Análise numérica do comportamento termomecânico de fixadores ortopédicos arquitetados de ligas com memória de forma Ni-Ti.

Abstract

Shape memory alloy (SMA) are functional metallic materials with the ability to recover large deformations induced by mechanical loading (superelasticity) and recovery of pseudoplastic deformations after heat application (shape memory effect). Among all SMA, those of the Ni-Ti binary system have impacted several medical fields, especially in the specific area of biomedical applications of orthopedic implants, due to the combination of biocompatibility with good mechanical properties. Associated to these particular features of the Ni-Ti SMA, it is known that Architected Cellular Structures present as main characteristic a high ratio between load capacity and optimized weight. Thus, the Ni-Ti SMA architected mechanical devices can come to meet demands of specific biomedical applications in orthopedic implants can be designed to be geometrically similar to the bone tissue and structurally optimized to allow control of stiffness. Moreover, it is known that osseointegration depends, among other factors, of a continuous and biologically compatible compression force. In this context, the evaluation of the thermo-mechanical behavior of Ni-Ti SMA architected orthopedic fixators obtained by investment casting techniques is the motivation of this study based on numerical analysis. The aim is to start the feasibility evaluation of low-cost alternative technologies to manufacture Ni-Ti biomedical devices (implants). Therefore, in this work, some prototypes of architected orthopedic fixators such as Ni-Ti SMA bone staples, embracing and patellar concentrator were designed and analyzed numerically using the finite element method using the ANSYS commercial software, before moving on to the future production stage using investment casting. Pores (voids) of hexagonal, circular, diamond and reentrant topologies were inserted along the structure of fixator models, evaluating the influence of void topology on the mechanical response of each studied mechanical device in terms of variation of stiffness and force restriction as a function of relative density.