Composite materials with complicated microstructures (such as ceramics) are important in many industrial applications. Previous analysis and computer simulations of their properties have been based on idealized simplifications of the microstructure. The goal of this project is to construct a finite-element computer model from a digitized image of a real microstructure, numerically distort the model, and identify the features of the microstructure responsible for the elastic and fracture properties of the material. The simulation uses object-oriented C++ in order to handle a wide variety of material grain types and a wide variety of computational elements. For example, the material could be a composite of grains with differing elastic moduli, differing degrees of elastic anisotropy, or differing fracture thresholds. It could contain voids or liquid regions. The computational elements could represent portions of single intact grains, fractured grains, or could be composite elements containing boundaries where two or more grains meet. The simulation takes advantage of state-of-the-art sparse matrix methods and is being designed with future parallel implementations in mind.
Currently, the project consists of two programs: OOF (``Object--Oriented Finite element'') which reads and analyzes a finite--element mesh, and PPM2OOF, which reads a ppm image file and creates a mesh. With them a user of the program can read an image (as in the first figure below), use a variety methods to select grains in the image and assign material properties, create a finite-element mesh for the material, apply a variety of boundary conditions, stresses, and strains, and analyze the resulting elastic deformation (as in the second figure below). Both OOF and PPM2OOF make use of an expandable general purpose graphical user interface being developed concurrently. Once a number of new features are implemented (e.g. general anisotropic materials, better analysis tools, faster and smaller input file formats) the programs will be made available to the public on the World Wide Web.
Caption: A micrograph of - used as input to PPM2OOF, and an intermediate step in its processing. In the second figure, the gray grains have been selected and material properties have been assigned.
Caption: Pattern of stresses induced in the - sample during tensile deformation by OOF.