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In the figure, the temperature of the system is increased. We are required to calculate the stresses in the bars.

My approach: By principle of superposition, deformation in each bar would be due to temperature change, and an axial load which will be developed as the free ends of the two bars press into each other while expanding. Total deformation must be 0.5 mm, and using this condition, I was able to calculate individual deformations in each bar and the axial load in the bar. To calculate stress, I have two approaches in which I am confused:

(i) Stress = Axial Load / Cross sectional Area

(ii) Stress = Elastic Modulus * (calculated deformation/original length)

I get different answers from the two approaches. I cannot tell which one is correct.

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