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Sample records for damage evolution law

  1. Glen's Law++: Transition to a Rate-Weakening Flow Law As a New Framework for Damage Evolution

    NASA Astrophysics Data System (ADS)

    Borstad, C. P.; Morlighem, M.; Khazendar, A.; Scheuchl, B.; Larour, E. Y.; Rignot, E. J.

    2014-12-01

    Continuum damage mechanics is gaining increasing acceptance as a framework for modeling flow enhancement caused by fractures in glaciers and ice shelves. To date, the temporal evolution of viscous damage has been handled using a transport equation with some kind of source term for damage. A number of empirical formulations for such a source term have been adopted, though no clear physical foundation exists for treating damage using flux terms. Furthermore, it remains to be demonstrated that the parameters of such a source term can be determined from observations. Here, we introduce a new framework for damage evolution that does not require specifying a damage source term and that results in a more intuitive physical interpretation of the coupled evolution of stress and damage. By postulating an explicit rate-weakening flow law above a threshold stress, damage can be calculated analytically from the results of a stress balance computation. A transport equation is still applied to advect damage, but the evolution of damage is explicitly linked to the evolving stress balance. This new damage formulation requires only two new parameters, both of which have clear physical interpretations and can be inferred from observations. Using the Ice Sheet System Model (ISSM), we determine values for both parameters by inverting for damage for the remnant Larsen B ice shelf using a time series of InSAR velocity data covering the years 2000-2010. The inferred patterns of damage and strain rate, in both space and time, are used to quantify the rate-weakening constitutive parameters using nonlinear regression. The resulting damage evolution framework is then applied in perturbation experiments to determine the conditions and timescales under which the remnant Larsen B ice shelf may collapse. We conclude by discussing advantages of this approach to damage evolution and applications to problems in iceberg calving, ice shelf stability, and buttressing at the grounding line.

  2. Evolution and the Law

    ERIC Educational Resources Information Center

    Mayer, William V.

    1973-01-01

    Some court cases and legislative bills have been filed in states to legalize the use of the creationist view (of life forms on earth) in biology textbooks superseding the organic theory of evolution. The law has not yet accepted the religious viewpoint. (PS)

  3. One damage law for different mechanisms

    NASA Astrophysics Data System (ADS)

    Lemaitre, J.; Sermage, J. P.

    1997-07-01

    We consider here a general three-dimensional kinetic damage law. It uses the thermodynamic of irreversible processes formalism and the phenomenological aspects of isotropic damage. It gives the damage rate as a function of its associated variable, the strain energy density release rate and the accumulated plastic strain rate. Associated with different plastic constitutive equations, this damage law takes into account brittle damage, ductile damage, low and high cycle fatigue and creep damage. In this paper we mainly focus on creep-fatigue interaction and high cycle fatigue. Associated to a viscoplastic constitutive equation having kinematic hardening, the damage law gives the non linear creep-fatigue interaction. The agreement with experiments is good. Associated to plastic constitutive equations also having kinematic hardening but introduced in a micromechanical two scale model based on the self-consistent scheme, it models the non linear accumulation of damage induced by a succession of sequences of different amplitudes as well as the effect of the mean stress and the influence of non proportional loading.

  4. Probabilistic constitutive law for damage in ligaments.

    PubMed

    Guo, Zheying; De Vita, Raffaella

    2009-11-01

    A new constitutive equation is presented to describe the damage evolution process in parallel-fibered collagenous tissues such as ligaments. The model is formulated by accounting for the fibrous structure of the tissues. The tissue's stress is defined as the average of the collagen fiber's stresses. The fibers are assumed to be undulated and straightened out at different stretches that are randomly defined according to a Weibull distribution. After becoming straight, each collagen fiber is assumed to be linear elastic. Damage is defined as a reduction in collagen fiber's stiffness and occurs at different stretches that are also randomly defined by a Weibull distribution. Due to the lack of experimental data, the predictions of the constitutive equation are analyzed by varying the values of its structural parameters. Moreover, the results are compared with the available stress-strain data in the biomechanics literature that evaluate damage produced by subfailure stretches in rat medial collateral ligaments. PMID:19665914

  5. Evolution of the Second Law of Thermodynamics

    ERIC Educational Resources Information Center

    Raman, V. V.

    1970-01-01

    Presents the history surrounding the evolution of the second law of thermodynamics. Discusses Sadi Carnot's contributions, but also refers to those by Clapeyron, Thomson, Joule, Clausius, and Boltzman among others. (RR)

  6. Evolution and the second law of thermodynamics

    NASA Astrophysics Data System (ADS)

    Bunn, Emory F.

    2009-10-01

    Skeptics of biological evolution often claim that evolution requires a decrease in entropy, giving rise to a conflict with the second law of thermodynamics. This argument is fallacious because it neglects the large increase in entropy provided by sunlight striking the Earth. A recent article provided a quantitative assessment of the entropies involved and showed explicitly that there is no conflict. That article rests on an unjustified assumption about the amount of entropy reduction involved in evolution. I present a refinement of the argument that does not rely on this assumption.

  7. Crack patterning effects in evolution of damage

    SciTech Connect

    Lacy, T.E.; McDowell, D.L.; Taireja, R.

    1995-12-31

    Recent micromechanically inspired phenomenological theories using internal state variable representations of damage have been used to predict the thermomechanical behavior of microcracking solids. These models do not, in an explicit manner, account for distributions of microcracks in a Representative Volume Element (RVE) and have been successfully used only to determine the effective moduli of damaged solids. It has been demonstrated that while the distribution. and interaction of damage entities within a RVE have a minor effect on the effective moduli, they have a significant effect on the evolution of damage and failure at the macroscale. Damage evolution rates cannot, in general, be adequately described by such theories because of their inability to account for interactions between damage entities in an arbitrary distribution. In the present work, finite element solutions to two-dimensional problems with growing microcracks are obtained for both uniform and non-uniform crack arrays. Effective moduli and RVE-averaged driving forces for non-uniformly distributed interacting crack systems are calculated across a range of microcrack distribution parameters. Results are compared to existing solutions. Damage evolution is studied by allowing incremental advance under specified growth criteria of different crack systems within a RVE. Concepts for the inclusion of discrete sub-RVE length scales in the specific Helmholtz free energy and dissipation potentials are outlined. Use of multivariate distribution functions to characterize damage is discussed.

  8. Evolution of bulk damage initiation in DKDP

    NASA Astrophysics Data System (ADS)

    Carr, Christopher W.; McMillian, T. H.; Staggs, Mike C.; Radousky, Harry B.; Demos, Stavros G.

    2003-05-01

    We investigate the evolution of laser-induced damage initiated in the bulk of DKDP crystals using in-situ microscopy. Experimental results indicate that at peek fluences greater than 10 J/cm2, damage sites are formed with increasing number as a function of the laser fluence. Following plasma formation, cracks are observed which grow in size for tens of seconds after the termination of the laser pulse. Subsequent irradiation leads to modest increase in size only during the initial 2-5 pulses. Experimental results suggest that there is also relaxation of the stresses adjacent to a damage site for several hours after initial damage.

  9. Radiation damage evolution in ceramics

    SciTech Connect

    Devanathan, Ramaswami

    2009-09-15

    A review is presented of recent results on radiation damage production, defect accumulation and dynamic annealing in a number of ceramics, such as silicon carbide, zircon and zirconia. Under energetic particle irradiation, ceramics can undergo amorphization by the accumulation of point defects and defect clusters (silicon carbide) or direct impact amorphization (zircon). Ceramics that resist radiation-induced amorphization have mechanisms to dissipate the primary knock-on atom energy, such as replacement collision sequences that leave the lattice undisturbed and low-energy cation site exchange. The presence of engineered mobile defects, such as structural vacancies in stabilized zirconia, can dynamically anneal radiation damage. Thus, defect engineering is a promising strategy to design radiation tolerance for applications such as nuclear waste disposal.

  10. Complexity, organization, evolution, and constructal law

    NASA Astrophysics Data System (ADS)

    Bejan, A.; Errera, M. R.

    2016-02-01

    Physics is concise, simple, unambiguous, and constantly improving. Yet, confusion reigns in the field especially with respect to complexity and the second law of thermodynamics. In this paper, we step back and take a look at these notions—their meaning and definition—on the background provided by nature and thermodynamics. We review the central concepts and words that underpin the physics of evolutionary design today: information, knowledge, evolution, change, arrow of time, pattern, organization, drawings, complexity, fractal dimension, object, icon, model, empiricism, theory, disorder, second law, the "any" system in thermodynamics, morphing freely, and the constructal law. We show, for example, that information is not knowledge, fractal dimension is not a measure of complexity, and pattern is not a live flow architecture. Drawings, as physical means to facilitate the flow of knowledge, are subject to the natural tendency toward design evolution. Complexity, organization, and evolution in nature are most powerful and useful when pursued as a discipline, with precise terms, rules, and principles.

  11. Stochastic damage evolution in textile laminates

    NASA Technical Reports Server (NTRS)

    Dzenis, Yuris A.; Bogdanovich, Alexander E.; Pastore, Christopher M.

    1993-01-01

    A probabilistic model utilizing random material characteristics to predict damage evolution in textile laminates is presented. Model is based on a division of each ply into two sublaminas consisting of cells. The probability of cell failure is calculated using stochastic function theory and maximal strain failure criterion. Three modes of failure, i.e. fiber breakage, matrix failure in transverse direction, as well as matrix or interface shear cracking, are taken into account. Computed failure probabilities are utilized in reducing cell stiffness based on the mesovolume concept. A numerical algorithm is developed predicting the damage evolution and deformation history of textile laminates. Effect of scatter of fiber orientation on cell properties is discussed. Weave influence on damage accumulation is illustrated with the help of an example of a Kevlar/epoxy laminate.

  12. Brittleness Effect on Rock Fatigue Damage Evolution

    NASA Astrophysics Data System (ADS)

    Nejati, Hamid Reza; Ghazvinian, Abdolhadi

    2014-09-01

    The damage evolution mechanism of rocks is one of the most important aspects in studying of rock fatigue behavior. Fatigue damage evolution of three rock types (onyx marble, sandstone and soft limestone) with different brittleness were considered in the present study. Intensive experimental tests were conducted on the chosen rock samples and acoustic emission (AE) sensors were used in some of them to monitor the fracturing process. Experimental tests indicated that brittleness strongly influences damage evolution of rocks in the course of static and dynamic loading. AE monitoring revealed that micro-crack density induced by the applied loads during different stages of the failure processes increases as rock brittleness increases. Also, results of fatigue tests on the three rock types indicated that the rock with the most induced micro-cracks during loading cycles has the least fatigue life. Furthermore, the condition of failure surfaces of the studied rocks samples, subjected to dynamic and static loading, were evaluated and it was concluded that the roughness of failure surfaces is influenced by loading types and rock brittleness. Dynamic failure surfaces were rougher than static ones and low brittle rock demonstrate a smoother failure surface compared to high brittle rock.

  13. A generalized law for aftershock rates in a damage rheology model

    NASA Astrophysics Data System (ADS)

    Ben Zion, Y.; Lyakhovsky, V.

    2003-12-01

    for the damage evolution contains error functions and is richer than a simple power law relation. However, the results associated with the analytical expression can be fitted well for various values of R with a power law similar to the modified Omori law for aftershocks. This also holds for 3D numerical simulations of aftershock sequences with our damage rheology model. Initial results based on 3D simulations indicate that high values of R corresponding to low viscosity material produce diffuse (swarm-like) aftershock sequences, while low values of R corresponding to more brittle material produce clear (Omori-like) aftershock sequences.

  14. The Damage Law of HTPB Propellant under Thermomechanical Loading

    NASA Astrophysics Data System (ADS)

    Liu, Cheng-wu; Yang, Jian-hong; Wang, Xian-meng; Ma, Yong-kang

    2016-01-01

    By way of measuring the acoustic emission (AE) signals of Hydroxyl-terminated polybutadiene (HTPB) propellant in condition of uniform speed, and combined with the scanning electron microscopy (SEM) fracture surface observation, the damage law of HTPB composite solid propellant under thermomechanical loading was studied. The results show that the effects of thermomechanical loading on HTPB propellant are related to the time and can be divided into three different stages. In the first stage, thermal air aging dominates; in the second stage, interface damage is dominant; and in the third stage, thermal air aging is once again dominant.

