Moire Interferometry Method Research Articles

Experimental Measurement of Residual Stress on Thermal Spray Coatings with Moire Interferometry and Hole-Drilling Method

Residual stress is one of the important factors in thermally sprayed deposits which affects both processing and performances. In the present study, the hole-drilling method and moire interferometry were used to determine the residual stress of thermally sprayed coatings to overcome certain limitations of the strain rosette version of hole drilling. The methodology was established based on the elastic theory and finite element method. The residual displacement was measured by moire interferometry and the residual stress of the thermally sprayed coating was calculated. The results have demonstrated that moire interferometry for surface displacement caused by hole-drilling is high sensitive, reliable and stable.

Study of the location of testing area in residual stress measurement by Moiré interferometry combined with hole-drilling method

This paper investigates the effect of the location of testing area in residual stress measurement by Moire interferometry combined with hole-drilling method. The selection of the location of the testing area is analyzed from theory and experiment. In the theoretical study, the factors which affect the surface released radial strain ɛ r were analyzed on the basis of the formulae of the hole-drilling method, and the relations between those factors and ɛ r were established. By combining Moire interferometry with the hole-drilling method, the residual stress of interference-fit specimen was measured to verify the theoretical analysis. According to the analysis results, the testing area for minimizing the error of strain measurement is determined. Moreover, if the orientation of the maximum principal stress is known, the value of strain will be measured with higher precision by the Moire interferometry method.

Surface Defect Detection for Some Ghanaian Textile Fabrics using Moire Interferometry

This analysis focused on using Moire Interferometry method to measure surface defects in woven fabrics. A laser imaging system based on moire Interferometry has been used as a tool for surface defect inspection of static textile fabric. Test textile fabrics samples with five different types of defects (hole, oil stains, warp-lacking, weft-lacking and dirt) were used. With the sample sand witched between two Ronchi rulings and illuminated by an expanded HeNe laser beam to form Moire configuration. The images from the fabric were acquired with a high resolution CCD camera. The recorded images were transferred to a computer for analysis by the image pro plus 5.0 software. By making use of image processing and FFT techniques, the surface defects such as lack of yarns and oil stains were analysed and detected. During the process of inspection and defect identification, it was observed that the three parameters, textual structure, the shape and size of the defect varied. In this paper, moire based technique for defect detection is presented. The result of the inspection of the textile fabric on the textile images revealed that FFT analysis serves as a filter in identifying such defects. Also, the fabric texture densities limited the intensity of the laser beam transmission through some fabrics. However, the variation of such intensities helped to deduce that the area covered with stain scatter most of the incident light and the more localised the defect the more the spread out of its transform. It explained the behaviour of the frequency spectrum of each sample and the smaller the width of the yarn spacing, the broader the entire diffraction pattern.

Application of model photomechanics technique in biomedicine and engineering

The theories of digital speckle correlation method, shadow moire method, photoelestic method,moire interferometry method and electronic speckle interferometry method were introduced. The applications of these modern photomechanics methods in biomedical engineering from both domestic and abroad were introduced, respectively. This review will provide inspiring methods and experimental technique for biomedical engineering research and promote profound exploration.in the field. Key words: Optical measuring technology; Biomedicine engineering; Displcement fields; Stress fields

Relationship Between the Depth of Drilling and Residual Strain Relief in Fiber Reinforced Composite Materials

The mechanical properties of fiber are quite different from matrix in composite laminates, and parameters, such as the angle of ply, and the temperature and pressure during composite forming, would play an important role in residual stress in the composite. The residual strains between layers depend on the forming parameters and their mechanical properties. In this article, grating rosette, Moire interferometry, and step drilling-hole method are used to measure the relief strains when drilling each single laminate step by step, and find some relationship between the depth of drilling and residual strain relief in fiber reinforced composite material.

3908 位相シフト画像の同時撮影によるモアレ干渉縞の位相解析(S17-2 光学的手法,S17 実験力学における最近の展開)

This paper describes a new simultaneous phase stepping method for moire interferometry. Conventional phase-stepping methods are widely accepted but the measured data are vulnerable to disturbances such as air fluctuations, temperature changes, vibrations and so on during the interferogram recording. To overcome this, a unique camera having a micro-retarder array on a CCD is used for observing interferograms. The specific structure makes it possible to calculate polarization states. Using this camera in a moire interferometer, the distribution of in-plane displacements is obtainable from a single image.

OS01W0302 Fringe analysis by fourier transform phase-shifting method for four-beam moire interferometry

OS01W0302 Fringe analysis by fourier transform phase-shifting method for four-beam moire interferometry

Residual strain measurement in composites using the cure-referencing method

This paper describes the details of a novel procedure called the cure-referencing method (CRM) to measure the strains associated with residual stresses on the surface of composite panels. The CRM involves the replication of diffraction gratings onto the surface of composite specimens during the autoclave during cycle. Residual strains associated with the curing process are measured using moire interferometry at room temperature after the specimens have been taken out of the autoclave. The procedures for both the grating replication and the moire interferometry experiment are described in detail. A method of high-temperature moire interferometry was developed to resolve the residual strains due to thermal expansion from those due to chemical matrix shrinkage and stress relaxation. These procedures are demonstrated on unidirectional and multidirectional laminates and on woven textile composites.

DEFORMATION ANALYSIS OF LASER PROCESSED GRAIN ORIENTED SILICON STEEL SHEET USING MOIRE INTERFEROMETRY

In this study, the residual deformation of silicon steel sheets with lowered core loss by strong power laser was investigated in combination of two deposited metal layers grating for high temperature with laser moire interferometry method. The silicon steel sheet was processed with different processing parameters under a CO2 and a YAG laser, respectively. The distributions of residual deformation in x and y axes were obtained. The experimental results showed that the silicon steel sheet was under the state of compressive residual strain, and were analyzed in detail.

