Acoustic Finite Element Analysis Research Articles

AI-based Model to Estimate the Flaws from Ultrasonic NDT Data

This study explores an artificial intelligence (AI) approach for assessing the geometrical features of flaws in nondestructive testing (NDT) using ultrasonic oscillograms. A validated numerical model, generated through acoustic finite element analysis (FEA), produced ultrasonic signals. The AI model was trained on 525, validated on 113, and tested on 112 oscillograms from models with varied flaw characteristics. Training inputs were parameters derived from ultrasonic signals, and the network's performance was evaluated by comparing its outputs for flaw location, length, and angle with desired values. Statistical analysis, including Root Mean Square Error (RMSE) and Efficiency (E), indicated promising results, suggesting the potential of the proposed AI-based method for estimating flaw geometrical features in ultrasonic NDT.

Numerical Simulation of Hit Noise Generation Due to Sloshing Phenomenon in a Rectangular Tank Under Periodic Excitation

Abstract Sloshing in fuel tanks is one of the major sources of noise in hybrid and high-end vehicles. During sloshing, the fluid causes impacts on tank walls resulting in their vibration, which further leads to noise, referred to as “hit noise.” Therefore, hit noise generation is a multi-physics phenomenon involving fluid flow, structural response, and acoustic radiation. This paper presents a multi-physics approach to predict hit noise in a rectangular tank. The methodology involves the prediction of fluid loading on tank walls and their structural response using transient fluid and structural analyses which are weakly coupled. Radiated hit noise is predicted using acoustic finite element analysis. Longitudinal periodic excitation is applied to the fluid domain at different frequencies to simulate the sloshing regime which has dominant fluid–structure interactions. Parameters like tank wall pressures, the resulting dynamic acceleration, and radiated sound pressure levels are monitored and validated with the experimental results available in the literature.

Assessment of Geometrical Features of Internal Flaws with Artificial Neural Network

In nondestructive testing (NDT), geometrical features of a flaw embedded in the material such as its location, length, and orientation are critical factors to assess the severity of the flaw and make post-manufacturing decisions to improve the design. In this study, artificial intelligence (AI) based NDT approach was applied to the ultrasonic oscillograms obtained from virtual ultrasonic NDT to estimate geometrical features of a flaw. First, a numerical model of NDT specimen was constructed using acoustic finite element analysis (FEA) to produce the ultrasonic signals. The model was validated by comparing the simulated signals produced from the numerical model with the experimental data from actual NDT tests. Then, 750 numerical models containing flaws with different locations, lengths, and orientation angles were generated by FEA. Next, the oscillograms produced by the models were divided into 3 datasets: 525 for training, 113 for validation, and 112 for testing. Training inputs of the network were parameters extracted from ultrasonic signals by fitting them to sine functions. Lastly, to evaluate the network performance, outputs of the network including flaw’s location, length, and angle were compared with the desired values for all datasets. Deviations of the outputs from desired values were calculated by a regression analysis. Statistical analysis was also performed by measuring root mean square error (RMSE) and efficiency. RMSE in x-location, y-location, length, and angle estimations are 0.09 mm, 0.19 mm, 0.46 mm, and 0.75°, with efficiencies of 0.9229, 0.9466, 0.9140, and 0.9154, respectively for the testing dataset. Results suggest that the proposed AI-based method has the potential to interpret the oscillograms from ultrasonic NDT to estimate geometrical features of flaws embedded in the material.

Wideband Hybrid Monolithic Lithium Niobate Acoustic Filter in the K-Band.

This article presents the design approach and the first demonstration of a wideband hybrid monolithic acoustic filter in the K -band, which exceeds the limitation of electromechanical coupling on the fractional bandwidth (FBW) of acoustic filters. The hybrid filter utilizes the codesign of electromagnetic (EM) and acoustic to attain wide bandwidth while keeping the advantages of small sizes and high Q in the acoustic domain. The performance trade space and design flow of the hybrid filter are also presented in this article, which allows this technology to be applied for filters with different center frequencies and FBWs. The hybrid filter is simulated by hybridizing the EM and acoustic finite element analysis, which are carried out separately and combined at a system level. The fabricated filter built with resonators having an electromechanical coupling of 0.7% based on the seventh-order antisymmetric Lamb wave mode (A7) has a 3-dB FBW of 2.4% at 19 GHz and a compact footprint of 1.4 mm2.

