$-8-$

$6\mathrm{.}10.$ A cylindrical rod of brass originally $10\mathrm{.}2$ mm in diameter is to be cold worked by drawing to the final diameter of $8\mathrm{.}1$ mm $.$ The circular cross section will be maintained during deformation. What is the cold work percent from this drawing process?

$($a$)24\mathrm{.}9\%$

$($b$)28\mathrm{.}9\%$

$($c$)32\mathrm{.}9\%$

$($d$)36\mathrm{.}9\%$

$6\mathrm{.}11$ A piece of chalk is twisted until it fractures. What is the angle of the fracture direction with respect to the chalk length direction?

$($a$)30$

$($b$)45$

$($c$)60$

$($d$)90$

$6\mathrm{.}12.$ Many Liberty ships built during World War II have failed catastrophically as shown in the right image. The following factors contributed to such failure:

$($a$)$ Temperature of water

$($b$)$ Rivet joining failure

$($c$)$ Brittle$-$to$-$ductile transition

$($d$)$ Impact by a foreign object

$6\mathrm{.}13.$ The following metal specimen $($right image$)$ was tensile tested until failure. Which type of metal would experience this type of failure?

$($a$)$ Very ductile

$($b$)$ Indeterminate

$($c$)$ Brittle

$($d$)$ Moderately ductile

$6\mathrm{.}14.$ Microstructure shown on the right image $($from Republic Steel Corporation$)$ is obtained from a $0\mathrm{.}38wt.\%C$ steel. What is the name of a phase indicated by an arrow?

$($a$)$ austenite

$($b$)$ ferrite

$($c$)$ pearlite

$($d$)$ cementite