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Full-Text Articles in Mechanical Engineering

Eddy Current Characterization Of Applied And Residual Stresses, W. R. Junker, W. G. Clark Jr. Jan 1983

Eddy Current Characterization Of Applied And Residual Stresses, W. R. Junker, W. G. Clark Jr.

Review of Progress in Quantitative Nondestructive Evaluation

An exploratory investigation was conducted to evaluate the applicability of state-of-the-art eddy current nondestructive evaluation techniques to the characterization of applied and residual stresses in structural steels. Eddy current response versus stress measurements were developed for ASTM Type A533B and A471 steels under tensile, bending and residual stress loading conditions. A “shrink fit” specimen was used to establish applicability to residual stresses. Results show that an eddy current approach can be used to provide an accurate quantitative measure of surface stresses. The technique can also be used to map surface stress contours. Details of the procedure are described along with ...


Acoustoelasticity: Scanning With Shear Waves, N. Shaikh, C. Steele, G. S. Kino Jan 1983

Acoustoelasticity: Scanning With Shear Waves, N. Shaikh, C. Steele, G. S. Kino

Review of Progress in Quantitative Nondestructive Evaluation

Acoustoelasticity is a promising method for the in situ analysis of both applied and residual stresses. The object of this investigation is to establish a technique for scanned shear wave measurements so as to determine the individual components of an inhomogeneous stress state and their directions. A computer-controlled scanning system with a dry contact rubber backed transducer has been developed which provides complete automation of scanning and data reduction.

The theory of acoustoelasticity for anisotropic material has been developed using perturbation techniques. The experimental results on rolled aluminum plates confirm that, to a reasonable approximation, the effects of material anisotropy ...


The Effect Of Texture On Acoustoelasticity, George C. Johnson Jan 1983

The Effect Of Texture On Acoustoelasticity, George C. Johnson

Review of Progress in Quantitative Nondestructive Evaluation

The theory for stress determination using acoustoelasticity is most frequently based on the evaluation of the motion of an infinitesimal plane wave propagating through an isotropic, elastic body which is subjected to a homogeneous deformation. The assumption of isotropy in this analysis allows the characterization of the acoustoelastic response to be carried out in terms of two second-order and three third-order elastic constants. Unfortunately, most structural materials do not behave isotropically, but instead have some degree of texture caused by the crystals aligning themselves in certain preferred orientations during the forming process. This paper examines the effect of texture on ...


Residual Stress Characterization By Use Of Elastic Wave Scattering Measurements, E. Domany, J. E. Gubermatis Jan 1983

Residual Stress Characterization By Use Of Elastic Wave Scattering Measurements, E. Domany, J. E. Gubermatis

Review of Progress in Quantitative Nondestructive Evaluation

The presence of a state of residual stress in a material can impair its structural quality by adversely affecting its elastic limit, yield point, etc.1 Most common nondestructive measurements of residual stress use x-ray techniques.2 However, these techniques determine only the surface residual stresses, while in many practical cases knowledge of the bulk residual stresses is desired. Ultrasonic methods3,4 appear most natural for measuring bulk residual stress but are used infrequently, in part because of difficulty in adequately measuring small effects and in part because of the absence of theoretical results treating the inhomogeneous nature of residual ...


Absolute Determination Of Stress In Textured Materials, R. Bruce Thompson, John F. Smith, S. S. Lee Jan 1983

Absolute Determination Of Stress In Textured Materials, R. Bruce Thompson, John F. Smith, S. S. Lee

Review of Progress in Quantitative Nondestructive Evaluation

The continuum theory of elastic wave propagation in deformed, anisotropic solids is reviewed with emphasis on those features which might be used to distinguish between stress induced changes in ultrasonic velocity and changes due to material anisotropy, such as would be produced by preferred grain orientation in a polycrystalline metal As noted by previous authors, one such feature is the difference in velocity of two shear waves, whose directions of propagation and polarization have been interchanged. In particular, when these directions fall along the symmetry axes of a rolled plate (assuming orthorhombic symmetry) and these are also the directions of ...


