| The knee joint is one of the most importan joints human body movement,and it is also a good site for clinical disease.Articular cartilage is the main component of the knee joint.As an important load-bearing tissue of the human body,it plays an important role in transmitting load and buffering shock,and plays an important role in protecting the joints in motion.With the advent of the great era of health,more teenagers participate in a large number of sports activities on the one hand,and on the other hand,patients with knee arthritis have a new feature of rejuvenation.Therefore,we focus on the mechanical properties of articular cartilage of different ages and carry out comparison of differences.Mechanical fatigue is the main cause of articular cartilage defects,and the ability to regenerate after articular cartilage defects is extremely limited.Therefore,The ratcheting behavior of adult and young articular cartilage under rolling cyclic load and the mechanical properties of various composite loads were studied under the basic conditions of cartilage defect and different age groups.These studies are of great significance for the prevention and treatment of cartilage diseases,and can also provide a mechanical reference for the development of artificial cartilage.In this paper,the mechanical properties of pig knee joint cartilage under cyclic rolling load were studied.By controlling the different rolling speed and compression volume with the new rolling device,the mechanical properties of the intact and defective cartilage under continuous loading were compared by using digital image correlation technology.Based on this experiment,we used the 3-4 weeks old young cartilage and fresh adult cartilage as the research object,and carried out the cyclic fatigue rolling loading test to measure the ratcheting effect of rolling load under different conditions.It was found that the greater the compression,the greater the strain of the defective cartilage than that of the intact cartilage,and there was stress concentration at the cartilage defect.The higher the rolling rate was,the faster the strain would reach maximum stability.The rolling ratchet strain and strain rate of each layer of young cartilage were higher than that of adult cartilage.The difference between the superficial layer and the middle layer was the greatest,while the difference between the deep layer was not obvious.Compression has a great influence on ratcheting strain of adult cartilage and juvenile cartilage,especially in superficial layer.The ability of cartilage to resist rolling varies with age.Young cartilage tissue responds more quickly to deformation.The change of strain rate of adult and young cartilage ratchet is inversely proportional to the rolling rate,but the rolling strain rate of each group is continuously decreasing under the rolling rate.Rolling ratcheting behavior of adult and young cartilage with different defect sizes was studied.It was found that there was no stress concentration in cartilage with miniature defect.Ratcheting strain of conventional defect cartilage increased to a certain extent,while ratcheting strain of articular cartilage with maximum defect size reached its peak.Static creep-dynamic rolling loading,static creep-creep recovery combined with dynamic rolling loading and dynamic compression-rolling cyclic loading were carried out on adult and young articular cartilage.It was found that the compressive creep-creep recovery still had a large deformation,but the viscoelastic recovery of young cartilage was better.The stress and strain of different layers of adult and young cartilage were observed by DIC technique.It was found that ratcheting strain of young cartilage was higher than that of adult cartilage under various loads.The ratcheting strain is restrained by the axial compression creep,and the restraining effect is strengthened with the increase of creep time.However,the effect of axial cyclic compression on the later rolling cycle loading was smaller than that of rolling load after creep.The inhibition effect of young cartilage was stronger than that of adult cartilage.Besides the obvious change of ratcheting strain in superficial layer,it was also found that the rolling loading after compression cycle can cause higher ratcheting strain in the middle layer of young cartilage. |
