Chapter 14 A Proposal of Dynamic Behaviour Design Based on Mode Shape Tracing: Numerical Application to a Motorbike Frame Elvio Bonisoli, Domenico Lisitano, Luca Dimauro, and Lorenzo Peroni Abstract A modal based method to design and to improve the dynamic behaviour of flexible multibody systems is proposed in this paper. The dynamic behaviour of a flexible multibody system depends on the dynamics of its components and on the effects of the connections. When dynamics problems are experienced in particular working conditions, changes to the design are required. Usually connections are standard and there is not space for changes, therefore the components should be improved. Changes at components level improve the global system behaviour, but it is not so easy to identify the most effective component for each specific case. The purpose of the proposed method is to identify the most influent components in specific working frequency ranges of a multibody system. The method is based on a hierarchical procedure from assembly to components which leads to the identification of the components to be modified in order to improve assembly performance. The method is applied to a whole motorbike frame, a multibody system with comparable components stiffnesses. Numerical modal analysis is performed on the full assembly with connections, front and rear sub-assemblies and on single components: chassis, swingarm, engine and wheel. The method is applied to the selection of the most influent components mode shapes in the motorbike behaviour during manoeuvres at high velocity. The selected components are the most suitable for structural, geometric and material modifications to effectively improve the global motorbike behaviour, performances and driveability. Keywords Flexible multibody dynamic · Numerical modal analysis · Motorbike dynamics · Components dynamic design · Weighted mode shape 14.1 Introduction The structural and dynamic design is the primary step for the manufacturing of a successful and high quality product. In this context, the design takes an even leading role, especially when the design requirements follow advanced and particular standards. Usually, the aim is to reduce and, if it is possible, to eliminate the problematic dynamic effects on the global behaviour of a multibody system. The quick selection of the most critical components of the system on which changes are expected is more and more required by industries. Usually this aim is achieved using Modal Assurance Criterion method (MAC) [1], which compares the mode shapes without weighting their modal participation factor. The method here proposed aims to operate as a filter in the preliminary dynamic design phase or in a re-design phase, to localise the regions suitable for changes. The presented method is an extension of the Design for Modal Assembly (DMA) method proposed by Bonisoli et al. in [2]. In DMA the system global mode shapes are compared with the mode shapes of each component changing a physical parameter of the model. In the actual method the parameter of variation is the excitation frequency and a tracing procedure is developed to follow the dynamic behaviour from system to components, considering a weighted mode shape that includes the modes participation factors. This work is focus on the frame of a racing motorcycle. In racing sector, very fast design is required to update year by year the motorcycle performance, and often this is done starting from the problems encountered in the release of the previous year. The study of the handling and dynamic behaviour of a two-wheeler vehicle requires a particular attention with respect to the much more known automobile dynamics, because also the roll and the steer angles must be taken into account, since they E. Bonisoli ( ) · D. Lisitano · L. Dimauro · L. Peroni Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino, Italy e-mail: elvio.bonisoli@polito.it © Society for Experimental Mechanics, Inc. 2020 A. Linderholt et al., Dynamic Substructures, Volume 4, Conference Proceedings of the Society for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-12184-6_14 149
RkJQdWJsaXNoZXIy MTMzNzEzMQ==