Metal magnetic memory characterization of fatigue crack propagation of Q345qD bridge steel under the influence of stress ratio

Abstract

Fatigue fracture failure has been one of the major causes of damage in steel bridges. To better use fracture mechanics to study this failure behavior, the fatigue crack growth behavior of bridge steel plates under different stress ratios was investigated by metal magnetic memory nondestructive testing technique. The changes of magnetic signals during fatigue crack growth were recorded and analyzed, and then the magnetic signal characterization method of fatigue crack growth length was discussed both theoretically and experimentally. The stress ratio was incorporated into the model to establish a quantitative relationship equation between the magnetic signal characteristic and the crack growth length. Subsequently, the proposed relationship was applied to the fatigue crack growth remaining life prediction study and verified by experimental results. The results showed that the magnetic signal gradient is suitable as a characteristic parameter to quantitatively evaluate the fatigue crack growth length, and the relative errors between the prediction results and the test results were all within 15 %.