Hybrid grid-moire method for measuring strain and displacement

M. Szanto; James W. Dally; David T. Read

doi:10.1117/12.130250

1 May 1993 Hybrid grid-moiré method for measuring strain and displacement

M. Szanto, James W. Dally, David T. Read

Author Affiliations +

Optical Engineering, Vol. 32, Issue 5, (May 1993). https://doi.org/10.1117/12.130250

Abstract

A hybrid grid-moiré method for measuring strain is presented. The method employs a line grating attached to a plane surface of the specimen. Images of undeformed and deformed gratings are acquired and stored using a video system and a frame digitizer. The magnification is adjusted to record 10 to 30 lines of a grating with a pitch of 4 μm over the frame width. A fast Fourier transform (FFT) of the intensity data gives a close estimate of the spatial line frequency. A moiré function is formed as the product of a reference sine function and the image intensity-position function. FFTs of the moiré function yield an improved estimate of the line frequency. The line frequency is related to an average strain over the recorded image. The method was demonstrated at a magnification of 1500 x with a grating pitch p_s = 4 μm. The accuracy achieved depended on strain. For strains in excess of 0.1%, the errors were usually less than 5% when compared to strain gauge results. For plastic strains, in excess of 1%, the differences between two comparable measurements were less than 3%.

Citation Download Citation

M. Szanto, James W. Dally, and David T. Read "Hybrid grid-moiré method for measuring strain and displacement," Optical Engineering 32(5), (1 May 1993). https://doi.org/10.1117/12.130250

Published: 1 May 1993

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available