This document summarizes a research project for the development of a novel class of active dampers based on magnetorheological elastomers MRE, a technology with a manifold of application spanning from aerospace to mechanical and civil engineering. Indeed, in many engineering applications, an excessive level of vibrations may lead to a significant decrease of the system performance and eventually cause the failure of structural components. This is mostly true in electronic devices such as radars, navigation systems, optical detectors, and other types of sensors. In particular:
- vibration-induced fatigue and performance degradation of airborne electronics represents a major technical concern.
- in aerospace applications, structural vibrations manifest themselves on a very wide range of frequencies and amplitudes due to the high variety of operating conditions that characterize the service life of helicopters, airplanes, and spacecrafts.
Therefore, the aim of this research project will be designing novel insulator configurations through the combined used of multiphysics modelling and experimental testing
In many engineering applications, an excessive level of vibrations may lead to a significant decrease of the system performance and eventually cause the failure of structural components. This is mostly true in electronic devices such as radars, navigation systems, optical detectors, and other types of sensors. In particular:
- vibration-induced fatigue and performance degradation of airborne electronics represents a major technical concern.
- in aerospace applications, structural vibrations manifest themselves on a very wide range of frequencies and amplitudes due to the high variety of operating conditions that characterize the service life of helicopters, airplanes, and spacecrafts.
Therefore, the use of tuneable dampers based on MRE may offer several advantages over existing technical solutions. Among the others, magneto-rheological fluids are often used in the automotive industry for vibration insultation. These materials have the advantage of having very fast response time and so be able to adapt to external excitations even at high frequency. However, their response is significantly affected by the operating temperature. For such a reason, MR fluid cannot be easily adopted in aerospace applications where the operating temperature can easily get below the freez-ing point of the fluid [12]. On the other hand, MRE are solid materials and, although they may show a temperature sensitive response, the variation of the mechanical characteristics is limited com-pared to fluid.
WP1. The key idea behind the modeling approach to be exploited in WP1 is to study magneto-elastic fibro-reinforced composite as material in which the relaxed configuration can evolve over time to adapt to external stimuli. In this sense, the composite can be treated as a material with mi-crostructure in which in addition to the classical kinematic descriptor representing the position of the material particle in the deformed configuration, there is another descriptor represented by a ro-tation tensor that provides the structure of the fiber in the remodeled configuration. The evolution of this tensor can be determined by requiring that the remodeling process be associated with posi-tive dissipation. The advantage of this approach is that it is possible to include any external sources such as magnetic or electric fields in the model. By appropriately calibrating the characteristic time associated with remodeling it is possible to describe the transition from liquid to solid, which is of importance in describing the realization process of the MRE.
WP2. In evaluating possible actuator configurations, a bi-directional mode of functioning will be exploited in conjunction with the possibility of controlling the surface roughness, thus the friction force of the damper. Such a configuration offers the possibility of integrating two vibration isolation systems that are independent with each other as well as realizing the two single mode vibration iso-lations that originally need combinations of two magnetic field systems with only one magnetic field actuation system [13]. This concept has also been employed in semi-active integrated MR fluid¿based seat suspension system. There are at least three particular advantages of the new proposed integrated vibration isolation system based on the ``bidirectional shear mode¿¿ concept listed as fol-lows: (1) only one mathematical model along with one coil current command for delivering magnet-ic field is enough to magnetically actuate two MREs that operates in shear mode at the same time. (2) Straightforward optimization design, simulation, and modelling of a prototype MRE-based vibra-tion isolator prior to fabricating and testing the final device. This can dramatically save time and de-sign budget, hence paving the way toward mass commercialization of MRE-based isolators. From manufacturing point of view, assembling of the proposed bi-directional shear mode MRE isolator is also quite straightforward compared to that of shear¿ compression mix-mode isolators, thereby re-ducing the installation area and cost of the system effectively.
[12] de Vicente, J., Klingenberg, D. J. & Hidalgo-Alvarez, R. Soft Matter 7, 3701. 2011.
[13] Jalali et al., Journal of Intelligent Material Systems and Structures, 31(17) 2002-2019, 2020.