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At least 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

AREVA NP MR Cladding benefits for proposed US NRC RIA and LOCA requirements

M5 is the reference alloy of AREVA NP for PWR cladding applications. It is a zirconium-based alloy containing 1% niobium, no tin, and well-controlled oxygen, iron, and sulfur contents. It has a fully recrystallized microstructure. The absence of tin in M5 results in a very low corrosion rate and hydrogen pick-up during normal operation, even at high burn-up and in high duty irradiation conditions. Due to this low hydrogen pick-up under irradiation (typically less than 100 ppm, End of Life), M5 retains a very good strength and an exceptional residual ductility during and after the accident. This allows utilities implementing M5 to simplify the safety analysis and to demonstrate significant margins regarding fuel related criteria. Simplified methods are easier for plants to implement and maintain for future plant operations and core design management. This paper specifically presents 3 examples on the safety improvement brought by M5 cladding. First, during a reactivity-induced accident (RIA), the properties of M5 are such that bounding analyses for future cycles are significantly simplified, in particular by demonstrating that fuel dispersal will not occur. The major aspects of the AREVA NP RIA methodology are presented. A second focus is made on the low hydrogen embrittlement of M5 and on its high ductility after quenching during a loss-of-coolant accident (LOCA). In a third part, the breakaway oxidation testing program currently under development in Paimboeuf (France) is described, including details about the testing devices and qualification. The tests have demonstrated that M5 cladding does not have breakaway at least up to 5000 s oxidation duration at 1000 C. degrees, which is much higher than the LOCA duration.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2016

The PROMETRA program: plane strain tests on fresh and highly irradiated zircaloy-4, ZIRLO and M5 fuel claddings

In the framework of the PROMETRA program, clad hardening constitutive laws (stress-strain curves) have been already implemented in the SCANAIR code. These laws were derived from uniaxial hoop tensile tests performed on narrow machined ring samples. However, they do not reproduce the conditions of strain multi-axiality acting on cladding during a RIA (Reactivity-Initiated Accident) in a PWR. As a consequence, a new specimen called Plane Strain Tensile (PST) similar to the annular sample developed by Pennsylvania State University has been developed at CEA on a wider notched ring. It aims to accurately predict the cladding failure in more prototypical conditions, close to plane strain hoop tension in the middle of the gage section. This paper details the PST tests implementation and results in the framework of the PROMETRA program on fresh and irradiated claddings. The development of this test has led also to the development of a technique to measure local deformations in the gage section of the PST specimen using 2-D Digital Image Correlation (DIC). Tests performed on fresh Zircaloy-4 and on irradiated Zircaloy-4, M5 and ZIRLO specimens are analyzed relying of post-test examinations and finite element simulations. In the case of tests performed on irradiated Zry-4 and ZIRLO at 280 and 350 Celsius degrees, the presence of a hydride rim favors the crack nucleation on the outer surface. In this case, rupture nucleation occurs preferentially in the vicinity of notches. Such tests are not representative of the rupture of a cladding subjected to plane strain loading. Nevertheless, they give a good representation of the initiation of rupture observed during RIA on irradiated cladding, resulting in a hydride damage. Zry-4 specimens tested at 480 Celsius degrees and M5TM at 280 and 350 C. degrees result in a ductile fracture nucleation in the center of the specimen. This rupture is prototypical of a ductile rupture of an irradiated specimen subjected to a plane strain loading. However, the nucleation on inner surface by shear at the mandrel contact is not prototypical of a clad rupture during the PCMI (Pellet Clad Mechanical Interaction) phase of a RIA (membrane stresses in the clad thickness in RIA). An important lesson learned from this experimental approach is that the PST test is a particularly complex test, both in its implementation and interpretation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Blending Compostable Plastics for Packaging Applications

Non-sustainable packaging materials (polymers) are a large portion of the increasing amount of plastic waste that become environmental pollutants. While many biodegradable or compostable polymers have been developed in recent years, most fail to compete with the non-sustainable polymers dominating the market, due to lack of certain desired properties, such as thermal (high melt temperature) and mechanical (high ductility) performance. For example, the popular compostable polymer polylactic acid (PLLA) has a high melt temperature but is very brittle. Another polymer, poly(d-valerolactone) (PVL) demonstrates great ductility but has a very low melt temperature. By blending PLLA and PVL, there is an opportunity to create a new biodegradable material with synergistic desired properties for packaging applications. In this study, we produce several (9) physical blends of PVL and PLLA with varying compositions of the two polymers while applying three different materials to make them more compatible (compatibilizers). We test the success of compatibilization by scanning electron microscopy (SEM), mechanic testing (strain at break) and differential scanning calorimetry (melting temperature). Overall, we highlight several promising materials with high compatibility and desired thermomechanical properties for sustainable packaging. Ideally, these materials could help mitigate future plastic pollution in Colorado and beyond.

