Actuation-Induced stable crack growth in near-equiatomic nickel-titanium shape memory alloys: Experimental and numerical analysis

Stable crack growth in NiTi shape memory alloys: 3D finite element modeling and experimental validation

“…In this case, the maximum shear stress occurs in planes normal to the plane of specimen and making 45°with the crack plane [44]. Although the variation of G I through the thickness may imply that the crack grows faster in the middle, crack front is found to remain straight during crack growth simulations which agrees with the post mortem examination of the fracture surfaces [23,25].…”

“…As reported based on experimental observations [13][14][15][16][17][18][19], and numerical calculations [20][21][22] loading of a cracked SMA body results in formation of a transformation/detwinning zone near the crack tip. This zone, acting as a energy dissipation mechanism, can lead to stable crack growth under isothermal mechanical loading [23] or thermal cycling under bias-loads [24,25]. Implementing constitutive models, e.g.…”

Structural fatigue and fracture of shape memory alloy actuators: Current status and perspectives

“…Cooling under constant applied tensile loads, which were substantially lower than the corresponding isothermal strength of the material, resulted in unstable fracture of double notched specimen NiTi (Baxevanis and Lagoudas, 2015; Iliopoulos et al, 2017). Jape et al (2021) performed experiments on pre-cracked compact tension specimens under actuation loading. Such a geometry allowed for stable crack growth through multiple actuation cycles where the crack advanced during cooling for every thermal cycle and stopped once the phase transformation was completed.…”

Crack growth behavior during actuation cycling of hot extruded and annealed Ni50Ti30Hf20 high temperature shape memory alloys

“…Iliopoulos et al [33] had experiments on the double notched Ni 60 Ti 40 (at.%) specimens during actuation under load and observed fracture due to an unstable crack propagation during cooling. Jape et al [34] conducted experiments on pre-notched compact tension Ni 49.5 Ti 50.5 (at.%) specimens under actuation loading and they found that the crack was advanced during cooling in actuation cycling. However, there are not many works investigating the crack growth behavior during actuation fatigue in NiTiHf HTSMAs.…”