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Role of crystallographic orientation in material behaviour under nanoindentation: Molecular Dynamics study

Kurgan Aneta, Madej Lukasz

Materials Science Poland

2023

Vol. 41, No. 3

18--26

The mechanical properties of materials can be analysed under deformation conditions by various laboratory tests. However, such experimental investigations become extremely complicated and often even impossible at the lower length scales where the arrangement of the atomic planes is considered. In this case, computational materials science is a robust alternative to extend the capabilities of laboratory tests. Therefore, the molecular dynamics technique was selected in the current work to evaluate the role of the local grain crystallographic orientation during nanoindentation testing. A pure aluminium sample was selected as a case study. For the sake of clarity, two distinctively different crystallographic orientations cube {100}<001> and hard {110}<011> were investigated in a set of arrangements: monocrystalline, bicrystalline, and polycrystalline. The influence of the substrate and the neighbouring grains on the material response to local deformation was evaluated. The research used two types of indenters: spherical and sharp-tipped. Results obtained were analysed with respect to the arrangement of atoms and load-displacement curves. This research proved that the role of crystallographic orientation in material behaviour under nanoindentation should not be neglected during the interpretation of data from this test.

Evaluation of capabilities of the nanoindentation test in the determination of flow stress characteristics of the matrix material in porous sinters

Madej Lukasz, Legwand Adam, Setty Mohan, Mojzeszko Mateusz, Perzyński Konrad, Roskosz Stanisław, Chrapoński Jacek

Archives of Civil and Mechanical Engineering

2022

Vol. 22, no. 1

art. no. e21, 2022

Herein, we evaluate the nanoindentation test capabilities in the determination of flow stress characteristics of the matrix material in porous sinters. The Distaloy AB sample with 15% porosity after the sintering operation is selected as a case study for the investigation. 2D and 3D imaging techniques are employed first to highlight difficulties in identifying reliable nano hardness measurement zones for further properties evaluation. Then, nanoindentation test results are acquired with Berkovich tip pressed under various loads at different locations in the sample. Systematic indentations in the quartz sample are used as a cleaning procedure to minimize the effect of the possible build-up around the indenter tip. The representative indentation load range is selected based on the extracted material characteristics. With that, the stress–strain response of the sinter matrix material is identified. The reliability of the determined flow stress curve is confirmed with the use of conical nanoindentation measurement results and finite element simulations. Obtained results show that it is possible to calculate reliable flow stress characteristics of the matrix in the porous samples, with the assumption that experiments under various loading conditions and from various locations in the matrix are performed. It is also pointed out that various indentation loads should be used to eliminate the influence of the pile-up or scale effects that affect the overall material response.

Capturing local material heterogeneities in numerical modelling of microstructure evolution

Madej Lukasz, Sitko Mateusz, Fular Aleksander, Sarzyn Rafal, Werminski Mariusz, Perzynski Konrad

Journal of Machine Engineering

2021

Vol. 21, No. 4

29--48

The work focuses on developing the complex digital shadow of the metallic material microstructure that can predict its evolution during metal forming operations. Therefore, such a digital shadow has to consider all major physical mechanisms influencing the particular investigated phenomenon. The motivation for the work is directly related to the development of modern metallic materials, often of multiphase nature. Such microstructure types lead to local heterogeneities influencing material behaviour and eventually macroscopic properties of the final product. The concept of the digital material shadow, stages of the model development, and examples of practical applications to simulation of microstructure evolution are presented within the work. Capturing local heterogeneities that have a physical origin and eliminating numerical artefacts is particularly addressed. Obtained results demonstrate the capabilities of such a digital microstructure shadow approach in the numerical design of final product properties.