Nonlinear vibrating automotive devices: theoretical, numerical and experimental analyses

The real world is not only described by linear systems. It is rather generally explained by nonlinear structures, which have a richer behaviour with respect to linear ones. This thesis is devoted to better understand the nonlinear features of vibrating mechanical structures involved in automotive subsystems. It starts from a method to discretise a complex system using Lupos, a MATLAB based software because nowadays simulation and numerical analyses are essential for both linear and nonlinear structures. The device in question is the right lever of the LEVIT F173, projected and assembled at Valeo, Santena. Then a deep look at the major distinctions of the two kinds of systems is performed, dealing with theoretical and practical aspects with the use of different approaches including Simulink numerical simulations of SDOF systems. To be more precise, their frequency contents are postprocessed with the use of: •??Spectrogram, that is based on the FFT, representing structures with summation of sines and cosines. It is used on a large scale to reduce the dimensions of the files that we daily handle; •??Wavelet, which employs waves of various shapes and now are widespread in the word of compressing sounds. At the end, an experiment test is carried out and has its frequency contents examined in order to spot the nonlinear symptoms and characteristics described in the previous sections. In particular, a beam is employed beam with two sources of nonlinearity, i.e. magnets and a non holonomic constraint. Moreover, numerical simulations with Lupos are executed with the idea of fully interpret the obtained results.