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At least 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

1,25-(OH){sub 2}-vitamin D{sub 3} prevents activation of hepatic stellate cells in vitro and ameliorates inflammatory liver damage but not fibrosis in the Abcb4{sup −/−} model

Background/Purpose of the study: Vitamin D{sub 3}-deficiency is common in patients with chronic liver-disease and may promote disease progression. Vitamin D{sub 3}-administration has thus been proposed as a therapeutic approach. Vitamin D{sub 3} has immunomodulatory effects and may modulate autoimmune liver-disease such as primary sclerosing cholangitis. Although various mechanisms of action have been proposed, experimental evidence is limited. Here we test the hypothesis that active 1,25-(OH){sub 2}-vitamin D{sub 3} inhibits activation of hepatic stellate cells (HSC) in vitro and modulates liver-injury in vivo. Methods: Proliferation and activation of primary murine HSC were assessed by BrdU- and PicoGreen{sup ®}-assays, immunoblotting, immunofluorescence-microscopy, quantitative-PCR, and zymography following calcitriol-treatment. Wild-type and ATP-binding cassette transporter b4{sup −/−} (Abcb4{sup −/−})-mice received calcitriol for 4 weeks. Liver-damage, inflammation, and fibrosis were assessed by serum liver-tests, Sirius-red staining, quantitative-PCR, immunoblotting, immunohistochemistry and hydroxyproline quantification. Results: In vitro, calcitriol inhibited activation and proliferation of murine HSC as shown by reduced α-smooth muscle actin and platelet-derived growth factor-receptor-β-protein-levels, BrdU and PicoGreen®-assays. Furthermore, mRNA-levels and activity of matrix metalloproteinase 13 were profoundly increased. In vivo, calcitriol ameliorated inflammatory liver-injury reflected by reduced levels of alanine aminotransferase in Abcb4{sup −/−}-mice. In accordance, their livers had lower mRNA-levels of F4/80, tumor necrosis factor-receptor 1 and a lower count of portal CD11b positive cells. In contrast, no effect on overall fibrosis was observed. Conclusion: Calcitriol inhibits activation and proliferation of HSCs in vitro. In Abcb4{sup −/−}-mice, administration of calcitriol ameliorates inflammatory liver-damage but has no effect on biliary fibrosis after 4 weeks of treatment. - Highlights: • Calcitriol inhibits activation and proliferation of murine HSC. • Calcitriol exerts antifibrotic properties by up-regulation of MMP 13 in HSC. • Calcitriol-treatment diminished hepatic inflammatory injury in Abcb4{sup −/−}-mice. • Calcitriol-treatment does not exert antifbrotic effects in Abcb4{sup −/−}-mice. • This study highlights potential hepatoprotective effects of calcitriol in PSC.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Nanoscale analysis of unstained biological specimens in water without radiation damage using high-resolution frequency transmission electric-field system based on FE-SEM

Scanning electron microscopy (SEM) has been widely used to examine biological specimens of bacteria, viruses and proteins. Until now, atmospheric and/or wet biological specimens have been examined using various atmospheric holders or special equipment involving SEM. Unfortunately, they undergo heavy radiation damage by the direct electron beam. In addition, images of unstained biological samples in water yield poor contrast. We recently developed a new analytical technology involving a frequency transmission electric-field (FTE) method based on thermionic SEM. This method is suitable for high-contrast imaging of unstained biological specimens. Our aim was to optimise the method. Here we describe a high-resolution FTE system based on field-emission SEM; it allows for imaging and nanoscale examination of various biological specimens in water without radiation damage. The spatial resolution is 8 nm, which is higher than 41 nm of the existing FTE system. Our new method can be easily utilised for examination of unstained biological specimens including bacteria, viruses and protein complexes. Furthermore, our high-resolution FTE system can be used for diverse liquid samples across a broad range of scientific fields, e.g. nanoparticles, nanotubes and organic and catalytic materials. - Highlights: • We developed a high-resolution frequency transmission electric-field (FTE) system. • High-resolution FTE system is introduced in the field-emission SEM. • The spatial resolution of high-resolution FTE method is 8 nm. • High-resolution FTE system enables observation of the intact IgM particles in water.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Co-administration of liposomal fasudil and tissue plasminogen activator ameliorated ischemic brain damage in occlusion model rats prepared by photochemically induced thrombosis

