RESUMO
Objective To obtain the ratcheting strain of articular cartilage under different loading conditions,and construct the theoretical model so as to predict the ratcheting strain of cartilage.Methods The fresh articular cartilage obtained from the trochlear of distal femur was used as experimental subject.The ratcheting strain of articular cartilage was tested under cyclic compressive loads by applying the non-contact digital image correlation technique.The theoretical model was constructed to predict the ratcheting strain of articular cartilage with different stress amplitudes and stress rates.The results from predictions were compared with the experimental results.Results The ratcheting strain of cartilage increased rapidly at initial stage and then showed the slower increase with cycles increasing.The ratcheting strain increased with stress amplitude increasing when the stress rate was constant.However,the ratcheting strain decreased with stress rate increasing when the stress amplitude was constant.When the stress rate increased,the ratcheting stain decreased.The prediction results of the established theoretical model were in good agreement with experimental results.Conclusions The ratcheting strain of articular cartilage is proportional to the stress amplitude,and inversely proportional to the stress rate.The established theoretical model can predict the ratcheting strain of articular cartilage and provide guidance for the construction of tissue engineered artificial cartilage.