Number of found documents: 967
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Determination of Mechanical Properties of Metallic Materials from Very Small Volumes by Means of Small Punch Test
Dymáček, Petr; Dobeš, Ferdinand; Kloc, Luboš
2017 - English
The paper summarizes capabilities of the small punch tests on miniature disc specimens\nfrom metallic materials. Results obtained by small punch tests can be correlated with mechanical\nproperties determined by conventional or other miniature tests. Three basic types of small punch test\nsetup: i) static/fracture, ii) creep and iii) stress relaxation are described and the basic quantities that\ncan be obtained are shown. Relations for an assessment of conventional mechanical properties from\nquantities obtained by small punch test are presented. Keywords: small punch test; uniaxial test; creep; stress relaxation Available at various institutes of the ASCR
Determination of Mechanical Properties of Metallic Materials from Very Small Volumes by Means of Small Punch Test

The paper summarizes capabilities of the small punch tests on miniature disc specimens\nfrom metallic materials. Results obtained by small punch tests can be correlated with mechanical\nproperties ...

Dymáček, Petr; Dobeš, Ferdinand; Kloc, Luboš
Ústav fyziky materiálů, 2017

Influence of Extension of Load Spectrum on Estimation of Residual\nFatigue Lifetime of Railway Axle
Pokorný, Pavel; Hutař, Pavel; Náhlík, Luboš
2017 - English
Railway axles are subjected to cyclic amplitude loading which can lead to fatigue failure.\nFor safe operation of railway axles a damage tolerance approach taking into account a possible\ndefect in railway axle is often required. Because of different operation regimes of trains (fast/slow\nride, ride on straight track, on curved track, over switches etc.) the load amplitude of axle is not\nconstant. The variability of load is defined by a load spectrum, which is determined experimentally\nby measuring of load in service conditions. Even though the load spectrum is measured on several\nhundreds or thousands of operation kilometres, the railway axles are in operation much longer time\n(often tens of years). Therefore, some load amplitudes higher than ones measured in the test can\noccur during a long-term axle service. The contribution presented deals with the effect of extension\nof load spectrum by rare high load amplitudes, which can occur during long-term operation, on\nresidual fatigue lifetime of railway axles. Keywords: railway axle; fatigue crack; load spectrum; overload Available at various institutes of the ASCR
Influence of Extension of Load Spectrum on Estimation of Residual\nFatigue Lifetime of Railway Axle

Railway axles are subjected to cyclic amplitude loading which can lead to fatigue failure.\nFor safe operation of railway axles a damage tolerance approach taking into account a possible\ndefect in ...

Pokorný, Pavel; Hutař, Pavel; Náhlík, Luboš
Ústav fyziky materiálů, 2017

3D Model of Crack Propagation in Particulate Ceramic Composite Containing Residual Stresses
Štegnerová, Kateřina; Majer, Zdeněk; Hutař, Pavel; Náhlík, Luboš
2017 - English
A crack propagation and fracture behaviour of particulate ceramic composite were investigated. Influence of 3D shape of particles on the crack propagation was studied together with influence of the presence of residual stresses, which are developed inside the composite during manufacturing process. Finite element (FE) method was used for numerical simulation of propagating crack in the composite. Basic numerical models of low-temperature co-fired ceramics (LTCC) with alumina particles homogenously dispersed in the glass matrix were developed. Volume fraction of alumina phase was 20vol.%, which is typical amount for LTCC. The results show that existence of residual stresses retards the crack propagating under conditions of sub-critical crack growth (SCG). Presented results contribute to a better understanding of the role of residual stresses in particulate ceramic composites. Keywords: ceramic particulate composite; sub-critical crack growth; residual stresses Available at various institutes of the ASCR
3D Model of Crack Propagation in Particulate Ceramic Composite Containing Residual Stresses

A crack propagation and fracture behaviour of particulate ceramic composite were investigated. Influence of 3D shape of particles on the crack propagation was studied together with influence of the ...

