Micro-deformation Measurement Research Articles

A DIC method for thermal micro-deformation measurement of satellite high stability composite structure in simulated space environment

In order to ensure the stability and reliability of the entire satellite and onboard equipment indicators, the satellite highly stable structure can only produce small deformation or “near zero deformation” under the space on-orbit (thermal/vacuum) environment. The effective measurement and verification of its dimensional stability indicators directly determine the success or failure of the development of highly stable satellites. This work proposes a method for measuring the thermal deformation of highly stable satellite structures based on digital image correlation, (DIC), which designs a combined methodology of the digital image correlation measurement scheme, a measurement instrument protection method, a highly uniform temperature measurement and control system in the simulated space on-orbit thermal/vacuum environment. The methodology proposed in the work makes the digital image correlation measurement system suitable for space on-orbit measurement, and verifies that the measurement system can maintain high measurement accuracy. The research results indicate that this method can effectively solve the problems of measurement field interference, high uniform temperature control, speckle measurement camera, and measurement baseline protection. The thermal stability measurement experiment of a highly stable structure of a certain satellite has been successfully completed, and it has been verified that this method can meet the effectiveness and measurement accuracy of simulating thermal deformation measurement of structures in the simulated space on-orbit thermal environment.

Tri-wavelength simultaneous ESPI for 3D micro-deformation field measurement.

Electronic speckle pattern interferometry (ESPI), a well-established technique for micro-deformation measurement, can be used to determine both in-plane and out-of-plane displacement components. Although many works in ESPI have been reported for three-dimensional (3D) displacement measurement, few works have focused on the simultaneous measurement of 3D deformation fields. Here we present an ESPI system that consists of three sub-interferometers for simultaneous measurement of all three displacement components and in-plane strain fields. A 3CCD color camera, a specially designed shifting stage, and three lasers with optimal wavelengths are used in this system. The lasers and 3CCD camera provide independent interferograms with different color signals, while the shifting stage allows the sub-interferometers to achieve simultaneous phase shifting. The results of color separation and experimental measurement demonstrate the utility of the system.

High-speed measurement of mechanical micro-deformations with an extended phase range using dual-wavelength digital holographic interferometry.

The implementation of a digital holographic interferometry setup for high-speed micro-deformation measurement is presented. This proposal uses a dual-wavelength recording strategy to reconstruct micro-deformations up to 4.85 µm with no phase wrapping. The numerical processing required to recover the phase maps containing the information of micro-deformations is carried out in a general-purpose computing on graphics processing unit environment to boost its performance. The method completely processes recorded holograms of 1024×1024pixels in 48 ms, i.e., 21 frames per second (FPS) for a single-wavelength acquisition and 96 ms or 11 FPS for dual-wavelength recordings. The method is experimentally evaluated measuring deformations ranging from 0.033 µm to 4.85 µm with no need for phase unwrapping algorithms for an 8 cm diameter aluminum plate in a 110cm2 field of view.

Effect of ultrasonic impact treatment on redistribution of residual stresses in dissimilar thickness girth welds

Effect of repeated ultrasonic impact treatment on redistribution of residual stresses in a dissimilar thickness girth butt weld of pipes with a diameter of 530 mm of low alloyed (0.9%C-2%Mn-1%Si) steel was studied. Residual stresses were measured by the X-ray method based on measurement of microdeformation of a crystal lattice of a material under its influence. The research results showed that tensile residual stresses in the girth weld were formed at the inner side of the pipe after welding. Ultrasonic impact treatment of the weld at the inner side caused complete transformation of residual stresses from tensile to compressive ones when speed was in the range from 0.06 to 0.12 m/min. However, reduce in speed of treatment down to 0.04 m/min gave a negative effect. The values of compressive residual stresses in heat affected zone on the side of the thinner pipe were decreased.

Study of a GB-SAR Rail Error Correction Method Based on an Incident Angle Model

With ground-based synthetic aperture radar (GB-SAR) discontinuous observation, the effect of rail error, caused by multiple installations, on imaging is difficult to eliminate with difference correction. In this article, the impact of rail error on each point, which is related to the incident angle of each point, is theoretically analyzed. This is the first attempt to introduce a baseline in the application of GB-SAR microdeformation to build a model that estimates the incident angle of each point in the image. Then, the rail error correction model is established using the incident angle, and the influence of the rail error on the image point is weakened using this model. The experimental results show that the precision of the estimated incidence angle cosine is 0.0132, which is comparable to the same angle cosine value measured by the total station. By applying the correction method in this article, different impacts of each point in the image, caused by rail error from multiple instrument installations, can be weakened to below 0.1 mm, meeting the requirement of GB-SAR microdeformation measurement submillimeter accuracy.

