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Full-Text Articles in Engineering Science and Materials

Elastic Property Estimation In Thin Graphite Epoxy Composite Plates Using Ultrasonic Nondestructive Evaluation, Douglas L. Van Otterloo Jan 1995

Elastic Property Estimation In Thin Graphite Epoxy Composite Plates Using Ultrasonic Nondestructive Evaluation, Douglas L. Van Otterloo

Retrospective Theses and Dissertations

The past few decades have seen a steady increase in the use of composite materials. First, as non-load bearing structures such as nose cones and control surfaces and more recently as primary structure. Composite materials can have strength to weight ratios higher than any homogeneous material which makes them very attractive structural materials for the aerospace industry. Unfortunately, in previous years, the failure and performance of composites was not well understood. This eliminated them from use as primary structure. Since the early years of their development, composites have become much more reliable and offer higher strength to weight ratios than ...


Quantitative Evaluation Of Material Composition Of Composites Using X-Ray Energy-Dispersive Nde Technique, Jason Ting Jan 1993

Quantitative Evaluation Of Material Composition Of Composites Using X-Ray Energy-Dispersive Nde Technique, Jason Ting

Retrospective Theses and Dissertations

In a wide range of situations the need for characterization of material properties of man-made and natural materials arises. These situations can include inspection during fabrication of material, and in-sexvice inspection of mechanical parts as they wear and near their design life. The need to characterize the material of interest involves all aspects of material performance, such as: the strength of the material, fracture toughness, density, hardness, material uniformity, and conductivity, etc. We present here a technique that is capable of quantitatively determining composition, density and material uniformity. It should be pointed out that no one technique can measure all ...


The Spatial Resolution Of Rayleigh Wave, Acoustoelastic Measurement Fo Stress, J. C. Johnson, R. Bruce Thompson Jan 1993

The Spatial Resolution Of Rayleigh Wave, Acoustoelastic Measurement Fo Stress, J. C. Johnson, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

One of the challenges in the acoustoelastic measurement of stress is the achievement of high spatial resolution. Since stress induced velocity shifts are generally small (~0.01%), the required precision of time and distance measurements can be quite high for the short propagation distances required. This paper presents a set of design criteria which can guide the experimentalist in choosing the most suitable measurement configuration for Rayleigh wave techniques. Three approaches for measuring the acoustic velocity are considered: measurement of arrival time versus transducer separation for several discrete positions, measurement of arrival time for a pair of transducers at a ...


Crack Length Determination By Ultrasonic Methods, David Kent Rehbein, R. Bruce Thompson, Otto Buck Jan 1993

Crack Length Determination By Ultrasonic Methods, David Kent Rehbein, R. Bruce Thompson, Otto Buck

Review of Progress in Quantitative Nondestructive Evaluation

Accurate calculation of the stress intensity factor on a given component under load relies on an accurate size determination of the flaws present in the component. The challenge to the NDE community has been development of reliable techniques to provide that accurate size determination. Many research groups have investigated this problem using ultrasonic methods with summaries of their techniques and results provided by various authors [1–3]. In general, the techniques developed fall into three general categories; (1) determination of crack length from signal amplitude measurements, (2) determination of crack length from time-of-flight measurements, and (3) determination of crack length ...


Correlation Of Nde Parameters With Fatigue Lifetime Of Aircraft Adhesive Bonds, H. Aglan, L. Kennebrew, D. K. Hsu, T. Patton Jan 1993

Correlation Of Nde Parameters With Fatigue Lifetime Of Aircraft Adhesive Bonds, H. Aglan, L. Kennebrew, D. K. Hsu, T. Patton

Review of Progress in Quantitative Nondestructive Evaluation

Various NDE methods and techniques have recently been developed to characterize adhesive bonds. These techniques simply detect voids. However, information about the presence of voids does not necessarily reflect the strength of the joints [1]. Moreover, it has been shown by Schonhorn [2] that the static failure load of joints is not largely affected by the size of a defect. Although this may be true for monotonic loading, it may not be the case under fatigue loading which is more representative of the in-service conditions. Under fatigue loading, inherent voids, cracks etc. can coalesce and form a considerably larger flaw ...


Low Frequency Ultrasonic Nondestructive Inspection Of Aluminum/Adhesive Fuselage Lap Splice, Thadd C. Patton Jan 1993

Low Frequency Ultrasonic Nondestructive Inspection Of Aluminum/Adhesive Fuselage Lap Splice, Thadd C. Patton

Retrospective Theses and Dissertations

The Federal Aviation Administration's (FAA) Center for Aviation Systems Reliability (CASR), located at Iowa State University (ISU), was established in 1990 in response to the Aviation Safety Act (Public Law 100-591) of 1988. The Aviation Safety Act, created primarily as the result of an in-flight mishap involving an Aloha Airlines' Boeing 737, mandated that the FAA develop research technologies to aid the aviation industry to (1) better predict the effects of design, maintenance, testing, wear, and fatigue life of an aircraft; (2) develop methods for improving aircraft maintenance technology and practices; and (3) expand general long-range research activities applicable ...


