# Search Results

Sort by:

Text:
Affiliation:
Display:

### Results

Viewing 1 to 30 of 41
1989-11-01
Technical Paper
891248
Wonjib Choi, Rae-Woong Chang, Peter P. Gillis, Stanley E. Jones
A mathematical model is presented to help understand sheet metal deformation during forming. The particular purpose of this model is to predict the forming limit diagram (FLD). The present model is an extension of a previous analysis by Jones and Gillis (JG) in which the deformation is idealized into three phases: (I) homogeneous deformation up to maximum load; (II) deformation localization under constant load; (III) local necking with a precipitous drop in load. In phase III the neck geometry is described by a Bridgman type neck. The present model extends the JG theory which was applied to the right hand side of the FLD only. The main difference in treating the two different sides of the FLD lies in the assumptions regarding the width direction deformations. For biaxial stretching, the right hand side, the minor strain rate is assumed to be homogeneous throughout the process.
1985-11-11
Technical Paper
852222
Benjamin Soenarko, A. F. Seybert
An advanced computational method is presented for calculating the sound radiated by vibrating engine of arbitrary shape. The method is based on the numerical evaluation of the Helmholtz Integral Equation. In particular an isoparametric element formulation is introduced in which both the surface geometry and the acoustic variables on the surface of the vibrating body are represented by second order shape functions within the local coordinate system. The formulation includes the case where the surface may have a non-unique normal (e.g. at edges or corners). A general result for the surface and field velocity potential is derived. Test cases involving spherical geometry are given for a pulsating sphere and for an oscillating sphere in which the analytical solutions are known. Examples for bodies with edges and corners are shown for the problems of radiation from a circular cylinder and from a pulsating cube.
2011-05-17
Technical Paper
2011-01-1721
J. Liu, L. Zhou, D. W. Herrin
The principle of vibro-acoustic reciprocity is reviewed and applied to model sound radiation from a shaker excited structure. Transfer functions between sound pressure at a point in the far field and the velocity of a patch were determined reciprocally both for the to-scale structure and also for a half-scale model. A point monopole source was developed and utilized for the reciprocal measurements. In order to reduce the measurement effort, the boundary element method (BEM) was used to determine the reciprocal transfer functions as an alternative to measurement. Acceleration and sound intensity were measured on patches of the vibrating structure. Reciprocally measured or BEM generated transfer functions were then used to predict the sound pressure in the far field from the vibrating structure. The predicted sound pressure compared favorably with that measured.
2011-05-17
Technical Paper
2011-01-1720
L. Zhou, D. W. Herrin
Partial enclosures are a very common way to reduce noise emissions from machinery. However, partial enclosures exhibit complex acoustic behavior that is difficult to predict. The boundary element method (BEM) was used to model the airborne path of a partial enclosure. Simulation results were compared to measurement with good agreement. Special attention is given to the determination of negative insertion loss. It is demonstrated that the enclosure insertion loss will be negative at the Helmholtz frequencies for the enclosure.
2009-05-19
Technical Paper
2009-01-2041
J. Liu, D. W. Herrin
The source in an intake/exhaust system is commonly modeled as a source strength and impedance combination. Both the strength and impedance are normally measured and measurement accuracy depends on selecting an appropriate acoustic load combination. An incident wave decomposition method is proposed which is based on acoustic wave decomposition concepts instead of an electric circuit analogy providing a more straightforward approach to investigating the effect of acoustic load selection. Based on studying wave reflections in the system, the uncertainty for determining source impedance is estimated.
2011-05-17
Technical Paper
2011-01-1732
David Copley, D. W. Herrin, Harvind Raman, Jiantie Zhen
Properly characterizing input forces is an important part of simulating structure-borne noise problems. The purpose of this work was to apply a known force reconstruction technique to an earthmoving machinery cab to obtain input functions for modeling purposes. The technique was performed on a cab under controlled laboratory conditions to gain confidence in the method prior to use on actual machines. Forces were measured directly using force transducers and compared to results from the force reconstruction technique. The measured forces and vibrations were used as input power to an SEA model with favorable results.
