Illinois Tool Works Inc.

Michael Ashman

Christian J Hoehl

Adrian Charles Riddick

Nicholas Francisco Salerno

Martin Allen Peterson

Richard Balcarek

Christian Hoehl

Disclosed example video extensometers include: a load string configured to secure a test specimen; an imaging device configured to capture images of a surface of the test specimen when secured in the load string; a storage device configured to store a plurality of first calibration parameters corresponding to intrinsic properties of the imaging device; and control circuitry configured to: perform a verification process using the first calibration parameters to verify that a plurality of second calibration parameters correspond to an arrangement of the test specimen with respect to the imaging device; and perform an optical strain measurement process to measure displacement of the test specimen based on the first calibration parameters and the second calibration parameters.

Systems and methods to calibrate optical extensometers

The present disclosure describes systems and methods to correct for edge-position error associated with brightness levels of an associated back screen in a video extensometer system. In some examples, to correct for edge-position error, a processing system is configured to execute an edge detection algorithm to measure and/or calculate a difference between a perceived edge-position and a reference edge-position associated with an amount of error, and calculate a correction term to address the error. The correction term can be added to the result of the edge detection algorithm in case of white-to black transition, and subtracted in case of black-to-white transition to correct for the error.

Systems for width measurement corrections of test specimens based on background brightness data of captured images

The present disclosure describes systems and methods to correct for perspective calibration variations of a variable thickness specimen with a single camera extensometer in a video extensometer system. In some examples, the systems and methods compensate for a change between a reference characteristic, such as a calibration plane, and an actual physical characteristic, such as a testing plane associated with a surface of a test specimen, during a testing operation. In some examples, a correction value is applied to an output (e.g., measured dimensions of the imaged test specimen) to compensate for the difference between the reference characteristic and the physical characteristic.

Thickness correction for video extensometer systems and methods

Brightness and contrast correction for video extensometer systems and methods

The present disclosure describes systems and methods for conducting deformation (e.g., extension and/or strain) measurements based on characteristics of a test specimen using light sourced from a single side of a test specimen. The light source and an imaging device are arranged on a single side of the test specimen relative to a back screen while the light source illuminates both a front surface of the test specimen and the back screen. The back screen reflects light to create a silhouette of the test specimen. The imaging device captures images of one or more markers on a front surface of the test specimen, as well as measuring position of the markers during the testing process. The imaging device also measures relative changes in position of the edges of the test specimen during the testing process, by analyzing the edges of the silhouetted image created by the reflective back screen.

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Natick, MA, United States of America

Michael Ashman