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Articles 1 - 15 of 15

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 ...


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 ...


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 ...