Damage tolerance and structural monitoring for wind turbine blades.

PubMed

McGugan, M; Pereira, G; Sørensen, B F; Toftegaard, H; Branner, K

2015-02-28

The paper proposes a methodology for reliable design and maintenance of wind turbine rotor blades using a condition monitoring approach and a damage tolerance index coupling the material and structure. By improving the understanding of material properties that control damage propagation it will be possible to combine damage tolerant structural design, monitoring systems, inspection techniques and modelling to manage the life cycle of the structures. This will allow an efficient operation of the wind turbine in terms of load alleviation, limited maintenance and repair leading to a more effective exploitation of offshore wind. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

An Approach to Risk-Based Design Incorporating Damage Tolerance Analyses

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.; Glaessgen, Edward H.; Sleight, David W.

2002-01-01

Incorporating risk-based design as an integral part of spacecraft development is becoming more and more common. Assessment of uncertainties associated with design parameters and environmental aspects such as loading provides increased knowledge of the design and its performance. Results of such studies can contribute to mitigating risk through a system-level assessment. Understanding the risk of an event occurring, the probability of its occurrence, and the consequences of its occurrence can lead to robust, reliable designs. This paper describes an approach to risk-based structural design incorporating damage-tolerance analysis. The application of this approach to a candidate Earth-entry vehicle is described. The emphasis of the paper is on describing an approach for establishing damage-tolerant structural response inputs to a system-level probabilistic risk assessment.

An Evaluation of the Applicability of Damage Tolerance to Dynamic Systems

NASA Technical Reports Server (NTRS)

Forth, Scott C.; Le, Dy; Turnberg, Jay

2005-01-01

The Federal Aviation Administration, the National Aeronautics and Space Administration and the aircraft industry have teamed together to develop methods and guidance for the safe life-cycle management of dynamic systems. Based on the success of the United States Air Force damage tolerance initiative for airframe structure, a crack growth based damage tolerance approach is being examined for implementation into the design and management of dynamic systems. However, dynamic systems accumulate millions of vibratory cycles per flight hour, more than 12,000 times faster than an airframe system. If a detectable crack develops in a dynamic system, the time to failure is extremely short, less than 100 flight hours in most cases, leaving little room for error in the material characterization, life cycle analysis, nondestructive inspection and maintenance processes. In this paper, the authors review the damage tolerant design process focusing on uncertainties that affect dynamic systems and evaluate the applicability of damage tolerance on dynamic systems.

Synthesis, Characterization And Modeling Of Functionally Graded Multifunctional Hybrid Composites For Extreme Environments

DTIC Science & Technology

2017-04-04

research thrust areas are designed to enable the development of reliable, damage tolerant, lightweight structures with excellent thermal management...46 2. RESEARCH THRUST AREA: MULTISCALE CHARACTERIZATION AND MODELING .................................... 56 2.1 DESIGN OF MATERIALS...The research thrust areas are designed to enable the development of reliable, damage tolerant, lightweight structures with excellent thermal

Damage Tolerance Applied to Design of Mid-Size Aircraft

NASA Astrophysics Data System (ADS)

Chaves, Carlos Eduardo

Most of the mid-size aircraft are certified according to FAA Part 25 requirements, and in order to comply with these requirements the majority of the aircraft structure must be damage tolerant. To assure damage tolerance, despite the overall structural behavior, one should look at the details. There is a great amount of analysis tasks and tests that must be carried out in order to guarantee the aircraft structural integrity. This paper presents an overview of Embraer experience with design and analysis for damage tolerance during the last 30 years. Aspects like DT analysis for metallic and composite structures, selection of appropriate materials, loads, definition of limits of validity and definition of inspection intervals will be addressed along this work. Selected structural tests that have been performed for validation of modeling predictions will be presented. Some aspects to be discussed are related to the design differences between commercial jets, which are usually subjected to high usage conditions, business jets and military aircraft. Further, the application of future technologies, such as structural health monitoring, and also of new materials and manufacturing processes that have been evaluated in order to improve the damage tolerance capability of the aircraft structures will be discussed.

Advanced information processing system - Status report. [for fault tolerant and damage tolerant data processing for aerospace vehicles

NASA Technical Reports Server (NTRS)

Brock, L. D.; Lala, J.

1986-01-01

The Advanced Information Processing System (AIPS) is designed to provide a fault tolerant and damage tolerant data processing architecture for a broad range of aerospace vehicles. The AIPS architecture also has attributes to enhance system effectiveness such as graceful degradation, growth and change tolerance, integrability, etc. Two key building blocks being developed by the AIPS program are a fault and damage tolerant processor and communication network. A proof-of-concept system is now being built and will be tested to demonstrate the validity and performance of the AIPS concepts.

The combined effect of glass buffer strips and stitching on the damage tolerance of composites

NASA Technical Reports Server (NTRS)

Kullerd, Susan M.

1993-01-01

Recent research has demonstrated that through-the-thickness stitching provides major improvements in the damage tolerance of composite laminates loaded in compression. However, the brittle nature of polymer matrix composites makes them susceptible to damage propagation, requiring special material applications and designs to limit damage growth. Glass buffer strips, embedded within laminates, have shown the potential for improving the damage tolerance of unstitched composite laminates loaded in tension. The glass buffer strips, less stiff than the surrounding carbon fibers, arrest crack growth in composites under tensile loads. The present study investigates the damage tolerance characteristics of laminates that contain both stitching and glass buffer strips.

Self-repairing composites for airplane components

NASA Astrophysics Data System (ADS)

Dry, Carolyn

2008-03-01

Durability and damage tolerance criteria drives the design of most composite structures. Those criteria could be altered by developing structure that repairs itself from impact damage. This is a technology for increasing damage tolerance for impact damage. Repaired damage would enable continued function and prevent further degradation to catastrophic failure in the case of an aircraft application. Further, repaired damage would enable applications to be utilized without reduction in performance due to impacts. Self repairing structures are designed to incorporate hollow fibers, which will release a repairing agent when the structure is impacted, so that the repairing agent will fill delaminations, voids and cracks in les than one minute, thus healing matrix voids. The intent is to modify the durability and damage tolerance criteria by incorporation of self-healing technologies to reduce overall weight: The structure will actually remain lighter than current conventional design procedures allow. Research objective(s) were: Prove that damage can be repaired to within 80-90% of original flexural strength in less than one minute, in laminates that are processed at 300-350F typical for aircraft composites. These were successfully met. The main focus was on testing of elements in compression after impact and a larger component in shear at Natural Process Design, Inc. Based on these results the advantages purposes are assessed. The results show potential; with self repairing composites, compressive strength is maintained sufficiently so that less material can be used as per durability and damage tolerance, yielding a lighter structure.

Progressive Fracture and Damage Tolerance of Composite Pressure Vessels

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Gotsis, Pascal K.; Minnetyan, Levon

1997-01-01

Structural performance (integrity, durability and damage tolerance) of fiber reinforced composite pressure vessels, designed for pressured shelters for planetary exploration, is investigated via computational simulation. An integrated computer code is utilized for the simulation of damage initiation, growth, and propagation under pressure. Aramid fibers are considered in a rubbery polymer matrix for the composite system. Effects of fiber orientation and fabrication defect/accidental damages are investigated with regard to the safety and durability of the shelter. Results show the viability of fiber reinforced pressure vessels as damage tolerant shelters for planetary colonization.

Damage Tolerant Design for Cold-Section Turbine Engine Disks

DTIC Science & Technology

1981-06-01

Ti-6Al-4V Disks ......... .. 59 28. FIOO 2nd-Stage Fan Disk Designs ........ ................ .. 61 29. Fan Disk Tangential Stress Profile... 61 30. Life-Limiting Features of Damage-Tolerant Disk .......... ... 62 31. Disk Life Limits .... ...................... 62 32. Life Test...Stress Rati• Model ..... .......... .. 113 61 . Thick-Section Center-Notched Specimen ....... ............. .. 116 62. Bolthole Specimen

Computational predictive methods for fracture and fatigue

NASA Technical Reports Server (NTRS)

Cordes, J.; Chang, A. T.; Nelson, N.; Kim, Y.

1994-01-01

The damage-tolerant design philosophy as used by aircraft industries enables aircraft components and aircraft structures to operate safely with minor damage, small cracks, and flaws. Maintenance and inspection procedures insure that damages developed during service remain below design values. When damage is found, repairs or design modifications are implemented and flight is resumed. Design and redesign guidelines, such as military specifications MIL-A-83444, have successfully reduced the incidence of damage and cracks. However, fatigue cracks continue to appear in aircraft well before the design life has expired. The F16 airplane, for instance, developed small cracks in the engine mount, wing support, bulk heads, the fuselage upper skin, the fuel shelf joints, and along the upper wings. Some cracks were found after 600 hours of the 8000 hour design service life and design modifications were required. Tests on the F16 plane showed that the design loading conditions were close to the predicted loading conditions. Improvements to analytic methods for predicting fatigue crack growth adjacent to holes, when multiple damage sites are present, and in corrosive environments would result in more cost-effective designs, fewer repairs, and fewer redesigns. The overall objective of the research described in this paper is to develop, verify, and extend the computational efficiency of analysis procedures necessary for damage tolerant design. This paper describes an elastic/plastic fracture method and an associated fatigue analysis method for damage tolerant design. Both methods are unique in that material parameters such as fracture toughness, R-curve data, and fatigue constants are not required. The methods are implemented with a general-purpose finite element package. Several proof-of-concept examples are given. With further development, the methods could be extended for analysis of multi-site damage, creep-fatigue, and corrosion fatigue problems.

Computational predictive methods for fracture and fatigue

NASA Astrophysics Data System (ADS)

Cordes, J.; Chang, A. T.; Nelson, N.; Kim, Y.

1994-09-01

The damage-tolerant design philosophy as used by aircraft industries enables aircraft components and aircraft structures to operate safely with minor damage, small cracks, and flaws. Maintenance and inspection procedures insure that damages developed during service remain below design values. When damage is found, repairs or design modifications are implemented and flight is resumed. Design and redesign guidelines, such as military specifications MIL-A-83444, have successfully reduced the incidence of damage and cracks. However, fatigue cracks continue to appear in aircraft well before the design life has expired. The F16 airplane, for instance, developed small cracks in the engine mount, wing support, bulk heads, the fuselage upper skin, the fuel shelf joints, and along the upper wings. Some cracks were found after 600 hours of the 8000 hour design service life and design modifications were required. Tests on the F16 plane showed that the design loading conditions were close to the predicted loading conditions. Improvements to analytic methods for predicting fatigue crack growth adjacent to holes, when multiple damage sites are present, and in corrosive environments would result in more cost-effective designs, fewer repairs, and fewer redesigns. The overall objective of the research described in this paper is to develop, verify, and extend the computational efficiency of analysis procedures necessary for damage tolerant design. This paper describes an elastic/plastic fracture method and an associated fatigue analysis method for damage tolerant design. Both methods are unique in that material parameters such as fracture toughness, R-curve data, and fatigue constants are not required. The methods are implemented with a general-purpose finite element package. Several proof-of-concept examples are given. With further development, the methods could be extended for analysis of multi-site damage, creep-fatigue, and corrosion fatigue problems.

Damage Tolerance Testing of a NASA TransHab Derivative Woven Inflatable Module

NASA Technical Reports Server (NTRS)

Edgecombe, John; delaFuente, Horacio; Valle, Gerard

2009-01-01

Current options for Lunar habitat architecture include inflatable habitats and airlocks. Inflatable structures can have mass and volume advantages over conventional structures. However, inflatable structures carry different inherent risks and are at a lower Technical Readiness Level (TRL) than more conventional metallic structures. One of the risks associated with inflatable structures is in understanding the tolerance to induced damage. The Damage Tolerance Test (DTT) is designed to study the structural integrity of an expandable structure. TransHab (Figure 1) was an experimental inflatable module developed at the NASA/Johnson Space Center in the 1990 s. The TransHab design was originally envisioned for use in Mars Transits but was also studied as a potential habitat for the International Space Station (ISS). The design of the TransHab module was based on a woven design using an Aramid fabric. Testing of this design demonstrated a high level of predictability and repeatability with analytical predictions of stresses and deflections. Based on JSC s experience with the design and analysis of woven inflatable structures, the Damage Tolerance Test article was designed and fabricated using a woven design. The DTT article was inflated to 45 psig, representing 25% of the ultimate burst pressure, and one of the one-inch wide longitudinal structural members was severed by initiating a Linear Shaped Charge (LSC). Strain gage measurements, at the interface between the expandable elements (straps) and the nonexpandable metallic elements for pre-selected longitudinal straps, were taken throughout pressurization of the module and strap separation. Strain gage measurements show no change in longitudinal strap loading at the bulkhead interface after strap separation indicating loads in the restraint layer were re-distributed local to the damaged area due to the effects of friction under high internal pressure loading. The test completed all primary objectives with better than expected results. This paper will discuss space inflatable structures, damage tolerance analysis, test results, and applicability to the Lunar architecture.

Electronic hybridisation implications for the damage-tolerance of thin film metallic glasses

PubMed Central

Schnabel, Volker; Jaya, B. Nagamani; Köhler, Mathias; Music, Denis; Kirchlechner, Christoph; Dehm, Gerhard; Raabe, Dierk; Schneider, Jochen M.

2016-01-01

A paramount challenge in materials science is to design damage-tolerant glasses. Poisson’s ratio is commonly used as a criterion to gauge the brittle-ductile transition in glasses. However, our data, as well as results in the literature, are in conflict with the concept of Poisson’s ratio serving as a universal parameter for fracture energy. Here, we identify the electronic structure fingerprint associated with damage tolerance in thin film metallic glasses. Our correlative theoretical and experimental data reveal that the fraction of bonds stemming from hybridised states compared to the overall bonding can be associated with damage tolerance in thin film metallic glasses. PMID:27819318

Electronic hybridisation implications for the damage-tolerance of thin film metallic glasses.

PubMed

Schnabel, Volker; Jaya, B Nagamani; Köhler, Mathias; Music, Denis; Kirchlechner, Christoph; Dehm, Gerhard; Raabe, Dierk; Schneider, Jochen M

2016-11-07

A paramount challenge in materials science is to design damage-tolerant glasses. Poisson's ratio is commonly used as a criterion to gauge the brittle-ductile transition in glasses. However, our data, as well as results in the literature, are in conflict with the concept of Poisson's ratio serving as a universal parameter for fracture energy. Here, we identify the electronic structure fingerprint associated with damage tolerance in thin film metallic glasses. Our correlative theoretical and experimental data reveal that the fraction of bonds stemming from hybridised states compared to the overall bonding can be associated with damage tolerance in thin film metallic glasses.

Recent Advances in Durability and Damage Tolerance Methodology at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Ransom, J. B.; Glaessgen, E. H.; Raju, I. S.; Harris, C. E.

2007-01-01

Durability and damage tolerance (D&DT) issues are critical to the development of lighter, safer and more efficient aerospace vehicles. Durability is largely an economic life-cycle design consideration whereas damage tolerance directly addresses the structural airworthiness (safety) of the vehicle. Both D&DT methodologies must address the deleterious effects of changes in material properties and the initiation and growth of damage that may occur during the vehicle s service lifetime. The result of unanticipated D&DT response is often manifested in the form of catastrophic and potentially fatal accidents. As such, durability and damage tolerance requirements must be rigorously addressed for commercial transport aircraft and NASA spacecraft systems. This paper presents an overview of the recent and planned future research in durability and damage tolerance analytical and experimental methods for both metallic and composite aerospace structures at NASA Langley Research Center (LaRC).

Demonstrating damage tolerance of composite airframes

NASA Technical Reports Server (NTRS)

Poe, Clarence C., Jr.

1993-01-01

Commercial transport aircraft operating in the United States are certified by the Federal Aviation Authority to be damage tolerant. On 28 April 1988, Aloha Airlines Flight 243, a Boeing 727-200 airplane, suffered an explosive decompression of the fuselage but landed safely. This event provides very strong justification for the damage tolerant design criteria. The likely cause of the explosive decompression was the linkup of numerous small fatigue cracks that initiated at adjacent fastener holes in the lap splice joint at the side of the body. Actually, the design should have limited the damage size to less than two frame spacings (about 40 inches), but this type of 'multi-site damage' was not originally taken into account. This cracking pattern developed only in the high-time airplanes (many flights). After discovery in the fleet, a stringent inspection program using eddy current techniques was inaugurated to discover these cracks before they linked up. Because of concerns about safety and the maintenance burden, the lap-splice joints of these high-time airplanes are being modified to remove cracks and prevent new cracking; newer designs account for 'multi-site damage'.

Design of Composite Structures for Reliability and Damage Tolerance

NASA Technical Reports Server (NTRS)

Rais-Rohani, Masoud

1999-01-01

A summary of research conducted during the first year is presented. The research objectives were sought by conducting two tasks: (1) investigation of probabilistic design techniques for reliability-based design of composite sandwich panels, and (2) examination of strain energy density failure criterion in conjunction with response surface methodology for global-local design of damage tolerant helicopter fuselage structures. This report primarily discusses the efforts surrounding the first task and provides a discussion of some preliminary work involving the second task.

Advanced information processing system

NASA Technical Reports Server (NTRS)

Lala, J. H.

1984-01-01

Design and performance details of the advanced information processing system (AIPS) for fault and damage tolerant data processing on aircraft and spacecraft are presented. AIPS comprises several computers distributed throughout the vehicle and linked by a damage tolerant data bus. Most I/O functions are available to all the computers, which run in a TDMA mode. Each computer performs separate specific tasks in normal operation and assumes other tasks in degraded modes. Redundant software assures that all fault monitoring, logging and reporting are automated, together with control functions. Redundant duplex links and damage-spread limitation provide the fault tolerance. Details of an advanced design of a laboratory-scale proof-of-concept system are described, including functional operations.

Damage tolerant design using collapse techniques

NASA Technical Reports Server (NTRS)

Haftka, R. T.

1982-01-01

A new approach to the design of structures for improved global damage tolerance is presented. In its undamaged condition the structure is designed subject to strength, displacement and buckling constraints. In the damaged condition the only constraint is that the structure will not collapse. The collapse load calculation is formulated as a maximization problem and solved by an interior extended penalty function. The design for minimum weight subject to constraints on the undamaged structure and a specified level of the collapse load is a minimization problem which is also solved by a penalty function formulation. Thus the overall problem is of a nested or multilevel optimization. Examples are presented to demonstrate the difference between the present and more traditional approaches.

Damage tolerance of candidate thermoset composites for use on single stage to orbit vehicles

NASA Technical Reports Server (NTRS)

Nettles, A. T.; Lance, D.; Hodge, A.

1994-01-01

Four fiber/resin systems were compared for resistance to damage and damage tolerance. One toughened epoxy and three toughened bismaleimide (BMI) resins were used, all with IM7 carbon fiber reinforcement. A statistical design of experiments technique was used to evaluate the effects of impact energy, specimen thickness, and impactor diameter on the damage area, as computed by C-scans, and residual compression-after-impact (CAI) strength. Results showed that two of the BMI systems sustained relatively large damage zones yet had an excellent retention of CAI strength.

Re-Tooling the Agency's Engineering Predictive Practices for Durability and Damage Tolerance

NASA Technical Reports Server (NTRS)

Piascik, Robert S.; Knight, Norman F., Jr.

2017-01-01

Over the past decade, the Agency has placed less emphasis on testing and has increasingly relied on computational methods to assess durability and damage tolerance (D&DT) behavior when evaluating design margins for fracture-critical components. With increased emphasis on computational D&DT methods as the standard practice, it is paramount that capabilities of these methods are understood, the methods are used within their technical limits, and validation by well-designed tests confirms understanding. The D&DT performance of a component is highly dependent on parameters in the neighborhood of the damage. This report discusses D&DT method vulnerabilities.

FAA/NASA International Symposium on Advanced Structural Integrity Methods for Airframe Durability and Damage Tolerance

NASA Technical Reports Server (NTRS)

Harris, Charles E. (Editor)

1994-01-01

International technical experts in durability and damage tolerance of metallic airframe structures were assembled to present and discuss recent research findings and the development of advanced design and analysis methods, structural concepts, and advanced materials. The symposium focused on the dissemination of new knowledge and the peer-review of progress on the development of advanced methodologies. Papers were presented on: structural concepts for enhanced durability, damage tolerance, and maintainability; new metallic alloys and processing technology; fatigue crack initiation and small crack effects; fatigue crack growth models; fracture mechanics failure, criteria for ductile materials; structural mechanics methodology for residual strength and life prediction; development of flight load spectra for design and testing; and advanced approaches to resist corrosion and environmentally assisted fatigue.

FAA/NASA International Symposium on Advanced Structural Integrity Methods for Airframe Durability and Damage Tolerance, part 2

NASA Technical Reports Server (NTRS)

Harris, Charles E. (Editor)

1994-01-01

The international technical experts in the areas of durability and damage tolerance of metallic airframe structures were assembled to present and discuss recent research findings and the development of advanced design and analysis methods, structural concepts, and advanced materials. The principal focus of the symposium was on the dissemination of new knowledge and the peer-review of progress on the development of advanced methodologies. Papers were presented on the following topics: structural concepts for enhanced durability, damage tolerance, and maintainability; new metallic alloys and processing technology; fatigue crack initiation and small crack effects; fatigue crack growth models; fracture mechanics failure criteria for ductile materials; structural mechanics methodology for residual strength and life prediction; development of flight load spectra for design and testing; and corrosion resistance.

On the monitoring and implications of growing damages caused by manufacturing defects in composite structures

NASA Astrophysics Data System (ADS)

Schagerl, M.; Viechtbauer, C.; Hörrmann, S.

2015-07-01

Damage tolerance is a classical safety concept for the design of aircraft structures. Basically, this approach considers possible damages in the structure, predicts the damage growth under applied loading conditions and predicts the following decrease of the structural strength. As a fundamental result the damage tolerance approach yields the maximum inspection interval, which is the time a damage grows from a detectable to a critical level. The above formulation of the damage tolerance safety concept targets on metallic structures where the damage is typically a simple fatigue crack. Fiber-reinforced polymers show a much more complex damage behavior, such as delaminationsin laminated composites. Moreover, progressive damage in composites is often initiated by manufacturing defects. The complex manufacturing processes for composite structures almost certainly yield parts with defects, e.g. pores in the matrix or undulations of fibers. From such defects growing damages may start after a certain time of operation. The demand to simplify or even avoid the inspection of composite structures has therefore led to a comeback of the traditional safe-life safety concept. The aim of the so-called safe-life flaw tolerance concept is a structure that is capable of carrying the static loads during operation, despite significant damages and after a representative fatigue load spectrum. A structure with this property does not need to be inspected, respectively monitored at all during its service life. However, its load carrying capability is thereby not fully utilized. This article presents the possible refinement of the state-of-the-art safe-life flaw tolerance concept for composite structures towards a damage tolerance approach considering also the influence of manufacturing defects on damage initiation and growth. Based on fundamental physical relations and experimental observations the challenges when developing damage growth and residual strength curves are discussed.

Structural Design Methodology Based on Concepts of Uncertainty

NASA Technical Reports Server (NTRS)

Lin, K. Y.; Du, Jiaji; Rusk, David

2000-01-01

In this report, an approach to damage-tolerant aircraft structural design is proposed based on the concept of an equivalent "Level of Safety" that incorporates past service experience in the design of new structures. The discrete "Level of Safety" for a single inspection event is defined as the compliment of the probability that a single flaw size larger than the critical flaw size for residual strength of the structure exists, and that the flaw will not be detected. The cumulative "Level of Safety" for the entire structure is the product of the discrete "Level of Safety" values for each flaw of each damage type present at each location in the structure. Based on the definition of "Level of Safety", a design procedure was identified and demonstrated on a composite sandwich panel for various damage types, with results showing the sensitivity of the structural sizing parameters to the relative safety of the design. The "Level of Safety" approach has broad potential application to damage-tolerant aircraft structural design with uncertainty.

Aerothermal performance and damage tolerance of a Rene 41 metallic standoff thermal protection system at Mach 6.7

NASA Technical Reports Server (NTRS)

Avery, D. E.

1984-01-01

A flight-weight, metallic thermal protection system (TPS) model applicable to Earth-entry and hypersonic-cruise vehicles was subjected to multiple cycles of both radiant and aerothermal heating in order to evaluate its aerothermal performance, structural integrity, and damage tolerance. The TPS was designed for a maximum operating temperature of 2060 R and featured a shingled, corrugation-stiffened corrugated-skin heat shield of Rene 41, a nickel-base alloy. The model was subjected to 10 radiant heating tests and to 3 radiant preheat/aerothermal tests. Under radiant-heating conditions with a maximum surface temperature of 2050 R, the TPS performed as designed and limited the primary structure away from the support ribs to temperatures below 780 R. During the first attempt at aerothermal exposure, a failure in the panel-holder test fixture severely damaged the model. However, two radiant preheat/aerothermal tests were made with the damaged model to test its damage tolerance. During these tests, the damaged area did not enlarge; however, the rapidly increasing structural temperature measuring during these tests indicates that had the damaged area been exposed to aerodynamic heating for the entire trajectory, an aluminum burn-through would have occurred.

Development of pressure containment and damage tolerance technology for composite fuselage structures in large transport aircraft

NASA Technical Reports Server (NTRS)

Smith, P. J.; Thomson, L. W.; Wilson, R. D.

1986-01-01

NASA sponsored composites research and development programs were set in place to develop the critical engineering technologies in large transport aircraft structures. This NASA-Boeing program focused on the critical issues of damage tolerance and pressure containment generic to the fuselage structure of large pressurized aircraft. Skin-stringer and honeycomb sandwich composite fuselage shell designs were evaluated to resolve these issues. Analyses were developed to model the structural response of the fuselage shell designs, and a development test program evaluated the selected design configurations to appropriate load conditions.

Impact Behavior of Composite Fan Blade Leading Edge Subcomponent with Thermoplastic Polyurethane Interleave

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Roberts, Gary D.; Kohlman, Lee W.; Heimann, Paula J.; Pereira, J. Michael; Ruggeri, Charles R.; Martin, Richard E.; McCorkle, Linda S.

2015-01-01

Impact damage tolerance and damage resistance is a critical metric for application of polymer matrix composites where failure caused by impact damage could compromise structural performance and safety. As a result, several materials and/or design approaches to improve impact damage tolerance have been investigated over the past several decades. Many composite toughening methodologies impart a trade-off between increased fracture toughness and compromised in-plane strength and modulus. In large part, mechanical tests to evaluate composite damage tolerance include static methods such as Mode I, Mode II, and mixed mode failures. However, ballistic impact damage resistance does not always correlate with static properties. The intent of this paper is to evaluate the influence of a thermoplastic polyurethane veil interleave on the static and dynamic performance of composite test articles. Static coupon tests included tension, compression, double cantilever beam, and end notch flexure. Measurement of the resistance to ballistic impact damage were made to evaluate the composites response to high speed impact. The interlayer material showed a decrease of in-plane performance with only a moderate improvement to Mode I and Mode II fracture toughness. However, significant benefit to impact damage tolerance was observed through ballistic tests.

Application of damage tolerance methodology in certification of the Piaggio P-180 Avanti

NASA Technical Reports Server (NTRS)

Johnson, Jerry

1992-01-01

The Piaggio P-180 Avanti, a twin pusher-prop engine nine-passenger business aircraft was certified in 1990, to the requirements of FAR Part 23 and Associated Special Conditions for Composite Structure. Certification included the application of a damage tolerant methodology to the design of the composite forward wing and empennage (vertical fin, horizontal stabilizer, tailcone, and rudder) structure. This methodology included an extensive analytical evaluation coupled with sub-component and full-scale testing of the structure. The work from the Damage Tolerance Analysis Assessment was incorporated into the full-scale testing. Damage representing hazards such as dropped tools, ground equipment, handling, and runway debris, was applied to the test articles. Additional substantiation included allowing manufacturing discrepancies to exist unrepaired on the full-scale articles and simulated bondline failures in critical elements. The importance of full-scale testing in the critical environmental conditions and the application of critical damage are addressed. The implication of damage tolerance on static and fatigue testing is discussed. Good correlation between finite element solutions and experimental test data was observed.

USAF Damage Tolerant Design Handbook: Guidelines for the analysis and Design of Damage Tolerant Aircraft Structures. Revision A

DTIC Science & Technology

1979-03-01

Fatigue Crack Growth (Schr~matic) 5.12 Sustained Load Crack Growth Rate Data for 7075-f651,7079- T651, and 2024 - T351 Aluminum Plate (Ref...Block Programming and Block Size on Crack Growth Life (All histories Have Same Cycle Content) Alloy : 2024 -T3 Aluminum (Ref. 38) 5.21 Yield Zone Due to...4340 Steel in Humid Air," ASM Trans 58, 46-53 (1965). 20. Meyn, D.A., "Frequency and Amplitude Effects on Corrosion Fatigue Cracks in a Titanium Alloy

USAF Damage Tolerant Design Handbook: Guidelines for the Analysis and Design of Damage Tolerant Aircraft Structures. Revision B

DTIC Science & Technology

1984-05-01

Effect of Block Programming and Block Size on Crack Growth Life (All Histories Have Same Cycle Content) Alloy : 2024 -T3 Aluminum (Reference 27...1 I 6 o T 1 >0 100 Crack Growth Life for l-in. Crack Growth 1000 Figure 5.1.10, Effect of Humidity on Fatigue Crack Propagation...Growth Life (All Histories Have Same Cycle Content) Alloy : 2024 -T3 Aluminum (Reference 27). 5.2.6 Yield Zone Due to Overload (r T), Current Crack

Advanced design for lightweight structures: Review and prospects

NASA Astrophysics Data System (ADS)

Braga, Daniel F. O.; Tavares, S. M. O.; da Silva, Lucas F. M.; Moreira, P. M. G. P.; de Castro, Paulo M. S. T.

2014-08-01

Current demand for fuel efficient aircraft has been pushing the aeronautical sector to develop ever more lightweight designs while keeping safe operation and required structural strength. Along with light-weighting, new structural design concepts have also been established in order to maintain the aircraft in service for longer periods of time, with high reliability levels. All these innovations and requirements have led to deeply optimized aeronautical structures contributing to more sustainable air transport. This article reviews the major design philosophies which have been employed in aircraft structures, including safe-life, fail-safe and damage tolerance taking into account their impact on the structural design. A brief historical review is performed in order to analyse what led to the development of each philosophy. Material properties are related to each of the design philosophies. Damage tolerant design has emerged as the main structural design philosophy in aeronautics, requiring deep knowledge on materials fatigue and corrosion strength, as well as potential failure modes and non-destructive inspection techniques, particularly minimum detectable defect and scan times. A discussion on the implementation of structural health monitoring and self-healing structures within the current panorama of structures designed according to the damage tolerant philosophy is presented. This discussion is aided by a review of research on these two subjects. These two concepts show potential for further improving safety and durability of aircraft structures.

Analysis and Support Initiative for Structural Technology (ASIST) Delivery Order 0016: USAF Damage Tolerant Design Handbook: Guidelines For the Analysis and Design of Damage Tolerant Aircraft Structures

DTIC Science & Technology

2002-11-01

hand crack tip (point B) and with angular displacement from the x-axis. As the stress element is moved closer to the crack tip, the stresses are...on the methods of obtaining the required relationships are presented by Broek [1974]. The necessary relationships for Vσ, VF, Vp and Vst ...4.5.18. Geometrical and Displacement Parameters Relative to the Crack Tip 4.5.21 Vσ + VF + Vp = Vst (4.5.15) substituting the expressions 4.5.6

Optimal Design and Damage Tolerance Verification of an Isogrid Structure for Helicopter Application

NASA Technical Reports Server (NTRS)

Baker, Donald J.; Fudge, Jack; Ambur, Damodar R.; Kassapoglou, Christos

2003-01-01

A composite isogrid panel design for application to a rotorcraft fuselage is presented. An optimum panel design for the lower fuselage of the rotorcraft that is subjected to combined in-plane compression and shear loads was generated using a design tool that utilizes a smeared-stiffener theory in conjunction with a genetic algorithm. A design feature was introduced along the edges of the panel that facilitates introduction of loads into the isogrid panel without producing undesirable local bending gradients. A low-cost manufacturing method for the isogrid panel that incorporates these design details is also presented. Axial compression tests were conducted on the undamaged and low-speed impact damaged panels to demonstrate the damage tolerance of this isogrid panel. A combined loading test fixture was designed and utilized that allowed simultaneous application of compression and shear loads to the test specimen. Results from finite element analyses are presented for the isogrid panel designs and these results are compared with experimental results. This study illustrates the isogrid concept to be a viable candidate for application to the helicopter lower fuselage structure.

Recent progress in NASA Langley Research Center textile reinforced composites program

NASA Technical Reports Server (NTRS)

Dexter, H. Benson; Harris, Charles E.; Johnston, Norman J.

1992-01-01

Research was conducted to explore the benefits of textile reinforced composites for transport aircraft primary structures. The objective is to develop and demonstrate the potential of affordable textile reinforced composite materials to meet design properties and damage tolerance requirements of advanced aircraft structural concepts. Some program elements include development of textile preforms, processing science, mechanics of materials, experimental characterization of materials, and development and evaluation of textile reinforced composite structural elements and subcomponents. Textile 3-D weaving, 3-D braiding, and knitting and/or stitching are being compared with conventional laminated tape processes for improved damage tolerance. Through-the-thickness reinforcements offer significant damage tolerance improvements. However, these gains must be weighted against potential loss in in-plane properties such as strength and stiffness. Analytical trade studies are underway to establish design guidelines for the application of textile material forms to meet specific loading requirements. Fabrication and testing of large structural parts are required to establish the potential of textile reinforced composite materials.

Design Manual for Impact Damage Tolerant Aircraft Structure

DTIC Science & Technology

1981-10-01

controlled AAA guns having a very high rate of fire, is a significant threat. The final type of non -exploding military projectile-missile warhead fragments...8217~ AGARD-AG-238 NORTH 4TLANTIC TR!EATY ORGANIZATION ADVISORY GROUP FOR AERGSPACE RESEARCH AND DEVELOPMENT (ORGANISATION DU TRAITE DE L’ATLANTIQUE NORD...within the Working Group on Impact Damage Tolerance of Structures and also at the Specialists’ Meeting held in Ankara in September 1975 (see AGARD

Optimization of Aerospace Structure Subject to Damage Tolerance Criteria

NASA Technical Reports Server (NTRS)

Akgun, Mehmet A.

1999-01-01

The objective of this cooperative agreement was to seek computationally efficient ways to optimize aerospace structures subject to damage tolerance criteria. Optimization was to involve sizing as well as topology optimization. The work was done in collaboration with Steve Scotti, Chauncey Wu and Joanne Walsh at the NASA Langley Research Center. Computation of constraint sensitivity is normally the most time-consuming step of an optimization procedure. The cooperative work first focused on this issue and implemented the adjoint method of sensitivity computation in an optimization code (runstream) written in Engineering Analysis Language (EAL). The method was implemented both for bar and plate elements including buckling sensitivity for the latter. Lumping of constraints was investigated as a means to reduce the computational cost. Adjoint sensitivity computation was developed and implemented for lumped stress and buckling constraints. Cost of the direct method and the adjoint method was compared for various structures with and without lumping. The results were reported in two papers. It is desirable to optimize topology of an aerospace structure subject to a large number of damage scenarios so that a damage tolerant structure is obtained. Including damage scenarios in the design procedure is critical in order to avoid large mass penalties at later stages. A common method for topology optimization is that of compliance minimization which has not been used for damage tolerant design. In the present work, topology optimization is treated as a conventional problem aiming to minimize the weight subject to stress constraints. Multiple damage configurations (scenarios) are considered. Each configuration has its own structural stiffness matrix and, normally, requires factoring of the matrix and solution of the system of equations. Damage that is expected to be tolerated is local and represents a small change in the stiffness matrix compared to the baseline (undamaged) structure. The exact solution to a slightly modified set of equations can be obtained from the baseline solution economically without actually solving the modified system. Sherrnan-Morrison-Woodbury (SMW) formulas are matrix update formulas that allow this. SMW formulas were therefore used here to compute adjoint displacements for sensitivity computation and structural displacements in damaged configurations.

Damage Progression in Bolted Composites

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C.; Gotsis, Pascal K.

1998-01-01

Structural durability, damage tolerance, and progressive fracture characteristics of bolted graphite/epoxy composite laminates are evaluated via computational simulation. Constituent material properties and stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for bolted composites. Single and double bolted composite specimens with various widths and bolt spacings are evaluated. The effect of bolt spacing is investigated with regard to the structural durability of a bolted joint. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulations. Results show the damage progression sequence and structural fracture resistance during different degradation stages. A procedure is outlined for the use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of experimental results with insight for design decisions.

Damage Progression in Bolted Composites

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos; Gotsis, Pascal K.

1998-01-01

Structural durability,damage tolerance,and progressive fracture characteristics of bolted graphite/epoxy composite laminates are evaluated via computational simulation. Constituent material properties and stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for bolted composites. Single and double bolted composite specimens with various widths and bolt spacings are evaluated. The effect of bolt spacing is investigated with regard to the structural durability of a bolted joint. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulations. Results show the damage progression sequence and structural fracture resistance during different degradation stages. A procedure is outlined for the use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of experimental results with insight for design decisions.

Design and evaluation of a foam-filled hat-stiffened panel concept for aircraft primary structural applications

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.

1995-01-01

A structurally efficient hat-stiffened panel concept that utilizes a structural foam as stiffener core has been designed for aircraft primary structural applications. This stiffener concept utilizes a manufacturing process that can be adapted readily to grid-stiffened structural configurations which possess inherent damage tolerance characteristics due to their multiplicity of load paths. The foam-filled hat-stiffener concept in a prismatically stiffened panel configuration is more efficient than most other stiffened panel configurations in a load range that is typical for both fuselage and wing structures. The prismatically stiffened panel concept investigated here has been designed using AS4/3502 preimpregnated tape and Rohacell foam core and evaluated for its buckling and postbuckling behavior with and without low-speed impact damage. The results from single-stiffener and multi-stiffener specimens suggest that this structural concept responds to loading as anticipated and has good damage tolerance characteristics.

Meta-analysis of attitudes toward damage-causing mammalian wildlife.

PubMed

Kansky, Ruth; Kidd, Martin; Knight, Andrew T

2014-08-01

Many populations of threatened mammals persist outside formally protected areas, and their survival depends on the willingness of communities to coexist with them. An understanding of the attitudes, and specifically the tolerance, of individuals and communities and the factors that determine these is therefore fundamental to designing strategies to alleviate human-wildlife conflict. We conducted a meta-analysis to identify factors that affected attitudes toward 4 groups of terrestrial mammals. Elephants (65%) elicited the most positive attitudes, followed by primates (55%), ungulates (53%), and carnivores (44%). Urban residents presented the most positive attitudes (80%), followed by commercial farmers (51%) and communal farmers (26%). A tolerance to damage index showed that human tolerance of ungulates and primates was proportional to the probability of experiencing damage while elephants elicited tolerance levels higher than anticipated and carnivores elicited tolerance levels lower than anticipated. Contrary to conventional wisdom, experiencing damage was not always the dominant factor determining attitudes. Communal farmers had a lower probability of being positive toward carnivores irrespective of probability of experiencing damage, while commercial farmers and urban residents were more likely to be positive toward carnivores irrespective of damage. Urban residents were more likely to be positive toward ungulates, elephants, and primates when probability of damage was low, but not when it was high. Commercial and communal farmers had a higher probability of being positive toward ungulates, primates, and elephants irrespective of probability of experiencing damage. Taxonomic bias may therefore be important. Identifying the distinct factors explaining these attitudes and the specific contexts in which they operate, inclusive of the species causing damage, will be essential for prioritizing conservation investments. © 2014 The Authors. Conservation Biology published by Wiley Periodicals, Inc., on behalf of the Society for Conservation Biology.

Damage Tolerance of Pre-Stressed Composite Panels Under Impact Loads

NASA Astrophysics Data System (ADS)

Johnson, Alastair F.; Toso-Pentecôte, Nathalie; Schueler, Dominik

2014-02-01

An experimental test campaign studied the structural integrity of carbon fibre/epoxy panels preloaded in tension or compression then subjected to gas gun impact tests causing significant damage. The test programme used representative composite aircraft fuselage panels composed of aerospace carbon fibre toughened epoxy prepreg laminates. Preload levels in tension were representative of design limit loads for fuselage panels of this size, and maximum compression preloads were in the post-buckle region. Two main impact scenarios were considered: notch damage from a 12 mm steel cube projectile, at velocities in the range 93-136 m/s; blunt impact damage from 25 mm diameter glass balls, at velocities 64-86 m/s. The combined influence of preload and impact damage on panel residual strengths was measured and results analysed in the context of damage tolerance requirements for composite aircraft panels. The tests showed structural integrity well above design limit loads for composite panels preloaded in tension and compression with visible notch impact damage from hard body impact tests. However, blunt impact tests on buckled compression loaded panels caused large delamination damage regions which lowered plate bending stiffness and reduced significantly compression strengths in buckling.

Tensile strength of composite sheets with unidirectional stringers and crack-like damage

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1984-01-01

The damage tolerance characteristics of metal tension panels with riveted and bonded stringers are well known. The stringers arrest unstable cracks and retard propagation of fatigue cracks. Residual strengths and fatigue lives are considerably greater than those of unstiffened or integrally stiffened sheets. The damage tolerance of composite sheets with bonded composite stringers loaded in tension was determined. Cracks in composites do not readily propagate in fatigue, at least not through fibers. Moreover, the residual strength of notched composites is sometimes even increased by fatigue loading. Therefore, the residual strength aspect of damage tolerance, and not fatigue crack propagation, was investigated. About 50 graphite/epoxy composite panels were made with two sheet layups and several stringer configurations. Crack-like slots were cut in the middle of the panels to simulate damage. The panels were instrumented and monotonically loaded in tension to failure. The tests indicate that the composite panels have considerable damage tolerance, much like metal panels. The stringers arrested cracks that ran from the crack-like slots, and the residual strengths were considerably greater than those of unstiffened composite sheets. A stress intensity factor analysis was developed to predict the failing strains of the stiffened panels. Using the analysis, a single design curve was produced for composite sheets with bonded stringers of any configuration.

NASA workshop on impact damage to composites

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1991-01-01

A compilation of slides presented at the NASA Workshop on Impact Damage to Composites held on March 19 and 20, 1991, at the Langley Research Center, Hampton, Virginia is given. The objective of the workshop was to review technology for evaluating impact damage tolerance of composite structures and identify deficiencies. Research, development, design methods, and design criteria were addressed. Actions to eliminate technology deficiencies were developed. A list of those actions and a list of attendees are also included.

Rotational 3D printing of damage-tolerant composites with programmable mechanics

PubMed Central

Raney, Jordan R.; Compton, Brett G.; Ober, Thomas J.; Shea, Kristina; Lewis, Jennifer A.

2018-01-01

Natural composites exhibit exceptional mechanical performance that often arises from complex fiber arrangements within continuous matrices. Inspired by these natural systems, we developed a rotational 3D printing method that enables spatially controlled orientation of short fibers in polymer matrices solely by varying the nozzle rotation speed relative to the printing speed. Using this method, we fabricated carbon fiber–epoxy composites composed of volume elements (voxels) with programmably defined fiber arrangements, including adjacent regions with orthogonally and helically oriented fibers that lead to nonuniform strain and failure as well as those with purely helical fiber orientations akin to natural composites that exhibit enhanced damage tolerance. Our approach broadens the design, microstructural complexity, and performance space for fiber-reinforced composites through site-specific optimization of their fiber orientation, strain, failure, and damage tolerance. PMID:29348206

Probabilistic modeling of condition-based maintenance strategies and quantification of its benefits for airliners

NASA Astrophysics Data System (ADS)

Pattabhiraman, Sriram

Airplane fuselage structures are designed with the concept of damage tolerance, wherein small damage are allowed to remain on the airplane, and damage that otherwise affect the safety of the structure are repaired. The damage critical to the safety of the fuselage are repaired by scheduling maintenance at pre-determined intervals. Scheduling maintenance is an interesting trade-off between damage tolerance and cost. Tolerance of larger damage would require less frequent maintenance and hence, a lower cost, to maintain a certain level of reliability. Alternatively, condition-based maintenance techniques have been developed using on-board sensors, which track damage continuously and request maintenance only when the damage size crosses a particular threshold. This effects a tolerance of larger damage than scheduled maintenance, leading to savings in cost. This work quantifies the savings of condition-based maintenance over scheduled maintenance. The work also quantifies converting the cost savings into weight savings. Structural health monitoring will need time to be able to establish itself as a stand-alone system for maintenance, due to concerns on its diagnosis accuracy and reliability. This work also investigates the effect of synchronizing structural health monitoring system with scheduled maintenance. This work uses on-board SHM equipment skip structural airframe maintenance (a subsect of scheduled maintenance), whenever deemed unnecessary while maintain a desired level of safety of structure. The work will also predict the necessary maintenance for a fleet of airplanes, based on the current damage status of the airplanes. The work also analyses the possibility of false alarm, wherein maintenance is being requested with no critical damage on the airplane. The work use SHM as a tool to identify lemons in a fleet of airplanes. Lemons are those airplanes that would warrant more maintenance trips than the average behavior of the fleet.

Ninth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design, volume 1

NASA Technical Reports Server (NTRS)

Soderquist, Joseph R. (Compiler); Neri, Lawrence M. (Compiler); Bohon, Herman L. (Compiler)

1992-01-01

This publication contains the proceedings of the Ninth DOD/NASA/FAA conference on Fibrous Composites in structural Design. Presentations were made in the following areas of composite structural design: perspectives in composites; design methodology; design applications; design criteria; supporting technology; damage tolerance; and manufacturing.

Recent progress in NASA Langley textile reinforced composites program

NASA Technical Reports Server (NTRS)

Dexter, H. Benson; Harris, Charles E.; Johnston, Norman J.

1992-01-01

The NASA LaRC is conducting and sponsoring research to explore the benefits of textile reinforced composites for civil transport aircraft primary structures. The objective of this program is to develop and demonstrate the potential of affordable textile reinforced composite materials to meet design properties and damage tolerance requirements of advanced aircraft structural concepts. In addition to in-house research, the program was recently expanded to include major participation by the aircraft industry and aerospace textile companies. The major program elements include development of textile preforms, processing science, mechanics of materials, experimental characterization of materials, and development and evaluation of textile reinforced composite structural elements and subcomponents. The NASA Langley in-house focus is as follows: development of a science-based understanding of resin transfer molding (RTM), development of powder-coated towpreg processes, analysis methodology, and development of a performance database on textile reinforced composites. The focus of the textile industry participation is on development of multidirectional, damage-tolerant preforms, and the aircraft industry participation is in the areas of design, fabrication and testing of textile reinforced composite structural elements and subcomponents. Textile processes such as 3D weaving, 2D and 3D braiding, and knitting/stitching are being compared with conventional laminated tape processes for improved damage tolerance. Through-the-thickness reinforcements offer significant damage tolerance improvements. However, these gains must be weighed against potential loss in in-plane properties such as strength and stiffness. Analytical trade studies are underway to establish design guidelines for the application of textile material forms to meet specific loading requirements. Fabrication and testing of large structural components are required to establish the full potential of textile reinforced composite materials.

Contamination avoidance devices for poppettype shutoff valves

NASA Technical Reports Server (NTRS)

Endicott, D. L.

1973-01-01

The determination of the cycle life is reported of the scal closure of a typical poppet-type shutoff valve in an uncontaminated GH2 environment and then compared this component performance with simulated operation with GN2 and LN2 containing controlled amounts of AL2O3 contaminant particles. The original valve design was tested for contamination damage tolerance characteristics under full-flow and cyclic-operating conditions, redesigned to improve the damage tolerance to contaminants, and then retested. The redesigned valve was found to have acceptable tolerance characteristics under all full-flow conditions and cyclic operation with small (25-75 microns) particulate contamination. The tolerance characteristics of the valve under cyclic conditions with large (75-250 microns) particulate contamination was improved but was not found to be completely satisfactory.

Advanced Information Processing System - Fault detection and error handling

NASA Technical Reports Server (NTRS)

Lala, J. H.

1985-01-01

The Advanced Information Processing System (AIPS) is designed to provide a fault tolerant and damage tolerant data processing architecture for a broad range of aerospace vehicles, including tactical and transport aircraft, and manned and autonomous spacecraft. A proof-of-concept (POC) system is now in the detailed design and fabrication phase. This paper gives an overview of a preliminary fault detection and error handling philosophy in AIPS.

Fatigue Crack Growth Database for Damage Tolerance Analysis

NASA Technical Reports Server (NTRS)

Forman, R. G.; Shivakumar, V.; Cardinal, J. W.; Williams, L. C.; McKeighan, P. C.

2005-01-01

The objective of this project was to begin the process of developing a fatigue crack growth database (FCGD) of metallic materials for use in damage tolerance analysis of aircraft structure. For this initial effort, crack growth rate data in the NASGRO (Registered trademark) database, the United States Air Force Damage Tolerant Design Handbook, and other publicly available sources were examined and used to develop a database that characterizes crack growth behavior for specific applications (materials). The focus of this effort was on materials for general commercial aircraft applications, including large transport airplanes, small transport commuter airplanes, general aviation airplanes, and rotorcraft. The end products of this project are the FCGD software and this report. The specific goal of this effort was to present fatigue crack growth data in three usable formats: (1) NASGRO equation parameters, (2) Walker equation parameters, and (3) tabular data points. The development of this FCGD will begin the process of developing a consistent set of standard fatigue crack growth material properties. It is envisioned that the end product of the process will be a general repository for credible and well-documented fracture properties that may be used as a default standard in damage tolerance analyses.

Damage-tolerant nanotwinned metals with nanovoids under radiation environments

PubMed Central

Chen, Y.; Yu, K Y.; Liu, Y.; Shao, S.; Wang, H.; Kirk, M. A.; Wang, J.; Zhang, X.

2015-01-01

Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from high density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials. PMID:25906997

Damage-tolerant nanotwinned metals with nanovoids under radiation environments.

PubMed

Chen, Y; Yu, K Y; Liu, Y; Shao, S; Wang, H; Kirk, M A; Wang, J; Zhang, X

2015-04-24

Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from high density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials.

Damage-tolerant nanotwinned metals with nanovoids under radiation environments

DOE PAGES

Chen, Y.; Yu, K. Y.; Liu, Y.; ...

2015-04-24

Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation induces significant damage in the form of dislocation loops and voids in irradiated materials, and continuous radiation often leads to void growth and subsequent void swelling in metals with low stacking fault energy. Here we show that by using in situ heavy ion irradiation in a transmission electron microscope, pre-introduced nanovoids in nanotwinned Cu efficiently absorb radiation-induced defects accompanied by gradual elimination of nanovoids, enhancing radiation tolerance of Cu. In situ studies and atomistic simulations reveal that such remarkable self-healing capability stems from highmore » density of coherent and incoherent twin boundaries that rapidly capture and transport point defects and dislocation loops to nanovoids, which act as storage bins for interstitial loops. This study describes a counterintuitive yet significant concept: deliberate introduction of nanovoids in conjunction with nanotwins enables unprecedented damage tolerance in metallic materials.« less

Rotational 3D printing of damage-tolerant composites with programmable mechanics.

PubMed

Raney, Jordan R; Compton, Brett G; Mueller, Jochen; Ober, Thomas J; Shea, Kristina; Lewis, Jennifer A

2018-02-06

Natural composites exhibit exceptional mechanical performance that often arises from complex fiber arrangements within continuous matrices. Inspired by these natural systems, we developed a rotational 3D printing method that enables spatially controlled orientation of short fibers in polymer matrices solely by varying the nozzle rotation speed relative to the printing speed. Using this method, we fabricated carbon fiber-epoxy composites composed of volume elements (voxels) with programmably defined fiber arrangements, including adjacent regions with orthogonally and helically oriented fibers that lead to nonuniform strain and failure as well as those with purely helical fiber orientations akin to natural composites that exhibit enhanced damage tolerance. Our approach broadens the design, microstructural complexity, and performance space for fiber-reinforced composites through site-specific optimization of their fiber orientation, strain, failure, and damage tolerance. Copyright © 2018 the Author(s). Published by PNAS.

Damage-tolerance strategies for nacre tablets.

PubMed

Wang, Shengnan; Zhu, Xinqiao; Li, Qiyang; Wang, Rizhi; Wang, Xiaoxiang

2016-05-01

Nacre, a natural armor, exhibits prominent penetration resistance against predatory attacks. Unraveling its hierarchical toughening mechanisms and damage-tolerance design strategies may provide significant inspiration for the pursuit of high-performance artificial armors. In this work, relationships between the structure and mechanical performance of nacre were investigated. The results show that other than their brick-and-mortar structure, individual nacre tablets significantly contribute to the damage localization of nacre. Affected by intracrystalline organics, the tablets exhibit a unique fracture behavior. The synergistic action of the nanoscale deformation mechanisms increases the energy dissipation efficiency of the tablets and contributes to the preservation of the structural and functional integrity of the shell. Copyright © 2016 Elsevier Inc. All rights reserved.

The Significance of Small Cracks in Fatigue Design Concepts as Related to Rotorcraft Metallic Dynamic Components

NASA Technical Reports Server (NTRS)

Everett, R. A., Jr.; Elber, W.

2000-01-01

In this paper the significance of the "small" crack effect as defined in fracture mechanics will be discussed as it relates to life managing rotorcraft dynamic components using the conventional safe-life, the flaw tolerant safe-life, and the damage tolerance design philosophies. These topics will be introduced starting with an explanation of the small-crack theory, then showing how small-crack theory has been used to predict the total fatigue life of fatigue laboratory test coupons with and without flaws, and concluding with how small cracks can affect the crack-growth damage tolerance design philosophy. As stated in this paper the "small" crack effect is defined in fracture mechanics where it has been observed that cracks on the order of 300 microns or less in length will propagate at higher growth rates than long cracks and also will grow at AK values below the long crack AK threshold. The small-crack effect is illustrated herein as resulting from a lack of crack closure and is explained based on continuum mechanics principles using crack-closure concepts in fracture mechanics.

Ninth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design, volume 2

NASA Technical Reports Server (NTRS)

Soderquist, Joseph R. (Compiler); Neri, Lawrence M. (Compiler); Bohon, Herman L. (Compiler)

1992-01-01

This publication contains the proceedings of the Ninth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design held at Lake Tahoe, Nevada, during 4-7 Nov. 1991. Presentations were made in the following areas of composite structural design: perspectives in composites, design methodology, design applications, design criteria, supporting technology, damage tolerance, and manufacturing.

Ninth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design, volume 3

NASA Technical Reports Server (NTRS)

Soderquist, Joseph R. (Compiler); Neri, Lawrence M. (Compiler); Bohon, Herman L. (Compiler)

1992-01-01

This publication contains the proceedings of the Ninth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design held at Lake Tahoe, Nevada, during 4-7 Nov. 1991. Presentations were made in the following areas of composite structural design: perspectives in composites, design methodology, design applications, design criteria, supporting technology, damage tolerance, and manufacturing.

77 FR 4890 - Damage Tolerance and Fatigue Evaluation for Composite Rotorcraft Structures, and Damage Tolerance...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-01

...-AJ52, 2120-AJ51 Damage Tolerance and Fatigue Evaluation for Composite Rotorcraft Structures, and Damage... Tolerance and Fatigue Evaluation for Composite Rotorcraft Structures'' (76 FR 74655), published December 1... December 2, 2011. In the ``Composite Rotorcraft Structures'' rule, the FAA amended its regulations to...

Damage Tolerance of Composite Laminates from an Empirical Perspective

NASA Technical Reports Server (NTRS)

Nettles, Alan T.

2009-01-01

Damage tolerance consists of analysis and experimentation working together. Impact damage is usually of most concern for laminated composites. Once impacted, the residual compression strength is usually of most interest. Other properties may be of more interest than compression (application dependent). A damage tolerance program is application specific (not everyone is building aircraft). The "Building Block Approach" is suggested for damage tolerance. Advantage can be taken of the excellent fatigue resistance of damaged laminates to save time and costs.

Impact Characteristics of Candidate Materials for Single-Stage-to-Orbit (SSTO) Technology

NASA Technical Reports Server (NTRS)

Nettles, Alan

1995-01-01

Four fiber/resin systems were compared for resistance to damage and damage tolerance. One toughened epoxy and three toughened bismaleimide (BMI) resins were used., all with IM7 carbon fiber reinforcement. A statistical design of experiments technique was used to evaluate the effects of impact energy, specimen thickness and tup diameter on the damage area and residual compression-after-impact (CAI) strength. Results showed that two of the BMI systems sustained relatively large damage areas yet had an excellent retention of CAI strength.

Adjoint Techniques for Topology Optimization of Structures Under Damage Conditions

NASA Technical Reports Server (NTRS)

Akgun, Mehmet A.; Haftka, Raphael T.

2000-01-01

The objective of this cooperative agreement was to seek computationally efficient ways to optimize aerospace structures subject to damage tolerance criteria. Optimization was to involve sizing as well as topology optimization. The work was done in collaboration with Steve Scotti, Chauncey Wu and Joanne Walsh at the NASA Langley Research Center. Computation of constraint sensitivity is normally the most time-consuming step of an optimization procedure. The cooperative work first focused on this issue and implemented the adjoint method of sensitivity computation (Haftka and Gurdal, 1992) in an optimization code (runstream) written in Engineering Analysis Language (EAL). The method was implemented both for bar and plate elements including buckling sensitivity for the latter. Lumping of constraints was investigated as a means to reduce the computational cost. Adjoint sensitivity computation was developed and implemented for lumped stress and buckling constraints. Cost of the direct method and the adjoint method was compared for various structures with and without lumping. The results were reported in two papers (Akgun et al., 1998a and 1999). It is desirable to optimize topology of an aerospace structure subject to a large number of damage scenarios so that a damage tolerant structure is obtained. Including damage scenarios in the design procedure is critical in order to avoid large mass penalties at later stages (Haftka et al., 1983). A common method for topology optimization is that of compliance minimization (Bendsoe, 1995) which has not been used for damage tolerant design. In the present work, topology optimization is treated as a conventional problem aiming to minimize the weight subject to stress constraints. Multiple damage configurations (scenarios) are considered. Each configuration has its own structural stiffness matrix and, normally, requires factoring of the matrix and solution of the system of equations. Damage that is expected to be tolerated is local and represents a small change in the stiffness matrix compared to the baseline (undamaged) structure. The exact solution to a slightly modified set of equations can be obtained from the baseline solution economically without actually solving the modified system.. Shennan-Morrison-Woodbury (SMW) formulas are matrix update formulas that allow this (Akgun et al., 1998b). SMW formulas were therefore used here to compute adjoint displacements for sensitivity computation and structural displacements in damaged configurations.

On the Influence of Nb/Ti Ratio on Environmentally-Assisted Crack Growth in High-Strength Nickel-Based Superalloys

NASA Astrophysics Data System (ADS)

Németh, A. A. N.; Crudden, D. J.; Collins, D. M.; Kuksenko, V.; Liebscher, C. H.; Armstrong, D. E. J.; Wilkinson, A. J.; Reed, R. C.

2018-05-01

The effect of Nb/Ti ratio on environmentally-assisted crack growth of three prototype Ni-based superalloys is studied. For these alloys, the yield strength is unaltered with increasing Nb/Ti ratio due to an increase in grain size. This situation has allowed the rationalization of the factors influencing damage tolerance at 700 °C. Primary intergranular cracks have been investigated using energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope and the analysis of electron back-scatter diffraction patterns. Any possible detrimental effect of Nb on the observed crack tip damage due to Nb-rich oxide formation is not observed. Instead, evidence is presented to indicate that the tertiary γ'-precipitates are dissolving ahead of the crack consistent with the formation of oxides such as alumina and rutile. Our results have implications for alloy design efforts; at any given strength level, both more and less damage-tolerant variants of these alloys can be designed.

Status Report on Irradiation Capsules Containing Welded FeCrAl Specimens for Radiation Tolerance Evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Kevin G.; Howard, Richard H.

2016-02-26

This status report provides the background and current status of a series of irradiation capsules, or “rabbits”, that were designed and built to test the contributions of microstructure, composition, damage dose, and irradiation temperature on the radiation tolerance of candidate FeCrAl alloys being developed to have enhanced weldability and radiation tolerance. These rabbits will also test the validity of using an ultra-miniature tensile specimen to assess the mechanical properties of irradiated FeCrAl base metal and weldments. All rabbits are to be irradiated in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) to damage doses up tomore » ≥15 dpa at temperatures between 200-550°C.« less

Realising damage-tolerant nacre-inspired CFRP

NASA Astrophysics Data System (ADS)

Narducci, F.; Lee, K.-Y.; Pinho, S. T.

