$!!!!$ If necessary, assume the minimum diameter as $12$ mm and the notch radius as $1$ mm $.$ Take the $K_t$ value in the discontinuities as $3\mathrm{.}5$ for bending loads, $2$ for torsional loads, and $4$ for the keyhole. Evaluation of $1^{st}$ question:

Static design of the shaft is $30$ points.

Dynamic design of the shaft is $35$ points.

Determining the dimensions after the design process is $15$

A $28$ mm diameter power screw has a $4$ mm pitch. The longitudinal load on the screw is $6\mathrm{.}4$ kN $.$ The maximum friction coefficient on the teeth is $0\mathrm{.}078.$ Determine whether the screw is selflocking. $(30$ points$).$

Note! State all the assumptions $($if necessary$)$ that you make in design process.