Numerical simulation on acoustic mode and pressure-oscillation decay in finocyl- and axil-grain combustion chambers

Combustion instability has long been one of the severe problems suffered by solid rocket motors (SRMs). Currently, acoustic instability is one of the most widely researched classifications in the field of instability combustion. This study focuses on the differences in the acoustic characteristics and the decay characteristics of the pressure oscillation excited by pulses between finocyl- and axil-grain combustion chambers. A method is proposed for the suppression of the acoustic instability combustion. The finocyl- and axil-grain combustion chambers were investigated via an acoustic finite-element analysis and computational fluid dynamics (CFD). The ideas of time–frequency joint analysis and pressure-pulse decay were applied to study the acoustic field and oscillating flow field in the combustion chamber. The results of the acoustic harmonic response analysis and CFD calculations indicated that the axil grain is more stable than the finocyl grain in low-order acoustic modes. The time-weighted average response amplitudes at the 1st-order acoustic frequency for the axil-grain motor at the combustion-chamber head and end were 54.8% and 75.4%, respectively, of those for the finocyl-grain motor.

A Helmholtz Resonator with Spiral Neck for Analyte Concentration Measurement in Low Frequency Range

Helmholtz resonators (HR) have been proven to have feasibility for sensor applications with good performance. However, for biosensor application, when the amount of test sample is limited, the operating frequency tends to be very high, which may bring challenges of resonance excitation and frequency measurement. In this paper, a modified HR was proposed for biosensor application at a lower frequency, by designing the neck of the HR as a type of an Archimedes spiral, which can increase the neck length as much as possible without occupying much space. The resonant frequency of the proposed HR was derived by treating it as an HR with a straight neck with the equivalent length. An analytical example was calculated and verified by acoustic finite element analysis, and the results clearly showed that the frequency decreases in comparison to that of the conventional HR. Based on the underlying theory, the measurement principle was proposed and the experiment setup was established using a 3D-printed structure. The experiment was done using test solutions with different glucose concentrations, whose results showed consistency with the analytical results and noticeable frequency increases with the glucose concentration. Prospective results of the proposed HR after miniaturization show an operating frequency around 3 kHz when the amount of test sample is 0.1 mL, which will facilitate use of the common acoustic power source and acoustic pressure sensors in the sensing system.

Muffler structure improvement based on acoustic finite element analysis

Aiming to obtain the acoustic attenuation performance of exhaust muffler of diesel engine and the influence of main structural parameters on its acoustic attenuation characteristics, the finite element analysis method and acoustic theory were adopted to numerically investigate the acoustic attenuation performance under the boundary condition of acoustic adiabatic propagation and muffler wall. It suggested that the noise cancellation effect of muffler was poor at the middle and low frequency in range of 0–3000 Hz, and the transfer loss of muffler was basically 0 dB pass frequency at 1100 Hz. According to previous single-factor study experience, the structural factors, such as the expansion ratio, insertion length of outlet perforated pipe, the distance between the diaphragm and the front part of muffler, have influences on the acoustic performance of muffler at low frequency. Thus, they were taken as the starting point to study the influence of multiple interaction factors on the muffling performance by using orthogonal design method combined with the finite element analysis method. The influence degree of different structure parameters on the acoustic performance of muffler and the optimized structure parameters were obtained. Through the analysis on the acoustic characteristic of the optimized muffler, it indicated that the transmission loss of the improved muffler had significant increase in other frequency range except the range of 650–800 Hz and 2500–2700 Hz, especially at frequency of 1100 Hz compared with the original muffler. In the range of 0–3000 Hz, the mean of transmission loss of the improved muffler was about 9.8 dB larger than that of original muffler, which indicated that better noise cancellation effect was achieved. The improved muffler also provided a certain reference for the structural improvement of similar muffler.

Multidisciplinary Analysis and Multiobjective Design Optimization of a Switched Reluctance Motor for Improving Sound Quality

In this study, the design optimization method for improving sound quality (SQ) of a switched reluctance motor (SRM) is proposed. The multidisciplinary finite element analysis (FEA) of an SRM is performed to evaluate both average torque and the SQ metrics to design the rotor configuration of the SRM. Specifically, the magneto-static FEA of the SRM is used to evaluate the average torque which is the most important performance of motors, and the local force distribution applied to the stator. Also, the transient structural FEA of the stator excited by the local force distribution, and the transient acoustic FEA are conducted to get the sound pressure radiated by the vibration of the stator. Then, the SQ metrics of loudness, sharpness, fluctuation strength and roughness can be obtained from the radiated sound pressure. We define the correlation function between the SQ metrics and the jury test results of the different types of SRMs. The weighted sum of the torque and the correlation function is set as an objective function. After that, design optimization method of the SRM using a design of experiments is discussed. This study does not consider the nonlinear material properties and is based on 2D analysis; however, with all these limitations, note that this is the first study to propose an overall procedure to increase the SQ of an SRM.

