Research On Vibro-acoustic Characteristics And Life Forecast Of The Marine Damaged Structures

The machining quality problems of Marine structures or scratches during transportation and installation can lead to the generation of crack. Marine structures in service are under complex Marine environment load, which can lead to crack’s growth and accumulation and threat to the production safety. Cracks can affect the strength and stiffness of the structure, if the detection and recognition can not be found on time, it will lead to greater damage accumulation, eventually lead to failure, which can cause significant safety accident. There would be important significance to detect structural damage on time as well as know the damage degree and the vibration features of damaged structure for estimating the structure life and preventing major accidents. In this paper, aspects of the vibration characteristic, vibration parameters’ visualization and fatigue life forecast of common structural damage are analyzed.Flat, cylindrical pipe and K type is the main component of offshore platform, each component strength will affect the security of the entire platform. Based on the research of common crack model and sound intensity technology, the approach of fracture mechanics theory, line spring model of the open type surface crack is established. Additional angle and additional displacement are put forward to describe the deformation of open-type crack under the action of load. According to the additional angle and additional displacement, the concept of additional structural intensity is put forward, and the expression of the relationship of structural intensity to the relative depth of crack is built, the expression to study the influence of cracks’ relative depth and position to the energy distribution and structural vibration is used.In order to verify the correctness of the theoretical analysis results, the finite element simulation is used, the influence of crack to the energy dissipation is studied. The visualization technology to map structure vibration displacement, equivalent stress, structural intensity vector diagram, cloud and contour map is used in this paper. The fatigue life under different damage location and degree is predicted, the result of elastic-plastic finite element by ANSYS is solved, the stress value of dangerous parts structure to estimate the fatigue life is obtained, which can provide a theoretical basis for the initial maintenance of the structure.Finally, based on the above theory, vibration characteristics of offshore platform structure under combined loading are studied. The strength of whole structure is checked. Vibration parameters of key points of the offshore platform structure under different frequencies are calculated, which can provide the theoretical basis for optimization.