2018-07-01

In this work, a nacre-inspired Carbon Fibre Reinforced Polymer (CFRP) composite is designed, synthesised and tested. Analytical and numerical models are used to design a tiled micro-structure, mimicking the staggered arrangement of ceramic platelets in nacre and exploiting geometrical interlocks for crack deflection and damage diffusion. The designed pattern of tiles is then laser-engraved in the laminate plies. In order to increase the damage-spreading capability of the material, a thin layer of poly(lactic acid) (PLA) is film-cast on the interlaminar region, both as a continuous film and as a pattern of fractal-shaped patches. Three-point bending tests show how the nacre-like micro-structure succeeds in deflecting cracks, with damage diffusion being significantly improved by the addition of PLA at the interface between tiles. It is observed that a texture of discontinuous fractal-shaped PLA patches can increase damage diffusion, by promoting the unlocking of tiles whilst preserving the interface strength.

Damage-Survivable and Damage-Tolerant Laminated Composites with Optimally Placed Piezoelectric Layers

DTIC Science & Technology

1992-11-13

AD-A269 879 Damage-Survivable j and Damage-Tolerant Laminated Composites .4.. with Optimally placed Piezoelectric Layers Final Report No. 1 S. P...Damage Surviable and Damage-Tolerant Laminated Composites With Optimally Placed Piezoelectric Layers 12. PERSONAL AUTHOR(S) S.P. Joshi, W.S. Chan ൕa...block number) The main objective of the research is to assure that the embedded sensors/actuators in a smart laminated composite structure are damage

The effect of resin on the impact damage tolerance of graphite-epoxy laminates

NASA Technical Reports Server (NTRS)

Williams, J. G.; Rhodes, M. D.

1981-01-01

The effect of the matrix resin on the impact damage tolerance of graphite-epoxy composite laminates was investigated. The materials were evaluated on the basis of the damage incurred due to local impact and on their ability to retain compression strength in the presence of impact damage. Twenty-four different resin systems were evaluated. Five of the systems demonstrated substantial improvements compared to the baseline system including retention of compression strength in the presence of impact damage. Examination of the neat resin mechanical properties indicates the resin tensile properties influence significantly the laminate damage tolerance and that improvements in laminate damage tolerance are not necessarily made at the expense of room temperature mechanical properties. Preliminary results indicate a resin volume fraction on the order of 40 percent or greater may be required to permit the plastic flow between fibers necessary for improved damage tolerance.

A service life extension (SLEP) approach to operating aging aircraft beyond their original design lives

NASA Astrophysics Data System (ADS)

Pentz, Alan Carter

With today's uncertain funding climate (including sequestration and continuing budget resolutions), decision makers face severe budgetary challenges to maintain dominance through all aspects of the Department of Defense (DoD). To meet war-fighting capabilities, the DoD continues to extend aircraft programs beyond their design service lives by up to ten years, and occasionally much more. The budget requires a new approach to traditional extension strategies (i.e., reuse, reset, and reclamation) for structural hardware. While extending service life without careful controls can present a safety concern, future operations planning does not consider how much risk is present when operating within sound structural principles. Traditional structural hardware extension methods drive increased costs. Decision makers often overlook the inherent damage tolerance and fatigue capability of structural components and rely on simple time- and flight-based cycle accumulation when determining aircraft retirement lives. This study demonstrates that decision makers should consider risk in addition to the current extension strategies. Through an evaluation of eight military aircraft programs and the application and simulation of F-18 turbine engine usage data, this dissertation shows that insight into actual aircraft mission data, consideration of fatigue capability, and service extension length are key factors to consider. Aircraft structural components, as well as many critical safety components and system designs, have a predefined level of conservatism and inherent damage tolerance. The methods applied in this study would apply to extensions of other critical structures such as bridges. Understanding how much damage tolerance is built into the design compared to the original design usage requirements presents the opportunity to manage systems based on risk. The study presents the sensitivity of these factors and recommends avenues for further research.

Specialists Meeting on Impact Damage Tolerance of Structures

DTIC Science & Technology

1976-01-01

example, fatigue, timl-de tectIable initial defects and in-fliglht d amalt such aS that inflicted by miilitary weapons or by debris from ’n din tegra t...relative to many types of damaging mechanisms, lncludlig for example: I. Fat Igue 2. Non-detectable Initial defects 3. In-flight damage, such as Inflicted...undetected flaw or defect . In both cases, the benefits of successful design are Improved safety and economics. With respect to In-flight darvqe, tre

Damage tolerance of a composite sandwich with interleaved foam core

NASA Astrophysics Data System (ADS)

Ishai, Ori; Hiel, Clement

A composite sandwich panel consisting of carbon fiber-reinforced plastic (CFRP) skins and a syntactic foam core was selected as an appropriate structural concept for the design of wind tunnel compressor blades. Interleaving of the core with tough interlayers was done to prevent core cracking and to improve damage tolerance of the sandwich. Simply supported sandwich beam specimens were subjected to low-velocity drop-weight impacts as well as high velocity ballistic impacts. The performance of the interleaved core sandwich panels was characterized by localized skin damage and minor cracking of the core. Residual compressive strength (RCS) of the skin, which was derived from flexural test, shows the expected trend of decreasing with increasing size of the damage, impact energy, and velocity. In the case of skin damage, RCS values of around 50 percent of the virgin interleaved reference were obtained at the upper impact energy range. Based on the similarity between low-velocity and ballistic-impact effects, it was concluded that impact energy is the main variable controlling damage and residual strength, where as velocity plays a minor role.

Damage tolerance of a composite sandwich with interleaved foam core

NASA Technical Reports Server (NTRS)

Ishai, Ori; Hiel, Clement

1992-01-01

A composite sandwich panel consisting of carbon fiber-reinforced plastic (CFRP) skins and a syntactic foam core was selected as an appropriate structural concept for the design of wind tunnel compressor blades. Interleaving of the core with tough interlayers was done to prevent core cracking and to improve damage tolerance of the sandwich. Simply supported sandwich beam specimens were subjected to low-velocity drop-weight impacts as well as high velocity ballistic impacts. The performance of the interleaved core sandwich panels was characterized by localized skin damage and minor cracking of the core. Residual compressive strength (RCS) of the skin, which was derived from flexural test, shows the expected trend of decreasing with increasing size of the damage, impact energy, and velocity. In the case of skin damage, RCS values of around 50 percent of the virgin interleaved reference were obtained at the upper impact energy range. Based on the similarity between low-velocity and ballistic-impact effects, it was concluded that impact energy is the main variable controlling damage and residual strength, where as velocity plays a minor role.

Optimization of composite sandwich cover panels subjected to compressive loadings

NASA Technical Reports Server (NTRS)

Cruz, Juan R.

1991-01-01

An analysis and design method is presented for the design of composite sandwich cover panels that include the transverse shear effects and damage tolerance considerations. This method is incorporated into a sandwich optimization computer program entitled SANDOP. As a demonstration of its capabilities, SANDOP is used in the present study to design optimized composite sandwich cover panels for for transport aircraft wing applications. The results of this design study indicate that optimized composite sandwich cover panels have approximately the same structural efficiency as stiffened composite cover panels designed to satisfy individual constraints. The results also indicate that inplane stiffness requirements have a large effect on the weight of these composite sandwich cover panels at higher load levels. Increasing the maximum allowable strain and the upper percentage limit of the 0 degree and +/- 45 degree plies can yield significant weight savings. The results show that the structural efficiency of these optimized composite sandwich cover panels is relatively insensitive to changes in core density. Thus, core density should be chosen by criteria other than minimum weight (e.g., damage tolerance, ease of manufacture, etc.).

Damage tolerance assessment handbook. Volume 2 : airframe damage tolerance evaluation

DOT National Transportation Integrated Search

1999-02-01

The handbook is presented in two volumes. Volume I introduces the damage tolerance concept with an historical perspective followed by the fundamentals of fracture mechanics and fatigue crack propagation. Various fracture criteria and crack growth rul...

Probabilistic Assessment of Fracture Progression in Composite Structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Minnetyan, Levon; Mauget, Bertrand; Huang, Dade; Addi, Frank

1999-01-01

This report describes methods and corresponding computer codes that are used to evaluate progressive damage and fracture and to perform probabilistic assessment in built-up composite structures. Structural response is assessed probabilistically, during progressive fracture. The effects of design variable uncertainties on structural fracture progression are quantified. The fast probability integrator (FPI) is used to assess the response scatter in the composite structure at damage initiation. The sensitivity of the damage response to design variables is computed. The methods are general purpose and are applicable to stitched and unstitched composites in all types of structures and fracture processes starting from damage initiation to unstable propagation and to global structure collapse. The methods are demonstrated for a polymer matrix composite stiffened panel subjected to pressure. The results indicated that composite constituent properties, fabrication parameters, and respective uncertainties have a significant effect on structural durability and reliability. Design implications with regard to damage progression, damage tolerance, and reliability of composite structures are examined.

Cold Expansion Effects on Cracked Fastener Holes Under Constant Amplitude and Spectrum Loading in the 2024-T351 Aluminum Alloy

DTIC Science & Technology

2012-05-01

1 1.2. History of Fatigue Designs ................................................................................... 2 1.3...of design . 1.2. History of Fatigue Designs 1.2.1. Safe Life Design The United States Air Force (USAF) has primarily used two design paradigms...for fatigue thus far. These paradigms are the Safe Life, and the Damage Tolerance fatigue designs . The American Society for Metals (ASM) Handbook

Experimental Verification of a Progressive Damage Model for IM7/5260 Laminates Subjected to Tension-Tension Fatigue

NASA Technical Reports Server (NTRS)

Coats, Timothy W.; Harris, Charles E.

1995-01-01

The durability and damage tolerance of laminated composites are critical design considerations for airframe composite structures. Therefore, the ability to model damage initiation and growth and predict the life of laminated composites is necessary to achieve structurally efficient and economical designs. The purpose of this research is to experimentally verify the application of a continuum damage model to predict progressive damage development in a toughened material system. Damage due to monotonic and tension-tension fatigue was documented for IM7/5260 graphite/bismaleimide laminates. Crack density and delamination surface area were used to calculate matrix cracking and delamination internal state variables to predict stiffness loss in unnotched laminates. A damage dependent finite element code predicted the stiffness loss for notched laminates with good agreement to experimental data. It was concluded that the continuum damage model can adequately predict matrix damage progression in notched and unnotched laminates as a function of loading history and laminate stacking sequence.

Composite Fuselage Technology

NASA Technical Reports Server (NTRS)

Lagace, Paul A.

1999-01-01

Work was conducted over a ten-year period to address the central issue of damage in primary load-bearing aircraft composite structure, specifically fuselage structure. This included the three facets of damage resistance, damage tolerance, and damage arrest. Experimental, analytical, and numerical work was conducted in order to identify and better understand the mechanisms that control the structural behavior of fuselage structures in their response to the three aspects of damage. Furthermore, work was done to develop straightforward design methodologies that can be employed by structural designers in preliminary design stages to make intelligent choices concerning the material, layup, and structural configurations so that a more efficient structure with structural integrity can be designed and built. Considerable progress was made towards achieving these goals via this work. In regard to damage tolerance considerations, the following were identified as important effects: composite layup and associated orthotropy/structural anisotropy, specifics of initial local damage mechanisms, role of longitudinal versus hoop stress, and large deformation and associated geometric nonlinearity. Means were established to account for effects of radius and for the nonlinear response. In particular, nondimensional parameters were identified to characterize the importance of nonlinearity in the response of pressurized cylinders. This led to the establishment of a iso-nonlinear-error plot for reference in structural design. Finally, in the case of damage tolerance, the general approach of the original methodology to predict the failure pressure involving extending basic plate failure data by accounting for the local stress intensification was accomplished for the general case by accounting for the mechanisms noted by utilizing the capability of the STAGS finite element code and numerically calculating the local stress intensification for the particular configuration to be considered. For the issue of damage arrest, placement of and configuration of stiffeners (including stiffener curvature), and magnitude and orientation of principal strains due to local bending were found to be key considerations. Means were established to account for stiffener effectiveness quantitatively based on radius, slit size, stiffener curvature' and relative bending stifffiesses involved. Geometric nonlinearity was also found to play an - 24 - important role here. Furthermore, it was determined that damage propagation is controlled by different mechanisms (hoop stress versus flapping stress and the associated factors involved in each) depending upon the direction of damage propagation. This latter item results in an inability to scale these phenomena in one test due to the different factors involved. Finally, the importance of shell curvature and associated instability in response to transverse loading including impact were found to be important considerations in damage resistance. A technique, involving asymmetric meshing of a finite element mesh, was developed to predict this behavior and showed excellent correlation with experimental results. Further details of these ten years of work are presented herein with references made to the fourteen documents produced during this work where full details can be found. Implications of this work are discussed and recommendations made. Although it is clear that there is more work to be done to fully understand composite fuselage technology and specifically the overall issue of damage in primary load-bearing composite structures, important understanding and capability has been extended via this work.

Impact response of graphite/epoxy fabric structures

NASA Technical Reports Server (NTRS)

Lagace, Paul A.; Kraft, Michael J.

1990-01-01

The impact damage resistance and damage tolerance of graphite/epoxy fabric plate (coupon) and cylinder structures were investigated and compared in an analytical and experimental study. Hercules A370-5H/3501-6 five-harness satin weave cloth in a quasi-isotropic (0,45)(sub s) laminate configuration was utilized. Specimens were impacted with 12.7 mm diameter steel spheres at velocities ranging from 10 m/s to 100 m/s. Damage resistance of the specimens was determined through the use of dye penetrant enhanced x-radiography, sectioning, epoxy burnoff, and visual methods. Damage tolerance of the flat plate structures was assessed in a residual tensile test while damage tolerance of the cylinder structures was assessed via pressurization tests. Impacted fabric laminates exhibited matrix crushing, fiber breakage, delamination, and fiber bundle disbonds; the latter being a unique damage mode for fabric laminates. Plate delamination and bundle disbonding was found to be more extensive around the central core area of fiber damage in the coupon specimens than in the cylinder specimens which showed a cleaner damage area due to impact. Damage resistance and damage tolerance were predicted by utilizing a five-step analysis approach previously utilized for coupon configurations. Two of the five steps were adapted to account for the effects of the structural configuration of the pressurized cylinder. The damage resistance analysis provided good correlation to the fiber damage region of both the coupon and cylinder specimens. There was little difference in the size of this region in the two specimen types. However, the analysis was not able to predict the distribution of damage through-the-thickness. This was important in assessing the damage tolerance of the cylinders. The damage tolerance analysis was able to predict the residual tensile strength of the coupons. A general methodology to predict the impact damage resistance and damage tolerance of composite structures utilizing coupon data is presented.

Development of Improved Composite Pressure Vessels for Hydrogen Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newhouse, Norman L.

2016-04-29

Hexagon Lincoln started this DOE project as part of the Hydrogen Storage Engineering Center of Excellence (HSECoE) contract on 1 February 2009. The purpose of the HSECoE was the research and development of viable material based hydrogen storage systems for on-board vehicular applications to meet DOE performance and cost targets. A baseline design was established in Phase 1. Studies were then conducted to evaluate potential improvements, such as alternate fiber, resin, and boss materials. The most promising concepts were selected such that potential improvements, compared with the baseline Hexagon Lincoln tank, resulted in a projected weight reduction of 11 percent,more » volume increase of 4 percent, and cost reduction of 10 percent. The baseline design was updated in Phase 2 to reflect design improvements and changes in operating conditions specified by HSECoE Partners. Evaluation of potential improvements continued during Phase 2. Subscale prototype cylinders were designed and fabricated for HSECoE Partners’ use in demonstrating their components and systems. Risk mitigation studies were conducted in Phase 3 that focused on damage tolerance of the composite reinforcement. Updated subscale prototype cylinders were designed and manufactured to better address the HSECoE Partners’ requirements for system demonstration. Subscale Type 1, Type 3, and Type 4 tanks were designed, fabricated and tested. Laboratory tests were conducted to evaluate vacuum insulated systems for cooling the tanks during fill, and maintaining low temperatures during service. Full scale designs were prepared based on results from the studies of this program. The operating conditions that developed during the program addressed adsorbent systems operating at cold temperatures. A Type 4 tank would provide the lowest cost and lightest weight, particularly at higher pressures, as long as issues with liner compatibility and damage tolerance could be resolved. A Type 1 tank might be the choice if the liner and damage tolerance issues were not resolved, particularly if the operating pressure was reduced.« less

Structural Integrity and Aging-Related Issues of Helicopters

DTIC Science & Technology

2000-10-01

inherently damage lolerant , any damage- inspection in critical locations where tests have indicated tolerant features in airframe design only enhances...required, so European Rotorcraft Forum. Marseilles, France, 15- that helicopters are equipped with such features as fly- 17 September 1998 . by-wire and...fatigue Evaluation of structural integrity issues of aging helicopters. The Structure," 29 April, 1998 . extended safe-life approach encompasses the best

Intraspecific competition facilitates the evolution of tolerance to insect damage in the perennial plant Solanum carolinense.

PubMed

McNutt, David W; Halpern, Stacey L; Barrows, Kahaili; Underwood, Nora

2012-12-01

Tolerance to herbivory (the degree to which plants maintain fitness after damage) is a key component of plant defense, so understanding how natural selection and evolutionary constraints act on tolerance traits is important to general theories of plant-herbivore interactions. These factors may be affected by plant competition, which often interacts with damage to influence trait expression and fitness. However, few studies have manipulated competitor density to examine the evolutionary effects of competition on tolerance. In this study, we tested whether intraspecific competition affects four aspects of the evolution of tolerance to herbivory in the perennial plant Solanum carolinense: phenotypic expression, expression of genetic variation, the adaptive value of tolerance, and costs of tolerance. We manipulated insect damage and intraspecific competition for clonal lines of S. carolinense in a greenhouse experiment, and measured tolerance in terms of sexual and asexual fitness components. Compared to plants growing at low density, plants growing at high density had greater expression of and genetic variation in tolerance, and experienced greater fitness benefits from tolerance when damaged. Tolerance was not costly for plants growing at either density, and only plants growing at low density benefited from tolerance when undamaged, perhaps due to greater intrinsic growth rates of more tolerant genotypes. These results suggest that competition is likely to facilitate the evolution of tolerance in S. carolinense, and perhaps in other plants that regularly experience competition, while spatio-temporal variation in density may maintain genetic variation in tolerance.

Variable Complexity Optimization of Composite Structures

NASA Technical Reports Server (NTRS)

Haftka, Raphael T.

2002-01-01

The use of several levels of modeling in design has been dubbed variable complexity modeling. The work under the grant focused on developing variable complexity modeling strategies with emphasis on response surface techniques. Applications included design of stiffened composite plates for improved damage tolerance, the use of response surfaces for fitting weights obtained by structural optimization, and design against uncertainty using response surface techniques.

Mechanical performance of pyrolytic carbon in prosthetic heart valve applications.

PubMed

Cao, H

1996-06-01

An experimental procedure has been developed for rigorous characterization of the fracture resistance and fatigue crack extension in pyrolytic carbon for prosthetic heart valve application. Experiments were conducted under sustained and cyclic loading in a simulated biological environment using Carbomedics Pyrolite carbon. While the material was shown to have modest fracture toughness, it exhibited excellent resistance to subcritical crack growth. The crack growth kinetics in pyrolytic carbon were formulated using a phenomenological description. A fatigue threshold was observed below which the crack growth rate diminishes. A damage tolerance concept based on fracture mechanics was used to develop an engineering design approach for mechanical heart valve prostheses. In particular, a new quantity, referred to as the safe-life index, was introduced to assess the design adequacy against subcritical crack growth in brittle materials. In addition, a weakest-link statistical description of the fracture strength is provided and used in the design of component proof-tests. It is shown that the structural reliability of mechanical heart valves can be assured by combining effective flaw detection and manufacturing quality control with adequate damage tolerance design.

Unprecedented simultaneous enhancement in damage tolerance and fatigue resistance of zirconia/Ta composites

NASA Astrophysics Data System (ADS)

Smirnov, A.; Beltrán, J. I.; Rodriguez-Suarez, T.; Pecharromán, C.; Muñoz, M. C.; Moya, J. S.; Bartolomé, J. F.

2017-03-01

Dense (>98 th%) and homogeneous ceramic/metal composites were obtained by spark plasma sintering (SPS) using ZrO2 and lamellar metallic powders of tantalum or niobium (20 vol.%) as starting materials. The present study has demonstrated the unique and unpredicted simultaneous enhancement in toughness and strength with very high flaw tolerance of zirconia/Ta composites. In addition to their excellent static mechanical properties, these composites also have exceptional resistance to fatigue loading. It has been shown that the major contributions to toughening are the resulting crack bridging and plastic deformation of the metallic particles, together with crack deflection and interfacial debonding, which is compatible with the coexistence in the composite of both, strong and weak ceramic/metal interfaces, in agreement with predictions of ab-initio calculations. Therefore, these materials are promising candidates for designing damage tolerance components for aerospace industry, cutting and drilling tools, biomedical implants, among many others.

Unprecedented simultaneous enhancement in damage tolerance and fatigue resistance of zirconia/Ta composites

PubMed Central

Smirnov, A.; Beltrán, J. I.; Rodriguez-Suarez, T.; Pecharromán, C.; Muñoz, M. C.; Moya, J. S.; Bartolomé, J. F.

2017-01-01

Dense (>98 th%) and homogeneous ceramic/metal composites were obtained by spark plasma sintering (SPS) using ZrO2 and lamellar metallic powders of tantalum or niobium (20 vol.%) as starting materials. The present study has demonstrated the unique and unpredicted simultaneous enhancement in toughness and strength with very high flaw tolerance of zirconia/Ta composites. In addition to their excellent static mechanical properties, these composites also have exceptional resistance to fatigue loading. It has been shown that the major contributions to toughening are the resulting crack bridging and plastic deformation of the metallic particles, together with crack deflection and interfacial debonding, which is compatible with the coexistence in the composite of both, strong and weak ceramic/metal interfaces, in agreement with predictions of ab-initio calculations. Therefore, these materials are promising candidates for designing damage tolerance components for aerospace industry, cutting and drilling tools, biomedical implants, among many others. PMID:28322343

In situ heavy ion irradiation studies of nanopore shrinkage and enhanced radiation tolerance of nanoporous Au

DOE PAGES

Li, Jin; Fan, Cuncai; Ding, Jie; ...

2017-01-03

High energy particle radiations induce severe microstructural damage in metallic materials. Nanoporous materials with a giant surface-to-volume ratio may alleviate radiation damage in irradiated metallic materials as free surface are defect sinks. We show, by using in situ Kr ion irradiation in a transmission electron microscope at room temperature, that nanoporous Au indeed has significantly improved radiation tolerance comparing with coarse-grained, fully dense Au. In situ studies show that nanopores can absorb and eliminate a large number of radiation-induced defect clusters. Meanwhile, nanopores shrink (self-heal) during radiation, and their shrinkage rate is pore size dependent. Furthermore, the in situ studiesmore » show dose-rate-dependent diffusivity of defect clusters. Our study sheds light on the design of radiation-tolerant nanoporous metallic materials for advanced nuclear reactor applications.« less

An overview of the NASA textile composites program

NASA Technical Reports Server (NTRS)

Dexter, H. Benson

1993-01-01

The NASA Langley Research Center is conducting and sponsoring research to explore the benefits of textile reinforced composites for civil transport aircraft primary structures. The objective of this program is to develop and demonstrate the potential of affordable textile reinforced composite materials to meet design properties and damage tolerance requirements of advanced aircraft structures. In addition to in-house research, the program includes major participation by the aircraft industry and aerospace textile companies. The major program elements include development of textile preforms, processing science, mechanics of materials, experimental characterization of materials, and development and evaluation of textile reinforced composite structural elements and subcomponents. The NASA Langley in-house research is focused on science-based understanding of resin transfer molding (RTM), development of powder-coated towpreg processes, analysis methodology, and development of a performance database on textile reinforced composites. The focus of the textile industry participation is on development of multidirectional, damage-tolerant preforms, and the aircraft industry participation is in the areas of innovative design concepts, cost-effective fabrication, and testing of textile reinforced composite structural elements and subcomponents. Textile processes such as 3-D weaving, 2-D and 3-D braiding, and knitting/stitching are being compared with conventional laminated tape processes for improved damage tolerance. Through-the-thickness reinforcements offer significant damage tolerance improvements. However, these gains must be weighed against potential loss in in-plane properties such as strength and stiffness. Analytical trade studies are underway to establish design guidelines for the application of textile material forms to meet specific loading requirements. Fabrication and testing of large structural components are required to establish the full potential of textile reinforced composite materials. The goals of the NASA Langley-sponsored research program are to demonstrate technology readiness with subscale composite components by 1995 and to verify the performance of full-scale composite primary aircraft structural components by 1997. The status of textile reinforced composite structural elements under development by Boeing, Douglas, Lockheed, and Grumman are presented. Included are braided frames and woven/stitched wing and fuselage panels.

Damage Tolerance of Composites

NASA Technical Reports Server (NTRS)

Hodge, Andy

2007-01-01

Fracture control requirements have been developed to address damage tolerance of composites for manned space flight hardware. The requirements provide the framework for critical and noncritical hardware assessment and testing. The need for damage threat assessments, impact damage protection plans, and nondestructive evaluation are also addressed. Hardware intended to be damage tolerant have extensive coupon, sub-element, and full-scale testing requirements in-line with the Building Block Approach concept from the MIL-HDBK-17, Department of Defense Composite Materials Handbook.

Damage Tolerance Analysis of a Pressurized Liquid Oxygen Tank

NASA Technical Reports Server (NTRS)

Forth, Scott C.; Harvin, Stephen F.; Gregory, Peyton B.; Mason, Brian H.; Thompson, Joe E.; Hoffman, Eric K.

2006-01-01

A damage tolerance assessment was conducted of an 8,000 gallon pressurized Liquid Oxygen (LOX) tank. The LOX tank is constructed of a stainless steel pressure vessel enclosed by a thermal-insulating vacuum jacket. The vessel is pressurized to 2,250 psi with gaseous nitrogen resulting in both thermal and pressure stresses on the tank wall. Finite element analyses were performed on the tank to characterize the stresses from operation. Engineering material data was found from both the construction of the tank and the technical literature. An initial damage state was assumed based on records of a nondestructive inspection performed on the tank. The damage tolerance analyses were conducted using the NASGRO computer code. This paper contains the assumptions, and justifications, made for the input parameters to the damage tolerance analyses and the results of the damage tolerance analyses with a discussion on the operational safety of the LOX tank.

14 CFR 23.574 - Metallic damage tolerance and fatigue evaluation of commuter category airplanes.

Code of Federal Regulations, 2014 CFR

2014-01-01

... evaluation of commuter category airplanes. 23.574 Section 23.574 Aeronautics and Space FEDERAL AVIATION... COMMUTER CATEGORY AIRPLANES Structure Fatigue Evaluation § 23.574 Metallic damage tolerance and fatigue evaluation of commuter category airplanes. For commuter category airplanes— (a) Metallic damage tolerance. An...

14 CFR 23.574 - Metallic damage tolerance and fatigue evaluation of commuter category airplanes.

Code of Federal Regulations, 2012 CFR

2012-01-01

... evaluation of commuter category airplanes. 23.574 Section 23.574 Aeronautics and Space FEDERAL AVIATION... COMMUTER CATEGORY AIRPLANES Structure Fatigue Evaluation § 23.574 Metallic damage tolerance and fatigue evaluation of commuter category airplanes. For commuter category airplanes— (a) Metallic damage tolerance. An...

14 CFR 23.574 - Metallic damage tolerance and fatigue evaluation of commuter category airplanes.

Code of Federal Regulations, 2013 CFR

2013-01-01

... evaluation of commuter category airplanes. 23.574 Section 23.574 Aeronautics and Space FEDERAL AVIATION... COMMUTER CATEGORY AIRPLANES Structure Fatigue Evaluation § 23.574 Metallic damage tolerance and fatigue evaluation of commuter category airplanes. For commuter category airplanes— (a) Metallic damage tolerance. An...

14 CFR 23.574 - Metallic damage tolerance and fatigue evaluation of commuter category airplanes.

Code of Federal Regulations, 2011 CFR

2011-01-01

... evaluation of commuter category airplanes. 23.574 Section 23.574 Aeronautics and Space FEDERAL AVIATION... COMMUTER CATEGORY AIRPLANES Structure Fatigue Evaluation § 23.574 Metallic damage tolerance and fatigue evaluation of commuter category airplanes. For commuter category airplanes— (a) Metallic damage tolerance. An...

14 CFR 23.574 - Metallic damage tolerance and fatigue evaluation of commuter category airplanes.

Code of Federal Regulations, 2010 CFR

2010-01-01

... evaluation of commuter category airplanes. 23.574 Section 23.574 Aeronautics and Space FEDERAL AVIATION... COMMUTER CATEGORY AIRPLANES Structure Fatigue Evaluation § 23.574 Metallic damage tolerance and fatigue evaluation of commuter category airplanes. For commuter category airplanes— (a) Metallic damage tolerance. An...

A Study of Damage Tolerance in Curved Composite Panels.

DTIC Science & Technology

1988-03-01

A198 617 A STUDY OF DAMAGE TOLERANCE IN CURVED COMPOSITE PANELS 1/2 I CNO O NGNERN BLNuE Hl(U) Ala FORCE INST OF TECH &IRIGHT-PATTERSON APR ON...OAL B PEAU OF STANOARDS- -T - % r . P.4 .% FILE CC R CDV OF DTIC MAR3 11988 *grr A STUDY OF DAMAGE TOLERANCE IN CURVED COMPOSITE PANELS THESIS...AFIT/GA/AA/88-.3 0 A STUDY OF DAMAGE TOLERANCE IN CURVED COMPOSITE PANELS THESIS - Brendan L. Wilder Captain, USAF S*2822 $$$*fltf$$*2*f$1fltf

High Performance COPVs for In-Space Storage of High Pressure Cryogenic Fuels

NASA Technical Reports Server (NTRS)

Schneider, Judy; Dyess, Mark; Hastings, Chad; Wang, Jun

2008-01-01

Polymeric composite overwrapped pressure vessels (COPVs) provide an attractive material system to support developing commercial launch business and alternate fuel ventures. However to be able to design with these materials, the mechanical behavior of the materials must be understood with regards to processing, performance, damage tolerance, and environment. For the storage of cryogenic propellants, it is important to evaluate the materials performance and impact damage resistance at cryogenic temperatures in order to minimize weight and to ensure safety and reliability. As part of this study, material tests of candidate fiber and resin systems were used as the basis for the selection of the material combinations for evaluation in a COPV at cryogenic conditions. This comprehensive approach has also been expanded to address issues with impact damage tolerance and material degradation due to environmental factors. KEY WORDS: Cryogenic testing, evaluation and applications for pressure vessels, COPVs, tanks, or storage vessels.

Effect of Buckling Modes on the Fatigue Life and Damage Tolerance of Stiffened Structures

NASA Technical Reports Server (NTRS)

Davila, Carlos G.; Bisagni, Chiara; Rose, Cheryl A.

2015-01-01

The postbuckling response and the collapse of composite specimens with a co-cured hat stringer are investigated experimentally and numerically. These specimens are designed to evaluate the postbuckling response and the effect of an embedded defect on the collapse load and the mode of failure. Tests performed using controlled conditions and detailed instrumentation demonstrate that the damage tolerance, fatigue life, and collapse loads are closely tied with the mode of the postbuckling deformation, which can be different between two nominally identical specimens. Modes that tend to open skin/stringer defects are the most damaging to the structure. However, skin/stringer bond defects can also propagate under shearing modes. In the proposed paper, the effects of initial shape imperfections on the postbuckling modes and the interaction between different postbuckling deformations and the propagation of skin/stringer bond defects under quasi-static or fatigue loads will be examined.

Water availability limits tolerance of apical damage in the Chilean tarweed Madia sativa

NASA Astrophysics Data System (ADS)

Gonzáles, Wilfredo L.; Suárez, Lorena H.; Molina-Montenegro, Marco A.; Gianoli, Ernesto

2008-07-01

Plant tolerance is the ability to reduce the negative impact of herbivory on plant fitness. Numerous studies have shown that plant tolerance is affected by nutrient availability, but the effect of soil moisture has received less attention. We evaluated tolerance of apical damage (clipping that mimicked insect damage) under two watering regimes (control watering and drought) in the tarweed Madia sativa (Asteraceae). We recorded number of heads with seeds and total number of heads as traits related to fitness. Net photosynthetic rate, water use efficiency, number of branches, shoot biomass, and the root:shoot biomass ratio were measured as traits potentially related to tolerance via compensatory responses to damage. In the drought treatment, damaged plants showed ≈43% reduction in reproductive fitness components in comparison with undamaged plants. In contrast, there was no significant difference in reproductive fitness between undamaged and damaged plants in the control watering treatment. Shoot biomass was not affected by apical damage. The number of branches increased after damage in both water treatments but this increase was limited by drought stress. Net photosynthetic rate increased in damaged plants only in the control watering treatment. Water use efficiency increased with drought stress and, in plants regularly watered, also increased after damage. Root:shoot ratio was higher in the low water treatment and damaged plants tended to reduce root:shoot ratio only in this water treatment. It is concluded that water availability limits tolerance to apical damage in M. sativa, and that putative compensatory mechanisms are differentially affected by water availability.

On Developing a Taxonomy for Multidisciplinary Design Optimization: A Decision-Based Perspective

NASA Technical Reports Server (NTRS)

Lewis, Kemper; Mistree, Farrokh

1995-01-01

In this paper, we approach MDO from a Decision-Based Design (DBD) perspective and explore classification schemes for designing complex systems and processes. Specifically, we focus on decisions, which are only a small portion of the Decision Support Problem (DSP) Technique, our implementation of DBD. We map coupled nonhierarchical and hierarchical representations from the DSP Technique into the Balling-Sobieski (B-S) framework (Balling and Sobieszczanski-Sobieski, 1994), and integrate domain-independent linguistic terms to complete our taxonomy. Application of DSPs to the design of complex, multidisciplinary systems include passenger aircraft, ships, damage tolerant structural and mechanical systems, and thermal energy systems. In this paper we show that Balling-Sobieski framework is consistent with that of the Decision Support Problem Technique through the use of linguistic entities to describe the same type of formulations. We show that the underlying linguistics of the solution approaches are the same and can be coalesced into a homogeneous framework with which to base the research, application, and technology MDO upon. We introduce, in the Balling-Sobieski framework, examples of multidisciplinary design, namely, aircraft, damage tolerant structural and mechanical systems, and thermal energy systems.

75 FR 24502 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures; Reopening of Comment...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-05

.... FAA-2009-0660; Notice No. 10-09] RIN 2120-AJ52 Damage Tolerance and Fatigue Evaluation of Composite... requirements of normal and transport category rotorcraft. The amendment would address advances in composite... 793) Notice No. 09-12, entitled ``Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft...

Damage Tolerance Characterisitics of Composite Sandwich Structures

DTIC Science & Technology

2000-02-01

requirements impose strict test program is devised and carried out, with hundreds of tests at constraints on the design of composite aircraft... design A particular effort was dedicated to the study of delamination methodologies, as well as static and fatigue strength and growth under...partition according to the theoretical tools, the industries are more or less forced, for the fundamental modes. design of primary composite structures

Design Optimization of Composite Structures under Uncertainty

NASA Technical Reports Server (NTRS)

Haftka, Raphael T.

2003-01-01

Design optimization under uncertainty is computationally expensive and is also challenging in terms of alternative formulation. The work under the grant focused on developing methods for design against uncertainty that are applicable to composite structural design with emphasis on response surface techniques. Applications included design of stiffened composite plates for improved damage tolerance, the use of response surfaces for fitting weights obtained by structural optimization, and simultaneous design of structure and inspection periods for fail-safe structures.

Structural Evaluation of Exo-Skeletal Engine Fan Blades

NASA Technical Reports Server (NTRS)

Kuguoglu, Latife; Abumeri, Galib; Chamis, Christos C.

2003-01-01

The available computational simulation capability is used to demonstrate the structural viability of composite fan blades of innovative Exo-Skeletal Engine (ESE) developed at NASA Glenn Research Center for a subsonic mission. Full structural analysis and progressive damage evaluation of ESE composite fan blade is conducted through the NASA in-house computational simulation software system EST/BEST. The results of structural assessment indicate that longitudinal stresses acting on the blade are in compression. At a design speed of 2000 rpm, pressure and suction surface outer most ply stresses in longitudinal, transverse and shear direction are much lower than the corresponding composite ply strengths. Damage is initiated at 4870 rpm and blade fracture takes place at rotor speed of 7735 rpm. Damage volume is 51 percent. The progressive damage, buckling, stress and strength results indicate that the design at hand is very sound because of the factor of safety, damage tolerance, and buckling load of 6811 rpm.

Phosphorylation of human INO80 is involved in DNA damage tolerance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kato, Dai; Waki, Mayumi; Umezawa, Masaki

Highlights: Black-Right-Pointing-Pointer Depletion of hINO80 significantly reduced PCNA ubiquitination. Black-Right-Pointing-Pointer Depletion of hINO80 significantly reduced nuclear dots intensity of RAD18 after UV irradiation. Black-Right-Pointing-Pointer Western blot analyses showed phosphorylated hINO80 C-terminus. Black-Right-Pointing-Pointer Overexpression of phosphorylation mutant hINO80 reduced PCNA ubiquitination. -- Abstract: Double strand breaks (DSBs) are the most serious type of DNA damage. DSBs can be generated directly by exposure to ionizing radiation or indirectly by replication fork collapse. The DNA damage tolerance pathway, which is conserved from bacteria to humans, prevents this collapse by overcoming replication blockages. The INO80 chromatin remodeling complex plays an important role in themore » DNA damage response. The yeast INO80 complex participates in the DNA damage tolerance pathway. The mechanisms regulating yINO80 complex are not fully understood, but yeast INO80 complex are necessary for efficient proliferating cell nuclear antigen (PCNA) ubiquitination and for recruitment of Rad18 to replication forks. In contrast, the function of the mammalian INO80 complex in DNA damage tolerance is less clear. Here, we show that human INO80 was necessary for PCNA ubiquitination and recruitment of Rad18 to DNA damage sites. Moreover, the C-terminal region of human INO80 was phosphorylated, and overexpression of a phosphorylation-deficient mutant of human INO80 resulted in decreased ubiquitination of PCNA during DNA replication. These results suggest that the human INO80 complex, like the yeast complex, was involved in the DNA damage tolerance pathway and that phosphorylation of human INO80 was involved in the DNA damage tolerance pathway. These findings provide new insights into the DNA damage tolerance pathway in mammalian cells.« less

Effect of resin on impact damage tolerance of graphite/epoxy laminates

NASA Technical Reports Server (NTRS)

Williams, J. G.; Rhodes, M. D.

1982-01-01

Twenty-four different epoxy resin systems were evaluated by a variety of test techniques to identify materials that exhibited improved impact damage tolerance in graphite/epoxy composite laminates. Forty-eight-ply composite panels of five of the material systems were able to sustain 100 m/s impact by a 1.27-cm-diameter aluminum projectile while statically loaded to strains of 0.005. Of the five materials with the highest tolerance to impact, two had elastomeric additives, two had thermoplastic additives, and one had a vinyl modifier; all the five systems used bisphenol A as the base resin. An evaluation of test results shows that the laminate damage tolerance is largely determined by the resin tensile properties, and that improvements in laminate damage tolerance are not necessarily made at the expense of room-temperature mechanical properties. The results also suggest that a resin volume fraction of 40 percent or greater may be required to permit the plastic flow between fibers necessary for improved damage tolerance.

Response of Composite Fuselage Sandwich Side Panels Subjected to Internal Pressure and Axial Tension

NASA Technical Reports Server (NTRS)

Rouse, Marshall; Ambur, Damodar R.; Dopker, Bernard; Shah, Bharat

1998-01-01

The results from an experimental and analytical study of two composite sandwich fuselage side panels for a transport aircraft are presented. Each panel has two window cutouts and three frames and utilizes a distinctly different structural concept. These panels have been evaluated with internal pressure loads that generate biaxial tension loading conditions. Design limit load and design ultimate load tests have been performed on both panels. One of the sandwich panels was tested with the middle frame removed to demonstrate the suitability of this two-frame design for supporting the prescribed biaxial loading conditions with twice the initial frame spacing of 20 inches. A damage tolerance study was conducted on the two-frame panel by cutting a notch in the panel that originates at the edge of a cutout and extends in the panel hoop direction through the window-belt area. This panel with a notch was tested in a combined-load condition to demonstrate the structural damage tolerance at the design limit load condition. Both the sandwich panel designs successfully satisfied all desired load requirements in the experimental part of the study, and experimental results from the two-frame panel with and without damage are fully explained by the analytical results. The results of this study suggest that there is potential for using sandwich structural concepts with greater than the usual 20-in. wide frame spacing to further reduce aircraft fuselage structural weight.

Effect of water availability on tolerance of leaf damage in tall morning glory, Ipomoea purpurea

NASA Astrophysics Data System (ADS)

Atala, Cristian; Gianoli, Ernesto

2009-03-01

Resource availability may limit plant tolerance of herbivory. To predict the effect of differential resource availability on plant tolerance, the limiting resource model (LRM) considers which resource limits plant fitness and which resource is mostly affected by herbivore damage. We tested the effect of experimental drought on tolerance of leaf damage in Ipomoea purpurea, which is naturally exposed to both leaf damage and summer drought. To seek mechanistic explanations, we also measured several morphological, allocation and gas exchange traits. In this case, LRM predicts that tolerance would be the same in both water treatments. Plants were assigned to a combination of two water treatments (control and low water) and two damage treatments (50% defoliation and undamaged). Plants showed tolerance of leaf damage, i.e., a similar number of fruits were produced by damaged and undamaged plants, only in control water. Whereas experimental drought affected all plant traits, leaf damage caused plants to show a greater leaf trichome density and reduced shoot biomass, but only in low water. It is suggested that the reduced fitness (number of fruits) of damaged plants in low water was mediated by the differential reduction of shoot biomass, because the number of fruits per shoot biomass was similar in damaged and undamaged plants. Alternative but less likely explanations include the opposing direction of functional responses to drought and defoliation, and resource costs of the damage-induced leaf trichome density. Our results somewhat challenge the LRM predictions, but further research including field experiments is needed to validate some of the preliminary conclusions drawn.

Advances in Composites Technology

NASA Technical Reports Server (NTRS)

Tenney, D. R.; Dexter, H. B.

1985-01-01

A significant level of research is currently focused on the development of tough resins and high strain fibers in an effort to gain improved damage tolerance. Moderate success has been achieved with the development of new resins such as PEEK and additional improvements look promising with new thermoplastic resins. Development of innovative material forms such as 2-D and 3-D woven fabrics and braided structural subelements is also expected to improve damage tolerance and durability of composite hardware. The new thrust in composites is to develop low cost manufacturing and design concepts to lower the cost of composite hardware. Processes being examined include automated material placement, filament winding, pultrusion, and thermoforming. The factory of the future will likely incorporate extensive automation in all aspects of manufacturing composite components.

Computational Simulation of Composite Structural Fatigue

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C. (Technical Monitor)

2005-01-01

Progressive damage and fracture of composite structures subjected to monotonically increasing static, tension-tension cyclic, pressurization, and flexural cyclic loading are evaluated via computational simulation. Constituent material properties, stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for composites. Damage initiation, growth, accumulation, and propagation to fracture due to monotonically increasing static and cyclic loads are included in the simulations. Results show the number of cycles to failure at different temperatures and the damage progression sequence during different degradation stages. A procedure is outlined for use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of results with insight for design decisions.

Computational Simulation of Composite Structural Fatigue

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

2004-01-01

Progressive damage and fracture of composite structures subjected to monotonically increasing static, tension-tension cyclic, pressurization, and flexural cyclic loading are evaluated via computational simulation. Constituent material properties, stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for composites. Damage initiation, growth, accumulation, and propagation to fracture due to monotonically increasing static and cyclic loads are included in the simulations. Results show the number of cycles to failure at different temperatures and the damage progression sequence during different degradation stages. A procedure is outlined for use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of results with insight for design decisions.

Ontogenetic patterns in the mechanisms of tolerance to herbivory in Plantago

PubMed Central

Barton, Kasey E.

2013-01-01

Background and Aims Herbivory and plant defence differ markedly among seedlings and juvenile and mature plants in most species. While ontogenetic patterns of chemical resistance have been the focus of much research, comparatively little is known about how tolerance to damage changes across ontogeny. Due to dramatic shifts in plant size, resource acquisition, stored reserves and growth, it was predicted that tolerance and related underlying mechanisms would differ among ontogenetic stages. Methods Ontogenetic patterns in the mechanisms of tolerance were investigated in Plantago lanceolata and P. major (Plantaginaceae) using the genetic sib-ship approach. Pot-grown plants were subjected to 50 % defoliation at the seedling, juvenile and mature stages and either harvested in the short-term to look at plasticity in growth and photosynthesis in response to damage or allowed to grow through seed maturation to measure phenology, shoot compensation and reproductive fitness. Key Results Tolerance to defoliation was high in P. lanceolata, but low in P. major, and did not vary among ontogenetic stages in either species. Mechanisms underlying tolerance did vary across ontogeny. In P. lanceolata, tolerance was significantly related to flowering (juveniles) and pre-damage shoot biomass (mature plants). In P. major, tolerance was significantly related to pre-damage root biomass (seedlings) and induction of non-photochemical quenching, a photosynthetic parameter (juveniles). Conclusions Biomass partitioning was very plastic in response to damage and showed associations with tolerance in both species, indicating a strong role in plant defence. In contrast, photosynthesis and phenology showed weaker responses to damage and were related to tolerance only in certain ontogenetic stages. This study highlights the pivotal role of ontogeny in plant defence and herbivory. Additional studies in more species are needed to determine how seedlings tolerate herbivory in general and whether mechanisms vary across ontogeny in consistent patterns. PMID:23589631

Damage Tolerant Design Handbook. A Compilation of Fracture and Crack- Growth Data for High-Strength Alloys. Volume 4

DTIC Science & Technology

1983-12-01

DAMAGTE (aduiTOLEATDSG ANBO.A TYPE OF REPORT 6 PERIOD COVERED DAMAE TLERAT DSIG HANBOO. ACOMPILATION OF FRACTURE AND CRACK GROWTH...4 Volumes (No copies furnished by DTIC) 13 KEY WORDS (Conitnue ate reverse side it necessa.ry and idenn’fy by. black flueoebr) * Fracture (Mechanics...Handbooks, *Titanium Alloys, *Nickel Alloys, *Stainless Steel, *Aluminum Alloys, High Strength Alloys, Structural Steel, Fracture Toughness, Damage

14 CFR 26.41 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Data for Repairs and Alterations § 26.41 Definitions. Affects (or Affected) means structure has been... increased or redistributed. Baseline structure means structure that is designed under the original type certificate or amended type certificate for that airplane model. Damage Tolerance Evaluation (DTE) means a...

14 CFR 26.41 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Data for Repairs and Alterations § 26.41 Definitions. Affects (or Affected) means structure has been... increased or redistributed. Baseline structure means structure that is designed under the original type certificate or amended type certificate for that airplane model. Damage Tolerance Evaluation (DTE) means a...

Fatigue crack growth and life prediction under mixed-mode loading

NASA Astrophysics Data System (ADS)

Sajith, S.; Murthy, K. S. R. K.; Robi, P. S.

2018-04-01

Fatigue crack growth life as a function of crack length is essential for the prevention of catastrophic failures from damage tolerance perspective. In damage tolerance design approach, principles of fracture mechanics are usually applied to predict the fatigue life of structural components. Numerical prediction of crack growth versus number of cycles is essential in damage tolerance design. For cracks under mixed mode I/II loading, modified Paris law (d/a d N =C (ΔKe q ) m ) along with different equivalent stress intensity factor (ΔKeq) model is used for fatigue crack growth rate prediction. There are a large number of ΔKeq models available for the mixed mode I/II loading, the selection of proper ΔKeq model has significant impact on fatigue life prediction. In the present investigation, the performance of ΔKeq models in fatigue life prediction is compared with respect to the experimental findings as there are no guidelines/suggestions available on the selection of these models for accurate and/or conservative predictions of fatigue life. Within the limitations of availability of experimental data and currently available numerical simulation techniques, the results of present study attempt to outline models that would provide accurate and conservative life predictions. Such a study aid the numerical analysts or engineers in the proper selection of the model for numerical simulation of the fatigue life. Moreover, the present investigation also suggests a procedure to enhance the accuracy of life prediction using Paris law.

Overexpression of the DNA mismatch repair factor, PMS2, confers hypermutability and DNA damage tolerance.

PubMed

Gibson, Shannon L; Narayanan, Latha; Hegan, Denise Campisi; Buermeyer, Andrew B; Liskay, R Michael; Glazer, Peter M

2006-12-08

Inherited defects in genes associated with DNA mismatch repair (MMR) have been linked to familial colorectal cancer. Cells deficient in MMR are genetically unstable and demonstrate a tolerance phenotype in response to certain classes of DNA damage. Some sporadic human cancers also show abnormalities in MMR gene function, typically due to diminished expression of one of the MutL homologs, MLH1. Here, we report that overexpression of the MutL homolog, human PMS2, can also cause a disruption of the MMR pathway in mammalian cells, resulting in hypermutability and DNA damage tolerance. A mouse fibroblast cell line carrying a recoverable lambda phage shuttle vector for mutation detection was transfected with either a vector designed to express hPMS2 or with an empty vector control. Cells overexpressing hPMS2 were found to have elevated spontaneous mutation frequencies at the cII reporter gene locus. They also showed an increase in the level of mutations induced by the alkylating agent, methynitrosourea (MNU). Clonogenic survival assays demonstrated increased survival of the PMS2-overexpressing cells following exposure to MNU, consistent with the induction of a damage tolerance phenotype. Similar results were seen in cells expressing a mutant PMS2 gene, containing a premature stop codon at position 134 and representing a variant found in an individual with familial colon cancer. These results show that dysregulation of PMS2 gene expression can disrupt MMR function in mammalian cells and establish an additional carcinogenic mechanism by which cells can develop genetic instability and acquire resistance to cytotoxic cancer therapies.

Structurally Integrated, Damage-Tolerant, Thermal Spray Coatings

NASA Astrophysics Data System (ADS)

Vackel, Andrew; Dwivedi, Gopal; Sampath, Sanjay

2015-07-01

Thermal spray coatings are used extensively for the protection and life extension of engineering components exposed to harsh wear and/or corrosion during service in aerospace, energy, and heavy machinery sectors. Cermet coatings applied via high-velocity thermal spray are used in aggressive wear situations almost always coupled with corrosive environments. In several instances (e.g., landing gear), coatings are considered as part of the structure requiring system-level considerations. Despite their widespread use, the technology has lacked generalized scientific principles for robust coating design, manufacturing, and performance analysis. Advances in process and in situ diagnostics have provided significant insights into the process-structure-property-performance correlations providing a framework-enhanced design. In this overview, critical aspects of materials, process, parametrics, and performance are discussed through exemplary studies on relevant compositions. The underlying connective theme is understanding and controlling residual stresses generation, which not only addresses process dynamics but also provides linkage for process-property relationship for both the system (e.g., fatigue) and the surface (wear and corrosion). The anisotropic microstructure also invokes the need for damage-tolerant material design to meet future goals.

A fault-tolerant intelligent robotic control system

NASA Technical Reports Server (NTRS)

Marzwell, Neville I.; Tso, Kam Sing

1993-01-01

This paper describes the concept, design, and features of a fault-tolerant intelligent robotic control system being developed for space and commercial applications that require high dependability. The comprehensive strategy integrates system level hardware/software fault tolerance with task level handling of uncertainties and unexpected events for robotic control. The underlying architecture for system level fault tolerance is the distributed recovery block which protects against application software, system software, hardware, and network failures. Task level fault tolerance provisions are implemented in a knowledge-based system which utilizes advanced automation techniques such as rule-based and model-based reasoning to monitor, diagnose, and recover from unexpected events. The two level design provides tolerance of two or more faults occurring serially at any level of command, control, sensing, or actuation. The potential benefits of such a fault tolerant robotic control system include: (1) a minimized potential for damage to humans, the work site, and the robot itself; (2) continuous operation with a minimum of uncommanded motion in the presence of failures; and (3) more reliable autonomous operation providing increased efficiency in the execution of robotic tasks and decreased demand on human operators for controlling and monitoring the robotic servicing routines.

Concepts for improving the damage tolerance of composite compression panels

NASA Technical Reports Server (NTRS)

Rhodes, M. D.; Williams, J. G.

1981-01-01

The results of an experimental evaluation of graphite-epoxy composite compression panel impact damage tolerance and damage propagation arrest concepts are reported. The tests were conducted on flat plate specimens and blade-stiffened structural panels such as those used in commercial aircraft wings, and the residual strength of damaged specimens and their sensitivity to damage while subjected to in-plane compression loading were determined. Results suggest that matrix materials that fail by delamination have the lowest damage tolerance, and it is concluded that alternative matrix materials with transverse reinforcement to suppress the delamination failure mode and yield the higher-strain value transverse shear crippling mode should be developed.

Ultraviolet-B-induced DNA damage and ultraviolet-B tolerance mechanisms in species with different functional groups coexisting in subalpine moorlands.

PubMed

Wang, Qing-Wei; Kamiyama, Chiho; Hidema, Jun; Hikosaka, Kouki

2016-08-01

High doses of ultraviolet-B (UV-B; 280-315 nm) radiation can have detrimental effects on plants, and especially damage their DNA. Plants have DNA repair and protection mechanisms to prevent UV-B damage. However, it remains unclear how DNA damage and tolerance mechanisms vary among field species. We studied DNA damage and tolerance mechanisms in 26 species with different functional groups coexisting in two moorlands at two elevations. We collected current-year leaves in July and August, and determined accumulation of cyclobutane pyrimidine dimer (CPD) as UV-B damage and photorepair activity (PRA) and concentrations of UV-absorbing compounds (UACs) and carotenoids (CARs) as UV-B tolerance mechanisms. DNA damage was greater in dicot than in monocot species, and higher in herbaceous than in woody species. Evergreen species accumulated more CPDs than deciduous species. PRA was higher in Poaceae than in species of other families. UACs were significantly higher in woody than in herbaceous species. The CPD level was not explained by the mechanisms across species, but was significantly related to PRA and UACs when we ignored species with low CPD, PRA and UACs, implying the presence of another effective tolerance mechanism. UACs were correlated negatively with PRA and positively with CARs. Our results revealed that UV-induced DNA damage significantly varies among native species, and this variation is related to functional groups. DNA repair, rather than UV-B protection, dominates in UV-B tolerance in the field. Our findings also suggest that UV-B tolerance mechanisms vary among species under evolutionary trade-off and synergism.

Tolerance to insect defoliation: biocenotic aspects

Treesearch

Andrey A. Pleshanov; Victor I. Voronin; Elena S. Khlimankova; Valentina I. Epova

1991-01-01

Woody plant resistance to insect damage is of great importance in forest protection, and tree tolerance is an important element of this resistance. The compensating mechanisms responsible for tolerance are nonspecific as a rule and develop after damage has been caused by phytophagous animals or other unfavorable effects. Beyond that, plant tolerance depends on duration...

Composite transport wing technology development

NASA Technical Reports Server (NTRS)

Madan, Ram C.

1988-01-01

The design, fabrication, testing, and analysis of stiffened wing cover panels to assess damage tolerance criteria are discussed. The damage tolerance improvements were demonstrated in a test program using full-sized cover panel subcomponents. The panels utilized a hard skin concept with identical laminates of 44-percent 0-degree, 44-percent plus or minus 45-degree, and 12-percent 90-degree plies in the skins and stiffeners. The panel skins were impacted at midbay between the stiffeners, directly over the stiffener, and over the stiffener flange edge. The stiffener blades were impacted laterally. Impact energy levels of 100 ft-lb and 200 ft-lb were used. NASTRAN finite-element analyses were performed to simulate the nonvisible damage that was detected in the panels by nondestructive inspection. A closed-form solution for generalized loading was developed to evaluate the peel stresses in the bonded structure. Two-dimensional delamination growth analysis was developed using the principle of minimum potential energy in terms of closed-form solution for critical strain. An analysis was conducted to determine the residual compressive stress in the panels after impact damage, and the analytical predictions were verified by compression testing of the damaged panels.

14 CFR 25.571 - Damage-tolerance and fatigue evaluation of structure.

Code of Federal Regulations, 2011 CFR

2011-01-01

... catastrophic failure (such as wing, empennage, control surfaces and their systems, the fuselage, engine... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Fatigue Evaluation § 25..., or by the service history of airplanes of similar structural design and sonic excitation environment...

14 CFR 25.571 - Damage-tolerance and fatigue evaluation of structure.

Code of Federal Regulations, 2014 CFR

2014-01-01

... contribute to a catastrophic failure (such as wing, empennage, control surfaces and their systems, the... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Fatigue Evaluation § 25... of similar structural design and sonic excitation environment, that— (1) Sonic fatigue cracks are not...

14 CFR 25.571 - Damage-tolerance and fatigue evaluation of structure.

Code of Federal Regulations, 2012 CFR

2012-01-01

... contribute to a catastrophic failure (such as wing, empennage, control surfaces and their systems, the... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Fatigue Evaluation § 25... of similar structural design and sonic excitation environment, that— (1) Sonic fatigue cracks are not...

14 CFR 25.571 - Damage-tolerance and fatigue evaluation of structure.

Code of Federal Regulations, 2013 CFR

2013-01-01

... contribute to a catastrophic failure (such as wing, empennage, control surfaces and their systems, the... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Fatigue Evaluation § 25... of similar structural design and sonic excitation environment, that— (1) Sonic fatigue cracks are not...

Radiation injury to the nervous system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gutin, P.H.; Leibel, S.A.; Sneline, G.E.

1991-01-01

This book is designed to describe to the radiation biologist, radiation oncologist, neurologist, neurosurgeon, medical oncologist, and neuro-oncologist, the current state of knowledge about the tolerance of the nervous system to various kinds of radiation, the mechanisms of radiation injury, and how nervous system tolerance and injury are related to the more general problem of radiation damage to normal tissue of all types. The information collected here should stimulate interest in and facilitate the growing research effort into radiation injury to the nervous system.

Design considerations for composite fuselage structure of commercial transport aircraft

NASA Technical Reports Server (NTRS)

Davis, G. W.; Sakata, I. F.

1981-01-01

The structural, manufacturing, and service and environmental considerations that could impact the design of composite fuselage structure for commercial transport aircraft application were explored. The severity of these considerations was assessed and the principal design drivers delineated. Technical issues and potential problem areas which must be resolved before sufficient confidence is established to commit to composite materials were defined. The key issues considered are: definition of composite fuselage design specifications, damage tolerance, and crashworthiness.

Some consideration for evaluation of structural integrity of aging aircraft

NASA Astrophysics Data System (ADS)

Terada, Hiroyuki; Asada, Hiroo

The objective of this paper is to examine the achievement and the limitation of state-of-the-art of the methodology of damage tolerant design and the subjects to be solved for further improvement. The topics discussed are: the basic concept of full-scale fatigue testing, fracture mechanics applications, repair of detected damages, inspection technology, and determination of inspection intervals, reliability assessment for practical application, and the importance of various kinds of data acquisition.

Influence of Fibre Architecture on Impact Damage Tolerance in 3D Woven Composites

NASA Astrophysics Data System (ADS)

Potluri, P.; Hogg, P.; Arshad, M.; Jetavat, D.; Jamshidi, P.

2012-10-01

3D woven composites, due to the presence of through-thickness fibre-bridging, have the potential to improve damage tolerance and at the same time to reduce the manufacturing costs. However, ability to withstand damage depends on weave topology as well as geometry of individual tows. There is an extensive literature on damage tolerance of 2D prepreg laminates but limited work is reported on the damage tolerance of 3D weaves. In view of the recent interest in 3D woven composites from aerospace as well as non-aerospace sectors, this paper aims to provide an understanding of the impact damage resistance as well as damage tolerance of 3D woven composites. Four different 3D woven architectures, orthogonal, angle interlocked, layer-to-layer and modified layer-to-layer structures, have been produced under identical weaving conditions. Two additional structures, Unidirectional (UD) cross-ply and 2D plain weave, have been developed for comparison with 3D weaves. All the four 3D woven laminates have similar order of magnitude of damage area and damage width, but significantly lower than UD and 2D woven laminates. Damage Resistance, calculated as impact energy per unit damage area, has been shown to be significantly higher for 3D woven laminates. Rate of change of CAI strength with impact energy appears to be similar for all four 3D woven laminates as well as UD laminate; 2D woven laminate has higher rate of degradation with respect to impact energy. Undamaged compression strength has been shown to be a function of average tow waviness angle. Additionally, 3D weaves exhibit a critical damage size; below this size there is no appreciable reduction in compression strength. 3D woven laminates have also exhibited a degree of plasticity during compression whereas UD laminates fail instantly. The experimental work reported in this paper forms a foundation for systematic development of computational models for 3D woven architectures for damage tolerance.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jin; Fan, Cuncai; Ding, Jie

High energy particle radiations induce severe microstructural damage in metallic materials. Nanoporous materials with a giant surface-to-volume ratio may alleviate radiation damage in irradiated metallic materials as free surface are defect sinks. We show, by using in situ Kr ion irradiation in a transmission electron microscope at room temperature, that nanoporous Au indeed has significantly improved radiation tolerance comparing with coarse-grained, fully dense Au. In situ studies show that nanopores can absorb and eliminate a large number of radiation-induced defect clusters. Meanwhile, nanopores shrink (self-heal) during radiation, and their shrinkage rate is pore size dependent. Furthermore, the in situ studiesmore » show dose-rate-dependent diffusivity of defect clusters. Our study sheds light on the design of radiation-tolerant nanoporous metallic materials for advanced nuclear reactor applications.« less

Multi-Functional Sandwich Composites for Spacecraft Applications: An Initial Assessment

NASA Technical Reports Server (NTRS)

Adams, Daniel O.; Webb, Nicholas Jason; Yarger, Cody B.; Hunter, Abigail; Oborn, Kelli D.

