Displacement recovery and energy dissipation of crimped NiTi SMA fibers during cyclic pullout tests

Abstract

Abstract This study examines the cyclic pullout behavior of two types of cold-drawn NiTi shape memory alloy fibers, such as paddled and crimped fibers. For this, two diameters of 1.0 and 0.7 mm are considered. The experimental cyclic pullout results show that the deep crimped fibers produce a higher maximum pullout resistance than the shallow crimped fibers. When heated, the shallow crimped fiber increases the diameter more significantly than the deep crimped fiber, whereas the fiber wave depth decreases more than the deep crimped fiber. Thus, the maximum pullout resistance increases for the heated shallow crimped fiber and decreases for the heated deep crimped fiber. The displacement recovery ratio (DRR) reduction with an increasing slip is significant for the fiber with a low anchoring bond. The high anchoring bond fiber also introduces a higher average DRR than the fiber with a relatively low anchoring bond. Under heating treatment, the average DRR increases due to the prestressing in the fiber due to the shape memory effect. However, the anchoring bond of the fiber is enough to produce prestressing in the fiber. The anchoring bond of the fiber and the prestressing also influence the energy dissipation (ED). The higher anchoring bond results in a higher ED value, and the prestressing in the fiber contributes more to the increased ED values.