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When the digital speckle correlation method captures images under certain working conditions, the extreme tilt of the camera leads to a weak correlation between the left and right images, which in turn makes the matching difficult. In order to solve the above problem, a digital speckle stereo matching algorithm based on epipolar correction is proposed in this paper, and an estimation method of deformational iterative initial values of the first-order shape function in the stereo matching process is given through theoretical derivation. The Newton–Raphson (NR) method can be directly used for fine matching in the original left and right images through the estimated deformational iterative initial value. The digital speckle matching experiment under different camera inclination angles of 24.2°, 34.2°, 41.15°, 47.3° and 52.4° was carried out to verify the effectiveness of the digital speckle stereo matching algorithm based on epipolar correction. The experimental results show that this method can complete the matching well under different inclined field of view, and the matching success rate is close to 100%, which can at least meet the requirement of digital speckle matching and deformation strain measurement under the inclination angle less than 52.4° field of view. [ABSTRACT FROM AUTHOR]

The deep mining of coal resources is accompanied by severe environmental challenges and various potential engineering hazards. The implementation of NPR (negative Poisson's ratio) bolts are capable of controlling large deformations in the surrounding rock effectively. This paper focuses on studying the mechanical properties of the NPR bolt under static disturbance load. The deep nonlinear mechanical experimental system was used to study the mechanical behavior of rock samples with different anchored types (unanchored/PR anchored/2G NPR anchored) under static disturbance load. The whole process of rock samples was taken by high-speed camera to obtain the real-time failure characteristics under static disturbance load. At the same time, the acoustic emission signal was collected to obtain the key characteristic parameters of acoustic emission such as acoustic emission count, energy, and frequency. The deformation at the failure of the samples was calculated and analyzed by digital speckle software. The findings indicate that the failure mode of rock is influenced by different types of anchoring. The peak failure strength of 2G NPR bolt anchored rock samples exhibits an increase of 6.5% when compared to the unanchored rock samples. The cumulative count and cumulative energy of acoustic emission exhibit a decrease of 62.16% and 62.90%, respectively. The maximum deformation of bearing capacity exhibits an increase of 59.27%, while the failure time demonstrates a delay of 42.86%. The peak failure strength of the 2G NPR bolt anchored ones under static disturbance load exhibits an increase of 5.94% when compared to the rock anchored by PR (Poisson's ratio) bolt. The cumulative count and cumulative energy of acoustic emission exhibit a decrease of 47.16% and 43.86%, respectively. The maximum deformation of the bearing capacity exhibits an increase of 50.43%, and the failure time demonstrates a delay of 32%. After anchoring by 2G NPR bolt, anchoring support effectively reduces the risk of damage caused by static disturbance load. These results demonstrate that the support effect of 2G NPR bolt materials surpasses that of PR bolt. [ABSTRACT FROM AUTHOR]

Mining activities are key triggers for strong mine earthquakes and even rock bursts in coal mines. This study explores the impact of mining speed on the overlying strata's deformation and energy release through theoretical analysis, numerical simulation, and the digital speckle method. The temporal and spatial evolution characteristics of the impact energy during mining are simulated. The digital speckle method illustrates a positive correlation between rapid mining and increased fracture block degree of overburden rock and roof separation, confirming that accelerated mining speed extends the fracture distance of the stope. Furthermore, numerical simulations establish that both the energy associated with overlying rock breaking and the frequency of energy occurrence events are amplified during rapid mining, in contrast to slow mining. This observation corroborates that escalating mining speed augments the energy dispensed by the breaking of the upper rock. Consequently, this escalation induces a transformation in the energy levels of mine earthquakes, culminating in a heightened incidence of large-energy mine earthquakes. [ABSTRACT FROM AUTHOR]

Users of the digital image correlation method are faced with the problem of poor operability, low repeatability, and lack of standardized specifications for spraying speckles. To solve the problem, the research proposed a rock deformation measurement method that obviates the need to spray speckles. A local binary model was established by using the local binary pattern (LBP) operator based on deep texture features on rock surfaces. The resulting LBP digital speckle pattern can substitute artificial speckle patterns and demonstrates high quality and strong applicability. Based on the LBP digital speckle pattern, the target tracking algorithm was employed to achieve non-contact measurement of the dynamic displacements of rocks. The feasibility and effectiveness of the algorithm in practical application were verified by conducting shear tests on granite and siltstone. Test results show that the deformation characteristics in the displacement nephograms are in line with the measured data pertaining to rock fracturing and conform to the basic characteristics of the shear failure of rocks. The deformation measurement method based on surface texture information can realize non-contact displacement measurement of rocks under conditions without speckles: this obviates the influence of the quality of sprayed speckles on the accuracy of the measurement of deformation.

