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János Ginsztler

Other affiliations: Hungarian Academy of Sciences
Bio: János Ginsztler is an academic researcher from Budapest University of Technology and Economics. The author has contributed to research in topics: Grain boundary & Creep. The author has an hindex of 8, co-authored 35 publications receiving 302 citations. Previous affiliations of János Ginsztler include Hungarian Academy of Sciences.

Papers
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TL;DR: In this article, the compressive behavior of eight different metal matrix syntactic foams (MMSFs) is investigated and the results showed that the engineering factors such as chemical compositions of the matrix material, the size of the microballoons, the previously applied heat treatment and the temperature of the compression tests have significant effects on the compression properties.
Abstract: The compressive behaviour of eight different metal matrix syntactic foams (MMSFs) are investigated and presented. The results showed that the engineering factors as chemical compositions of the matrix material, the size of the microballoons, the previously applied heat treatment and the temperature of the compression tests have significant effects on the compressive properties. The smaller microballoons with thinner wall ensured higher compressive strength due to their more flawless microstructure and better mechanical stability. According to the heat treatments, the T6 treatments were less effective than expected; the parameters of the treatment should be further optimised. The elevated temperature tests revealed ∼30% drop in the compressive strength. However, the strength remained high enough for structural applications; therefore MMSFs are good choices for light structural parts working at elevated or room temperature. The chemical composition – microballoon type – heat treatment combinations give good potential for tailoring the compressive characteristics of MMSFs.

125 citations

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TL;DR: In this article, a quantitative analysis of activation process during hold time under creep-fatigue interaction conditions has been interpreted for 1Cr-Mo-V steel and it is suggested that the rate controlling dislocation mechanism is either cross slip, or overcoming Peierls-Nabarro stress.
Abstract: A quantitative analysis of activation process during hold time under creep–fatigue interaction conditions has been interpreted for 1Cr–Mo–V steel. The apparent activation energy for stress relaxation at the saturated stage was the same for the lattice diffusion activation energy of iron i.e. 251 kJ mol −1 independent of the total strain range. Analyzing the value of the activation volume for the initial transient relaxation behavior, it is suggested that the rate controlling dislocation mechanism is either cross slip, or overcoming Peierls–Nabarro stress. The trend of increasing activation energy with the relaxed stress was found to be due to the effective stress which was decreased with time and approached to zero.

46 citations

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TL;DR: In this paper, the effect of carbon on grain boundary serration was investigated in three kinds of 316 stainless steels with different carbon content for an experiment with three different types of grain boundaries.

22 citations

Journal ArticleDOI
TL;DR: In this article, a quantitative analysis of the stress dependence on stress relaxation creep rate during hold time under creep-fatigue interaction conditions has been conducted for 1Cr-Mo-V steel and it was shown that the transient behavior of the Norton power law relation is observed in the early stage of stress relaxation in which the instantaneous stress is relaxed drastically, which occurs due to the initial loading condition.
Abstract: A quantitative analysis of the stress dependence on stress relaxation creep rate during hold time under creep-fatigue interaction conditions has been conducted for 1Cr-Mo-V steel. It was shown that the transient behavior of the Norton power law relation is observed in the early stage of stress relaxation in which the instantaneous stress is relaxed drastically, which occurs due to the initial loading condition. But after the initial transient response in a 5 hour tensile hold time, the relations between strain rate and instantaneous stress represented the same creep behavior, which is independent of the initial strain level. The value of stress exponent after transition was 17 which is the same as that of the typical monotonic creep suggested from several studies for 1Cr-Mo-V steel. Considering the value of the activation energy for the saturated relaxation stage, it is suggested that the creep rate is related to instantaneous stress and temperature by the Arrhenius type power law.

20 citations

01 Jan 2012
TL;DR: In this paper, the compressive behaviour of three different metal matrix syntactic foams (MMSFs) was investigated, and the results showed that the engineering factors such as the size of the used hollow spheres, the aspect ratio (height / diameter ratio) of the specimens and the temperature of the tests have significant effects on compressive strength and properties.
Abstract: The compressive behaviour of three different metal matrix syntactic foams (MMSFs) was investigated. The results showed that the engineering factors such as the size of the used hollow spheres, the aspect ratio (height / diameter ratio) of the specimens and the temperature of the tests have significant effects on the compressive strength and properties. The smaller microballoons with thinner wall ensured higher compressive strength due to their more flawless microstructure and better mechanical stability. The higher aspect ratio of the specimens resulted in worse compressive characteristics (lower strength, lower specific energy consuming capacity). The elevated temperature tests revealed ~30% drop in the compressive strength. However, the strength remained high enough for structural applications; therefore MMSFs are good choices for light structural parts working at elevated or room temperature. The proper size selection of the reinforcing hollow spheres ensures potential for tailoring the compressive characteristics of MMSFs.

14 citations


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Abstract: This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

1,668 citations

Journal ArticleDOI
TL;DR: In this article, an experimental study on the ballistic impact behavior of hybrid composites is presented, and it is observed that ballistic limit velocity, V 50 can be increased by adding E-glass layers to T300 carbon layers compared with only carbon composites for the same laminate thickness.

136 citations

Journal ArticleDOI
TL;DR: In this article, a study of the cyclic stress partitioning is presented, where the authors identify the microstructural mechanisms leading to the softening effect usually presented by martensitic steels under cyclic loadings.
Abstract: In order to identify the microstructural mechanisms leading to the softening effect usually presented by martensitic steels under cyclic loadings (with or without hold times), a study of the cyclic stress partition is presented. As the usual stress partitioning methods were found to be inadequate in the present case, a new method based both on Cottrell's method and on the Statistical Process Control principles, is proposed. This new method is used to distinguish between the kinematic, the isotropic and the viscous parts of the cyclic stress. The evolutions of these different stresses are evaluated for several strain amplitudes and temperatures under pure fatigue loading in this first part. It is shown that the softening effect is mainly due to a decrease of the backstress: the higher the strain amplitude, the stronger and the faster the softening effect. The isotropic stress is found to be independent of the strain amplitude, but increases when the temperature decreases. Whereas the viscous stress represents a large part of the total stress at 823 K, it becomes almost negligible below 673 K. These results are finally linked to the microstructural coarsening previously observed and modelled. Therefore, the decrease of the kinematic stress can be related to grain size effect.

118 citations

Journal ArticleDOI
TL;DR: In this paper, four Al alloys (Al99.5, AlSi12, AlMgSi1 and AlCu5) and Globomet grade iron hollow spheres were used as matrix and reinforcing material, respectively.

118 citations

Journal ArticleDOI
TL;DR: An updated overview of the different manufacturing processes of composite and nanocomposite metal foams is provided.
Abstract: Open-cell and closed-cell metal foams have been reinforced with different kinds of micro- and nano-sized reinforcements to enhance their mechanical properties of the metallic matrix. The idea behind this is that the reinforcement will strengthen the matrix of the cell edges and cell walls and provide high strength and stiffness. This manuscript provides an updated overview of the different manufacturing processes of composite and nanocomposite metal foams.

103 citations