EXAMPLE $6-13$ A grade $30$ gray cast iron is subjected to a load $F$ applied to a $25$ by $10-mm$ crosssection link with a $6-$mm$-$diameter hole drilled in the center as depicted in Fig $6-31$a$.$ The surfaces are machined. In the neighborhood of the hole, what is the factor of safety guarding against failure under the following conditions:

$($a$)$ The load $F=4500N$ lbf tensile, steady.

$($b$)$ The load is $4500$ N repeatedly applied.

$($c$)$ The load fluctuates between $-4500$ N and $1300$ N without column action. Use the Smith$-$Dolan fatigue locus.

$($a$)$

Figure $6-31$

The grade $30$ cast$-$iron part in axial fatigue with $($a$)$ its geometry displayed and $($b$)$ its designer's fatigue diagram for the circumstances of Ex$.6-13.$