Abstract
It is important for structure and machine maintenance to detect the damage location and to evaluate the level of damage at that point. To understand the relation between damping ratio and cut depth of structure component which was made by steel, dynamic behavior of structure component was investigated by vibration test. Damping ratio of slight damage case is bigger than that of no damage case. But the relation of this does not indicate linear relation. So it may be possible to detect damage but is difficult to evaluate the level of damage.
