To obtain the certificate of airworthiness,it is essential to conduct a full-scale aircraft static test.During such test,accurate and comprehensive wing deformation measurement is crucial for assessing its strength,st...To obtain the certificate of airworthiness,it is essential to conduct a full-scale aircraft static test.During such test,accurate and comprehensive wing deformation measurement is crucial for assessing its strength,stiffness,and bearing capability.This paper proposes a novel and cost-effective videogrammetric method using multi-camera system to achieve the non-contact,highprecision,and 3D measurement of overall static deformation for the large-scale wing structure.To overcome the difficulties of making,carrying,and employing the large 2D or 3D target for calibrating the cameras with large field of view,a flexible stereo cameras calibration method combining 1D target and epipolar geometry is proposed.The global calibration method,aided by a total station,is employed to unify the 3D data obtained from various binocular subsystems.A series of static load tests using a 10-meter-long large-scale wing have been conducted to validate the proposed system and methods.Furthermore,the proposed method was applied to the practical wing deformation measurement of both wings with a wingspan of 33.6 m in the full-size civil aircraft static test.The overall 3D profile and displacement data of the tested wing under various loads can be accurately obtained.The maximum error of distance and displacement measurement is less than 4.5 mm within the measurement range of 35 m in all load cases.These results demonstrate that the proposed method achieves effective,high-accuracy,on-site,and visualized wing deformation measurement,making it a promising approach for full-scale aircraft wing static test.展开更多
The recovery of coseismic 3-dimensional(3D)surface deformation field plays a crucial role in studying seismic source characteristics and earthquake hazards.As of now,there are two main types of methods for recovering ...The recovery of coseismic 3-dimensional(3D)surface deformation field plays a crucial role in studying seismic source characteristics and earthquake hazards.As of now,there are two main types of methods for recovering coseismic 3D surface deformations:the first type is to solve the problem directly by using the least squares method based on observations from three or more viewpoints,and the second type solves the problem by combining ascending and descending In SAR line-of-sight(LOS)observations with constraint models.The former type is mainly applicable to surface rupture earthquakes,because when an earthquake ruptures to the surface,we can usually obtain surface deformation observations from three or more views.The latter type applies to earthquakes that do not cause surface ruptures and have extensive blind faults.Currently,most research focuses on improving the above types of methods.However,some key factors in the coseismic 3D surface deformation inversion are rarely mentioned,such as the influence of window size on the inversion results in the strain model and variance component estimation method(SM-VCE),and whether the outliers in the observational data are considered.So,we developed a new chain of integrating In SAR observation and SM-VCE model to systematically assess the impacts of window size and outliers on coseismic 3D surface deformation inversions.Through simulation experiments,we observed that the selection of window size significantly impacts the accuracy of the results.Specifically,larger window sizes lead to wider residuals ranges in the fault region,resulting in the loss of extreme solution values when using a window of 15×15 pixels(i.e.,7.5 km×7.5 km).Hence,we recommend utilizing windows with 7×7 pixels or 9×9 pixels for optimal accuracy,as larger window sizes diminish the significance of the outcomes.The elimination of points displaying different deformation directions helps reduce residuals and preserves near-field deformation results.Furthermore,the residuals along the 3D direction can be reduced by 10%-30%when a small set of points is selected using a method based on Euclidean distances.However,when 441 points were selected,the vertical residuals increased by 22%compared to 81 points.Integration of the SM-VCE algorithm with robust estimation techniques effectively minimizes far-field deformation errors in data,thereby marginally enhancing the near-field deformation solution.展开更多
