Suppose I pull a bar at both ends and there’s no movement in the bar. Now strain in this case is 0. But I know the stress is nonzero (right?) However strain is linearly related to stress, implying stress must be 0. Could someone point out what my misunderstanding is?
And let’s assume this is a simple material, and we aren’t concerning temperature or gravity. Make the system as simple as possible, as I’m taking a my first continuum mechanics course so I’m not super understanding with everything. I’d like to understand how strain can be 0, but stress is non-zero despite the linear relationship between the two.
Best Answer
Thermal expansion of a constrained object can produce nonzero stress with zero strain, for example. This occurs because generalized Hooke’s Law contains a thermal expansion term. But pulling a stable unconstrained and initially unloaded solid will always produce a nonzero strain, as the elastic moduli are always positive.