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Showing 1 to 20 of 335 for “"Engineering, Metallurgy."”.
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PRINCIPLES OF INCREMENTAL FORGING.
PRINCIPLES OF INCREMENTAL FORGING.
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The effect of copper on the eutectoid transformation in ductile iron
As a result of the shortage in the availability of suitable steel scrap, trace elements are unintentionally added to ductile iron from the scrap available for melting. The effect of some of these trace elements on graphite shape, the resulting microstructure, and the dimensional behavior of the …
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Transient Study of Turbulent Flow and Particle Transport During Continuous Casting of Steel Slabs
Using the computed three-dimensional time-dependent flow velocities, the motion and capture of impurity particles during continuous casting were simulated using a Lagrangian approach. A criterion was developed to model particle pushing and capture by the solidifying shell and was incorporated into …
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Efficient Thermo-Mechanical Model for Solidification Processes and Its Applications in Steel Continuous Casting
The model is then improved to add coupling of heat flow and stress generation that are increment-wise coupled through the size of the interfacial gap. Coupled results are first verified with a solidifying slice, and then quantitatively against the CON2D 2D model of billet casting by fully employing …
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Mesoscale Models for Stacking Faults, Deformation Twins and Martensitic Transformations: Linking Atomistics to Continuum
Finally, we extend the present work to martensitic transformations and determine the energy pathway for B2→B19 transformation in NiTi. Based on our ab initio DFT calculations, we propose a combined distortion-shuffle pathway for B2→B19 transformation in NiTi. Our results indicate that in …
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Micromechanics of Hydrogen-Induced Crack Initiation in Pipeline Steels and Subcritical Crack Growth
To further explore the influence of hydrogen on ductile fracture, we model sustained-load cracking in the iron-base superalloy 1N903 at hydrogen pressures at which fracture is governed by plasticity. Through a micromechanics analysis, we quantify the void growth dependence on stress triaxiality and …
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The Effect of Stress State and Precipitation on Stress-Induced Martensitic Transformations in Polycrystalline and Single Crystal Shape Memory Alloys: Experiments and Micro-Mechanical Modeling
To properly understand stress-induced transformations in aged NiTi single crystals, a micro-mechanical model is used to quantify the stress fields outside perfectly coherent Ti$\sb{11}$Ni$\sb{14}$ precipitates in NiTi. Using the model, the decrease in the orientation dependence of $\sigma\sb{\rm …
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The Competing Roles of Microstructure and Flaw Size on the Fatigue Limit of Metals
Research includes the development and verification of an analytical model that addresses the fatigue process, namely the threshold condition of non-propagating cracks. Two parameters are identified to govern the fatigue resistance: non-propagating crack size and crack barrier strength. The concept …
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Argon Bubble Behavior in Slide-Gate Tundish Nozzles During Continuous Casting of Steel Slabs
"Argon injection into a tundish nozzle is an efficient and widely employed method to reduce nozzle clogging in the continuous casting process. It also affects casting operation and product quality by changing the flow pattern in the nozzle and mold. The current work combines mathematical modeling …
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A Numerical Investigation of Loading Rate Effects on Pre-Cracked Charpy V-Notch Specimens
To quantify the effects of loading rate on ductile crack growth in CVN specimens, plane strain, finite element analyses are used to model ductile crack extension in specimens subjected to quasi-static and impact loading. The Gurson-Tvergaard dilatant plasticity model for voided materials describes …
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Elastic-Damaging Plasticity Model for Ductile Fracture
… steels and that can be used in practical engineering problems. Ductile fracture occurs by a sequential process of nucleation, growth and coalescence of microvoids or microcracks. However, the model uses a continuum approach that can capture the global effect of ductile fracture behavior. …
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Molecular Dynamics Study of Microstructural Evolution in Alloys Subjected to Severe Plastic Deformation
The atomic transport resulting from plastic deformation has been analyzed in new depths by tracking the evolution of pair of marker atoms. This analysis has proved to be a powerful tool in identifying the deformation mechanisms, including the glide of leading and trailing partial dislocations, and …
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Synthesis, Consolidation, and Mechanical Testing of Nanophase Metals
Indentation creep experiments were performed on nanocrystalline copper and palladium specimens and also on sinterforged Ti-48Al specimens. The copper and palladium specimens showed a higher creep rate than their microcrystalline counterparts, exhibiting creep even at room temperature. The …
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Densification and Mechanical Properties of Nanocrystalline FeAl
Impression creep measurements were performed on nanocrystalline FeAl specimens sinterforged to full density. The tests were conducted over the temperature range of 500--600°C, and using punches with diameters of 0.5 and 0.2 mm. For specimens sinterforged at 500°C, a decrease in creep rate …
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Pathways to a Family of Low-Cost, High-Performance, Metal Matrix Composites Based on Aluminum Diboride in Aluminum
The continued development of a new family of metal matrix composites based on the in-situ formation of AlB2 flakes in liquid aluminum is described. First, a new synthesis technique for the preparation of high aspect ratio AlB2 is demonstrated. Borax and B2O 3 were reacted with molten aluminum to …
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Thermal Reversibility of the Flow Stress in Single Crystal Titanium-56 Aluminum
The [021] oriented samples were also analyzed in order to observe ordinary dislocation motion without the presence of superdislocations. It was found that all ordinary dislocations observed were mostly 60°, mixed dislocations, with relatively few screw ordinary dislocations. At room …
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A Heat Transfer Modeling Study of Rail Thermite Welding
This investigation is concerned with the effect of welding conditions on the development of fatigue-critical weld defects in rail thermite welds. Finite Element Modeling (FEM) was used to analyze the heat transfer behavior during the thermite welding process. The results of the thermal analyses …
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Modeling Interfacial Slag Layer Phenomena in the Shell /Mold Gap in Continuous Casting of Steel
The model was also applied to interpret the crystallization behavior of slag. A mechanism for the formation of this crystalline layer was proposed that combined the effects of a shift in the viscosity curve, a decrease in the liquid slag conductivity due to partial crystallization, and an increase …
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Plastic Instability Due to Collective Dislocation Effect in Portevin-Le Châtelier Effect and Dislocation Nucleation
Two manifestations of plastic instability, the Portevin-Le Châtelier (PLC) effect and the cooperative nucleation of dislocation loops, have been studied. In the experimental part of the work, two creep-type mechanical tests have been conducted on a Cu-10at.%Al single crystal and a Mg single …
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Structure and Phase Transformation of Nanocrystalline and Amorphous Alloy Thin Films
The systematic study on the structure and morphology of Ag-Si alloy thin films shows nanocrystalline Ag clusters embedded in amorphous Si matrix for samples of different compositions and thicknesses. Ag cluster sizes increase from 2.5 nm to 3.5 nm as annealing temperature increases from room …
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