Parameterized construction method of numerical model of pit-corrosion-randomly-distributed cylindrical shell

Abstract

The invention discloses a parameterized construction method of a numerical model of a pit-corrosion-randomly-distributed cylindrical shell. The parameterized construction method of the numerical model of the pit-corrosion-randomly-distributed cylindrical shell comprises the following steps of first, carrying out parameterized setting on the dimensions of the cylindrical shell and corrosion pits in finite element software, dividing a geometric model of the cylindrical shell into geometric meshes which are uniform in size, and regarding the angular points of the geometric meshes as positions where the corrosion pits possibly appear; afterwards, generating a random number to determine the position and the depth of one corrosion pit, when a new corrosion pit is generated each time, always judging necessarily whether the new corrosion pit is overlapped with an existing corrosion pit or not, and if the new corrosion pit is overlapped with the existing corrosion pit, anew generating a random number to determine the position of another corrosion pit; structuring geometric models of the corrosion pits on the cylindrical shell by utilizing the geometric parameters of the corrosion pits, and establishing integral geometric models of the pit-corrosion-randomly-distributed cylindrical shell; finally, grouping the integral geometric models, dividing finite element meshes for the integral geometric models, and constructing the numerical model of the pit-corrosion-randomly-distributed cylindrical shell. The numerical model constructed by using the parameterized construction method of the numerical model of the pit-corrosion-randomly-distributed cylindrical shell has universality and authenticity.

Description

technical field [0001] The invention relates to a numerical model construction technology of pitting corrosion components, specifically a parametric construction method of a numerical model of a cylindrical shell with pitting corrosion randomly distributed, which can simulate the distribution position of pitting pits on the cylindrical shell and the randomness of the wall thickness damage depth. The state is used to study the stress concentration of cylindrical shell structures caused by randomly distributed pitting damage, and to reveal the law of pitting damage affecting the structural bearing capacity. Background technique [0002] Components such as pile legs and submarine pipelines of pile-based platforms have been in a corrosive marine environment for a long time, and the weakening of the bearing capacity of components caused by corrosion is inevitable. However, due to the complexity of the corrosion mechanism, the degradation of static and dynamic strength and fatigue ...

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Problems solved by technology

[0003] In the study of the bearing capacity of pitting damage components, the API579-1 specification of the American Petroleum Institute proposed an empirical formula to calculate the remaining strength of metal pipelines in 8 standard pitting modes, but human factors have too much influence on determining the pitting mode

Chinese Patent Publication No. CN103558356A, titled "A Seamless Characterization Model for the Remaining Strength of Pitting Corrosion Metal Pipelines" proposes to use the proportion of pitting area m and remaining wall thickness ratio Rwt The two parameters characterize the pitting mode that includes and is between the 8 standard pittings, and introduce them into the API specification to calculate the remaining strength of the pitting pipeline, but it does not make essential innovations in the distribution mode of pitting , unable to reflect the influence of differences in pitting distribution patterns on the bearing capacity of members

The Chinese patent announcement number is CN203132482U, the name is "a pitting depth measuring instrument" and the Chinese patent publication number is CN103969472A, the name is "a kind of in-situ observation device and method of pitting formation process" and the literature respectively discloses the measurement The in-situ dynamic observation device and method for pitting depth and pitting formation process morphology features, the Chinese patent publication number CN102708588A discloses a three-dimensional reconstruction method for pitting damage morphology of metal flat plates, but these measuring instruments and methods are not Complex imaging equipment, sensors, advanced computing tools and other equipment and accessories must be used, and the testing process and methods are extremely complicated. At present, it can only solve the problem of model construction of specific pitting components, and cannot provide the necessary information for carrying out a large number of scientific researches. The mass computing model of

However, the numerical models of pitting components used in existing studies (only plates have been reported, and cylindrical shells have not been reported) can only be used to study the impact of pitting on components by uniformly distributing or constructing pitting on specified positions. The influence of the bearing capacity, the established numerical model is specific, lacks universality, cannot carry out a large number of theoretical research and analysis, and does not conform to the actual observed distribution of pitting corrosion

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