In order to investigate the influence of the inclination angle of soft rocks on the evolution process of composite rock mass rupture, this paper conducted uniaxial compression experiments on composite rock masses with different inclination angles of soft rock. Digital speckle and acoustic emission methods were used as observation tools to explore the combined effects of different soft rock dip angles. The fracture evolution process of the rock mass was analyzed, and the change in mechanical properties of the composite rock mass with angle was studied. The fracture mode of the soft and hard composite rock mass with different inclination angles was obtained. The results show that the deformation and failure of the composite rock mass is a dynamic evolution process in which damage occurs inside the rock mass, with cracks appearing around the soft rock, and extend along and around the soft rock layer, eventually penetrating through the fracture. The deformation and failure process of the combined rock mass is manifested in four stages: original fissure compaction, elastic deformation, plastic deformation and failure. With an increase of the inclination angle of soft rocks, the compaction stage of the rock mass gradually increased, and the elastic modulus gradually decreased. When the inclination angle of soft rock is θ=0° or 15°, the rock mass rupture appears as a combination of soft and hard rock mass failure. When the inclination angle of soft rock is θ=30° or 45°, the rock mass failure mainly occurs in the soft rock area, and the form of rock mass changes from shear failure penetrating the soft rock layer to sliding shear failure along the soft rock layer. The greater the inclination angle of the soft rock layer, the more likely the rock mass is to undergo unstable failure. This study provides a reference for the long-term stability analysis of rock mass engineering containing soft and hard composites and the mechanical behavior of complex layered composite rock mass.

Copyright of Chinese Journal of Geological Hazard & Control is the property of China Institute of Geological Environmental Monitoring (CIGEM) Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mining activities are key triggers for strong mine earthquakes and even rock bursts in coal mines. This study explores the impact of mining speed on the overlying strata’s deformation and energy release through theoretical analysis, numerical simulation, and the digital speckle method. The temporal and spatial evolution characteristics of the impact energy during mining are simulated. The digital speckle method illustrates a positive correlation between rapid mining and increased fracture block degree of overburden rock and roof separation, confirming that accelerated mining speed extends the fracture distance of the stope. Furthermore, numerical simulations establish that both the energy associated with overlying rock breaking and the frequency of energy occurrence events are amplified during rapid mining, in contrast to slow mining. This observation corroborates that escalating mining speed augments the energy dispensed by the breaking of the upper rock. Consequently, this escalation induces a transformation in the energy levels of mine earthquakes, culminating in a heightened incidence of large-energy mine earthquakes.

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the engineering background that rock masses of underground reservoirs in mines are frequently disturbed by cyclic loads such as mine earthquake and mining stress, uniaxial compression and cyclic loading tests for sandstones with different water contents were carried out in laboratory. The crack propagation and failure laws of sandstones with different water contents were revealed by digital speckle technique. Based on scanning electron microscopic (SEM) analysis, the micro deterioration mechanism of sandstones with different water contents under cyclic loading was obtained. The test results show that the peak strength of sandstone decreases gradually with the increase of water content under both uniaxial compression and cyclic loading conditions. The peak axial strain variation of dry sandstone experiences four stages of initial deformation, constant velocity deformation, accelerated deformation, and instability failure, and that of the water-bearing sandstone experiences three stages of initial deformation, constant velocity deformation, and instability failure. With the increase of water content, the peak axial strain in the corresponding stage gradually decreases. It is verified by the deformation rate analysis method that water has no effect on the deformation memory characteristics of sandstone. Under uniaxial cyclic loading condition, the failure mode of sandstone gradually transits from tension−splitting failure at dryness to tension−shear mixed failure, and presents a single shear failure at saturation. SEM results show that with the increase of water content, the fracture structure plane gradually transits from smooth structure, round structure, and sheet structure to completely broken structure. With the increase of water content, the absolute damage parameter increases, which reflects the positive correlation of water−rock coupling damage, and the cumulative damage parameter larger at the same cycle accumulates faster.

