Experimental and Theoretical Multiscale Analysis of Materials and Structures
July 4, 2011 — July 8, 2011
- Bernhard Pichler (Vienna University of Technology (TU Wien), Vienna, Austria)
Man-made structures and the materials making up these structures are hierarchically organized, i.e. characteristic heterogeneities manifest themselves at different, size-separated scales of observation. Physico-chemical processes taking place at small scales frequently trigger the apparent behavior at larger scales, and this is the motivation for bottom-up multiscale analysis of materials and structures. Holistic multiscale mechanics approaches start at atomistic scales. Related ab initio quantum methods and atomistic simulation techniques, which originate from statistical physics, are employed to enlighten, from knowledge on the chemical composition, the behavior of the smallest building blocks of materials, providing access to their mechanical stiffness and strength. Successive upscaling via intermediate nano-, micro-, and mesostructural scales, up to levels on which quasi-homogeneous properties of heterogeneous materials may be defined, is commonly based on two complementary approaches: numerical upscaling techniques and “Eshelby-based” closed form homogenization methods. These approaches are applicable to natural materials such as shales and rock, as well as to engineered media such as cementitious materials and metal alloys. Recent developments in the field include homogenization of elastic stiffness and of strength properties, considering either elasto-brittle or elastoplastic-ductile failure, and failure mechanisms such as bulk failure, interface failure, and microcrack propagation. Use of the resulting multiscale material models for the analysis of structures results in “multiscale structural simulations”. They allow for studying how microstructural processes govern the observed behavior of natural and engineering structures.
This completes holistic multiscale mechanics approaches.
Reliable multiscale modeling includes strict quantitative testing of the predictive capabilities of the developed material models. To this end, it is essential to combine theoretical with experimental approaches. Thereby, it is beneficial to collect experimental data on as many different scales as possible, in particular on the smaller hierarchical levels. Material characterization at microstructural scales is a dynamically evolving field. It includes 2D and 3D imaging techniques which are capable of providing insight into qualitative microstructural properties as well as of measuring strain fields and of tracking particles in granular media. As for mechanical testing at smallest scales, nanoindentation methods have been shown to be particularly powerful. Grid indentation techniques together with statistical deconvolution approaches open the door to identify volume fractions as well as elasticity and strength properties of quasi-homogeneous material phases constituting micro-heterogeneous materials, and nano-scratch-tests provide access to fracture parameters at smallest scales.
The aim of the course is to present theoretical fundamentals, the current state-of-the art, and future directions of “combined experimental and theoretical multiscale analysis of materials and structures” in a consistent, broad, and equilibrated format, using the language of Engineering Mechanics as the transport vehicle. The course will appeal to doctoral students and postdoctoral researchers from academia and industry with an interest in multiscale mechanics and a background in civil or mechanical engineering or in material sciences.
KEYWORDS: Composite materials, Multiscale analysis, Experimental mechanics, Materials testing.