Experimental Study On Constitutive Relation Of Monotonic And Cyclic Loading Of Corroded Steel Under General Atmospheric

Steel structure engineers, which are in the environment corrodes by industrial and marine atmosphere for a long time, are often difficult to prevent corrosion through the protection and construction measures. Rust pit on steel structure surface changes the surface topography, then causing the local stress centralization of steel surface, leading to the local yield of surface prior to the overall yield, and then causing the uneven plastic deformation of core and surface, reducing plastic property and fracture toughness of steel, this will undoubtedly have a great impact on the static and dynamic performance of the steel structure.This paper uses natural corrosion of Q235 B steel in atmospheric environment as the study subject. By the experimental study the monotonic tensile properties and low cyclic loading hysteretic behavior of corroded steel, revealing the relationship between corrosion degree of corroded steel plate surface, corrosion feature and the monotonic tensile properties, hysteretic behavior of cyclic loading under the general atmospheric environment. The main process is as follows:The three-dimensional non-contact optical profiler is used to test the surface morphology of 18 pieces steel plate corroded naturally in the general atmosphere environment, get the three-dimensional surface topography and surface parameters of the corroded steel specimen. Building the calculation model of depth, diameter, ratio of diameter to depth and volume of the rust pit in corroded steel plate surface, method to calculate the rate of volume loss of the corroded steel plate is proposed. Useing the method of probability and statistics to analyze the distribution characteristics of depth, diameter, ratio of diameter to depth and the maximum corrosion depth, and establishing the relationship between probability statistical parameters of rust pit dimensions and the volume loss rate.By monotonic tensile test of 10 pieces steel plate corroded naturally in the general atmosphere environment, exploreing the influence of corrosion on some mechanical parameters, such as steel strength, elongation, elastic modulus. A calculation method of corroded steel's strength, elongation, elastic modulus with different degree of corrosion is put forward. Based on the quadratic yield model, establish the constitutive model of steel under different corrosion extent.By low cyclic loading hysteretic test of 8 pieces steel plate corroded naturally in the general atmosphere environment, comparing the difference between hysteretic curve and skeleton curve of corroded steel with different degree. Exploring the effects of corrosion on the hysteretic performance when steel is under low cyclic loading. Using the Ramberg-Osgood model, to establish the relationship between the model parameters of circular skeleton curves of corroded steel and the rate of volume loss, investigating the effects of corrosion on the circular hardening characteristics of steel when the steel is under low cyclic loading.