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Groupe de soutien

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Stepan Saveliev
Stepan Saveliev

Dod ( 387 ) Mp4 ^NEW^


Our Group is interested in the quantitative and qualitative measurement of materials behavior at lower(micron to sub-micron to nanometer) length scales over various material systems. Our research is focused on these main areas:




Dod ( 387 ) mp4



This project utilizes an integrated experimental (Iowa State University) and computational (Dr. Garritt Tucker, Colorado School of Mines) effort funded by the Army Research Office to engineer multilayered nanocomposite materials with unprecedented tunable strength and toughness. The nanocomposite is composed of alternating layers of metallic and MAX phase layers with lamellar thickness reduced to the nanoscale. Unique to other multilayered systems, the metal-MAX architecture detailed here is composed of a hierarchical topology with interfaces between the layers in direct competition with internal atomistic interfaces within the MAX layer to drive enhanced macroscopic mechanical behavior. Experimental synthesis and novel nanomechanical testing (i.e. nanoindentation, micropillar compression, and micro-tensile tension) performed at Iowa State University will look to quantify and qualify material properties and behaviors, providing experimental feedback for computational modeling and simulations developed by collaborators at the Colorado School of Mines investigating the interfacial structures and stability to elucidate the relationship between the hierarchical structure and improved mechanical properties.


We seek to exploit the inherent uniformity, reasonable compressibility, and thermally-activated sintering of gas atomization reaction synthesis (GARS) precursor oxide dispersoid strengthened (ODS) ferritic steel powder to produce full density powder compacts by conventional vacuum warm pressing. Resulting billets will be cold cross-rolled to sheet material for duct applications. Hollow preforms, with a dissimilar powder core that can be readily removed, will be produced for cladding applications.The flow of information between the four tasks to cyclically refine the design of damage-resistant material. The proposed work combines discovery and material design elements to achieve the project goal.Grain Interface Functional Design to Create Damage Resistance in Polycrystalline Metallic Materials


Even though polycrystalline metallic materials are ubiquitous in daily life, when and where metallic structural components damage and fail is difficult to predict, which generally leads to overdesign. This collaborative project addresses control of feature and defect character along with the internal stress state present for the manufacturing of polycrystalline metals against failure. Our group is responsible for material processing and sample preparation of a high-purity body-centered cubic tantalum, followed by micromechanical investigations, micro-pillar testing, and dynamic testing at the microscale. This project aims to design a manufacturing process to produce material that reduces damage by 30% over that in the as-received and annealed state.


This work focuses on the powder-fed AM technique- Laser Directed Energy Deposition (LDED) because of its inherent advantages when compared to the traditional route of producing Lamellar Shape Memory Alloy Structures (LSMAS). The AM LDED can be used for tailoring properties by controlling the elementally blended powder feedstock. The present work concentrates on understanding the anisotropy in the distribution in the precipitate morphology, grain texture and grain orientation along the LDED AM build height and build directions. The project aims to develop novel nano-/micro- scale test approaches that will establish the dependence of multi-scale deformation mechanisms on the differential microstructure length scales: precipitates and grains (nm-μm), AM layer/pass build plan (10-100 μm) and lamella of LSMAS (μm to mm). The interfaces between the build layers and between lamellae are in direct competition with the martensitic morphology and interactions with micro-constituents in the SMA to drive a tailored macroscopic mechanical behavior.


Furthermore, these techniques are of special advantage in studies of extreme environments, such as the study of mechanical degradation of irradiated materials (Fig), where nanoindentation shows the greatest promise due to its non-destructive nature, ease of experimentation (only a polished surface prior to ion irradiation is needed), high throughput and versatility. Our 2013 DOE-NEET and 2019 DOE Nuclear Energy University Program fellowship grants on this topic aims to combine the information obtained from spherical nanoindentation with different indenter sizes with structure characterization methods (e.g. EBSD) and physics-based finite element simulations of indentations to arrive at reliable estimates of the local properties.


