Internal Friction in Carbon Steels under High Loading Frequencies : 3rd Report, Characteristics of Tensiled Specimens

Abstract

Internal friction in carbon steels at around 17 kHz is studied by means of a sensitive electromagnetic amplitude sensor attached to an ultrasonic fatigue testing machine under a strain amplitude within 10^-3. In this report, characteristics of tensiled specimens and their changes with the lapse of time after working are focused on. The following conclusions are presented. (1) The measurement of internal friction is extremely useful when estimating the progress of the recovery process after plastic working. (2) The internal friction increases with the tensile working of 1∼6% strain, and decreases with the lapse of time after working. (3) The above tendency is much influenced by the temperature at which the specimens are kept. (4) The change of the internal friction of specimens which are quenched at low temperature before working becomes remarkable as the quenching temperature rises. (5) These phenomena can be explained by the interaction between moving dislocations and point defects as interstitial atoms such as carbon.