In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic ...In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic emission technique was used to monitor the acoustic signal characteristics of composite rock specimens during the entire loading process. At the same time, an optical non-contact 3 D digital image correlation technique was used to study the evolution of axial strain field and the maximal strain field before and after the peak strength at different stress levels during the loading process. The effect of bedding plane inclination on the deformation and strength during uniaxial loading was analyzed. The methods of solving the elastic constants of hard and weak rock were described. The damage evolution process, deformation and failure mechanism, and failure mode during uniaxial loading were fully determined. The experimental results show that the θ = 0?–45?specimens had obvious plastic deformation during loading, and the brittleness of the θ = 60?–90?specimens gradually increased during the loading process. When the anisotropic angle θincreased from 0?to 90?, the peak strength, peak strain,and apparent elastic modulus all decreased initially and then increased. The failure mode of the composite rock specimen during uniaxial loading can be divided into three categories:tensile fracture across the discontinuities(θ = 0?–30?), slid-ing failure along the discontinuities(θ = 45?–75?), and tensile-split along the discontinuities(θ = 90?). The axial strain of the weak and hard rock layers in the composite rock specimen during the loading process was significantly different from that of the θ = 0?–45?specimens and was almost the same as that of the θ = 60?–90?specimens. As for the strain localization highlighted in the maximum principal strain field, the θ = 0?–30?specimens appeared in the rock matrix approximately parallel to the loading direction,while in the θ = 45?–90?specimens it appeared at the hard and weak rock layer interface.展开更多
To verify the effectiveness of digital optical 3D image analyzer EvaSKIN in the objective and quantitative evaluation of wrinkles.A total of 115 subjects were recruited,the facial images of the subjects were collected...To verify the effectiveness of digital optical 3D image analyzer EvaSKIN in the objective and quantitative evaluation of wrinkles.A total of 115 subjects were recruited,the facial images of the subjects were collected by digital optical 3D image analyzer and manual camera,the changes of crow’s feet with age were analyzed.Pictures obtained by manual photography can be directly used for observation and preliminary grading of wrinkles.However,the requirements for evaluators are high,and the results are prone to errors,which will affect the accuracy of the evaluation.Therefore,skilled raters are needed.Compared with the manual photography method,the digital optical 3D image analyzer EvaSKIN can realize three-dimensional extraction of wrinkles,and obtain the change trend of crow’s feet with age.20~30 years old,wrinkles begin to appear slowly;wrinkles will increase rapidly at the age of 30~50;The length of 50~60 year old wrinkles is basically fixed,the wrinkles develop longitudewise,gradually widen and deepen,and the area,depth and volume increase is obvious,and the skin aging condition is intensified.the digital optical 3D image analyzer EvaSKIN realizes the 3D extraction of wrinkles,quantifies the circumference,area,average depth,maximum depth and volume of wrinkles,realizes the objective and quantitative evaluation of wrinkle state,is more accurate in the measurement of wrinkles,and provides a new instrument and method for the evaluation of wrinkles.it is a perfect and supplement to the traditional evaluation methods,and to a certain extent,it helps the research and development and evaluation institutions of cosmetics to obtain more abundant and three-dimensional data support.展开更多
In thermal-structural testing of hypersonic materials and structures,deformation measurement on the front surface of an object directly heated by quartz lamps is highly necessary and very challenging.This work describ...In thermal-structural testing of hypersonic materials and structures,deformation measurement on the front surface of an object directly heated by quartz lamps is highly necessary and very challenging.This work describes a novel front-surface high-temperature deformation measurement technique,which adopts ultraviolet 3D digital image correlation(UV 3D-DIC)to observe and measure the high-temperature deformation fields on front surfaces directly heated by quartz lamps.Compared with existing blue light DIC techniques,the established UV 3D-DIC,which combines UV CCD camera,active UV illumination and bandpass filter imaging,can effectively suppress the strong disturbing light emitted by the quartz lamps and the heated sample itself during heating process.Two experiments were carried out to verify the robustness and accuracy of the developed technique:(1)direct observation of front surfaces of a hypersonic thermal structure sample heated from room temperature to 1050℃,and(2)front-surface thermal stain and coefficient of thermal expansion(CTE)measurement of an Inconel 718 sample up to 800℃.The well matched strain and CTE results with literature data show that UV 3D-DIC system is an effective technique for front-surface deformation measurement and has great potential in characterizing deformation response of hypersonic materials and structures subjected to transient aerodynamic heating.展开更多
