Refer to Fig. 4.7b and make measurements of the external and internal diameters (in the horizontal direction

Question:

Refer to Fig. 4.7b and make measurements of the external and internal diameters (in the horizontal direction in the photograph) of the four specimens shown. Remembering that in plastic deformation the volume of the rings remains constant, calculate
(a) The reduction in height
(b) The coefficient of friction for each of the three compressed specimens.