Multiscale characterization of materials with distributed pores and inclusions and application to crack formation in an aluminum alloy

The paper reports a study on the mechanical behavior of materials containing pores and inclusions distributed over a wide range of length scales. Utilizing a wavelet-based multiscale process such microstructures are characterized and their effects on material properties is studied. In order to present the process in a semi-analytical fashion, the variance of the strain field for an approximated one-dimensional deformation problem is examined in detail. It is shown that with respect to crack initiation, there is a strong interplay between the distribution of pores and inclusions. Furthermore, their interaction with boundaries proves to be paramount. The process is applied to a particular cast aluminum alloy where pores are, in general, about two orders of magnitude larger than the silicon particles (inclusions). Results agree well with recent experimental reports on crack initiation where the interplay of pores, inclusions, and boundaries is observed, yet not explained on a fundamental basis. The present work extends recent efforts on porous materials [Frantziskonis G. Wavelet-based analysis of multiscale phenomena-application to material porosity and identification of dominant scales. Prob Eng Mech (this issue). PII: S0266-8920(2)00032-2] to include the interaction of pores at certain scales with inclusions at other scales as well as the interaction of both with boundaries. (C) 2002 Elsevier Science Ltd. All rights reserved.