I have done a compression experiment where a sample is teste

I have done a compression experiment where a sample is tested to see its stress strain behaviour. And the question that \'What do you think the \"peak force\" is in this force distance graph and what is the difference between the \"peak force\" and other peak in the graph?\'

18 13.5 First local 9 maximum 4.5 Absolute maximum Extension (mm)

Solution

The first peak gives you the yield load whereas as the second load is the ultimate load.

The curve goes down after the first peak which is the plastic deformation region, i.e. if you stop the test in region the sample will get its orginal shape back.

Whereas after the second peak the sample will undergo a permanent failure.