Measurement of Structural Stresses by Hole-Drilling and DIC
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Evaluation of stresses in structures such as bridges, buildings, pipelines and railways is challenging because the loads cannot easily be manipulated to allow direct measurements. This paper focuses on the development of a method that combines the hole-drilling technique with Digital Image Correlation (DIC) to evaluate these difficult-to-measure structural stresses. The hole-drilling technique works by relating local displacements caused by the removal of a small amount of stressed material to the original stresses within the drilled hole. Adaptation of this method to measure structural stresses requires scaling up the hole size and modifying the calculation approach to measure deeper into a material. DIC provides a robust means to measure full-field displacements that can easily be scaled to different hole sizes and corrected for typical artifacts that occur in practical on-site measurements. There are two primary areas of investigation: the adaptation of the DIC/hole-drilling method to measure structural stresses and the development of a correction method to remove coexisting stresses such as residual and machining stresses from the measurement. Experimental measurements are made to demonstrate the measurement method on different structure types including the example practical problem of measuring thermally induced stresses in railroad tracks.
KeywordsStructural stresses Hole-drilling DIC Stress datum Residual stress
This work was financially supported by the Natural Science and Engineering Research Council of Canada (NSERC) and by American Stress Technologies, Inc., Pittsburgh, PA, USA. Dr. Richard Stock, LB Foster Rail Technologies Corp., Burnaby, Canada kindly provided rail specimens.
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