Development of a CAE-basedapproach for the concurrent design, manufacturing and testing of hybrid metal-composite spur gears

Abstract

Trends in emission limitations and fuel efficiency impose a more efficient energy exploitation in many application fields of mechanical systems. In this direction, the lightweighting of mechanical structures represents a powerful strategy, above all in the transportation industry, where geared transmissions play a key role. Here, these components are designed in such a way that performance criteria are met at the minimum weight, without compromising the requirements of reliability and safety. In this context, the aim of the present work is the development of new strategies for the design of geared systems, where the concept of gear body lightweighting with geometrical modifications is substituted by the one applied to the material, in order to improve the strength-to-weight ratio and reduce vibrations in the overall mechanical system. In particular, the research is focused on innovative methods for the simulation, manufacturing and testing of a hybrid gear, in which a metal rim is joined with a composite body. In detail, the contribution of the gear body stiffness is studied by means of a multi-scale approach, which starts from the interaction between matrix and fibres at the micro-scale to derive the lamina properties at the macro-scale. In this way, the anisotropy of the composite material can be accounted for, leading to an accurate modelling and evaluation of the mechanical properties of the gear. Additionally, two assembly techniques are used for joining the rim part to the body, which include adhesive bonding and interference fitting. Both techniques are analysed with experimental modal tests to characterize dynamic stiffness and damping in comparison to a lightweight metal gear with the same mass. At the same time, non-linear finite element (FE) simulations are executed for the evaluation of the static transmission error and meshing stiffness. Finally, the last part of the work deals with the experimental analysis of a hybrid gear pair during meshing in a dedicated test-rig, where the dynamic behaviour is analysed with respect to the variation of applied torque and rotational velocity. Noise and vibration behaviour of a solid-hybrid gear pair is compared to that of a pair composed by a solid and a lightweight metal gear. Experimental results show the great potentiality of the multi-material approach in mechanical power transmissions.