Crack Width Measurement for Non-Planar Surfaces by Triangle Mesh Analysis in Civil Engineering Material Testing

Liebold, Frank; Maas, Hans‐Gerd; Heravi, Ali A.

doi:10.5194/isprs-archives-xlii-2-w18-107-2019

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…It is also possible to use and extend the algorithms here presented to measurements with stereo camera systems in order to analyze non-planar surfaces as shown by Liebold et al [23,24].…”

Section: Photogrammetric Techniques For Crack Detection and Crack Widmentioning

confidence: 99%

Crack Propagation Velocity Determination by High-speed Camera Image Sequence Processing

Liebold

Heravi

Mosig

et al. 2020

Preprint

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The determination of crack propagation velocities can provide valuable information for a better understanding of damage processes of concrete. The spatio-temporal analysis of crack patterns developing at a speed of several hundred meters per second is a rather challenging task. In the paper, a photogrammetric procedure for the determination of crack propagation velocities in concrete specimens using high-speed camera image sequences is presented. A cascaded image sequence processing which starts with the computation of displacement vector fields for a dense pattern of points on the specimen’s surface between consecutive time steps of the image sequence chain has been developed. These surface points are triangulated into a mesh, and as representations of cracks, discontinuities in the displacement vector fields are found by a deformation analysis applied to all triangles of the mesh. Connected components of the deformed triangles are computed using region-growing techniques. Then, the crack tips are determined using principal component analysis. The tips are tracked in the image sequence and the velocities between the time stamps of the images are derived. A major advantage of this method as compared to established techniques is in the fact of its allowing for spatio-temporally resolved, full-field measurements rather than point-wise measurements and that information on crack width can be obtained simultaneously. To validate the experimentation, the authors processed image sequences of tests on four compact-tension specimens performed on a split-Hopkinson tension bar. The images were taken by a high-speed camera at a frame rate of 160,000 images per second. By applying to these datasets the image sequence processing procedure as developed, crack propagation velocities of about 800 m/s were determined with a precision in the order of 50 m/s.

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“…It is also possible to use and extend the algorithms here presented to measurements with stereo camera systems in order to analyze non-planar surfaces as shown by Liebold et al [23,24].…”

Section: Photogrammetric Techniques For Crack Detection and Crack Widmentioning

confidence: 99%

Crack Propagation Velocity Determination by High-speed Camera Image Sequence Processing

Liebold

Heravi

Mosig

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…Scheme for the triangle split, reference state on the left, deformed on the right. Based on (Liebold et al, 2019).…”

Section: Deformation Analysismentioning

confidence: 99%

“…This approach is more suitable for brittle material and can also be used for crack propagation measurements (Liebold et al, 2020a). (Liebold et al, 2019) extended the method to non-planar object surfaces observed with stereo camera image sequences, and (Liebold et al, 2020b) showed how to compute full 3D crack opening vectors from 3D displacement fields.…”

Section: Introductionmentioning

confidence: 99%

An Approach to Subpixel Accuracy Widening Crack Width Determination in Image Sequences

Liebold¹,

Maas²

2022

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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Abstract. As an extension to existing work on crack detection and subpixel accuracy crack width determination as a tool for civil engineering material testing, the paper shows an algorithmic approach to handle widening cracks with relative rotations between related crack borders. In the first time step under zero-load, a set of points to be tracked through consecutive frames of an image sequence is defined. Then, subpixel-precise displacement fields are computed for the image data of the following time steps using an 8-parameter least-squares matching approach. The points are triangulated into a mesh, and the changes of the inner geometry of the triangles are considered with a mathematical model assuming a split of each triangle. With this model, subpixel-precise deformation vectors are derived. Crack candidates are determined by a thresholding applied to the vectors’ lengths. After an estimation of the crack normal, a decomposition of the deformation vectors is applied, allowing to compute crack widths and shear movements. As a novel contribution to the technique, a model extension is proposed for the case of a relative rotation between the crack borders in order to reduce systematic errors. The model includes two separate rigid transformations for each crack side.

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“…It is also possible to use and extend the algorithms presented here to measurements with stereo camera systems in order to analyze non-planar surfaces as shown by Liebold et al [ 23 , 24 ].…”

Section: Photogrammetric Techniques For Crack Detection and Crack mentioning

confidence: 99%

Crack Propagation Velocity Determination by High-speed Camera Image Sequence Processing

et al. 2020

Self Cite

View full text Add to dashboard Cite

The determination of crack propagation velocities can provide valuable information for a better understanding of damage processes of concrete. The spatio-temporal analysis of crack patterns developing at a speed of several hundred meters per second is a rather challenging task. In the paper, a photogrammetric procedure for the determination of crack propagation velocities in concrete specimens using high-speed camera image sequences is presented. A cascaded image sequence processing which starts with the computation of displacement vector fields for a dense pattern of points on the specimen’s surface between consecutive time steps of the image sequence chain has been developed. These surface points are triangulated into a mesh, and as representations of cracks, discontinuities in the displacement vector fields are found by a deformation analysis applied to all triangles of the mesh. Connected components of the deformed triangles are computed using region-growing techniques. Then, the crack tips are determined using the principal component analysis. The tips are tracked in the image sequence and the velocities between the time stamps of the images are derived. A major advantage of this method as compared to the established techniques is in the fact that it allows spatio-temporally resolved, full-field measurements rather than point-wise measurements. Furthermore, information on the crack width can be obtained simultaneously. To validate the experimentation, the authors processed image sequences of tests on four compact-tension specimens performed on a split-Hopkinson tension bar. The images were taken by a high-speed camera at a frame rate of 160,000 images per second. By applying the developed image sequence processing procedure to these datasets, crack propagation velocities of about 800 m/s were determined with a precision in the order of 50 m/s.

show abstract

Crack Width Measurement for Non-Planar Surfaces by Triangle Mesh Analysis in Civil Engineering Material Testing

Cited by 6 publications

References 8 publications

Crack Propagation Velocity Determination by High-speed Camera Image Sequence Processing

Crack Propagation Velocity Determination by High-speed Camera Image Sequence Processing

An Approach to Subpixel Accuracy Widening Crack Width Determination in Image Sequences

Crack Propagation Velocity Determination by High-speed Camera Image Sequence Processing

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