Search

The influence of elevated temperatures on mechanical behavior of glued laminated timber beams is examined on the basis of tensile tests. Dog bone samples prepared from beams exposed to fire of variable duration were categorized with respect to the type and position of the failure crack, type and number of discontinuities such as knots, and the level of browning. The acquired experimental results suggest that the wood variability and the effect of growth discontinuities are probably more significant than the effect of elevated temperatures. To support this conclusion, further study is currently under way, exploring samples from the second series of the fire tests.

Q-P process is one of the latest techniques for heat treatment of high-strength steels with increased silicon levels. It is believed to be based on diffusion and migration of carbon between martensite and untransformed austenite, where the latter becomes enriched with carbon, and therefore becomes thermodynamically stable. However, the question remains whether much of the carbon partitioning in the Q-P process might be the result of the competing bainitic transformation induced by arrested quenching below the Ms temperature. This paper explores the use of dilatometry for identifying the products of austenite decomposition during Q-P processing of medium-carbon 42SiCr low-alloy steel.

The paper describes a finite element simulation of the response of a real underground structure subjected to earthquake using GEO5 FEM program. It concentrates on the influence of material damping with respect to a specific type of boundary condition prescribed at the bottom of the analyzed domain. It is seen that considering material damping is inevitable particularly in case of so called fixed boundary conditions to arrive at meaningful results. This is demonstrated on an artificial earthquake generated according to a design spectrum defined in Eurocode 8. A viscous damping ratio combined with the results of eigenvalue analysis is used to derive parameters of Rayleigh damping for three specific scenarios promoting the approach based on the lowest natural frequency as sufficiently accurate for the present task.

Na základě známého chemického složení lze v dnešní době pomocí různých výpočetních programů získat mnoho informací o daném materiálu. Mezi takové informace patří například teploty fázových přeměn, jako jsou teploty Ac1, Ac3 nebo teploty Ms a Mf, ale i celý postup rozpadu austenitu představovaný IRA a ARA diagramy. V případě ochlazování pak probíhá rozpad těchto austenitických zrn na perlit, ferit, cementit a zákalné struktury. Dnes jsou tyto přeměny již zcela dobře popsány, zejména jak se jednotlivé fáze tvoří, jakou vznikají rychlostí a při jakých telotách. Neexistuje ale příliš velké množství vizuálních záznamů z průběhů techto transformací. Za pomoci vysokoteplotní komory Linkam TS1400XY s možností ohřevu materiálu až do teploty 1400°C integrované do světelného mikroskopu s objektivem s upravenou pracovní vzdáleností je možné tyto fázové přeměny pozorovat. Tento článek se věnuje především možnostem využití vysokoteplotní komory pro různé typy materiálů a jejich specifické tepelné zpracování a dále i způsobu přípravy vzorků pro použití v komoře umístěné ve světelném mikroskopu. Today, extensive information on a particular material can be obtained from its chemical composition using vari-ous computer programs. Such information includes phase transformation temperatures, such as Ac1 and Ac3 or the Ms and Mf, as well as the entire austenite decomposition sequence, as shown in TTT and CCT diagrams. When steel is heated, austenite grains begin to form, grow and eventually coarsen. On cooling, these grains de-compose into pearlite, ferrite, cementite and hardening phases. Transformations of this kind are well understood nowadays, namely the ways the individual phases form and the rates and temperatures involved. Yet, in-situ visual recordings of such transformations are relatively rare. Using the Linkam TS1400XY heating stage, which is capable to heat samples up to 1400°C and is integrated in an optical microscope featuring objective lenses with modified working distances, these phase transformations can be observed directly. This paper explores the po-tential of the heating stage for studying various materials and their specific heat treatments. It also discusses the method of sample preparation for use in the heating stage placed in an optical microscope.

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.

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.

