Fabrication of a DIC sensor for in-plane deformation measurement

Abstract

A thin epoxy film with a micro speckle pattern was developed as a deformation sensor, and replicated on the surface of a sample. In order to improve the toughness of the thin epoxy film, a flexibilizer was added into the epoxy compound and the mechanical property of the thin epoxy film was analyzed. The measurement results show that the toughness of the thin film has been improved greatly, which enlarges the range of application of deformation measurement. Finally, the feasibility of application of the thin film digital image correlation (DIC) sensor was verified using a standard tensile experiment. And the interface deformation of the signal lap joint was measured by using fabrication and replication of the micro speckle pattern and micro digital image correlation. The failure mode of a single lap joint at micro-scale lengths was determined by analyzing the captured images of the micro speckle pattern.

Fabrication and optimization of micro-scale speckle patterns for digital image correlation

“…For (3) Easy transfer and good adhesion: The pattern film can be transferred to samples with a hole, crack or notch. The maximum elongation of the patterned film is about 3% and the adhesion is good enough to ensure that the pattern sticks well to the sample [21].…”

“…Microscale speckle patterns fabricated by spinning a compound of epoxy resin and powder particles were proposed and successfully applied to micro-scale deformation measurements [20]. Furthermore, a micro-scale speckle pattern was fabricated on a thin epoxy film that could be transferred to the surface of a specimen for use as a deformation sensor [21]. Although the fabrication method had good performance and had applications, the experimental configuration was far from optimal.…”

“…Wang et al have described the details of the fabrication and replication processes for micro-scale speckle patterns, as shown in figure 1 [20,21]. For deformation measurements with DIC in a field of view of approximately 1~2 mm, the optimal size for the powder particles is approximately 3 μm.…”

Digital Image Correlation Analysis of Displacement Based on Corrected Three Surface Fitting Algorithm

“…Based on the actual data, the SFA obtains the analytical expression between the function f(x, y) and the variables x and y, and it can pass or approximate all data points, which can be distributed in the function f(x, y) on the spatial surface represented. Taking the two polynomials as an example, the fitting function is [24]…”

“…en according to equation (2) [24], the position of the extreme point of the fitting surface is obtained [24]:…”