"Photoelastic stress analysis is one of the most effective methods available to the engineer for solving problems of stress distribution. The effect of forces, such as pressure and tension may be studied using a scale model of a structural part. Special transparent models are subjected to forces proportional to those acting on the real object. The stress problem produced in the model indicates the stress distribution through a cross-section of the structural part.
Analysis of the photographic record of the stress analysis pattern provides data with a high degree of accuracy within a relatively short time. In simple cases, this data can be used either alone or as a check of mathematical solutions. They also yield reliable information on problems which are insolvable mathematically or at least involve complicated and tedious calculations. Examples include the stresses around notches and holes in bars, in riveted joints, spoked wheels, gear teeth and frame works with welded joints or in redundant members.
Other methods of stress analysis used in the design and testing of structural forms described briefly as follows:
BRITTLE COATING: The structure is covered with a special coating designed to crack wherever strain exceeds a fixed amount. This method indicates regions of dangerous stress and provides an over all picture of surface stresses. This method is mainly used to indicate the directions of the principal stresses so that electric strain gages may be accurately oriented.
ELECTRIC STRAIN GAGES: These are the most versatile devices for use by the stress analyst. They are readily adaptable to all kinds of structures and materials. With the electronic equipment available today the variable resistance wire strain gage is without a doubt the most favorable means of measuring dynamic and transient surface strains. However, the wire is very susceptible to temperature changes whereby a thermocouple effect may be established.
Photoelastic stress analysis, however, has certain advantages: (1) A more complete view of the stress pattern is obtained, instead of surface stresses at a limited number of points. (2) Stresses in relatively inaccessible places can be studied such as points of stress concentrations. (3) Tests can be quickly made and inexpensively before its structural counterpart is made"--Introduction, page 1.
Miles, Aaron J.
Mechanical and Aerospace Engineering
M.S. in Mechanical Engineering
Missouri School of Mines and Metallurgy
v, 29 pages
© 1952 Lloyd E. Byrd, Jr., All rights reserved.
Thesis - Open Access
Library of Congress Subject Headings
Materials -- Testing
Strains and stresses
Print OCLC #
Electronic OCLC #
Link to Catalog Recordhttp://laurel.lso.missouri.edu/record=b2614215~S5
Byrd, Lloyd E. Jr., "Photoelastic investigation of notched corners in square apertures in flat plates subjected to tension" (1952). Masters Theses. 2045.