Grid Method for Microscale Discontinuous Deformation Measurement

Abstract

The objective of this paper is to explore both grid method and Digital Image Correlation (DIC) technique for microscale and discontinuous displacement measurements, such as those associated with crack tips. First, the principle of the grid method is revisited. The grid method and DIC technique are then applied to computer generated images to calculate the displacement field around crack tips. Finally, the grid method is applied to actual experimental images of fracture tests which are conducted inside a Scanning Electron Microscope (SEM) chamber. A new technique is developed to generate microscale pattern that is suitable for both grid method and DIC technique. The displacement fields calculated from grid method are compared with those from DIC technique to identify the strengths and weaknesses of each technique for the microscale and discontinuous displacement measurements. It has been determined that grid method can obtain data closer to the discontinuity than DIC; however, DIC produces smoother displacement fields at the far field. Using this new pattern generation technique, both grid method and DIC technique can be applied to the fracture test at the microscale to complement with each other to achieve the best experiment results.

The Grid Method for In‐plane Displacement and Strain Measurement: A Review and Analysis

“…Even though the progressive dissemination of affordable digital cameras and powerful computational resources together with recent advances in image processing led finding the coordinates of the points automatically and more precisely than by hand , this technique was mainly used for measuring large displacements and strains like those occurring in composite or metal sheet forming . It is now only scarcely mentioned in recent papers such as and seems to fall progressively into disuse. The main cause is the emergence and dissemination of DIC in the experimental mechanics community .…”

“…The zone underneath the mesh bars was not coated contrary to the space inside each grid, thus generating regular arrays of spots. Pitches equal to 12.5 μ m are reported in , but other pitch values can potentially be obtained with the same technique: from 12.5 to 500 μ m in .…”

Quantitative Strain Analysis of the Large Deformation at the Scale of Microstructure: Comparison between Digital Image Correlation and Microgrid Techniques

“…Jin et al [27] investigated both the grid method and the DIC technique to measure the discontinuous displacement field around the tip of a propagating crack at relatively low magnifications. The applied deformation was in the range of linear elastic deformation and no quantitative comparison was made between the results obtained from DIC and those obtained with their grid technique.…”

Characterization of dynamic damage mechanisms in Palmetto wood as biological inspiration for impact resistant polymer composites

“…Recently, Jin et al (2011) have shown that both the grid method and DIC can be used simultaneously for microscale deformation measurements. Lord et al (2010) reviewed the experimental techniques for miniaturized testing for strength and strain measurement, and detailed the evolution and strengths of the DIC method.…”