  15. Fracture and damage evolution of fluorinated polymers

    SciTech Connect

    Brown, E. N.; Rae, P.; Orler, E. B.; Thissell, W. R.; Dattelbaum, D. M.

    2004-01-01

    Fluoropolymers are often semi-crystalline in nature, with their linear chains forming complicated phases near room temperature and ambient pressure. The most widely used fluorocarbon polymer for engineering applications is polytetrafluoroethylene (PTFE), due to its extremely low coefficient of friction, outstanding resistance to corrosion, and excellent electrical properties. The phase structure of PTFE is complex with four well-characterized crystalline phases (three observed at atmospheric pressure) and substantial molecular motion well below the melting point. The first-order transition at 19 C between phases II and IV is an unraveling in the helical conformation. Further rotational disordering and untwisting of the helices occurs above 30 C giving way to phase I. The mechanical behavior, including fracture and damage evolution, of PTFE depends on the chain and segment motions dictated by crystalline phase microstructure. The presence of three unique phases at ambient pressure near room temperature implies that failure during standard operating conditions may be strongly dependent on the phase. This paper presents a preliminary study of fracture and damage evolution in PTFE with the effects of temperature-induced phase on fracture mechanisms. The quasi-static fracture of PTFE in the atmospheric pressure regime, over a range of temperatures, was found to be strongly phase dependent: phase II exhibits brittle-fracture, phase IV displays ductile-fracture with crazing and some stable crack growth, and plastic flow dominates phase 1. The bulk failure properties are correlated to failure mechanisms through fractography of the fracture surfaces (optical microscopy and scanning electron microscopy (SEM)).

  16. A continuum theory of grain size evolution and damage

    NASA Astrophysics Data System (ADS)

    Ricard, Y.; Bercovici, D.

    2009-01-01

    Lithospheric shear localization, as occurs in the formation of tectonic plate boundaries, is often associated with diminished grain size (e.g., mylonites). Grain size reduction is typically attributed to dynamic recrystallization; however, theoretical models of shear localization arising from this hypothesis are problematic because (1) they require the simultaneous action of two creep mechanisms (diffusion and dislocation creep) that occur in different deformation regimes (i.e., in grain size stress space) and (2) the grain growth ("healing") laws employed by these models are derived from normal grain growth or coarsening theory, which are valid in the absence of deformation, although the shear localization setting itself requires deformation. Here we present a new first principles grained-continuum theory, which accounts for both coarsening and damage-induced grain size reduction in a monomineralic assemblage undergoing irrecoverable deformation. Damage per se is the generic process for generation of microcracks, defects, dislocations (including recrystallization), subgrains, nuclei, and cataclastic breakdown of grains. The theory contains coupled macroscopic continuum mechanical and grain-scale statistical components. The continuum level of the theory considers standard mass, momentum, and energy conservation, as well as entropy production, on a statistically averaged grained continuum. The grain-scale element of the theory describes both the evolution of the grain size distribution and mechanisms for both continuous grain growth and discontinuous grain fracture and coalescence. The continuous and discontinuous processes of grain size variation are prescribed by nonequilibrium thermodynamics (in particular, the treatment of entropy production provides the phenomenological laws for grain growth and reduction); grain size evolution thus incorporates the free energy differences between grains, including both grain boundary surface energy (which controls coarsening

  17. Evolution equations: Frobenius integrability, conservation laws and travelling waves

    NASA Astrophysics Data System (ADS)

    Prince, Geoff; Tehseen, Naghmana

    2015-10-01

    We give new results concerning the Frobenius integrability and solution of evolution equations admitting travelling wave solutions. In particular, we give a powerful result which explains the extraordinary integrability of some of these equations. We also discuss ‘local’ conservations laws for evolution equations in general and demonstrate all the results for the Korteweg-de Vries equation.

  18. Scale-Dependent Friction and Damage Interface law: implications for effective earthquake rupture dynamics and radiation

    NASA Astrophysics Data System (ADS)

    Festa, Gaetano; Vilotte, Jean-Pierre; Raous, Michel; Henninger, Carole

    2010-05-01

    Propagation and radiation of an earthquake rupture is commonly considered as a friction dominated process on fault surfaces. Friction laws, such as the slip weakening and the rate-and-state laws are widely used in the modeling of the earthquake rupture process. These laws prescribe the traction evolution versus slip, slip rate and potentially other internal variables. They introduce a finite cohesive length scale over which the fracture energy is released. However faults are finite-width interfaces with complex internal structures, characterized by highly damaged zones embedding a very thin principal slip interface where most of the dynamic slip localizes. Even though the rupture process is generally investigated at wavelengths larger than the fault zone thickness, which should justify a formulation based upon surface energy, a consistent homogeneization, a very challenging problem, is still missing. Such homogeneization is however be required to derive the consistent form of an effective interface law, as well as the appropriate physical variables and length scales, to correctly describe the coarse-grained dissipation resulting from surface and volumetric contributions at the scale of the fault zone. In this study, we investigate a scale-dependent law, introduced by Raous et al. (1999) in the context of adhesive material interfaces, that takes into account the transition between a damage dominated and a friction dominated state. Such a phase-field formalism describes this transition through an order parameter. We first compare this law to standard slip weakening friction law in terms of the rupture nucleation. The problem is analyzed through the representation of the solution of the quasi-static elastic problem onto the Chebyshev polynomial basis, generalizing the Uenishi-Rice solution. The nucleation solutions, at the onset of instability, are then introduced as initial conditions for the study of the dynamic rupture propagation, in the case of in-plane rupture

  19. Evidence of microstructure evolution in solid elastic media based on a power law analysis

    NASA Astrophysics Data System (ADS)

    Scalerandi, M.; Idjimarene, S.; Bentahar, M.; El Guerjouma, R.

    2015-05-01

    Complex and consolidated granular media or microcracked composites and metals usually exhibit a high level of nonlinearity in their elastic response already at low amplitudes of excitation. To quantify it, a proper nonlinear indicator y is introduced and its dependence on the excitation amplitude x is studied. The dependence of y on x is found in experiments to be a power law. Here we show that the different power law exponents measured for different materials could be predicted by proper classes of discrete models. An application is presented to link the exponent evolution and the changes of the microstructure due to the progression of damage mechanically induced.

  20. Evolution of damage and plasticity in

    NASA Astrophysics Data System (ADS)

    Majumdar, B. S.; Newaz, G. M.; Ellis, J. R.

    1993-07-01

    The inelastic deformation mechanisms were evaluated for a model titanium-based, fiber-reinforced composite: a beta titanium alloy (Ti-15V-3Al-3Cr-3Sn) reinforced with SiC (SCS-6) fibers. The primary emphasis of this article is to illustrate the sequence in which damage and plasticity evolved for this system. The mechanical responses and the results of detailed microstructural evaluations for the [0]8, [90]8, and [±45]2s, laminates are provided. It is shown that the char- acteristics of the reaction zone around the fiber play a very important role in the way damage and plasticity evolve, particularly in the microyield regime of deformation, and must be included in any realistic constitutive model. Fiber-matrix debonding was a major damage mode for the off-axis systems. The tension test results are also compared with the predictions of a few con- stitutive models.

  1. The constructal law and the evolution of design in nature

    NASA Astrophysics Data System (ADS)

    Bejan, Adrian; Lorente, Sylvie

    2011-10-01

    The constructal law accounts for the universal phenomenon of generation and evolution of design (configuration, shape, structure, pattern, rhythm). This phenomenon is observed across the board, in animate, inanimate and human systems. The constructal law states the time direction of the evolutionary design phenomenon. It defines the concept of design evolution in physics. Along with the first and second law, the constructal law elevates thermodynamics to a science of systems with configuration. In this article we review the more recent work of our group, with emphasis on the advances made with the constructal law in the natural sciences. Highlighted are the oneness of animate and inanimate designs, the origin of finite-size organs on animals and vehicles, the flow of stresses as the generator of design in solid structures (skeletons, vegetation), the universality and rigidity of hierarchy in all flow systems, and the global design of human flows. Noteworthy is the tapestry of distributed energy systems, which balances nodes of production with networks of distribution on the landscape, and serves as key to energy sustainability and empowerment. At the global level, the constructal law accounts for the geography and design of human movement, wealth and communications.

  2. Emergence of Zipf's law in the evolution of communication.

    PubMed

    Corominas-Murtra, Bernat; Fortuny, Jordi; Solé, Ricard V

    2011-03-01

    Zipf's law seems to be ubiquitous in human languages and appears to be a universal property of complex communicating systems. Following the early proposal made by Zipf concerning the presence of a tension between the efforts of speaker and hearer in a communication system, we introduce evolution by means of a variational approach to the problem based on Kullback's Minimum Discrimination of Information Principle. Therefore, using a formalism fully embedded in the framework of information theory, we demonstrate that Zipf's law is the only expected outcome of an evolving communicative system under a rigorous definition of the communicative tension described by Zipf. PMID:21517566

  3. Law of genome evolution direction: Coding information quantity grows

    NASA Astrophysics Data System (ADS)

    Luo, Liao-Fu

    2009-06-01

    The problem of the directionality of genome evolution is studied. Based on the analysis of C-value paradox and the evolution of genome size, we propose that the function-coding information quantity of a genome always grows in the course of evolution through sequence duplication, expansion of code, and gene transfer from outside. The function-coding information quantity of a genome consists of two parts, p-coding information quantity that encodes functional protein and n-coding information quantity that encodes other functional elements. The evidences on the law of the evolutionary directionality are indicated. The needs of function are the motive force for the expansion of coding information quantity, and the information quantity expansion is the way to make functional innovation and extension for a species. Therefore, the increase of coding information quantity of a genome is a measure of the acquired new function, and it determines the directionality of genome evolution.

  4. Exact Conservation Laws and Exclusion Principle of Biological Evolution

    NASA Astrophysics Data System (ADS)

    Azbel', Mark Ya.

    2003-03-01

    Biological evolution is dynamics of diversity and complexity of living beings from cells to humans. Metabolism, which allows for entropy decrease, and mortality, which allows for natural selection, are its biological must. Their characteristics are known to yield approximate (and rather noisy) universal relations. I conjecture they are accurate for certain ("canonic") fractions of these characteristics. (The conjecture is verified with experimental tests of its counterintuitive predictions). A relation, which is conserved under (invariant to) transformations from one species in its living conditions to another, is a conservation law of biological evolution. Of course, all parameters of such transformations can hardly be comprehensively specified. However, when canonic fractions are additive, the very invariance of the law to an extraordinary wide class of transformations, with no other experimental data, in any given interval of canonic fraction values accurately predicts [1]: either their conservation law is linear, or the population is homogeneous with respect to their values (an "exclusion principle" of their heterogeneity in an otherwise heterogeneous population). To be specific. Metabolism conservation laws (e.g., the dependence of oxygen consumption at rest per heartbeat on the animal mass) are linear. They imply [2] the existence of fundamental biological constants, which are similar to those crucial in physics. Survivability conservation law (the relation between the probabilities to survive to any two given ages) is piecewise linear (with four linear intervals). At the intersections mortality is homogeneous, and its susceptibility to living conditions vanishes. The law predicts that a dominant canonic fraction of mortality in protected populations is reversible for species as different as humans and flies, and may be eliminated. All these predictions agree with experimental data. (For instance, mortality of Swedish females, born in 1916, at 48 years

  5. A Procedure to Construct Conservation Laws of Nonlinear Evolution Equations

    NASA Astrophysics Data System (ADS)

    Yaşar, Emrullah; San, Sait

    2016-05-01

    In this article, we established abundant local conservation laws to some nonlinear evolution equations by a new combined approach, which is a union of multiplier and Ibragimov's new conservation theorem method. One can conclude that the solutions of the adjoint equations corresponding to the new conservation theorem can be obtained via multiplier functions. Many new families of conservation laws of the Pochammer-Chree (PC) equation and the Kaup-Boussinesq type of coupled KdV system are successfully obtained. The combined method presents a wider applicability for handling the conservation laws of nonlinear wave equations. The conserved vectors obtained here can be important for the explanation of some practical physical problems, reductions, and solutions of the underlying equations.

