The temperature rise at the tip of dynamically propagating cracks in Beta-C titanium is measured using an array of high speed infrared detectors. For a crack propagating at 396 m/s the maximum crack tip temperature rise is 450°C. This is high enough that the mechanical properties of the material at the crack tip will be changed, thus affecting the fracture process in a significant manner.

In this paper, the effect of the variations of material combinations on the fracture behavior of an inclined crack terminated at a bimaterial interface was investigated. By using the complex-variable method, a comprehensive analysis of the state of stress and stress intensity factors (SIFs) was performed. Digital photoelastic technique was also employed to verify the theoretical results. Six specimens of different material combinations were prepared for a particular crack inclination angle. It was concluded that far-field effects usually found in the homogeneous case had to be included in the stress equations.

The use of a coherent gradient sensing (CGS) apparatus is explored in dynamic fracture mechanics investigations. The ability of the method to accurately quantify mixed-mode crack tip deformation fields is tested under dynamic loading conditions. The specimen geometry and loading follow that of Lee and Freund^1,2 who give the theoretical and numerical mixed mode K values as a function of time for the testing conditions. The CGS system’s measurements of K_I and K_II are compared with the predicted results, and good agreement is found.

The 3-dimensional coordinates of a cross grating on a mainly plane surface are determined by stereo imaging. Instead of a photogrammetric method a comparably simple set of approximating imaging functions is used, which transform every point of the interesting spatial region into the stereo image coordinates. The inverse problem, evaluating 3d-coordinates from a related pair of image coordinates, is also solved by means of the imaging functions. Contour and plane strain of a crack tip were investigated by this method.

When an experimental analysis on the shearing phenomenon, including large strain and stress which arise concentrated in a narrow region, is conducted using the conventional grid method, there are problems such as difficulty in obtaining accurate results due to grid lines subjected to large deformation, or in a worst case, impossibility in reading the coordinate values of grid pattern intersections, leading to a total failure of the analysis itself. Therefore, in order to solve such problems, the authors propose the remeshing visioplasticity method. This method has proved that an experimental analysis of the entire stress and strain in a shearing area, which has not been successful so far either theoretically or experimentally, can be possible. The results show, for example, that just before cracks are formed in a shearing deformation area, contour lines of a large increment of maximum shearing strain appear parallel to the line connecting respective cutting edges of a punch and a die, and also that the hydrostatic pressure values in its vicinity decrease (approaching a tensile level).

Following a brief review of analytical studies of the dominant eigenvalues associated with the crack border-boundary surface intersection problem, analytical findings are summarized and experimental results obtained from moiré interferometry, frozen stress photoelasticity and holographic interferometry are critically assessed. The engineering significance of these findings are discussed.

This paper presents a method for measuring residual stresses in plastic materials. The approach is based on measuring the out-of-plane displacement caused by a blind hole drilled on the surface of the test object. The out-of-plane displacement is measured by electronic shearography at video camera speed and hence the results are obtained almost in real-time. Unlike holography, electronic shearography does not require special vibration isolation nor ambient light dependence. These advantageous features make the method practical for qualitative analysis of residual stresses in a production/field environment.

In this paper, the digital caustic technique was used to determine the transient thermal stress intensity factors (SIFs) of edge-cracked semi-infinite plates subjected to a sudden temperature change on the plate edge. Effects of different crack lengths and orientations on SIFs were studied. By using the self-developed image processing software on a locally supported digital caustic system, caustic patterns were analyzed and SIFs were then obtained. The correlation expressions between the variations of transient thermal SIFs with the time, temperature difference and geometrical parameters of the cracks were obtained by a regression procedure.

Experimental investigations of crack-branching on central-notched plates in polymer are presented using dynamic photoelasticity. From a multiparameter representation of the stresses around the crack-tip, the stress-intensity factor is determined by a multiple-point method which couples iterative process and minimization procedure. The experimental device (high-speed camera, loading system) is described and the results are discussed. The polymer tested seems to correlate with the macroscopic branching criteria commonly found in dynamic fracture analysis.

A computer-oriented hybrid method will be described to determine the principal stresses in plane objects, which are composed to different materials by means of photoelastic experiments. The difference of the principal stresses is obtained by digital image processing of the isochromatic fringe pattern, the sum of the principal stresses is calculated by means of the boundary element method. Thus the values of the principal stresses in arbitrary points of the object are given without needing the isoclines. These are necessary now only to get information on the direction of the stress tensor axes.

Crack-tip photomechanics are based on certain simplifying assumptions which are seldom discussed. In a recent paper of the authors theoretical bases of the shadow optical method of caustics have been analyzed and tested using results obtained by three analytical-experimental procedures, namely classical strain gages, isodynes and gradient-index method. It has been concluded that the gradient-index method appears to be a suitable tool for analysis of stress state near crack tips and notches and, in particular, for testing pertinent singular solutions of linear elastic fracture mechanics and ranges of their applicability. In the present paper, a more detailed analysis of all results obtained in light deflection experiments allows to quantify the contribution of both involved effects and to determine the distortion of the faces of the investigated plates along their crack planes. The ability of the strain-gradient method to analyze some features of the three-dimensional stress-state is reported. Finally, presented experimental evidence allows to draw conclusions related to limits of applicability of certain photomechanical measurements near crack tips.

Computer automated high-accuracy strain-field mapper (HASMAP) was used to measure strains responsible for crack tip shielding in partially stabilized zirconia containing 9% MgO (Mg-PSZ). HASMAP is used to determine the strain fields from the measured displacement fields by cross-correlation analysis of the relative positions of visible surface texture on the micrograph. The system is used to determine the relative displacement fields by comparing a pair of SEM or optical micrographs, one recorded before the load is applied (the reference micrograph) and the other afterwards. This system is capable of measuring both in-plane and out-of-plane displacements to accuracies approaching ± 60 A for optical microscopy, and ±10 A for scanning electron microscopy. Measured strains were used to evaluate the crack tip shielding stress intensity factor. Dilatational strain accounts for most, but not all, of toughening in Mg-PSZ.

A real time, full field, lateral shearing interferometry - coherent gradient sensing (CGS) - has recently been developed for investigating fracture in transparent and opaque solids. The resulting interference patterns are related to the mechanical fields by means of a first order diffraction analysis. The method has been successfully applied to quasi-static and dynamic crack tip deformation field mapping in homogeneous and bimaterial fracture specimens.

This paper deals with the technique of scattered light photoelasticity, used to determine three dimensional stress distribution in transparent, birefringent materials. A novel implementation of the technique using materials that exhibit permanent birefringence in addition to stress induced birefringence is discussed. The basic equations of photoelasticity are derived and then application to both transmitted light photoelasticity and scattered light photoelasticty are described. Finally, some examples of the application of scattered light photoelasticity are discussed.

