Open Access. Powered by Scholars. Published by Universities.®

Mechanical Engineering Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 30 of 186

Full-Text Articles in Mechanical Engineering

Scattering Of A Sagittal Surface Acoustic Wave From A Large Amplitude Ridge Or A Deep Groove, A. Baghai-Wadji, A. A. Maradudin Jan 1993

Scattering Of A Sagittal Surface Acoustic Wave From A Large Amplitude Ridge Or A Deep Groove, A. Baghai-Wadji, A. A. Maradudin

Review of Progress in Quantitative Nondestructive Evaluation

In [1] we presented a Green’s function theory for obtaining the frequencies of acoustic surface shape resonances of sagittal polarization associated with an isolated ridge or groove of rather general shape on a planar, stress-free surface of an isotropic elastic medium (for details we refer to [2]). It was shown that employing Green’s second theorem, and using tensor Green’s functions associated with the boundary value problem, the initial coupled partial differential equations can be converted into a coupled system of integral equations. Further, it was shown that by discretizing the boundary and using the method of moments ...


Interaction Of Gaussian Acoustic Beams With Plane And Cylindrical Fluid-Loaded Elastic Structures, Jinguang Zhang, Dale E. Chimenti, Smaine Zeroug, Leopold B. Felsen Jan 1993

Interaction Of Gaussian Acoustic Beams With Plane And Cylindrical Fluid-Loaded Elastic Structures, Jinguang Zhang, Dale E. Chimenti, Smaine Zeroug, Leopold B. Felsen

Review of Progress in Quantitative Nondestructive Evaluation

Nonspecular reflection effects for ultrasonic beams incident from a fluid onto solid surfaces have been studied continuously since the early investigations by Schoch [1]. He calculated the reflected held for both the fluid-loaded halfspace and the plate using a series expansion for the phase of the reflection coefficient. A more accurate expression for Gaussian beam reflection has been derived by Bertoni and Tamir [2], who approximated the reflection coefficient by leading terms in a Laurent series, performing the resulting integrals analytically. Many researchers have contributed to this literature from the experimental [3–5], theoretical [6,7], and numerical sides [8 ...


Acoustic Emissions From Pressurized Microballoons, G. Hawkins, James R. Lhota, J. R. Hribar, E. C. Johnson Jan 1993

Acoustic Emissions From Pressurized Microballoons, G. Hawkins, James R. Lhota, J. R. Hribar, E. C. Johnson

Review of Progress in Quantitative Nondestructive Evaluation

Microballoons are tiny, hollow, thin-walled, glass spheres ranging in diameter from ~ 1 to 160 μm. They are commercially available in bulk for use as low cost, lightweight filler to be mixed with resins and other materials. As reported last year, the unique properties of microballoons have been exploited in a number of instances for recording the maximum of a pressure excursion [1]. To understand the technique, consider first what happens when microballoons are mixed in a carrier fluid, placed on the surface of an Acoustic Emission (AE) transducer and then subjected to a pneumatic pressure. Since the microballoons within a ...


Laser Generation Of Rayleigh And Lamb Waves For Ultrasonic Nondestructive Testing, R. Costley Jr., Yves H. Berthelot Jan 1993

Laser Generation Of Rayleigh And Lamb Waves For Ultrasonic Nondestructive Testing, R. Costley Jr., Yves H. Berthelot

Review of Progress in Quantitative Nondestructive Evaluation

Laser ultrasonics has been the focus of several research efforts over the last two decades. The main advantage of the technique is its noncontact nature which alleviates the problem of sensor coupling inherent in conventional techniques. However, laser ultrasonics has some limitations When operated in the thermoelastic regime, where no damage is inflicted on the surface of the specimen, the signal-to-noise ratio (SNR) is very small, particularly when compared with conventional piezoelectric generation.[1] Several authors have proposed increasing the SNR by producing a source with spatial periodicity designed to enhance a particular wavelength. Royer and Dieulasaint [2] have used ...


