Micro/Nano-scale Strain Distribution Measurement from Sampling Moiré Fringes

Abstract

This work describes the measurement procedure and principles of a sampling moiré technique for full-field micro/nano-scale deformation measurements. The developed technique can be performed in two ways: using the reconstructed multiplication moiré method or the spatial phase-shifting sampling moiré method. When the specimen grid pitch is around 2 pixels, 2-pixel sampling moiré fringes are generated to reconstruct a multiplication moiré pattern for a deformation measurement. Both the displacement and strain sensitivities are twice as high as in the traditional scanning moiré method in the same wide field of view. When the specimen grid pitch is around or greater than 3 pixels, multi-pixel sampling moiré fringes are generated, and a spatial phase-shifting technique is combined for a full-field deformation measurement. The strain measurement accuracy is significantly improved, and automatic batch measurement is easily achievable. Both methods can measure the two-dimensional (2D) strain distributions from a single-shot grid image without rotating the specimen or scanning lines, as in traditional moiré techniques. As examples, the 2D displacement and strain distributions, including the shear strains of two carbon fiber-reinforced plastic specimens, were measured in three-point bending tests. The proposed technique is expected to play an important role in the non-destructive quantitative evaluations of mechanical properties, crack occurrences, and residual stresses of a variety of materials.

Interlaminar Shear Behavior of Laminated Carbon Fiber Reinforced Plastic from Microscale Strain Distributions Measured by Sampling Moiré Technique

“…However, with the development of grid fabrication techniques, it becomes easy to fabricate a grid on CFRP. The Moiré methods [ 12 , 13 ] have been widely used in the deformation measurement of composite materials [ 14 ], including CFRP [ 15 , 16 , 17 , 18 ]. Due to the advantages of deformation visualization, high noise resistance and large field of view, the Moiré methods are at the center of attention, and expected to be used to visualize the shear strain concentration of CFRP.…”

“…The reconstructed multiplication Moiré method from 2-pixel sampling Moiré allows high-sensitivity deformation measurement in a large field of view [ 29 ]. The combination between the sampling Moiré method and the phase differential way capacitates accurate normal strain measurement and has been used for deformation measurement of CFRP [ 16 ]. The two-dimensional (2D) Moiré phase analysis method enables both high-accuracy shear strain and normal strain measurement and has been applied for crack occurrence prediction [ 30 ].…”

Interlaminar Shear Behavior of Laminated Carbon Fiber Reinforced Plastic from Microscale Strain Distributions Measured by Sampling Moire Technique

“…The reconstructed multiplication Moiré method from 2-pixel sampling Moiré allows high-sensitivity deformation measurement in a large field of view [14]. The combination between the sampling Moiré method and the phase differential way capacitates accurate normal strain measurement and has been used for deformation measurement of CFRP [15]. The twodimensional (2D) Moiré phase analysis method enables both high-accuracy shear strain and normal strain measurement and has been applied for crack occurrence prediction [16].…”