2014-04-01
Journal Article
2014-01-0016
David W. Herrin, Xin Hua, Yitian Zhang, Tamer Elnady
In many industries, muffler and silencer design is primarily accomplished via trial and error. Prototypes are developed and tested, or numerical simulation (finite or boundary element analysis) is used to assess the performance. While these approaches reliably determine the transmission loss, designers often do not understand why their changes improve or degrade the muffler performance. Analyses are time consuming and models cannot be changed without some effort. The intent of the current work is to demonstrate how plane wave muffler models can be used in industry. It is first demonstrated that plane wave models can reliably determine the transmission loss for complicated mufflers below the cutoff frequency. Some tips for developing dependable plane wave models are summarized. Moreover, it is shown that plane wave models used correctly help designers develop intuition and a better understanding of the effect of their design changes.
2005-05-16
Technical Paper
2005-01-2497
F. Martinus, D. W. Herrin, Z. Tao, A. F. Seybert
This paper explores the use of inverse boundary element method to identify aeroacoustic noise sources. In the proposed approach, sound pressure at a few locations out of the flow field is measured, followed by the reconstruction of acoustic particle velocity on the surface where the noise is generated. Using this reconstructed acoustic particle velocity, the acoustic response anywhere in the field, including in the flow field, can be predicted. This approach is advantageous since only a small number of measurement points are needed and can be done outside of the flow field, and a relatively fast computational time. As an example, a prediction of vortex shedding noise from a circular cylinder is presented.
2005-05-16
Technical Paper
2005-01-2324
D. W. Herrin, F. Martinus, A. F. Seybert
Numerical acoustics has traditionally been relegated to a prediction only role. However, recent work has shown that numerical acoustics techniques can be used to diagnose noise problems. The starting point for these techniques is the acoustic transfer vector (ATV). First of all, ATV's can be used to conduct contribution analyses which can assess which parts of a machine are the predominant noise sources. As an example, the sound power contribution and radiation efficiency from parts of a running diesel engine are presented in this paper. Additionally, ATV's can be used to reliably reconstruct the vibration on a machine surface. This procedure, commonly called inverse numerical acoustics (INA), utilizes measured sound pressures along with ATV's to reconstruct the surface velocity. The procedure is demonstrated on an engine cover for which the reconstructed vibration had excellent agreement with experimental results.
2015-04-14
Technical Paper
2015-01-0737
Sadegh Poozesh, Nelson Akafuah, Kozo Saito
Abstract Lack of a precise control over paint droplets released from current coating sprayers has motivated this study to develop an atomizer capable of generating a uniform flow of mono-dispersed droplets. In the current study, a numerical investigation based on CFD incorporating volume of fluid (VOF) multiphase model has been developed to capture the interface between air and paint phases for a typical atomizer equipped with piezoelectric actuator. Effects of inlet flow rate and actuator frequency on ejected droplets' characteristics, droplet diameter and their successive spacing are studied in detail. It will be shown that for a determined flow rate of paint, there is an optimum actuator frequency in which droplet size is minimum. Besides, there exists a direct relationship between the inlet paint velocity and obtained optimal actuator frequency.
2009-05-19
Technical Paper
2009-01-2225
C. Jiang, T. W. Wu, D. W. Herrin
In this paper, the transmission loss (TL) of mufflers with a built-in catalytic converter (CC) and/or a diesel particulate filter (DPF) is predicted using the boundary element method (BEM) by either modeling the CC or DPF as a block of bulk-reacting material or by using the “element-to-element four-pole connection” between two BEM substructures. The four-pole parameters of the CC or DPF can be obtained by a measurement procedure that involves using the two-source method on a test rig with a pair of transition cones followed by a few 1-D four-pole matrix inverse operations to extract the parameters. A 3-D BEM based optimization may be further applied to fine-tune the extracted four-pole parameters. To use the bulk-reacting material modeling in BEM, the four-pole parameters will have to be converted into an equivalent set of bulk-reacting material properties. Test cases including a muffler with a series connection of CC and DPF are presented in this paper.
2013-04-08
Technical Paper
2013-01-0645
Johnson Joseph, Y Charles Lu
Carbon nanomaterials such as vertically aligned carbon nanotubes arrays are emerging new materials that have demonstrated superior mechanical, thermal, and electrical properties. The carbon nanomaterials have the huge potential for a wide range of vehicular applications, including lightweight and multifunctional composites, high-efficiency batteries and ultracapacitors, durable thermal coatings, etc. In order to design the carbon nanomaterials for various applications, it is very important to develop effective computational methods to model such materials and structures. The present work presents a structural mechanics approach to effectively model the mechanical behavior of vertically aligned carbon nanotube arrays. The carbon nanotube may be viewed as a geometrical space frame structure with primary bonds between any two neighboring atoms and thus can be modeled using three-dimensional beam elements.
