THE ACCURACY OF DIGITAL IMAGE-BASED FINITE-ELEMENT MODELS

Digital image-based finite element meshing is an alternative approach to time-consuming conventional meshing techniques for generating reali stic three-dimensional (3D) models of complex structures. Although not limited to biological applications, digital image-based modeling has been used to generate structure-specific (i.e., nongeneric) models of whole bones and trabecular bone microstructures. However questions rem ain regarding the solution accuracy provided by the digital meshing ap proach, particularly at model or material boundaries. The purpose of t his study was to compare the accuracy of digital and conventional smoo th boundary models based on theoretical solutions for a two-dimensiona l (2D) compression plate and a 3D circular cantilever beam. For both t he plate and beam analyses, the predicted solution at digital model bo undaries was characterized by local oscillations, which produced poten tially high errors within individual boundary elements. Significantly, however, the digital model boundary solution oscillated approximately about the theoretical solution. A marked improvement in solution accu racy was therefore achieved by considering average results within a re gion composed of several elements. Absolute errors for Von Mises stres s averaged over the beam cross section, for example, converged to less than 4 percent, and the predicted free-end displacement of the cantil ever beam was within 1 percent of the theoretical solution, Analyses a t several beam orientations and mesh resolutions suggested a minimum d iscretization of three to four digital finite elements through the bea m cross section to avoid high numerical stiffening errors under bendin g.