The Study On Dynamic Characteristics Of The Cracked Roller

Roll contains the barrel, the roll neck and the rollerr head.It is an important component in steel rolling mill and also one of the main consumption parts in the production. Roll quality directly determines the quality of the product and service life .Crack Roll for damage detection has long been highly concerned, physical detection methods such as ultrasonic testing, magnetic particle testing, eddy current testing and penetration testing. Due to know the damage location in advance, to require the site of injury easily, Therefore, it is necessary to find reasonable and effective detection methods to ensure the safe operation of roll and to prevent the occurrence of roll fracture.The emergence of the crack makes stiffness component decreased, affects the vibration characteristics and vibration response of structures. Therefore it can detect the vibration of crack by changing vibration of components. The method for identification damage cracks by structures vibration has been successfully applied to cracked rotor, marine platforms and aircraft damage detection in recent years. However, the roller vibration method of crack detection work has not been carried out and still to be studied.The roll finite element models with cracks and no cracks are established, the natural frequency and mode are obtained by modal analysis method. The amount of damage such as the rate of natural frequency change, the displacement rate of modal change, the rate of strain mode change and the first component of modal difference between the axial displacement change rate of identity, are studied on the roll damage location and damage extent. In the four selected amount of damage identification, the natural frequency change rate is widely used in damage detection, and the latter three are put forward for the structure of roll in this paper. The results showed that: when the surface cracks, the natural frequency will reduce, the first order natural frequency change is the largest, and increase with the crack depth, but it is not sensitive to crack location. The change of displacement modal rate, the change of strain mode rate and the curve of axial displacement rate in the first modal are at peak in the crack, and with the depth of the crack, the peaks are more obvious. Viewed from the change, the change amount of the natural frequencies and the component of displacement modes are small, and the component of strain mode rate and the change of axial displacement in the first mode are large. The latter two identified amounts are more sensitive. When the internal cracks are present, the natural frequency of roll is reduced, the first natural frequency is changed the largest, and increase with the crack depth. The curves of displacement modal component change rate for crack location and depth regularity are not obvious. The component of strain mode rate and the curve of axial displacement rate in the first modal are at peak in the in the crack position, and with the depth increase, the peak is more obvious. The above dates showed that the component of strain mode rate and the axial displacement rate in the first modal can be identified as the amount of the damage in the crack. The conclusions of this study can be the basis for further study dynamic crack damage monitoring of the roll.