Knowledge of the three-dimensional contact stress between roller and rolling road for a strain-hardening material in an elasto-plastic state is limited, to say the least. Mathematical analyses of stress for this problem meet with extreme difficulties. Therefore, experimental approaches are desirable. The experimental elasto-plastic stress analysis method proposed by A.R. Hunter is extended in this investigation. The model material is epoxy resin which exhibits a frozen nonlinear effective stress-strain behavior similar to that of bearing steel when subjected to a thermal cycle whose maximum temperature is significantly less than the critical temperature of the material. This effective stress-strain curve and an effective birefringence-stress curve were obtained by subjecting uniaxial tensile specimens to constant stress and the appropriate thermal cycle. Then the model was subjected to the same thermal cycle and a uniform distributed load which would develop a plastic zone. The stress distributions on the contact surface and the plastic-zone expansion law were obtained from photomechanical analysis of the slices removed from the model. Several important conclusions were also summed up which would greatly improve the roller bearing design.

Paper presents an assessment of capacity of three-dimensional isodyne stress analysis and its efficiency in nondestructive experimental stress analysis of plane and three-dimensional stress states. The actual three-dimensional stress state in the ASTM Standard Compact Specimen C(T) was taken as a representative example. Models of the Standard Compact Specimen C(T) were made of transparent polyester resins Palatal P6 and Homalite H101. Three families of optical isodynes, which represent three families of isodyne surfaces, were produced to determine all components of the stress state. Optical isodynes were produced using the scattered laser light as the information-carrying energy flow. To increase the resolution of the recordings the spatial modulation technique was used. Principles and techniques of measurements, recordings, and evaluation of isodyne fields are outlined. Two sets of normal and maximal shear stresses acting in the plane of the crack, between the crack tip and specimen boundary, are presented and discussed: stresses in direction of the crack; and stresses normal to direction of the crack. It is shown that the concept of a generalized plane stress state is not admissible in regions of high stress gradients. Results pertain to reliability of theoretical foundations of various analytical-experimental procedures of photomechanics.

In this paper, dynamic caustic method is applied to analyse the crack propagating problem of a plexiglass double cantilever beam (DCB) specimen. The varying curve of dynamic stress intensity factor (DSIF) with crack propagating velocity (v) has been drawn. The results show that this method will find a wide use in those transparent materials which has no optical double-refracted character for dynamic fracture mechanics research.

By means of the laser speckle strain gauge, which directly detects the elongation or contraction of microscopic structures of a diffusely reflecting surface from speckle displacement, we measured both stress-strain curve of polymer materials in the biaxial mode by loading specimens on a commercial testing machine and thermal strain of metal and polymers. In the experiments we derived Poisson's ratio and thermal expansion coefficients of various materials. We observed good agreement of the results with those obtained by other methods.

A series of frozen stress experiments were conducted on a rocket motor grain geometry containing a natural surface flaw of varying aspect ratios in order to study the stress intensity factor distribution along the flaw border and to estimate the loss of the inverse square root singularity when the crack border intersects the inner star surface at right angles. By applying a refined optical method, the photoelastic data are converted into classical stress intensity factors resulting from the three dimensional stress state existing at the inner surface to indicate the nearly uniform distribution of the stress intensity factors along the crack border.

Often the direct experimental analysis of deformation fields on crack specimens is a necessary tool accompanying the application of modern fracture mechanics concepts. A speckle photographic technique for the measurement of in-plane displacement fields and respective elements of the distortion tensor on crack specimen surfaces has been developed which includes automatic specklegram evaluation by means of digital image processing. Short Q-switch pulses of a ruby laser permit to freeze specklegrams from solid state waves travelling through crack specimens. Mode I crack opening strain fields on impact loaded specimens have been measured and compared with theoretic results.

The present paper describes a four-point bending fixture which has been designed for testing ceramic materials and the experimental procedures developed to obtain full-field representation of the out-of-plane displacements on the specimen surface under traction. The testing procedure, which can be extended to three-point bending tests, enables the errors due to a possible misalignment of the applied load to be detected and eliminated. The possibility of determining the elastic constants of the material from the displacements measured is also discussed.

Three-dimensional moire interferometry technique has been used to study the interaction between cylindrical void/voids and an edge crack in aluminum single crystals. Tensile specimens made of aluminum single crystal have crystal orientation with crack surface on (102) plane and its tip along [251] direction, and undergo power-law hardening with hardening index of n = 3.43. Deformation fields near and in-between the crack tip and the cylindrical void/voids are quantitatively obtained and analyzed. The results show that voids inclined to crack surface at ±30° have greater influence on deformation field than those directly ahead of crack tip; the effects of voids on near tip deformation field are found to be significant in the region between —60° to +60°. It is also observed that the very near tip deformation fields are characterized by the formation of angular sectors in which equivalent strain and maximum shear strain are independent of 6 within certain sectors, and change abruptly across sector boundaries. This is consistent with the experimental results of Li et al 28, in which single crystal crack tip deformation field without the presence of void/voids were investigated.

Possibilities to apply integrated photoelasticity for residual stress analysis in glass specimens of complicated shape are considered. In the general case algorithms for the interpretation of experimental data in integrated photoelasticity are complicated. However, if birefringence of the specimen is weak, simple integral relationships can be used for stress calculations. It is shown that normal stress distribution can be determined in a plane of a specimen of arbitrary shape. In the case of an axisymmetric specimen residual stresses can be completely determined using a combination of integrated photoelasticity and of a tomographic technique. Several examples illustrate application of the methods developed.

In the present report the main conception of research developing in the Laboratory of Photoelasticity of Moscow Civil Engineering Institute (MCEI) is stated.

Some examples of investigations of complex three-dimensional constructions of a nuclear power and hydro-power stations, machinary constructions are represented. Expediency of joint applying calculating and experimental techniques also is shown.

In this paper, the experimental model for the toughening of brittle matrixes with ductile particles is proposed. The specimens are made from polymethyl methacrylate (PMMA) , rubber particles were embedded in crack front of specimen. Using holographic photoelasticity method, we make a lot of test, and obtain many photographs of isoline of stress sum. The stress intensity factor Ki is calculated from extrapolation of maximum diameter of isoline of stress sum (isopachics), and compared with theoretical values.

This paper presents the developed techniques for determining all rheo-optical and mechanical functions of creep and relaxation within microsecond time scale for viscoelastic birefringent polymer on the base of the epoxy resin and application of this techniques for solving some practical problems of dynamic viscoelasticity. New experimental procedure using modified compound Hopkinson bars has been developed for the study of optical and mechanical properties of birefringent materials with the help of the photoelasticity and tensometry methods. This gives the possibility to register simultaneously stress, strain and optical retardation impulses in the viscoelastic bar under pulsed loading. The experimental investigations of longitudinal wave diffraction on circular holes of different diameter in the viscoelastic plates are described.

