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Michal Šejnoha
Department of Mechanics, Faculty of Civil Engineering, Czech Technical University in Prague, 166 29 Prague, Czech Republic

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Journal article
Published: 16 August 2021 in Materials
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A combined experimental and numerical study on titanium porous microstructures intended to interface the bone tissue and the solid homogeneous part of a modern dental implant is presented. A specific class of trabecular geometries is compared to a gyroid structure. Limitations associated with the application of the adopted selective laser melting technology to small microstructures with a pore size of 500 μm are first examined experimentally. The measured effective elastic properties of trabecular structures made of Ti6Al4V material support the computational framework based on homogenization with the difference between the measured and predicted Young’s moduli of the Dode Thick structure being less than 5%. In this regard, the extended finite element method is promoted, particularly in light of the complex sheet gyroid studied next. While for plastic material-based structures a close match between experiments and simulations was observed, an order of magnitude difference was encountered for titanium specimens. This calls for further study and we expect to reconcile this inconsistency with the help of computational microtomography.

ACS Style

Aleš Jíra; Michal Šejnoha; Tomáš Krejčí; Jan Vorel; Luboš Řehounek; Guido Marseglia. Mechanical Properties of Porous Structures for Dental Implants: Experimental Study and Computational Homogenization. Materials 2021, 14, 4592 .

AMA Style

Aleš Jíra, Michal Šejnoha, Tomáš Krejčí, Jan Vorel, Luboš Řehounek, Guido Marseglia. Mechanical Properties of Porous Structures for Dental Implants: Experimental Study and Computational Homogenization. Materials. 2021; 14 (16):4592.

Chicago/Turabian Style

Aleš Jíra; Michal Šejnoha; Tomáš Krejčí; Jan Vorel; Luboš Řehounek; Guido Marseglia. 2021. "Mechanical Properties of Porous Structures for Dental Implants: Experimental Study and Computational Homogenization." Materials 14, no. 16: 4592.

Journal article
Published: 22 June 2021 in Construction and Building Materials
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This paper presents a combined experimental and numerical investigation of the behavior of glued laminated timber beams when exposed to fire. The influence on the time variation of charring rates based on the evolution of temperature profiles is examined for different fire scenarios and durations as well as different beam’s cross-section sizes. Predictions of charring depths provided by numerical simulations of heat transfer and simplified charring rate models are compared. In the absence of a mass transport representation, a Bayesian inference is introduced to identify the temperature-dependent material parameters for the conventional heat transfer model. A similar approach is adopted when adjusting the selected parameters of the charring rate models to account for variations in actual fire scenarios, which potentially depart from standard fire exposure. When compared to experimental results, both approaches confirmed their predictive capabilities, particularly in the stage of initial design. Since presented in the framework of Bayesian statistics, they open the door to fully stochastic analysis with an emphasis on the load bearing capacity of the studied beams.

ACS Style

Lucie Kucíková; Tomáš Janda; Jan Sýkora; Michal Šejnoha; Guido Marseglia. Experimental and numerical investigation of the response of GLT beams exposed to fire. Construction and Building Materials 2021, 299, 123846 .

AMA Style

Lucie Kucíková, Tomáš Janda, Jan Sýkora, Michal Šejnoha, Guido Marseglia. Experimental and numerical investigation of the response of GLT beams exposed to fire. Construction and Building Materials. 2021; 299 ():123846.

Chicago/Turabian Style

Lucie Kucíková; Tomáš Janda; Jan Sýkora; Michal Šejnoha; Guido Marseglia. 2021. "Experimental and numerical investigation of the response of GLT beams exposed to fire." Construction and Building Materials 299, no. : 123846.

