Project ForgeConsider the stress-strain curve for an ideal elastic-plastic strain-hardening metal, loaded in uniaxial tension from O. The curve passes through initial yield point P (180 MPa) and strain-hardens to point Q (210 MPa), where loading stopped. From Q, the specimen is unloaded to point R (zero stress). If the same specimen is reloaded in tension from R, the value of stress at which the material yields again is ___ MPa.
Explanation
Unloading from Q to R is purely elastic (following a line parallel to the initial elastic loading line). Reloading from R retraces this same elastic line back up to Q, so the material yields again at exactly the stress it was unloaded from: 210 MPa.
Source: GATE ME 2019 Session 1 (Set 1) (2019)
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