Energy-based fatigue model for shape memory alloys including thermomechanical coupling

Abstract

This paper is aimed at developing a low cycle fatigue criterion for pseudoelastic shape memory alloys to take into account thermomechanical coupling. To this end, fatigue tests are carried out at different loading rates under strain control at room temperature using NiTi wires. Temperature distribution on the specimen is measured using a high speed thermal camera. Specimens are tested to failure and fatigue lifetimes of specimens are measured. Test results show that the fatigue lifetime is greatly influenced by the loading rate: as the strain rate increases, the fatigue lifetime decreases. Furthermore, it is shown that the fatigue cracks initiate when the stored energy inside the material reaches a critical value. An energy-based fatigue criterion is thus proposed as a function of the irreversible hysteresis energy of the stabilized cycle and the loading rate. Fatigue life is calculated using the proposed model. The experimental and computational results compare well.

Thermomechanical and electrical response of a superelastic NiTi shape memory alloy cable

“…This leads to an increase in the residual strains and a decrease in the mean temperatures, as less material transforms with each loading cycle. A similar phenomenon was also observed for SMA wires with a 1-mm diameter that was subjected to 20 loading cycles (Zhang et al, 2016).…”

On the Fatigue Behavior of Nanocrystalline NiTi Shape Memory Alloys: A Review

“…On the other hand, the damage-tolerant approach requires introducing a defect into the sample and measuring the crack growth from this defect to analyze fatigue crack propagation [25]. Energy-based methods depend upon finding the relationship between the dissipated energy and the number of cycles to establish a comparison between the superelastic behavior and plastic deformation [54,55].…”

Hysteretic Behavior and Ultimate Energy Dissipation Capacity of Large Diameter Bars Made of Shape Memory Alloys under Seismic Loadings

“…Some recent works aspire to gain a better understanding of the structural fatigue of NiTi SMAs based on both experimental and theoretical investigations [14,22,23]. Several fatigue failure models have been developed following an energy criterion that appears to keep a good correlation between experimental and prediction approaches.…”