Structural transition of force chains observed by mechanical   spectroscopy
  The dissipation properties of a fine sand system are investigated by a low-frequency mechanical spectroscopy. The experiments show many interesting profiles of the relative energy dissipation, which imply that some structural transition of force chains in dense granular media has occurred. The following data and discussion indicate that the transition of force chains will lead to the small deformation of arrangement in the granular system, which is responsible for the historical effects. We hope this research can improve our knowledge of the microstructure of the granular materials. 
Wan-Jing Wang, Kai-Wei Yang, Xue-Bang Wu, Yu-Bing Wang, and Zhen-Gang   Zhu