Question $3$: A simply supported rotating shaft with grooves, as shown in Figure Q$2,$ supports a mechanism which imposes a constant load $F$ of magnitude $100$N$.$ The shaft is made of AISI $1018$ HR with $S_{ut}=400$MPa and $S_y=220$MPa. The grooves have machined surface finish and groove radius of $1$ mm $.$ Assuming the reliability requirement is $99\%,$ estimate the factor of safety against fatigue failure.

$1$

Asst. Prof. Dr$.$ Dogus Hurdoganoglu

Question $4$: If there is no limitation on the geometry, the new cross$-$ribbed wall design can be based on a requirement for a reduction in material used.

Known: present un$-$ribbed wall thickness, $t_A=1\mathrm{.}7mm$

Required: $40\%$ reduction in material used

Question $5$: Moulding flow limits the redesigned wall thickness.

Known: Present wall thickness, $t_A=1\mathrm{.}25mm$

Required: Minimum wall thickness, $t_B=0\mathrm{.}5mm$

Question $6$: External size of the ribbed plate is limited$.$

Known: Present wall thickness, $t_A=6\mathrm{.}5mm$

Required: Maximum height of ribbed wall, $T=10\mathrm{.}8mm$

Question $7$: Number of ribs per centimetre is limited$,$ for example to match an adjoining Structure.

Known: Present wall thickness, $t_A=2\mathrm{.}2mm$

Required: $0\mathrm{.}08$ ribs per mm$,$ i$.$e$.,8$ ribs per $100$ mm