Experimental Mechanics

, Volume 33, Issue 2, pp 110–116

Scanning moiré at high magnification using optical methods

Authors

  • D. T. Read
    • Materials Reliability DivisionNational Institute of Standards and Technology
  • J. W. Dally
    • Mechanical Engineering DepartmentUniversity of Maryland
  • M. Szanto
    • Ben Gurion University
Article

DOI: 10.1007/BF02322486

Cite this article as:
Read, D.T., Dally, J.W. & Szanto, M. Experimental Mechanics (1993) 33: 110. doi:10.1007/BF02322486

Abstract

Methods of employing scanning moiré at high magnification are developed and demonstrated. Modern lithographic techniques for producing custom moiré gratings with a frequency up to 250l/mm are described. On a probing station equipped with a video system, pseudo-color moiré fringes are produced using the scannning lines of the color charge-coupled-device (CCD) camera. Fringe multiplication from 1 to 5 is possible with correct combinations of magnification and grating pitch. An analysis is given to show that strain sensitivity depends only on the number of scanning lines used to record the image. The grating pitch and the magnification are important because they reduce the gage length of the strain measurement. The high-magnification scanning moiré was used to study plastic- strain fields in an aluminum tensile specimen. Local disturbances in the strain field were observed at 2 to 2.5 percent applied strain. These discontinuities became more significant at higher levels of applied strain.

Copyright information

© Society for Experimental Mechanics, Inc. 1993