Mini-Symposia

Non-destructive 3D imaging techniques, such as X-ray, neutron and magnetic resonance computer tomography, are nowadays increasingly used for the identification of the 3D geometry of complex, spatially highly heterogeneous multi-phase materials. These techniques potentially permit to track changes in the structure of samples during mechanical tests or in-situ experiments. Recently, the adoption of 3D imaging techniques in different fields, e.g. to support or supply realistic data in computational models, increased thanks to significant technological improvements leading, in particular, to a reduced measurement time and higher spatial/temporal resolutions. Temporal resolution is especially important to obtain, during experimental tests, 3D images with any type of radiation (e.g., in tomography).

Although 3D imaging permits a significant leap forward into the material characterization, it also opens different challenges such as development of new imaging systems and image processing/analysis algorithms and the application of 3D imaging during experimental tests. As also evinced by the recent activation of the GAMM Activity Group on 'Data-driven modeling and numerical simulation of microstructured materials', such approaches are very actual and promising, especially when dealing with complex micro- and meso-structure arrangements. However, different issues still prevent their large diffusion, such as the efficient and statistically robust segmentation of targeted material phases out of the overall heterogeneous material structure. This mini-symposium aims at gathering new contributions in the field of 3D imaging/image analysis of highly heterogeneous materials.

The topics include, but are not limited to, the following:

• 3D imaging techniques and systems
• Numerical analysis using 3D imaging data
• Segmentation, geometry reconstruction and mesh generation
• Validation of simulated systems via 3D imaging
• Applications to multi-scale modeling
• 3D imaging during in-situ mechanical tests

In order to meet the requirements of tomorrow’s world engineers and architects must design extremely efficient structures. Making structures adaptive is a promising approach to reach that target. The efficiency of structures can be increased noticeably by the employment of sensors, actuators and control units. Hence modelling, simulation and evaluation of the active manipulation of deformations, forces, stiffness and vibrations in a structural system become important in recent years.

Adaptive structures play already an important role in the fields of mechanical and aeronautical engineering. In civil engineering applications this role becomes increasingly larger. The field of smart structures requires a very interdisciplinary approach of working. In this sense this mini-symposium will provide a platform for discussion and meetings. It covers topics concerning development, optimization, construction and evaluation of all kind of adaptive structures. As well as theoretical topics, modelling issues and results of numerical simulation or experiments can be presented at the mini-symposium.

Topics

• form finding and optimization of adaptive structures
• sensing and actuation in structures
• computational methods and simulation techniques
• structural control and identification
• engineering applications of smart systems

Today's high performance computing (HPC) systems are able to deliver peak performance at petascale. Even though this massive computing power enables simulation results of outstanding quality, a critical fact one has to regard is, that today's HPC systems generate their performance by facilitating hundreds of thousands of cores. With this massive parallelism several challenges concerning parallelization strategies, parallel input and output and data analytics arise affecting the efficient and sustainable usage of such systems. The Mini-Symposium will discuss how these challenges affect current and emerging applications in the fields of computational mechanics, computational biomechanics, optimization problems and data analytics.

Computational analysis of experimental results play a central role in the development and understanding of complex material behavior. This mini-symposium is intended for the presentation and discussion of latest scientific developments related to the computational simulation of mechanical tests under high strain rate condition, such as: Split Hopkinson Bar experiments, impact tests, drop weight tests and related experiments in the dynamic loading regime. Typically these tests lead to fracture and failure under high strain rate which has high technological and economic impact in many engineering applications.

This mini-symposium will cover academic and industrial computational mechanics problems including different materials such as metals, polymer, composites, biomaterials, concrete and ceramics. The goal of this mini-symposium is to gather a group of young scientists to discuss methods and approaches to bring together the disparate multidisciplinary aspects of computational mechanic under dynamic loading regime which are necessary for the future developments.

Computational contact mechanics and related disciplines have received fast-growing attention in recent years. This mini-symposium addresses the most important and active research topics in contact mechanics, including

• robust discretization methods for large deformations,
• accurate constraint enforcement techniques,
• efficient solution algorithms,
• parallel and high-performance computing,
• interface mechanics (friction, wear, adhesion, debonding, failure, etc.),
• multi-scale methods for contact,
• coupled multi-field problems,
• applications in biomechanics and bioengineering.

The aim of this mini-symposium is to provide a forum for young researchers to discuss promising developments and advances in computational contact mechanics and to give new impulses towards future research in this area.

Biomimetics is a continually growing research field as "learning from nature" is starting to play a more important role in improving, optimizing and developing of technical products. Biomimetics is an interdisciplinary field in which principles from engineering, physics, chemistry and biology are applied to develop materials, systems or machines having functions that mimic biological processes. By definition, a special focus lies on the interdisciplinary work between different sciences. Natural scientists and engineers go the whole way from understanding a principle in nature by investigating a biological role mode to transferring the findings to an application in technical products. This research field is therefore not only related to the development of technical applications, but also to fundamental research in the different disciplines.