2007-01-01

Current spacecraft implement relatively uncoupled material and structural systems to address a variety of design requirements, including structural integrity, damage tolerance, radiation protection, debris shielding and thermal insulation. This investigation provided an initial assessment of multi-functional sandwich composites to integrate these diverse requirements. The need for radiation shielding was addressed through the selection of polymeric constituents with high hydrogen content. To provide increased damage tolerance and debris shielding, manufacturing techniques were developed to incorporate transverse stitching reinforcement, internal layers, and a self-healing ionomer membrane. To assess the effects of a space environment, thermal expansion behavior of the candidate foam materials was investigated under a vacuum and increasing temperature. Finally, a thermal expansion model was developed for foam under vacuum conditions and its predictive capability assessed.

Multi-Functional Composite Fatigue

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C.

2008-01-01

Damage and fracture of composites subjected to monotonically increasing static, tension-tension cyclic, pressurization, and flexural cyclic loading are evaluated via a recently developed composite mechanics code that allows the user to focus on composite response at infinitely small scales. Constituent material properties, stress and strain limits are scaled up to the laminate level to evaluate the overall damage and durability. Results show the number of cycles to failure at different temperatures. A procedure is outlined for use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of results with insight for design decisions.

Tolerance to deer herbivory and resistance to insect herbivores in the common evening primrose (Oenothera biennis).

PubMed

Puentes, A; Johnson, M T J

2016-01-01

The evolution of plant defence in response to herbivory will depend on the fitness effects of damage, availability of genetic variation and potential ecological and genetic constraints on defence. Here, we examine the potential for evolution of tolerance to deer herbivory in Oenothera biennis while simultaneously considering resistance to natural insect herbivores. We examined (i) the effects of deer damage on fitness, (ii) the presence of genetic variation in tolerance and resistance, (iii) selection on tolerance, (iv) genetic correlations with resistance that could constrain evolution of tolerance and (v) plant traits that might predict defence. In a field experiment, we simulated deer damage occurring early and late in the season, recorded arthropod abundances, flowering phenology and measured growth rate and lifetime reproduction. Our study showed that deer herbivory has a negative effect on fitness, with effects being more pronounced for late-season damage. Selection acted to increase tolerance to deer damage, yet there was low and nonsignificant genetic variation in this trait. In contrast, there was substantial genetic variation in resistance to insect herbivores. Resistance was genetically uncorrelated with tolerance, whereas positive genetic correlations in resistance to insect herbivores suggest there exists diffuse selection on resistance traits. In addition, growth rate and flowering time did not predict variation in tolerance, but flowering phenology was genetically correlated with resistance. Our results suggest that deer damage has the potential to exert selection because browsing reduces plant fitness, but limited standing genetic variation in tolerance is expected to constrain adaptive evolution in O. biennis. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

ACEE Composite Structures Technology: Review of selected NASA research on composite materials and structures

NASA Technical Reports Server (NTRS)

1984-01-01

The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program was designed to develop technology for advanced composites in commercial aircraft. Research on composite materials, aircraft structures, and aircraft design is presented herein. The following parameters of composite materials were addressed: residual strength, damage tolerance, toughness, tensile strength, impact resistance, buckling, and noise transmission within composite materials structures.

Pre-damage biomass allocation and not invasiveness predicts tolerance to damage in seedlings of woody species in Hawaii.

PubMed

Lurie, Matthew H; Barton, Kasey E; Daehler, Curtis C

2017-12-01

Plant-herbivore interactions have been predicted to play a fundamental role in plant invasions, although support for this assertion from previous research is mixed. While plants may escape from specialist herbivores in their introduced ranges, herbivory from generalists is common. Tolerance traits may allow non-native plants to mitigate the negative consequences of generalist herbivory that they cannot avoid in their introduced range. Here we address whether tolerance to herbivory, quantified as survival and compensatory growth, is associated with plant invasion success in Hawaii and investigate traits that may enhance tolerance in seedlings, the life stage most susceptible to herbivory. In a greenhouse experiment, we measured seedling tolerance to simulated herbivory through mechanical damage (50% leaf removal) of 16 non-native woody plant species differing in invasion status (invasive vs. non-invasive). Seedlings were grown for 2 weeks following damage and analyzed for biomass to determine whether damaged plants could fully compensate for the lost leaf tissue. Over 99% of all seedlings survived defoliation. Although species varied significantly in their levels of compensation, there was no consistent difference between invasive and non-invasive species. Seedlings of 11 species undercompensated and remained substantially smaller than control seedlings 2 weeks after damage; four species were close to compensating, while one species overcompensated. Across species, compensation was positively associated with an increased investment in potential storage reserves, specifically cotyledons and roots, suggesting that these organs provide resources that help seedlings re-grow following damage. Our results add to a growing consensus that pre-damage growth patterns determine tolerance to damage, even in young seedlings which have relatively low biomass. The lack of higher tolerance in highly invasive species may suggest that invaders overcome herbivory barriers to invasion in other ways, such as resistance traits, or that herbivory does not play an important role in the seedling invasion dynamics of these woody species in Hawaii. © 2017 by the Ecological Society of America.

Damage-Tolerant Polymer Composite Systems

NASA Astrophysics Data System (ADS)

Reifsnider, Kenneth L.

1988-11-01

One of the reasons for the rapid growth in the application of polymer composites is the opportunity they provide for the design and construction of composite structures that are especially resistant to losses of strength or reduced life resulting from damage during service. The usefulness of such materials is enhanced by the variety of reinforcement schemes that can be chosen to reflect specific service conditions. Under cyclic loading and demanding mechanical situations (e.g., helicopter parts, vehicle springs and high-speed rotors), polymer composites are considerably superior to competing materials.

Experimental investigation of reinforced bonded joints for composite laminates.

PubMed

Bisagni, Chiara; Furfari, Domenico; Pacchione, Marco

2018-02-01

An experimental study has been carried out to investigate the behaviour of co-bonded carbon fibre reinforced plastics joints with a novel design incorporating a through the thickness local reinforcement. Different specimens were manufactured to investigate static and fatigue behaviour, as well as delamination size after impact and damage tolerance characteristics. The mechanical performances of the specimens with local reinforcement, consisting of the insertion of spiked thin metal sheets between co-bonded laminates, were compared with those ones obtained from specimens with purely co-bonded joints. This novel design demonstrated by tests that damage progression under cycling load results significantly delayed by the reinforcements. A significant number of experimental results were obtained that can be used to define preliminary design guidelines.

Experimental investigation of reinforced bonded joints for composite laminates

PubMed Central

Bisagni, Chiara; Furfari, Domenico; Pacchione, Marco

2017-01-01

An experimental study has been carried out to investigate the behaviour of co-bonded carbon fibre reinforced plastics joints with a novel design incorporating a through the thickness local reinforcement. Different specimens were manufactured to investigate static and fatigue behaviour, as well as delamination size after impact and damage tolerance characteristics. The mechanical performances of the specimens with local reinforcement, consisting of the insertion of spiked thin metal sheets between co-bonded laminates, were compared with those ones obtained from specimens with purely co-bonded joints. This novel design demonstrated by tests that damage progression under cycling load results significantly delayed by the reinforcements. A significant number of experimental results were obtained that can be used to define preliminary design guidelines. PMID:29568127

Advanced Technology Composite Fuselage - Repair and Damage Assessment Supporting Maintenance

NASA Technical Reports Server (NTRS)

Flynn, B. W.; Bodine, J. B.; Dopker, B.; Finn, S. R.; Griess, K. H.; Hanson, C. T.; Harris, C. G.; Nelson, K. M.; Walker, T. H.; Kennedy, T. C.;

Sandwich Structure Risk Reduction in Support of the Payload Adapter Fitting

NASA Technical Reports Server (NTRS)

Nettles, A. T.; Jackson, J. R.; Guin, W. E.

2018-01-01

Reducing risk for utilizing honeycomb sandwich structure for the Space Launch System payload adapter fitting includes determining what parameters need to be tested for damage tolerance to ensure a safe structure. Specimen size and boundary conditions are the most practical parameters to use in damage tolerance inspection. The effect of impact over core splices and foreign object debris between the facesheet and core is assessed. Effects of enhanced damage tolerance by applying an outer layer of carbon fiber woven cloth is examined. A simple repair technique for barely visible impact damage that restores all compression strength is presented.

Effect of Translaminar Reinforcements and Hybridization on Damage Resistance and Tolerance of Composite Laminates

DTIC Science & Technology

2012-01-01

REINFORCEMENTS AND HYBRIDIZATION ON DAMAGE RESISTANCE AND TOLERANCE OF COMPOSITE LAMINATES It was shown that the damage resistance and tolerance of... laminated composites can be enhanced by the employment of translaminar reinforcements (TLR) such as stitching, z-pinning and 3D weaving and also by hybrid...Park, NC 27709-2211 Composite Laminates Resistance REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 10. SPONSOR/MONITOR’S ACRONYM

The US Navy’s Helicopter Integrated Diagnostics System (HIDS) Program: Power Drive Train Crack Detection Diagnostics and Prognostics Life Usage Monitoring and Damage Tolerance; Techniques, Methodologies, and Experiences

DTIC Science & Technology

2000-02-01

HIDS] Program: Power Drive Train Crack Detection Diagnostics and Prognostics ife Usage Monitoring and Damage Tolerance; Techniques, Methodologies, and...and Prognostics , Life Usage Monitoring , and Damage Tolerance; Techniques, Methodologies, and Experiences Andrew Hess Harrison Chin William Hardman...continuing program and deployed engine monitoring systems in fixed to evaluate helicopter diagnostic, prognostic , and wing aircraft, notably on the A

14 CFR 29.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Composite Rotorcraft Structures. 29.573 Section 29.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

14 CFR 27.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Composite Rotorcraft Structures. 27.573 Section 27.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

14 CFR 27.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Composite Rotorcraft Structures. 27.573 Section 27.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

14 CFR 29.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Composite Rotorcraft Structures. 29.573 Section 29.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

14 CFR 27.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Composite Rotorcraft Structures. 27.573 Section 27.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

14 CFR 29.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Composite Rotorcraft Structures. 29.573 Section 29.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

7 CFR 51.2954 - Tolerances for grade defects.

Code of Federal Regulations, 2011 CFR

2011-01-01

... damaged by mold or insects or seriously damaged by other means, of which not more than 5/6 or 5 pct may be damaged by insects, but no part of any tolerance shall be allowed for walnuts containing live insects No... adhering hulls 15 pct total, by count, including not more than 8 pct which are damaged by mold or insects...

A Damage Tolerance Comparison of Composite Hat-Stiffened and Honeycomb Sandwich Structure for Launch Vehicle Interstage Applications

NASA Technical Reports Server (NTRS)

Nettles, A. T.

2011-01-01

In this study, a direct comparison of the compression-after-impact (CAI) strength of impact-damaged, hat-stiffened and honeycomb sandwich structure for launch vehicle use was made. The specimens used consisted of small substructure designed to carry a line load of approx..3,000 lb/in. Damage was inflicted upon the specimens via drop weight impact. Infrared thermography was used to examine the extent of planar damage in the specimens. The specimens were prepared for compression testing to obtain residual compression strength versus damage severity curves. Results show that when weight of the structure is factored in, both types of structure had about the same CAI strength for a given damage level. The main difference was that the hat-stiffened specimens exhibited a multiphase failure whereas the honeycomb sandwich structure failed catastrophically.

Damage and strength of composite materials: Trends, predictions, and challenges

NASA Technical Reports Server (NTRS)

Obrien, T. Kevin

1994-01-01

Research on damage mechanisms and ultimate strength of composite materials relevant to scaling issues will be addressed in this viewgraph presentation. The use of fracture mechanics and Weibull statistics to predict scaling effects for the onset of isolated damage mechanisms will be highlighted. The ability of simple fracture mechanics models to predict trends that are useful in parametric or preliminary designs studies will be reviewed. The limitations of these simple models for complex loading conditions will also be noted. The difficulty in developing generic criteria for the growth of these mechanisms needed in progressive damage models to predict strength will be addressed. A specific example for a problem where failure is a direct consequence of progressive delamination will be explored. A damage threshold/fail-safety concept for addressing composite damage tolerance will be discussed.

Seed tolerance to predation: Evidence from the toxic seeds of the buckeye tree (Aesculus californica; Sapindaceae).

PubMed

Mendoza, Eduardo; Dirzo, Rodolfo

2009-07-01

Tolerance, the capacity of plants to withstand attack by animals, as opposed to resistance, has been poorly examined in the context of seed predation. We investigated the role that the seed mass of the large-seeded endemic tree Aesculus californica plays as a tolerance trait to rodent attack by comparing, under greenhouse conditions, patterns of germination, and subsequent seedling growth, of seeds with a wide range of natural damage. Germination percentage was reduced by 50% and time to germination by 64% in attacked compared to intact seeds, and germination probability was negatively correlated with damage. Seedlings that emerged from intact seeds were taller and bore more leaves than those from damaged seeds. This species' large seed mass favors tolerance to damage because heavily damaged seeds are able to germinate and produce seedlings. This finding is significant given that seeds of this species are known to contain chemical compounds toxic to vertebrates, a resistance trait. We posit that this combination of tolerance and resistance traits might be a particularly effective antipredation strategy when seeds are exposed to a variety of vertebrate predators.

Ideal sinks are not always ideal. Radiation damage accumulation in nanocomposites

DOE PAGES

Uberuaga, Blas Pedro; Choudhury, Samrat; Caro, Alfredo

2014-11-27

Designing radiation tolerant materials is one of the primary challenges associated with advanced nuclear energy systems. One attractive route that has received much attention world-wide is to introduce a high density of sinks, often in the form of interfaces or secondary phases. Here, we develop a simple model of such nanocomposites and examine the ramifications of various factors on the overall radiation stability of the material. In particular, we determine how the distribution of secondary phases, the relative sink strength of those phases, and the irradiation temperature influence the radiation tolerance of the matrix. We find that the best scenariomore » is one in which the sinks have intermediate strength, transiently trapping defects before releasing them back into the matrix.This provides new insight into the optimal properties of nanocomposites for radiation damage environments.« less

Effect of Impact Damage and Open Hole on Compressive Strength of Hybrid Composite Laminates

NASA Technical Reports Server (NTRS)

Hiel, Clement; Brinson, H. F.

1993-01-01

Impact damage tolerance is a frequently listed design requirement for composites hardware. The effect of impact damage and open hole size on laminate compressive strength was studied on sandwich beam specimens which combine CFRP-GFRP hybrid skins and a syntactic foam core. Three test specimen configurations have been investigated for this study. The first two were sandwich beams which were loaded in pure bending (by four point flexure). One series had a skin damaged by impact, and the second series had a circular hole machined through one of the skins. The reduction of compressive strength with increasing damage (hole) size was compared. Additionally a third series of uniaxially loaded open hole compression coupons were tested to generate baseline data for comparison with both series of sandwich beams.

Consolidation of graphite thermoplastic textile preforms for primary aircraft structure

NASA Technical Reports Server (NTRS)

Suarez, J.; Mahon, J.

1991-01-01

The use of innovative cost effective material forms and processes is being considered for fabrication of future primary aircraft structures. Processes that have been identified as meeting these goals are textile preforms that use resin transfer molding (RTM) and consolidation forming. The Novel Composites for Wing and Fuselage Applications (NCWFA) program has as its objective the integration of innovative design concepts with cost effective fabrication processes to develop damage-tolerant structures that can perform at a design ultimate strain level of 6000 micro-inch/inch. In this on-going effort, design trade studies were conducted to arrive at advanced wing designs that integrate new material forms with innovative structural concepts and cost effective fabrication methods. The focus has been on minimizing part count (mechanical fasteners, clips, number of stiffeners, etc.), by using cost effective textile reinforcement concepts that provide improved damage tolerance and out-of-plane load capability, low-cost resin transfer molding processing, and thermoplastic forming concepts. The fabrication of representative Y spars by consolidation methods will be described. The Y spars were fabricated using AS4 (6K)/PEEK 150g commingled angle interlock 0/90-degree woven preforms with +45-degree commingled plies stitched using high strength Toray carbon thread and processed by autoclave consolidation.

A damage tolerance comparison of IM7/8551 and IM8G/8553 carbon/epoxy composites

NASA Technical Reports Server (NTRS)

Lance, D. G.; Nettles, A. T.

1991-01-01

A damage tolerance study of two new toughened carbon fiber/epoxy resin systems was undertaken as a continuation of ongoing work into screening new opposites for resistance to foreign object impact. This report is intended to be a supplement to NASA TP 3029 in which four new fiber/resin systems were tested for damage tolerance. Instrumented drop weight impact testing was used to inflict damage to 16-ply quasi-isotropic specimens. Instrumented output data and cross-sectional examinations of the damage zone were utilized to quantify the damage. It was found that the two fiber/resin systems tested in this study were much more impact resistant than an untoughened composite such as T300/934, but were not as impact resistant as other materials previously studied.

Evaluation of Progressive Failure Analysis and Modeling of Impact Damage in Composite Pressure Vessels

NASA Technical Reports Server (NTRS)

Sanchez, Christopher M.

2011-01-01

NASA White Sands Test Facility (WSTF) is leading an evaluation effort in advanced destructive and nondestructive testing of composite pressure vessels and structures. WSTF is using progressive finite element analysis methods for test design and for confirmation of composite pressure vessel performance. Using composite finite element analysis models and failure theories tested in the World-Wide Failure Exercise, WSTF is able to estimate the static strength of composite pressure vessels. Additionally, test and evaluation on composites that have been impact damaged is in progress so that models can be developed to estimate damage tolerance and the degradation in static strength.

An Experimental Investigation of Damage Resistances and Damage Tolerance of Composite Materials

NASA Technical Reports Server (NTRS)

Prabhakaran, R.

2003-01-01

The project included three lines of investigation, aimed at a better understanding of the damage resistance and damage tolerance of pultruded composites. The three lines of investigation were: (i) measurement of permanent dent depth after transverse indentation at different load levels, and correlation with other damage parameters such as damage area (from x-radiography) and back surface crack length, (ii) estimation of point stress and average stress characteristic dimensions corresponding to measured damage parameters, and (iii) an attempt to measure the damage area by a reflection photoelastic technique. All the three lines of investigation were pursued.

Advanced Composite Wind Turbine Blade Design Based on Durability and Damage Tolerance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abumeri, Galib; Abdi, Frank

2012-02-16

The objective of the program was to demonstrate and verify Certification-by-Analysis (CBA) capability for wind turbine blades made from advanced lightweight composite materials. The approach integrated durability and damage tolerance analysis with robust design and virtual testing capabilities to deliver superior, durable, low weight, low cost, long life, and reliable wind blade design. The GENOA durability and life prediction software suite was be used as the primary simulation tool. First, a micromechanics-based computational approach was used to assess the durability of composite laminates with ply drop features commonly used in wind turbine applications. Ply drops occur in composite joints andmore » closures of wind turbine blades to reduce skin thicknesses along the blade span. They increase localized stress concentration, which may cause premature delamination failure in composite and reduced fatigue service life. Durability and damage tolerance (D&DT) were evaluated utilizing a multi-scale micro-macro progressive failure analysis (PFA) technique. PFA is finite element based and is capable of detecting all stages of material damage including initiation and propagation of delamination. It assesses multiple failure criteria and includes the effects of manufacturing anomalies (i.e., void, fiber waviness). Two different approaches have been used within PFA. The first approach is Virtual Crack Closure Technique (VCCT) PFA while the second one is strength-based. Constituent stiffness and strength properties for glass and carbon based material systems were reverse engineered for use in D&DT evaluation of coupons with ply drops under static loading. Lamina and laminate properties calculated using manufacturing and composite architecture details matched closely published test data. Similarly, resin properties were determined for fatigue life calculation. The simulation not only reproduced static strength and fatigue life as observed in the test, it also showed composite damage and fracture modes that resemble those reported in the tests. The results show that computational simulation can be relied on to enhance the design of tapered composite structures such as the ones used in turbine wind blades. A computational simulation for durability, damage tolerance (D&DT) and reliability of composite wind turbine blade structures in presence of uncertainties in material properties was performed. A composite turbine blade was first assessed with finite element based multi-scale progressive failure analysis to determine failure modes and locations as well as the fracture load. D&DT analyses were then validated with static test performed at Sandia National Laboratories. The work was followed by detailed weight analysis to identify contribution of various materials to the overall weight of the blade. The methodology ensured that certain types of failure modes, such as delamination progression, are contained to reduce risk to the structure. Probabilistic analysis indicated that composite shear strength has a great influence on the blade ultimate load under static loading. Weight was reduced by 12% with robust design without loss in reliability or D&DT. Structural benefits obtained with the use of enhanced matrix properties through nanoparticles infusion were also assessed. Thin unidirectional fiberglass layers enriched with silica nanoparticles were applied to the outer surfaces of a wind blade to improve its overall structural performance and durability. The wind blade was a 9-meter prototype structure manufactured and tested subject to three saddle static loading at Sandia National Laboratory (SNL). The blade manufacturing did not include the use of any nano-material. With silica nanoparticles in glass composite applied to the exterior surfaces of the blade, the durability and damage tolerance (D&DT) results from multi-scale PFA showed an increase in ultimate load of the blade by 9.2% as compared to baseline structural performance (without nano). The use of nanoparticles lead to a delay in the onset of delamination. Load-displacement relationships obtained from testing of the blade with baseline neat material were compared to the ones from analytical simulation using neat resin and using silica nanoparticles in the resin. Multi-scale PFA results for the neat material construction matched closely those from test for both load displacement and location and type of damage and failure. AlphaSTAR demonstrated that wind blade structures made from advanced composite materials can be certified with multi-scale progressive failure analysis by following building block verification approach.« less

State-of-the-Art Review on Composite Material Fatigue/Damage Tolerance.

DTIC Science & Technology

1985-12-01

Automobile Structures," Plastic Rubber Material Application, Vol. 3, No. 2, May 1978. 148. Nguyen, D.T., Arora, J.S., and Belegundu, A.D., "Design...Vanthier, D., " Kunststoff -Verstaerkung MIT Kevlar 49," [Reinforcing Plastics With "Kevlar" 49], Plastverarbeiter, Vol. 31, No. 9, September 1980. 232

Boron/aluminum fan blades for SCAR engines

NASA Technical Reports Server (NTRS)

Stabrylla, R. G.; Carlson, R. G.

1977-01-01

Processing procedures were developed to enhance boron/aluminum bond behavior and foreign object damage (FOD) tolerance. Design and analysis indicated that the J101 Stage 1 fan blade meets the required frequencies without a midspan shroud. The fabricability of full size J101 blades was assessed, while six blades were fabricated and finished machined.

Modular container assembled from fiber reinforced thermoplastic sandwich panels

DOEpatents

Donnelly, Mathew William; Kasoff, William Andrew; Mcculloch, Patrick Carl; Williams, Frederick Truman

2007-12-25

An improved, load bearing, modular design container structure assembled from thermoformed FRTP sandwich panels in which is utilized the unique core-skin edge configuration of the present invention in consideration of improved load bearing performance, improved useful load volume, reduced manufacturing costs, structural weight savings, impact and damage tolerance and repair and replace issues.

Damage Tolerance Assessment Branch

NASA Technical Reports Server (NTRS)

Walker, James L.

2013-01-01

The Damage Tolerance Assessment Branch evaluates the ability of a structure to perform reliably throughout its service life in the presence of a defect, crack, or other form of damage. Such assessment is fundamental to the use of structural materials and requires an integral blend of materials engineering, fracture testing and analysis, and nondestructive evaluation. The vision of the Branch is to increase the safety of manned space flight by improving the fracture control and the associated nondestructive evaluation processes through development and application of standards, guidelines, advanced test and analytical methods. The Branch also strives to assist and solve non-aerospace related NDE and damage tolerance problems, providing consultation, prototyping and inspection services.

Low velocity instrumented impact testing of four new damage tolerant carbon/epoxy composite systems

NASA Technical Reports Server (NTRS)

Lance, D. G.; Nettles, A. T.

1990-01-01

Low velocity drop weight instrumented impact testing was utilized to examine the damage resistance of four recently developed carbon fiber/epoxy resin systems. A fifth material, T300/934, for which a large data base exists, was also tested for comparison purposes. A 16-ply quasi-isotropic lay-up configuration was used for all the specimens. Force/absorbed energy-time plots were generated for each impact test. The specimens were cross-sectionally analyzed to record the damage corresponding to each impact energy level. Maximum force of impact versus impact energy plots were constructed to compare the various systems for impact damage resistance. Results show that the four new damage tolerant fiber/resin systems far outclassed the T300/934 material. The most damage tolerant material tested was the IM7/1962 fiber/resin system.

Local-based damage detection of cyclically loaded bridge piers using wireless sensing units

NASA Astrophysics Data System (ADS)

Hou, Tsung-Chin; Lynch, Jerome P.; Parra-Montesinos, Gustavo

2005-05-01

Concrete bridge piers are a common structural element employed in the design of bridges and elevated roadways. In order to ensure adequate behavior under earthquake-induced displacements, extensive reinforcement detailing in the form of closely spaced ties or spirals is necessary, leading to congestion problems and difficulties during concrete casting. Further, costly repairs are often necessary in bridge piers after a major earthquake which in some cases involve the total or partial shutdown of the bridge. In order to increase the damage tolerance while relaxing the transverse reinforcement requirements of bridge piers, the use of high-performance fiber reinforced cementitious composites (HPFRCC) in earthquake-resistant bridge piers is explored. HPFRCCs are a relatively new class of cementitious material for civil structures with tensile strain-hardening behavior and high damage tolerance. To monitor the behavior of this new class of material in the field, low-cost wireless monitoring technologies will be adopted to provide HPFRCC structural elements the capability to accurately monitor their performance and health. In particular, the computational core of a wireless sensing unit can be harnessed to screen HPFRCC components for damage in real-time. A seismic damage index initially proposed for flexure dominated reinforced concrete elements is modified to serve as an algorithmic tool for the rapid assessment of damage (due to flexure and shear) in HPFRCC bridge piers subjected to large shear reversals. Traditional and non-traditional sensor strategies of an HPFRCC bridge pier are proposed to optimize the correlation between the proposed damage index model and the damage observed in a circular pier test specimen. Damage index models are shown to be a sufficiently accurate rough measure of the degree of local-area damage that can then be wirelessly communicated to bridge officials.

Simulation of Spacecraft Damage Tolerance and Adaptive Controls

DTIC Science & Technology

2013-06-01

completed this without it. I thank him from the bottom of my heart . xviii THIS PAGE INTENTIONALLY LEFT BLANK 1 I. INTRODUCTION A. BACKGROUND...resulting point, and [ ]*Q is the conjugate quaternion (MathWorks, 2013). When Equation 19 is expanded, the following DCM can be extracted (Wie...E., (1999). Spacecraft design and sizing. In J. Wertz & W. Larson (Eds.), Space mission analysis and design (3rd ed.) (pp. 301–351). Hawthorne , CA

Fused slurry silicide coatings for columbium alloys reentry heat shields. Volume 1: Evaluation analysis

NASA Technical Reports Server (NTRS)

Fitzgerald, B.

1973-01-01

The R-512E (Si-20Cr-20Fe) fused slurry silicide coating process was optimized to coat full size (20in x 20in) single face rib and corrugation stiffened panels fabricated from FS-85 columbium alloy for 100 mission space shuttle heat shield applications. Structural life under simulated space shuttle lift-off stresses and reentry conditions demonstrated reuse capability well beyond 100 flights for R-512E coated FS-85 columbium heat shield panels. Demonstrated coating damage tolerance showed no immediate structural failure on exposure. The FS-85 columbium alloy was selected from five candidate alloys (Cb-752, C-129Y, WC-3015, B-66 and FS-85) based on the evaluation tests which have designed to determine: (1) change in material properties due to coating and reuse; (2) alloy tolerance to coating damage; (3) coating emittance characteristics under reuse conditions; and (4) new coating chemistries for improved coating life.

Probabilistic Methods for Structural Design and Reliability

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Whitlow, Woodrow, Jr. (Technical Monitor)

2002-01-01

This report describes a formal method to quantify structural damage tolerance and reliability in the presence of a multitude of uncertainties in turbine engine components. The method is based at the material behavior level where primitive variables with their respective scatter ranges are used to describe behavior. Computational simulation is then used to propagate the uncertainties to the structural scale where damage tolerance and reliability are usually specified. Several sample cases are described to illustrate the effectiveness, versatility, and maturity of the method. Typical results from this method demonstrate, that it is mature and that it can be used to probabilistically evaluate turbine engine structural components. It may be inferred from the results that the method is suitable for probabilistically predicting the remaining life in aging or in deteriorating structures, for making strategic projections and plans, and for achieving better, cheaper, faster products that give competitive advantages in world markets.

Static and fatigue testing of full-scale fuselage panels fabricated using a Therm-X(R) process

NASA Technical Reports Server (NTRS)

Dinicola, Albert J.; Kassapoglou, Christos; Chou, Jack C.

1992-01-01

Large, curved, integrally stiffened composite panels representative of an aircraft fuselage structure were fabricated using a Therm-X process, an alternative concept to conventional two-sided hard tooling and contour vacuum bagging. Panels subsequently were tested under pure shear loading in both static and fatigue regimes to assess the adequacy of the manufacturing process, the effectiveness of damage tolerant design features co-cured with the structure, and the accuracy of finite element and closed-form predictions of postbuckling capability and failure load. Test results indicated the process yielded panels of high quality and increased damage tolerance through suppression of common failure modes such as skin-stiffener separation and frame-stiffener corner failure. Finite element analyses generally produced good predictions of postbuckled shape, and a global-local modelling technique yielded failure load predictions that were within 7% of the experimental mean.

Alumina additions may improve the damage tolerance of soft machined zirconia-based ceramics.

PubMed

Oilo, Marit; Tvinnereim, Helene M; Gjerdet, Nils Roar

2011-01-01

The aim of this study was to evaluate the damage tolerance of different zirconia-based materials. Bars of one hard machined and one soft machined dental zirconia and an experimental 95% zirconia 5% alumina ceramic were subjected to 100,000 stress cycles (n = 10), indented to provoke cracks on the tensile stress side (n = 10), and left untreated as controls (n = 10). The experimental material demonstrated a higher relative damage tolerance, with a 40% reduction compared to 68% for the hard machined zirconia and 84% for the soft machined zirconia.

75 FR 16696 - Airworthiness Directives; Airbus Model A330-223, -321, -322, and -323 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-02

... Damage Tolerant--Airworthiness Limitation Item task 712106-01-01 from A330 ALS Part 2, an A330 operator...: During accomplishment of Damage Tolerant--Airworthiness Limitation Item task 712106-01-01 from A330 ALS... Tolerant--Airworthiness Limitation Item task 712106-01-01 from A330 ALS Part 2, an A330 operator found a...

Damage-Tolerance and Fatigue Evaluation of Structure

DOT National Transportation Integrated Search

1997-02-18

This advisory circular (AC) sets forth an acceptable means of compliance : with the provisions of Part 25 of the Federal Aviation Regulations (FAR) dealing with the damage-tolerance and fatigue evaluation requirements of transport category aircraft s...

Damage-tolerant metallic composites via melt infiltration of additively manufactured preforms

DOE PAGES

Pawlowski, Alexander E.; Cordero, Zachary C.; French, Matthew R.; ...

2017-04-22

A facile two-step approach for 3D printing metal-metal composites with precisely controlled microstructures is described. Composites made with this approach exhibit tailorable thermal and mechanical properties as well as exceptional damage tolerance.

Damage-tolerant metallic composites via melt infiltration of additively manufactured preforms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawlowski, Alexander E.; Cordero, Zachary C.; French, Matthew R.

A facile two-step approach for 3D printing metal-metal composites with precisely controlled microstructures is described. Composites made with this approach exhibit tailorable thermal and mechanical properties as well as exceptional damage tolerance.

Foreign Object Impact Design Criteria. Volume 3

DTIC Science & Technology

1982-02-01

of turbine engine fan and compressor blading . The program will aid in the design of more efficient, damage-tolerant Iblading by replacing trial-and...sign criteria that account for the transient overloads produced by bird and ice impacts on turbine engine first-stage fan/compressor blades . This pro...3.81 cm (0.15 in.) thick was chosen as repre- sentative of medium-sized jet engine fan blades . The geometry is sh’wn ill Figure 19. The material

Impact testing of textile composite materials

NASA Technical Reports Server (NTRS)

Portanova, Marc

1995-01-01

The objectives of this report were to evaluate the impact damage resistance and damage tolerance of a variety of textile composite materials. Static indentation and impact tests were performed on the stitched and unstitched uniweave composites constructed from AS4/3501-6 Carbon/Epoxy with a fiberglass yarn woven in to hold the fibers together while being stitched. Compression and tension were measured after the tests to determine the damage resistance, residual strength and the damage tolerance of the specimens.

Enhancing radiation tolerance by controlling defect mobility and migration pathways in multicomponent single-phase alloys

NASA Astrophysics Data System (ADS)

Lu, Chenyang; Niu, Liangliang; Chen, Nanjun; Jin, Ke; Yang, Taini; Xiu, Pengyuan; Zhang, Yanwen; Gao, Fei; Bei, Hongbin; Shi, Shi; He, Mo-Rigen; Robertson, Ian M.; Weber, William J.; Wang, Lumin

2016-12-01

A grand challenge in material science is to understand the correlation between intrinsic properties and defect dynamics. Radiation tolerant materials are in great demand for safe operation and advancement of nuclear and aerospace systems. Unlike traditional approaches that rely on microstructural and nanoscale features to mitigate radiation damage, this study demonstrates enhancement of radiation tolerance with the suppression of void formation by two orders magnitude at elevated temperatures in equiatomic single-phase concentrated solid solution alloys, and more importantly, reveals its controlling mechanism through a detailed analysis of the depth distribution of defect clusters and an atomistic computer simulation. The enhanced swelling resistance is attributed to the tailored interstitial defect cluster motion in the alloys from a long-range one-dimensional mode to a short-range three-dimensional mode, which leads to enhanced point defect recombination. The results suggest design criteria for next generation radiation tolerant structural alloys.

Damage tolerance assessment handbook. Volume 1 : introduction, fracture mechanics, fatigue crack propagation

DOT National Transportation Integrated Search

1999-02-01

The handbook is presented in two volumes. This volume, Volume I, introduces the damage tolerance concept with an historical perspective followed by the fundamentals of fracture mechanics and fatigue crack propagation. Various fracture criteria and cr...

A passively controlled appendage deployment system for the San Marco D/L spacecraft

NASA Technical Reports Server (NTRS)

Lang, W. E.; Frisch, H. P.; Schwartz, D. A.

1984-01-01

The analytical simulation of deployment dynamics of these two axis concepts as well as the evolution of practical designs for the add on deployable inertia boom units is described. With the boom free to swing back in response to Coriolis forces as well as outwards in response to centrifugal forces, the kinematics of motion are complex but admit the possibility of absorbing deployment energy in frictional or other damping devices about the radial axis, where large amplitude motions can occur and where the design envelope allows more available volume. An acceptable range is defined for frictional damping for any given spin rate. Inadequate damping allows boom motions which strike the spacecraft; excessive damping causes the boom to swing out and latch with damaging violence. The acceptable range is a design parameter and must accommodate spin rate tolerance and also the tolerance and repeatability of the damping mechanisms.

Metrics for the technical performance evaluation of light water reactor accident-tolerant fuel

DOE PAGES

Bragg-Sitton, Shannon M.; Todosow, Michael; Montgomery, Robert; ...

2017-03-26

The safe, reliable, and economic operation of the nation’s nuclear power reactor fleet has always been a top priority for the nuclear industry. Continual improvement of technology, including advanced materials and nuclear fuels, remains central to the industry’s success. Enhancing the accident tolerance of light water reactors (LWRs) became a topic of serious discussion following the 2011 Great East Japan Earthquake, resulting tsunami, and subsequent damage to the Fukushima Daiichi nuclear power plant complex. The overall goal for the development of accident-tolerant fuel (ATF) for LWRs is to identify alternative fuel system technologies to further enhance the safety, competitiveness, andmore » economics of commercial nuclear power. Designed for use in the current fleet of commercial LWRs or in reactor concepts with design certifications (GEN-III+), fuels with enhanced accident tolerance would endure loss of active cooling in the reactor core for a considerably longer period of time than the current fuel system while maintaining or improving performance during normal operations. The complex multiphysics behavior of LWR nuclear fuel in the integrated reactor system makes defining specific material or design improvements difficult; as such, establishing desirable performance attributes is critical in guiding the design and development of fuels and cladding with enhanced accident tolerance. Research and development of ATF in the United States is conducted under the U.S. Department of Energy (DOE) Fuel Cycle Research and Development Advanced Fuels Campaign. The DOE is sponsoring multiple teams to develop ATF concepts within multiple national laboratories, universities, and the nuclear industry. Concepts under investigation offer both evolutionary and revolutionary changes to the current nuclear fuel system. This study summarizes the technical evaluation methodology proposed in the United States to aid in the optimization and prioritization of candidate ATF designs.« less

Delamination Assessment Tool for Spacecraft Composite Structures

NASA Astrophysics Data System (ADS)

Portela, Pedro; Preller, Fabian; Wittke, Henrik; Sinnema, Gerben; Camanho, Pedro; Turon, Albert

2012-07-01

Fortunately only few cases are known where failure of spacecraft structures due to undetected damage has resulted in a loss of spacecraft and launcher mission. However, several problems related to damage tolerance and in particular delamination of composite materials have been encountered during structure development of various ESA projects and qualification testing. To avoid such costly failures during development, launch or service of spacecraft, launcher and reusable launch vehicles structures a comprehensive damage tolerance verification approach is needed. In 2009, the European Space Agency (ESA) initiated an activity called “Delamination Assessment Tool” which is led by the Portuguese company HPS Lda and includes academic and industrial partners. The goal of this study is the development of a comprehensive damage tolerance verification approach for launcher and reusable launch vehicles (RLV) structures, addressing analytical and numerical methodologies, material-, subcomponent- and component testing, as well as non-destructive inspection. The study includes a comprehensive review of current industrial damage tolerance practice resulting from ECSS and NASA standards, the development of new Best Practice Guidelines for analysis, test and inspection methods and the validation of these with a real industrial case study. The paper describes the main findings of this activity so far and presents a first iteration of a Damage Tolerance Verification Approach, which includes the introduction of novel analytical and numerical tools at an industrial level. This new approach is being put to the test using real industrial case studies provided by the industrial partners, MT Aerospace, RUAG Space and INVENT GmbH

Orchid flowers tolerance to gamma-radiation

NASA Astrophysics Data System (ADS)

Kikuchi, Olivia Kimiko

2000-03-01

Cut flowers are fresh goods that may be treated with fumigants such as methyl bromide to meet the needs of the quarantine requirements of importing countries. Irradiation is a non-chemical alternative to substitute the methyl bromide treatment of fresh products. In this research, different cut orchids were irradiated to examine their tolerance to gamma-rays. A 200 Gy dose did inhibit the Dendrobium palenopsis buds from opening, but did not cause visible damage to opened flowers. Doses of 800 and 1000 Gy were damaging because they provoked the flowers to drop from the stem. Cattleya irradiated with 750 Gy did not show any damage, and were therefore eligible for the radiation treatment. Cymbidium tolerated up to 300 Gy and above this dose dropped prematurely. On the other hand, Oncydium did not tolerate doses above 150 Gy.

Composite Structures Damage Tolerance Analysis Methodologies

NASA Technical Reports Server (NTRS)

Chang, James B.; Goyal, Vinay K.; Klug, John C.; Rome, Jacob I.

2012-01-01

This report presents the results of a literature review as part of the development of composite hardware fracture control guidelines funded by NASA Engineering and Safety Center (NESC) under contract NNL04AA09B. The objectives of the overall development tasks are to provide a broad information and database to the designers, analysts, and testing personnel who are engaged in space flight hardware production.

A method of calculating the safe fatigue life of compact, highly-stressed components

NASA Technical Reports Server (NTRS)

Cardick, Arthur W.; Pike, Vera J.

1994-01-01

This paper describes a method which has been developed for estimating the safe fatigue life of compact, highly-stressed and inaccessible components for aeroplanes and helicopters of the Royal Air Force. It is explained why the Design Requirements for British Military Aircraft do not favor the use of a damage-tolerance approach in these circumstances.

Comparison of resin film infusion, resin transfer molding, and consolidation of textile preforms for primary aircraft structure

NASA Technical Reports Server (NTRS)

Suarez, J.; Dastin, S.

1992-01-01

Innovative design concepts and cost effective fabrication processes were developed for damage tolerant primary structures that can perform at a design ultimate strain level of 6000 micro inch/inch. Attention focused on the use of textile high performance fiber reinforcement concepts that provide improved damage tolerance and out-of-plane load capability, low cost resin film infusion (RFI) and resin transfer molding (RTM) processes, and thermoplastic forming concepts. The fabrication of wing 'Y' spars by four different materials and/or processes methods is described: fabricated using IM7 angle interlock 0 to 90 deg woven preforms with + or - 45 deg plies stitched with Toray high strength graphite thread and processed using RFI and 3501-6 epoxy; fabricated using G40-800 knitted/stitched preforms and processed using RFI and 3501-6 epoxy; fabricated using G40-800 knitted/stitched preforms using RTM and Tactix 123/H41 epoxy; and fabricated preforms using AS4(6K)/PEEK 150 g commingled angle interlock 0 to 90 deg woven preforms with + or - 45 deg commingled plies stitched using high strength graphite thread and processed by consolidation. Structural efficiency, processability, and acquisition cost are compared.

Conducting field trials for frost tolerance breeding in cereals.

PubMed

Cattivelli, Luigi

2014-01-01

Cereal species can be damaged by frost either during winter or at flowering stage. Frost tolerance per se is only a part of the mechanisms that allow the plants to survive during winter; winterhardiness also considers other biotic or physical stresses that challenge the plants during the winter season limiting their survival rate. While frost tolerance can also be tested in controlled environments, winterhardiness can be determined only with field evaluations. Post-heading frost damage occurs from radiation frost events in spring during the reproductive stages. A reliable evaluation of winterhardiness or of post-heading frost damage should be carried out with field trials replicated across years and locations to overcome the irregular occurrence of natural conditions which satisfactorily differentiate genotypes. The evaluation of post-heading frost damage requires a specific attention to plant phenology. The extent of frost damage is usually determined with a visual score at the end of the winter.

Damage Simulation in Composite Materials: Why It Matters and What Is Happening Currently at NASA in This Area

NASA Technical Reports Server (NTRS)

McElroy, Mack; de Carvalho, Nelson; Estes, Ashley; Lin, Shih-yung

2017-01-01

Use of lightweight composite materials in space and aircraft structure designs is often challenging due to high costs associated with structural certification. Of primary concern in the use of composite structures is durability and damage tolerance. This concern is due to the inherent susceptibility of composite materials to both fabrication and service induced flaws. Due to a lack of general industry accepted analysis tools applicable to composites damage simulation, a certification procedure relies almost entirely on testing. It is this reliance on testing, especially compared to structures comprised of legacy metallic materials where damage simulation tools are available, that can drive costs for using composite materials in aerospace structures. The observation that use of composites can be expensive due to testing requirements is not new and as such, research on analysis tools for simulating damage in composite structures has been occurring for several decades. A convenient approach many researchers/model-developers in this area have taken is to select a specific problem relevant to aerospace structural certification and develop a model that is accurate within that scope. Some examples are open hole tension tests, compression after impact tests, low-velocity impact, damage tolerance of an embedded flaw, and fatigue crack growth to name a few. Based on the premise that running analyses is cheaper than running tests, one motivation that many researchers in this area have is that if generally applicable and reliable damage simulation tools were available the dependence on certification testing could be lessened thereby reducing overall design cost. It is generally accepted that simulation tools if applied in this manner would still need to be thoroughly validated and that composite testing will never be completely replaced by analysis. Research and development is currently occurring at NASA to create numerical damage simulation tools applicable to damage in composites. The Advanced Composites Project (ACP) at NASA Langley has supported the development of composites damage simulation tools in a consortium of aerospace companies with a goal of reducing the certification time of a commercial aircraft by 30%. And while the scope of ACP does not include spacecraft, much of the methodology and simulation capabilities can apply to spacecraft certification in the Space Launch System and Orion programs as well. Some specific applications of composite damage simulation models in a certification program are (1) evaluation of damage during service when maintenance may be difficult or impossible, (2) a tool for early design iterations, (3) gaining insight into a particular damage process and applying this insight towards a test coupon or structural design, and (4) analysis of damage scenarios that are difficult or impossible to recreate in a test. As analysis capabilities improve, these applications and more will become realized resulting in a reduction in cost for use of composites in aerospace vehicles. NASA is engaged in this process from both research and application perspectives. In addition to the background information discussed previously, this presentation covers a look at recent research at NASA in this area and some current/potential applications in the Orion program.

Fracture mechanisms and fracture control in composite structures

NASA Astrophysics Data System (ADS)

Kim, Wone-Chul

Four basic failure modes--delamination, delamination buckling of composite sandwich panels, first-ply failure in cross-ply laminates, and compression failure--are analyzed using linear elastic fracture mechanics (LEFM) and the J-integral method. Structural failures, including those at the micromechanical level, are investigated with the aid of the models developed, and the critical strains for crack propagation for each mode are obtained. In the structural fracture analyses area, the fracture control schemes for delamination in a composite rib stiffener and delamination buckling in composite sandwich panels subjected to in-plane compression are determined. The critical fracture strains were predicted with the aid of LEFM for delamination and the J-integral method for delamination buckling. The use of toughened matrix systems has been recommended for improved damage tolerant design for delamination crack propagation. An experimental study was conducted to determine the onset of delamination buckling in composite sandwich panel containing flaws. The critical fracture loads computed using the proposed theoretical model and a numerical computational scheme closely followed the experimental measurements made on sandwich panel specimens of graphite/epoxy faceskins and aluminum honeycomb core with varying faceskin thicknesses and core sizes. Micromechanical models of fracture in composites are explored to predict transverse cracking of cross-ply laminates and compression fracture of unidirectional composites. A modified shear lag model which takes into account the important role of interlaminar shear zones between the 0 degree and 90 degree piles in cross-ply laminate is proposed and criteria for transverse cracking have been developed. For compressive failure of unidirectional composites, pre-existing defects play an important role. Using anisotropic elasticity, the stress state around a defect under a remotely applied compressive load is obtained. The experimentally observed complex compressive failure modes, such as shear crippling and pure compressive fiber failure of fibers are explained by the predicted stress distributions calculated in this work. These fracture analyses can be damage tolerant design methodology for composite structures. The proposed fracture criteria and the corresponding critical fracture strains provide the designer with quantitative guidelines for safe-life design. These have been incorporated into a fracture control plan for composite structures, which is also described. Currently, fracture control plans do not exist for composite structures; the proposed plan is a first step towards establishing fracture control and damage tolerant design methodology for this important class of materials.

Influence of Impact Damage on Carbon-Epoxy Stiffener Crippling

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.

2010-01-01

NASA, the Air Force Research Laboratory and The Boeing Company have worked to develop new low-cost, light-weight composite structures for aircraft. A Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept has been developed which offers advantages over traditional metallic structure. In this concept a stitched carbon-epoxy material system has been developed with the potential for reducing the weight and cost of transport aircraft structure by eliminating fasteners, thereby reducing part count and labor. By adding unidirectional carbon rods to the top of stiffeners, the panel becomes more structurally efficient. This combination produces a more damage tolerant design. This document describes the results of experimentation on PRSEUS specimens loaded in unidirectional compression subjected to impact damage and loaded in fatigue and to failure. A comparison with analytical predictions for pristine and damaged specimens is included.

Neutron Radiation Tolerance of Two Benchmark Thiophene-Based Conjugated Polymers: the Importance of Crystallinity for Organic Avionics.

PubMed

Paternò, G M; Robbiano, V; Fraser, K J; Frost, C; García Sakai, V; Cacialli, F

2017-01-23

Aviation and space applications can benefit significantly from lightweight organic electronics, now spanning from displays to logics, because of the vital importance of minimising payload (size and mass). It is thus crucial to assess the damage caused to such materials by cosmic rays and neutrons, which pose a variety of hazards through atomic displacements following neutron-nucleus collisions. Here we report the first study of the neutron radiation tolerance of two poly(thiophene)s-based organic semiconductors: poly(3-hexylthiophene-2,5-diyl), P3HT, and the liquid-crystalline poly(2,5-bis (3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene), PBTTT. We combine spectroscopic investigations with characterisation of intrinsic charge mobility to show that PBTTT exhibits significantly higher tolerance than P3HT. We explain this in terms of a superior chemical, structural and conformational stability of PBTTT, which can be ascribed to its higher crystallinity, in turn induced by a combination of molecular design features. Our approach can be used to develop design strategies for better neutron radiation-tolerant materials, thus paving the way for organic semiconductors to enter avionics and space applications.

Neutron Radiation Tolerance of Two Benchmark Thiophene-Based Conjugated Polymers: the Importance of Crystallinity for Organic Avionics

NASA Astrophysics Data System (ADS)

Paternò, G. M.; Robbiano, V.; Fraser, K. J.; Frost, C.; García Sakai, V.; Cacialli, F.

2017-01-01

Aviation and space applications can benefit significantly from lightweight organic electronics, now spanning from displays to logics, because of the vital importance of minimising payload (size and mass). It is thus crucial to assess the damage caused to such materials by cosmic rays and neutrons, which pose a variety of hazards through atomic displacements following neutron-nucleus collisions. Here we report the first study of the neutron radiation tolerance of two poly(thiophene)s-based organic semiconductors: poly(3-hexylthiophene-2,5-diyl), P3HT, and the liquid-crystalline poly(2,5-bis (3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene), PBTTT. We combine spectroscopic investigations with characterisation of intrinsic charge mobility to show that PBTTT exhibits significantly higher tolerance than P3HT. We explain this in terms of a superior chemical, structural and conformational stability of PBTTT, which can be ascribed to its higher crystallinity, in turn induced by a combination of molecular design features. Our approach can be used to develop design strategies for better neutron radiation-tolerant materials, thus paving the way for organic semiconductors to enter avionics and space applications.

Neutron Radiation Tolerance of Two Benchmark Thiophene-Based Conjugated Polymers: the Importance of Crystallinity for Organic Avionics

PubMed Central

Paternò, G. M.; Robbiano, V.; Fraser, K. J.; Frost, C.; García Sakai, V.; Cacialli, F.

2017-01-01

Aviation and space applications can benefit significantly from lightweight organic electronics, now spanning from displays to logics, because of the vital importance of minimising payload (size and mass). It is thus crucial to assess the damage caused to such materials by cosmic rays and neutrons, which pose a variety of hazards through atomic displacements following neutron-nucleus collisions. Here we report the first study of the neutron radiation tolerance of two poly(thiophene)s-based organic semiconductors: poly(3-hexylthiophene-2,5-diyl), P3HT, and the liquid-crystalline poly(2,5-bis (3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene), PBTTT. We combine spectroscopic investigations with characterisation of intrinsic charge mobility to show that PBTTT exhibits significantly higher tolerance than P3HT. We explain this in terms of a superior chemical, structural and conformational stability of PBTTT, which can be ascribed to its higher crystallinity, in turn induced by a combination of molecular design features. Our approach can be used to develop design strategies for better neutron radiation-tolerant materials, thus paving the way for organic semiconductors to enter avionics and space applications. PMID:28112195

Test and analysis results for composite transport fuselage and wing structures

NASA Technical Reports Server (NTRS)

Deaton, Jerry W.; Kullerd, Susan M.; Madan, Ram C.; Chen, Victor L.

1992-01-01

Automated tow placement (ATP) and stitching of dry textile composite preforms followed by resin transfer molding (RTM) are being studied as cost effective manufacturing processes for obtaining damage tolerant fuselage and wing structures for transport aircraft. Data are presented to assess the damage tolerance of ATP and RTM fuselage elements with stitched-on stiffeners from compression tests of impacted three J-stiffened panels and from stiffener pull-off tests. Data are also presented to assess the damage tolerance of RTM wing elements which had stitched skin and stiffeners from impacted single stiffener and three blade stiffened compression tests and stiffener pull-off tests.

Mitochondrial DNA repair and damage tolerance.

PubMed

Stein, Alexis; Sia, Elaine A

2017-01-01

The accurate maintenance of mitochondrial DNA (mtDNA) is required in order for eukaryotic cells to assemble a functional electron transport chain. This independently-maintained genome relies on nuclear-encoded proteins that are imported into the mitochondria to carry out replication and repair processes. Decades of research has made clear that mitochondria employ robust and varied mtDNA repair and damage tolerance mechanisms in order to ensure the proper maintenance of the mitochondrial genome. This review focuses on our current understanding of mtDNA repair and damage tolerance pathways including base excision repair, mismatch repair, homologous recombination, non-homologous end joining, translesion synthesis and mtDNA degradation in both yeast and mammalian systems.

Full-Scale Test and Analysis of a PRSEUS Fuselage Panel to Assess Damage-Containment Features

NASA Technical Reports Server (NTRS)

Bergan, Andrew; Bakuckas, John G.; Lovejoy, Andrew E.; Jegley, Dawn C.; Linton, Kim A.; Korkosz, Gregory; Awerbuch, Jonathan; Tan, Tein-Min

2011-01-01

Stitched composite technology has the potential to substantially decrease structural weight through enhanced damage containment capabilities. The most recent generation of stitched composite technology, the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept, has been shown to successfully arrest damage at the sub-component level through tension testing of a three stringer panel with damage in the form of a two-bay notch. In a joint effort undertaken by the National Aeronautics and Space Administration (NASA), the Federal Aviation Administration (FAA), and the Boeing Company, further studies are being conducted to characterize the damage containment features of the PRSEUS concept. A full-scale residual strength test will be performed on a fuselage panel to determine if the load capacity will meet strength, deformation, and damage tolerance requirements. A curved panel was designed, fabricated, and prepared for residual strength testing. A pre-test Finite Element Model (FEM) was developed using design allowables from previous test programs to predict test panel deformation characteristics and margins of safety. Three phases of testing with increasing damage severity include: (1) as manufactured; (2) barely visible impact damage (BVID) and visible impact damage (VID); and (3) discrete source damage (DSD) where the panel will be loaded to catastrophic failure. This paper presents the background information, test plan, and experimental procedure. This paper is the first of several future articles reporting the test preparations, results, and analysis conducted in the test program.

77 FR 50576 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures; OMB Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-22

... Composite Rotorcraft Structures; OMB Approval of Information Collection AGENCY: Federal Aviation... requirement contained in the FAA's final rule, ``Damage Tolerance and Fatigue Evaluation of Composite... and Fatigue Evaluation of Composite Rotorcraft Structures,'' published in the Federal Register (76 FR...

Cumulative herbivory outpaces compensation for early floral damage on a monocarpic perennial thistle

USDA-ARS?s Scientific Manuscript database

Floral herbivory presents a threat to plant reproductive success. Monocarpic plants should tolerate early apical damage with compensatory reproductive effort by subsequent flower heads during their single flowering season. However, the actual contribution of this tolerance response to net fitness is...

Transparency and damage tolerance of patternable omniphobic lubricated surfaces based on inverse colloidal monolayers

DOE PAGES

Vogel, Nicolas; Belisle, Rebecca A.; Hatton, Benjamin; ...

2013-07-31

A transparent coating that repels a wide variety of liquids, prevents staining, is capable of self-repair and is robust towards mechanical damage can have a broad technological impact, from solar cell coatings to self-cleaning optical devices. Here we employ colloidal templating to design transparent, nanoporous surface structures. A lubricant can be firmly locked into the structures and, owing to its fluidic nature, forms a defect-free, self-healing interface that eliminates the pinning of a second liquid applied to its surface, leading to efficient liquid repellency, prevention of adsorption of liquid-borne contaminants, and reduction of ice adhesion strength. We further show howmore » this method can be applied to locally pattern the repellent character of the substrate, thus opening opportunities to spatially confine any simple or complex fluids. The coating is highly defect-tolerant due to its interconnected, honeycomb wall structure, and repellency prevails after the application of strong shear forces and mechanical damage. The regularity of the coating allows us to understand and predict the stability or failure of repellency as a function of lubricant layer thickness and defect distribution based on a simple geometric model.« less

Improving glucose tolerance by muscle-damaging exercise.

PubMed

Ho, Chien-Te; Otaka, Machiko; Kuo, Chia-Hua

2017-04-01

Tissue damage is regarded as an unwanted medical condition to be avoided. However, introducing tolerable tissue damages has been used as a therapeutic intervention in traditional and complementary medicine to cure discomfort and illness. Eccentric exercise is known to cause significant necrosis and insulin resistance of skeletal muscle. The purpose of this study was to determine the magnitude of muscle damage and blood glucose responses during an oral glucose tolerance test (OGTT) after eccentric training in 21 young participants. They were challenged by 5 times of 100-meter downhill sprinting and 20 times of squats training at 30 pounds weight load for 3 days, which resulted in a wide spectrum of muscle creatine kinase (CK) surges in plasma, 48 h after the last bout of exercise. Participants were then divided into two groups according the magnitude of CK increases (low CK: +48% ± 0.3; high CK: +137% ± 0.5, P < 0.05). Both groups show comparable decreases in blood glucose levels in OGTT, suggesting that this muscle-damaging exercise does not appear to decrease but rather improve glycemic control in men. The result of the study rejects the hypothesis that eccentric exercise decreases glucose tolerance. Improved glucose tolerance with CK increase implicates a beneficial effect of replacing metabolically weaker muscle fibers by eccentric exercise in Darwinian natural selection fashion.

Detector Damage at X-Ray Free-Electron Laser Sources

NASA Astrophysics Data System (ADS)

Blaj, G.; Carini, G.; Carron, S.; Haller, G.; Hart, P.; Hasi, J.; Herrmann, S.; Kenney, C.; Segal, J.; Stan, C. A.; Tomada, A.

2016-06-01

Free-electron lasers (FELs) opened a new window on imaging the motion of atoms and molecules. At SLAC, FEL experiments are performed at LCLS using 120 Hz pulses with 1012 to 1013 photons in 10 fs (billions of times brighter than at the most powerful synchrotrons). Concurrently, users and staff operate under high pressure due to flexible and often rapidly changing setups and low tolerance for system malfunction. This extreme detection environment raises unique challenges, from obvious to surprising, and leads to treating detectors as consumables. We discuss in detail the detector damage mechanisms observed in 7 years of operation at LCLS, together with the corresponding damage mitigation strategies and their effectiveness. Main types of damage mechanisms already identified include: (1) x-ray radiation damage (from “catastrophic” to “classical”), (2) direct and indirect damage caused by optical lasers, (3) sample induced damage, (4) vacuum related damage, (5) high-pressure environment. In total, 19 damage mechanisms have been identified. We also present general strategies for reducing damage risk or minimizing the impact of detector damage on the science program. These include availability of replacement parts and skilled operators and also careful planning, incident investigation resulting in updated designs, procedures and operator training.

Progressive failure methodologies for predicting residual strength and life of laminated composites

NASA Technical Reports Server (NTRS)

Harris, Charles E.; Allen, David H.; Obrien, T. Kevin

1991-01-01

Two progressive failure methodologies currently under development by the Mechanics of Materials Branch at NASA Langley Research Center are discussed. The damage tolerance/fail safety methodology developed by O'Brien is an engineering approach to ensuring adequate durability and damage tolerance by treating only delamination onset and the subsequent delamination accumulation through the laminate thickness. The continuum damage model developed by Allen and Harris employs continuum damage laws to predict laminate strength and life. The philosophy, mechanics framework, and current implementation status of each methodology are presented.

Tough and deformable glasses with bioinspired cross-ply architectures.

