Hologram Interferometry Research Articles

Quantitative description of low-cycle fatigue damage accumulation in contact interaction zone by local strain evolution

The novel non-destructive method for quantitative description of low-cycle fatigue damage accumulation is expanded to a case of contact interaction in the stress concentration area. Investigated objects are plane aluminium specimens with the centred hole filled by cylindrical steel inclusion. The specimen is subjected to cyclic pull-push loading. The key point, that defines scientific novelty and powerfulness of the developed approach, consists of involving local deformation parameters as current damage indicators. Required strain values follow from distributions of all three displacement components along the filled hole edge measured by reflection hologram interferometry. The data, which are derived at different stages of low-cycle fatigue for the single specimen, provide normalized dependencies of local strain values from number of loading cycle, which are a source of damage accumulation functions. These functions are constructed for the specimen with the filled hole and geometrically analogous specimen with the open hole. Obtained data quantitatively describe a difference in damage accumulation rates for two cases.

Quantification of low-cycle fatigue damage accumulation in stress concentration area by local strain evolution

The novel non-destructive method for quantitative description of low-cycle fatigue damage accumulation is proposed and implemented. The key point, that defines scientific novelty and powerfulness of this approach, consists of involving various deformation parameters referred to critical point belonging to the hole boundary as current damage indicator. Required strain values follow from distributions of all three displacement components along the hole edge measured by reflection hologram interferometry. The derived data at different stage of low-cycle fatigue lead to normalized dependencies of various strain parameters from number of loading cycle, which are a source of damage accumulation functions.

Residual Stresses Determination near FSW Joints by Combining the Hole Drilling Method and Reflection Hologram Interferometry

The results of residual stress characterization near friction stir welded (FSW) butt joint of aluminum plates are reported. The experimental analysis employs two-side measurements of local deformation response on small hole drilling by reflection hologram interferometry. The approach developed is based on the unequivocally solution of the properly posed inverse problem thus deriving both membrane and bending residual stress components. Residual stress components of high level are derived inside the tool shoulder borders on both specimen faces.

Residual stress determination by optical interferometric measurements of hole diameter increments

The main questions, related to the residual stresses determination in thin welded plates by the general approach, are considered. The values of hole diameter increments in principal stress directions, obtained by both reflection hologram interferometry and electronic speckle-pattern interferometry, serve as the initial experimental information. The analytical basis shows that the formulae, which connect experimental data with residual stress components, represent unequivocally solution of the properly posed inverse problem. Simultaneous measurements of the local deformation response on the opposite faces of thin-walled object under study, when a single probe hole is drilled, is the essential condition of the general approach implementing. To do this, an optical system of combined interferometer is developed. The main feature of this optical set-up resides in a capability of simultaneous recording fringe patterns inherent in electronic speckle-pattern interferometry (ESPI) and reflection hologram interferometry on opposite specimen faces for the same through hole. The accuracy of the proposed method with respect to the residual stress components determination has been assessed by three different ways. It is shown that ESPI based interference fringe patterns of high density provides a fast and reliable way of determining residual stress values of the order 160–180 MPa at the weld seam proximity. Residual stress evolution due to cyclic loading is described through the use of ESPI data.

Post-Process of Density Streaks Image of Flow Field in Supersonic Jet Device Captured by Laser Dual Hologram Interferometry

Wind tunnel test can not simulate effectively the flow field of fuze electrical machinery at flight test conditions. In order to deeply research the structure of flow field and measure the flow field density out of fuze electrical machinery, the laser dual hologram interferometry was applied and the streaks photos were obtained clearly. To recognize the contours of density field, identification is needed to deal with interference streaks, and the density of local streaks is calculated with interference principle. The hologram interferometry photos of density field were pro-processed in the thesis, for the problem of photos that the left part was much brighter than the right, the method of multiple threshold was used to binary image. It can be seen that the method gives consistent results to a certain extent of human perception and gives ideal results to find uniform regions in the image plane. Then the binary image is thinned by pixels searching algorithm according to the lines to get coordinates of the pixels of each streak and to lay the foundation for extracting density field from density interference streak in future research.