The interplay of computational modelling with experiments also leads to reverse biomimetics. The aim of this approach is to infer, analyze and understand, through this interplay, the functional and regulatory mechanisms of biological systems in settings where experiments alone deliver only limited results.

This mini-symposium is addressed to researchers in engineering and natural sciences who contribute to biomimetic research with any role model and application through numerical simulations.

Multi-field porous media can be modelled using continuum theories of multiphase materials such as the Theory of Porous Media, Biot's theory and their extensions. The related applications are found in different fields of science and engineering, and cover a wide spectrum starting from simulation of damage and fracture in porous geomaterials towards understanding the mechanical behaviour of biological tissues. Due to the inherent interaction among distinct components, the mathematical modelling of such phenomena often results in complex systems of coupled partial differential equations in space and time. Thus, to propose a valid mathematical model, on the one side, and to choose an efficient solution strategy for the numerical treatment of the problem, on the other side, play crucial roles in the success or failure of the simulation process.

This mini-symposium aims at providing an opportunity for the young researchers interested in the continuum-mechanical modelling and numerical treatment of porous-media problems to present their recent advances and exchange ideas.

The analysis of damage evolution and failure plays a crucial role in the design of structures or structural components in numerous engineering applications. Further, there is a huge variety of materials, for which damage analysis is relevant, such as metals, polymers, composites, biological materials, and many more. In most cases, different failure modes need to be taken into account even on different scales. The aim of this minisymposium is to present and discuss recent trends in modelling of damage initiation and progression for different materials and the corresponding numerical treatment. Both, academic and applied talks, are highly welcome.

In this minisymposium, latest developments related to the mechanics of dissipative solids will be discussed with a special focus on plasticity, fracture and damage mechanics. The considered problems include local and gradient- extended models of phenomenologically based and crystal plasticity, brittle-to-ductile failure mode transition, crack propagation in inelastic solids and phase-field modeling of fracture in multi-physics problems. The goal is to address new constitutive models formulated on both the phenomenological and the micro-mechanical basis and examine their validity by comparison of simulations with experiments.

Today’s engineering problems are not restricted to one domain. Although the focus may be directed to answering a question of a specific discipline, problems cannot be considered separately. One has to understand interdependencies and regard neighboring effects in simulation models. Reasonable modeling assumptions, multi-scale phenomena as well as efficient, accurate and robust coupling or co-simulation methods have to be taken into account. Superimposed optimization and control strategies further motivate but also complicate the research between the coupled disciplines, mechanics, electromagnetics, hydraulics, fluid-mechanics, and physics in general. This symposium invites contributions on the following possible topics, but is not limited to

• Coupling methods
• Co-simulation methods
• Multi-scale methods
• Control schemes devoted to multi-physical phenomena
• Robust optimization methods focusing on multi-physical phenomena
• Practical examples from academia and industry highlighting challenges and solutions for multi-physical couplings

Multidisciplinary and structural design optimization is the pursuit of the optimal in engineering design. Especially with the advance of computational technology in recent years, multidisciplinary and structural design optimization has seen great developments, in both academia and industry. The scope as well as size of problems has increased drastically, which in turn has complicated both implementation and theory. Problems have far exceeded the static structural problems of the past to include parameter uncertainty, fluid–structure interaction and nonlinear problems (including even automotive crash cases).

In this minisymposium, the current state-of-the-research is to be presented in this ever advancing field in search of the optimum. Contributions are welcome in the following topics of interest:

• New algorithms for engineering optimization
• Efficient sensitivity analysis methods
• Approximation-based design optimization methods
• Novel topology and shape parametrization
• Postprocessing methods of design optimization results
• Inclusion of manufacturing aspects in design optimization, especially (but not limited to) for additive manufacturing
• Design optimization under uncertainty
• Design optimization of highly nonlinear problems, including crash
• Multibody dynamic applications
• Design optimization with fluid–structure interaction
• Structural-mechanical optimization with automotive and aerospace applications

This minisymposium is dedicated to discuss recent advances in multiscale modelling of materials with complex microstructures. Scale transitions in space and time, involving at least two scales, are of interest as well as computational issues and efficiency for the simulation of complex materials such as concrete or polycrystalline metals. The main focus of this minisymposium are the topics

• Homogenisation techniques and FE² methods for microheterogeneous materials
• Multiscale modelling of degrading materials
• Multiphysics phenomena across the scales
• Multiscale and multiphysics modelling of cementitious materials
• Creep, shrinkage, fatigue and fracture in cementitious materials
• Coupling between atomistic and continuum models
• Reduced order modelling and other numerical techniques to reduce the computational effort within multiscale strategies
• Numerical and experimental validation of multiscale techniques

A variety of durability issues in cementitious materials result from the interaction of transport processes combined with chemical reactions, e.g. the attack of chloride and sulphate ions as well as alkali silica reaction (ASR). Two major topological factors mainly influence transport processes in fracturing cementitious materials: (i) the complex micro-structure of the pore-space spanning multiple length scales (ii) the formed micro-cracks and macro-cracks by providing new pathways and enhancing the existing connectivity of the pore-space. Hence, modeling of transport processes and fracture of concrete structures is crucial for life-time prognosis and preventive maintenance of concrete structures. However, this is a non-trivial task as concrete is an extremely complex heterogeneous material with a random microstructure at different length scales. The objective of this mini-symposium will focus on recent advances, challenges, and on going research in multiscale computational models for describing transport processes, fracture and their mutual interactions within the context of the durability of concrete structures.