blending↗
DOE OSTI2025

Recent Advances in Pipeline Integrity for Transporting Blended Hydrogen-Natural Gas

To achieve US decarbonization goals, hydrogen is being considered as an alternative energy source to reduce carbon emissions. Blending hydrogen into existing natural gas pipelines is an intuitive first step to enable near term emission reductions. However, there are numerous challenges and uncertainties that complicate the transition to transporting hydrogen long-distance through existing natural gas pipelines. The main challenge is hydrogen embrittlement (HE), which reduces the ductility, fracture toughness and fatigue resistance of pipeline steels. This work delivers a technical review on HE effects on the material properties of pipeline carbon steels, such as Grade B, X52, X65, X70, X80, and X100. An important aspect of laboratory tests to capture the HE effect is the hydrogen test environment. This includes hydrogen pre-charged specimens tested in air and specimens tested in a hydrogen gas environment. A review of the mechanical properties of pipeline steel in different hydrogen environments determined through tensile testing is given first, which includes HE effects on yield strength, ultimate tensile strength, and ductility for blended hydrogen-natural gas pipelines. Then, the HE effects on fracture toughness and fatigue crack growth resistance are discussed. Last, impacts of HE to pipeline integrity and major technical challenges are discussed.

: Hydrogen Embrittlement↗
DOE OSTI2025

Microstructural Characteristics, Mechanical Properties, and Corrosion Behavior of Field-Assisted Diffusion Welded Alloy 617

This study investigated the microstructural characteristics, mechanical response, and corrosion resistance of Alloy 617 diffusion welded by electric field-assisted sintering (EFAS). The microstructure exhibited good grain boundary (GB) migration across the interface and flat interface in the samples bonded at different conditions. Graded grain size was observed, with grain coarsening being more significant near sample surface due to EFAS-induced temperature gradient. Tensile testing revealed that the specimens fractured in the matrix away from the interface. The peak strength of 807 MPa was obtained in the samples welded at 1000°C. The materials obtained at 1100°C exhibited reduced tensile strength but improved ductility. Strain maps revealed by digital image correlation showed the flat interfaces were less ductile compared to the matrix. The hardness reduced near sample surfaces due to enlarged grains induced by temperature gradient. The interfaces with GB migration exhibited improved corrosion resistance in molten salt compared to the flat interfaces.

36 - MATERIALS SCIENCE↗
DOE OSTI2026

RidgeAlloy: A high pressure die casting alloy that captures the approaching wave of automotive body sheet scrap

Oak Ridge National Laboratory (ORNL) has recently launched an effort to economically expand the North American aluminum supply chain by designing and developing a new family of Al-Mg-Si-Fe-Mn structural die cast aluminum alloys that can be made from up to 100% mixed 5xxx and 6xxx series automotive post-consumer sheet scrap and do not require heat treatment. The goal is to develop an alloy capable of capturing the approaching scrap wave of aluminum sheet intensive vehicles (in the 2030’s) into integrated structural high pressure die castings, rather than down-cycling these high-grade sheet alloys into non-structural castings. ORNL discovered a significant gap in the commercial thermodynamic databases that were unable to predict the trends of a key primary intermetallic phase as a function of composition. Experiments were performed to correct this gap and to create a unique, corrected quaternary database for Al-Mg-Si-Fe. High throughput computational methods, including solidification simulations, were used to identify a composition volume capable of avoiding this embrittling primary intermetallic phase, even at higher Fe + Si contents. Laboratory scale castings validated the thermodynamic and solidification predictions and resulted in lab-cast alloys with little primary intermetallic, and which met or exceeded structural casting properties requirements for yield strength and ductility. An accelerated demonstration of an HPDC automotive part was conducted in collaboration with two U.S. small businesses. Ingots made from 100% recycled 5xxx and 6xxx series scrap (plus Fe) were used to die cast one variant of this new family of Al-Mg-Si-Fe-Mn alloys (with high Si + Fe content) into a mid-sized HPDC structural-type automotive component. The HPDC alloy demonstration part showed good properties (especially ductility) and good castability for a complex component.

