Optimal layout design of three-dimensional geometrically non-linear structures using the element connectivity parameterization method

The topology design optimization of ‘three-dimensional geometrically-non-linear’ continuum structures is still difficult not only because of the size of the problem but also because of the unstable continuum finite elements that arise during the optimization. To overcome these difficulties, the element connectivity parameterization (ECP) method with two implementation formulations is proposed. In ECP, structural layouts are represented by inter-element connectivity, which is controlled by the stiffness of elementconnecting zero-length links. Depending on the link location, ECP may be classified as an external ECP (E-ECP) or an internal ECP (I-ECP). In this paper, I-ECP is newly developed to substantially enhance computational efficiency. The main idea in I-ECP is to reduce system matrix size by eliminating some internal degrees of freedom associated with the links at voxel level. As for ECP implementation with commercial software, E-ECP, developed earlier for two-dimensional problems, is easier to use even for three-dimensional problems because it requires only numerical analysis results for design sensitivity calculation. The characteristics of the I-ECP and E-ECP methods are compared, and these methods are validated with numerical examples. Copyright q 2006 John Wiley & Sons, Ltd