射流密度场激光双曝光全息干涉图像的后处理

射流密度场激光双曝光全息干涉图像的后处理

Checking the permanent joint quality using the hologram interferometry method

The possibilities of applying holography for checking defects of soldering and welding in composite structural parts are considered.

Combined implementing the hole-drilling method and reflection hologram interferometry for residual stresses determination in cylindrical shells and tubes

Main features inherent in simplified approach to residual stresses determination in cylindrical shells and tubes, external diameter of which is not less than 60 mm, by combing the hole-drilling method and reflection hologram interferometry are discussed in detail. Initial experimental information in a form of hole diameter increments in principal stress directions is derived from high-quality reflection holograms recorded near cylindrical objects of intermediate curvature value. Converting measured parameters into required stress values is based on the transition model that corresponds to plane stress conditions of pure membrane type. The technique developed is capable of determining residual stress component values within 5% accuracy in an absence of stress gradients over the probe hole diameter when a type of residual stress field corresponds to the transition model adopted. The accuracy analysis involved is based on matrix formulation of conventionally direct problem and an assumption on a pure membrane character of residual stress field under study for thin-walled shell. Required error estimations in a case of inspecting thick-walled cylindrical tube are obtained by combining the above-mentioned approach and an analogy of reconstructed fringe patterns with actual and artificial interferograms, which follow from drilling blind hole of the same geometrical parameters in thick-walled plates. Experimental verification of the developed approach is founded upon a determination of actual stresses in thin-walled cylindrical shell and obtaining residual stress distributions at the proximity of welded joint in thick-walled cylindrical tube.

General approach to residual stresses determination in thin-walled structures by combining the hole drilling method and reflection hologram interferometry

Main questions, which are connected with a determination of residual stresses by combining the hole-drilling method and whole-field displacement measurements, are considered in detail. The relations, which are needed for converting initial experimental data into stress values of interest, are presented for thin-walled plane structures. Required input data are obtained by simultaneous measurements of probe hole distortions in two principal strain directions on opposite sides of thin plane specimen. Emphasis is made on a careful quantitative formulation of the inverse problem, a solution of which is capable of deriving both membrane and bending residual stress components with the highest possible accuracy. It is shown that an availability of two-side initial data is both an essential and a necessary condition of such formulation. Detailed analysis of accuracy of the results obtained is performed proceeding from three different criteria. All presented considerations are supported with a set of high-quality actual interferograms and analogous reference fringe patterns related to weld-induced residual stress fields.

Characterization of Turbulent Flow in a Flume with Surfactant

Summary The drag reducing effect of a surfactant additive from the alkylpolyglycosides family was investigated experimentally. In thepresent study, PIV measurements were done to investigate theturbulent flow in the streamwise-spanwise plane of a flume aty 1 580, in the buffer zone, where about 80% of the energy pro- Fig. 4 PDF’s of the u rms8 O U q for water —circles– and surfactant—squares–. u rms8 —x,z– ˜ −—u—x,z– A −u—x,z–‰– 2 ‰and the PDF is rep-resenting the spatial distribution of the rms values, normalizedby the flow-rate velocity U q .Fig. 5 Two-point—auto–correlation function R uu of the stream-wise velocity along the streamwise x and spanwise z coordi-nates, for water —circles and plus symbols– and for surfactant—square and triangular markers–, respectively.Table 1 Statistical properties of the Reynolds stress A −u 8 w 8 ‰ O U q2 .Statistics Maximum Minimum Average Std. dev. SkewnessWater 0.05 20.035 0.35310 23 0.0045 0.93Surfactant 0.03 20.035 0.35310 24 0.0032 0.003Table 2 Statistical properties of the turbulent energy production term

Residual stresses deriving from holographic interferometry data on a base of inverse problem solution

