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Item type:Publication, Access status: without files , Multistability and localization in forced cyclic symmetric structures modelled by weakly-coupled Duffing oscillatorsMany engineering structures are composed of weakly coupled sectors assembled in a cyclic and ideally symmetric configuration, which can be simplified as forced Duffing oscillators. In this paper, we study the emergence of localized states in the weakly nonlinear regime. We show that multiple spatially localized solutions may exist, and the resulting bifurcation diagram strongly resembles the snaking pattern observed in a variety of fields in physics, such as optics and fluid dynamics. Moreover, in the transition from the linear to the nonlinear behaviour isolated branches of solutions are identified. Localization is caused by the hardening effect introduced by the nonlinear stiffness, and occurs at large excitation levels. Contrary to the case of mistuning, the presented localization mechanism is triggered by the nonlinearities and arises in perfectly homogeneous systems.Publicationtype: Journal Article164 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , On adhesive theories in multilayered interfaces, with particular regard to "surface force apparatus" geometryAdhesion is a key factor in many tribological processes, especially wear. We generalize a recent formulation for the indentation of a multilayered material using an efficient integral transform method, to the case of adhesion, using a simple energetic transformation in the JKR regime. Then, we specialize the study for the geometry of the Surface Force Apparatus, which consists of two thin layers on a substrate, where the intermediate layer is softer than the other two. We find the pull-off force under "force control" (i.e. for "soft" loading systems), as well as under "displacement control" (i.e. for "rigid" systems), as a function of the geometrical thicknesses and material properties ratios, and the method is fully implemented in a fast Mathematica code, available to the public (see Appendix).Publicationtype: Journal ArticleScopus© Citations 2 470 344 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Subcritical bifurcation in a self-excited single-degree-of-freedom system with velocity weakening-strengthening friction law: analytical results and comparison with experimentsThe dynamical behavior of a single-degree-of-freedom system that experiences friction-induced vibrations is studied with particular interest on the possibility of the so-called hard effect of a subcritical Hopf bifurcation, using a velocity weakening–strengthening friction law. The bifurcation diagram of the system is numerically evaluated using as bifurcation parameter the velocity of the belt. Analytical results are provided using standard linear stability analysis and nonlinear stability analysis to large perturbations. The former permits to identify the lowest belt velocity (vlw) at which the full sliding solution is stable, the latter allows to estimate a priori the highest belt velocity at which large amplitude stick–slip vibrations exist. Together the two boundaries [ vlw, vup] define the range where two equilibrium solutions coexist, i.e., a stable full sliding solution and a stable stick–slip limit cycle. The model is used to fit recent experimental observations.Publicationtype: Journal ArticleScopus© Citations 55 256 373 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Load-separation curves for the contact of self-affine rough surfacesThere are two main approximate theories in the contact of rough solids: Greenwood-Williamson asperity theories (GW) and Persson theories. Neither of them has been fully assessed so far with respect to load-separation curves. Focusing on the most important case of low fractal dimension (D f = 2.2) with extensive numerical studies we find that: (i) Persson's theory describes well the regime of intermediate pressures/contact area, but requires significant corrective factors: the latter depend also on upper wavevector cutoff of the roughness; hence, (ii) Persson's theory does not predict the correct functional dependence on magnification; (iii) asperity theories in the discrete version even neglecting interaction effects are more appropriate in the range of relatively large separations, also to take into consideration of the large scatter in actual realization of the surface.Publicationtype: Journal ArticleScopus© Citations 47 246 315 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Friction-induced vibrations during tightening of bolted joints: insights from a multi-body model(American Society of Mechanical Engineers (ASME), 2017); ; The tightening process of bolted joints shows a highly dynamic behavior, which depends on numerous factors and can therefore be challenging to be adequately quantitatively reproduced. The presented model solves this problem by combining a multi-body model of the joint with the sophisticated LuGre friction model. This allows for a detailed simulation while simultaneously reducing the computational work in comparison to a standard finite element simulation. We demonstrate that, with a constant tightening angular velocity, the progression of the tightening torque and the preload force can be described by three constants. The model further allows to implement custom torque sources, screw types, and materials to further extend its capabilities. In this contribution, we focus on the basic relationships of acting torques on the joint and friction-induced vibrations during the tightening process. Furthermore, effects of typical geometric and material changes on the stick-slip frequency are demonstrated and discussed.Publicationtype: Conference Paper109