Investigation of the distribution of residual stresses in dissimilar thickness girth welds

Investigation of the distribution of residual stresses in girth welds of pipes is a rather laborious process. It is not always possible to predict how residual stress fields will be formed after welding. The result depends on steel grade, technological process of welding (heat input welding, welding speeds), temperature of environment, geometrical parameters of pipes. Distribution of residual stresses in a dissimilar thickness girth butt weld of pipes with a diameter of 530 mm of low alloyed (0.9%C-2%Mn-1%Si) steel was studied. Residual stresses were measured by the X-ray method based on measurement of microdeformation of a crystal lattice of a material under its influence. The research results showed that tensile residual stresses in the girth weld were formed at the inner side of the pipe after welding. It was revealed that the magnitude and distribution of residual stresses depend on the wall thickness of the pipes. In a thinner pipe, the level of tensile residual stresses is 40-50% higher than that of a thicker pipe. Investigation of the distribution of residual stresses in welded joints can be useful for developing methods to reduce the high residual stresses that occur after welding and also at deciding of constructive and technological task in the process of welding works.

Research of Micro-deformation Measurement for High-resolution Space Camera Complex Structured

High-frequency vibration in the process of launching and complex environmental conditions of the outer space generate micro deformation in components of space cameras. As a result, images from the space cameras are blurred. Therefore, it is necessary to measure the micro deformations in components of space cameras in various experiment conditions.This paper presents a high-accuracy micro deformation measurement method. The method is implemented as follows: (1) fix Invar balls onto a space camera being measured and measure the coordinate for each ball under the standard condition; (2) simulate high-frequency vibrations and environmental conditions like the outer space to measure coordinates for each ball under each combination of test conditions; and (3) compute the deviation of a coordinate of a ball under a test condition combination from the coordinate of the ball under the standard condition and the deviation is the micro deformation of the space camera component associated with the ball. This method was applied to micro deformation measurement for space cameras of different models. Measurement data for these space cameras validated the proposed method.

Sampling moiré method and its application to determine modulus of thermal barrier coatings under scanning electron microscope

The sampling moiré method has been widely utilized to determine the displacement and strain distributions of materials and structures at macroscales. The method exhibits a simple operation and low requirements regarding the specimen grating. Further, a single image is required for the phase analysis. The method is a promising method in the field of experimental mechanics. In this study, the mechanisms of moiré pattern generation are systematically studied using simulations. Two essential conditions for their generation are presented and the applicability of the control equation to moiré-spacing determination is discussed. To promote the application of the sampling moiré method in microdeformation measurements, three-point bending tests using thermal-barrier coating (TBC) specimens (bilayer beam structure) are performed under a scanning electron microscope (SEM). Using the soft-imprint technique, a high-frequency grating is fabricated on the side surface of the TBC specimen to generate sampling moiré patterns under the SEM. The microdisplacement and strain components are calculated using the sampling moiré method and their values are used to determine the TBC Young's modulus. To examine the reliability of the sampling moiré method, the measured strains are compared with those obtained with the geometric phase analysis (GPA). The results are in good agreement. Consequently, the sampling moiré method encourages further applications in microdeformation measurements and mechanical-property characterizations of other materials.

Simultaneous measurement of contour and micro-deformation using full-field optical methods

Simultaneous measurement of contour and micro-deformation using full-field optical methods

Design and Experimental Study of a Composite Materials Micro-Deformation Measurement Device

In the space environments, the size and weight of composite materials will produce small changes. In order to measure the small changes accurately, a micro-deformation measurement device has been designed. The carbon fiber tube was made from cyanate ester resin or epoxy resin was tested in vacuum and hygrothermal environments. The deformation in the vacuum test is -1.7 to 3.8 microns, in the hygrothermal test, the deformation is -1.3 to -6.4 microns. The same as theoretical analysis, the environmental stability of cyanate ester resin better than epoxy resin.

A New Technology of Ultrathin AlN Piezoelectric Sensor for Pulse Wave Measurement

In this study the design and characterization of a new technology of ultrathin AlN piezoelectric sensors able to measure micro-deformations is reported. The sensors are fabricated using a CMOS compatible clean room process in which the sensitive part is embedded into a thin bio-compatible and conformal layer of parylene (total thickness below 10μm). That makes the sensors very flexible and sensitive to micro-deformation measurements. In this study, this technology is applied to monitor heart activity: heart rate, blood pulse wave, pulse wave velocity. Blood pulse wave could be measured with a very good accuracy; this technology could thus be used for the prediction of cardiovascular diseases by analyzing the pulse wave shape.

Early results of micro-deformation measurements in Magdalena Jama (Slovenia) by a vertical static pendulum

Vertical static pendulums have been installed in mines or caves in Central Europe since 2007. Two-dimensional optical measurement of the tilt of a rock mass and continuous fully digital on-line evaluation of results makes possible the detection of a small tilt of the surroundings with a resolution of tens of nanoradians or the deformation of the surroundings in the horizontal plane with resolution of hundreds of nanometres. The paper describes the measurement device and the first results of the measurements in Magdalena Jama, which is part of the Postojna Cave System (Slovenia). The correlation of deformation between distant stations shows the existence of stress variations that are not only of local origin (high floods, local seismicity, and aseismic deformations). The stress field has a wider, and not only regional, character with effects that can be observed very far from the origin.