A transition model, which is capable of obtaining both membrane and bending residual stress components from initial experimental information, is developed for thin-walled plane structures. The determination of residual stresses is based on the combined implementing of the hole-drilling method and reflection hologram interferometry. Required input data are obtained by simultaneous measurements on through hole distortions in two principal strain directions on opposite sides of thin plane specimen. These sides are faces of the drill entrance and exit. Superimposed residual stresses field, which consists of both membrane and bending components, is a reason for the various deviations of each specific fringe pattern from an ideal form. This fact is a clear experimental indication of the bending stress contribution in a total stress field. Two ways of decomposition of superimposed residual stresses field are proposed and analysed in detail. Emphasis is laid on a careful quantitative formulation of the inverse problem needed for an accurate deriving both membrane and bending residual stress components. It is shown that an availability of two-side initial data is both an essential and necessary condition of such a formulation. Detailed analysis of an accuracy of the results obtained is performed. This analysis is based on a wide set of both actual interferograms and analogous reference fringe patterns related to superimposed residual stress field under study. Comparing residual stress values obtained proceeding from one-side and two-side data are presented for different types of superimposed field of interest.

Classification of holographic fringe patterns inherent in through hole drilling in residual stress field

Comparative analysis of actual fringe patterns, which are induced by combined implementing the hole drilling method and reflection hologram interferometry for residual stresses determination, is presented. Involved considerations are related to plane thin-walled structural elements. A set of interferograms of perfect (ideal) form is selected proceeding from one-side measurements. A base for recognising each specific ideal configuration is a fine coincidence between actual interferograms and analogous reference fringe patterns constructed for the same stress state. Perfect (ideal) both actual and reference fringe patterns are defined as a response of pure membrane 2D stress field on through hole drilling between exposures. Main principles of creating the regular catalogue of reference fringe patterns inherent in through hole drilling in thin-walled components are formulated. Emphasis is made on a careful collecting and classifying actual interferograms with clear indications of bending stress presence in total residual stress field. Evidences needed for a reliable classification of the type of residual stresses field of interest are established and verified. A response of superimposed residual stress field, which consists of both membrane and bending components, is characterised by various deviations of each specific fringe pattern from an ideal form. More deep analysis of fringe patterns related to superimposed residual stress field is based on specially designed technique. The main essence of the approach developed is simultaneous measurements of through hole distortions in two principal strain directions on opposite sides of thin plane specimen. These sides are faces of the drill entrance and exit. Sophisticated optical set-up that is capable of obtaining high-quality fringe patterns in the course of two-side measurements is developed and implemented. Typical set of fringe patterns obtained for single probe hole on opposite specimen faces is presented.

A role of fringe pattern catalogue in the course of interferometrically based determination of residual stresses by the hole-drilling method

A further development of the technique for residual stresses determination in thick-walled structures, which is based on a combination of the hole-drilling method and reflection hologram interferometry, is presented. A plane specimen welded from two equal parts of dimensions 130×80 mm 2 in plane and thickness 12 mm is the object of investigation. Weld seam is performed along the shortest side of the specimen. Residual stress field of interest is formed by a superposition of initial welding-induced field and secondary stress field caused by plastic deformation of the specimen. A set of actual fringe patterns, which corresponds to a wide variety of residual stress components both ratio and sign, are reconstructed and presented as illustrations. A series of reference fringe patterns is simulated for the most typical cases inherent in residual stress field under study. It is shown that actual interferograms obtained belong to three main groups depending on a typical form of fringes configuration. On this base the main principles of creating the general catalogue of fringe patterns are established and the first version of this catalogue, which is related to reflection hologram interferometry, is developed. A structure of the catalogue that consists of both actual interferograms and reference fringe patterns is described. Possible ways of further catalogue completing and its direct implementing in the course of quantitative determination of residual stresses are discussed. It is shown that both experimental and numerical data aggregated into the first version of the catalogue can be effectively used for a verification of various coherent optics techniques with respect to a determination of residual stress components by means of hole drilling. An analysis of capabilities of reflection hologram interferometry in the field of residual stresses determination comparing with dual-beam speckle-interferometric techniques is presented. Superimposed residual stress field is quantitatively described in detail for both specimen sides of dimensions 260×80 mm 2. It is shown that fine nuances inherent in residual stress distributions over different specimen faces can be reliably derived from recorded fringe patterns of any type. This study serves as an example of residual stress components determination in real structure with a type of residual stress field to be investigated is unknown before the experiment.

