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207 results on '"HUNTLEY, J. M."'

60. Deformation, Fracture and Explosive Properties of Reactive Materials

Author

CAMBRIDGE UNIV (UNITED KINGDOM) CAVENDISH LAB, Field, J. E., Bourne, N. K., Huntley, J. M., Walley, S. M., Palmer, S. J., CAMBRIDGE UNIV (UNITED KINGDOM) CAVENDISH LAB, Field, J. E., Bourne, N. K., Huntley, J. M., Walley, S. M., and Palmer, S. J.

Abstract

A range of techniques has been developed for studies of the behavior of explosives when impacted and for recording their strength, failure and ignition properties. They include a drop-weight facility with transparent anvils, an instrumented drop-weight machine, a miniaturized Hopkinson bar system for high rate of strain property measurement, laser speckle for studies of deformation and fracture of PBX's, an automated system for analysing speckle and moire records, and a heat sensitive film technique for recording the position and temperatures of hot spots. The report describes impact tests using transparent anvil drop-weight apparatus. It discusses the latest developments and recent applications with laser speckle and moire research. We now have the ability to combine these high spatial resolution techniques with high speed photographic recording. Impact on 2-D composite disc samples shows the importance of 'liner' materials in reducing impact stresses. The application of laser speckle photography to measure the in-plane displacement fields resulting from the compression loading of cylindrical grains of inert solid propellants for guns is discussed. Microstructural studies on the failure surface of PBX's are presented. Results on a photographic study of shock-induced cavity collapse of both inert gels and reactive materials are presented.

Published
1991

79. Multiple-view Shape and Deformation Measurement by Combining Fringe Projection and Digital Image Correlation.

Author

Nguyen, T. N., Huntley, J. M., Burguete, R. L., and Coggrave, C. R.

Subjects
*DEFORMATIONS (Mechanics), *THREE-dimensional imaging, *DIGITAL images, *STATISTICAL correlation, *PROJECTORS, *CAMERAS, *FINITE element method
Abstract

We present a new method that combines the fringe projection and the digital image correlation (DIC) techniques on a single hardware platform to simultaneously measure both shape and deformation fields of three-dimensional (3-D) surfaces with complex geometries. The method in its basic form requires only a single camera and single projector, but this can be easily extended to a multi-camera multi-projector system to obtain complete 360° measurements. Multiple views of the surface profile and displacement field are automatically co-registered in a unified global coordinate system, thereby avoiding the significant errors that can arise through the use of statistical point cloud stitching techniques. Experimental results from a two-camera two-projector sensor are presented and compared with results from both a standard stereo-DIC approach and a finite element model. [ABSTRACT FROM AUTHOR]

Published
2012
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87. Speckle photography fringe analysis: assessment of current algorithms

Author

Huntley, J. M.

Abstract

The accuracy and reliability of four fringe analysis algorithms have been assessed, using Young's fringe patterns calculated from computer generated speckle patterns. The 1-D integration, 1-D autocorrelation, 2-D Fourier transform, and 2-D Walsh transform methods all estimated the two in-plane displacement components with negligible systematic error; the random errors were found to vary in proportion to σ^2/VR (speckle diameter = σ, fringe visibility = V, and radius of laser probe beam = R), with the lowest errors given by the 2-D Fourier transform method.

Published
1989

88. Speckle photography fringe analysis by the Walsh transform

Author

Huntley, J. M.

Abstract

Two-dimensional Walsh spectral analysis is presented as a new method of numerically processing the Young's fringes diffraction pattern from a double-exposure speckle photograph. The Walsh spectrum of the fringes is more complex than the Fourier spectrum but can be interpreted reliably by further cross correlation of the fringes with square waves. Compared with Fourier spectral analysis, the new technique gives results of almost identical accuracy but with substantially reduced computational effort. The ideas presented have relevance to the general problem of detecting and accurately determining the frequency components of a 2-D sinusoid in the presence of noise.

Published
1986

89. Measurement of time-varying displacement fields by multiple-exposure speckle photography

Author

Huntley, J. M. and Field, J. E.

Abstract

It is shown how multiple-exposure speckle photography may be used to measure the time-varying in-plane displacement field of a specimen undergoing deformation. The technique is based on holographic speckle photography, which involves recording a shifted reference speckle pattern on the same photograph. An image processing system analyzes the photograph by calculating the autocorrelation function region by region. Results from a six-exposure photograph are presented. This new technique is compared with conventional double-exposure speckle photography in terms of accuracy, sensitivity, and spatial resolution.

Published
1986

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