2011-04-12
Journal Article
2011-01-0218
Johnson Joseph, S Raja, Y Charles Lu
Piezoelectric materials are smart materials that can undergo mechanical deformation when electrically or thermally activated. An electric voltage is generated on the surfaces when a piezoelectric material is subjected to a mechanical stress. This is referred to as the ‘direct effect’ and finds application as sensors. The external geometric form of this material changes when it is subjected to an applied voltage, known as ‘converse effect’ and has been employed in the actuator technology. Such piezoelectric actuators generate enormous forces and make highly precise movements that are extremely rapid, usually in the micrometer range. The current work is focused towards the realization and hence application of the actuator technology based on piezoelectric actuation. Finite element simulations are performed on different types of piezoelectric actuations to understand the working principle of various actuators.
2009-05-19
Journal Article
2009-01-2215
D. W. Herrin, J. Liu
Over 30 years ago, A. H. Vincent of Westland Helicopters demonstrated that if a structure is excited harmonically, the response at another position (at a fixed frequency) will trace a circle in the complex plane as a result of a dynamic stiffness modification between two points. As either the real or imaginary part of an introduced dynamic stiffness is varied from minus infinity to plus infinity, the structural or acoustic response on any position will map a circle in the complex plane. This paper reviews the basis for this little known principle for vibro-acoustics problems and illustrates the viability for a cantilevered plate example. The applicability of the method is then considered for strictly acoustic systems like intake and exhaust systems. Specifically, it is shown that the response traces a circle in the complex plane if either the real or imaginary parts of the source or termination impedance are varied from minus to plus infinity.
1997-05-20
Technical Paper
971955
Andrew F. Seybert, Tiemin Hu, David W. Herrin, Robert S. Ballinger
This paper is concerned with the prediction and experimental verification of the interior noise of cabs used on construction, highway, and farm equipment. The typical heavy equipment cab is totally enclosed and partially lined with absorbing materials but is much stiffer and more massive than automobile passenger compartments. The process to analyze a construction cab is explained in detail. Selected results are also presented to show the value of the method.
1997-05-20
Technical Paper
971954
A. F. Seybert, D. A. Hamilton, P. A. Hayes
This paper examines the feasibility of using the boundary element method (BEM) and the Rayleigh integral to assess the sound radiation from engine components such as oil pans. Two oil pans, one cast aluminum and the other stamped steel, are used in the study. All numerical results are compared to running engine data obtained for each of these oil pans on a Cummins engine. Measured running-engine surface velocity data are used as input to the BEM calculations. The BEM models of the oil pains are baffled in various ways to determine the feasibility of analyzing the sound radiated from the oil pan in isolation of the engine. Two baffling conditions are considered: an infinite baffle in which the edge of the oil pan are attached to an infinite, flat surface; and a closed baffle in which the edge of the oil pan is sealed with a rigid structure. It is shown that either of these methods gives satisfactory results when compared to experiment.
1992-10-01
Technical Paper
921943
C. B. Gil, G. S. Su, L. C. Chow, J. E. Beam
Experiments were performed to investigate the convective heat transfer from a two-dimensional slot jet of the dielectric liquid PAO to a smooth 15.2 mm by 9.5 mm film resistor surface. The effects of nozzle width, nozzle-to-plate distance, impinging velocity, and liquid properties have been examined. Heat transfer correlations and a discussion of relative parametric effects are provided.
1995-05-01
Technical Paper
951407
A. V. Radun, Y. Q. Xiang
Abstract - System modeling and simulation results for an experimental switched reluctance external integral starter/generator (EISG) are reported. The EISG system employs a single switched reluctance machine and a generating system architecture that produces two separate 270 Vdc buses from that single switched reluctance machine. The machine has six phases with three of the phases connected to one converter supplying 125 kW to one 270 Vdc bus while the other three phases are connected to a second converter supplying 125 kW to the other 270 Vdc bus. Each bus has its own EMI filter and control in addition to its own converter. Two separate system models have been developed for the EISG. One of these models has been denoted the averaged model and the other has been denoted the detailed model. Both models include the switched reluctance machine and power electronics, the EMI filter, and the feedback control. The development of both of these models is described.
