Conceptual development of a knee simulating device for friction and wear testing of biomaterials

• Κύριος συγγραφέας: Μωραΐτης, Κωνσταντίνος
• Άλλοι συγγραφείς: Moraitis, Konstantinos
• Γλώσσα: English
• Έκδοση: 2022
• Θέματα: Knee simulators; Biomechanics; Conceptual design; Static structural analysis; Modal analysis; Εξομοιωτές γονάτου; Εμβιομηχανική; Θεωρητικός σχεδιασμός; Στατική δομική ακεραιότητα; Μελέτη ιδιοσυχνοτήτων

Over the past decades, the field of knee joint simulating devices has been constantly evolving. Different kinds of experimental simulators offered valuable insight over kinematic and loading behavior of a natural or artificial knee joint. However, as human life expectancy constantly increases, people tend to experience more and more fatigue around their knee joint, resulting in intense wear and pain, thus experiments over the new prosthetic technologies introduced have to accommodate accelerated and more demanding testing regimes of variant daily and sport activities. The main objective of this study was to develop a novel dynamic knee simulator that not only abide to but surpassed the requirements of the ISO 14243 Standard [1, 2], including the operating frequency,specimen mounting, positioning & alignment, range of motion and in-vitro conditions such as the incorporation of lubrication, temperature, and pH control systems. The first development step included the conceptual design of the simulator and its optimization using CATIA (Dassault Systèmes, Vélizy-Villacoublay, France) designing software, where factors such as design for assembly (DFA), design for manufacturing (DFM), ease of maintenance, safety measures and modularity determined the final result. Some of the key characteristics of the apparatus were the 6 degrees of freedom permitted between the two articulating bones with five controlled axes, the option to mount and investigate the performance of specimens regardless of their size, as well as a custom fluid test medium enclosing capsule that did not interfere with the outgoing procedure, even at the maximum flexion angle of 120 degrees. The next step was to investigate the structural integrity of the conceptual design introduced, by imposing severe static loading conditions to replicate complex daily activities by using the ANSYS Static structural software. Finally, through a modal analysis, vibration characteristics were inspected to ensure that the machine operated at a frequency different from its natural ones, so resonance could be avoided. Throughout the simulations, a mesh independence study in conjunction with non-linearities were included, to obtain more realistic and accurate results. According to the findings of this study, the introduced conceptual design of the knee simulating device was functional and reliable.