Originally Posted by
sigma relief
Now the drawbacks, most DoE trials use linear interpolation and assume straight line relationships between the high and low test points used for each varriable. 3 and 4 point per variable tests are possible, but the required samples begin to increase dramatically. Surprisingly, this is rarely a problem, but EG may be a bit unique. The other problem is the requirement to break the test down into individual independent variables. While this may not be possible for some of the aggregate tests, the "other" factors like epoxy, and addins are certainly a candidate.
John
Hi John.
I think this is the nub of the problem with EG, and from two standpoints.
In your own example, buying springs from Acme Springs Inc. or Zebedee International should not make a difference to anyone trying to reproduce your clutch design, an assumption being that springs will always be used in the linear part of their behaviour.
But in the EG, the ability of a mix to absorb energy is, I would guess, non-linear in the extreme, depending on several unpredictable or non-linear variables.
The general angularity of the aggregates, their relative fracture strengths, and the packing density achieved, the first two being dependant on locally sourced material, and the last being geometrically non-linear.
The ratio of epoxy to aggregate will also have a non-linear effect (akin to the effect of adding water to dry sand), moving from its adhesive properties to becoming the vehicle for fracture propagation.
I think the best we might hope for is that Cameron's testing will give us good pointers to what might be achieved regarding ultimate EG strength in terms of particular recipes, along with a guide to what improvements are possible in terms of additives.
Regards
Greybeard John
The above was written before I read Cameron's posting, but I think you get the layman's drift.
Also thanks for the wiki link. I'm going to add the "milk in tea" reference to my list of important trivia.
It's like doing jigsaw puzzles in the dark.
Enjoy today's problems, for tomorrow's may be worse.