Nitrile-butadiene rubber (NBR) has been wildly applied in vibration controltechnology, it is usually mixed with organic small molecular modifiers and well vulcanized, which can greatly enhance the mechanical and damping properties of the material. This work aims to design the optimum blending ratio of hindered phenol A/B/NBR composite with the best damping property by means of molecular dynamics (MD) simulation, and investigate the mechanical performance from the molecular level. The shear deformation simulation is conducted on pure NBR models to study the impact of rubber crosslink degree (CD) on elasticity and plasticity of NBR. To research the damping mechanism of the material, detailed analyses of the micro molecular structure and reciprocating shear simulation are carried out on NBR composite models with different hindered phenol A/B ratio. The simulation results indicate a strong positive correlation between intermolecular H-bonds and loss factor 𝜼, and the NBR composite with hindered phenol A/B per hundred rubber (phr) 30/30 shows the best damping performance.
Viscoelastic dampers are conventional passive vibration control devices with excellent energy dissipation performance. The fractional derivative has a simple form and high accuracy in the modelling of viscoelastic materials/dampers. The internal variables reflect the internal state evolution of materials, and are often used to analyze the deformation and thermal process of materials. In the present work, the mechanical properties of a plate-shear-type viscoelastic damper at room temperature are tested under sinusoidal displacement excitations. The impacts of frequency and displacement amplitude on the dynamic properties of the viscoelastic damper in a wide frequency domain (0.1–25 Hz) are investigated. The higher-order fractional derivative model and the temperature–frequency equivalent principle are employed to characterize the frequency and temperature influence, and the internal variable theory considering the internal/microscale structure evolutions is introduced to capture the displacement affection. The higher-order fractional derivative model modified with the internal variable theory and temperature–frequency equivalent principle (ITHF) is accurate enough in describing the dynamic behaviors of viscoelastic dampers with varying frequencies and displacement amplitudes.
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