The scientists have analyzed the mechanisms which reside behind the phenomenon of dynamic fragmentationof ductile metallic materials, that is, those that exhibit large permanent deformations when they are subjected to severe mechanical loading (steel, aluminum, tantalum...). Previously it was thought that dynamic fragmentation was basically triggeredby the inherent defects of the material (pores). What this research suggests is thatthe key mechanism which controls dynamic fragmentation may not be the porosity of the metallic material (defects), but the inertia effects.
One of the authors of the study, Komi Espoir N'Souglo, pointed out that "we have developed a simple analytical model to shed light into the mechanisms which control dynamic fragmentation in porous metals used in the aerospace industry and the civilian-security sector". This scientist works in this research line at UC3M within the European research project OUTCOME.
"This work provides a new approach for analyzing and designing structures for which it is important to predict and control the size of the fragments that form when a metallic material fractures under impact loading," added OUTCOME project coordinator, José Antonio Rodríguez, from the Department of Continuum Mechanics and Structural Analysis, and coauthor of the paper recently published in the journal Proceedings of the Royal Society A.
The identification of the mechanisms which control dynamic fragmentation of a material used to build protective structures will lead to the optimization of their manufacturing processes, reducing costs (economic, environmental...) and improving the quality of the final products. For example, in the case of protective structures of industrial facilities such as nuclear power plants, it is very important that these will be capable of withstanding extrememechanical loads such as explosions and impacts without fragmenting, thus maintaining their load-carrying capacity. "This knowledge can also be applied in the design of structures that can easily be fragmented, as in the case of space debris that sometimes falls to the earth's surface. In this case, the aim is that during the atmospheric re-entry the space debris will be fragmented so that the structures that eventually reach the earth's surface are not of a large size," the researchers explained.
OUTCOME is a project of the European Union Research, Technological Development and Innovation Programme (reference number GA 675602). This research consortium, coordinated by UC3M and formed by SMEs and Universities from Spain, France and Israel, aims to train early stage researchers in the analysis and design of structures subjected to extreme loading conditions, used in the aerospace and civilian-security sectors. These types of structures, such as components and parts of satellites, must be designed to withstand extreme temperatures, which can vary hundreds of degrees in short spans of time and extreme mechanical loads, such as hypervelocity impacts.
K. E. N'souglo, A. Srivastava, S. Osovski and J. A. Rodríguez-Martínez. Random distributions of initial porosity trigger regular necking patterns at high strain rates. Proceedings of the Royal Society A, rspa.royalsocietypublishing.org Proc R Soc A 0000000 (2018).
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