2003-05-05
Technical Paper
2003-01-1456
F. Martinus, D. W. Herrin, A. F. Seybert
This paper explores the use of inverse numerical acoustics to reconstruct the surface vibration of a noise source. Inverse numerical acoustics is mainly used for source identification. This approach uses the measured sound pressure at a set of field points and the Helmholtz integral equation to reconstruct the normal surface velocity. The number of sound pressure measurements is considerably less than the number of surface vibration nodes. A brief guideline on choosing the number and location of the field points to provide an acceptable reproduction of the surface vibration is presented. The effect of adding a few measured velocities to improve the accuracy will also be discussed. Other practical considerations such as the shape of the field point mesh and effect of experimental errors on reconstruction accuracy will be presented. Examples will include a diesel engine and a transmission housing.
2007-09-17
Technical Paper
2007-01-3911
Jamey D. Jacob, Suzanne W. Smith, Dave Cadogan, Steve Scarborough
The paper presents work on development, testing and vehicle integration of inflatable wings for small UAVs. Recent advances in the design of inflatable lifting surfaces have removed previous deterrents to their use and multiple wing designs have been successfully flight tested on UAVs. Primary benefits of inflatable wings include stowability (deploy upon command) and robustness (highly resistant to damage). The inflatable planforms can be either full- or partial-span designs allowing a large design space and mission adaptability. The wings can be stowed when not in use and inflated prior to or during flight. Since inflatable designs have improved survivability over rigid wings, this has the prospect of increasing vehicle robustness and combat survivability. Damage resistance of inflatable wings is shown from results of laboratory and flight tests.
2007-05-15
Technical Paper
2007-01-2417
Y. Charles Lu, Michael E. Anderson, David A. Nash
Finite element modeling has been used extensively nowadays for predicting the noise and vibration performance of whole engines or subsystems. However, the elastomeric components on the engines or subsystems are often omitted in the FE models due to some known difficulties. One of these is the lack of the material properties at higher frequencies. The elastomer is known to have frequency-dependent viscoelasticity, i.e., the dynamic modulus increases monotonically with frequency and the damping exhibits a peak. These properties can be easily measured using conventional dynamic mechanical experiments but only in the lower range of frequencies. The present paper describes a method for characterizing the viscoelastic properties at higher frequencies using fractional calculus. The viscoelastic constitutive equations based on fractional derivatives are discussed. The method is then used to predict the high frequency properties of an elastomer.
2007-05-15
Technical Paper
2007-01-2285
Y. Charles Lu
Engine exterior cover seals are typically made of elastomeric materials and used to seal the interfaces. The design of engine/transmission seals has been traditionally considered from the sealibility aspects. Recently, there have been additional demands that these seals be designed to reduce the vibration transmitted from engine/transmission and to attenuate the radiated noise. To accomplish this goal, the frequency-dependent viscoelastic properties of the seals will have to be considered. This article examines the frequency-dependent viscoelastic properties of some common elastomeric seals. The impacts of these materials on an engine valve cover noise and vibration are particularly investigated. Some design strategies are also discussed to optimize the viscoelastic effects of the elastomeric seals.
2007-05-15
Technical Paper
2007-01-2196
J. Liu, D. W. Herrin, A. F. Seybert
The sound attenuation performance of microperforated panels (MPP) with adjoining air cavity is demonstrated. First of all, simulated results are shown based upon Maa's work investigating the parameters which impact MPP performance [1]. It is shown that the most important parameter is the depth of the adjoining cavity. Following this, an experimental study was undertaken to compare the performance of an MPP to that of standard foam. Following this, two strategies to improve the MPP performance are implemented. These include partitioning the air cavity and having a cavity with varying depth. Both strategies show a marked improvement in MPP attenuation.
2007-05-15
Technical Paper
2007-01-2224
J. Han, D. W. Herrin, A. F. Seybert
In this paper procedures for estimating the sound absorption coefficient when the specimen has inherently low absorption are discussed. Examples of this include the measurement of the absorption coefficient of pavements, closed cell foams and other barrier materials whose absorption coefficient is nevertheless required, and the measurement of sound absorption of muffler components such as perforates. The focus of the paper is on (1) obtaining an accurate phase correction and (2) proper correction for tube attenuation when using impedance tube methods. For the latter it is shown that the equations for tube attenuation correction in the standards underestimate the actual tube attenuation, leading to an overestimate of the measured absorption coefficient. This error could be critical, for example, when one is attempting to qualify a facility for the measurement of pass-by noise.