S. Pathak, J. Gregory Swadener, S. R. Kalidindi, H.-W. Courtland, K. J. Jepsen and H. M. Goldman,Journal of the Mechanical Behavior of Biomedical Materials,2011,4,34-43. S. Pathak, S. J. Vachhani, K. J. Jepsen, H. M. Goldman and S. R. Kalidindi,Journal of the Mechanical Behavior of Biomedical Materials,2012


In this work we explored the mechanical behavior of vertically aligned carbon nanotubes (VACNTs) also known as carbon nanotube (CNT) arrays, bundles, brushes, foams, forests, mats, and turfs. VACNTs are complex, hierarchical structures of intertwined tubes arrayed in a nominally vertical alignment due to their perpendicular growth from a stiff substrate. They are a unique class of materials having many of the desirable thermal, electrical, and mechanical properties of individual carbon nanotubes, while exhibiting these properties through the collective interaction of thousands of tubes on a macroscopic scale.


We investigated the synthesis techniques by which VACNTs are synthesized, which is the primary factor affecting their complex, hierarchical morphology. This microstructure, in turn, affects their mechanical behavior, in particular the modulus, buckling strength, and recoverability. Using nanomechanical testing techniques, we compared the mechanical response of VACNTs under different loading conditions, namely compression and indentation. We analyzed the resultant large variation in structure and properties of VACNTs (porosity, CNT tube thickness, modulus, buckling strength), their large scale deformation and buckling behavior, viscoelasticity and potential applications.


You've all heard by now that The Great Reset is upon us. But what is The Great Reset, exactly, and what does it mean for the future of humanity? Join James for this in-depth exploration of the latest rebranding of the New World Order agenda and its vision of a post-human Fourth Industrial Revolution.


Let the testing begin. Each of the great resetters will be tracked 24/7 for the next years. Their movements and all camera images will be posted on each of these nobel people dedicated to a better world for the others. Watch Bill and Malinada as they travel about the world on live internet tracking with daily summaries. See all the points of intersection with each resetter among the other resetters. See all their biometrics 24/7. Daily summaries by resetter interst groups.


I remember reading about slavery from the colonial point of view. Colonialism. The colonialists all said that the slaves and colonized loved their oppression and that they volunteered for a life of servitude.


For those that wish to choose their associations fine. But those of us old enough have heard the dog whistles before. and this is something Tucker Carlson does very, very well and why he is paid, a lot of money, this is just the same rap we heard under slavery and Jim Crow.


As to QAnon it is not that it personally bothers me, it is that it is a dress rehearsal for the death of critical thinking and a very good example of how many Americans fail to understand both the country and the world they live in and why they are so easily duped.


WeilunionI agree that labels are not as helpful as they once were. The right wing is as spendthrift as the left and the left is as authoritarian as the right. They really are very much the same party bent on keeping themselves in a job and others out THIS freakanomics told me what I already knew. -radio/e/77432868


While I dont like racism why would I want to force racists to live with people they dontlike? Would that make racists happier? Would it make people racists hate happier? Making people that dont have a common bond live together ends up in Yugoslavia or Rwanda.


The powers that control the Media want to create a Left/Right Paradigm so they needed someone to balance the likes of Rachel Mad-dog. Without Tucker I am guessing that many people would never turn on the Propaganda Box, and that would be bad for business, eh!


This post is not about Tucker, readers can research his long ties to white supremacists and fascists,it is about how people gravitate towards TV personalities even when they are trying to figure out and embrace freedom.


Elitism is a distasteful characteristic that a few of your posts imbued touting the benefits of socialism for example. Not everyone wants that. Nor do people want to be made to feel guilty for being white which they have little choice.


You make good points about the left not being liberal. And I do think many of your posts are very good. I mean no offense to you as a person with my comments. I apologize if my post came off as insulting to you. I mean no insult.


As to your impressions they are assumptions which you have not probed through rigid questioning. We need critical thinking now, not impressionistic thinking. And we certainly do not need people trying to push others into categories that suit their own self justifying belief systems.


Me too.I grasp the dark ugliness of the future where the train is headed.Corbett did not dance around its ugliness.I had to watch it in parts, and take breaks.When completed, I had to go work in the yard to try to unwind.Needed a breather.I slept on it before trying to comment.I awoke with this on my mind.And now, I comment. 041b061a72


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