Testing Wood Samples Under Compression 3

[MatthewMansfield]

Hi all

Matt here again.

This is my problem: -

Two timber cubes of similar dimension (+/-1mm all round), of the same tree, was placed under compressive load until they failed. What characteristics or properties of the wood, would have led to its failure?

In other words what is it about the wood that was tested that help towards its failure? I have: -

1) Whether the load was placed parallel or perpendicular to the grain
2) Any defects in the timber.

Any other factors?

Thoughts?

Thanks

 

[oldestguy]

Different moisture content. Why the test anyhow?

 

[MatthewMansfield]

I thought of that thanks oldestGuy. Would the size and shape negatively affect in compression?

 

[MIStructE_IRE]

We tested approx 50 samples years ago. Failure stress varied by approx 300%! Hence the reason the old BS used large factors of safety with the allowable stress method. Its a natural material with a huge number of variables.

 

[dhengr]

MatthewMansfield:
You would do well to invest in a few good textbooks and ref. books on wood as a building material and on the design of wood structures. As Oldestguy suggested, the U.S. Ag. Dept., Forest Products Lab is a fantastic source for knowledge of wood. And, their Handbook No. 72, “Wood Handbook, Wood as an Engineering Material” is a good starting point. ASTM will have testing stds. and various grading rules and their organizations will shed light on how various material weaknesses and mech. prop. variables are accounted for in arriving at working strengths. You still haven’t answered the questions ‘why are you doing this, and why do you care?’ I’ll add another question, are you an engineer and what is your training and background? The conversation here, on E-Tips, goes both ways, if you want it to continue.

 

[Ron]

OG and dhengr are exactly on target as usual....