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1.
A holographic interferometric technique, combining an image hologram with a grating approach, is proposed for three-dimensional
deformation measurements on opaque planar object surfaces. In this technique, the holographic plate is brought close to the
object surface, onto which a high-frequency crossed-line diffraction grating has been replicated. The grating surface produces
multiple object waves rather than the usual diffusely reflected object waves. The double-exposed single holograms can be reconstructed
at multiple off-axis angles. Four independent high-contrast fringe patterns are extracted simultaneously. Displacement vectors
over the entire measurement area are separated in three orthogonal directions. The resultant displacements are presented as
three-dimensional meshed plots and topographic contour maps. The optical system for both recording and reconstruction of the
holograms has been simplified compared to conventional holographic interferometry. Experimental errors associated with fringe
readout and system geometry are reduced because of the sharp images and the well-defined spatial orientation in the reconstruction
system. 相似文献
2.
Geometrical considerations are used to obtain quantitative data for the components of the displacement vector. Use is made of a dual-beam illumination and a variant is described, using point light sources and a single point of observation. Contour lines for the displacement vector in the viewing direction and in a perpendicular direction are obtained as the algebraic sum and difference of two interference patterns. Densification of the initial pattern is used to obtain moiré patterns for the out-of-plane and in-plane displacements of flat Surfaces and for the derivatives of these displacements. To determine the complete displacement field of objects of arbitrary shape, one holographic plate is sufficient, using two times two-point light sources. 相似文献
3.
V. P. Tyrin 《Journal of Applied Mechanics and Technical Physics》1990,31(1):142-145
Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 155–158, January–February, 1990. 相似文献
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Holographic interferometry was utilized to determine the three orthogonal components of displacement in elastic surface waves. A pulsed ruby laser was used as the light source and techniques to improve its coherence properties are described. Procedures for the formation and reconstruction of the hologram, fringe interpretation, and data reduction and presentation are detailed. The elastic-wave velocities and material constants for pink westerly granite were obtained. Solutions for an explosively generated Rayleigh wave in a half space and its reflection from a free edge are presented. 相似文献
6.
This article provides an overview of all the experimental research studies in the field of heat and mass transfer by means
of the holographic interferometry which were performed under the supervision of Professor Franz Mayinger during his professorship.
The principle objective of this paper is to contribute to the knowledge base of the heat and mass transfer processes in various
fields as well as to illustrate the capabilities of the holographic interferometry. Investigations of the heat transfer pattern
in grooved channels and in various geometries of compact heat exchangers, drying processes of a dispersed, water-based varnish
on paper, mixed convection in bent ducts, the growth and condensation of vapor bubbles in subcooled boiling and the simultaneous
heat and mass transfer are presented. The results of all these studies demonstrate the successful application of the holographic
interferometry and Professor Mayinger's highly valuable contribution in this area.
Received on 11 April 2001 相似文献
7.
William G. Gottenberg 《Experimental Mechanics》1968,8(9):405-410
Holographic interferometry, a new technique for measuring small displacements, is discussed. Application is made to the measure of surface displacements of strained bodies in two specific examples. The curvature of one face of a statically bent bar was examined in detail and compared with the three-dimensional elastic solution. In the second example, the radial-displacement field was measured in the area of the leading edge of a longitudinal compressional stress wave propagating through a bar. 相似文献
8.
A particular optical configuration has been used by the authors to holographically obtain interference patterns which are unsensitive to rigid body translations. The fringe pattern depends on the strains and any rotations of the body. When a curved surface or several flat surfaces of a homogeneous body are viewed simultaneously, rotations can be eliminated from the fringe pattern, and the strain in the viewing direction can be determined from a single view of the hologram. This technique has been used to measure the thermal expansion coefficients of a beryllium rod and the shear modulus of an aluminum bar with an accuracy of a few percent. 相似文献
9.
The technique of double-exposure holographic interferometry was used to record transverse waves propagating in a long beam. The wave was initiated by striking the beam in the center with a ballistic pendulum. Pulsedlaser interferograms were obtained which showed the bending waves at three different times after the initiation of impact for three different experiments. From the interferograms, plots of the transverse displacement vs. distance along the beam were obtained. The experimental data compared favorably with analytical results for the problems. The experimental technique, differential interferometry, was also introduced to facilitate measurement of largeamplitude motions using holography. 相似文献
10.
Holographic interferometry is a non-intrusive optical measuring technique which can potentially capture instantaneous information about a complete three-dimensional flow field onto a single holographic image. However subsequently extracting the flow data so that it can be used to validate CFD results, is for most practical wind tunnel applications not yet possible.An approach applied in this paper, is to compare experimental interferograms with equivalent images obtained by post-processing the CFD solution. We have investigated transonic flow in a wind tunnel environment and computationally reconstructed both 2D image-plane interferograms and full 3D holographic interferograms. These comparisons have subsequently helped us to evaluate and improve our 3D Reynolds Averaged Navier-Stokes calculations.The main part of this study was conducted by the authors at Cambridge University Engineering Department where the work was funded by RAE Farnborough under contract 2029/233 XR Aero and monitored by Dr. B. Williams and Dr. P. Smith 相似文献
11.