Laser Ultrasonic And Photoacoustic Characterization Of Subsurface Structures, Meng-Chou Wu, F. Raymond Parker, William P. Winfree Jan 1993

Laser Ultrasonic And Photoacoustic Characterization Of Subsurface Structures, Meng-Chou Wu, F. Raymond Parker, William P. Winfree

Review of Progress in Quantitative Nondestructive Evaluation

There is a strong interest in applying laser ultrasonic and photoacoustic techniques to the NDE of some high performance structures, for example, the actively cooled panels of the National Aero-Space Plane. Both laser ultrasonic and photoacoustic techniques have been developed for years. Much significant work has been done on either the generation of waves, the mechanisms [1–3] or various techniques for the detection of these waves [4–6]. A few applications being pursued or conducted since the early stage of the development for these techniques [5–7]. However, there is little work concentrating on the interaction of these waves ...


An Application Of Object-Oriented Technology To Unified Life Cycle Engineering, Samuel Wormley, H. Shah, D. Sheth, B. Forouraghi, Lester W. Schmerr Jan 1993

An Application Of Object-Oriented Technology To Unified Life Cycle Engineering, Samuel Wormley, H. Shah, D. Sheth, B. Forouraghi, Lester W. Schmerr

Review of Progress in Quantitative Nondestructive Evaluation

The Center for Nondestructive Evaluation (CNDE) at Iowa State University and in conjunction with Northwestern University is involved in continued development of an integrated system that assesses the inspectability and reliability of manufactured parts from a description of their geometry, materials, expected loads, and performance requirements. The main objective of this program, Integrated Design, NDE, and the Manufacturing Sciences, is to combine a variety of rapidly emerging disciplines associated with structural integrity with established techniques of computer-aided design (CAD) and computer-aided manufacturing (CAM). The contributing disciplines include quantitative nondestructive evaluation, statistical modeling for quality assurance, process control, fracture mechanics and ...


Custom Pvdf Transducers For Pulse-Echo Testing Of Solid Rocket Motors For Detection Of Propellant-To-Boot-Liner Unbonds, Lewis Brown, William M. Sisson, Christopher P. Guerin Jan 1993

Custom Pvdf Transducers For Pulse-Echo Testing Of Solid Rocket Motors For Detection Of Propellant-To-Boot-Liner Unbonds, Lewis Brown, William M. Sisson, Christopher P. Guerin

Review of Progress in Quantitative Nondestructive Evaluation

Solid rocket motor segments (SRMs) typically consist of a rigid cylindrical shell, an elastomeric insulation liner, and a core of solid propellant. A rubber boot-liner is often included to relieve stresses between the propellant and insulation liner, produced near the ends of the SRM during the cure of the solid propellant. In the manufacture of the SRM, good bond integrity is required between the boot liner and propellant to prevent detrimental effects on motor performance, thus, a reliable NDE technique is required to detect possible unbond regions. One SRM manufacturer’s approach was a radiographic method consisting of analyzing overlapping ...


Ultrasonic Propagation Through A Surface With A Step Discontinuity: Validation Of A Hybrid, Gauss-Hermite Ray Tracing Beam Model, M. Greenwood, J.-L. Mai, A. Minachi, I. Yalda-Mooshabad, R. Bruce Thompson Jan 1993

Ultrasonic Propagation Through A Surface With A Step Discontinuity: Validation Of A Hybrid, Gauss-Hermite Ray Tracing Beam Model, M. Greenwood, J.-L. Mai, A. Minachi, I. Yalda-Mooshabad, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

This research continues our cooperative effort to study the effects of large-scale surface roughness on ultrasonic transmission through interfaces and updates our previously-reported results [1], The Center for Nondestructive Evaluation has developed a model for the propagation of ultrasound through a surface and into an isotropic metal and this model is undergoing experimental validation at Battelle PNL. Once validated, this model will be used as an engineering tool to study the effects of surface conditions upon an ultrasonic inspection of nuclear reactor components. The goal is to quantify and develop requirements to limit the adverse effects of surface conditions during ...


