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Characterisation Of Porous Materials Viscoelastic Properties Involving The Vibroacoustical Behaviour Of Coated Panels, Olivier Doutres, Nicolas Dauchez
Characterisation Of Porous Materials Viscoelastic Properties Involving The Vibroacoustical Behaviour Of Coated Panels, Olivier Doutres, Nicolas Dauchez
Olivier Doutres Ph.D.
Porous materials are widely used as passive acoustic absorbers. For optimal design, it is often necessary to know the viscoelastic properties of these materials in the frequency range relevant to their application. The viscoelastic properties are obtained by fitting an analytical model to acoustical radiation experimental measurements carried out on a circular coated plate clamped in a rigid baffle. Compared with quasistatic method, the viscoelastic properties are here achieved at high frequency corresponding to the first resonance in the thickness of the porous layer and coupling between porous materials and external fluid is taken into account. The analytical model, developped …
Design Of A Reliable Remote Surface Detector Based On Ultrasonic Pulse-Transit Technique To Detect Uneven & Non-Smooth Porous Snow Surfaces, Raman Attri
Raman K. Attri
This paper discusses design control techniques used to design ultrasonic pulse echo method based remote surface detector to detect objects with porous, un-even, irregular surfaces like snow. For such surfaces there is ample possibility of scatter of reflected beam in multiple directions, absorption of ultrasonic energy within the pores and reflected energy too feeble to detect. In some cases the reflected beam may altogether miss the receiver resulting in no surface detection at all. Scatter and penetration of ultrasonic energy at such irregular porous uneven surfaces poses great difficulties in designing a reliable Remote Surface detector. In this paper, we …
Modelling Of The Acoustic Radiation Of A Structure Covered By A Porous Layer, Olivier Doutres, Nicolas Dauchez
Modelling Of The Acoustic Radiation Of A Structure Covered By A Porous Layer, Olivier Doutres, Nicolas Dauchez
Olivier Doutres Ph.D.
In many applications, porous materials such as polymers foams are attached to a structure subjected to vibration. This allows to diminish vibration by increasing structural damping or to reduce noise level in cavities by sound absorption. The radiation efficiency of the coupled system is studied. An analytical model has been carried out, separating the acoustical and vibratory behaviors: - The vibratory analysis is based on a dynamic study of an equivalent plate of the coupled system. In this case the porous layer is considered as a viscoelastic layer. - In the acoustical analysis, a surface impedance is applied on this …
The Influence Of Titanium And Cerium On Microstructure And Properties Of Fe-C-Cr-Nb Alloys, Zeljko J. Kamberovic
The Influence Of Titanium And Cerium On Microstructure And Properties Of Fe-C-Cr-Nb Alloys, Zeljko J. Kamberovic
Zeljko J Kamberovic
In this paper, the influence of titanium and cerium on the microstructure and properties of Fe- C-Cr-Nb alloys are examined, in both as-cast and heat treated state. These elements affect the crystallisation process of Fe-C-Cr-Nb alloys and the transformation of austenite during the cooling process after solidification. Titanium changed the morphology of NbC carbides. Further, in the austenite of the examined Fe-C-Cr-Nb-Ti alloys, very fine particles of precipitated secondary carbide can be seen. The alloy containing 0,28%Ti and 0,19%Ce has martensite-perlite-austenitic matrix microstructure in as-cast condition. Adding titanium and cerium to Fe-C-Cr-Nb alloys will also changed its properties, since the …