Evaluation Of Residual Stress States Using Horizontally Polarized Shear Waves, R. B. King, C. M. Fortunko Jan 1983

Evaluation Of Residual Stress States Using Horizontally Polarized Shear Waves, R. B. King, C. M. Fortunko

Review of Progress in Quantitative Nondestructive Evaluation

A new approach for using acoustic measurements to evaluate residual stresses in the presence of unknown material property variations is presented. It is shown that measurements using shear waves propagating along the normal to the surface of a plate do not provide sufficient information to separate the influences of stress and material property variations. To overcome this fundamental limitation, an alternative theory is developed that governs the propagation of shear waves polarized horizontally with respect to the surface of a plate (SH-waves), but propagating at oblique angles with respect to the surface normal. The question of separating the effects of ...


Detection Of Strain Induced Microstructural Changes In Aluminum (6061-T6) Using Ultrasonic Signal Analysis, G. H. Thomas, S. H. Goods, A. F. Emery Jan 1983

Detection Of Strain Induced Microstructural Changes In Aluminum (6061-T6) Using Ultrasonic Signal Analysis, G. H. Thomas, S. H. Goods, A. F. Emery

Review of Progress in Quantitative Nondestructive Evaluation

A correlation between the change in ultrasonic wave forms and applied strain in aluminum (6061-T6) has been obtained at high strain levels. Sophisticated signal processing techniques have indicated a complex interaction of the frequency components of a high frequency ultrasonic pulse as it passes through an aluminum tensile specimen. Strain induced microstructural changes in the aluminum attenuate the acoustic energy. One of the attenuation mechanisms is the formation of deformation induced cavities at precipitates and inclusions which scatter the ultrasonic energy. Measuring the signal attenuation at the appropriate frequencies determines the degree of deformation induced damage.


The Use Of Acoustic Signal Attenuation In The Examination Of Residual Strains: Part B — The Use Of Experimentally Derived Acoustic Strain Correlations In The Evaluation Of Residual Strains And Stresses, A. F. Emery, G. H. Thomas Jan 1983

The Use Of Acoustic Signal Attenuation In The Examination Of Residual Strains: Part B — The Use Of Experimentally Derived Acoustic Strain Correlations In The Evaluation Of Residual Strains And Stresses, A. F. Emery, G. H. Thomas

Review of Progress in Quantitative Nondestructive Evaluation

In a previous conference we presented a comparison of several different acoustic techniques to estimate residual stresses in complex situations.1 Of the several methods, the use of the attenuation of broad band pulses appeared to be better than the usual method of inferring strain from changes in the propagation velocity. The measurement of strain through changes in the velocity is effected through the equations 1 ΔV/V = f(εij), 2 Δt/t=Δd/d−ΔV/V where εij = strain tensor, t = time for the wave to traverse the specimen, d = specimen thickness, V = wave velocity.


The Use Of The Temperature Dependence Of Ultrasonic Velocity To Measure Residual Stress, K. Salama, J. J. Wang, G. C. Barber Jan 1983

The Use Of The Temperature Dependence Of Ultrasonic Velocity To Measure Residual Stress, K. Salama, J. J. Wang, G. C. Barber

Review of Progress in Quantitative Nondestructive Evaluation

The behavior of the temperature dependence of longitudinal ultrasonic velocity in type A533B steel in the presence of external as well as residual stresses has been investigated. In all measurements, the ultrasonic velocity in the vicinity of room temperature is found to vary linearly with temperature, and the slope of the linear relationship increases or decreases according to whether the stress is applied in tension or in compression respectively. The results also indicate that the temperature dependence of the velocity is a linear function of applied stress, and the slope of this linear relationship is the same for all specimens ...


Finding Through Nde The Thermal History And Metallurgical Status Of A Heat Treatable Aluminum Alloy, Russell A. Chihoski Jan 1983

Finding Through Nde The Thermal History And Metallurgical Status Of A Heat Treatable Aluminum Alloy, Russell A. Chihoski

Review of Progress in Quantitative Nondestructive Evaluation

In heat-treatable aluminum alloys it has long been accepted that decreased values of strength were accompanied by increases in electrical conductivity (C). In quality or processing control and trouble-shooting situations this has been useful for finding anomalies in or among aluminum alloy maill products. But the regression was always found as a wide scatterband where conductivity could not give a narrow range of possible strengths.

