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At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Mechanical Surface Treatments of AISI 304 Stainless Steel: Effects on Surface Microrelief, Residual Stress, and Microstructure

The surface roughness, residual stress, and microstructure of AISI 304 stainless steel specimens after laser shock peening (LSP), water jet cavitation peening (WjCP), water jet shot peening (WjSP), and multi-pin ultrasonic impact treatment (UIT) were studied in this work. Compared to the initial state, the surface roughness (Ra) was, respectively, decreased by approx. 5.5, 7.8, 38.2, and 91.1% after the LSP, WjCP, WjSP, and UIT processes. The volume fraction of ε-martensite of ~ 3-5% was observed in all treated specimens except for the LSP-treated ones. The volume fraction of α′-martensite was increased in the following sequence: WjCP (~ 5%), LSP (~ 5%), WjSP (~ 25%), UIT (~ 50%). The studied mechanical surface treatments promote a significant reduction in grains size of both austenite (~ 15-20 nm) and martensite (~ 20-37 nm) leading to essential hardening. All studied processes result in the formation of compressive residual stresses (− 377…693 MPa) and the improvement in the bearing curve parameters. The microhardness estimated accounting for the contributions of different hardening mechanisms to the yield strength magnitude correlates well with the experimental data. The grain boundary hardening and dislocation hardening are concluded to be the most influential mechanisms.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microstructure and residual elastic strain at graphite nodules in ductile cast iron analyzed by synchrotron X-ray microdiffraction

The microstructure and residual elastic strain at graphite nodules (GNs) in ductile cast iron produced using either a fast or slow cooling rate have been characterized using synchrotron 3D X-ray Laue microdiffraction. The results demonstrate that thermal stress is introduced during cooling and that part of this stress is relaxed by plastic deformation of the polycrystalline ferrite matrix. It is observed that the plastic deformation is accommodated by the formation of dislocations and dislocation boundaries, which are organized in a cell structure. The dislocation density quantified based on the microstructure is most pronounced at the GN/matrix interface around small GNs in the fast cooled sample. Residual elastic strain is also present, which is mainly compressive with a maximum of 6.0–9.9 × 10 -4 near the GNs. Gradients of plastic deformation and elastic strain field around the GNs are observed. The results document for the first time that both the elastic strain field and the plastic strain field averaged over the grains around the GNs is approximately scaling with GN size and not affected by the cooling rate. The experimental data are compared with simulations by a finite element method, and agreement and disagreement are considered in detail.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Island scanning pattern optimization for residual deformation mitigation in laser powder bed fusion via sequential inherent strain method and sensitivity analysis

Laser powder bed fusion (L-PBF) has emerged as one of the mainstream additive manufacturing approaches for fabricating metal parts with complex geometries and intricate internal structures. However, large deformation associated with rapid heating and cooling can lead to build failure and requires post-processing which may increase manufacturing cost and prolong the production period. Here in this work, an island scanning pattern design method is proposed to optimize the scanning direction of each island in order to reduce part deformation after cutting off the build platform. The objective of this optimization is to minimize the upward bending of the part after sectioning, which allows the part deformation to satisfy the tolerance requirement or reduce the post heat treatment time. Inherent strain method is employed in the sequential finite element analysis consisting of layer-by-layer activations and sectioning for fast residual distortion prediction. Full sequential sensitivity analysis for the formulated optimization is provided to update the island scanning directions. To show the feasibility and effectiveness of the proposed method, the scanning patterns of a block structure and a connecting rod were designed and parts were fabricated using an open architecture L-PBF machine. The fabrication experiments demonstrated that the residual deformation of both parts fabricated by optimized scanning pattern can be reduced by over 50% compared to the initial scanning patterns, which demonstrate the effectiveness of the proposed method.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Prediction of residual stresses in additively manufactured parts using lumped capacitance and classical lamination theory

