Open Access

ARTICLE

Strain Measurement in a Microstructure Using Digital Image Correlation for a Laser-Scanning Microscopic Image

by N. Shishido, T. Ikeda, N. Miyazaki

Computer Modeling in Engineering & Sciences 2008, 35(1), 1-20. https://doi.org/10.3970/cmes.2008.035.001

Abstract

We propose an image correction method that will accurately measure full-field displacement in a microstructure using the digital image correlation method (DICM); the proposed method is suitable for use with laser-scanned images. Laser scanning microscopes have higher spatial resolution and deeper depth of field than optical microscopes, but errors in laser scanning position (time-dependent distortion) affect the accuracy of the DICM. The proposed image correction method involves the removal of both time-dependant and time-independent distortions. Experimental results using images of prescribed rigid-body motions demonstrate that the proposed correction method is capable of identifying and removing both types of distortion. Specifically, the DICM employing the proposed image correction technique can eliminate both types of distortion in a laser-scanned image and measure full-field displacement within 0.04 pixel of the standard deviation. In addition, we used the proposed method to measure the thermal strain in both a copper specimen and a printed circuit board (PCB) during a thermal cycle test. For copper, the relative error between the measured strain and the reference strain is less than 0.0003 without the slant and bias of the strain field, which proves sufficient applicability of the developed system to measuring the distribution of strain caused by temperature change. The distribution of strain in the measured section of a PCB specimen was very complicated, but the average strain in the longitudinal direction showed good linearity. The variation in the average strain corresponds with that expected from beam theory for the macroscopic warpage of the PCB. This proves indirectly the accuracy of strain measurement using a laser microscope with the proposed method.

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Keywords

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