Answer these mechanic questions.

$\backslash$end$\{$array$\}]$

The fracture toughness of the bolt material is $K_c=25$MPa$\sqrt[\phantom{2}]{m}.$ Its resistance to fatigue crack growth can be expressed by the Paris law with $A=2{10}^{-26}m\frac{m}{?}$ cycle and $n=3$ :

${\displaystyle \underset{0}{\overset{N}{}}}dN=\frac{1}{A}{\displaystyle \underset{a_0}{\overset{a}{}}}\frac{da}{(K{)}^n}$

Determine the number of load cycles the bolt can withstand.

$6.($a$)($i$)$ Describe the creep deformation mechanism.

$($ii$)$ Explain the relaxation phenomenon and how relaxation test is performed.

$($b$)$ A tensile creep test on a steel alloy showed that the sample underwent rupture in $20h$ at a stress level of $100$MPa and a temperature of $750C.$ Calculate the time rupture at $650C$ and $100$MPa according to the following methods.

$($i$)$ Larson$-$Miller $($Take $C=22)$

$3$