged end-product.

Currently, the most popular way to measure a tree’s MOE is through a method called Time of Flight (TOF). To set-up a TOF measurement a transmitter and receiver probe are inserted on either side of a tree’s trunk. Acoustic waves are generated by a hammer tap on the transmitter probe. The tap creates waves that sing along the trunk. That singing, or acoustic wave velocity, is what the scopemeter measures in order to produce TOF measurements.

Time-of-flight acoustic measurement on a standing tree.

Although TOF has been a mostly reliable physical testing technique, questions still remain.

Depending on how the TOF measurement is conducted, as well as the variance of tree age, diameter, species, and juvenile wood, measuring results can differ. A more reliable measurement model is still needed in order to consistently assess wood properties in standing trees.

FPL Forest Products Technologist Xiping Wang and his colleagues from the School of Technology Beijing Forestry University and Research Institute of Wood Industry Chinese Academy of Forestry are developing a new software program to simulate TOF measurements in standing trees and reliably translate those results.

COMSOL Multiphysics® software was developed to measure acoustic wave patterns in a virtual tree trunk through numerical simulation. The accuracy of the software results was compared with on-the-ground TOF testing methods. And what the researchers found was that their software simulations were reliably and accurately producing the same results.

If there was a Rosetta Stone for trees, COMSOL Multiphysics® software would be their language program. Its mathematical computations decode the acoustic wave velocity of a given tree to produce a real-time answer about its structural properties.

A more in-depth explanation of this science and software can be found in the journal, Wood and Fiber Science. “Acoustic Wave Propagation in Standing Trees—Part I. Numerical Simulation,” is just the first part of an ongoing study. Stay tuned for more about the language of trees in future FPL blog posts.

To find out more about the amazing advancements our scientists are making, visit the Forest Products Laboratory website at: https://www.fpl.fs.fed.us/