Analytical modelling and experimental analysis of functionalized nonlinear link for jointed structures

Friction damping is one of the most effective methods to decrease the effects of resonances phenomena, on an extensive range of frequencies. As a matter of fact, unlike piezoelectric damping and visco-elastic solutions, the friction damping treated in this work has not sharp discontinuities on its effectiveness varying temperature. The goal of the research community is to develop a predictive model capable of describing how friction affects the damping proprieties of the joint. This work aims to focus on one limited set of cases, in particular a kind of bolted joints connection similar to the one proposed by Butaud (2017) and Teloli (2022). The aim of this work is the analytical study and simulation of the dynamical behaviour of a jointed structure, composed of two beams overlapped and linked by bolts. A linear wave spring is thereafter added to enhance the damping effect. The lap joint utilizes the shifting local displacement to convert friction into dissipation energy useful for the damping. Initially, analytic modelling of the jointed structure is studied, applying Dahl's model to compute the dissipate energy due to friction, distinguishing stick-slip local phenomena from global displacement. A FEM simulation is subsequently performed to compute the displacement field of mode shapes and eigenfrequencies. Contact pairs and friction are then deployed in the stationary solver simulation. A solid-shell interface is therefore added to simulate and describe accurately the presence of the linear wave spring. Two geometries of lap joint beam assembly are proposed for the experimental tests, to examine the influence of scale effects on modal analysis and displacement field. The non-linear behaviour of damping could be analysed experimentally starting from the system without any damping solution. Then a damping device (linear wave-shape spring) is added, and the experimental data are gathered. A post-treatment of data (through Fourier transform, Hilbert transform and so forth) allowed a comparison of damping and a confirmation of the nonlinear behaviour of damped lap joint. The process of identification of mode shapes and resonance to study the influence of geometry features takes into account all the parameters, both geometrical (as dimensions and material) and structural (constraints, clamping settings, tightening force). The final goal is the identification and quantification of the advantage obtained by the insertion of damping solutions (as wave-springs) to minimize the resonance peaks. This solution offers a chance to increase the lifespan of components in the mechanical and aeronautical industries.