Contact detection is the most time-consuming stage in 3D discontinuous deformation analysis(3D-DDA)computation.Improving the efficiency of 3D-DDA is beneficial for its application in large-scale computing.In this stud...Contact detection is the most time-consuming stage in 3D discontinuous deformation analysis(3D-DDA)computation.Improving the efficiency of 3D-DDA is beneficial for its application in large-scale computing.In this study,aiming at the continuous-discontinuous simulation of 3D-DDA,a highly efficient contact detection strategy is proposed.Firstly,the global direct search(GDS)method is integrated into the 3D-DDA framework to address intricate contact scenarios.Subsequently,all geometric elements,including blocks,faces,edges,and vertices are divided into searchable and unsearchable parts.Contacts between unsearchable geometric elements would be directly inherited,while only searchable geometric elements are involved in contact detection.This strategy significantly reduces the number of geometric elements involved in contact detection,thereby markedly enhancing the computation efficiency.Several examples are adopted to demonstrate the accuracy and efficiency of the improved 3D-DDA method.The rock pillars with different mesh sizes are simulated under self-weight.The deformation and stress are consistent with the analytical results,and the smaller the mesh size,the higher the accuracy.The maximum speedup ratio is 38.46 for this case.Furthermore,the Brazilian splitting test on the discs with different flaws is conducted.The results show that the failure pattern of the samples is consistent with the results obtained by other methods and experiments,and the maximum speedup ratio is 266.73.Finally,a large-scale impact test is performed,and approximately 3.2 times enhanced efficiency is obtained.The proposed contact detection strategy significantly improves efficiency when the rock has not completely failed,which is more suitable for continuous-discontinuous simulation.展开更多
This paper presents,for the first time,an effective numerical approach based on the isogeometric analysis(IGA)and the six-variable quasi-three dimensional(3D)higher-order shear deformation theory(HSDT)to study the fre...This paper presents,for the first time,an effective numerical approach based on the isogeometric analysis(IGA)and the six-variable quasi-three dimensional(3D)higher-order shear deformation theory(HSDT)to study the free vibration characteristics of functionally-graded(FG)graphene origami(GOri)-enabled auxetic metamaterial(GOEAM)plates submerged in a fluid medium.The plate theory incorporates the thickness stretching and the effects of transverse shear deformation without using any shear correction factors.The velocity potential function and Bernoulli's equation are used to derive the hydrodynamic pressure acting on the plate surface.Both horizontally and vertically immersed plate configurations are considered here in the form of inertia effects.The plates are composed of multilayer GOEAMs,with the GOri content varying through the plate's thickness in a layer-wise manner.This design results in graded auxetic growth.The material properties are evaluated by mixing rules and a genetic programming(GP)-assisted micromechanical model.The governing equations of motion for the FG-GOEAM plates immersed in a fluid medium are derived by Hamilton's principle.After validating the convergence and accuracy of the present model,a comprehensive parametric study is carried out to examine the effects of the GOri content,GOri distribution pattern,GOri folding degree,fluid level,immersed depth,and geometric parameter on the natural frequencies of the FG-GOEAM plates.The results show that the natural frequencies for the four GOri distribution patterns increase with the increase in the layer number when the lay number is fewer than 10,and then stabilize after the layer number reaches 10.Besides,in general,the natural frequency of the FG-GOEAM plate in a vacuum or fluid increases when the GOri content increases,while decreases when the GOri folding degree increases.Some additional findings related to the numerical results are presented in the conclusions.It is believed that the present results are useful for the precise design and optimization of FG-GOEAM plates immersed in a fluid medium.展开更多
Landslide is the second largest natural disaster after earthquake. It is of significance to study the evolution laws and failure mechanism of landslides based on its surface 3D deformation information. Based on the ra...Landslide is the second largest natural disaster after earthquake. It is of significance to study the evolution laws and failure mechanism of landslides based on its surface 3D deformation information. Based on the rainfall-triggered waste dump instability model test, we studied the failure mechanisms of the waste dump by integrating surface deformation and internal slope stress and proposed novel parameters for identifying landslide stability. We developed a noncontact measurement device, which can obtain millimeter-level 3D deformation data for surface scene in physical model test;Then we developed the similar materials and established a test model for a waste dump. Based on the failure characteristics of slope surface, internal stress of slope body and displacement contours during the whole process, we divided the slope instability process in model test into four stages: rainfall infiltration and surface erosion, shallow sliding, deep sliding, and overall instability. Based on the obtained surface deformation data, we calculated the volume change during slope instability process and compared it with the point displacement on slope surface. The results showed that the volume change can not only reflect the slow-ultra acceleration process of slope failure, but also fully reflect the above four stages and reduce the fluctuations caused by random factors. Finally, this paper proposed two stability identification parameters: the volume change rate above the slip surface and the relative velocity of volume change rate. According to the calculation of these two parameters in model test, they can be used for study the deformation and failure mechanism of slope stability.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