2007-05-15
Technical Paper
2007-01-2180
D. W. Herrin, J. Han, F. Martinus, J. Shi
This paper documents an inverse visible element Rayleigh integral (VERI) approach. The VERI is a fast though approximate method for predicting sound radiation that can be used in the place of the boundary element method. This paper extends the method by applying it to the inverse problem where the VERI is used to generate the acoustic transfer matrix relating the velocity on the surface to measurement points. Given measured pressures, the inverse VERI can be used to reconstruct the vibration of a radiating surface. Results from an engine cover and diesel engine indicate that the method can be used to reliably quantify the sound power and also approximate directivity.
2016-04-05
Technical Paper
2016-01-1301
Shishuo Sun, David W. Herrin, John Baker
Abstract One of the more useful metrics to characterize the high frequency performance of an isolator is insertion loss. Insertion loss is defined as the difference in transmitted vibration in decibels between the non-isolated and isolated cases. Insertion loss takes into account the compliance on the source and receiver sides. Accordingly, it has some advantages over transmissibility especially at higher frequencies. In the current work, the transfer matrix of a spring isolator is determined using finite element simulation. A static analysis is performed first to preload the isolator so that stress stiffening is accounted for. This is followed by modal and forced response analyses to identify the transfer matrix of the isolator. In this paper, the insertion loss of spring isolators is examined as a function of several geometric parameters including the spring diameter, wire diameter, and number of active coils.
1965-02-01
Technical Paper
650515
David K. Blythe, John A. Dearinger, Russell E. Puckett
This paper presents an analysis of axle weight data collected during the performance testing of the Broken Bridge dynamic electronic highway scale. Test results are analyzed by comparing the in-motion axle weights as measured by the Broken Bridge scale with the corresponding static values for an instrumented two-axle test vehicle and for a sample of trucks diverted from an Interstate highway. Analysis of the two-axle test truck data shows that the actual loads applied to the highway surface by the wheels of a moving vehicle vary above and below the static equivalents in a manner that is typical for a specific location and range of speeds. For a random selection of different types of trucks, the variation of dynamic from static axle weight is further affected by axle position (front, second, third, and so forth) and spacing.
2005-05-16
Technical Paper
2005-01-2282
Z. Tao, B. Zhang, D. W. Herrin, A. F. Seybert
Micro-perforated panels have tiny pores which attenuate sound based on the Helmholtz resonance principle. That being the case, an appropriate cavity depth should be chosen to fully capitalize on the attenuation potential of the panel. Generally, the panel's sound absorbing performance can be predicted by Maa's theory given information about the panel and the cavity depth. However, in some cases, one cannot use the theory to predict the panel's performance precisely, especially when the micro-perforate has varying diameters and/or irregular hole shapes. In these cases, the sound-absorbing performance of the micro-perforate is different from that of a uniform pore diameter perforate. This paper presents an alternative method to predict the micro-perforated panel's performance precisely. As a first step, the transfer impedance of the micro-perforate should be measured.
2017-06-05
Journal Article
2017-01-1876
Weiyun Liu, David W. Herrin, Emanuele Bianchini
Abstract Microperforated panel absorbers are best considered as the combination of the perforate and the backing cavity. They are sometimes likened to Helmholtz resonators. This analogy is true in the sense that they are most effective at the resonant frequencies of the panel-cavity combination when the particle velocity is high in the perforations. However, unlike traditional Helmholtz resonators, microperforated absorbers are broader band and the attenuation mechanism is dissipative rather than reactive. It is well known that the cavity depth governs the frequency bands of high absorption. The work presented here focuses on the development, modeling and testing of novel configurations of backing constructions and materials. These configurations are aimed at both dialing in the absorption properties at specific frequencies of interest and creating broadband sound absorbers. In this work, several backing cavity strategies are considered and evaluated.
2017-06-05
Technical Paper
2017-01-1884
Ruimeng Wu, David W. Herrin
Abstract Sound absorbing materials are commonly compressed when installed in passenger compartments or underhood applications altering the sound absorption performance of the material. However, most prior work has focused on uncompressed materials and only a few models based on poroelastic properties are available for compressed materials. Empirical models based on flow resistivity are commonly used to characterize the complex wavenumber and characteristic impedance of uncompressed sound absorbing materials from which the sound absorption can be determined. In this work, the sound absorption is measured for both uncompressed and compressed samples of fiber and foam, and the flow resistivity is curve fit using an appropriate empirical model. Following this, the flow resistivity of the material is determined as a function of the compression ratio.
Viewing 1 to 30 of 41