Searched for: author:"Kumar, A."
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Ravi, A.M. (author), Kumar, A. (author), Herbig, Michael (author), Sietsma, J. (author), Santofimia, Maria Jesus (author)
The rate of bainite formation depends on several factors such as austenite grain size, decomposition of austenite into other phases and austenite composition. Although studies have been carried out to understand various factors affecting bainite formation, open lines of investigation still remain. In this work, the effect of ferrite formation...
journal article 2020
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Kumar, A. (author)
In this PhD thesis, we investigate the microstructural evolution and damage in different steel grades used in railway applications such as switches, crossings and curved tracks, which are the key components in the rail transportation industries around the world. The damage in these components leads to a maintenance cost of billions of Euros per...
doctoral thesis 2019
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Messaadi, M. (author), Oomen, Matthijs (author), Kumar, A. (author)
Bainitic steels are gaining popularity for application in the railway switches and crossing, thanks to their better rolling contact fatigue (RCF) and wear resistance. The rail degradation caused by RCF and wear could be also reduced by the use of friction modifiers (FM) through their ability to reduce the lateral load during wheel passage....
journal article 2019
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Kumar, A. (author), Agarwal, G. (author), Petrov, R.H. (author), Goto, S. (author), Sietsma, J. (author), Herbig, M. (author)
The formation of White (WEL) and Brown Etching Layers (BEL) on rail raceways during service causes the initiation of microcracks which finally leads to failure. Detailed characterization of the WEL and the BEL in a pearlitic rail steel is carried out from micrometer to atomic scale to understand their microstructural evolution. A...
journal article 2019
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Saxena, A.K. (author), Kumar, A. (author), Herbig, M. (author), Brinckmann, S. (author), Dehm, G. (author), Kirchlechner, C. (author)
The fracture behavior of a white etching layer formed on the rail surface in pearlitic steels during the rail-wheel contact is investigated using indentation-based microcantilever fracture tests. The sample thickness is in the order of 5 μm. The local fracture toughness of the white etching layer, its neighboring brown etching layer, martensite...
journal article 2019
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Goulas, C. (author), Kumar, A. (author), Mecozzi, M.G. (author), Castro-Cerda, Felipe Manuel (author), Herbig, Michael (author), Petrov, R.H. (author), Sietsma, J. (author)
Atomic-scale investigation was performed on 51CrV4 steel, isothermally held at different temperatures within the bainitic temperature range. Transmission electron microscopy (TEM) analysis revealed three different morphologies: lower, upper, and inverse bainite. Atom Probe Tomography (APT) analysis of lower bainite revealed cementite...
journal article 2019
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Agarwal, G. (author), Kumar, A. (author), Richardson, I.M. (author), Hermans, M.J.M. (author)
Solidification cracking susceptibility during laser welding was studied experimentally and numerically in advanced high strength steel sheets, namely transformation-induced plasticity (TRIP) and dual phase (DP) steel. Using the same heat input, laser bead-on-plate welding was carried out on single sided clamped specimens at various starting...
journal article 2019
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Valdes-Tabernero, M. A. (author), Celada-Casero, Carola (author), Sabirov, I. (author), Kumar, A. (author), Petrov, R.H. (author)
This work focuses on the effect of soaking time on the microstructure during ultrafast heat treatment of a 50% cold rolled low carbon steel with initial ferritic-pearlitic microstructure. Dilatometry analysis was used to estimate the effect of heating rate on the phase transformation temperatures and to select an appropriate inter-critical...
journal article 2019
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Hajizad, O. (author), Kumar, A. (author), Li, Z. (author), Petrov, R.H. (author), Sietsma, J. (author), Dollevoet, R.P.B.J. (author)
Wheel–rail contact creates high stresses in both rails and wheels, which can lead to different damage, such as plastic deformation, wear and rolling contact fatigue (RCF). It is important to use high-quality steels that are resistant to these damages. Mechanical properties and failure of steels are determined by various microstructural...
