STP1318: BISMAP: A Non-Contact Biaxial Displacement Measurement System

    McKeighan, PC
    Sr. Research Engineer, Sr. Research Engineer, Institute Scientist and Institute Scientist, Southwest Research Institute, San Antonio, TX

    Seida, SB
    Sr. Research Engineer, Sr. Research Engineer, Institute Scientist and Institute Scientist, Southwest Research Institute, San Antonio, TX

    Franke, EA
    Sr. Research Engineer, Sr. Research Engineer, Institute Scientist and Institute Scientist, Southwest Research Institute, San Antonio, TX

    Davidson, DL
    Sr. Research Engineer, Sr. Research Engineer, Institute Scientist and Institute Scientist, Southwest Research Institute, San Antonio, TX

    Pages: 22    Published: Jan 1997


    Abstract

    The development and validation of a prototype BISMAP (Biaxial Displacement Measurement by Machine Vision Processing) system is described. The non-contact biaxial displacement measurement system adapts machine vision technology to create a unique extensometer. The BISMAP system is built around a vision processing system that tracks and recognizes surface texture features around specific control points by using a normalized correlation technique. The system has numerous advantageous features including non-contact measurement in two-dimensions, variable gage length, direct surface measurement (no attached target) and real-time measurement of multiple, discrete points. The performance of the system is demonstrated with evaluations of the monotonic (and in some cases cyclic) stress-strain response for four different materials: aluminum, LEXAN, rubber and baboon tendon. The system has a measured accuracy of 370 μϵ with ±50 μϵ variability when compared to a strain gage. It is best-suited for measuring strains in excess of 5000 μϵ and there is no practical upper limit on the measurable strain with retraining. The BISMAP system shows promise for development from prototype into a laboratory instrument capable of measuring strains in pliable or delicate materials.

    Keywords:

    extensometer, biaxial, non-contact, stress, strain, displacement, vision system, normalized correlation, aluminum, LEXAN, tendon, rubber


    Paper ID: STP11895S

    Committee/Subcommittee: E08.04

    DOI: 10.1520/STP11895S


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