Fundamentals Of Manufacturing Excellence, J. Heim Jan 1993

Fundamentals Of Manufacturing Excellence, J. Heim

Review of Progress in Quantitative Nondestructive Evaluation

Manufacturing excellence, world-class stature, being the best of the best—the ability to provide high quality, competitively priced products and services in a global marketplace—is a major hurdle confronting manufacturers. The challenges they face are well known: the need to improve product quality, drastically shorten product development cycles, increase productivity growth, stimulate product and process innovation, and respond quickly to changing customer demands. Many U.S. manufacturers, however, are woefully unaware of the widening performance gap between them and their competitors, insufficiently cognizant of their customers’ needs, and naively preoccupied with near term achievements of their firm, while neglecting ...


National Issues In Technology Transfer, J. David Roessner Jan 1993

National Issues In Technology Transfer, J. David Roessner

Review of Progress in Quantitative Nondestructive Evaluation

A well-accepted definition of technology transfer is “the movement of know how, technique, and technology across organizational boundaries.” If you accept this definition, then what is interesting about it is that nobody knows how to do it very well… as a nation, that is. Different nations do different pieces of it better than others. You find the Japanese running around looking at us to see how to do technology transfers from universities to industry, which they do badly. We run around looking at the Japanese to find out how to transfer technology from corporate R&D to manufacturing. And the ...


Numerical Calculation Of Diffraction Coefficients In Anisotropic Media, J. Temple, L. White Jan 1993

Numerical Calculation Of Diffraction Coefficients In Anisotropic Media, J. Temple, L. White

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic inspection is used to detect and size crack-like defects in pressure vessels and pipework used in the nuclear industry. Reliable inspection can only be achieved if the inspection technique is understood, is optimised and subsequently applied correctly. Austenitic steels are used because of their corrosion resistance and toughness. Welds and centrifugally cast materials tend to crystallise with grains larger than the ultrasonic wavelength required to achieve the desired resolution in the inspection and thus appear anisotropic. Since the grains in a weld grow along the, varying, directions of maximum heat flux during cooling, the welds are inhomogeneous as well ...


Ultrasonic Scattering From Spherically Orthotropic Shells, John Mittleman, Ron Roberts, R. Bruce Thompson Jan 1993

Ultrasonic Scattering From Spherically Orthotropic Shells, John Mittleman, Ron Roberts, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

Concerns over the detectability of embrittlement in high strength alloys has led to studying a simple anisotropic shell model [1] for grain boundaries decorated by precipitates, or otherwise enriched by segregated inhomogenieties. In this model the shell is presumed to be “spherically orthotropic,” having five independent elastic constants and symmetry about the origin of a spherical coordinate system. This structure is analogous to transversely isotropic materials in a Cartesian coordinate system. By studying ultrasonic scattering from such shells (embedded in an isotropic host, and surrounding an isotropic core), we hope to learn whether their presence could be detected, and differentiated ...


2-D Elastodynamic Scattering From A Finite Closed Crack, Gert Persson Jan 1993

2-D Elastodynamic Scattering From A Finite Closed Crack, Gert Persson

Review of Progress in Quantitative Nondestructive Evaluation

In the present paper the problem of 2-D elastodynamic scattering of horizontally polarized transverse waves from a finite planar or nonplanar closed crack is studied. The boundary conditions on the flaw are of a type which incorporate restoring forces (as well as energy dissipation), and this enables the modelling of a crack which is partly closed under a static background pressure. Given an incident plane wave and the crack geometry we calculate the backscattered far field in the time-harmonic case. In this study there are also a numerical comparison between two well known theoretical methods for 2-D scattering of ultrasonic ...


The T Matrix For Elastic Scattering By A Partly Closed Circular Crack, Arne Eriksson Jan 1993

The T Matrix For Elastic Scattering By A Partly Closed Circular Crack, Arne Eriksson

Review of Progress in Quantitative Nondestructive Evaluation

The object of this work is to calculate the T (transition) matrix for a circular crack in a homogeneous, isotropic, linear elastic medium. The T matrix method is a building block technique for multiple scattering, where the T matrix is calculated for each scatterer separately without prior knowledge of the other scatterers (cracks, inclusions, surfaces, etc.).This means that we solve the scattering problem for arbitrary incoming time harmonic elastic waves. A solution for the scattering by an open circular crack can be found in [1], and for multiple scattering see [2]. On the crack surface the so called spring ...