文摘To obtain the certificate of airworthiness,it is essential to conduct a full-scale aircraft static test.During such test,accurate and comprehensive wing deformation measurement is crucial for assessing its strength,stiffness,and bearing capability.This paper proposes a novel and cost-effective videogrammetric method using multi-camera system to achieve the non-contact,highprecision,and 3D measurement of overall static deformation for the large-scale wing structure.To overcome the difficulties of making,carrying,and employing the large 2D or 3D target for calibrating the cameras with large field of view,a flexible stereo cameras calibration method combining 1D target and epipolar geometry is proposed.The global calibration method,aided by a total station,is employed to unify the 3D data obtained from various binocular subsystems.A series of static load tests using a 10-meter-long large-scale wing have been conducted to validate the proposed system and methods.Furthermore,the proposed method was applied to the practical wing deformation measurement of both wings with a wingspan of 33.6 m in the full-size civil aircraft static test.The overall 3D profile and displacement data of the tested wing under various loads can be accurately obtained.The maximum error of distance and displacement measurement is less than 4.5 mm within the measurement range of 35 m in all load cases.These results demonstrate that the proposed method achieves effective,high-accuracy,on-site,and visualized wing deformation measurement,making it a promising approach for full-scale aircraft wing static test.
基金supported by the National Natural Science of Foundation of China(42104008,42204006)the Jiangxi Provincial Natural Science Foundation(20232BAB213075)the Open Fund of Hubei Luojia Laboratory(grant 230100019,230100020)。
文摘The recovery of coseismic 3-dimensional(3D)surface deformation field plays a crucial role in studying seismic source characteristics and earthquake hazards.As of now,there are two main types of methods for recovering coseismic 3D surface deformations:the first type is to solve the problem directly by using the least squares method based on observations from three or more viewpoints,and the second type solves the problem by combining ascending and descending In SAR line-of-sight(LOS)observations with constraint models.The former type is mainly applicable to surface rupture earthquakes,because when an earthquake ruptures to the surface,we can usually obtain surface deformation observations from three or more views.The latter type applies to earthquakes that do not cause surface ruptures and have extensive blind faults.Currently,most research focuses on improving the above types of methods.However,some key factors in the coseismic 3D surface deformation inversion are rarely mentioned,such as the influence of window size on the inversion results in the strain model and variance component estimation method(SM-VCE),and whether the outliers in the observational data are considered.So,we developed a new chain of integrating In SAR observation and SM-VCE model to systematically assess the impacts of window size and outliers on coseismic 3D surface deformation inversions.Through simulation experiments,we observed that the selection of window size significantly impacts the accuracy of the results.Specifically,larger window sizes lead to wider residuals ranges in the fault region,resulting in the loss of extreme solution values when using a window of 15×15 pixels(i.e.,7.5 km×7.5 km).Hence,we recommend utilizing windows with 7×7 pixels or 9×9 pixels for optimal accuracy,as larger window sizes diminish the significance of the outcomes.The elimination of points displaying different deformation directions helps reduce residuals and preserves near-field deformation results.Furthermore,the residuals along the 3D direction can be reduced by 10%-30%when a small set of points is selected using a method based on Euclidean distances.However,when 441 points were selected,the vertical residuals increased by 22%compared to 81 points.Integration of the SM-VCE algorithm with robust estimation techniques effectively minimizes far-field deformation errors in data,thereby marginally enhancing the near-field deformation solution.
基金financially supported by the National Key R&D Program of China(Grant No.2023YFC3081200)the National Natural Science Foundation of China(Grant Nos.U21A20159 and 52179117).
