Surface Cracks Propagation On 14MnNbq Stiffened Panel

The surface crack is one type of the faults frequently found in many structures and components. Seriously, the surface crack propagation leads to breakages of structures and components. Therefore, it is very important to study the surface crack propagation and to predict the life of structures or components with surface cracks.The characteristics of surface crack propagation of the steeling 14MnNbq stiffened panel used in Tianxingzhou Bridge are studied in this thesis. Firstly, the basic theory of surface crack propagation is introduced. Then, tests on surface crack propagation of stiffened panel are done. Each specimen is cut a half-elliptical crack on the center. The welds welding procedure refer to Tianxingzhou Bridge design. The specimens are tested under four-point bending. The test method is in accordance with the related national standards.Secondly, the characteristics of surface crack propagation can be predicted using the basic experimental results of through cracks, integrated with Paris formula. The predicted results are compared with the experimental data of surface cracks. The comparison shows that the method predicting surface crack propagation with bending load is efficient, and the predicted growth ratio of surface crack propagation is conservative.Finally, considering the effect of crack closure, the original experimental data are newly fitted. It is found that new fitted results agree with theoretical predictions better. The results indicated it is very necessary to consider crack closure effect in study on surface crack propagation of the stiffened panel.