Highlights: • Thrombolytic agent t-PA increased liposome accumulation in ischemic brain. • Liposome accumulation was observed in wide area of ischemic region by t-PA treatment. • Extravasation of injected liposomes into brain parenchyma was facilitated by t-PA. • Co-administration of liposomal fasudil and t-PA ameliorated ischemic brain damage. Delivery of neuroprotectants with liposomes has been shown to be effective for the treatment of ischemic stroke. We have recently revealed that intravenous administration of liposomal fasudil (Fasudil-Lip), a Rho-kinase inhibitor, prior to thrombolysis with tissue plasminogen activator (t-PA) can extend the narrow therapeutic time window (TTW) of t-PA. In the present study, we examined the influence of t-PA treatment on liposomal accumulation into the ischemic region and cerebroprotective effect of combined treatment with Fasudil-Lip and t-PA performed at the same timing after the onset of ischemia in middle cerebral artery occlusion (MCAO) prepared by photochemically induced thrombosis. The t-PA administration into MCAO rats 3 h after occlusion brought about significantly higher accumulation of intravenously injected PEGylated liposomes in wide area of ischemic region. Confocal images showed that extravasation of the liposomes from cerebral vessels into brain parenchyma was markedly facilitated by the t-PA treatment which increased blood flow in cerebral vessels. Importantly, co-administration of Fasudil-Lip and t-PA after 3 h occlusion, beyond the TTW of t-PA in MCAO rats, significantly suppressed brain cell damage compared with t-PA treatment alone. These findings suggest that co-administration of Fasudil-Lip and t-PA should lead to prolong t-PA's TTW and become a useful therapeutic option for ischemic stroke.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Mitochondrial dynamics and protective effects of a mitochondrial division inhibitor, Mdivi-1, in lipopolysaccharide-induced brain damage

Highlights: • Mdivi-1 ameliorated brain damage in a lipopolysaccharide-induced sepsis model. • Drp1 was up-regulated, while p-Drp1 and OPA1 were down-regulated in hippocampus. • The protective effect of Mdivi-1 could be associated with its inhibition of Drp1 and its activation of p-Drp1 and OPA1. Sepsis is one of the most common reasons for mortality in Intensive Care Units. As a common but severe neurological complication, sepsis associated encephalopathy (SAE) has always been ignored and there is no generally accepted treatment. In this study, we demonstrated that Mdivi-1 ameliorated brain damage assessed by Nissl staining. Furthermore, Mdivi-1 reduced TUNEL-positive cells in hippocampus, and inhibited S100 calcium binding protein B (S100B) and neuron-specific enolase (NSE) release into plasma. Biochemical analysis also showed that Mdivi-1 protected hippocampus from oxidative stresses. Western blot analysis revealed that Mdivi-1, as a Drp1 inhibitor, inhibited LPS induced dynamin-related GTPase (Drp1) increase. Interestingly, it can also attenuate LPS induced optic atrophy 1 (OPA1) and phosphorylated Drp1 (p-Drp1) decrease. Thus Mdivi-1 protected rats from SAE, and this protective effect could be associated with its inhibition of Drp1 and its activation of p-Drp1 and OPA1. Mitochondrial dynamics may be a potential pharmacological therapeutic target for treating SAE.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

IGF-1 resist oxidative damage to HaCaT and depigmentation in mice treated with H2O2

Vitiligo, an acquired pigmentary disorder of the skin, is characterized by a chronic and progressive loss of melanocyte from the epidermis and follicular reservoir. Growth factor of surrounding cells impacted on melanocytes survival. In this study, lower level of IGF-1 in the lesion was found than that in the donor area of vitiligo patients. IGF-1 improved activation of Nrf2, and inhibited ROS generation and endoplasmic reticulum dilation in HaCaT. C57BL/6 mice were treated with 5% H{sub 2}O{sub 2}, and combined with 50 μg/kg of IGF-1 pre-treatment or not once every day for 50 consecutive days. After 50 days, IGF-1 obviously ameliorated depigmentation of mice skin and reduced hair follicle length, skin thickness and Tyrosinase induced by H{sub 2}O{sub 2.} Moreover, IGF-1 significantly suppressed CD8{sup +} T cells infiltration in mice skin, inhibited the production of IL-2 and IFN-γ, and decreased the expression of CXCL10 and CXCR3. Thus, the results indicated that IGF-1 could resist oxidative damage to HaCaT, suppress CD8{sup +} T cells infiltration and pro-inflammatory cytokines secretion, and suppresses the thinning of epidermal layer in vivo. It suggests that IGF-1 inhibits oxidative damage to HaCaT and immunosuppressive effects on CD8{sup +} T cells proliferation and activation to resist depigmentation induced by H{sub 2}O{sub 2}. This disclosed its multiple roles in the vitiligo, and shed a light on developing the application potential for IGF-1 in vitiligo.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Hepatic conditional knockout of ATF6 exacerbates liver metabolic damage by repressing autophage through MTOR pathway

