Dimensions of specimens for Impact Testing

[diretz]

What if the effect of the dimensions of a test specimen to the impact energy during impact testing?
I mean: If the thickness is decreased two times, will the impact energy also be decreased two times?
Has anybody any idea about this?

 

[diamondjim]

I responded to this on the mechanical engineering
area. The answer is basically a Shear Stress equation
for thin parts where Ss = F/A.
Since in effect you are halving the Area the force
would be halved.
If you doubled the Area, the force would be twice
as great.

 

[Gourile]

If the volume of the specimen is halved, which is the case when halving the thickness, we expect the absorbed energy would be halved as well. But be careful about the slenderness effects which come into account when the with/thk. ratio inceases. In this case a tendency to lateral buckling increases, which tends to decrease the absorbed energy of failure. If this would be the case, you can readily see it in the specimen as some kind of torsion happens in it, instead of a plain failure surface in the notch position. I haven't practice it in an standard charpy test, but I have seen it in a notched plug whcih was supposed to fail under shear after the load increased a certain amount. The plug failed by a torsional buckling instead of shear in a lower load as the thk. was so small.

 

[ansari]

in impact strength test by IZODS TESTING MACHINE, the reading shown by the pointer is the residual energy or the energy taken by the nodge?

engransari@yahoo.com