calculating compression requirments

[amirsarmad]

Hi,

I am trying to substitute wood with plastic for one of our projects.

Basically, I would need to know what is the compression force that is currently being exerted on the wooden runner and then find a suitable polymer that can withstand the same amount of force.

Each Billet weights 2000kg and is resting on a flat surface area of 8cm X 1.5cm (with height of the runner being 8 cm).

According to our supplier the compression properties of the wood we use is 4000~5000 psi.

According to my calculations, each billet would be requiring 2444 psi.

I have calculated this by doing the following

1)convert KG to Lbs ( 2000kg X 2.2= 4440 lbs)
2)converted the surface area where billet is resting ( 8cm X 1.5cm =3.1in X 0.55in = 1.7in2 )
3)Converted = 4440lbs/1.7in2= 2444psi

I would like your input on the following

A) Have i calculated my pressure requirements correctly?
B) What effect does having a wooden runner with 8cm height have in comparison to the same runner with a 4cm height. Is the compression property of the wooden runner dependent on its height?

hoping for assistance.
Amir

 

[chicopee]

Get a ME handbook or get on the internet for "contact stresses" between cylindrical and flat surfaces.

 

[rb1957]

a 2 ton billet is sitting on an area of 2in2 ?? ... isn't that a very small area ? i mean, a 2 ton billet has a volume of 4500/.3 = 15000 in3 (assuming steel) ... doesn't sound like it's well supported ??

 

[lisa247]

You calculation is correct providing that the billets aren't round as they are in your diagram - your surface area needs to be the actual surface contact area between the billet and the support - it does seem like a very small area though! The compressive stress in the support will be the same no matter what height they are - the only thing to consider is stability to make sure the thing doesn't tip over.