| In the urban industrial atmospheric environment,steel corrosion is one of the most common forms of damage to steel structures.Even if coating technology is used for corrosion protection,steel corrosion has not been solved.Steel corrosion will lead to a reduction in the effective stress area of steel members and the occurrence of pits.The resulting stress concentration of steel members is an important factor for the failure of existing steel structures.Especially under the action of dynamic load,the rapid decline in the fatigue performance of the steel after corrosion will bring huge economic losses and social harm.With the support of the National Natural Science Foundation of China(51578357),this article took Q235 B steel as the object,and conducted fatigue test research and related theoretical analysis.The main work contents and conclusions are as follows:(1)First prepare intact test pieces and Q235 B steel with a 10% quality corrosion rate,and use the constant amplitude loading method to perform the tensile fatigue test on the MTS fatigue testing machine.Statistical analysis of the data obtained from the constant amplitude fatigue test shows that Fatigue life is significantly reduced compared to intact specimens.(2)Establish a three-dimensional finite element model of the Q235 B steel intact specimen,combine the finite element software Abaqus and the fatigue design software FE-safe to simulate the fatigue life,change the magnitude of the stress amplitude,and fit the 16 points to obtain the fatigue life curve.At the same time,it is more reasonable to establish a steel fatigue model with an initial crack of 0.7mm × 0.7mm and a quality corrosion rate of 10%.Change the magnitude of the stress amplitude to obtain the fatigue life curve of the corrosion specimen.(3)Secondly,based on the XFEM module,the crack tip stress intensity factor is solved and compared with the analytical solution,which verifies the accuracy of the finite element method for calculating the stress intensity factor.At the same time,using the log(da / d N)? log(? K)curve,the values of the constants c and m are obtained.Based on the Paris formula,a fatigue model that conforms to the actual fatigue life of Q235 B steel isestablished to analyze the high-cycle fatigue fracture of Q235 B steel.Provide an effective analysis method.(4)By observing the surface inclusions and structural forms of fatigue failure fractures under electron microscope scanning,the results show that each fatigue failure fracture contains fatigue source zone,extension zone and transient fracture zone,and at the same time corrodes the fatigue crack strip of the specimen The distance is greater than the intact specimen,which reflects that the fatigue life of the rusted specimen is less than that of the intact specimen. |
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