Search NASA⌕ Search

SEARCH · Search NASA

Results for “REPAIR”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Repair process and a repaired component

Matrix composite component repair processes are disclosed. The matrix composite repair process includes applying a repair material to a matrix composite component, securing the repair material to the matrix composite component with an external securing mechanism and curing the repair material to bond the repair material to the matrix composite component during the securing by the external securing mechanism. The matrix composite component is selected from the group consisting of a ceramic matrix composite, a polymer matrix composite, and a metal matrix composite. In another embodiment, the repair process includes applying a partially-cured repair material to a matrix composite component, and curing the repair material to bond the repair material to the matrix composite component, an external securing mechanism securing the repair material throughout a curing period, In another embodiment, the external securing mechanism is consumed or decomposed during the repair process.

42 ENGINEERING↗
DOE OSTI2024

Provable Repair of Vision Transformers

Vision Transformers have emerged as state-of-the-art image recognition tools, but may still exhibit incorrect behavior. Incorrect image recognition can have disastrous consequences in safety-critical real-world applications such as self-driving automobiles. In this paper, we present Provable Repair of Vision Transformers (PRoViT), a provable repair approach that guarantees the correct classification of images in a repair set for a given Vision Transformer without modifying its architecture. PRoViT avoids negatively affecting correctly classified images (drawdown) by minimizing the changes made to the Vision Transformer’s parameters and original output. Here, we observe that for Vision Transformers, unlike for other architectures such as ResNet or VGG, editing just the parameters in the last layer achieves correctness guarantees and very low drawdown. We introduce a novel method for editing these last-layer parameters that enables PRoViT to efficiently repair state-of-the-art Vision Transformers for thousands of images, far exceeding the capabilities of prior provable repair approaches.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

Peripherally Inserted Central Catheters in Pediatric Patients: To Repair or Not Repair

IntroductionPreservation of venous access in children is a major concern in pediatric interventional radiology. If a peripherally inserted central catheter (PICC) breaks, there are two options: repair the line with a repair kit or exchange the line over a wire in the interventional suite. The purpose of this study is to assess the outcome of PICC repairs in children and to compare these with the outcomes of PICC exchange.Materials and MethodsThis is a single-center, retrospective study of central line-associated bloodstream infection (CLABSI) following management of externally broken PICCs (2010–2014). The occurrence of CLABSI within 30 days after repair (Group A) or exchange (Group B) of a line was analyzed, as well as PICCs exchanged following an initial and failed repair.ResultsA total of 235 PICC breaks were included in the study, of which 161 were repaired, and 116 of whom were successful (68%, Group A). No repair was performed in 74 PICCs—55/74 of these were exchanged over a wire (74%, Group B), and 19/74 lines were removed. The 30 days post-repair CLABSI rate (Group A) was 2.0 infections per 1000 catheter days, and the calculated risk was 4.3%. In comparison the 30 days post-exchange CLABSI rate (Group B) was 4.0 per 1000 catheter days and the calculated risk 10.9%. This difference was significant when adjusted for antibiotic use (OR 3.87; 95% CI 1.07–14.0, p = 0.039).ConclusionThe results of this study support repairing a broken PICC instead of removing or replacing the line.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2024

Base excision repair and double strand break repair cooperate to modulate the formation of unrepaired double strand breaks in mouse brain

Abstract We lack the fundamental information needed to understand how DNA damage in the brain is generated and how it is controlled over a lifetime in the absence of replication check points. To address these questions, here, we integrate cell-type and region-specific features of DNA repair activity in the normal brain. The brain has the same repair proteins as other tissues, but normal, canonical repair activity is unequal and is characterized by high base excision repair (BER) and low double strand break repair (DSBR). The natural imbalance creates conditions where single strand breaks (SSBs) can convert to double strand breaks (DSBs) and reversibly switch between states in response to oxidation both in vivo and in vitro. Our data suggest that, in a normal background of repair, SSBs and DSBs are in an equilibrium which is pushed or pulled by metabolic state. Interconversion of SSB to DSBs provides a physiological check point, which would allow the formation of unrepaired DSBs for productive functions, but would also restrict them from exceeding tolerable limits.

