Design and Modeling of Viscoelastic Layers for Locomotive Wheel Damping

Rail–wheel interaction is one of the most significant and studied aspects of rail vehicle dynamics. The vibrations caused by rail–wheel interaction can become critical when the radial, lateral and longitudinal loads of the vehicle, cargo and passengers are experienced while the vehicle is in motion along winding railroad paths. This mainly causes an excessive production of vibrations that may lead to discomfort for the passengers and shortening of the life span of the vehicle’s body parts. The use of harmonic response analysis (HRA) shows that the wheel experiences high vibrational amplitudes from both radial and lateral excitation. The present study describes a numerical and experimental design procedure that allows mitigation of the locomotive wheel resonance during radial and lateral excitations through viscoelastic layers. It is proven that these high frequencies can be reduced through the proper design of damping layer mechanisms. In particular, three parametric viscoelastic damping layer arrangements were analyzed (on the web of both wheel sides, under the rim of both wheel sides and on the web and under the rim of both wheel sides). The results demonstrate that the correct design and dimensions of these viscoelastic damping layers reduce the high-amplitude resonance peaks of the wheel successfully during both radial and lateral excitation.

Hybrid Composite Material Reinforced with Carbon Nanolaminates for Gradient Stiffness: Preparation and Characterization

Currently, the procurement of lightweight, tough, and impact resistant materials is garnering significant industrial interest. New hybrid materials can be developed on the basis of the numerous naturally found materials with gradient properties found in nature. However, previous studies on granular materials demonstrate the possibility of capturing the energy generated by an impact within the material itself, thus deconstructing the initial impulse into a series of weaker impulses, dissipating the energy through various mechanisms, and gradually releasing undissipated energy. This work focuses on two production methods: spin coating for creating a granular material with composition and property gradients (an acrylonitrile–butadiene–styrene (ABS) polymer matrix reinforced by carbon nanolaminates at 0.10%, 0.25%, and 0.50%) and 3D printing for generating viscoelastic layers. The aim of this research was to obtain a hybrid material from which better behaviour against shocks and impacts and increased energy dissipation capacity could be expected when the granular material and viscoelastic layers were combined. Nondestructive tests were employed for the morphological characterization of the nanoreinforcement and testing reinforcement homogeneity within the matrix. Furthermore, the Voronoï tessellation method was used as a mathematical method to supplement the results. Finally, mechanical compression tests were performed to reveal additional mechanical properties of the material that had not been specified by the manufacturer of the 3D printing filaments.

New Version of High-Damping PCB with Multi-Layered Viscous Lamina

In a previous study, a high-damping printed circuit board (PCB) implemented by multilayered viscoelastic acrylic tapes was investigated to increase the fatigue life of solder joints of electronic packages by vibration attenuation in a random vibration environment. However, the main drawback of this concept is its inability to mount electronic parts on the PCB surface area occupied by interlaminated layers. For the efficient spatial accommodation of electronics, this paper proposes a new version of a high-damping PCB with multilayered viscoelastic tapes interlaminated on a thin metal stiffener spaced from a PCB. Compared to the previous study, this concept ensures efficient utilization of the PCB area for mounting electronic parts as well as the vibration attenuation capability. Free vibration tests were performed at various temperatures to obtain the basic characteristics of the proposed PCB. The effectiveness of the proposed PCB was verified by random vibration fatigue tests of sample PCBs with various numbers of viscoelastic layers to compare the fatigue life of electronic packages.

Comparison of passive damping treatments based on constrained viscoelastic layers and multi-resonant piezoelectric networks.

This work aims at comparing the damping performances of two passive damping treatments based on piezoelectric or viscoelastic patches. The motivation for such a comparison stems from the fact that the two damping techniques have been developed fairly independently, and are rarely compared. First, the dynamic response of a simply-supported metallic plate is measured experimentally after being equipped with constrained viscoelastic patches or piezoelectric patches connected to an electrical network. In order to extend the comparison, a numerical model of the structure is set up and validated to evaluate the damping performances of both passive treatments under different configurations (for instance equal-mass and equal-thickness configurations). Finally, with regard to these experimental and numerical results, the advantages and the limitations in using viscoelastic or piezoelectric treatments are discussed.