Chapter $8-$ Power Screws and Threaded Fasteners

Due Date$-2-12-2024$

Problem $1(20$ Marks$)$

Design a hard steel $($screw and nut$)$ lubricated power screw for raising and lowering a load of $\backslash (\backslash$mathbf$\{50\}\backslash$mathbf$\{$k N$\}\backslash )$ using a square $-$ thread with major diameter of $\backslash (\backslash$mathbf$\{40$ ~ m m$\}\backslash ),$ pitch of $\backslash (\backslash$mathbf$\{6$ ~ m m$\}\backslash )$ with triple threads and a plain bronze thrust collar of $\backslash (\backslash$mathbf$\{60$ ~ m m$\}\backslash )(\backslash (\backslash$mathrm$\{$f$\}\_\{\backslash$mathrm$\{$c$\}\}=0\mathrm{.}08\backslash ))($Assume maximum friction$).$

$($a$)$ Find the torque for raising and lowering the load. Is the design self$-$locking? If not, please change the design accordingly

$($b$)$ Find the largest axial and shear body stresses. Also, find the bending stresses

$($c$)$ Find the factor of safety against yielding of power screw root using the DE approach with $\backslash (\backslash$boldsymbol$\{$S$\}\_\{\backslash$boldsymbol$\{$y$\}\}=\backslash$mathbf$\{260\}\backslash$mathbf$\{$M P a$\}\backslash ).$ Is this a suitable material $?$