Damage Identification Of Crane Metal Structure Based On Modal Curvature Difference And Wavelet Transform

Crane is a modern lifting and transportation equipment,which can not only improve work efficiency,but also greatly reduce the labor intensity of workers,so it is widely used in the industrial transportation industry.At the same time,the safety of cranes has also attracted more and more attention.With the increase of service life,the metal structure of the crane,which belongs to the welded structure,is inevitably damaged by cracks and corrosion due to the impact of alternating loads and harsh environments.But these early structural minor damages cannot be discovered in time,which is the main cause of the crane's special and major accidents,often causing huge property losses and bad social impact.At present,there are many cases of structural damage identification in academia,but there is very little research on the metal structure damage identification of gantry cranes.In view of this,this paper focuses on the damage identification of gantry crane metal structures.At present,there are two main types of damage identification methods: one is local damage identification,and the other is global damage identification.The local damage recognition mainly includes intuitive judgment method,ultrasonic method,electromagnetic field application,etc.The premise of applying these methods is to know the approximate location of the damage,and then use high-tech instruments to scan the damage location to finally identify the damage location,but this process It takes a lot of manpower and financial resources.It is a global damage identification method to judge the health of the structure through the change of structural vibration characteristics,which can quantify the change in performance.Based on the global damage identification method,this paper takes the41-ton double-girder gantry crane metal structure as the research object,and conducts structural damage identification research.First,the ANSYS APDL language was used to establish the finite element model of the gantry crane metal structure,and its structural model was verified from three aspects ofstrength,static stiffness and dynamic stiffness,and the accuracy of the model was verified;Second,based on the established finite element model,damages were simulated by modifying the elastic modulus values of the local elements of the main beam.A total of 13 damage conditions were simulated at one location,two locations and three locations.And we conducted a modal analysis of the finite element model of the crane metal structure;Third,we studied whether we can determine the damage of the structure through the overall frequency of the structure.Fourth,the effect of the first four orders of mode shapes on the location of damage is studied,and it is found that the location of damage cannot be identified from the complete mode shape map,but the partially enlarged view of mode shapes can determine the location of the abnormal protrusions in the figure.The db3 wavelet is used to detect the singularity of the vibration mode data,and finally the location of the damage is accurately identified;In order to further improve the damage identification ability of the modal mode shape damage index,finally,two damage indexes of modal curvature and modal curvature difference were calculated by the central difference method,and the research found that these two indexes identify damage ability has been significantly improved.After comparison,it is finally concluded that the modal curvature difference can accurately identify the damage at multiple locations and different damage levels,and this index is the optimal damage index.At the same time,it is verified that under the single damage condition,the quadratic curve of modal curvature difference and damage degree can better identify the damage degree of the structure.Finally,it provides a new idea for the identification of crane metal structure damage.