Finite element analysis of the influence of surface layer on frictional wear in a follow-up screw-rod kinematic node in GGS stabilization.

The aim of this study was to numerically analyse the influence of the surface layer on the mechanical properties in a follow-up screw-rod kinematic pair in Growth Guidance Stabilization System. In addition, the polymer insert on the sliding part of the support rod, which is designed to eliminate frictional wear effects, was also analysed. Numerical simulations were carried out by loading the model with short-term repeated load tests to represent the operation of the stabilizer under near-real conditions. Analysis of the reduced stresses according to the Huber - von Mises hypothesis of the cooperating elements, i.e. the rod and the sliding screw cap, showed a point concentration of stresses. In the pairs covered with the additional coating, the maximum stress values do not exceed 4 MPa on both mentioned elements and are similar in all analysed configurations. The modification of the geometry in the form of an additional insert resulted in a different stress distribution, with the maximum values observed at the insert being around 10 MPa. The numerical simulations carried out showed areas of stress concentration at locations that may be indicative of frictional wear occurring. The design modification changed the stress distribution on the mating components, which may be preferable to point contact in standard kinematic pairs. The stress values in the coated models are similar to each other, suggesting that the choice of a particular coating does not significantly affect the mechanical performance, but nevertheless the presence of the coating is crucial.