Prediction of the response of microstructured materials on an external loading can be achieved by means of various methods. In (quasi)statics, homogenization methods are suitable in most situations, but this is not the case for functionally graded materials, e.g. Strain gradient models are quite sufficient if only the influence of a microscale length is taken into account. The most general approach is provided by generalized continuum theories, which include microdeformation into consideration. One more possibility is the introduction of internal variables for the description of microstructure.

In the paper, we compare different descriptions of microstructured solids on the simple example of wave propagation in the one-dimensional setting. In the classical continuum mechanics the existence of a microstructure is neglected. Thus, the classical wave equation needs to be modified to include the observed dispersive effects due to the microstructure. We consider modifications of the wave equation which follow from homogenization, continualization of lattice models, and from generalized continuum theories. The linear version of the Boussinesq equation for elastic crystals, the Love-Rayleigh equation for rods accounting for lateral inertia, the Maxwell-Rayleigh model of anomalous dispersion, etc., are compared with dispersive wave equations obtained by means of single and dual internal variables.
 

in collaboration with Mart Ratas

In case of 1D wave propagation the discrete spectral analysis is very helpful method in order to analyze the space-time behavior of different wave structures. Here we generalize the method to 2D case. The Kadomtsev–Petviashvili equation is applied as a model equation. For numerical integration the pseudo-spectral method is applied. We demonstrate how 2D spectral characteristics can be applied for analysis of complicated wave structures that can be formed from different initial pulses in case of the Kadomtsev–Petviashvili equation. Recurrence phenomenon, temporal periodicity and temporal symmetry of the solution will be discussed.

in collaboration with Anne Schäuble, Prof. Manfred Bischoff

Standard explicit dynamic simulation relies on diagonal or lumped mass matrices. Lumped mass enables a trivial computation of the nodal accelerations from the total force vector. Moreover, critical time step estimators and contact-impact algorithms for such mass types are well understood and developed. A disadvantage of the exlicit time integration with the lumped mass is huge number of the time steps even for short time dynamics. Recently, several approaches for reciprocal mass matrix that allows higher time steps and reduction of the total computational cost were proposed. A reciprocal mass is a sparse inverse of mass matrix that usually has a mask/structure of consistent mass or stiffness matrix. It can be constructed directly and cheaply either with variational or with algebraic methods. Achievable speed-up with respect to lumped mass is from 20% to 50%.

In this talk, an overview of existing approaches of construction reciprocal mass matrices is given and recent advances in reciprocal mass matrices for impact algorithms, time step estimation and assessment of the error in heterogeneous materials are presented. 

The spider fang is a natural injection needle, built as a multi-scale composite material with outstanding mechanical properties. In this study we introduce a hierarchical modeling for the spider fang, based on computer tomography and SAXS measurement, and analyze the correlation between the fang architectural motifs and its macroscopic elastic behavior. Analytical methods and Finite-Element simulations are used for the mechanical analysis and the effects of small- and large-scale structural gradients on the macroscopic mechanical properties are investigated.

It is found that the multi-scale structural gradients of the spider fang optimize its performances in term of load-bearing stiffness and strength, and that the naturally evolved fang architecture provides optimal mechanical properties compared to other alternative structural configurations.

The seminar will present overview of computational mechanics research at the Centre for Multifunctional and Composite Materials of RMIT University, Australia. Our research covers both fundamental and applied aspects of material behaviour and failure processes. This presentation will encompass computational modelling of material deformation, damage and fracture using multi-scale techniques in conjunction with mesh-less methods, novel composite materials development and damage tolerance structural optimisation.
Multi-scale modelling of damage and fracture progression linking nano to macro scales and associated development of coupled computational modelling tools will be highlighted. The strengths of mesh-less methods will be illustrated with reference to both low to high-speed impact induced fractures and small to large scale problems. These include several dynamic fracture and fragmentation processes, such as hypervelocity impact fracture, nano-scale machining, large scale geo-mechanical failures (magma intrusion, caving, slope stability, etc).
One of our core areas to be presented is novel impact and blast resistant, light weight composite material developments for aerospace components subjected to high-speed loading and extreme deformations, as occurs in the cases of debris impact on spacecrafts, bird strike on aircraft engines, blast induced failures, etc. Lastly novel shape and topology optimisation methodologies for damage tolerance optimisation, i.e. maximising the residual strength and fatigue life, of aero-structures will be highlighted. Case studies from projects with Royal Australian Air Force and Defence Science and Technology Organisation will be presented to demonstrate the practical implementation and utilities of the developed design and analysis methodologies.
 

 The lecture will be addressed the following topics in Additive Manufacturing (AM) of metals:

· Draw some observations from various attitudes to AM world-wide.
· Review shortly various additive manufacturing technologies, their virtues and drawbacks.
· Address cases, in which additive can/cannot replace conventional manufacturing - problems with distortions, variability in micro-structure and consequences, etc.
· Comparison of additive and conventional micro-structures and their impact on macro-mechanical properties: strength, fragility, fatigue, impact resistance, etc.
· Use of additive manufacturing for meta-materials (auxetic and other) for the purposes of "energy absorption or distribution" and "mechanical strength with low weight".
· Additive manufacturing process certification and/or serial production of components - competitiveness in terms of both function and price.
· Design of components for Additive Manufacturing - material only there "where needed" and the related development of software (e.g. topology optimization).
· Future of AM - visions and expectations.
· Describe and introduce FIESC - SENAI focus in AM.

Dr. Edson Costa Santos spent more than a decade in various laboratories related to Additive Manufacturing in Europe, South America and Japan. In the presentation, it will be drawn from his experience, and present a view of current AM layout – technologies, directions and main leaders.
 