The deformations and stresses in a typical bridge bearing have been evaluated by testing a three dimensional photoelastic model, supported upon a flexible foundation. This investigation has revealed the form of the pressure distribution on the foundation, and provides quantitative values for the bending stresses and fillet stress concentrations in the bearing pot base. Attention has been focused on the deformation mechanism which induces a significant all round tension in the pot base. This confirms the importance of the interaction between the base and rim, and provides the information necessary to develop a realistic analytical model of the bearing.

The dynamic processes of stress waves propagation and cracks extension from adjacent boreholes in epoxy resin have been recorded with the dynamic photo-elastic apparatus (WZDD -1). New type synchronism control of large power multiple-row rounds detonate is solved. The general laws of break through of cracks have been analysed and studied preliminarily for adjacent boreholes detonated simultaneously or with a short delay time. New experimental techniques and useful information on practical basis have been offered for studying the mechanism of short delay blasting multiple-row rounds.

An instrument to measure three components of the strain tensor at the surface of the examined body using the photoelastic effect has been developed. The method applied is based on the utilisation of three oblique incidence light beams from three laser diodes. The isochromatic fringes in the photoelastic coating are observed by three independent channels. The data collected in this way is used to define the state of strain and stress from one single point measurement. The measuring head equipped with three or more lasers scans the surface of the tested body and transfers the data on the light intensities into the computer memory. This data is then converted into the values of strains and stresses. The computer also controls the head motion. The obtained results (three components of the strain tensor), are presented in the form of diagrams on the screen of the monitor or using the plotter. The stresses are calculated from strains using the physical properties of the examined body. The device is equipped with a specially designed software for recording and processing the data. Application of the described device eliminates all problems with the separation of strain components in the photoelastic stress measurements. The apparatus is portable and provides the stress distribution in the examined body in a very short time.

In this paper,the principle for calculating six stress components of structure is proposed when symmetric structure bears symmetric loads, through observation of orthogonal slices twice by normal incidences and obique incidence once. Three dimensional photoelastic experimental methods imitating of the Wan — An Lock, which bears gravity, earthfill pressure and water pressure, the separation and superposition of stresses, the main results of stress analysis on the structure are introduced. In this paper the method and the results of experimental stress analysis for Wan — An Lock structure by the three dimensional photoelasticity are described.

The development of systems of automatic measurement and data processing is of current interest for the experimental investigation of stressed and strained states.

As for polarized-interferometric techniques of researches in photoelastic laboratory of MCEI by V.V.Kuibyshev, the search of this problem solution is being carried out in following main directions:

- automatization of measuring the birefringent parameters by the polarized-optical set-ups;

- automatization of processign of fixed interferograms;

- computer aided processing of experimental data.

In general, there are two methods of measurements in polarization interferometry; the real time measurements in points on the model or a posterior field measurements on interferograms fixed on photoregistrator.

The development of many-year-frost rock (MYFR) region hydrotechnic construction, the MYFR being quite a reliable construction base, provided it is situated outside the seasonal temperature fluctuation layer, requires the rock stress-deformed state evaluating criteria working out with maximal possible account of static, dynamic, blast-hole drilling and temperature effect on their properties.

In estimating the Hydroelectrical Power Station (HPS) underground building stress-deformed state the present work refers to experimental data and calculations, received by solving a linear task with further account of the building profile changing effect in the process of construction and the concrete and rock mechanic properties heterogeneity. The proposed order is justified, provided the rock mass defrosting depth value is small as compared to the rock separate block dimensions and when it corresponds to the building construction period. The results are given for the Kolymskaya Hudroelectrical Power Station building cross-section, considered under flat deformation conditions.

This paper considers the examples of the experimental solution of some engineering dynamic problems studied at the Photoelasticity Laboratory of Moscow Civil Engineering Institute: the stress state of the holes located either near the free surface or deep in the medium under the impulsive and seismic loadings, the stress state of concrete gravitational dams, the defensive effect of screens under the loading by surfacing explosives and three-dimensional dynamic stress state of forging hammer striking elements.

Photoelastic sensor with fringe image transfer by an image-guide to a computer for stress analysis was constructed for those applications where the place of measurements is hard to reach and electrical instruments are not permissible. Two types of sensors are presented: one, disc-like, for uniaxial stress observations and the second one, called a hollow glass cylinder, with axially bored stress concentrator for biaxial stress measurements. Sensor is a central cylinder glass cemented in a cubical concrete block. The sensor is connected to autocollimating polariscope, which allows the sensor to be lit and transport an isochrome image to digital image processor card. The numerical analysis of the fringes images is done in many ways. The original programs for the analysis are presented.

Stress analysis by analytical method has made remarkable progress in recent years as more sophisticated finite-element programs are developed for use with computer. However, there still remains many stress problems that cannot be rationally approached using finite-element analysis and only an experimental stress analysis test on the actual structure or part will provide the quantitative information necessary to achieve a safe reliable design. For example, the detection of local yield, analytical method cannot infallibly predict the occurrence of localized yield since it is random and its exact location is unpredictable.

3 series of new, optically sensitive polymers have been synthetized: by copolymerization of bis-cyclopentadienyl oligomers and diallyl bis-dienophiles; on the basis of branched oligo ester acids and on the basis of interpenetrating networks of the epoxy anhydride polymer and polybis- (allyl carbonate) - polypropylene glycol.

In this paper, stress distribution in patella was studies by 3-D photoelastic experiments and finite element calculations. The experimental conditions were in good agreement with that of body mechanics: (1) The ratios of m. quadriceps femoris force F_Q to lig. patella force F_P were 1.03-1.42. (2) The angles between F_Q and F_P were 8.4°-18.7°. (3) The ratio of modulus of elasticity for epoxy resin and silicone rubber matched that for patella and cartilage, i.e., 145:1.

The principal stresses and their path line, normal stresses, contact stresses between patella and ossis femoris were determined in various flexion angles (15°, 30°, 45°, 60°, 75°, 90°). Two of the correlations were:

(1) Maximum principal stress in the front of patella

σ_max=35.8Wexp(0.024α) KPa

(2) Maximum contact stress between patella and ossis femoris

σ_max=−(6.86−0.14α+0.02α²)W KPa

where W was body weight subjected by a single foot.

It was proved that the transverse break of patella resulted from the case that the principal stress in the front of patella exceeded ultimate tensile strength. And Tension Band Wiring (TBW) therapy conformed to the law of physiological stress field. A modified K-needles position in TBW therapy was suggested. These results are useful for further research of human patella mechanics and recovery therapy. No similar result has been found in American MEDLIN Data Bank.

In this paper, the speckle holophotoelastic interference method has been applied to study the state of elasto-plastic strain and a new optical method for strain separation in photoplasticity is given.

