Modeling and Simulation of a Screw-Worm Gear Mechanical Transmission to Achieve its Optimal Design under Imposed Constraints

This work deals with the modeling and simulation of a screw-worm gear mechanical transmission, abbreviated screw-jack, to achieve its optimal design under imposed constraints. Optimal design is sought under two different conditions: to maximize the screw-jack´s efficiency (energy saving) and to minimize its overall size (compact design). Several different models of buckling for the screwed shaft are taken into account by introducing a variable coefficient of fixity. Different strength theories of failure for the screwed shaft are taken into account, according to the type of material used, by introducing a variable weighting coefficient of the shear stress relative to the normal stress in evaluation of the equivalent stress. Variation of the mechanical transmission´s efficiency and its overall size versus the coefficient of fixity and the shear stress weighting coefficient are presented and discussed.