Values for small $\frac{a}{b}$ and limits for $10\%$ accuracy:

$($a$,$ b$)K=1\mathrm{.}12S_g\sqrt[\phantom{2}]{a}$

$)(0\mathrm{.}4$

Expressions for any $=\frac{a}{b}$;

$($a$)F=\sqrt[\phantom{2}]{\frac{2}{}tan(\frac{}{2})}[\frac{0\mathrm{.}923+0\mathrm{.}199(1-sin(\frac{}{2}){)}^4}{cos(\frac{}{2})}],($large h$/$b$)$

$($b$)F=\frac{1\mathrm{.}99-(1-)(2\mathrm{.}15-3\mathrm{.}93+2\mathrm{.}7{}^2)}{\sqrt[\phantom{2}]{}(1+2)(1-{)}^{\frac{3}{2}}}$

$)=(2$

Fig. $2$: Stress intensity factors for two cases of cracked plates under bending

A member is subjected to bending as in Fig. $2$a$.$ The depth $b=50mm$ and thickness $t=10mm$ are

made out of Ni Maraging Steel $(K_{IC}=176$Mpa$\sqrt[\phantom{2}]{m},{}_{YS}=1290$Mpa $).$ During service operation,

the bending moment may be as high as $M=3\mathrm{.}5kN.$m and members with edge cracks larger than

$a=1\mathrm{.}0mm$ are normally found in inspection and scrapped.

a$)$ Estimate the moment M necessary to cause brittle failure?. What is the Safety Factor?

b$)$ Assume some of these members had accidentally skipped inspection and found their way

into service with cracks as large as $a=3\mathrm{.}0mm.$ Replacement is expensive. You as the

engineer responsible for this project, must make a decision on replacement. What would

you decide? Support your decision with additional calculations as needed.