It is always desirable to know the interior deformation pattern when a rock is subjected to mechanicalload. Few experimental techniques exist that can represent full-field three-dimensional （3D） straindistribution i...It is always desirable to know the interior deformation pattern when a rock is subjected to mechanicalload. Few experimental techniques exist that can represent full-field three-dimensional （3D） straindistribution inside a rock specimen. And yet it is crucial that this information is available for fully understandingthe failure mechanism of rocks or other geomaterials. In this study, by using the newlydeveloped digital volumetric speckle photography （DVSP） technique in conjunction with X-ray computedtomography （CT） and taking advantage of natural 3D speckles formed inside the rock due to materialimpurities and voids, we can probe the interior of a rock to map its deformation pattern under load andshed light on its failure mechanism. We apply this technique to the analysis of a red sandstone specimenunder increasing uniaxial compressive load applied incrementally. The full-field 3D displacement fieldsare obtained in the specimen as a function of the load, from which both the volumetric and the deviatoricstrain fields are calculated. Strain localization zones which lead to the eventual failure of the rock areidentified. The results indicate that both shear and tension are contributing factors to the failuremechanism. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
Two speckle patterns are recorded using a video cameracorresponding to undisplaced and displaced states into the memory ofa computer. After one pattern is added to another, the displacementof the measured points can b...Two speckle patterns are recorded using a video cameracorresponding to undisplaced and displaced states into the memory ofa computer. After one pattern is added to another, the displacementof the measured points can be calculated by using the Fouriertransform. The expression of displacement field is deduced fornon-uniform displacement, and as an example, a rotatanle disc istested for illustration. The re- sults prove that the present methodis promising.展开更多
In this work, an experimental approach of speckle photography was used for measuring birefringence of thermotropic liquid crystals mixtures at different wavelengths in the visible region. Also the dispersion relations...In this work, an experimental approach of speckle photography was used for measuring birefringence of thermotropic liquid crystals mixtures at different wavelengths in the visible region. Also the dispersion relations were investigated. The values of the refractive indices were measured for these mixtures of thermotropic liquid crystals in isotropic and liquid crystal phase at different wavelengths. The effect of the end group of these LCs used on the values of birefringence was investigated and discussed.展开更多
The refractive index of a liquid medium is an important optical parameter since it exhibits the optical properties of the liquid. Its values are often required to interpret various types of spectroscopic data. The int...The refractive index of a liquid medium is an important optical parameter since it exhibits the optical properties of the liquid. Its values are often required to interpret various types of spectroscopic data. The intensity distribution and contrast of image speckle patterns obtained for Zamzam, bottled drinking and distilled waters are investigated on a computer as a function of six discrete wavelengths across the visible spectrum. The present novel computer simulation speckle photography using Fourier transform study and the new theoretical background have been confirmed with previous experimental results. Uncertainty of refractive index measurements was studied on a wide range of discrete wavelengths using the computer simulation and the new theoretical formulae.展开更多
The efficient development of new materials with defined properties requires fast methods of testing low volumes of material,such as a high-throughput investigation of spherical metallic micro samples with varying comp...The efficient development of new materials with defined properties requires fast methods of testing low volumes of material,such as a high-throughput investigation of spherical metallic micro samples with varying compositions and structuring treatments.A classical material testing method for macro samples,the tensile test cannot be employed for analyzing the mechanical properties of spherical samples with diameters below 1 mm since there are currently no methods for holding and stretching them.A combination between the incremental electrohydraulic extrusion as stress actuation unit and the speckle photography as strain measuring method is presented for obtaining the required mechanical characteristics.Positive longitudinal strain is generated at stepwise extrusion through<1 mm wide forming channels using a liquid punch and the deformation is observed in situ after each forming step at the interface between the micro sample and a transparent window integrated into the forming die.The occurring local strain fields with a lateral extension down to 100 pm and high gradients require displacement measurements with high lateral resolution over a large range of local dislocations between 0.1 and>10 μm.It is unknown,whether the speckle strain measuring method is able to provide the necessary low uncertainty for the required resolution in the whole measuring range.Therefore,theoretical and experimental investigations of the deformation measurability using the speckle correlation method are presented,showing that local displacements up to 10 μm can be measured with a spatial resolution between 3 and 10μm depending on the displacement size.The dominant effect influencing the measurement uncertainty for displacements at this high spatial resolution is the speckle noise,resulting into measurement uncertainties of less than 100 μm.Hence,speckle photography is shown to be applicable for tensile test on micro samples.展开更多
A new method of measuring gear tooth dynamic deformation is proposed. Dynamic speckle photographs of the rotating gear tooth have been achieved by combining the pulsed ruby laser with the out-syn-signal. Double speckl...A new method of measuring gear tooth dynamic deformation is proposed. Dynamic speckle photographs of the rotating gear tooth have been achieved by combining the pulsed ruby laser with the out-syn-signal. Double speckle patterns of the whole mesh period of gear tooth are obtained by accurate time delay of the ruby laser. Gear tooth dynamic deformation of the whole mesh period is achieved using the automatic image processing. Testing results show that the trends of gear tooth deformation coincides with the calculation by the finite element method. The success of this new trying provides a new technique for the measurement of gear tooth dynamic deformation.展开更多