Metrological justification of reflection hologram interferometry with respect to residual stresses determination by means of blind hole drilling

A description of practical implementing combined technique for residual stress determination in plane thick-walled structures is presented. The main features, which are inherent in a procedure of reconstruction and quantitative interpretation of fringe patterns arising as a result of blind hole drilling in residual stress field, are discussed in detail. Two plane aluminium specimens welded from two equal parts having dimensions 130×80 mm in-plane and thickness of 18 and 12 mm are the objects of investigation. Weld seam is performed along the shortest side of both specimens. A wide set of actual fringe patterns related to both uniform and non-uniform residual stress field is reconstructed. Most of typical fringe patterns are presented as illustrations. A whole set of available interferograms shows that a residual stress field in both thick-walled plane specimens investigated consists of both a uniform and non-uniform part. It is shown that a form of both non-uniform and uniform stress fields remains practically the same along the weld line. Moreover, non-uniform residual stress field at the proximity of weld seam is of similar form for both specimens. Emphasis is made in a choice of the transition model proceeding from a comparison of actual interferograms and reference fringe patterns. For the first time reference fringe patterns are constructed by using data obtained from corresponding actual fringe patterns, which reveal a non-coincidence between specimen's symmetry cross-sections and principal strain directions. It is shown that relations developed for a probe hole drilled in uniform 2-D stress field can be used for deriving residual stress components when fringe patterns obtained reveal a presence of local strain gradients. A good agreement between actual and reference fringe patterns is achieved in a case of local strain gradients existing. Comparing two types of interferograms related to uniform residual stress fields demonstrates their full coincidence. It is shown that the whole set of obtained fringe patterns consists of three main groups. The main evidence, which reveals an interferogram belonging to each specific class, is a typical form of fringes configuration. The main principles of creating the general fringe patterns catalogue are established and initial draft of this catalogue is developed. Distributions of residual stress components are constructed for different surfaces of both specimens under study. Quantitative results have a form that is typical for welded joints of structures bounded by plane surfaces. It is shown that fine nuances inherent in residual stress distributions over different specimen faces can be reliably derived from recorded fringe patterns of any type.

Reflection hologram interferometry combined with hole drilling technique as an effective tool for residual stresses fields investigation in thin-walled structures

A detailed description of unconventional two-step technique of residual stresses determination is presented. This technique has the highest possible sensitivity with respect to plane residual stress components compared with all other destructive mechanical methods. The first step is a high-precision measurement of in-plane displacement components describing a distortion of drilled hole in principal strain directions due to residual stresses redistribution. The second stage is a choice of the most reliable transition model that is capable of deriving accurate residual stresses values from holographic interferometry data. A full metrological justification of both steps is established. Specific approach to a quantitative interpretation of fringe patterns arising near probe hole in terms of absolute fringe order difference is proposed and effectively implemented. Basic relations that allow us a quantitative determination of residual stress components are derived. A wide series of high-quality actual fringe patterns inherent in the procedure involved is obtained. Sophisticated technique for reference fringe patterns constructing is developed and implemented in order to carefully estimate and verify an accuracy of results obtained. A capability of the developed technique is demonstrated in the course of residual stress fields determination at the proximity of welded joints of thin aluminium specimens. Residual stress distributions corresponding to four different welding technologies are presented. An excellent correlation between most of the actual and numerically simulated fringe patterns is demonstrated for different types of residual stress state. It is shown how residual stresses of high level up to 200 MPa in aluminium alloy can be measured by means of the technique developed.

Real-time and two-reference-beam hologram interferometry: effects of emulsion shrinkage

When transmission holograms are recorded on photographic materials, any change in the thickness of the photographic emulsion due to processing can produce a change in the spacing of the carrier fringes. We show that the resulting change in the angle at which the image is reconstructed when the hologram is illuminated with the original reference beam can give rise to significant errors in real-time and two-reference-beam hologram interferometry.