PubMed

Yin, Zhen; Dastjerdi, Ahmad; Barthelat, Francois

2018-05-15

Glasses are optically transparent, hard materials that have been in sustained demand and usage in architectural windows, optical devices, electronics and solar panels. Despite their outstanding optical qualities and durability, their brittleness and low resistance to impact still limits wider applications. Here we present new laminated glass designs that contain toughening cross-ply architectures inspired from fish scales and arthropod cuticles. This seemingly minor enrichment completely transforms the way laminated glass deforms and fractures, and it turns a traditionally brittle material into a stretchy and tough material with little impact on surface hardness and optical quality. Large ply rotation propagates over large volumes, and localization is delayed in tension, even if a strain softening interlayer is used, in a remarkable mechanism which is generated by the kinematics of the plies and geometrical hardening. Compared to traditional laminated glass which degrades significantly in performance when damaged, our cross-ply architecture glass is damage-tolerant and 50 times tougher in energy terms. Despite the outstanding optical qualities and durability of glass, its brittleness and low resistance to impact still limits its wider application. Here we present new laminated glass designs that contain toughening cross-ply architectures inspired from fish scales and arthropod cuticles. Enriching laminated designs with crossplies completely transforms the material deforms and fractures, and turns a traditionally brittle material into a stretchy and tough material - with little impact on surface hardness and optical quality. Large ply rotation propagates over large volumes and localization is delayed in tension because of a remarkable and unexpected geometrical hardening effect. Compared to traditional laminated glass which degrades significantly in performance when damaged, our cross-ply architecture glass is damage-tolerant and it is 50 times tougher in energy terms. Our glass-based, transparent material is highly innovative and it is the first of its kind. We believe it will have impact in broad range of applications in construction, coatings, chemical engineering, electronics, photovoltaics. Copyright © 2018. Published by Elsevier Ltd.

The impact behaviour of silk cocoons.

PubMed

Chen, Fujia; Hesselberg, Thomas; Porter, David; Vollrath, Fritz

2013-07-15

Silk cocoons, constructed by silkmoths (Lepidoptera), are protective structural composites. Some cocoons appear to have evolved towards structural and material optimisation in order to sustain impact strikes from predators and hinder parasite ingress. This study investigates the protective properties of silk cocoons with different morphologies by evaluating their impact resistance and damage tolerance. Finite element analysis was used to analyse empirical observations of the quasi-static impact response of the silk cocoons, and to evaluate the separate benefits of the structures and materials through the deformation and damage mechanism. We use design principles from composite engineering in order to understand the structure-property-function relationship of silkworm cocoons. Understanding the highly evolved survival strategies of the organisms building natural cocoons will hopefully lead to inspiration that in turn could lead to improved composite design.

Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein

PubMed Central

Hashimoto, Takuma; Horikawa, Daiki D.; Saito, Yuki; Kuwahara, Hirokazu; Kozuka-Hata, Hiroko; Shin-I, Tadasu; Minakuchi, Yohei; Ohishi, Kazuko; Motoyama, Ayuko; Aizu, Tomoyuki; Enomoto, Atsushi; Kondo, Koyuki; Tanaka, Sae; Hara, Yuichiro; Koshikawa, Shigeyuki; Sagara, Hiroshi; Miura, Toru; Yokobori, Shin-ichi; Miyagawa, Kiyoshi; Suzuki, Yutaka; Kubo, Takeo; Oyama, Masaaki; Kohara, Yuji; Fujiyama, Asao; Arakawa, Kazuharu; Katayama, Toshiaki; Toyoda, Atsushi; Kunieda, Takekazu

2016-01-01

Tardigrades, also known as water bears, are small aquatic animals. Some tardigrade species tolerate almost complete dehydration and exhibit extraordinary tolerance to various physical extremes in the dehydrated state. Here we determine a high-quality genome sequence of Ramazzottius varieornatus, one of the most stress-tolerant tardigrade species. Precise gene repertoire analyses reveal the presence of a small proportion (1.2% or less) of putative foreign genes, loss of gene pathways that promote stress damage, expansion of gene families related to ameliorating damage, and evolution and high expression of novel tardigrade-unique proteins. Minor changes in the gene expression profiles during dehydration and rehydration suggest constitutive expression of tolerance-related genes. Using human cultured cells, we demonstrate that a tardigrade-unique DNA-associating protein suppresses X-ray-induced DNA damage by ∼40% and improves radiotolerance. These findings indicate the relevance of tardigrade-unique proteins to tolerability and tardigrades could be a bountiful source of new protection genes and mechanisms. PMID:27649274

Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein.

PubMed

Hashimoto, Takuma; Horikawa, Daiki D; Saito, Yuki; Kuwahara, Hirokazu; Kozuka-Hata, Hiroko; Shin-I, Tadasu; Minakuchi, Yohei; Ohishi, Kazuko; Motoyama, Ayuko; Aizu, Tomoyuki; Enomoto, Atsushi; Kondo, Koyuki; Tanaka, Sae; Hara, Yuichiro; Koshikawa, Shigeyuki; Sagara, Hiroshi; Miura, Toru; Yokobori, Shin-Ichi; Miyagawa, Kiyoshi; Suzuki, Yutaka; Kubo, Takeo; Oyama, Masaaki; Kohara, Yuji; Fujiyama, Asao; Arakawa, Kazuharu; Katayama, Toshiaki; Toyoda, Atsushi; Kunieda, Takekazu

2016-09-20

Tardigrades, also known as water bears, are small aquatic animals. Some tardigrade species tolerate almost complete dehydration and exhibit extraordinary tolerance to various physical extremes in the dehydrated state. Here we determine a high-quality genome sequence of Ramazzottius varieornatus, one of the most stress-tolerant tardigrade species. Precise gene repertoire analyses reveal the presence of a small proportion (1.2% or less) of putative foreign genes, loss of gene pathways that promote stress damage, expansion of gene families related to ameliorating damage, and evolution and high expression of novel tardigrade-unique proteins. Minor changes in the gene expression profiles during dehydration and rehydration suggest constitutive expression of tolerance-related genes. Using human cultured cells, we demonstrate that a tardigrade-unique DNA-associating protein suppresses X-ray-induced DNA damage by ∼40% and improves radiotolerance. These findings indicate the relevance of tardigrade-unique proteins to tolerability and tardigrades could be a bountiful source of new protection genes and mechanisms.

Lightweight Towed Howitzer Demonstrator. Phase 1 and Partial Phase 2. Volume A. Overview.

DTIC Science & Technology

1987-04-01

Reliability Floyd Manson............................... Test Plans Errol Quick................................. Systems Engrnq Coordi nati on Bob Schmidt ...FMC Structur*1 Verification o Beam stress calculations on the supporting trails which allow 70kpsi in a quasi-isotropic lay up of graphite epoxy...addressed utilizing a damage tolerant design criteria. o Strength calculations are questionable because of the dry room temperature values used. The

Advanced manufacturing development of a composite empennage component for L-1011 aircraft. Phase 4: Full scale ground test

NASA Technical Reports Server (NTRS)

Jackson, A. C.; Dorwald, F.

1982-01-01

The ground tests conducted on the advanced composite vertical fin (ACVF) program are described. The design and fabrication of the test fixture and the transition structure, static test of Ground Test Article (GTA) No. 1, rework of GTA No. 2, and static, damage tolerance, fail-safe and residual strength tests of GTA No. 2 are described.

AGARD Engine Disc Cooperative Test Programme, Addendum, (Rapport sur le Programme d’Essais Commun des DIsques Moteur (Supplement)

DTIC Science & Technology

1993-04-01

In-, 0- Sensbtng D recteur Scieintiiquce des Stnictures Chief Enggineer for Snztrur 0I’EMA IBB, Flu~amEueFEZ 29 -me de ]a Diision Lcderc POSifad 801160...lives. industry to enhance the safe-life design of rotating engine components by including The SMP/SC.33 subcommittee appointed a damage tolerant lifing

Improved damage tolerance of titanium by adhesive lamination

NASA Technical Reports Server (NTRS)

Johnson, W. S.

1982-01-01

Basic damage tolerance properties of Ti-6A1-4V titanium plate can be improved by laminating thin sheets of titanium with adhesives. Compact tension and center cracked tension specimens made from thick plate, thin sheet, and laminated plate (six plies of thin sheet) were tested. The fracture toughness of the laminated plate was 39 percent higher than the monolithic plate. The laminated plate's through the thickness crack growth rate was about 20 percent less than that of the monolithic plate. The damage tolerance life of the surface cracked laminate was 6 to over 15 times the life of a monolithic specimen. A simple method of predicting crack growth in a crack ply of a laminate is presented.

Evaluation of Fatigue Crack Growth and Fracture Properties of Cryogenic Model Materials

NASA Technical Reports Server (NTRS)

Newman, John A.; Forth, Scott C.; Everett, Richard A., Jr.; Newman, James C., Jr.; Kimmel, William M.

2002-01-01

The criteria used to prevent failure of wind-tunnel models and support hardware were revised as part of a project to enhance the capabilities of cryogenic wind tunnel testing at NASA Langley Research Center. Specifically, damage-tolerance fatigue life prediction methods are now required for critical components, and material selection criteria are more general and based on laboratory test data. The suitability of two candidate model alloys (AerMet 100 and C-250 steel) was investigated by obtaining the fatigue crack growth and fracture data required for a damage-tolerance fatigue life analysis. Finally, an example is presented to illustrate the newly implemented damage tolerance analyses required of wind-tunnel model system components.

Is sexual reproduction of high-mountain plants endangered by heat?

PubMed

Ladinig, Ursula; Pramsohler, Manuel; Bauer, Ines; Zimmermann, Sonja; Neuner, Gilbert; Wagner, Johanna

2015-04-01

Strong solar irradiation in combination with still air and dry soil can cause prostrate high-mountain plants to heat up considerably and ultimately suffer heat damage. Such heat damage has been repeatedly shown for vegetative structures, but not for reproductive structures, which we expected to be particularly vulnerable to heat. Heat effects on cold-adapted plants may increase with rising global temperatures and the predicted increase in heat waves. We have tested the heat tolerance of reproductive versus vegetative shoots at different reproductive stages, comparing ten common plant species from different elevation belts in the European Alps. Plant samples were exposed to temperatures in 2-K steps of 30 min each between 42 and 56 °C. Heat damage was assessed by visual rating and vital staining. Reproductive shoots were on average 2.5 K less heat tolerant (LT50, i.e. the mean temperature causing 50 % heat damage, 47.2 °C) than vegetative shoots (mean LT50 49.7 °C). Initial heat injuries (mean LT10) were observed at 43-45 °C in heat-susceptible species and at 45-47 °C in more heat-tolerant species, in at least one reproductive stage. Generally, heat tolerance was significantly higher during fruiting than during the bud stages and anthesis. Prostrate species with acaulescent buds and flowers tolerated heat better than those with caulescent buds and flowers. Petals were the most heat-susceptible plant structure and mature pollen the most heat tolerant. Based on these data, heat tolerance of reproductive structures appears to be adapted to the prevailing maximum temperatures which the plants experience during different reproductive stages in their environment. During hot spells, however, heat tolerance thresholds may be exceeded. More frequent heat waves would decrease the reproductive output and, consequently, the competitiveness of heat-susceptible species.

New discoveries linking transcription to DNA repair and damage tolerance pathways.

PubMed

Cohen, Susan E; Walker, Graham C

2011-01-01

In Escherichia coli, the transcription elongation factor NusA is associated with all elongating RNA polymerases where it functions in transcription termination and antitermination. Here, we review our recent results implicating NusA in the recruitment of DNA repair and damage tolerance mechanisms to sites of stalled transcription complexes.

Structural Performance of a Compressively Loaded Foam-Core Hat-Stiffened Textile Composite Panel

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Dexter, Benson H.

1996-01-01

A structurally efficient hat-stiffened panel concept that utilizes a structural foam as a stiffener core material has been designed and developed for aircraft primary structural applications. This stiffener concept is fabricated from textile composite material forms with a resin transfer molding process. This foam-filled hat-stiffener concept is structurally more efficient than most other prismatically stiffened panel configurations in a load range that is typical for both fuselage and wing structures. The panel design is based on woven/stitched and braided graphite-fiber textile preforms, an epoxy resin system, and Rohacell foam core. The structural response of this panel design was evaluated for its buckling and postbuckling behavior with and without low-speed impact damage. The results from single-stiffener and multi-stiffener specimen tests suggest that this structural concept responds to loading as anticipated and has excellent damage tolerance characteristics compared to a similar panel design made from preimpregnated graphite-epoxy tape material.

Evaluation of a Composite Sandwich Fuselage Side Panel with Damage and Subjected to Internal Pressure

NASA Technical Reports Server (NTRS)

Rouse, Marshall; Ambur, Damodar R.; Bodine, Jerry; Dopker, Bernhard

1997-01-01

The results from an experimental and analytical study of a composite sandwich fuselage side panel for a transport aircraft are presented. The panel has two window cutouts and three frames, and has been evaluated with internal pressure loads that generate biaxial tension loading conditions. Design limit load and design ultimate load tests have been performed on the graphite-epoxy sandwich panel with the middle frame removed to demonstrate the suitability of this two-frame design for supporting the prescribed biaxial loading conditions with twice the initial frame spacing of 20 inches. The two-frame panel was damaged by cutting a notch that originates at the edge of a cutout and extends in the panel hoop direction through the window-belt area. This panel with a notch was tested in a combined-load condition to demonstrate the structural damage tolerance at the design limit load condition. The two panel configurations successfully satisfied all design load requirements in the experimental part of the study, and the three-frame and two-frame panel responses are fully explained by the analysis results. The results of this study suggest that there is potential for using sandwich structural concepts with greater than the usual 20-in.-wide frame spacing to further reduce aircraft fuselage structural weight.

Enhancing radiation tolerance by controlling defect mobility and migration pathways in multicomponent single-phase alloys

DOE PAGES

Lu, Chenyang; Niu, Liangliang; Chen, Nanjun; ...

2016-12-15

A grand challenge in material science is to understand the correlation between intrinsic properties and defect dynamics. Radiation tolerant materials are in great demand for safe operation and advancement of nuclear and aerospace systems. Unlike traditional approaches that rely on microstructural and nanoscale features to mitigate radiation damage, this study demonstrates enhancement of radiation tolerance with the suppression of void formation by two orders magnitude at elevated temperatures in equiatomic single-phase concentrated solid solution alloys, and more importantly, reveals its controlling mechanism through a detailed analysis of the depth distribution of defect clusters and an atomistic computer simulation. The enhancedmore » swelling resistance is attributed to the tailored interstitial defect cluster motion in the alloys from a long-range one-dimensional mode to a short-range three-dimensional mode, which leads to enhanced point defect recombination. Finally, the results suggest design criteria for next generation radiation tolerant structural alloys.« less

Recent development in the design, testing and impact-damage tolerance of stiffened composite panels

NASA Technical Reports Server (NTRS)

Williams, J. G.; Anderson, M. S.; Rhodes, M. D.; Starnes, J. H., Jr.; Stroud, W. J.

1979-01-01

Structural technology of laminated filamentary-composite stiffened-panel structures under combined inplane and lateral loadings is discussed. Attention is focused on: (1) methods for analyzing the behavior of these structures under load and for determining appropriate structural proportions for weight-efficient configurations; and (2) effects of impact damage and geometric imperfections on structural performance. Recent improvements in buckling analysis involving combined inplane compression and shear loadings and transverse shear deformations are presented. A computer code is described for proportioning or sizing laminate layers and cross-sectional dimensions, and the code is used to develop structural efficiency data for a variety of configurations, loading conditions, and constraint conditions. Experimental data on buckling of panels under inplane compression is presented. Mechanisms of impact damage initiation and propagation are described.

Cell cycle stage-specific roles of Rad18 in tolerance and repair of oxidative DNA damage

PubMed Central

Yang, Yang; Durando, Michael; Smith-Roe, Stephanie L.; Sproul, Chris; Greenwalt, Alicia M.; Kaufmann, William; Oh, Sehyun; Hendrickson, Eric A.; Vaziri, Cyrus

2013-01-01

The E3 ubiquitin ligase Rad18 mediates tolerance of replication fork-stalling bulky DNA lesions, but whether Rad18 mediates tolerance of bulky DNA lesions acquired outside S-phase is unclear. Using synchronized cultures of primary human cells, we defined cell cycle stage-specific contributions of Rad18 to genome maintenance in response to ultraviolet C (UVC) and H2O2-induced DNA damage. UVC and H2O2 treatments both induced Rad18-mediated proliferating cell nuclear antigen mono-ubiquitination during G0, G1 and S-phase. Rad18 was important for repressing H2O2-induced (but not ultraviolet-induced) double strand break (DSB) accumulation and ATM S1981 phosphorylation only during G1, indicating a specific role for Rad18 in processing of oxidative DNA lesions outside S-phase. However, H2O2-induced DSB formation in Rad18-depleted G1 cells was not associated with increased genotoxin sensitivity, indicating that back-up DSB repair mechanisms compensate for Rad18 deficiency. Indeed, in DNA LigIV-deficient cells Rad18-depletion conferred H2O2-sensitivity, demonstrating functional redundancy between Rad18 and non-homologous end joining for tolerance of oxidative DNA damage acquired during G1. In contrast with G1-synchronized cultures, S-phase cells were H2O2-sensitive following Rad18-depletion. We conclude that although Rad18 pathway activation by oxidative lesions is not restricted to S-phase, Rad18-mediated trans-lesion synthesis by Polη is dispensable for damage-tolerance in G1 (because of back-up non-homologous end joining-mediated DSB repair), yet Rad18 is necessary for damage tolerance during S-phase. PMID:23295675

Assessment of the Damage Tolerance of Postbuckled Hat-Stiffened Panels Using Single-Stringer Specimens

NASA Technical Reports Server (NTRS)

Bisagni, Chiara; Vescovini, Riccardo; Davila, Carlos G.

2010-01-01

A procedure is proposed for the assessment of the damage tolerance and collapse of stiffened composite panels using a single-stringer compression specimen. The dimensions of the specimen are determined such that the specimen s nonlinear response and collapse are representative of an equivalent multi-stringer panel in compression. Experimental tests are conducted on specimens with and without an embedded delamination. A shell-based finite element model with intralaminar and interlaminar damage capabilities is developed to predict the postbuckling response as well as the damage evolution from initiation to collapse.

Study on Damage Evaluation and Machinability of UD-CFRP for the Orthogonal Cutting Operation Using Scanning Acoustic Microscopy and the Finite Element Method.

PubMed

Wang, Dongyao; He, Xiaodong; Xu, Zhonghai; Jiao, Weicheng; Yang, Fan; Jiang, Long; Li, Linlin; Liu, Wenbo; Wang, Rongguo

2017-02-20

Owing to high specific strength and designability, unidirectional carbon fiber reinforced polymer (UD-CFRP) has been utilized in numerous fields to replace conventional metal materials. Post machining processes are always required for UD-CFRP to achieve dimensional tolerance and assembly specifications. Due to inhomogeneity and anisotropy, UD-CFRP differs greatly from metal materials in machining and failure mechanism. To improve the efficiency and avoid machining-induced damage, this paper undertook to study the correlations between cutting parameters, fiber orientation angle, cutting forces, and cutting-induced damage for UD-CFRP laminate. Scanning acoustic microscopy (SAM) was employed and one-/two-dimensional damage factors were then created to quantitatively characterize the damage of the laminate workpieces. According to the 3D Hashin's criteria a numerical model was further proposed in terms of the finite element method (FEM). A good agreement between simulation and experimental results was validated for the prediction and structural optimization of the UD-CFRP.

Study on Damage Evaluation and Machinability of UD-CFRP for the Orthogonal Cutting Operation Using Scanning Acoustic Microscopy and the Finite Element Method

PubMed Central

Wang, Dongyao; He, Xiaodong; Xu, Zhonghai; Jiao, Weicheng; Yang, Fan; Jiang, Long; Li, Linlin; Liu, Wenbo; Wang, Rongguo

2017-01-01

Owing to high specific strength and designability, unidirectional carbon fiber reinforced polymer (UD-CFRP) has been utilized in numerous fields to replace conventional metal materials. Post machining processes are always required for UD-CFRP to achieve dimensional tolerance and assembly specifications. Due to inhomogeneity and anisotropy, UD-CFRP differs greatly from metal materials in machining and failure mechanism. To improve the efficiency and avoid machining-induced damage, this paper undertook to study the correlations between cutting parameters, fiber orientation angle, cutting forces, and cutting-induced damage for UD-CFRP laminate. Scanning acoustic microscopy (SAM) was employed and one-/two-dimensional damage factors were then created to quantitatively characterize the damage of the laminate workpieces. According to the 3D Hashin’s criteria a numerical model was further proposed in terms of the finite element method (FEM). A good agreement between simulation and experimental results was validated for the prediction and structural optimization of the UD-CFRP. PMID:28772565

Materials and processes laboratory composite materials characterization task, part 1. Damage tolerance

NASA Technical Reports Server (NTRS)

Nettles, A. T.; Tucker, D. S.; Patterson, W. J.; Franklin, S. W.; Gordon, G. H.; Hart, L.; Hodge, A. J.; Lance, D. G.; Russel, S. S.

1991-01-01

A test run was performed on IM6/3501-6 carbon-epoxy in which the material was processed, machined into specimens, and tested for damage tolerance capabilities. Nondestructive test data played a major role in this element of composite characterization. A time chart was produced showing the time the composite material spent within each Branch or Division in order to identify those areas which produce a long turnaround time. Instrumented drop weight testing was performed on the specimens with nondestructive evaluation being performed before and after the impacts. Destructive testing in the form of cross-sectional photomicrography and compression-after-impact testing were used. Results show that the processing and machining steps needed to be performed more rapidly if data on composite material is to be collected within a reasonable timeframe. The results of the damage tolerance testing showed that IM6/3501-6 is a brittle material that is very susceptible to impact damage.

Burst annealing of high temperature GaAs solar cells

NASA Technical Reports Server (NTRS)

Brothers, P. R.; Horne, W. E.

1991-01-01

One of the major limitations of solar cells in space power systems is their vulnerability to radiation damage. One solution to this problem is to periodically heat the cells to anneal the radiation damage. Annealing was demonstrated with silicon cells. The obstacle to annealing of GaAs cells was their susceptibility to thermal damage at the temperatures required to completely anneal the radiation damage. GaAs cells with high temperature contacts and encapsulation were developed. The cells tested are designed for concentrator use at 30 suns AMO. The circular active area is 2.5 mm in diameter for an area of 0.05 sq cm. Typical one sun AMO efficiency of these cells is over 18 percent. The cells were demonstrated to be resistant to damage after thermal excursions in excess of 600 C. This high temperature tolerance should allow these cells to survive the annealing of radiation damage. A limited set of experiments were devised to investigate the feasibility of annealing these high temperature cells. The effect of repeated cycles of electron and proton irradiation was tested. The damage mechanisms were analyzed. Limitations in annealing recovery suggested improvements in cell design for more complete recovery. These preliminary experiments also indicate the need for further study to isolate damage mechanisms. The primary objective of the experiments was to demonstrate and quantify the annealing behavior of high temperature GaAs cells. Secondary objectives were to measure the radiation degradation and to determine the effect of repeated irradiation and anneal cycles.

Damage tolerance of bonded composite aircraft repairs for metallic structures

NASA Astrophysics Data System (ADS)

Clark, Randal John

This thesis describes the development and validation of methods for damage tolerance substantiation of bonded composite repairs applied to cracked plates. This technology is used to repair metal aircraft structures, offering improvements in fatigue life, cost, manufacturability, and inspectability when compared to riveted repairs. The work focuses on the effects of plate thickness and bending on repair life, and covers fundamental aspects of fracture and fatigue of cracked plates and bonded joints. This project falls under the UBC Bonded Composite Repair Program, which has the goal of certification and widespread use of bonded repairs in civilian air transportation. This thesis analyses the plate thickness and transverse stress effects on fracture of repaired plates and the related problem of induced geometrically nonlinear bending in unbalanced (single-sided) repairs. The author begins by developing a classification scheme for assigning repair damage tolerance substantiation requirements based upon stress-based adhesive fracture/fatigue criteria and the residual strength of the original structure. The governing equations for bending of cracked plates are then reformulated and line-spring models are developed for linear and nonlinear coupled bending and extension of reinforced cracks. The line-spring models were used to correct the Wang and Rose energy method for the determination of the long-crack limit stress intensity, and to develop a new interpolation model for repaired cracks of arbitrary length. The analysis was validated using finite element models and data from mechanical tests performed on hybrid bonded joints and repair specimens that are representative of an in-service repair. This work will allow designers to evaluate the damage tolerance of the repaired plate, the adhesive, and the composite patch, which is an airworthiness requirement under FAR (Federal Aviation Regulations) 25.571. The thesis concludes by assessing the remaining barriers to certification of bonded repairs, discussing the results of the analysis, and making suggestions for future work. The developed techniques should also prove to be useful for the analysis of fibre-reinforced metal laminates and other layered structures. Some concepts are general and should be useful in the analysis of any plate with large in-plane stress gradients that lead to significant transverse stresses.

Fault-Tolerant Sequencer Using FPGA-Based Logic Designs for Space Applications

DTIC Science & Technology

2013-12-01

Prototype Board SBU single bit upset SDK software development kit SDRAM synchronous dynamic random-access memory SEB single-event burnout ...current VHDL VHSIC hardware description language VHSIC very-high-speed integrated circuits VLSI very-large- scale integration VQFP very...transient pulse, called a single-event transient (SET), or even cause permanent damage to the device in the form of a burnout or gate rupture. The SEE

Design Manual for Impact Damage Tolerant Aircraft Structure. Addendum

DTIC Science & Technology

1988-03-01

Effective Flaw Size 20 22 Effective Flaws for Cubical Fragments Impacting Graphite/Epoxy Laminates 21 23 Effective Flaws for Aligned and Tumbled Armour ... armour -piercing projectiles impact, penetrate, and traverse a fuel tank and generate intensive pressure waves that act on the fuel tank. Since...eg. aerodynamic smoothnessflutter, etc.) and the repai concept (eag boiled repar external bonded pateh. flush scar bonded patch, etc., and (3) dhe

Development of a stitched/RFI composite transport wing

NASA Technical Reports Server (NTRS)

Kropp, Yury

1995-01-01

Development of a composite wing primary structure for commercial transport aircraft is being undertaken at McDonnell Douglas under NASA contract. The focus of the program is to design and manufacture a low cost composite wing which can effectively compete with conventional metal wing structures in terms of cost, weight, and ability to withstand damage. These goals are being accomplished by utilizing the stitched/RFI manufacturing process during which the dry fiber preforms consisting of several stacks of warp-knit material are stitched together, impregnated with resin and cured. The stitched/RFI wing skin panels have exceptional damage tolerance and fatigue characteristics, are easily repairable, and can carry higher gross stress than their metal counterparts. This paper gives an overview of the program, describes the key features of the composite wing design and addresses major issues on analysis and manufacturing.

Mathematical Modeling of Early Cellular Innate and Adaptive Immune Responses to Ischemia/Reperfusion Injury and Solid Organ Allotransplantation

PubMed Central

Day, Judy D.; Metes, Diana M.; Vodovotz, Yoram

2015-01-01

A mathematical model of the early inflammatory response in transplantation is formulated with ordinary differential equations. We first consider the inflammatory events associated only with the initial surgical procedure and the subsequent ischemia/reperfusion (I/R) events that cause tissue damage to the host as well as the donor graft. These events release damage-associated molecular pattern molecules (DAMPs), thereby initiating an acute inflammatory response. In simulations of this model, resolution of inflammation depends on the severity of the tissue damage caused by these events and the patient’s (co)-morbidities. We augment a portion of a previously published mathematical model of acute inflammation with the inflammatory effects of T cells in the absence of antigenic allograft mismatch (but with DAMP release proportional to the degree of graft damage prior to transplant). Finally, we include the antigenic mismatch of the graft, which leads to the stimulation of potent memory T cell responses, leading to further DAMP release from the graft and concomitant increase in allograft damage. Regulatory mechanisms are also included at the final stage. Our simulations suggest that surgical injury and I/R-induced graft damage can be well-tolerated by the recipient when each is present alone, but that their combination (along with antigenic mismatch) may lead to acute rejection, as seen clinically in a subset of patients. An emergent phenomenon from our simulations is that low-level DAMP release can tolerize the recipient to a mismatched allograft, whereas different restimulation regimens resulted in an exaggerated rejection response, in agreement with published studies. We suggest that mechanistic mathematical models might serve as an adjunct for patient- or sub-group-specific predictions, simulated clinical studies, and rational design of immunosuppression. PMID:26441988

Modulation of inflammation and disease tolerance by DNA damage response pathways.

PubMed

Neves-Costa, Ana; Moita, Luis F

2017-03-01

The accurate replication and repair of DNA is central to organismal survival. This process is challenged by the many factors that can change genetic information such as replication errors and direct damage to the DNA molecule by chemical and physical agents. DNA damage can also result from microorganism invasion as an integral step of their life cycle or as collateral damage from host defense mechanisms against pathogens. Here we review the complex crosstalk of DNA damage response and immune response pathways that might be evolutionarily connected and argue that DNA damage response pathways can be explored therapeutically to induce disease tolerance through the activation of tissue damage control processes. Such approach may constitute the missing pillar in the treatment of critical illnesses caused by multiple organ failure, such as sepsis and septic shock. © 2016 Federation of European Biochemical Societies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Chenyang; Niu, Liangliang; Chen, Nanjun

A grand challenge in material science is to understand the correlation between intrinsic properties and defect dynamics. Radiation tolerant materials are in great demand for safe operation and advancement of nuclear and aerospace systems. Unlike traditional approaches that rely on microstructural and nanoscale features to mitigate radiation damage, this study demonstrates enhancement of radiation tolerance with the suppression of void formation by two orders magnitude at elevated temperatures in equiatomic single-phase concentrated solid solution alloys, and more importantly, reveals its controlling mechanism through a detailed analysis of the depth distribution of defect clusters and an atomistic computer simulation. The enhancedmore » swelling resistance is attributed to the tailored interstitial defect cluster motion in the alloys from a long-range one-dimensional mode to a short-range three-dimensional mode, which leads to enhanced point defect recombination. Finally, the results suggest design criteria for next generation radiation tolerant structural alloys.« less

Fatigue Damage Mechanisms in Advanced Hybrid Titanium Composite Laminates

NASA Technical Reports Server (NTRS)

Johnson, W. Steven; Rhymer, Donald W.; St.Clair, Terry L. (Technical Monitor)

2000-01-01

Hybrid Titanium Composite Laminates (HTCL) are a type of hybrid composite laminate with promise for high-speed aerospace applications, specifically designed for improved damage tolerance and strength at high-temperature (350 F, 177 C). However, in previous testing, HTCL demonstrated a propensity to excessive delamination at the titanium/PMC interface following titanium cracking. An advanced HTCL has been constructed with an emphasis on strengthening this interface, combining a PETI-5/IM7 PMC with Ti-15-3 foils prepared with an alkaline-perborate surface treatment. This paper discusses how the fatigue capabilities of the "advanced" HTCL compare to the first generation HTCL which was not modified for interface optimization, in both tension-tension (R = 0.1) and tension-compression (R=-0.2). The advanced HTCL under did not demonstrate a significant improvement in fatigue life, in either tension-tension or tension-compression loading. However, the advanced HTCL proved much more damage tolerant. The R = 0.1 tests revealed the advanced HTCL to increase the fatigue life following initial titanium ply damage up to 10X that of the initial HTCL at certain stress levels. The damage progression following the initial ply damage demonstrated the effect of the strengthened PMC/titanium interface. Acetate film replication of the advanced HTCL edges showed a propensity for some fibers in the adjacent PMC layers to fail at the point of titanium crack formation, suppressing delamination at the Ti/PMC interface. The inspection of failure surfaces validated these findings, revealing PMC fibers bonded to the majority of the titanium surfaces. Tension compression fatigue (R = -0.2) demonstrated the same trends in cycles between initial damage and failure, damage progression, and failure surfaces. Moreover, in possessing a higher resistance to delamination, the advanced HTCL did not exhibit buckling following initial titanium ply cracking under compression unlike the initial HTCL.

Architectural design of diamond-like carbon coatings for long-lasting joint replacements.

PubMed

Liu, Yujing; Zhao, Xiaoli; Zhang, Lai-Chang; Habibi, Daryoush; Xie, Zonghan

2013-07-01

Surface engineering through the application of super-hard, low-friction coatings as a potential approach for increasing the durability of metal-on-metal replacements is attracting significant attention. In this study innovative design strategies are proposed for the development of diamond-like-carbon (DLC) coatings against the damage caused by wear particles on the joint replacements. Finite element modeling is used to analyze stress distributions induced by wear particles of different sizes in the newly-designed coating in comparison to its conventional monolithic counterpart. The critical roles of architectural design in regulating stress concentrations and suppressing crack initiation within the coatings is elucidated. Notably, the introduction of multilayer structure with graded modulus is effective in modifying the stress field and reducing the magnitude and size of stress concentrations in the DLC diamond-like-carbon coatings. The new design is expected to greatly improve the load-carrying ability of surface coatings on prosthetic implants, in addition to the provision of damage tolerance through crack arrest. Copyright © 2013 Elsevier B.V. All rights reserved.

Composite transport wing technology development: Design development tests and advanced structural concepts

NASA Technical Reports Server (NTRS)

Griffin, Charles F.; Harvill, William E.

1988-01-01

Numerous design concepts, materials, and manufacturing methods were investigated for the covers and spars of a transport box wing. Cover panels and spar segments were fabricated and tested to verify the structural integrity of design concepts and fabrication techniques. Compression tests on stiffened panels demonstrated the ability of graphite/epoxy wing upper cover designs to achieve a 35 percent weight savings compared to the aluminum baseline. The impact damage tolerance of the designs and materials used for these panels limits the allowable compression strain and therefore the maximum achievable weight savings. Bending and shear tests on various spar designs verified an average weight savings of 37 percent compared to the aluminum baseline. Impact damage to spar webs did not significantly degrade structural performance. Predictions of spar web shear instability correlated well with measured performance. The structural integrity of spars manufactured by filament winding equalled or exceeded those fabricated by hand lay-up. The information obtained will be applied to the design, fabrication, and test of a full-scale section of a wing box. When completed, the tests on the technology integration box beam will demonstrate the structural integrity of an advanced composite wing design which is 25 percent lighter than the metal baseline.

An Overview of Innovative Strategies for Fracture Mechanics at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Ransom, Jonathan B.; Glaessgen, Edward H.; Ratcliffe, James G.

2010-01-01

Engineering fracture mechanics has played a vital role in the development and certification of virtually every aerospace vehicle that has been developed since the mid-20th century. NASA Langley Research Center s Durability, Damage Tolerance and Reliability Branch has contributed to the development and implementation of many fracture mechanics methods aimed at predicting and characterizing damage in both metallic and composite materials. This paper presents a selection of computational, analytical and experimental strategies that have been developed by the branch for assessing damage growth under monotonic and cyclic loading and for characterizing the damage tolerance of aerospace structures

Controlling the self-organizing dynamics in a sandpile model on complex networks by failure tolerance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qi, Junjian; Pfenninger, Stefan

In this paper, we propose a strategy to control the self-organizing dynamics of the Bak-Tang-Wiesenfeld (BTW) sandpile model on complex networks by allowing some degree of failure tolerance for the nodes and introducing additional active dissipation while taking the risk of possible node damage. We show that the probability for large cascades significantly increases or decreases respectively when the risk for node damage outweighs the active dissipation and when the active dissipation outweighs the risk for node damage. By considering the potential additional risk from node damage, a non-trivial optimal active dissipation control strategy which minimizes the total cost inmore » the system can be obtained. Under some conditions the introduced control strategy can decrease the total cost in the system compared to the uncontrolled model. Moreover, when the probability of damaging a node experiencing failure tolerance is greater than the critical value, then no matter how successful the active dissipation control is, the total cost of the system will have to increase. This critical damage probability can be used as an indicator of the robustness of a network or system. Copyright (C) EPLA, 2015« less

Antioxidant enzymatic activity is linked to waterlogging stress tolerance in citrus.

PubMed

Arbona, Vicent; Hossain, Zahed; López-Climent, María F; Pérez-Clemente, Rosa M; Gómez-Cadenas, Aurelio

2008-04-01

Soil flooding constitutes a seasonal factor that negatively affects plant performance and crop yields. In this work, the relationship between oxidative damage and flooding sensitivity was addressed in three citrus genotypes with different abilities to tolerate waterlogging. We examined leaf visible damage, oxidative damage in terms of malondialdehyde (MDA) concentration, leaf proline concentration, leaf and root ascorbate and glutathione contents and the antioxidant enzyme activities superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11), catalase (EC 1.11.1.6) and glutathione reductase (EC 1.8.1.7). No differences in the extent of oxidative damage relative to controls were found among genotypes. However, a different ability to delay the apparition of oxidative damage was associated to a higher tolerance to waterlogging. This ability was linked to an enhanced activated oxygen species' scavenging capacity in terms of an increased antioxidant enzyme activity and higher content in polar antioxidant compounds. Therefore, the existence of a direct relationship between stress sensitivity and the early accumulation of MDA is proposed. In addition, data indicate that the protective role of proline has to be considered minimal as its accumulation was inversely correlated with tolerance to the stress. The positive antioxidant response in Carrizo citrange (Poncirus trifoliata L. Raf. x Citrus sinensis L. Osb.) and Citrumelo CPB 4475 (Poncirus trifoliata L. Raf. x Citrus paradisi L. Macf.) might be responsible for a higher tolerance to flooding stress, whereas in Cleopatra mandarin (Citrus reshni Hort. Ex Tan.), the early accumulation of MDA seems to be associated to an impaired ability for H2O2 scavenging.

Evaluation of a threshold-based model of fatigue in gamma titanium aluminide following impact damage

NASA Astrophysics Data System (ADS)

Harding, Trevor Scott

2000-10-01

Recent interest in gamma titanium aluminide (gamma-TiAl) for use in gas turbine engine applications has centered on the low density and good elevated temperature strength retention of gamma-TiAl compared to current materials. However, the relatively low ductility and fracture toughness of gamma-TiAl leads to serious concerns regarding its ability to resist impact damage. Furthermore, the limited fatigue crack growth resistance of gamma-TiAl means that the potential for fatigue failures resulting from impact damage is real if a damage tolerant design approach is used. A threshold-based design approach may be required if fatigue crack growth from potential impact sites is to be avoided. The objective of the present research is to examine the feasibility of a threshold-based approach for the design of a gamma-TiAl low-pressure turbine blade subjected to both assembly-related impact damage and foreign object damage. Specimens of three different gamma-TiAl alloys were damaged in such a way as to simulate anticipated impact damage for a turbine blade. Step-loading fatigue tests were conducted at both room temperature and 600°C. In terms of the assembly-related impact damage, the results indicate that there is reasonably good agreement between the threshold-based predictions of the fatigue strength of damaged specimens and the measured data. However, some discrepancies do exist. In the case of very lightly damaged specimens, prediction of the resulting fatigue strength requires that a very conservative small-crack fatigue threshold be used. Consequently, the allowable design conditions are significantly reduced. For severely damaged specimens, an analytical approach found that the potential effects of residual stresses may be related to the discrepancies observed between the threshold-based model and measured fatigue strength data. In the case of foreign object damage, a good correlation was observed between impacts resulting in large cracks and a long-crack threshold-based approximation of the fatigue strength. However, in the case of smaller impact sites, a lower small-crack threshold appears to be more appropriate. In some cases, a complete perforation of the material, or blowout, would result from the impact. Prediction of the reduction in fatigue strength resulting from this form of damage required the use of a stress concentration factor, rather than a threshold-based prediction.

Damage Mechanisms and Mechanical Properties of High-Strength Multiphase Steels.

PubMed

Heibel, Sebastian; Dettinger, Thomas; Nester, Winfried; Clausmeyer, Till; Tekkaya, A Erman

2018-05-09

The usage of high-strength steels for structural components and reinforcement parts is inevitable for modern car-body manufacture in reaching lightweight design as well as increasing passive safety. Depending on their microstructure these steels show differing damage mechanisms and various mechanical properties which cannot be classified comprehensively via classical uniaxial tensile testing. In this research, damage initiation, evolution and final material failure are characterized for commercially produced complex-phase (CP) and dual-phase (DP) steels in a strength range between 600 and 1000 MPa. Based on these investigations CP steels with their homogeneous microstructure are characterized as damage tolerant and hence less edge-crack sensitive than DP steels. As final fracture occurs after a combination of ductile damage evolution and local shear band localization in ferrite grains at a characteristic thickness strain, this strain measure is introduced as a new parameter for local formability. In terms of global formability DP steels display advantages because of their microstructural composition of soft ferrite matrix including hard martensite particles. Combining true uniform elongation as a measure for global formability with the true thickness strain at fracture for local formability the mechanical material response can be assessed on basis of uniaxial tensile testing incorporating all microstructural characteristics on a macroscopic scale. Based on these findings a new classification scheme for the recently developed high-strength multiphase steels with significantly better formability resulting of complex underlying microstructures is introduced. The scheme overcomes the steel designations using microstructural concepts, which provide no information about design and production properties.

Aldehyde dehydrogenase 2 protects human umbilical vein endothelial cells against oxidative damage and increases endothelial nitric oxide production to reverse nitroglycerin tolerance.

PubMed

Hu, X Y; Fang, Q; Ma, D; Jiang, L; Yang, Y; Sun, J; Yang, C; Wang, J S

2016-06-10

Medical nitroglycerin (glyceryl trinitrate, GTN) use is limited principally by tolerance typified by a decrease in nitric oxide (NO) produced by biotransformation. Such tolerance may lead to endothelial dysfunction by inducing oxidative stress. In vivo studies have demonstrated that aldehyde dehydrogenase 2 (ALDH2) plays important roles in GTN biotransformation and tolerance. Thus, modification of ALDH2 expression represents a potentially effective strategy to prevent and reverse GTN tolerance and endothelial dysfunction. In this study, a eukaryotic expression vector containing the ALDH2 gene was introduced into human umbilical vein endothelial cells (HUVECs) by liposome-mediated transfection. An indirect immunofluorescence assay showed that ALDH2 expression increased 24 h after transfection. Moreover, real-time polymerase chain reaction and western blotting revealed significantly higher ALDH2 mRNA and protein expression in the gene-transfected group than in the two control groups. GTN tolerance was induced by treating HUVECs with 10 mM GTN for 16 h + 10 min, which significantly decreased NO levels in control cells, but not in those transfected with ALDH2. Overexpression of ALDH2 increased cell survival against GTN-induced cytotoxicity and conferred protection from oxidative damage resulting from nitrate tolerance, accompanied by decreased production of intracellular reactive oxygen species and reduced expression of heme oxygenase 1. Furthermore, ALDH2 overexpression promoted Akt phosphorylation under GTN tolerance conditions. ALDH2 gene transfection can reverse and prevent tolerance to GTN through its bioactivation and protect against oxidative damage, preventing the development of endothelial dysfunction.

A unified technology plan for fatigue and fracture design

NASA Technical Reports Server (NTRS)

Hardrath, H. F.

1973-01-01

An integrated research program is proposed that seeks to improve the technology of designing against fatigue and fracture and to develop a computerized capability for assessing the adequacy of a given design. Both fatigue life prediction and damage tolerance considerations are incorporated. The research for each of these considerations is organized to account for material behavior, the effect of structural configurations, the cumulative effects of the operating loadings, and for the effects of environment - temperature and corrosion. The goal is to achieve a viable fatigue and fracture design procedure for any practical problem. The overall program is outlined, assessments are made of the state of the art, subgoals are proposed, and means for achieving them are suggested.

Review of fatigue and fracture research at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Everett, Richard A., Jr.

1988-01-01

Most dynamic components in helicopters are designed with a safe-life constant-amplitude testing approach that has not changed in many years. In contrast, the fatigue methodology in other industries has advanced significantly in the last two decades. Recent research at the NASA Langley Research Center and the U.S. Army Aerostructures Directorate at Langley are reviewed relative to fatigue and fracture design methodology for metallic components. Most of the Langley research was directed towards the damage tolerance design approach, but some work was done that is applicable to the safe-life approach. In the areas of testing, damage tolerance concepts are concentrating on the small-crack effect in crack growth and measurement of crack opening stresses. Tests were conducted to determine the effects of a machining scratch on the fatigue life of a high strength steel. In the area of analysis, work was concentrated on developing a crack closure model that will predict fatigue life under spectrum loading for several different metal alloys including a high strength steel that is often used in the dynamic components of helicopters. Work is also continuing in developing a three-dimensional, finite-element stress analysis for cracked and uncracked isotropic and anisotropic structures. A numerical technique for solving simultaneous equations called the multigrid method is being pursued to enhance the solution schemes in both the finite-element analysis and the boundary element analysis. Finally, a fracture mechanics project involving an elastic-plastic finite element analysis of J-resistance curve is also being pursued.

Damage to the microbial cell membrane during pyrolytic sugar utilization and strategies for increasing resistance.

PubMed

Jin, Tao; Rover, Marjorie R; Petersen, Elspeth M; Chi, Zhanyou; Smith, Ryan G; Brown, Robert C; Wen, Zhiyou; Jarboe, Laura R

2017-09-01

Lignocellulosic biomass is an appealing feedstock for the production of biorenewable fuels and chemicals, and thermochemical processing is a promising method for depolymerizing it into sugars. However, trace compounds in this pyrolytic sugar syrup are inhibitory to microbial biocatalysts. This study demonstrates that hydrophobic inhibitors damage the cell membrane of ethanologenic Escherichia coli KO11+lgk. Adaptive evolution was employed to identify design strategies for improving pyrolytic sugar tolerance and utilization. Characterization of the resulting evolved strain indicates that increased resistance to the membrane-damaging effects of the pyrolytic sugars can be attributed to a glutamine to leucine mutation at position 29 of carbon storage regulator CsrA. This single amino acid change is sufficient for decreasing EPS protein production and increasing membrane integrity when exposed to pyrolytic sugars.

Damage Tolerance and Reliability of Turbine Engine Components

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1999-01-01

A formal method is described to quantify structural damage tolerance and reliability in the presence of multitude of uncertainties in turbine engine components. The method is based at the materials behaviour level where primitive variables with their respective scatters are used to describe the behavior. Computational simulation is then used to propagate those uncertainties to the structural scale where damage tolerance and reliability are usually specified. Several sample cases are described to illustrate the effectiveness, versatility, and maturity of the method. Typical results from these methods demonstrate that the methods are mature and that they can be used for future strategic projections and planning to assure better, cheaper, faster, products for competitive advantages in world markets. These results also indicate that the methods are suitable for predicting remaining life in aging or deteriorating structures.

Damage Tolerance and Reliability of Turbine Engine Components

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1998-01-01

A formal method is described to quantify structural damage tolerance and reliability in the presence of multitude of uncertainties in turbine engine components. The method is based at the materials behavior level where primitive variables with their respective scatters are used to describe that behavior. Computational simulation is then used to propagate those uncertainties to the structural scale where damage tolerance and reliability are usually specified. Several sample cases are described to illustrate the effectiveness, versatility, and maturity of the method. Typical results from these methods demonstrate that the methods are mature and that they can be used for future strategic projections and planning to assure better, cheaper, faster products for competitive advantages in world markets. These results also indicate that the methods are suitable for predicting remaining life in aging or deteriorating structures.

Interactive effects of juvenile defoliation, light conditions, and interspecific competition on growth and ectomycorrhizal colonization of Fagus sylvatica and Pinus sylvestris seedlings.

PubMed

Trocha, Lidia K; Weiser, Ewa; Robakowski, Piotr

2016-01-01

Seedlings of forest tree species are exposed to a number of abiotic (organ loss or damage, light shortage) and biotic (interspecific competition) stress factors, which may lead to an inhibition of growth and reproduction and, eventually, to plant death. Growth of the host and its mycorrhizal symbiont is often closely linked, and hence, host damage may negatively affect the symbiont. We designed a pot experiment to study the response of light-demanding Pinus sylvestris and shade-tolerant Fagus sylvatica seedlings to a set of abiotic and biotic stresses and subsequent effects on ectomycorrhizal (ECM) root tip colonization, seedling biomass, and leaf nitrogen content. The light regime had a more pronounced effect on ECM colonization than did juvenile damage. The interspecific competition resulted in higher ECM root tip abundance for Pinus, but this effect was insignificant in Fagus. Low light and interspecific competition resulted in lower seedling biomass compared to high light, and the effect of the latter was partially masked by high light. Leaf nitrogen responded differently in Fagus and Pinus when they grew in interspecific competition. Our results indicated that for both light-demanding (Pinus) and shade-tolerant (Fagus) species, the light environment was a major factor affecting seedling growth and ECM root tip abundance. The light conditions favorable for the growth of seedlings may to some extent compensate for the harmful effects of juvenile organ loss or damage and interspecific competition.

Probabilistic Evaluation of Blade Impact Damage

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Abumeri, G. H.

2003-01-01

The response to high velocity impact of a composite blade is probabilistically evaluated. The evaluation is focused on quantifying probabilistically the effects of uncertainties (scatter) in the variables that describe the impact, the blade make-up (geometry and material), the blade response (displacements, strains, stresses, frequencies), the blade residual strength after impact, and the blade damage tolerance. The results of probabilistic evaluations results are in terms of probability cumulative distribution functions and probabilistic sensitivities. Results show that the blade has relatively low damage tolerance at 0.999 probability of structural failure and substantial at 0.01 probability.

Titanium Damage Tolerant Design Data for Propulsion Systems

DTIC Science & Technology

1977-08-01

for the threshold and 30 Hz tests were measured using cellulose acetate tape replicas with an accuracy of 0.001 in. (0.0025 mm) for changes in crack...monitored with the traveling telescope and verified with cellulose acetate tape replicas. Testing was performed in load control on servo-hydraulic...34 Contract F33615-75-C-5064, First Semiannual Report, AFML, December 1975. 2. Erdogan F. and M. Ratwani, "Fatigue and Fracture of Cylindrical Shells

A native plant competitor mediates the impact of above- and belowground damage on an invasive tree.

PubMed

Carrillo, Juli; Siemann, Evan

2016-10-01

Plant competition may mediate the impacts of herbivory on invasive plant species through effects on plant growth and defense. This may predictably depend on whether herbivory occurs above or below ground and on relative plant competitive ability. We simulated the potential impact of above- or belowground damage by biocontrol agents on the growth of a woody invader (Chinese tallow tree, Triadica sebifera) through artificial herbivory, with or without competition with a native grass, little bluestem (Schizachyrium scoparium). We measured two defense responses of Triadica through quantifying constitutive and induced extrafloral nectar production and tolerance of above- and belowground damage (root and shoot biomass regrowth). We examined genetic variation in plant growth and defense across native (China) and invasive (United States) Triadica populations. Without competition, aboveground damage had a greater impact than belowground damage on Triadica performance, whereas with competition and above- and belowground damage impacted Triadica similarly. Whole plant tolerance to damage below ground was negatively associated with tolerance to grass competitors indicating tradeoffs in the ability to tolerate herbivory vs. compete. Competition reduced investment in defensive extrafloral nectar (EFN) production. Aboveground damage inhibited rather than induced EFN production while belowground plant damage did not impact aboveground nectar production. We found some support for the evolution of increased competitive ability hypothesis for invasive plants as United States plants were larger than native China plants and were more plastic in their response to biotic stressors than China plants (they altered their root to shoot ratios dependent on herbivory and competition treatments). Our results indicate that habitat type and the presence of competitors may be a larger determinant of herbivory impact than feeding mode and suggest that integrated pest management strategies including competitive dynamics of recipient communities should be incorporated into biological control agent evaluation at earlier stages. © 2016 by the Ecological Society of America.

Technology of civil usage of composites. [in commercial aircraft structures

NASA Technical Reports Server (NTRS)

Kemp, D. E.

1977-01-01

The paper deals with the use of advanced composites in structural components of commercial aircraft. The need for testing the response of a material system to service environment is discussed along with methods for evaluating design and manufacturing aspects of a built-up structure under environmental conditions and fail-safe (damage-tolerance) evaluation of structures. Crashworthiness aspects, the fire-hazard potential, and electrical damage of composite structures are considered. Practical operational experience with commercial aircraft is reviewed for boron/epoxy foreflaps, Kevlar/epoxy fillets and fairings, graphite/epoxy spoilers, graphite/polysulfone spoilers, graphite/epoxy floor posts, boron/aluminum aft pylon skin panels, graphite/epoxy engine nose cowl outer barrels, and graphite/epoxy upper aft rudder segments.

Tensile strength of composite sheets with unidirectional stringers and crack-like damage: A brief report

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1984-01-01

The residual strength of composite sheets with bonded composite stringers loaded in tension was determined. The results are summarized. About 50 graphite/epoxy composite panels with crack-like slots were monotonically loaded in tension to failure. Both sheet layup and stringer configuration were varied. The composite panels have considerable damage tolerance. The stringers arrested cracks that ran from the crack-like slots, and the residual strengths were considerably greater than those of unstiffened composite sheets. A stress-intensity factor analysis was developed to predict the failing strains of the stiffened panels. Using the analysis, a single design curve was produced for composite sheets with bonded stringers of any configuration.

A Comparison of Quasi-Static Indentation and Drop-Weight Impact Testing on Carbon-Epoxy Laminates

NASA Technical Reports Server (NTRS)

Prabhakaran, R.

2001-01-01

The project had two objectives: 1) The primary objective was to characterize damage tolerance of composite materials. To accomplish this, polymer matrix composites were to be subjected to static indentation as well as low-velocity impacts and the results analyzed. 2) A second objective was to investigate the effects of laser shock peening on the damage tolerance of aerospace materials, such as aluminum alloys, in terms of crack nucleation and crack propagation. The impact testing was proposed to be performed using a Dynatup drop tower. The specimens were to be placed over a square opening in a steel platen and impacted with a hemispherical tup. The damage was to be characterized in the laminate specimens. The damage tolerance of aerospace alloys was to be studied by conducting fatigue tests on aluminum alloy specimens with prior shock peening treatment. The crack length was to be monitored by a microscope and the crack propagation rate, da/dN, determined.

Minimizing the regrets of long-term urban floodplain management decisions under deeply uncertain climate change

NASA Astrophysics Data System (ADS)

Hecht, J. S.; Kirshen, P. H.; Vogel, R. M.

2016-12-01

Making long-term floodplain management decisions under uncertain climate change is a major urban planning challenge of the 21stcentury. To support these efforts, we introduce a screening-level optimization model that identifies adaptation portfolios by minimizing the regrets associated with their flood-control and damage costs under different climate change trajectories that are deeply uncertain, i.e. have probabilities that cannot be specified plausibly. This mixed integer program explicitly considers the coupled damage-reduction impacts of different floodwall designs and property-scale investments (first-floor elevation, wet floodproofing of basements, permanent retreat and insurance), recommends implementation schedules, and assesses impacts to stakeholders residing in three types of homes. An application to a stylized municipality illuminates many nonlinear system dynamics stemming from large fixed capital costs, infrastructure design thresholds, and discharge-depth-damage relationships. If stakeholders tolerate mild damage, floodwalls that fully protect a community from large design events are less cost-effective than portfolios featuring both smaller floodwalls and property-scale measures. Potential losses of property tax revenue from permanent retreat motivate municipal property-tax initiatives for adaptation financing. Yet, insurance incentives for first-floor elevation may discourage locally financed floodwalls, in turn making lower-income residents more vulnerable to severe flooding. A budget constraint analysis underscores the benefits of flexible floodwall designs with low incremental expansion costs while near-optimal solutions demonstrate the scheduling flexibility of many property-scale measures. Finally, an equity analysis shows the importance of evaluating the overpayment and under-design regrets of recommended adaptation portfolios for each stakeholder and contrasts them to single-scenario model results.

Radiation tolerant passive and active optical fiber products for use in space environments

NASA Astrophysics Data System (ADS)

Hill, Mark; Hankey, Judith; Gray, Rebecca

2017-11-01

This paper reports the radiation performance results of several new product types designed for high radiation environments. The products tested include radiation hardened highly birefringent (HiBi) passive products for polarised applications and radiation tolerant active erbium doped fiber products for amplifiers. Radiation hardened, short beatlength HiBi fiber products have been developed for high accuracy polarisation maintaining (PM) gyros and sensors at both 1310nm and 1550nm operation in the space environment. The fibers have been tested up to 5kGy (500krad) - levels which could be expected in extreme, extra-terrestrial space environments. Results show a consistently low Radiation Induced Attenuation (RIA) of <7dB/km at 5kGy, giving a RIA value of 1.37×10-2 dB/km/krad at 1550nm for this product range. Radiation tolerant EDF AstroGain™ fibers are intended for use in multichannel amplifiers in optical intersatellite communications. The structure of the fibers have been designed to deliver an accelerated recovery of radiation damage through photo-annealing using only the residual energy already available in an amplifier using a 980nm pumping regime. These products have been tested up to 200Gy (20krad) - levels which can be expected in Earth orbit environments over a 20-30 mission lifetime. Results show up to 100% recovery under continuous use for dose rates of 0.11rad/hr. It has also been demonstrated through analysis of the optical spectral output that this effect reverses the gain tilt, or spectral narrowing, induced by radiation damage through the C and L band. These combined fiber characteristics allow performance stability of the amplifier over the lifetime of the space mission.

Mechanisms of DNA damage, repair and mutagenesis

PubMed Central

Chatterjee, Nimrat; Walker, Graham C.

2017-01-01

Living organisms are continuously exposed to a myriad of DNA damaging agents that can impact health and modulate disease-states. However, robust DNA repair and damage-bypass mechanisms faithfully protect the DNA by either removing or tolerating the damage to ensure an overall survival. Deviations in this fine-tuning are known to destabilize cellular metabolic homeostasis, as exemplified in diverse cancers where disruption or deregulation of DNA repair pathways results in genome instability. Because routinely used biological, physical and chemical agents impact human health, testing their genotoxicity and regulating their use have become important. In this introductory review, we will delineate mechanisms of DNA damage and the counteracting repair/tolerance pathways to provide insights into the molecular basis of genotoxicity in cells that lays the foundation for subsequent articles in this issue. PMID:28485537

Tolerance and resistance of invasive and native Eupatorium species to generalist herbivore insects

NASA Astrophysics Data System (ADS)

Wang, Rui-Fang; Feng, Yu-Long

2016-11-01

Invasive plants are exotic species that escape control by native specialist enemies. However, exotic plants may still be attacked by locally occurring generalist enemies, which can influence the dynamics of biological invasions. If invasive plants have greater defensive (resistance and tolerance) capabilities than indigenous plants, they may experience less damage from native herbivores. In the present study, we tested this prediction using the invasive plant Eupatorium adenophorum and two native congeners under simulated defoliation and generalist herbivore insect (Helicoverpa armigera and Spodoptera litura) treatments. E. adenophorum was less susceptible and compensated more quickly to damages in biomass production from both treatments compared to its two congeners, exhibiting greater herbivore tolerance. This strong tolerance to damage was associated with greater resource allocation to aboveground structures, leading to a higher leaf area ratio and a lower root: crown mass ratio than those of its native congeners. E. adenophorum also displayed a higher resistance index (which integrates acid detergent fiber, nitrogen content, carbon/nitrogen ratio, leaf mass per area, toughness, and trichome density) than its two congeners. Thus, H. armigera and S. litura performed poorly on E. adenophorum, with less leaf damage, a lengthened insect developmental duration, and decreased pupating: molting ratios compared to those of the native congeners. Strong tolerance and resistance traits may facilitate the successful invasion of E. adenophorum in China and may decrease the efficacy of leaf-feeding biocontrol agents. Our results highlight both the need for further research on defensive traits and their role in the invasiveness and biological control of exotic plants, and suggest that biocontrol of E. adenophorum in China would require damage to the plant far in excess of current levels.

