Computation of stress relaxation function and apparent viscosity from dynamic data of synovial fluids

Relaxation spectra and relaxation functions are calculated for some synovial fluids using the dynamic moduli data available in the literature. The importance of the relaxation function in relation to the rheological equation of state, both linear and nonlinear, is noted. Further, the calculation shows that a pathological synovial fluid can have a much shorter relaxation time than the fluid from young healthy specimens. Calculations of apparent viscosities for some synovial fluids are also made using the nonlinear BKZ rheological equation with the relaxation spectra obtained from the dynamic moduli. This procedure yields good agreement between the calculated result and experimental data.