Several industries are interested in Laser Powder Bed Fusion (L-PBF) Additively Manufactured (AM) metal parts because their designs can be made arbitrarily complex while retaining bulk-type material properties. However, the residual stresses (RS) and distortions caused by the heat gradients inherent to L-PBF processes are detrimental to the structural integrity of the parts and must be taken into consideration during the part design cycle. Predicting the state of stresses in as-built 3D printed parts is a difficult problem that is typically approached with the use of transient thermomechanical Finite Element Models (FEMs). However, the nonlinearities associated with AM processes are difficult to capture in these FEMs without increasing the computational cost of the simulation, limiting their ability to be incorporated into practical design cycles. This work presents a novel analytical framework that combines lumped capacitance nonlinear heat transfer with time dependent classical lamination theory to efficiently and accurately predict RS in as-built L-PBF parts without the need of FEMs. The simulation was compared to Neutron Diffraction (ND) residual strain measurements taken at Oak Ridge National Laboratories (ORNL) as well as Synchrotron X-ray Diffraction (XRD) strain data published by the National Institute of Standards and Technology (NIST). The simulation predictions and the experimental data showed excellent agreement for the in-plane strain directions, and general agreement for the out of plane strain component, highlighting an area where further development can be implemented.

42 ENGINEERING↗
DOE OSTI2013

The metalloid arsenite induces nuclear export of Id3 possibly via binding to the N-terminal cysteine residues

Highlights: •Sodium arsenite induces cytoplasmic accumulation of Id3. •Arsenite binds to closely spaced N-terminal cysteine residues of Id3. •N-terminal cysteines are essential for arsenite-induced nuclear export of Id3. •Nuclear export of Id3 counteracts its transcriptional repression activity. -- Abstract: Ids are versatile transcriptional repressors that regulate cell proliferation and differentiation, and appropriate subcellular localization of the Id proteins is important for their functions. We previously identified distinct functional nuclear export signals (NESs) in Id1 and Id2, but no active NES has been reported in Id3. In this study, we found that treatment with the stress-inducing metalloid arsenite led to the accumulation of GFP-tagged Id3 in the cytoplasm. Cytoplasmic accumulation was impaired by a mutation in the Id3 NES-like sequence resembling the Id1 NES, located at the end of the HLH domain. It was also blocked by co-treatment with the CRM1-specific nuclear export inhibitor leptomycin B (LMB), but not with the inhibitors for mitogen-activated protein kinases (MAPKs). Importantly, we showed that the closely spaced N-terminal cysteine residues of Id3 interacted with the arsenic derivative phenylarsine oxide (PAO) and were essential for the arsenite-induced cytoplasmic accumulation, suggesting that arsenite induces the CRM1-dependent nuclear export of Id3 via binding to the N-terminal cysteines. Finally, we demonstrated that Id3 significantly repressed arsenite-stimulated transcription of the immediate-early gene Egr-1 and that this repression activity was inversely correlated with the arsenite-induced nuclear export. Our results imply that Id3 may be involved in the biological action of arsenite.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Critical lysine residues of Klf4 required for protein stabilization and degradation

Highlights: • Klf4 undergoes the 26S proteasomal degradation by ubiquitination on its multiple lysine residues. • Essential Klf4 ubiquitination sites are accumulated between 190–263 amino acids. • A mutation of lysine at 232 on Klf4 elongates protein turnover. • Klf4 mutants dramatically suppress p53 expression both under normal and UV irradiated conditions. - Abstract: The transcription factor, Krüppel-like factor 4 (Klf4) plays a crucial role in generating induced pluripotent stem cells (iPSCs). As the ubiquitination and degradation of the Klf4 protein have been suggested to play an important role in its function, the identification of specific lysine sites that are responsible for protein degradation is of prime interest to improve protein stability and function. However, the molecular mechanism regulating proteasomal degradation of the Klf4 is poorly understood. In this study, both the analysis of Klf4 ubiquitination sites using several Klf4 deletion fragments and bioinformatics predictions showed that the lysine sites which are signaling for Klf4 protein degradation lie in its N-terminal domain (aa 1–296). The results also showed that Lys32, 52, 232, and 252 of Klf4 are responsible for the proteolysis of the Klf4 protein. These results suggest that Klf4 undergoes proteasomal degradation and that these lysine residues are critical for Klf4 ubiquitination.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Development of sulfonated carbon-based solid-acid catalysts derived from biorefinery residues and biomass ash for xylan hydrolysis

