4. A circular specimen of MgO is loaded using a three-point bending mode. Compute the minimum
possible radius of the specimen without fracture, given that the applied load is 5560 N, the flexural
strength is 105 MPa, and the separation between load points is 45 mm. (10 points)
$\sigma_{fs} = \frac{FL}{\pi R^3}$
5. For a metallic alloy, which has an elastic modulus of 105 GPa, the stress at which plastic
deformation begins is 220 MPa (15 points)
(a) What is the maximum load that may be applied to a specimen with a cross-sectional area of
300 mm² without plastic deformation? (10 points)
(b) If the original specimen length is 120 mm, what is the maximum length to which it may be
stretched without causing plastic deformation? (5 points)
6. The figure given below shows the Pb-Sn binary phase diagram. a) Cite the phases present, b) their
compositions and c) calculate the relative amounts (in terms of mass fractions) of the phases for
the alloy 75 wt.% Sn at temperatures of 175°C (A) and 250°C (B), respectively. (24 points)