journal article 2019
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Kumar, A. (author), Saxena, A. K. (author), Kirchlechner, C. (author), Herbig, M. (author), Brinkmann, S. (author), Petrov, R.H. (author), Sietsma, J. (author)
Failure in engineering materials like steels is strongly affected by in-service deleterious alterations in their microstructure. White Etching Layers (WELs) are an example of such in-service alterations in the pearlitic microstructure at the rail surface. Cracks initiate in the rails due to delamination and fracture of these layers and...
journal article 2019
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Agarwal, G. (author), Kumar, A. (author), Gao, H. (author), Amirthalingam, M. (author), Moon, S. C. (author), Dippenaar, R. J. (author), Richardson, I.M. (author), Hermans, M.J.M. (author)
In situ high-temperature laser scanning confocal microscopy is applied to study solidification cracking in a TRIP steel. Solidification cracking was observed in the interdendritic region during the last stage of solidification. Atom probe tomography revealed notable enrichment of phosphorus in the last remaining liquid. Phase field...
journal article 2018
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Ganesh Kumar, A. (author)
master thesis 2017
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Suresh Kumar, A. (author)
master thesis 2016
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Kumar, A. (author)
Detailed investigation of factors that influence Wind-Tunnel modeling in vehicle thermal simulation. Tasks involved observing and investigating the additional equipment attached to the wind tunnel model that could alter the results when compared with the computational simulation results. All the study is based on computational simulation finally...
master thesis 2016
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Kumar, A. (author)
A seismic survey should be designed such that imaging of the acquired data leads to a sufficiently accurate subsurface image. For that purpose, methods for acquisition geometry analysis and design are available. These methods are used to judge whether an acquisition geometry is suited for the specified objectives. Conventional 2D and 3D...
doctoral thesis 2015
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We perform renormalization group analysis (RG) of the Navier-Stokes equation in the presence of constant mean velocity field $\mathbf U_0$, and show that the renormalized viscosity is unaffected by $\mathbf U_0$, thus negating the ``sweeping effect", proposed by Kraichnan [Phys. Fluids {\bf 7}, 1723 (1964)] using random Galilean invariance....
conference paper 2015
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We construct a unified shell model for stably stratified and convective turbulence. Shell model simulation of stably stratified flow in turbulent regime exhibit Bolgiano-Obukhbov (BO) scaling in which the kinetic energy spectrum varies as $k^{-11/5}$. However, simulation of convective turbulence shows Kolmogorov's spectrum. These results are...
conference paper 2015
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Kumar, A. (author), Blacquiere, G. (author), Pedersen, M.W. (author), Goertz, A. (author)
Despite a tremendous leap in efficiency and wave field sampling over the last two decades, it is sometimes still difficult to achieve adequate coverage and resolution with marine streamer acquisition. It is therefore necessary to carefully study the acquisition geometry, especially with respect to resolution and image quality in the cross-line...
conference paper 2015
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Kumar, A. (author), Blacquiere, G. (author), Verschuur, D.J. (author)
Recent advances in survey design have led to conventional common-midpoint-based analysis being replaced by the subsurface-based seismic acquisition analysis and design, with the emphasis on advance techniques of illumination analysis. Amongst them are wave-equation-based seismic illumination analyses such as the so-called focal beam method. The...
conference paper 2014
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Kumar, A. (author), Kumar, P. (author), Anandan, A. (author), Fernandes, T.F. (author), Ayoko, G.A. (author), Biskos, G. (author)
The aim of this study is to identify current knowledge gaps in fate, exposure, and toxicity of engineered nanomaterials (ENMs), highlight research gaps, and suggest future research directions. Humans and other living organisms are exposed to ENMs during production or use of products containing them. To assess the hazards of ENMs, it is important...
journal article 2014
Searched for: author:"Kumar, A."
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