Study On Mechanical Properties Of Corroded Cold-formed Thin-walled Steel

Cold-formed thin-walled steel is widely used because of its advantages of flexible section shape,light weight,high strength,convenient construction,energy saving and environmental protection.Although there are protective measures,many cold-formed thin-walled steel structures in corrosive environment inevitably have corrosion problems,which affect the safety and reliability of the structure.In this paper,based on the 10-year-old profiled steel sheet in the industrial environment,the surface morphology and mechanical property degradation of the cold-formed thin-walled steel were systematically studied by the method of the experimental research and the numerical simulation.(1)With the help of ST400 three-dimensional surface topography instrument,the surface of corroded cold-formed thin-walled steel was scanned,and the surface topography and three-dimensional coordinate data of corroded steel plate were obtained.Based on the statistical analysis of surface morphology data,the frequency histogram of corrosion depth was obtained,and the relationship between the surface characteristic parameters and the mass loss rate was established.Finally,the relationship between the surface morphology characteristic parameters of the corroded cold-formed thin-walled steel and the corroded hot-rolled steel with the mass loss rate was analyzed.(2)The stress-strain curves of cold-formed thin-walled steel with different corrosion degree were obtained by monotonic tensile test on 7 specimens made on the flat part of corroded profiled steel plate.The effects of corrosion on the mechanical properties such as fracture form,yield strength,ultimate strength,elastic modulus and elongation were studied.The relationship between the mechanical property index and the mass loss rate was established.(3)The influence of size and quantity of corrosion pits on the mechanical properties of cold-formed thin-walled steel were studied by numerical simulation.Eight finite element models with corrosion pits were established to analyze the influence of the size and number of corrosion pits on the Mises stress and the equivalent plastic strain nephogram,and to reveal the damage mechanism of corrosion pits.According to the numerical simulation results,the empirical formula between the ultimate bearing capacity and the corrosion parametersof the cold-formed thin-walled steel was fitted.