How would you calculate the maximum plastic deformation (expansion) a steel pipe can handle before it actually fails?
You can calculate the maximum reversible strain, for elastic loading as follows: You need to look up the yield strength (for that particular type of steel). Divide this yield strength by the elastic modulus of steel (also called Young's modulus). That gives you the strain at the onset of yielding, the maximum you can strain the steel fibers before crossing the point of no return. If you are interested in the strain until failure, you need to take tensile test measurements. Seldom do people document an equation to model the non-elastic portion of the stress-strain curve of the specimen, because seldom do we design systems to operate with materials which yield. We want systems which only deform reversibly and elastically. This means you need to perform an experiment to find what you are actually desiring to know.