Journal article
Published: 04 June 2021 in Computers & Structures
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Prediction of effective elastic and strength parameters of both regular and irregular masonry walls from homogenization is presented. To that end, the widely accepted first order homogenization method is adopted to provide the homogenized elastic stiffnesses or compliances as well as macroscopic parameters of the selected nonlinear constitutive models. These include the tensile and compressive strength and fracture energies of a generally orthotropic material extracted from the computationally derived macroscopic stress strain curves. In this regard, two types of boundary/loading conditions resulting from the strain-based and mix type formulation of the homogenization problem are examined. The response provided by an orthotropic damage model, expected to describe the behavior of the homogenized structure on macroscale, is compared to that derived via a classical isotropic scalar damage model. It reveals that strong constraints of the orthotropic damage model offer results inapplicable for estimating the macroscopic fracture properties thus promoting the application of a simple isotropic damage model when solving the homogenization problem. The results also show that the mixed boundary conditions, allowing us to represent a pure tension/compression loading mode while being capable of tracking the softening branch of the stress–strain curve, deliver the response comparable to that of a purely strain-based formulation.

ACS Style

Tomáš Krejčí; Tomáš Koudelka; Vasco Bernardo; Michal Šejnoha. Effective elastic and fracture properties of regular and irregular masonry from nonlinear homogenization. Computers & Structures 2021, 254, 106580 .

AMA Style

Tomáš Krejčí, Tomáš Koudelka, Vasco Bernardo, Michal Šejnoha. Effective elastic and fracture properties of regular and irregular masonry from nonlinear homogenization. Computers & Structures. 2021; 254 ():106580.

Chicago/Turabian Style

Tomáš Krejčí; Tomáš Koudelka; Vasco Bernardo; Michal Šejnoha. 2021. "Effective elastic and fracture properties of regular and irregular masonry from nonlinear homogenization." Computers & Structures 254, no. : 106580.

Review article
Published: 31 May 2021 in Journal of Computational and Applied Mathematics
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This paper describes the numerical analysis of the three-point bending test of glued-laminated timber arches with the fibers aligned with the longitudinal direction. The arches were cut with the vertical notch of 0.5 or 0.25 times the cross-sectional height in the middle of the arch span of 1700mm or 1830mm. The 2D homogeneous orthotropic constitutive model of tensile and shear fracture in timber, which has been recently proposed by the authors, was used for the non-linear finite element simulation. The off-axis and the compact tension test results, from the authors’ experimental campaign, were used to calibrate the model components. These are (i) orthotropic failure criterion, (ii) crack-type criterion, and (iii) cohesive (traction-separation) law for a crack along or across the grain. The numerical results show that the model can adequately simulate the quantitative response of the arches, including both the linear and non-linear behavior. Furthermore, the model captures well the most distinctive features of the cracking.

ACS Style

Eliška Šmídová; Petr Kabele; Michal Šejnoha. Finite element simulation of single edge notched timber arch. Journal of Computational and Applied Mathematics 2021, 400, 113676 .

AMA Style

Eliška Šmídová, Petr Kabele, Michal Šejnoha. Finite element simulation of single edge notched timber arch. Journal of Computational and Applied Mathematics. 2021; 400 ():113676.

Chicago/Turabian Style

Eliška Šmídová; Petr Kabele; Michal Šejnoha. 2021. "Finite element simulation of single edge notched timber arch." Journal of Computational and Applied Mathematics 400, no. : 113676.

Journal article
Published: 14 May 2021 in Sustainability
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Heating wood to high temperature changes either temporarily or permanently its physical properties. This issue is addressed in the present contribution by examining the effect of high temperature on residual mechanical properties of spruce wood, grounding on the results of full-scale fire tests performed on GLT beams. Given these tests, a computational model was developed to provide through-thickness temperature profiles allowing for the estimation of a charring depth on the one hand and on the other hand assigning a particular temperature to each specimen used subsequently in small-scale tensile tests. The measured Young’s moduli and tensile strengths were accompanied by the results from three-point bending test carried out on two groups of beams exposed to fire of a variable duration and differing in the width of the cross-section, b=100 mm (Group 1) and b=160 mm (Group 2). As expected, increasing the fire duration and reducing the initial beam cross-section reduces the residual bending strength. A negative impact of high temperature on residual strength has also been observed from simple tensile tests, although limited to a very narrow layer adjacent to the charring front not even exceeding a typically adopted value of the zero-strength layer d0=7 mm. On the contrary, the impact on stiffness is relatively mild supporting the thermal recovery property of wood.