Highlights: • Conditional knockout of ATF6 exacerbates liver metabolic damage. • Conditional knockout of ATF6 represses autophage. • Conditional knockout of ATF6 activates MTOR pathway. The liver is a central metabolic organ. Activating transcription factor 6 (ATF6) acts as an ER stress responsive gene and is reported to attenuate hepatic steatosis. Over expressing a dominant-negative form of ATF6 exacerbates glucose intolerance and insulin resistance. In the present study, we used the conditional knockout technique to specifically knockout ATF6 in the mouse liver. We used qPCR to detect the mRNA levels of related genes. Western blot analysis was used to evaluate protein levels. Flow cytometry assay showed the apoptosis status. Glucose tolerance tests and insulin tolerance tests were used to determine glucose and insulin sensitivity. The results showed that liver specific knockout of ATF6 exacerbated HFD-induced hepatic steatosis and glucose tolerance. Abolished ATF6 exacerbated gluconeogenic metabolism by MTOR mediated down regulation of autophage. In conclusion, these findings suggest that therapeutic strategies by supplementing ATF6 may be beneficial for the treatment of glucose intolerance as well as insulin resistance in the high fat induced liver metabolic damage condition.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Arctigenin shows preferential cytotoxicity to acidity-tolerant prostate carcinoma PC-3 cells through ROS-mediated mitochondrial damage and the inhibition of PI3K/Akt/mTOR pathway

Highlights: • Arctigenin induces preferential cytotoxicity to acid-tolerant PC-3AcT cells. • Arctigenin induced cytotoxicity is linked to ROS-mediated mitochondrial damage. • Arctigenin-induced ROS accumulation was associated with ATP depletion. • PI3K/Akt/mTOR pathway is one of the targets of arctigenin-induced oxidative insults. Extracellular acidity in the tumor microenvironment contributes to chemoresistance of malignant tumors. The objective of this study was to determine anticancer effects of arctigenin, a novel anti-inflammatory lignan extracted from seeds of Arctium lappa, on acidity-tolerant prostate cancer PC-3AcT cells. The PC-3AcT cells manifested increased tolerance to low-pH media with enhanced percent cell viability and increased resistance to docetaxel compared to their parental PC-3 cells. Arctigenin alone or in combination with docetaxel induced potent cytotoxicity. Preferential sensitization of PC-3AcT cells to arctigenin was accompanied by increased cell fractions with sub-G{sub 0}/G{sub 1} peak and annexin V-PE(+), increased ROS levels, decreased mitochondrial membrane potential and cellular ATP content, and inhibition of PI3K/Akt/mTOR pathway. A series of changes caused by arctigenin were efficiently reversed through reducing ROS levels by radical scavenger N-acetylcysteine, thus placing ROS upstream of arctigenin-driven cytotoxicity. Collectively, these results demonstrate that arctigenin can increase oxidative stress-mediated mitochondrial damage of acidity-tolerant PC-3AcT cells, suggesting that arctigenin might be a potential therapeutic candidate to overcome acidic-microenvironment-associated chemotherapeutic resistance in prostate cancer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Influence of the distribution of expansive sites in aggregates on microscopic damage caused by alkali-silica reaction: Insights into the mechanical origin of expansion

The origin of damage in concrete due to the alkali-silica reaction (ASR) is attributed to the expansion site in the aggregate. To investigate the cracking process of the aggregate during ASR and its consequences on concrete damage, the effect of the distribution of the expansive sites in the aggregate on ASR expansion and the crack patterns must be evaluated. Thus, in this study, a mesoscale discrete model was applied to ASR modeling to represent the propagation of cracking during ASR accurately. The distribution of the expansive sites in the aggregate was based on the gel pocket and reaction rim models, which are two ASR mechanisms reported in the literature. These two expansion models highlight the different crack patterns obtained based on the aggregate characteristics. Further, the expansion cracking processes determined based on the gel pocket and reaction rim models are consistent with the evolution of cracking with the expansion level.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Predicting oxidation damage in ultra high-temperature borides: A machine learning approach

