Title: Changes of the Internai Friction in Copper After

Abstract approved Investigations of the effect f cold working on the internai friction of copper have become numerous in the last few years due to the discovers that part of the internai friction is due to the motion of dislocations in the metal. Most of the investigations so far have been done at frequencies of about lO kiiocycles per second. At these frequencies the internal friction ias been found to be airnlitude uependent and a function of the amount of cold work performed on the metal. This experiment was performed at a frequency of 5L cycles per second by vibrating the reed transversely in a vacuated symmetrical transducer at room temperature. The reed was annealed by placing it in a vacuum and passing electric current through it so that it was heate