Can the Flexural Strain Formula Determine Strain in a 3 Point Flexural Test?

[FischerBob]

I've been tasked with designing an experimental rig for some students and have run into a bit of a cul de sac with this particular issue. Allow me to elaborate:

A beam of known geometry (length, depth, width, etc.) is being bent over a hollow cylinder. The beam has holes machined through at each end. The cylinder is hollow but has a tourniquet-style system attached (via string/rope) that when twisted can bend the beam over it. My question is, can I employ the flexural strain formula to determine how far each end needs to be pulled down via the tourniquet to achieve a desired strain? Does this approach make any logical sense in approaching the problem? I'd like to be able to guide the students in answering this question.

Any help would be greatly appreciated.

 

[paisiello2]

I assume you are talking about providing a 3 point flexural test. I also assume that the diameter of the cylinder is large compared to the depth of the beam e.g. D > 4h.

Then the answer to your question is yes, you can use the flexural strain formula but you'll also need to know the deflection formula for the beam. Your approach seems fine to me.