Study of the nature of the dynamic coefficient of internal friction of grainmaterialsDmitriy Savenkov, Oleg Kirischiev, Ylia Kirischieva, Tatiana Tupolskikh, Tatiana Maltseva, Magomed Magomedov and Andrey ChistyakovE3S Web Conf., 135 (2019) 01102DOI: https://doi.org/10.1051/e3sconf/201913501102