Laurent Champaney

Variability of a Bolted Assembly Through an Experimental Modal Analysis

Industrial structures are mainly assemblies with complex geometries and non-linear characteristics. Friction and joint preload added to fabrication imperfections lead to a substantial gap between numerical models and real structures. In order to develop accurate generic models, it is then necessary to quantify the behavior variability, especially the one related to the joint conditions. The first part of this paper describes the iterative sizing procedure of an academic assembly which characteristics may vary depending on several input variables (e.g. value of the bolt torque, number and position of preloaded bolts, etc.). The properties of the bolted joint were optimized in order to satisfy a set of conditions in terms of tangential slipping, normal displacement and maximum stress level. The second part concerns the experimental modal analysis of the assembly. The main purpose is to characterize the relationship that exists between the input variables and the measured eigenfrequencies and modal damping of the assembly.

Tolerance Analysis of Compliant Assemblies Using FEM Simulations and Modal Description of Shape Defects

This paper propose to perform tolerance analysis on compliant structure. The objective is to limit shape defects and connection defects in accordance to mechanical criteria instead of geometrical criteria. The idea is to elaborate a finite element model of the structure and to observe the stress induced by assembling non ideal parts. Firstly, a method to take into account the stiffness variation induced by the shape defects is tested on an elementary example. Secondly this method is applied on an large structure from aeronautical industry with a lot of variability. A method is also presented to find the geometrical defects which are mostly responsible of overloading the connections.Copyright