THE STEEL-COMPOSITE FLEXSPLINES OF HARMONIC DRIVE
Piotr Folęga
Quarterly No. 4, 2010 pages 356-361
DOI:
keywords: composites, flexspline, harmonic drive
abstract In harmonic drives, the way of transferring the external moment via cyclic deformation of the flexspline with a wave generator causes the occurrence of a complex state of stress in this element. Therefore, when designing the flexspline, it is very important to determine properly and choose its geometrical features. Significant enhancement of the drive operational parameters is possible through a rational selection of geometrical parameters of the flexspline, but also through applying suitable materials or technological treatments. Using composites for the flexspline of harmonic drives enables reducing the weight of the flexspline and to increase significantly its radial susceptibility and capability of damping the vibration. The producing of flexsplines entirely from composites is, however, constrained by technological difficulties connected with the making of toothed rims of the flexsplines. A solution to this problem may be the application of the so-called „complex” steel-composite flexsplines. An advantage of this solution is the possibility of producing a steel flexspline with teeth of the toothed wheel rim, whereas a composite is applied onto the internal surface of a steel flexspline, thus significantly improving its mechanical properties in those areas. As part of the study, a numerical analysis was made using FEM for the developed models of steel and steel-composite flexsplines, using two types of composites with an epoxy resin matrix, reinforced with carbon fibres, and with glass fibres. Numerical calculations have confirmed a reduction of maximum stresses in the analysed sections in the steel-composite flexsplines in comparison to the traditional steel flexsplines. The stress values reduce the most where an epoxy resin based composite, reinforced with carbon fibres, is used. When analysing the calculation results regarding proper vibration, it can be confirmed that application of steel-composite flexsplines increases the value of vibration periodicity in relation to steel flexsplines.