A Smart Grid demonstrator was implemented within the framework of the "Israel Smart Grid
– ISG" Magnet project. The goal of the project was to implement and develop technologies for
optimizing and controlling Smart Grids. The main achievement of the project is its operation
system which is hierarchical in nature. Namely, the control and commands are not centralized
but rather distributed from top levels downwards. Every such control level can also be selfcontained.
The project consists of a demonstration of rout of electric power that is delivered to
a modern "Procumer" (Producer and Consumer), precisely upon its request, with minimum
power failures, energy optimization and minimal electricity costs. The demonstrator is
constructed in various sites and controlled by a virtual network. The virtual network consists
of controllable loads and some generators. Some of the actual controllable loads are motors,
air conditioning chiller, air treatment units and others. The loads are controlled by an
Intelligent Home Gateway Unit (IHGU) which operates in accordance to the contract between
the grid and the prosumer or consumer. The system also controls, via web services, two
remote sites of the Israel Electric Company – IEC, consisting of a virtual neighborhood.

Large-scale dynamics models of power systems are mostly based on time-varying phasors.
However, with increasing integration of distributed and renewable sources into existing power
grids, the assumption of time-varying phasors (or quasi-static models) becomes less accurate,
and may even lead to misleading conclusions regarding the system dynamics and stability.
During the lecture I will briefly review and compare several types of dynamic models,
describe several paradoxes that result from misuse of these models, and describe our group's
approach to this problem.

Pokusíme se ukázat, že určité nestandardní volby funkcí a(.), b(.) přirozeně vedou k popisu „nestandardních” mechanických jevů: Coulombovo tření, neroztažitelná struna, či, obecněji, náraz tělesa na pevnou stěnu. Díky jazyku NSA zároveň zůstaneme v rámci klasické teorie diferenciálních rovnic.

Převážná část tekutin na zemském povrchu se nachází v atmosféře a oceánech. Těmito tekutinami se zabývá tzv. geofyzikální mechanika tekutin. Při jejím pohybu, v jisté analogii s klasickou teorií mechaniky tekutin, je její oblast přiléhající zemskému povrchu označována jako Mezní vrstva atmosféry. Její vlastnosti, metody výzkumu, s přihlédnutím jejich nedostatků, budou naznačeny v následujících bodech.

1. Úvod: zavedení pojmu a důvody jejího sledování;
2. Základní vlastnosti. (Pohybové rovnice v rámci aproximace mechaniky kontinua, Proudění v rotující soustavě souřadné, Teplotní zvrstvení, Turbulence a determinismus)
3. Metody výzkumu (Experimentální, Numerické)
4. Případy řešené v Laboratoři aerodynamiky prostředí;
5. Nové problémy k řešení: Verifikace a validace matematických modelů, Problém mnoha měřítek;
6. Závěr: možnosti aplikace získaných poznatků.

Thermal plasmas have been expected as a promising tool for mass-production of nanopowders [1] because thermal plasmas offer a distinctive thermal-fluid field involving high temperature, high chemical reactivity and variable properties. Furthermore, thermal plasmas have steep temperature gradients at their fringes where many small nanoparticles are produced rapidly from the material vapour as a result of the highly supersaturated state. However, it is still difficult to investigate the formation mechanism of nanoparticles generated in/around a thermal plasma because the process involves remarkably intricate mass transfer of phase conversions in micro-second scales. Moreover, the plasma fringe is fluid-dynamically unstable and consequently it forms a turbulent mixing field composed of multiscale eddies [2]. The growing nanoparticles are transported by the complicated convection as well as diffusion and thermophoresis. In this lecture, several modelling works to simulate those complex processes are explained.
 

Žárové stříkání je proces vzniku vrstev a povlaků, při kterém se roztavený nebo ohřátý materiály nastříká na povrch. K dispozici je široká škála primárních surovin, které mohou být žárově stříkané včetně prášků a suspenzních kapalin. K dispozici je také široká škála žárových nástřiků používaných pro mnoho různých aplikací, včetně například tepelných bariér v proudových motorech. Plazmové stříkání patří do skupiny technik žárového stříkání. Využívá plazmový hořák pro vytvoření proudu plazmatu, který taví materiál vstupní suroviny. Tato přednáška nebude předkládat kompletní přehled plazmově stříkaných povlaků a jejich aplikací. Místo toho představí řadu zajímavých a někdy i fascinujících příkladů toho, čeho lze dosáhnout pomocí plazmového stříkání. Příklady budou obsahovat nanoprášky, epitaxní růst krystalů v plazmových nástřicích, amorfní a nanokompozitní povlaky, stříkání suspenzí a další.
 

Procedura časové reverzace akustických a ultrazvukových signálů ("Time Reversal Acoustics", TRA) je efektivním nástrojem řešení složitých problémů v mnoha oblastech jako jsou nedestruktivní zkoušení a hodnocení materiálů a konstrukcí (NDT/NDE), neboť TRA umožňuje fokusaci vln v čase i prostoru a přesnou lokalizaci a rekonstrukci zdrojů signálu i v silně nehomogenních, anizotropních a dispersních prostředích. Vlastnosti TRA lze využít při zpracování signálů v akustické emisi (AE) a nelineární spektroskopii elastických vln (NEWS), ale také např. v seismologii, medicíně, telekomunikacích apod.
V přednášce budou zmíněny principy metody TRA a diskutovány zejména její možnosti při lokalizaci a identifikaci zdrojů AE a nastíněny problémy nového přístupu k řešení těchto inverzních úloh pomocí přenosu ultrazvukových signálů z nepřístupného reálného tělesa na laboratorní resp. výpočetní model, kde mohou být snáze analyzovány.