Research On Buckling Assessment Method Of Hull Structure With Corrosion Damnification

The hull structure is a typical thin-walled composed structure and it buckles easily under combined loads. It is inevitable that corrosion damnification happens on the hull structure, and thickness loss due to corrosion of hull structural plate results in ultimate strength of the hull structural plates degrade significantly. If the thickness loss of the whole plate is not uniform, it is hard to assess the ultimate strength of the plate. Until now, there is still no acknowledged method to assess the ultimate strength of the plate with nonuniform corrosion damnification and pitting corrosion damnification.The purpose of the present paper is to develop a buckling assessment method of hull structural plate with nonuniform corrosion damnification and pitting corrosion damnification and the method is applicable in engeering. The main researches are as follows:(1) Based on the corrosion measurements during ship structural surveys, five corrosion parameters were transformed into a parameter, i.e. corroded volume loss. All available corrosion parameters were considered, such as the number of pits, the average diameter of pits, the maximum diameter of pits, the average depth of pits and the maximum depth of pits. The corroded volume loss was calculated by statistics and the corresponding program was compiled. The research results indicated that the error between the calculated corroded volume loss and the actual corroded volume loss is acceptable in engineering.(2) The ultimate strength reduction and the buckling assessment method of the hull structural plate with corrosion damnification on the two sides were analyzed on the basis of the corroded volume loss. The quantitative ultimate strength reduction formulae of the hull structural plate with corrosion damnification on the two sides under the axial in-plane compression loading, the biaxial in-plane compression loading and the shear loading based on the corroded volume loss were obtained by the theoretical analysis and finite element analysis. Moreover, the effects of the corrosion parameters, the geometric parameters and the load parameters on the ultimate strength and the ultimate strength reduction were analyzed. The proposed buckling assessment method of the hull structural plate with corrosion damnification on the two sides based on the corroded volume loss is applicable in engineering.(3) The ultimate strength reduction of the hull structural plate with corrosion damnification on the one side was analyzed on the basis of the corroded volume loss. The quantitative ultimate strength reduction formula of the hull structural plate with corrosion damnification on the one side under the combined loading based on the corroded volume loss was obtained by the theoretical analysis and finite element analysis. Moreover, the effects of the corrosion parameters, the geometric parameters and the load parameters on the ultimate strength and the ultimate strength reduction were analyzed. The proposed formula can be used in the buckling assessment of the hull structural plate with corrosion damnification on the one side in engineering.(4) The buckling experimental investigation of the actual hull structural plates with corrosion damnification was carried out. For the actual hull structural plates with corrosion damnification, the corrosion survey, the tensile test and the compressive buckling test were performed and the results were compared with the above research results. The accuracy of the corroded volume loss calculation, the finite element buckling analysis of the hull structural plate with corrosion damnification and the buckling assessment method of the hull structural plate with corrosion damnification based on the corroded volume loss and the applicability of the assessement method was validated.(5) The buckling assessment software of the hull structural plate with corrosion damnification was developed by combining the above researches. All available parameters were input into the software, including the corrosion parameters, the geometric parameters and the load parameters. Based on the above researches, the corroded volume loss, the ultimate strength reduction, the ultimate strength utilization factor and the parameters relative to the buckling assessment were calculated and the ultimate strength of the hull structural plate was assessed. The operation of the software is simple, and the ultimate strength can be assessed if only the available parameters are input into the software. The buckling assessment software is applicable in engineering.