It was discovered for several alloys and quantified for 2219, that the scatterband formed by data from several lots and sources actually could be divided into groups with different histories. When specimens produced by created ...


Fiber Optics For A Damage Assessment System For Fiber Reinforced Plastic Composite Structures, Roger M. Crane, Aleksander B. Macander, James Gagorik Jan 1983

Fiber Optics For A Damage Assessment System For Fiber Reinforced Plastic Composite Structures, Roger M. Crane, Aleksander B. Macander, James Gagorik

Review of Progress in Quantitative Nondestructive Evaluation

There are a limited number of nondestructive evaluation techniques available for field inspection of large composite structures and practically no viable techniques for in-service inspection. With this in mind, an innovative Damage Assessment System is proposed which is based on a concept of using an optical fiber mesh, implanted into the body of a fiber reinforced composite structure. Such a mesh would become an integral part of the structure during the course of its fabrication. The selection of the mesh fibers would be predicated on their strain to failure characteristics and strain compatibility with the base, composite reinforcing fibers. This ...


Ultrasonic Steel Cleanliness System, James M. Smith Jan 1983

Ultrasonic Steel Cleanliness System, James M. Smith

Review of Progress in Quantitative Nondestructive Evaluation

It is well known that nonmetallic inclusions can adversely affect the metallurgical properties of engineering alloys. For critical components such as aircraft engine gears and bearings it is important then to quantitatively assess the severity of the inclusion content in the alloy material before performing costly manufacturing operations. This poster paper will describe the operation and the initial results of a computer controlled steel cleanliness inspection system.

The severity of the inclusion content is determined by this system through a statistical analysis of the internally reflected ultrasonic indications from the alloy material as a transducer is scanned in a raster ...


The Clamping Force Of Heat Shrinkable Fittings, David K. Rehbein, B. J. Skillings, J. F. Smith, Donald O. Thompson Jan 1983

The Clamping Force Of Heat Shrinkable Fittings, David K. Rehbein, B. J. Skillings, J. F. Smith, Donald O. Thompson

Review of Progress in Quantitative Nondestructive Evaluation

A number of alloys exhibit a phenomenon which has come to be known as ‘shape memory’. Without exception these alloys undergo a rather special type of martensitic transformation which results from one or another of the elastic constants1–7 weakening with changing temperature to the point that at the transformation temperature the transforming phase becomes both mechanically and thermodynamically unstable. ‘Shape memory’ is exhibited in the following way. A specimen at a temperature above the martensitic transformation is shaped to some desired form. The specimen is then cooled below its transformation temperature and deformed. Subsequent heating of the specimen through ...


Cure Monitoring Of Thermosetting Polymers By An Ultrasonic Technique, Donald L. Hunston Jan 1983

Cure Monitoring Of Thermosetting Polymers By An Ultrasonic Technique, Donald L. Hunston

Review of Progress in Quantitative Nondestructive Evaluation

In the fabrication of components with thermosetting polymers, an essential step is the proper optimization of the cure cycle. In the early phases of the cure the polymer must have the appropriate flow properties to assure the proper wetting, spreading, and forming. It must then harden without excessive build up of residual stresses and flaws or the loss of adhesion at any interfaces that are present. To complicate the situation further, many applications such as composites, adhesives, paints, and protective coatings involve thin films whose cure behavior is significantly different than that for bulk samples. To help address this problem ...


Ultrasonic Signal Processing For Multilayered Nde, Ramesh Shankar, Stephen S. Lane, Jeffrey M. Warren Jan 1983

Ultrasonic Signal Processing For Multilayered Nde, Ramesh Shankar, Stephen S. Lane, Jeffrey M. Warren

Review of Progress in Quantitative Nondestructive Evaluation

The interpretation of ultrasonic signals in the inspection for flaws in bonded regions of multilayered specimens is difficult because of signal energy loss due to material attenuation, undesired reverberations within certain layers, and overlapping responses from different interfaces because of finite transducer bandwidth. The flaws are usually air gaps, lack of adhesion, and porosity within the bonding agent.

