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Articles 1 - 14 of 14

Full-Text Articles in Mechanical Engineering

On The Space Shuttle Wing Thermal-Structural Analysis, Kumar Krishna Tamma Apr 1983

On The Space Shuttle Wing Thermal-Structural Analysis, Kumar Krishna Tamma

Mechanical & Aerospace Engineering Theses & Dissertations

A finite element approach for efficient thermal-structural analysis of structures with thermal protection systems (TPS) is described. The approach is applied to Space Shuttle wing structure configurations subjected to reentry heating. New two and three-dimensional finite elements are developed to model heat transfer in the TPS and supporting structure. A typical TPS/Structural element predicts transient nonlinear temperature variations through the TPS thickness and detailed structural temperatures at the TPS/Structure interface. The accuracy of the TPS/Structure approach in two and three-dimensions is evaluated by comparisons with the conventional approach for various configurations of the wing structure. The results ...


Progress On Ultrasonic Flaw Sizing In Turbine Engine Rotor Components: Bore And Web Geometries, James H. Rose, T. A. Gray, R. Bruce Thompson, J. L. Opsal Jan 1983

Progress On Ultrasonic Flaw Sizing In Turbine Engine Rotor Components: Bore And Web Geometries, James H. Rose, T. A. Gray, R. Bruce Thompson, J. L. Opsal

Review of Progress in Quantitative Nondestructive Evaluation

The application of generic flaw sizing techniques to specific components generally involves difficulties associated with geometrical complexity and simplifications arising from a knowledge of the expected flaw distribution. This paper is concerned with the case of ultrasonic flaw sizing in turbine engine rotor components. The sizing of flat penny shaped cracks in the web geometry will be discussed and new crack sizing algorithms based on the Born and Kirchhoff approximations will be introduced. Additionally we propose a simple method for finding the size of a flat, penny shaped crack given only the magnitude of the scattering amplitude. The bore geometry ...


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 ...


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 ...


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 ...


Elastic Wave Scattering From Multiple Voids (Porosity), Donald O. Thompson, Samuel J. Wormley, James H. Rose, R. Bruce Thompson Jan 1983

Elastic Wave Scattering From Multiple Voids (Porosity), Donald O. Thompson, Samuel J. Wormley, James H. Rose, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

The purpose of the work described in this paper is the development of an ultrasonic measurement technique which provides a convenient way to detect dilute porosity conditions in materials and to extract certain properties of the flaw distribution which are important in failure prediction. Use has been made entirely of ultrasonic backscatter measurements; thus, the technique differs considerably from other investigations which lead to porosity determinations in that no reliance is placed upon either attenuation measurements or precise ultrasonic velocity measurements [1,2]. The technique thus possesses a distinct advantage for practical implementation, i.e., it is a “one-sided” measurement ...


Inverse Ray Tracing In Anisotropic Elastic Solids, Andrew Norris Jan 1983

Inverse Ray Tracing In Anisotropic Elastic Solids, Andrew Norris

Review of Progress in Quantitative Nondestructive Evaluation

The problem of inverse ray tracing in a homogeneous anisotropic elastic solid is considered, with specific application to crack sizing. The data is assumed to be in the form of travel times of diffracted ultrasonic signals between transducers positioned on an exterior surface of the body. Both pulse-echo and pitch-catch data are considered. First, it is assumed that the wave speeds are unknown and must be obtained as part of the inversion procedure. The specific problem of locating a crack tip in a two-dimensional geometry is investigated. It is found that travel time data on the exterior surface suffices to ...