Press-hardening představuje intenzivně se rozvíjející technologii tváření, která se převážně používá pro výrobu dílů karoserií aut. Protože se jedná o tváření za tepla, je možné využít malých tvářecích sil a díky nižšímu springback efektu jsou dosahovány přesnější výrobky. V karoseriích aut se do částí vystavených nárazu používají hlavně materiály s vysokou absorpcí energie a dostatečným koeficientem zpevnění. Jedním z těchto materiálu jsou vícefázové oceli typu TRIP s různým chemickým složením. U těchto ocelí je možné dosáhnout meze pevnosti až 1000 MPa s tažnostmi 20-30%. Pro dosažení požadovaných vlastností je nutné zvolit vhodné tepelné zpracování, které umožní dosáhnout požadovanou vícefázovou strukturu. Fázové přeměny i mechanické vlastnosti je možné ovlivnit použitím vhodných legujících prvků. Pro experimentální program byly zvoleny tři nízkolegované vícefázové oceli typu TRIP s různým chemickým složením s obsahem uhlíku 0,2%. První ocel byla legována pouze manganem a křemíkem, ve druhé byl přidán niob a ve třetí byl zjišťován vliv chromu na zvýšení prokalitelnosti a meze pevnosti. Press-hardening is an intensively developing forming technology which is mainly used for the production of car body parts. Because it is a hot forming technology, small forming forces can be utilized and, due to the lower spring-back effect, more accurate products are achieved. In car bodies, materials with high energy absorption and a sufficient hardening coefficient are mainly used in impacted parts. One of these materials is TRIP multiphase steels with different chemical composition. In these steels, it is possible to achieve an ultimate strength up to 1000 MPa with the ductility of 20-30%. In order to achieve the desired properties, it is necessary to select a suitable heat treatment that allows to achieve a multiphase structure. Phase transformations and mechanical properties are influenced by the use of suitable alloying elements. Three low-alloy, multiphase TRIP steels with different chemical compositions with a carbon content of 0.2% were chosen for the experimental program. The first steel was alloyed only with manganese and silicon, in the second niobium was added, and in the third the influence of chromium on increase of hardenability and strength was investigated. Press-hardening was performed in a heated forming tool. To describe the effect of the cooling rate, the forming was carried out in a tool at room temperature and after preheating to 425°C. The influence of holding time in the tool at 425°C to support the formation of bainite and retained austenite stabilization was also investigated. Mixed ferritic-bainitic-martensitic structures with some retained austenite content were obtained.

Korozivzdorná austenitická ocel 08Ch18N10T stabilizovaná titanem je díky svým vlastnostem často používána v jaderné energetice. Z této oceli jsou vyráběny díly primárního okruhu jaderného reaktoru, materiál tedy musí dosahovat jak dobré korozní odolnosti, tak teplotní stálosti struktury – je předepsána mez kluzu při teplotě 350°C nejméně 177 MPa. Zpracování této oceli zahrnuje několik důležitých etap, které ovlivňují výsledné mechanické vlastnosti. Zejména etapy rozpouštěcího a stabilizačního žíhání po kování nebo válcování jsou časově i energeticky velmi náročné, a proto se hledají různé způsoby, jak tyto časy zkrátit. Na vzorcích z oceli 08Ch18N10T byla odzkoušena kombinace rozpouštěcího žíhání na teplotě 1020°C s dobou prodlevy 15 a 30 minut a stabilizačního žíhání při teplotě 720°C s dobou prodlevy 2,5 hodin až 15 hodin. Doby výdrže na teplotách byly přizpůsobeny velikosti použitých polotovarů. Cílem bylo zjistit nejen vliv doby prodlevy při stabilizačním žíhání na mechanické vlastnosti, ale také vliv různé doby rozpouštěcího žíhání. Výsledky ukázaly, že prodloužení doby prodlevy při rozpouštěcím žíhání má výrazný vliv na snížení rozptylu v mechanických vlastnostech. Při všech kombinacích byla získána mez kluzu při 350°C přesahující 200 MPa a mez pevnosti přes 380 MPa. Titanium-stabilized austenitic stainless steel 08Ch18N10T is often used in nuclear power due to its properties. The parts of the primary circuit of the nuclear reactor are manufactured from this steel, so the material must achieve both very good corrosion resistance and thermal stability of the structure - yield strength of at least 177 MPa at 350 °C is prescribed. The treatment of this steel involves several important stages that affect the resulting mechanical properties. In particular, the solution and stabilization annealing stages after forging or rolling are very time and energy-intensive, and therefore various ways to reduce these times are sought. The combination of solution annealing at 1020 °C with a holding time of 15 and 30 minutes and stabilization annealing at 720 °C with a holding time of 2.5 hours to 15 hours was tested on samples from the 08Ch18N10T steel. The holding times at temperatures were adapted to the size of the used semi-products. The aim was to find out not only the effect of holding time during stabilization annealing on mechanical properties but also the effect of different solution annealing time. The results showed that prolonging the holding time during solution annealing has a significant impact on reducing the variance in mechanical properties. In all combinations, yield strength at 350 °C higher than 200 MPa and tensile strength over 380 MPa were obtained.