To achieve full-surface strain measurement of variable curvature objects,a 360°3D digital image correlation(DIC)system is proposed.The measurement system consists of four double-camera systems,which capture the o...To achieve full-surface strain measurement of variable curvature objects,a 360°3D digital image correlation(DIC)system is proposed.The measurement system consists of four double-camera systems,which capture the object’s entire surface from multiple angles,enabling comprehensive full-surface measurement.To increase the stitching quality,a hierarchical coordinate matching method is proposed.Initially,a 3D rigid body calibration auxiliary block is employed to track motion trajectory,which enables preliminary matching of four 3D-DIC sub-systems.Subsequently,secondary precise matching is performed based on feature points on the test specimen’s surface.Through the hierarchical coordinate matching method,the local 3D coordinate systems of each double-camera system are unified into a global coordinate system,achieving 3D surface reconstruction of the variable curvature cylindrical shell,and error analysis is conducted on the results.Furthermore,axial compression buckling experiment is conducted to measure the displacement and strain fields on the cylindrical shell’s surface.The experimental results are compared with the finite element analysis,validating the accuracy and effectiveness of the proposed multi-camera 3D-DIC measuring system.展开更多
为研究层状复合岩石破坏过程和形态,采用相似理论制作出层状复合岩石相似模型,在单轴压缩条件下观测岩石的破坏特征,结合三维数字图像相关技术(3D digital image correlation,DIC)对试件的整体变形及破坏进行全过程的观测,得到复合岩石...为研究层状复合岩石破坏过程和形态,采用相似理论制作出层状复合岩石相似模型,在单轴压缩条件下观测岩石的破坏特征,结合三维数字图像相关技术(3D digital image correlation,DIC)对试件的整体变形及破坏进行全过程的观测,得到复合岩石三维场的位移和应变,同时基于试件表面应变场的变化,建立了表面损伤程度与损伤因子D之间的量化关系,进而得到基于DIC表征的层状复合岩石损伤演化模型,研究结果表明:层状复合岩石的破坏形态与脆性岩石特征相似,以拉伸劈裂破坏和Y型剪切破坏为主;DIC试验记录的表面应变与损伤因子之间的量化关系可有效反映岩石破坏的全过程,以此为基础建立的损伤演化方程与实验数据拟合效果较好,证明了模型的合理性。展开更多
As a novel three dimensional digital image correlation （3D DIC） method, the bi-prism-based single lens （BSL） 3D DIC method has been proposed and developed in recent years. Making use ofa bi-prism, this method is a...As a novel three dimensional digital image correlation （3D DIC） method, the bi-prism-based single lens （BSL） 3D DIC method has been proposed and developed in recent years. Making use ofa bi-prism, this method is able to perform a 3D DIC measurement using only a single camera. Thus, the integration level of a BSL 3D DIC system could be much higher than that of the double-camera 3D DIC system. In this paper, using a small-angle bi-prism and a camera with a longer focal length, a special BSL 3D DIC system with a long working distance is designed for measurements in extreme environments. The principle of the system is first studied, and practical methods are then proposed for the system set-up and the determination of system parameters. Then, feasibility of the measurement system is verified by out-of-plane rigid-body translation tests. Finally, the BSL 3D DIC system is proven to be capable of combining with a high-temperature testing instrument to perform deformation tests in a high-temperature environment of up to 1500℃.展开更多
基金supported by the National Basic Research 973 Program of China (Grant 2014CB046905)the Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars (Grant BK20150005)+1 种基金the Fundamental Research Funds for the Central Universities (China University of Mining and Technology) (Grant 2014XT03)the innovation research project for academic graduate of Jiangsu Province (Grant KYLX16_0536)
文摘In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic emission technique was used to monitor the acoustic signal characteristics of composite rock specimens during the entire loading process. At the same time, an optical non-contact 3 D digital image correlation technique was used to study the evolution of axial strain field and the maximal strain field before and after the peak strength at different stress levels during the loading process. The effect of bedding plane inclination on the deformation and strength during uniaxial loading was analyzed. The methods of solving the elastic constants of hard and weak rock were described. The damage evolution process, deformation and failure mechanism, and failure mode during uniaxial loading were fully determined. The experimental results show that the θ = 0?–45?specimens had obvious plastic deformation during loading, and the brittleness of the θ = 60?–90?specimens gradually increased during the loading process. When the anisotropic angle θincreased from 0?to 90?, the peak strength, peak strain,and apparent elastic modulus all decreased initially and then increased. The failure mode of the composite rock specimen during uniaxial loading can be divided into three categories:tensile fracture across the discontinuities(θ = 0?–30?), slid-ing failure along the discontinuities(θ = 45?–75?), and tensile-split along the discontinuities(θ = 90?). The axial strain of the weak and hard rock layers in the composite rock specimen during the loading process was significantly different from that of the θ = 0?–45?specimens and was almost the same as that of the θ = 60?–90?specimens. As for the strain localization highlighted in the maximum principal strain field, the θ = 0?–30?specimens appeared in the rock matrix approximately parallel to the loading direction,while in the θ = 45?–90?specimens it appeared at the hard and weak rock layer interface.
