The effect of cellular architecture on the ductility and strength of metal foams
- PDF / 1,798,406 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 12 Downloads / 225 Views
1188-LL02-03
The effect of cellular architecture on the ductility and strength of metal foams K. R. Mangipudi and P. R. Onck Zernike Institute for Advanced Materials, Applied Physics Department, University of Groningen, Nijenborgh 4, 9737AG, Groningen, The Netherlands. ABSTRACT A multiscale finite element model has been developed to study the fracture behaviour of two-dimensional random Voronoi structures. The influence of materials parameters and cellular architecture on the damage initiation and accumulation has been analyzed. The effect of the solid material’s strain hardening, relative density and architectural randomness on the ductility and fracture strength of the cellular solid are investigated. The results suggest materials-design directions in which the heat treatment, the solid material properties, its microstructure and the cellular architecture can be tuned for an optimized performance of cellular materials.
INTRODUCTION In many engineering materials for structural applications the ultimate material would be the one that is both strong and tough/ductile. The traditional approach in metallurgy is to employ alloying and/or heat treatment to modify the physical microstructure of the metal (grain-size, impurities, second phase particles, etc.). Compared to dense materials, cellular materials have a two-level microstructure: (i) the solid microstructure of the constituting material and (ii) the cellular architecture. The latter describes the architectural information on how the solid material is distributed into space, forming a three-dimensional interconnected network. The cellular architecture puts in additional degrees of freedom which opens the exciting opportunity for a materials-by-design approach for cellular metals. The overall fracture behaviour of metal foams is closely related to the microstructure of the cell-wall material. In open-cell foams made by investment casting, grain-boundary-covering, plate-like precipitates were found to be the primary cause for a knock-down in ductility. Ductility-enhancing heat treatments often result in reduction of the yield stress and an increase in hardening capacity. The overall behaviour of the structure depends not only on the underlying solid material microstructure, but also sensitively on the cellular architecture, e.g. the cell size and shape distribution, the cross-sectional geometry of the strut, the strut connectivity and its relative density. The goal of this work is study these dependencies using a multiscale modelling framework that takes all these ingredients into account and enables optimal design of cellular materials. MODEL A finite element model based on a Voronoi description of the cellular structure is used. Layered Euler-Bernoulli beam elements in a co-rotational framework [1] are used to model the strut deformation. Figure 1 outlines the modeling approach and the exchange of information among various length scales. Each beam element contains fibers or integration points at which
the axial strain and curvature increments from the beam fin
Data Loading...
