Question

What is a plastic moment of resistance?

Answer 1

We identify this as one part of the stress strain curve. We initially define and see what a stress and strain are individually and then what the stress strain curve is (with example). Then we define the above asked plastic moment of resistance and with the definition, we spot the plastic moment of resistance in the respected stress strain curve.

Complete answer:
Stress can be defined as the physical quantity that expresses the internal forces that neighboring particles exert on each other.
When this stress is applied to a body, it becomes deformed, this physical quantity that is able to describe the deformation is called strain.
Now that we have defined stress and strain, we can move onto the stress strain curve. As the name suggests, the stress strain curve gives us the relation between stress and strain of a material.

The plastic moment of resistance is defined as the moment at which the entire cross section has reached its yield stress.
In conclusion, in the stress strain curve, the maximum moment is reached at a point where the curvature can increase indefinitely, neglecting the strain hardening benefits. This maximum moment is called plastic moment of resistance and the portion where this moment occurs is called plastic hinge.

Note:
Stress strain curve tells us a lot about a material. For instance, taking the part before the proportional limit in the given graph and finding its slope, gives us the value of the young’s modulus of the material. The part from the lower-yield point is called the plastic region.