Apport des analyses numériques temporelle et fréquentielle dans l'étude des instabilités de contact: validation expérimentale

Abstract : The instabilities generated by friction are responsible for various noises such as squealing, squeaking and chatter. The literature includes many studies that show that the contact instability phenomenon is complex (since it's interdisciplinary and multi scale) and has yet to be brought under full control. To model and understand this instability phenomenon, dynamic transient and complex eigenvalue analyses are performed on a model system composed of two beams with a frictional contact point. This work is composed on four main parts. After a review of the main studies on contact instabilities to position this work (I), the two analyses of the system are programmed on the same platform, thereby making it possible to control the calculation hypotheses. Firstly, non linear (transient dynamic analysis) and linear (complex eigenvalue analysis) models are described (II) and compared (III). In the dynamic transient analysis, the values of displacements, velocities and accelerations at the different nodes, as well as the values of the forces and surfaces of the contact are calculated through time. The frictional contact point between two deformable beams is controlled by algorithms based on the forward Lagrange multiplier method. This analysis takes account of the non-linear aspect of a friction contact, instability is characterised by stick and separation zones occurring at the surface of the contact. In the linear complex eigenvalue analysis, the eigenvalues and eigenvectors of the system are calculated by integrating the contact forces in the stiffness matrix. The equations of movement are written around the steady sliding state of the system. The contact is controlled by a spring of stiffness introduced between the two nodes in contact. Instability occurs via the coalescence of two eigenmodes of the system. The results stemming from the two analyses are coherent and complementary, despite several differences in prediction. Then an experimental validation (IV) is performed and shows good correlation between the results obtained by numerical transient dynamic analysis and those obtained from experiments. The experimental trends are predicted with high precision thus highlighting the pertinence of the dynamic transient analysis in studying the complex vibratory phenomena of contact instabilities. It is also shown that the complex eigenvalue analysis gives goods results even though it does not appear sufficient for characterising phenomenon of contact instability. In this experimental analysis, tribological aspects are also considered and highlight permanent interactions between micro- and macro-scales during contact instabilities.
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Anissa Meziane. Apport des analyses numériques temporelle et fréquentielle dans l'étude des instabilités de contact: validation expérimentale. Acoustique [physics.class-ph]. INSA de Lyon, 2007. Français. ⟨tel-00780573⟩

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