ESTIMATING THE EFFECTIVE YOUNGS MODULUS OF SOFT-TISSUES FROM INDENTATION TESTS - NONLINEAR FINITE-ELEMENT ANALYSIS OF EFFECTS OF FRICTION AND LARGE-DEFORMATION

A nonlinear finite element model was developed to investigate the biom echanics of indentation, particularly the influence of friction and la rge deformation on the calculation of the effective Young's modulus fr om the cylindrical, flat-ended indentation test of soft tissues. A new kappa table was given for calculation of the effective Young's modulu s to account for the effects of layered geometry with consideration of the larger deformation. The results indicate that the effect of frict ion on the calculation of Young's modulus becomes significant with a l arge aspect ratio and with a large Poisson's ratio. It is found that t he factor kappa increases almost proportionally to the increase of the indentation depth, especially obvious with a large Poisson's ratio nu and a larger aspect ratio a/h. (C) 1997 IPEM. Published by Elsevier S cience Ltd.