Fracture of prismatic aluminum tubes under reverse straining

The effect of loading history on fracture was thoroughly investigated at the material and structural level. Tests on tensile fracture of initially pre-compressed round specimens were analyzed and two alternative methods were developed to account for the effect of strain reversal on initiation of fracture in uncracked bodies. A complete calibration for plasticity and fracture without and with history effect was performed for 2024-T351 aluminum alloy. In the present approach, it is postulated that fracture occurs when the accumulated plastic strain modified by the effect of stress triaxiality and the loading history reaches a critical value. The newly developed theory then was applied to predict initiation of fracture in prismatic square aluminum tubes subjected to crush loading. Compression tests were performed on small columns with the width to thickness ratio covering the range 10–30. First fracture was observed at different locations depending on the thickness of the tube. The numerically predicted point of fracture initiation and the displacement corresponding to formation of crack agreed well with test results. It is concluded that the effect of loading history must be included in the formulation of fracture criteria and in the application to the failure analysis of structural components where large pre-compression should be expected.