A novel system for in situ determination of heat tolerance of plants: first results on alpine dwarf shrubs

PubMed Central

2013-01-01

Background Heat stress and heat damage to plants gain globally increasing importance for crop production and plant survival in endangered habitats. Therefore the knowledge of heat tolerance of plants is of great interest. As many heat tolerance measurement procedures require detachment of plants and protocols expose samples to various heat temperatures in darkness, the ecological relevance of such results may be doubted. To overcome these constraints we designed a novel field compatible Heat Tolerance Testing System (HTTS) that opens the opportunity to induce controlled heat stress on plants in situ under full natural solar irradiation. Subsequently, heat tolerance can be evaluated by a variety of standard viability assays like the electrolyte leakage test, chlorophyll fluorescence measurements and visual assessment methods. Furthermore, recuperation can be studied under natural environmental conditions which is impossible when detached plant material is used. First results obtained on three alpine dwarf - shrubs are presented. Results When heat tolerance of Vaccinium gaultherioides Bigelow was tested with the HTTS in situ, the visual assessment of leaves showed 50% heat injury (LT50) at 48.3°C, while on detached leaves where heat exposure took place in small heat chambers this already happened at 45.8°C. Natural solar irradiation being applied during heat exposure in the HTTS had significantly protective effects: In Loiseleuria procumbens L. (Desv.), if heat exposure (in situ) took place in darkness, leaf heat tolerance was 50.6°C. In contrast, when heat exposure was conducted under full natural solar irradiation heat tolerance was increased to 53.1°C. In Rhododendron ferrugineum L. heat tolerance of leaves was 42.5°C if the exposure took place ex situ and in darkness, while it was significantly increased to 45.8°C when this happened in situ under natural solar irradiation. Conclusions The results obtained with the HTTS tested in the field indicate a mitigating effect of natural solar irradiation during heat exposure. Commonly used laboratory based measurement procedures expose samples in darkness and seem to underestimate leaf heat tolerance. Avoidance of detachment by the use of the HTTS allows studying heat tolerance and recuperation processes in the presence of interacting external abiotic, biotic and genetic factors under field conditions. The investigation of combined effects of heat exposure under full solar irradiation, of recuperation and repair processes but also of possible damage amplification into the results with the HTTS appears to be particularly useful as it allows determining heat tolerance of plants with a considerably high ecological significance. PMID:23497517

Behavior of Frame-Stiffened Composite Panels with Damage

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.

2013-01-01

NASA, the Air Force Research Laboratory and The Boeing Company have worked to develop new low-cost, light-weight composite structures for aircraft. A Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept has been developed which offers advantages over traditional metallic structures. In this concept, a stitched carbon-epoxy material system has been developed with the potential for reducing the weight and cost of transport aircraft structure by eliminating fasteners, thereby reducing part count and labor. Stitching and the use of thin skins with rod-stiffeners to move loading away from the morevulnerable outer surface produces a structurally efficient, damage tolerant design. This study focuses on the behavior of PRSEUS panels loaded in the frame direction and subjected to severe damage in the form of a severed central frame in a three-frame panel. Experimental results for a pristine two-frame panel and analytical predictions for pristine two-frame and three-frame panels as well as damaged three-frame panels are described.

Effects of chemical alternation on damage accumulation in concentrated solid-solution alloys

DOE PAGES

Ullah, Mohammad W.; Xue, Haizhou; Velisa, Gihan; ...

2017-06-23

Single-phase concentrated solid-solution alloys (SP-CSAs) have recently gained unprecedented attention due to their promising properties. To understand effects of alloying elements on irradiation-induced defect production, recombination and evolution, an integrated study of ion irradiation, ion beam analysis and atomistic simulations are carried out on a unique set of model crystals with increasing chemical complexity, from pure Ni to Ni 80Fe 20, Ni 50Fe 50, and Ni 80Cr 20 binaries, and to a more complex Ni 40Fe 40Cr 20 alloy. Both experimental and simulation results suggest that the binary and ternary alloys exhibit higher radiation resistance than elemental Ni. The modelingmore » work predicts that Ni 40Fe 40Cr 20 has the best radiation tolerance, with the number of surviving Frenkel pairs being factors of 2.0 and 1.4 lower than pure Ni and the 80:20 binary alloys, respectively. While the reduced defect mobility in SP-CSAs is identified as a general mechanism leading to slower growth of large defect clusters, the effect of specific alloying elements on suppression of damage accumulation is clearly demonstrated. This work suggests that concentrated solid-solution provides an effective way to enhance radiation tolerance by creating elemental alternation at the atomic level. The demonstrated chemical effects on defect dynamics may inspire new design principles of radiation-tolerant structural alloys for advanced energy systems.« less

Test and analysis results for composite transport fuselage and wing structures

NASA Technical Reports Server (NTRS)

Deaton, Jerry W.; Kullerd, Susan M.; Madan, Ram C.; Chen, Victor L.

1992-01-01

Automated tow placement (ATP) and stitching of dry textile composite preforms followed by resin transfer molding (RTM) are being investigated by researchers at NASA LaRC and Douglas Aircraft Company as cost-effective manufacturing processes for obtaining damage tolerant fuselage and wing structures for transport aircraft. The Douglas work is being performed under a NASA contract entitled 'Innovative Composites Aircraft Primary Structures (ICAPS)'. Data are presented in this paper to assess the damage tolerance of ATP and RTM fuselage elements with stitched-on stiffeners from compression tests of impacted three-J-stiffened panels and from stiffener pull-off tests. Data are also presented to assess the damage tolerance of RTM wing elements which had stitched skin and stiffeners from impacted single stiffener and three blade-stiffened compression tests and stiffener pull-off tests.

Effects of ionizing radiation on embryos of the tardigrade Milnesium cf. tardigradum at different stages of development.

PubMed

Beltrán-Pardo, Eliana; Jönsson, K Ingemar; Wojcik, Andrzej; Haghdoost, Siamak; Harms-Ringdahl, Mats; Bermúdez-Cruz, Rosa M; Bernal Villegas, Jaime E

2013-01-01

Tardigrades represent one of the most desiccation and radiation tolerant animals on Earth, and several studies have documented their tolerance in the adult stage. Studies on tolerance during embryological stages are rare, but differential effects of desiccation and freezing on different developmental stages have been reported, as well as dose-dependent effect of gamma irradiation on tardigrade embryos. Here, we report a study evaluating the tolerance of eggs from the eutardigrade Milnesium cf. tardigradum to three doses of gamma radiation (50, 200 and 500 Gy) at the early, middle, and late stage of development. We found that embryos of the middle and late developmental stages were tolerant to all doses, while eggs in the early developmental stage were tolerant only to a dose of 50 Gy, and showed a declining survival with higher dose. We also observed a delay in development of irradiated eggs, suggesting that periods of DNA repair might have taken place after irradiation induced damage. The delay was independent of dose for eggs irradiated in the middle and late stage, possibly indicating a fixed developmental schedule for repair after induced damage. These results show that the tolerance to radiation in tardigrade eggs changes in the course of their development. The mechanisms behind this pattern are unknown, but may relate to changes in mitotic activities over the embryogenesis and/or to activation of response mechanisms to damaged DNA in the course of development.

Effects of Ionizing Radiation on Embryos of the Tardigrade Milnesium cf. tardigradum at Different Stages of Development

PubMed Central

Beltrán-Pardo, Eliana; Jönsson, K. Ingemar; Wojcik, Andrzej; Haghdoost, Siamak; Harms-Ringdahl, Mats; Bermúdez-Cruz, Rosa M.; Bernal Villegas, Jaime E.

2013-01-01

Tardigrades represent one of the most desiccation and radiation tolerant animals on Earth, and several studies have documented their tolerance in the adult stage. Studies on tolerance during embryological stages are rare, but differential effects of desiccation and freezing on different developmental stages have been reported, as well as dose-dependent effect of gamma irradiation on tardigrade embryos. Here, we report a study evaluating the tolerance of eggs from the eutardigrade Milnesium cf. tardigradum to three doses of gamma radiation (50, 200 and 500 Gy) at the early, middle, and late stage of development. We found that embryos of the middle and late developmental stages were tolerant to all doses, while eggs in the early developmental stage were tolerant only to a dose of 50 Gy, and showed a declining survival with higher dose. We also observed a delay in development of irradiated eggs, suggesting that periods of DNA repair might have taken place after irradiation induced damage. The delay was independent of dose for eggs irradiated in the middle and late stage, possibly indicating a fixed developmental schedule for repair after induced damage. These results show that the tolerance to radiation in tardigrade eggs changes in the course of their development. The mechanisms behind this pattern are unknown, but may relate to changes in mitotic activities over the embryogenesis and/or to activation of response mechanisms to damaged DNA in the course of development. PMID:24039737

76 FR 74655 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-01

... and discrete flaws, and impact or other accidental damage (including the discrete source of the... discrete manufacturing defects or accidental damage, is avoided throughout the operational life or... and discrete flaws, and impact or other accidental damage (including the discrete source of the...

Structural Integrity Evaluation of the Lear Fan 2100 Aircraft

NASA Technical Reports Server (NTRS)

Kan, H. P.; Dyer, T. A.

1996-01-01

An in-situ nondestructive inspection was conducted to detect manufacturing and assembly induced defects in the upper two wing surfaces (skin s) and upper fuselage skin of the Lear Fan 2100 aircraft E009. The effects of the defects, detected during the inspection, on the integrity of the structure was analytically evaluated. A systematic evaluation was also conducted to determine the damage tolerance capability of the upper wing skin against impact threats and assembly induced damage. The upper wing skin was divided into small regions for damage tolerance evaluations. Structural reliability, margin of safety, allowable strains, and allowable damage size were computed. The results indicated that the impact damage threat imposed on composite military aircraft structures is too severe for the Lear Fan 2100 upper wing skin. However, the structural integrity is not significantly degraded by the assembly induced damage for properly assembled structures, such as the E009 aircraft.

Comparison of resin film infusion, resin transfer molding, and consolidation of textile preforms for primary aircraft structure

NASA Technical Reports Server (NTRS)

Suarez, J.; Dastin, S.

1992-01-01

Under NASA's Novel Composites for Wing and Fuselage Applications (NCWFA) Program, Grumman is developing innovative design concepts and cost-effective fabrication processes for damage-tolerant primary structures that can perform at a design ultimate strain level of 6000 micro-inch/inch. Attention has focused on the use of textile high-performance fiber-reinforcement concepts that provide improved damage tolerance and out-of-plane load capability, low-cost resin film infusion (RFI) and resin transfer molding (RTM) processes, and thermoplastic forming concepts. The fabrication of wing 'Y' spars by four different materials/processes methods is described: 'Y' spars fabricated using IM7 angle interlock 0/90 deg woven preforms with +/- 45 deg plies stitched with Toray high-strength graphite thread and processed using RFI and 3501-6 epoxy; 'Y' spars fabricated using G40-800 knitted/stitched preforms and processed using RFI and 3501-6 epoxy; 'Y' spars fabricated using G40-800 knitted/stitched preforms and processed using RTM and Tactix 123/H41 epoxy; and 'Y' spars fabricated using AS4(6k)/PEEK 150-g commingled angle interlock 0/90 deg woven preforms with +/- 45 deg commingled plies stitched using high-strength graphite thread and processed by consolidation. A comparison of the structural efficiency, processability, and projected acquisition cost of these representative spars is presented.

Residual strength and crack propagation tests on C-130 airplane center wings with service-imposed fatigue damage

NASA Technical Reports Server (NTRS)

Snider, H. L.; Reeder, F. L.; Dirkin, W. J.

1972-01-01

Fourteen C-130 airplane center wings, each containing service-imposed fatigue damage resulting from 4000 to 13,000 accumulated flight hours, were tested to determine their fatigue crack propagation and static residual strength characteristics. Eight wings were subjected to a two-step constant amplitude fatigue test prior to static testing. Cracks up to 30 inches long were generated in these tests. Residual static strengths of these wings ranged from 56 to 87 percent of limit load. The remaining six wings containing cracks up to 4 inches long were statically tested as received from field service. Residual static strengths of these wings ranged from 98 to 117 percent of limit load. Damage-tolerant structural design features such as fastener holes, stringers, doublers around door cutouts, and spanwise panel splices proved to be effective in retarding crack propagation.

Drought Adaptation Mechanisms Should Guide Experimental Design.

PubMed

Gilbert, Matthew E; Medina, Viviana

2016-08-01

The mechanism, or hypothesis, of how a plant might be adapted to drought should strongly influence experimental design. For instance, an experiment testing for water conservation should be distinct from a damage-tolerance evaluation. We define here four new, general mechanisms for plant adaptation to drought such that experiments can be more easily designed based upon the definitions. A series of experimental methods are suggested together with appropriate physiological measurements related to the drought adaptation mechanisms. The suggestion is made that the experimental manipulation should match the rate, length, and severity of soil water deficit (SWD) necessary to test the hypothesized type of drought adaptation mechanism. Copyright © 2016 Elsevier Ltd. All rights reserved.

Mus308 Processes Oxygen and Nitrogen Ethylation DNA Damage in Germ Cells of Drosophila

PubMed Central

Díaz-Valdés, Nancy; Comendador, Miguel A.; Sierra, L. María

2010-01-01

The D. melanogaster mus308 gene, highly conserved among higher eukaryotes, is implicated in the repair of cross-links and of O-ethylpyrimidine DNA damage, working in a DNA damage tolerance mechanism. However, despite its relevance, its possible role on the processing of different DNA ethylation damages is not clear. To obtain data on mutation frequency and on mutation spectra in mus308 deficient (mus308−) conditions, the ethylating agent diethyl sulfate (DES) was analysed in postmeiotic male germ cells. These data were compared with those corresponding to mus308 efficient conditions. Our results indicate that Mus308 is necessary for the processing of oxygen and N-ethylation damage, for the survival of fertilized eggs depending on the level of induced DNA damage, and for an influence of the DNA damage neighbouring sequence. These results support the role of mus308 in a tolerance mechanism linked to a translesion synthesis pathway and also to the alternative end-joinig system. PMID:20936147

Damage Mechanisms and Mechanical Properties of High-Strength Multiphase Steels

PubMed Central

Heibel, Sebastian; Dettinger, Thomas; Nester, Winfried; Tekkaya, A. Erman

2018-01-01

The usage of high-strength steels for structural components and reinforcement parts is inevitable for modern car-body manufacture in reaching lightweight design as well as increasing passive safety. Depending on their microstructure these steels show differing damage mechanisms and various mechanical properties which cannot be classified comprehensively via classical uniaxial tensile testing. In this research, damage initiation, evolution and final material failure are characterized for commercially produced complex-phase (CP) and dual-phase (DP) steels in a strength range between 600 and 1000 MPa. Based on these investigations CP steels with their homogeneous microstructure are characterized as damage tolerant and hence less edge-crack sensitive than DP steels. As final fracture occurs after a combination of ductile damage evolution and local shear band localization in ferrite grains at a characteristic thickness strain, this strain measure is introduced as a new parameter for local formability. In terms of global formability DP steels display advantages because of their microstructural composition of soft ferrite matrix including hard martensite particles. Combining true uniform elongation as a measure for global formability with the true thickness strain at fracture for local formability the mechanical material response can be assessed on basis of uniaxial tensile testing incorporating all microstructural characteristics on a macroscopic scale. Based on these findings a new classification scheme for the recently developed high-strength multiphase steels with significantly better formability resulting of complex underlying microstructures is introduced. The scheme overcomes the steel designations using microstructural concepts, which provide no information about design and production properties. PMID:29747417

The merging of fatigue and fracture mechanics concepts: a historical perspective

NASA Astrophysics Data System (ADS)

Newman, J. C.

1998-07-01

In this review, some of the technical developments that have occurred during the past 40 years are presented which have led to the merger of fatigue and fracture mechanics concepts. This review is made from the viewpoint of “crack propagation”. As methods to observe the “fatigue” process have improved, the formation of fatigue micro-cracks have been observed earlier in life and the measured crack sizes have become smaller. These observations suggest that fatigue damage can now be characterized by “crack size”. In parallel, the crack-growth analysis methods, using stress-intensity factors, have also improved. But the effects of material inhomogeneities, crack-fracture mechanisms, and nonlinear behavior must now be included in these analyses. The discovery of crack-closure mechanisms, such as plasticity, roughness, and oxide/corrosion/fretting product debris, and the use of the effective stress-intensity factor range, has provided an engineering tool to predict small- and large-crack-growth rate behavior under service loading conditions. These mechanisms have also provided a rationale for developing new, damage-tolerant materials. This review suggests that small-crack growth behavior should be viewed as typical behavior, whereas large-crack threshold behavior should be viewed as the anomaly. Small-crack theory has unified “fatigue” and “fracture mechanics” concepts; and has bridged the gap between safe-life and durability/damage-tolerance design concepts.

The Use of the STAGS Finite Element Code in Stitched Structures Development

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.; Lovejoy, Andrew E.

2014-01-01

In the last 30 years NASA has worked in collaboration with industry to develop enabling technologies needed to make aircraft more fuel-efficient and more affordable. The focus on the airframe has been to reduce weight, improve damage tolerance and better understand structural behavior under realistic flight and ground loading conditions. Stitched structure is a technology that can address the weight savings, cost reduction, and damage tolerance goals, but only if it is supported by accurate analytical techniques. Development of stitched technology began in the 1990's as a partnership between NASA and Boeing (McDonnell Douglas at the time) under the Advanced Composites Technology Program and has continued under various titles and programs and into the Environmentally Responsible Aviation Project today. These programs contained development efforts involving manufacturing development, design, detailed analysis, and testing. Each phase of development, from coupons to large aircraft components was supported by detailed analysis to prove that the behavior of these structures was well-understood and predictable. The Structural Analysis of General Shells (STAGS) computer code was a critical tool used in the development of many stitched structures. As a key developer of STAGS, Charles Rankin's contribution to the programs was quite significant. Key features of STAGS used in these analyses and discussed in this paper include its accurate nonlinear and post-buckling capabilities, its ability to predict damage growth, and the use of Lagrange constraints and follower forces.

The Merging of Fatigue and Fracture Mechanics Concepts: A Historical Perspective

NASA Technical Reports Server (NTRS)

Newman, James C., Jr.

1997-01-01

The seventh Jerry L. Swedlow Memorial Lecture presents a review of some of the technical developments, that have occurred during the past 40 years, which have led to the merger of fatigue and fracture mechanics concepts. This review is made from the viewpoint of 'crack propagation.' As methods to observe the 'fatigue' process have improved, the formation of fatigue micro-cracks have been observed earlier in life and the measured crack sizes have become smaller. These observations suggest that fatigue damage can now be characterized by 'crack size.' In parallel, the crack-growth analysis methods, using stress-intensity factors, have also improved. But the effects of material inhomogeneities, crack-fracture mechanisms, and nonlinear behavior must now be included in these analyses. The discovery of crack-closure mechanisms, such as plasticity, roughness, and oxide/corrosion/fretting product debris, and the use of the effective stress-intensity factor range, has provided an engineering tool to predict small- and large-crack-growth rate behavior under service loading, conditions. These mechanisms have also provided a rationale for developing, new, damage-tolerant materials. This review suggests that small-crack growth behavior should be viewed as typical behavior, whereas large-crack threshold behavior should be viewed as the anomaly. Small-crack theory has unified 'fatigue' and 'fracture mechanics' concepts; and has bridged the cap between safe-life and durability/damage-tolerance design concepts.

Vernal freeze damage and genetic variation alter tree growth, chemistry, and insect interactions.

PubMed

Rubert-Nason, Kennedy F; Couture, John J; Gryzmala, Elizabeth A; Townsend, Philip A; Lindroth, Richard L

2017-11-01

Anticipated consequences of climate change in temperate regions include early spring warmup punctuated by intermittent hard freezes. Warm weather accelerates leaf flush in perennial woody species, potentially exposing vulnerable young tissues to damaging frosts. We employed a 2 × 6 randomized factorial design to examine how the interplay of vernal (springtime) freeze damage and genetic variation in a hardwood species (Populus tremuloides) influences tree growth, phytochemistry, and interactions with an insect herbivore (Chaitophorus stevensis). Acute effects of freezing included defoliation and mortality. Surviving trees exhibited reduced growth and altered biomass distribution. Reflushed leaves on these trees had lower mass per area, lower lignin concentrations, and higher nitrogen concentrations, altered chemical defence profiles, and supported faster aphid population growth. Many effects varied among plant genotypes and were related with herbivore performance. This study suggests that a single damaging vernal freeze event can alter tree-insect interactions through effects on plant growth and chemistry. Differential responses of various genotypes to freeze damage suggest that more frequent vernal freeze events could also influence natural selection, favouring trees with greater freeze hardiness, and more resistance or tolerance to herbivores following damage. © 2017 John Wiley & Sons Ltd.

High damage tolerance of electrochemically lithiated silicon

PubMed Central

Wang, Xueju; Fan, Feifei; Wang, Jiangwei; Wang, Haoran; Tao, Siyu; Yang, Avery; Liu, Yang; Beng Chew, Huck; Mao, Scott X.; Zhu, Ting; Xia, Shuman

2015-01-01

Mechanical degradation and resultant capacity fade in high-capacity electrode materials critically hinder their use in high-performance rechargeable batteries. Despite tremendous efforts devoted to the study of the electro–chemo–mechanical behaviours of high-capacity electrode materials, their fracture properties and mechanisms remain largely unknown. Here we report a nanomechanical study on the damage tolerance of electrochemically lithiated silicon. Our in situ transmission electron microscopy experiments reveal a striking contrast of brittle fracture in pristine silicon versus ductile tensile deformation in fully lithiated silicon. Quantitative fracture toughness measurements by nanoindentation show a rapid brittle-to-ductile transition of fracture as the lithium-to-silicon molar ratio is increased to above 1.5. Molecular dynamics simulations elucidate the mechanistic underpinnings of the brittle-to-ductile transition governed by atomic bonding and lithiation-induced toughening. Our results reveal the high damage tolerance in amorphous lithium-rich silicon alloys and have important implications for the development of durable rechargeable batteries. PMID:26400671

Damage Tolerance and Reliability of Turbine Engine Components

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1999-01-01

This report describes a formal method to quantify structural damage tolerance and reliability in the presence of a multitude of uncertainties in turbine engine components. The method is based at the material behavior level where primitive variables with their respective scatter ranges are used to describe behavior. Computational simulation is then used to propagate the uncertainties to the structural scale where damage tolerance and reliability are usually specified. Several sample cases are described to illustrate the effectiveness, versatility, and maturity of the method. Typical results from this method demonstrate that it is mature and that it can be used to probabilistically evaluate turbine engine structural components. It may be inferred from the results that the method is suitable for probabilistically predicting the remaining life in aging or deteriorating structures, for making strategic projections and plans, and for achieving better, cheaper, faster products that give competitive advantages in world markets.

A damage-tolerant glass.

PubMed

Demetriou, Marios D; Launey, Maximilien E; Garrett, Glenn; Schramm, Joseph P; Hofmann, Douglas C; Johnson, William L; Ritchie, Robert O

2011-02-01

Owing to a lack of microstructure, glassy materials are inherently strong but brittle, and often demonstrate extreme sensitivity to flaws. Accordingly, their macroscopic failure is often not initiated by plastic yielding, and almost always terminated by brittle fracture. Unlike conventional brittle glasses, metallic glasses are generally capable of limited plastic yielding by shear-band sliding in the presence of a flaw, and thus exhibit toughness-strength relationships that lie between those of brittle ceramics and marginally tough metals. Here, a bulk glassy palladium alloy is introduced, demonstrating an unusual capacity for shielding an opening crack accommodated by an extensive shear-band sliding process, which promotes a fracture toughness comparable to those of the toughest materials known. This result demonstrates that the combination of toughness and strength (that is, damage tolerance) accessible to amorphous materials extends beyond the benchmark ranges established by the toughest and strongest materials known, thereby pushing the envelope of damage tolerance accessible to a structural metal.

High damage tolerance of electrochemically lithiated silicon

NASA Astrophysics Data System (ADS)

Wang, Xueju; Fan, Feifei; Wang, Jiangwei; Wang, Haoran; Tao, Siyu; Yang, Avery; Liu, Yang; Beng Chew, Huck; Mao, Scott X.; Zhu, Ting; Xia, Shuman

2015-09-01

Mechanical degradation and resultant capacity fade in high-capacity electrode materials critically hinder their use in high-performance rechargeable batteries. Despite tremendous efforts devoted to the study of the electro-chemo-mechanical behaviours of high-capacity electrode materials, their fracture properties and mechanisms remain largely unknown. Here we report a nanomechanical study on the damage tolerance of electrochemically lithiated silicon. Our in situ transmission electron microscopy experiments reveal a striking contrast of brittle fracture in pristine silicon versus ductile tensile deformation in fully lithiated silicon. Quantitative fracture toughness measurements by nanoindentation show a rapid brittle-to-ductile transition of fracture as the lithium-to-silicon molar ratio is increased to above 1.5. Molecular dynamics simulations elucidate the mechanistic underpinnings of the brittle-to-ductile transition governed by atomic bonding and lithiation-induced toughening. Our results reveal the high damage tolerance in amorphous lithium-rich silicon alloys and have important implications for the development of durable rechargeable batteries.

The research and development of damage tolerant carbon fiber composites

NASA Astrophysics Data System (ADS)

Miranda, John Armando

This record of study takes a first hand look at corporate research and development efforts to improve the damage tolerance of two unique composite materials used in high performance aerospace applications. The professional internship with The Dow Chemical Company---Dow/United Technologies joint venture describes the intern's involvement in developing patentable process technologies for interleave toughening of high temperature resins and their composites. The subsequent internship with Hexcel Corporation describes the intern's involvement in developing the damage tolerance of novel and existing honeycomb sandwich structure technologies. Through the Doctor of Engineering professional internship experience this student exercised fundamental academic understanding and methods toward accomplishing the corporate objectives of the internship sponsors in a resource efficient and cost-effective manner. Also, the student gained tremendous autonomy through exceptional training in working in focused team environments with highly trained engineers and scientists in achieving important corporate objectives.

7 CFR 51.2557 - Tolerances.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) Damage 2.0 2.5 3.0 (b) Serious Damage (Minor Insect or Vertebrate Injury, Mold, Rancid, Decay) 1.5 2.0 2.5 (1) Insect Damage, included in (b) .3 .4 .5 (c) Foreign Material .03 .05 .1 [55 FR 28747, July 13...

7 CFR 51.2557 - Tolerances.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) Damage 2.0 2.5 3.0 (b) Serious Damage (Minor Insect or Vertebrate Injury, Mold, Rancid, Decay) 1.5 2.0 2.5 (1) Insect Damage, included in (b) .3 .4 .5 (c) Foreign Material .03 .05 .1 [55 FR 28747, July 13...

7 CFR 51.307 - Application of tolerances.

Code of Federal Regulations, 2010 CFR

2010-01-01

... STANDARDS) United States Standards for Grades of Apples Application of Tolerances § 51.307 Application of... least one apple which is seriously damaged by insects or affected by decay or internal breakdown may be... have more than 3 times the tolerance specified, except that at least three defective apples may be...

7 CFR 51.307 - Application of tolerances.

Code of Federal Regulations, 2011 CFR

2011-01-01

... STANDARDS) United States Standards for Grades of Apples Application of Tolerances § 51.307 Application of... least one apple which is seriously damaged by insects or affected by decay or internal breakdown may be... have more than 3 times the tolerance specified, except that at least three defective apples may be...

7 CFR 51.307 - Application of tolerances.

Code of Federal Regulations, 2012 CFR

2012-01-01

... STANDARDS) United States Standards for Grades of Apples Application of Tolerances § 51.307 Application of... least one apple which is seriously damaged by insects or affected by decay or internal breakdown may be... have more than 3 times the tolerance specified, except that at least three defective apples may be...

A novel two-step method for screening shade tolerant mutant plants via dwarfism

USDA-ARS?s Scientific Manuscript database

When subjected to shade, plants undergo rapid shoot elongation, which often makes them more prone to disease and mechanical damage. It has been reported that, in turfgrass, induced dwarfism can enhance shade tolerance. Here, we describe a two-step procedure for isolating shade tolerant mutants of ...

Constraints on the evolution of tolerance to herbicide in the common morning glory: resistance and tolerance are mutually exclusive.

PubMed

Baucom, Regina S; Mauricio, Rodney

2008-11-01

Evolutionary biologists explain the maintenance of intermediate levels of defense in plant populations as being due to trade-offs, or negative genetic covariances among ecologically important traits. Attempts at detecting trade-offs as constraints on the evolution of defense have not always been successful, leading some to conclude that such trade-offs rarely explain current levels of defense in the population. Using the agricultural pest Ipomoea purpurea, we measured correlations between traits involved in defense to glyphosate, the active ingredient in Roundup, a widely used herbicide. We found significant allocation costs of tolerance, as well as trade-offs between resistance and two measures of tolerance to glyphosate. Selection on resistance and tolerance exhibited differing patterns: tolerance to leaf damage was under negative directional selection, whereas resistance was under positive directional selection. The joint pattern of selection on resistance and tolerance to leaf damage indicated the presence of alternate peaks in the fitness landscape such that a combination of either high tolerance and low resistance, or high resistance and low tolerance was favored. The widespread use of this herbicide suggests that it is likely an important selective agent on weed populations. Understanding the evolutionary dynamics of herbicide defense traits is thus of increasing importance in the context of human-mediated evolution.

Damage tolerance protein Mus81 associates with the FHA1 domain of checkpoint kinase Cds1.

PubMed

Boddy, M N; Lopez-Girona, A; Shanahan, P; Interthal, H; Heyer, W D; Russell, P

2000-12-01

Cds1, a serine/threonine kinase, enforces the S-M checkpoint in the fission yeast Schizosaccharomyces pombe. Cds1 is required for survival of replicational stress caused by agents that stall replication forks, but how Cds1 performs these functions is largely unknown. Here we report that the forkhead-associated-1 (FHA1) protein-docking domain of Cds1 interacts with Mus81, an evolutionarily conserved damage tolerance protein. Mus81 has an endonuclease homology domain found in the XPF nucleotide excision repair protein. Inactivation of mus81 reveals a unique spectrum of phenotypes. Mus81 enables survival of deoxynucleotide triphosphate starvation, UV radiation, and DNA polymerase impairment. Mus81 is essential in the absence of Bloom's syndrome Rqh1 helicase and is required for productive meiosis. Genetic epistasis studies suggest that Mus81 works with recombination enzymes to properly replicate damaged DNA. Inactivation of Mus81 triggers a checkpoint-dependent delay of mitosis. We propose that Mus81 is involved in the recruitment of Cds1 to aberrant DNA structures where Cds1 modulates the activity of damage tolerance enzymes.

A statistical method for determining the dimensions, tolerances and specification of optics for the Laser Megajoule facility (LMJ)

NASA Astrophysics Data System (ADS)

Denis, Vincent

2008-09-01

This paper presents a statistical method for determining the dimensions, tolerance and specifications of components for the Laser MegaJoule (LMJ). Numerous constraints inherent to a large facility require specific tolerances: the huge number of optical components; the interdependence of these components between the beams of same bundle; angular multiplexing for the amplifier section; distinct operating modes between the alignment and firing phases; the definition and use of alignment software in the place of classic optimization. This method provides greater flexibility to determine the positioning and manufacturing specifications of the optical components. Given the enormous power of the Laser MegaJoule (over 18 kJ in the infrared and 9 kJ in the ultraviolet), one of the major risks is damage the optical mounts and pollution of the installation by mechanical ablation. This method enables estimation of the beam occultation probabilities and quantification of the risks for the facility. All the simulations were run using the ZEMAX-EE optical design software.

Detecting damage in full-scale honeycomb sandwich composite curved fuselage panels through frequency response

NASA Astrophysics Data System (ADS)

Leone, Frank A., Jr.; Ozevin, Didem; Mosinyi, Bao; Bakuckas, John G., Jr.; Awerbuch, Jonathan; Lau, Alan; Tan, Tein-Min

2008-03-01

Preliminary tests were conducted using frequency response (FR) characteristics to determine damage initiation and growth in a honeycomb sandwich graphite/epoxy curved panel. This investigation was part of a more general study investigating the damage tolerance characteristics of several such panels subjected to quasi-static internal pressurization combined with hoop and axial loading. The panels were tested at the Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) facility located at the Federal Aviation Administration William J. Hughes Technical Center in Atlantic City, NJ. The overall program objective was to investigate the damage tolerance characteristics of full-scale composite curved aircraft fuselage panels and the evolution of damage under quasi-static loading up to failure. This paper focuses on one aspect of this comprehensive investigation: the effect of state-of-damage on the characteristics of the frequency response of the subject material. The results presented herein show that recording the frequency response could be used for real-time monitoring of damage growth and in determining damage severity in full-scale composites fuselage aircraft structures.

Fault Tolerant State Machines

NASA Technical Reports Server (NTRS)

Burke, Gary R.; Taft, Stephanie

2004-01-01

State machines are commonly used to control sequential logic in FPGAs and ASKS. An errant state machine can cause considerable damage to the device it is controlling. For example in space applications, the FPGA might be controlling Pyros, which when fired at the wrong time will cause a mission failure. Even a well designed state machine can be subject to random errors us a result of SEUs from the radiation environment in space. There are various ways to encode the states of a state machine, and the type of encoding makes a large difference in the susceptibility of the state machine to radiation. In this paper we compare 4 methods of state machine encoding and find which method gives the best fault tolerance, as well as determining the resources needed for each method.

Damage Tolerant Design Handbook. A Compilation of Fracture and Crack- Growth Data for High-Strength Alloys. Volume 3

DTIC Science & Technology

1983-12-01

Effects on the Fatigue Crack Growth Rate of Aluminum Alloy 2024 - T351 ", University of Dayton Research Institute, Dayton, OH, Contract No. F33615-80-C-5011...ASSOCIATED WITH FIGURE 7.5.3.9 INDICATING EFFECT OF STRESS RATIO MATERIAL: ALUMINUM 2024 CONDITION: T351 ENVIRONMENT: R.T. LAB AIR DELTA K .DA/DN (10...OF STRESS INTENSITY FACTOR DATA ASSOCIATED WITH FIGURE 7.5.3.10 INDICATING EFFECT OF STRESS RATIO MATERIAL: ALUMINUM 2024

Recent and Future Enhancements in NDI for Aircraft Structures (Postprint)

DTIC Science & Technology

2015-11-01

manufacture, use, or sell any patented invention that may relate to them. Qualified requestors may obtain copies of this report from the Defense...and was also used to establish the safe-life of earlier designs that were subjected to a fatigue test. Losses of an F-111 in December 1969 and an F-5...Accidents / Incidents, March 2010. [2] Lincoln, J.W., “Damage Tolerance – USAF Experience,” Proceedings of the 13th Symposium of the International

RECENT AND FUTURE ENHANCEMENTS IN NDI FOR AIRCRAFT STRUCTURES (POSTPRINT)

DTIC Science & Technology

2015-09-10

manufacture, use, or sell any patented invention that may relate to them. Qualified requestors may obtain copies of this report from the Defense...and was also used to establish the safe-life of earlier designs that were subjected to a fatigue test. Losses of an F-111 in December 1969 and an F-5...Accidents / Incidents, March 2010. [2] Lincoln, J.W., “Damage Tolerance – USAF Experience,” Proceedings of the 13th Symposium of the International

RECENT AND FUTURE ENHANCEMENTS IN NDI FOR AIRCRAFT STRUCTURES POSTPRINT

DTIC Science & Technology

2015-09-10

manufacture, use, or sell any patented invention that may relate to them. Qualified requestors may obtain copies of this report from the Defense...and was also used to establish the safe-life of earlier designs that were subjected to a fatigue test. Losses of an F-111 in December 1969 and an F-5...Accidents / Incidents, March 2010. [2] Lincoln, J.W., “Damage Tolerance – USAF Experience,” Proceedings of the 13th Symposium of the International

Recent and Future Enhancements in NDI for Aircraft Structures (POSTPRINT)

DTIC Science & Technology

2015-11-01

manufacture, use, or sell any patented invention that may relate to them. Qualified requestors may obtain copies of this report from the Defense...and was also used to establish the safe-life of earlier designs that were subjected to a fatigue test. Losses of an F-111 in December 1969 and an F-5...Accidents / Incidents, March 2010. [2] Lincoln, J.W., “Damage Tolerance – USAF Experience,” Proceedings of the 13th Symposium of the International

RECENT AND FUTURE ENHANCEMENTS IN NDI FOR AIRCRAFT STRUCTURES (POSTPRINT)

DTIC Science & Technology

2015-11-16

manufacture, use, or sell any patented invention that may relate to them. Qualified requestors may obtain copies of this report from the Defense...and was also used to establish the safe-life of earlier designs that were subjected to a fatigue test. Losses of an F-111 in December 1969 and an F-5...Accidents / Incidents, March 2010. [2] Lincoln, J.W., “Damage Tolerance – USAF Experience,” Proceedings of the 13th Symposium of the International

Damage Tolerance Enhancement of Carbon Fiber Reinforced Polymer Composites by Nanoreinforcement of Matrix

NASA Astrophysics Data System (ADS)

Fenner, Joel Stewart

Nanocomposites are a relatively new class of materials which incorporate exotic, engineered nanoparticles to achieve superior material properties. Because of their extremely small size and well-ordered structure, many nanoparticles possess properties that exceed those offered by a wide range of other known materials, making them attractive candidates for novel materials engineering development. Their small size is also an impediment to their practical use, as they typically cannot be employed by themselves to realize those properties in large structures. Furthermore, nanoparticles typically possess strong self-affinity, rendering them difficult to disperse uniformly into a composite. However, contemporary research has shown that, if well-dispersed, nanoparticles have great capacity to improve the mechanical properties of composites, especially damage tolerance, in the form of fracture toughness, fatigue life, and impact damage mitigation. This research focuses on the development, manufacturing, and testing of hybrid micro/nanocomposites comprised of woven carbon fibers with a carbon nanotube reinforced epoxy matrix. Material processing consisted of dispersant-and-sonication based methods to disperse nanotubes into the matrix, and a vacuum-assisted wet lay-up process to prepare the hybrid composite laminates. Various damage tolerance properties of the hybrid composite were examined, including static strength, fracture toughness, fatigue life, fatigue crack growth rate, and impact damage behavior, and compared with similarly-processed reference material produced without nanoreinforcement. Significant improvements were obtained in interlaminar shear strength (15%), Mode-I fracture toughness (180%), shear fatigue life (order of magnitude), Mode-I fatigue crack growth rate (factor of 2), and effective impact damage toughness (40%). Observations by optical microscopy, scanning electron microscopy, and ultrasonic imaging showed significant differences in failure behavior and fracture morphology between the two materials, related to the differences in properties. Altogether these results provided a means for proposing an explanation of the mechanism of reinforcement (and damage tolerance enhancement) provided by carbon nanotubes in hybrid composite materials.

Rate of Dehydration and Cumulative Desiccation Stress Interacted to Modulate Desiccation Tolerance of Recalcitrant Cocoa and Ginkgo Embryonic Tissues1

PubMed Central

Liang, Yongheng; Sun, Wendell Q.

2002-01-01

Rate of dehydration greatly affects desiccation tolerance of recalcitrant seeds. This effect is presumably related to two different stress vectors: direct mechanical or physical stress because of the loss of water and physicochemical damage of tissues as a result of metabolic alterations during drying. The present study proposed a new theoretic approach to represent these two types of stresses and investigated how seed tissues responded differently to two stress vectors, using the models of isolated cocoa (Theobroma cacao) and ginkgo (Ginkgo biloba) embryonic tissues dehydrated under various drying conditions. This approach used the differential change in axis water potential (ΔΨ/Δt) to quantify rate of dehydration and the intensity of direct physical stress experienced by embryonic tissues during desiccation. Physicochemical effect of drying was expressed by cumulative desiccation stress [∫\\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\pagestyle{empty} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{o}^{t}}}\\end{equation*}\\end{document}f(ψ,t)], a function of both the rate and time of dehydration. Rapid dehydration increased the sensitivity of embryonic tissues to desiccation as indicated by high critical water contents, below which desiccation damage occurred. Cumulative desiccation stress increased sharply under slow drying conditions, which was also detrimental to embryonic tissues. This quantitative analysis of the stress-time-response relationship helps to understand the physiological basis for the existence of an optimal dehydration rate, with which maximum desiccation tolerance could be achieved. The established numerical analysis model will prove valuable for the design of experiments that aim to elucidate biochemical and physiological mechanisms of desiccation tolerance. PMID:11950981

The impact of emerging technologies on an advanced supersonic transport

NASA Technical Reports Server (NTRS)

Driver, C.; Maglieri, D. J.

1986-01-01

The effects of advances in propulsion systems, structure and materials, aerodynamics, and systems on the design and development of supersonic transport aircraft are analyzed. Efficient propulsion systems with variable-cycle engines provide the basis for improved propulsion systems; the propulsion efficienies of supersonic and subsonic engines are compared. Material advances consist of long-life damage-tolerant structures, advanced material development, aeroelastic tailoring, and low-cost fabrication. Improvements in the areas of aerodynamics and systems are examined. The environmental problems caused by engine emissions, airport noise, and sonic boom are studied. The characteristics of the aircraft designed to include these technical advances are described.

Aligned composite structures for mitigation of impact damage and resistance to wear in dynamic environments

DOEpatents

Mulligan, Anthony C.; Rigali, Mark J.; Sutaria, Manish P.; Popovich, Dragan; Halloran, Joseph P.; Fulcher, Michael L.; Cook, Randy C.

2005-12-13

Fibrous monolith composites having architectures that provide increased flaw insensitivity, improved hardness, wear resistance and damage tolerance and methods of manufacture thereof are provided for use in dynamic environments to mitigate impact damage and increase wear resistance.

Aligned composite structures for mitigation of impact damage and resistance to wear in dynamic environments

DOEpatents

Mulligan, Anthony C.; Rigali, Mark J.; Sutaria, Manish P.; Popovich, Dragan; Halloran, Joseph P.; Fulcher, Michael L.; Cook, Randy C.

2009-04-14

Fibrous monolith composites having architectures that provide increased flaw insensitivity, improved hardness, wear resistance and damage tolerance and methods of manufacture thereof are provided for use in dynamic environments to mitigate impact damage and increase wear resistance.

Aligned composite structures for mitigation of impact damage and resistance to wear in dynamic environments

DOEpatents

Rigali, Mark J.; Sutaria, Manish P.; Mulligan, Anthony C.; Popovich, Dragan

2004-03-23

Fibrous monolith composites having architectures that provide increased flaw insensitivity, improved hardness, wear resistance and damage tolerance and methods of manufacture thereof are provided for use in dynamic environments to mitigate impact damage and increase wear resistance.

Progressive Fracture of Fiber Composite Thin Shell Structures Under Internal Pressure and Axial Loads

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.; Chamis, Christos C.; Minnetyan, Levon

1996-01-01

Graphite/epoxy composite thin shell structures were simulated to investigate damage and fracture progression due to internal pressure and axial loading. Defective and defect-free structures (thin cylinders) were examined. The three different laminates examined had fiber orientations of (90/0/+/-0)(sub s), where 0 is 45, 60, and 75 deg. CODSTRAN, an integrated computer code that scales up constituent level properties to the structural level and accounts for all possible failure modes, was used to simulate composite degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture were included in the simulation. Burst pressures for defective and defect-free shells were compared to evaluate damage tolerance. The results showed that damage initiation began with matrix failure whereas damage and/or fracture progression occurred as a result of additional matrix failure and fiber fracture. In both thin cylinder cases examined (defective and defect-free), the optimum layup configuration was (90/0/+/-60)(sub s) because it had the best damage tolerance with respect to the burst pressure.

Damage Tolerant Analysis of Cracked Al 2024-T3 Panels repaired with Single Boron/Epoxy Patch

NASA Astrophysics Data System (ADS)

Mahajan, Akshay D.; Murthy, A. Ramachandra; Nanda Kumar, M. R.; Gopinath, Smitha

2018-06-01

It is known that damage tolerant analysis has two objectives, namely, remaining life prediction and residual strength evaluation. To achieve the these objectives, determination of accurate and reliable fracture parameter is very important. XFEM methodologies for fatigue and fracture analysis of cracked aluminium panels repaired with different patch shapes made of single boron/epoxy have been developed. Heaviside and asymptotic crack tip enrichment functions are employed to model the crack. XFEM formulations such as displacement field formulation and element stiffness matrix formulation are presented. Domain form of interaction integral is employed to determine Stress Intensity Factor of repaired cracked panels. Computed SIFs are incorporated in Paris crack growth model to predict the remaining fatigue life. The residual strength has been computed by using the remaining life approach, which accounts for both crack growth constants and no. of cycles to failure. From the various studies conducted, it is observed that repaired panels have significant effect on reduction of the SIF at the crack tip and hence residual strength as well as remaining life of the patched cracked panels are improved significantly. The predicted remaining life and residual strength will be useful for design of structures/components under fatigue loading.

Radiation-induced amorphization resistance and radiation tolerance in structurally related oxides.

PubMed

Sickafus, Kurt E; Grimes, Robin W; Valdez, James A; Cleave, Antony; Tang, Ming; Ishimaru, Manabu; Corish, Siobhan M; Stanek, Christopher R; Uberuaga, Blas P

2007-03-01

Ceramics destined for use in hostile environments such as nuclear reactors or waste immobilization must be highly durable and especially resistant to radiation damage effects. In particular, they must not be prone to amorphization or swelling. Few ceramics meet these criteria and much work has been devoted in recent years to identifying radiation-tolerant ceramics and the characteristics that promote radiation tolerance. Here, we examine trends in radiation damage behaviour for families of compounds related by crystal structure. Specifically, we consider oxides with structures related to the fluorite crystal structure. We demonstrate that improved amorphization resistance characteristics are to be found in compounds that have a natural tendency to accommodate lattice disorder.

7 CFR 51.1405 - Application of tolerances.

Code of Federal Regulations, 2010 CFR

2010-01-01

... STANDARDS) United States Standards for Grades of Pecans in the Shell 1 Application of Tolerances § 51.1405... that at least one pecan which is seriously damaged by live insects inside the shell is permitted...

A novel biomimetic approach to the design of high-performance ceramic–metal composites

PubMed Central

Launey, Maximilien E.; Munch, Etienne; Alsem, Daan Hein; Saiz, Eduardo; Tomsia, Antoni P.; Ritchie, Robert O.

2010-01-01

The prospect of extending natural biological design to develop new synthetic ceramic–metal composite materials is examined. Using ice-templating of ceramic suspensions and subsequent metal infiltration, we demonstrate that the concept of ordered hierarchical design can be applied to create fine-scale laminated ceramic–metal (bulk) composites that are inexpensive, lightweight and display exceptional damage-tolerance properties. Specifically, Al2O3/Al–Si laminates with ceramic contents up to approximately 40 vol% and with lamellae thicknesses down to 10 µm were processed and characterized. These structures achieve an excellent fracture toughness of 40 MPa√m at a tensile strength of approximately 300 MPa. Salient toughening mechanisms are described together with further toughening strategies. PMID:19828498

A novel cold-regulated gene, COR25, of Brassica napus is involved in plant response and tolerance to cold stress.

PubMed

Chen, Liang; Zhong, Hui; Ren, Feng; Guo, Qian-Qian; Hu, Xu-Peng; Li, Xue-Bao

2011-04-01

Cold stress, which causes dehydration damage to the plant cell, is one of the most common abiotic stresses that adversely affect plant growth and crop productivity. To improve its cold-tolerance, plants often enhance expression of some cold-related genes. In this study, a cold-regulated gene encoding 25 KDa of protein was isolated from Brassica napus cDNA library using a macroarray analysis, and is consequently designated as BnCOR25. RT-PCR analysis demonstrated that BnCOR25 was expressed at high levels in hypocotyls, cotyledons, stems, and flowers, but its mRNA was found at low levels in roots and leaves. Northern blot analysis revealed that BnCOR25 transcripts were significantly induced by cold and osmotic stress treatment. The data also showed that BnCOR25 gene expression is mediated by ABA-dependent pathway. Overexpression of BnCOR25 in yeast (Schizosaccharomyces pombe) significantly enhanced the cell survival probability under cold stress, and overexpression of BnCOR25 in Arabidopsis enhances plant tolerance to cold stress. These results suggested that the BnCOR25 gene may play an important role in conferring freezing/cold tolerance in plants.

DNA lesion identity drives choice of damage tolerance pathway in murine cell chromosomes.

PubMed

Cohen, Isadora S; Bar, Carmit; Paz-Elizur, Tamar; Ainbinder, Elena; Leopold, Karoline; de Wind, Niels; Geacintov, Nicholas; Livneh, Zvi

2015-02-18

DNA-damage tolerance (DDT) via translesion DNA synthesis (TLS) or homology-dependent repair (HDR) functions to bypass DNA lesions encountered during replication, and is critical for maintaining genome stability. Here, we present piggyBlock, a new chromosomal assay that, using piggyBac transposition of DNA containing a known lesion, measures the division of labor between the two DDT pathways. We show that in the absence of DNA damage response, tolerance of the most common sunlight-induced DNA lesion, TT-CPD, is achieved by TLS in mouse embryo fibroblasts. Meanwhile, BP-G, a major smoke-induced DNA lesion, is bypassed primarily by HDR, providing the first evidence for this mechanism being the main tolerance pathway for a biologically important lesion in a mammalian genome. We also show that, far from being a last-resort strategy as it is sometimes portrayed, TLS operates alongside nucleotide excision repair, handling 40% of TT-CPDs in repair-proficient cells. Finally, DDT acts in mouse embryonic stem cells, exhibiting the same pattern—mutagenic TLS included—despite the risk of propagating mutations along all cell lineages. The new method highlights the importance of HDR, and provides an effective tool for studying DDT in mammalian cells.

DNA lesion identity drives choice of damage tolerance pathway in murine cell chromosomes

PubMed Central

Cohen, Isadora S.; Bar, Carmit; Paz-Elizur, Tamar; Ainbinder, Elena; Leopold, Karoline; de Wind, Niels; Geacintov, Nicholas; Livneh, Zvi

2015-01-01

DNA-damage tolerance (DDT) via translesion DNA synthesis (TLS) or homology-dependent repair (HDR) functions to bypass DNA lesions encountered during replication, and is critical for maintaining genome stability. Here, we present piggyBlock, a new chromosomal assay that, using piggyBac transposition of DNA containing a known lesion, measures the division of labor between the two DDT pathways. We show that in the absence of DNA damage response, tolerance of the most common sunlight-induced DNA lesion, TT-CPD, is achieved by TLS in mouse embryo fibroblasts. Meanwhile, BP-G, a major smoke-induced DNA lesion, is bypassed primarily by HDR, providing the first evidence for this mechanism being the main tolerance pathway for a biologically important lesion in a mammalian genome. We also show that, far from being a last-resort strategy as it is sometimes portrayed, TLS operates alongside nucleotide excision repair, handling 40% of TT-CPDs in repair-proficient cells. Finally, DDT acts in mouse embryonic stem cells, exhibiting the same pattern—mutagenic TLS included—despite the risk of propagating mutations along all cell lineages. The new method highlights the importance of HDR, and provides an effective tool for studying DDT in mammalian cells. PMID:25589543

Acoustic Emission of Large PRSEUS Structures (Pultruded Rod Stitched Efficient Unitized Structure)

NASA Technical Reports Server (NTRS)

Horne, Michael R.; Juarez, Peter D.

2016-01-01

In the role of structural health monitoring (SHM), Acoustic Emission (AE) analysis is being investigated as an effective method for tracking damage development in large composite structures under load. Structures made using Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) for damage tolerant, light, and economical airframe construction are being pursued by The Boeing Company and NASA under the Environmentally Responsible Aircraft initiative (ERA). The failure tests of two PRSEUS substructures based on the Boeing Hybrid Wing Body fuselage concept were conducted during third quarter 2011 and second quarter 2015. One fundamental concern of these tests was determining the effectiveness of the stitched integral stiffeners to inhibit damage progression. By design, severe degradation of load carrying capability should not occur prior to Design Ultimate Load (DUL). While minor damage prior to DUL was anticipated, the integral stitching should not fail since this would allow a stiffener-skin delamination to progress rapidly and alter the transfer of load into the stiffeners. In addition, the stiffeners should not fracture because they are fundamental to structural integrity. Getting the best information from each AE sensor is a primary consideration because a sparse network of sensors is implemented. Sensitivity to stiffener-contiguous degradation is supported by sensors near the stiffeners, which increases the coverage per sensor via AE waveguide actions. Some sensors are located near potentially critical areas or "critical zones" as identified by numerical analyses. The approach is compared with the damage progression monitored by other techniques (e.g. ultrasonic C-scan).

Low cost damage tolerant composite fabrication

NASA Technical Reports Server (NTRS)

Palmer, R. J.; Freeman, W. T.

1988-01-01

The resin transfer molding (RTM) process applied to composite aircraft parts offers the potential for using low cost resin systems with dry graphite fabrics that can be significantly less expensive than prepreg tape fabricated components. Stitched graphite fabric composites have demonstrated compression after impact failure performance that equals or exceeds that of thermoplastic or tough thermoset matrix composites. This paper reviews methods developed to fabricate complex shape composite parts using stitched graphite fabrics to increase damage tolerance with RTM processes to reduce fabrication cost.

Gaussian process regression of chirplet decomposed ultrasonic B-scans of a simulated design case

NASA Astrophysics Data System (ADS)

Wertz, John; Homa, Laura; Welter, John; Sparkman, Daniel; Aldrin, John

2018-04-01

The US Air Force seeks to implement damage tolerant lifecycle management of composite structures. Nondestructive characterization of damage is a key input to this framework. One approach to characterization is model-based inversion of the ultrasonic response from damage features; however, the computational expense of modeling the ultrasonic waves within composites is a major hurdle to implementation. A surrogate forward model with sufficient accuracy and greater computational efficiency is therefore critical to enabling model-based inversion and damage characterization. In this work, a surrogate model is developed on the simulated ultrasonic response from delamination-like structures placed at different locations within a representative composite layup. The resulting B-scans are decomposed via the chirplet transform, and a Gaussian process model is trained on the chirplet parameters. The quality of the surrogate is tested by comparing the B-scan for a delamination configuration not represented within the training data set. The estimated B-scan has a maximum error of ˜15% for an estimated reduction in computational runtime of ˜95% for 200 function calls. This considerable reduction in computational expense makes full 3D characterization of impact damage tractable.

Intrinsic Hardware Evolution for the Design and Reconfiguration of Analog Speed Controllers for a DC Motor

NASA Technical Reports Server (NTRS)

Gwaltney, David A.; Ferguson, Michael I.

2003-01-01

Evolvable hardware provides the capability to evolve analog circuits to produce amplifier and filter functions. Conventional analog controller designs employ these same functions. Analog controllers for the control of the shaft speed of a DC motor are evolved on an evolvable hardware platform utilizing a second generation Field Programmable Transistor Array (FPTA2). The performance of an evolved controller is compared to that of a conventional proportional-integral (PI) controller. It is shown that hardware evolution is able to create a compact design that provides good performance, while using considerably less functional electronic components than the conventional design. Additionally, the use of hardware evolution to provide fault tolerance by reconfiguring the design is explored. Experimental results are presented showing that significant recovery of capability can be made in the face of damaging induced faults.

The desert moss Pterygoneurum lamellatum (Pottiaceae) exhibits an inducible ecological strategy of desiccation tolerance: effects of rate of drying on shoot damage and regeneration

USDA-ARS?s Scientific Manuscript database

Premise of the study: Bryophytes are regarded as a clade incorporating constitutive desiccation tolerance, especially terrestrial species. Here we test the hypothesis that the opposing ecological strategy of desiccation tolerance, inducibility, is present in a desert moss, and addressed by varying r...

Freezing tolerance of winter wheat as influenced by extended growth at low temperature and exposure to freeze-thaw cycles

USDA-ARS?s Scientific Manuscript database

As the seasons progress, autumn-planted winter wheat plants (Triticum aestivum L.) first gain, then progressively lose freezing tolerance. Exposing the plants to freeze-thaw cycles of -3/3°C results in increased ability to tolerate subsequent freezing to potentially damaging temperatures. This stu...

7 CFR 51.1861 - Tolerances.

Code of Federal Regulations, 2011 CFR

2011-01-01

... damaged by shoulder bruises or by discolored or sunken scars on any parts of the tomatoes; and, (iii) Ten... percent for tomatoes which are seriously damaged by shoulder bruises or by discolored or sunken scars on... affected by decay; (ii) Ten percent for tomatoes which are seriously damaged by shoulder bruises or by...

7 CFR 51.1861 - Tolerances.

Code of Federal Regulations, 2012 CFR

2012-01-01

... damaged by shoulder bruises or by discolored or sunken scars on any parts of the tomatoes; and, (iii) Ten... percent for tomatoes which are seriously damaged by shoulder bruises or by discolored or sunken scars on... affected by decay; (ii) Ten percent for tomatoes which are seriously damaged by shoulder bruises or by...

Low Velocity Impact Damage to Carbon/Epoxy Laminates

NASA Technical Reports Server (NTRS)

Nettles, Alan T.

2011-01-01

Impact damage tends to be more detrimental to a laminate's compression strength as compared to tensile strength. Proper use of Non Destructive Evaluation (NDE) Techniques can remove conservatism (weight) from many structures. Test largest components economically feasible as coupons. If damage tolerance is a driver, then consider different resin systems. Do not use a single knockdown factor to account for damage.

Hypoxic pretreatment protects against neuronal damage of the rat hippocampus induced by severe hypoxia.

PubMed

Gorgias, N; Maidatsi, P; Tsolaki, M; Alvanou, A; Kiriazis, G; Kaidoglou, K; Giala, M

1996-04-01

The present study investigates whether under conditions of successive hypoxic exposures pretreatment with mild (15% O(2)) or moderate (10% O(2)) hypoxia, protects hippocampal neurones against damage induced by severe (3% O(2)) hypoxia. The ultrastructural findings were also correlated with regional superoxide dismutase (SOD) activity changes. In unpretreated rats severe hypoxia induced ultrastructural changes consistent with the aspects of delayed neuronal death (DND). However, in preexposed animals hippocampal damage was attenuated in an inversely proportional way with the severity of the hypoxic pretreatment. The ultrastructural hypoxic tolerance findings were also closely related to increased regional SOD activity levels. Thus the activation of the endogenous antioxidant defense by hypoxic preconditioning, protects against hippocampal damage induced by severe hypoxia. The eventual contribution of increased endogenous adenosine and/or reduced excitotoxicity to induce hypoxic tolerance is discussed.

Limiting damage during infection: lessons from infection tolerance for novel therapeutics.

PubMed

Vale, Pedro F; Fenton, Andy; Brown, Sam P

2014-01-01

The distinction between pathogen elimination and damage limitation during infection is beginning to change perspectives on infectious disease control, and has recently led to the development of novel therapies that focus on reducing the illness caused by pathogens (‘‘damage limitation’’)rather than reducing pathogen burdens directly (‘‘pathogen elimination’’). While beneficial at the individual host level, the population consequences of these interventions remain unclear. To address this issue,we present a simple conceptual framework for damage limitation during infection that distinguishes between therapies that are either host-centric (pro-tolerance) or pathogen-centric (anti-virulence). We then draw on recent developments from the evolutionary ecology of disease tolerance to highlight some potential epidemiological and evolutionary responses of pathogens to medical interventions that target the symptoms of infection. Just as pathogens are known to evolve in response to antimicrobial and vaccination therapies, we caution that claims of ‘‘evolution-proof’’ anti-virulence interventions may be premature, and further, that in infections where virulence and transmission are linked, reducing illness without reducing pathogen burden could have non-trivial epidemiological and evolutionary consequences that require careful examination.

High damage tolerance of electrochemically lithiated silicon

DOE PAGES

Wang, Xueju; Fan, Feifei; Wang, Jiangwei; ...

2015-09-24

Mechanical degradation and resultant capacity fade in high-capacity electrode materials critically hinder their use in high-performance rechargeable batteries. Despite tremendous efforts devoted to the study of the electro–chemo–mechanical behaviours of high-capacity electrode materials, their fracture properties and mechanisms remain largely unknown. In this paper, we report a nanomechanical study on the damage tolerance of electrochemically lithiated silicon. Our in situ transmission electron microscopy experiments reveal a striking contrast of brittle fracture in pristine silicon versus ductile tensile deformation in fully lithiated silicon. Quantitative fracture toughness measurements by nanoindentation show a rapid brittle-to-ductile transition of fracture as the lithium-to-silicon molar ratiomore » is increased to above 1.5. Molecular dynamics simulations elucidate the mechanistic underpinnings of the brittle-to-ductile transition governed by atomic bonding and lithiation-induced toughening. Finally, our results reveal the high damage tolerance in amorphous lithium-rich silicon alloys and have important implications for the development of durable rechargeable batteries.« less

Genome-scale analyses of butanol tolerance in Saccharomyces cerevisiae reveal an essential role of protein degradation

PubMed Central

2013-01-01

Background n-Butanol and isobutanol produced from biomass-derived sugars are promising renewable transport fuels and solvents. Saccharomyces cerevisiae has been engineered for butanol production, but its high butanol sensitivity poses an upper limit to product titers that can be reached by further pathway engineering. A better understanding of the molecular basis of butanol stress and tolerance of S. cerevisiae is important for achieving improved tolerance. Results By combining a screening of the haploid S. cerevisiae knock-out library, gene overexpression, and genome analysis of evolutionary engineered n-butanol-tolerant strains, we established that protein degradation plays an essential role in tolerance. Strains deleted in genes involved in the ubiquitin-proteasome system and in vacuolar degradation of damaged proteins showed hypersensitivity to n-butanol. Overexpression of YLR224W, encoding the subunit responsible for the recognition of damaged proteins of an ubiquitin ligase complex, resulted in a strain with a higher n-butanol tolerance. Two independently evolved n-butanol-tolerant strains carried different mutations in both RPN4 and RTG1, which encode transcription factors involved in the expression of proteasome and peroxisomal genes, respectively. Introduction of these mutated alleles in the reference strain increased butanol tolerance, confirming their relevance in the higher tolerance phenotype. The evolved strains, in addition to n-butanol, were also more tolerant to 2-butanol, isobutanol and 1-propanol, indicating a common molecular basis for sensitivity and tolerance to C3 and C4 alcohols. Conclusions This study shows that maintenance of protein integrity plays an essential role in butanol tolerance and demonstrates new promising targets to engineer S. cerevisiae for improved tolerance. PMID:23552365

Lipophilic components of the brown seaweed, Ascophyllum nodosum, enhance freezing tolerance in Arabidopsis thaliana.