  6. The constructal law of design and evolution in nature

    PubMed Central

    Bejan, Adrian; Lorente, Sylvie

    2010-01-01

    Constructal theory is the view that (i) the generation of images of design (pattern, rhythm) in nature is a phenomenon of physics and (ii) this phenomenon is covered by a principle (the constructal law): ‘for a finite-size flow system to persist in time (to live) it must evolve such that it provides greater and greater access to the currents that flow through it’. This law is about the necessity of design to occur, and about the time direction of the phenomenon: the tape of the design evolution ‘movie’ runs such that existing configurations are replaced by globally easier flowing configurations. The constructal law has two useful sides: the prediction of natural phenomena and the strategic engineering of novel architectures, based on the constructal law, i.e. not by mimicking nature. We show that the emergence of scaling laws in inanimate (geophysical) flow systems is the same phenomenon as the emergence of allometric laws in animate (biological) flow systems. Examples are lung design, animal locomotion, vegetation, river basins, turbulent flow structure, self-lubrication and natural multi-scale porous media. This article outlines the place of the constructal law as a self-standing law in physics, which covers all the ad hoc (and contradictory) statements of optimality such as minimum entropy generation, maximum entropy generation, minimum flow resistance, maximum flow resistance, minimum time, minimum weight, uniform maximum stresses and characteristic organ sizes. Nature is configured to flow and move as a conglomerate of ‘engine and brake’ designs. PMID:20368252

  7. Permeability of WIPP Salt During Damage Evolution and Healing

    SciTech Connect

    BODNER,SOL R.; CHAN,KWAI S.; MUNSON,DARRELL E.

    1999-12-03

    The presence of damage in the form of microcracks can increase the permeability of salt. In this paper, an analytical formulation of the permeability of damaged rock salt is presented for both initially intact and porous conditions. The analysis shows that permeability is related to the connected (i.e., gas accessible) volumetric strain and porosity according to two different power-laws, which may be summed to give the overall behavior of a porous salt with damage. This relationship was incorporated into a constitutive model, known as the Multimechanism Deformation Coupled Fracture (MDCF) model, which has been formulated to describe the inelastic flow behavior of rock salt due to coupled creep, damage, and healing. The extended model was used to calculate the permeability of rock salt from the Waste Isolation Pilot Plant (WIPP) site under conditions where damage evolved with stress over a time period. Permeability changes resulting from both damage development under deviatoric stresses and damage healing under hydrostatic pressures were considered. The calculated results were compared against experimental data from the literature, which indicated that permeability in damaged intact WIPP salt depends on the magnitude of the gas accessible volumetric strain and not on the total volumetric strain. Consequently, the permeability of WIPP salt is significantly affected by the kinetics of crack closure, but shows little dependence on the kinetics of crack removal by sintering.

  8. Evolution of the violin: The law of effect in action.

    PubMed

    Wasserman, Edward A; Cullen, Patrick

    2016-01-01

    As is true for most other human inventions, the origin of the violin is unknown. What is known is that this popular and versatile instrument has notably changed over the course of several hundred years. At issue is whether those evolutionary changes in the construction of the violin are the result of premeditated, intelligent design or whether they arose through a trial-and-error process. Recent scientific evidence favors the latter account. Our perspective piece puts these recent empirical findings into a comprehensive selectionist framework. According to this view, the many things we do and make--like violins--arise from a process of variation and selection which accords with the law of effect. Contrary to popular opinion, there is neither mystique nor romance in this process; it is as fundamental and ubiquitous as the law of natural selection. As with the law of natural selection in the evolution of organisms, there is staunch resistance to the role of the law of effect in the evolution of human inventions. We conclude our piece by considering several objections to our perspective. PMID:26569015

  9. Damage evolution and clustering in shock loaded tantalum

    SciTech Connect

    Thissell, W.R.; Zurek, A.K.; Rivas, J.M.; Tonks, D.L.; Hixson, R.S.

    1998-12-31

    Two grades of tantalum were shock loaded by plate impact and recovered. The loading conditions were varied to study the damage evolution in te materials from incipient to full spallation. The authors performed quantitative image analysis and optical profilometry on the recovered specimens. Statistical analyses are shown of the void sizes, void clustering, and void linking in the two material grades.

  10. Early-state damage detection, characterization, and evolution using high-resolution computed tomography

    NASA Astrophysics Data System (ADS)

    Grandin, Robert John

    Safely using materials in high performance applications requires adequately understanding the mechanisms which control the nucleation and evolution of damage. Most of a material's operational life is spent in a state with noncritical damage, and, for example in metals only a small portion of its life falls within the classical Paris Law regime of crack growth. Developing proper structural health and prognosis models requires understanding the behavior of damage in these early stages within the material's life, and this early-stage damage occurs on length scales at which the material may be considered "granular'' in the sense that the discrete regions which comprise the whole are large enough to require special consideration. Material performance depends upon the characteristics of the granules themselves as well as the interfaces between granules. As a result, properly studying early-stage damage in complex, granular materials requires a means to characterize changes in the granules and interfaces. The granular-scale can range from tenths of microns in ceramics, to single microns in fiber-reinforced composites, to tens of millimeters in concrete. The difficulty of direct-study is often overcome by exhaustive testing of macro-scale damage caused by gross material loads and abuse. Such testing, for example optical or electron microscopy, destructive and further, is costly when used to study the evolution of damage within a material and often limits the study to a few snapshots. New developments in high-resolution computed tomography (HRCT) provide the necessary spatial resolution to directly image the granule length-scale of many materials. Successful application of HRCT with fiber-reinforced composites, however, requires extending the HRCT performance beyond current limits. This dissertation will discuss improvements made in the field of CT reconstruction which enable resolutions to be pushed to the point of being able to image the fiber-scale damage structures and

  11. Progressive damage state evolution and quantification in composites

    NASA Astrophysics Data System (ADS)

    Patra, Subir; Banerjee, Sourav

    2016-04-01

    fatigue cycles was performed to extract the useful information about the damage state. This study has potential to investigate progressive damage evolution and to quantify at different fatigue cycles.

  12. 26 CFR 1.162-22 - Treble damage payments under the antitrust laws.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 2 2010-04-01 2010-04-01 false Treble damage payments under the antitrust laws. 1.162-22 Section 1.162-22 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Itemized Deductions for Individuals and Corporations § 1.162-22 Treble damage payments...

  13. Dollo's law and the re-evolution of shell coiling.

    PubMed Central

    Collin, Rachel; Cipriani, Roberto

    2003-01-01

    Gastropods have lost the quintessential snail feature, the coiled shell, numerous times in evolution. In many cases these animals have developed a limpet morphology with a cap-shaped shell and a large foot. Limpets thrive in marginal habitats such as hydrothermal vents, the high-energy rocky intertidal areas and fresh water, but they are considered to be evolutionary dead-ends, unable to re-evolve a coiled shell and therefore unable to give rise to the diversity seen among coiled snails. The re-evolution of a coiled shell, or any complex character, is considered unlikely or impossible (Dollo's law) because the loss of the character is followed by the loss of the genetic architecture and developmental mechanisms that underlie that character. Here, we quantify the level of coiling in calyptraeids, a family of mostly uncoiled limpets, and show that coiled shells have re-evolved at least once within this family. These results are the first demonstration, to our knowledge, of the re-evolution of coiling in a gastropod, and show that the developmental features underlying coiling have not been lost during 20-100 Myr of uncoiled evolutionary history. This is the first example of the re-evolution of a complex character via a change in developmental timing (heterochrony) rather than a change in location of gene expression (heterotopy). PMID:14728776

  14. Generic incubation law for laser damage and ablation thresholds

    NASA Astrophysics Data System (ADS)

    Sun, Zhanliang; Lenzner, Matthias; Rudolph, Wolfgang

    2015-02-01

    In multi-pulse laser damage and ablation experiments, the laser-induced damage threshold (LIDT) usually changes with the number of pulses in the train, a phenomenon known as incubation. We introduce a general incubation model based on two physical mechanisms—pulse induced change of (i) absorption and (ii) critical energy that must be deposited to cause ablation. The model is applicable to a broad class of materials and we apply it to fit data for dielectrics and metals. It also explains observed changes of the LIDT as a function of the laser repetition rate. We discuss under which conditions the crater-size method to determine LIDTs can be applied in multi-pulse experiments.

  15. Cohesive Laws and Progressive Damage Analysis of Composite Bonded Joints, a Combined Numerical/Experimental Approach

    NASA Technical Reports Server (NTRS)

    Girolamo, Donato; Davila, Carlos G.; Leone, Frank A.; Lin, Shih-Yung

    2015-01-01

    The results of an experimental/numerical campaign aimed to develop progressive damage analysis (PDA) tools for predicting the strength of a composite bonded joint under tensile loads are presented. The PDA is based on continuum damage mechanics (CDM) to account for intralaminar damage, and cohesive laws to account for interlaminar and adhesive damage. The adhesive response is characterized using standard fracture specimens and digital image correlation (DIC). The displacement fields measured by DIC are used to calculate the J-integrals, from which the associated cohesive laws of the structural adhesive can be derived. A finite element model of a sandwich conventional splice joint (CSJ) under tensile loads was developed. The simulations, in agreement with experimental tests, indicate that the model is capable of predicting the interactions of damage modes that lead to the failure of the joint.

  16. Damage evolution in metal matrix composites subjected to thermomechanical fatigue

    SciTech Connect

    Allen, D.H.; Hurtado, L.D.; Helms, K.L.E.

    1995-05-01

    A thermomechanical analysis of unidirectional continuous fiber metal matrix composites is presented. The analysis includes the effects of processing induced residual thermal stresses, interface cracking, and inelastic matrix behavior on damage evolution. Due to the complexity of the nonlinear effects, the analysis is performed computationally using the finite element method. The interface fracture is modeled by a nonlinear constitutive model. The problem formulation is summarized and results are presented for a four-ply unidirectional SCS-6/{beta}21S titanium composite under high temperature isothermal mechanical fatigue.

  17. Boundary damage effects on the evolution of creep strain

    NASA Astrophysics Data System (ADS)

    Gullickson, J.; Needleman, A.; Staroselsky, A.; Cassenti, B.

    2008-10-01

    The effect of a reduced section thickness leading to creep strain greater than that observed in the creep response of thicker sections is termed the thickness debit effect. We carry out three-dimensional analyses of the creep response of specimens with rectangular cross sections under uniaxial tensile loading having a boundary damage layer and explore whether this can account for the thickness debit effect. The particular damage mechanism modeled is plastic void nucleation, growth and coalescence with void nucleation taken to be confined to a surface layer and the material characterized as an elastic-power law creeping solid. Three-dimensional transient analyses are carried out but used to simulate quasi-static loading conditions. Results are presented for the effect of the thickness of the boundary damage layer on the creep response. The effect of varying the parameters characterizing the void nucleation process is also investigated. The results qualitatively exhibit a variety of features of the thickness debit effect seen in experiments.

