The Research On Assessment Of Ultimate Strength Of Ship Plates With Corrosion Wastage Based On Fractal Theory

Corrosion can lead to the loss of material and the destruction of structure.As for old ships,the ultimate bearing capacity of the structure can be greatly reduced due to damage of corrosion,resulting in heavy casualties and direct economic losses.With the expanding application of high strength steel in ship area,the size of structure section is decreased making the problem of structure buckling more prominent.Also,the presence of corrosion damage will largely increase the possibility of buckling failure.Therefore,it is of great significance to evaluate the ultimate bearing capacity of the non-uniform corrosion plate to ensure the safety of the structure.In this study,the study of failure behavior of non-corrosive plate in buckling defect and thin-horse defect mode are investigated and compared at first.Then,the random corrosion surface is constructed with fractal theory to explore of the fractal characteristics of corrosion surface.Also,the non-uniform model is established based on the corrosive surface.The study of damage behavior of corrosion plate is conducted by finite element method to analyze the ultimate strength distribution of the corrosion surface with the same corrosion parameters.Finally,the ultimate strength reduction coefficient evaluation method is established for non-uniform corrosion hull plate by fitting method.Through the research mentioned above,it is concluded that the failure modes of noncorrosive plate with buckling defects are half-wave failure mode along both sides of the plate,and the unloading failure mode in other area.In comparison,the non-corrosion plate with thin-horse defects has only half wave failure zone.The failure mode of corrosion damage plate is similar to non-corrosive thin-horse defects and the failure area is the half wave region with most serious corrosion status.Based on the mid-displacement method,a corrosion surface with single fractal characteristic is constructed and a random corrosion model is established with fractal theory.The finite element calculation results show that the ultimate strength values of corrosion plate with same surface corrosion parameters are in normal distribution.Finally,the ultimate strength reduction coefficient evaluation method for non-uniform corrosion hull plate is established based on superior ?-position point,which can provide basis for the evaluation in practical project.