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

In this work, the characteristics of the deformation behaviour of metal meshes knitted from thin NiTi wires have been studied and an experimental evaluation of their biological compatibility has been carried out. The experimental stress-strain diagrams obtained fully correspond to the typical tensile diagrams of superelastic NiTi alloys with marten-sitic transformation. The nonlinear dependencies of the stress of the metal mesh knitted from NiTi wire are rheologically similar to hyperelastic materials and differ from the ob-tained stress diagrams of the wire. It was found that the tensegrity structure of the knit-ted fabric limits the manifestation of the superelasticity effect characteristic of the wire. The tensile strength of the knitted fabric was found to be significantly lower than that of the wire. Using numerical modelling methods, it has been shown that the complex stress state of the metal mesh during deformation leads to inhomogeneity of the stress distribution in the structure and localisation of its maximum values in the contact area of the loops, confirming the hypothesis of suppression of superelasticity due to design features. An analysis of the stress distribution in the loops showed that stretching in the range of physiological loads does not lead to local destruction of the NiTi metal mesh. The results of an experimental macroscopic evaluation of the implantation area showed that there were no hernia defects in the endoprosthesis area and the adhesive process was recorded in only 3 (15 %) cases. The replacement area of the endoprosthesis was elastic and easily deformable. The porous surface structure of the NiTi wire, as well as the biomechanical and biochemical properties of the bilayer metal mesh, ensure optimal integration of the endoprosthesis into the body tissues and contribute to the formation of an elastic frame close to the natural one. Bilayer NiTi knitted mesh has shown promis-ing results in the replacement of complex anatomical structures, opening up prospects for further clinical research.