Experimental Study On Monotonic Tensile Behavior Of Corroded Steel In Neutral Salt Spray Environment

With the increasing application of steel in the construction of more extensive,corrosion of steel structure in the service of the increasingly prominent,the problem of corrosion of steel structures has attracted more and more attention of Engineering field.Steel corrosion will not only cause the waste of the material,the more important is the inhomogeneous structure and surface morphology of section loss caused by corrosion,the strength of steel,the performance of plastic material degradation,thereby reducing the bearing capacity and the safety performance of the structure.Therefore,study on the different degree of corrosion of steel in the variation of mechanical properties of monotonic tensile loads of steel corrosion,the constitutive response,is the basis of the research on both the safety performance and service life of steel structure.In this paper,through the method of outdoor atmospheric neutral salt fog spray cycle accelerated corrosion of Q235 steel plate coating,the corrosion speed for more than one year,the natural corrosion in simulated marine atmosphere of steel.Analysis and corrosion process of the steel in the neutral salt spray environment,to establish the relationship between steel corrosion rate and time.With the help of PS50 three-dimensional non-contact surface profilometer measured three-dimensional coordinates of the corrosion of steel surface data,3D image3D roughness parameters.According to the test results of comparative analysis of the development and changes of morphology of corrosion of steel under different corrosion degrees and localized corrosion depth statistics.Analysis of the development rules of the roughness parameters change with the degree of corrosion;and the relation formula of 3D roughness parameters between S_a(S_q)and the time,the corrosion rate of establishment,the formula for calculating the local corrosion rate of steel in different corrosion time and average corrosion rate;fitting formula of local corrosion depth is S_p,the maximum corrosion depth S_zwas established to extract the maximum pitting corrosion;each surface of the studied separately,analyzes the relationship between the maximum corrosion pit depth,width and depth to width ratio and corrosion rate with time.Finally,through the monotonic tensile tests of steel,discusses the mode of failure,corrosion of steel and the difference of stress-strain curve;analyzed the relationship of different mechanical properties and the corrosion parameters,and puts forward the calculation formula of pit corrosion influence coefficient,and its value has good correlation with the strength index;then establish the corrosion of steel the monotonic tensile constitutive model.The research results show that the uniform corrosion,the section loss is the main reason for the decline of bearing capacity of steel corrosion and local corrosion,the formation of corrosion pits on the stress concentration is the main factors of corrosion of steel and the nominal stress drop.