| Corrosion of bar may lead to structural cracking,weakening of load capacity,shortening of service life and resulting in major economic losses and potential safety hazards.In view of the corrosion behavior of rebar,this paper proposes a method combining X-ray tomography(XCT)and finite element(FEM)simulation to track the entire process of corrosion behavior of steel bars,and to accurately quantify the internal corrosion morphology and corrosion information.Besides,the behavior of penetration of rust into matrix is investigated.Based on the corrosion mechanism,a non-uniform corrosion test under the effect of wet and dry cycles was designed.After appropriate shooting parameters were selected,and the whole process of corrosion of the test block was continuously and non-destructively tracked using XCT monitoring.After acquiring XCT image data,CT image processing and statistics were performed using digital image processing techniques and statistical methods,and the morphological characterization and accurate quantitative calculation of the corrosion behavior of rebar were realized.Finally,the results of the CT test were qualitatively verified by SEM-EDS.In simulation,based on the plastic damage model(CDP),the finite element model was established,and the corrosion expansion and cracking behavior of the steel bar was simulated by displacement loading.The fracture energy theory is used as a criterion to determine the cracking moment and the cracking position by means of the maximum principal stress and equivalent plastic strain(PEEQT).The stress is returned to the classical non-uniform corrosion model to obtain the corrosion rate of the steel under the main crack width of the CT test.After obtaining the simulated value of the corrosion level of the steel bar and the CT monitoring value under equal crack width,the two were compared.By comparison,the penetrated reduction factor of the corrosion product of was proposed to quantify the influence of the corrosion product corrosion product.Research indicates:(1)As for the corrosion of the interior morphology of the steel bar,it was found that the growth law of the corrosion product basically conformed to the traditional three-stage corrosion theory,which indirectly proved the rationality of the three stages of corrosion;besides,the penetration behavior of the corrosion product was directly observed.(2)The position of the maximum corrosion section and the corrosion rate in the whole process have been established;Corrosion depths of cracks in cracking time and failure time are obtained by binarization and Boolean operations;The development law of main crack width is obtained.The results show that the crack width increases slowly at the initial stage of cracking,and the corrosion rate increases fastest.(3)The feasibility of observing corrosion behavior of rebar by CT test method was verified by SEM-EDS;in addition,the rationality of corrosion behavior of rebar corrosion products was also verified.(4)The corrosion cracking of bar extends from the reinforcement bar to the outside,and the main cracks gradually extend from the minimum outer protective layer thickness of the test piece to the inside;(5)With the continuous expansion of corrosion cracks,the corrosion level obtained by CT testing will always exceed the calculation results of the finite element model at the same time,and the error will gradually increase.(6)The penetrated reduction factor of corrosion gradually decreases with time,which means that the difference between the calculated value of the corrosion level and the CT test results gradually increases.(7)The corrosion penetrated reduction coefficient is inversely proportional to thecorrosion expansion rate of the steel bar.Combining XCT test technology with finite element method,this study provides an effective monitoring method for the non-destructive and continuous tracking of corrosion behavior of steel bar,and provides a quantitative method for the study of corrosion penetration behavior of corrosion products. |
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