基金financially supported by National Basic Research Program of China (973 Program) (No. 2010CB732002)National Natural Science Foundation of China (Nos. 51374211, 51374215)+1 种基金National Key Foundation for Exploring Scientific Instrument of China (No. 2013YQ240803)Fundamental Research Funds for the Central Universities (No. 2009QM02)
文摘It is always desirable to know the interior deformation pattern when a rock is subjected to mechanicalload. Few experimental techniques exist that can represent full-field three-dimensional （3D） straindistribution inside a rock specimen. And yet it is crucial that this information is available for fully understandingthe failure mechanism of rocks or other geomaterials. In this study, by using the newlydeveloped digital volumetric speckle photography （DVSP） technique in conjunction with X-ray computedtomography （CT） and taking advantage of natural 3D speckles formed inside the rock due to materialimpurities and voids, we can probe the interior of a rock to map its deformation pattern under load andshed light on its failure mechanism. We apply this technique to the analysis of a red sandstone specimenunder increasing uniaxial compressive load applied incrementally. The full-field 3D displacement fieldsare obtained in the specimen as a function of the load, from which both the volumetric and the deviatoricstrain fields are calculated. Strain localization zones which lead to the eventual failure of the rock areidentified. The results indicate that both shear and tension are contributing factors to the failuremechanism. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
文摘Two speckle patterns are recorded using a video cameracorresponding to undisplaced and displaced states into the memory ofa computer. After one pattern is added to another, the displacementof the measured points can be calculated by using the Fouriertransform. The expression of displacement field is deduced fornon-uniform displacement, and as an example, a rotatanle disc istested for illustration. The re- sults prove that the present methodis promising.
文摘In this work, an experimental approach of speckle photography was used for measuring birefringence of thermotropic liquid crystals mixtures at different wavelengths in the visible region. Also the dispersion relations were investigated. The values of the refractive indices were measured for these mixtures of thermotropic liquid crystals in isotropic and liquid crystal phase at different wavelengths. The effect of the end group of these LCs used on the values of birefringence was investigated and discussed.
文摘The refractive index of a liquid medium is an important optical parameter since it exhibits the optical properties of the liquid. Its values are often required to interpret various types of spectroscopic data. The intensity distribution and contrast of image speckle patterns obtained for Zamzam, bottled drinking and distilled waters are investigated on a computer as a function of six discrete wavelengths across the visible spectrum. The present novel computer simulation speckle photography using Fourier transform study and the new theoretical background have been confirmed with previous experimental results. Uncertainty of refractive index measurements was studied on a wide range of discrete wavelengths using the computer simulation and the new theoretical formulae.
基金This research is funded by Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-project number 276397488-SFB 1232 and the support is gratefully acknowledged.
文摘The efficient development of new materials with defined properties requires fast methods of testing low volumes of material,such as a high-throughput investigation of spherical metallic micro samples with varying compositions and structuring treatments.A classical material testing method for macro samples,the tensile test cannot be employed for analyzing the mechanical properties of spherical samples with diameters below 1 mm since there are currently no methods for holding and stretching them.A combination between the incremental electrohydraulic extrusion as stress actuation unit and the speckle photography as strain measuring method is presented for obtaining the required mechanical characteristics.Positive longitudinal strain is generated at stepwise extrusion through<1 mm wide forming channels using a liquid punch and the deformation is observed in situ after each forming step at the interface between the micro sample and a transparent window integrated into the forming die.The occurring local strain fields with a lateral extension down to 100 pm and high gradients require displacement measurements with high lateral resolution over a large range of local dislocations between 0.1 and>10 μm.It is unknown,whether the speckle strain measuring method is able to provide the necessary low uncertainty for the required resolution in the whole measuring range.Therefore,theoretical and experimental investigations of the deformation measurability using the speckle correlation method are presented,showing that local displacements up to 10 μm can be measured with a spatial resolution between 3 and 10μm depending on the displacement size.The dominant effect influencing the measurement uncertainty for displacements at this high spatial resolution is the speckle noise,resulting into measurement uncertainties of less than 100 μm.Hence,speckle photography is shown to be applicable for tensile test on micro samples.
文摘A new method of measuring gear tooth dynamic deformation is proposed. Dynamic speckle photographs of the rotating gear tooth have been achieved by combining the pulsed ruby laser with the out-syn-signal. Double speckle patterns of the whole mesh period of gear tooth are obtained by accurate time delay of the ruby laser. Gear tooth dynamic deformation of the whole mesh period is achieved using the automatic image processing. Testing results show that the trends of gear tooth deformation coincides with the calculation by the finite element method. The success of this new trying provides a new technique for the measurement of gear tooth dynamic deformation.