PubMed

Rayirath, Prasanth; Benkel, Bernhard; Mark Hodges, D; Allan-Wojtas, Paula; Mackinnon, Shawna; Critchley, Alan T; Prithiviraj, Balakrishnan

2009-06-01

Extracts of the brown seaweed Ascophyllum nodosum enhance plant tolerance against environmental stresses such as drought, salinity, and frost. However, the molecular mechanisms underlying this improved stress tolerance and the nature of the bioactive compounds present in the seaweed extracts that elicits stress tolerance remain largely unknown. We investigated the effect of A. nodosum extracts and its organic sub-fractions on freezing tolerance of Arabidopsis thaliana. Ascophyllum nodosum extracts and its lipophilic fraction significantly increased tolerance to freezing temperatures in in vitro and in vivo assays. Untreated plants exhibited severe chlorosis, tissue damage, and failed to recover from freezing treatments while the extract-treated plants recovered from freezing temperature of -7.5 degrees C in in vitro and -5.5 degrees C in in vivo assays. Electrolyte leakage measurements revealed that the LT(50) value was lowered by 3 degrees C while cell viability staining demonstrated a 30-40% reduction in area of damaged tissue in extract treated plants as compared to water controls. Moreover, histological observations of leaf sections revealed that extracts have a significant effect on maintaining membrane integrity during freezing stress. Treated plants exhibited 70% less chlorophyll damage during freezing recovery as compared to the controls, and this correlated with reduced expression of the chlorphyllase genes AtCHL1 and AtCHL2. Further, the A. nodosum extract treatment modulated the expression of the cold response genes, COR15A, RD29A, and CBF3, resulting in enhanced tolerance to freezing temperatures. More than 2.6-fold increase in expression of RD29A, 1.8-fold increase of CBF3 and two-fold increase in the transcript level of COR15A was observed in plants treated with lipophilic fraction of A. nodosum at -2 degrees C. Taken together, the results suggest that chemical components in A. nodosum extracts protect membrane integrity and affect the expression of stress response genes leading to freezing stress tolerance in A. thaliana.

Simplification of Fatigue Test Requirements for Damage Tolerance of Composite Interstage Launch Vehicle Hardware

NASA Technical Reports Server (NTRS)

Nettles, A. T.; Hodge, A. J.; Jackson, J. R.

2010-01-01

The issue of fatigue loading of structures composed of composite materials is considered in a requirements document that is currently in place for manned launch vehicles. By taking into account the short life of these parts, coupled with design considerations, it is demonstrated that the necessary coupon level fatigue data collapse to a static case. Data from a literature review of past studies that examined compressive fatigue loading after impact and data generated from this experimental study are presented to support this finding. Damage growth, in the form of infrared thermography, was difficult to detect due to rapid degradation of compressive properties once damage growth initiated. Unrealistically high fatigue amplitudes were needed to fail 5 of 15 specimens before 10,000 cycles were reached. Since a typical vehicle structure, such as the Ares I interstage, only experiences a few cycles near limit load, it is concluded that static compression after impact (CAI) strength data will suffice for most launch vehicle structures.

Ocular tolerance of preservatives on the murine cornea.

PubMed

Furrer, P; Mayer, J M; Plazonnet, B; Gurny, R

1999-03-01

We investigated the effects of instilling 13 commonly used preservatives on the murine cornea in vivo. Due to the instillation of preservatives, micro-lesions are formed on the cornea and can be selectively marked by fluorescein. The sum of the resulting fluorescent areas was measured using an episcopic microscope coupled to an image processing system. All the tested preservatives proved to be well-tolerated by the eye at commonly used concentrations. However, in some cases, increased concentrations of preservatives or combinations resulted in significant increase of the amount of corneal damage. With increasing the concentration, corneal lesion increased the most in the case of cetylpyridinium. While a combination of chlorobutanol 0.5% and phenylethylalcohol 0.5% did not result in an increase in corneal damage (when compared to the use of each separately), the associations of thiomersal 0.02% and phenylethylalcohol 0.4% on one hand and of edetate disodium (EDTA) 0.1% and benzalkonium 0.01% on the other, resulted in significant increases in the amount of corneal damage. However, in none of the tested combinations, the increase in the observed damage exceed the limit of ocular intolerance we had defined beforehand: thus, they were all deemed relatively well-tolerated. In the last part of the study, we investigated the effects of combining several preservatives, at usual concentrations, with an anesthetic solution of oxybuprocaine and found no notable increase in ocular damage.

Radiation Tolerance of 65nm CMOS Transistors

DOE PAGES

Krohn, M.; Bentele, B.; Christian, D. C.; ...

2015-12-11

We report on the effects of ionizing radiation on 65 nm CMOS transistors held at approximately -20°C during irradiation. The pattern of damage observed after a total dose of 1 Grad is similar to damage reported in room temperature exposures, but we observe less damage than was observed at room temperature.

Damage-Tolerance Characteristics of Composite Fuselage Sandwich Structures with Thick Facesheets

NASA Technical Reports Server (NTRS)

McGowan, David M.; Ambur, Damodar R.

1997-01-01

Damage tolerance characteristics and results from experimental and analytical studies of a composite fuselage keel sandwich structure subjected to low-speed impact damage and discrete-source damage are presented. The test specimens are constructed from graphite-epoxy skins borided to a honeycomb core, and they are representative of a highly loaded fuselage keel structure. Results of compression-after-impact (CAI) and notch-length sensitivity studies of 5-in.-wide by 10-in.long specimens are presented. A correlation between low-speed-impact dent depth, the associated damage area, and residual strength for different impact-energy levels is described; and a comparison of the strength for undamaged and damaged specimens with different notch-length-to-specimen-width ratios is presented. Surface strains in the facesheets of the undamaged specimens as well as surface strains that illustrate the load redistribution around the notch sites in the notched specimens are presented and compared with results from finite element analyses. Reductions in strength of as much as 53.1 percent for the impacted specimens and 64.7 percent for the notched specimens are observed.

40 CFR 180.1180 - Kaolin; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., fungus, and bacterial damage to plants. This temporary exemption from the requirement of a tolerance will... control of insects, fungi, and bacteria (food/feed use). [62 FR 19685, Apr. 23, 1997, as amended at 63 FR...

40 CFR 180.1180 - Kaolin; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., fungus, and bacterial damage to plants. This temporary exemption from the requirement of a tolerance will... control of insects, fungi, and bacteria (food/feed use). [62 FR 19685, Apr. 23, 1997, as amended at 63 FR...

40 CFR 180.1180 - Kaolin; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., fungus, and bacterial damage to plants. This temporary exemption from the requirement of a tolerance will... control of insects, fungi, and bacteria (food/feed use). [62 FR 19685, Apr. 23, 1997, as amended at 63 FR...

Seasonal variation in hybrid poplar tolerance to glyphosate.

Treesearch

Daniel Netzer; Edward Hansen

1992-01-01

Reports that glyphosate applied during April or May in hybrid poplar plantations usually results in tree growth increases and that later summer applications often result in tree damage, growth loss, or mortality. Introduces the concept of "physiological" and "morphological" herbicide tolerance.

40 CFR 180.1180 - Kaolin; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., fungus, and bacterial damage to plants. This temporary exemption from the requirement of a tolerance will... control of insects, fungi, and bacteria (food/feed use). [62 FR 19685, Apr. 23, 1997, as amended at 63 FR...

40 CFR 180.1180 - Kaolin; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., fungus, and bacterial damage to plants. This temporary exemption from the requirement of a tolerance will... control of insects, fungi, and bacteria (food/feed use). [62 FR 19685, Apr. 23, 1997, as amended at 63 FR...

International SAMPE Symposium and Exhibition, 35th, Anaheim, CA, Apr. 2-5, 1990, Proceedings. Books 1 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janicki, G.; Bailey, V.; Schjelderup, H.

The present conference discusses topics in the fields of ultralightweight structures, producibility of thermoplastic composites, innovation in sandwich structures, composite failure processes, toughened materials, metal-matrix composites, advanced materials for future naval systems, thermoplastic polymers, automated composites manufacturers, advanced adhesives, emerging processes for aerospace component fabrication, and modified resin systems. Also discussed are matrix behavior for damage tolerance, composite materials repair, testing for damage tolerance, composite strength analyses, materials workplace health and safety, cost-conscious composites, bismaleimide systems, and issues facing advanced composite materials suppliers.

A preliminary damage tolerance methodology for composite structures

NASA Technical Reports Server (NTRS)

Wilkins, D. J.

1983-01-01

The certification experience for the primary, safety-of-flight composite structure applications on the F-16 is discussed. The rationale for the selection of delamination as the major issue for damage tolerance is discussed, as well as the modeling approach selected. The development of the necessary coupon-level data base is briefly summarized. The major emphasis is on the description of a full-scale fatigue test where delamination growth was obtained to demonstrate the validity of the selected approach. A summary is used to review the generic features of the methodology.

Dynamics Impact Tolerance of Shuttle RCC Leading Edge Panels Using LS-DYNA

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Jackson, Karen E.; Lyle, Karen H.; Jones, Lisa E.; Hardy, Robin C.; Spellman, Regina L.; Carney, Kelly S.; Melis, Matthew E.; Stockwell, Alan E.

2005-01-01

This paper describes a research program conducted to enable accurate prediction of the impact tolerance of the shuttle Orbiter leading-edge wing panels using physics-based codes such as LS-DYNA, a nonlinear, explicit transient dynamic finite element code. The shuttle leading-edge panels are constructed of Reinforced-Carbon-Carbon (RCC) composite material, which is used because of its thermal properties to protect the shuttle during reentry into the Earth's atmosphere. Accurate predictions of impact damage from insulating foam and other debris strikes that occur during launch required materials characterization of expected debris, including strain-rate effects. First, analytical models of individual foam and RCC materials were validated. Next, analytical models of foam cylinders impacting 6- in. x 6-in. RCC flat plates were developed and validated. LS-DYNA pre-test models of the RCC flat plate specimens established the impact velocity of the test for three damage levels: no-detectable damage, non-destructive evaluation (NDE) detectable damage, or visible damage such as a through crack or hole. Finally, the threshold of impact damage for RCC on representative Orbiter wing panels was predicted for both a small through crack and for NDE-detectable damage.

Dynamic Impact Tolerance of Shuttle RCC Leading Edge Panels using LS-DYNA

NASA Technical Reports Server (NTRS)

Fasanella, Edwin; Jackson, Karen E.; Lyle, Karen H.; Jones, Lisa E.; Hardy, Robin C.; Spellman, Regina L.; Carney, Kelly S.; Melis, Matthew E.; Stockwell, Alan E.

2008-01-01

This paper describes a research program conducted to enable accurate prediction of the impact tolerance of the shuttle Orbiter leading-edge wing panels using 'physics-based- codes such as LS-DYNA, a nonlinear, explicit transient dynamic finite element code. The shuttle leading-edge panels are constructed of Reinforced-Carbon-Carbon (RCC) composite material, which issued because of its thermal properties to protect the shuttle during re-entry into the Earth's atmosphere. Accurate predictions of impact damage from insulating foam and other debris strikes that occur during launch required materials characterization of expected debris, including strain-rate effects. First, analytical models of individual foam and RCC materials were validated. Next, analytical models of individual foam cylinders impacting 6-in. x 6-in. RCC flat plates were developed and validated. LS-DYNA pre-test models of the RCC flat plate specimens established the impact velocity of the test for three damage levels: no-detectable damage, non-destructive evaluation (NDE) detectable damage, or visible damage such as a through crack or hole. Finally, the threshold of impact damage for RCC on representative Orbiter wing panels was predicted for both a small through crack and for NDE-detectable damage.

Modelling biofilm-induced formation damage and biocide treatment in subsurface geosystems

PubMed Central

Ezeuko, C C; Sen, A; Gates, I D

2013-01-01

Biofilm growth in subsurface porous media, and its treatment with biocides (antimicrobial agents), involves a complex interaction of biogeochemical processes which provide non-trivial mathematical modelling challenges. Although there are literature reports of mathematical models to evaluate biofilm tolerance to biocides, none of these models have investigated biocide treatment of biofilms growing in interconnected porous media with flow. In this paper, we present a numerical investigation using a pore network model of biofilm growth, formation damage and biocide treatment. The model includes three phases (aqueous, adsorbed biofilm, and solid matrix), a single growth-limiting nutrient and a single biocide dissolved in the water. Biofilm is assumed to contain a single species of microbe, in which each cell can be a viable persister, a viable non-persister, or non-viable (dead). Persisters describe small subpopulation of cells which are tolerant to biocide treatment. Biofilm tolerance to biocide treatment is regulated by persister cells and includes ‘innate’ and ‘biocide-induced’ factors. Simulations demonstrate that biofilm tolerance to biocides can increase with biofilm maturity, and that biocide treatment alone does not reverse biofilm-induced formation damage. Also, a successful application of biological permeability conformance treatment involving geologic layers with flow communication is more complicated than simply engineering the attachment of biofilm-forming cells at desired sites. PMID:23164434

A novel biomimetic approach to the design of high-performance ceramic/metal composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Launey, Maximilien E.; Munch, Etienne; Alsem, Daan Hein

2009-08-01

The prospect of extending natural biological design to develop new synthetic ceramic-metal composite materials is examined. Using ice-templating of ceramic suspensions and subsequent metal infiltration, we demonstrate that the concept of ordered hierarchical design can be applied to create fine-scale laminated ceramic-metal (bulk) composites that are inexpensive, lightweight and display exceptional damage-tolerance properties. Specifically, Al{sub 2}O{sub 3}/Al-Si laminates with ceramic contents up to approximately 40 vol% and with lamellae thicknesses down to 10 {micro}m were processed and characterized. These structures achieve an excellent fracture toughness of 40 MPa{radical}m at a tensile strength of approximately 300 MPa. Salient toughening mechanisms aremore » described together with further toughening strategies.« less

Temperature-stress resistance and tolerance along a latitudinal cline in North American Arabidopsis lyrata.

PubMed

Wos, Guillaume; Willi, Yvonne

2015-01-01

The study of latitudinal gradients can yield important insights into adaptation to temperature stress. Two strategies are available: resistance by limiting damage, or tolerance by reducing the fitness consequences of damage. Here we studied latitudinal variation in resistance and tolerance to frost and heat and tested the prediction of a trade-off between the two strategies and their costliness. We raised plants of replicate maternal seed families from eight populations of North American Arabidopsis lyrata collected along a latitudinal gradient in climate chambers and exposed them repeatedly to either frost or heat stress, while a set of control plants grew under standard conditions. When control plants reached maximum rosette size, leaf samples were exposed to frost and heat stress, and electrolyte leakage (PEL) was measured and treated as an estimate of resistance. Difference in maximum rosette size between stressed and control plants was used as an estimate of tolerance. Northern populations were more frost resistant, and less heat resistant and less heat tolerant, but-unexpectedly-they were also less frost tolerant. Negative genetic correlations between resistance and tolerance to the same and different thermal stress were generally not significant, indicating only weak trade-offs. However, tolerance to frost was consistently accompanied by small size under control conditions, which may explain the non-adaptive latitudinal pattern for frost tolerance. Our results suggest that adaptation to frost and heat is not constrained by trade-offs between them. But the cost of frost tolerance in terms of plant size reduction may be important for the limits of species distributions and climate niches.

The roles of tolerance in the evolution, maintenance and breakdown of mutualism

NASA Astrophysics Data System (ADS)

Edwards, David P.

2009-10-01

Tolerance strategies are cost-reduction mechanisms that enable organisms to recover some of the fitness lost to damage, but impose limited or no cost on antagonists. They are frequently invoked in studies of plant-herbivore and of host-parasite interactions, but the possible roles of tolerance in mutualism (interspecific cooperation) have yet to be thoroughly examined. This review identifies candidate roles for tolerance in the evolution, maintenance and breakdown of mutualism. Firstly, by reducing the cost of damage, tolerance provides a key pathway by which pre-mutualistic hosts can reduce the cost of association with their parasites, promoting cooperation. This holds for the evolution of ‘evolved dependency’ type mutualism, where a host requires an antagonist that does not direct any reward to their partner for some resource, and of ‘outright mutualism’, where participants directly trade benefits. Secondly, in outright mutualism, tolerance might maintain cooperation by reducing the cost of a persisting negative trait in a symbiotic partner. Finally, the evolution of tolerance might also provide a pathway out of mutualism because the host could evolve a cheaper alternative to continued cooperation with its mutualistic partner, permitting autonomy. A key consequence of tolerance is that it contrasts with partner choice mechanisms that impose large costs on cheats, and I highlight understanding any trade-off between tolerance and partner choice as an important research topic in the evolution of cooperation. I conclude by identifying tolerance as part of a more general phenomenon of co-adaptation in mutualism and parasitism that drives the evolution of the cost/benefit ratio from the interaction.

Biology and control of Varroa destructor.

PubMed

Rosenkranz, Peter; Aumeier, Pia; Ziegelmann, Bettina

2010-01-01

The ectoparasitic honey bee mite Varroa destructor was originally confined to the Eastern honey bee Apis cerana. After a shift to the new host Apis mellifera during the first half of the last century, the parasite dispersed world wide and is currently considered the major threat for apiculture. The damage caused by Varroosis is thought to be a crucial driver for the periodical colony losses in Europe and the USA and regular Varroa treatments are essential in these countries. Therefore, Varroa research not only deals with a fascinating host-parasite relationship but also has a responsibility to find sustainable solutions for the beekeeping. This review provides a survey of the current knowledge in the main fields of Varroa research including the biology of the mite, damage to the host, host tolerance, tolerance breeding and Varroa treatment. We first present a general view on the functional morphology and on the biology of the Varroa mite with special emphasis on host-parasite interactions during reproduction of the female mite. The pathology section describes host damage at the individual and colony level including the problem of transmission of secondary infections by the mite. Knowledge of both the biology and the pathology of Varroa mites is essential for understanding possible tolerance mechanisms in the honey bee host. We comment on the few examples of natural tolerance in A. mellifera and evaluate recent approaches to the selection of Varroa tolerant honey bees. Finally, an extensive listing and critical evaluation of chemical and biological methods of Varroa treatments is given. This compilation of present-day knowledge on Varroa honey bee interactions emphasizes that we are still far from a solution for Varroa infestation and that, therefore, further research on mite biology, tolerance breeding, and Varroa treatment is urgently needed. Copyright 2009 Elsevier Inc. All rights reserved.

Effects of Oxygen Availability on Acetic Acid Tolerance and Intracellular pH in Dekkera bruxellensis.

PubMed

Capusoni, Claudia; Arioli, Stefania; Zambelli, Paolo; Moktaduzzaman, M; Mora, Diego; Compagno, Concetta

2016-08-01

The yeast Dekkera bruxellensis, associated with wine and beer production, has recently received attention, because its high ethanol and acid tolerance enables it to compete with Saccharomyces cerevisiae in distilleries that produce fuel ethanol. We investigated how different cultivation conditions affect the acetic acid tolerance of D. bruxellensis We analyzed the ability of two strains (CBS 98 and CBS 4482) exhibiting different degrees of tolerance to grow in the presence of acetic acid under aerobic and oxygen-limited conditions. We found that the concomitant presence of acetic acid and oxygen had a negative effect on D. bruxellensis growth. In contrast, incubation under oxygen-limited conditions resulted in reproducible growth kinetics that exhibited a shorter adaptive phase and higher growth rates than those with cultivation under aerobic conditions. This positive effect was more pronounced in CBS 98, the more-sensitive strain. Cultivation of CBS 98 cells under oxygen-limited conditions improved their ability to restore their intracellular pH upon acetic acid exposure and to reduce the oxidative damage to intracellular macromolecules caused by the presence of acetic acid. This study reveals an important role of oxidative stress in acetic acid tolerance in D. bruxellensis, indicating that reduced oxygen availability can protect against the damage caused by the presence of acetic acid. This aspect is important for optimizing industrial processes performed in the presence of acetic acid. This study reveals an important role of oxidative stress in acetic acid tolerance in D. bruxellensis, indicating that reduced oxygen availability can have a protective role against the damage caused by the presence of acetic acid. This aspect is important for the optimization of industrial processes performed in the presence of acetic acid. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Effects of Oxygen Availability on Acetic Acid Tolerance and Intracellular pH in Dekkera bruxellensis

PubMed Central

Capusoni, Claudia; Arioli, Stefania; Zambelli, Paolo; Moktaduzzaman, M.; Mora, Diego

2016-01-01

ABSTRACT The yeast Dekkera bruxellensis, associated with wine and beer production, has recently received attention, because its high ethanol and acid tolerance enables it to compete with Saccharomyces cerevisiae in distilleries that produce fuel ethanol. We investigated how different cultivation conditions affect the acetic acid tolerance of D. bruxellensis. We analyzed the ability of two strains (CBS 98 and CBS 4482) exhibiting different degrees of tolerance to grow in the presence of acetic acid under aerobic and oxygen-limited conditions. We found that the concomitant presence of acetic acid and oxygen had a negative effect on D. bruxellensis growth. In contrast, incubation under oxygen-limited conditions resulted in reproducible growth kinetics that exhibited a shorter adaptive phase and higher growth rates than those with cultivation under aerobic conditions. This positive effect was more pronounced in CBS 98, the more-sensitive strain. Cultivation of CBS 98 cells under oxygen-limited conditions improved their ability to restore their intracellular pH upon acetic acid exposure and to reduce the oxidative damage to intracellular macromolecules caused by the presence of acetic acid. This study reveals an important role of oxidative stress in acetic acid tolerance in D. bruxellensis, indicating that reduced oxygen availability can protect against the damage caused by the presence of acetic acid. This aspect is important for optimizing industrial processes performed in the presence of acetic acid. IMPORTANCE This study reveals an important role of oxidative stress in acetic acid tolerance in D. bruxellensis, indicating that reduced oxygen availability can have a protective role against the damage caused by the presence of acetic acid. This aspect is important for the optimization of industrial processes performed in the presence of acetic acid. PMID:27235432

Numerical Modeling, Thermomechanical Testing, and NDE Procedures for Prediction of Microcracking Induced Permeability of Cryogenic Composites

NASA Technical Reports Server (NTRS)

Noh, Jae; Whitcomb, John; Oh, Bongtaek; Lagoudas, Dimitris; Maslov, Konstatin; Ganpatyre, Atul; Kinra, Vikram

2003-01-01

Reusable Space Vehicles will include light cryogenic composite fuel tanks that must not leak excessively even after multiple launches. Damage in cryogenic composite fuel tanks induced during manufacturing and advanced by thermomechanical cycling can accelerate leakage of the propellant. Whether the leakage exceeds tolerable levels depends on many factors, including pressure gradients, microcrack density, other damage such as delamination, connectivity of the cracks, residual stresses from manufacture, service-induced stresses from thermal and mechanical loads, and composite lay-up. Although it is critical to experimentally characterize permeability during various thermal and mechanical load histories, optimal design depends on having analytical models that can predict the effect of various parameters on performance. Our broad goal is to develop such models that are experimentally validated by destructive and non-destructive evaluation means.

Mechanisms of radiation-induced segregation in CrFeCoNi-based single-phase concentrated solid solution alloys

DOE PAGES

He, Mo-Rigen; Wang, Shuai; Shi, Shi; ...

2016-12-31

Single-phase concentrated solid solution alloys have attracted wide interest due to their superior mechanical properties and enhanced radiation tolerance, which make them promising candidates for the structural applications in next-generation nuclear reactors. However, little has been understood about the intrinsic stability of their as-synthesized, high-entropy configurations against radiation damage. In this paper, we report the element segregation in CrFeCoNi, CrFeCoNiMn, and CrFeCoNiPd equiatomic alloys when subjected to 1250 kV electron irradiations at 400 °C up to a damage level of 1 displacement per atom. Cr/Fe/Mn/Pd can deplete and Co/Ni can accumulate at radiation-induced dislocation loops, while the actively segregating elementsmore » are alloy-specific. Moreover, electron-irradiated matrix of CrFeCoNiMn and CrFeCoNiPd shows L1 0 (NiMn)-type ordering decomposition and <001>-oriented spinodal decomposition between Co/Ni and Pd, respectively. Finally, these findings are rationalized based on the atomic size difference and enthalpy of mixing between the alloying elements, and identify a new important requirement to the design of radiation-tolerant alloys through modification of the composition.« less

Neural Networks for Flight Control

NASA Technical Reports Server (NTRS)

Jorgensen, Charles C.

1996-01-01

Neural networks are being developed at NASA Ames Research Center to permit real-time adaptive control of time varying nonlinear systems, enhance the fault-tolerance of mission hardware, and permit online system reconfiguration. In general, the problem of controlling time varying nonlinear systems with unknown structures has not been solved. Adaptive neural control techniques show considerable promise and are being applied to technical challenges including automated docking of spacecraft, dynamic balancing of the space station centrifuge, online reconfiguration of damaged aircraft, and reducing cost of new air and spacecraft designs. Our experiences have shown that neural network algorithms solved certain problems that conventional control methods have been unable to effectively address. These include damage mitigation in nonlinear reconfiguration flight control, early performance estimation of new aircraft designs, compensation for damaged planetary mission hardware by using redundant manipulator capability, and space sensor platform stabilization. This presentation explored these developments in the context of neural network control theory. The discussion began with an overview of why neural control has proven attractive for NASA application domains. The more important issues in control system development were then discussed with references to significant technical advances in the literature. Examples of how these methods have been applied were given, followed by projections of emerging application needs and directions.

Advanced information processing system: Local system services

NASA Technical Reports Server (NTRS)

Burkhardt, Laura; Alger, Linda; Whittredge, Roy; Stasiowski, Peter

1989-01-01

The Advanced Information Processing System (AIPS) is a multi-computer architecture composed of hardware and software building blocks that can be configured to meet a broad range of application requirements. The hardware building blocks are fault-tolerant, general-purpose computers, fault-and damage-tolerant networks (both computer and input/output), and interfaces between the networks and the computers. The software building blocks are the major software functions: local system services, input/output, system services, inter-computer system services, and the system manager. The foundation of the local system services is an operating system with the functions required for a traditional real-time multi-tasking computer, such as task scheduling, inter-task communication, memory management, interrupt handling, and time maintenance. Resting on this foundation are the redundancy management functions necessary in a redundant computer and the status reporting functions required for an operator interface. The functional requirements, functional design and detailed specifications for all the local system services are documented.

Ceramic Composite Development for Gas Turbine Engine Hot Section Components

NASA Technical Reports Server (NTRS)

DiCarlo, James A.; VANrOODE, mARK

2006-01-01

The development of ceramic materials for incorporation into the hot section of gas turbine engines has been ongoing for about fifty years. Researchers have designed, developed, and tested ceramic gas turbine components in rigs and engines for automotive, aero-propulsion, industrial, and utility power applications. Today, primarily because of materials limitations and/or economic factors, major challenges still remain for the implementation of ceramic components in gas turbines. For example, because of low fracture toughness, monolithic ceramics continue to suffer from the risk of failure due to unknown extrinsic damage events during engine service. On the other hand, ceramic matrix composites (CMC) with their ability to display much higher damage tolerance appear to be the materials of choice for current and future engine components. The objective of this paper is to briefly review the design and property status of CMC materials for implementation within the combustor and turbine sections for gas turbine engine applications. It is shown that although CMC systems have advanced significantly in thermo-structural performance within recent years, certain challenges still exist in terms of producibility, design, and affordability for commercial CMC turbine components. Nevertheless, there exist some recent successful efforts for prototype CMC components within different engine types.

Tolerance of Cottonwood to Damage by Cottonwood Leaf Beetle

Treesearch

F. L. Oliveria; D. T. Cooper

1977-01-01

Wide variation in tolerance to the cottonwood leaf beetle was found in fourteen hundred eastern cottonwood clones, originating from 36 young natural stands along the Mississippi River from Memphis, Tennessee, to Baton Rouge, Louisiana. Expected genetic gains were large enough to justify further research.

Overexpression of CsCaM3 Improves High Temperature Tolerance in Cucumber

PubMed Central

Yu, Bingwei; Yan, Shuangshuang; Zhou, Huoyan; Dong, Riyue; Lei, Jianjun; Chen, Changming; Cao, Bihao

2018-01-01

High temperature (HT) stress affects the growth and production of cucumbers, but genetic resources with high heat tolerance are very scarce in this crop. Calmodulin (CaM) has been confirmed to be related to the regulation of HT stress resistance in plants. CsCaM3, a CaM gene, was isolated from cucumber inbred line “02-8.” Its expression was characterized in the present study. CsCaM3 transcripts differed among the organs and tissues of cucumber plants and could be induced by HTs or abscisic acid, but not by salicylic acid. CsCaM3 transcripts exhibited subcellular localization to the cytoplasm and nuclei of cells. Overexpression of CsCaM3 in cucumber plants has the potential to improve their heat tolerance and protect against oxidative damage and photosynthesis system damage by regulating the expression of HT-responsive genes in plants, including chlorophyll catabolism-related genes under HT stress. Taken together, our results provide useful insights into stress tolerance in cucumber. PMID:29946334

Radiation Tolerant Interfaces: Influence of Local Stoichiometry at the Misfit Dislocation on Radiation Damage Resistance of Metal/Oxide Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shutthanandan, Vaithiyalingam; Choudhury, Samrat; Manandhar, Sandeep

To understand how variations in interface properties such as misfit-dislocation density and local chemistry affect radiation-induced defect absorption and recombination, we have explored a model system of CrxV1-x alloy epitaxial films deposited on MgO single crystals. By controlling film composition, the lattice mismatch with MgO was adjusted so that the misfit-dislocation density varies at the interface. These interfaces were exposed to irradiation and in situ results show that the film with a semi-coherent interface (Cr) withstands irradiation while V film, which has similar semi-coherent interface like Cr, showed the largest damage. Theoretical calculations indicate that, unlike at metal/metal interfaces, themore » misfit dislocation density does not dominate radiation damage tolerance at metal/oxide interfaces. Rather, the stoichiometry, and the precise location of the misfit-dislocation density relative to the interface, drives defect behavior. Together, these results demonstrate the sensitivity of defect recombination to interfacial chemistry and provide new avenues for engineering radiation-tolerant nanomaterials.« less

Biochemical indicators of root damage in rice (Oryza sativa) genotypes under zinc deficiency stress.

PubMed

Lee, Jae-Sung; Wissuwa, Matthias; Zamora, Oscar B; Ismail, Abdelbagi M

2017-11-01

Zn deficiency is one of the major soil constraints currently limiting rice production. Although recent studies demonstrated that higher antioxidant activity in leaf tissue effectively protects against Zn deficiency stress, little is known about whether similar tolerance mechanisms operate in root tissue. In this study we explored root-specific responses of different rice genotypes to Zn deficiency. Root solute leakage and biomass reduction, antioxidant activity, and metabolic changes were measured using plants grown in Zn-deficient soil and hydroponics. Solute leakage from roots was higher in sensitive genotypes and linked to membrane damage caused by Zn deficiency-induced oxidative stress. However, total root antioxidant activity was four-fold lower than in leaves and did not differ between sensitive and tolerant genotypes. Root metabolite analysis using gas chromatography-mass spectrometry and high performance liquid chromatography indicated that Zn deficiency triggered the accumulation of glycerol-3-phosphate and acetate in sensitive genotypes, while less or no accumulation was seen in tolerant genotypes. We suggest that these metabolites may serve as biochemical indicators of root damage under Zn deficiency.

Modelling of Damage Evolution in Braided Composites: Recent Developments

NASA Astrophysics Data System (ADS)

Wang, Chen; Roy, Anish; Silberschmidt, Vadim V.; Chen, Zhong

2017-12-01

Composites reinforced with woven or braided textiles exhibit high structural stability and excellent damage tolerance thanks to yarn interlacing. With their high stiffness-to-weight and strength-to-weight ratios, braided composites are attractive for aerospace and automotive components as well as sports protective equipment. In these potential applications, components are typically subjected to multi-directional static, impact and fatigue loadings. To enhance material analysis and design for such applications, understanding mechanical behaviour of braided composites and development of predictive capabilities becomes crucial. Significant progress has been made in recent years in development of new modelling techniques allowing elucidation of static and dynamic responses of braided composites. However, because of their unique interlacing geometric structure and complicated failure modes, prediction of damage initiation and its evolution in components is still a challenge. Therefore, a comprehensive literature analysis is presented in this work focused on a review of the state-of-the-art progressive damage analysis of braided composites with finite-element simulations. Recently models employed in the studies on mechanical behaviour, impact response and fatigue analyses of braided composites are presented systematically. This review highlights the importance, advantages and limitations of as-applied failure criteria and damage evolution laws for yarns and composite unit cells. In addition, this work provides a good reference for future research on FE simulations of braided composites.

Nitrogen nutrition and drought hardening exert opposite effects on the stress tolerance of Pinus pinea L. seedlings.

PubMed

Villar-Salvador, Pedro; Peñuelas, Juan L; Jacobs, Douglass F

2013-02-01

Functional attributes determine the survival and growth of planted seedlings in reforestation projects. Nitrogen (N) and water are important resources in the cultivation of forest species, which have a strong effect on plant functional traits. We analyzed the influence of N nutrition on drought acclimation of Pinus pinea L. seedlings. Specifically, we addressed if high N fertilization reduces drought and frost tolerance of seedlings and whether drought hardening reverses the effect of high N fertilization on stress tolerance. Seedlings were grown under two N fertilization regimes (6 and 100 mg N per plant) and subjected to three drought-hardening levels (well-watered, moderate and strong hardening). Water relations, gas exchange, frost damage, N concentration and growth at the end of the drought-hardening period, and survival and growth of seedlings under controlled xeric and mesic outplanting conditions were measured. Relative to low-N plants, high-N plants were larger, had higher stomatal conductance (27%), residual transpiration (11%) and new root growth capacity and closed stomata at higher water potential. However, high N fertilization also increased frost damage (24%) and decreased plasmalemma stability to dehydration (9%). Drought hardening reversed to a great extent the reduction in stress tolerance caused by high N fertilization as it decreased frost damage, stomatal conductance and residual transpiration by 21, 31 and 24%, respectively, and increased plasmalemma stability to dehydration (8%). Drought hardening increased tissue non-structural carbohydrates and N concentration, especially in high-fertilized plants. Frost damage was positively related to the stability of plasmalemma to dehydration (r = 0.92) and both traits were negatively related to the concentration of reducing soluble sugars. No differences existed between moderate and strong drought-hardening treatments. Neither N nutrition nor drought hardening had any clear effect on seedling performance under xeric outplanting conditions. However, fertilization increased growth under mesic conditions, whereas drought hardening decreased growth. We conclude that drought hardening and N fertilization applied under typical container nursery operational conditions exert opposite effects on the physiological stress tolerance of P. pinea seedlings. While drought hardening increases overall stress tolerance, N nutrition reduces it and yet has no effect on the drought acclimation capacity of seedlings.

Root Damage under Alkaline Stress Is Associated with Reactive Oxygen Species Accumulation in Rice (Oryza sativa L.)

PubMed Central

Zhang, Hui; Liu, Xiao-Long; Zhang, Rui-Xue; Yuan, Hai-Yan; Wang, Ming-Ming; Yang, Hao-Yu; Ma, Hong-Yuan; Liu, Duo; Jiang, Chang-Jie; Liang, Zheng-Wei

2017-01-01

Alkaline stress (high pH) severely damages root cells, and consequently, inhibits rice (Oryza sativa L.) seedling growth. In this study, we demonstrate the accumulation of reactive oxygen species (ROS) in root cells under alkaline stress. Seedlings of two rice cultivars with different alkaline tolerances, ‘Dongdao-4’ (moderately alkaline-tolerant) and ‘Jiudao-51’ (alkaline-sensitive), were subjected to alkaline stress simulated by 15 mM sodium carbonate (Na2CO3). Alkaline stress greatly reduced seedling survival rate, shoot and root growth, and root vigor. Moreover, severe root cell damage was observed under alkaline stress, as shown by increased membrane injury, malondialdehyde accumulation, and Evan’s Blue staining. The expression of the cell death-related genes OsKOD1, OsHsr203j, OsCP1, and OsNAC4 was consistently upregulated, while that of a cell death-suppressor gene, OsBI1, was downregulated. Analysis of the ROS contents revealed that alkaline stress induced a marked accumulation of superoxide anions (O2•-) and hydrogen peroxide (H2O2) in rice roots. The application of procyanidins (a potent antioxidant) to rice seedlings 24 h prior to alkaline treatment significantly alleviated alkalinity-induced root damage and promoted seedling growth inhibition, which were concomitant with reduced ROS accumulation. These results suggest that root cell damage, and consequently growth inhibition, of rice seedlings under alkaline stress is closely associated with ROS accumulation. The antioxidant activity of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase increased under alkaline stress in the roots, probably in response to the cellular damage induced by oxidative stress. However, this response mechanism may be overwhelmed by the excess ROS accumulation observed under stress, resulting in oxidative damage to root cells. Our findings provide physiological insights into the molecular mechanisms of alkalinity-induced damage to root cells, and will contribute to the improvement of alkaline stress tolerance in rice plants. PMID:28943882

Root Damage under Alkaline Stress Is Associated with Reactive Oxygen Species Accumulation in Rice (Oryza sativa L.).

PubMed

Zhang, Hui; Liu, Xiao-Long; Zhang, Rui-Xue; Yuan, Hai-Yan; Wang, Ming-Ming; Yang, Hao-Yu; Ma, Hong-Yuan; Liu, Duo; Jiang, Chang-Jie; Liang, Zheng-Wei

2017-01-01

Alkaline stress (high pH) severely damages root cells, and consequently, inhibits rice ( Oryza sativa L.) seedling growth. In this study, we demonstrate the accumulation of reactive oxygen species (ROS) in root cells under alkaline stress. Seedlings of two rice cultivars with different alkaline tolerances, 'Dongdao-4' (moderately alkaline-tolerant) and 'Jiudao-51' (alkaline-sensitive), were subjected to alkaline stress simulated by 15 mM sodium carbonate (Na 2 CO 3 ). Alkaline stress greatly reduced seedling survival rate, shoot and root growth, and root vigor. Moreover, severe root cell damage was observed under alkaline stress, as shown by increased membrane injury, malondialdehyde accumulation, and Evan's Blue staining. The expression of the cell death-related genes OsKOD1 , OsHsr203j , OsCP1 , and OsNAC4 was consistently upregulated, while that of a cell death-suppressor gene, OsBI1 , was downregulated. Analysis of the ROS contents revealed that alkaline stress induced a marked accumulation of superoxide anions ([Formula: see text]) and hydrogen peroxide (H 2 O 2 ) in rice roots. The application of procyanidins (a potent antioxidant) to rice seedlings 24 h prior to alkaline treatment significantly alleviated alkalinity-induced root damage and promoted seedling growth inhibition, which were concomitant with reduced ROS accumulation. These results suggest that root cell damage, and consequently growth inhibition, of rice seedlings under alkaline stress is closely associated with ROS accumulation. The antioxidant activity of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase increased under alkaline stress in the roots, probably in response to the cellular damage induced by oxidative stress. However, this response mechanism may be overwhelmed by the excess ROS accumulation observed under stress, resulting in oxidative damage to root cells. Our findings provide physiological insights into the molecular mechanisms of alkalinity-induced damage to root cells, and will contribute to the improvement of alkaline stress tolerance in rice plants.

Micro-Energy Rates for Damage Tolerance and Durability of Composite Structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Minnetyan, Levon

2006-01-01

In this paper, the adhesive bond strength of lap-jointed graphite/aluminum composites is examined by computational simulation. Computed micro-stress level energy release rates are used to identify the damage mechanisms associated with the corresponding acoustic emission (AE) signals. Computed damage regions are similarly correlated with ultrasonically scanned damage regions. Results show that computational simulation can be used with suitable NDE methods for credible in-service monitoring of composites.

Structure of a Novel DNA-binding Domain of Helicase-like Transcription Factor (HLTF) and Its Functional Implication in DNA Damage Tolerance.

PubMed

Hishiki, Asami; Hara, Kodai; Ikegaya, Yuzu; Yokoyama, Hideshi; Shimizu, Toshiyuki; Sato, Mamoru; Hashimoto, Hiroshi

2015-05-22

HLTF (helicase-like transcription factor) is a yeast RAD5 homolog found in mammals. HLTF has E3 ubiquitin ligase and DNA helicase activities, and plays a pivotal role in the template-switching pathway of DNA damage tolerance. HLTF has an N-terminal domain that has been designated the HIRAN (HIP116 and RAD5 N-terminal) domain. The HIRAN domain has been hypothesized to play a role in DNA binding; however, the structural basis of, and functional evidence for, the HIRAN domain in DNA binding has remained unclear. Here we show for the first time the crystal structure of the HIRAN domain of human HLTF in complex with DNA. The HIRAN domain is composed of six β-strands and two α-helices, forming an OB-fold structure frequently found in ssDNA-binding proteins, including in replication factor A (RPA). Interestingly, this study reveals that the HIRAN domain interacts with not only with a single-stranded DNA but also with a duplex DNA. Furthermore, the structure unexpectedly clarifies that the HIRAN domain specifically recognizes the 3'-end of DNA. These results suggest that the HIRAN domain functions as a sensor to the 3'-end of the primer strand at the stalled replication fork and that the domain facilitates fork regression. HLTF is recruited to a damaged site through the HIRAN domain at the stalled replication fork. Furthermore, our results have implications for the mechanism of template switching. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Biosentinel: Improving Desiccation Tolerance of Yeast Biosensors for Deep-Space Missions

NASA Technical Reports Server (NTRS)

Dalal, Sawan; Santa Maria, Sergio R.; Liddell, Lauren; Bhattacharya, Sharmila

2017-01-01

BioSentinel is one of 13 secondary payloads to be deployed on Exploration Mission 1 (EM-1) in 2019. We will use the budding yeast Saccharomyces cerevisiae as a biosensor to determine how deep-space radiation affects living organisms and to potentially quantify radiation levels through radiation damage analysis. Radiation can damage DNA through double strand breaks (DSBs), which can normally be repaired by homologous recombination. Two yeast strains will be air-dried and stored in microfluidic cards within the payload: a wild-type control strain and a radiation sensitive rad51 mutant that is deficient in DSB repairs. Throughout the mission, the microfluidic cards will be rehydrated with growth medium and an indicator dye. Growth rates of each strain will be measured through LED detection of the reduction of the indicator dye, which correlates with DNA repair and the amount of radiation damage accumulated. Results from BioSentinel will be compared to analog experiments on the ISS and on Earth. It is well known that desiccation can damage yeast cells and decrease viability over time. We performed a screen for desiccation-tolerant rad51 strains. We selected 20 re-isolates of rad51 and ran a weekly screen for desiccation-tolerant mutants for five weeks. Our data shows that viability decreases over time, confirming previous research findings. Isolates L2, L5 and L14 indicate desiccation tolerance and are candidates for whole-genome sequencing. More time is needed to determine whether a specific strain is truly desiccation tolerant. Furthermore, we conducted an intracellular trehalose assay to test how intracellular trehalose concentrations affect or protect the mutant strains against desiccation stress. S. cerevisiae cell and reagent concentrations from a previously established intracellular trehalose protocol did not yield significant absorbance measurements, so we tested varying cell and reagent concentrations and determined proper concentrations for successful protocol use.

Preliminary Assessment of a New Antireflux Ureteral Stent Design in Swine Model.

PubMed

Soria, Federico; Morcillo, Esther; Serrano, Alvaro; Rioja, Jorge; Budia, Alberto; Moreno, Jesús; Sanchez-Margallo, Francisco M

2015-08-01

To assess a new antireflux ureteral stent in animal model. The design expects to reduce morbidity associated with JJ ureteral stents. Twelve pigs were used in this study. The study began with a nephrosonographic assessment and excretory urography. Afterward, measurement of the internal diameter of both ureteropelvic junctions (UPJ) by retrograde ureteropyelography was performed. A 3 Fr (ARS group) antireflux ureteral stent was placed in the right kidney and a JJ 4 Fr (JJ group) stent was placed in the left. Follow-ups were performed at 3-6 weeks; both stents were removed at 6 weeks. The final follow-up was completed at 5 months. This includes the above-mentioned diagnostic methods and an anatomopathological study. There were no significant differences in UPJ diameter evolution between groups. During renal damage assessment, significant differences at 3 and 6 weeks were found, renal dilation being larger in JJ group. The JJ group shows a higher degree of vesicoureteral reflux at 3 and 6 weeks. After assessment of ureteral orifice, significant differences between groups were found at 3 weeks, 6 weeks, and 5 months, damage being more severe in the JJ group. After anatomopathological assessment, no statistical significance at UPJ was observed. However, statistical significance was found at ureterovesical junction, damage being more severe in the JJ group. The antireflux ureteral stent design dilates the upper urinary tract without affecting ureterovesical junction, and consequently reduces morbidity associated with JJ ureteral stents. Therefore, its patient tolerance will possibly be better than that to existent designs. Copyright © 2015 Elsevier Inc. All rights reserved.

Meta-Analysis of Attitudes toward Damage-Causing Mammalian Wildlife

PubMed Central

KANSKY, RUTH; KIDD, MARTIN; KNIGHT, ANDREW T

2014-01-01

Many populations of threatened mammals persist outside formally protected areas, and their survival depends on the willingness of communities to coexist with them. An understanding of the attitudes, and specifically the tolerance, of individuals and communities and the factors that determine these is therefore fundamental to designing strategies to alleviate human-wildlife conflict. We conducted a meta-analysis to identify factors that affected attitudes toward 4 groups of terrestrial mammals. Elephants (65%) elicited the most positive attitudes, followed by primates (55%), ungulates (53%), and carnivores (44%). Urban residents presented the most positive attitudes (80%), followed by commercial farmers (51%) and communal farmers (26%). A tolerance to damage index showed that human tolerance of ungulates and primates was proportional to the probability of experiencing damage while elephants elicited tolerance levels higher than anticipated and carnivores elicited tolerance levels lower than anticipated. Contrary to conventional wisdom, experiencing damage was not always the dominant factor determining attitudes. Communal farmers had a lower probability of being positive toward carnivores irrespective of probability of experiencing damage, while commercial farmers and urban residents were more likely to be positive toward carnivores irrespective of damage. Urban residents were more likely to be positive toward ungulates, elephants, and primates when probability of damage was low, but not when it was high. Commercial and communal farmers had a higher probability of being positive toward ungulates, primates, and elephants irrespective of probability of experiencing damage. Taxonomic bias may therefore be important. Identifying the distinct factors explaining these attitudes and the specific contexts in which they operate, inclusive of the species causing damage, will be essential for prioritizing conservation investments. Meta-Análisis de las Posturas hacia la Mamíferos Silvestres Causantes de Daños Resumen Muchas poblaciones de mamíferos amenazados persisten fuera de áreas protegidas formales y su supervivencia depende de la buena voluntad de las comunidades que coexisten con ellos. Un entendimiento de las posturas, y específicamente de la tolerancia, de los individuos y las comunidades y los factores que los determinan es fundamental para diseñar estrategias que alivien el conflicto humano – vida silvestre. Llevamos a cabo un meta-análisis para identificar los factores que afectaron las posturas hacia cuatro grupos de mamíferos terrestres. Los elefantes (65%) provocaron las posturas más positivas. Los siguieron los primates (55%), los ungulados (53%) y los carnívoros (44%). Los residentes urbanos presentaron las posturas más positivas (80%), seguidos por los granjeros comerciales (51%) y los granjeros comunales (26%). Un índice de tolerancia a los daños mostró que la tolerancia humana a los ungulados y primates fue proporcional a la probabilidad de experimentar daños mientras que los elefantes provocaron niveles de tolerancia más altos de lo esperado y los carnívoros provocaron niveles de tolerancia más bajos de lo esperado. Contrario a la sabiduría convencional, experimentar daños no fue siempre el factor dominante para determinar las posturas. Los granjeros comunales tuvieron una baja probabilidad de ser positivos hacia los carnívoros independientemente de la probabilidad de experimentar daños, mientras que los granjeros comerciales y los residentes urbanos tuvieron mayor probabilidad de ser positivos hacia los carnívoros independientemente de los daños. Los residentes urbanos tuvieron mayor probabilidad de ser positivos hacia los ungulados, los elefantes y los primates cuando la probabilidad de daños fue baja, pero no cuando fue alta. Los granjeros comerciales y comunales tuvieron una mayor probabilidad de ser positivos hacia los ungulados, los primates y los elefantes independientemente de la probabilidad de experimentar daños. El prejuicio taxonómico por eso puede ser importante. El identificar los distintos factores que explican estas posturas y los contextos específicos en los cuales operan, inclusivo de especies que causan daños, será esencial para priorizar las inversiones en la conservación. PMID:24661270

Nano-enhanced aerospace composites for increased damage tolerance and service life damage monitoring

NASA Astrophysics Data System (ADS)

Paipetis, A.; Matikas, T. E.; Barkoula, N. M.; Karapappas, P.; Vavouliotis, A.; Kostopoulos, V.

2009-03-01

This study deals with new generation composite systems which apart from the primary reinforcement at the typical fiber scale (~10 μm) are also reinforced at the nanoscale. This is performed via incorporation of nano-scale additives in typical aerospace matrix systems, such as epoxies. Carbon Nanotubes (CNTs) are ideal candidates as their extremely high aspect ratio and mechanical properties render them advantageous to other nanoscale materials. The result is the significant increase in the damage tolerance of the novel composite systems even at very low CNT loadings. By monitoring the resistance change of the CNT network, information both on the real time deformation state of the composite is obtained as a reversible change in the bulk resistance of the material, and the damage state of the material as an irreversible change in the bulk resistance of the material. The irreversible monotonic increase of the electrical resistance can be related to internal damage in the hybrid composite system and may be used as an index of the remaining lifetime of a structural component.

A Numerical Study on the Edgewise Compression Strength of Sandwich Structures with Facesheet-Core Disbonds

NASA Technical Reports Server (NTRS)

Bergan, Andrew C.

2017-01-01

Damage tolerant design approaches require determination of critical damage modes and flaw sizes in order to establish nondestructive evaluation detection requirements. A finite element model is developed to assess the effect of circular facesheet-core disbonds on the strength of sandwich specimens subjected to edgewise compressive loads for the purpose of predicting the critical flaw size for a variety of design parameters. Postbuckling analyses are conducted in which an initial imperfection is seeded using results from a linear buckling analysis. Both the virtual crack closure technique (VCCT) and cohesive elements are considered for modeling disbond growth. Predictions from analyses using the VCCT and analyses using cohesive elements are in good correlation. A series of parametric analyses are conducted to investigate the effect of core thickness and material, facesheet layup, facesheet-core interface properties, and curvature on the criticality of facesheet-core disbonds of various sizes. The results from these analyses provide a basis for determining the critical flaw size for facesheet-core disbonds subjected to edgewise compression loads and, therefore, nondestructive evaluation flaw detection requirements for this configuration.

Fabrication of micro-optical components using femtosecond oscillator pulses

NASA Astrophysics Data System (ADS)

Rodrigues, Vanessa R. M.; Ramachandran, Hema; Chidangil, Santhosh; Mathur, Deepak

2017-06-01

With a penchant for integrated photonics and miniaturization, the fabrication of micron sized optical elements using precision laser pulse management is drawing attention due to the possibility of minimizing tolerances for collateral material damage. The work presented here deals with the design, fabrication and characterization of a range of diffractive optics - gratings, grids and Fresnel zone plates - on transparent and metallic samples. Their low volume, light weight, transmission bandwidth, high damage threshold and flexible design make them suited for replacing conventional refractive optical elements. Our one-step, mask-less, 3-D laser direct writing process is a green fabrication technique which is in stark contrast to currently popular Photo-lithography based micro-structuring. Our method provides scope for modifications on the surface as well as within the bulk of the material. The mechanism involved in the fabrication of these optics on transparent and thin metallic substrates differ from each other. Our studies show that both amplitude and phase versions of micro-structures were achieved successfully with performances bearing 98% accuracy vis-a-vis theoretical expectations.

Shielding requirements for the Space Station habitability modules

NASA Technical Reports Server (NTRS)

Avans, Sherman L.; Horn, Jennifer R.; Williamsen, Joel E.

1990-01-01

The design, analysis, development, and tests of the total meteoroid/debris protection system for the Space Station Freedom habitability modules, such as the habitation module, the laboratory module, and the node structures, are described. Design requirements are discussed along with development efforts, including a combination of hypervelocity testing and analyses. Computer hydrocode analysis of hypervelocity impact phenomena associated with Space Station habitability structures is covered and the use of optimization techniques, engineering models, and parametric analyses is assessed. Explosive rail gun development efforts and protective capability and damage tolerance of multilayer insulation due to meteoroid/debris impact are considered. It is concluded that anticipated changes in the debris environment definition and requirements will require rescoping the tests and analysis required to develop a protection system.

Isolation of a lead tolerant novel bacterial species, Achromobacter sp. TL-3: assessment of bioflocculant activity.

PubMed

Batta, Neha; Subudhi, Sanjukta; Lal, Banwari; Devi, Arundhuti

2013-11-01

Lead is one of the four heavy metals that has a profound damaging effects on human health. In the recent past there has been an increasing global concern for development of sustainable bioremediation technologies for detoxification of lead contaminant. Present investigation highlights for lead biosorption by a newly isolated novel bacterial species; Achromobacter sp. TL-3 strain, isolated from activated sludge samples contaminated with heavy metals (collected from oil refinery, Assam, North-East India). For isolation of lead tolerant bacteria, sludge samples were enriched into Luria Broth medium supplemented separately with a range of lead nitrate; 250, 500, 750, 1000, 1250 and 1500 ppm respectively. The bacterial consortium that could tolerate 1500 ppm of lead nitrate was selected further for purification of lead tolerant bacterial isolates. Purified lead tolerant bacterial isolates were then eventually inoculated into production medium supplemented with ethanol and glycerol as carbon and energy source to investigate for bioflocculant production. Bioflocculant production was estimated by monitoring the potential of lead tolerant bacterial isolate to flocculate Kaolin clay in presence of 1% CaCl2. Compared to other isolates, TL-3 isolate demonstrated for maximum bioflocculant activity of 95% and thus was identified based on 16S rRNA gene sequence analysis. TL3 isolate revealed maximum homology (98%) with Achromobacter sp. and thus designated as Achromobacter sp. TL-3. Bioflocculant activity of TL-3 isolate was correlated with the change in pH and growth. Achromobacter sp. TL-3 has significant potential for lead biosorption and can be effectively employed for detoxification of lead contaminated waste effluents/waste waters.

Loss of desiccation tolerance in Copaifera langsdorffii Desf. seeds during germination.

PubMed

Pereira, W V S; Faria, J M R; Tonetti, O A O; Silva, E A A

2014-05-01

This study evaluated the loss of desiccation tolerance in C. langsdorffii seeds during the germination process. Seeds were imbibed for 24, 48, 72, 96, 120 and 144 hours and dried to the initial moisture content, kept in this state for 3 days after which they were submitted to pre-humidification and rehydration. Ultraestructural evaluations were done aiming to observe the cell damage caused by the dry process. Desiccation tolerance was evaluated in terms of the percentage of normal seedlings. Seeds not submitted to the drying process presented 61% of normal seedlings, and after 24 hours of imbibition, followed by drying, the seeds presented the same percentage of survival. However, after 48 hours of imbibition, seeds started to lose the desiccation tolerance. There was twenty six percent of normal seedlings formed from seeds imbibed for 96 hours and later dried and rehydrated. Only 5% of seeds imbibed for 144 hours, dried and rehydrated formed normal seedlings. At 144 hours of imbibition followed the dry process, there was damage into the cell structure, indicating that the seeds were unable to keep the cell structure during the drying process. Copaifera langsdorffii seeds loses the desiccation tolerance at the start of Phase 2 of imbibition.

ALA Pretreatment Improves Waterlogging Tolerance of Fig Plants

PubMed Central

An, Yuyan; Qi, Lin; Wang, Liangju

2016-01-01

5-aminolevulinic acid (ALA), a natural and environmentally friendly plant growth regulator, can improve plant tolerance to various environmental stresses. However, whether ALA can improve plant waterlogging tolerance is unknown. Here, we investigated the effects of ALA pretreatment on the waterlogging-induced damage of fig (Ficus carica Linn.) plants, which often suffer from waterlogging stress. ALA pretreatment significantly alleviated stress-induced morphological damage, increased leaf relative water content (RWC), and reduced leaf superoxide anion (O2⋅¯) production rate and malonaldehyde (MDA) content in fig leaves, indicating ALA mitigates waterlogging stress of fig plants. We further demonstrated that ALA pretreatment largely promoted leaf chlorophyll content, photosynthetic electron transfer ability, and photosynthetic performance index, indicating ALA significantly improves plant photosynthetic efficiency under waterlogging stress. Moreover, ALA pretreatment significantly increased activities of leaf superoxide dismutase (SOD) and peroxidase (POD), root vigor, and activities of root alcohol dehydrogenase (ADH), and lactate dehydrogenase (LDH), indicating ALA also significantly improves antioxidant ability and root function of fig plants under waterlogging stress. Taken together, ALA pretreatment improves waterlogging tolerance of fig plants significantly, and the promoted root respiration, leaf photosynthesis, and antioxidant ability may contribute greatly to this improvement. Our data firstly shows that ALA can improve plant waterlogging tolerance. PMID:26789407

77 FR 42547 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-19

... and Fatigue Evaluation of Composite Rotorcraft Structures AGENCY: Federal Aviation Administration (FAA... Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures. Form Numbers: There are no FAA forms... ``Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures'' final rule (76 FR 74655...

Recent Advances in Composite Damage Mechanics

NASA Technical Reports Server (NTRS)

Reifsnider, Ken; Case, Scott; Iyengar, Nirmal

1996-01-01

The state of the art and recent developments in the field of composite material damage mechanics are reviewed, with emphasis on damage accumulation. The kinetics of damage accumulation are considered with emphasis on the general accumulation of discrete local damage events such as single or multiple fiber fractures or microcrack formation. The issues addressed include: how to define strength in the presence of widely distributed damage, and how to combine mechanical representations in order to predict the damage tolerance and life of engineering components. It is shown that a damage mechanics approach can be related to the thermodynamics of the damage accumulation processes in composite laminates subjected to mechanical loading and environmental conditions over long periods of time.

Impact Damage and Strain Rate Effects for Toughened Epoxy Composite Structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Minnetyan, Levon

2006-01-01

Structural integrity of composite systems under dynamic impact loading is investigated herein. The GENOA virtual testing software environment is used to implement the effects of dynamic loading on fracture progression and damage tolerance. Combinations of graphite and glass fibers with a toughened epoxy matrix are investigated. The effect of a ceramic coating for the absorption of impact energy is also included. Impact and post impact simulations include verification and prediction of (1) Load and Impact Energy, (2) Impact Damage Size, (3) Maximum Impact Peak Load, (4) Residual Strength, (5) Maximum Displacement, (6) Contribution of Failure Modes to Failure Mechanisms, (7) Prediction of Impact Load Versus Time, and (8) Damage, and Fracture Pattern. A computer model is utilized for the assessment of structural response, progressive fracture, and defect/damage tolerance characteristics. Results show the damage progression sequence and the changes in the structural response characteristics due to dynamic impact. The fundamental premise of computational simulation is that the complete evaluation of composite fracture requires an assessment of ply and subply level damage/fracture processes as the structure is subjected to loads. Simulation results for the graphite/epoxy composite were compared with the impact and tension failure test data, correlation and verification was obtained that included: (1) impact energy, (2) damage size, (3) maximum impact peak load, (4) residual strength, (5) maximum displacement, and (6) failure mechanisms of the composite structure.

Damage Tolerant Design Handbook. A Compilation of Fracture and Crack- Growth Data for High-Strength Alloys. Volume 1

DTIC Science & Technology

1983-12-01

34. Report MCR -74-43, Martin Marietta Corp.. Denver Division, Deaver, CO. Contract HAS 9-13599 (Jamnary 1974). 0981" T!-6AL-IV da/dN ’ rI-6L-6V-2Sn KIc...34Lockheed-Palo Alto M. J. Rebholz Martin Marietta Alumi•um D. Mellem Materials Laboratory C. Harmsworth, J. Larsen, and T. Nicholas (Wright-Patterson AFB...Applications,’ Report AFML- TR-73-182, Boeing Comercial Airplane Co., Seattle, WA., Contract ?33615- 71 -C-1550, September 1973. 88136 PH 13-8 Mo KIc Dill

The ACEE program and basic composites research at Langley Research Center (1975 to 1986): Summary and bibliography

NASA Technical Reports Server (NTRS)

Dow, Marvin B.