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to improve the efficiency and quality of transplanting vegetables in dry land, based on the seedling technology, transplanting effect and analysis of the planting process, a potted vegetable seedlings transplanting machine was designed. It mainly comprised rotary disc type feeding mechanism, five-bar duckbill type planting mechanism (simulated duckbill mechanism, disc cam, connecting rod, crank, fork, cable) and power transmission system. Based on the physical parameters of the seedlings and design requirements, it was determined that the diameter of the duckbill was D=90 mm, the opening and closing angle was 25°, and the taper angle was 17°. A test bench with adjustable parameters was built by analyzing the structure of the planting mechanism and the motion of the working process. The digital speckle technique was used to optimize the parameters, so that the length of the crankshaft I was S1=100 mm, the length of the crankshaft II was S2= 80 mm, the length of the connecting rod I was S3=140 mm, the length of the connecting rod II was S4=260 mm, the length of rod to connecting the rack was S6=314 mm, and the height of planting track was H=450 mm. According to the above parameters and the control requirements of the duckbill mechanism, the cam stroke was determined to be S=15 mm. And the initial phase difference between the two cams was 180°. The experiment was carried out with pepper seedlings as transplanting objects. The results showed that when the planting frequency was 50-70 plants/min, the seedling upright rate was 93%-91.1%, the planting depth qualified rate was 96%-92%. The leakage rate was 0-0.26%, the variation coefficient of plant spacing was 0.37%-0.67%, the injury rate was 0%, and the mechanical damage degree of the mining surface was 2.43-3.77 mm/m2. The machine can effectively improve the quality of transplanting, which can meet the production needs and design requirements of the mechanism. [ABSTRACT FROM AUTHOR]

The emission of infrared radiation from oil shale is, compared with other rocks, more intense due to the anisotropy during deformation. In this research, cracks in oil shale specimens were scanned with computed tomography (CT) scanning equipment, and the infrared radiation from their surface, as well as surface strain during uniaxial compression were analyzed. The results show that the specimens surface temperature constantly changes. Prior to the fluctuation of the internal stress of a test specimen, the temperature curve exhibits varying degrees of decline. Then the curve abruptly rises close to the specimen's point of failure. By analyzing the coefficient of variation of the surface temperature distribution of the specimens, it was found that the turning point on the curve from the horizontal fluctuation to rapid increase can serve as a warning of impending specimen failure. In a low-stress state, the location of a crack is indicative of the low-temperature infrared anomaly. With increasing stress, the high-temperature infrared anomaly will appear at the crack tip. Near the failure of the specimen, the appearance of an anomalous infrared precursor on its surface is related to the mode of failure. A hightemperature infrared precursor will occur in a shear failure zone, while a lowtemperature infrared precursor will occur in a tensile zone. These regularities are very important to be taken into account to understand the development of the internal fracture network and deformation of oil shale deposits during insitu pyrolysis. [ABSTRACT FROM AUTHOR]

The key to improving the hydraulic fracturing effect is to activate the weak bedding planes and form complicated fractures in an unconventional shale reservoir. In this paper, an experimental method, based on the digital speckle correlation technique, is put forward to measure the fracture tip displacement field when a type I fracture is cross-coupled with a weak bedding plane; the experimental specimen is similar to the material of a shale reservoir. Through observing the fracture tip displacement field, we can determine the location of the fracture tip and calculate the fracture tip stress intensity factor. This can reveal the changing characteristics of fracture tips after the artificial fracture intersects with the bedding plane. Experimental results show that the weak bedding plane is easily activated to form a shearing slip and fracture blunting, and then the fracture type changes from a type I to type I–II composite fracture and extends along the bedding plane. A weaker bedding plane, results in a bigger angle of the bedding plane, a bigger lateral load, larger angle of the crack turned, making it easier for the bedding to be activated and allowing more complex fracture morphology. [ABSTRACT FROM AUTHOR]