초음파 센서의 혼 가이드에 의한 음향 수신 특성

This study addresses the acoustic reception characteristics of a horn guide applied to an ultrasonic sensor for distance measurement. In order to design a horn guide to improve the acoustic directivity of ultrasonic sensors for both transmission and reception, identifying the reception performance as well as the transmission directivity of the ultrasound is necessary. The purpose of this study was to find the horn guide angle maximizing the ultrasonic reception performance by comparing it according to the angle of the cone-shaped horn guide. Acoustic finite element analysis was performed to identify the ultrasonic reception performance depending on the horn guide angle. For the horn guide with a cone shape, acoustic analysis was performed after modeling horns of various angles in the range from 0° to 40° of the wall angle of the horn. Horn guides made using a 3D printer were attached to an ultrasonic sensor to measure the received sound pressure. From the experimental results, the validity of the finite element analysis results was verified. Analysis and experiment consistently showed that the maximum reception was observed at horn angles in the range from 20° to 25°.

Acoustic Wave Propagation in Air-Filled Pipes Using Finite Element Analysis

The major objective of this work is to develop an efficient Finite Element Analysis (FEA) procedure to simulate wave propagation in air-filled pipes accurately. The development of such a simulation technique is essential in the study of wave propagation in pipe networks such as oil and gas pipelines and urban water distribution networks. While numerical analysis using FEA seems superficially straight forward, this paper demonstrates that the element type and refinement used for acoustic FEA have a significant effect on the accuracy of the result achieved and the efficiency of the computation. In particular, it is shown that the well-known, better overall performance achieved with 3D solid hexahedral elements in comparison with 2D-type elements in most stress and thermal applications does not occur with acoustic analysis. In this paper, FEA models were developed taking into account the influence of element type and sizes using 2D-like and 3D element formulations, as well as linear and quadratic nodal interpolations. Different mesh sizes, ranging from large to very small acoustic wavelengths, were considered. The simulation scheme was verified using the Time of Flight approach to derive the predicted acoustic wave velocity which was compared with the true acoustic wave velocity, based on the input bulk modulus and density of air. For finite element sizes of the same order as acoustic wavelengths which correspond to acoustic frequencies between 1 kHz and 1 MHz, the errors associated with the predictions based on the 3D solid hexahedral acoustic elements were mostly greater than 15%. However, for the same element sizes, the errors associated with the predictions based on the 2D-like axisymmetric solid acoustic elements were mostly less than 2%. This indicates that the 2D-like axisymmetric solid acoustic elements are much more efficient than the 3D hexahedral acoustic elements in predicting acoustic wave propagation in air-filled pipes, as they give higher accuracies and are less computationally intensive. In most stress and thermal FEA, the 3D solid hexahedral elements are much more efficient than 2D-type elements. However, for acoustic FEA, the results show that 2D-like axisymmetric elements are much more efficient than 3D solid hexahedral elements.

Finite element analysis and experimental measurement of acoustic wave propagation for leakage detection in an air-filled pipe

