inherent wood properties - deformation (a bermuda triangle)

Inherent Wood PropertiesProperties

Moisture Deformation

A Wooden Bermuda Triangle?g

Johannes Welling

Johannes WellingEDG Seminar in Bled 2009

Caribbean Bermuda Triangle


Bermuda Triangle

In the Bermuda Triangle a number of aircraft and gsurface vessels are alleged to have disappeared in mysterious circumstances which fall beyond the b d i f h i i f ilboundaries of human error, pirates, equipment failure, or natural disasters.

Reference: Wikepedia


Wooden Bermuda Triangle

DistortionDistortion

Moisture Inherentproperties


Wooden Bermuda Triangle

For reasons, which seem to be paranormal, and under , p ,suspension of the laws of physics, deformations in wood occur in conjunction with inherent properties

hil i t t t hwhile moisture content changes.

Reference: Platitude from sawmillers' fairy tales


What is a tree?

50% Wood tissue50% Wood tissue 45% Water

5% Others5% Ot e s


Function of wood in a living tree

• Transport of water• Transport of water

• Storage of water and nutrients

L d b i• Load bearing

• Disposal of metabolic residues


What is wood?

• A tree builds wood tissue in reaction to its living conditions and ambiental environmentconditions and ambiental environment

• In wood, the history of a tree becomes manifested– Growing conditions ring width– Growing conditions ring width

– Site conditions (hillside situation, compression wood,competition for light/water) sudden ring width change

– Reaction to physical enjuries resin pockets

p g ) g g

T h bit b h l l l f i– Tree habitus, branches local slop of grainvarious types of knots

– Parentage/evolution/genetics grain angle

– Extreme weather conditions ring shake,frost shakes

Parentage/evolution/genetics grain angle


frost shakes

What do we expect from wood in use?in use?

High strength• High strength

G d i l ti• Good insulation

• Dimensional stability

• Durability

• Good looking


What else?

We want it straight!We want it straight!


If we could design a tree,how would it look like?how would it look like?

• Straight fibre, no slope of grain• No branches to avoid the knots• No earlywood/latewood

to get homogeneous densityN di l/t ti l i t• No radial/tangential anisotropy

• No roots, because they are difficult to utilisei i i i h i k ?• Low moisture content to minimise shrinkage?

How would such a tree look like?How would such a tree look like?


We better accept,what nature offers to uswhat nature offers to us


But, if we do so, we have to accept that there are:• Knots

• Slope of grain

C i /t i d• Compression/tension wood

• High moisture content

• Rings with different width

• Earlywood and latewood tissue with density variation• Earlywood and latewood, tissue with density variation

• Resin pockets and all the other defects


How can we produce good products from non-uniformHow can we produce good products from non uniform trees?

• Inform people about methods on how to– Inspect inherent properties of trees and sawn timber– Sort and grade material so that it fits to specific end uses– Dry and measure moisture content properly to avoid overdrying

and unnecessary dimensional change and deformationsand unnecessary dimensional change and deformations

• Additional measures:• Additional measures:– split wood into small pieces with uniform properties

and produce new engineered products with desired properties


p g p p p

How can we help this poor guywho got lost

in the Wooden Bermuda Triangle?


Task list

• Propose a COST Action dealingp gwith quality issues

• Make European experts work together p p gtowards improving quality

• Open up new info channels to get knowledge and innovation transferred to practitioners

• Organise seminars and workshopsg p

• Translate and publish results ☺• Use the internet to inform scientific

community and practitioners


What about the wooden Bermuda Triangle?Bermuda Triangle?

• There is no mystery behind distortiony y• For all types of distortion a physical explanation

can be given• We should not try to correct nature, because most

probably we will fail• We should accept nature's ability to adapt to almost

any ambiental condition and try to make the best out f itof it

• We have very powerful means, namelyS i f i h t ti– Scanning for inherent properties

– Sorting and grading to reduce natural variability– Measuring MC and high quality drying


Measuring MC and high quality drying

• We even have created COST E53 and we are on a good way to finish itgood way to finish it

• So, let's try to get rid of sawmiller's fairy tail, which says that users of timber have to accept distortionsays, that users of timber have to accept distortion and defects in timber because they are built-in.

• We better should proclaim that distortion and defectsWe better should proclaim that distortion and defects have not be accepted because the propensity for their development can be detected beforehand

• With sorting, grading and proper drying, we do have efficient methods for improving quality of sawn timber

So, let’s just do it!Johannes WellingEDG Seminar in Bled 2009

So, let s just do it!

inherent wood properties - deformation (a bermuda triangle)

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