The Simulation Study Of Mechanical Loading Promote Mass Transfer In Cartilage

Articular cartilage has a milky white and light blue color, and a smooth and translucent surface. It possesses multiple irreplaceable special features and plays an important role. But articular cartilage is the predilection site of clinical disease and it is of poor repair ability.Articular cartilage defect often causes joint dysfunction and other diseases, which affects the normal activities and daily life of human. Thus the study of articular cartilage has received wide attention at home and abroad. The normal transfer process of articular cartilage needs some external loads. In this paper, the Finite Element Method is used to simulate and analyze the articular cartilage transfer under the external loads. According to the simulation results,the regularity of mass transfer under different loads is studied, which provides a scientific basis for clinical treatment and tissue repair.According to the Fick’s second law, the law of conservation of mass and the mathematical identity between heat and mass diffusion in the theory of mass transfer, the simulation method of mass transfer was proposed. By using the finite element software- ANSYS to establish cartilage model, applying the static compression to load model, and comparing the simulation results with the experimental results, it is found that they have a good correlation. Thus the correctness of the simulation method is proved.By studying mass transfer under the dynamic compression and mass transfer under the different dynamic compression parameters on the basis of simulation model in the static compression, the results show that:(1) When applying load on the articular cartilage, the velocity of mass transfer becomes quicker.(2) Under dynamic compression loading, the mass transfer is very slow in the deep and the middle layer during the initial period, while it is very fast in the superficial layer. But with the increase of time, the concentration grows slowly in the superficial layer and tends to a stable density, while grows faster in the deep and the middle layer.(3) Compared the static compression with dynamic compression under the same compression amplitude, the solute inside cartilage diffuses more easily.(4) With the increase of dynamic compression amplitude, the solute concentration in cartilage increases with time prolonging and it is more obvious in the superficial layer. But with the increase of amplitude,solute diffusion is restrained. And the more amplitude, the more inhibitory effect.(5) An increased frequency of dynamic compression is benefit to the solute diffusion of all the layers.The greater of the frequency, the more obvious of the diffusion velocity increase. And the variation in the superficial layer is the most obvious.Through the study the law of mass transfer under the sliding load, some conclusions were obtained as follows:(1) The mass transfer in the deep layer is very slow during the initial period, while in the superficial and the middle layer is very fast. But with the increase of time,the concentration in the surface layer starts to grow slowly and tends to a stable density and inthe middle layer there is also a little decline, but the mass transfer speed in the deep layer grows obviously.(2) When the compression of sliding loading increased, the solute concentration in the cartilage are tend to upward with time prolonging. But with the increase of the compression, it produces the inhibitory effect to the solute diffusion. And the effect is the greatest in the middle layer and the smallest in the deep layer.(3) The increase of sliding velocity is benefit to the diffusion of the solute in each layer and the diffusion velocity of the middle and deep layer increases obviously. The simulation result provides a certain theoretical basis for further research.By investigating the effect of different model to the simulation results, it is found that:(1)When using ANSYS to simulate, it is not important to layer or not in similar studies. In order to simplify operation and improve efficiency, the layering of the articular cartilage can be cancelled.(2) When using ANSYS to simulate, there are differences between 3D model and2 D model. Due to that the construction and load-imposing of 3D model are more close to reality, we should give priority to the 3D model to improve the accuracy of calculation when studying mass transfer. The simulation results provide a certain basis for choosing the model of future simulation.