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Stresses in power screws Design of a power screw must be based on the stresses developed in the constituent parts. A power screw is subjected to an axial load and a turning moment. The following stresses would be developed due to the loading: | Module 6 Power Screws Version 2 ME IIT Kharagpur Lesson 2 Design of power screws Version 2 ME IIT Kharagpur Instructional Objectives At the end of this lesson the students should have the knowledge of Stresses in power screw. Design procedure of a power screw. 6.2.1 Stresses in power screws Design of a power screw must be based on the stresses developed in the constituent parts. A power screw is subjected to an axial load and a turning moment. The following stresses would be developed due to the loading a Compressive stress is developed in a power screw due to axial load. Depending on the slenderness ratio it may be necessary to analyze for P . buckling. The compressive stress oc is given by oc - where dc is the ndc2 core diameter and if slenderness ratio X is more than 100 or so buckling criterion must be used. X is defined as X L where I Ak2 and L is the length of the screw. Buckling analysis yields a critical load Pc and if both 2 EI . ends are assumed to be hinged critical load is given by PC n . In L EI general the equation may be written as PC nn2 where n is a constant L2 that depends on end conditions. b Torsional shear stress is developed in the screw due to the turning moment and this is given by t -16 where T is the torque applied. ndc Version 2 ME IIT .