  18. Chromosome damage evolution after low and high LET irradiation

    NASA Astrophysics Data System (ADS)

    Andreev, Sergey; Eidelman, Yuri

    Ionizing radiation induces DNA and chromatin lesions which are converted to chromosome lesions detected in the first post-irradiation mitosis by classic cytogenetic techniques as chromosomal aberrations (CAs). These techniques allow to monitor also delayed aberrations observed after many cell generations post-irradiation - the manifestation of chromosomal instability phenotype (CIN). The problem discussed is how to predict time evolution from initial to delayed DNA/chromosome damage. To address this question, in the present work a mechanistic model of CIN is elaborated which integrates pathways of (*) DNA damage induction and its conversion to chromosome lesions (aberrations), (**) lesion transmission and generation through cell cycles. Delayed aberrations in subsequent cycles are formed in the model owing to two pathways, DNA damage generation de novo as well as CA transmission from previous cycles. DNA damage generation rate is assumed to consist of bystander and non-bystander components. Bystander signals impact all cells roughly equally, whereas non-bystander DSB generation rate differs for the descendants of unirradiated and irradiated cells. Monte Carlo simulation of processes underlying CIN allows to predict the time evolution of initial radiation-induced damage - kinetics curve for delayed unstable aberrations (dicentrics) together with dose response and RBE as a function of time after high vs low LET irradiation. The experimental data for radiation-induced CIN in TK6 lymphoblastoid cells and human lymphocytes irradiated with low (gamma) and high (Fe, C) LET radiation are analyzed on the basis of the proposed model. One of the conclusions is that without bystander signaling, just taking into account the initial DNA damage and non-bystander DSB generation, it is impossible to describe the available experimental data for high-LET-induced CIN. The exact contribution of bystander effects for high vs low LET remains unknown, but the relative contribution may be

  19. The Evolution of Health Care Advance Planning Law and Policy

    PubMed Central

    Sabatino, Charles P

    2010-01-01

    Context: The legal tools of health care advance planning have substantially changed since their emergence in the mid-1970s. Thirty years of policy development, primarily at the state legislative level addressing surrogate decision making and advance directives, have resulted in a disjointed policy landscape, yet with important points of convergence evolving over time. An understanding of the evolution of advance care planning policy has important implications for policy at both the state and federal levels. Methods: This article is a longitudinal statutory and literature review of health care advance planning from its origins to the present. Findings: While considerable variability across the states still remains, changes in law and policy over time suggest a gradual paradigm shift from what is described as a “legal transactional approach” to a “communications approach,” the most recent extension of which is the emergence of Physician Orders for Life-Sustaining Treatment, or POLST. The communications approach helps translate patients’ goals into visible and portable medical orders. Conclusions: States are likely to continue gradually moving away from a legal transactional mode of advance planning toward a communications model, albeit with challenges to authentic and reliable communication that accurately translates patients’ wishes into the care they receive. In the meantime, the states and their health care institutions will continue to serve as the primary laboratory for advance care planning policy and practice. PMID:20579283

  20. Phase dependent fracture and damage evolution of polytetrafluoroethylene (PTFE)

    SciTech Connect

    Brown, E. N.; Rae, P.; Orler, E. B.; Thissell, W. R.; Dattelbaum, D. M.

    2004-01-01

    Compared with other polymers, polytetrafluoroethylene (PTFE) presents several advantages for load-bearing structural components including higher strength at elevated temperatures and higher toughness at lowered temperatures. Failure sensitive applications of PTFE include surgical implants, aerospace components, and chemical barriers. Polytetrafluoroethylene is semicrystalline in nature with their linear chains forming complicated phases near room temperature and ambient pressure. The presence of three unique phases near room temperature implies that failure during standard operating conditions may be strongly dependent on the phase. This paper presents a comprehensive and systematic study of fracture and damage evolution in PTFE to elicit the effects of temperature-induced phase on fracture mechanisms. The fracture behavior of PTFE is observed to undergo transitions from brittle-fracture below 19 C to ductile-fracture with crazing and some stable crack growth to plastic flow aver 30 C. The bulk failure properties are correlated to failure mechanisms through fractography and analysis of the crystalline structure.

  1. Defect and damage evolution quantification in dynamically-deformed metals using orientation-imaging microscopy

    SciTech Connect

    Gray, George T., III; Livescu, Veronica; Cerreta, Ellen K

    2010-03-18

    Orientation-imaging microscopy offers unique capabilities to quantify the defects and damage evolution occurring in metals following dynamic and shock loading. Examples of the quantification of the types of deformation twins activated, volume fraction of twinning, and damage evolution as a function of shock loading in Ta are presented. Electron back-scatter diffraction (EBSD) examination of the damage evolution in sweeping-detonation-wave shock loading to study spallation in Cu is also presented.

  2. Beyond Rio? The Evolution of International Environmental Law.

    ERIC Educational Resources Information Center

    Brunnee, Jutta

    1993-01-01

    Discusses the expansion and innovation in the use of international environmental law mechanisms to address the problems of global environmental protection. Presents initiatives involving customary international law, forms of international agreements, nonbinding "soft law," and an example involving Canada's biodiversity commitments. (MDH)

  3. Scale Invariance in Landscape Evolution Models Using Stream Power Laws

    NASA Astrophysics Data System (ADS)

    Kwang, J. S.; Parker, G.

    2014-12-01

    Landscape evolution models (LEM) commonly utilize stream power laws to simulate river incision with formulations such as E = KAmSn, where E is a vertical incision rate [L/T], K is an erodibility constant [L1-2m/T], A is an upstream drainage area [L2], S is a local channel gradient [-], and m and n are positive exponents that describe the basin hydrology. In our reduced complexity model, the landscape approached equilibrium by balancing an incision rate with a constant, uniform, vertical rock uplift rate at every location in the landscape. From our simulations, for a combination of m and n, the landscape exhibited scale invariance. That is, regardless of the size and scale of the basin, the relief and vertical structure of the landscape remained constant. Therefore, the relief and elevation profile of the landscape at equilibrium were only dependent on the coefficients for erodibility and uplift and an equation that described how upstream area, A, increased as the length of a stream increased. In our analytical 1D models, we utilized two equations that described upslope area, (a) A = Bl, where B is the profile width [L], and l is the stream length from the ridge [L] and (b) A = Clh, Hack's Law, where C is a constant [L2-h] and h is a positive exponent. With these equations, (a) m = n and (b) hm = n resulted in scale invariance. In our numerical 2D models, the relationship between A and l was inherent in the actual structure of the drainage network. From our numerical 2D results, scale invariance occurred when 2m = n. Additionally, using reasonable values from the literature for exponents, n, m and h, resulted in singularities at the ridges in the landscape, which caused truncation error. In consequence, the elevation of the ridge increased as the number of grid cells in the domain increased in the numerical model, and the model was unable to converge. These singularities at the ridges appeared when (a) m ≥ n and (b) hm ≥ n in the analytical model and 2m ≥ n in

  4. On-site inspections of pavement damages evolution using GPR

    NASA Astrophysics Data System (ADS)

    Tosti, Fabio; D'Amico, Fabrizio; Calvi, Alessandro; Benedetto, Andrea

    2014-05-01

    Ground-penetrating radar (GPR) is being increasingly used for pavements maintenance due to the wide range of applications spanning from physical to geometrical inspections, thereby allowing for a reliable diagnosis of the main causes of road structural damages. In this work, an off-ground GPR system was used to investigate a large-scale rural road network. Two sets of surveys were carried out in different time periods, with the main goals to i) localize the most critical sections; ii) monitor the evolution of previous damages and localize newborn deep faults, although not revealed at the pavement surface level; iii) analyze the causes of both evolution and emergence of faults by considering environmental and human factors. A 1-GHz GPR air-launched antenna was linked to an instrumented van for collecting data at traffic speed. Other support techniques (e.g. GPS data logger, odometer, HD video camera) were used for cross-checking,. Such centre frequency of investigation along with a 25-ns time window allow for a signal penetration of 900 mm, consistent with the deepest layer interfaces. The bottom of the array was 400 mm over the surface, with a minimum distance of 1200 mm from the van body. Scan length of maximum 10 km were provided for avoiding heavy computational loads. The rural road network was located in the District of Rieti, 100 km north from Rome, Italy, and mostly develops in a hilly and mountainous landscape. In most of the investigated roads, the carriageway consists in two lanes of 3.75 meters wide and two shoulders of 0.50 meters wide. A typical road section includes a HMA layer (65 mm average thickness), a base layer (100 mm average thickness), and a subbase layer (300 mm average thickness), as described by pavement design charts. The first set of surveys was carried out in two days at the beginning of spring in moderately dry conditions. Overall, 320-km-long inspections were performed in both travel directions, thereby showing a productivity of

  5. A biophysical model of cell evolution after cytotoxic treatments: Damage, repair and cell response.

    PubMed

    Tomezak, M; Abbadie, C; Lartigau, E; Cleri, F

    2016-01-21

    We present a theoretical agent-based model of cell evolution under the action of cytotoxic treatments, such as radiotherapy or chemotherapy. The major features of cell cycle and proliferation, cell damage and repair, and chemical diffusion are included. Cell evolution is based on a discrete Markov chain, with cells stepping along a sequence of discrete internal states from 'normal' to 'inactive'. Probabilistic laws are introduced for each type of event a cell can undergo during its life: duplication, arrest, senescence, damage, reparation, or death. We adjust the model parameters on a series of cell irradiation experiments, carried out in a clinical LINAC, in which the damage and repair kinetics of single- and double-strand breaks are followed. Two showcase applications of the model are then presented. In the first one, we reconstruct the cell survival curves from a number of published low- and high-dose irradiation experiments. We reobtain a very good description of the data without assuming the well-known linear-quadratic model, but instead including a variable DSB repair probability. The repair capability of the model spontaneously saturates to an exponential decay at increasingly high doses. As a second test, we attempt to simulate the two extreme possibilities of the so-called 'bystander' effect in radiotherapy: the 'local' effect versus a 'global' effect, respectively activated by the short-range or long-range diffusion of some factor, presumably secreted by the irradiated cells. Even with an oversimplified simulation, we could demonstrate a sizeable difference in the proliferation rate of non-irradiated cells, the proliferation acceleration being much larger for the global than the local effect, for relatively small fractions of irradiated cells in the colony. PMID:26549470

  6. Constructal law of design and evolution: Physics, biology, technology, and society

    NASA Astrophysics Data System (ADS)

    Bejan, Adrian; Lorente, Sylvie

    2013-04-01

    This is a review of the theoretical and applied progress made based on the Constructal law of design and evolution in nature, with emphasis on the last decade. The Constructal law is the law of physics that accounts for the natural tendency of all flow systems (animate and inanimate) to change into configurations that offer progressively greater flow access over time. The progress made with the Constructal law covers the broadest range of science, from heat and fluid flow and geophysics, to animal design, technology evolution, and social organization (economics, government). This review presents the state of this fast growing field, and draws attention to newly opened directions for original research. The Constructal law places the concepts of life, design, and evolution in physics.

  7. Law, evolution and the brain: applications and open questions.

    PubMed

    Jones, Owen D

    2004-11-29

    This paper discusses several issues at the intersection of law and brain science. It focuses principally on ways in which an improved understanding of how evolutionary processes affect brain function and human behaviour may improve law's ability to regulate behaviour. It explores sample uses of such 'evolutionary analysis in law' and also raises questions about how that analysis might be improved in the future. Among the discussed uses are: (i) clarifying cost-benefit analyses; (ii) providing theoretical foundation and potential predictive power; (iii) assessing comparative effectiveness of legal strategies; and (iv) revealing deep patterns in legal architecture. Throughout, the paper emphasizes the extent to which effective law requires: (i) building effective behavioural models; (ii) integrating life-science perspectives with social-science perspectives; (iii) considering the effects of brain biology on behaviours that law seeks to regulate; and (iv) examining the effects of evolutionary processes on brain design. PMID:15590611

  8. Securing recompense under nuisance law for crop damages from pesticide applications.

    PubMed

    Centner, Terence J

    2012-08-15

    In areas where several crops are grown or where organic practices have been adopted, conflicts may arise due to the use of pesticides. Accompanying the use of specialized pesticides for individualized crops are possibilities that spray applications or volatilization will result in airborne pesticide particulates damaging nontarget crops. American jurisprudence provides several major causes of action that may be used to secure recompense for damages to crops from applications of pesticides. However, defenses and limitations for each of these causes of action create impediments that make recovery difficult. An evaluation of nuisance law discloses that defenses often preclude recoveries for damages to nontarget crops from airborne pesticide particulates. Policy makers may want to evaluate the defenses due to their interference with property rights. The defenses may discourage changes in crop production resulting in suboptimal uses of resources. PMID:22721686

  9. Numerical Simulation of Rock Mass Damage Evolution During Deep-Buried Tunnel Excavation by Drill and Blast

    NASA Astrophysics Data System (ADS)

    Yang, Jianhua; Lu, Wenbo; Hu, Yingguo; Chen, Ming; Yan, Peng

    2015-09-01

    Presence of an excavation damage zone (EDZ) around a tunnel perimeter is of significant concern with regard to safety, stability, costs and overall performance of the tunnel. For deep-buried tunnel excavation by drill and blast, it is generally accepted that a combination of effects of stress redistribution and blasting is mainly responsible for development of the EDZ. However, few open literatures can be found to use numerical methods to investigate the behavior of rock damage induced by the combined effects, and it is still far from full understanding how, when and to what degree the blasting affects the behavior of the EDZ during excavation. By implementing a statistical damage evolution law based on stress criterion into the commercial software LS-DYNA through its user-subroutines, this paper presents a 3D numerical simulation of the rock damage evolution of a deep-buried tunnel excavation, with a special emphasis on the combined effects of the stress redistribution of surrounding rock masses and the blasting-induced damage. Influence of repeated blast loadings on the damage extension for practical millisecond delay blasting is investigated in the present analysis. Accompanying explosive detonation and secession of rock fragments from their initial locations, in situ stress in the immediate vicinity of the excavation face is suddenly released. The transient characteristics of the in situ stress release and induced dynamic responses in the surrounding rock masses are also highlighted. From the simulation results, some instructive conclusions are drawn with respect to the rock damage mechanism and evolution during deep-buried tunnel excavation by drill and blast.