A Theoretical Approach For The Discrimination Of Crack Tip And Small Defect Echoes, Alain Lhemery, Raphaele Raillon, Mourad Ouamer Jan 1993

A Theoretical Approach For The Discrimination Of Crack Tip And Small Defect Echoes, Alain Lhemery, Raphaele Raillon, Mourad Ouamer

Review of Progress in Quantitative Nondestructive Evaluation

Due to diffraction of US by crack tips, a misinterpretation of C-Scans can be made by mistaking detection of a large misoriented crack for a small flaw. As the latter is often tolerable, the former jeopardizes the life of the piece. Fig. 1. shows C-Scans at various amplification levels. The two spots due to diffraction by the near and far tips of a crack can be interpreted as arising from two small defects, even at high amplification level (+18 dB) for which S/N ratio becomes unacceptable.


Ultrasonic Scattering From A Crack Which Emanates From A Rivet Hole, David Budreck Jan 1993

Ultrasonic Scattering From A Crack Which Emanates From A Rivet Hole, David Budreck

Review of Progress in Quantitative Nondestructive Evaluation

In this article we present the exact solution, to first order of the interacting field, of the following canonical problem. We consider the scattering system consisting of an isotropic elastic medium containing an infinite cylindrical void (= hole), from which emanates a half-penny-shaped crack. The crack lies in a plane containing the axis of the cylindrical void, also the crack intersects the void at its own axis of symmetry. In the paragraph below we define what is meant by obtaining the solution ‘to first order’.


Reflection Of Elastic Waves By An Array Of Interface Cracks, Jianmin Qu Jan 1993

Reflection Of Elastic Waves By An Array Of Interface Cracks, Jianmin Qu

Review of Progress in Quantitative Nondestructive Evaluation

An imperfect diffusion bond between two dissimilar materials may be modeled by an interface with an array of interface cracks. The analytical treatment of the reflection and transmission of elastic waves by an array of interface cracks provides the prerequisite for nondestructive characterization of the diffusion bond by ultrasonic techniques. This paper is to develop approximate solutions for the reflection and transmission coefficients from an array of interface cracks.


Scattering By An Infinite Array Of Randomly Spaced Coplanar Cracks, Yozo Mikata Jan 1993

Scattering By An Infinite Array Of Randomly Spaced Coplanar Cracks, Yozo Mikata

Review of Progress in Quantitative Nondestructive Evaluation

In this paper, the investigation is carried out for the scattering of an anti-plane shear (SH) wave by an infinite array of randomly spaced coplanar cracks. This study was motivated by the desire to better understand the detection and characterization of a flaw plane, i.e., a plane of microcracks, in a more realistic situation. The first thing we can do to model a flaw plane is to model it as a periodic array of cracks [1–5]. In reality, however, an array of cracks is never periodic but rather random. Thus in a previous paper [6], we have treated ...


Acoustic Ray Tracing With The Connection Machine, C. Sullivan, Y. Wang, R. A. Kline, R. B. Mignogna, R. S. Schechter, P. P. Delsanto, L. Ferrero Jan 1993

Acoustic Ray Tracing With The Connection Machine, C. Sullivan, Y. Wang, R. A. Kline, R. B. Mignogna, R. S. Schechter, P. P. Delsanto, L. Ferrero

Review of Progress in Quantitative Nondestructive Evaluation

Acoustic rays do not travel in straight raypaths in nonhomogeneous media. This causes difficulty in tomographic image reconstruction. A method for acoustic ray tracing in nonhomogeneous media has been developed using the parallel processing capabilities of the Connection Machine. This method of ray tracing is intended to facilitate a parallel processing approach to tomographic image reconstruction.