Plotkowski, Alex [ORNL] (ORCID:0000000154718681)↗
DOE OSTI2013

Mechanical properties of irradiated single-layer graphene

The mechanical properties of irradiated single-layer graphene sheets are determined as a function of inserted vacancy concentration. We find that the vacancy-induced crystalline-to-amorphous transition is accompanied by a brittle-to-ductile transition in the failure response of irradiated graphene sheets for inserted vacancy concentrations of 8%-12%. While point defects and larger voids appreciably degrade the strength of pristine graphene, we find that even heavily damaged samples ({approx}20% vacancies) exhibit tensile strengths of {approx}30 GPa, in significant excess of those typical of engineering materials. Our results suggest that defect engineering of graphene is feasible without incurring a complete loss of its desirable mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effect of pore pressure buildup on slowness of rupture propagation

Pore fluid pressure is known to play an important role in brittle fracture initiation and propagation, yet the underlying mechanisms remain unclear. We conducted triaxial experiments on saturated porous sandstones to investigate effects of pore pressure buildup on the slowness of shear rupture propagation at different confining pressures. At low to intermediate confinements, rocks fail by brittle faulting, and pore pressure buildup causes a reduction in rock’s shear strength but does not induce measurable differences in slip behavior. When the confinement is high enough to prohibit dynamic faulting, rocks fail in the brittle-ductile transitional regime. In the transitional regime, pore pressure buildup promotes slip instability on an otherwise stably sliding fracture. Compared to those observed in the brittle regime, the slip rate, stress drop, and energy dissipated during rupture propagation with concurrent pore pressure buildup in the transitional regime are distinctively different. When decreasing confining pressure instead, the slip behavior resembles the ones of the brittle regime, emphasizing h ow the observed slowness is related to excess pore pressure beyond the effective pressure phenomenon. Analysis of the mechanical data using existing theoretical models confirms these observations. Quantitative microstructural analyses reveal that increasing pore pressure lessens the dilatancy hardening during failure, thus enhances slip along the localized zone in the transitional regime. Lastly, our experimental results suggest that pore pressure buildup induces slow slip in the transitional regime, and slip rates along a shear fracture may vary considerably depending on effective stress states.

58 GEOSCIENCES↗
DOE OSTI2022

A review of the fabrication methods and mechanical behavior of continuous thermoplastic polymer fiber–thermoplastic polymer matrix composites

Abstract Thermoplastic polymer fiber–thermoplastic polymer matrix composites (PPCs or PRFPs), often recognized as self‐reinforced or single polymer composites, are potential candidates for future advanced polymer composites because of various advantages ( e.g., recyclability, formability, low‐cost, ultra‐lightweight, environmental friendliness, etc.). The manufacturability and mechanical behavior of these composites compared to conventional carbon‐/glass‐/aramid‐fiber‐reinforced polymers is of great interest to the composites community, but there are a limited number of studies in this area. To this end, this paper reviewed fabrication methods with different processing parameters and mechanical behavior of uni‐/multi‐directional thermoplastic PPCs featuring continuous thermoplastic polymer fibers from limited data in the literature. It was shown that most specific behaviors (normalized by density) of these materials in various loading conditions (e.g., quasi‐static tension/shear/flexure, tension‐tension fatigue, and out‐of‐plane impacting, etc.) are comparable to or better than glass‐/aramid‐fiber‐reinforced polymers. Particularly, the specific ductility in the foregoing conditions outperforms all the carbon‐/glass‐/aramid‐fiber‐reinforced polymers. Thermoplastic PPCs with remarkable performance can be achieved through several uncomplicated methods (e.g., film stacking, hot compaction, powder and solution impregnations, matrix infusion and injection molding, additive manufacturing, etc.), which have some similarities to the methods used for carbon‐/glass‐/aramid‐fiber‐reinforced polymers. Moreover, several opportunities and challenging problems of thermoplastic PPCs were summarized at the end of this review paper. Efficient solutions may require countless efforts in the composites community to further strengthen the performance and understanding of thermoplastic PPCs for wide applications in various engineering fields in the future.

36 MATERIALS SCIENCE↗
DOE OSTI2017

A degradation function consistent with Cocks–Ashby porosity kinetics

Here, the load carrying capacity of ductile materials degrades as a function of porosity, stress state and strain-rate. The effect of these variables on porosity kinetics is captured by the Cocks–Ashby model; however, the Cocks–Ashby model does not account for material degradation directly. This work uses a yield criteria to form a degradation function that is consistent with Cocks–Ashby porosity kinetics and is a function of porosity, stress state and strain-rate dependence. Approximations of this degradation function for pure hydrostatic stress states are also explored.