PurposeThe purpose of this paper is to employ the acoustic wave propagation method for leakage detection in pipes. The first objective is to use acoustic finite element analysis (AFEA) method to simulate acoustic wave propagation and acoustic wave reflectometry in an intact pipe and in pipes with leaks of various sizes. This is followed by the second objective which is to validate the effectiveness and the practicability of the acoustic wave method via experimental testing. The third objective involves the decomposition and de-noising of the measured acoustic waves using stationary wavelet transform (SWT). It is shown that this approach, which is used for the first time on leakage detection in pipes, can be used to identify, locate and estimate the size of a leakage defect in a pipe.Design/methodology/approachThe research work was designed inline with best practices and acceptable standards. The research methodology focusses on five basic areas: literature review; experimental measurements; simulations; data analysis and writing-up of the study with clear-cut communication of the findings. The approach used was acoustic wave propagation-based method in conjunction with SWT for leakage detection in fluid-filled pipe.FindingsFirst, the simulation of acoustic wave propagation and acoustic wave reflectometry in fluid-filled pipes with and without leakage have great potential in leakage detection in pipeline systems and can detect very small leaks of 1 mm diameter. Second, the measured noise-contaminated acoustic wave propagation in a fluid-filled pipe can be successfully de-noised using the SWT method in order to clearly identify and locate leakage as little as 5 mm diameter in a pipe. Third, AFEA of a fluid-filled pipe can be achieved with the simulation of only the fluid content of the pipe and without the inclusion of the pipe in the model. This eliminates contact interaction of the solid pipe walls and the fluid, and as a consequence reduces computational time and resources. Fourth, the relationship of the ratio of the leakage diameter to the ratio of the first and second secondary wave amplitudes caused by the leakage can be represented by a second-order polynomial function. Fifth, the identification of leakage in a pipe is intuitive from mere comparison of the acoustic waveforms of an intact pipe with that of a pipe with a leakage.Originality/valueThe research work is a novelty and was developed from the scratch. The AFEA of acoustic wave propagation and acoustic wave reflectometry in a static fluid-filled pipe, and the SWT method have been used for the first time to detect, locate and estimate the size of a leakage in a fluid-filled pipe.

The Effect of Honeycomb Core Geometry on the Sound Transmission Performance of Sandwich Panels

Abstract The authors present numerical results for a systematic parametric study of the effect of honeycomb core geometry on the sound transmission and vibration properties of in-plane loaded honeycomb core sandwich panels using structural acoustic finite element analysis (FEA). Honeycomb cellular structures offer many distinct advantages over homogenous materials because their effective material properties depend on both their constituent material properties and their geometric cell configuration. From these structures, a wide range of targeted effective material properties can be achieved thus supporting forward design-by-tailoring honeycomb cellular structures for specific applications. One area that has not been fully explored is the set of acoustic properties of honeycomb and understanding of how designers can effectively tune designs in different frequency ranges. One such example is the insulation of target sound frequencies to prevent sound transmission through a panel. This work explored the effect of geometry of in-plane honeycomb cores in sandwich panels on the acoustic properties the panel. The two acoustic responses of interest are the general level of sound transmission loss (STL) of the panel and the location of the resonance frequencies that exhibit high levels of sound transmission, or low sound pressure transmission loss. Constant mass honeycomb core models were studied with internal cell angles ranging in increments from −45 deg to +45 deg. Effective honeycomb moduli based on static analysis of honeycomb unit cells are calculated and correlated to the shift in resonance frequencies for the different geometries, with all panels having the same total mass. This helps explain the direction of resonance frequency shift found in the panel natural frequency solutions. Results show an interesting trend of the first resonance frequencies in relation to effective structural properties. Honeycomb geometries with smaller core internal cell angles, under constant mass constraints, shifted natural frequencies lower, and had more resonances in the 1–1000 Hz range, but exhibited a higher sound pressure transmission loss between resonant frequencies.

Finite element acoustic analysis of a steel stud based double-leaf wall

Optimum acoustic performance of building components is a fundamental factor towards sustainable building design. Accordingly, it is essential that designers have the capability to effectively predict the acoustic performance to achieve sustainable designs. This paper introduces a 2-D Harmonic Acoustic Finite Element Analysis to predict the sound insulation of stud based double-leaf walls. This research was motivated by the necessity to develop acoustically efficient light weight building structures, which are both affordable and sustainable. Prediction of the Sound Reduction Index (R) of plasterboard partitions with structural links is a challenging problem due to the fluid-structure interaction (FSI) between the structural and fluid systems. Several finite element models to predict the sound reduction index of double-leaf walls were developed in compliance with BSENISO 717 and 140. The validity of the finite element predictions were assessed by comparison with experimental test results carried out in a certified laboratory. The effect of using different mesh sizes, fixing mechanisms and sound source locations on the predicted sound reduction index were looked into. The effects of air humidity and temperature on the experimental measurements of R values were also investigated. The FEA model presented in this work is capable of predicting the weighted sound reduction index (Rw) along with A-weighted pink noise (C) and A-weighted urban noise (Ctr) to within an accuracy of ±1 dB. Furthermore, the finite element modelling procedure reported can be extended to efficiently predict the acoustic behaviour of other building components undergoing FSI.