Thermoelastic Structures For High Density Ultrasonic Energy, R. J. Von Gutfeld, D. R. Vigliotti, C. S. Oh, W. R. Scott Jan 1983

Thermoelastic Structures For High Density Ultrasonic Energy, R. J. Von Gutfeld, D. R. Vigliotti, C. S. Oh, W. R. Scott

Review of Progress in Quantitative Nondestructive Evaluation

The use of lasers to generate thermoelastic waves has received considerable attention since the publication of the theoretical work of White.1 The author derives equations for the propagation of longitudinal elastic waves produced by surface heating of a semi-infinite medium with harmonic thermal (laser) excitation. The importance of the boundary conditions in determining the magnitude of the resulting elastic waves is described. Two conditions are imposed and the resulting amplitudes derived: (1) Laser absorption at x = 0 with elastic amplitude u=0 at x = 0 for all times t ≥ 0 (perfectly clamped or constrained surface) and (2) for the ...


Ultrasonic Transducer Standards, N. Jayasundere, Leonard J. Bond Jan 1983

Ultrasonic Transducer Standards, N. Jayasundere, Leonard J. Bond

Review of Progress in Quantitative Nondestructive Evaluation

The piezoelectric transducer is the electromechanical conversion element in NDE. Existing transducers of this type are found to impose limits on the improvement in system performance and, at present, there is a lack of standards as required for calibration procedures. Physical “standards” based on equivalent circuits have been produced which model individual transducers, single transducers in pulse-echo mode and two-transducer configurations. The performance of these “standards” is shown to be in good agreement with that given by real transducers, and subject to less variability.


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 ...


Effect Of Crack Presence On In-Flight Airframe Noises In A Wing Attachment Component, S. L. Mcbride, J. W. Maclachlan Jan 1983

Effect Of Crack Presence On In-Flight Airframe Noises In A Wing Attachment Component, S. L. Mcbride, J. W. Maclachlan

Review of Progress in Quantitative Nondestructive Evaluation

The relation of the occurrence of airframe acoustic emissions to aircraft manoeuvre are reported for Avro CF-100 upper forward wing trunnions. Periods of excessive noise are found when the airframe load is changing during entry to and exit from sustained-G manoeuvres. During constant-G periods, the airframe noise level is reduced by a factor of more than one hundred. These quiet periods provide a suitable signal-to-noise level for the in-flight detection and monitoring of slow, stable crack growth in common airframe materials, even in a noisy load transfer component such as the wing trunnion studied here. Simultaneous in-flight acoustic emission measurements ...


Leaky Rayleigh Waves In The Presence Of Loading And Stiffening Layers, A. H. Nayfeh, Dale E. Chimeti Jan 1983

Leaky Rayleigh Waves In The Presence Of Loading And Stiffening Layers, A. H. Nayfeh, Dale E. Chimeti

Review of Progress in Quantitative Nondestructive Evaluation

The distortion and displacement of a finite-aperture acoustic wave incident from a fluid onto a fluid-solid interface at or near the Rayleigh critical angle is phenomenon which has received considerable attention recently1–5. Physically, resonant generation of Rayleigh-like waves and rapid reradiation of the surface-wave energy into the fluid are responsible for the characteristic displacement and distortion of the acoustic beam. These effects typically lead to a bimodal reflected acoustic field, composed of a remnant specular reflection summed coherently with the radiating surface wave. When conditions of beam width and wavelength are favorable, a portion of the field distribution shows ...


Computer Evaluation Of Real-Time X-Ray And Acoustic Images, M. H. Jacoby, R. S. Loe, P. A. Dondes Jan 1983

Computer Evaluation Of Real-Time X-Ray And Acoustic Images, M. H. Jacoby, R. S. Loe, P. A. Dondes

Review of Progress in Quantitative Nondestructive Evaluation

The weakest link in the inspection process is the subjective interpretation of data by inspectors. To overcome this troublesome fact computer based analysis systems have been developed. In the field of nondestructive evaluation (NDE) there is a large class of inspections that can benefit from computer analysis. X-ray images (both film and fluoroscopic) and acoustic images lend themselves to automatic analysis as do the one-dimensional signals associated with ultrasonic, eddy current and acoustic emission testing.

Computer analysis can enhance and evaluate subtle details. Flaws can be located and measured, and acceptance decisions made by computer in a consistent and objective ...