Ultrasonic Field Patterns And Broadband Imaging-Simulations In Transversely Isotropic Media, M. Spies, P. Fellinger, U. Schleichert, K. J. Langenberg Jan 1993

Ultrasonic Field Patterns And Broadband Imaging-Simulations In Transversely Isotropic Media, M. Spies, P. Fellinger, U. Schleichert, K. J. Langenberg

Review of Progress in Quantitative Nondestructive Evaluation

Thorough application of NDE — and imaging techniques in anisotropic media has to overcome those inherent problems like beam splitting, beam distortion and deviation between wave propagation direction and energy flow, known as beam skewing. A theory of elastic wave propagation in transversely isotropic media which properly accounts for these effects has been presented previously [1], an overview has been presented at last year’s conference [2]. Analytic expressions have been derived characterizing the propagation of Gaussian Wave Packets (GWPs) in these media thus making possible the simulation of real pulse propagation. In order to provide information from a practical point ...


An Efficient Fem Approach For The Study Of Ultrasonic Wave Propagation In Solids, John Sullivan Jr., R. Ludwig, W. J. Grimes Jan 1993

An Efficient Fem Approach For The Study Of Ultrasonic Wave Propagation In Solids, John Sullivan Jr., R. Ludwig, W. J. Grimes

Review of Progress in Quantitative Nondestructive Evaluation

The need for the numerical analysis of the elastic wave equation in solids is driven by the application of ultrasonic techniques to non-destructive evaluation of adhesive bonds and bondlines. Unfortunately, the physics of the problem require numerical models with an excessive number of degrees of freedom and time steps to analyze the response of a system to an ultrasonic pulse input. In the past, super computers and vector processors were used to tackle these problems. Alternately, purely closed form solutions were investigated with idealized boundary conditions. This work presents plane strain and axisymmetric finite element formulations which include viscous damping ...


Improved Finite Difference Method For Long Distance Propagation Of Waves, Doron Kishoni, Shlomo Ta'asan Jan 1993

Improved Finite Difference Method For Long Distance Propagation Of Waves, Doron Kishoni, Shlomo Ta'asan

Review of Progress in Quantitative Nondestructive Evaluation

Evaluation of aging aircraft involves inspection of large areas of plates, including lap joints, bonded material and other complex geometries. These inspections need to be done within a reasonable time in order to be economical. Ultrasonic measurements of plate-modes propagating for large distances [1] are a promising method for fast detection of these defects in a commercial environment. There is a need to predict the waveforms of such waves in order to analyze the results of the experimental data. Analytic solution cannot always be found for general cases, therefore, numerical prediction of elastic wave propagation for long distances is desired ...


High Accuracy Method Of Measuring Travelling Time Of Ultrasonic Waves, A. Khedher, B. De Halleux Jan 1993

High Accuracy Method Of Measuring Travelling Time Of Ultrasonic Waves, A. Khedher, B. De Halleux

Review of Progress in Quantitative Nondestructive Evaluation

In this paper we consider a method of measuring travelling time of ultrasonic waves with high accuracy. The block diagram of this method is shown in figure 1.


Phase Velocity And Attenuation Of Sh Waves In A Fiber-Reinforced Composite, Ruey-Bin Yang, Ajit K. Mal Jan 1993

Phase Velocity And Attenuation Of Sh Waves In A Fiber-Reinforced Composite, Ruey-Bin Yang, Ajit K. Mal

Review of Progress in Quantitative Nondestructive Evaluation

We consider SH wave propagation in a fiber-reinforced composite which consists of a homogeneous, isotropic matrix, containing long, parallel, randomly distributed circular fibers of identical properties. The scattering of waves in the elastically inhomogeneous medium results in a frequency dependent velocity and attenuation of the coherent wave.


Ultrasonic Oblique Incidence In Anisotropic Media, Xiang Zhao, Davis M. Egle Jan 1993

Ultrasonic Oblique Incidence In Anisotropic Media, Xiang Zhao, Davis M. Egle

Review of Progress in Quantitative Nondestructive Evaluation

Determining the elastic moduli of anisotropic materials via non-destructive testing techniques is one of the most difficult subjects of acoustoelasticity theory today. The major difficulty comes from the fact that the elastic waves propagating in anisotropic media have different phase and group velocities in both magnitude and direction, which was considered to greatly complicate the analysis of the problem. Therefore, previous work in this area has been restricted to either measurements conducted only in symmetry planes, as mentioned in [1,2], or the slight anisotropy case in which the ultrasonic measurement was approximately related to the phase velocity, such as ...


