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Full-Text Articles in Mechanical Engineering

Variable Structure End Point Control Of A Flexible Manipulator, Shailaja Chenumalla, Sahjendra N. Singh Jul 1993

Variable Structure End Point Control Of A Flexible Manipulator, Shailaja Chenumalla, Sahjendra N. Singh

Electrical and Computer Engineering Faculty Publications

We treat the question of control and stabilization of the elastic multibody system developed in the Phillips Laboratory, Edwards Air Force Base, California. The controlled output is judiciously chosen such that the zero dynamics are stable or almost stable. A variable structure control (VSC) law is derived for the end point trajectory control. Although, the VSC law accomplishes precise end point tracking, elastic modes are excited during the maneuver of the arm. A Linear stabilizer is designed for the final capture of the terminal state.


Numerical Algorithms For Squaring-Up Non-Square Systems Part Ii: General Case, Pradeep Misra May 1993

Numerical Algorithms For Squaring-Up Non-Square Systems Part Ii: General Case, Pradeep Misra

Pradeep Misra

In this paper, we present numerical algorithms for
squaring a non-square system by finding -additional
columns in input matrix (for tall systems) and by
finding additional rows in output matrix (for wide systems).
Several case are considered depending up the
requirements on the ra of the input-output interaction
matrix.


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 ...


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 ...


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.


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 ...


Photothermal Measurement Of Metal Film Thickness In Integrated Circuit Devices, Xioa-Dung Wu, Gordon S. Kino Jan 1993

Photothermal Measurement Of Metal Film Thickness In Integrated Circuit Devices, Xioa-Dung Wu, Gordon S. Kino

Review of Progress in Quantitative Nondestructive Evaluation

Metal films have been used extensively in very-large-scale integration (VLSI) devices. They are used to build interconnects, field-effect transistor gates, diffusion barriers, and conduction pads for input or output leads. Metals such as aluminum, tungsten, titanium and platinum are deposited on an insulating layer [1,2]. The metal film thicknesses range from 100 Å to 1 µm. Due to the ever-growing need for high speed, high density, and low power dissipation in integrated circuit (IC) technology, accurate control of the metallization process becomes essential to ensure the quality and yield of the final product. One of the important parameters in ...


Progress Towards The Application Of Laser-Ultrasonics In Industry, Jean-Pierre Monchalin Jan 1993

Progress Towards The Application Of Laser-Ultrasonics In Industry, Jean-Pierre Monchalin

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic techniques are widely used in industry for thickness gauging, flaw detection and materials characterization. The ultrasonic waves are usually generated and detected by piezoelectric transducers and coupled to the inspected part either by direct contact or through a water bath or a water jet. Although widespread and generally cost effective, these conventional ultrasonic techniques suffer from essentially two severe limitations, which impact upon their use for on-line process control and the inspection of advanced materials.


Reception Of Laser Generated Ultrasound From A Cfrp Plate By An Air Matched Piezoelectric Composite Transducer, L. Scudder, D. A. Hutchins, G. Hayward Jan 1993

Reception Of Laser Generated Ultrasound From A Cfrp Plate By An Air Matched Piezoelectric Composite Transducer, L. Scudder, D. A. Hutchins, G. Hayward

Review of Progress in Quantitative Nondestructive Evaluation

Laser generated ultrasound is being investigated [1,2] for testing structures made of both conventional metals and carbon fibre reinforced polymer (CFRP). Laser interferometers are widely used in such work to detect the normal surface motion caused by ultrasonic pulses. Interferometers offer non-contact, remote and high-fidelity detection, together with a potential to cover large areas rapidly by optical scanning. However their cost is high and only in testing large and/or expensive structures may the cost be justified. A lower cost alternative, but with some compromise on the virtues of an interferometer, would be to use an air transducer as ...