This article concerns numerical simulations of glass plates loaded by a force impulse caused by a low velocity impact. Three types of numerical models of different complexity – the spring-mass system, the modal decomposition based model, and the conventional finite element method – all exploiting the Hertz contact law are compared and their advantages and limitations are discussed. Their performance is verified against the results provided by the commercial software LS-DYNA and validated by two full scale experiments. It is observed that the accuracy of the spring-based model decreases with increasing dimension of the plate and increasing stiffness of the impactor. Nevertheless, the models based on modal decomposition and finite element methods deliver results reasonably close to experimental measurements.

In this combined experimental-numerical study, we intend to clarify how the interlayer properties of laminated glass plates affect their response to the low-velocity impact of a hard object. To this end, we tested twelve large laminated glass plates with polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA) interlayers combined with two annealed or heat-strengthened soda-lime-silica glass layers—three testing samples for each combination. In laboratory impact tests, both the laminated glass plate and the impactor were suspended on thin steel wire ropes to minimise the effects of boundary conditions; the velocities of the impactor and the resultant contact force were increased in repeated tests until the glass fractured. Because of the large scatter of fracture strengths, we derived the contact force for all non-destructive and destructive tests using the motion of the impactor and analysed how the contact force evolved. The laboratory impact tests also provided a dataset for validation of numerical simulations that reliably predicted the velocities at measured points and contact forces for both kinds of polymer interlayer foils, thereby validating the viscoelastic parameters of polymers determined in our previous experimental study. Using the validated numerical model, we analysed how the type of interlayer polymer material influences the impact response of laminated glass in terms of contact force and stresses and in relation to surrounding temperature conditions and impactor mass and velocity. Finally, we approximated time/temperature-dependent foil as being an elastic material with different values of constant shear moduli. For laminated glass plates containing PVB, such approximation remained valid only at low temperatures and responses could be estimated using the temperature-independent initial shear modulus. For simulations with EVA-based laminated glass plates, the elastic model with the shear modulus for prescribed temperatures and load durations provided an accurate approximation of the viscoelastic response.

The paper deals with the prediction of the response of a real underground structure subjected to earthquake. A fully dynamic analysis is carried out in the GEO5 FEM program using the Finite Element Method. Limiting our attention to a two-dimensional analysis we focus on the implementation of special boundary conditions along the vertical edges of the computational model. A simple study is carried out first to show that incorrectly applied boundary conditions may significantly influence the actual design of underground structures loaded by vertically propagating shear waves. This study promotes the combination of so called free-field and static boundary conditions as demonstrated on a simple example.

The paper deals with the evaluation of tunnel construction subjected to earthquake using a pseudostatic analysis combined with the finite element method. The initial stage of calculation is concerned with the design of computational model and subsequent analysis of the actual excavation process. The case study of the response of a selected construction to earthquake follows next. To that end, the so called 1D free filed dynamic analysis is performed first to generate appropriate loading conditions in terms of a layered-wise constant shear strain. Therein, two particular boundary conditions, termed the fixed and absorbing boundary, are examined. The corresponding loading conditions are finally introduced in a 2D plane strain analysis to yield the internal forces developed in the tunnel lining. The results clearly show inadequacy of the fixed boundary and promote the use of absorbing boundary conditions for the present soil profile.

This paper focuses on the modal analysis of laminated glass beams. In these multilayer elements, the stiff glass plates are connected by compliant interlayers with frequency/temperature-dependent behavior. The aim of our study is (i) to assess whether approximate techniques can accurately predict the behavior of laminated glass structures and (ii) to propose an easy tool for modal analysis based on the enhanced effective thickness concept by Galuppi and Royer-Carfagni. To this purpose, we consider four approaches to the solution of the related nonlinear eigenvalue problem: a complex-eigenvalue solver based on the Newton method, the modal strain energy method, and two effective thickness concepts. A comparative study of free vibrating laminated glass beams is performed considering different geometries of cross-sections, boundary conditions, and material parameters for interlayers under two ambient temperatures. The viscoelastic response of polymer foils is represented by the generalized Maxwell model. We show that the simplified approaches predict natural frequencies with an acceptable accuracy for most of the examples. However, there is a considerable scatter in predicted loss factors. The enhanced effective thickness approach adjusted for modal analysis leads to lower errors in both quantities compared to the other two simplified procedures, reducing the extreme error in loss factors to one half compared to the modal strain energy method or to one quarter compared to the original dynamic effective thickness method., 31 pages, 12 figures, 10 tables