Ultra-high temperature (UHT) borides are ceramics materials with melting points above 3000 °C for structural applications in extreme environments. However, at temperatures exceeding 1600 °C and under oxidizing conditions, the material suffers from detrimental degradation. Optimized design and performance of diboride materials under such extreme conditions requires filling the missing composition-microstructure-oxidation gap. This study proposes a computational data-driven framework to connect the processing and microstructure of Ultra-high temperature borides with the oxidation damage. Random Forest Regressor (RFR) model is adopted to forecast the oxide scale thickness developed after oxidation testing based on processing variables and microstructural features. The model trained on a dataset consisting of 107 samples of experimental data extracted from the literature aims to predict oxidation damage. With proper data manipulation and fine model tuning, the predictor could forecast the oxide scale thickness of UHT diborides with a Mean Absolute Error of 37.45 μm and an R-square of 0.83. This model could be used as a high-throughput scheme to design and test new UHT diborides materials computationally. Furthermore, a model with larger composition capabilities could also be developed in the future as more experimental data become available.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Representing ductile damage with the dual domain material point method

In this study, we incorporate a ductile damage material model into a computational framework based on the Dual Domain Material Point (DDMP) method. As an example, simulations of a flyer plate experiment involving ductile void growth and material failure are performed. The results are compared with experiments performed on high purity tantalum. We also compare the numerical results obtained from the DDMP method with those obtained from the traditional Material Point Method (MPM). Effects of an overstress model, artificial viscosity, and physical viscosity are investigated. Our results show that a physical bulk viscosity and overstress model are important in this impact and failure problem, while physical shear viscosity and artificial shock viscosity have negligible effects. A simple numerical procedure with guaranteed convergence is introduced to solve for the equilibrium plastic state from the ductile damage model.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Scaling Relations for Intercalation Induced Damage in Electrodes

Mechanical degradation, owing to intercalation induced stress and microcrack formation, is a key contributor to the electrode performance decay in lithium-ion batteries (LIBs). The stress generation and formation of microcracks are caused by the solid state diffusion of lithium in the active particles. Here in this work, scaling relations are constructed for diffusion induced damage in intercalation electrodes based on an extensive set of numerical experiments with a particle-level description of microcrack formation under disparate operating and cycling conditions, such as temperature, particle size, C-rate, and drive cycle. The microcrack formation and evolution in active particles is simulated based on a stochastic methodology. A reduced order scaling law is constructed based on an extensive set of data from the numerical experiments. The scaling relations include combinatorial constructs of concentration gradient, cumulative strain energy, and microcrack formation. Lastly, the reduced order relations are further employed to study the influence of mechanical degradation on cell performance and validated against the high order model for the case of damage evolution during variable current vehicle drive cycle profiles.

25 ENERGY STORAGE↗
DOE OSTI2016

Comparative toxicities of selected rare earth elements: Sea urchin embryogenesis and fertilization damage with redox and cytogenetic effects

Background: Broad-ranging adverse effects are known for rare earth elements (REE), yet only a few studies tested the toxicity of several REE, prompting studies focusing on multi-parameter REE toxicity. Methods: Trichloride salts of Y, La, Ce, Nd, Sm, Eu and Gd were tested in Paracentrotus lividus sea urchin embryos and sperm for: (1) developmental defects in either REE-exposed larvae or in the offspring of REE-exposed sperm; (2) fertilization success; (3) mitotic anomalies in REE-exposed embryos and in the offspring of REE-exposed sperm, and (4) reactive oxygen species (ROS) formation, and malondialdehyde (MDA) and nitric oxide (NO) levels. Results: REEs affected P. lividus larvae with concentration-related increase in developmental defects, 10{sup −6} to 10{sup −4} M, ranking as: Gd(III)>Y(III)>La(III)>Nd(III)≅Eu(III)>Ce(III)≅Sm(III). Nominal concentrations of REE salts were confirmed by inductively coupled plasma mass spectrometry (ICP-MS). Significant increases in MDA levels, ROS formation, and NO levels were found in REE-exposed embryos. Sperm exposure to REEs (10{sup −5} to 10{sup −4} M) resulted in concentration-related decrease in fertilization success along with increase in offspring damage. Decreased mitotic activity and increased aberration rates were detected in REE-exposed embryos and in the offspring of REE-exposed sperm. Conclusion: REE-associated toxicity affecting embryogenesis, fertilization, cytogenetic and redox endpoints showed different activities of tested REEs. Damage to early life stages, along with redox and cytogenetic anomalies should be the focus of future REE toxicity studies. - Highlights: • Seven rare earth elements exerted different effects on sea urchin early life stages. • Embryo-, spermio- and mitotoxicity, and oxidative/ nitrosative stress were found. • Nominal vs. analytical REE concentrations were checked. • Comparative toxicities were evaluated for the different REE.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Coupled phase field damage and crystal plasticity analysis of intragranular fracture: The role of crystallographic orientation and voids

