Strength of Products Made of Ultrafine-Grained Titanium for Bone Osteosynthesis

This paper evaluates the fatigue strength of ultrafine-grained (UFG) Grade 4 Ti in the low-cycle fatigue region, as well as the strength of medical implants (plates and screws) made of UFG Ti under various types of loading in comparison with the strength of products made of coarse-grained (CG) Ti. To produce a UFG state, titanium billets after annealing were processed by the ECAP-Conform technique. The fatigue of the prismatic specimens with a thickness of 10 mm from CG and UFG Ti was tested by the three-point bending method using an Instron 8802 facility. The modeling and evaluation of the stress-strain state in the ANSYS software package for finite-element analysis revealed, in particular, the localization of equivalent stresses in the area of hole edges and at fillets during the tension of the plates. The performed research has demonstrated that medical implants (plates and screws) from UFG Grade 4 Ti have a higher strength under different types of loading (tension, fatigue strength, torsion) in comparison with products from CG Ti. This opens up a possibility for the miniaturization of medical products from UFG Ti while preserving their main performance properties at an acceptable level.