  10. The evolution of Zipf's law indicative of city development

    NASA Astrophysics Data System (ADS)

    Chen, Yanguang

    2016-02-01

    Zipf's law of city-size distributions can be expressed by three types of mathematical models: one-parameter form, two-parameter form, and three-parameter form. The one-parameter and one of the two-parameter models are familiar to urban scientists. However, the three-parameter model and another type of two-parameter model have not attracted attention. This paper is devoted to exploring the conditions and scopes of application of these Zipf models. By mathematical reasoning and empirical analysis, new discoveries are made as follows. First, if the size distribution of cities in a geographical region cannot be described with the one- or two-parameter model, maybe it can be characterized by the three-parameter model with a scaling factor and a scale-translational factor. Second, all these Zipf models can be unified by hierarchical scaling laws based on cascade structure. Third, the patterns of city-size distributions seem to evolve from three-parameter mode to two-parameter mode, and then to one-parameter mode. Four-year census data of Chinese cities are employed to verify the three-parameter Zipf's law and the corresponding hierarchical structure of rank-size distributions. This study is revealing for people to understand the scientific laws of social systems and the property of urban development.

  11. Experimental and Analytical Evaluation of Stressing-Rate State Evolution in Rate-State Friction Laws

    NASA Astrophysics Data System (ADS)

    Bhattacharya, P.; Rubin, A. M.; Bayart, E.; Savage, H. M.; Marone, C.; Beeler, N. M.

    2013-12-01

    Standard rate and state friction laws fail to explain the full range of observations from laboratory friction experiments. A new state evolution law has been proposed by Nagata et al. (2012) that adds a linear stressing-rate-dependent term to the Dieterich (aging) law, which may provide a remedy. They introduce a parameter c that controls the contribution of the stressing rate to state evolution. We show through analytical approximations that the new law can transition between the responses of the traditional Dieterich (aging) and Ruina (slip) laws in velocity step up/down experiments when the value of c is tuned properly. In particular, for c = 0 the response is pure aging while for finite, non-zero c one observes slip law like behavior for small velocity jumps but aging law like response for larger jumps. The magnitude of the velocity jump required to see this transition between aging and slip behaviour increases as c increases. In the limit of c >> 1 the response to velocity steps becomes purely slip law like. In this limit, numerical simulations show that this law loses its appealing time dependent healing property. An approach using Markov Chain Monte Carlo parameter search on data for large magnitude velocity step tests reveals that it is only possible to determine a lower bound on c using datasets that are well explained by the slip law. For a dataset with velocity steps of two orders of magnitude on simulated fault gouge we find this lower bound to be c ≈ 10.0. This is significantly larger than c ≈ 2.0 used by Nagata et al. (2012) to fit their data (mainly bare rock experiments with smaller excursions from steady state than our dataset). Similar parameter estimation exercises on slide hold slide data reveal that none of the state evolution laws considered - Dieterich, Ruina, Kato-Tullis and Nagata - match the relevant features of the data. In particular, even the aging law predicts only the correct rate of healing for long hold times but not the correct

  12. [Evolution of pharmaceutical regulations from the origins to Germinal law].

    PubMed

    Lafont, Olivier

    2003-01-01

    The rising of pharmaceutical regulations took place in the civilisations located around the Mediterranean Sea. Egypt, Mesopotamia, Greco-Roman world, Byzantine Empire, were followed by Bagdad, where sayadila, inspections and grabadins appeared. The creation of Universities, during the XIIth and XIIIth centuries, plaid a role in the rising of apothecaries communities in Occident. Melfi Constitutions (Constititiones Melfiae, 1231) and new constitutions (1241) inspired most of the regulations of apothecaries communities in Europe. Declaration of the King of France in April 1777 announced the famous "Loi de Germinal", Germinal law, which organized the modern Pharmacy, in 1803. PMID:14763458

  13. The Evolution of the Exponent of Zipf's Law in Language Ontogeny

    PubMed Central

    Baixeries, Jaume; Elvevåg, Brita; Ferrer-i-Cancho, Ramon

    2013-01-01

    It is well-known that word frequencies arrange themselves according to Zipf's law. However, little is known about the dependency of the parameters of the law and the complexity of a communication system. Many models of the evolution of language assume that the exponent of the law remains constant as the complexity of a communication systems increases. Using longitudinal studies of child language, we analysed the word rank distribution for the speech of children and adults participating in conversations. The adults typically included family members (e.g., parents) or the investigators conducting the research. Our analysis of the evolution of Zipf's law yields two main unexpected results. First, in children the exponent of the law tends to decrease over time while this tendency is weaker in adults, thus suggesting this is not a mere mirror effect of adult speech. Second, although the exponent of the law is more stable in adults, their exponents fall below 1 which is the typical value of the exponent assumed in both children and adults. Our analysis also shows a tendency of the mean length of utterances (MLU), a simple estimate of syntactic complexity, to increase as the exponent decreases. The parallel evolution of the exponent and a simple indicator of syntactic complexity (MLU) supports the hypothesis that the exponent of Zipf's law and linguistic complexity are inter-related. The assumption that Zipf's law for word ranks is a power-law with a constant exponent of one in both adults and children needs to be revised. PMID:23516390

  14. Effects of grain size distribution on the creep damage evolution of polycrystalline materials

    NASA Astrophysics Data System (ADS)

    Yu, Tao; Shi, Huiji

    2010-04-01

    It is evident that realistic microstructures of polycrystalline materials demonstrate a certain distribution of grain size, which has not been widely studied in most analyses of mechanical properties of materials at high temperatures. In this work, the effects of grain size distribution on the creep damage evolution induced by void growth of polycrystalline materials were investigated by the Voronoi tessellation approach, taking into account the void evolution on the grain boundaries in a grain aggregate cell. The results indicate that with the decrease in mean grain size, the damage variable increases faster. When the mean grain sizes are the same, the more uniform the grain size is, the faster the damage variable increases.

  15. Structural damage evolution assessment using the regularised time step integration method

    NASA Astrophysics Data System (ADS)

    Chen, Hua-Peng; Maung, Than Soe

    2014-09-01

    This paper presents an approach to identify both the location and severity evolution of damage in engineering structures directly from measured dynamic response data. A relationship between the change in structural parameters such as stiffness caused by structural damage development and the measured dynamic response data such as accelerations is proposed, on the basis of the governing equations of motion for the original and damaged structural systems. Structural damage parameters associated with time are properly chosen to reflect both the location and severity development over time of damage in a structure. Basic equations are provided to solve the chosen time-dependent damage parameters, which are constructed by using the Newmark time step integration method without requiring a modal analysis procedure. The Tikhonov regularisation method incorporating the L-curve criterion for determining the regularisation parameter is then employed to reduce the influence of measurement errors in dynamic response data and then to produce stable solutions for structural damage parameters. Results for two numerical examples with various simulated damage scenarios show that the proposed method can accurately identify the locations of structural damage and correctly assess the evolution of damage severity from information on vibration measurements with uncertainties.

  16. A universal scaling law for the evolution of granular gases

    NASA Astrophysics Data System (ADS)

    Hummel, Mathias; Clewett, James P. D.; Mazza, Marco G.

    2016-04-01

    Dry, freely evolving granular materials in a dilute gaseous state coalesce into dense clusters only due to dissipative interactions. Here we show that the evolution of a dilute, freely cooling granular gas is determined in a universal way by the ratio of inertial flow and thermal velocities, that is, the Mach number. Theoretical calculations and direct numerical simulations of the granular Navier-Stokes equations show that irrespective of the coefficient of restitution, density or initial velocity distribution, the density fluctuations follow a universal quadratic dependence on the system's Mach number. We find that the clustering exhibits a scale-free dynamics but the clustered state becomes observable when the Mach number is approximately of O(1) . Our results provide a method to determine the age of a granular gas and predict the macroscopic appearance of clusters.

  17. A universal scaling law for the evolution of granular gases

    NASA Astrophysics Data System (ADS)

    Hummel, Mathias; Clewett, James; Mazza, Marco G.

    Dry, freely evolving granular materials in a dilute gaseous state coalesce into dense clusters only due to dissipative interactions. This clustering transition is important for a number of problems ranging from geophysics to cosmology. Here we show that the evolution of a dilute, freely cooling granular gas is determined in a universal way by the ratio of inertial flow and thermal velocities, that is, the Mach number. Theoretical calculations and direct numerical simulations of the granular Navier-Stokes equations show that irrespective of the coefficient of restitution, density or initial velocity distribution, the density fluctuations follow a universal quadratic dependence on the system's Mach number. We find that the clustering exhibits a scale-free dynamics but the clustered state becomes observable when the Mach number is approximately of O(1). Our results provide a method to determine the age of a granular gas and predict the macroscopic appearance of clusters.

  18. The effects of self-interstitial clusters on cascade defect evolution beyond the primary damage state

    SciTech Connect

    Heinisch, H.L.

    1997-04-01

    The intracascade evolution of the defect distributions of cascades in copper is investigated using stochastic annealing simulations applied to cascades generated with molecular dynamics (MD). The temperature and energy dependencies of annihilation, clustering and free defect production are determined for individual cascades. The annealing simulation results illustrate the strong influence on intracascade evolution of the defect configuration existing in the primary damage state. Another factor significantly affecting the evolution of the defect distribution is the rapid one-dimensional diffusion of small, glissile interstitial loops produced directly in cascades. This phenomenon introduces a cascade energy dependence of defect evolution that is apparent only beyond the primary damage state, amplifying the need for further study of the annealing phase of cascade evolution and for performing many more MD cascade simulations at higher energies.

  19. Evolution of damage during deformation in porous granular materials (Louis Néel Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Main, Ian

    2014-05-01

    'Crackling noise' occurs in a wide variety of systems that respond to external forcing in an intermittent way, leading to sudden bursts of energy release similar to those heard when crunching up a piece of paper or listening to a fire. In mineral magnetism ('Barkhausen') crackling noise occurs due to sudden changes in the size and orientation of microscopic ferromagnetic domains when the external magnetic field is changed. In rock physics sudden changes in internal stress associated with microscopically brittle failure events lead to acoustic emissions that can be recorded on the sample boundary, and used to infer the state of internal damage. Crackling noise is inherently stochastic, but the population of events often exhibits remarkably robust scaling properties, in terms of the source area, duration, energy, and in the waiting time between events. Here I describe how these scaling properties emerge and evolve spontaneously in a fully-dynamic discrete element model of sedimentary rocks subject to uniaxial compression at a constant strain rate. The discrete elements have structural disorder similar to that of a real rock, and this is the only source of heterogeneity. Despite the stationary loading and the lack of any time-dependent weakening processes, the results are all characterized by emergent power law distributions over a broad range of scales, in agreement with experimental observation. As deformation evolves, the scaling exponents change systematically in a way that is similar to the evolution of damage in experiments on real sedimentary rocks. The potential for real-time failure forecasting is examined by using synthetic and real data from laboratory tests and prior to volcanic eruptions. The combination of non-linearity and an irreducible stochastic component leads to significant variations in the precision and accuracy of the forecast failure time, leading to a significant proportion of 'false alarms' (forecast too early) and 'missed events' (forecast

  20. A damage mechanics model for power-law creep and earthquake aftershock and foreshock sequences

    NASA Astrophysics Data System (ADS)

    Main, Ian G.