Magnetic properties are commonly used to identify new aromatic molecules because it is generally believed that magnetization and energetic stability are correlated. To verify the potential correlation between the energy and magnetic response properties, we examined a set of 198 isomers of C6 H6 . The energy and magnetic properties of these molecules can be directly compared with no need to invoke any arbitrary reference state because the studied systems are all isomers. Benzene is the global minimum on the potential energy surface of C6 H6 , 35 kcal mol-1 lower in energy than the second most stable isomer, fulvene. Unlike its electronic energy, isotropic magnetizability of benzene is slightly lower than the average magnetizability of its isomers. Altogether, 44 isomers of C6 H6 were identified to have more negative magnetic susceptibility than benzene but were between 67.0 to 168.6 kcal mol-1 higher in energy than benzene. However, benzene is unique in two ways. Analyzing the paramagnetic contribution to the magnetic susceptibility as originally suggested by Bilde and Hansen (Mol. Phys., 1997, 92, 237) revealed that 53 molecules have lower paramagnetic susceptibility than benzene but among monocyclic systems benzene has the least paramagnetic susceptibility. Furthermore, benzene has the largest out-of-plane magnetic susceptibility that originates from the strongest ring current among all studied species.

The experiment described herein focused on quantitative evaluation of carbides in the martensitic microstructure of X105CrMo17 steel. Carbides form as a result of the varying solubility of carbon and alloying elements during solidification and cooling. They possess high strength and hardness and their morphology plays a major role in mechanical properties of steel. In order to determine the relationship between carbide morphology and mechanical properties, several characteristics must be measured accurately. In this case, quantitative evaluation of carbides by means of optical microscopy and image analysis software were employed. Samples of the above-identified steel were quenched from various temperatures in order to obtain various levels of chromium and carbon dissolved in the martensitic matrix. They were then tempered at various temperatures to provide secondary hardening through precipitation. Furthermore, volume fractions and equivalent diameters of particles and the surface area density of particles were measured by metallographic techniques. Hardness was measured to assess the impact of heat treatment on strength. From the values collected in this manner, relationships between heat treatment and hardness were derived and an optimal heat treatment sequence was proposed for obtaining maximum hardness.

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.

The paper is concerned with our ongoing research effort devoted to the development of reliable computational tools for the calibration of advanced constitutive models of soils. At present, such software is available for the hypoplastic model of clays applicable to soft soils. This software provides a stepping stone for the determination of potential links between individual model parameters and fundamental characteristics of soils. Identifying such links would allow for tuning the model without performing time consuming experiments, particularly in the case of an initial design. Some preliminary results are presented in the paper.

A stochastic hierarchical model of a glued laminated timber beam loaded in bending is formulated in this paper. Being attributed to the limited number of observed data the model captures both the inherent variability of the elastic properties of individual timber boards making up the laminated beam and the uncertainty of the parameters controlling their probability distributions. Apart from the deflection measurements obtained from the full scale displacement-controlled, four point bending tests the model also incorporates the data from numerous nondestructive macroindentation measurements. The forward deterministic model of laminated beam is based on the Mindlin beam theory combined with the finite element method to simulate the laboratory measurements numerically. The inference of the model parameters is performed in the framework of Bayesian statistics. Apart from improved posterior distributions of material data, we also offer an improved formula for estimating the longitudinal elastic modulus from indentation measurements.

It has been shown that the microfibril angle may severely reduce the longitudinal elastic stiffness of wood. The present paper addresses this issue by combining experimental measurements on various scales, homogenization and Bayesian statistical method. To that end, the variation of effective stiffness as a function of microfibril angle is first estimated by combining nanoindentation and homogenization. The results from a series of tensile tests carried out on thin samples of wood containing only a few growth rings are expected to give additional source of information. In the present study both types of data, microscopic as well as macroscopic measurements, are exploited in the framework of Bayesian inference to get improved, posterior, knowledge of the microfibril angle distribution. Owing to a computational demand associated with the Markov chain Monte Carlo method, as the engine of the updating process, the homogenization based on classical micromechanics is adopted.