The deformation measurement of a specular surface is of great importance during the quality inspection and installation of optical elements or wafers, especially those with large apertures. We propose a deflectometry method with speckle digital image correlation (DeSDIC) to realize the dynamic and high-accuracy measurement of the deformation on specular surfaces, with a simple system structure and robustness to noises and environmental vibrations. Random speckle pattern displayed on liquid crystal display is reflected by the original surface under test (SUT), and the distorted pattern is recorded by a camera. This originally distorted pattern is taken as the reference image, and the patterns captured afterwards are digitally correlated with the reference image to calculate the gradient change and deformation of the SUT. The theoretical relationships and an experimental one-step calibration scheme are proposed. Both static and dynamic deformations of a deformable mirror were experimentally measured to demonstrate the feasibility and accuracy of DeSDIC, which is comparable to phase-measuring deflectometry and interferometry.

This paper based on the aluminum matrix composites as an example to establish the resistance real-time digital speckle real-time measurement experiment field, the stretching process of aluminum matrix composites for real-time detection, especially for digital speckle correlation method (DSCM) the characteristics of the object cannot be directly measured strain, for the improvement of the algorithm for digital speckle correlation method (DSCM), this paper concluded that compared with the new algorithm for digital speckle correlation method data and resistance method of the experimental data in real time. By comparing the experimental data analysis, puts forward Suggestions for the composite material experiment method. [ABSTRACT FROM AUTHOR]

• Based on the digital speckle technology, the full-process images and data of the crack field, strain field and displacement field of the specimen during the test are obtained. • The localized deformation and strain evolution characteristics of the specimen are analyzed. • The internal relationship between strain evolution, crack development, horizontal displacement and coal failure is clarified. • Obtained the precursor information and early warning indicators of coal sample failure. In order to achieve effective early warning of coal sample failure under uniaxial compression, the digital speckle technology is used to analyze the evolution process of the crack field and strain field of the specimen from the global and local aspects, and the development laws of the crack and the characteristics of the strain evolution are clarified. And obtained the precursor information and early warning indicators of coal sample failure. The results showed that: there are often obvious strain concentration and deformation localization in the places where the cracks develop faster. When the crack opens or expands rapidly, the horizontal displacement of the specimen has obvious regional characteristics, the horizontal displacement and the maximum principal strain increase rapidly, and the direction of the displacement vector and the maximum principal strain also change significantly. Therefore, the rapid evolution period of deformation localization (69.4 % ∼ 70 % of the failure frame), the loading load of the specimen (66.08 % ∼ 69.51 % of the peak load), the direction of the displacement vector and the direction of the maximum principal strain can be used as important early warning indicators and effective precursor information before the specimen failure. [ABSTRACT FROM AUTHOR]

This paper presents a novel fringe projection technique for fast three-dimensional (3-D) shape measurements of moving highly reflective objects. By combining the standard three-step phase-shifting fringe patterns with a digital speckle image, dynamic 3-D reconstructions of shiny surfaces can be efficiently achieved with only four projected patterns. The phase measurement is performed by three-step phase-shifting algorithm as it uses the theoretical minimum number of fringe patterns for phase-shifting profilometry. To avoid the camera saturation, a dual-camera fringe projection system is built to measure shiny objects from two different directions. The erroneous phase obtained from a saturated pixel is corrected by the phase of its corresponding pixel in the other view which is free from the saturation problem. To achieve high measurement accuracy, the corresponding high light intensity areas in cameras are found by sub-pixel matches of the speckle pattern in either view. Benefited from the trifocal tensor constraint, the corresponding points in the two wrapped phase maps can be directly established, and thus, the difficulties in determining the correct fringe order for the discontinuous or isolated surfaces can be effectively bypassed. Experimental results indicate that the proposed method is able to successfully measure highly reflective surfaces for both stationary and dynamic scenes. [ABSTRACT FROM AUTHOR]