    2000-07-01

    It is common practice to refer to three independent stages of creep under static loading conditions in the laboratory: namely transient, steady-state, and accelerating. Here we suggest a simple damage mechanics model for the apparently trimodal behaviour of the strain and event rate dependence, by invoking two local mechanisms of positive and negative feedback applied to constitutive rules for time-dependent subcritical crack growth. In both phases, the individual constitutive rule for measured strain ɛ takes the form ɛ(t)=ɛ0[1+t/mτ]m, where τ is the ratio of initial crack length to rupture velocity. For a local hardening mechanism (negative feedback), we find that transient creep dominates, with 0∞ can be defined at a finite failure time, resulting in the localization of damage and the formation of a throughgoing fracture. In the hybrid model, transient creep dominates in the early stages of damage and accelerating creep in the latter stages. At intermediate times the linear superposition of the two mechanisms spontaneously produces an apparent steady-state phase of relatively constant strain rate, with a power-law rheology, as observed in laboratory creep test data. The predicted acoustic emission event rates in the transient and accelerating phases are identical to the modified Omori laws for aftershocks and foreshocks, respectively, and provide a physical meaning for the empirical constants measured. At intermediate times, the event rate tends to a relatively constant background rate. The requirement for a finite event rate at the time of the main shock can be satisfied by modifying the instability criterion to having a finite crack velocity at the dynamic failure time, dx/dt->VR, where VR is the dynamic rupture velocity. The same hybrid

  1. von Baer's law for the ages: lost and found principles of developmental evolution.

    PubMed

    Abzhanov, Arhat

    2013-12-01

    In 1828, Karl Ernst von Baer formulated a series of empirically defined rules, which became widely known as the 'Law of Development' or 'von Baer's law of embryology'. This was one the most significant attempts to define the principles that connected morphological complexity and embryonic development. Understanding this relation is central to both evolutionary biology and developmental genetics. Von Baer's ideas have been both a source of inspiration to generations of biologists and a target of continuous criticism over many years. With advances in multiple fields, including paleontology, cladistics, phylogenetics, genomics, and cell and developmental biology, it is now possible to examine carefully the significance of von Baer's law and its predictions. In this review, I argue that, 185 years after von Baer's law was first formulated, its main concepts after proper refurbishing remain surprisingly relevant in revealing the fundamentals of the evolution-development connection, and suggest that their explanation should become the focus of renewed research. PMID:24120296

  2. A new conceptual model for damage zone evolution with fault growth

    NASA Astrophysics Data System (ADS)

    de Joussineau, G.; Aydin, A.

    2006-12-01

    Faults may either impede or enhance fluid flow in the subsurface, which is relevant to a number of economic issues (hydrocarbon migration and entrapment, formation and distribution of mineral deposits) and environmental problems (movement of contaminants). Fault zones typically comprise a low-permeability core made up of intensely deformed fault rock and a high-permeability damage zone defined by fault-related fractures. The geometry, petrophysical properties and continuity of both the fault core and the damage zone have an important influence on the mechanical properties of the fault systems and on subsurface fluid flow. Information about fault components from remote seismic methods is limited and is available only for large faults (slip larger than 20-100m). It is therefore essential to characterize faults and associated damage zones in field analogues, and to develop conceptual models of how faults and related structures form and evolve. Here we present such an attempt to better understand the evolution of fault damage zones in the Jurassic Aztec Sandstone of the Valley of Fire State Park (SE Nevada). We document the formation and evolution of the damage zone associated with strike-slip faults through detailed field studies of faults of increasing slip magnitudes. The faults initiate as sheared joints with discontinuous pockets of damage zone located at fault tips and fault surface irregularities. With increasing slip (slip >5m), the damage zone becomes longer and wider by progressive fracture infilling, and is organized into two distinct components with different geometrical and statistical characteristics. The first component of the damage zone is the inner damage zone, directly flanking the fault core, with a relatively high fracture frequency and a thickness that scales with the amount of fault slip. Parts of this inner zone are integrated into the fault core by the development of the fault rock, contributing to the core's progressive widening. The second

  3. General introduction to microstructural evolution under cascade damage conditions

    SciTech Connect

    Wiedersich, H.

    1993-06-01

    A short overview of the processes that affect the evolution of the microstructure during irradiation is given. The processes include defect production with an emphasis on the effects of the dynamic cascade events, defect clustering, irradiation-enhanced diffusion, radiation-induced segregation, phase decompositions and phase transformations. A simple model for the description of the development of the defect microstructure in a pure metal during cascade producing irradiation is also outlined which can provide, in principle, defect fluxes required for the description of the microstructural processes such as phase decomposition and irradiation-induced precipitation.

  4. Ductile damage evolution and experimental simulation under high rates of strain in 10100 copper.

    SciTech Connect

    Thissell, W. R.; McKirgan, J. B.; Chen, S. R.; Trujillo, C. P.; Macdougall, D. A. S.

    2001-01-01

    The high strain-rate damage evolution and Eracture behavior of half-hard 10 LOO Cu was investigated by experiments and computer simulations. Testing of uniaxial stress and axisymmetric notched bars of the Hancock-Mackenzie geometries were performetl using a momentum trapped tensile split Hopkinson pressure bar. Specimens were. tested to fracture and to several stages of incipient failure prior to fracture. Recovered specimens were sectioned and metallographically examined using image analysis and optical profilornelry to quantify the resulting damage. The quantified damage is described by spatially resolved porosity distributions, spatially resolved volumetric number densiries, and spatia Ily resolved void size distributions. Concurrent to mechanical testing, explicit finite element simulations of the tensile split Hopkinson pressure bar experiments were perfornicd to quantify the local stress-state and strain-state within the material and to determine the evolution of damage within the notch region. The coinpressive plasticity behavior of the material was fit to the mechanical threshold stress constitutive model, and was used in the simulations. The quantified damage was coniprued with damage model (TEPLA) predictions and used to refine model parameters and damage nucleation criteria. The simulation results also show that the maximum stress triaxiality in the specimens quickly enlarges after the onset of plastic flow or tensile instability to almost twice that of the Bridgman predicted levels.

  5. Microstructure: Property correlation. [multiaxial fatigue damage evolution in waspaloy

    NASA Technical Reports Server (NTRS)

    Jayaraman, N.

    1990-01-01

    Strain controlled torsional and biaxial (tension-torsion) low cycle fatigue behavior of Waspaloy was studied at room temperature as a function of heat treatment. Biaxial tests were conducted under proportional (when the axial and torsional strain cycles are in-phase) and non-proportional (when the axial and torsional strain cycles are 90 deg out-of-phase) cyclic conditions. The deformation behavior under these different cyclic conditions were evaluated by slip trace analysis. For this, a Schmidt-type factor was defined for multiaxial loading conditions and it was shown that when the slip deformation is predominant, non-proportional cycles are more damaging than proportional or pure axial or torsional cycles. This was attributed to the fact that under non-proportional cyclic conditions, deformation was through multiple slip as opposed single slip for other loading conditions, which gave rise to increased hardening. The total life for a given test condition was found to be independent of heat treatment. This was interpreted as being due to the differences in the cycles to initiation and propagation of cracks.

  6. Asymmetrical Damage Partitioning in Bacteria: A Model for the Evolution of Stochasticity, Determinism, and Genetic Assimilation

    PubMed Central

    Chao, Lin; Rang, Camilla Ulla; Proenca, Audrey Menegaz; Chao, Jasper Ubirajara

    2016-01-01

    Non-genetic phenotypic variation is common in biological organisms. The variation is potentially beneficial if the environment is changing. If the benefit is large, selection can favor the evolution of genetic assimilation, the process by which the expression of a trait is transferred from environmental to genetic control. Genetic assimilation is an important evolutionary transition, but it is poorly understood because the fitness costs and benefits of variation are often unknown. Here we show that the partitioning of damage by a mother bacterium to its two daughters can evolve through genetic assimilation. Bacterial phenotypes are also highly variable. Because gene-regulating elements can have low copy numbers, the variation is attributed to stochastic sampling. Extant Escherichia coli partition asymmetrically and deterministically more damage to the old daughter, the one receiving the mother’s old pole. By modeling in silico damage partitioning in a population, we show that deterministic asymmetry is advantageous because it increases fitness variance and hence the efficiency of natural selection. However, we find that symmetrical but stochastic partitioning can be similarly beneficial. To examine why bacteria evolved deterministic asymmetry, we modeled the effect of damage anchored to the mother’s old pole. While anchored damage strengthens selection for asymmetry by creating additional fitness variance, it has the opposite effect on symmetry. The difference results because anchored damage reinforces the polarization of partitioning in asymmetric bacteria. In symmetric bacteria, it dilutes the polarization. Thus, stochasticity alone may have protected early bacteria from damage, but deterministic asymmetry has evolved to be equally important in extant bacteria. We estimate that 47% of damage partitioning is deterministic in E. coli. We suggest that the evolution of deterministic asymmetry from stochasticity offers an example of Waddington’s genetic

  7. Asymmetrical Damage Partitioning in Bacteria: A Model for the Evolution of Stochasticity, Determinism, and Genetic Assimilation.

    PubMed

    Chao, Lin; Rang, Camilla Ulla; Proenca, Audrey Menegaz; Chao, Jasper Ubirajara

    2016-01-01

    Non-genetic phenotypic variation is common in biological organisms. The variation is potentially beneficial if the environment is changing. If the benefit is large, selection can favor the evolution of genetic assimilation, the process by which the expression of a trait is transferred from environmental to genetic control. Genetic assimilation is an important evolutionary transition, but it is poorly understood because the fitness costs and benefits of variation are often unknown. Here we show that the partitioning of damage by a mother bacterium to its two daughters can evolve through genetic assimilation. Bacterial phenotypes are also highly variable. Because gene-regulating elements can have low copy numbers, the variation is attributed to stochastic sampling. Extant Escherichia coli partition asymmetrically and deterministically more damage to the old daughter, the one receiving the mother's old pole. By modeling in silico damage partitioning in a population, we show that deterministic asymmetry is advantageous because it increases fitness variance and hence the efficiency of natural selection. However, we find that symmetrical but stochastic partitioning can be similarly beneficial. To examine why bacteria evolved deterministic asymmetry, we modeled the effect of damage anchored to the mother's old pole. While anchored damage strengthens selection for asymmetry by creating additional fitness variance, it has the opposite effect on symmetry. The difference results because anchored damage reinforces the polarization of partitioning in asymmetric bacteria. In symmetric bacteria, it dilutes the polarization. Thus, stochasticity alone may have protected early bacteria from damage, but deterministic asymmetry has evolved to be equally important in extant bacteria. We estimate that 47% of damage partitioning is deterministic in E. coli. We suggest that the evolution of deterministic asymmetry from stochasticity offers an example of Waddington's genetic assimilation

  8. The evolution of damage control orthopedics: current evidence and practical applications of early appropriate care.

    PubMed

    D'Alleyrand, Jean-Claude G; O'Toole, Robert V

    2013-10-01

    This article summarizes the evolution of literature and practice related to fracture care in polytrauma patients. Particular emphasis is given to the management of femoral shaft fractures and the concept of damage control in these complex patients. The application of these guidelines in common clinical practice is also discussed. PMID:24095066

  9. Damage evolution in Au-implanted Ho2Ti2O7 titanate pyrochlore

    SciTech Connect

    Zhang, Yanwen; Jagielski, Jacek; Bae, In-Tae; Xiang, Xia; Thome, Lionel; Balakrishnan, G.; Paul, D. M.; Weber, William J.

    2010-10-01

    Damage evolution at room temperature in Ho2Ti2O7 single crystals is studied under 1 MeV Au2+ ion irradiation by Rutherford backscattering spectroscopy along the <001> direction. For a better determination of ion-induced disorder profile, an iterative procedure and a Monte Carlo code (McChasy) were used to analyze ion channeling spectra. A disorder accumulation model, with contributions from the amorphous fraction and the crystalline disorder, is fit to the Ho damage accumulation data. The damage evolution behavior indicates that the relative disorder on the Ho sublattice follows a nonlinear dependence on dose and that defect-stimulated amorphization is the primary amorphization mechanism. Similar irradiation behavior previously was observed in Sm2Ti2O7. A slower damage accumulation rate for Ho2Ti2O7, as compared with damage evolution in Sm2Ti2O7, is mainly attributed to a lower effective cross section for defect-simulated amorphization.