Robust Signal Processing For Material Noise Suppression In Ultrasonic Nondestructive Testing, Lars Ericsson, Tadeusz Stepinski Jan 1993

Robust Signal Processing For Material Noise Suppression In Ultrasonic Nondestructive Testing, Lars Ericsson, Tadeusz Stepinski

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic nondestructive inspection of materials is often limited by the presence of backscattered echoes from the material structure, known as material or grain noise. The material noise can be difficult to distinguish from flaw echoes because their spectra overlap to a large extent. Due to the overlapping, application of conventional linear filters is generally not adequate for attenuating this type of noise. However, a suitable choice of the inspection frequency will cause the grain response to be considerable more noncoherent than the flaw response. This property arise from the fact that the material noise can be considered as an interference ...


Model-Based Signal Processing Techniques For Ultrasonic Flaw Detection: Simulation Studies, Chien-Ping Chiou, R. Bruce Thompson, Lester W. Schmerr Jan 1993

Model-Based Signal Processing Techniques For Ultrasonic Flaw Detection: Simulation Studies, Chien-Ping Chiou, R. Bruce Thompson, Lester W. Schmerr

Review of Progress in Quantitative Nondestructive Evaluation

The ultrasonic signals observed in inspection processes can often be accurately predicted by suitable measurement models. These model predictions can be used to provide important information to guide the development of subsequent signal processing algorithms. Here such a hybrid use of ultrasonic modeling and signal processing is demonstrated in the context of the problem of detecting ultrasonic flaw signals in noise. In particular, we wish to apply this hybrid methodology as an initial approach to solving the problem of detecting hard-alpha inclusions in titanium alloys.


Evaluation Of Waveform Mapping As A Signal Processing Tool For Quantitative Ultrasonic Nde, Patrick Johnston, Doron Kishoni Jan 1993

Evaluation Of Waveform Mapping As A Signal Processing Tool For Quantitative Ultrasonic Nde, Patrick Johnston, Doron Kishoni

Review of Progress in Quantitative Nondestructive Evaluation

The mapping of one pulsed waveform into another, more desirable waveform by the application of a time-domain filter has been employed in a number of NDE situations [1-3]. The primary goal of these applications has been to improve the range resolution of an ultrasonic signal for detection of echoes arising from particular interfaces masked by the response of the transducer. The work presented here addresses the use of this technique for resolution enhancement in imaging situations and in mapping signals from different transducers to a common target waveform, allowing maintenance of quantitative calibration of ultrasonic systems. We also describe the ...


Wavelets And Their Application To Digital Signal Processing In Ultrsaonic Nde, D. Patterson, B. Defacio, Steven P. Neal, Charles R. Thompson Jan 1993

Wavelets And Their Application To Digital Signal Processing In Ultrsaonic Nde, D. Patterson, B. Defacio, Steven P. Neal, Charles R. Thompson

Review of Progress in Quantitative Nondestructive Evaluation

As the use of digital based ultrasonic testing systems becomes more prevalent, there will be an increased emphasis on the development of digital signal processing techniques. In the past, various Fourier based digital signal processing approaches have been formulated and applied in the ultrasonic nondestructive evaluation (NDE) research community. In many cases, the inherent inability of Fourier methods to handle non-stationary signals has been exposed as the Fourier methods are applied to non-stationary ultrasonic signals. Our intent is to investigate the application of wavelet based signals processing techniques to a variety of problems in ultrasonic NDE. Wavelet methods have a ...


Wavelets And Nondestructive Evaluation, Sif-Eddine Moubarik, Daniel De Vadder, P. Benoist Jan 1993

Wavelets And Nondestructive Evaluation, Sif-Eddine Moubarik, Daniel De Vadder, P. Benoist

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonics plays an important role in quantitative nondestructive evaluation of materials. Useful information on the integrity of the material can be obtained by analyzing ultrasonic wave reflection and diffraction from flaws. However, the interpretation of ultrasonic data may be in some situations very difficult due to poor signal-to-noise ratio or complex multiple scattering phenomena, as for instance in the case of coarse-structured materials.


