HIGH-CYCLE FATIGUE BEHAVIOUR OF WELDED THIN SHS-CHS T-JOINTS UNDER IN-PLANE BENDING

摘要

T-joints made up of square hollow section (SHS) chords and circular hollow section (CHS) braces are used in the road transport and agricultural industry. The hollow sections are thin-walled with thicknesses less than 4mm. Static tests were carried out on welded thin-walled SHS-CHS T-joints under in-plane bending load to determine the linear response between applied load and deformation. The loads corresponding to the linear part of the load-deformation curves were used in subsequent fatigue tests and resulted in a high cycle fatigue response. A formula for determining the maximum linear response moment in an SHS-CHS T-joint is derived as a function of brace diameter to chord width ratio, β and chord width to chord wall thickness ratio, 2γ. Fatigue tests were carried out to determine through-thickness fatigue life (N3) and an end of test fatigue life (N4). The fatigue data from the welded thin-walled SHS-CHS T-joints is compared to the S-N data of welded thin-walled SHS-SHS T-joints and found to be within the same scatter band. An analysis has been carried out in terms of the classification method and shows that there is a minimal difference between the fatigue design S-N curve obtained by using N4 instead of N3, when the inherent scatter in fatigue data is taken into account.