Science & Technology - Other Topics↗
DOE OSTI2022

Property-structure-process relationships in dissimilar material repair with directed energy deposition: Repairing gray cast iron using stainless steel 316L

Directed energy deposition (DED) based remanufacturing leverages the flexibility of additive manufacturing to add value to broken or worn components. DED offers the ability to repair cast iron, a material difficult to repair with traditional welding techniques. Despite this, development of appropriate DED process conditions for bimetallic cast iron structures lags low- and medium-carbon steel repair. Thermal stresses and porosity generated by high-temperature deposition on cast iron often lower mechanical properties and hinder the qualification process. In this report scanning speed, powder mass flow rate, and stepover width are studied in multiple-track structures deposited on gray cast iron. Dilution and residual stresses are found to be highly dependent on the selected process parameters. Samples with a higher volumetric energy input, e.g., slower scanning speeds and higher powder feed rates, showed improved density and lower residual stresses but suffered lower dilution into the substrate. The presented conditions further the development of additive manufacturing technologies for automotive repair.

42 ENGINEERING↗
DOE OSTI2022

Dynamic properties of 316l stainless steel repaired using electron beam additive manufacturing

Additive manufacturing has the potential to be used for repair of high-value parts, but the strength and integrity of such repaired parts, especially under dynamic loading, in still unknown. This work presents the results of high strain-rate dynamic testing of additively repaired stainless steel samples. The 316L samples were intentionally damaged and subsequently repaired with 308L stainless steel wire using electron beam additive manufacturing. The repaired samples were subjected to gas-gun impact testing to induce incipient damage and determine the role played by the repaired region in dictating damage and failure. The results show the following: 1) the equation of state of the repaired region is comparable to the original material as shown by the unchanged spall plane location, 2) the deformation behavior is similar to the original material as shown by the similar Hugoniot Elastic limit, 3) the spall strength of the repaired region is slightly higher than the original material due to varying grain size, and 4) the damage morphology in the repaired region is different and involves a high rate of void coalescence. In conclusion, despite these minor differences in the spall strength and the damage morphology, the overall dynamic response of the original material and repaired samples is similar suggesting that AM is a promising approach for repairing high-value components.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Escherichia coli single-stranded DNA binding protein SSB promotes AlkB-mediated DNA dealkylation repair

Highlights: • E. coli single stranded DNA binding protein (SSB) wraps single-stranded DNA (ssDNA). • SSB is known to be involved in base excision repair and recombination repair but not in DNA dealkylation repair. • The alkyl-adduct positioned at the 5′ of ssDNA is more accessible to AlkB compared to the internally located alkyl-adducts. • The presence of SSB lowers the K{sub M} of AlkB-catalyzed reaction and promote repair of the longer substrate. • AlkB-mediated repair of methyl adducts from very short ssDNA is rather efficient and SSB-independent. Repair of alkylation damage in DNA is essential for maintaining genome integrity. Escherichia coli (E.coli) protein AlkB removes various alkyl DNA adducts including N1-methyladenine (N{sup 1}meA) and N3-methylcytosine (N{sup 3}meC) by oxidative demethylation. Previous studies showed that AlkB preferentially removes N{sup 1}meA and N{sup 3}meC from single-stranded DNA (ssDNA). It can also remove N{sup 1}meA and N{sup 3}meC from double-stranded DNA by base-flipping. Notably, ssDNA produced during DNA replication and recombination, remains bound to E. coli single-stranded DNA binding protein SSB and it is not known whether AlkB can repair methyl adduct present in SSB-coated DNA. Here we have studied AlkB-mediated DNA repair using SSB-bound DNA as substrate. In vitro repair reaction revealed that AlkB could efficiently remove N{sup 3}meC adducts inasmuch as DNA length is shorter than 20 nucleotides. However, when longer N{sup 3}meC-containing oligonuleotides were used as the substrate, efficiency of AlkB catalyzed reaction was abated compared to SSB-bound DNA substrate of identical length. Truncated SSB containing only the DNA binding domain could also support the stimulation of AlkB activity, suggesting the importance of SSB-DNA interaction for AlkB function. Using 70-mer oligonucleotide containing single N{sup 3}meC we demonstrate that SSB-AlkB interaction promotes faster repair of the methyl DNA adducts.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Nonhomologous end-joining uses distinct mechanisms to repair each strand of a double strand break

Abstract Nonhomologous end-joining repairs chromosomal double strand breaks, but it is unknown whether both strands are repaired by this pathway, and if one strand break’s repair path impacts the other. Here, we show that nonhomologous end-joining employs both of two a priori possible strategies. Strand breaks that can be directly ligated are joined near-simultaneously, with no effect of one strand break’s repair path on the other. More complex end structures require obligatorily ordered repair. The first strand to be repaired is used as template for repair of the opposite/second strand break, with the latter repair reaction occurring fastest when also coupled to nonhomologous end-joining. Enforced asymmetry in repair of each strand break can extend to the gap-filling polymerase employed, and whether the polymerases incorporate RNA or DNA. Our results resolve questions about pathway mechanism and identify a requirement for flexibility of the nonhomologous end-joining machinery for efficient repair of both strand breaks within diverse cellular double strand breaks.

