The Workshop is organised by the Chair for Microsystems Technology and the Chair of Applied Electrodynamics and Plasma Technology at the Ruhr University Bochum. For further details and registration please see the link below.
MAT4HY.NRW und H2Raum laden erneut zur Vernetzung: Entwickeln Sie gemeinsam mit uns Ideen zu Projekten und Wasserstoffthemen weiter und testen Sie Ihr Wasserstoffwissen!
Weitere Informationen, Agenda und Anmeldemöglichkeit zur Veranstaltung:
The behavior of a material is highly influenced by its microstructure. In order to use a material resource-
efficiently, it is important to know its behavior as precisely as possible and to be able to simulate it in a time-
efficient manner. To capture complex local microstructural effects such as phase transformations or crystal
plasticity, we present a two-scale approach which utilizes a finite element (FE) formulation at the macroscale and
a fast Fourier transformation (FFT)-based description at the microscale [1, 2]. We would like to present the two-
scale method’s ability to model highly resolved thermo-mechanically coupled problems and its application in the
field of microstructural evolutions in polycrystalline materials, e.g. [4]. An additional focus of our presentation is
on the introduction of model order reduction techniques. We propose an approach, which is based on an
adaptively chosen reduced set of Fourier modes [3] and thus decreases the high computational costs of the FFT-
based microstructure simulation.
[1] J. Spahn, H. Andrae, M. Kabel, and R. Müller. A multiscale approach for modeling progressive damage of composite materials using fast
fourier transforms. Computer Methods in Applied Mechanics and Engineering, 268, 871-883, 2014.
[2] J. Kochmann, J. R. Mianroodi, S. Wulfinghoff, B. Svendsen, and S. Reese. Two-scale, FE-FFT- and phase-field based computational
modeling of bulk microstructure evolution and macroscopic material behavior. Computer Methods in Applied Mechanics and
Engineering, 305, 89-110, 2016.
[3] C. Gierden, J. Waimann, B. Svendsen, and S. Reese. FFT-based simulation using a reduced set of frequencies adapted to the underlying
microstructure, Computer Methods in Material Science 21.1, 51-58, 2021.
[4] J. Waimann, C. Gierden, and S. Reese. Simulation of phase transformations in polycrystalline shape memory alloys using fast Fourier
transforms. Proceeding of ECCOMAS Congress (Scipedia), 1-9, 2022.
A rapidly expanding research area involves the development of routes to shape programmable three-dimensional (3D) structures with feature sizes in the mesoscopic range (that is, between tens of nanometres and hundreds of micrometres). A goal is to establish methods to control the properties of materials systems and the function of devices, through not only static architectures, but also morphable structures and shape-shifting processes. Soft matter equipped with responsive
components can switch between designed shapes, but cannot support the types of dynamic morphing capabilities needed to reproduce continuous shape-shifting processes of interest for many applications. Challenges lie in the establishment of 3D assembly/fabrication techniques compatible with wide classes of materials and 3D geometries, and schemes to program target shapes after fabrication.
In this talk, I will introduce a mechanics-guided assembly approach that exploits controlled buckling for constructing complex 3D micro/nanostructures from patterned two-dimensional (2D) micro/nanoscale precursors that can be easily formed using established semiconductor technologies. This approach applies to a very broad set of materials (e.g., semiconductors, poly-
mers, metals, and ceramics) and even their heterogeneous integration, over a wide range of length scales (e.g., from 100 nm to 10 cm).
To allow realization of 3D mesostructures that are capable of qualitative shape reconfiguration, we devise a loading-path controlled strategy that relies on elastomer platforms deformed in different time sequences to elastically alter the 3D geometries of supported mesostructures via nonlinear buckling. I will also introduce a recent work on shape programmable soft surface, constructed from a matrix of filamentary metal traces, driven by programmable, distributed electromagnetic forces that follow from the passage of electrical currents in the presence of a static magnetic field. Under the guidance of a mechanics model-based strategy to solve the inverse problem, the surface can morph into a wide range of 3D target shapes and shape-shifting processes. The compatibility of our approaches with the state-of-the-art fabrication/processing techniques, along with the versatile capabilities, allow transformation of diverse existing 2D microsystems into complex configurations,
providing unusual design options in the development of novel functional devices.
