Masumi Saka
Tohoku University, Japan
Title: Crack / Damage Evaluation and Micro-Materials Fabrication in the Relation with Electric Field
Biography
Biography: Masumi Saka
Abstract
Evaluation of materials subjected to electric current and Joule heating has been studied by many researchers and fruitful results have been reported. In my presentation, crack problems in a conductive material are first discussed. The path-independent integral for an electric crack problem in a plate subjected to current is explained with its relations to Joule heating near the crack tip and the increase in electric resistance of the plate due to a unit crack extension. Regarding nondestructive evaluation of cracks, highly sensitive direct current potential drop technique, that is closely coupled probes potential drop (CCPPD) technique, is explained with its principle and superior characteristics for evaluation of closed cracks. Also evaluation of multiple cracks is mentioned. In the second, a topic in the field of micro and nano materials evaluation is explained, which is a subject of electrical failure of a metallic nanowire mesh due to Joule heating. Characteristic nature of sequential melting of nanowires in the mesh is explained for respective conditions of current control and voltage control. Next, electro migration (EM) phenomenon, which is atomic diffusion due to electron flow in high density, in metallic thin-film materials related to reliability of integrated circuits is discussed, where the effect of passivation on damage suppression is focused. Finally, application of EM to fabrication of micro materials of wire and sphere is explained, where the effect of temperature caused by Joule heating on the shape of formed micro material is mentioned. In addition, a comparison of EM with the other phenomena of atomic diffusion such as stress migration and ionic migration is discussed from a few points of view. Electric current and Joule heating are connected with materials science and evaluation on many equipments, machines and structures. As written above, four topics related to these phenomena are reviewed in this presentation.