Luthman, Adam J.↗
DOE OSTI2024

A non-melting additive approach to structural repair of aluminum aircraft fastener holes

The damage to fastener holes in aerospace aluminum structures presents significant challenges for aircraft durability, and conventional bushing methods for repairing oversized holes often fall short due to the lack of metallurgical bonding and limited edge distance availability. This study investigates additive friction stir deposition, a non-melting additive process, as a viable alternative for the structural repair of aerospace fastener holes. The repair process, demonstrated on AA7050 (Al-Zn-Mg-Cu-Zr) hole structures, involves filling oversized holes with new material and machining to restore the original hole size. The repaired hole coupons are defect-free and exhibit good fatigue performance under fully reversed tension-compression loading (R = -1). At a nominal stress amplitude of 123.5 MPa, the average number of cycles to failure is 12,666 for unrepaired baseline coupons and 17,372 for effectively repaired coupons. Restoring complex geometries without compromising fatigue performance has been difficult in aerospace applications; this study marks the first demonstration of additive repair that consistently outperforms the unrepaired baseline coupons. Notably, the result is achieved through a low-energy, cost-effective solution without the need for post-repair heat treatment. Except for a few outliers, the post-repair fatigue performance generally remains inferior to that of undamaged, pristine coupons, likely due to precipitate evolution in AA7050 caused by the thermomechanical processing nature of additive friction stir deposition. This evolution weakens the repair region and the adjacent base material, leading to faster crack initiation and growth compared to the properly aged base material, AA7050-T7451.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Laser additive manufacturing for infrastructure repair: A case study of a deteriorated steel bridge beam

As our transportation infrastructure ages, its deterioration is becoming a growing concern. Rapid and effective methods for repair can reduce the need for time-and cost-intensive replacement of structures such as roadway bridges. In this work, laser-based additive manufacturing (AM) was developed for the re-pair of damaged beams in steel bridges. A corroded structural beam of low-carbon A36 steel was selected for this case study and 316L stainless steel was used for repair due to its excellent mechanical properties and corrosion resistance. Simulated repair experiments were performed on specimens extracted from the beam, and prepared with various groove shapes (Rectangular, Trapezoidal, and U-shaped). More in-depth parametric and microstructural studies were carried out with a series of U-shaped specimens repaired with the linear laser input energy varied from 19.5 to 30.0 J mm -1 . The tensile properties of the repaired specimens and interface structures were also investigated in detail. It was found that the repaired specimens had a slightly higher tensile strength despite a reduction in tensile elongation compared to the A36 steel base metal. The influence of interfacial microstructure and heterogeneity on the mechanical proper-ties of the repaired specimens was discussed. Furthermore, our work suggests the promising potential to employ AM for structural repair and provides fundamental insights into processing-structure-property relationships in laser AM-repaired materials.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Wellbore Seal Repair Using Nanocomposite Materials

Nanocomposite wellbore repair materials have been developed, tested, and modeled through an integrated program of laboratory testing and numerical modeling. Numerous polymer-cement nanocomposites were synthesized as candidate wellbore repair materials using various combinations of base polymers and nanoparticles. Based on tests of bond strength to steel and cement, ductility, stability, flowability, and penetrability in opening of 50 microns and less, we identified Novolac epoxy reinforced with multi-walled carbon nanotubes and/or alumina nanoparticles to be a superior wellbore seal material compared to conventional microfine cements. A system was developed for testing damaged and repaired wellbore specimens comprised of a cement sheath cast on a steel casing. The system allows independent application of confining pressures and casing pressures while gas flow is measured through the specimens along the wellbore axis. Repair with the nanocomposite epoxy base material was successful in dramatically reducing the flow through flaws of various sizes and types, and restoring the specimen comparable to an intact condition. In contrast, repair of damaged specimens with microfine cement was less effective, and the repair degraded with application of stress. Post-test observations confirm the complete penetration and sealing of flaws using the nanocomposite epoxy base material. A number of modeling efforts have supported the material development and testing efforts. We have modeled the steel-repair material interface behavior in detail during slant shear tests, which we used to characterize bond strength of candidate repair materials. A numerical model of the laboratory testing of damaged wellbore specimens was developed. This investigation found that microannulus permeability can satisfactorily be described by a joint model. Finally, a wellbore model has been developed that can be used to evaluate the response of the wellbore system (casing, cement, and microannulus), including the use of either cement or a nanocomposite in the microannulus to represent a repaired system. This wellbore model was successfully coupled with a field-scale model of CO 2 injection, to enable predictions of stress and strains in the wellbore subjected to subsurface changes (i.e. domal uplift) associated with fluid injection.

