Investigating Mechanical Properties of Porcine Articular Cartilage by Flat Plate Compression Tests

An inverse iterative finite element analysis procedure was developed to investigate mechanical properties of porcine articular cartilage under compression load. Specimen consists of articular cartilage and bone was cut from porcine femur for this study. The specimen was mounted on metal base plate and the compression tests were performed by using material test machine with flat compression plate. The ramp-hold compression tests with different ramping displacement rates and long-term compression test with very low displacement rate were performed on the specimens. The force and compression displacement as function of time were recorded. The profile of specimen was obtained from for generating the geometry model of specimen. The finite element model which consists of bone and cartilage parts was generated from the geometry model of specimen. In this study, bone and cartilage were considered as linear elastic material and hyperviscoelastic material respectively. The generalized pattern search method was used for the optimization process to find the long-term hyperelastic and viscoelastic parameters of cartilage by minimize the experimental loading forces and the reaction forces computed form finite element analysis. The results shows 2

nd

order reduce polynomial hyperelastic model with two viscoelastic time constants can well describe the mechanical response of articular cartilage and bone specimen under flat plate compression.