Ultrasonic Signal Analysis Using Wavelet Transform, J. Chao, L. Udpa, S. S. Udpa Jan 1993

Ultrasonic Signal Analysis Using Wavelet Transform, J. Chao, L. Udpa, S. S. Udpa

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic methods of nondestructive evaluation are used extensively in industry owing to the versatility and inherent advantages of the method. A major area of research in ultrasonic NDE is the analysis of reflected waveforms representing the interaction between an ultrasonic wave and inhomogeneties in the material under inspection. The objective of the analysis technique described in this paper is to extract information contained in the signal for estimating the size, shape, and location of the defects. Although full defect reconstruction schemes call for considerable computational effort, defect characterization algorithms based on pattern recognition methods are being increasingly used for signal ...


Morphological Filters: Statistical Evaluation And Applications In Ultrasonic Nde, M. Mohamed, J. Saniie Jan 1993

Morphological Filters: Statistical Evaluation And Applications In Ultrasonic Nde, M. Mohamed, J. Saniie

Review of Progress in Quantitative Nondestructive Evaluation

In this paper, morphological filters [1-4] have been applied to detect flaw echoes in ultrasonic signals contaminated by grain scattering noise (i.e., clutters or speckles). In particular, the statistical properties of morphological operations (i.e., dilation, closing, clos-erosion and clos-opening) are examined using Monte Carlo simulation when applied to signals with uniform and Rayleigh distributions. The simulated results and their statistics (mean and variance) present an interpretation of the noise suppression capability of morphological filters and their biasing effects. This information has been utilized to design a suitable structuring element to enhance flaw-to-clutter ratio in ultrasonic testing. The processed ...


Support Minimized Nonlinear Acoustic Inversion With Absolute Phase Error Correction, Ali Safaeinili, Ronald A. Roberts Jan 1993

Support Minimized Nonlinear Acoustic Inversion With Absolute Phase Error Correction, Ali Safaeinili, Ronald A. Roberts

Review of Progress in Quantitative Nondestructive Evaluation

The predominant factors which prohibit the inversion of acoustic scattering data for the purposes of flaw characterization are 1) limited angular access to the flaw, 2) limited temporal frequency signal bandwidth, and 3) lack of absolute phase information between individual measurements (zero of time problem). An additional complication which impedes the data inversion is the non-linear dependence of the scattering data on the scattering object. This problem must be handled by either linearizing the problem or by applying an iterative procedure which may have questionable convergence properties. An approach to data inversion is presented here which shows potential in overcoming ...


Software For Signal Processing And Display Of Large 3-D Data Sets, Cedric Zala, J. Michael Berkley Jan 1993

Software For Signal Processing And Display Of Large 3-D Data Sets, Cedric Zala, J. Michael Berkley

Review of Progress in Quantitative Nondestructive Evaluation

We have recently developed a software system, called DETECT/NDE, which provides a powerful environment for processing and visualizing large ultrasonic data sets. This system runs on X-Windows UNIX workstations and on VAX/VMS computers, and combines interactive graphics-based visualization with signal processing algorithms. The two main features of this package are: (1) the interactive generation and display of B-scans and C-scans from the 3-D data sets; and (2) the provision of high resolution deconvolution and inversion procedures for improving the interpretability of the data. In addition, numerous other utilities allow image processing, animation and 3-D rendering of the data.


Accounting For Ultrasonic Signal Attenuation Through Model Parameter Interpolation, Myung-Hyun Yoon, Tenkasi V. Ramabadran Jan 1993

Accounting For Ultrasonic Signal Attenuation Through Model Parameter Interpolation, Myung-Hyun Yoon, Tenkasi V. Ramabadran

Review of Progress in Quantitative Nondestructive Evaluation

In ultrasonic NDE of materials, deconvolution techniques are widely used to improve time/space resolution, minimize spectral coloring, and compensate for different experimental settings, e.g., transducer variations, pulser-receiver energy/damping settings, etc. The reference signal that is used for deconvolution is typically obtained as the front (or back) surface echo from a suitable sample under conditions identical to those used in acquiring the signal to be processed (deconvolved). When the signal to be processed is acquired from an attenuating medium, the effect of signal attenuation should be appropriately accounted for in the deconvolution technique. If the signal arises from ...