36 MATERIALS SCIENCE↗
DOE OSTI2012

ON MEASUREMENT OF CARBON CONTENT IN RETAINED AUSTENITE IN A NANOSTRUCTURED BAINITIC STEEL

In this study, the carbon content of retained austenite in a nanostructured bainitic steel was measured by atom probe tomography and compared with data derived from the austenite lattice parameter determined by X-ray diffraction. The results provide new evidence about the heterogeneous distribution of carbon in austenite, a fundamental issue controlling ductility in this type of microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Investigation on the Influence of EVA Content on the Mechanical and Thermal Characteristics of Poly(lactic acid) Blends

Poly(lactic acid) (PLA) has gained considerable attention nowadays as a biocompatible polymer owing to its advantage of being prepared from renewable resources. PLA exhibits excellent tensile strength, fabricability, thermal plasticity and biocompatibility properties comparable to many petroleum based plastics. However, low heat distortion temperature, brittleness and slow crystallization rate limit the practical applications of PLA. In order to address these limitations, an attempt has been made in the current work to prepare binary blends of PLA with ethylene vinyl acetate (EVA) at different compositions via melt mixing technique. Systematic investigation on the mechanical properties, thermal degradation and crystallization behavior for PLA-EVA blends was carried out. The impact strength of binary blends of PLA–EVA was found to increase significantly by 176% for 15 wt% of EVA compared to virgin PLA. This is due to the strong interfacial adhesion among PLA and EVA resulting in brittle to ductile transition. Scanning electron microscopy analysis for impact fractured surfaces of binary blends of PLA implied the toughening effect of PLA by EVA. Thermogravimetry analysis results revealed that the activation energy of PLA–EVA blends decreased with increase in EVA content in the PLA matrix. While, differential scanning calorimetry results obtained for PLA–EVA blends revealed the improvement in crystallinity when compared with neat PLA. The effect of EVA on non-isothermal melt crystallization kinetics of PLA was also examined via DSC at various heating rates. Decreasing trend in the t{sub 1/2} values indicated the faster rate of crystallization mechanism after addition of EVA in the PLA matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Novel Tough Crystalline Blends of Polylactide with Ethylene Glycol Derivative of POSS

Blending of polylactide (PLA) with low stereoregularity and polyhedral oligomeric silsesquioxane grafted with arms of poly(ethylene glycol) methyl ether, acting as a plasticizer, allowed us previously to obtain a novel stable elastomeric-like material. The present contribution focuses on the properties of semi-crystalline PLA plasticized with this compound. Melt blends of PLA with 5–15 wt% of the plasticizer, were compression molded, quenched and annealed, which enabled cold-crystallization. The glass transition temperature of the blends and their drawability depended on their crystallinity and plasticizer content. The best ductility was reached at the plasticizer content of 15 wt%; the achieved strain at break was 6.5 (650%) and 1.3 (130%), for the quenched and annealed material, respectively. The latter value exceeded 20 times the strain at break of neat crystalline PLA. The tensile toughness of the annealed 15 wt% blend was 12 times larger than that of crystalline PLA. Moreover, annealing of 15 wt% blend improved its yield strength by 40%. Despite the two peaks of the loss modulus, indicating the two glass transitions in this blend, no heterogeneities were found by scanning electron microscopy, indicating that the plasticizer enriched phase formed instead of distinct inclusions of the plasticizer.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Natural Glyceryl Tributyrate as Plasticizer and Compatibilizer on the Performance of Bio-Based Polylactic Acid/poly(3-hydroxybutyrate) Blends

Bio-based poly(lactic acid)/poly(3-hydroxybutyrate) (PLA/PHB) films were melt-blended with a natural hydrophobic plasticizer (glyceryl tributyrate, TB) at three different concentrations (10, 15 and 20% by weight per 100 parts of the blends) to study the effect of TB on the final properties of the materials. The pursued aim was to obtain a material with potential use in the packaging industry. Two different PLA/PHB ratios were used, 70/30 and 60/40, respectively. A full characterization of the developed blends was carried out, including the morphological, thermal, mechanical and barrier properties. The thermal test revealed the immiscibility between PLA and PHB by showing two glass transition temperatures for the blends and biphasic melt. Mechanical tests showed the increased in the elongation at break as the plasticizer content in films increased. The incorporation of PHB crystals in the PLA matrix displayed an improvement in the water barrier properties of materials. Finally, formulations PLA/PHB-TB with 15 wt% of plasticizer presented the best combination of properties suitable for the intended use in films manufacturing, showing toughness and ductility, good water barrier properties and transparency with slightly amber color.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Development of PBT/Recycled-PET Blends and the Influence of Using Chain Extender

