EXTENDED TWO COMPARTMENTAL SWELLING STRESS MODEL AND ISOTROPIC CAUCHY STRESS EQUATION FOR ARTICULAR CARTILAGE PROTEOGLYCANS

摘要

Proteoglycans (PGs), a constituent of cartilaginous tissues, have a negative fixed charge (FC) that causes an intratissue swelling stress [1]. This swelling stress is thought to balance tensile stress in the collagen network and contribute to the aggregate modulus of articular cartilage (AC) [1]. Stress constitutive equations that accurately characterize mechanical behavior of individual tissue constituents are crucial for the development of accurate total tissue models. The goal of this study is to extend the range of an existing two compartmental model for PG swelling stress by Basser et al. [1], and develop a continuum level equation for PG Cauchy stress. Specifically, the first aim is to increase the accuracy of the two compartmental model proposed in [1], to a lower range of FC density (FCD) typically found in bovine calf AC. The second aim is to use the extended model to develop a continuum level strain energy function and associated isotropic PG Cauchy stress constitutive equation.