Augmented Use of Standard Mechanical Testing Measurements for Sheet Metal Forming: Digital Image Correlation for Localized Necking

摘要

Standard test methods are often well developed to perform specific measurements with frequent updates as measurement technologies mature. Digital image correlation (DIC) is a prime example of a widely used research tool that could replace existing measurement techniques applied in various standard tests. This broad applicability has led to new insights and misunderstandings. In this work, the DIC pattern and processing parameters are investigated to measure shape and displacements on necked samples. Uncertainties of the measured shapes and displacements are determined on unstrained, but 3D surfaces. Large correlation subsets are found to degrade the ability to interrogate even slight grooves in the generally flat surface. Even with optimized patterns and subset sizes, it is difficult to measure vertical (out of plane) displacements <10 μm, due to uncertainties.