The measurement of flow-induced surface displacement on a compliant surface by optical holographic interferometry

Flow-induced surface displacements that form on a singlelayer passive isotropic viscoelastic compliant surface as a result of the interaction with a turbulent boundary layer are measured by non-intrusive optical holographic interferometry in connection with an interactive fringe-processing system. The purpose for developing this method is to obtain the instantaneous topographic features of a whole field of the displacements of the compliant surface. Information about dimensions of the foot prints of the turbulence on the compliant surface are obtained in the form of line contours and isometric phase maps. These experimental data are essential in order to determine statistical measures of the random topography of the compliant surface. Furthermore, by coupling with the simultaneous measurements of the turbulence field, the physics of the alteration of the turbulent boundary layer by the undulating surface can then be better understood.List of symbols A light amplitude - A ₀ light amplitude of object beam - A _r light amplitude of reference beam - _c light speed - d _e diameter of laser beam - d _p diameter of pinhole - d _s spatial frequency - E exposure energy - f focal length - I _in light intensity at photographic plate - I ₀ light intensity of object beam - I _r light intensity of reference beam - k wave number, 2 / - L _in light amplitude records on the emulsion surface - L ₀ light ray of object beam - L _r light ray of reference beam - R Reynolds number based on momentum thickness, V / - t time - t _e exposure time - T ₀ uniform background light transmittance - T _re reconstructed light through hologram - T _t amplitude transmittance of hologram - V freestream flow speed - radian frequency, k c - x distance from the leading edge of the flat plate - z position - slope - optical path difference - phase - ₀ phase of object beam - _r phase of reference beam - wavelength - momentum thickness - ₀ angle between the object beam with respect to the normal of the photographic plate - _r angle between the reference beam with respect to the normal of the photographic plate - kinematic viscosity of water     

Determination of displacement of hole profile in cylindrical shells subjected to torsion using holographic interferometry

Moscow Engineering and Physics Institute. Translated from Prikladnaya Mekhanika, Vol. 24, No. 7, pp. 63–69, July, 1988.     

A fringe-compensation technique for stress analysis by reflection holographic interferometry

The use of holographic interferometry for stress analysis of nontransparent objects is limited by rigid-body displacements of the object. These displacements can alter the fringe patterns and often cause the fringes to disappear completely. A technique of compensation for this deterioration of the fringe pattern forreal-time holographic interferometry is described in this paper. It is especially designed to permit the accurate measurement of the out-of-plane component of strain near regions of stress concentration in plates that are subjected to in-plane loading. It is first shown that the fringes caused by a pure rigid-body displacement can be eliminated almost completely by translations of the hologram and rotation of the illumination wave. This procedure is first described when the displacement is known; then when it is unknown. A method to estimate the error made in the correction is presented. In actual stress-analysis problems, the object is both rigidly displaced and strained. Assuming the rigid displacement is known and corrected as previously, the analysis is developed to relate the fringe pattern to the strain-related displacement. This analysis takes into account the optical modifications of the system that are necessary to achieve the rigid-body-displacement correction. When the rigid-body displacement is unknown, the method is shown still to be workable through the use of various symmetries and boundary conditions. Two sample interferograms are presented as illustrations. Quantitative treatment of data from one of these are presented in a companion paper.     

Displacement field around a circular hole in a viscoelastic plate

Moiré experimental techniques are used to measure displacement fields in viscoelastic plates undergoing large deformations at elevated temperatures. These experimental procedures are applicable to determining displacement fields in nonlinear materials. As preliminary information, the material properties are determined from creep studies. The moiré method is used to determine the strains under constant load and isothermal conditions. Tests are conducted for several combinations of load and temperature for 2.5 decades of time. Assuming thermorheologically simple behavior, the data are shifted to establish the creep extensional compliance over ten decades in time. The constitutive equations are formulated as integral equations, the kernels of which are the functions that were measured in this work. These equations are solved exactly for the infinitesimal case. The finite case is then approximated by an incremental superposition of a series of successiye infinitesimal solutions. The results are applied to a plate initially containing a circular hole, and are shown to agree closely with the experimental measurements.     

Residual-stress determination by single-axis holographic interferometry and hole drilling—Part II: Experiments

Experiments to assess the ability of the holographic/hole-drilling technique to accurately determine uniaxial stresses are described. The experimental data are in the form of optical interference fringe patterns. Different patterns obtained by varying the direction of laser light illuminating a test specimen with respect to the direction of stress are shown. Stresses estimated by the technique are compared with known values in specimens of aluminum alloy 7075-T651 and hardened Type 304L stainless steel. D. Williams was Senior Technical Aide, Sandia National Laboratories.     