ACS Style

Lucie Kucíková; Michal Šejnoha; Tomáš Janda; Jan Sýkora; Pavel Padevět; Guido Marseglia. Mechanical Properties of Spruce Wood Extracted from GLT Beams Loaded by Fire. Sustainability 2021, 13, 5494 .

AMA Style

Lucie Kucíková, Michal Šejnoha, Tomáš Janda, Jan Sýkora, Pavel Padevět, Guido Marseglia. Mechanical Properties of Spruce Wood Extracted from GLT Beams Loaded by Fire. Sustainability. 2021; 13 (10):5494.

Chicago/Turabian Style

Lucie Kucíková; Michal Šejnoha; Tomáš Janda; Jan Sýkora; Pavel Padevět; Guido Marseglia. 2021. "Mechanical Properties of Spruce Wood Extracted from GLT Beams Loaded by Fire." Sustainability 13, no. 10: 5494.

Journal article
Published: 16 November 2020 in Materials
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A phase-field description of brittle fracture is employed in the reported four-point bending analyses of monolithic and laminated glass plates. Our aims are: (i) to compare different phase-field fracture formulations applied to thin glass plates, (ii) to assess the consequences of the dimensional reduction of the problem and mesh density and refinement, and (iii) to validate for quasi-static loading the time-/temperature-dependent material properties we derived recently for two commonly used polymer foils made of polyvinyl butyral or ethylene-vinyl acetate. As the nonlinear response prior to fracture, typical of the widely used Bourdin–Francfort–Marigo model, can lead to a significant overestimation of the response of thin plates under bending, the numerical study investigates two additional phase-field fracture models providing the linear elastic phase of the stress-strain diagram. The typical values of the critical fracture energy and tensile strength of glass lead to a phase-field length-scale parameter that is challenging to resolve in the numerical simulations. Therefore, we show how to determine the fracture energy concerning the applied dimensional reduction and the value of the length-scale parameter relative to the thickness of the plate. The comparison shows that the phase-field models provide very good agreement with the measured stresses and resistance of laminated glass, despite the fact that only one/two cracks are localised using the quasi-static analysis, whereas multiple cracks evolve during the experiment. It was also observed that the stiffness and resistance of the partially fractured laminated glass can be well approximated using a 2D plane-stress model with initially predefined cracks, which provides a better estimation than the one-glass-layer limit.

ACS Style

Jaroslav Schmidt; Alena Zemanová; Jan Zeman; Michal Šejnoha. Phase-Field Fracture Modelling of Thin Monolithic and Laminated Glass Plates under Quasi-Static Bending. Materials 2020, 13, 5153 .

AMA Style

Jaroslav Schmidt, Alena Zemanová, Jan Zeman, Michal Šejnoha. Phase-Field Fracture Modelling of Thin Monolithic and Laminated Glass Plates under Quasi-Static Bending. Materials. 2020; 13 (22):5153.

Chicago/Turabian Style

Jaroslav Schmidt; Alena Zemanová; Jan Zeman; Michal Šejnoha. 2020. "Phase-Field Fracture Modelling of Thin Monolithic and Laminated Glass Plates under Quasi-Static Bending." Materials 13, no. 22: 5153.

Journal article
Published: 11 July 2019 in Materials
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An accurate material representation of polymeric interlayers in laminated glass panes has proved fundamental for a reliable prediction of their response in both static and dynamic loading regimes. This issue is addressed in the present contribution by examining the time–temperature sensitivity of the shear stiffness of two widely used interlayers made of polyvinyl butyral (TROSIFOL BG R20) and ethylene-vinyl acetate (EVALAM 80-120). To that end, an experimental program has been executed to compare the applicability of two experimental techniques, (i) dynamic torsional tests and (ii) dynamic single-lap shear tests, in providing data needed in a subsequent calibration of a suitable material model. Herein, attention is limited to the identification of material parameters of the generalized Maxwell chain model through the combination of linear regression and the Nelder–Mead method. The choice of the viscoelastic material model has also been supported experimentally. The resulting model parameters confirmed a strong material variability of both interlayers with temperature and time. While higher initial shear stiffness was observed for the polyvinyl butyral interlayer in general, the ethylene-vinyl acetate interlayer exhibited a less pronounced decay of stiffness over time and a stiffer response in long-term loading.