Damage evolution in engineering metal alloys at the grain scale exhibits significant microstructural heterogeneity and anisotropy. These heterogeneities create local hotspots for stress and strain localization, leading to void nucleation. Crystal orientation influences the active slip systems around voids, affecting lattice rotation and potentially forming discontinuities. At low triaxiality, voids may change shape due to lower stress, rotation, elongation, and coalescence. At high triaxiality, the correlation between crystal orientation and void growth rate becomes stronger, resembling the behavior observed in isolated single crystals. Therefore, understanding the effects of crystal orientation, heterogeneous strain, and defect evolution is crucial for single crystal fracture characterization. Here, in this work, a coupled phase-field damage (PFD) and crystal plasticity (CP) model is implemented within a finite element framework to analyze crystal deformation and failure. The CP method employs a dislocation density-based constitutive model, while intragranular failure is modeled using an anisotropic PFD method. The PFD model considers both the stored energy due to elastic stretching and the energy release due to defect formation and crack formation. A single crystal Al2219 with an intracrystalline spherical void is chosen to analyze fracture. The study finds that fracture propagation is strongly correlated with crystal orientations. This coupled CP-PFD model provides accurate failure prediction in crystalline materials by incorporating the effects of crystal orientations and existing voids. This study demonstrates how the local microstructure and defects influence plastic deformation and failure mechanisms in metal alloys.

Aluminum alloy↗
DOE OSTI2021

A probabilistic creep model incorporating test condition, initial damage, and material property uncertainty

Uncertainty is prevalent in the creep resistance of alloys, where at elevated temperature and low pressure, rupture can range across logarithmic decades. In this study, a probabilistic continuum-damage-mechanics (CDM)-based model is derived to capture the uncertainty of creep resistance. To meet this objective, creep data for alloy 304 Stainless Steel is gathered. A constitutive model, “Sinh”, is calibrated deterministically to determine the statistical variability of the material properties. Three sources of uncertainty are injected into the model: test condition (stress and temperature), initial damage, and material properties. Probabilistic simulations are carried out by (a) calibrating probability distribution functions (pdfs) for each source of uncertainty (b) randomly sampling the pdfs using Monte Carlo methods and (c) executing simulations to replicate the uncertain creep behavior. A sensitivity analysis is performed to evaluate the relative effect of each source of uncertainty. In full probabilistic simulations, the cumulative uncertainty of creep behavior is evaluated. The probabilistic model accurately predicts the creep deformation and rupture of the available experiments. The probabilistic model is validated for interpolation but lacks extrapolation ability. Several future works are proposed to further improve the model.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Persistent DNA Damage in Spermatogonial Stem Cells After Fractionated Low-Dose Irradiation of Testicular Tissue

Purpose: Testicular spermatogenesis is extremely sensitive to radiation-induced damage, and even low scattered doses to testis from radiation therapy may pose reproductive risks with potential treatment-related infertility. Radiation-induced DNA double-strand breaks (DSBs) represent the greatest threat to the genomic integrity of spermatogonial stem cells (SSCs), which are essential to maintain spermatogenesis and prevent reproduction failure. Methods and Materials: During daily low-dose radiation with 100 mGy or 10 mGy, radiation-induced DSBs were monitored in mouse testis by quantifying 53 binding protein 1 (53BP-1) foci in SSCs within their stem cell niche. The accumulation of DSBs was correlated with proliferation, differentiation, and apoptosis of testicular germ cell populations. Results: Even very low doses of ionizing radiation arrested spermatogenesis, primarily by inducing apoptosis in spermatogonia. Eventual recovery of spermatogenesis depended on the survival of SSCs and their functional ability to proliferate and differentiate to provide adequate numbers of differentiating spermatogonia. Importantly, apoptosis-resistant SSCs resulted in increased 53BP-1 foci levels during, and even several months after, fractionated low-dose radiation, suggesting that surviving SSCs have accumulated an increased load of DNA damage. Conclusions: SSCs revealed elevated levels of DSBs for weeks after radiation, and if these DSBs persist through differentiation to spermatozoa, this may have severe consequences for the genomic integrity of the fertilizing sperm.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