While ultrasonic NDE signal interpretation can always be improved with appropriate instrumentation — broader bandwidth transducers for increased resolution, for example — signal processing allows for further enhancement using a digital computer. Material attenuation can be compensated for by using digital filters that preferentially ...


Interferometric Techniques Using Embedded Optical Fibers For The Quantitative Nde Of Composites, Janet C. Wade, Richard O. Claus Jan 1983

Interferometric Techniques Using Embedded Optical Fibers For The Quantitative Nde Of Composites, Janet C. Wade, Richard O. Claus

Review of Progress in Quantitative Nondestructive Evaluation

Optical interferometric techniques using single mode optical fiber waveguide embedded in composites and other layered materials have been used to measure one- and two-dimensional stress distributions and acoustic emission caused by applied point source loads. By interferometrically comparing the phases of coherent optical signals propagated through an embedded sample fiber and a bypass reference fiber, a signal proportional to the instantaneous strain integrated along the embedded length of the sample fiber has been detected. System calibration has been obtained by applying a one-dimensional dc strain field to a cantilever beam containing the fiber. Using this calibrated system, an array of ...


A Computerized Ultrasonic Scanning Bridge For Defect Imaging: Composite Materials, Donald Boyd, William Mcdonald, Andrew Simmons Jan 1983

A Computerized Ultrasonic Scanning Bridge For Defect Imaging: Composite Materials, Donald Boyd, William Mcdonald, Andrew Simmons

Review of Progress in Quantitative Nondestructive Evaluation

A computerized ultrasonic scanning bridge has been developed for the scanning and imaging of defects in structures. The raster scaning pattern can be implemented with any pair of the six available axes. The digitized ultrasonic signal can be imaged using a Peritek Graphic system. Details of the ultrasonic scanning bridge and imaging system will be reviewed.

Examples of the evaluation of a graphite epoxy component will be reviewed. The scanning of the composite part requires the use of the two angulation axis for the raster scanning. The correlation of the ultrasonic inspection with failure pressure of the graphite epoxy component ...


Development Of An Acoustic Model For Multilayered Nde, Ramesh Shankar, Stephen S. Lane Jan 1983

Development Of An Acoustic Model For Multilayered Nde, Ramesh Shankar, Stephen S. Lane

Review of Progress in Quantitative Nondestructive Evaluation

A computer based acoustic model has been developed for the NDE of multilayered structures [1]. The model is applicable for normal or off-normal incident excitation, with receiver in pulse-echo, pitch-catch or in array mode. The model can simulate the observed signal for arbitrary frequency response of the transmitting and receiving transducer. In addition, the model considers attenuation and mode conversion effects in each layer in predicting the ultrasonic response.

While earlier works [2,3,4] considered normal incidence and non attenuative media, the current model’s capabilities have been expanded to include off-normal incident angles and the attendant mode conversions ...


The Middle Ground Of The Nde R&D Spectrum, H. M. Burte, Dale E. Chimeti, R. Bruce Thompson, Donald O. Thompson Jan 1983

The Middle Ground Of The Nde R&D Spectrum, H. M. Burte, Dale E. Chimeti, R. Bruce Thompson, Donald O. Thompson

Review of Progress in Quantitative Nondestructive Evaluation

Our keynote talk today has several objectives: First, we want to call attention, as some of us have before, to the interdisciplinary nature of NDE science and technology and some approaches for fostering R&D in such a situation. Next, we want to describe the objective of the DARPA, Air Force (and now Navy) core program for developing a science base for NDE and how it has evolved during the past two years. Some changes have indeed taken place; we feel that they were both necessary and evolutionary. Many of you are probably familiar with these changes by now but there may be some residual concerns or questions in your minds. Since I was the initiating influence behind most of them, it is appropriate for you to hear me say what they are and what they aren’t, and to have an opportunity to question ...


