Early since 1950, a systematic study was made on the anomalous internal friction peaks appeared in cold-worked Al-Cu and Al-Mg specimens around room temperature. The activation energy associated with these internal friction peaks was found to be close to that associated with the pipe diffusion along dislocations. Consequently the internal friction peaks were attributed to the diffusion of Cu or Mg atoms in the dislocation core in aluminium. A physical model of these internal friction peaks was suggested in terms of the dislocation kink concept. The manifestation of these anomalous internal friction peaks was found to be similar to that predicted through a detailed mathematical analysis of the dislocation core diffusion by Winkler-Gneiwek et al. according to the string model. In this paper, a critical comparison has been made between the string model and the kink model concerning this problem and it is shown that the predictions derived from the string model can be adequately applied to the case of the kink model. This confirms further that the nonlinear anelastic internal friction peaks we observed are originated from dislocation core diffusion.