A hypothetical engineering stress-strain curve shown in

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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 _______.

1. 0.85 MJ/m³
2. 8.5 MJ/m³
3. 15.85 MJ/m³
4. 0.085 MJ/m³

Correct Option: A

Toughness = Area under diagram

=	1	×	0.2	× 100 +	1		0.2		(100 + 140) +	1		0.2		(140 + 130)
	2		100		2		100			2		100

T = 0.1 + 0.48 + 0.27 = 0.85 MJ/m³