A new method of measuring the normal and sliding loads associated with multiple point contact is introduced. A multiple point contact is modeled with a steel die with a profile that simulates a rough surface. A very large scale factor is used in modeling this surface. The steel die is placed in contact with a photoelastic model of a half plane and is subjected to a normal load. This normal load is partitioned over the multiple points of contact producing an isochromatic fringe pattern that describes the stress distribution in the local neighborhood of the contact points. A sliding load is then imposed on the model which destroys the symmetry of this fringe pattern. The fringe data in this pattern is sufficient to determine the local loads Pi and Qi and the local coefficient of friction fi= Qi/Pi at each contact point. An overdeterministic method is introduced which gives the solution for Pi , Qi and fi using many data points taken from the isochromatic pattern in the local neighborhood of the contacts. An image analysis method was employed in collecting the data sets used in the overdeterministic computations.

Calculation techniques determining crack-resistance parameters, finite element techniques among them, can not still provide a full-scale solution of problems emerging in design of crack-resistance structures. Of increasing value therefore become development and improvement of experimental methods, in particular, of photoelasticity method for determining crack resistance parameters on models of polymer birefringent materials and also on natural materials using birefringent coatings.

A new whole—field isochromatic fringe compensation technique is presented. In the method, the isochromatic fringe pattern is modulated by the carrier using a carrier generator, and the shifting technique of the moire method and the optical filtering technique are applied. Its applications in diesel engine crankshaft and dynamic thermal analysis are introduced.

Optical isodynes, produced by scattered laser light, constitute experimental basis of two-dimensional and three-dimensional isodyne stress analysis. Paper presents theoretical basis of optical isodynes, discusses major components of the theoretical model and presents examples of efficiency of the nondestructive isodyne stress analysis in determination of the actual three-dimensional stress states in composite structures, contact problems, and fracture mechanics. Stress is put on theoretical admissibility of major components of the involved mathematical models which are taken as analytical foundation of the experimental and analytical procedures of stress analysis. Reliability of isodyne stress analysis is compared with reliability of other methods of stress analysis.

The Report deals with two aspects of an analytical & experimental approach to the optimization of intricately shaped lightened structures exposed to mass forces. Examples illustrate diverse possibilities of the approach and its efficiency.

Linear and nonlinear creep by an optical polarization technique, functional similarity applied, is considered. Two trends of modelling - direct modelling based on special selection of optically sensitive materials with required viscoelastic and optical polarization properties, for models and an elastic analogy technique, when the solution of a creep volumetric problem is connected with solutions of auxiliary problems, are discussed. Dependencies for stresses and strains definition in a model by measured interference fringe-orders, similarity conditions, and stress-strain recalculation formulae for a full-scale structure are presented.

As an illustration the samples of linear and nonlinear creep problem solution are also presented.

The stress fields around a noncharged borehole (NCB) due to blasting stress waves were researched by dynamic photoelasticity and gauges. The action of stress concentration and reflection by a NCB were analysed according to the dynamic recorded results. The guiding mechanism of a NCB was further explored.

It is known that there is not any three-dimensional analytical solution in the analysis of the contact stress for roll-shape member of the limited length. To discuss this kind of questions, the paper presents a method which is known as the photoelastical mixed solution method combined photoelastical technology, Hertz's theory, numerical calculation method and theory of similarity.

Two practical examples in engineering — a working-roll in the mill and a levelling-roll in the levelling machine — have been analyzed here. The analysis results are in complete accord with the phenomenons of the damage of the real components. This denotes that the method presented in the paper is quite reliable.

A holographic method suited for the measurement of flatness deviation is presented. This method takes advantage of the basic Fizeau arrangement usually meant for contouring analysis of relatively flat bodies. A desensitized interferometer is described allowing the measurement of rough objects, as frequently encountered in engineering practice. The key component of this interferometer is a diffractive optical element produced by recording two-wave interference patterns. Desensitization factors ranging from 1 to 100 with respect to a Fizeau interferometer can be achieved. Flatness checks of computer disks demonstrate the possibilities of the interferometer; deformation measurements performed with the desensitized interferometer on classical experimental mechanics specimens are presented: static testing on notched C-rings and on welds, and fatigue testing on notched three-point bend tests.

To evaluate the displacements of three-dimensional partially curved object surfaces taken by means of automatic digital image processing from multiple hologram analysis in order to determine the strain- and stress state on the surface as well as inside the objects. The informations are to retransform from the hologram plane, i.e. the image plane, into the spatial object configurations. In doing that the image scale, the perspective distortions and the three-dimensional grid of the discrete evaluation algorithm, which is independent of the holographic set-up, must be taken into consideration too. Having evaluated the holograms (at least three in order to determine the displacement vector u on the object surface) the order of the interference fringes in the nodes of the evaluation grid are to fix in the object space. Two different procedures will be described in the following to perform this transformation.

Experimental results are presented for the microscopic aspect of friction between two surfaces of dissimilar materials. The frictional behavior is studied using the fiber-pull-out experiment for glass/gold and glass/acrylate interfaces. The experiments are carried out with optical fibers of 125 and 200 μm diameters. The optical glass fiber coated with various layers such as 0.1 μm thick gold or 62.5 μm thick acrylate is imbedded in an epoxy matrix. Then the fiber is pulled out with various speeds. The frequency and amplitude of the stick slip friction is dependent on the speed of pulling, imbedded length of the fiber and the compliance of the system. The unstable sliding is believed not only due to the local constitutive behavior of the contact interface but also due to non-uniform sliding of the two deformable surfaces. The non- uniform sliding process of the two deformable surfaces is studied with photoelasticity and optical fiber signal processing. Delineating the non-uniform sliding process with the photomechanical experiment, the relaxation and creep behavior of interface friction may be modelled accurately.

The influence of thermal effect induced by optical pumping on YAG crystal rod in a pulse solid laser on the wave surface of the output laser beam is studied in this paper. A series of time-resolved instantaneous interferograms during and after the pumping is obtained with a Mach—Zehnder interferometer, and three-dimension time-resolved pictures of the distorting wave surfaces and the curve of thermal focal length of laser rod versus time are gained after the treatment and calculation for interferograms.

The thermoelastic stress wave stimulated by laser inside a solid medium is studied theoretically and experimentally, and the speed of the wave inside epoxy resin is measured.

The paper presents some results of the stress state and strength study of the power unit steel butt of the nuclear power station. The studies have been performed by employing an optical polarization technique. On the basis of the results obtained experimentally strength design methods of structures reinforcement have been developed. Methods of photoelasticity and moire helped evaluate the concrete rheological properties effect on the reactor body prestress forces.

This article shows the possibility to use traditional holographic interferometry in order to determine mechanical characteristics of non-traditional structural materials - monocrystals of metals with body-centred cubic structure. The proposed procedure permits to determine elastic constants of monocrystalline samples by dynamic method taking into account anisotropy of elastic waves propagation in body-centred cubic crystals. The obtained results correlate well with calculated data from publication.

