Computational Acoustics in Multi-Field Problems

KALTENBACHER, MANFRED

doi:10.1142/s0218396x11004286

Cited by 10 publications

(8 citation statements)

References 60 publications

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“…For the following remarks, it is assumed that the wave propagation direction is perpendicular to the interface. In this case, the reflection coefficient R and the transmission coefficient T can be expressed in terms of acoustic impedances for a wave travelling from medium Z i into the adjacent medium Z i+1 , respectively (Bergman, 2018;Kaltenbacher, 2018;Rose, 2014)…”

Section: Theory On Acoustic Impedance Matchingmentioning

confidence: 99%

A numerical study on planar gradient acoustic impedance matching for guided ultrasonic wave detection

Rottmann

Roloff

Rauter

et al. 2023

Journal of Vibration and Control

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Increasing the service-life of engineering structures such as aeroplanes is a major issue in order to enhance their cost-effectiveness and to reduce the carbon footprint. One possibility to achieve this goal is to determine the current structural health state and to derive respective measures in order to increase the structure’s technical reliability. For doing so, a structural health monitoring system consisting of both an actuator and a sensor network may be applied. Whereas the actuator induces a wave field of guided ultrasonic waves, the measuring data of the sensors allows to determine the health state of the respective structure. However, both actuators and sensors in most cases distort these wave fields. This distortion may lead to false-detection of damage: both the number and severity of damage may be over- or underestimated. The former leads to an unnecessary high effort for retrofitting the structure, whereas the latter reduces the structure’s technical reliability. Several measures exist in order to avoid such false-detections. In the present contribution, focus is set on reducing the distortion of the wave field which is caused by an embedded sensor. The reduced distortion of the wave field is achieved by an acoustic impedance matching with a functionally graded material which is based on a mechanical model. The approach additionally results in amplified measuring signals of the sensor. The applicability of the proposed approach is shown by means of a numerical study.

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Section: Theory On Acoustic Impedance Matchingmentioning

confidence: 99%

A numerical study on planar gradient acoustic impedance matching for guided ultrasonic wave detection

Rottmann

Roloff

Rauter

et al. 2023

Journal of Vibration and Control

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“…This can be described recording to Refs. [18–20] with the reflection coefficient R and the transmission coefficient T as functions of acoustic impedances of a wave that propagates from material

Z_i

into material

Z_{i+1}

\begin{align} R = \frac{Z_{i+1} - Z_{i}}{Z_{i+1} + Z_{i}}, \end{align}

\begin{align} T = \frac{2 Z_{i+1}}{Z_{i+1} + Z_{i}}. \end{align}

…”

Section: Theory On Acoustic Impedance Matchingmentioning

confidence: 99%

“…This can be described recording to Refs. [18][19][20] with the reflection coefficient 𝑅 and the transmission coefficient 𝑇 as functions of acoustic impedances of a wave that propagates from material 𝑍 𝑖 into material 𝑍 𝑖+1 :…”

Section: Theory On Acoustic Impedance Matchingmentioning

confidence: 99%

An approach for improving SHM systems with GUW detection and embedded sensors by a planar gradient acoustic impedance matching

Rottmann,

Weber

2023

Proc Appl Math and Mech

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For technical structures, such as airplanes, the service life must be increased to satisfy the requirements for high efficiency in terms of costs and sustainability. Monitoring the system's current health and providing solutions to maintain it reliably is one way to accomplish this objective. A structural health monitoring system, in which actuators induce a guided ultrasonic wave or wavefield monitored by a sensor or a network of sensors, is a standard for thin‐walled structures, which are made of, for example, fibre‐metal‐laminates. The sensor measurements provide information that can be used to determine the respective health state of the system. However, embedding the actuator and sensors in the system typically results in a distortion of the wavefield, for example, mode‐conversion and reflections. The distortion can lead to over‐ or underestimation of the quantity, location and severity of the damage. Due to these false detections, both an unnecessary high effort for retrofitting the structure and a reduction of the structure's technical reliability may be needed. The objective of the current contribution is to reduce the wave‐field distortion/reflections caused by the sensors to prevent or minimise these false detections. To reduce the distortion and reflection of the wavefield, a functionally graded material with an acoustic impedance matching based on a mechanical model is used. In order to control and adjust the acoustic impedance, which is the leading parameter concerning distortion and reflections of waves, tungsten particles were added to the uncured epoxy resin. The design of an interphase between the sensor or its glass housing and the surrounding structure is achieved by this novel approach. The interphase properties are varying in the radial direction to the sensor and are depending on the tungsten particle content in the epoxy resin. In this work, several models regarding the radial distribution of the tungsten particle content and the excitation frequency are investigated. Additionally, the dependence on geometrical influence is also addressed. The approach results, for specific configurations, in (i) reduced reflections from the sensor (less distortion) and (ii) amplified measuring signals of the sensor. Numerous numerical examples demonstrate the benefit of the presented approach.

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“…All these propagation environments constitute a large number of inputs for a numerical acoustic propagation model, such as bellhop [4]. Using this software across all oceanographic results completes our oceanographic dataset from an acoustic point of view, providing signal arrival times via the ray tracing method [8], [9]. The amplitudes of the paths are also calculated, and knowledge of the position of the floats and sources over time also gives us access to their relative velocities and hence Doppler compression factor.…”

Section: B An Oceano-acoustic Datasetmentioning

confidence: 99%

An Oceano-Acoustic Simulation Framework for the Design of Lagrangian Systems Drifting in Mesoscale and Sub-Mesoscale Currents

Grangeon,

Socheleau,

Ponte

et al. 2023

OCEANS 2023 - MTS/IEEE U.S. Gulf Coast

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Sub-mesoscale currents are of great interest for oceanographers but unfortunately their observation is a very difficult task. Lagrangian systems can be used to monitor them and require the implementation of an acoustic signal processing chain leading to the localization of each node of that system. In order to help the design of the Lagrangian system prior to sea trials, a simulation framework coupling the results of an oceanographic model with a ray trace software is presented. To illustrate the benefit of this framework, an experimental set-up composed of 5 sources and 20 floats which are drifting for 15 days is analyzed. A dataset of 358,000 frequency responses reflecting sub-mesoscale dynamics is built up. From this dataset, relevant statistics are calculated to define the best transmission parameters of the acoustic sources and to choose the right ranging method. It turns out that using pseudo-random sequences and allocating the spectral resources with Code Division Multiple Access method is a relevant design in our context. Also, it appears that a noncoherent ranging processor gives the best performance.

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Computational Acoustics in Multi-Field Problems

Cited by 10 publications

References 60 publications

A numerical study on planar gradient acoustic impedance matching for guided ultrasonic wave detection

A numerical study on planar gradient acoustic impedance matching for guided ultrasonic wave detection

An approach for improving SHM systems with GUW detection and embedded sensors by a planar gradient acoustic impedance matching

An Oceano-Acoustic Simulation Framework for the Design of Lagrangian Systems Drifting in Mesoscale and Sub-Mesoscale Currents

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