Rolling stock manufacturers face the challenge of manufacturing lightweight high-speed trains without deteriorating comfort. One of the difficulties is to mantain or increase structural stiffness and damping as the car bodies become lighter. Leaving aside active solutions, which are expensive and generally complex to implement, increasing structural damping by means of viscoelastic patches (via Constrained Layer Damping) seems to be a viable solution which is in fact already used for acoustic insulation in automotive, aerospace and even railway applications. Although there are works in the literature that try to optimise viscoelastic panels, this work presents an experimental study with two essential contributions: (i) to analyse the influence of a broad set of design parameters such as type of the constraining layer (uniform or honeycomb), thickness of the viscoelastic layer, location, covered area and continuity between patches; and (ii) to consider absolute and specific (per unit mass) damping depending on the design scenario. To locally increase the structural damping of an existing lightweight structure without compromising its weight, partial application of thin viscoelastic and constraining layers turned out to be the best solution. To enhance structural damping from the design stages, disregarding constraining layer mass by incorporating its stiffness into the overall stiffness of the structure, full coverage with thick viscoelastic layer and a honeycomb constraining layer with a high cross-section moment of inertia turned out to be the best option, reaching modal damping ratios up to 22 times higher than structures without viscoelastic materials.

This paper presents an experimental study of the vibration attenuation achieved by the combined action of Constrained Layer Damping (CLD) and piezoelectric patches. The test structure is a cantilever beam excited at the clamped end, and the objective is to reduce the vibration of the free end. It will be shown that the most effective combination is to clad 25% of the length of the beam with CLD on just one side, and adhere a piezoelectric patch on the constraining layer rather than on the beam itself. It will also be shown that adding CLD and patches on both sides does not further improve attenuation. To guide the experimental analysis, and predict beam behaviour prior to testing, a model has been developed to include CLD cladding and piezoelectric patches. The model is based on the simplified Euler–Bernoulli beam but taking into account the stepped or segmented nature of the beams under consideration. Mode shapes are obtained for each segment and assembled imposing continuity. Experimental results show that the model can be used as a valid first approximation.

1. The assessment of passenger comfort in railway vehicles has been investigated for decades to guide the design of rolling stock and define operator comfort requirements. The most widely used metr...

Este trabajo presenta un estudio experimental cuyo objetivo es identificar métodos efectivos para reducir las vibraciones en estructuras ligeras. Se comparan específicamente dos enfoques pasivos aplicados a una viga de aluminio en voladizo: parches piezoeléctricos y recubrimientos viscoelásticos. A diferencia de las soluciones activas, que requieren un consumo constante de energía, los métodos pasivos destacan por su simplicidad, bajo mantenimiento y eficacia a largo plazo.La primera técnica propuesta utiliza parches piezoeléctricos, con tres valores de capacitancia distintos, ubicados en diferentes zonas de la viga y conectados a dos tipos de circuitos de derivación: resistivo e inductivo. Esta técnica logra una reducción de vibraciones del 92%. La segunda estrategia explora el amortiguamiento de la viga revistiéndola con un material viscoelástico disipativo y diferentes capas constrictoras (constrained layer damping, CLD), alcanzando una reducción del 89%. Ambos enfoques muestran un potencial significativo para reducir vibraciones indeseadas, proporcionando soluciones prácticas para su aplicación en estructuras ligeras.Finalmente, se ha estudiado la combinación de ambas técnicas mediante la selección de las configuraciones que logren los mejores resultados, alcanzando una reducción del 95%. Los resultados de este trabajo ofrecen una perspectiva detallada sobre la efectividad de estos métodos pasivos, tanto por separado como en conjunto, con importantes implicaciones para aplicaciones que demanden sistemas con cierto amortiguamiento estructural.