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1

A remark on material parameter identification using finite elements based on constitutive models of evolutionary-type

Hartmann S.

Computer Assisted Methods in Engineering and Science

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2017

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Vol. 24, no. 2

113--126

EN

In this paper, we show that sensitivity analysis in connection with material parameter identification problems – using implicit finite elements of quasi-static problems on the basis of evolutionary-type constitutive equations – is related to simultaneous sensitivity equations and internal numerical differentiation. Thus, this study mainly focuses on investigating how these approaches are connected to the solution procedures based on finite elements. In addition, we discuss how to consider reaction forces in the sensitivity analysis, as this aspect is often neglected despite the fact that experimental results often involve force data.

2

Selected aspects of designing deep excavations

Obrzud R. F., Hartmann S., Podleś K.

Studia Geotechnica et Mechanica

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2016

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Vol. 38, nr 3

49--66

EN

This paper analyzes two approaches to serviceability limit state (SLS) verification for the deep excavation boundary value problem. The verification is carried out by means of the finite element (FE) method with the aid of the commercial program ZSoil v2014. In numerical simulations, deep excavation in non-cohesive soil is supported with a diaphragm wall. In the first approach, the diaphragm wall is modeled with the Hookean material assuming reduced average stiffness and possible concrete cracking. The sec-ond approach is divided into two stages. In the first stage, the wall is modeled by defining its stiffness with the highest nominal Young’s modulus. The modulus makes it possible to find design bending moments which are used to compute the minimal design cross-section reinforcement for the retaining structure. The computed reinforcement is then used in a non-linear structural analysis which is viewed as the “actual” SLS verification. In the second part, the paper examines the same boundary value problem assuming that the excavation takes place in quasi- impermeable cohesive soils, which are modeled with the Hardening Soil model. This example demonstrates the consequences of applying the steady-state type analysis for an intrinsically time-dependent problem. The results of this analysis are compared to the results from the consolidation-type analysis, which are considered as a reference. For both analysis types, the two-phase formulation for partially-saturated medium, after Aubry and Ozanam, is used to describe the interaction between the soil skeleton and pore water pressure.

3

Removal of chlorides from waste incineration residues

Hartmann S., Matysek D., Stary M., Skrobankova H.

Inżynieria Mineralna

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2015

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R. 16, nr 1

145--150

EN

Chlorides were removed from the medical waste bottom ash and the municipal solid waste incineration fly ash samples using washing/leaching procedure. The treatment procedures as well as mineralogical phase analysis of raw and washed/leached samples were discussed. Pozzolanic/hydraulic properties of samples were determined and discussed in relationship to bottom ash/fly ash utilization.

PL

Chlorki zostały usunięte z próbek popiołu dennego odpadów medycznych oraz popiołu lotnego ze spopielenia miejskich odpadów stałych przy zastosowaniu procedur czyszczących/ługujących. Przeprowadzono dyskusje na temat procedur procesu, jak również analizy faz mineralogicznych próbek przed i po procesie oczyszczania/ługowania. Właściwości pucolaniczne/hydrauliczne próbek zostały określone i omówione w związku z wykorzystaniem popiołu dennego/lotnego.

4

Theoretical and numerical aspects in weak-compressible finite strain thermo-elasticity

Hamkar A.-W., Hartmann S.

Journal of Theoretical and Applied Mechanics

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2012

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Vol. 50 nr 1

3-22

EN

In this essay, a constitutive model for nearly incompressible elastic behavior is extended to the case to thermal effects. First, the use is made of the multiplicative decomposition of the deformation gradient into a thermal and a mechanical part. The thermal part is purely volumetric. Additionally, the mechanical part is multiplicatively decomposed into a volume-preserving and a volume-changing part so that the final stress state shows the influences of the temperature-dependence. The proposed model is carefully studied in view of the thermo-mechanical coupling effects. Second, the model is implemented into a time-adaptive finite element formulation based on higher-order Rosenbrock-type methods, which is a completely iteration-free procedure so that really fast computations are available. The article concludes with a three-dimensional numerical simulation of a representative elastomeric tensile specimen.

PL

W pracy przedstawiono model niemal nieściśliwego, sprężystego zachowania się materiału, rozszerzając go na efekty termiczne. Na początku rozważań dokonano multiplikatywnej dekompozycji gradientu deformacji na część termiczną i mechaniczną. Część termiczna wykazuje charakter czysto objętościowy. Dodatkowo, część mechaniczną zdekomponowano na element zachowujący objętość i element o zmiennej objętości w ten sposób, że wypadkowy stan naprężeń wykazuje wrażliwość na temperaturę. Zaproponowany model szczegółowo zbadano w kontekście efektów sprzężenia termomechanicznego. W dalszej części pracy, analizowany model zastosowano do czasowo adaptacyjnej metody elementów skończonych sformułowanej na podstawie metod Rosenbrocka wyższych rzędów. Takie sformułowanie umożliwia uzyskanie procedury beziteracyjnej, co z kolei pozwala na wykonanie wyjątkowo szybkich obliczeń numerycznych. Artykuł zamyka przykład symulacji numerycznej trójwymiarowej próbki elastomeru poddanej próbie rozciągania.

5

On Inferences of Weak Multivalued Dependencies

Hartmann S., Link S.

Fundamenta Informaticae

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2009

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Vol. 92, nr 1-2

83-102

EN

Nesting is a useful technique in many areas of database practice. For instance, nesting is a fundamental operation for the nested relational data model, it can be applied to reduce the level of data redundancy in a database instance, to improve query processing or to convert data from one model to another. We further address the question when nesting operations commute with one another, i.e., when the final nested database relation is independent of the order in which the nesting operations are applied. In fact, it has been shown that the satisfaction of weakmultivalued dependencies provides a sufficient and necessary condition for the commutativity of nesting operations. We study inference systems for different notions of implication for weak multivalued dependencies. First, we establish an axiomatisation with the property that every weak multivalued dependency can be inferred either without any application of the complementation rule or by a single application of the complementation rule necessary only in the very last step of the inference. Consequently, the complementation rule is a mere means to achieve a decomposition of the database. Secondly, we drop the assumption of having a fixed underlying schema, and establish an axiomatisation of weak multivalued dependencies for the notion of implication in this context.

6

Error-Robust Functional Dependencies

Hartmann S., Link S., Schewe K-D., Thalheim B.

Fundamenta Informaticae

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2004

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Vol. 59, nr 4

365--372

EN

A database user may be confronted with a relation that contains errors. These errors may result from transmission through a noisy channel, or they may have been added deliberately in order to hide or spoil information. Error-robust functional dependencies provide dependencies that still hold in the case of errors. The paper investigates the finite axiomatisation of such dependencies. It presents a sound and complete system of axioms and rules for the implication of error-robust dependencies including disjunctions.