Dr. Harry Millwater is the Samuel G. Dawson Professor of Mechanical Engineering at the University of Texas at San Antonio. He has 30 years of experience in structural reliability methods. He has prior experience developing the Nessus and Darwin probabilistic codes. Currently he leads the development of the probabilistic airframe risk assessment codes, Smart|LD & Smart|DT, for the FAA. He is the originator of the hypercomplex finite element method under funding from AFRL, AFOSR, ONR, and DoD.
The hypercomplex finite element method, ZFEM, is an extension of the traditional finite element method to hypercomplex algebras. The advantage of the method is that highly accurate arbitrary-order derivatives can be obtained with respect to shape, material or loading parameters as a direct output of the analysis. The key concept is the introduction of imaginary nodal coordinates, which are used to perturb the geometry and to store the derivatives. The method has been implemented as a user element within the Abaqus commercial finite element program. The method is general but has natural applications in fracture mechanics in that the energy release rate can be computed simply and with high accuracy, obviating the need to compute the J integral, for both linear and nonlinear materials. Applications to linear elastic, thermal fracture, elasto-plastic, and progressive fracture will be presented.