The loss of thin films is one of the critical parameters that limit the performances of optical thin film devices. Photothermal deflection technique has been used to measure the attenuation coefficients of the different modes in thin film guiding layers. Due to the high sensitivity of the attenuations of guided modes to the imperfaction factors of thin film, a new method is proposed to analyze the loss mechanisms of the thin film samples on separating the absorption and scattering losses. The experimental results are given, and the anealing process of thin film is also studied with this method.

The method of spectral analysis for studying the TEM micrograph of thin film replicas is presented. It has been proved that there are spectral losses in the TEM micrograph, which are concerned with the thickness of the replica. A TEM micrograph of the thin film cross section replica is studied with the aid of a computer.

At certain grain sizes, alumina R curves have been shown to increase with crack growth. This phenomenon is in contrast to R curves for metals, which exhibit a steady-state plateau effect with increasing crack growth. Recent results show R curves for calcium silicate geomaterials also increase. The specimen geometry employed for both alumina and geomaterials is a generalized plane stress double cantilever beam (DCB). The specimens are under direct pin loading with fixed displacement. This note will discuss the common mechanisms of increasing R curve behavior of these quasi brittle materials. Finally, a hypothesis on the discrepancy between the fracture toughness of single crack rock samples and in large seismic events is presented.

For measuring 3D surface movement by means of Electronic-Speckle-Pattern-Interferometry the decorrelation of the out-of-plane component due to the additional inplane movement must be minimized by a resampling of the speckle images or the calculated phase maps in dependence of the measured inplane movement.

The grating objective speckle method was applied for whole field displacement measurements to a high transition temperature superconductor (Y Ba₂Cu₃O_x) disk under diametral-compression. Four fringe patterns were obtained from one single specklegram, indicating the displacement components along four different directions, with 45 degree intervals. The spatial frequencies, which represent the sensitivities of the fringe intervals, were 2400 lines/mm for U_x and U_y, and 1697 lines/mm for U₄₅ and U₁₃₅, respectively. The normal strain components, ε_x, ε_y, ε₄₅, and ε₁₃₅, can be directly transformed. The shear strain, γ_xy, can therefore, be calculated by the rosette equations without the need for first cross-derivatives from two displacement contour maps, which is highly sensitive to accidental rigid-body rotations. The technique provides an extremely simple set-up for the recording system. There axe no laser, no camera, no laborious optical alignment and no requirement for vibration isolation.

The laser speckle photography method is applied to study the deformation behavior of aluminum, stainless steel and high-purity alumina ceramics specimens during the cooling down process from the room to the liquid nitrogen temperatures. The in-plane displacements were measured by the image plane speckle photography and the out-of-plane displacements by the defocused speckle photography, respectively. The surface of ceramics specimen was coated with vacuum-evaporated aluminum film to keep the correlation of speckle patterns during the cooling down process. The experimental values of the in-plane displacement are compared with those of the FEM thermal analysis. The applicability of laser speckle photography method to cryogenic engineering is discussed.

The dynamic laser speckle from a skin surface involves the information about skin blood flow. Both the moving red blood cells and the tissue around are regarded as scatters, from which laser light is scattered to form the speckle pattern. In this paper, we propose and study a new method to monitor skin blood flow changes, and experimented results are also presented.

An application of ASA 5 black and white cinefilm combined with a specialized developer instead of holo film as a new recording medium for double pulse YAG laser speckle is reported. With this recording medium, multi-frame dynamic laser speckle patterns for relatively distant, real bodies are obtained.

Due to the restriction of the upper bound for fringe visibility, the large deformation and nonlinear problem can not be solved by the experimental method of laser or white light speckle photography directly. The applied load may have to be divided into several intervals. Recording the double-exposure specklegram for each loading inerval, the displacement field can be constructed by point-wise or whole field method. A multiquadric surface function is employed to accumulate the displacement components. A new approach to treat the nonlinear experimental problems is proposed.

The feasibility of two-beam speckle interferometry for the study of time-varying mechanical deformation of diffusely reflecting bodies is demonstrated. A sequence of speckle patterns produced by a vibrating cantilever beam was recorded photographically by means of a high-speed camera. These speckle photographs were subsequently digitized using a CCD camera for input into an image processing computer. By gray-level subtraction of carefully registered pairs of speckle images, fringes corresponding to the relative surface displacements were obtained. A sequence of these fringe patterns was reconstructed to obtain the time-history of deformation. These are compared with time-frozen (strobed) patterns for the same body.

Fundamental properties of phase modulation ability of a nematic liquid crystal cell is first studied. Based on the phase modulation property of the liquid crystal cell, a new type of speckle shearing interferometer is proposed and studied experimentally. In the method, a liquid crystal cell is employed as a phase shifter to implement the phase shifting method for the conventional speckle shearing interferometer. From the experiments to measure the deformation of an object, usefulness of the method is confirmed.

The simple and effective optical arrangement synthesizing holographic fringe and speckle photography is presented. This optical system is based on image holography. Cantilever beam located on the precision translator is used to evaluate this system. Experimental results agree well with the actual displacements within the error of 5%. The measurement of 3-D contact deformation is demonstrated as an its application.

The statistical properties of a dynamic speckle field produced by a cascade of two thin diffusers (one moving and one static) which are placed at conjugate planes of an imaging system have been investigated both theoretically and experimentally. We find that the linear dependence of the reciprocal l/rc of the time-correlation length on the velocity of the moving diffuser is still hold in this case, and that because the speckle field has a higher time-varying rate of intensity fluctuations, the measuring time can be reduced greatly, i.e. this speckle field is more sensitive to the motion of the diffuser than when using normal speckles produced by a single moving diffuser. An experimental study has been conducted to verify the theoretical results, and good agreements are obtained.

A method using objective speckle and mismatched subjective speckle photography to improve the sensitivity of dynamic white light speckle method is described in this paper. To be based on this, two hybrid methods which combine dynamic white light speckle method with boundary integral representation and with isochromatic patterns to analysis transient stresses and strains of a structure are presented.

In this paper, the objective white speckle method is applied to detect defects in Graphite/epoxy composites. The coherence of white light is analysed.

A contouring technique based on digital speckle pattern interferometry is developed for investigation of surface defects in deterioration studies. A specific software is proposed for an automatic quantitative evaluation of defect dimensions. Some experimental tests effected on laboratory samples have demonstrated the suitability of the method.

Electronic Speckle Pattern Interferometry is used extensively throughout the Engineering sector as an analytical tool. The full potential of the instrument may be realized by the ability to record and shape data without alterations to the optical present here a method of shape measurement which may be optical apparatus identical to conventional out-of-plane instruments. The shape measurement is achieved by small shifts of optical fibres carrying the object and reference beams. We show that the fringe patterns produced are identical to projected fringe contours, and may be analysed in the usual way.

This paper presents a novel technique for generating contours of diffused objects using a dual beam speckle interferometric setup and a PC-based digital image processor. With the object illuminated by two coherent beams , two speckle patterns are digitized, one before arid one after the object is slightly rotated. By taking the difference between the two digitized images, a fringe pattern is formed which depicts the object contours. The phase distribution relating to the depth information of the object surface is automatically extracted by means of an image processing technique employing two dimensional digital Fourier transform.