In this study, PBT/recycled-PET blends were developed using a twin-screw extruder. A commercial chain extender (Joncryl ADR 4468) was also used to melt mix with PBT/recycled-PET blend systems. Firstly, Joncryl at different loadings was extruded with recycled-PET to explore the influence of branching on melt behavior and crystallization of PET. The effect of blending recycled-PET with PBT on the final properties was then explored at different blending ratios (25w/75w, 50w/50w and 75w/25w). Similar blends were subsequently prepared while incorporating chain extender. Melt behavior, phase miscibility, crystallization behavior, solid viscoelastic properties, tensile and impact properties of the blends were eventually analyzed using differential scanning calorimeter (DSC), melt flow indexer (MFI), dynamic mechanical analyzer (DMA), and tensile and Izod notched impact testing, respectively. The results showed that the addition of chain extender increased the melt viscosity of PET and at the low contents enhanced the PET’s crystallization rate. On the other hand, the blends of PBT/recycled-PET are fully miscible in the amorphous region whereas the crystalline phases are immiscible subsequent to a fast cooling. The PBT and PET molecules could also co-crystallize and be fully miscible in crystalline phases upon slow cooling of the melt. Blending recycled-PET with PBT didn’t suppress the tensile properties of PBT, however it could enhance the PBT’s ductility and reduce its impact strength. The chain extender didn’t influence the mechanical properties much. Graphical Abstract: .

36 MATERIALS SCIENCE↗
DOE OSTI2018

Theoretical Investigation of the Mechanical and Thermodynamic Properties of the Layered Yttrium Diborocarbides

The mechanical, electronic, and thermodynamic properties of typical layered structure yttrium diborocarbides (YB{sub 2}C{sub 2}) were investigated by the density functional theory. The calculated lattice constants were slightly higher than the available experimental data. The elastic constants revealed that YB{sub 2}C{sub 2} was mechanically stable. The bulk modulus (190.8 GPa), shear modulus (127.4 GPa), Young’s modulus (312.7 GPa), Poisson’s ratio (0.227), and Vickers hardness (18–19 GPa) were obtained, and the ductility, plasticity, and elastic anisotropy were further analyzed. The total and partial density of states were also calculated, indicating that the metallic character was mainly attributed to the contribution from Y-4d states and weakly hybridized with the 2p states from the B and C atoms. Finally, we obtained the Debye, melting, and the superconducting transition temperatures of YB{sub 2}C{sub 2} as 824, 2239 and 2.38 K, respectively. Our study showed that YB{sub 2}C{sub 2} offers potential in superconductivity or ultrahigh temperature applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

The Ideal Strengths of Superconducting MgCNi{sub 3} and CdCNi{sub 3}

The stress-strain curves under tensile deformation in the 〈100〉, 〈110〉, and 〈111〉 directions and under shear deformation in the (001)〈110〉, (110)〈1̄10〉, (111)〈11̄0〉, and (111)〈112̄〉 slip systems have been systematically calculated by first-principles method to study the ideal strengths of superconducting MgCNi{sub 3} and CdCNi{sub 3}. The ideal strengths in the three tensile directions are found to be reduced in the order of 〈100〉 → 〈110〉 → 〈111〉 and those for the four shear slip systems in the order of (110)〈1̄10〉→(111)〈112̄〉→(111)〈11̄0〉→(001)〈110〉 for both superconductors. Their lowest ideal tensile strengths are found to be larger than the corresponding highest ideal shear strengths, which could explain why both superconductors have the ductility. The obtained lattice constants and elastic properties coincide well with the the available experimental and theoretical values.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

The Influence of the Regimes of Thermomechanical Treatments on the Features of Heterophase and Grain Structure of A V–Cr–Zr–Ta Alloy

A comparative investigation of the influence of thermomechanical treatment modes on the structural-phase state and mechanical properties of a V–Cr–Zr–Ta low-activation vanadium alloy is performed. It is demonstrated that the use of thermomechanical treatment improves the level of short-term strength at room and elevated temperatures. The alloy is characterized by high ductility in a wide range of temperatures irrespective of the regimes of thermomechanical treatment. It is found out that the V–Cr–Zr–Ta alloy possesses higher thermal microstructure stability and mechanical properties compared to those of the V–Ti–Cr alloys.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