Shape memory alloy (SMA) strips for fatigue strengthening of cracked steel plates

This paper aims to show the feasibility of application of iron-based shape memory alloy (Fe-SMA) for fatigue strengthening of steel plates. The effectiveness of the proposed retrofit system was also compared with that of prestressed carbon-fiber reinforced polymer (CFRP) system. The Fe-SMAs are smart materials that can be selfprestressed via using their so-called shape memory effect (SME) characteristics. In this study, the Fe-SMA strips are anchored on the steel plates using a mechanical anchorage system. The SME in the Fe-SMAs is activated when the material is heated up to a characteristic temperature. Two precracked steel plates with different Fe-SMA strengthening schemes were prepared. Additionally, a precracked steel plate without strengthening served as a reference specimen. Fatigue tests were then performed on the SMA-strengthened steel plates. All specimens were subjected to fatigue loading with a stress range of 75 MPa and a load ratio of 0.2. It was observed that the fatigue life of the steel plates enhanced substantially by using the Fe-SMA strips. The activated (i.e., prestressed) Fe-SMA strips apply a compressive stress to the critical cracked detail in the steel plate, which decreases the tension stress at the crack tip and resulting in an increased fatigue life of the steel plates. The results of the tests were compared with the existing tests results on CFRP strengthening of steel plates.