Guided Waves In Piezoelectric Plates, Hual-Te Chien, Adnan H. Nayfeh, Che-Hua Yang, Dale E. Chimenti Jan 1993

Guided Waves In Piezoelectric Plates, Hual-Te Chien, Adnan H. Nayfeh, Che-Hua Yang, Dale E. Chimenti

Review of Progress in Quantitative Nondestructive Evaluation

In recent paper [1] Nayfeh and Chimenti presented the analysis of the propagation of free waves in a general anisotropic plate. Closed form secular equations which isolate the mathematical conditions for symmetric and antisymmetric wave mode propagation in completely separate terms were obtained. By paralleling the procedure of Nayfeh and Chimenti [1], Nayfeh and Chien [2] presented exact solutions for the interaction of elastic waves with fluid-loaded piezoelectric plates. The technique used was shown to formally handle the most general anisotropy (i.e. the triclinic) case. The plate was immersed in liquid and incident waves impinged upon it from the ...


Interaction Of Ultrasound With Imperfectly Contacting Interfaces, R. Bruce Thompson Jan 1993

Interaction Of Ultrasound With Imperfectly Contacting Interfaces, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

The need to characterize imperfectly contacting interfaces is encountered in a wide variety of scientific and engineering problems, as illustrated in Fig. 1. Parts (a)–(c) illustrate the stages of diffusion bonding, [1,2] in which the condition of the interface evolves from one of isolated contacts at the initial stages of bonding through one containing distributed micropores, which exist during intermediate stages, to a state in which the material is fully bonded but in which there may be some near-interface microstructural variations. The ability to determine the degree to which bonding has passed through these conditions is presently needed ...


Visualization Of Displacement Fields Generated By Axisymmetric Sources On An Elastic Half-Space, F. Stulen, D. B. Pape, L. J. House Jan 1993

Visualization Of Displacement Fields Generated By Axisymmetric Sources On An Elastic Half-Space, F. Stulen, D. B. Pape, L. J. House

Review of Progress in Quantitative Nondestructive Evaluation

Different analytical methods have been used to study the waves generated by transient sources of finite extent. Methods have included: high-frequency approximations, Fourier superposition, linear superposition of the fields from elementary sources, and finite difference and finite element methods. Bresse and Hutchins [1] reported an exact analytical solution to an axisymmetric source on an elastic half-space, which is more numerically efficient compared with the previous methods.


Quantitative Thickness Measurements Of Ice Layers With Remote Ir Detection, D. Heath, William P. Winfree Jan 1993

Quantitative Thickness Measurements Of Ice Layers With Remote Ir Detection, D. Heath, William P. Winfree

Review of Progress in Quantitative Nondestructive Evaluation

Accretion of ice on aerospace structures is a problem affecting take-off safety and aerodynamic performance. The problem is of concern for commercial and military aircraft, on the runway and in flight, when adverse weather conditions allow ice formation to occur. Ice accretion also occurs on aerospace structures when cryogenic fuels are used, if defects in insulators allow cold spots to develop. In particular, ice formation on the space shuttle external tank can result in structural damage during launching if ice of appreciable mass detaches and impacts the orbiter surface.


Capactitance Imaging System For Monitoring Bubble Formation And Flow In Fluid Bed Simulators, Dave Paton, G. Edward Fasching, Nelson S. Smith Jr. Jan 1993

Capactitance Imaging System For Monitoring Bubble Formation And Flow In Fluid Bed Simulators, Dave Paton, G. Edward Fasching, Nelson S. Smith Jr.

Review of Progress in Quantitative Nondestructive Evaluation

The U. S. Department of Energy’s Morgantown Energy Technology Center (METC) has developed a multi-level capacitance imaging system (CIS) for imaging flow patterns in its fluidized-bed research program. The CIS measures displacement current across a cold fluidized bed and provides researchers with a 3-Dimensional realtime display of bed density estimates while simultaneously recording data for post-run analysis. The CIS has evolved from a single level, 16-electrode, 49-pixel system to the present four-level, 32-electrode, 193-pixel system.