Štegnerová, Kateřina; Majer, Zdeněk; Hutař, Pavel; Náhlík, Luboš
Ústav fyziky materiálů, 2017

Short-term stable crack propagation through polyolefin singleand bilayered structures - Influence of welding, composition and direction of crack propagation
Lach, R.; Krolopp, T.; Hutař, Pavel; Nezbedová, E.; Grellmann, W.
2017 - English
The overall stable crack initiation and propagation behaviour of specimens cut from plastic pipes that were composed of different polyolefin materials were investigated using concepts of elastic–plastic fracture mechanics including the crack propagation kinetics. The effect of specimen shape, orientation, welding, lading rate, composition/microstructure and direction of crack propagation on the crack resistance (R) behaviour of these materials has been thereby assessed. Keywords: Plastic pipes; single- and bilayered structures; stable crack propagation; plastic constraint Available at various institutes of the ASCR
Short-term stable crack propagation through polyolefin singleand bilayered structures - Influence of welding, composition and direction of crack propagation

The overall stable crack initiation and propagation behaviour of specimens cut from plastic pipes that were composed of different polyolefin materials were investigated using concepts of ...

Lach, R.; Krolopp, T.; Hutař, Pavel; Nezbedová, E.; Grellmann, W.
Ústav fyziky materiálů, 2017

Estimation of Anisotropy of Creep Properties in Al and Mg Alloys by Means of Small Punch Test
Dobeš, Ferdinand; Dymáček, Petr
2017 - English
Small punch test was used to determine the properties of light alloys and composites in various directions. Three different materials were studied:\n(i) magnesium alloy WE54 prepared by a powder metallurgical route with final hot extrusion,\n(ii) aluminium alloy reinforced with 20 vol. % of Saffil fibres with planar orientation, and\n(iii) Al-Al4C3 composite prepared by mechanical alloying and subjected to equal channel angularpressing as a final step.\nSmall punch tests were performed under constant force at elevated temperatures. The observed orientation dependence of creep properties is strongly material dependent. The results confirm the feasibility of the small punch test for determination of anisotropy of mechanical properties. Keywords: creep; small punch test; aluminium composite Available at various institutes of the ASCR
Estimation of Anisotropy of Creep Properties in Al and Mg Alloys by Means of Small Punch Test

Small punch test was used to determine the properties of light alloys and composites in various directions. Three different materials were studied:\n(i) magnesium alloy WE54 prepared by a powder ...

Dobeš, Ferdinand; Dymáček, Petr
Ústav fyziky materiálů, 2017

High cycle fatigue life of Ti6Al4V alloy produced by direct metal laser sintering
Konečná, R.; Nicoletto, G.; Bača, A.; Kunz, Ludvík
2017 - English
High cycle fatigue life of Ti6Al4V alloy specimens manufactured by Direct Metal Laser Sintering (DMLS) was experimentally determined. The DMLS fabrication process was characterized by a 400 W laser power and 50 micrometer layer melted thickness. Post-fabrication heat treatment consisted in stress relieving for 3 h at 720 °C in vacuum with subsequent cooling in argon atmosphere. Fatigue testing of specimens oriented in three different directions with respect to the material build direction was performed with the aim to examine the influence of the layered microstructure on the fatigue behavior. Results of measurement of surface roughness, metallographic examinations of the layered material and fractographic investigation of the fatigue fracture surfaces were employed in the discussion of fatigue crack initiation in DMLS fabricated Ti6Al4V alloy. Keywords: Additive Manufacturing; Fatigue Life; Laser Powder Melting; Titanium Alloy Available at various institutes of the ASCR
High cycle fatigue life of Ti6Al4V alloy produced by direct metal laser sintering

High cycle fatigue life of Ti6Al4V alloy specimens manufactured by Direct Metal Laser Sintering (DMLS) was experimentally determined. The DMLS fabrication process was characterized by a 400 W laser ...

Konečná, R.; Nicoletto, G.; Bača, A.; Kunz, Ludvík
Ústav fyziky materiálů, 2017

Assessment of Crack Stability in a Quasi-brittle Particle Composite
Malíková, Lucie; Klusák, Jan; Keršner, Z.
2017 - English
Fracture behaviour of a crack in a particle (silicate based) composite is studied. The crack propagation depends not only on mutual elastic mismatch of matrix and aggregate but also the influence of the interfacial transition zone (ITZ) between the matrix and the aggregate is discussed. Various combinations of materials and geometry of matrix, aggregate and ITZ can improve or degrade fracture properties of the composite. Extensive numerical simulations on a basic 3-point-bending cracked specimen via the finite element method are performed in order to analyze the stress field near the crack tip. Linear elastic fracture mechanics approach is utilized in order to assess the crack stability and summarize several conclusions. Keywords: Stress intensity factor; Particle composite; Interfacial transition zone; Crack stability Available at various institutes of the ASCR
Assessment of Crack Stability in a Quasi-brittle Particle Composite

Fracture behaviour of a crack in a particle (silicate based) composite is studied. The crack propagation depends not only on mutual elastic mismatch of matrix and aggregate but also the influence of ...

