The Research On The Ultimate Strength Assessment Method Of Ship Plates With Non-uniform Corrosion In The Whole Life Cycle

The ultimate strength of ocean-going ships sailing in sea water for a long time is greatly reduced after corrosion,which leads to many maritime accidents.In order to reduce the economic and property losses caused by corrosion damage,it is absolutely essential to study the assessment method of ultimate strength of corroded ship plates in the whole life cycle.However,many scholars usually thinned the corroded plate uniformly in their research,completely ignoring the influence of the non-uniformity of the corroded surface on the ultimate strength,resulting in the significant errors in the assessment results.The non-uniformity of corrosion surface is quantified by multi-fractal parameter to establish an assessment model with high accuracy and convenient use.The main contents of this paper include:(1)Random corrosion surfaces satisfying certain statistical rules are generated.According to the corrosion law,the statistical characteristics of the corrosion surface of ship plates in different years are calculated,and the random corrosion depth of each position of ship plate is calculated.Finally,we can get the random corrosion surface in different years.(2)Verification and extraction of multi-fractal features of simulated corrosion surfaces and corrosion surfaces of ship plates.The multi-fractal feature is verified and extracted according to the residual corrosion thickness at each node of the simulated surface and the corroded surface of the ship plates.(3)An assessment method for ultimate strength of non-uniform corroded plate under specific years is established and verified by experiments.The surfaces of corrosion plates in 10 years are simulated and their characteristic information is extracted,the ultimate strength of corrosion plates are also calculated.According to the physical meaning of the parameters and their influence on the ultimate strength,appropriate parameters are selected to fit the assessment formula of the ultimate strength.The correctness of the numerical simulation method is verified by the buckling experimental results.(4)The ultimate strength assessment model of non-uniform corrosion plates in the whole life cycle was established.Based on the above research,the year is extended to the whole life cycle of ships,the distribution and time-varying law of assessment parameters is explored.Finally,the lower limit values of ultimate strength reduction factor under each year is obtained.In this paper,the ultimate strength of corroded ship plates under a specific service life is evaluated firstly.Then,the assessment method is extended to the whole life cycle of the ships,according to the selected corrosion model.The functional relationship between the lower limit value of the ultimate strength reduction factor and the service life is given eventually,which will play a guiding role in the maintenance and repair of the ships in the whole life cycle.