To investigate the influence of prefabricated fissure size on the directional propagation law of rock type-I cracks, a simple device for simulating rock crack directional propagation was developed. Subsequently, loading tests for white sandstone samples with different prefabricated fissure lengths and widths were performed. The evolution laws of the deformation field and acoustic emission (AE) were analyzed during the entire crack propagation process. Finally, the influence of fissure size on the crack directional propagation mechanism was elucidated. The obtained results indicate that: The initial crack angle was mainly influenced by the prefabricated fissure width. The initial crack angle increased with the increase in the prefabricated fissure width. The crack directional propagation process can be divided into four stages: local strain-band initiation, local strain-band development, crack initiation, and crack coalescence. The crack maximum relative strain increases with an increase in the prefabricated fissure length but decreases with an increase in the prefabricated fissure width. This phenomenon indicates that increasing the prefabricated fissure length is advantageous to crack propagation at the fissure tip. The AE evolution process includes quiet, slowly increasing, booming, and decreasing periods. When the prefabricated fissure length increased, the durations of the quiet and slowly increasing periods decreased, but the durations of booming and decreasing periods increased. However, the durations of quiet, slowly increasing, and booming periods decreased as the prefabricated fissure width increased. In other words, increasing the prefabricated fissure length can enhance the stability of crack directional propagation, but increasing the prefabricated fissure width leads to the instability of main crack propagation path. In underground engineering practice, increasing the prefabricated fissure length and decreasing the prefabricated fissure width may be excellent approaches to realizing the crack directional propagation of rock or coal fracturing. [ABSTRACT FROM AUTHOR]

Aiming at the problem of camera pixel saturation caused by the high reflective area on the metal surface of a relay, we adopt speckle projection profilometry to detect the magnetic circuit drop height of the relay. The main problem is solved through a detailed analysis of characteristics according to different speckle gray values, speckle sizes, and shapes to effectively distinguish the confusion between the speckle reflection spots and background light reflection spots. The enhanced normalized cross-correlation sub-pixel algorithm is used to get a dense matching pair of points of the right and left images, and three-dimensional reconstruction is based on the triangulation parallax principle. The random sampling consensus algorithm and European clustering algorithm are used to segment the point cloud to obtain the core and yoke iron planes and measure the distance between the two planes. We measured two standard blocks with height difference of 1 mm, and the error is within 2% by the proposed method. The correctness is verified through real-time measurement for a magnetic circuit drop height of the relay assembly line. [ABSTRACT FROM AUTHOR]

Experiments simulating the effect of coal mine stopping through a fault zone were designed based on a working face of the Qianqiu coal mine in Yima, China. Through simulation of the physical process of fault reactivation and coal bumps, the displacement of the surrounding strata and evolution characteristics of fault stress under the effect of mining were studied. The mechanism of fault reactivation induced by coal mining was analyzed. The results show that shortly before fault reactivation, the normal stress and shear stress increased rapidly and the risk of a fault slip occurring was also increased. The fault reactivation, caused by the mining activity, occurred when the working face was 25–35 m from the fault along the hanging wall. The influence of mining increased the possibility of fault reactivation, while the local failure of the bearing capacity of the working face was the direct cause of the fault slip. Our results indicate that the influence of fault slip on the coal of the working face had a transient impact and acted as a loading-unloading function. [ABSTRACT FROM AUTHOR]

On the basis of double-sided shear experimental model, sliding friction experiments under different axial loads to the combination of sandstone-coal samples were done by using digital cameras and acoustic emission recorder to build a sound and light monitoring system, and overcome the problem that the displacement was not easy to be observed in previous coal rock friction experiments. The experiment studied the unstable sliding production condition of the combination of coal and rock samples, the sliding type under certain conditions, displacement evolution law as well as the acoustic emission law accompanied by sliding process. The experiment shows that the sliding form of composite structures are relevant to the axial load, the greater the axial load is, the unstable sliding is more likely to appear; no obvious signs of displacement appear before unstable sliding and the sliding displacement grow rapidly after unstable sliding; the peak value of shear stress is positively correlated to axial load while sliding, and the displacement generated by unstable sliding has no correlation with axial stress. The maximum unstable sliding displacement of the test was 35. 5 µm, and the minimum value was 5. 6 µm; there are intensive acoustic emission events before the specimen sliding, after sliding becoming stable, acoustic emission counts decreased. The experiment simulated the occurrence process of structural instability of rock burst, and it is of great significance for understanding the fault activation, as well as the physical process that the coal overcomes the roof and floor clamping action and sudden sliding off. [ABSTRACT FROM AUTHOR]

