Experiment study and the Influence of the stress state to structure steel fracture

In order to study crack mechanism in stress triaxiality and fracture design of structure steel, the fracture experiments and numerical simulations were performed on 8 Q345 notched bar. Test results showed that crack initiated at the edge of the hole and the minimum section of the notched bars, quickly propagating perpendicular to loading direction. And that had obviously shear fracture trace, the fracture plane was ductile rupture induced apparently by shear stress, Triaxial stress reaches maximum at most dangerous section thickness center point and the center of the location of the notch. Through the analysis of simulated fracture stress field to the bar with holes indicated that fracture strength of structural steel and stress triaxiality have close relations, Application fracture of stress field of regression analysis, the relation expression between the fracture strength and stress triaxiality is obtained. By taking the stress triaxiality σm /σe for basic physical quantity, further quantitative analysis show that structural steel fracture with the equivalent strain and fracture surface of the average stress triaxiality have close relations, based on regression analysis, get the corresponding relation curves.