The method is simple, fast, relatively accurate, and provides a very wide range of sensitivity. The sensitivity depends on the amount of object rotation which can be easily varied. Theory of the method together with experimental results are presented.

This paper studies the deformation priniciple of rock and clay by means of the method of multilight beams and double explosure. The relationship between stress and strain, the deformation principle and elastic modulus of Chongqing sandstone and mudstone as well as Chengdu's clay were measured. The Poisson Ratio of clay, which couldn't be obtained by normal test, was also measured.

An alternate approach of fully-automatic speckle interferometry is developed. Two speckle patterns of a specimen, one before and one after deformation, are registered by a video camera. These digital speckle patterns are segmented into many very small subimages. Analysis of corresponding subimage pairs is performed pointwise at various locations from both speckle patterns. Basic data process involves two-step fast Fourier transform (FFT). Local displacement vector is revealed by detecting a signal hill in the secondary spectral domain. Accurate characterization of displacement components is achieved by a biparabolic fitting and maximum-searching near the signal hill. Whole field displacement distribution is deduced by analysis of all subimage pairs. An artificial rigid shift between the two speckle patterns is introduced in case of very large displacement. The range of measurable displacement is unlimited as long as the two speckle patterns remain correlated. Incremental deformations in a dynamic loading process can be measured by registering more speckle patterns at consective deformation stages and analyzing each pair of successive speckle patterns. The technique has been applied to the study of crack tip deformation fields.

A new technique of optical interferometry based on the statistics of the fully developed speckle field is proposed. It is revealed that the complete randomness of the speckle phase can play a role of a standard phase in a statistical sense, and the phase of the object under testing can be derived in a statistical way, in contrast to conventional interferometry. The technique is first described in relation to the phase-shifting interferometry and the compensation problem for the phase-shift error. Next the method is generalized as an independent interferometric technique.

The use of in-plane ESPI is generally limited to the laboratory because of the need for component stability. This paper details some of the solutions used to take reliable in-plane measurements on a high speed rotating specimen in an environment consisting of severe turbulence, electromagnetic interference and vibrations. Experimental results are included.

Based on the statistical optics, the mechanism and principle of the dual-beam speckle interferometry are studied, and it's mathematical expression of frequency distribution is derived. The experiment shows an agreeable result with the theoretical analysis. The research shows that both the speckle photography and interference fringes exist in the dual-beam speckle pattern.The only interference fringe remains still as the filtering aperture moves. Besides, the interference fringe appears first, is gradually concentrated in pace with adding the load on a sample, and disappears lastly with the photography fringe at the same time.

In the paper, the feasibility of realizing the electronic shearing speckle interference was analysed in theory, the formula describing the light intensity received through the camera target was deduced and the visibility of the fringes formed from electronic interference was analysed. The three methods of electronic shearing speckle, real time, double exposure and real time interval method, are proposed and realized by the authors. The electronic shearing speckle fringe patterns of the contours of the displacement gradient were obtained too.

A rotating mirror camera and pulsed ruby laser have been combined to record laser speckle photographs at framing rates in the range 105 - 106 frames s"1. The laser is repetitively Q-switched by means of a Pockels cell, which is controlled by photodetectors inside the camera. This allows well-correlated double exposure speckle photographs to be recorded on two separate runs of the camera. The photographs are analysed by an automated image processing system to give whole-field displacement data with submicron accuracy. The paper is illustrated with results showing the dynamic displacement field in polymethyl methacrylate due to solid particle impact.

We present an automatic procedure, with digital image analyzer for measuring displacements on specimen using speckle method. Speckle fringe patterns are projected on a translucent blackening screen. In order to improve the camera sensitivity and the fringe contrast, we eliminate the central order and we attenuate the blurring to increase the usable part of the image. Two programs are presented :

- the first Automatic Data Processing (ADP1) uses a one dimensional Fourier transform applied on signals extracted from the image. ADP1 creates a longer signal by joining series of parallel lines together in order to reduce errors. Manual and numerical results are identical.

- the second Automatic Data Processing (ADP2) utilizes a two dimensional Fourier transform coupled with an appropriate spectral interpolation. This procedure is less sensitive to the image quality. So, non detectable manual displacement can be obtained by this process.

Speckle pattern interferometry using phase stepping and digital processing is proposed and has been used to measure the shape and deformation of a 3D surface. A four beam arrangement, in which one beam is chosen to act as the reference beam, is described. A low cost piezo-electric translator is incorporated in the arrangement to permit the implementation of phase-stepping. Images are acquired by a CCD camera and PC based image processing system.

As well as providing 3D deformation measurements, the arrangement has also been used to determine the object shape by moving one of the illuminating beams. For the shape and deformation measurements, thirteen independent speckle patterns are acquired and processed. Phase maps are produced using a conventional 3-step technique and hence surface contours, displacements and strains can be obtained.

A speckled object-reference beam is used and has the advantage that the measurements are less sensitive to vibration and whole body motion than a smooth reference beam arrangement. A flat surface mounted in proximity to the surface under investigation acts as a reference plane and is used to improve the accuracy of the measurements by validating the phase-stepping steps and verifying geometric and sensitivity parameters.

The technique has been applied to the measurement of a cylinder under internal pressure. The experimental results are compared with conventional point measurements. The optical arrangement and experimental methodology are described. Advantages and limitations of the technique, together with sources of error and measurement uncertainties are discussed.

In this paper we demonstrate fringe formation in speckle interferometry using the scheme shown in fig.1

A new adaptive filtering and enhancement approach is proposed to use local orientation and statistical information of speckle pattern as adaptive image measurements in digital speckle image processing. By the use of combining speckle pattern orientation field with median filtering,some processing of 2-D specklegram can be completed through 1-D digital processing techniquess. Moreover, a polygonal window function with local direction is presented and applied to further smooth noise and to eliminate streak phenomenon produced by 1-D median filtering. Then,a new scanning method,perpendicularly across all the fringes which possess the same direction's proposed to remove thick noise that is very difficut to eliminate by ordinary digital processing techniques. Lastly,a directional enhancement filtering and double extremum detecting method are used to improve speckle pattern contrast, visibility and overcome unfavorable effect of diffraction halo to the discrimination of fringes.

A higher-order theory of caustics for mixed-mode running cracks is developed by using the general asymptotic solutions for a dynamically propagating crack-tip. The analytical expressions are obtained for the Jacobian equation that determines the initial curve, and for the image equations on a screen. Using the higher-order coefficients determined by the finite element simulations of actual dynamic fracture experiments, effects of the higher-order terms on the caustic curve are investigated on the basis of the present theory. It was found that the √r stress field plays important roles in the formation of caustic pattern.

