Name:

NOTE: Box your answer. One point will be deducted for each missing box. Clearly mention the source of your data $($Table number, Equation Number$).$ One point will be deducted for each missing source.

Problem#$1/2[75$ points$]$

The press shown in Figure $1$ has a rated load of $6,000lbf.$ The twin screws have squarethread, a diameter of $2\mathrm{.}25$ in $,$ and a pitch of $\frac{1}{4}in.$ Coefficients of friction are $0\mathrm{.}045$ for the threads and $0\mathrm{.}078$ for the collar bearings. Collar diameters are $3\mathrm{.}5$ in $.$ The gears inside the gear box have an efficiency of $90$ percent and a speed ratio of $1$:$1.$ A control unit $($VFD$)$ controls the motor speed at $27re\frac{v}{m}in.$

$($a$)$ Find the thread depth, thread width, pitch diameter, minor diameter, and lead. $[5$ points$]$

$($b$)$Find the torque required to press $($raise$)$ the load. $[5$ points$]$

$($c$)$ When the motor is turned on$,$ how fast $($speed$)$ will the press head move? $[5$ points$]$

$($d$)$ What should be the horsepower rating of the motor? $[15$ points$]$

$($e$)$ Find the efficiency during pressing the load. $[5$ points$]$

$($f$)$ Find the body stresses: torsional and compressive. $[10$ points$]$

$($g$)$ Find the bearing stresses. $[5$ points$]$

$($h$)$ Which location of the first thread would be critical if the screw is fully loaded? Please show the location, drawing a simple sketch. $[5$ points$]$

$($i$)$ Find all the six components of the general stress state at the root of the thread, showing a free hand sketch. $[10$ points$]$

$($j$)$ Determine the von Mises stress at the root of the thread $[5$ points$]$

$($k$)$If the yield strength of the power screw thread and body is made out of steel and its yield strength is $200$ MPa $,$ what would be the factor of safety? $15$ points$]$