[Stoves] [Gasification] Chip Guillotine was Re: Wood heating in the UK - whole log gasification

[ajheggie at gmail.com]

[Default] On Sat, 04 Jan 2014 15:46:31 -0600,Paul Anderson
<psanders at ilstu.edu> wrote:

>Also the comment about the "glue" made me think of the difference 
>between cutting green wood verses dry wood.   Dry "glue" lack 
>lubricating function and becomes a hardened obstacle to cut.   BUT dry 
>"glue" allows for pieces to be snapped / broken cleanly whereas the 
>green wood bend and is hard to get a full break. (This might be all 
>wrong, but it just seems logical.   Can anyone confirm or refute the 
>comments?)

My observation is that cleaving a dry piece of wood (as in log
splitting) gets harder as the wood dries.

This differs from breaking a stick in bending. The term "greenstick
fracture" is used to denote a beam/bone that had broken through
bending stress and is a special case. Half the wood is stressed in
tension and the other half is in compression. If the tension side
fails first the wood parts to its middle  and then a split develops
along the pith either side of the failure, the remaining compression
side often then just bending with the stress but not parting. The
corollary is where the wood first fails in compression, the fibres
then buckle to the mid point and again a split develops, this is a
shear beam crack. As you say when the wood is dry it tends to snap all
the way through in a brittle failure.