In this study, biorefinery residues and biomass ash were used to develop sulfonated carbon-based solid-acid catalysts to enhance xylan hydrolysis. Here, metals extracted from the biomass ash were impregnated into a carbon support prepared from biorefinery residues to synthesize sulfonated ash-impregnated carbon-based catalyst. Metals present in the ash most probably are responsible for the increased acid density in the catalyst. Using this catalyst, 11.4 % xylose yield was produced, an increase of 171 % over the yield obtained from a catalyst without ash impregnation. Using a xylan-to-catalyst ratio of 1:2, 72.9 % xylose yield was obtained, comparable to using 0.5 wt% sulfuric acid under the same reaction condition. Moreover, this catalyst significantly inhibited xylose dehydration, only forming 11.3 % furfural compared to that generated using dilute acid. Hence, these results show the potential for using biomass ash as a metal source to increase the number of acid sites in solid-acid catalysts used for biomass pretreatment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Influence of Combustion Conditions on Yields of Solvent-Extractable Anhydrosugars and Lignin Phenols in Chars: Implications for Characterizations of Biomass Combustion Residues

Anhydrosugars, such as levoglucosan and its isomers (mannosan, galactosan), as well as the solvent-extractable lignin phenols (methoxylated phenols) are thermal degradation products of cellulose/hemicellulos and lignin, respectively. These two groups of biomarkers are often used as unique tracers of combusted biomass inputs in diverse environmental media. However, detail characterization of the relative proportion and signatures of these compounds in highly heterogeneous plant-derived chars/charcoals are still scarce. Here we conducted a systematic study to investigate the yields of solvent-extractable anhydrosugars and lignin phenols in twenty-five lab-made chars produced from different plant materials under different combustion conditions. Solvent extractable anhydrosugars and lignin phenols were only observed in chars formed below 350 C and yields were variable across different combustion temperatures. The yields mannosan (M) and galactosan (G) decreased more rapidly than those of levoglucosan (L) under increasing combustion severity (temp. and duration), resulting in variable L/M and L/(M+G) ratios, two diagnostic ratios often used for identification of combustion sources (e.g. hardwoods vs. softwoods vs. grasses). On the other hand, the results of this study suggest that the ratios of the major solvent-extractable lignin phenols (vanillyls (V), syringyls (S), cinnamyls (C)) provide additional source reconstruction potential despite observed variations with combustion temperature. We thus propose using a property property plot (L/M vs. S/V) as an improved means for source characterization of biomass combustion residues. The L/M-S/V plot has shown to be effective in environmental samples (soil organic matter, atmospheric aerosols) receiving substantial inputs of biomass combustion residues.

09 BIOMASS FUELS↗
DOE OSTI2019

Matrix-free subcell residual distribution for Bernstein finite element discretizations of linear advection equations

In this work, we introduce a new residual distribution (RD) framework for the design of bound-preserving high-resolution finite element schemes. The continuous and discontinuous Galerkin discretizations of the linear advection equation are modified to construct local extremum diminishing (LED) approximations. To that end, we perform mass lumping and redistribute the element residuals in a manner which guarantees the LED property. The hierarchical correction procedure for high-order Bernstein finite element discretizations involves localization to subcells and definition of bound-preserving weights for subcell contributions. Using strong stability preserving (SSP) Runge–Kutta methods for time integration, we prove the validity of discrete maximum principles under CFL-like time step restrictions. The low-order version of our method has roughly the same accuracy as the one derived from a piecewise (multi)-linear approximation on a submesh with the same nodal points. In high-order extensions, we use an element-based flux-corrected transport (FCT) algorithm which can be interpreted as a nonlinear RD scheme. The proposed LED corrections are tailor-made for matrix-free implementations which avoid the rapidly growing cost of matrix assembly for high-order Bernstein elements. The results for 1D, 2D, and 3D test problems compare favorably to those obtained with the best matrix-based approaches.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