The dynamic deformation measurement of the high speed heated LY12 aluminium plate with moire interferometry

Using the moire interferometry method, the dynamic deformation of a pre-loaded LY12 aluminium tensile specimen under a thermal heating was studied. The dynamic deformation of the specimen under high speed heating procedures was recorded with a film video camera. The experimental results showed that it is feasible to use moire interferometry for measuring dynamic deformations under conditions of fast heating.

The Creep Measurement of 475°C Pipeline Using Moire Interferometry

In this study, a new experimental method for measuring the creep of pipeline using moire interferometry was proposed. Curved-surface-deformed grating replicating technique was combined with the high-temperature-resistant grating and moire interferometry method, and was applied to measure the creep of a 475°C main steam pipeline in the Qinghe Power Plant for 3600 h. The measuring principle and experimental techniques are described. The measuring error and experimental results are discussed in detail.

Experimental analysis for thermal stress in functionally gradient material

Studies of displacement fields and stress concentration, due to uniform temperature change in a functionally gradient material (FGM) specimen and bimaterial (NFGM) specimen, have been made by Moire interferometry and finite element method. Results show that the thermal stresses concentration has been effectively reduced, and the distribution of the thermal deformations and thermal strains have also been relaxed and improved by transition layer of FGM.

Development of hybrid method coupling moire interferometry and finite element analysis

A hybrid method of stress analysis coupling moire interferometry and finite element analysis to solve two-dimensional elasticity problems is proposed. This method has the advantage of reliability of experimental measurement and fastness of data reduction using the finite element method. In this method, the moire fringe patterns of u and v displacements are superimposed to form the optimal mesh pattern, ensuring the required density and grading of mesh. The u and v displacements obtained from moire fringe patterns are specified at the nodes to achieve reliability of results. The concept and mathematical formulation of the hybrid method are shown. The effectiveness of the method is tested on a problem of a disk under diametrical compression, resulting in a theoretical solution. A comparison of results indicates that the mesh formed by the hybrid method and analyzed by an eight-noded isoparametric element provides accurate results and the same is also verified with simulated moire fringes of another example of cantilever beam.

The application of two-refractive-index contouring on the contour difference of two compared specimens

The development of comparative holographic Moire interferometry is accelerated by the need for nondestructive evaluation. It is based on a comparison of a master and test objects and a visualization of the difference in the mechanical responses under identical loading condition. In this paper, the hybrid method of comparative holographic Moire interferometry and the two-refractive-index contouring technique are used to generate contour difference for two compared specimens. The interference pattern of the master and test specimens are superimposed by a reconstruction beam. Moire fringes, produced between the two interference patterns, outline the contour differences in the compared specimens. The proposed experimental approach provides an advantage that full knowledge of the optical arrangement during construction and reconstruction of the hologram does not have to be accurately available. A partial-spherical object and its rotated status were simulated as the master and test objects.

A study ofJ-integral of the orthotropic composite material

The relation between J-integral near model I crack tip in the orthotropic plate and displacement derivative is derived in this paper. Meanwhile, the relation between stress intensity factor KI and displacement is also given in this paper. With sticking film moire interferometry method, the three-point bending beam is tested, thus the values of J-integral and KI can be obtained from the displacement field, and then the truth of relation formula between J-integral and KI in the orthotropic composite materials is experimentally verified.

Strain distribution measurement in a coarse-grained titanium alloy

Strain distributions in a coarse-grained titanium alloy under tensile loading were measured using a moire-interferometry method. Analysis of the interferograms show that variations of more than 25 percent away from the mean level are present, most noticeably in the direction transverse to the loading axis.

Automated fringe pattern analysis for moiré interferometry

The theory of an automated fringe-pattern analysis using temporal phase stepping method for moire interferometry is presented. The automated method provides a fast and accurate strain measurement for moire interferometry. Measurements on a tapered composite specimen with a dropped ply are shown to highlight the capability of this technique to obtain the strain distribution, particularly around the region with a dropped ply.

Polarized shearing-moire interferometry for separated 3-D strain fringe patterns

Utilizing laser's properties of both polarization and temporal coherence, a real time method of moire interferometry is proposed to obtain the separated 3-D displacement derivative fringe patterns. For dual beams that contain identical polarization components, the optical-path difference is larger than that of the coherent length to eliminate the interaction between the wavefronts due to the shearing. For dual beams that contain no identical components of polarization, the vibration planes are perpendicular to each other to have the frame-separation of the in-plane derivative patterns. The out-of-plane displacement derivative patterns are achieved by the shearing of the zero-order diffractions of the grating.

Polarization phase shifting method for moire interferometry and flatness testing

Described in this short paper is an implementation of the phase shifting technique for computer-aided processing of interference fringes obtained by the moire interferometry method for in-plane displacement measurements or in a similar arrangement used for out-of-plane displacement (flatness) determination. The polarized light approach was selected because of the common path propagation of the interfering beams. The experimental verification is presented.

Using moiré interferometry and boundary integral hybrid method to determine mixed-mode stress intensity factor

The paper describes a hybrid experimental and numerical method of Moire Interferometry and the boundary-integral-element method. The interference patterns used for the evaluation of the displacement vector are obtained by Moire Interferometry. The boundary displacements obtained experimentally are conveniently used for the calculation of the stress intensity factor in the body by the boundary-integral-method. Some examples bear witness to the effectiveness and accuracy of the hybrid technique.