Vibra-Acoustic Characteristic Matching of Mini-Car Body Structure and Interior Acoustic Cavity in Low Frequency Range

This paper focused on the interior boom noise of a mini-car when driving at high speeds. Vehicle interior noise rotor drum tests in semi-anechoic room showed that vehicle interior boom noise in narrow frequency band exited near 250Hz. Structural and acoustic finite element analysis certified the front roof and rear floor coupled with interior acoustic cavity around this frequency, causing acoustic cavity resonance. On the base of sensitivity analysis technology, a structural improvement schemes pasting free damping fin on the front roof and rear floor of mini-car body for vibration and noise reduction was proposed. Finite element Modal analysis of the mini-car body after improving indicated that local modal amplitude of the mini-car body at the front roof and rear floor around 250Hz was controlled effectively. Mini-car rotating drum test results after improving showed that vehicle interior boom noise was decreased obviously after pasting free damping fin at the front roof and rear floor. The improving schemes and noise reduction effects proposed in this paper were validated.

Acoustic source separation for the detection of coronary artery sounds

Coronary artery disease (CAD) is the leading cause of death in the United States, being responsible for more than 20% of all deaths in the country. This is in large part due to the difficulty of diagnostic screening for CAD. Phonoangiography seeks to detect CAD via the acoustic signature associated with turbulent flow near an abnormally constricted, or stenosed, region. However, the usefulness of the technique is severely hindered by the low strength of the CAD signal compared to the background noise within the chest. In this work, acoustic finite element analysis (FEA) was performed on physiologically accurate chest geometries to demonstrate the feasibility of an original acoustic source separation methodology for isolating coronary sounds. This approach is based upon pseudoinversion of mixing matrices determined through a combination of experiment and computation. This allows calculation of the sound emitted by the coronary arteries based upon measurements of the acoustic velocity on the chest surface. This work demonstrates the feasibility of such a technique computationally and examines the vulnerability of the proposed approach to measurement errors.

Membrane/thin elastic plate matrix of modal expansion type for acoustic finite element analysis

Membrane/thin elastic plate matrix of modal expansion type for acoustic finite element analysis

MODEL REDUCTION AND FREQUENCY WINDOWING FOR ACOUSTIC FEM ANALYSIS

Model degrees-of-freedom reduction and frequency windowing via interpolation are combined for application to acoustic finite element analysis problems. Projection operators are employed for the model reduction or condensation process. Interpolation is then introduced over a user defined frequency window, which can have real and imaginary boundaries and be quite large. Hermitian interpolation functions (which require derivative information) as well as standard Lagrangian functions, which can be linear, quadratic or cubic, have been used to construct the windows. For one-dimensional windows, the location of interior evaluation points can be varied to increase accuracy. Results are excellent for example problems, even for large d.o.f. reduction and large frequency windows containing numerous resonances (eigenvalues). The reduced models within the windows appear to indicate accurately the location of the resonances.

音響ビルディングブロック法の開発とその適用 (第1報)

Due to compact and light-weight design, modern machines are strongly suffering from vibration and induced noise. In order to solve the noise problem, the structure of machine is so complex as to be accuractely modeled, therefore an Acoustic Building Block Approach (ABBA) is developed where the structure is divided into several components and the total acoustic characteristics of the machine in terms of natural frequencies and acoustic mode shapes can be predicted based on the individual acoustic characteristics of each component. Numerical models for pipe structure using acoustic Finite Element Analysis are used to verify the effectiveness of ABBA. Also the basic consideration on experimental methods is discussed to provide accurate measurement on acoustic characteristics of component.

Three-dimensional acoustic finite element analysis

Three-dimensional acoustic modeling is a novel application of finite element analysis (FEA) techniques and the successful use of FEA modeling towards the simulation of an empirically tested prototype assembly is described. The finite element analysis method is well known for its applications in structural design. The technique has attained widespread usage in numerous industries and it has enabled engineers to make structural design decisions long before the availability of test hardware or prototypes. The finite element methods, however, are not restricted to structural applications. In fact, this method provides a general approximation scheme, based upon the representation of a continuum by a finite number of interconnected elements. The method is applicable to numerous nonstructural problems and for many of these, the element properties have the same basic features as in the structural model. This paper describes the successful execution of finite element analysis techniques for three-dimensional acoustical analysis.

Acoustic Finite Element Analysis of Duct Boundaries

Acoustic Finite Element Analysis of Duct Boundaries