  10. Damage and permiability evolution in creep-failed microgranite

    NASA Astrophysics Data System (ADS)

    Odling, N.; Elphick, S.; Main, I.; Meredith, P.; Ngwenya, B.

    2003-04-01

    The importance of crack generation during deformation is now becoming widely recognized as one of the key factors that control important processes involving fluid flow in rocks of low permeability e.g., hydro-thermal circulation at mid-ocean ridges, energy recovery from geothermal reservoirs, and accelerating deformation preceding volcanic eruptions. Here we describe experiments that extend the study of Meredith et al. (2000) by examining the relationship between slow deformation, the growth of micro-fractures, and permeability in Ailsa Craig microgranite (ACM) close to the fracture interconnection percolation threshold. To examine the inter-relationship between the above factors we have undertaken creep experiments on cores of ACM during which we have measured acoustic emissions, solute breakthrough curves, and electrical impedance (EI), at a strain rate of 10e(-6). The initial network of distributed damage was generated in a 38mm-diameter core of ACM by heating at 1°C/hr to 900°C then cooling to room temperature at the same rate. The treated core was then placed in a Hasler cell with integral acoustic emission and electrical impedance sensors and initially loaded to 20MPa. To measure breakthrough curves, solutions of deionized/distilled/degassed water was alternated with a degassed 1M NaCl solution at a flow rate of 1cc/hr. Differential fluid pressures were monitored by piezoelectric pressure gauges and the strain in the sample was monitored by LVDTs attached to the pistons. Initial 'breakthrough' tests under hydrostatic conditions show that the EI response detects first a linear change in impedance as the solute front advances through the core followed by a more gradual decrease as the front ‘breaks out’ of the core end. The EI response, therefore, describes both the advection and dispersion terms associated with the solute front in the core. The data allow the inter-relationship between crack generation/growth, effective cumulative aperture, permeability

  11. Law.

    ERIC Educational Resources Information Center

    Walker, W. R.; Cox, W. E.

    1978-01-01

    Presents a literature review of the legal issues relative to water quality covering publications of 1977. Consideration is given to federal laws, Supreme Court cases, and the impact of federal environmental laws on local government. A list of 47 references is also presented. (HM)

  12. Moving on from bland: the evolution of the law and minimally conscious patients.

    PubMed

    Heywood, Rob

    2014-01-01

    The decision in Bland centred on the withdrawal of artificial nutrition and hydration from a patient in a persistent vegetative state (PVS). Since then, a new medical condition has emerged, known as a minimally conscious state (MCS). In W v M, the Court of Protection was asked to authorise the withdrawal of artificial nutrition and hydration from a patient in a MCS. Baker J refused to grant the declaration. More recently, however, the courts were also asked to rule on the lawfulness of withholding treatment in a similar, albeit factually different, case. In the Court of Appeal decision in Aintree University Hospitals NHS Foundation Trust v David James and Others, Sir Alan Ward, with the agreement of Arden LJ and Laws LJ, granted a declaration that it would be lawful to withhold treatment. The Supreme Court then upheld this ruling, Lady Hale stating that the Court of Appeal reached the right result but for the wrong reasons. This article seeks to critically appraise the evolution of the law in regard to withdrawing treatment from MCS patients. The piece begins by explaining the differences between the two conditions of PVS and MCS and defines the law from the starting point of Bland. From here, the discussion progresses to focus on the challenges that the law has had to face in trying to keep pace with the advancing nature of medical understanding of conditions of the brain and explains how it has responded to these. The narrative then critiques the legal mechanism of best interests as it has been employed in the case law concerning MCS patients to date by analysing the various judicial perspectives on the concept. After addressing both the narrow and wide viewpoints, a conclusion is ventured as to how the balancing of best interests should be approached in respect of future MCS cases. PMID:24618294

  13. Critical evaluation of state evolution laws in rate and state friction: Fitting large velocity steps in simulated fault gouge with time-, slip-, and stress-dependent constitutive laws

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Pathikrit; Rubin, Allan M.; Bayart, Elsa; Savage, Heather M.; Marone, Chris

    2015-09-01

    The variations in the response of different state evolution laws to large velocity increases can dramatically alter the style of earthquake nucleation in numerical simulations. But most velocity step friction experiments do not drive the sliding surface far enough above steady state to probe this relevant portion of the parameter space. We try to address this by fitting 1-3 orders of magnitude velocity step data on simulated gouge using the most widely used state evolution laws. We consider the Dieterich (Aging) and Ruina (Slip) formulations along with a stress-dependent state evolution law recently proposed by Nagata et al. (2012). Our inversions confirm the results from smaller velocity step tests that the Aging law cannot explain the observed response and that the Slip law produces much better fits to the data. The stress-dependent Nagata law can produce fits identical to, and sometimes slightly better than, those produced by the Slip law using a sufficiently large value of an additional free parameter c that controls the stress dependence of state evolution. A Monte Carlo search of the parameter space confirms analytical results that velocity step data that are well represented by the Slip law can only impose a lower bound on acceptable values of c and that this lower bound increases with the size of the velocity step being fit. We find that our 1-3 orders of magnitude velocity steps on synthetic gouge impose this lower bound on c to be 10-100, significantly larger than the value of 2 obtained by Nagata et al. (2012) based on experiments on initially bare rock surfaces with generally smaller departures from steady state.

  14. Fatigue-damage evolution and damage-induced reduction of critical current of a Nb3Al superconducting composite

    NASA Astrophysics Data System (ADS)

    Ochiai, S.; Sekino, F.; Sawada, T.; Ohno, H.; Hojo, M.; Tanaka, M.; Okuda, H.; Koganeya, M.; Hayashi, K.; Yamada, Y.; Ayai, N.; Watanabe, K.

    2003-09-01

    We have studied the fatigue-damage mechanism of a Nb3Al superconducting composite at room temperature, and the influences of the fatigue damages introduced at room temperature on the critical current at 4.2 K and the residual strength at room temperature. The main (largest) fatigue crack arose first in the clad copper and then extended into the inner core with an increasing number of stress cycles. The cracking of the Nb3Al filaments in the core region occurred at a late stage (around 60-90% of the fatigue life). Once the fracture of the core occurred, it extended very quickly, resulting in a quick reduction in critical current and the residual strength with increasing stress cycles. Such a behaviour was accounted for by the crack growth calculated from the S-N curves (the relation of the maximum stress to the number of stress cycles at failure) combined with the Paris law. The size and distribution of the subcracks along the specimen length, and therefore the reduction in critical current of the region apart from the main crack, were dependent on the maximum stress level. The large subcracks causing fracture of the Nb3Al filaments were formed when the maximum stress was around 300-460 MPa, resulting in large reduction in critical current, but not when the maximum stress was outside such a stress range.

  15. The relationship between microstructure and damage evolution in hot-rolled complex-phase steel sheet

    NASA Astrophysics Data System (ADS)

    Bell, Grant A. S.

    Complex-phase (CP) steels are employed in applications that require high-strength and good edge formability. These steels derive their strength from a fine-grained bainite-ferrite microstructure, and alloying to provide solid-solution and precipitation strengthening. CP steels are produced industrially through a process of controlled rolling and cooling to produce desirable microstructures. Hole-expansion tests are typically used as a measure of edge formability for applications such as stretch-flanges. It has been shown that CP microstructures are susceptible to large fluctuations in hole-expansion performance with little change in processing or resulting tensile properties. The steel's characteristics of damage evolution are critical to the hole-expansion performance. This study investigates the role of microstructure in the development of damage in CP microstructural variants. Two variant pairs of different thicknesses were produced from the leading and trailing edge of industrially produced hot-rolled sheet. Each pair consisted of a variant with poor hole-expansion performance, and a variant with good hole-expansion performance. Each variant was tested via interrupted double-notched uniaxial tension testing to induce damage. Damage evolution in each variant was quantified by X-ray micro-computed tomography (XmicroCT), and supplementary optical micrography. The damage results were correlated with microstructural characteristics. It was shown that poor hole-expansion variants failed by intergranular fracture. In these variants, void damage induced by hard martensite and retained austenite was not critical in producing failure. Purely void-damaged microstructures failed by ductile fracture, whereas cracked microstructures failed in a mixed brittle-ductile failure initiated by planar cracks. Microstructural banding of large elongated ferrite grains correlated with the existence of intergranular planar fractures.

  16. Modeling of delamination damage evolution in laminated composites subjected to low velocity impact

    NASA Technical Reports Server (NTRS)

    Lo, David C.; Allen, David H.

    1994-01-01

    This study examines the delamination evolution, under quasi-static conditions, of laminated polymeric composites with mechanically nonlinear resin rich interfaces. The constitutive behavior of the interface is represented by two models developed by Needleman and Tvegaard. These models assumed that the interfacial tractions, a function of only the interfacial displacement, will behave similarly to the interatomic forces generated during the interatomic seperation. The interface material's parameters control the load at which the delamination growth initiates and the final delamination size. A wide range of damage accumulation responses have been obtained by varying the model parameters. These results show that Tvergaard's model has been found to be better suited of the two models in predicting damage evolution for the configurations examined.

  17. The Influence of Grain Boundary Type upon Damage Evolution at Grain Boundary Interfaces

    SciTech Connect

    Perez-Bergquist, Alejandro G; Brandl, Christian; Escobedo, Juan P; Trujillo, Carl P; Cerreta, Ellen K; Gray III, George T; Germann, Timothy C

    2012-07-09

    In a prior work, it was found that grain boundary structure strongly influences damage evolution at grain boundaries in copper samples subjected to either shock compression or incipient spall. Here, several grain boundaries with different grain boundary structures, including a {Sigma}3 (10-1) boundary, are interrogated via conventional transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) to investigate the effects of atomic-scale structural differences on grain boundary strength and mobility. Boundaries are studied both before and after shock compression at a peak shock stress of 10 GPa. Results of the TEM and HRTEM work are used in conjunction with MD modeling to propose a model for shock-induced damage evolution at grain boundary interfaces that is dependent upon coincidence.

  18. Cumulative creep-fatigue damage evolution in an austenitic stainless steel

    NASA Technical Reports Server (NTRS)

    Mcgaw, Michael A.

    1992-01-01

    A model of cumulative creep-fatigue damage has been developed which is based on the use of damage curve equations to describe the evolution of creep-fatigue damage for four basic creep-fatigue cycle types. These cycle types correspond to the four fundamental cycles of the Strain Range Partitioning Life Prediction approach of Manson, Halford, and Hirschberg. A concept referred to as Damage Coupling is introduced to analytically account for the differences in the nature of the damage introduced by each cycle type. For application of this model, the cumulative creep-fatigue damage behavior of type 316 stainless steel at 816 C has been experimentally established for the two-level loading cases involving fatigue and creep-fatigue, in various permutations. The tests were conducted such that the lower life (high strain) cycling was applied first, for a controlled number of cycles, and the higher life (lower strain) cycling was conducted at the second level, to failure. The proposed model correlated the majority of the observed cumulative creep-fatigue data.

  19. The second law of thermodynamics under unitary evolution and external operations

    SciTech Connect

    Ikeda, Tatsuhiko N.; Sakumichi, Naoyuki; Polkovnikov, Anatoli; Ueda, Masahito

    2015-03-15

    The von Neumann entropy cannot represent the thermodynamic entropy of equilibrium pure states in isolated quantum systems. The diagonal entropy, which is the Shannon entropy in the energy eigenbasis at each instant of time, is a natural generalization of the von Neumann entropy and applicable to equilibrium pure states. We show that the diagonal entropy is consistent with the second law of thermodynamics upon arbitrary external unitary operations. In terms of the diagonal entropy, thermodynamic irreversibility follows from the facts that quantum trajectories under unitary evolution are restricted by the Hamiltonian dynamics and that the external operation is performed without reference to the microscopic state of the system.

