http://ieeexplore.ieee.org/iel5/5/31047/01444179.pdf

Fundamentals of acoustics

Tunable frequency response of topologically protected interface modes for membrane-type metamaterials via voltage control

Cement is widely used in wellbores to stabilize the steel casing used in wellbore operations for oil and gas production, enhanced geothermal systems and carbon sequestration, and to limit fluid movement between sub-surface strata. Flaws such as microcracks in wellbore cement can lead to leakage along the wellbore compromising wellbore integrity. There is an increasing need for methods to monitor cement crack propagation in wellbore environments. In this study, we develop and report the first cementitious sensors capable of exhibiting high frequency acoustic bandgaps (ABGs) using carbon nanotubes (CNTs). Computational simulations of a sensor unit cell are used to design cement-multi walled carbon nanotubes (MWCNTs) sensors that show a wide bandgap. When the cement-MWCNTs sensors is embedded in cement specimens, bandgaps were measured experimentally under 300 kHz and under 600 kHz, consistent with the computationally predicted bandgaps in the range of 290–360 kHz, 410–460 kHz and 515–585 kHz. These bandgap features were absent in homogeneous cement specimens. X-ray tomographic reconstructions showed microscopic debonding at cement-MWCNTs sensor interface. Frequency response analysis of a three-dimensional computational model indicated a shift of frequency of minimum transmission due to the interface debonding, but no perturbation of bandgap response was observed. The cement-MWCNTs sensors developed in this study show the potential of a packed CNT inclusion material in cementitious matrix to create ABGs in a cement matrix.

Cement sensors with acoustic bandgaps using carbon nanotubes

Acoustic metamaterials (AM) have emerged as an academic discipline within the last decade. When used for sound insulation, metamaterials can show high transmission loss at low frequencies, despite having low mass per unit area. This paper investigates the possibility of using AMs to increase the sound insulation of finite single leaf walls (SLWs), focusing on the coincidence effect problem. Formulas are derived using a variational technique for the forced sound transmission of finite SLWs with a coupled array of single degree of freedom resonators. An analytical model is presented for this simple case, and the effects of the band gap in sound transmission and radiation are analyzed. Moreover, the influence of each parameter is studied, especially the presence of losses, giving way to an optimized way of designing this type of structure using constrained parameter optimization. Numerical validations are performed and discussed. Finally, some conclusions are drawn regarding the effectiveness of the proposed model, including possible applications.

/pdf/an-analytical-model-for-broadband-sound-transmission-loss-of-4wkaijp674.pdf

An Analytical Model for Broadband Sound Transmission Loss of a Finite Single Leaf Wall using a Metamaterial

Acoustic metamaterials (AM) have emerged as an academic discipline within the last decade. Metamaterials can exhibit high transmission loss at low frequencies despite having low mass per unit area. This paper investigates the possibility of using AMs for increasing the sound insulation of finite single leaf walls (SLW), focusing on the coincidence effect problem. Formulas are derived using a variational technique for the forced sound transmission of finite SLW with a coupled array of two degree of freedom resonators. An analytical model is presented and the effects of the band gap in sound transmission and radiation are analyzed and compared to the single degree of freedom case. Moreover, numerical simulations verify the two degree of freedom model. Finally, some conclusions are drawn regarding the effectiveness of the proposed model, possible applications, and future work.

/pdf/an-analytical-model-for-broadband-sound-transmission-loss-of-30pe99q3eb.pdf

Javier Hernan Vazquez

Papers

An Analytical Model for Broadband Sound Transmission Loss of a Finite Single Leaf Wall using a Metamaterial

An analytical model for broadband sound transmission loss of a Finite Single Leaf Wall using a two degree of freedom resonant Metamaterial