36 MATERIALS SCIENCE↗
DOE OSTI2022

AI-Enabled Robots for Automated Nondestructive Evaluation and Repair of Power Plant Boilers. Final Report

Boiler failure could cause loss of life and safety issues, cost hundreds of thousands of dollars in equipment repairs, property damage and production losses, and drive up the cost of electric power. Boiler maintenance is challenging and risky for inspectors working on scaffolding in confined hazardous spaces inside of a boiler and sometimes the space is hard to access. The operation is also time-consuming due to the large area of vertical structures for inspection and the tremendous effort needed for scaffolding. Recently, the use of robotics (e.g., drones and crawlers) in power plants for maintenance is growing rapidly. However, the existing robotics solutions show two notable technological gaps: no live repair capability, and no Artificial Intelligence (AI) for smart autonomy. The objective of this project is to develop an integrated autonomous robotic platform that is equipped with compact non-destructive evaluation (NDE) sensors to perform live inspection, operates onboard repair devices to perform live repair, and uses AI for intelligent data fusion and predictive analysis for automated and smart spatiotemporal inspection, analysis and repair of the furnace walls in coal-fired boilers. The approach to achieve the objective includes developing NDE sensors with signal processing techniques, designing and evaluating repair devices for robots based on fusion and solid-state technologies, and an autonomous robotic platform that can attach to and navigate on boiler furnace walls using magnetic drive tracks. The robot is also powered by AI to automate data gathering (e.g., 3D mapping and damage localization) and predictive analysis. This project has advanced the state-of-the-art by providing technological breakthroughs including compact NDE and repair tools for robots, AI capabilities for smart autonomy, and a robotic platform for automated boiler maintenance. This project has great potential to result in significant benefits including limiting or eliminating the need to send operators to assess difficult-to-access or hazardous areas, enabling automated live inspection and repair, avoiding time consuming scaffolding (especially for partial maintenance during unplanned outage), collecting comprehensive and well-organized data smartly, and avoiding or limiting the need for onsite or remote piloting technicians. The impacts can be tremendous in terms of the time and cost savings, reducing the risk for human operators, and increasing boiler reliability, usability, and efficiency. In addition, by developing the new technologies on the autonomous inspection and repair robot, by involving multiple undergraduate and graduate students working together with the faculty members on this project, and by generating knowledge and building up collaborations with industrial partners, this effort will significantly update the education capabilities, support long-term fundamental research, and maintain the leadership of Colorado School of Mines and Michigan State University in energy fields.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2019

Influence of FSW Repairing Process on the Microstructures and Mechanical Properties of Friction Stir-Welded 6082Al Alloy

When two 42-mm 6082Al plates were welded by friction stir welding (FSW), a discontinuously distributing groove defect is formed on the surface of the joint. Subsequently, the FSW repairing process was conducted at the defect location. The influence of the repairing process on the microstructures and mechanical properties of the joints were studied, and a description of the softening mechanism of the repaired joints is provided. The results show that TMAZ at the advance side is the weakest zone of the as-welded joints. The repairing process increases the heat input into the joints and thus promotes the coarsening and transformation of the precipitates in the joints, which further weakens the repaired joints. The average tensile strength of the joints repaired with a 24-mm pin is 205 MPa, which is 91% of that of the as-welded joint. The tensile strength generally increases when the size of the repaired pin decreases. The average tensile strength of the joints repaired with an 8-mm pin is 220 MPa, which is equivalent to the initial joints.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Metabolite damage and repair in metabolic engineering design

The necessarily sharp focus of metabolic engineering and metabolic synthetic biology on pathways and their fluxes has tended to divert attention from the damaging enzymatic and chemical side-reactions that pathway metabolites can undergo. Although historically overlooked and underappreciated, such metabolite damage reactions are now known to occur throughout metabolism and to generate (formerly enigmatic) peaks detected in metabolomics datasets. It is also now known that metabolite damage is often countered by dedicated repair enzymes that undo or prevent it. Metabolite damage and repair are highly relevant to engineered pathway design: metabolite damage reactions can reduce flux rates and product yields, and repair enzymes can provide robust, host-independent solutions. Herein, after introducing the core principles of metabolite damage and repair, we use case histories to document how damage and repair processes affect efficient operation of engineered pathways - particularly those that are heterologous, non-natural, or cell-free. We then review how metabolite damage reactions can be predicted, how repair reactions can be prospected, and how metabolite damage and repair can be built into genome-scale metabolic models. Lastly, we propose a versatile 'plug and play' set of well-characterized metabolite repair enzymes to solve metabolite damage problems known or likely to occur in metabolic engineering and synthetic biology projects.