Residual-stress determination by single-axis holographic interferometry and hole drilling—Part I: Theory

A method is described for the rapid, accurate determination of residual stresses from a holographic interference fringe pattern. The pattern is generated by the displacement field caused by localized relief of residual stresses via the introduction of a small, shallow hole into the surface of a component or test specimen. The theoretical development of the holographic method is summarized. An example is given showing how the method can be applied to a typical experimentally observed fringe pattern to determine principal residual stresses and directions.     

The scattered energy around a circular hole by SH wave in anisotropic media

A new approach based on complex function for solving the SH-wave scattering problem around a circular hole in an anisotropic media is desribed in this paper. It is found that the scattered energy depends on the incident wave number and the hole radius. Finally, some numerical results of scattered energy of a circular hole in an anisotropic media are given.The project has been supported by National Natural Science Foundation of China.     

Large-deformation measurements by real-time holographic interferometry

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.     

全息干涉法在条形药包离面位移场研究中的应用

以新型红宝石激光照相装置为基础,进行动态全息实验系统研究及设计,实现了一次爆破加载获取四个动态过程爆破模型的位移场条纹图,用此研究了线型载荷爆破时质点离面位移振动的变化规律。研究表明：端部延长线方向离面位移值在全场所有剖面始终最小,发现在线型载荷离面位移场和应力场一样,同样存在端部效应现象;中垂线上的最大位移值在不同时间都高于其它计算剖面位移极值;瑞利波产生的位移衰减很慢。     

New aspects of surface displacement and strain analysis by speckle interferometry

The application of two allied laser-speckle-interferometric techniques to the measurement of surface displacements and strains is described. One technique uses the ‘double-aperture speckle camera’ and the other uses a similar interferometer called a ‘double-aperture speckle-shearing camera’. Although these cameras are not new, the theory for their application to general deformation of a flat surface was presented only recently with ‘new’ equations governing the formation of fringes. These equations are reviewed briefly and particular applications of them are presented. Three experiments demonstrating the use of the cameras are described. The good results obtained verify the validity of the new equations.     

Stress concentration around a circular hole in a transversely isotropic spherical shell

Analytical expressions for the stresses near a circular hole in a transversely isotropic shallow spherical shell under uniform pressure are derived. The form of the solution depends on the range of change in the compliance to transverse shear. The influence of the relative radius of the hole and the compliance to transverse shear on the stress concentration is analyzed.__________Translated from Prikladnaya Mekhanika, Vol. 40, No. 12, pp. 99–106, December 2004.     

Estimation of plated-hole barrel stress from thermally induced out-of-plane displacement gradients measured by electro-optic holographic interferometry

Electro-optic holographic interferometry was used to measure the thermally induced out-of-plane displacement field around both sides of a plated hole on a single layer, FR-4 laminate. The unique features of the electro-optic holographic interferometry technique are described as well as a method for estimating the stress in the barrel from the deflections of the pad. The pad deflections were observed to be roughly axisymmetric and were nearly the same on the front and back of the laminate. The stress was observed to increase at a more rapid rate for temperatures above the glass temperature than below and is of sufficient magnitude to cause plastic deformation in the barrel although none was observed.     

Stress state around a circular hole in a prestressed transversely isotropic spherical shell

The stress state around a circular hole in a prestressed hollow spherical shell is found by expanding the unknown functions into Fourier-Legendre series __________ Translated from Prikladnaya Mekhanika, Vol. 44, No. 2, pp. 61–68, February 2008.     

Axisymmetric vibrations of a cylindrical resonator measured by holographic interferometry

A circular, cylindrical, ultrasonic resonator excited at one of its resonant frequencies is studied by holographic interferometry. Displacement distributions associated with the axisymmetric oscillations of the resonator are measured with the aid of time-average holograms, and are compared with a simple one-dimensional theory of rod vibrations, corrected for radial inertia. Analysis shows the overall error bounds on measured displacements to be ±9 percent of the maximum displacement at the resonator tip. Although the accuracy of measurements could be increased by refinements in experimental techniques, the work reported here represents substantial improvement in measuring the vibratory motion characteristics of ultrasonic devices over the point-by-point technique used heretofore.     

Measurement of mixed-mode crack profiles by holographic interferometry

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.     

Dynamic stress concentration around a circular hole due to SH-wave in anisotropic media

A new approach based on complex function to solve the SH-wave scattering problem around a circular hole in anisotropic media is introduced in this paper. It is found that the dynamic stress concentration factor is dependent on the incident wave number and the hole radius. Finally, some numerical results of dynamic stress concentration factor of a circular hole in anisotropic media are given. The Project Supported by National Natural Science Foundation of China