An Integrated Approach to Characterize the Dynamic Behaviour of a Mechanical Chain Tensioner by Functional Tolerancing

Abstract

In the aerospace and automotive industries 65 % to 70 % of failures and breakdowns of mechanical systems are caused by geometric and/or size variations whose consequences were not accurately predicted during the design phase [1]. Dimensional and geometrical variations can significantly influence the functionality of assembled mechanical systems, especially those consisting of highly deformable components subjected to shock and vibration [2] and [3]. These systems characterized by the presence of sliding contacts and yielding constraints are generally used in mechanics to dampen vibrations and store or dissipate energy. Their reliability is as important as the need to precisely predict and control the variability of their dynamic characteristics since their geometrical properties (e.g. shape and dimension) are subjected to change. Examples of such assemblies include civil, military, automotive, naval and aerospace applications [4] to [6]. According to the available numerical analysis methods (i.e. finite element method (FEM) and multibody), simulations of these systems appear to be particularly complex, since it is difficult to determine the presence of extended sliding contacts and moving impacts between flexible components, as well as a high degree of geometric non-linearity [7] and [8]. Usually constitutive equations or rate constitutive equations are used in finite element software to model these systems and characterization of such systems is carried out by means of experimental testing [9] and [10]. This study proposes a replicable semi -empirical procedure, based on few targeted experimental displacement measurements and modal analyses, where functional tolerance specifications are used to predict and control the variability of the dynamic behaviour in such systems. The actual tolerance specifying method is geometric dimensioning and tolerancing (GD&T) as indicated in the ASME Y14.5 [11] and ISO 1101 [12] standards. The application of GD&T can be ensured by different approaches, mainly attributable to tolerance analysis and tolerance synthesis. In tolerance analysis [13] and [14] the contribution to the accumulation of variations at one or more functional features in a tolerance stack-up is considered, while tolerance synthesis [15] to [17] studies the influence of geometrical variations in parts on the behaviour of a An Integrated Approach to Characterize the Dynamic Behaviour of a Mechanical Chain Tensioner by Functional Tolerancing Calì, M. – Oliveri, S.M. – Ambu, R. – Fichera, G. Michele Calì1,* – Salvatore Massimo Oliveri1 – Rita Ambu2 – Gabriele Fichera3 1University of Catania, Electric, Electronics and Computer Engineering Department, Italy 2University of Cagliari, Department of Mechanical, Chemical and Materials Engineering, Italy 3University of Catania, Civil Engineering and Architecture Department, Italy