The Tensile Stress-strain Model And Analysis For Corroded Steel Bars

This paper takes the tensile constitutive relationship and characteristic law of corroded steel bars as the main research content.Combined with physical model experiments,theoretical derivation and finite element methods,construction of tensile stress-strain models of corroded steel bars and multi-level analysis were carried out.The main work and results are as follows:1)After the forming work of the steel bars in three different working conditions was completed,the uniaxial tensile test was performed on intact steel bars to obtain their constitutive curves,and a database of their constitutive feature points was constructed and the strength distribution verification was carried out,providing a basis for the regularity study of the randomness of materials on the performance of steel bars.Slotted steel bars and accelerated corroded steel bars were successively 3D scanned to obtain their apparent morphology data and uniaxial experimental stretching to obtain constitutive relations,which provided data support for the construction of finite element models and theoretical analytical models,respectively.2)Based on the basic understanding of the impact of the appearance parameters of corroded steel bars on its performance,the slotted method was used to simulate the corrosion of steel bars,and a simplified analytical model of the tensile constitutive of corroded steel bars was derived.On the basis of the experimental data verification of slotted steel bars,this analytical model can properly characterize the constitutive characteristics of corroded steel bars.The performance degradation mechanism of corroded steel bars and their influencing factors were analyzed.The results show that the strength of the corroded steel bar decreases with the increase of the cross-section corrosion rate;the yield strain and the strengthening strain decrease with the increase of the corrosion depth,and however,the ultimate strain decreases in the first place and then remains unchanged as the corrosion depth increases;when the corroded steel bar is lightly corroded,it still has a long yield platform.Otherwise,the yield platform of the steel bar becomes shorter.3)The finite element model of corroded steel bar was constructed based on the apparent shape data of the corroded steel bar,and its effectiveness was verified by the tensile test results of the corroded steel bar.Based on that,the change characteristics of the tensile stress-strain of the corroded steel bar and its internal mechanism were analyzed.The numerical simulation analysis shows that the corrosion of the steel bar will affect the stress transmission law inside the steel bar,and the pitting caused by the corrosion will change the stress state of the internal material.4)Given the analysis accuracy and calculation cost and feasibility,based on the singular function model of corroded steel bar,the tensile constitutive relation of the corroded bar was analyzed by Monte Carlo simulation.The random numerical simulation was adopted to study the influence law of material randomness on the tensile constitutive relation and the minimum cross-section failure probability of the corroded bar.The results show that the material randomness will cause the difference in the ultimate strain.The coefficients of variation of the ultimate strain increases with the degree of corrosion,but they are small,so the effect of material randomness on mechanical properties of corroded bars can be ignored.When the strength of the corroded steel bar follows different distributions,the corresponding minimum section failure probability is affected and shows different sensitivities,but the effect of strength randomness on the failure probability of the smallest cross-section becomes smaller as the difference between the two sections increases.