The optical caustic method is re-examined considering the presence of transient effects. Based on the higher-order asymptotic expansion provided by Freund and Rosakis¹, regarding the stress field near a non-uniformly propagating crack tip, the caustic mapping and the initial curve equations are derived. The dynamic stress intensity factor, K^d_I(t), is related to experimentally measurable quantities of the caustic pattern by an explicit expression. It is shown that the classical analysis of caustics is a special case of the new interpretation method. The Broberg problem is used as an example problem to check the feasibility of analysing caustics in the presence of higher-order transient terms. It is shown that the caustic patterns are sensitive to transient effects, and that use of the classical analysis of caustics in the interpretation of the optical patterns for this problem may result in large errors in the value of the stress intensity factor, especially at short times after initiation.

The optical method of reflected caustics was applied up-to-now to various elastic problems containing singularities and especially to problems with cracked plates from isotropic materials. In this paper the influence of the stress-assisted diffusion is studied. Around the crack tip a core-region is developed by the stress-assisted diffusion. This core-region is a strongly brittle area which depends on the sum of the principal stresses at the crack tip and on phenomenological coefficients. So, this core-region influences the initial curve of the caustic and consiquently the shape and size of the caustic. Also, the effect of line - plastic zones developed ahead of crack tip in orthotropic plates on the shape and size of reflected caustics is discussed.

During the past 25 vears the optical method of caustics has matured to a very powerful tool for application in fracture mechanics for the determination of stress intensity factors or the J-integral, in contact mechanics for the determination of contact forces etc. The technique is applicable to two-dimensional static or dynamic problems and works for any kind of stress-strain relationship. The method displays its full power when employed in conjunction with interactive numerical data reduction and evaluation procedures. Recently, the industrial application of high strength-low weight composite materials has boomed. Application of the method of caustics to anisotropic materials requires the development of the theoretical background. This contribution focuses on the theoretical development of the method of caustics and its applicability to anisotropic materials.

The method ol’ caustics is applied to the problem of a finite interface crack situated along the inclined interface separating two dissimilar wedge-type quarter-planes close to the free surface. A new interactive computer graphics-based if-determination procedure will be presented and discussed.

The recorded optical interference fringes are often expanded and blurred, therefore a suitable thinning procedure is necessary and important in image processing.

This paper presents a new thinning method of optical interference fringes. After scanning the fringe pattern row by row, the distribution of the gray level along a row is obtained. After fitting, the extrema of the curves are determined, which denote the position of the integer, minimal light intensity fringes. The advantage of presented method is that the evaluation is simple, the processing speed is faster, and the results are satisfactorily precise, compared with the classical methods.

Moire-holographic techniques are utilized to analyse the mechanical behaviour of structural elements made of thermoplastic materials in the critical temperature domain. Several extensions of the basic set-up are described, which consist mainly in the computation of in-plane displacement components by a phase-shifting technique and in the computation of the derivatives of these components, either by pure numerical means or by a hybrid procedure involving an analog optical recording followed by an automatic phase calculation. The results of tests carried out with ring shaped perspex specimens subjected to compression, under various boundary conditions and different temperature domains, are also provided.

In this paper, an accuracy and high speed method for auto-processing of young’s fringes is proposed. A group of 1-D sampled intensity values along three or more different directions are taken from young’s fringes, and the fringe spacings of every direction are obtained by 1-D FFT respectively. Two directions which have smaller fringe spacing are selected from all directions. The accurate fringe spacings along these two directions are obtained by using orthogonal coherent phase detection technique (OCPD). The actual spacing and angle of young’s fringes, therefore, can be calculated. In this paper the principle of OCPD is introduced in detail. The accuracy of the method is evaluated theoretically and experimentally.

It is a very important problem to process photomechanical fringe pattern quickly and automatically in the aspect of advanced photomechanics research. After analyzing the characteristics of photomechanical fringe pattern and comparing different methods for automatic detection of brightest ridge line of photomechanical fringe, we put forward a kind of synthetic and practical method, which includes image sub-processing, two-dimensional gray level fringe peak detection, binary image labelling by using different thresholds, dilating and thinning processing for gray level sub-peak line, removal of false line and connection of the fringe ridge line by using a cursor, copy of the fringe ridge line and its coordinate into printer. With the method, typical photomechanical fringe patterns have been processed on the HAMAMATSU DIPS C2000 and satisfactory results have been obtained.

Digital speckle pattern interferometry(DSPI) is a promising Optoelectronic testing technique for a wide range of applications. Comparing with holographic and speckle interferometry, it has some attractive features, such as needlessness of tedious film processing, high measuring accuracy, satisfactory automaticity. The measuring data can be displayed on the monitor at real time. In this paper, the vibration of a clamped steel plate is tested using stroboscopic Digital Speckle Pattern Interferometry. The advantages of stroboscopic technique are that it can give both the amplitude and phase information of a harmonic vibration . This is very useful for the vibration modal analysis of engineering structures. This work is realised on an image processing system based on IBM-PC/AT personal computer. The stroboscopic wavefronts are obtained by chopping a CW He-Ne laser using acousto-optic modulator. The fringe patterns obtained with stroboscopic DSPI are superior to that with time-averaging TV holography (ESPI or DPI). The interpretation of the stroboscopic DSPI fringes and selection of the system parameters are discussed in details. The Measured results are also given.

A real time moiré spatial filtering system using cheap white light source is proposed in the paper. The system is characterized by its simple set, easy operation and more moiré informations obtained than using coherent monochromatic light source. Through different filtering various colour moiré patterns will be appeared. The increasing or decreasing of fringe orders can be demonstrated by the orders of fringe colours and the centre lines of fringes may be determined precisely through edge-strengthened colour fringes. The theoretical analyses and derivations about these basic relationships are given. Experimental results of curved bar and circular ring agree well with theoretical solutions, also the relationship between the colour orders of fringes and the increasing or decreasing of fringe orders is verified.

A digital speckle correlation method based on principle of area correlation in pattern recognition technique is proposed. The effect of speckle displacement gradients on correlation is neglected, only displacements are into account. It much simplify the correlation iterative process and save computer run time. The selection of correlation function, the reliability of search recognition and the sensitivity of the method are discussed. The rigid body motion and strain measurement test were done to verify the method. Application examples are given on measuring fluid velocity field and forging deformation. The method also was used to process photographs of very high magnification taken by scanning electron microscope. These results demonstrate that it has the potential to be an quantitatively measuring tool for micro mechanics.

Measurable area, accuracy, and ranges of displacement, strain and rotation of the CASI are estimated. The measurable area for a given video camera is proportional to the area of each individual speckle. The displacement uncertainty is proportional to speckle size. The measurable displacement ranges from a few percent of speckle size to several centimeters. Strain and rotation up to 3 ~ 5% can be detected. Experimental results from CASI on crack opening displacement (COD) and normal strain distribution ahead of a crack tip of an aluminum specimen under mode I loading are presented.