Matrix-free subcell residual distribution for Bernstein finite elements: Monolithic limiting

This paper is focused on the aspects of limiting in residual distribution (RD) schemes for high-order finite element approximations to advection problems. Both continuous and discontinuous Galerkin methods are considered in this work. Discrete maximum principles are enforced using algebraic manipulations of element contributions to the global nonlinear system. The required modifications can be carried out without calculating the element matrices and assembling their global counterparts. The components of element vectors associated with the standard Galerkin discretization are manipulated directly using localized subcell weights to achieve optimal accuracy. Low-order nonlinear RD schemes of this kind were originally developed to calculate local extremum diminishing predictors for flux-corrected transport (FCT) algorithms. In the present paper, we incorporate limiters directly into the residual distribution procedure, which makes it applicable to stationary problems and leads to well-posed nonlinear discrete problems. To circumvent the second-order accuracy barrier, the correction factors of monolithic limiting approaches and FCT schemes are adjusted using smoothness sensors based on second derivatives. Finally, the convergence behavior of presented methods is illustrated by numerical studies for two-dimensional test problems.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Maximizing oil production from water alternating gas (CO 2 ) injection into residual oil zones: The impact of oil saturation and heterogeneity

Residual oil zones (ROZs) are widespread reservoirs, characterized by oil at residual saturation, either underlying oil fields (brownfield) or lateral (greenfield) to such fields. These reservoirs have the potential to produce volumes of oil sufficiently significant to make appreciable impacts on the US’s oil reserves and associated incidental CO 2 sequestration. The objective of this study is to improve our understanding the impact of heterogeneous and low oil saturations, in brownfield ROZs, on the effectiveness of water alternating gas (WAG) injection strategies. ROZs occur in the Permian Basin and elsewhere, and operators are using CO 2 injection for enhanced oil recovery (EOR) in these zones. The consensus model for the formation of ROZs is that they were formed by the effect of faster regional aquifer flow, acting over millions of years. Both the magnitude of oil saturation and the spatial distribution of oil differ from water-flooded main pay zones (MPZs). To explore the most effective injection strategies, we conducted simulations of CO 2 injection into synthetic geologic reservoirs. These simulations focused on injection into reservoirs subject to either man-made waterflooding or long-term natural waterflooding. By exploring the impact of varying: oil saturation; well patterns; reservoir heterogeneity; and permeability anisotropy, we attempt to quantify the factors that most influence the effectiveness of WAG injection. WAG ratios (the ratio of injected water and CO 2 , in reservoir volumes) of interest are those that either minimize the net CO 2 utilization ratios or maximize oil production rates. In general, the most effective WAG ratios for ROZs, are consistently less than those observed undergoing CO 2 injection in the same geologic reservoir models after traditional (man-made) waterflooding. This work demonstrates that most favorable WAG ratios for oil production in ROZs are different from those in traditional MPZs because of oil saturation differences. Therefore, CO 2 injection into both zones or directly copying WAG injection designs from MPZs to ROZs might not maximize oil production.