Among others, the following topics will be covered by the minisymposium:

• Modeling of fracture through novel numerical approaches (phase-field model, gradient (non-local) damage model, cohesive zone model, XFEM etc),
• Micromechanics models for permeability and diffusivity (tortuosity, percolation) in intact and microcracked concrete,
• Analytical and numerical modeling of the effect of cracks on permeability and diffusivity of concrete,
• Modeling of fracture induced by transport-driven chemical reactions, e.g. sulphate attack, ASR etc),
• Novel approaches of obtaining micro- and mesostructure of concrete,
• Multiscale modeling of transport processes and fracture linking micro- and macroscale.

In recent years, an increased activity in the scientific field of formulations and discretization methods for plate and shell structures can be observed. The topic has received a major boost due to the popularity of the isogeometric concept along with finite element methods using NURBS or B-Splines as shape functions. Here, one of the decisive features is a relatively easy control of continuity of shape functions, facilitating discretization of problems for which the weak form has a variational index of 2 or larger. This applies, for instance, to the classical Kirchhoff-Love thin shell model, which currently experiences a renaissance.

The proposed mini-symposium invites all contributions from the field of non-standard formulations and discretization methods for thin-walled structures, both from method development and application. Typical topics are expected to be, but not restricted to: spline-based discretizations, formulations based on subdivision surfaces, non-local (patch-based) or smoothed finite elements, meshless methods, finite cell methods, isogeometric analysis and integration of CAD and CAE, rotation-free formulations for plates and shells, non-linear analyses, treatment of boundary conditions or trimmed surfaces as well as multi-layer and solid shell elements.

The minisymposium addresses computational aspects of challenging engineering applications in technology and science. It is dedicated to strongly heterogeneous materials with multiple length scales and multiple interacting phases. The computational complexity of those problems may be driven by the consideration of real-data, for example arising from a X-Ray Computed Tomography or Field Ion Beam Tomography analysis, and/or by electro-, magneto-, hydro- or chemo-mechanical coupling phenomena.

Computational two-scale approaches employing a FE model at the RVE level for each point of the macroscopic problem have several limitations. First, the computing time is intense and the memory requirements are enormous. Second, systematic short-comings for nonlinear problems such as high number of iterations can occur and the robustness requirements for the RVE solver in nested finite element methods are demanding.

Reduced order models can help in several of the aforementioned aspects. They can reduce the computing time and the memory requirements on the one hand while they can also lead to new problem formulations on the other hand. Thereby, novel solution schemes can emerge as well as physical coupling can sometimes be understood in better way in the reduced framework.

Other promising applications for reduced order models are found in the many query context, e.g. for uncertainty quantification (UQ). The minisymposium welcomes contributions from various domains of model order reduction related to multiscale and multiphysics problems.

This Mini-Symposium will particularly focus on the experimental characterization, modelling, and simulation of coupled-field material behavior under electric and magnetic excitations. Such field-responsive functional materials can be used for actuation and sensing in smart and active materials. These fast growing smart materials include magneto-rheological elastomers, electro-active polymers, ferroelectrics, dielectric elastomer composites, and multi-ferroic composite materials. Experimental, numerical and theoretical methods that will be covered by the Mini-Symposium are advanced constitutive modelling, micro- and nano-characterization, phase field modelling, multi-scale and multi-physics material models, finite element implementations. The aim of the colloquium is to bring together researchers from the materials science, mechanics, and physics communities with common interests in coupled material properties and multi-functional materials. Hence, this will offer a platform for the presentation and discussion of advanced experimental methods, modelling and simulation techniques for multi-field-coupled phenomena.

Polymers, composite materials and their combination with metals are increasingly applied in various engineering application fields due to their specific material properties and their resource-efficient design possibilities. The material behavior of these materials is highly influenced by the material composition and the manufacturing process, leading to a non-homogeneous microstructure. Thus, predictive computational engineering methods need to account for this heterogeneous microstructure. The aim of this Mini-Symposium is to present holistic integrated simulation approaches in the fields of fluid mechanic and phase field simulations, structure optimization, as well as micromechanical simulations and homogenization methods. Therefore, the presented material models are associated with multiscale and Multiphysics modeling and constitutive modeling with respect to thermomechanical, kinetic (phase field), interface, damage or dynamic failure approaches.