Abstract
In protoplanetary disks, dust grains grow through mutual collisions, gradually settle to the midplane of a disk and forms a dense dust layer at the midplane. This process is very important in the formation of planetary system. Collisions between dust grains results in not only their coalescence but also fragmentation. If collisional fragmentation occur major part of collisions, it significantly changes the size distribution of dust grains be affected by fragmentation of dust grains. The outcomes of collisions are governed by collisional velocities. The criterion of collisional fragmentation is whether the kinetic energy per unit mass at a collision than the tensile strength of grains or not. Another way of saying, the criterion is that collisional velocity is higher than a critical velocity. In this study, we examine collisional velocity in the process of dust growth to clarify whether collisional fragmentation of dust grains occurs in protoplanetary disks and where collisional fragmentation occurs as the first step of the development of the dust evolution model taking into account fragmentation.
