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Development of Creep Damage in Similar Weld Joints of P92 Steel Pipe
Král, Petr; Sklenička, Václav; Kuchařová, Květa; Svobodová, M.; Kvapilová, Marie; Dvořák, Jiří
2017 - English
The microstructure and creep behaviour of the welded joints of P92 steel pipe were\ninvestigated in order to determine the influence of orbital heat welding technology on the creep\nresistance. Creep specimens were machined from the welded joints. Tensile creep tests of welded\njoints were performed at 873 K using different stresses. The microstructure of tested specimens was\ninvestigated by scanning electron microscope Tescan equipped with an electron-back scatter\ndiffraction. The creep results showed that the creep fracture strain of the welded joints decreases\nwith decreasing value of applied stress. Microstructure investigation showed that fracture behaviour\nof welded joints is influenced by an enhanced cavity formation at grain boundaries in the heataffected\nzone causing lower fracture ductility.
Keywords:
P92 steel; welding; creep damage; creep fracture; microstructure
Available at various institutes of the ASCR
Development of Creep Damage in Similar Weld Joints of P92 Steel Pipe
The microstructure and creep behaviour of the welded joints of P92 steel pipe were\ninvestigated in order to determine the influence of orbital heat welding technology on the creep\nresistance. Creep ...
Influence of surface morphology on fatigue behavior of metastable austenitic stainless steel AISI 347 at ambient temperature and 300°C
Smaga, M.; Skorupski, R.; Mayer, P.; Kirsch, B.; Aurich, J. C.; Raid, I.; Seewig, J.; Man, Jiří; Eifler, D.; Beck, T.
2017 - English
The effect of surface modification by cryogenic turning on fatigue behavior of metastable austenitic stainless steel AISI 347 was investigated in stress-controlled fatigue tests at ambient temperature (AT) and 300 °C in air. Five different surface morphologies were manufactured by the variation of turning parameters. Surface and near surface morphology were comprehensively characterized by various experimental techniques. The experimental data on the cyclic deformation behavior, stress-strain response and fatigue life for all surface morphologies are reported.
Keywords:
metastable austenitic stainless steel; cryogenic turning; fatigue; surface morphology; martensite
Available at various institutes of the ASCR
Influence of surface morphology on fatigue behavior of metastable austenitic stainless steel AISI 347 at ambient temperature and 300°C
The effect of surface modification by cryogenic turning on fatigue behavior of metastable austenitic stainless steel AISI 347 was investigated in stress-controlled fatigue tests at ambient temperature ...
Detekce plasticity v tenkých hliníkových vrstvách pomocí bulge testu
Holzer, Jakub; Pikálek, Tomáš; Buchta, Zdeněk; Lazar, Josef; Tinoco, H.A.; Chlupová, Alice; Náhlík, Luboš; Sobota, Jaroslav; Fořt, Tomáš; Kruml, Tomáš
2017 - English
The Bulge test proved to be a useful tool for measuring elastic properties of thin films and\nfree standing membranes, particularly Young’s modulus and residual stress. The basic principle\nof bulge test is application of differential pressure on one side of the a membrane, measurement of\nthe shape of bulged surface as a function of pressure, in this case via laser interferometer, and\nevaluation of a pressure-deflection relationship. In this study, bilayer membrane consisting of a\nsilicon nitride supporting layer and an aluminium layer deposited by means of magnetron\nsputtering is subjected to the bulge test. The results clearly show signs of a non-linear behavior\nthat is caused by plastic deformation in the aluminium layer. Finite element analysis is being\ndeveloped to describe this behavior because analytical model using deflection of central point and\npressure relation falls apart in case of non-linearity.
Keywords:
Bulge test; thin films; mechanical test
Available at various institutes of the ASCR
Detekce plasticity v tenkých hliníkových vrstvách pomocí bulge testu
The Bulge test proved to be a useful tool for measuring elastic properties of thin films and\nfree standing membranes, particularly Young’s modulus and residual stress. The basic principle\nof bulge ...
ON THE ENERGY RELEASE RATE OF THE CRACK EMANATING FROM THE INCLUSION INTERPHASE
Profant, T.; Hrstka, M.; Klusák, Jan; Kersner, Z.