Neural Network Based Processing Of Thermal Nde Data For Corrosion Detection, D. Prabhu, W. P. Winfree Jan 1993

Neural Network Based Processing Of Thermal Nde Data For Corrosion Detection, D. Prabhu, W. P. Winfree

Review of Progress in Quantitative Nondestructive Evaluation

Subsurface corrosion in aircraft structure is a major concern in lap joints and other joints. Small open gaps in the joints form regions where moisture can be trapped. The trapped water often produces a chemical environment in the regions which accelerates the corrosion process. Corrosion considerably reduces structural strength and load-bearing capacity of the structure. To ensure flight safety, it is imperative to detect subsurface corrosion as early as possible during aircraft maintenance operations. Since long downtimes of commercial aircraft translate to large operating costs for airline industries, it is desirable to develop techniques that can consistently and reliably detect ...


Quantitative Radioscopic Profile Analysis Via Neural Networks, Edward Greenawald, Chester F. Poranski Jan 1993

Quantitative Radioscopic Profile Analysis Via Neural Networks, Edward Greenawald, Chester F. Poranski

Review of Progress in Quantitative Nondestructive Evaluation

Artificial neural networks have been studied over a 30 year period and are a well developed computational technology applicable to a variety of difficult problems [1]. All neural networks are simulations of neurons and synapses based upon a primitive understanding of these biological structures. The distinctive feature of these networks is that they are trainable. By various iterative schemes, a set of well characterized data can be used to create a network which will produce a correct output function of an input vector. The learning is generalized, resulting in the ability to provide correct results for input vectors not contained ...


Ultrasonic Flaw Detection Using Neural Network Models And Statistical Analysis: Simulation Studies, Chien-Ping Chiou, Lester W. Schmerr, R. Bruce Thompson Jan 1993

Ultrasonic Flaw Detection Using Neural Network Models And Statistical Analysis: Simulation Studies, Chien-Ping Chiou, Lester W. Schmerr, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

Flaw detection problems in ultrasonic NDE can be considered as two-class classification problems, i.e., determining whether a flaw is present or not present. To be practical, a flaw classification method must be able to handle the uncertainties associated with interference from grain noise which leads to poor signal-to-noise ratios (SNR). In this work, the use of neural network models and statistical correlation is demonstrated for one such detection/classification problem. In particular, based on simulation studies, we wish to establish practical strategies in detecting weak volumetric flaw signals corrupted by high grain noise. An example of this type that ...


Neural Network For Automating Diagnosis In Aircraft Inspection, Christine Brousset, Gilles Baudrillard Jan 1993

Neural Network For Automating Diagnosis In Aircraft Inspection, Christine Brousset, Gilles Baudrillard

Review of Progress in Quantitative Nondestructive Evaluation

As and when aircraft aged, fatigue problems appeared and the necessity for detecting cracks in the lap joint parts became obvious. Numerous systems were then developed to follow up cracks appearance and growth in rivet holes. If most of the inspection used to be manual, it is now partially automated since AEROSPATIALE developed the System of Inspection Assisted by Microprocessor (SIAM) in which an EC probe slides on the rivet lines [1]. At present, our research is focused on the diagnosis, last phase of the inspection. In order to process the inspection data, to speed up the control, and to ...


