Complete fatigue crack arrest in metallic structures using bonded prestressed iron-based shape memory alloy repairs

Vast aging metallic structures are suffering from fatigue cracking, jeopardizing structural integrity and personnel safety. Therefore it is of great benefit to develop strengthening solutions to achieve complete fatigue crack arrest. A bonded and prestressed fatigue strengthening solution on the basis of an iron-based shape memory alloy (Fe-SMA) shows great potential in this term. An experimental campaign has been carried out in this paper to achieve complete fatigue crack arrest in metallic plates. Several activation methods greatly affecting the prestressing level have been experimentally tested, it has been found that the gas torch activation is the most effective method, extending the fatigue crack growth life by 6.9 times. The experimental campaign has demonstrated that prestressing forces required to achieve complete fatigue crack arrest capability could be realized by increasing the Fe-SMA patch width combined with the most effective activation method. In addition, the results show that the length of the Fe-SMA repair together with the activation length can be reduced without sacrificing the repair efficiency. The findings of this paper are greatly beneficial for industrial sectors suffering from fatigue cracking in metallic structures, small bonded Fe-SMA patches can be easily activated to achieve complete fatigue crack arrest capability.