چكيده به لاتين
One-piece bearing is the latest type of total disc replacement (TDR). The most important challenges in this type of disc is to choose the type of material that has a longer fatigue life, appropriate mechanical properties and proper adhesion. Due to the unique properties of shape memory polymers (SMPs), self-healing, shape-memory, adhesion control and self-deployable, these materials can be a good candidate for this method. The aim of this study was to investigate the behavior of SMPs as intervertebral discs (IVDs) in pure bending, pure torsion and flexion-extension using analytical and numerical methods. Also, their behavior under compressive loads is investigated using numerical methods. For this purpose, an appropriate 3D constitutive equation for SMPs was selected and Then, an analytical solution for torsional and bending response of SMP circular beam in a full cycle of stress-free strain recovery is derived. Also the 3D constitutive equations were implemented in the UMAT code in Abacus 2017 software and simulate angle changes due to different torsional and bending moments of a circular SMP beam as IVD. Internal compressive stress and displacement under different conditions were also investigated in compressive loading. Proper compliance of the results with the experimental findings in previous research sources shows the accuracy of the static biomechanical behavior of these materials as an IVD. It should be noted that all these results are taken in the L4-L5 spinal segment because the most damage to the lumbar disc is related to this disc.