The 6th Materials Chain International Conference (MCIC) brings together researchers, scientists and industry professionals to explore the latest advancements and applications of inorganic functional materials. The event will feature 12 invited talks and a poster session, providing a platform to discuss cutting-edge research, share insights and foster collaborations.
Abstract:
In this presentation, Noel will discuss the use of multiscale tests and models to investigate the deformation behaviour of a martensitic (body centre cubic) steel P91, used in power plant piping. At the microscale electron back scattered diffraction (EBSD )is used to track the orientation changes in the material, while digital image correlation is used to monitor strain at the meso-scale. A novel shear test specimen has been developed to allow large deformations ( > 40% strain) to be monitored in-situ in a scanning electron microscope (SEM) in conjunction with EBDS measurement. Micro-pillar compression using a nano-indenter is also used to examine deformation of a single crystal (grain) of the material and to determine the relevant slip systems to be used in a crystal plasticity finite element model. The ability of the crystal plasticity model to predict the deformation in the shear test and micropillar compression test is assessed.
Bio:
Noel O’Dowd has been Professor of Mechanical Engineering at the University of Limerick since 2006. Prior to this, he was Reader at the Department of Mechanical Engineering, Imperial College London. From 2010 to 2016 he was director of the Materials and Surface Science Research Institute (now part of the Bernal Institute) at the University of Limerick. Noel’s research interests are in the mechanical behaviour of materials, including fracture mechanics, computational mechanics and constitutive modelling, He published over 150 articles on these topics with web of science h-index of 33. His research on constraint based fracture mechanics and residual stress have been incorporated into the British Standard’s Guide to methods for assessing the acceptability of flaws in metallic structures (BS 7910).
The Materials Science and Technology Seminar is jointly organized by the IM (Institute for Materials) and ICAMS (Interdisciplinary Centre for Advanced Materials Simulation). Mem-bers of the RUB Materials Research Department MRD, the Materials Chain and of the DGM Regionalforum Rhein-Ruhr are cordially invited to participate in the seminar.
Phase-field simulations based on the Landau-Ginzburg-Devonshire theory extend the time and length scales in comparison to molecular dynamics (MD) simulations. The interpretation and adaption of the continuum model parameters is not trivial, but crucial for a correct up-scaling of MD results from ideal and defective ferroelectric single crystals.
MD simulations using a core-shell potential for polarization switching in ferroelectric barium titanate (BTO) with and without vacancy defects are carried out. Crucial material properties such as elastic and piezoelectric tensor components, kinetic coefficients, as well as domain wall characteristics are extracted from the MD data to adjust the anisotropic gradient energy. To generate a complete energy landscape, a proposed parametrization workflow involves determining all coefficients for the 6th order Landau polynomial from polarization reversal characteristics. Polarization switching in BTO involves localized nucleation and subsequent domain growth, driven by an applied electric field. MD simulation data proves the role of thermal activation in domain nucleation, resulting in a notable scatter in coercive fields within small systems. From statistic analysis of this data we calculate the activation parameters for BTO that govern polarization switching at coercive fields not only for perfect, but also those containing vacancy defects, and the domain wall energies. An approach comparable to the nudged elastic band method is applied in the phase-field simulations to probe the barriers by transitions over the critical nucleus.
The method is important for phase-field simulations of domain nucleation and domain wall motion in presence of point defects carrying mono- or dipolar electric fields as well as elastic strain fields, and for the motion and interactions of multiple domain walls.
Our research focuses on employing Focused Ion Beam (FIB) and Atom Probe
Tomography (APT) to investigate the atomic and molecular signatures in
biological systems. We will first present how to tune various materials using
charged particle beams to fabricate unprecedented 1D and 3D nanostructures.
The fundamental insights into dynamics provide knowledge for precisely
controlling these nanostructures across a wide spectrum of applications.
Additionally, we explore new routes for APT imaging, including the use of
graphene coating to ‘disguise’ the surface of insulated and biological samples.
Successful APT imaging of biological targets, such as antibiotic-resistant bacteria
(superbugs) and proteins, provides us unique atom-by-atom views. New
opportunities for adding laser micromachining to achieve high-throughput
imaging will also be discussed.
The Materials Science and Technology Seminar is jointly organized by the IM (Institute for Materials) and ICAMS (Interdisciplinary Centre for Advanced Materials Simulation). Mem-bers of the RUB Materials Research Department MRD and of the DGM Regionalforum Rhein-Ruhr are cordially invited to participate in the seminar.
