Biaxial high-cycle fatigue life assessment of ductile aluminium cruciform specimens

• A biaxial cruciform specimen for low load capacity test machines is presented.
• Several high cycle fatigue experimental tests carried on cruciform specimens are presented.
• Experimental fatigue results were compared with numerical estimations.
• MCE together with the non-linear modified C–S criterion provided better estimations.

Several results of experimental high-cycle fatigue tests carried out on a new biaxial in plane testing system are presented, covering a wide range of biaxial stress states, including proportional and non-proportional, performed on cruciform specimens machined from ductile aluminium (A1050-H14) sheet plate with 3 mm thickness. A specially designed cruciform specimen for crack initiation and low capacity test machines was used to perform fatigue tests. This specimen was optimized for the test machine in order to achieve the maximum uniform stress at the centre gauge area, while keeping the remaining stresses at least 20% lower than the stress at centre. Several of the most common multiaxial fatigue criteria were used to determine an equivalent uniaxial fatigue damage parameter for all the specimens that were tested experimentally and to determine which criteria provide a better correlation to the experimental results. From the results it was shown that most of the criteria provide non-conservative estimations. In overall, better results were found by the Minimum Circumscribed Ellipse criterion and also when using the damage parameter related with the shear stress computed by the Minimum Circumscribed Ellipse in the modified non-linear criterion proposed by Carpinteri and Spagnoli.