FATIGUE CRACK PROPAGATION OF TUBULAR T-JOINTS UNDER COMBINED LOADS

摘要

Experimental fatigue studies are conducted on three identical steel tubular T-joints subjected to in-plane bending (IPB), combination of IPB and out-of-plane bending (OPB) and combination of axial loading (AX), IPB and OPB respectively. The fatigue performances of the joints subjected to these basic and combined load cases are investigated, and the Alternating Current Potential Drop (ACFD) technique is used to monitor their joint crack growth and crack shape developments. The test results confirmed that the tubular joint fatigue design S-N curve which is based on single axis test data is still valid for T-joints subjected to combined load cases. The specimens are also simulated numerically using a modelling procedure which can include a semi-elliptical surface crack located at any position and any length along its brace-chord intersection within the joint finite element model. The numerical results are validated against those obtained from experiments using the Paris' law equations. Good agreement between these results confirmed that the proposed modelling procedure is reliable and appropriate for fracture mechanics analysis.