Malíková, Lucie; Klusák, Jan; Keršner, Z.
Ústav fyziky materiálů, 2017

W-B-C Nanostructured Layers - Microstructure and Mechanical Properties
Buršík, Jiří; Kuběna, Ivo; Buršíková, V.; Souček, P.; Zábranský, L.; Mirzaei, S.; Vašina, P.
2017 - English
Several W-B-C layers were prepared by magnetron sputtering. The microstructure of thin layers was observed by means of scanning and transmission electron microscopy on cross sections prepared using a focused ion beam. Both undisturbed layers and the volume under indentation prints were inspected. Keywords: coating; nanostructure; electron microscopy Available at various institutes of the ASCR
W-B-C Nanostructured Layers - Microstructure and Mechanical Properties

Several W-B-C layers were prepared by magnetron sputtering. The microstructure of thin layers was observed by means of scanning and transmission electron microscopy on cross sections prepared using a ...

Buršík, Jiří; Kuběna, Ivo; Buršíková, V.; Souček, P.; Zábranský, L.; Mirzaei, S.; Vašina, P.
Ústav fyziky materiálů, 2017

Spin-dependent electrical transport at finite temperatures from the first principles
Wagenknecht, David; Carva, K.; Turek, Ilja
2017 - English
A theoretical method for finite-temperature electronic transport properties of metallic systems is presented. The developed formalism is applied to pure platinum and to random Cu-Ni alloys. Keywords: elektrical transport; finite temperature; ferromagnetic alloys Available at various institutes of the ASCR
Spin-dependent electrical transport at finite temperatures from the first principles

A theoretical method for finite-temperature electronic transport properties of metallic systems is presented. The developed formalism is applied to pure platinum and to random Cu-Ni alloys.

Wagenknecht, David; Carva, K.; Turek, Ilja
Ústav fyziky materiálů, 2017

Quantum-mechanical study of tensorial elastic and high-temperature thermodynamic properties of grain boundary states in superalloy-phase Ni3Al
Friák, Martin; Všianská, Monika; Holec, D.; Šob, Mojmír
2017 - English
Grain boundaries (GBs), the most important defects in solids and their properties are crucial for many materials properties including (in-)stability. Quantum-mechanical methods can reliably compute properties of GBs and we use them to analyze (tensorial) anisotropic elastic properties of interface states associated with GBs in one of the most important intermetallic compounds for industrial applications, Ni3Al. Selecting the Sigma 5(210) GBs as a case study because of its significant extra volume, we address the mechanical stability of the GB interface states by checking elasticity-based Born stability criteria. One critically important elastic constant, C 55, is found nearly three times smaller at the GB compared with the bulk, contributing thus to the reduction of the mechanical stability of Ni3Al polycrystals. Next, comparing properties of Sigma 5(210) GB state which is fully relaxed with those of a Sigma 5(210) GB state when the supercell dimensions are kept equal to those in the bulk we conclude that lateral relaxations have only marginal impact on the studied properties. Having the complete elastic tensor of Sigma 5(210) GB states we combine Green's-function based homogenization techniques and an approximative approach to the Debye model to compare thermodynamic properties of a perfect Ni3Al bulk and the Sigma 5(210) GB states. In particular, significant reduction of the melting temperature (to 79-81% of the bulk value) is predicted for nanometer-size grains. Keywords: Anisotropic elastic properties; Defects in solids; Elastic tensors Available at various institutes of the ASCR
Quantum-mechanical study of tensorial elastic and high-temperature thermodynamic properties of grain boundary states in superalloy-phase Ni3Al

Grain boundaries (GBs), the most important defects in solids and their properties are crucial for many materials properties including (in-)stability. Quantum-mechanical methods can reliably compute ...

Friák, Martin; Všianská, Monika; Holec, D.; Šob, Mojmír
Ústav fyziky materiálů, 2017

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