1987-01-01

Composites research conducted at the Langley Research Center during the period from 1975 to 1986 is described, and an annotated bibliography of over 600 documents (with their abstracts) is presented. The research includes Langley basic technology and the composite primary structures element of the NASA Aircraft Energy Efficiency (ACEE) Program. The basic technology documents cited in the bibliography are grouped according to the research activity such as design and analysis, fatigue and fracture, and damage tolerance. The ACEE documents cover development of composite structures for transport aircraft.

An assessment of buffer strips for improving damage tolerance of composite laminates at elevated temperature

NASA Technical Reports Server (NTRS)

Bigelow, C. A.

1981-01-01

Buffer strips greatly improve the damage tolerance of graphite/epoxy laminates loaded in tension. Graphite/polyimide buffer strip panels were made and tested to determine their residual strength at ambient and elevated (177 C) temperature. Each panel was cut in the center to represent damage. Panels were radiographed and crack-opening displacements were recorded to indicate fracture, fracture arrest, and the extent of damage in the buffer strip after arrest. All panels had the same buffer strip spacing and width. The buffer strip material was 0 deg S-glass/PMR-15. The buffer strips were made by replacing narrow strips of the 0 deg graphite plies with strips of the 0 deg S-glass on either a one-for-one or a two-for-one basis. Half of the panels were heated to 177 + or - 3 C before and during the testing. Elevated temperature did not alter the fracture behavior of the buffer configuration.

Towards a damage tolerance philosophy for composite materials and structures

NASA Technical Reports Server (NTRS)

O'Brien, T. Kevin

1990-01-01

A damage-threshold/fail-safe approach is proposed to ensure that composite structures are both sufficiently durable for economy of operation, as well as adequately fail-safe or damage tolerant for flight safety. Matrix cracks are assumed to exist throughout the off-axis plies. Delamination onset is predicted using a strain energy release rate characterization. Delamination growth is accounted for in one of three ways: either analytically, using delamination growth laws in conjunction with strain energy release rate analyses incorporating delamination resistance curves; experimentally, using measured stiffness loss; or conservatively, assuming delamination onset corresponds to catastrophic delamination growth. Fail-safety is assessed by accounting for the accumulation of delaminations through the thickness. A tension fatigue life prediction for composite laminates is presented as a case study to illustrate how this approach may be implemented. Suggestions are made for applying the damage-threshold/fail-safe approach to compression fatigue, tension/compression fatigue, and compression strength following low velocity impact.

Towards a damage tolerance philosophy for composite materials and structures

NASA Technical Reports Server (NTRS)

Obrien, T. Kevin

1988-01-01

A damage-threshold/fail-safe approach is proposed to ensure that composite structures are both sufficiently durable for economy of operation, as well as adequately fail-safe or damage tolerant for flight safety. Matrix cracks are assumed to exist throughout the off-axis plies. Delamination onset is predicted using a strain energy release rate characterization. Delamination growth is accounted for in one of three ways: either analytically, using delamination growth laws in conjunction with strain energy release rate analyses incorporating delamination resistance curves; experimentally, using measured stiffness loss; or conservatively, assuming delamination onset corresponds to catastrophic delamination growth. Fail-safety is assessed by accounting for the accumulation of delaminations through the thickness. A tension fatigue life prediction for composite laminates is presented as a case study to illustrate how this approach may be implemented. Suggestions are made for applying the damage-threshold/fail-safe approach to compression fatigue, tension/compression fatigue, and compression strength following low velocity impact.

Assessing inspection sensitivity as it relates to damage tolerance in composite rotor hubs

NASA Astrophysics Data System (ADS)

Roach, Dennis P.; Rackow, Kirk

2001-08-01

Increasing niche applications, growing international markets, and the emergence of advanced rotorcraft technology are expected to greatly increase the population of helicopters over the next decade. In terms of fuselage fatigue, helicopters show similar trends as fixed-wing aircraft. The highly unsteady loads experienced by rotating wings not only directly affect components in the dynamic systems but are also transferred to the fixed airframe structure. Expanded use of rotorcraft has focused attention on the use of new materials and the optimization of maintenance practices. The FAA's Airworthiness Assurance Center (AANC) at Sandia National Labs has joined with Bell Helicopter andother agencies in the rotorcraft industry to evaluate nondestructive inspection (NDI) capabilities in light of the damage tolerance of assorted rotorcraft structure components. Currently, the program's emphasis is on composite rotor hubs. The rotorcraft industry is constantly evaluating new types of lightweight composite materials that not only enhance the safety and reliability of rotor components but also improve performance and extended operating life as well. Composite rotor hubs have led to the use of bearingless rotor systems that are less complex and require less maintenance than their predecessors. The test facility described in this paper allows the structural stability and damage tolerance of composite hubs to be evaluated using realistic flight load spectrums of centrifugal force and bending loads. NDI was integrated into the life-cycle fatigue tests in order to evaluate flaw detection sensitivity simultaneously wiht residual strength and general rotor hub peformance. This paper will describe the evolving use of damage tolerance analysis (DTA) to direct and improve rotorcraft maintenance along with the related use of nondestructive inspections to manage helicopter safety. OVeralll, the data from this project will provide information to improve the producibility, inspectability, serviceability, and cost effectively of rotorcraft components.

Distribution of pines in the Iberian Peninsula agrees with species differences in foliage frost tolerance, not with vulnerability to freezing-induced xylem embolism.

PubMed

Fernández-Pérez, Laura; Villar-Salvador, Pedro; Martínez-Vilalta, Jordi; Toca, Andrei; Zavala, Miguel A

2018-04-01

Drought and frosts are major determinants of plant functioning and distribution. Both stresses can cause xylem embolism and foliage damage. The objective of this study was to analyse if the distribution of six common pine species along latitudinal and altitudinal gradients in Europe is related to their interspecific differences in frost tolerance and to the physiological mechanisms underlying species-specific frost tolerance. We also evaluate if frost tolerance depends on plant water status. We studied survival to a range of freezing temperatures in 2-year-old plants and assessed the percentage loss of hydraulic conductivity (PLC) due xylem embolism formation and foliage damage determined by needle electrolyte leakage (EL) after a single frost cycle to -15 °C and over a range of predawn water potential (ψpd) values. Species experiencing cold winters in their range (Pinus nigra J.F. Arnold, Pinus sylvestris L. and Pinus uncinata Raymond ex A. DC.) had the highest frost survival rates and lowest needle EL and soluble sugar (SS) concentration. In contrast, the pines inhabiting mild or cool winter locations (especially Pinus halepensis Mill. and Pinus pinea L. and, to a lesser extent, Pinus pinaster Ait.) had the lowest frost survival and highest needle EL and SS values. Freezing-induced PLC was very low and differences among species were not related to frost damage. Reduction in ψpd decreased leaf frost damage in P. pinea and P. sylvestris, increased it in P. uncinata and had a neutral effect on the rest of the species. This study demonstrates that freezing temperatures are a major environmental driver for pine distribution and suggests that interspecific differences in leaf frost sensitivity rather than vulnerability to freezing-induced embolism or SS explain pine juvenile frost survival.

Choline supplementation in children with fetal alcohol spectrum disorders has high feasibility and tolerability.

PubMed

Wozniak, Jeffrey R; Fuglestad, Anita J; Eckerle, Judith K; Kroupina, Maria G; Miller, Neely C; Boys, Christopher J; Brearley, Ann M; Fink, Birgit A; Hoecker, Heather L; Zeisel, Steven H; Georgieff, Michael K

2013-11-01

There are no biological treatments for fetal alcohol spectrum disorders (FASDs), lifelong conditions associated with physical anomalies, brain damage, and neurocognitive abnormalities. In preclinical studies, choline partially ameliorates memory and learning deficits from prenatal alcohol exposure. This phase I pilot study evaluated the feasibility, tolerability, and potential adverse effects of choline supplementation in children with FASD. We hypothesized that choline would be well tolerated with minimal adverse events. The study design was a double-blind, randomized, placebo-controlled trial. Participants included 20 children aged 2.5 to 4.9 years with prenatal alcohol exposure and FASD diagnoses. Participants were randomly assigned to 500 mg choline or placebo daily for 9 months (10 active, 10 placebo). Primary outcome measures included feasibility, tolerability, adverse effects, and serum choline levels. Seventeen participants completed the study. Compliance was 82% to 87%, as evidenced by parent-completed log sheets and dose counts. Periodic 24-hour dietary recalls showed no evidence of dietary confounding. Adverse events were minimal and were equivalent in the active and placebo arms with the exception of fishy body odor, which occurred only in the active group. There were no serious adverse events to research participants. This phase I pilot study demonstrates that choline supplementation at 500 mg/d for 9 months in children aged 2 to 5 years is feasible and has high tolerability. Further examination of the efficacy of choline supplementation in FASD is currently underway. © 2013.

Choline supplementation in children with Fetal Alcohol Spectrum Disorders (FASD) has high feasibility and tolerability

PubMed Central

Wozniak, Jeffrey R.; Fuglestad, Anita J.; Eckerle, Judith K.; Kroupina, Maria G.; Miller, Neely C.; Boys, Christopher J.; Brearley, Ann M.; Fink, Birgit A.; Hoecker, Heather L.; Zeisel, Steven H.; Georgieff, Michael K.

2013-01-01

There are no biological treatments for fetal alcohol spectrum disorders (FASD), lifelong conditions associated with physical anomalies, brain damage, and neurocognitive abnormalities. In pre-clinical studies, choline partially ameliorates memory and learning deficits from prenatal alcohol exposure. This Phase I pilot study evaluated the feasibility, tolerability, and potential adverse effects of choline supplementation in children with FASD. We hypothesized that choline would be well-tolerated with minimal adverse events. The study design was a double-blind, randomized, placebo-controlled trial. Participants included 20 children, ages 2.5–4.9y, with prenatal alcohol exposure and FASD diagnoses. Participants were randomly assigned to 500 mg. choline or placebo daily for nine months (10 active; 10 placebo). Primary outcome measures included feasibility, tolerability, adverse effects, and serum choline levels. Seventeen participants completed the study. Compliance was 82–87% as evidenced by parent-completed logsheets and dose counts. Periodic 24-hour dietary recalls showed no evidence of dietary confounding. Adverse events were minimal and were equivalent in the active and placebo arms with the exception of fishy body odor, which occurred only in the active group. There were no serious adverse events to research participants. This Phase I pilot study demonstrates that choline supplementation at 500 mg per day for nine months in children ages 2–5 is feasible and has high tolerability. Further examination of the efficacy of choline supplementation in FASD is currently underway. PMID:24176229

Softening due to Grain Boundary Cavity Formation and its Competition with Hardening in Helium Implanted Nanocrystalline Tungsten

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cunningham, W. Streit; Gentile, Jonathan M.; El-Atwani, Osman

The unique ability of grain boundaries to act as effective sinks for radiation damage plays a significant role in nanocrystalline materials due to their large interfacial area per unit volume. Leveraging this mechanism in the design of tungsten as a plasma-facing material provides a potential pathway for enhancing its radiation tolerance under fusion-relevant conditions. In this study, we explore the impact of defect microstructures on the mechanical behavior of helium ion implanted nanocrystalline tungsten through nanoindentation. Softening was apparent across all implantation temperatures and attributed to bubble/cavity loaded grain boundaries suppressing the activation barrier for the onset of plasticity viamore » grain boundary mediated dislocation nucleation. An increase in fluence placed cavity induced grain boundary softening in competition with hardening from intragranular defect loop damage, thus signaling a new transition in the mechanical behavior of helium implanted nanocrystalline tungsten.« less

Softening due to Grain Boundary Cavity Formation and its Competition with Hardening in Helium Implanted Nanocrystalline Tungsten

DOE PAGES

Cunningham, W. Streit; Gentile, Jonathan M.; El-Atwani, Osman; ...

2018-02-13

The unique ability of grain boundaries to act as effective sinks for radiation damage plays a significant role in nanocrystalline materials due to their large interfacial area per unit volume. Leveraging this mechanism in the design of tungsten as a plasma-facing material provides a potential pathway for enhancing its radiation tolerance under fusion-relevant conditions. In this study, we explore the impact of defect microstructures on the mechanical behavior of helium ion implanted nanocrystalline tungsten through nanoindentation. Softening was apparent across all implantation temperatures and attributed to bubble/cavity loaded grain boundaries suppressing the activation barrier for the onset of plasticity viamore » grain boundary mediated dislocation nucleation. An increase in fluence placed cavity induced grain boundary softening in competition with hardening from intragranular defect loop damage, thus signaling a new transition in the mechanical behavior of helium implanted nanocrystalline tungsten.« less

Plant compensatory growth in aspen seedlings: the role of frequency and intensity of herbivory and resource availability

Treesearch

Nadir Erbilgin; David A. Galvez; Bin Zhang

2012-01-01

Plant ecologists have debated the mechanisms used by plants to cope with the impact of herbivore damage for more than a century. During that time, plant resistance mechanisms, which reduce the amount of herbivore damage before and during herbivory, have received most of the attention, while plant tolerance mechanisms, which may minimize the impacts of damage after...

QTL analysis of frost damage in pea suggests different mechanisms involved in frost tolerance.

PubMed

Klein, Anthony; Houtin, Hervé; Rond, Céline; Marget, Pascal; Jacquin, Françoise; Boucherot, Karen; Huart, Myriam; Rivière, Nathalie; Boutet, Gilles; Lejeune-Hénaut, Isabelle; Burstin, Judith

2014-06-01

Avoidance mechanisms and intrinsic resistance are complementary strategies to improve winter frost tolerance and yield potential in field pea. The development of the winter pea crop represents a major challenge to expand plant protein production in temperate areas. Breeding winter cultivars requires the combination of freezing tolerance as well as high seed productivity and quality. In this context, we investigated the genetic determinism of winter frost tolerance and assessed its genetic relationship with yield and developmental traits. Using a newly identified source of frost resistance, we developed a population of recombinant inbred lines and evaluated it in six environments in Dijon and Clermont-Ferrand between 2005 and 2010. We developed a genetic map comprising 679 markers distributed over seven linkage groups and covering 947.1 cM. One hundred sixty-one quantitative trait loci (QTL) explaining 9-71 % of the phenotypic variation were detected across the six environments for all traits measured. Two clusters of QTL mapped on the linkage groups III and one cluster on LGVI reveal the genetic links between phenology, morphology, yield-related traits and frost tolerance in winter pea. QTL clusters on LGIII highlighted major developmental gene loci (Hr and Le) and the QTL cluster on LGVI explained up to 71 % of the winter frost damage variation. This suggests that a specific architecture and flowering ideotype defines frost tolerance in winter pea. However, two consistent frost tolerance QTL on LGV were independent of phenology and morphology traits, showing that different protective mechanisms are involved in frost tolerance. Finally, these results suggest that frost tolerance can be bred independently to seed productivity and quality.

Post Test Evaluation of HSCT Nozzle Acoustic Liner Subcomponents Subjected to a Hot Acoustic Durability Test

NASA Technical Reports Server (NTRS)

Verrilli, Michael J.; Lee, Kuan

2008-01-01

The acoustic liner system designed for use in the High Speed Civil Transport (HSCT) was tested in a thermal-acoustic environment. Five ceramic matrix composite (CMC) acoustic tile configurations, five bulk acoustic absorbers, and one thermal protection system design were tested. The CMC acoustic tiles were subjected to two 2 3/4 hr ambient temperature acoustic exposures to measure their dynamic response. One exposure was conducted on the tiles alone and the second exposure included the tiles and the T-foam bulk absorber. The measured tile RMS strains were small. With or without the T-foam absorber, the dynamic strains were below strain levels that would cause damage during fatigue loading. After the ambient exposure, a 75-hr durability test of the entire acoustic liner system was conducted using a thermal-acoustic cycle that approximated the anticipated service cycle. Acoustic loads up to 139 dB/Hz and temperatures up to 1670 F (910 C) were employed during this 60 cycle test. During the durability test, the CMC tiles were exposed to temperatures up to 1780 F and a transient through thickness gradient up to 490 F. The TPS peak temperatures on the hot side of the panels ranged from 750 to 1000 F during the 60 cycles. The through thickness delta T ranged from 450 to 650 F, varying with TPS location and cycle number. No damage, such as cracks or chipping, was observed in the CMC tiles after completion of the testing. However, on tile warped during the durability test and was replaced after 43 or 60 cycles. No externally observed damage was found in this tile. No failure of the CMC fasteners occurred, but damage was observed. Cracks and missing material occurred, only in the fastener head region. No indication of damage was observed in the T-foam acoustic absorbers. The SiC foam acoustic absorber experienced damage after about 43 cycles. Cracking in the TPS occurred around the attachment holes and under a vent. In spite of the development of damage, the TPS maintained its insulative capability throughout the durability test. The durability test results demonstrate damage-tolerant CMC tile, CMC fastener, TPS, and T-foam absorber designs for the combined thermal and acoustic engine nozzle environment.

Quantitative nondestructive evaluation of materials and structures

NASA Technical Reports Server (NTRS)

Smith, Barry T.

1991-01-01

An experimental investigation was undertaken to quantify damage tolerance and resistance in composite materials impacted using the drop-weight method. Tests were conducted on laminates of several different carbon-fiber composite systems, such as epoxies, modified epoxies, and amorphous and semicrystalline thermoplastics. Impacted composite specimens were examined using destructive and non-destructive techniques to establish the characteristic damage states. Specifically, optical microscopy, ultrasonic, and scanning electron microscopy techniques were used to identify impact induced damage mechanisms. Damage propagation during post impact compression was also studied.

Error Mitigation of Point-to-Point Communication for Fault-Tolerant Computing

NASA Technical Reports Server (NTRS)

Akamine, Robert L.; Hodson, Robert F.; LaMeres, Brock J.; Ray, Robert E.

2011-01-01

Fault tolerant systems require the ability to detect and recover from physical damage caused by the hardware s environment, faulty connectors, and system degradation over time. This ability applies to military, space, and industrial computing applications. The integrity of Point-to-Point (P2P) communication, between two microcontrollers for example, is an essential part of fault tolerant computing systems. In this paper, different methods of fault detection and recovery are presented and analyzed.

Registration of an oilseed sunflower germplasm line HA-BSR1 highly tolerant to Sclerotinia basal stalk rot

USDA-ARS?s Scientific Manuscript database

Basal stalk rot (BSR) caused by Sclerotinia sclerotiorum (Lib.) de Bary is a devastating disease that causes a significant damage to worldwide sunflower (Helianthus annuus L.) production by reducing seed yield and quality. The objective of this research was to develop highly BSR tolerant sunflower g...

Exploring heteroplasmy as the basis for maternally-transmitted cold tolerance in cucumber

USDA-ARS?s Scientific Manuscript database

Cucumber is a warm-season crop that can be severely damaged by short periods of cold temperatures. Growers would benefit from cold tolerant cucumbers by preventing crop loss in inclement weather as well as by allowing for earlier planting and harvest, thus avoiding heavy late-season disease pressure...

Tolerance as a potential control method for Hessian fly (Diptera:Cecidomyiidae) in winter wheat.

USDA-ARS?s Scientific Manuscript database

Tolerance in wheat may hold the key to reducing damage caused by the Hessian fly, Mayetiola destructor, while enabling the plant to grow normally and reducing the selection pressures leading to increased virulence in fly populations. The susceptible lines Pioneer 25R75, susceptible wheat cultivar ‘N...

Stress-tolerance of baker's-yeast (Saccharomyces cerevisiae) cells: stress-protective molecules and genes involved in stress tolerance.

PubMed

Shima, Jun; Takagi, Hiroshi

2009-05-29

During the fermentation of dough and the production of baker's yeast (Saccharomyces cerevisiae), cells are exposed to numerous environmental stresses (baking-associated stresses) such as freeze-thaw, high sugar concentrations, air-drying and oxidative stresses. Cellular macromolecules, including proteins, nucleic acids and membranes, are seriously damaged under stress conditions, leading to the inhibition of cell growth, cell viability and fermentation. To avoid lethal damage, yeast cells need to acquire a variety of stress-tolerant mechanisms, for example the induction of stress proteins, the accumulation of stress protectants, changes in membrane composition and repression of translation, and by regulating the corresponding gene expression via stress-triggered signal-transduction pathways. Trehalose and proline are considered to be critical stress protectants, as is glycerol. It is known that these molecules are effective for providing protection against various types of environmental stresses. Modifications of the metabolic pathways of trehalose and proline by self-cloning methods have significantly increased tolerance to baking-associated stresses. To clarify which genes are required for stress tolerance, both a comprehensive phenomics analysis and a functional genomics analysis were carried out under stress conditions that simulated those occurring during the commercial baking process. These analyses indicated that many genes are involved in stress tolerance in yeast. In particular, it was suggested that vacuolar H+-ATPase plays important roles in yeast cells under stress conditions.

Induction of cross-tolerance between protective effect of morphine and nicotine in 6-hydroxydopamine-induce neurotoxicity in SH-SY5Y human dopaminergic neuroblastoma cells.

PubMed

Elyasi, Leila; Eftekhar-Vaghefi, Seyed Hassan; Asadi-Shekaaria, Majid; Esmaeili-Mahani, Saeed

2018-06-27

Parkinson's disease is a progressive neurodegenerative disease characterized by progressive and selective death of dopaminergic neurons. It has been reported that nicotine and morphine have protective roles during neuronal damage in Parkinson's disease. In addition, the induction of cross-tolerance between their biological effects has been shown in numerous reports. Here, we investigated the effects of nicotine and morphine on 6-OHDA-induced neurotoxicity in human neuroblastoma SH-SY5Y cell line as an in vitro model of Parkinson's disease. Cell damage was induced by 150 μM 6-OHDA and the cells viability was examined by MTT assay. Intracellular reactive oxygen species, calcium level and mitochondrial membrane potential were determined by fluorescence spectrophotometer method. Biochemical markers of apoptosis were also evaluated by immunoblotting. The data showed that morphine and nicotine prevent 6-OHDA- induced cell damage and apoptosis. However, the protective effects of nicotine were not observed in chronic morphine-pretreated cells. Morphine had no protective effects in chronic nicotine-incubated cells. A cross-tolerance between protective effects of morphine and nicotine was occurred in 6-OHDA-induced SH-SY5Y cell toxicity.

Turtle anoxia tolerance: Biochemistry and gene regulation.

PubMed

Krivoruchko, Anastasia; Storey, Kenneth B

2015-06-01

While oxygen limitation can be extremely damaging for many animals, some vertebrates have perfected anaerobic survival. Freshwater turtles belonging to the Trachemys and Chrysemys genera, for example, can survive many weeks without oxygen, and as such are commonly used as model animals for vertebrate anoxia tolerance. In the present review we discuss the recent advances made in understanding the biochemical and molecular nature of natural anoxia tolerance of freshwater turtles. Research in recent years has shown that activation of several important pathways occurs in response to anoxia in turtles, including those that function in the stress response, cell cycle arrest, inhibition of gene expression and metabolism. These likely contribute to anoxia tolerance in turtle tissues by minimizing cell damage in response to anoxia, as well as facilitating metabolic rate depression. The research discussed in the present review contributes to the understanding of how freshwater turtles can survive without oxygen for prolonged periods of time. This could also improve understanding of the molecular nature of hypoxic/ischemic injuries in mammalian tissues and suggest potential ways to avoid these. Copyright © 2015 Elsevier B.V. All rights reserved.

CORSSTOL: Cylinder Optimization of Rings, Skin, and Stringers with Tolerance sensitivity

NASA Technical Reports Server (NTRS)

Finckenor, J.; Bevill, M.

1995-01-01

Cylinder Optimization of Rings, Skin, and Stringers with Tolerance (CORSSTOL) sensitivity is a design optimization program incorporating a method to examine the effects of user-provided manufacturing tolerances on weight and failure. CORSSTOL gives designers a tool to determine tolerances based on need. This is a decisive way to choose the best design among several manufacturing methods with differing capabilities and costs. CORSSTOL initially optimizes a stringer-stiffened cylinder for weight without tolerances. The skin and stringer geometry are varied, subject to stress and buckling constraints. Then the same analysis and optimization routines are used to minimize the maximum material condition weight subject to the least favorable combination of tolerances. The adjusted optimum dimensions are provided with the weight and constraint sensitivities of each design variable. The designer can immediately identify critical tolerances. The safety of parts made out of tolerance can also be determined. During design and development of weight-critical systems, design/analysis tools that provide product-oriented results are of vital significance. The development of this program and methodology provides designers with an effective cost- and weight-saving design tool. The tolerance sensitivity method can be applied to any system defined by a set of deterministic equations.

A minimum cost tolerance allocation method for rocket engines and robust rocket engine design

NASA Technical Reports Server (NTRS)

Gerth, Richard J.

1993-01-01

Rocket engine design follows three phases: systems design, parameter design, and tolerance design. Systems design and parameter design are most effectively conducted in a concurrent engineering (CE) environment that utilize methods such as Quality Function Deployment and Taguchi methods. However, tolerance allocation remains an art driven by experience, handbooks, and rules of thumb. It was desirable to develop and optimization approach to tolerancing. The case study engine was the STME gas generator cycle. The design of the major components had been completed and the functional relationship between the component tolerances and system performance had been computed using the Generic Power Balance model. The system performance nominals (thrust, MR, and Isp) and tolerances were already specified, as were an initial set of component tolerances. However, the question was whether there existed an optimal combination of tolerances that would result in the minimum cost without any degradation in system performance.

Hurricane Katrina winds damaged longleaf pine less than loblolly pine

Treesearch

Kurt H. Johnsen; John R. Butnor; John S. Kush; Ronald C. Schmidtling; C. Dana Nelson

2009-01-01

Some evidence suggests that longleaf pine might be more tolerant of high winds than either slash pine (Pinus elliotii Englem.) or loblolly pine (Pinus taeda L.). We studied wind damage to these three pine species in a common garden experiment in southeast Mississippi following Hurricane Katrina,...

Beauveria bassiana, Metarhizium anisopliae, and Metarhizium anisopliae var. acridum conidia: tolerance to imbibitional damage

USDA-ARS?s Scientific Manuscript database

When dry fungal cells are immersed in water, rapid imbibition (water uptake) may compromise the plasma membrane, killing the cell. This study investigated the impact of imbibitional damage (measured in terms of reduced viability) on Beauveria bassiana (Bb), Metarhizium anisopliae (Ma) and M. anisop...

7 CFR 51.1861 - Tolerances.

Code of Federal Regulations, 2014 CFR

2014-01-01

...; (ii) Ten percent for tomatoes which are damaged by shoulder bruises or by discolored or sunken scars... affected by decay; (ii) Ten percent for tomatoes which are seriously damaged by shoulder bruises or by... shoulder bruises or by discolored or sunken scars on any parts of the tomatoes; and, (iii) Ten percent for...

7 CFR 51.1861 - Tolerances.

Code of Federal Regulations, 2013 CFR

2013-01-01

...; (ii) Ten percent for tomatoes which are damaged by shoulder bruises or by discolored or sunken scars... affected by decay; (ii) Ten percent for tomatoes which are seriously damaged by shoulder bruises or by... shoulder bruises or by discolored or sunken scars on any parts of the tomatoes; and, (iii) Ten percent for...

Influence of G-forces and hypodynamia on the portal system of the liver

NASA Technical Reports Server (NTRS)

Drozdova, A. V.

1975-01-01

Longitudinally and transversely applied g-forces as intolerable levels cause damage to the interlobular veins of the liver, with maximum damage caused by dorso-ventral g-force application. The portal vein system is more resilient with respect to g-forces at the limit of tolerance.

Recent Advances in Thermoplastic Puncture-Healing Polymers

NASA Technical Reports Server (NTRS)

Bogert, Philip B.; Working, Dennis C.; Wise, Kristopher E.; Smith, Janice Y.; Topping, Crystal C.; Britton, Sean M.; Bagby, Paul R.; Siochi, Emilie J.

2010-01-01

The motivation for this work is to develop self-healing polymeric materials to enable damage tolerant systems, and to tailor puncture healing for use temperatures and applications. This will be a benefit in environments and conditions where access for manual repair is limited or impossible, or where damage may not be detected.

7 CFR 993.97 - Exhibit A; minimum standards.

Code of Federal Regulations, 2010 CFR

2010-01-01

... condition; (3) end cracks; (4) fermentation; (5) skin or flesh damage; (6) scab; (7) burned; (8) mold; (9...) Fermentation means damage to the flesh by fermentation to the extent that the characteristic appearance or..., and decay shall not exceed five percent (5%). (3) The combined tolerance allowance for fermentation...

Timing matters: error-prone gap filling and translesion synthesis in immunoglobulin gene hypermutation

PubMed Central

Sale, Julian E.; Batters, Christopher; Edmunds, Charlotte E.; Phillips, Lara G.; Simpson, Laura J.; Szüts, Dávid

2008-01-01

By temporarily deferring the repair of DNA lesions encountered during replication, the bypass of DNA damage is critical to the ability of cells to withstand genomic insults. Damage bypass can be achieved either by recombinational mechanisms that are generally accurate or by a process called translesion synthesis. Translesion synthesis involves replacing the stalled replicative polymerase with one of a number of specialized DNA polymerases whose active sites are able to tolerate a distorted or damaged DNA template. While this property allows the translesion polymerases to synthesize across damaged bases, it does so with the trade-off of an increased mutation rate. The deployment of these enzymes must therefore be carefully regulated. In addition to their important role in general DNA damage tolerance and mutagenesis, the translesion polymerases play a crucial role in converting the products of activation induced deaminase-catalysed cytidine deamination to mutations during immunoglobulin gene somatic hypermutation. In this paper, we specifically consider the control of translesion synthesis in the context of the timing of lesion bypass relative to replication fork progression and arrest at sites of DNA damage. We then examine how recent observations concerning the control of translesion synthesis might help refine our view of the mechanisms of immunoglobulin gene somatic hypermutation. PMID:19008194

Recent Developments and Challenges Implementing New and Improved Stress Intensity Factor (K) Solutions in NASGRO for Damage Tolerance Analyses

NASA Technical Reports Server (NTRS)

Cardinal, Joseph W.; McClung, R. Craig; Lee, Yi-Der; Guo, Yajun; Beek, Joachim M.

2014-01-01

Fatigue crack growth analysis software has been available to damage tolerance analysts for many years in either commercial products or via proprietary in-house codes. The NASGRO software has been publicly available since the mid-80s (known as NASA/FLAGRO up to 1999) and since 2000 has been sustained and further developed by a collaborative effort between Southwest Research Institute® (SwRI®), the NASA Johnson Space Center (JSC), and the members of the NASGRO Industrial Consortium. Since the stress intensity factor (K) is the foundation of fracture mechanics and damage tolerance analysis of aircraft structures, a significant focus of development efforts in the past fifteen years has been geared towards enhancing legacy K solutions and developing new and efficient numerical K solutions that can handle the complicated stress gradients computed by today’s analysts using detailed finite element models of fatigue critical locations. This paper provides an overview of K solutions that have been recently implemented or improved for the analysis of geometries such as two unequal through cracks at a hole and two unequal corner cracks at a hole, as well as state-of-the-art weight function models capable of computing K in the presence of univariant and/or bivariant stress gradients and complicated residual stress distributions. Some historical background is provided to review how common K solutions have evolved over the years, including selective examples from the literature and from new research. Challenges and progress in rectifying discrepancies between older legacy solutions and newer models are reviewed as well as approaches and challenges for verification and validation of K solutions. Finally, a summary of current challenges and future research and development needs is presented. A key theme throughout the presentation of this paper will be how members of the aerospace industry have collaborated with software developers to develop a practical analysis tool that is used world-wide to support new design as well as the ongoing sustainment and airworthiness of commercial and military aircraft.

Optimization of composite sandwich cover panels subjected to compressive loadings

NASA Technical Reports Server (NTRS)

Cruz, Juan R.

1991-01-01

An analysis and design method is presented for the design of composite sandwich cover panels that includes transverse shear effects and damage tolerance considerations. This method is incorporated into an optimization program called SANDOP (SANDwich OPtimization). SANDOP is used in the present study to design optimized composite sandwich cover panels for transport aircraft wing applications as a demonstration of its capabilities. The results of this design study indicate that optimized composite sandwich cover panels have approximately the same structural efficiency as stiffened composite cover panels designed to identical constraints. Results indicate that inplane stiffness requirements have a large effect on the weight of these composite sandwich cover panels at higher load levels. Increasing the maximum allowable strain and the upper percentage limit of the 0 degree and plus or minus 45 degree plies can yield significant weight savings. The results show that the structural efficiency of these optimized composite sandwich cover panels is relatively insensitive to changes in core density.

Micromechanics of fatigue in woven and stitched composites

NASA Technical Reports Server (NTRS)

Cox, B. N.; Carter, W. C.; Dadkhah, M. S.; Morris, W. L.

1994-01-01

The goals of this research program were to: (1) determine how microstructural factors, especially the architecture of reinforcing fibers, control stiffness, strength, and fatigue life in 3D woven composites; (2) identify mechanisms of failure; (3) model composite stiffness; (4) model notched and unnotched strength; and (5) model fatigue life. We have examined a total of eleven different angle and orthogonal interlock woven composites. Extensive testing has revealed that these 3D woven composites possess an extraordinary combination of strength, damage tolerance, and notch insensitivity in compression and tension and in monotonic and cyclic loading. In many important regards, 3D woven composites far outstrip conventional 2D laminates or stitched laminates. Detailed microscopic analysis of damage has led to a comprehensive picture of the essential mechanisms of failure and how they are related to the reinforcement geometry. The critical characteristics of the weave architecture that promote favorable properties have been identified. Key parameters are tow size and the distributions in space and strength of geometrical flaws. The geometrical flaws should be regarded as controllable characteristics of the weave in design and manufacture. In addressing our goals, the simplest possible models of properties were always sought, in a blend of old and new modeling concepts. Nevertheless, certain properties, especially regarding damage tolerance, ultimate failure, and the detailed effects of weave architecture, require computationally intensive stochastic modeling. We have developed a new model, the 'binary model,' to carry out such tasks in the most efficient manner and with faithful representation of crucial mechanisms. This is the final report for contract NAS1-18840. It covers all work from April 1989 up to the conclusion of the program in January 1993.

Reduction of female copulatory damage by resilin represents evidence for tolerance in sexual conflict

PubMed Central

Michels, Jan; Gorb, Stanislav N.; Reinhardt, Klaus

2015-01-01

Intergenomic evolutionary conflicts increase biological diversity. In sexual conflict, female defence against males is generally assumed to be resistance, which, however, often leads to trait exaggeration but not diversification. Here, we address whether tolerance, a female defence mechanism known from interspecific conflicts, exists in sexual conflict. We examined the traumatic insemination of female bed bugs via cuticle penetration by males, a textbook example of sexual conflict. Confocal laser scanning microscopy revealed large proportions of the soft and elastic protein resilin in the cuticle of the spermalege, the female defence organ. Reduced tissue damage and haemolymph loss were identified as adaptive female benefits from resilin. These did not arise from resistance because microindentation showed that the penetration force necessary to breach the cuticle was significantly lower at the resilin-rich spermalege than at other cuticle sites. Furthermore, a male survival analysis indicated that the spermalege did not impose antagonistic selection on males. Our findings suggest that the specific spermalege material composition evolved to tolerate the traumatic cuticle penetration. They demonstrate the importance of tolerance in sexual conflict and genitalia evolution, extend fundamental coevolution and speciation models and contribute to explaining the evolution of complexity. We propose that tolerance can drive trait diversity. PMID:25673297

Reduction of female copulatory damage by resilin represents evidence for tolerance in sexual conflict.

PubMed

Michels, Jan; Gorb, Stanislav N; Reinhardt, Klaus

2015-03-06

Intergenomic evolutionary conflicts increase biological diversity. In sexual conflict, female defence against males is generally assumed to be resistance, which, however, often leads to trait exaggeration but not diversification. Here, we address whether tolerance, a female defence mechanism known from interspecific conflicts, exists in sexual conflict. We examined the traumatic insemination of female bed bugs via cuticle penetration by males, a textbook example of sexual conflict. Confocal laser scanning microscopy revealed large proportions of the soft and elastic protein resilin in the cuticle of the spermalege, the female defence organ. Reduced tissue damage and haemolymph loss were identified as adaptive female benefits from resilin. These did not arise from resistance because microindentation showed that the penetration force necessary to breach the cuticle was significantly lower at the resilin-rich spermalege than at other cuticle sites. Furthermore, a male survival analysis indicated that the spermalege did not impose antagonistic selection on males. Our findings suggest that the specific spermalege material composition evolved to tolerate the traumatic cuticle penetration. They demonstrate the importance of tolerance in sexual conflict and genitalia evolution, extend fundamental coevolution and speciation models and contribute to explaining the evolution of complexity. We propose that tolerance can drive trait diversity. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

In field damage of high and low cyanogenic cassava due to a generalist insect herbivore Cyrtomenus bergi (Hemiptera: Cydnidae).

PubMed

Riis, Lisbeth; Bellotti, Anthony Charles; Castaño, Oscar

2003-12-01

The hypothesis that cyanogenic potential in cassava roots deters polyphagous insects in the field is relevant to current efforts to reduce or eliminate the cyanogenic potential in cassava. To test this hypothesis, experiments were conducted in the field under natural selection pressure of the polyphagous root feeder Cyrtomenus bergi Froeschner (Hemiptera: Cydnidae). A number of cassava varieties (33) as well as 13 cassava siblings and their parental clone, each representing a determined level of cyanogenic potential (CNP), were scored for damage caused by C. bergi and related to CNP and nonglycosidic cyanogens, measured as hydrogen cyanide. Additionally, 161 low-CNP varieties (< 50 ppm hydrogen cyanide, fresh weight) from the cassava germplasm core collection at Centro Internacional de Agricultura Tropical (CIAT) were screened for resistance/tolerance to C. bergi. Low root damage scores were registered at all levels of CNP. Nevertheless, CNP and yield (or root size) partly explained the damage in cassava siblings (r2 = 0.82) and different cassava varieties (r2 = 0.42), but only when mean values of damage scores were used. This relation was only significant in one of two crop cycles. A logistic model describes the underlying negative relation between CNP and damage. An exponential model describes the underlying negative relation between root size and damage. Damage, caused by C. bergi feeding, released nonglycosidic cyanogens, and an exponential model fits the underlying positive relation. Fifteen low-CNP clones were selected for potential resistance/tolerance against C. bergi.

Dehydration rate determines the degree of membrane damage and desiccation tolerance in bryophytes.

PubMed

Cruz de Carvalho, Ricardo; Catalá, Myriam; Branquinho, Cristina; Marques da Silva, Jorge; Barreno, Eva

2017-03-01

Desiccation tolerant (DT) organisms are able to withstand an extended loss of body water and rapidly resume metabolism upon rehydration. This ability, however, is strongly dependent on a slow dehydration rate. Fast dehydration affects membrane integrity leading to intracellular solute leakage upon rehydration and thereby impairs metabolism recovery. We test the hypothesis that the increased cell membrane damage and membrane permeability observed under fast dehydration, compared with slow dehydration, is related to an increase in lipid peroxidation. Our results reject this hypothesis because following rehydration lipid peroxidation remains unaltered, a fact that could be due to the high increase of NO upon rehydration. However, in fast-dried samples we found a strong signal of red autofluorescence upon rehydration, which correlates with an increase in ROS production and with membrane leakage, particularly the case of phenolics. This could be used as a bioindicator of oxidative stress and membrane damage. © 2016 Scandinavian Plant Physiology Society.

Value contamination avoidance devices

NASA Technical Reports Server (NTRS)

Endicott, D. L.

1975-01-01

Mechanical redesign methods were used to minimize contamination damage of conventional fluid components and a contamination separator device was developed for long term reusable space vehicles. These were incorporated into an existing 50.8 mm poppet valve and tested for damage tolerance in a full size open loop flow system with gaseous and liquid nitrogen. Cyclic and steady flow conditions were tested with particles of 125 to 420 micrometers aluminum oxide dispersed in the test fluids. Nonflow life tests (100,000 cycles) were made with two valve configurations in gaseous hydrogen. The redesigned valve had an acceptable cycle life and improved tolerance to contamination damage when the primary sealing surfaces were coated with thin coatings of hard plastic (Teflon S and Kynar). Analytical studies and flow testing were completed of four different versions of the separator. overall separation efficiencies in the 55-90% range were measured with these non-optimum configurations.

Recent developments in analysis of crack propagation and fracture of practical materials. [stress analysis in aircraft structures

NASA Technical Reports Server (NTRS)

Hardrath, H. F.; Newman, J. C., Jr.; Elber, W.; Poe, C. C., Jr.

1978-01-01

The limitations of linear elastic fracture mechanics in aircraft design and in the study of fatigue crack propagation in aircraft structures are discussed. NASA-Langley research to extend the capabilities of fracture mechanics to predict the maximum load that can be carried by a cracked part and to deal with aircraft design problems are reported. Achievements include: (1) improved stress intensity solutions for laboratory specimens; (2) fracture criterion for practical materials; (3) crack propagation predictions that account for mean stress and high maximum stress effects; (4) crack propagation predictions for variable amplitude loading; and (5) the prediction of crack growth and residual stress in built-up structural assemblies. These capabilities are incorporated into a first generation computerized analysis that allows for damage tolerance and tradeoffs with other disciplines to produce efficient designs that meet current airworthiness requirements.

Designing Radiation Resistance in Materials for Fusion Energy

NASA Astrophysics Data System (ADS)

Zinkle, S. J.; Snead, L. L.

2014-07-01

Proposed fusion and advanced (Generation IV) fission energy systems require high-performance materials capable of satisfactory operation up to neutron damage levels approaching 200 atomic displacements per atom with large amounts of transmutant hydrogen and helium isotopes. After a brief overview of fusion reactor concepts and radiation effects phenomena in structural and functional (nonstructural) materials, three fundamental options for designing radiation resistance are outlined: Utilize matrix phases with inherent radiation tolerance, select materials in which vacancies are immobile at the design operating temperatures, or engineer materials with high sink densities for point defect recombination. Environmental and safety considerations impose several additional restrictions on potential materials systems, but reduced-activation ferritic/martensitic steels (including thermomechanically treated and oxide dispersion-strengthened options) and silicon carbide ceramic composites emerge as robust structural materials options. Materials modeling (including computational thermodynamics) and advanced manufacturing methods are poised to exert a major impact in the next ten years.

Structural modeling for multicell composite rotor blades

NASA Technical Reports Server (NTRS)

Rehfield, Lawrence W.; Atilgan, Ali R.

1987-01-01

Composite material systems are currently good candidates for aerospace structures, primarily for the design flexibility they offer, i.e., it is possible to tailor the material and manufacturing approach to the application. A working definition of elastic or structural tailoring is the use of structural concept, fiber orientation, ply stacking sequence, and a blend of materials to achieve specific performance goals. In the design process, choices of materials and dimensions are made which produce specific response characteristics, and which permit the selected goals to be achieved. Common choices for tailoring goals are preventing instabilities or vibration resonances or enhancing damage tolerance. An essential, enabling factor in the design of tailored composite structures is structural modeling that accurately, but simply, characterizes response. The objective of this paper is to present a new multicell beam model for composite rotor blades and to validate predictions based on the new model by comparison with a finite element simulation in three benchmark static load cases.

Design and testing of integrated Bragg grating sensor systems for advanced grid structure

NASA Astrophysics Data System (ADS)

Amano, Masataro; Mizutani, Tadahito; Okabe, Yoji; Takeda, Nobuo; Ozaki, Tsuyoshi

2006-03-01

In this research, the authors target on the construction of structural health monitoring system of Advanced Grid Structure (AGS) made of Carbon fiber reinforced plastic (CFRP). AGS has often been applied to aerospace structures because of the following advantages: (1) Since ribs carry only axial forces, the weakness in the transverse direction of the CFRP unidirectional laminates is negligible. (2) AGS has damage tolerance because the fracture of a rib hardly affects other ribs, namely AGS is a fail-safe structure. In this research, in order to detect existence and regions of rib fractures in AGS, we embedded multiplexed fiber Bragg grating (FBG) sensors into AGS in rib longitudinal directions for measurement of strains. Monitoring of the change in rib longitudinal strains is the most effective SHM system for AGS. In order to confirm our proposal, we carried out following discussions. First, we analytically revealed that the change in rib longitudinal strains was the most sensitive signal for damage detection because of AGS's structural redundancy. Then, we introduced a statistical outlier analysis technique into the SHM system for damage recognition. Finally, we established AGS with the SHM system and verified experimentally. The result of the test showed that damage existence and regions in AGS could be detected with the proposed SHM system.

Influence of preliminary damage on the load-bearing capacity of zirconia fixed dental prostheses.

PubMed

Kohorst, Philipp; Butzheinen, Lutz Oliver; Dittmer, Marc Philipp; Heuer, Wieland; Borchers, Lothar; Stiesch, Meike

2010-12-01

The objective of this investigation was to evaluate the influence of differently shaped preliminary cuts in combination with artificial aging on the load-bearing capacity of four-unit zirconia fixed dental prostheses (FDPs). Forty frameworks were fabricated from white-stage zirconia blanks (InCeram YZ, Vita) by means of a computer-aided design/computer-aided manufacturing system (Cerec inLab, Sirona). Frameworks were divided into four homogeneous groups with ten specimens each. Prior to veneering, frameworks of two groups were "damaged" by defined saw cuts of different dimensions, to simulate accidental flaws generated during shape cutting. After the veneering process, FDPs, with the exception of a control group without preliminary damage, were subjected to thermal and mechanical cycling (TMC) during 200 days storage in distilled water at 36°C. Following the aging procedure, all specimens were loaded until fracture, and forces at fracture were recorded. The statistical analysis of force at fracture data was performed using two-way ANOVA, with the level of significance chosen at 0.05. Neither type of preliminary mechanical damage significantly affected the load-bearing capacity of FDPs. In contrast, artificial aging by TMC proved to have a significant influence on the load-bearing capacity of both the undamaged and the predamaged zirconia restorations (p < 0.001); however, even though load-bearing capacity decreased by about 20% due to simulated aging, the FDPs still showed mean load-bearing capacities of about 1600 N. The results of this study reveal that zirconia restorations have a high tolerance regarding mechanical damages. Irrespective of these findings, damage to zirconia ceramics during production or finishing should be avoided, as this may nevertheless lead to subcritical crack growth and, eventually, catastrophic failure. Furthermore, to ensure long-term clinical success, the design of zirconia restorations has to accommodate the decrease in load-bearing capacity due to TMC in the oral environment. © 2010 by The American College of Prosthodontists.

Rad18 confers hematopoietic progenitor cell DNA damage tolerance independently of the Fanconi Anemia pathway in vivo

PubMed Central

Yang, Yang; Poe, Jonathan C.; Yang, Lisong; Fedoriw, Andrew; Desai, Siddhi; Magnuson, Terry; Li, Zhiguo; Fedoriw, Yuri; Araki, Kimi; Gao, Yanzhe; Tateishi, Satoshi; Sarantopoulos, Stefanie; Vaziri, Cyrus

2016-01-01

In cultured cancer cells the E3 ubiquitin ligase Rad18 activates Trans-Lesion Synthesis (TLS) and the Fanconi Anemia (FA) pathway. However, physiological roles of Rad18 in DNA damage tolerance and carcinogenesis are unknown and were investigated here. Primary hematopoietic stem and progenitor cells (HSPC) co-expressed RAD18 and FANCD2 proteins, potentially consistent with a role for Rad18 in FA pathway function during hematopoiesis. However, hematopoietic defects typically associated with fanc-deficiency (decreased HSPC numbers, reduced engraftment potential of HSPC, and Mitomycin C (MMC) -sensitive hematopoiesis), were absent in Rad18−/− mice. Moreover, primary Rad18−/− mouse embryonic fibroblasts (MEF) retained robust Fancd2 mono-ubiquitination following MMC treatment. Therefore, Rad18 is dispensable for FA pathway activation in untransformed cells and the Rad18 and FA pathways are separable in hematopoietic cells. In contrast with responses to crosslinking agents, Rad18−/− HSPC were sensitive to in vivo treatment with the myelosuppressive agent 7,12 Dimethylbenz[a]anthracene (DMBA). Rad18-deficient fibroblasts aberrantly accumulated DNA damage markers after DMBA treatment. Moreover, in vivo DMBA treatment led to increased incidence of B cell malignancy in Rad18−/− mice. These results identify novel hematopoietic functions for Rad18 and provide the first demonstration that Rad18 confers DNA damage tolerance and tumor-suppression in a physiological setting. PMID:26883629

Proceedings of the Annual Mechanics of Composites Review (6th),

DTIC Science & Technology

1981-02-01

containing and resisting damage in compression-loaded composite structural components. 176( CONTRACTS INCREMENTAL ANALYSIS OF IMPACT DAMAGE NASI -15888 79...EVALUATION OF THE DURABILITY AND DAMAGE TOLERANCE OF CTOL COMPOS- ITE STRUCTURES NASI -15107 77 October 12 - 80 October 11 Project Engineer: Edward P...DEVELOPMENT OF AN ORTHOTROPIC HOLE ELEMENT NASI -15890 79 July 9 - 80 September 24 Project Engineer: Dr. John H. Crews, Jr. Mail Stop 18BE NASA Langley

Genetic compensation of high dose radiation-induced damage in an anhydrobiotic insect

NASA Astrophysics Data System (ADS)

Gusev, Oleg; Nakahara, Yuichi; Sakashita, Tetsuya; Kikawada, Takahiro; Okuda, Takashi

Anhydrobiotic larvae of African chironomid Polypedilum vanderplanki are known to show an extremely high tolerance against a range of stresses. The tolerance against various extreme environments exhibited by that insect might be due to being almost completely desiccated replacing water with trehalose, a state where little or no chemical reactions occur. From 2005 dried larvae of this insect are being used in a number of space experiments, both inside and outside of ISS as a model organism for estimation the limits of higher organisms' resistance to space environment stresses and long-term storage of the alive anhydrobiotic organisms during continues spaceflight. We have shown previously that both hydrated and dried larvae of Polypedilum vanderplanki have very higher tolerance against both highand low-linear energy transfer (LET), surviving after 7000Gy irradiation. It was suggested that the larvae would have effective DNA-reparation system in addition to artificial protection provided by glass-stage without water. In the present study we conducted analysis of stress-related gene expression in the larvae after 70-2000 Gy irradiations. Both DNA damage level and activity of DNA-reparation, anti-apoptotic and protein-damage related genes were analyzed. Direct visualization of DNA damage in the larvae fat body cells using Comet Assay showed that fragmented by radiation DNA is re-arranged within 76-98 hours after exposure. We found that massive overexpression of hsp and anti-oxidant genes occur in larvae entering anhydrobiosis , and provides refolding of proteins after rehydration. In the irradiated larvae overexpression of DNA-reparation enzymes anti-apoptotic genes was confirmed, suggesting that survival after high-dose irradiation is a result of combination of highly effective blocking of entering the apoptosis after severe DNA damage and DNA reparation.

Laboratory test methodology for evaluating the effects of electromagnetic disturbances on fault-tolerant control systems

NASA Technical Reports Server (NTRS)

Belcastro, Celeste M.

1989-01-01

Control systems for advanced aircraft, especially those with relaxed static stability, will be critical to flight and will, therefore, have very high reliability specifications which must be met for adverse as well as nominal operating conditions. Adverse conditions can result from electromagnetic disturbances caused by lightning, high energy radio frequency transmitters, and nuclear electromagnetic pulses. Tools and techniques must be developed to verify the integrity of the control system in adverse operating conditions. The most difficult and illusive perturbations to computer based control systems caused by an electromagnetic environment (EME) are functional error modes that involve no component damage. These error modes are collectively known as upset, can occur simultaneously in all of the channels of a redundant control system, and are software dependent. A methodology is presented for performing upset tests on a multichannel control system and considerations are discussed for the design of upset tests to be conducted in the lab on fault tolerant control systems operating in a closed loop with a simulated plant.

SGD1, a key enzyme in tocopherol biosynthesis, is essential for plant development and cold tolerance in rice.

PubMed

Wang, Di; Wang, Yunlong; Long, Wuhua; Niu, Mei; Zhao, Zhigang; Teng, Xuan; Zhu, Xiaopin; Zhu, Jianping; Hao, Yuanyuan; Wang, Yongfei; Liu, Yi; Jiang, Ling; Wang, Yihua; Wan, Jianmin

2017-07-01

Tocopherols, a group of Vitamin E compounds, are essential components of the human diet. In contrast to well documented roles in animals, the functions of tocopherols in plants are less understood. In this study, we characterized two allelic rice dwarf mutant lines designated sgd1-1 and sgd1-2 (small grain and dwarf1). Histological observations showed that the dwarf phenotypes were mainly due to cell elongation defects. A map-based cloning strategy and subsequent complementation test showed that SGD1 encodes homogentisate phytyltransferase (HPT), a key enzyme in tocopherol biosynthesis. Mutation of SGD1 resulted in tocopherol deficiency in both sgd1mutants. No oxidant damage was detected in the sgd1 mutants. Further analysis showed that sgd1-2 was hypersensitive to cold stress. Our results indicate that SGD1 is essential for plant development and cold tolerance in rice. Copyright © 2017 Elsevier B.V. All rights reserved.

Adaptations of quaking aspen for defense against damage by herbivores and related environmental agents

Treesearch

Richard L. Lindroth

2001-01-01

Quaking aspen (Populus tremuloides) employs two major systems of defense against damage by environmental agents: chemical defense and tolerance. Aspen accumulates appreciable quantities of phenolic glycosides (salicylates) and condensed tannins in most tissues and accumulates coniferyl benzoate in flower buds. Phenolic glycosides are toxic and/or deterrent to pathogens...

Pharmacodynamic Assay Panel for Monitoring Phospho-Signaling Networks | Office of Cancer Clinical Proteomics Research

Cancer.gov

The DNA damage response (DDR) is a highly regulated signal transduction network that orchestrates the temporal and spatial organization of protein complexes required to repair (or tolerate) DNA damage (e.g., nucleotide excision repair, base excision repair, homologous recombination, non-homologous end joining, post-replication repair).

Reversing Optical Damage In LiNbO3 Switches

NASA Technical Reports Server (NTRS)

Gee, C. M.; Thurmond, G. D.

1985-01-01

One symptom of optical damage in Ti-diffused LiNbO3 directional-coupler switch reversed by temporarily raising input illumination to higher-thannormal power level. Healing phenomenon used to restore normal operation, increase operating-power rating, and stabilize operating characteristics at lower powers. Higher operating power is tolerated after treatment.

The stomatopod dactyl club: a formidable damage-tolerant biological hammer.

PubMed

Weaver, James C; Milliron, Garrett W; Miserez, Ali; Evans-Lutterodt, Kenneth; Herrera, Steven; Gallana, Isaias; Mershon, William J; Swanson, Brook; Zavattieri, Pablo; DiMasi, Elaine; Kisailus, David

2012-06-08

Nature has evolved efficient strategies to synthesize complex mineralized structures that exhibit exceptional damage tolerance. One such example is found in the hypermineralized hammer-like dactyl clubs of the stomatopods, a group of highly aggressive marine crustaceans. The dactyl clubs from one species, Odontodactylus scyllarus, exhibit an impressive set of characteristics adapted for surviving high-velocity impacts on the heavily mineralized prey on which they feed. Consisting of a multiphase composite of oriented crystalline hydroxyapatite and amorphous calcium phosphate and carbonate, in conjunction with a highly expanded helicoidal organization of the fibrillar chitinous organic matrix, these structures display several effective lines of defense against catastrophic failure during repetitive high-energy loading events.

Nanotechnology

NASA Technical Reports Server (NTRS)

Biaggi-Labiosa, Azlin

2016-01-01

Present an overview of the Nanotechnology Project at NASA's Game Changing Technology Industry Day. Mature and demonstrate flight readiness of CNT reinforced composites for future NASA mission applications?Sounding rocket test in a multiexperiment payload?Integrate into cold gas thruster system as propellant storage?The technology would provide the means for reduced COPV mass and improved damage tolerance and flight qualify CNT reinforced composites. PROBLEM/NEED BEING ADDRESSED:?Reduce weight and enhance the performance and damage tolerance of aerospace structuresGAME-CHANGING SOLUTION:?Improve mechanical properties of CNTs to eventually replace CFRP –lighter and stronger?First flight-testing of a CNT reinforced composite structural component as part of an operational flight systemUNIQUENESS:?CNT manufacturing methods developed?Flight qualify CNT reinforced composites

Improving the Fatigue Crack Propagation Resistance and Damage Tolerance of 2524-T3 Alloy with Amorphous Electroless Ni-P Coating

NASA Astrophysics Data System (ADS)

Chen, Lai; Zeng, Diping; Liu, Zhiyi; Bai, Song; Li, Junlin

2018-02-01

The surface microhardness, as well as the fatigue crack propagation (FCP) resistance of 2524-T3 alloy, is improved by producing a 20-μm-thick amorphous electroless Ni-12% P coating on its surface. Compared to the substrate, this deposited EN coating possesses higher strength properties and exhibits a greater ability of accommodating the plastic deformation at the fatigue crack tip, thereby remarkably improving the FCP resistance in near-threshold and early Paris regimes. Regardless of the similar FCP rates in Paris regime (Δ K ≥ 16.2 MPa m0.5), the coated sample exhibits extended Paris regime and enhanced damage tolerance.

The Stomatopod Dactyl Club: A Formidable Damage-Tolerant Biological Hammer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weaver J. C.; DiMasi E.; Milliron, G.W.

2012-06-08

Nature has evolved efficient strategies to synthesize complex mineralized structures that exhibit exceptional damage tolerance. One such example is found in the hypermineralized hammer-like dactyl clubs of the stomatopods, a group of highly aggressive marine crustaceans. The dactyl clubs from one species, Odontodactylus scyllarus, exhibit an impressive set of characteristics adapted for surviving high-velocity impacts on the heavily mineralized prey on which they feed. Consisting of a multiphase composite of oriented crystalline hydroxyapatite and amorphous calcium phosphate and carbonate, in conjunction with a highly expanded helicoidal organization of the fibrillar chitinous organic matrix, these structures display several effective lines ofmore » defense against catastrophic failure during repetitive high-energy loading events.« less

Fully Integral, Flexible Composite Driveshaft

NASA Technical Reports Server (NTRS)

Lawrie, Duncan

2014-01-01

An all-composite driveshaft incorporating integral flexible diaphragms was developed for prime contractor testing. This new approach makes obsolete the split lines required to attach metallic flex elements and either metallic or composite spacing tubes in current solutions. Subcritical driveshaft weights can be achieved that are half that of incumbent technology for typical rotary wing shaft lengths. Spacing tubes compose an integral part of the initial tooling but remain part of the finished shaft and control natural frequencies and torsional stability. A concurrently engineered manufacturing process and design for performance competes with incumbent solutions at significantly lower weight and with the probability of improved damage tolerance and fatigue life.

Design and evaluation of a bolted joint for a discrete carbon-epoxy rod-reinforced hat section

NASA Technical Reports Server (NTRS)

Rousseau, Carl Q.; Baker, Donald J.

1996-01-01

The use of prefabricated pultruded carbon-epoxy rods has reduced the manufacturing complexity and costs of stiffened composite panels while increasing the damage tolerance of the panels. However, repairability of these highly efficient discrete stiffeners has been a concern. Design, analysis, and test results are presented in this paper for a bolted-joint repair for the pultruded rod concept that is capable of efficiently transferring axial loads in a hat-section stiffener on the upper skin segment of a heavily loaded aircraft wing component. A tension and a compression joint design were evaluated. The tension joint design achieved approximately 1.0% strain in the carbon-epoxy rod-reinforced hat-section and failed in a metal fitting at 166% of the design ultimate load. The compression joint design failed in the carbon-epoxy rod-reinforced hat-section test specimen area at approximately 0.7% strain and at 110% of the design ultimate load. This strain level of 0.7% in compression is similar to the failure strain observed in previously reported carbon-epoxy rod-reinforced hat-section column tests.

Some Biological Hints on the Control of Heat and Mass Transfer

NASA Astrophysics Data System (ADS)

Hagiwara, Yoshimichi

This review paper explores the possibilities of the control of heat and mass transfer associated with drought tolerance and freeze tolerance. The accumulation of some metabolites, such as proline and trehalose, are effective for drought tolerance. The special microstructures on the surfaces of some plants and insects in deserts are effective for collecting moisture in the air. Methods of preserving crops will be improved by the mimetic of the drought tolerance. Calcium ions and a protein are effective for the retrieval of damaged cell membrane due to ice formation. Ice crystal growth is inhibited by some substances such as antifreeze proteins. The cryopreservation of foods and organs will be improved by the mimetic of the freeze tolerance.