文摘Contact detection is the most time-consuming stage in 3D discontinuous deformation analysis(3D-DDA)computation.Improving the efficiency of 3D-DDA is beneficial for its application in large-scale computing.In this study,aiming at the continuous-discontinuous simulation of 3D-DDA,a highly efficient contact detection strategy is proposed.Firstly,the global direct search(GDS)method is integrated into the 3D-DDA framework to address intricate contact scenarios.Subsequently,all geometric elements,including blocks,faces,edges,and vertices are divided into searchable and unsearchable parts.Contacts between unsearchable geometric elements would be directly inherited,while only searchable geometric elements are involved in contact detection.This strategy significantly reduces the number of geometric elements involved in contact detection,thereby markedly enhancing the computation efficiency.Several examples are adopted to demonstrate the accuracy and efficiency of the improved 3D-DDA method.The rock pillars with different mesh sizes are simulated under self-weight.The deformation and stress are consistent with the analytical results,and the smaller the mesh size,the higher the accuracy.The maximum speedup ratio is 38.46 for this case.Furthermore,the Brazilian splitting test on the discs with different flaws is conducted.The results show that the failure pattern of the samples is consistent with the results obtained by other methods and experiments,and the maximum speedup ratio is 266.73.Finally,a large-scale impact test is performed,and approximately 3.2 times enhanced efficiency is obtained.The proposed contact detection strategy significantly improves efficiency when the rock has not completely failed,which is more suitable for continuous-discontinuous simulation.
基金Project supported by the National Natural Science Foundation of China(Nos.12162004 and 11562001)the Doctoral Research Start-up Fund Project at University of South China(No.Y00043-13)。
文摘This paper presents,for the first time,an effective numerical approach based on the isogeometric analysis(IGA)and the six-variable quasi-three dimensional(3D)higher-order shear deformation theory(HSDT)to study the free vibration characteristics of functionally-graded(FG)graphene origami(GOri)-enabled auxetic metamaterial(GOEAM)plates submerged in a fluid medium.The plate theory incorporates the thickness stretching and the effects of transverse shear deformation without using any shear correction factors.The velocity potential function and Bernoulli's equation are used to derive the hydrodynamic pressure acting on the plate surface.Both horizontally and vertically immersed plate configurations are considered here in the form of inertia effects.The plates are composed of multilayer GOEAMs,with the GOri content varying through the plate's thickness in a layer-wise manner.This design results in graded auxetic growth.The material properties are evaluated by mixing rules and a genetic programming(GP)-assisted micromechanical model.The governing equations of motion for the FG-GOEAM plates immersed in a fluid medium are derived by Hamilton's principle.After validating the convergence and accuracy of the present model,a comprehensive parametric study is carried out to examine the effects of the GOri content,GOri distribution pattern,GOri folding degree,fluid level,immersed depth,and geometric parameter on the natural frequencies of the FG-GOEAM plates.The results show that the natural frequencies for the four GOri distribution patterns increase with the increase in the layer number when the lay number is fewer than 10,and then stabilize after the layer number reaches 10.Besides,in general,the natural frequency of the FG-GOEAM plate in a vacuum or fluid increases when the GOri content increases,while decreases when the GOri folding degree increases.Some additional findings related to the numerical results are presented in the conclusions.It is believed that the present results are useful for the precise design and optimization of FG-GOEAM plates immersed in a fluid medium.
基金funded by the National Key R&D Program of China (Grant No. 2021YFB3901402)the Fundamental Research Funds for the Central Universities (Project No. 2022CDJKYJH037)。
文摘Landslide is the second largest natural disaster after earthquake. It is of significance to study the evolution laws and failure mechanism of landslides based on its surface 3D deformation information. Based on the rainfall-triggered waste dump instability model test, we studied the failure mechanisms of the waste dump by integrating surface deformation and internal slope stress and proposed novel parameters for identifying landslide stability. We developed a noncontact measurement device, which can obtain millimeter-level 3D deformation data for surface scene in physical model test;Then we developed the similar materials and established a test model for a waste dump. Based on the failure characteristics of slope surface, internal stress of slope body and displacement contours during the whole process, we divided the slope instability process in model test into four stages: rainfall infiltration and surface erosion, shallow sliding, deep sliding, and overall instability. Based on the obtained surface deformation data, we calculated the volume change during slope instability process and compared it with the point displacement on slope surface. The results showed that the volume change can not only reflect the slow-ultra acceleration process of slope failure, but also fully reflect the above four stages and reduce the fluctuations caused by random factors. Finally, this paper proposed two stability identification parameters: the volume change rate above the slip surface and the relative velocity of volume change rate. According to the calculation of these two parameters in model test, they can be used for study the deformation and failure mechanism of slope stability.
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.
