A new result enables direct calculation of thermoelastic damping in vibrating elastic solids. The mechanism for energy loss is thermal diffusion caused by inhomogeneous deformation, flexure in thin plates. The general result is combined with the Kirchhoff assumption to obtain a new equation for the flexural vibration of thin plates incorporating thermoelastic loss as a damping term. The thermal...

A new approach to spatialisation, based on the idea of projecting sounds through virtual sounding objects, is proposed, and initial experiments are carried out using a modal synthesis model of a rectangular membrane. The effects of varying the dimensions and damping parameters of the model on the perception of spatial attributes are discussed, as well as the relevance to sound diffusion.

Model updating is an inverse eigenvalue problem which concerns the modification of an existing but inaccurate model with measured modal data. In this paper, an efficient gradient based iterative method for updating the mass, damping and stiffness matrices simultaneously using a few of complex measured modal data is developed. Convergence analysis indicates that the iterative solutions always co...

Often structural dynamic systems cannot be modeled with constant stiffness, mass and damping. For example, wind turbines, helicopters, turbomachinery, and a variety of nonlinear structures linearized about a periodic limit cycle all may contain time-periodic terms in their equations of motion even if the equations are still linear. Linear time periodic systems such as these may exhibit parametr...

Mechanical metamaterials are advanced engineering materials that exhibit unusual properties cannot be found in nature. The elastic (i.e., modulus and Poisson's ratio) of mechanical can tuned by changing the geometry their fundamental unit cells. This allows for design metamaterial lattices with targeted quasi-static properties. However, it is not clear how these freedoms contribute to dynamic m...

We consider two finite element model updating problems, which incorporate the measured modal data into the analytical finite element model, producing an adjusted model on the (mass) damping and stiffness, that closely matches the experimental modal data. We develop two efficient numerical algorithms for solving these problems. The new algorithms are direct methods that require O(nk2) and O(nk2 ...

Damping of two deformation modes by one control loop has been demonstrated by simulation for a typcial 3 MW wind turbine. The vibration levels of the 2 and 3 in-plane modal modes were significantly reduced. Calculations with the aerodynamic code PHATAS showed an overall in-plane fatigue load reduction by ca 40%. The control loop includes a Kalman filter that estimates state variables for the mo...

Modal acoustics is one of the main sources of annoyance in the low frequency range in rooms. Active noise control techniques can be deployed to reach sufficient acoustic benefit, but limited to a single frequency, whereas broader efficiency would require complex systems with a large number of transducers. This paper introduces the semi-active/active concept of “electroacoustic absorbers”, which...