Reciprocity-Based Measurement Models For Ultrasonic Nde, David D. Bennink, Anna L. Pate Jan 1989

Reciprocity-Based Measurement Models For Ultrasonic Nde, David D. Bennink, Anna L. Pate

Review of Progress in Quantitative Nondestructive Evaluation

Quantitative NDE objectives such as the evaluation of flaw signals and the assessment of inspection capabilities generate the need for models of ultrasonic scattering measurements capable of including all aspects of the measurement process: radiation and reception characteristics of probes, propagation of finite beams, scattering of nonplane-wave fields, and the like. Once such models are developed and validated, that is, proven able to predict the received voltages obtained in actual ultrasonic experiments, they can be used to gain a thorough understanding of the NDE inspection process. Specifically, these models will be useful in investigations of the factors that significantly affect ...


Ultrasonic Transducer Calibration For Reciprocity-Based Measurement Models, David D. Bennink, Anna L. Pate Jan 1989

Ultrasonic Transducer Calibration For Reciprocity-Based Measurement Models, David D. Bennink, Anna L. Pate

Review of Progress in Quantitative Nondestructive Evaluation

A general formulation regarding the relationship between scatterer properties and experimental signals was presented in a companion paper[1]. This formulation was developed for the case of acoustic wave scattering in an immersion measurement. In order to perform the theoretical calculations, the formulation requires knowledge of the radiation and reception characteristics of the probes involved and the combined properties of the pulser and the receiver (system efficiency). Thus, the objective of this paper is to discuss methods for obtaining the characteristics of measurement systems as required in the above-mentioned formulation. As an example, the case of acoustic wave scattering from ...


The Scattering Response Of A Flat-Bottom Hole, Lester W. Schmerr Jr., Alexander Sedov Jan 1989

The Scattering Response Of A Flat-Bottom Hole, Lester W. Schmerr Jr., Alexander Sedov

Review of Progress in Quantitative Nondestructive Evaluation

The flat-bottom hole is one of the oldest reference/calibration standards in the field of ultrasonic nondestructive evaluation (NDE). It has been used for both calibration of ultrasonic test equipment sensitivity and for the generation of distance-amplitude correction (DAC) curves [1]. Flat-bottom holes are also useful for equivalent flaw sizing applications since they can represent the response, at normal incidence, of ideal “perfect” scatterers, such as flat cracks.


A Generalized Eigenfunction Expansion For Elastodynamics, David E. Budreck, James H. Rose Jan 1989

A Generalized Eigenfunction Expansion For Elastodynamics, David E. Budreck, James H. Rose

Review of Progress in Quantitative Nondestructive Evaluation

The use of composite materials in structural components is limited, in part, by the need to develop quantitative inspection techniques. Composites present many challenges to the development of such quantitative methods. For example, composite materials are typically anisotropic. Thus a necessary prerequisite for ultrasonic flaw detection and characterization in composite materials is an understanding of the propagation and scattering of waves in a general anisotropic media. Work towards such an understanding has been typically limited to such issues as beam propagation effects (see, for ex., Ref. [1]). The elastic wave inverse scattering problem (flaw characterization), as well as the simpler ...


Propagation Of Guided Elastic Waves In Orthotropic Plates, Y. Li, R. Bruce Thompson Jan 1989

Propagation Of Guided Elastic Waves In Orthotropic Plates, Y. Li, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

Numerical studies of wave propagation in free anisotropic plates were conducted at Stanford University in the early 70’s [1,2], followed by a flurry of related work. Yet, this subject has not been completely understood. Recent years, however, have seen greatly increased interests in the influence of the anisotropy of composites and textured metal plates on Lamb wave propagation characteristics. This paper presents the basic theory for the propagation of guided elastic waves in orthotropic plates. Included are both numerical results and analytical or semianalytical expressions for the generalized Rayleigh-Lamb dispersion equations. As examples, comparisons are made of the ...


Elastic Wave Scattering By Arbitrarily Shaped Voids, Paul J. Schafbuch`, R. Bruce Thompson, F. J. Rizzo, Thomas J. Rudolphi Jan 1989

Elastic Wave Scattering By Arbitrarily Shaped Voids, Paul J. Schafbuch`, R. Bruce Thompson, F. J. Rizzo, Thomas J. Rudolphi

Review of Progress in Quantitative Nondestructive Evaluation

This work is motivated by the need for realistic ultrasonic probability of detection (POD) models in nondestructive evaluation (NDE). Past POD models have utilized flaw farfield scattering amplitudes along with other system parameters to predict the expected signal in postulated measurement geometries [1]. However, numerical evaluations of scattering amplitudes have generally been restricted to idealized flaw shapes and, to our knowledge, no scheme to calculate scattering amplitudes of arbitrary shape has ever been implemented in 3D. Volumetric shapes with an axis of symmetry have been examined with T-matrix and MOOT [2,3] but the axisyrametric limitation precludes a large portion ...


Transducer Effects On Ultrasonic Attenuation Measurements, Mary A. Paul Jan 1989

Transducer Effects On Ultrasonic Attenuation Measurements, Mary A. Paul

Retrospective Theses and Dissertations

Ultrasonic nondestructive evaluation can be used to quantitatively interpret received electrical signals from ultrasonic measurements. In order to preform this interpretation, several techniques have been used. Two of these techniques are the standard procedure and the measurement model. The standard procedure compares the waves reflected from the flawed specimen with the waves reflected from many specimens of the same host material with different known flaws in the interior. By matching reflections, the approximate size of the flaw can be estimated by comparison with the response from the known standard flaw model; however, this method requires a large number of known ...