Considerations For Quantitative Nde And Nde Reliability Improvement, Ward. D. Rummel Jan 1983

Considerations For Quantitative Nde And Nde Reliability Improvement, Ward. D. Rummel

Review of Progress in Quantitative Nondestructive Evaluation

A challenge has been presented to the scientific community to apply “first principles” to the understanding, prediction, and control of nondestructive evaluation (NDE) processes and applications. The success of the program is evident in the attention of new researchers and in the diversity of scientific specializations that have been directed to NDE problems. Critique of the program has been in awareness of existing technology and in focus of resources. An approach based on “lessons learned” is suggested for meeting continuing challenges and projected challenges of the future. “Lessons learned” from NDE reliability assessment programs are reviewed. Quantitative NDE performance as ...


Effects Of Crack Closure On Ultrasonic Transmission, R. Bruce Thompson, B. J. Skillings, L. W. Zachary, L. W. Schmerr, Otto Buck Jan 1983

Effects Of Crack Closure On Ultrasonic Transmission, R. Bruce Thompson, B. J. Skillings, L. W. Zachary, L. W. Schmerr, Otto Buck

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic waves are attenuated as they propagate past the tip of a crack due to the reflection of the energy at the crack face and diffraction at the crack tip. Crack closure modifies the situation since partial transmission can occur at points along the crack face where asperities come in contact. This phenomenon is important in defining the ability to nondestructively detect closed cracks and in developing a more detailed understanding of the closure phenomenon itself. Modified compact tension specimens were used to investigate the effects of partial crack closure on focussed, through-transmission ultrasonic signals. Data obtained from fatigue cracks ...


Simulation Of Closure: Effects On Crack Detection Probability And Stress Distributions, Otto Buck, B. J. Skillings `, L. K. Reed Jan 1983

Simulation Of Closure: Effects On Crack Detection Probability And Stress Distributions, Otto Buck, B. J. Skillings `, L. K. Reed

Review of Progress in Quantitative Nondestructive Evaluation

It is well known that partial contact of two rough crack surfaces will lead to transmission of an acoustic signal across the crack, thus giving rise to a reduced probability of detection (POD). To explore the effects and consequences of such partial contact, impression experiments—using small spheres—have been performed to determine the effects of contact area on the amplitude transmitted. The results have been compared with a theory described elsewhere in these Proceedings. Based on the experimental results it will be speculated that the residual stress field responsible for the crack closure may be calculated based on a ...


Detection Of Closed Internal Fatigue Cracks, B. R. Tittmann, L. Ahlberg, Otto Buck, F. Cohen-Tenoudji, G. Quentin Jan 1983

Detection Of Closed Internal Fatigue Cracks, B. R. Tittmann, L. Ahlberg, Otto Buck, F. Cohen-Tenoudji, G. Quentin

Review of Progress in Quantitative Nondestructive Evaluation

This paper reviews some recent work on the detection and sizing of closed internal fatigue cracks by ultrasonic techniques. Major emphasis is put on the diffraction of shear waves at the crack tip. Both fully open as well as partially closed cracks were considered. The effect of crack closure stress on back- scattered (pulse-echo) shear waves was studied with the aid of an A1 compact tension specimen. Noticeable changes with crack closure stress were documented for the structure of both the time- domain and frequency-domain representations. The techniques acquired with this specimen were applied to the study of a 50 ...


Nondestructive Evaluation Of Low Density Fibrous Ceramics, D. J. Green Jan 1983

Nondestructive Evaluation Of Low Density Fibrous Ceramics, D. J. Green

Review of Progress in Quantitative Nondestructive Evaluation

In order to ensure a minimum strength for the low density fibrous tiles to be used in the thermal protection system of the Space Shuttle an NDE test that uses sonic velocity measurements to predict strength has been developed. The empirical correlation between strength and sonic velocity which is the basis of this test, is shown to be consistent with a previously developed micro-mechanical model. The model is reviewed and is shown to describe the fracture behavior of these fibrous materials regardless of their density or testing direction. Measurement of the density and sonic velocity in these materials allows Young ...