Critical Speed of Flexible Coupling - Determining with CAE Software

Abstract

The present article deals with FEM analysis of flexible coupling with rubber elastic element. Working parts of coupling are half of all cylinders made with carrying ring. Elastic elements are subjected to compression loading when transmitting torque. At certain load level, forces, acting on cylinders, cause their radial deformation. By default - metal fingers, with their shape, must limit radial deformation. However, in the process of operation, under torque and speed of rotation, it deforms and changes its overall size. Fingers press the loaded cylinders and deform them plastically at certain speed and load. As a result of this deformation, the elastic element loses a work stable and needs to be replaced. Elastic elements of couplings are made of a variety of polymeric materials whose properties have a significant impact on dynamic properties of coupling.

Radial deformation of the loaded cylinders is determined by FEA method using CAE software. Critical speeds are defined, resulting in pinching of rubber elastic element that depends on properties of the used material. Critical rotational speed increases with increase elastic modulus of the elastic element of 4 to 8 MPa and decreases with increased density of the material from 1080 to 1900 kg/m³. Results show, that achieving maximum rotational speed for investigated flexible coupling without plastic deformation requires elastomer with a modulus of elasticity of E ≥ 6 MPa and density ρ ≤ 1100 kg/m³. Results of these tests will be used to correct some of the geometric parameters of an elastic element or more suitable geometry of metal fingers to ensure the required coupling load.