Problem $3$:

The AM$1004-$T$61$ magnesium alloy tube $AB$ is capped with a rigid plate $E.$ The gap

between E and end C of the $6061-$T$6$ aluminum alloy solid circular rod CD is $0\mathrm{.}2$ mm

when the temperature is at $30C.$ The outer radius of the tube is $25$ mm $,$ and its inner

radius is $20$ mm $.$ The diameter of the rod CD is $25$ mm $.$ Use EAM$1004-$T$61=44\mathrm{.}7(10{)}^9\frac{N}{m}{m}^2$

and and $[$:${}_{AL6061-T6}=24\frac{(10{)}^{-6}}{}C$