Residual Stresses in Enameled Sheet‐iron Specimens*

A bstract A method of quantitatively measuring the magnitude of the stresses existing in porcelain enameled specimens is explained. The method involves measuring with a mechanical strain gauge the dimensional changes which occur when an enameled‐metal specimen is de‐enameled. The theoretical approach to the problem is reviewed, and equations are derived. The results obtained in tests on a series of ground‐coated specimens are presented and indicate that with a normal application of a commercial, 3‐frit ground coat on 20‐gauge enameling iron a compressive stress of about 35,000 1b. per sq. in. is present in the enamel.