A micro region measuring system has been developed to achieve the time-dependent deformation of multi-layer coating at high temperature. The proposed system uses a long-distance microscope and digital speckle correlation method to evaluate the full creep strain fields, which is especially suited for the long-term measurement of the nonuniform deformation. The creep tension tests are performed to obtain the creep strain distribution and evolution inside the thermal barrier coating specimen. According to the deformation measured from different micro regions, we obtained some fundamental knowledge about the time-dependent behavior of the failure mechanism in multi-layer coatings. The accuracy of the new measuring system and the corresponding error analyses are also discussed in this paper. [ABSTRACT FROM AUTHOR]

The digital speckle correlation method (DSCM) used to measure blood flow velocity is here analyzed. The experiment is designed to obtain the dynamic speckle pattern of blood which is shot by CCD. Then the DSCM is used to process the sequential images and the experiment is simulated. The experimental results show that the DSCM can measure blood flow velocity, and have a good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

Experimental study of the formation and propagation of three-dimensional (3D) faults is of great significance in the understanding of the propagation process developing from initial natural faults. In the study described in this paper, experimental investigations of 3D propagation processes of a type of surface fault are carried out under biaxial compression. The strain field near the surface fault is dynamically measured and fully analyzed with a high-density Multi-Channel Digital Strain Gauge (MCDSG) and Digital Speckle Correlation Method (DSCM) based on the white-light image analysis. Simultaneously the micro-fracture process involved in fault formation is observed by a 3D acoustic emission (AE) location system with a set of multi-channel whole-wave record equipment. The experimental results show that the 3D propagation process of surface fault differs greatly from that of the two-dimensional (2D) state and that a new more complicated type of 3D morphological characters and deformation mechanisms are produced. The 3D propagation process of surface faults may be divided into three stages: 1) the first stage of crack propagation initiated by wing cracks; 2) the conversion stage propagated by petal cracks; and 3) the second stage of crack propagation formed by shell-shaped fracture surface. The primary propagation patterns of the three stages are different. The corresponding deformation fields and micro-fracture distributions are likewise different. The fracture activities from petal cracks especially are of vital importance during surface fault propagation. This is also a key conversion state and marks an intrinsic difference between 2D-like and the 3D state in fault development. [ABSTRACT FROM AUTHOR]

Digital speckle micro-metrology system, which is a combination of a long-focus microscope and a digital image-measuring device, is developed for studying the micro-mechanics behavior of the interphase of bimaterials. The natural texture of a specimen''s surface is thought as a carrier of deformation''s information and is analyzed to obtain the displacement field in each step, strain field and their real-time variation of the interphase. The resolution of the micro-metrology system is 10 nm for in-plane displacements. In this paper, the micro-metrology system is employed to investigate the micro-mechanics behavior of the interphase under thermal impulsing. The experimental results show that the interphase is the main factor affecting the mechanical characteristic of the whole composite structure. [Copyright &y& Elsevier]

Abstract: Used digital speckle correlation method (DSCM) to realize orientation function of optical mouse is researched. The experiment is designed to obtain the dynamic speckle patterns which are shot by CCD, then the DSCM is used to process the sequential images and also the experiment is simulated. The experimental results show the DSCM can confirm orientation function of the optical mouse, and have a good agreement with the simulation results, and the resolution we obtained is higher than the resolution of mouse on the market. [Copyright &y& Elsevier]

Abstract: Digital speckle three-shearing-aperture interferometry used for the measurement of curvature distribution fields of a deformation object is proposed for the first time. In this method, pure curvature distribution fringes without containing slope distribution fringes can be obtained by using digital speckle three-shearing-aperture interferometry. Two specklegrams, one before and the other after object deformation, are recorded by a CCD camera and stored in a computer. A 2-D fast Fourier transform (FFT) and a 2-D inverse FFT (IFFT) are performed on the two specklegrams. The subtraction of the transformed specklegrams will produce curvature distribution fringes, and the speckle noises in curvature distribution fringes can be removed after these fringes pass through low-pass filtering. Results from theory and experiments are in good agreement. [Copyright &y& Elsevier]

