[en] A fundamental aim of many industrial sectors is the reduction of structural vibration in order to increase the service life of mechanical components and diminish noise radiation. Viscoelastic sandwiches have been widely applied to attenuate structural vibration as they are cost-effective and simple to employ. However, the constantly increasing requirements for vibration control have made the latest research move towards smart structures able to adapt to random vibrations in real time. Magnetorheological materials are a class of smart materials able to modify their rheological properties in response to magnetic fields. Thus, they offer attractive features for constructing smart sandwich structure with enhanced vibration control. The present thesis studies the dynamics of thin viscoelastic-magnetorheological sandwich structures. These sandwiches are analogous to thin viscoelastic sandwiches in the absence of a magnetic field, whereas when magnetic fields are applied their dynamic behaviour is modified as a result of the coupling of multiple physical phenomena generated in their skins and core. The dynamic behaviour of thin viscoelastic sandwiches was analysed as a way of studying the behaviour of thin viscoelastic-magnetorheological sandwiches in the absence of a magnetic field. To that end, sandwiches of different compositions were characterized and numerical models were defined. From the joint analysis of the experimental and numerical results, the influence of the nature and thickness of both viscoelastic adhesive and metallic skins on the dynamic properties of the sandwich were determined. The phenomenon of eddy currents generated in metallic skins was studied in order to determine its influence on the dynamic behaviour of viscoelasticmagnetorheological sandwiches. To do this, an experimental modal analysis with a metallic beam, with and without induced eddy currents, was carried out. Then, in view of the damping capacity of eddy currents, a new hybrid sandwich structure combining viscoelastic and eddy current damping was proposed. Afterwards, a new inverse method was developed to estimate and model the influence of eddy currents. The phenomena generated in the viscoelastic-magnetorheological core, the magnetorheological effect and magnetic force, were studied. To that end, a magneto-dynamic model of viscoelastic-magnetorheological sandwiches including both phenomena was proposed and validated with experimental results. Finally, the dynamic behaviour of a thin viscoelastic-magnetorheological sandwich was analysed experimentally, and the influence of the magnetic particles and the intensity and position of the magnetic field was studied. The knowledge acquired in the course of this research enables determining the physical phenomena governing the dynamics of thin viscoelastic-magnetorheological sandwiches and explain the experimentally observed magneto-dynamic behaviour.

[eu] Sektore industrial askoren helburua egiturazko bibrazioak murriztea da, honela, osagai mekanikoen bizitza erabilgarria luzatu eta erradiazio akustikoa murrizten baita. Sandwich biskoelastikoak oso erabiliak izan dira egiturazko bibrazioak moteltzeko, izan ere, inplementatzeko errazak eta kostu baxukoak baitira. Gaur egun, gero eta bibrazio-kontrol efikazagoa eskatzen denez, denbora errealean ausazko bibrazioetara egokitzeko gai diren estruktura adimendunetan ardaztu dira azken ikerketak. Material magnetoerreologikoak material adimendunak dira, zeinen propietate erreologikoak eremu magnetiko baten bidez aldatu daitezkeen. Hortaz, ohiko sandwichen nukleoa material magnetoerreologikoekin ordezkatu daiteke, sandwich estruktura adimenduak sortzeko. Tesi doktoral honen helburu nagusia sandwich biskoelastiko-magnetoerreologiko meheen dinamika aztertzea da. Eremu magnetikorik aplikatu ezean, sandwich hauen izaera dinamikoa sandwich biskoelastikoen bera da. Eremu magnetikoak aplikatzean, berriz, sandwichen izaera dinamikoa aldatu egiten da, beraien azal eta nukleoetan sortzen diren fenomeno ezberdinen akoplamenduagatik. Lehenik, sandwich biskoelastiko meheen jokaera dinamikoa aztertu da, sandwich biskoelastiko-magnetoerreologikoen jokaera eremu magnetikorik gabe analizatzeko asmoz. Horretarako, konposizio ezberdineko sandwich biskoelastikoak karakterizatu eta zenbakizko ereduak definitu dira. Itsasgarri biskoelastikoek eta azal metalikoek sandwicharen propietate dinamikoetan duten eragina zehaztu da emaitza esperimental eta zenbakizkoei esker. Azal metalikoetan sortutako Foucault-en korronteen fenomenoa ere aztertu da, korronte hauek sandwich biskoelastiko-magnetorreologikoen jokaera dinamikoaren gain duten eragina zehazteko. Horretarako, metalezko habe baten analisi modal esperimentala gauzatu da, habeak Foucault-en korronteak induzituta eta induzitu gabe dituelarik. Jarraian Foucault-en korronteen moteltze-gaitasuna ikusirik, sandwich hibrido berria proposatu da, zeinak moteltze biskoelastikoa eta Foucault-ena batzen dituen. Ondoren, metodo alderantzikatu berria garatu da, korronte hauen eragina zenbatetsi eta modelatzeko. Nukleo biskoelastiko-magnetoerreologikoetan sortutako fenomenoak ere aztertu dira, hau da, efektu magnetoerreologikoa eta indar magnetikoa. Horretarako, bi fenomeno hauek kontutan hartzen dituen sandwich biskoelastikomagnetoerreologikoen eredu dinamikoa proposatu eta emaitza esperimentalekin egiaztatu da. Azkenik, sandwich biskoelastiko-magnetoerreologiko meheen jokaera dinamikoa esperimentalki ebaluatu da. Partikula magnetikoek eta eremu magnetikoaren intentsitateak eta posizioak sandwicharen propietate dinamikoetan duten eragina aztertu da. Tesi doktoral honetan zehar sortutako ezagutzak, sandwich hauen erantzun magnetodinamikoa gidatzen duten fenomeno fisikoak ezagutzea ahalbidetu du.