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Learn the relationship between stress and strain for various loads using Generalized Hooke's Law and Bulk Modulus. Explore a practical example involving a copper bar to determine its dimensional changes under uniform loading. Gain insight into plane stress states and calculations.
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Lecture # 10 Material - Property Relationships Objective: To develop relationship between stress and strain for general loads.
Example: The copper bar as shown in figure is subjected to a uniform loading along its edges. If it has a length a = 300 mm, width b = 50 mm and thickness t = 20 mm before the load is applied, determine its new length, width and thickness after application of the load. Take Ecu = 120 GPa, vcu = 0.34.
Solution: By inspection, the bar is subjected to a state of plane stress. From the loading, we have,
The associated normal strains are determined from the generalized Hooke’s law, that is,
The new bar length, width and thickness are therefore, a’ = 300 mm + 0.00808 (300 mm) = 302.4mm Ans…. b’ = 50 mm + (-0.00643)(50 mm) = 49.68mm Ans…. t’ = 20 mm + (-0.000850)(20mm) = 19.98 mm Ans….