DISMAP Technology Upgrade, 18-9105

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 Principal Investigators
Daniel P. Nicolella
Michael P. Rigney
J. Steve Bird
Jian Ling

Inclusive Dates: 12/28/98 - 09/21/00

Background - DISMAP (Displacement Mapping) is a unique material displacement measurement system developed at SwRI in the mid 1980's through two internal research and development projects. The DISMAP system has been successfully used in a number of materials and mechanics research projects totaling more than $7 million in basic science research funding. Although highly successful, the first-generation DISMAP is based on technology that is over ten years old and does not perform at speeds comparable to today's technology. Furthermore, the image-acquisition subsystem is limited in resolution, thus limiting the measurement resolution of the system. Finally, the image-processing computer is a closed proprietary system that is not amenable to expansion or modifications.

Approach - The goals of this project were to: 1) develop an open, modular, and expandable software analysis and control system; 2) combine all capabilities of the current system (up to three computers) into one self-contained system; 3) provide for multiple modes of image capture including high-resolution digital camera input, importing stored digital images, and scanning photographs at high resolution. A personal computer (PC)-based computational platform and the LabView graphical programming development environment were used for the new DISMAP-II system.

 Accomplishments - All these objectives were met with the DISMAP-II system. This system is centered on a powerful, easily upgraded PC platform that encompasses all the major functionality of the original DISMAP, which required three separate computer systems. The software environment, LabView, allows for easy system modification and capabilities upgrade through its modular programming environment. The use of the digital camera, digital flatbed scanner, and the digital image import capabilities allows for analysis flexibility and increased displacement measurement resolution and resulting strain computation compared to the original system. The DISMAP-II configuration allows for direct upgrade paths in computational hardware, digital imaging, and analysis capabilities.

System accuracy and resolution were determined using undeformed image sets subjected to controlled displacement levels. Displacement measurement accuracy is at the subpixel level and varies from 0.012  to 0.049 pixel using a high-contrast image and from 0.18 to 0.48 pixel using a mixed contrast image. Measurement accuracy is a function of image quality and correlation parameter settings. Maximum strain resolution using the high-contrast image varied from 49 to 133 me and was dependent on the correlation parameters and the maximum applied displacement. Errors in the correlation resulted in significant errors in the strain computation for the mixed-contrast image.

Materials Research and Structural Mechanics Program
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