04 OIL SHALES AND TAR SANDS↗
DOE OSTI2018

Production of new activated bio-carbons by chemical activation of residue left after supercritical extraction of hops

Highlights: • An alternative method for bio-waste utilization has been proposed. • Activated bio-carbons were prepared from hops by Na{sub 2}CO{sub 3} activation. • The activated bio-carbons has been used for NO{sub 2}, methylene blue and iodine adsorption. A technology of activated bio-carbons production from the residue left after supercritical extraction of hops is described. The effect of the variant of chemical activation and impregnation ratio on the physicochemical properties as well as sorption capacity towards toxic gas of acidic character (nitrogen dioxide), basic organic dye (aqueous solution of methylene blue - MB) and iodine was investigated. The materials obtained were activated bio-carbons of well-developed surface area ranging between 897 and 1095 m{sup 2}/g, showing clearly acidic character of the surface. The sorption tests results proved that chemical activation of the residue left after supercritical extraction of hops allows obtaining activated bio-carbons with very high sorption capacity towards nitrogen dioxide, reaching to 77.2 and 155.3 mg/g in dry and wet conditions, respectively. The maximum sorption capacity of the adsorbents towards methylene blue was 328.75 mg/g, while towards iodine 1815 mg/g. The equilibrium data for aqueous solution of MB were analyzed by the Langmuir and Freundlich models, whereas the kinetics of the adsorption process was studied using pseudo-first and second-order models. According to the obtained data, the adsorption of MB from aqueous solution is better described by Langmuir model and pseudo-second order kinetic model.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Evaluation of a self-equilibrium cutting strategy for the contour method of residual stress measurement

An assessment of cutting-induced plasticity (CIP) is performed, by finite element (FE) prediction of the plastic strain accumulation along the cut tip when the EDM wire sections the NeT TG4 weld benchmark specimen along two cutting directions. The first direction corresponds to a conventional (C) cutting strategy, whereby the EDM wire cuts through the thickness of the weld specimen and travels in a direction transverse to the weld. The second direction corresponds to a self-equilibrating cutting (SE) strategy, whereby the EDM wire cuts across the transverse direction of the weld specimens and travels through the thickness of the plate. The cutting thus progresses simultaneously through the compression-tension-compression regions of present weld residual stress (WRS) field. This type of cutting strategy is believed to minimize the CIP by minimising residual stress redistribution during cutting, due to stress equilibration across the sectioned material. The simulated cutting procedures are conducted under a range of clamping conditions to assess whether mechanical restraint has a primary or secondary influence on CIP accumulation. Both predictions of CIP and the resultant back-calculated WRS demonstrate that (i) mechanical restraint is the primary variable influencing CIP development, and (ii) under no circumstance does a self-equilibrating cutting strategy perform significantly better than a conventional cutting approach. Furthermore, the reason that self-equilibrating cuts are not effective is illustrated by calculating the Mode I (K I ) stress intensity factor (SIF) along the cut tip, and correlating trends in K I to CIP development.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Relationship between dislocations and residual stresses in cold-drawn pearlitic steel analyzed by energy-dispersive X-ray diffraction

We analyzed the dislocation distribution of cold-drawn pearlitic-steel wire by using the line-profile analysis based on the energy dispersive X-ray diffraction (EDXD). Although this line-profile analysis requires a high resolution in reciprocal space, the resolution for EDXD is generally poor due to the energy resolution of the detector. Our analysis demonstrated that the resolution in the reciprocal space can be maximized at small scattering angles. Using the line-profile analysis based on the EDXD, the microstructural parameters such as the crystallite size and the dislocation density of the ferrite phase in the pearlitic steel were successfully analyzed. In addition, the distribution of the residual stress of the ferrite phase of a pearlitic steel wire was also analyzed using the EDXD measurement. - Highlights: • Energy dispersive X-ray diffraction is applied to the line-profile analysis. • Distribution of dislocations in ferrite in the pearlitic steel wire is analyzed. • Relationship between dislocations and residual stress is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Residual stresses distribution, correlated with bending tests, within explosively welded Ti gr. 2/A1050 bimetals

