Numerical Simulation And Experiment On Mechanical Properties Of Articular Cartilage

Cartilage with complex structure is a porous viscoelastic material. The direction ofarrangement of collagen fibers in different layer regions directly affects the mechanicalproperties of the cartilage layer region. It is very important to use the method of numericalsimulation for studying cartilage damage and repair through experimental measurements ofcartilage mechanical parameters of the different layers. Because of the relatively small size ofthe cartilage, it is very difficult to measure mechanical parameters of cartilages by tensile test.The paper for main problems in the tensile test of cartilages, first by porcine articularcartilage compression testing, measuring the displacement of cartilage areas of differentlayers, according to the characteristics of the displacement determines the size of areas ofdifferent layers of cartilage, and then designed the cartilage and substrate stretching models.Model includes two forms of direct bonding and embedding bonding to simulate stretchingprocess of different layers of the cartilage area in numerical way, displacement fields andstress-strain fields of stretching cartilage in different layer regions are derived. The numericalresults show that using the way of embedded bonding can make stress of articularwell-distributed without stress concentration, so it is a good way of bonding methods. Thedistributions of the displacement, stress, strain of stretching model with different layers areanalyzed by FEA after the final size of stretching model determined. And then thedistributions and variations of the stain along the different direction of different layers ofarticular cartilage are illustrated by the stretching experiment on prepared stretching modeland digital image technology. Compared with the results of experiment and numericalsimulation, the numerical results are obtained by modifying mechanical parameter valuessuch as elastic modulus, etc as consistent as possible with experimental results.The normal stress and normal strain of articular cartilage are gained by numericalcaculation on stress of stretching model according to the formula of materials mechanics. Thetorsion model is constructed and simulated by above method. The torsion jig is designed byPro/E and manufactured as a utility for torsion experiment. Compared with the results ofexperiment and numerical simulation, the numerical results of torsion experiment are obtainedby modifying mechanical parameter values as consistent as possible with the experimentalresults. It is the foundation of measuring the mechanical parameters by stretch and torsionexperiments that is researched in this paper.