The papers in this special edition came from lectures delivered at the Fifth International Conference on Materials Processing Defects (MPD-5) held at Cornell University July 18–20, 2007 at Cornell University in Ithaca, New York. The previous four MPD conferences were held in France and Germany with the aim of providing a timely forum for the presentation and discussion of cutting-edge approaches to the issues confronting researchers in understanding the occurrence of materials processing defects. While the historical focus of the MPD conferences has been on advanced simulation methods for predicting and preventing the occurrence of defects in manufactured products, MPD-5 also highlighted progress in understanding the micromechanical origins of defects and in quantifying the influence of defects on the success of the process and the integrity of the product.  Sessions included presentations covering methods that employ experiments, simulations, and combinations of the two, to reach improved characterization of defect initiation and growth. Contributions to the conference introduced emerging experimental and simulation technologies, including high-energy x-ray scattering and computational environments for multiscale modeling. The scope of processing was also expanded to include issues surrounding the occurrence of defects in the fabrication of MEMS devices.

The papers in this issue span the conference themes. There are process simulation papers devoted to formability of sheet metals, porosity growth in solid state welding, and voiding in polymer processing, as well as papers focusing on new methods to employ multiscale material representations in process modeling. A number of contributions concentrate on the micromechanics of defect formation, including microcracking around twin lamellae and strain localization around voids or second-phase particles. Several classes of materials are represented—from mineral wool to polymers to metallic alloys. There is also a set of papers that present the potential of synchrotron x-ray scattering methods for the characterization of microstructural defects in processed materials. Together, this collection of papers captures the breadth of the conference. Further, the content of these papers illustrates the application of new experimental and simulation technologies toward the goal of eliminating costly defects in both traditional and recent processing methods.

As editors of this special edition, we want to thank the Editor of Journal of Engineering Materials and Technology, Professor Huseyin Sehitoglu, from the University of Illinois for providing space for these papers. We also thank his Assistant, Linda Conway, for her effort and organization. Of course, we especially thank the authors of the papers.