Research On Biomechanical Properties And Bio-tribology Of Bionic Articular Cartilage

The wear of artificial joint is one of the important reasons for the aseptic loosening of joint replacement. When the artificial joint prosthesis is implanted into the human body, due to the wear of prosthesis interfaces, wear particles can cause localized interface osteolysis, resulting in aseptic loosening of the prosthesis, which leads artificial joint replacement failure finally. To solve the wear of artificial joint and aseptic loosening fundamentally, it is necessary to improve the lubrication mechanism and design artificial joint matches of cartilage-cartilage by imitating the structure of the human body’s natural joint with the effect of antifriction, thus achieving the lubrication of artificial joint and reducing wear.Bionic articular cartilage structure is prepared by the method of chemical combination in this article and the biocompatibility of bionic cartilage structure is studied by MTT assay. Cytotoxicity grade is one, showing no cytotoxicity, according with the medical standards of biological material. Surface profile and mechanical property of bionic articular cartilage are similar to natural articular cartilage. Basing on viscosity-elasticity theory, models of creep and stress relaxation behavior for bionic articular cartilage are established and creep and stress relaxation mechanism are analyzed by the finite element method. Moreover, dynamic mechanical properties of bionic articular cartilage are systematically studied. The results show creep deformation and pore flow velocity showed the relationship of exponential function. Multivariate Kelvin model and generalized Maxwell model can describe creep and stress relaxation behavior of bionic articular cartilage well. The storage modulus and frequency shows the relationship of logarithmic function. The storage modulus decreases gradually with liquid-solid ratio decreasing. Loss factor of bionic articular cartilage is more close to that of natural articular cartilage.Start-up friction behavior of bionic articular cartilage is investigated by finite element method to investigate fluid load support lubrication mechanism. Relationships of sliding speed-friction coefficient and load-friction coefficient are established with adsorption theory and friction mechanism of bionic articular cartilage is analyzed deeply. According to the two-phase theory, the relationship between sliding friction and fluid load support is established. The results show the internal fluid of the bionic articular cartilage exudates from contact surface to support load. The relationship equation between friction coefficient and fluid load support is 1.17 1.51 /f? ? ?W W. According to absorption theory, during sliding friction, the relationship between friction coefficient and load shows exponent(0.28? ?0.077 p). The relationship equation between friction coefficient and fluid load support is 1.4 1.83 /f? ? ?W W.According to human physiological movements, swing and torsional friction behavior of bionic articular cartilage are investigated and effects of load, swing angle and torsional angle on friction behavior are studied. Finite element method is used to establish the friction model of bionic articular cartilage to study fluid load support mechanism, contact mechanics characteristic and lubrication mechanism, and then the relationship between friction coefficient and fluid load support is established. The results show swing and torsional friction coefficients present a power exponent relationship with normal load, swing angle and torsional angle, and friction coefficient and fluid load support present a negative linear correlation. As load and angle increase, water loss of the contact interface increases, void ratio decreases and net structure of contact interface combines more closely, then the shear strength increases, the energy required for movement of friction increases, and thus the frictional resistance increases. When torsional friction occurs, the fluid at bionic articular cartilage surface slowly losses, which leads to the decline of fluid load support, the state of the contact interface turns into stick-slip state from full slip state. With the increase of load, the adhesion zone at bionic articular cartilage centre gradually increases, and with the increase of torsional angle, sliding tendency between Co Cr Mo ball and bionic articular cartilage increases, resulting in sliding zone increasing, adhesion zone of bionic articular cartilage center decreases.Bionic joint fossa with bionic articular cartilage layer is prepared by the method of chemical combination firstly and the hip joint simulator is used to study the property. The results show bionic joint fossa has excellent load buffering capacity, which is improved about 10% than the UHMWPE bionic joint. However, under high load cycle, fluid of bionic articular cartilage matrix loses largely, making fluid load support of bionic articular cartilage declines, which causes the wear of bionic articular cartilage, eventually leading to the rupture of bionic articular cartilage.