Abstract
An aluminum foam can be characterized by its architecture and by the solid phase’ microstructure. Our aim is to link the foam's morphological and microstructural features with its mechanical properties thanks to X-ray tomography and finite element (FE). An approach combining X-ray tomography at different resolutions, image processing, and FE modeling was developed to take into account the influence of the intermetallics on the foam's fracture. First, the samples were scanned with “local” tomography, where the specimen is placed close to the X-ray source. These images allowed for observing intermetallics. Then an in situ tensile test was performed in the tomograph to follow the sample's deformation at low resolution. The images obtained from local tomography were processed to create one low-resolution image of the initial sample including details from high resolution. This was done by a series of thresholding and scaling of the high-resolution images. This image was used to generate a FE mesh. A FE input file was obtained thanks to Java programs associating the elements to the phases. At the local scale, the calculated stress distribution and the images of the struts were analysed. Our work confirms that the presence of inclusions can explain the fracture of struts.
Highlights
Cellular metals have received more and more attention due to their unique combination of properties [1]
Some voxels at the interface between the phases can be assigned to the air whereas they belong to the solid phase or inversely
This paper reports an original approach based on X-ray tomography to characterize and model the mechanical behavior of an aluminum foam taking into account its microstructural features at two length scales
Summary
Cellular metals have received more and more attention due to their unique combination of properties (i.e., lightness, shock and sound absorption) [1]. 3D microstructural characterization at a higher resolution was made possible using the so-called "local tomography" mode [16, 17] In this mode, the sample is placed near the X-ray source and a high-resolution image of the irradiated part of the sample is obtained. These high-resolution images can be analysed to characterize the mechanical behavior of the samples, especially the initiation and the propagation of cracks [16] This approach has been developed initially for the study of the tensile fracture of Duocel foams. A tensile test was chosen to follow the progressive fracture of the foam and to make the link with its microstructural features. The highresolution images obtained from local tomography were processed to create a FE model at low resolution, including the presence of the inclusions in the calculation. The stress fields calculated by FE taking into account the inclusions enable us to explain the fracture of some struts in which no architectural feature was found
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