GATE 2019 ME (ME1) – Question 35
The stress–strain curve of an ideal elastic–plastic strain-hardening metal is shown. It was loaded from O through initial yield P to Q, unloaded to zero-stress point R, then reloaded in tension. At what stress (MPa) does it yield again?
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Correct answer: 210 to 210
Explanation
Unloading follows an elastic line and leaves permanent plastic strain. On reloading in the same direction, the stress follows this elastic path back to the previous maximum before further plastic deformation begins. The new yield stress is therefore **210 MPa**, rather than the original180 MPa.