Question

triple-threaded power screw is to taise/lower à 100kN load. This s square threads. Thread kinematic friction is 0.05. The loading collar has a Problem#2020pts). A 5andiameter diameter of 25cm and is a) Continuous torque required to raise the load? b) Efficiency of the system during raising the load screw has a pitch of 0.5cm and has threads using bal bearing design with a static/kinematic friction of 0.01. Determine e Considering ductile behavior with a Yield strength of 100MPa, what is its Fos against yielding? (eote consider drd-p)

Answer 1

Diameter of screw, D_1 = 5 cm load, w = 100 kN pinch p = 0.5 cm start, n = 3 Thread friction = 0.05 = mu collar diameter, D_2 = 25 cm collar friction = 0.01 = mu_1 Torque to raise the load = Torque to overcome friction between screw and nut + Torque to overcome collar friction Torque required at crew and nut = w tan (phi + alpha) D_1/2 = T_1 phi = tan^-1 mu - friction angle = tan^-1 0.05 = 2.862 degree tan alpha = Load/circumference = np/xD_1 = 3 times 0.5/pi times 5 alpha = tan^-1 (0.0955) = 5.454 degree T_1 = 100 tan (2.862 + 5.454) 0.05/2 times 10^3 = 365.46 Nm T_2 = 1/2 middot mu_1 w (R_1 + R_2) (Assuming uniform wear) = 1/2 times 0.01 times 100 times 10^3 (0.05 + 0.25) = 150 Nm Total Torque to raise load = T_1 + T_2