Enzyme promiscuity↗
DOE OSTI2018

Timely double-strand break repair and pathway choice in pericentromeric heterochromatin depend on the histone demethylase dKDM4A

Repair of DNA double-strand breaks (DSBs) must be orchestrated properly within diverse chromatin domains in order to maintain genetic stability. Euchromatin and heterochromatin domains display major differences in histone modifications, biophysical properties, and spatiotemporal dynamics of DSB repair. However, it is unclear whether differential histone-modifying activities are required for DSB repair in these distinct domains. Here, we showed previously that the Drosophila melanogaster KDM4A (dKDM4A) histone demethylase is required for heterochromatic DSB mobility. Here we used locus-specific DSB induction in Drosophila animal tissues and cultured cells to more deeply interrogate the impact of dKDM4A on chromatin changes, temporal progression, and pathway utilization during DSB repair. We found that dKDM4A promotes the demethylation of heterochromatin-associated histone marks at DSBs in heterochromatin but not euchromatin. Most importantly, we demonstrate that dKDM4A is required to complete DSB repair in a timely manner and regulate the relative utilization of homologous recombination (HR) and nonhomologous end-joining (NHEJ) repair pathways but exclusively for heterochromatic DSBs. We conclude that the temporal kinetics and pathway utilization during heterochromatic DSB repair depend on dKDM4A-dependent demethylation of heterochromatic histone marks. Thus, distinct pre-existing chromatin states require specialized epigenetic alterations to ensure proper DSB repair.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Using Additive Manufacturing to Repair Gas Turbine Hot Section Components

Ni-based superalloys are used in the hot sections of gas turbine engines due to their excellent high temperature performance. During service the material degrades due to exposure at high temperature and mechanical loads. Hence, utility provides often inspect, service, and repair components in gas turbine engines to ensure safe operation. A major challenge, however, is that the most heat-resistant alloys are generally considered ‘non-weldable’ rendering them difficult to repair via welding operations. In these cases components are often scrapped and then replaced by parts which must be re-manufactured. This burdens utilities with additional cost and supply chain issues can result in long term outages or reduced operating limtis. In this work EPRI and ORNL investigated a proposed repair strategy for gas turbine hot section components. Hot section superalloy GTD-111 was selected as a candidate repair material system and AM material ABD-900 the repair material. Sandwich structures were fabricated via electron beam melting additive manufacturing (EBM-AM) producing tensile bars with gage sections consisting of dissimilar ABD-900 / GTD-111 / ABD-900 material. Metallography revealed that the interface exhibited no deleterious phases or processing defeats. Creep rupture experiments on heat treated material demonstrates that the emulated repair coupons exhibit creep resistance between GTD-111 and ABD-900. This study demonstrates that the proposed EBM-AM repair strategy presents a viable opportunity towards enabling AM repair of gas turbine engine components.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2024

Using Additive Manufacturing to Repair Gas Turbine Hot Section Components

Ni-based superalloys are used in the hot sections of gas turbine engines due to their excellent high temperature performance. During service the material degrades due to exposure at high temperature and mechanical loads. Hence, utility provides often inspect, service, and repair components in gas turbine engines to ensure safe operation. A major challenge, however, is that the most heat-resistant alloys are generally considered ‘non-weldable’ rendering them difficult to repair via welding operations. In these cases components are often scrapped and then replaced by parts which must be re-manufactured. This burdens utilities with additional cost and supply chain issues can result in long term outages or reduced operating limits. In this work EPRI and ORNL investigated a proposed repair strategy for gas turbine hot section components. Hot section superalloy GTD-111 was selected as a candidate repair material system and AM material ABD-900 the repair material. Sandwich structures were fabricated via electron beam melting additive manufacturing (EBM-AM) producing tensile bars with gage sections consisting of dissimilar ABD-900 / GTD-111 / ABD-900 material. Metallography revealed that the interface exhibited no deleterious phases or processing defeats. Creep rupture experiments on heat treated material demonstrates that the emulated repair coupons exhibit creep resistance between GTD-111 and ABD-900. This study demonstrates that the proposed EBM-AM repair strategy presents a viable opportunity towards enabling AM repair of gas turbine engine components.

36 MATERIALS SCIENCE↗