2. Examine the significance of the stress function Co where C is a constant. Apply it to a ring a <r<b; and to an infinite plate. A ring is fixed at ra and subjected to a uniform circumferential shear at rb forming a couple M. Using Eqs. (49), (50), (51), find an expression for the circumferential displacement vat r = b. = ar 42 ди (49) ↓ av r að + 312 (50) Ύσθ ди მ + гдв др - (51)