桑勇

个人信息Personal Information

教授

博士生导师

硕士生导师

性别:男

毕业院校:北京航空航天大学

学位:博士

所在单位:机械工程学院

学科:机械电子工程

电子邮箱:sangyong@dlut.edu.cn

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A novel optical method for measuring 3D full-field strain deformation in geotechnical tri-axial testing

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论文类型:期刊论文

发表时间:2020-01-01

发表刊物:MEASUREMENT SCIENCE AND TECHNOLOGY

收录刊物:EI、SCIE

卷号:31

期号:1

ISSN号:0957-0233

关键字:geotechnical tri-axial apparatus; 3D-DIC; 3D full-field deformation; subpixel edge detector; volume strain

摘要:Soil is a complex multiphase material and has anisotropic properties; meanwhile, soil behaviour is typically evaluated in tri-axial testing. Until now, there have still been some challenges in measuring the total strain, the local strain deformation and the volume changes during tri-axial testing. In conventional geotechnical testing, it cannot acquire enough deformation characteristics. To improve the situation, a digital image measurement system has been constructed and calibrated on a geotechnical tri-axial apparatus. In the digital image measurement system, the three-dimensional digital image correlation (3D-DIC) technique was applied to measure the soil specimen's 3D large deformation and reconstruct the 3D surface topography of the specimen. To improve the measurement accuracy, a standard spatial calibration procedure to rectify the 3D reconstruction data in tri-axial testing is proposed to improve the effect of the projective transformation in stereovision. Through rectification, the root-mean-squared error in terms of displacement measurement in the tri-axial testing was reduced by more than half. Furthermore, a subpixel edge detector was applied to estimate the volume changes based on the 3D-DIC results. Finally, comparing the results between the image measurement system and the conventional measurement method, the proposed method not only can obtain the specimen's distribution of 3D full-field deformation, volume strain and so on, but also can provide a method for rectifying the 3D data measured by the image measurement technique in tri-axial testing. The results from 3D reconstruction can describe directly the characteristics of anisotropy and non-uniformity in geotechnical materials. The results can provide more information than conventional testing when establishing a constitutive model in soil mechanics.