ACS Style

Tomáš Hána; Tomáš Janda; Jaroslav Schmidt; Alena Zemanová; Michal Šejnoha; Martina Eliášová; Miroslav Vokáč. Experimental and Numerical Study of Viscoelastic Properties of Polymeric Interlayers Used for Laminated Glass: Determination of Material Parameters. Materials 2019, 12, 2241 .

AMA Style

Tomáš Hána, Tomáš Janda, Jaroslav Schmidt, Alena Zemanová, Michal Šejnoha, Martina Eliášová, Miroslav Vokáč. Experimental and Numerical Study of Viscoelastic Properties of Polymeric Interlayers Used for Laminated Glass: Determination of Material Parameters. Materials. 2019; 12 (14):2241.

Chicago/Turabian Style

Tomáš Hána; Tomáš Janda; Jaroslav Schmidt; Alena Zemanová; Michal Šejnoha; Martina Eliášová; Miroslav Vokáč. 2019. "Experimental and Numerical Study of Viscoelastic Properties of Polymeric Interlayers Used for Laminated Glass: Determination of Material Parameters." Materials 12, no. 14: 2241.

Journal article
Published: 21 May 2019 in Computers & Structures
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A micromechanics based approach is outlined in this paper to predict evolution of moisture induced strains in spruce wood. Both analytical and numerical homogenization techniques are adopted first to provide estimates of effective coefficients of hygroexpansion to be multiplied by the current change in moisture content. This latter quantity is addressed next within the framework of non-Fickian constitutive model. Experimental measurements of coefficients of hygroexpansion exploiting the digital image correlation as well as determination of moisture transport using the cup model are carried out to support both applicability and numerical implementation of the presented approach.

ACS Style

Michal Šejnoha; Jan Sýkora; Jan Vorel; Lucie Kucíková; Jakub Antoš; Jaroslav Pokorný; Zbyšek Pavlík. Moisture induced strains in spruce from homogenization and transient moisture transport analysis. Computers & Structures 2019, 220, 114 -130.

AMA Style

Michal Šejnoha, Jan Sýkora, Jan Vorel, Lucie Kucíková, Jakub Antoš, Jaroslav Pokorný, Zbyšek Pavlík. Moisture induced strains in spruce from homogenization and transient moisture transport analysis. Computers & Structures. 2019; 220 ():114-130.

Chicago/Turabian Style

Michal Šejnoha; Jan Sýkora; Jan Vorel; Lucie Kucíková; Jakub Antoš; Jaroslav Pokorný; Zbyšek Pavlík. 2019. "Moisture induced strains in spruce from homogenization and transient moisture transport analysis." Computers & Structures 220, no. : 114-130.

Journal article
Published: 06 April 2019 in Computers & Structures
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A simple approach to the identification of geometrical and material uncertainties of wood is presented. This stochastic mechanics problem combines classical micromechanics, computational homogenization and experimental measurements with Bayesian inference to estimate the model parameters including the characteristics of errors in macroscopic elastic properties of wood caused by randomness of microstructural details on the one hand and the experimental errors on the other hand. The former source of uncertainty includes, for example, variability in microfibril angle and growth ring density. Even such limiting consideration of random input illustrates the need for combined computational and experimental approach in a reliable prediction of the desired material properties. Tying the two approaches in the framework of Bayesian statistical method proves useful when addressing their limitations and as such giving better notion on the credibility of the prediction. This is demonstrated here on one particular example of spruce wood.

ACS Style

Michal Šejnoha; Tomáš Janda; Jan Vorel; Lucie Kucíková; Pavel Padevět; Vladimír Hrbek. Bayesian inference as a tool for improving estimates of effective elastic parameters of wood. Computers & Structures 2019, 218, 94 -107.