This paper investigates a time-stepping procedure of the Newmark type for dynamic analyses of viscoelastic structures characterized by a generalized Maxwell model. We depart from a scheme developed for a three-parameter model by Hatada et al. in 2000, which we extend to a generic Maxwell chain and demonstrate that the resulting algorithm can be derived from a suitably discretized Hamilton variational principle. This variational structure manifests itself in an excellent stability and a low artificial damping of the integrator, as we confirm with a mass-spring-dashpot example. After a straightforward generalization to distributed systems, the integrator may find use in, e.g., fracture simulations of laminated glass units, once combined with variationally-based fracture models., 9 pages, 4 figures, 1 table

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&ndash, 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&ndash, 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.

Inovativními metodami tepelného zpracování (TZ) vysokopevných ocelí jako je QP proces lze dosáhnout velmi příznivého poměru tažnosti a pevnosti. Materiál zpracovaný touto technologií má vyšší obsah zbytkového austenitu a dosahuje tak vyšší tažnosti. Popisovaný experiment se zabývá tepelným zpracováním oceli 42SiCr, prorovnává konvenční metody TZ a QP proces z hlediska vlivu různých kalicích medií na vlastnosti materiálu. V rámci experimentu bylo provedeno variantní TZ, metalografické analýzy, meření tvrdosti, rentgenová difrakční fázová analýza pro zjištění obsahu zbytkového austenitu a zkouška tahem. U kalených vzorků byl posuzován vliv rychlosti ochlazování na mikrostrukturu a reálné výsledky byly porovnávány se simulací provedenou v programu DeformTM na základě záznamů z termočlánků. Při konvenčním TZ projevoval materál malou citlivost na rychlosti ochlazování. Oproti tomu QP procesem bylo při vyšších teplotách zakalení dosaženo vyššího podílu austenitu ve struktuře a tažnosti až 15% při současné pevnosti 1800 MPa. Using innovative methods of heat treatment (HT) for high-strength steels, such as the Q&P process, very favoura-ble ratios of ductility and strength can be achieved. Materials processed by this technology have higher content of retained austenite, and therefore better ductility. This experiment deals with HT of 42SiCr steel. The conventional HT and the Q&P processing are compared with respect to material properties. Metallographic analysis, hardness measurement, X-ray diffraction phase analysis (of retained austenite content) and tensile testing were performed. For the hardened samples, the effects of the cooling rate on their microstructure were assessed and the measured real-world data were compared with the simulations performed in the FEA simulation software DEFORMTM based on the thermocouple records. After a conventional HT, the material showed little sensitivity to the cooling rate. In contrast, the Q&P process with higher quenching temperatures resulted in a higher austenite content and elonga-tion of up to 15 % at a strength of 1800 MPa.

Preliminary outcomes on a novel modular additive manufacturing technology are presentedin this contribution. The capabilities of the proposed system to synthesize materials with conventionalor meta properties are explored. Two limiting and a single mixed compositions are tested in com-pression in order to reveal both, global and local behaviours of the conglomerates. The experimentalmeasurements are supported by DIC (Digital Image Correlation) observations.

The paper presents the project of an open source C/C++ library of analytical solutions to micromechanical fields within media with ellipsoidal heterogeneities. The solutions are based on Eshelby's stress-free, in general polynomial, eigenstrains and equivalent inclusion method. To some extent, the interactions among inclusions in a non-dilute medium are taken into account by means of the self-compatibility algorithm. Moreover, the library is furnished with a powerful I/O interface and conventional homogenization tools. Advantages and limitations of the implemented strategies are addressed through comparisons with reference solutions by means of the Finite Element Method., Comment: 28 pages, 10 figures, 7 tables

Summary The paper describes an approach to the simulation of arbitrary laboratory tests with homogeneous stress and strain fields applicable to most constitutive models common in geomechanics. The method by Bardet and Choucair [Int. J. Numer. Anal. Meth. Geomech. 15(1):1–19, 1991] is generalized for an arbitrary number of controlling and controlled variables. The approach is illustrated for time-dependent thermo–hydro–mechanical constitutive models. The purpose of the method is to define an endless variety of different laboratory tests declaratively by means of two matrices E and S, which define the constraints on the controlled quantities such as stress, strains, suction, or temperature. Copyright © 2016 John Wiley & Sons, Ltd.

