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Because the lateral expansion that occurs on the compression side of the Charpy V-notch specimen, directly opposite the notch, appears to be a direct measure of notch ductility and appears to be independent of strength variation and of chemical composition, its use as a notch-ductility criterion is increasing. During the years that U. S. Steel Corporation has been measuring lateral expansion, a gage was developed for measuring this value rapidly. This paper describes the gage and the method for using it and presents the results of a test program conducted on standard specimens of A36 and ASTM 514 Type F steels to determine the accuracy and reproducibility of lateral-expansion measurements made with this gage. Measurements were made at several U. S. Steel Corporation plants that produce or use plates to ensure that plant personnel are able to obtain the same values as those obtained at a research laboratory, within an allowable tolerance.
The results of the test program may be summarized as follows: (1) The accuracy of the measurements was the same as the accuracy of the dial indicator that was integral with the gage; for the standard 1-mil gage, this accuracy is ±2 mils (1 mil = 0.001 in.). (2) The reproducibility of measurements made with the standard gage was about the same as the accuracy, that is, ±2 mils. (3) Prior experience in using the gage is not necessary to obtain this degree of reproducibility. (4) Plant personnel can obtain values that are in agreement with those obtained at a research laboratory. (5) Measurements made with micrometers were accurate and were generally reproducible to the same degree as the gage; however, considerably greater care is required in making micrometer measurements, and, for this reason, the use of the dial gage is recommended over the use of micrometers.
Improved precision can be obtained by replacing the standard 1-mil dial indicator with a 1/10-mil (0.0001 in.) dial indicator at modest additional cost.
mechanical tests, Charpy impact tests, measurement, mechanical properties
Senior research engineer, U. S. Steel Corp., Monroeville, Pa.