2017 - English
The problem of the crack emanating from the interphase region of the circular inclusion is investigated. The problem combines an application of dislocation distribution technique for a crack modelling and the method of boundary integral equations to approximate the loading along the boundary of the domain containing an inclusion. The topological derivative method provides the combination of both approaches and results to the evaluation of the energy release rate of the arbitrary oriented microcrack emanating from the inclusion and matrix interphase. The fundamental solution intended to the boundary integral method such as the continuously distributed dislocation technique is based on the application of Muschelishvili complex potentials in the form of the Laurent series. The coefficients of the series are evaluated from the compatibility conditions along the interfaces of inclusion, interface and matrix.
Keywords:
Microcrack; Inclusion; Interphase; Singular integral equation; Dislocation distribution technique; Complex potentials
Available at various institutes of the ASCR
ON THE ENERGY RELEASE RATE OF THE CRACK EMANATING FROM THE INCLUSION INTERPHASE
The problem of the crack emanating from the interphase region of the circular inclusion is investigated. The problem combines an application of dislocation distribution technique for a crack modelling ...
Characterization of Mo-B-C nanostructured coating microstructure by means of AEM and GDOES
Buršík, Jiří; Svoboda, Milan; Švábenská, Eva; Buršíková, V.; Souček, P.; Zábranský, L.; Vašina, P.
2017 - English
A Mo-B-C nanostructured coating was prepared on WC-Co hard-metal substrate by magnetron sputtering. The details of microstructure of deposited thin layer as well as elements redistribution caused by subsequent annealing at 1000°C were studied by several experimental techniquec.
Keywords:
coating; nanostructure; analytical electron microscopy
Available at various institutes of the ASCR
Characterization of Mo-B-C nanostructured coating microstructure by means of AEM and GDOES
A Mo-B-C nanostructured coating was prepared on WC-Co hard-metal substrate by magnetron sputtering. The details of microstructure of deposited thin layer as well as elements redistribution caused by ...
Low cycle fatigue behaviour and fatigue crack initiation in MAR-M247 at 700 °c
Šulák, Ivo; Obrtlík, Karel; Hrbáček, K.
2017 - English
The second generation nickel-based superalloy MAR-M247 offersa satisfying combination of fatigue and creep properties and oxidation and corrosion resistance that arerequired for application at elevated temperatures in hostile environments. The microstructure consists mainly oftheface centred cubic γ matrix and ordered γ ́ strengthening precipitates (L12crystal structure). The present work focuses on low cycle fatigue (LCF) behaviour of polycrystalline nickel-based superalloy MAR-M247 at high temperature. LCF tests were conducted on cylindrical specimens in symmetrical push-pull cycle under strain control with constant total strain amplitude and strain rate at 700 °C in ambientair. Cyclic stress-strain curvesand fatigue life curves in the representation ofplastic strain amplitude vs. stress amplitude andstress amplitude vs. the number of cycles to failure, respectively,were plotted and compared with data obtained on Inconel 713LC. Special attention waspaid to the investigation of crack initiation in MAR-M247 during low cycle fatigue. Crack initiation sites were studied by means of scanning electron microscopy (SEM) in dual beam microscope TESCAN LYRA 3 XMU FESEM equipped with focus ion beam (FIB). Specimens’ surface observations revealed the formation of pronounced surface relief indicating localisation of plastic deformation.Observations in transmission electron microscope (TEM)confirmed localisation of cyclic plastic deformation in persistent slip bands along {111} slip planes. Fractographic analysis revealed fatigue crack initiation sites. Fatigue crack propagation in stage I was typical of smooth facets up to 500 μm long.
Keywords:
Cyclic stress-strain curve; Fatigue crack initiation; Fatigue life
Available at various institutes of the ASCR
Low cycle fatigue behaviour and fatigue crack initiation in MAR-M247 at 700 °c
The second generation nickel-based superalloy MAR-M247 offersa satisfying combination of fatigue and creep properties and oxidation and corrosion resistance that arerequired for application ...
Magnetic properties of 42CrMo4 steel
Bulín, T.; Švábenská, Eva; Hapla, Miroslav; Roupcová, Pavla; Ondrušek, C.; Schneeweiss, Oldřich
2017 - English
Low alloyed high-grade chrome-molybdenum ferritic steel was investigated from the point of views of magnetic properties in dependence on heat and mechanical treatment. This steel can be used as components of magnetic circuits or some parts in electrical equipment. The basic information on structure and phase composition was obtained by optical and scanning electron microscopy, X-ray Powder Diffraction and Mössbauer Spectroscopy. The temperature stability of the material was proved by measurements of temperature dependences of magnetic moment. The magnetic parameters were obtained by measuring of magnetic hysteresis loops in dependence on saturation field and their frequencies. The results are discussed from the point of view of possible applications as a magnetic material in the very extremely environment, where high mechanical stresses and elevated temperatures can occur.
