GATE 2016 ME (ME1) – Question 58
A hypothetical engineering stress-strain curve shown in the figure has three straight lines PQ, QR, RS with coordinates P(0,0), Q(0.2,100), R(0.6,140) and S(0.8,130). 'Q' is the yield point, 'R' is the UTS point and 'S' the fracture point. The toughness of the material (in MJ/m3) is __________
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Correct answer: 0.849 to 0.851
Explanation
Toughness is the total area under the curve to fracture. Convert percentage strains to fractions:0.2%=0.002,0.6%=0.006 and0.8%=0.008. Areas are0.5·100·0.002=0.10, (100+140)·0.004/2=0.48 and(140+130)·0.002/2=0.27. Sum is **0.85MJ/m³**, since MPa equals MJ/m³ for dimensionless strain.