AMPLITUDE-DEPENDENT INTERNAL-FRICTION IN LEAD AT AMBIENT-TEMPERATURE

Amplitude-dependent internal friction of polycrystalline commercial le ad has been studied in wide frequency and strain amplitude ranges. The strain amplitude dependence shows two stages characterized by differe nt recovery times. These stages are attributed to different mechanisms : dislocation-point obstacle interaction at moderate amplitudes and in teraction between dislocations along with their multiplication at the high ones. Pronounced and nonmonotonous dependence of the amplitude-de pendent internal friction and elastic limit on prestrain is revealed. This peculiarity is attributed to transition from relatively homogeneo us dislocation distribution to the inhomogeneous one due to formation of the cellular structure.