Holographic microscope for measuring displacements of vibrating microbeams using time-averaged, electro-optic holography

An optical microscope, utilizing the principles of time- averaged hologram interferometry, is described for microelectrome- chanical systems (MEMS) applications. MEMS are devices fabricated via techniques such as microphotolithography to create miniature actua- tors and sensors. Many of these sensors are currently deployed in auto- motive applications which rely on, or depend on, the dynamic behavior of the sensor, e.g., airbag sensors, ride monitoring suspensions sensors, etc. Typical dimensions of current MEMS devices are measured in mi- crometers, a small fraction of the diameter of a human hair, and the current trend is to further decrease the size of MEMS devices to submi- crometer dimensions. However, the smaller MEMS become, the more challenging it is to measure with accuracy the dynamic characteristics of these devices. An electro-optic holographic microscope (EOHM) for the purpose of studying the dynamic behavior of MEMS type devices is de- scribed. Additionally, by performing phase measurements within an EOHM image, object displacements are determined as illustrated by rep- resentative examples. With the EOHM, devices with surface sizes rang- ing from approximately 353400 to 5318 mm are studied while undergo- ing resonant vibrations at frequencies as high as 2 MHz. © 1998 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(98)00505-4)

Digital recording and numerical reconstruction of holograms: reduction of the spatial frequency spectrum

Direct recording of Fresnel holograms on a charge-coupled device and their numerical reconstruction is possible if the maximum spatial frequency of the holographic microstructure is adapted to the spatial resolution of the detector array. The maximum spatial frequency is determined by the angle between the interfering waves. For standard CCDs with spatial resolutions of ;100 lines/mm, the angle between ref- erence and object wave is limited to a few degrees. This limits the size of the objects to be recorded or requires a great distance between object and CCD target. A method is described in which the primary object angle is optically reduced so that objects with larger dimensions can be re- corded. The principle is demonstrated for the example of deformation analysis. Two Fresnel holograms, which represent the undeformed and the deformed states of the object, are generated on a CCD target, stored electronically, and the wave fields are reconstructed numerically. The interference phase can be calculated directly from the digital holograms, without generating an interference pattern. As an application of this method, we present the transient deformation field of a plate that is loaded by an impact. © 1996 Society of Photo-Optical Instrumentation Engineers. Subject terms: digital holography; hologram interferometry; numerical hologram reconstruction; charge-coupled devices.

GENERATING AND RECORDING TRANSIENT BENDING WAVES IN PLATES BY PULSED LASERS

We have presented a method to generate bending waves in a plate by focusing a Q-switched Nd:YAG-laser pulse on its surface. These waves are recorded by double pulsed hologram interferometry. Evaluation of the interferograms show that the bending wave pattern is very similar to what is predicted by the Kirchhoff plate equation assuming a point impact of infinitesimally short duration. This indicates that a short Nd:YAG-laser pulse may be considered as a Dirac pulse in space and time. Future investigations will be performed with a more powerful and “cleaner” laser to get a higher energy and impulse transfer to the plate thus giving bending waves of larger amplitude. Promising preliminary experiments have also begun using a double pulsed ruby laser both for generating and recording of bending waves.

Theoretical and experimental study of coupled vibrations of channel beams

Abstract Studies of the free vibrational behavior of channel beams, which are partly constrained along one end or one flange, are of prime importance for structural engineers. In this paper, studies of thin-walled channel beams with different cross-sectional areas and lengths were conducted using theoretical and experimental approaches. The theoretical approach was based on analytical and finite element methods. The experimental approach utilized the methods of laser hologram interferometry. In the studies reported herein, emphasis was placed on dependence of the natural frequencies and the mode shapes on the cross-sectional area, and on determination of the prediction capability of the Timoshenko model considered in the analytical analysis. The results show that lower modes of slender channel beams are characterized by global beam motions and a non-deforming cross-section. More pronounced C-shapes are increasingly influenced by plate deformations in the web and flanges. The Timoshenko theory compares well with experimental data on natural frequencies, but only for slender beams. The results of the finite element analysis generally compare well with experimental data.