AMA Style

Michal Šejnoha, Tomáš Janda, Jan Vorel, Lucie Kucíková, Pavel Padevět, Vladimír Hrbek. Bayesian inference as a tool for improving estimates of effective elastic parameters of wood. Computers & Structures. 2019; 218 ():94-107.

Chicago/Turabian Style

Michal Šejnoha; Tomáš Janda; Jan Vorel; Lucie Kucíková; Pavel Padevět; Vladimír Hrbek. 2019. "Bayesian inference as a tool for improving estimates of effective elastic parameters of wood." Computers & Structures 218, no. : 94-107.

Correction
Published: 25 July 2011 in Micromachines
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Note: In lieu of an abstract, this is an excerpt from the first page. We have discovered a mistake in our original derivation related to the definition of the apparent conductivity due to orientation averaging.

ACS Style

Jan Stránský; Jan Vorel; Jan Zeman; Michal Sejnoha. Correction: Sejnoha, M. et al. Mori-Tanaka Based Estimates of Effective Thermal Conductivity of Various Engineering Materials. Micromachines 2011, 2, 129–149. Micromachines 2011, 2, 344 -344.

AMA Style

Jan Stránský, Jan Vorel, Jan Zeman, Michal Sejnoha. Correction: Sejnoha, M. et al. Mori-Tanaka Based Estimates of Effective Thermal Conductivity of Various Engineering Materials. Micromachines 2011, 2, 129–149. Micromachines. 2011; 2 (3):344-344.

Chicago/Turabian Style

Jan Stránský; Jan Vorel; Jan Zeman; Michal Sejnoha. 2011. "Correction: Sejnoha, M. et al. Mori-Tanaka Based Estimates of Effective Thermal Conductivity of Various Engineering Materials. Micromachines 2011, 2, 129–149." Micromachines 2, no. 3: 344-344.

Journal article
Published: 15 April 2011 in Micromachines
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The purpose of this paper is to present a simple micromechanics-based model to estimate the effective thermal conductivity of macroscopically isotropic materials of matrix-inclusion type. The methodology is based on the well-established Mori-Tanaka method for composite media reinforced with ellipsoidal inclusions, extended to account for imperfect thermal contact at the matrix-inclusion interface, random orientation of particles and particle size distribution. Using simple ensemble averaging arguments, we show that the Mori-Tanaka relations are still applicable for these complex systems, provided that the inclusion conductivity is appropriately modified. Such conclusion is supported by the verification of the model against a detailed finite-element study as well as its validation against experimental data for a wide range of engineering material systems.

ACS Style

Jan Stránský; Jan Vorel; Jan Zeman; Michal Šejnoha. Mori-Tanaka Based Estimates of Effective Thermal Conductivity of Various Engineering Materials. Micromachines 2011, 2, 129 -149.

AMA Style

Jan Stránský, Jan Vorel, Jan Zeman, Michal Šejnoha. Mori-Tanaka Based Estimates of Effective Thermal Conductivity of Various Engineering Materials. Micromachines. 2011; 2 (2):129-149.

Chicago/Turabian Style

Jan Stránský; Jan Vorel; Jan Zeman; Michal Šejnoha. 2011. "Mori-Tanaka Based Estimates of Effective Thermal Conductivity of Various Engineering Materials." Micromachines 2, no. 2: 129-149.

Journal article
Published: 22 December 2006 in Probabilistic Engineering Mechanics
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ACS Style

Michal Šejnoha; Jiří Šejnoha; Marie Kalousková; Jan Zeman. Stochastic analysis of failure of earth structures. Probabilistic Engineering Mechanics 2006, 22, 206 -218.

AMA Style

Michal Šejnoha, Jiří Šejnoha, Marie Kalousková, Jan Zeman. Stochastic analysis of failure of earth structures. Probabilistic Engineering Mechanics. 2006; 22 (2):206-218.

Chicago/Turabian Style

Michal Šejnoha; Jiří Šejnoha; Marie Kalousková; Jan Zeman. 2006. "Stochastic analysis of failure of earth structures." Probabilistic Engineering Mechanics 22, no. 2: 206-218.