Microdeformation measurement via single-element extended digital image correlation

The microdeformation measurement of biomaterials is a crucial issue in the field of experimental mechanics. The single-element extended digital image correlation (single-element X-DIC) method was developed in this paper. If the actual deformation of the specimen is in accordance with the displacement hypothesis, single-element X-DIC possesses a higher measurement accuracy and a higher computational efficiency. With the assistance of a novel discretization method, single-element X-DIC could be used to measure the complex deformation. All results of the verification experiment show that single-element X-DIC is suitable for the measurement of various deformations. Furthermore, combined with optical microscopy, single-element X-DIC was applied to measure the microdeformation of bovine bone, which demonstrates that single-element X-DIC has wide application prospects in the microdeformation measurement of biomaterials.

Micro-deformation measurement on the concrete roadway surface slabs using Fiber Bragg Grating and analysis by computational simulation

This work shows a non-invasive method for micro-deformation measurements on concrete structures using Bragg grating sensors in optical fibers adhered to the surface. We present the measurements on roadway slabs under a load of 10 kN, and we find an approximated ratio of 2:1 between the deformation registered by the sensors and the values from a computational simulation with the finite element method. We propose the use of these sensors for structural monitoring of the slabs and this installation shape for avoiding bends that can damage the edges in the optical fiber in embebed sensors in vertical shape.

電子線モアレ法とマイクログリッドを用いた脆性/延性複層鋼板の積層界面近傍の変形挙動観察(<小特集>M&P2009機械材料・材料加工部門技術講演会)

電子線モアレ法とマイクログリッドを用いた脆性/延性複層鋼板の積層界面近傍の変形挙動観察(<小特集>M&P2009機械材料・材料加工部門技術講演会)

Micro-Deformation Measurement on a Specular Surface by DIC with Nanoparticles

This paper proposes a method of applying Cu nanoparticles on the surface of miniature specimen for micro-deformation measurement. The microscope image processing system, making and preparation of Cu nanoparticles are described. Use of the nanoparticles on a miniature specimen to determine the Young’s modulus is demonstrated through a tensile testing with an image resolution of 0.3 μm/pixel. Comparable well result is shown and discussed.

Quantitative Measurement of Micro-Deformation of Electropolished Carbon Steel Using an Image Processing Technique

An automatic technique for the quantitative measurement of micro-surface deformation of a specimen using image-processing is introduced. Static tensile and torsional tests of two kinds of electropolished carbon steels are carried out. One has a banded structure and another has not. The banded structure gives a great influence on the micro-deformation depending on the type of loads. The characteristics of micro-deformations under these static loads are made clear from the results obtained by the image-processing technique.

High resolution AFM scanning Moiré method and its application to the micro-deformation in the BGA electronic package

The formation mechanism of atomic force microscope (AFM) Moiré is explained using the transmittance function. The technique for preparing the AFM Moiré specimen grating is described. The sensitivity and accuracy of this method is analyzed. AFM Moiré method is used to measure the thermal deformation ball grid array (BGA) electronic package. The shear strain at the different solders in the BGA package is measured. The result is compared with that from electron beam Moiré method. The consistent comparison result verifies the AFM Moiré method is reliable and effective in the micro-deformation measurement in the electronic package.

Electron moiré method and its application to micro-deformation measurement

In this paper, the single and two deposited metal layers method were proposed to produce the model grating for electron moiré method. The measurement principle of electron moiré method and the techniques for manufacturing model grid are expounded in detail. The accuracy of measuring strain using this method is discussed. The gratings with single deposited layer and two deposited layers with high frequency up to 5000 lines/mm were produced on different substrates. From the experimental results, both single deposited metal layer and two deposited metal layers gratings showed their heat resistance ability. Using the gratings produced and a replicated model grid, the electron moiré method was applied to measure the deformation of the strain around holes in a polyimide resin substrate, thermal strain of electronic packaging component and tensile creep around grain boundary in a pure copper specimen.

Measurement of Microdeformation by Transparent-Type Diffraction Moire Interferometry Using Light Control Plate

Moire interferometry is a method of measuring submicron displacement distribution using two or four collimated beams incident to a specimen diffraction grating. In this paper, in order to form these two or four beams, a transparent diffraction grating is used. Two types of transparent diffraction moire interferometry are developed. One uses oblique incident beams for measuring one-dimensional displacement. The other uses normal incident beams for measuring one- or two-dimensional displacement components. In the latter, the 0th-order diffraction beam is noise. This noise is removed using light control plates which were developed recently. By using this diffraction moire interferometry, a compact system for microdeformation measurement is developed.