Research Of Fatigue Crack Growth Behavior Of Cable For The Suspension Bridge

With the adverse effect of environmental degradation, corrosion, aging and other factors, and with the long-term action of the static load and dynamic load, will the cable system be deteriorated and even fracture in the service process. According to fracture mechanics theory, almost every component has many small cracks hard to be found. Under the work of fatigue load or Stress corrosion, the cracks will gradually extend to the critical value, and then the component fractures. As more bridges with cable system has been built, the cable fatigue is more obvious increasely.The main problems in the fatigue analysis theories is that the researcher always divide the fatigue process into two physical processes: fatigue crack formation and fatigue crack growth, and using different theories and methods for analysis and calculation, respectively. In recent years, many researchers are trying to use the appropriate mechanical model to analysis how the small crack grows. The newly progress of mesoscopic fracture mechanics to establish multiscale micro-/macro-crack model that try to describe the fatigue damage process with mesoscopic stress intensity and local energy density. It is the core content of this paper how to analyze the fatigue crack growth behavior of cable and steel wires for Hangzhou Jiangdong Bridge, based on Multiscale micro-/macro-crack model.After summarized up all kinds of research methods in fracture mechanics theory, the paper will describe the fracture mechanism of high-strength steel wires and try to calculate theoretically the fracture strength of the wire with a crack with different shape and the size on the background of Hangzhou Jiangdong Bridge. According to cable force in the known, taking into account of the pre-tension, relaxation and other effects, the paper try to analyze the stress level and stress amplitude of the cable, establish Multiscale micro-/macro-crack model wirh design information, and then discuss fatigue crack growth behavior of cables and steel wires. The main research work in the article are as follows:1. Having carefully studied all kinds of literatures, based on a variety of metallic materials of the fatigue crack growth results are analyzed and summed up, the paper described the general rules, the factors, and the micro-mechanism of metal fatigue crack growth of t factors. 2. After summarized up all kinds of research methods in fracture mechanics theory, the paper will describe the fracture mechanism of high-strength steel wires and try to calculate theoretically the fracture strength of the wire with a crack with different shape and the size with two methods on the background of Hangzhou Jiangdong Bridge.3. Establish overall finite element model of the bridge with the finite element program ANSYS, and get a detailed calculations of the cable forces.4. Establish Multiscale micro-/macro-crack model with the local energy density factor as the control parameters, and analyze the fatigue crack growth behavior of cables and steel wires forHangzhou Jiangdong Bridge.5. Discussed the different patterns of micro-defects, pre-tension and relaxation effects, etc.on the fatigue life of the cable steel wires.6. Based on the results of theoretical calculations and engineering practice, gave some advices on the fatigue life design, Operation and maintenance of the cable.