The paper is concerned with hypoplastic models for both coarse and fine grained soils. It concentrates on the description of models parameters and presents procedures for their evaluation based on actual laboratory tests. The sample of sand for the calibration of the hypoplastic model for coarse grained soil comes from the Třeboň basin. The sample was classified as Sa. The second sample was classified as saCl. This sample comes from the street Evropská in Prague and was used for the calibration of the hypoplastic model for fine grained soils. The classification was performed according to ČSN EN ISO 14688-2. Keywords: hypoplasticity, fine grained soils, coarse grained soils, calibration, parameters.

PING 2019 is organized with the support of funds for specific university research project SVK1-2019-002. Induction hardening technology is mainly used for processing parts where high hardness, as well as wear-resistance and ductile core, is required. Normally induction hardening is used for spur gears, wind turbine rings, and bearings. Innovative induction hardening processes are also developed for complex automotive components such as camshafts and crankshafts. In this process, steel is heated by passing high-frequency alternating current through a coil which is considered as the primary winding of the transformer. The area where heat-treated material lies or passing through is considered as a short circuit secondary winding. Device for incremental forming of round bars HDQT-R 30-12 is equipped with such heat treatment modules which can be used for heat treatment after rolling of rods or even without rolling. Heating of steel bars is provided by five induction coils, which can heat the material faster than the chamber furnace, and there is less oxidation of the material surface. This paper shows the microstructural and hardness results from testing 42CrMo4 steel, 13CrMo4 steel, and S235JR steel after heating at different inductor coil power settings with subsequent hardening into the water bath.

PING 2019 is organized with the support of funds for specific university research project SVK1-2019-002. This paper deals with the innovative Quenching and partitioning (QP) heat treatment (HT) of low-alloyed chromium steel, and is especially focused on the higher temperatures of partitioning as well as longer holding times and its influence on mechanical properties of the material. As part of the experiment various HT, metallographic analysis, hardness measurement, X-ray diffraction phase analysis (to determine retained austenite content), tensile test and Charpy impact test were performed. In QP treated specimens the best combination of UTS and elongation was observed after quenching in 200 °C salt bath and partitioning at 250 °C for 30 minutes. This specimen showed the UTS above 1900 MPa, elongation of 14 % and also good impact toughness (34 J). Equally good values of impact toughness (36 J) were also observed in the specimens partitioned at 300 °C or 320 °C for holding times up to 30 minutes. On the other side longer partitioning times at the temperature of 320 °C affected the elongation and impact toughness negatively.

A concept of a planar modular mechanical metamaterial inspired by the nature's principle of local adaptivity is proposed. The metamaterial consists of identical pieces similar to jigsaw puzzle tiles. Their rotation within assembly provides a substantial flexibility in terms of structural behavior and mechanical interlocks enable reassembly. The tile design with a diagonal elliptical opening allows us to vary elastic properties--from stiff to compliant, with positive, zero, or negative Poisson's ratio. The outcomes of experimental testing on additively manufactured specimens confirm that the assembly properties can be accurately designed using optimization approaches with finite element analysis at heart., 9 pages, 8 figures

To improve the mechanical properties of high strength steels the application of innovative methods is often necessary. One of such technology used in the field of heat treatment (HT) is the quenching and partitioning process. By this method higher content of stabile retained austenite (RA) can be achieved, which increase material ductility while its strength remains only slightly reduced. The experiment compares the mechanical properties of the 42SiCr steel heat treated conventionally or by the QP process. Parameters were designed for both HT modes to achieve approximately the same tensile strength and then the elongations and RA contents were compared. As part of the experiment the metallographic analysis, the X-ray diffraction analysis, hardness measurement and tensile test were performed. The results showed improvement of mechanical properties of the samples treated by QP process. The conventionally treated material (with RA content of 8 %) showed the elongation of 10% at the tensile strength of 1980 MPa while the specimen processed by QP reached elongation of 14% at a tensile strength of 2000 MPa and RA content was also higher (11%). On the basis of this knowledge the future research will be focused on the optimization of QP process parameters.