Near-Resonant Holographic Interferometry is a powerful technique which extends the established advantages of conventional
holographic interferometry by allowing a species-specific number density to be determined. It has been tested in the harsh
flow conditions generated in a high enthalpy facility yielding information about the shock shape on a cylindrical body and
on the distribution of a trace species seeded into the flow.
Received 7 April 2000 / Accepted 1 November 2000 相似文献
12.
Toshiharu Mizukaki 《Shock Waves》2010,20(1):19-27
Digital phase-shift holographic interferometry was applied to visualize weak shock waves and related phenomena quantitatively.
This method of interferometry is an improved version of double-exposure holographic interferometry using digital image processing
and a phase shift method. The obtained interferograms were analyzed using the Carré method. To evaluate the applicability
of the interferometry to quantitatively visualize the phenomena, density profiles behind weak spherical shock waves generated
with 500 μg of silver azide were examined. The results of the numerical analysis performed with the hydrocode AUTODYN were
compared with those of the experiment. The Mach number of visualized shock waves was estimated to be 1.007 ± 0.001 at the
pressure transducer near the test section. At the shock fronts, the density difference between the experimental and numerical
results was within 0.3%. 相似文献
13.
14.
T. R. Hsu 《Experimental Mechanics》1974,14(10):408-411
This paper describes a simple technique for desensitizing real-time holographic interferometry so that it can be more easily used in investigating large deformation of solid structures. 相似文献
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Holographic interferometry was used to study the mixed-mode fracture characteristics of mortar. The nature of crack propagation
in such quasibrittle materials and the theoretical model used to interpret the experimental results indicated that a highly
sensitive measurement technique was required. The gradual curvature of the propagating crack at different sections of the
specimen necessitated full-field observation capability. The nature of the problem made holographic interferometry the ideal
technique for this application.
To measure the in-plane components of the opening and sliding of the crack surfaces during propagation, a single holographic
plate was placed very close to the specimen. This allowed four independent observations of any point on the specimen from
the four corners of the plate without any need for additional optics of exposures. Double-exposure holograms were made at
different crack-propagation stages. The developed plate was illuminated by an unexpanded reference beam to form a real image
of the object and observe displacement fringes. Fringe data were interpreted by using computer software written for this research. 相似文献
17.
For blunt bodies the reduced bow shock wave stand-off distance and the shock layer density rise in the stagnation region as compared to ideal gas flow are phenomena caused by dissociative effects. In this work experiments with aR
BODY=45 mm radius cylinder and an aspect ratio ofL/R
BODY 11 are described. The tests were carried out in the High Enthalpy Shock Tunnel in Göttingen (HEG), a free piston driven shock tunnel. Two different test conditions at reservoir enthalpies of around 21 MJ/kg and Mach numbers of around 9 in air and nitrogen were available.Optical measurements with a holographic phase step interferometer to obtain complete flow field density gradients have been carried out. By increasing the signal-to-noise ratio with the technique of phase stepping over the original recording quality, high quality interferograms are obtained. The high spatial resolution of the holograms results in the creation of hologram-schlieren images which are compared to directly recorded laser-schlieren images.Infinite and finite fringe interferograms and the complete density fields for the two free-stream conditions are presented. The stagnation line densities are quantified. The measured results are shown and compared with Navier-Stokes calculations which account for chemical reactions in the flow. The numerical code underpredicts the stand-off distance of the bow shock wave. It is shown that the flow behind the bow shock wave is in non-equilibrium and that it reaches equilibrium before the body for one condition.This work was an offshoot of an ESA research contract monitored by Dr. D. Vennemann, whose support is gratefully acknowledged. This study of stagnating high enthalpy flows has exceedingly benefited from discussions with S. Brück and V. Hannemann. The operation of the large wind tunnel HEG is the result of a team effort. The with to thank the whole team, represented by Dr. W.H. Beck, for keeping the tunnel going. 相似文献
18.
In order to test the accuracy of theoretical fracture models for mortar and concrete, it is necessary to have accurate measurements of the crack profiles. In this study, sandwich holographic interferometry has been used to find the crack profiles in a center-notched plate specimen loaded at the center of the notch. The results have shown that at low load levels with corresponding short crack lengths, there is little difference between the measured crack profiles and elastic crack profiles computed by finite-element analysis. At high loads with long crack lengths there is a large difference between measured and computed elastic crack profiles. The data suggest the presence of a closing pressure at the crack tip and that there may be a limit to crack-tip-opening displacement (CTOD) before the crack propagates. 相似文献
19.
A technique using holographic interferometry and models of thin-sheet PMMA has been adapted to study the effective crack length for slots with rounded tips of various radii. The results suggest a rational means of applying sharp-crack fracture mechanics in certain nonideal situations and are compared with earlier studies. 相似文献
20.
It is proposed that the residual stresses due to curing in a spin-coated polyimide film can be determined using the solution to the problem of a vibrating membrane. The membrane is biaxially constrained and supported on a metal washer or copper substrate. A piezoelectric transducer is used to excite the sample. The membrane vibrates uniformly in response to its resonant frequencies. The vibration pattern is recorded using time-average holographic interferometry. The pattern produced is indicative of the mode of vibration. The biaxial stress in the film can be calculated from measuring the characteristic frequency, the density of the material, and the mode of vibration. The effect of mass loading of air on the apparent stress in these membranes is also investigated. Measurements made in vacuum appear to resolve this problem. The stresses calculated are on the order of 10 MPa. 相似文献