Crack-Depth Determination By A Neural Network With A Synthetic Training Data Set, M. Takadoya, M. Notake, M. Kitahara, J. D. Achenbach, Q. C. Guo, M. L. Peterson Jan 1993

Crack-Depth Determination By A Neural Network With A Synthetic Training Data Set, M. Takadoya, M. Notake, M. Kitahara, J. D. Achenbach, Q. C. Guo, M. L. Peterson

Review of Progress in Quantitative Nondestructive Evaluation

A neural network with an analog output is presented for crack-depth estimation from ultrasonic signals backscattered from a surface-breaking crack in a steel plate. The network has only one response unit and this unit directly reports the crack depth from the measured signals. A completely synthetic data set, spot-checked by comparison with experimental results, is utilized for the training of the network. The synthetic data set has been obtained by solving governing boundary integral equations by the boundary element method. A Gaussian modulated sinusoid has been utilized as incident signal. The architecture of the present network, which is a feedforward ...


Radial Basis Functions Network For Defect Sizing, S. Nair, S. Udpa, L. L. Udpa Jan 1993

Radial Basis Functions Network For Defect Sizing, S. Nair, S. Udpa, L. L. Udpa

Review of Progress in Quantitative Nondestructive Evaluation

An important aspect of non-destructive testing is the interpretation and classification of signal obtained by NDT methods such as eddy current and ultrasound. These signals are typically complex, non-stationary waveforms, with signals corresponding to a particular class of defect in a specimen having similar form and shape. However, distortions and noise introduced by the measurement system make the manual classification of these signals a time-consuming and unreliable process, with the results affected by operator fatigue and measurement quality. The design of traditional classifiers for this task also poses many difficulties, due to a number of parameters that influence measurement, and ...


An Inversion Approach To Ultrasonic Imaging Through Reflective Interfaces In Multi-Layered Structures, K. Mcrae, Cedric A. Zala Jan 1993

An Inversion Approach To Ultrasonic Imaging Through Reflective Interfaces In Multi-Layered Structures, K. Mcrae, Cedric A. Zala

Review of Progress in Quantitative Nondestructive Evaluation

The increased use of composite materials and adhesively bonded joints has resulted in the need for the development of inspection techniques appropriate for multi-layered structures. Normal incidence ultrasonic pulse-echo imaging has been and continues to be a principal technique for the detection of interface condition. Ideally, only a single reflection from each interface in the layered structure would be received and the ultrasonic image would be based upon a single parameter intrinsic to the material, such as the reflection coefficient. The reflection coefficient is, in turn, primarily determined by the relative change in ultrasonic impedance across the interface. In the ...


An Experimental Study Of Tomographic Imaging In Layered Media, Y. Wang, R. A. Kline Jan 1993

An Experimental Study Of Tomographic Imaging In Layered Media, Y. Wang, R. A. Kline

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic tomography has found its applications in material evaluation since the later 70’s. However, the techniques in this field are far less developed compared to their x-ray counterparts, which have been widely used in the medical community. One of the practical problems in acoustic tomography is that acoustic waves will not necessarily propagate along straight paths in a nonhomogeneous medium. The situation will be more complicated when material inhomogeneities are coupled with anisotropy as the approach is applied to composite media. In order to resolve the situation, one has either to tolerate the consequence of using straight line ray ...


Application Of A Finite-Difference Modeling Scheme For Ultrasonic Defect Characterization, P. Van't Veen, E. J. M. Giling, L. F. Van Der Wal Jan 1993

Application Of A Finite-Difference Modeling Scheme For Ultrasonic Defect Characterization, P. Van't Veen, E. J. M. Giling, L. F. Van Der Wal

Review of Progress in Quantitative Nondestructive Evaluation

Modeling schemes, which compute the propagation of ultrasonic wave fields, serve as research tools in NDE. The objectives to use such schemes are diverse. Firstly, they may be used to set the requirements for the ultrasonic data acquisition method and the processing algorithm. Secondly, they may be used to improve understanding of the actual measurement, i.e. for interpretation. Thirdly, they may play a central role in the inversion of the measurement for defect characterization, i.e. model driven inversion and neural network training.