The paradox of higher light tolerance during desiccation in rare old forest cyanolichens than in more widespread co-occurring chloro- and cephalolichens

PubMed Central

Gauslaa, Yngvar; Coxson, Darwyn S; Solhaug, Knut Asbjørn

2012-01-01

Desiccation tolerance was quantified in four cyanolichens (Lobaria hallii, Lobaria retigera, Lobaria scrobiculata, Pseudocyphellaria anomala), one cephalolichen (Lobaria pulmonaria) and one chlorolichen (Platismatia glauca) from xeric and mesic, open and closed North American boreal forests. These sympatric epiphytes were exposed to 0%, 33%, 55% and 75% relative humidity with or without medium light (200 μmol m−2 s−1) for 7 d. Permanent and temporary photoinhibitory damage was recorded as viability measures. All species tolerated well the drying in darkness, but L. hallii and L. retigera, associated with a very humid climate, showed minor damage at the hardest drying (silica gel). Simultaneous exposure to medium light severely aggravated the drying damage at all relative humidity levels. Combined drying–light exposure was particularly devastating for the widespread chloro- and cephalolichens, whereas cyanolichens, including rare old forest species, were fairly resistant. The ability to recover after combined drying–light stress (this study) correlated positively with increasing species-specific water holding capacities (from the literature). Cyanolichens, depending on liquid water and large internal water storage, probably require strong drying–light resistance to handle long periods between hydration events, whereas chlorolichens can regularly maintain their photosynthetic apparatus during frequent and rapid activation by humid air on clear mornings. PMID:22762452

Insensitivity to Flaws Leads to Damage Tolerance in Brittle Architected Meta-Materials

NASA Astrophysics Data System (ADS)

Montemayor, L. C.; Wong, W. H.; Zhang, Y.-W.; Greer, J. R.

2016-02-01

Cellular solids are instrumental in creating lightweight, strong, and damage-tolerant engineering materials. By extending feature size down to the nanoscale, we simultaneously exploit the architecture and material size effects to substantially enhance structural integrity of architected meta-materials. We discovered that hollow-tube alumina nanolattices with 3D kagome geometry that contained pre-fabricated flaws always failed at the same load as the pristine specimens when the ratio of notch length (a) to sample width (w) is no greater than 1/3, with no correlation between failure occurring at or away from the notch. Samples with (a/w) > 0.3, and notch length-to-unit cell size ratios of (a/l) > 5.2, failed at a lower peak loads because of the higher sample compliance when fewer unit cells span the intact region. Finite element simulations show that the failure is governed by purely tensile loading for (a/w) < 0.3 for the same (a/l); bending begins to play a significant role in failure as (a/w) increases. This experimental and computational work demonstrates that the discrete-continuum duality of architected structural meta-materials may give rise to their damage tolerance and insensitivity of failure to the presence of flaws even when made entirely of intrinsically brittle materials.

Association mapping provides insights into the origin and the fine structure of the sorghum aluminum tolerance locus, AltSB

USDA-ARS?s Scientific Manuscript database

Root damage caused by aluminum (Al) toxicity is a major cause of grain yield reduction on acid soils, which are prevalent in tropical and subtropical regions of the world where food security is most tenuous. In sorghum, Al tolerance is conferred by SbMATE, an Al-activated root citrate efflux transpo...

Hematopoietic tissue repair under chronic low daily dose irradiation

NASA Astrophysics Data System (ADS)

Seed, T. M.

The capacity of the hematopoietic system to repair constantly accruing cellular damage under chronic, low daily dose gamma irradiation is essential for the maintenance of a functional hematopoietic system, and, in turn, long term survival. In certain individuals, however, such continuous cycles of damage and repair provide an essential inductive environment for selected types of hematopathologies, e.g., myeloid leukemia (ML). In our laboratory we have been studying temporal and causal relationships between hematopoietic capacity, associated repair functions, and propensities for hematologic disease in canines under variable levels of chronic radiation stress (0.3-26.3 cGy d^-1). Results indicate that the maximum exposure rate tolerated by the hematopoietic system is highly individual-specific (three major responding subgroups identified) and is based largely on the degree to which repair capacity, and, in turn, hematopoietic restoration, is augmented under chronic exposure. In low-tolerance individuals (prone to aplastic anemia, subgroup 1), the failure to augment basic repair functions seemingly results in a progressive accumulation of genetic and cellular damage within vital progenitorial marrow compartments (particularly marked within erythroid compartments) that results in loss of reproductive capacity and ultimately in collapse of the hematopoietic system. The high-tolerance individuals (radioaccommodated and either prone- or not prone to ML, subgroup 2 & 3) appear to minimize the accumulating damage effect of daily exposures by extending repair functions, which preserves reproductive integrity and fosters regenerative hematopoietic responses. As the strength of the regenerative response manifests the extent of repair augmentation, the relatively strong response of high-tolerance individuals progressing to patent ML suggests an insufficiency of repair quality rather than repair quantity. The kinetics of these repair-mediated, regenerative hematopoietic responses within the major subgroups are under study and should provide useful insights into the nature of hematopoietic accommodation (or its failure) under greatly extended periods of chronic, low-daily-dose ionizing radiation exposure.

Removal of nutrient limitations in forest gaps enhances growth rate and resistance to cavitation in subtropical canopy tree species differing in shade tolerance.

PubMed

Villagra, Mariana; Campanello, Paula I; Montti, Lia; Goldstein, Guillermo

2013-03-01

A 4-year fertilization experiment with nitrogen (N) and phosphorus (P) was carried out in natural gaps of a subtropical forest in northeastern Argentina. Saplings of six dominant canopy species differing in shade tolerance were grown in five control and five N + P fertilized gaps. Hydraulic architectural traits such as wood density, the leaf area to sapwood area ratio (LA : SA), vulnerability to cavitation (P50) and specific and leaf-specific hydraulic conductivity were measured, as well as the relative growth rate, specific leaf area (SLA) and percentage of leaf damage by insect herbivores. Plant growth rates and resistance to drought-induced embolisms increased when nutrient limitations were removed. On average, the P50 of control plants was -1.1 MPa, while the P50 of fertilized plants was -1.6 MPa. Wood density and LA : SA decreased with N + P additions. A trade-off between vulnerability to cavitation and efficiency of water transport was not observed. The relative growth rate was positively related to the total leaf surface area per plant and negatively related to LA : SA, while P50 was positively related to SLA across species and treatments. Plants with higher growth rates and higher total leaf area in fertilized plots were able to avoid hydraulic dysfunction by becoming less vulnerable to cavitation (more negative P50). Two high-light-requiring species exhibited relatively low growth rates due to heavy herbivore damage. Contrary to expectations, shade-tolerant plants with relatively high resistance to hydraulic dysfunction and reduced herbivory damage were able to grow faster. These results suggest that during the initial phase of sapling establishment in gaps, species that were less vulnerable to cavitation and exhibited reduced herbivory damage had faster realized growth rates than less shade-tolerant species with higher potential growth rates. Finally, functional relationships between hydraulic traits and growth rate across species and treatments were maintained regardless of soil nutrient status.

Genome-wide map of Apn1 binding sites under oxidative stress in Saccharomyces cerevisiae.

PubMed

Morris, Lydia P; Conley, Andrew B; Degtyareva, Natalya; Jordan, I King; Doetsch, Paul W

2017-11-01

The DNA is cells is continuously exposed to reactive oxygen species resulting in toxic and mutagenic DNA damage. Although the repair of oxidative DNA damage occurs primarily through the base excision repair (BER) pathway, the nucleotide excision repair (NER) pathway processes some of the same lesions. In addition, damage tolerance mechanisms, such as recombination and translesion synthesis, enable cells to tolerate oxidative DNA damage, especially when BER and NER capacities are exceeded. Thus, disruption of BER alone or disruption of BER and NER in Saccharomyces cerevisiae leads to increased mutations as well as large-scale genomic rearrangements. Previous studies demonstrated that a particular region of chromosome II is susceptible to chronic oxidative stress-induced chromosomal rearrangements, suggesting the existence of DNA damage and/or DNA repair hotspots. Here we investigated the relationship between oxidative damage and genomic instability utilizing chromatin immunoprecipitation combined with DNA microarray technology to profile DNA repair sites along yeast chromosomes under different oxidative stress conditions. We targeted the major yeast AP endonuclease Apn1 as a representative BER protein. Our results indicate that Apn1 target sequences are enriched for cytosine and guanine nucleotides. We predict that BER protects these sites in the genome because guanines and cytosines are thought to be especially susceptible to oxidative attack, thereby preventing large-scale genome destabilization from chronic accumulation of DNA damage. Information from our studies should provide insight into how regional deployment of oxidative DNA damage management systems along chromosomes protects against large-scale rearrangements. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Mechanisms of Oryza sativa (Poaceae) resistance to Tagosodes orizicolus (Homoptera: Delphacidae) under greenhouse condition in Venezuela.

PubMed

González, Alex; Labrín, Natalia; Alvarez, Rosa M; Jayaro, Yorman; Gamboa, Carlos; Reyes, Edicta; Barrientos, Venancio

2012-03-01

Tagosodes orizicolus is one of the main plagues of rice in tropical America causing two types of damages, the direct one, feeding and oviposition effect, and an indirect one, by the transmission of the "Rice hoja blanca virus". During 2006-2007 we carried out research under greenhouse conditions at Fundaci6n Danac, Venezuela, in order to determine the mechanisms of antixenosis, antibiosis and tolerance to T. orizicolus, which could be acting in commercial varieties and advanced lines of the rice genetic breeding programs of INIA and Fundaci6n Danac. The method of free feeding was used for the antixenosis evaluation, whereas the method of forced feeding was used for antibiosis evaluation (effect on survival and oviposition). Additionally, we used the indirect method based on biomass depression to estimate the tolerance. Some of the evaluated traits included: grade of damage, number of insects settling on rice plants, percentage of sogata mortality at the mature state, number of eggs in the leaf midrib and an index of tolerance. The results showed that rice genotypes possess different combinations of resistance mechanisms, as well as different grades of reactions. The susceptible control 'Bluebonnet 50' was consistently susceptible across experiments and the resistant control 'Makalioka' had high antixenosis and high antibiosis based on survival and oviposition. The rest of the genotypes presented lower or higher degrees of antixenosis and antibiosis for survival and oviposition. The genotype 'FD0241-M-17-6-1-1-1-1' was identified with possible tolerance to the direct damage of sogata.

Solidago gigantea plants from nonnative ranges compensate more in response to damage than plants from the native range.

PubMed

Liao, Huixuan; Gurgel, Priscila C S; Pal, Robert W; Hooper, David; Callaway, Ragan M

2016-09-01

Resistance and tolerance are two ways that plants cope with herbivory. Tolerance, the ability of a plant to regrow or reproduce after being consumed, has been studied less than resistance, but this trait varies widely among species and has considerable potential to affect the ecology of plant species. One particular aspect of tolerance, compensatory responses, can evolve rapidly in plant species; providing insight into interactions between consumers and plants. However, compensation by invasive species has rarely been explored. We compared compensatory responses to the effects of simulated herbivory expressed by plants from seven Solidago gigantea populations from the native North American range to that expressed by plants from nine populations from the nonnative European range. Populations were also collected along elevational gradients to compare ecotypic variation within and between ranges. Solidago plants from the nonnative range of Europe were more tolerant to herbivory than plants from the native range of North America. Furthermore, plants from European populations increased in total biomass and growth rate with elevation, but decreased in compensatory response. There were no relationships between elevation and growth or compensation for North American populations. Our results suggest that Solidago gigantea may have evolved to better compensate for herbivory damage in Europe, perhaps in response to a shift to greater proportion of attack from generalists. Our results also suggest a possible trade-off between rapid growth and compensation to damage in European populations but not in North American populations. © 2016 by the Ecological Society of America.

Elevated Temperature and CO2 Stimulate Late-Season Photosynthesis But Impair Cold Hardening in Pine.

PubMed

Chang, Christine Y; Fréchette, Emmanuelle; Unda, Faride; Mansfield, Shawn D; Ensminger, Ingo

2016-10-01

Rising global temperature and CO 2 levels may sustain late-season net photosynthesis of evergreen conifers but could also impair the development of cold hardiness. Our study investigated how elevated temperature, and the combination of elevated temperature with elevated CO 2 , affected photosynthetic rates, leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening in Eastern white pine (Pinus strobus). We designed an experiment where control seedlings were acclimated to long photoperiod (day/night 14/10 h), warm temperature (22°C/15°C), and either ambient (400 μL L -1 ) or elevated (800 μmol mol -1 ) CO 2 , and then shifted seedlings to growth conditions with short photoperiod (8/16 h) and low temperature/ambient CO 2 (LTAC), elevated temperature/ambient CO 2 (ETAC), or elevated temperature/elevated CO 2 (ETEC). Exposure to LTAC induced down-regulation of photosynthesis, development of sustained nonphotochemical quenching, accumulation of soluble carbohydrates, expression of a 16-kD dehydrin absent under long photoperiod, and increased freezing tolerance. In ETAC seedlings, photosynthesis was not down-regulated, while accumulation of soluble carbohydrates, dehydrin expression, and freezing tolerance were impaired. ETEC seedlings revealed increased photosynthesis and improved water use efficiency but impaired dehydrin expression and freezing tolerance similar to ETAC seedlings. Sixteen-kilodalton dehydrin expression strongly correlated with increases in freezing tolerance, suggesting its involvement in the development of cold hardiness in P. strobus Our findings suggest that exposure to elevated temperature and CO 2 during autumn can delay down-regulation of photosynthesis and stimulate late-season net photosynthesis in P. strobus seedlings. However, this comes at the cost of impaired freezing tolerance. Elevated temperature and CO 2 also impaired freezing tolerance. However, unless the frequency and timing of extreme low-temperature events changes, this is unlikely to increase risk of freezing damage in P. strobus seedlings. © 2016 American Society of Plant Biologists. All Rights Reserved.

Elevated Temperature and CO2 Stimulate Late-Season Photosynthesis But Impair Cold Hardening in Pine[OPEN

PubMed Central

2016-01-01

Rising global temperature and CO2 levels may sustain late-season net photosynthesis of evergreen conifers but could also impair the development of cold hardiness. Our study investigated how elevated temperature, and the combination of elevated temperature with elevated CO2, affected photosynthetic rates, leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening in Eastern white pine (Pinus strobus). We designed an experiment where control seedlings were acclimated to long photoperiod (day/night 14/10 h), warm temperature (22°C/15°C), and either ambient (400 μL L−1) or elevated (800 μmol mol−1) CO2, and then shifted seedlings to growth conditions with short photoperiod (8/16 h) and low temperature/ambient CO2 (LTAC), elevated temperature/ambient CO2 (ETAC), or elevated temperature/elevated CO2 (ETEC). Exposure to LTAC induced down-regulation of photosynthesis, development of sustained nonphotochemical quenching, accumulation of soluble carbohydrates, expression of a 16-kD dehydrin absent under long photoperiod, and increased freezing tolerance. In ETAC seedlings, photosynthesis was not down-regulated, while accumulation of soluble carbohydrates, dehydrin expression, and freezing tolerance were impaired. ETEC seedlings revealed increased photosynthesis and improved water use efficiency but impaired dehydrin expression and freezing tolerance similar to ETAC seedlings. Sixteen-kilodalton dehydrin expression strongly correlated with increases in freezing tolerance, suggesting its involvement in the development of cold hardiness in P. strobus. Our findings suggest that exposure to elevated temperature and CO2 during autumn can delay down-regulation of photosynthesis and stimulate late-season net photosynthesis in P. strobus seedlings. However, this comes at the cost of impaired freezing tolerance. Elevated temperature and CO2 also impaired freezing tolerance. However, unless the frequency and timing of extreme low-temperature events changes, this is unlikely to increase risk of freezing damage in P. strobus seedlings. PMID:27591187

Hypothermia for preventing chemotherapy-induced neuropathy - a pilot study on safety and tolerability in healthy controls.

PubMed

Bandla, Aishwarya; Sundar, Raghav; Liao, Lun-De; Sze Hui Tan, Stacey; Lee, Soo-Chin; Thakor, Nitish V; Wilder-Smith, Einar P V

2016-01-01

Chemotherapy-induced peripheral neuropathy (CIPN) is a major dose-limiting side effect of several chemotherapeutic agents, often leading to treatment discontinuation. Up to 20% of patients treated with weekly paclitaxel experience severe CIPN and no effective treatment has been established so far. The mechanisms of CIPN damage are unclear, but are directly dose-related. We had earlier demonstrated, in rats, the influence of hypothermia in reducing nerve blood flow. Here, we hypothesize that continuous flow limb hypothermia during chemotherapy reduces the incidence and severity of CIPN, by limiting deliverance of the neurotoxic drug to the peripheral nerves. In this study, prior to assessing the effect of hypothermia in preventing CIPN in cancer subjects undergoing paclitaxel chemotherapy, we assess the safety and tolerable temperatures for limb hypothermia in healthy human subjects. In 15 healthy human subjects, hypothermia was administered as continuous flow cooling, unilaterally, via a thermoregulator setup covering the digits up to the elbow/knee, along with continuous skin temperature monitoring. Thermoregulator coolant temperatures between 25 °C and 20 °C were tested for tolerability, based on a carefully designed temperature regulation protocol, and maintained for three hours mimicking the duration of chemotherapy. Tolerability was evaluated using various safety and tolerability scores to monitor the subjects. At the end of the cooling session the healthy subjects presented without significant adverse effects, the main being brief mild skin erythema and transient numbness. Coolant temperatures as low as 22 °C were well tolerated continuously over three hours. Our results confirm the safety and tolerability of continuous flow limb hypothermia in healthy subjects. Further studies will use 22 °C thermoregulator temperature to investigate hypothermia in preventing CIPN in breast cancer patients receiving adjuvant weekly paclitaxel. This pilot study may contribute to alleviating chemotherapy dose limitation due to CIPN and increase the likelihood of success of chemotherapy.

New iron-sulfur clusters help hydrogenases tolerate oxygen.

PubMed

Grubel, Katarzyna; Holland, Patrick L

2012-04-02

One S less: recent crystallographic studies have revealed a new, oxygen-tolerant kind of iron-sulfide cluster [4Fe-3S], which contains only three rather than four sulfur atoms in its cage (see picture; yellow=S, red=Fe, blue=N, green=cysteine). It is proposed that the cluster's ability to transfer multiple electrons increases the oxygen tolerance by enabling the enzyme to reduce O(2) rapidly, converting the dioxygen into harmless water before it can damage the protein. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimum Tolerance Design Using Component-Amount and Mixture-Amount Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piepel, Gregory F.; Ozler, Cenk; Sehirlioglu, Ali Kemal

2013-08-01

One type of tolerance design problem involves optimizing component and assembly tolerances to minimize the total cost (sum of manufacturing cost and quality loss). Previous literature recommended using traditional response surface (RS) designs and models to solve this type of tolerance design problem. In this article, component-amount (CA) and mixture-amount (MA) approaches are proposed as more appropriate for solving this type of tolerance design problem. The advantages of the CA and MA approaches over the RS approach are discussed. Reasons for choosing between the CA and MA approaches are also discussed. The CA and MA approaches (experimental design, response modeling,more » and optimization) are illustrated using real examples.« less

Flaw Tolerance In Lap Shear Brazed Joints. Part 2

NASA Technical Reports Server (NTRS)

Wang, Len; Flom, Yury

2003-01-01

This paper presents results of the second part of an on-going effort to gain better understanding of defect tolerance in braze joints. In the first part of this three-part series, we mechanically tested and modeled the strength of the lap joints as a function of the overlap distance. A failure criterion was established based on the zone damage theory, which predicts the dependence of the lap joint shear strength on the overlap distance, based on the critical size of a finite damage zone or an overloaded region in the joint. In this second part of the study, we experimentally verified the applicability of the damage zone criterion on prediction of the shear strength of the lap joint and introduced controlled flaws into the lap joints. The purpose of the study was to evaluate the lap joint strength as a function of flaw size and its location through mechanical testing and nonlinear finite element analysis (FEA) employing damage zone criterion for definition of failure. The results obtained from the second part of the investigation confirmed that the failure of the ductile lap shear brazed joints occurs when the damage zone reaches approximately 10% of the overlap width. The same failure criterion was applicable to the lap joints containing flaws.

Electrochemical activity evaluation of chemically damaged carbon nanotube with palladium nanoparticles for ethanol oxidation

NASA Astrophysics Data System (ADS)

Ahmed, Mohammad Shamsuddin; Jeon, Seungwon

2015-05-01

The carbon nanotube (CNT) has unique electrical and structural properties due to it's sp2 π-conjugative structure that leads to the higher electrocatalysis. The π-conjugative structure, that allows the CNT interact with various compounds and metal nanoparticles (NPs) through π-π electronic interaction. However, the damage of π-conjugative sidewall of CNT that can be hinder the electrocatalytic activity has found. For this study, the CNT, as base material, has been prepared through a conventional acid treatment method up to 15 h; the higher degree of sidewall damage has been observed in last 5 h during treatment period. The short and long term acid treated (denoted as CNT and CNT-COOH, respectively) CNTs have been subsequently fabricated with palladium NPs (denoted as CNT/Pd and CNT-Pd, respectively) and employed as ethanol oxidation reaction (EOR) catalysts. The CNT-Pd displays a poor electrocatalytic performance towards EOR than that of CNT/Pd due to the damage of π-conjugative sidewall. The kinetic parameters including poisoning tolerance have also been hampered by the surface damage. The CNT/Pd (∼3.3 folds) and CNT-Pd (∼1.5 folds) are express higher electrocatalytic activity and poisoning tolerance than that of Pd/C while Pd mass loading remains in the same amount.

Comparative Proteomic Analysis of Tolerance and Adaptation of Ethanologenic Saccharomyces cerevisiae to Furfural, a Lignocellulosic Inhibitory Compound▿ †

PubMed Central

Lin, Feng-Ming; Qiao, Bin; Yuan, Ying-Jin

2009-01-01

The molecular mechanism involved in tolerance and adaptation of ethanologenic Saccharomyces cerevisiae to inhibitors (such as furfural, acetic acid, and phenol) represented in lignocellulosic hydrolysate is still unclear. Here, 18O-labeling-aided shotgun comparative proteome analysis was applied to study the global protein expression profiles of S. cerevisiae under conditions of treatment of furfural compared with furfural-free fermentation profiles. Proteins involved in glucose fermentation and/or the tricarboxylic acid cycle were upregulated in cells treated with furfural compared with the control cells, while proteins involved in glycerol biosynthesis were downregulated. Differential levels of expression of alcohol dehydrogenases were observed. On the other hand, the levels of NADH, NAD+, and NADH/NAD+ were reduced whereas the levels of ATP and ADP were increased. These observations indicate that central carbon metabolism, levels of alcohol dehydrogenases, and the redox balance may be related to tolerance of ethanologenic yeast for and adaptation to furfural. Furthermore, proteins involved in stress response, including the unfolded protein response, oxidative stress, osmotic and salt stress, DNA damage and nutrient starvation, were differentially expressed, a finding that was validated by quantitative real-time reverse transcription-PCR to further confirm that the general stress responses are essential for cellular defense against furfural. These insights into the response of yeast to the presence of furfural will benefit the design and development of inhibitor-tolerant ethanologenic yeast by metabolic engineering or synthetic biology. PMID:19363068

Estimation of probability of failure for damage-tolerant aerospace structures

NASA Astrophysics Data System (ADS)

Halbert, Keith

The majority of aircraft structures are designed to be damage-tolerant such that safe operation can continue in the presence of minor damage. It is necessary to schedule inspections so that minor damage can be found and repaired. It is generally not possible to perform structural inspections prior to every flight. The scheduling is traditionally accomplished through a deterministic set of methods referred to as Damage Tolerance Analysis (DTA). DTA has proven to produce safe aircraft but does not provide estimates of the probability of failure of future flights or the probability of repair of future inspections. Without these estimates maintenance costs cannot be accurately predicted. Also, estimation of failure probabilities is now a regulatory requirement for some aircraft. The set of methods concerned with the probabilistic formulation of this problem are collectively referred to as Probabilistic Damage Tolerance Analysis (PDTA). The goal of PDTA is to control the failure probability while holding maintenance costs to a reasonable level. This work focuses specifically on PDTA for fatigue cracking of metallic aircraft structures. The growth of a crack (or cracks) must be modeled using all available data and engineering knowledge. The length of a crack can be assessed only indirectly through evidence such as non-destructive inspection results, failures or lack of failures, and the observed severity of usage of the structure. The current set of industry PDTA tools are lacking in several ways: they may in some cases yield poor estimates of failure probabilities, they cannot realistically represent the variety of possible failure and maintenance scenarios, and they do not allow for model updates which incorporate observed evidence. A PDTA modeling methodology must be flexible enough to estimate accurately the failure and repair probabilities under a variety of maintenance scenarios, and be capable of incorporating observed evidence as it becomes available. This dissertation describes and develops new PDTA methodologies that directly address the deficiencies of the currently used tools. The new methods are implemented as a free, publicly licensed and open source R software package that can be downloaded from the Comprehensive R Archive Network. The tools consist of two main components. First, an explicit (and expensive) Monte Carlo approach is presented which simulates the life of an aircraft structural component flight-by-flight. This straightforward MC routine can be used to provide defensible estimates of the failure probabilities for future flights and repair probabilities for future inspections under a variety of failure and maintenance scenarios. This routine is intended to provide baseline estimates against which to compare the results of other, more efficient approaches. Second, an original approach is described which models the fatigue process and future scheduled inspections as a hidden Markov model. This model is solved using a particle-based approximation and the sequential importance sampling algorithm, which provides an efficient solution to the PDTA problem. Sequential importance sampling is an extension of importance sampling to a Markov process, allowing for efficient Bayesian updating of model parameters. This model updating capability, the benefit of which is demonstrated, is lacking in other PDTA approaches. The results of this approach are shown to agree with the results of the explicit Monte Carlo routine for a number of PDTA problems. Extensions to the typical PDTA problem, which cannot be solved using currently available tools, are presented and solved in this work. These extensions include incorporating observed evidence (such as non-destructive inspection results), more realistic treatment of possible future repairs, and the modeling of failure involving more than one crack (the so-called continuing damage problem). The described hidden Markov model / sequential importance sampling approach to PDTA has the potential to improve aerospace structural safety and reduce maintenance costs by providing a more accurate assessment of the risk of failure and the likelihood of repairs throughout the life of an aircraft.

Crack Detection in Fibre Reinforced Plastic Structures Using Embedded Fibre Bragg Grating Sensors: Theory, Model Development and Experimental Validation

PubMed Central

Pereira, G. F.; Mikkelsen, L. P.; McGugan, M.

2015-01-01

In a fibre-reinforced polymer (FRP) structure designed using the emerging damage tolerance and structural health monitoring philosophy, sensors and models that describe crack propagation will enable a structure to operate despite the presence of damage by fully exploiting the material’s mechanical properties. When applying this concept to different structures, sensor systems and damage types, a combination of damage mechanics, monitoring technology, and modelling is required. The primary objective of this article is to demonstrate such a combination. This article is divided in three main topics: the damage mechanism (delamination of FRP), the structural health monitoring technology (fibre Bragg gratings to detect delamination), and the finite element method model of the structure that incorporates these concepts into a final and integrated damage-monitoring concept. A novel method for assessing a crack growth/damage event in fibre-reinforced polymer or structural adhesive-bonded structures using embedded fibre Bragg grating (FBG) sensors is presented by combining conventional measured parameters, such as wavelength shift, with parameters associated with measurement errors, typically ignored by the end-user. Conjointly, a novel model for sensor output prediction (virtual sensor) was developed using this FBG sensor crack monitoring concept and implemented in a finite element method code. The monitoring method was demonstrated and validated using glass fibre double cantilever beam specimens instrumented with an array of FBG sensors embedded in the material and tested using an experimental fracture procedure. The digital image correlation technique was used to validate the model prediction by correlating the specific sensor response caused by the crack with the developed model. PMID:26513653

Environment assisted degradation mechanisms in aluminum-lithium alloys

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Stoner, Glenn E.; Swanson, Robert E.

1988-01-01

Section 1 of this report records the progress achieved on NASA-LaRC Grant NAG-1-745 (Environment Assisted Degradation Mechanisms in Al-Li Alloys), and is based on research conducted during the period April 1 to November 30, 1987. A discussion of work proposed for the project's second year is included. Section 2 provides an overview of the need for research on the mechanisms of environmental-mechanical degradation of advanced aerospace alloys based on aluminum and lithium. This research is to provide NASA with the basis necessary to permit metallurgical optimization of alloy performance and engineering design with respect to damage tolerance, long term durability and reliability. Section 3 reports on damage localization mechanisms in aqueous chloride corrosion fatigue of aluminum-lithium alloys. Section 4 reports on progress made on measurements and mechanisms of localized aqueous corrosion in aluminum-lithium alloys. Section 5 provides a detailed technical proposal for research on environmental degradation of Al-Li alloys, and the effect of hydrogen in this.

Lattice thermal conductivity of multi-component alloys

DOE PAGES

Caro, Magdalena; Béland, Laurent K.; Samolyuk, German D.; ...

2015-06-12

High entropy alloys (HEA) have unique properties including the potential to be radiation tolerant. These materials with extreme disorder could resist damage because disorder, stabilized by entropy, is the equilibrium thermodynamic state. Disorder also reduces electron and phonon conductivity keeping the damage energy longer at the deposition locations, eventually favoring defect recombination. In the short time-scales related to thermal spikes induced by collision cascades, phonons become the relevant energy carrier. In this paper, we perform a systematic study of phonon thermal conductivity in multiple component solid solutions represented by Lennard-Jones (LJ) potentials. We explore the conditions that minimize phonon meanmore » free path via extreme alloy complexity, by varying the composition and the elements (differing in mass, atomic radii, and cohesive energy). We show that alloy complexity can be tailored to modify the scattering mechanisms that control energy transport in the phonon subsystem. Finally, our analysis provides a qualitative guidance for the selection criteria used in the design of HEA alloys with low phonon thermal conductivity.« less

Flight Test Comparison of Different Adaptive Augmentations for Fault Tolerant Control Laws for a Modified F-15 Aircraft

NASA Technical Reports Server (NTRS)

Burken, John J.; Hanson, Curtis E.; Lee, James A.; Kaneshige, John T.

2009-01-01

This report describes the improvements and enhancements to a neural network based approach for directly adapting to aerodynamic changes resulting from damage or failures. This research is a follow-on effort to flight tests performed on the NASA F-15 aircraft as part of the Intelligent Flight Control System research effort. Previous flight test results demonstrated the potential for performance improvement under destabilizing damage conditions. Little or no improvement was provided under simulated control surface failures, however, and the adaptive system was prone to pilot-induced oscillations. An improved controller was designed to reduce the occurrence of pilot-induced oscillations and increase robustness to failures in general. This report presents an analysis of the neural networks used in the previous flight test, the improved adaptive controller, and the baseline case with no adaptation. Flight test results demonstrate significant improvement in performance by using the new adaptive controller compared with the previous adaptive system and the baseline system for control surface failures.

Mechanical behavior of glass/epoxy composite laminate with varying amount of MWCNTs under different loadings

NASA Astrophysics Data System (ADS)

Singh, K. K.; Rawat, Prashant

2018-05-01

This paper investigates the mechanical response of three phased (glass/MWCNTs/epoxy) composite laminate under three different loadings. Flexural strength, short beam strength and low-velocity impact (LVI) testing are performed to find an optimum doping percentage value for maximum enhancement in mechanical properties. In this work, MWCNTs were used as secondary reinforcement for three-phased composite plate. MWCNT doping was done in a range of 0–4 wt% of the thermosetting matrix system. Symmetrical design eight layered glass/epoxy laminate with zero bending extension coupling laminate was fabricated using a hybrid method i.e. hand lay-up technique followed by vacuum bagging method. Ranging analysis of MWCNT mixing highlighted the enhancement in flexural, short beam strength and improvement in damage tolerance under LVI loading. While at higher doping wt%, agglomeration of MWCNTs are observed. Results of mechanical testing proposed an optimized doping value for maximum strength and damage resistance of the laminate.

Development of COPVS for High pressure, In-Space, Cryogenic Fuel Storage

NASA Technical Reports Server (NTRS)

DeLay, Tom; Schneider, Judy; Dyess, Mark; Hastings, Chad; Noorda, Ryan; Noorda, Jared; Patterson, James

2008-01-01

Polymeric composite overwrapped pressure vessels (COPVs) provide an attractive material system to support developing commercial launch business and alternate fuel ventures. However to be able to design with these materials, the mechanical behavior of the materials must be understood with regards to processing, performance, damage tolerance, and environment. For the storage of cryogenic propellants, it is important to evaluate the materials performance and impact damage resistance at cryogenic temperatures in order to minimize weight and to ensure safety and reliability. To evaluate the ultimate performance, various polymeric COPV's have been statically burst tested at cryogenic conditions before and after exposure to irradiation. Materials selected for these COPVs were based on the measured mechanical properties of candidate resin systems and fibers that were also tested at cryogenic conditions before and after exposure to irradiation. The correlation of COPV burst pressures with the constituent material properties has proven to be a valuable screening method for selection of suitable candidate materials with resistance to material degradation due to exposure to temperature and radiation.

Simplified Models for the Study of Postbuckled Hat-Stiffened Composite Panels

NASA Technical Reports Server (NTRS)

Vescovini, Riccardo; Davila, Carlos G.; Bisagni, Chiara

2012-01-01

The postbuckling response and failure of multistringer stiffened panels is analyzed using models with three levels of approximation. The first model uses a relatively coarse mesh to capture the global postbuckling response of a five-stringer panel. The second model can predict the nonlinear response as well as the debonding and crippling failure mechanisms in a single stringer compression specimen (SSCS). The third model consists of a simplified version of the SSCS that is designed to minimize the computational effort. The simplified model is well-suited to perform sensitivity analyses for studying the phenomena that lead to structural collapse. In particular, the simplified model is used to obtain a deeper understanding of the role played by geometric and material modeling parameters such as mesh size, inter-laminar strength, fracture toughness, and fracture mode mixity. Finally, a global/local damage analysis method is proposed in which a detailed local model is used to scan the global model to identify the locations that are most critical for damage tolerance.

Development of GENOA Progressive Failure Parallel Processing Software Systems

NASA Technical Reports Server (NTRS)

Abdi, Frank; Minnetyan, Levon

1999-01-01

A capability consisting of software development and experimental techniques has been developed and is described. The capability is integrated into GENOA-PFA to model polymer matrix composite (PMC) structures. The capability considers the physics and mechanics of composite materials and structure by integration of a hierarchical multilevel macro-scale (lamina, laminate, and structure) and micro scale (fiber, matrix, and interface) simulation analyses. The modeling involves (1) ply layering methodology utilizing FEM elements with through-the-thickness representation, (2) simulation of effects of material defects and conditions (e.g., voids, fiber waviness, and residual stress) on global static and cyclic fatigue strengths, (3) including material nonlinearities (by updating properties periodically) and geometrical nonlinearities (by Lagrangian updating), (4) simulating crack initiation. and growth to failure under static, cyclic, creep, and impact loads. (5) progressive fracture analysis to determine durability and damage tolerance. (6) identifying the percent contribution of various possible composite failure modes involved in critical damage events. and (7) determining sensitivities of failure modes to design parameters (e.g., fiber volume fraction, ply thickness, fiber orientation. and adhesive-bond thickness). GENOA-PFA progressive failure analysis is now ready for use to investigate the effects on structural responses to PMC material degradation from damage induced by static, cyclic (fatigue). creep, and impact loading in 2D/3D PMC structures subjected to hygrothermal environments. Its use will significantly facilitate targeting design parameter changes that will be most effective in reducing the probability of a given failure mode occurring.

The importance of fracture toughness in ultrafine and nanocrystalline bulk materials

PubMed Central

Pippan, R.; Hohenwarter, A.

2016-01-01

ABSTRACT The suitability of high-strength ultrafine and nanocrystalline materials processed by severe plastic deformation methods and aimed to be used for structural applications will strongly depend on their resistance against crack growth. In this contribution some general available findings on the damage tolerance of this material class will be summarized. Particularly, the occurrence of a pronounced fracture anisotropy will be in the center of discussion. In addition, the great potential of this generated anisotropy to obtain high-strength materials with exceptionally high fracture toughness in specific loading and crack growth directions will be enlightened. IMPACT STATEMENT Severely plastically deformed materials are reviewed in light of their damage tolerance. The frequently observed toughness anisotropy allows unprecedented fracture toughness – strength combinations. PMID:27570712

Failure models for textile composites

NASA Technical Reports Server (NTRS)

Cox, Brian

1995-01-01

The goals of this investigation were to: (1) identify mechanisms of failure and determine how the architecture of reinforcing fibers in 3D woven composites controlled stiffness, strength, strain to failure, work of fracture, notch sensitivity, and fatigue life; and (2) to model composite stiffness, strength, and fatigue life. A total of 11 different angle and orthogonal interlock woven composites were examined. Composite properties depended on the weave architecture, the tow size, and the spatial distributions and strength of geometrical flaws. Simple models were developed for elastic properties, strength, and fatigue life. A more complicated stochastic model, called the 'Binary Model,' was developed for damage tolerance and ultimate failure. These 3D woven composites possessed an extraordinary combination of strength, damage tolerance, and notch insensitivity.

Design study of Software-Implemented Fault-Tolerance (SIFT) computer

NASA Technical Reports Server (NTRS)

Wensley, J. H.; Goldberg, J.; Green, M. W.; Kutz, W. H.; Levitt, K. N.; Mills, M. E.; Shostak, R. E.; Whiting-Okeefe, P. M.; Zeidler, H. M.

1982-01-01

Software-implemented fault tolerant (SIFT) computer design for commercial aviation is reported. A SIFT design concept is addressed. Alternate strategies for physical implementation are considered. Hardware and software design correctness is addressed. System modeling and effectiveness evaluation are considered from a fault-tolerant point of view.

Resin Film Infusion (RFI) Process Modeling for Large Transport Aircraft Wing Structures

NASA Technical Reports Server (NTRS)

Knott, Tamara W.; Loos, Alfred C.

2000-01-01

Resin film infusion (RFI) is a cost-effective method for fabricating stiffened aircraft wing structures. The RFI process lends itself to the use of near net shape textile preforms manufactured through a variety of automated textile processes such as knitting and braiding. Often, these advanced fiber architecture preforms have through-the-thickness stitching for improved damage tolerance and delamination resistance. The challenge presently facing RFI is to refine the process to ensure complete infiltration and cure of a geometrically complex shape preform with the high fiber volume fraction needed for structural applications. An accurate measurement of preform permeability is critical for successful modeling of the RFI resin infiltration process. Small changes in the permeability can result in very different infiltration behavior and times. Therefore, it is important to accurately measure the permeabilities of the textile preforms used in the RFI process. The objective of this investigation was to develop test methods that can be used to measure the compaction behavior and permeabilities of high fiber volume fraction, advanced fiber architecture textile preforms. These preforms are often highly compacted due to through-the-thickness stitching used to improve damage tolerance. Test fixtures were designed and fabricated and used to measure both transverse and in-plane permeabilities. The fixtures were used to measure the permeabilities of multiaxial warp knit and triaxial braided preforms at fiber volume fractions from 55% to 65%. In addition, the effects of stitching characteristics, thickness, and batch variability on permeability and compaction behavior were investigated.

[The immune system and the eye].

PubMed

Faber, Carsten; Nissen, Mogens Holst

2008-09-15

The special relationship between the eye and the immune system rests on a number of anatomical, physiological and immunological mechanisms. These mechanisms prevent the delicate structures of the eye from potentially damaging immunogenic inflammation while protecting against pathogens. Rather than inflammation, antigen induces a form of systemic and antigen-specific immunological tolerance. Owing to its systemic nature, this tolerance may be utilised to achieve successful treatment of immunological disorders.

Tolerance to multiple climate stressors: a case study of Douglas-fir drought and cold hardiness

Treesearch

Sheel Bansal; Connie Harrington; Brad St. Clair

2016-01-01

1. Drought and freeze events are two of the most common forms of climate extremes which result in tree damage or death, and the frequency and intensity of both stressors may increase with climate change. Few studies have examined natural covariation in stress tolerance traits to cope with multiple stressors among wild plant populations. 2. We assessed the...

Damage tolerance of nuclear graphite at elevated temperatures

DOE PAGES

Liu, Dong; Gludovatz, Bernd; Barnard, Harold S.; ...

2017-06-30

Nuclear-grade graphite is a critically important high-temperature structural material for current and potentially next generation of fission reactors worldwide. It is imperative to understand its damage-tolerant behaviour and to discern the mechanisms of damage evolution under in-service conditions. Here we perform in situ mechanical testing with synchrotron X-ray computed micro-tomography at temperatures between ambient and 1,000 °C on a nuclear-grade Gilsocarbon graphite. We find that both the strength and fracture toughness of this graphite are improved at elevated temperature. Whereas this behaviour is consistent with observations of the closure of microcracks formed parallel to the covalent-sp 2-bonded graphene layers atmore » higher temperatures, which accommodate the more than tenfold larger thermal expansion perpendicular to these layers, we attribute the elevation in strength and toughness primarily to changes in the residual stress state at 800–1,000 °C, specifically to the reduction in significant levels of residual tensile stresses in the graphite that are ‘frozen-in’ following processing.« less

Damage tolerance of nuclear graphite at elevated temperatures

PubMed Central

Liu, Dong; Gludovatz, Bernd; Barnard, Harold S.; Kuball, Martin; Ritchie, Robert O.

2017-01-01

Nuclear-grade graphite is a critically important high-temperature structural material for current and potentially next generation of fission reactors worldwide. It is imperative to understand its damage-tolerant behaviour and to discern the mechanisms of damage evolution under in-service conditions. Here we perform in situ mechanical testing with synchrotron X-ray computed micro-tomography at temperatures between ambient and 1,000 °C on a nuclear-grade Gilsocarbon graphite. We find that both the strength and fracture toughness of this graphite are improved at elevated temperature. Whereas this behaviour is consistent with observations of the closure of microcracks formed parallel to the covalent-sp2-bonded graphene layers at higher temperatures, which accommodate the more than tenfold larger thermal expansion perpendicular to these layers, we attribute the elevation in strength and toughness primarily to changes in the residual stress state at 800–1,000 °C, specifically to the reduction in significant levels of residual tensile stresses in the graphite that are ‘frozen-in’ following processing. PMID:28665405

Evolution of resistance and tolerance to herbivores: testing the trade-off hypothesis.

PubMed

Kariñho-Betancourt, Eunice; Núñez-Farfán, Juan

2015-01-01

Background. To cope with their natural enemies, plants rely on resistance and tolerance as defensive strategies. Evolution of these strategies among natural population can be constrained by the absence of genetic variation or because of the antagonistic genetic correlation (trade-off) between them. Also, since plant defenses are integrated by several traits, it has been suggested that trade-offs might occur between specific defense traits. Methodology/Principal Findings. We experimentally assessed (1) the presence of genetic variance in tolerance, total resistance, and leaf trichome density as specific defense trait, (2) the extent of natural selection acting on plant defenses, and (3) the relationship between total resistance and leaf trichome density with tolerance to herbivory in the annual herb Datura stramonium. Full-sib families of D. stramonium were either exposed to natural herbivores (control) or protected from them by a systemic insecticide. We detected genetic variance for leaf trichome density, and directional selection acting on this character. However, we did not detect a negative significant correlation between tolerance and total resistance, or between tolerance and leaf trichome density. We argue that low levels of leaf damage by herbivores precluded the detection of a negative genetic correlation between plant defense strategies. Conclusions/Significance. This study provides empirical evidence of the independent evolution of plant defense strategies, and a defensive role of leaf trichomes. The pattern of selection should favor individuals with high trichomes density. Also, because leaf trichome density reduces damage by herbivores and possess genetic variance in the studied population, its evolution is not constrained.

Evolution of resistance and tolerance to herbivores: testing the trade-off hypothesis

PubMed Central

Kariñho-Betancourt, Eunice

2015-01-01

Background. To cope with their natural enemies, plants rely on resistance and tolerance as defensive strategies. Evolution of these strategies among natural population can be constrained by the absence of genetic variation or because of the antagonistic genetic correlation (trade-off) between them. Also, since plant defenses are integrated by several traits, it has been suggested that trade-offs might occur between specific defense traits. Methodology/Principal Findings. We experimentally assessed (1) the presence of genetic variance in tolerance, total resistance, and leaf trichome density as specific defense trait, (2) the extent of natural selection acting on plant defenses, and (3) the relationship between total resistance and leaf trichome density with tolerance to herbivory in the annual herb Datura stramonium. Full-sib families of D. stramonium were either exposed to natural herbivores (control) or protected from them by a systemic insecticide. We detected genetic variance for leaf trichome density, and directional selection acting on this character. However, we did not detect a negative significant correlation between tolerance and total resistance, or between tolerance and leaf trichome density. We argue that low levels of leaf damage by herbivores precluded the detection of a negative genetic correlation between plant defense strategies. Conclusions/Significance. This study provides empirical evidence of the independent evolution of plant defense strategies, and a defensive role of leaf trichomes. The pattern of selection should favor individuals with high trichomes density. Also, because leaf trichome density reduces damage by herbivores and possess genetic variance in the studied population, its evolution is not constrained. PMID:25780756

Intelligent failure-tolerant control

NASA Technical Reports Server (NTRS)

Stengel, Robert F.

1991-01-01

An overview of failure-tolerant control is presented, beginning with robust control, progressing through parallel and analytical redundancy, and ending with rule-based systems and artificial neural networks. By design or implementation, failure-tolerant control systems are 'intelligent' systems. All failure-tolerant systems require some degrees of robustness to protect against catastrophic failure; failure tolerance often can be improved by adaptivity in decision-making and control, as well as by redundancy in measurement and actuation. Reliability, maintainability, and survivability can be enhanced by failure tolerance, although each objective poses different goals for control system design. Artificial intelligence concepts are helpful for integrating and codifying failure-tolerant control systems, not as alternatives but as adjuncts to conventional design methods.

Balancing repair and tolerance of DNA damage caused by alkylating agents.

PubMed

Fu, Dragony; Calvo, Jennifer A; Samson, Leona D

2012-01-12

Alkylating agents constitute a major class of frontline chemotherapeutic drugs that inflict cytotoxic DNA damage as their main mode of action, in addition to collateral mutagenic damage. Numerous cellular pathways, including direct DNA damage reversal, base excision repair (BER) and mismatch repair (MMR), respond to alkylation damage to defend against alkylation-induced cell death or mutation. However, maintaining a proper balance of activity both within and between these pathways is crucial for a favourable response of an organism to alkylating agents. Furthermore, the response of an individual to alkylating agents can vary considerably from tissue to tissue and from person to person, pointing to genetic and epigenetic mechanisms that modulate alkylating agent toxicity.

SERIES: Genomic instability in cancer Balancing repair and tolerance of DNA damage caused by alkylating agents

PubMed Central

Fu, Dragony; Calvo, Jennifer A.; Samson, Leona D

2013-01-01

Alkylating agents comprise a major class of frontline chemotherapeutic drugs that inflict cytotoxic DNA damage as their main mode of action, in addition to collateral mutagenic damage. Numerous cellular pathways, including direct DNA damage reversal, base excision repair (BER), and mismatch repair (MMR) respond to alkylation damage to defend against alkylation-induced cell death or mutation. However, maintaining a proper balance of activity both within and between these pathways is crucial for an organism's favorable response to alkylating agents. Furthermore, an individual's response to alkylating agents can vary considerably from tissue to tissue and from person to person, pointing to genetic and epigenetic mechanisms that modulate alkylating agent toxicity. PMID:22237395

Design, Fabrication, and Testing of Composite Energy-Absorbing Keel Beams for General Aviation Type Aircraft

NASA Technical Reports Server (NTRS)

Kellas, Sotiris; Knight, Norman F., Jr.

2002-01-01

A lightweight energy-absorbing keel-beam concept was developed and retrofitted in a general aviation type aircraft to improve crashworthiness performance. The energy-absorbing beam consisted of a foam-filled cellular structure with glass fiber and hybrid glass/kevlar cell walls. Design, analysis, fabrication and testing of the keel beams prior to installation and subsequent full-scale crash testing of the aircraft are described. Factors such as material and fabrication constraints, damage tolerance, crush stress/strain response, seat-rail loading, and post crush integrity, which influenced the course of the design process are also presented. A theory similar to the one often used for ductile metal box structures was employed with appropriate modifications to estimate the sustained crush loads for the beams. This, analytical tool, coupled with dynamic finite element simulation using MSC.Dytran were the prime design and analysis tools. The validity of the theory as a reliable design tool was examined against test data from static crush tests of beam sections while the overall performance of the energy-absorbing subfloor was assessed through dynamic testing of 24 in long subfloor assemblies.

Experimental Behavior of Fatigued Single Stiffener PRSEUS Specimens

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.

2009-01-01

NASA, the Air Force Research Laboratory and The Boeing Company have worked to develop new low-cost, light-weight composite structures for aircraft. A Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept has been developed which offers advantages over traditional metallic structure. In this concept a stitched carbon-epoxy material system has been developed with the potential for reducing the weight and cost of transport aircraft structure by eliminating fasteners, thereby reducing part count and labor. By adding unidirectional carbon rods to the top of stiffeners, the panel becomes more structurally efficient. This combination produces a more damage tolerant design. This document describes the results of experimentation on PRSEUS specimens loaded in unidirectional compression in fatigue and to failure.

Radiation Tolerant Interfaces: Influence of Local Stoichiometry at the Misfit Dislocation on Radiation Damage Resistance of Metal/Oxide Interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shutthanandan, Vaithiyalingam; Choudhury, Samrat; Manandhar, Sandeep

The interaction of radiation with materials controls the performance, reliability, and safety of many structures in nuclear power systems. Revolutionary improvements in radiation damage resistance may be attainable if methods can be found to manipulate interface properties to give optimal interface stability and point defect recombination capability. To understand how variations in interface properties such as misfit dislocation density and local chemistry affect radiation-induced defect absorption and recombination, a model system of metallic Cr xV 1-x (0 ≤ x ≤ 1) epitaxial films deposited on MgO(001) single crystal substrates has been explored in this paper. By controlling film composition, themore » lattice mismatch between the film and MgO is adjusted to vary the misfit dislocation density at the metal/oxide interface. The stability of these interfaces under various irradiation conditions is studied experimentally and theoretically. The results indicate that, unlike at metal/metal interfaces, the misfit dislocation density does not dominate radiation damage tolerance at metal/oxide interfaces. Rather, the stoichiometry and the location of the misfit dislocation extra half-plane (in the metal or the oxide) drive radiation-induced defect behavior. Finally, together, these results demonstrate the sensitivity of defect recombination to interfacial chemistry and provide new avenues for engineering radiation-tolerant nanomaterials for next-generation nuclear power plants.« less

Radiation Tolerant Interfaces: Influence of Local Stoichiometry at the Misfit Dislocation on Radiation Damage Resistance of Metal/Oxide Interfaces

DOE PAGES

Shutthanandan, Vaithiyalingam; Choudhury, Samrat; Manandhar, Sandeep; ...

2017-04-24

The interaction of radiation with materials controls the performance, reliability, and safety of many structures in nuclear power systems. Revolutionary improvements in radiation damage resistance may be attainable if methods can be found to manipulate interface properties to give optimal interface stability and point defect recombination capability. To understand how variations in interface properties such as misfit dislocation density and local chemistry affect radiation-induced defect absorption and recombination, a model system of metallic Cr xV 1-x (0 ≤ x ≤ 1) epitaxial films deposited on MgO(001) single crystal substrates has been explored in this paper. By controlling film composition, themore » lattice mismatch between the film and MgO is adjusted to vary the misfit dislocation density at the metal/oxide interface. The stability of these interfaces under various irradiation conditions is studied experimentally and theoretically. The results indicate that, unlike at metal/metal interfaces, the misfit dislocation density does not dominate radiation damage tolerance at metal/oxide interfaces. Rather, the stoichiometry and the location of the misfit dislocation extra half-plane (in the metal or the oxide) drive radiation-induced defect behavior. Finally, together, these results demonstrate the sensitivity of defect recombination to interfacial chemistry and provide new avenues for engineering radiation-tolerant nanomaterials for next-generation nuclear power plants.« less

DNA damage tolerance pathway involving DNA polymerase ι and the tumor suppressor p53 regulates DNA replication fork progression.

PubMed

Hampp, Stephanie; Kiessling, Tina; Buechle, Kerstin; Mansilla, Sabrina F; Thomale, Jürgen; Rall, Melanie; Ahn, Jinwoo; Pospiech, Helmut; Gottifredi, Vanesa; Wiesmüller, Lisa

2016-07-26

DNA damage tolerance facilitates the progression of replication forks that have encountered obstacles on the template strands. It involves either translesion DNA synthesis initiated by proliferating cell nuclear antigen monoubiquitination or less well-characterized fork reversal and template switch mechanisms. Herein, we characterize a novel tolerance pathway requiring the tumor suppressor p53, the translesion polymerase ι (POLι), the ubiquitin ligase Rad5-related helicase-like transcription factor (HLTF), and the SWI/SNF catalytic subunit (SNF2) translocase zinc finger ran-binding domain containing 3 (ZRANB3). This novel p53 activity is lost in the exonuclease-deficient but transcriptionally active p53(H115N) mutant. Wild-type p53, but not p53(H115N), associates with POLι in vivo. Strikingly, the concerted action of p53 and POLι decelerates nascent DNA elongation and promotes HLTF/ZRANB3-dependent recombination during unperturbed DNA replication. Particularly after cross-linker-induced replication stress, p53 and POLι also act together to promote meiotic recombination enzyme 11 (MRE11)-dependent accumulation of (phospho-)replication protein A (RPA)-coated ssDNA. These results implicate a direct role of p53 in the processing of replication forks encountering obstacles on the template strand. Our findings define an unprecedented function of p53 and POLι in the DNA damage response to endogenous or exogenous replication stress.

Damage-Tolerant Fan Casings for Jet Engines

NASA Technical Reports Server (NTRS)

2006-01-01

All turbofan engines work on the same principle. A large fan at the front of the engine draws air in. A portion of the air enters the compressor, but a greater portion passes on the outside of the engine this is called bypass air. The air that enters the compressor then passes through several stages of rotating fan blades that compress the air more, and then it passes into the combustor. In the combustor, fuel is injected into the airstream, and the fuel-air mixture is ignited. The hot gasses produced expand rapidly to the rear, and the engine reacts by moving forward. If there is a flaw in the system, such as an unexpected obstruction, the fan blade can break, spin off, and harm other engine components. Fan casings, therefore, need to be strong enough to contain errant blades and damage-tolerant to withstand the punishment of a loose blade-turned-projectile. NASA has spearheaded research into improving jet engine fan casings, ultimately discovering a cost-effective approach to manufacturing damage-tolerant fan cases that also boast significant weight reduction. In an aircraft, weight reduction translates directly into fuel burn savings, increased payload, and greater aircraft range. This technology increases safety and structural integrity; is an attractive, viable option for engine manufacturers, because of the low-cost manufacturing; and it is a practical alternative for customers, as it has the added cost saving benefits of the weight reduction.

Silicon Priming Created an Enhanced Tolerance in Alfalfa (Medicago sativa L.) Seedlings in Response to High Alkaline Stress.

PubMed

Liu, Duo; Liu, Miao; Liu, Xiao-Long; Cheng, Xian-Guo; Liang, Zheng-Wei

2018-01-01

Alkaline stress as a result of higher pH usually triggers more severe physiological damage to plants than that of saline stress with a neutral pH. In the present study, we demonstrated that silicon (Si) priming of alfalfa ( Medicago sativa L.) seedlings increased their tolerance to high alkaline stress situations. Gongnong No. 1 seedlings were subjected to alkaline stress simulated by 25 mM Na 2 CO 3 (pH 11.2). Alkaline stress greatly decreased the biomass and caused severe lodging or wilting of alfalfa seedlings. In contrast, the application of Si to alfalfa seedlings 36 h prior to the alkaline treatment significantly alleviated the damage symptoms and greatly increased the biomass and chlorophyll content. Because of being concomitant with increasing photosynthesis and water use efficiency, decreasing membrane injury and malondialdehyde content, and increasing peroxidase and catalase ascorbate activities in alfalfa leaves, thereby alleviating the triggered oxidative damage by alkaline stress to the plant. Furthermore, Si priming significantly decreased the accumulation of protein and proline content in alfalfa, thus reducing photosynthetic feedback repression. Si priming significantly accumulated more Na in the roots, but led to a decrease of Na accumulation and an increase of K accumulation in the leaves under alkaline stress. Meanwhile, Si priming decreased the accumulation of metal ions such as Mg, Fe, Mn, and Zn in the roots of alfalfa seedlings under alkaline stress. Collectively, these results suggested that Si is involved in the metabolic or physiological changes and has a potent priming effect on the alkaline tolerance of alfalfa seedlings. The present study indicated that Si priming is a new approach to improve the alkaline tolerance in alfalfa and provides increasing information for further exploration of the alkaline stress response at the molecular level in alfalfa.

Increase in Furfural Tolerance in Ethanologenic Escherichia coli LY180 by Plasmid-Based Expression of thyA

PubMed Central

Zheng, Huabao; Wang, Xuan; Yomano, Lorraine P.; Shanmugam, Keelnatham T.

2012-01-01

Furfural is an inhibitory side product formed during the depolymerization of hemicellulose by mineral acids. Genomic libraries from three different bacteria (Bacillus subtilis YB886, Escherichia coli NC3, and Zymomonas mobilis CP4) were screened for genes that conferred furfural resistance on plates. Beneficial plasmids containing the thyA gene (coding for thymidylate synthase) were recovered from all three organisms. Expression of this key gene in the de novo pathway for dTMP biosynthesis improved furfural resistance on plates and during fermentation. A similar benefit was observed by supplementation with thymine, thymidine, or the combination of tetrahydrofolate and serine (precursors for 5,10-methylenetetrahydrofolate, the methyl donor for ThyA). Supplementation with deoxyuridine provided a small benefit, and deoxyribose was of no benefit for furfural tolerance. A combination of thymidine and plasmid expression of thyA was no more effective than either alone. Together, these results demonstrate that furfural tolerance is increased by approaches that increase the supply of pyrimidine deoxyribonucleotides. However, ThyA activity was not directly affected by the addition of furfural. Furfural has been previously shown to damage DNA in E. coli and to activate a cellular response to oxidative damage in yeast. The added burden of repairing furfural-damaged DNA in E. coli would be expected to increase the cellular requirement for dTMP. Increased expression of thyA (E. coli, B. subtilis, or Z. mobilis), supplementation of cultures with thymidine, and supplementation with precursors for 5,10-methylenetetrahydrofolate (methyl donor) are each proposed to increase furfural tolerance by increasing the availability of dTMP for DNA repair. PMID:22504824

Increase in furfural tolerance in ethanologenic Escherichia coli LY180 by plasmid-based expression of thyA.

PubMed

Zheng, Huabao; Wang, Xuan; Yomano, Lorraine P; Shanmugam, Keelnatham T; Ingram, Lonnie O

2012-06-01

Furfural is an inhibitory side product formed during the depolymerization of hemicellulose by mineral acids. Genomic libraries from three different bacteria (Bacillus subtilis YB886, Escherichia coli NC3, and Zymomonas mobilis CP4) were screened for genes that conferred furfural resistance on plates. Beneficial plasmids containing the thyA gene (coding for thymidylate synthase) were recovered from all three organisms. Expression of this key gene in the de novo pathway for dTMP biosynthesis improved furfural resistance on plates and during fermentation. A similar benefit was observed by supplementation with thymine, thymidine, or the combination of tetrahydrofolate and serine (precursors for 5,10-methylenetetrahydrofolate, the methyl donor for ThyA). Supplementation with deoxyuridine provided a small benefit, and deoxyribose was of no benefit for furfural tolerance. A combination of thymidine and plasmid expression of thyA was no more effective than either alone. Together, these results demonstrate that furfural tolerance is increased by approaches that increase the supply of pyrimidine deoxyribonucleotides. However, ThyA activity was not directly affected by the addition of furfural. Furfural has been previously shown to damage DNA in E. coli and to activate a cellular response to oxidative damage in yeast. The added burden of repairing furfural-damaged DNA in E. coli would be expected to increase the cellular requirement for dTMP. Increased expression of thyA (E. coli, B. subtilis, or Z. mobilis), supplementation of cultures with thymidine, and supplementation with precursors for 5,10-methylenetetrahydrofolate (methyl donor) are each proposed to increase furfural tolerance by increasing the availability of dTMP for DNA repair.