• CNTFC was prepared as a surrounding rock filling and pressure relief material. • The law of force, deformation and energy drop release of CNTFC was studied. • The deformation localization of the CNTFC specimens was proposed as the start determination condition. • The optimal proportion of CNTs in the CNTFC specimens was determined. In this study, uniaxial compression tests and digital speckle collection technology are used to study the applicability of carbon nanotube-reinforced foam concrete, which is prepared with micro-doped carbon nanotubes, as a pressure-relieving energy-absorbing material. Moreover, the effects of different carbon nanotube contents on the load-deformation characteristics, including the stress-strain response, displacement field, maximum shear strain field, Poisson's ratio and energy drop release law, of carbon nanotube-reinforced foam concrete materials are investigated. The results show that the ultimate strain of the carbon nanotube-reinforced foam concrete materials is much larger than that of brittle materials, such as ordinary concrete and rock. As the carbon nanotube content increases, the carbon nanotube-reinforced foam concrete specimen provides higher post-peak compressive resistance under certain deformation conditions. This property is a performance requirement of surrounding rock support pressure relief materials. It is proposed that the deformation localization starting conditions of the carbon nanotube-reinforced foam concrete specimens are divided into strain decision conditions and stress decision conditions. The strain decision condition is 86.8% of the peak strain, and the stress decision condition is 80.2% of the peak stress. It is suggested that the strain condition is more reasonable than the stress condition as the starting condition for deformation localization in the carbon nanotube-reinforced foam concrete specimens. So on after deformation localization starts, the corresponding Poisson's ratio-strain curve exhibits a steep increase. The energy release process of carbon nanotube-reinforced foam concrete is measured by the energy drop release rate. The energy release process of the carbon nanotube-reinforced foam concrete specimens with 0.05% carbon nanotubes best satisfies the surrounding rock support pressure relief requirements. [ABSTRACT FROM AUTHOR]

In order to achieve microcapsules' higher encapsulating capacity and better self-healing efficiency, the graphene oxide (GO)-modified double-walled Polyurea microcapsules were synthesized with 1, 6-Diaminohexane as the inner core and isophorone diisocyanate (IPDI)-based prepolymer as the outer core. Measured were the morphology, structure, thermal property and mechanical property of the microcapsules by using the Optical and Scanning Electron Microscopy (OM, SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Nanoindentation tests. And the mechanical testing machine, Digital Speckle Correlation Method (DSCM) and Electrochemical Impedance Spectroscopy (EIS) measurement were used to evaluate their mechanical and anticorrosive properties. The results showed that the GO-modified microcapsules obtained possessed a good spherical shape with a mean diameter of 0.5 μm. The microcapsules with excellent thermostability containing a urea bond, the GO had been successfully embedded into the wall materials and the contents of the inner core materials and outer core materials were 26.75 wt% and 10.88 wt% respectively. The average Young's modulus, hardness and load during the holding time of the microcapsules were 2.708GPa, 0.088GPa and 28.51mN respectively. The mechanical and anticorrosive self-healing efficiency of epoxy coating with 3.0 wt% of microcapsules could gain up to 80.43% and 62.50% respectively. Unlabelled Image • Double-walled Polyurea microcapsules modified by graphene oxide were successfully prepared via interfacial polymerization. • The self-healing coatings showed better mechanical property and marine corrosion resistance than ordinary coatings. • Self-healing mechanism of the coatings was verified by Digital Speckle Correlation Method and Electrochemical Measurement. [ABSTRACT FROM AUTHOR]

The deformation measurement of a specular surface is of great importance during the quality inspection and installation of optical elements or wafers, especially those with large apertures. We propose a deflectometry method with speckle digital image correlation (DeSDIC) to realize the dynamic and high-accuracy measurement of the deformation on specular surfaces, with a simple system structure and robustness to noises and environmental vibrations. Random speckle pattern displayed on liquid crystal display is reflected by the original surface under test (SUT), and the distorted pattern is recorded by a camera. This originally distorted pattern is taken as the reference image, and the patterns captured afterwards are digitally correlated with the reference image to calculate the gradient change and deformation of the SUT. The theoretical relationships and an experimental one-step calibration scheme are proposed. Both static and dynamic deformations of a deformable mirror were experimentally measured to demonstrate the feasibility and accuracy of DeSDIC, which is comparable to phase-measuring deflectometry and interferometry. [ABSTRACT FROM AUTHOR]