Effect Of Pitting Damage On Compressive Mechanical Properties Of High Strength Steel

Due to the long-term exposure to the harsh marine environment,corrosion of ship structure is inevitable.Corrosion is one of the main factors leading to instability and failure of ship structure,which can strongly weaken the bearing capacity and deformation capacity of the structure,and increase the risk of structural damage caused by other loading conditions.Pitting and uniform corrosion are two typical types of ship corrosion.Due to the stress concentration effect,pitting may have a greater effect on the structure than uniform corrosion.The existence of pitting corrosion will cause structural embrittlement and weaken the deformation capacity,increasing the possibility of buckling failure of pressurized hull plate.Therefore,it is of practical significance to accurately predict and judge the failure mode and ultimate strength of corroded hull plate to prolong the service life of the ship and guarantee the safety of the ship.The high-strength steel DH36,which is commonly used in ships,is selected as the research object in the present paper,the following work has been done in this paper.(1)The compression specimen was designed according to the standard and the influencing factors of the failure mode of intact specimen under compression were explored,By changing the geometrical size,length,width and thickness of the test section.The corresponding numerical model was established to verify the conclusion.(2)Based on the two failure modes of intact specimens,single pitting pits with different diameters and depths were added on the basis of different specimen thicknesses to explore the influence of pitting on the elastic modulus,yield strength,ultimate strength and ductility section length of the specimens under compression.(3)The ability of four commonly used pitting comprehensive evaluation indexes to evaluate the mechanical properties of pitted steel was compared with the test data,and the most sensitive evaluation index to mechanical properties was determined.The relationship between volume loss rate and modulus of elasticity,yield strength,ultimate strength and mechanical properties of ductile segment length was obtained by the test data.Based on the Ramberg-Osgood,the generalized constitutive model of pitted DH36 steel under different failure modes was proposed and modified by taking volume loss rate as variable.This model can be used to predict the stress-strain relationship curve of material compression strength failure and the stress-strain relationship of buckling failure under different corrosion degrees.(4)The steel plate model with multi corrosion pits was established by ABAQUS,theeffectiveness of cross section loss rate,pitting density and pitting volume loss rate in evaluating the comprehensive mechanical properties of pitting plates was discussed.the effects of the plate aspect ratio,pitting diameter and depth on the compressive buckling strength of pitted plate were studied respectively,the effects of nine different erosion distributions on the mechanical properties of plates were added to verify the applicability of the pitting corrosion constitutive model...