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Full-Text Articles in Mechanical Engineering

A New Set-Up To Measure The Viscoelastic Properties Of Porous Media Using A Specific Electrodynamic Transducer, Dauchez Nicolas, Olivier Doutres Ph.D., Jean-Michel Génevaux, Guy Lemarquand Dec 2008

A New Set-Up To Measure The Viscoelastic Properties Of Porous Media Using A Specific Electrodynamic Transducer, Dauchez Nicolas, Olivier Doutres Ph.D., Jean-Michel Génevaux, Guy Lemarquand

Olivier Doutres Ph.D.

A new method for measuring viscoelastic properties of sound absorbing materials is presented. This method is derived from the quasistatic method using a loudspeaker as actuator and sensor. Previous results carried out with a traditional electrodynamic loudspeaker were limited to 100 Hz because of transducer nonlinearities. In this paper, viscoelastic properties are determined up to 500 Hz due to the design of a specific loudspeaker devoid of the main nonlinearities.


Broadband Measurement Of Rate-Dependent Viscoelasticity At Nanoscale Using Scanning Probe Microscope: Poly(Dimethylsiloxane) Example, Zhonghua Xu, Kyongsoo Kim, Qingze Zou, Pranav Shrotriya Sep 2008

Broadband Measurement Of Rate-Dependent Viscoelasticity At Nanoscale Using Scanning Probe Microscope: Poly(Dimethylsiloxane) Example, Zhonghua Xu, Kyongsoo Kim, Qingze Zou, Pranav Shrotriya

Mechanical Engineering Publications

A control approach to achieve nanoscale broadband viscoelasticmeasurement using scanning probe microscope(SPM) is reported. Current SPM-based force measurement is too slow to measure rate-dependent phenomena, and large (temporal) measurement errors can be generated when the sample itself changes rapidly. The recently developed model-less inversion-based iterative control technique is used to eliminate the dynamics and hysteresis effects of the SPM hardware on the measurements, enabling rapid excitation and measurement of rate-dependent material properties. The approach is illustrated by the mechanical characterization of poly(dimethylsiloxane) over a broad frequency range of three orders of magnitude (∼1 Hz to 4.5 KHz).


Validity Of The One-Dimensional Limp Model For Porous Media, Olivier Doutres, Nicolas Dauchez, Jean-Michel Génevaux, Olivier Dazel Dec 2007

Validity Of The One-Dimensional Limp Model For Porous Media, Olivier Doutres, Nicolas Dauchez, Jean-Michel Génevaux, Olivier Dazel

Olivier Doutres Ph.D.

A straightforward criterion for determining the validity of the limp model validity for porous materials is addressed here. The limp model is an “equivalent fluid” model which gives a better description of porous behavior than the well known “rigid frame” model. It is derived from the poroelastic Biot model, assuming that the frame has no bulk stiffness. A criterion is proposed for identifying the porous materials for which the limp model can be used. It relies on a new parameter, the Frame Stiffness Influence FSI, based on porous material properties. The critical values of FSI under which the limp model ...