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Applied mechanics; Dynamics and Vibrations

Ramathasan Thevamaran's picture

Independent control of dynamic material properties by exploiting structural hierarchy and intrinsic structural gradients

Achieving high damping and stiffness is challenging in common materials because of their inter-dependent scaling. Controlling extreme mechanical waves requires synergistically enhanced damping and stiffness. We demonstrate superior damping and stiffness in vertically aligned carbon nanotube (VACNT) foams that are also independently controllable by exploiting their synthesis-tailored structural hierarchy and structural gradients. They exhibit frequency- and amplitude-dependent responses with dramatically tunable dynamic stiffness while maintaining constant damping.

Antonio Papangelo's picture

Self-excited vibrations due to viscoelastic interactions

Self-excited vibrations represent a big concern in engineering, particularly in automotive, railway and aeronautic industry. Many lumped models have been proposed over the years to analyze the stability of such systems. Among the instability mechanisms a falling characteristic of the friction law and mode coupling have been shown to give friction-excited oscillations. The mass-on-moving-belt system has been studied extensively in Literature, very often adopting a prescribed form of the friction law and linearizing the contact stiffness.

Arzhang's picture

Mini-symposium on Current and Future Needs in Sub-microscale Vibration Analysis

We would like to invite contributions to a session on current and future needs in sub-microscale vibration analysis at the 2019 Engineering Mechanics Institute Conference at the California Institute of Technology.

Please see call for presentations attached.

Thank you.

Arzhang Alimoradi, Ph.D., P.E.

Giorgio Carta's picture

Quasi-periodicity and multi-scale resonators for the reduction of seismic vibrations in fluid-solid systems

This paper presents a mathematical model for an industry-inspired problem of vibration isolation applied to elastic fluid-filled containers. A fundamental problem of suppression of vibrations within a finite-width frequency interval for a multi-scale fluid-solid system has been solved. We have developed a systematic approach employing full fluid-solid interaction and dispersion analysis, which can be applied to finite and periodic multi-scale systems.

Payam Soltani's picture

A short note on equal peak design for the pendulum tuned mass dampers

By: A. Deraemaeker and Payam Soltani
Pendulum tuned mass dampers (PTMDs) are used to passively mitigate the vibrations of tall structures and buildings. The main objective of this short note is to introduce analytical formulae for the optimum design of the linear PTMD coupled to an undamped primary system. Den Hartog's equal peak method is applied to derive the optimum design. With the mass ratio between the primary system and the PTMD, the optimum length and optimum damping of the pendulum are calculated. The formulae are presented in both dimensional and non-dimensional forms and are simple to apply in real applications. It is also shown that the vibration mitigation performance of the proposed optimum design precisely matches the results obtained by numerical optimisation techniques.
doi: 10.1177/1464419316652558

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