Keywords:
Magnetic materials; magnetic properties; steel
Available at various institutes of the ASCR
Magnetic properties of 42CrMo4 steel
Low alloyed high-grade chrome-molybdenum ferritic steel was investigated from the point of views of magnetic properties in dependence on heat and mechanical treatment. This steel can be used as ...
A numerical investigation of the stress intensity factor for a bent chevron notched specimen: Comparison of 2D and 3D solutions
Seitl, Stanislav; Miarka, Petr; Sobek, J.; Klusák, Jan
2017 - English
In the contribution, normalized stress intensity factors for three- and four-point bending specimens with a chevron notch is introduced by varying the chevron notch angle and length. The three- and two-dimensional models of bent chevron notched specimens in the software ANSYS were prepared by using possible symmetrical conditions. The 2D model was used with variable thicknesses of the layers representing the characteristic shape of the chevron notch (with the plane stress boundary condition). The numerically obtained results from the 2D and 3D solutions are compared with data from literature.
Keywords:
Fracture mechanics; Calibration curve; Stress intensity factors
Available at various institutes of the ASCR
A numerical investigation of the stress intensity factor for a bent chevron notched specimen: Comparison of 2D and 3D solutions
In the contribution, normalized stress intensity factors for three- and four-point bending specimens with a chevron notch is introduced by varying the chevron notch angle and length. The three- and ...
Fatigue damage prediction of short edge crack under various load: Direct Optimized Probabilistic Calculation
Krejsa, M.; Seitl, Stanislav; Brožovský, J.; Lehnert, P.
2017 - English
Fatigue crack propagation depends on a number and value of stress range cycles. This is a time factor in the course of reliability for the entire designed service life. Three sizes are important for the characteristics of the propagation of fatigue cracks - initial size, detectable size and acceptable size. The theoretical model of a fatigue crack progression can be based on a linear elastic fracture mechanics (uses Paris-Erdogan law). Depending on location of an initial crack, the crack may propagate in structural element (e.g. from the edge or from the surface under various load) that could be described by calibration functions. When determining the required degree of reliability, it is possible to specify the time of the first inspection of the construction which will focus on the fatigue damage. Using a conditional probability and Bayesian approach, times for subsequent inspections can be determined based on the results of the previous inspection. For probabilistic modelling of a fatigue crack progression was used the original and a new probabilistic method - the Direct Optimized Probabilistic Calculation ('DOProC'), which uses a purely numerical approach without any simulation techniques or approximation approach based on optimized numerical integration. Compared to conventional simulation techniques is characterized by greater accuracy and efficiency of the computation.
Keywords:
fatigue; crack propagation; calibration function
Available at various institutes of the ASCR
Fatigue damage prediction of short edge crack under various load: Direct Optimized Probabilistic Calculation
Fatigue crack propagation depends on a number and value of stress range cycles. This is a time factor in the course of reliability for the entire designed service life. Three sizes are important for ...
Effect of alloying and thermal processing on mechanical properties of tial alloys
Chlupová, Alice; Heczko, Milan; Obrtlík, Karel; Beran, Přemysl; Kruml, Tomáš
2017 - English
Two -based TiAl alloys with 7 at.% of Nb, alloyed with 2 at.% Mo and 0.5 at.% C, were studied. A heat treatment leading to very fine lamellar microstructure was applied on both alloys. Microstructure after the heat treatment was described and mechanical properties including fatigue behaviour were measured. The as-received material alloyed with C possesses high strength and very limited ductility, especially at RT. After application of selected heat treatment it becomes even more brittle; therefore, this process could be considered as not appropriate for this alloy. On the contrary, in the case of Mo alloyed material, both strength and ductility are improved by the heat treatment at RT and usual working temperature (~750 °C). Presence of the phase is responsible for this effect. The selected heat treatment thus can be an alternative for this alloy to other thermomechanical treatments as high temperature forging.
Keywords:
Fatigue; Heat treatment; Lamellar microstructure; Mechanical properties; TiAl alloys
Available at various institutes of the ASCR
Effect of alloying and thermal processing on mechanical properties of tial alloys
Two -based TiAl alloys with 7 at.% of Nb, alloyed with 2 at.% Mo and 0.5 at.% C, were studied. A heat treatment leading to very fine lamellar microstructure was applied on both alloys. Microstructure ...
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