Modelling low-cycle fatigue behaviour of structural aluminium alloys

Recently, use of 6000 series aluminium alloys in braced frame structures has been increased due to their superior structural properties. Fracturing of braces as a result of low-cycle fatigue has a major impact on nonlinear behaviour of structures under earthquake loading. Therefore, modelling low-cycle fatigue life, i.e., number of reversals to failure, is important to understanding braced-frame structural performance. To date, there are no readily available methods for predicting the low-cycle fatigue behaviour of 6000 series aluminium alloys. This research study aims to provide structural engineers with a computationally efficient approach to assess aluminium alloy structures in the context of potential low cycle fatigue. For this purpose, 18 low-cycle high amplitude fatigue tests (up to ± 6% strain amplitude) were conducted to establish strain − life relationships for 6082-T6, 6063-T6 and 6060-T5 aluminium alloys. The obtained experimental results were then used to calibrate a low-cycle fatigue life model to capture the fracture behaviour of the studied materials. The comparison of experimental results and predicted fatigue behaviour shows the capability of the proposed model to predict to a high degree of precision the onset of fracture and the overall low-cycle fatigue behaviour of material.