Highlights: • Ti gr.2/A1050 clad was slightly affected by the explosive welding since negative sign values of stress tensor were detected. • Upon bending higher negative compression stresses were detected in this area. • Twins morphology changed from parallel to cross-shaped arrangement as a consequence of bending. • The compressive twinning was the dominant system before and after three point bending. - Abstract: Synchrotron radiation and XRD{sup 2} method were used to investigate the residual stress distribution before and after three point bending tests within an explosively welded composite composed of two light metals, namely: Ti gr. 2 and A1050. The analysis has shown that the bimetal is slightly affected by the explosive welding process since negative sign values of stress tensor were detected only in the immediate vicinity of interface of Ti gr. 2 characterized by a width of about 0.25 mm. Upon bending higher negative compression stresses are detected in this area as the σ{sub 11} value changes from −500 MPa to −1200 MPa. Additionally, the analysis of microstructure has revealed significant changes in twins morphology with primary and conjugate twinning before and after bending, respectively. However, the compressive twinning was the dominant system in both cases. Bending has changed the initial bimodal texture developing more spread basal components towards the transverse direction. The sample surface has been also significantly affected as the presence of compressive residual stress (−500 MPa) after bending was measured.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Coupled experimental and computational study of residual stresses in additively manufactured Ti-6Al-4V components

The production of metallic parts via laser-powder bed fusion (L-PBF) additive manufacturing is rapidly growing. To use components produced via L-PBF in safety-critical applications, a high degree of confidence is required in their quality. This qualification can be supported by means of a validated thermomechanical model capable of predicting the final residual stress state and subsequent performance. In this study, we use high-energy X-ray diffraction to determine a three-dimensional residual strain and stress state in a Ti-6Al-4V L-PBF component. The experimental results are used to provide validation of simulations, showing strong quantitative agreement.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Effects of thermal cycling parameters on residual stresses in alumina scales of CoNiCrAlY and NiCoCrAlY bond coats

In this paper, furnace cycling experiments were performed on free-standing high-velocity oxygen-fuel bond coat samples to investigate the effect of material composition, surface texture, and cycling conditions on the average stresses in the formed oxide scales after cooling. The oxide scale thicknesses were determined by SEM image analyses and information about the stresses were acquired by photo-stimulated luminescence-spectroscopy. Additionally, the scale thickness dependent stress fields were calculated in finite-element analyses including approximation functions for the surface roughness derived on the basis of profilometry data. The evolution of the average residual stress as a function of oxide scale thickness was subject to stochastic fluctuations predominantly caused by local scale spallations. In comparison to the supplemental modeling results, thermal stresses due to mismatch of thermal expansion coefficients are identified as the main contribution to the residual stresses. Finally, the theoretical results emphasize that analyses of spectroscopic data acquired for average stress investigations of alumina scales rely on detailed information about microstructural features.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Greenhouse gases emissions accounting for typical sewage sludge digestion with energy utilization and residue land application in China

Highlights: Black-Right-Pointing-Pointer GHGs emissions from sludge digestion + residue land use in China were calculated. Black-Right-Pointing-Pointer The AD unit contributes more than 97% of total biogenic GHGs emissions. Black-Right-Pointing-Pointer AD with methane recovery is attractive for sludge GHGs emissions reduction. - Abstract: About 20 million tonnes of sludge (with 80% moisture content) is discharged by the sewage treatment plants per year in China, which, if not treated properly, can be a significant source of greenhouse gases (GHGs) emissions. Anaerobic digestion is a conventional sewage sludge treatment method and will continue to be one of the main technologies in the following years. This research has taken into consideration GHGs emissions from typical processes of sludge thickening + anaerobic digestion + dewatering + residue land application in China. Fossil CO{sub 2}, biogenic CO{sub 2}, CH{sub 4,} and avoided CO{sub 2} as the main objects is discussed respectively. The results show that the total CO{sub 2}-eq is about 1133 kg/t DM (including the biogenic CO{sub 2}), while the net CO{sub 2}-eq is about 372 kg/t DM (excluding the biogenic CO{sub 2}). An anaerobic digestion unit as the main GHGs emission source occupies more than 91% CO{sub 2}-eq of the whole process. The use of biogas is important for achieving carbon dioxide emission reductions, which could reach about 24% of the total CO{sub 2}-eq reduction.

09 BIOMASS FUELS↗