文摘To verify the effectiveness of digital optical 3D image analyzer EvaSKIN in the objective and quantitative evaluation of wrinkles.A total of 115 subjects were recruited,the facial images of the subjects were collected by digital optical 3D image analyzer and manual camera,the changes of crow’s feet with age were analyzed.Pictures obtained by manual photography can be directly used for observation and preliminary grading of wrinkles.However,the requirements for evaluators are high,and the results are prone to errors,which will affect the accuracy of the evaluation.Therefore,skilled raters are needed.Compared with the manual photography method,the digital optical 3D image analyzer EvaSKIN can realize three-dimensional extraction of wrinkles,and obtain the change trend of crow’s feet with age.20~30 years old,wrinkles begin to appear slowly;wrinkles will increase rapidly at the age of 30~50;The length of 50~60 year old wrinkles is basically fixed,the wrinkles develop longitudewise,gradually widen and deepen,and the area,depth and volume increase is obvious,and the skin aging condition is intensified.the digital optical 3D image analyzer EvaSKIN realizes the 3D extraction of wrinkles,quantifies the circumference,area,average depth,maximum depth and volume of wrinkles,realizes the objective and quantitative evaluation of wrinkle state,is more accurate in the measurement of wrinkles,and provides a new instrument and method for the evaluation of wrinkles.it is a perfect and supplement to the traditional evaluation methods,and to a certain extent,it helps the research and development and evaluation institutions of cosmetics to obtain more abundant and three-dimensional data support.
基金supported by the National Natural Science Foundation of China(Nos.11602011,11872009,and 11632010)the National S&T Major Project of China(No.ZX069)+1 种基金the Aeronautical Science Foundation of China(No.2016ZD51034)the Postdoctoral Science Foundation of China(No.2017M610029)。
文摘In thermal-structural testing of hypersonic materials and structures,deformation measurement on the front surface of an object directly heated by quartz lamps is highly necessary and very challenging.This work describes a novel front-surface high-temperature deformation measurement technique,which adopts ultraviolet 3D digital image correlation(UV 3D-DIC)to observe and measure the high-temperature deformation fields on front surfaces directly heated by quartz lamps.Compared with existing blue light DIC techniques,the established UV 3D-DIC,which combines UV CCD camera,active UV illumination and bandpass filter imaging,can effectively suppress the strong disturbing light emitted by the quartz lamps and the heated sample itself during heating process.Two experiments were carried out to verify the robustness and accuracy of the developed technique:(1)direct observation of front surfaces of a hypersonic thermal structure sample heated from room temperature to 1050℃,and(2)front-surface thermal stain and coefficient of thermal expansion(CTE)measurement of an Inconel 718 sample up to 800℃.The well matched strain and CTE results with literature data show that UV 3D-DIC system is an effective technique for front-surface deformation measurement and has great potential in characterizing deformation response of hypersonic materials and structures subjected to transient aerodynamic heating.
基金funded by the National Natural Science Foundations of China(Nos.12272176,U2037603).
文摘To achieve full-surface strain measurement of variable curvature objects,a 360°3D digital image correlation(DIC)system is proposed.The measurement system consists of four double-camera systems,which capture the object’s entire surface from multiple angles,enabling comprehensive full-surface measurement.To increase the stitching quality,a hierarchical coordinate matching method is proposed.Initially,a 3D rigid body calibration auxiliary block is employed to track motion trajectory,which enables preliminary matching of four 3D-DIC sub-systems.Subsequently,secondary precise matching is performed based on feature points on the test specimen’s surface.Through the hierarchical coordinate matching method,the local 3D coordinate systems of each double-camera system are unified into a global coordinate system,achieving 3D surface reconstruction of the variable curvature cylindrical shell,and error analysis is conducted on the results.Furthermore,axial compression buckling experiment is conducted to measure the displacement and strain fields on the cylindrical shell’s surface.The experimental results are compared with the finite element analysis,validating the accuracy and effectiveness of the proposed multi-camera 3D-DIC measuring system.
文摘为研究层状复合岩石破坏过程和形态,采用相似理论制作出层状复合岩石相似模型,在单轴压缩条件下观测岩石的破坏特征,结合三维数字图像相关技术(3D digital image correlation,DIC)对试件的整体变形及破坏进行全过程的观测,得到复合岩石三维场的位移和应变,同时基于试件表面应变场的变化,建立了表面损伤程度与损伤因子D之间的量化关系,进而得到基于DIC表征的层状复合岩石损伤演化模型,研究结果表明:层状复合岩石的破坏形态与脆性岩石特征相似,以拉伸劈裂破坏和Y型剪切破坏为主;DIC试验记录的表面应变与损伤因子之间的量化关系可有效反映岩石破坏的全过程,以此为基础建立的损伤演化方程与实验数据拟合效果较好,证明了模型的合理性。
基金supported by the National Natural Science Foundation of China(Grant Nos.11672153,11232008&11227801)
文摘As a novel three dimensional digital image correlation （3D DIC） method, the bi-prism-based single lens （BSL） 3D DIC method has been proposed and developed in recent years. Making use ofa bi-prism, this method is able to perform a 3D DIC measurement using only a single camera. Thus, the integration level of a BSL 3D DIC system could be much higher than that of the double-camera 3D DIC system. In this paper, using a small-angle bi-prism and a camera with a longer focal length, a special BSL 3D DIC system with a long working distance is designed for measurements in extreme environments. The principle of the system is first studied, and practical methods are then proposed for the system set-up and the determination of system parameters. Then, feasibility of the measurement system is verified by out-of-plane rigid-body translation tests. Finally, the BSL 3D DIC system is proven to be capable of combining with a high-temperature testing instrument to perform deformation tests in a high-temperature environment of up to 1500℃.
