Mechanical behavior of titanium nickelide material under stretch and evaluation of biomechanical compatibility

The work investigated the features of the deformation behavior of metal knitwear knitted from thin wire made of a TiNi-based alloy, and also carried out an experimental assessment of its biological compatibility. The obtained experimental stress-strain diagrams fully correspond to the typical tensile diagrams of superelastic TiNi alloys with a martensitic transition. The obtained nonlinear dependences of the tension of metal knitted fabric knitted from TiNi wire are rheologically similar to hyperelastic materials and differ from the obtained tension diagrams of the original wire. It was found that the tension-bonded design of the knitted fabric limits the manifestation of the superelasticity effect characteristic of wire. It has been shown that the tensile strength of knitwear is significantly lower than the tensile strength of wire. Using numerical modeling methods, a complex stress state during deformation is shown, which leads to inhomogeneity in the distribution of stresses in the metal knitted fabric structure and the localization of their maximum values in the contact area, thereby confirming the hypothesis about the suppression of superelasticity due to design features. An analysis of the stress distribution in the material of the loops showed that stretching in the range of physiological loads does not lead to local destruction of titanium nickelide metal knitwear. The results of an experimental study with a macroscopic assessment of the implantation zone demonstrated the absence of hernia defects in the area of endoprosthetics, and the adhesive process was recorded only in 3 (15%) cases. The endoprosthesis replacement area was elastic and easily deformable. The porous structure of the TiNi wire, as well as the biomechanical and biochemical properties of the two-layer metal jersey ensure optimal integration of the endoprosthesis in the body tissues and contribute to the formation of an elastic frame close to the natural one. Bilayer TiNi knitwear has shown promising results in replacing complex anatomical structures, which opens up prospects for further clinical research.