A study on the corrosion fatigue behaviour of laser-welded shape memory NiTi wires in a simulated body fluid

Silva

2019

Smart Mater. Struct.

This work evaluates the effect of welding energy and cycling strain amplitude on fatigue behavior of welded joints obtained by micro Tungsten Inert Gas spots in NiTi SMA superelastic wires. For this purpose, a Dynamic Mechanical Analyzer operating in single cantilever bending mode is employed. The equipment monitors the evolution of the force level to maintain constant the strain amplitude as cycling proceeds. Fatigue lives of as-received and welded NiTi wires are compared for different strain amplitudes applied during mechanical cycling. In the evaluated range of strain amplitude, as-received NiTi wires showed fatigue lives between 10 3 and 10 4 cycles. The fatigue life of the welded joints is lower, although it remains in the same range observed for the asreceived wires.

Section: Fatigue Lifesupporting

confidence: 92%

Mechanical behavior and fatigue life of micro welded joints obtained by TIG spots in NiTi wires

Silva

2019

Smart Mater. Struct.

“…To investigate the degradation behavior of CNTs/PLA suture in human body, HANKs fluid was created to simulated the body fluid, which was composed of 8.0 g/L NaCl, 0.4 g/L KCl, 0.14 g/L CaCl, 0.1 g/L MgCl 2 , 0.06 g/L MgSO 4 , 0.06 g/L KH 2 PO 4 , 0.06 g/L Na 2 HPO 4 , 0.35 g/L NaHCO 3 , 1.0 g/L C 6 H 12 O 6 [35,36]. The CNTs/PLA sutures were put into HANKs fluid which was maintained at 37 °C, the same as the temperature of inner body.…”

Section: Methodsmentioning

confidence: 99%

Degradation Behavior In Vitro of Carbon Nanotubes (CNTs)/Poly(lactic acid) (PLA) Composite Suture

Liu

Chen

et al. 2019

Polymers

Poly(lactic acid) (PLA) suture can be absorbed by the human body, and so have wide applications in modern surgery operations. The degradation period of PLA suture is expected to meet with the healing time of different types of wounds. In order to control the degradation period of the PLA suture, the carbon nanotubes (CNTs) were composited with PLA suture, and the degradation experiment in vitro was performed on sutures. The structure and properties of sutures during degradation, such as surface morphology, breaking strength, elongation, mass and chemical structure, were tracked and analyzed. The results indicated that the degradation brought about surface defects and resulted in 13.5 weeks for the strength valid time of the original PLA suture. By contrast, the strength valid time of the CNTs/PLA suture was increased to 26.6 weeks. Whilst the toughness of both the pure PLA and CNTs/PLA sutures decreased rapidly and almost disappeared after 3 to 4 weeks of degradation. The mass loss demonstrated that the time required for complete degradation of the two sutures was obviously different, the pure PLA suture 49 weeks, while CNTs/PLA sutures 63 to 73 weeks. The research proved that CNTs delayed PLA degradation and prolonged its strength valid time in degradation.

Corrosion fatigue crack propagation behavior of A7N01P‐T4 aluminum alloy welded joints from high‐speed train underframe after 1.8 million km operation

Lü

Gou

et al. 2020

Materials & Corrosion

Using the potentiodynamic polarization analysis, the fatigue crack propagation behavior of A7N01P‐T4 aluminum alloy metal inert gas welded joints cut from a high‐speed train underframe after 1.8 million km operation was studied in air and in a 3.5 wt% NaCl solution. The fracture surface and crack growth path were analyzed using optical microscopy, scanning electron microscopy, and electron backscattered diffraction. The results reveal that the corrosion fatigue crack growth rate of an A7N01P‐T4 welded joint in a 3.5 wt% NaCl solution is higher than that in air. Furthermore, the corrosion fatigue crack growth rate is noted to be the fastest in the heat‐affected zone, followed by the base metal, whereas it is the slowest in the weld metal, which is consistent with the corrosion resistance of the A7N01P‐T4 joints. The second phase is observed to exhibit a significant influence on the corrosion fatigue crack propagation path. The cracks are noted to grow toward the soft orientation and have obvious plastic deformation during the propagation process, which indicates that the anodic dissolution is the main cause of the corrosion fatigue crack growth.