Despite the recent rapid growth of numerical techniques and their application in almost every held of engineering experimental techniques have proven an invaluable tool for the investigation of numerous complex problems in academia and industry. Among the various traditional and more recently developed photomechanical technqiues photoelasticity and the method of caustics only will be addressed in this contribution. Problems associated with the interaction of cracks and stress waves, wave focussing, and dynamic contacts will be investigated. Main emphasis will be placed on improved understanding of the underlying physics and therefore, qualitative rather than quantitative results will form the main part of this contribution. However, where necessary, quantitative results will be presented. Applications have been selected in view of showing the wide spectrum of applicability of the optical techniques ranging from micromechanics in electronics to geophysics.

Recently, there are considerable research activities in the development of optical methods for nondestructive testing in production/field environments, because of the full-field and noncontacting nature of these methods. Among the various optical methods such as thermography, holography, moire and ESPI etc., shearography appears to be more practical and it is rapidly gaining acceptance by industry. This paper reviews the state-of-the-art of shearography.

This paper reports on two holographic techniques which allow one to obtain the contour maps of arbitrarily shaped objects. The most important feature of these methods is that their sensitivities can be varied continuously and in real-time in a wide range. The intersection planes can be pivoted at will to provide for oblique slicing of the models.

In this paper we discuss a fiber optic electronic speckle pattern interferometer (ESPI) for obtaining 3D information about surface deformation. Phase stepping is introduced by stretching the fiber wrapped around a piezo-electric transducer. Two schemes to stretch the fiber are discussed. Also calibration of the phase step is critical in phase measurement techniques for obtaining good phase plots. In this paper we outline a method used for calibrating the stretcher. We also discuss the error in the phase caused by temperature changes.

This work presents an approach to compute, at the same time, the displacement field and its derivatives from a two-dimensional representation of the fringe order function. Those concepts are very convenient to be used with digital image processing systems. Some simplifications of those general equations for particular cases are discussed. The complete displacement field and its derivatives, strains and rotations are measured in a disc under diametrical compression as an example of application. A digital image filtering technique, for speckle noise reduction, is also introduced.

The application of pulse holographic interferometry in investigating the stress state by dynamic photoelasticity is discussed. The polarized-holographic set-up with three pairs of reference beams having the orthogonal polarizations has been developed. The space-time control of reference beams allows to record the interferograms of absolute retardations for three moments at a single hologram.

A new holographic system for measuring 3D amplitude field of the opaque object is proposed. This system has the single reference beam and the three object beams of spatial distribution, and the three overlapping time- average holograms used for analyzing amplitude are recorded on the same plate with the help of the rotation unit of the plate. The related analytical formulas are derived in accordance with the property of the surface shape of the measured object and the optical system designed. Experimental results are given.

The homogenous degree of deformation of the bearing cap of the motor under axial load is measured by combining reflection holography and digital image processing method and its result of quantitative analysis is presented in the paper. So the laser nondestructive testing technique was used successfully.

In this paper, fundamental procedures for static and dynamic measurements using Electro-Optic Holography are presented and illustrated with representative examples. These procedures are developed for the cases of double-exposure and time-average applications.

A microcomputer-controlled pulse laser holographic system is constructed by using a high performance hardware and a software based on a graphical language. The development of the hardwares and the intelligent man-machine interface software is described. Complexity of the hardwares for studying dynamic events is reduced. Tests and simulations of this system on a vibrating blade demonstrated its usefulness. The system is relatively simple, easy to control for various applications.

New techniques for high speed holography are being developed for use in the investigation of transient events with lifetimes between 10 and 500 nanoseconds. Typically, multiple Q-switching of a pulsed laser allows optical pulse separations no shorter than 10 microseconds. To study crack propagation in brittle materials and shock wave propagation in air, optical pulses with temporal separations less than 1 microsecond are required. By employing a beam profile preserving optical delay line, pulse separations ranging from 25 to 450 nanoseconds have been generated. Using this technique, shock waves travelling at Mach 20 have been recorded, and crack propagation through glass has been studied. In order to investigate crack propagation through brittle 100 micron thick films, sub-nanosecond holographic techniques are being developed using gated pulses from a mode-locked Nd:YAG laser.

The optical technique combined the holographic interferometry and speckle photography was applied to measure three dimensional deformation. Out-of-plane and in-plane displacements of the contact deformation were determined experimentally and compared with the numerical analysis. The experimental results are in good agreement with the numerical results.

This scheme investigated the necessity of pulsed laser holographic interferometry (PLHl) through the use of flexible optical fiber elements for, the objects in enclosed system or otherwise inaccessible, poisonous environments. In Sec. II, the transmission characteristics, and the merit and demerit of the mono- and multi-mode optical fiber for pulsed laser were described. The paper indicated the advantages of -using multimode optical fibers in PLHI, simultaneously, two types of optical fiber system were presented. And finally in Sec. IV, the experimental results and conclusions were presented.

Standard phase-displacement equations, used for both double exposure and real time holo-interferometry, are combined with the geometrical mapping and optical characteristics of panoramic annular lenses to accurately measure surface displacement on the interior wall of a pipe. In this approach, one panoramic annular lens is used to illuminate the surface with coherent light, and the resulting intensity distribution is holographically recorded through a second panoramic annular lens. Interference fringes are obtained in real-time by comparing holograms recorded before and after the pipe is displaced. The annular images and the holographic fringes are acquired and stored digitally in a computer system. Image transformation algorithms are applied to remove optical distortions in the holographic pattern and fringe loci are compared to those predicted on the basis of theory.

In view of the fact that the details of the electro-hydraulic wave propagation is of great importance to the operational development of the extracorporeal shock wave lithotripter. In this paper, perfectly spherical shock waves were obtained with excellent repeatability by micro-explosions of underwater discharges, the movement of the spherical shock wave was measured by using a double exposure holographic interferometer and the interaction of the shock wave with the electrode was first observed. The experiments show that the method can be applied to studying the problem of the electro-hydraulic shock wave, especially to determining the wave front pressure distribution by measuring the wave front displacements.

The thermal deformation of the plate was measured by phase shifting holographic interferometry. The boundary conditions of the plate are simply supported at two edges and free at two edges. The anticlastic effect is shown in holographic fringe patterns. The strain obtained from the phase shifting holographic interferometry is only slightly different from those from the strain gages.

By means of the off-axis collimated plane wave coherent light arrangement and a loading device by pure bending, Poisson's ratio values of CFRP ( carbon fiber-reinforced plactics plates, lay-up 0°, 90° ), GFRP ( glass fiber-reinforced plactics plates, radial direction ) and PMMA ( polymethyl methacrylate, x, y direction ) have been measured.

In virtue of this study, the ministry standard for Ministry of Aeronautical Industry ( Testing method for the measurement of Poisson's ratio of non-metallic by laser holographic interferometry ) had been published. The measurement process is fast and simple. The measuring results are reliable and accurate.