A Real-time Evaluation Method For Fatigue Cracks Of Bridge Cranes

Bridge crane is one of the most used lifting equipment in the production process. It’s security is crucial to the daily production and workers safety of enterprise. While the fatigue damage of metal structure is a major threat to the security of the crane, thus assessing the fatigue life of metal structure is the key to keeping the crane running safely.Fatigue damage analysis and fatigue life assessment is mainly base on the load spectrum. Currently extensively used method to getting the load spectrum is posted the strain gauge on the specified position.although this method is simple and straightforward, but can only obtain stress data of several specified point on the whole structure.This paper will describes a method which can obtain the long-term loading history data continuously. Using the software which is based on the formula derived from the structure mechanics to translating the operating data recording by the lifting appliances-Managing system of safety monitoring into stress data, can solve the problem that lack of load history data.The main contents of this paper is divided into the following sections:(1) Described the state of the art of internal force analysis methods of crane structure, fatigue life assessment and load spectrum statistical methods. Analyzed the advantages and disadvantages of each method.(2) In order to work out the stress data according to the operating data which is recorded by the lifting appliances-Managing system of safety monitoring, established an accurate mathematical model of bridge crane based on structure mechanics. Then compared the results with the finite element model to verify the accuracy of the mathematical model.(3) Writed a program according to the mathematical model that can transform the operating data into the stress-time data of the crane’s metal structure fast, and use this program to get some stress data of specified point on the structure.(4) With analyzed the operating characteristics of overhead crane, built a method to simulate the operating data. To test the performance of the program, processing different amount of operating data. The result shows that programe can meet the requirements.(5) Expounded the detail of rainflow counting method and its different forms. Discussed the advantages and disadvantages of fatigue crack assessment method which is based on the fracture mechanics. According to the operating characteristics of overhead crane, established the fatigue crack realtime assessment method of overhead crane.The operating data fast processing program described by this paper, can obtain the stress-time history data of the crane according to the operating data recoded by the lifting appliances-Managing system of safety monitoring. it provides a important idea. The establishment of the fatigue crack length real-time evaluation method provides some reference for the establishment of the crane health real-time detection system.