The Relationship between Stress and Strain in the Tensile Impact Test

Apparatus has been devised for the measurement of the relationship between stress and strain on metallic specimens broken in tensile impact. The stress was measured piezo-electrically and the strain photo-electrically.

Five ferrous materials have been examined at rates of extensional strain ranging up to 800 inches per inch per second, with the following results.

With wrought iron there was an increase in tensile strength and considerable increase in yield point as the rate of strain was raised. With medium-carbon steel there was some increase in the yield point. With low-carbon manganese steel, nickel-chromium steel and “Vibrac” steel there was little difference between the impact and static stress-strain diagrams. The energy absorbed in fracture of the specimens in the impact tests was only slightly greater than that absorbed in the static tests.