A study of damage-free in-situ etching of GaN in metalorganic chemical vapor deposition (MOCVD) by tertiarybutylchloride (TBCl)

This paper reports a study of the effect of NH 3 flow rate and reactor temperature on the tertiarybutylchloride (TBCl) etching of patterned GaN-on-sapphire templates. It is found that a reduced NH 3 flow rate and an elevated reactor temperature can eliminate islands or dots on the surface, while at the same time, enhance the etching around dislocations. TBCl etching was also performed on planar bulk GaN templates with much lower dislocation density. We find an atomically flat and layer-by-layer etching behavior within the region free of dislocations. Surface kinetics analysis reveals a short diffusion length of etching products. Room-temperature photoluminescence (PL) and x-ray photoelectron spectroscopy (XPS) measurements confirm that TBCl etching is capable of removing the damage and impurities induced by plasma etching without introducing additional damage.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Heterogeneous damage in Li-ion batteries: Experimental analysis and theoretical modeling

We assess the heterogeneous electrochemistry and mechanics in a composite electrode of commercial batteries using synchrotron X-ray tomography analysis and microstructure-resolved computational modeling. We visualize the morphological defects at multi-scales ranging from the macroscopic composite, particle ensembles, to individual single particles. Particle fracture and interfacial debonding are identified in a large set of tomographic data of active particles. Mechanical failure in the regime near the separator is more severe than toward the current collector. The active particles close to the separator experience deeper charge and discharge over cycles and thus are more mechanically loaded. The difference in the Li activity originates from the polarization of the electrolyte potential and the non-uniform distribution of the activation energy for the charge transfer reaction. We model the kinetics of intergranular fracture and interfacial degradation to confirm that the various Li activities are the major cause of the heterogeneous damage. The interfacial failure may reconstruct the conductive network and redistribute the electrochemical activities that render a dynamic nature of electrochemistry and mechanics evolving over time in the composite electrode. We further quantify the influence of the mechanical damage on the metrics of battery performance. We simulate the electrochemical impedance profile to build a relationship between the interfacial debonding and the impedance of electron transport and surface charge transfer. Lastly, the mechanical failure disrupts the conduction path of electrons and results in significant polarization and capacity loss in batteries.

25 ENERGY STORAGE↗
DOE OSTI2025

A phase-field fracture formulation for generalized standard materials: The interplay between thermomechanics and damage

Accurately modeling fracture of ductile materials poses open challenges in the field of computational mechanics due to the multiphysics nature of their failure processes. Integrating the interplay between thermodynamics and damage into ductile fracture models is vital for predicting critical failure modes. Here, in this paper, we develop a versatile phase-field (PF) framework for modeling ductile fracture, taking into account finite-strain elasto-plasticity. The framework stems from a variational formulation of constitutive relations for generalized standard materials (GSMs), whose response is described by a Helmholtz free energy and a dissipation pseudo-potential. Its variational structure is based on a minimum principle for a functional that expresses the sum of power densities for reversible and irreversible processes. By minimizing this functional with a constraint on a von Mises yield function, we derive the evolution equation for the equivalent plastic strain and an associative flow rule. This constrained optimization problem is analytically solved for a wide class of thermo-viscoplasticity models. The key innovations of the current work include (i) a cubic plastic degradation function that accounts for a non-vanishing damage-dependent yield stress, (ii) closed-form expressions of the Helmholtz free energy and dissipation pseudo-potential for three thermo-viscoplasticity models, (iii) an extended Johnson–Cook plasticity model with a nonlinear hardening law, and (iv) a plastic work heat source that depends on the plastic degradation function and a variable Taylor–Quinney (TQ) coefficient. The capabilities of the proposed framework are tested with the aid of four ductile fracture problems, including the Sandia Fracture Challenge. In each of these problems, we examine the evolution of relevant field variables such as the PF order parameter, the equivalent plastic strain, the temperature, and the internal power dissipation density, in addition to the overall structural response quantified by the force–displacement curve. These numerical studies demonstrate that the proposed framework effectively represents ductile fracture, yielding computational results that exhibit good agreement with experimental data.

36 MATERIALS SCIENCE↗