  20. Unification of Small and Large Time Scales for Biological Evolution: Deviations from Power Law

    NASA Astrophysics Data System (ADS)

    Chowdhury, Debashish; Stauffer, Dietrich; Kunwar, Ambarish

    2003-02-01

    We develop a unified model that describes both “micro” and “macro” evolutions within a single theoretical framework. The ecosystem is described as a dynamic network; the population dynamics at each node of this network describes the “microevolution” over ecological time scales (i.e., birth, ageing, and natural death of individual organisms), while the appearance of new nodes, the slow changes of the links, and the disappearance of existing nodes accounts for the “macroevolution” over geological time scales (i.e., the origination, evolution, and extinction of species). In contrast to several earlier claims in the literature, we observe strong deviations from power law in the regime of long lifetimes.

  1. Damage evolution in GLARE fibre-metal laminate under repeated low-velocity impact tests

    NASA Astrophysics Data System (ADS)

    Morinière, Freddy; Alderliesten, René; Tooski, Mehdi; Benedictus, Rinze

    2012-12-01

    An experimental study was performed on the repeated low-velocity impact behaviour of GLARE. Damage evolution in the material constituents was characterised with successive number of impacts. Records were correlated with visual inspection, ultrasound C-scan and chemical etching. The stiffness of the plate varied when cumulating the number of impacts. Damage accumulation was limited thanks to the synthesis of unidirectional composite and metal. The glass/epoxy plies with high elastic tensile strength could withstand several impacts before perforation despite delamination growth in the vicinity of the impacted area. The damage tolerant aluminium layers prevented the penetration of the projectile and avoided the expansion of delamination. This efficient mechanism preserved the structural integrity of GLARE until first aluminium cracking at the non-impacted side. Among the different failure modes, plate deformation absorbed most of the impact energy. The findings will support the development of a generic quasi-static analytical model and numerical methods.

  2. 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. PMID:22684886

  3. Dynamic damage evolution in aluminum as a model system for understanding FCC materials in extreme conditions

    NASA Astrophysics Data System (ADS)

    Sanchez, Nathaniel Jonathon

    Materials play a key role in many emerging technologies. Future technologies in the energy and defense sectors will place huge demands on material performance with respect to stress, strain, temperature, and pressure. These applications require that the response of materials on dynamic (microsecond) time scales be predictable and controllable. Hence, the goal of this research project was to study the extreme environment of shock loaded damage evolution in aluminum as a model system for understanding dynamic response of FCC metals in these environments. Phase one utilized plate impact experiments to study the influence of spatial effects (in the form of microstructural defect distributions) on the dynamic damage evolution process. Samples were soft recovered for shot analysis and comparison to real time laser velocimetry. Results revealed that the length scale of defects controls the failure mechanisms of the microstructure; suggesting defect density and the spatial distribution of defects are critical factors in the deformation process in extreme environments. Phase two studied the influence of kinetic effects (in the form of dynamic tensile loading rate) to reveal time dependence on the dynamic deformation process. Results concluded damage nucleation and growth rates are highly time dependent and can be overdriven as higher tensile loading rates result in extremely short time durations. It was shown that laser velocimetry provides an adequate means for understanding the dynamic damage evolution process when soft recovery of the sample is unavailable. This was shown by comparing laser velocimetry results with data obtained from optical analysis on recovered specimens. The methodology here provides a means to systematically study materials of interest in extreme conditions and provides a pathway for obtaining the relevant physics needed for model development leading to a predictive capability.

  4. A Numerical Method for Simulating the Microscopic Damage Evolution in Composites Under Uniaxial Transverse Tension

    NASA Astrophysics Data System (ADS)

    Zhi, Jie; Zhao, Libin; Zhang, Jianyu; Liu, Zhanli

    2016-06-01

    In this paper, a new numerical method that combines a surface-based cohesive model and extended finite element method (XFEM) without predefining the crack paths is presented to simulate the microscopic damage evolution in composites under uniaxial transverse tension. The proposed method is verified to accurately capture the crack kinking into the matrix after fiber/matrix debonding. A statistical representative volume element (SRVE) under periodic boundary conditions is used to approximate the microstructure of the composites. The interface parameters of the cohesive models are investigated, in which the initial interface stiffness has a great effect on the predictions of the fiber/matrix debonding. The detailed debonding states of SRVE with strong and weak interfaces are compared based on the surface-based and element-based cohesive models. The mechanism of damage in composites under transverse tension is described as the appearance of the interface cracks and their induced matrix micro-cracking, both of which coalesce into transversal macro-cracks. Good agreement is found between the predictions of the model and the in situ experimental observations, demonstrating the efficiency of the presented model for simulating the microscopic damage evolution in composites.

  5. Investigation of surface damage precursor evolutions and laser-induced damage threshold improvement mechanism during Ion beam etching of fused silica.

    PubMed

    Shi, Feng; Zhong, Yaoyu; Dai, Yifan; Peng, Xiaoqiang; Xu, Mingjin; Sui, Tingting

    2016-09-01

    Surface damage precursor evolution has great influence on laser-induced damage threshold improvement of fused silica surface during Ion beam etching. In this work, a series of ion sputtering experiment are carried out to obtain the evolutions of damage precursors (dot-form microstructures, Polishing-Induced Contamination, Hertz scratches, and roughness). Based on ion sputtering theory, surface damage precursor evolutions are analyzed. The results show that the dot-form microstructures will appear during ion beam etching. But as the ion beam etching depth goes up, the dot-form microstructures can be mitigated. And ion-beam etching can broaden and passivate the Hertz scratches without increasing roughness value. A super-smooth surface (0.238nm RMS) can be obtained finally. The relative content of Fe and Ce impurities both significantly reduce after ion beam etching. The laser-induced damage threshold of fused silica is improved by 34% after ion beam etching for 800nm. Research results can be a reference on using ion beam etching process technology to improve laser-induced damage threshold of fused silica optics. PMID:27607688

  6. Use of atomic force microscopy for characterizing damage evolution during fatigue

    NASA Astrophysics Data System (ADS)

    Cretegny, Laurent

    2000-10-01

    A study of the development of surface fatigue damage in PH 13-8 Mo stainless steel and copper by atomic force microscopy (AFM) was performed. AFM observations allow highly automated, quantitative characterization of surface deformation with a resolution of 5 nm or better, which is ideal for understanding fatigue damage evolution. A secondary objective was to establish a correlation between fatigue life exhausted and impedance spectroscopy. Strain controlled fatigue tests were conducted both in high and low cycle fatigue regimes, and interruptions of the fatigue tests allowed characterizing the evolution of the surface upset at various life-fractions. In the low strain amplitude tests on stainless steel (Deltaepsilonpl/2 = 0.0026%), surface damage occurred in the shape of narrow streaks at the interface between martensite laths where reverted austenite was present. The streaks eventually coalesced to form crack nuclei. In high strain amplitude tests (Deltaepsilon pl/2 = 0.049%), fatigue surface damage was essentially dominated by the formation of extrusions. In copper, both low (Deltaepsilonpl/2 = 0.061%) and high (Deltaepsilonpl/2 = 0.134%) strain amplitude tests showed the formation of slip bands (mainly extrusions) across entire grains. Protrusions were present only in copper specimens tested at the high strain amplitude. Crack nucleation in the low strain amplitude tests occurred in both materials at the interface between a region that sustained a high level of deformation and one with little evidence of surface upset. This commonality between these two materials that are otherwise very dissimilar in nature suggests a universal scheme for location of fatigue crack nucleation sites during HCF. A procedure was developed in this study to quantitatively characterize the amount of irreversible surface strain. The proposed formalism is applicable to any material, independently of the type of surface damage, and leads to a criterion for crack nucleation based on

  7. Damage evolution and mechanical response of cross-ply ceramic composite laminates

    SciTech Connect

    Weitsman, Y.; Yu, N.; Zhu, H.

    1995-12-31

    A mechanistic model for the damage evolution and mechanical response of cross-ply ceramic composite laminates under monotonically increasing uniaxial tension is presented. The model accounts for a variety of damage mechanisms evolving in cross-ply ceramic composite laminates, such as fiber-bridged matrix cracks in 0{degrees}-plies, transversely oriented matrix cracks in 90{degrees}-plies, and slips at 0{degrees}/90{degrees} ply interfaces as well as at the fiber/matrix interfaces. Energy criteria are developed to determine the creation and progression of matrix cracks and slip zones. The model predicts that the crack density in 0{degrees}-plies becomes higher than that within the 90{degrees}-plies as the applied load is incrementally increased, which agrees with the experimental observation. It is also shown that the model provides a reasonable prediction for the nonlinear stress-strain behavior of crossply SiC/CAS ceramic composites.

  8. Effect of Temperature on Damage Evolution of Cr25Ni35Nb Alloy Subjected to Combined Mechanical and Environmental Degradation

    NASA Astrophysics Data System (ADS)

    Shen, Limin; Liu, Huansheng; Gong, Jianming; Geng, Luyang

    2015-07-01

    Due to combined mechanical and environmental degradation, i.e. coupled creep and carburization, Cr25Ni35Nb alloy often fails prior to the expected design life. In the present paper, based on the continuum damage mechanics, the constitutive model of coupled multi-damage factors for computing the damage evolution of Cr25Ni35Nb alloy was proposed. The damage prediction was carried out by using finite element method based on ABAQUS code. And then damage evolution processes at different operating temperatures (950 °C and 1050 °C) were simulated and the effect of service temperature on the damage evolution was discussed. The results showed that the rate of damage increased obviously with operating temperature increasing. The location with maximum damage is along the inner surface of tube, which implies that fracture begins along the inner surface of tube under the action of coupled creep and carburization damage and this is coincident with the actual observation of the failure of furnace tube.

  9. 26 CFR 1.162-22 - Treble damage payments under the antitrust laws.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... criminal conspiracy between X Co. and Y Co. forced Z Co. to pay excessive prices for electrical... example (1) except that Z Co.'s claim for treble damages was based on a conspiracy to fix and maintain... by the defendants' fraudulent concealment of their conspiracy. Since the United States has...

  10. 26 CFR 1.162-22 - Treble damage payments under the antitrust laws.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... criminal conspiracy between X Co. and Y Co. forced Z Co. to pay excessive prices for electrical... example (1) except that Z Co.'s claim for treble damages was based on a conspiracy to fix and maintain... by the defendants' fraudulent concealment of their conspiracy. Since the United States has...

  11. 26 CFR 1.162-22 - Treble damage payments under the antitrust laws.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... criminal conspiracy between X Co. and Y Co. forced Z Co. to pay excessive prices for electrical... example (1) except that Z Co.'s claim for treble damages was based on a conspiracy to fix and maintain... by the defendants' fraudulent concealment of their conspiracy. Since the United States has...

  12. 26 CFR 1.162-22 - Treble damage payments under the antitrust laws.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... criminal conspiracy between X Co. and Y Co. forced Z Co. to pay excessive prices for electrical... example (1) except that Z Co.'s claim for treble damages was based on a conspiracy to fix and maintain... by the defendants' fraudulent concealment of their conspiracy. Since the United States has...

  13. Damage and the Gutenberg-Richter Law: from simple models to natural earthquake fault systems

    NASA Astrophysics Data System (ADS)

    Tiampo, K. F.; Klein, W.; Rundle, J. B.; Dominguez, R.; Serino, C.

    2010-12-01

    Natural earthquake fault systems are highly nonhomogeneous in space, where these inhomogeneities occur because the earth is made of a variety of materials which hold and dissipate stress differently. One way that the inhomogeneous nature of fault systems manifests itself is in the spatial patterns which emerge in seismicity graphs (Tiampo et al., 2002, 2007). Despite their inhomogeneous nature, real faults are often modeled as spatially homogeneous systems. One argument for this approach is that earthquake faults experience long range stress transfer, and if this range is longer than the length scales associated with the inhomogeneities of the system, the dynamics of the system may be unaffected by their presence. However, it is not clear that this is the case. In this work we study the scaling of an earthquake model that is a variation of the Olami-Feder-Christensen (OFC) model, in order to explore the effect of spatial inhomogeneities on earthquake-like systems when interaction ranges are long, but not necessarily longer than the distances associated with those inhomogeneities (Rundle and Jackson, 1977; Olami et al., 1988). For long ranges and without inhomogeneities, such models have been found to produce scaling similar to GR scaling found in real earthquake systems (Rundle and Klein, 1993). In the earthquake models discussed here, damage is distributed inhomogeneously throughout and the interaction ranges, while long, are not longer than all of the damage length scales. We find that the scaling depends not only on the amount of damage, but also on the spatial distribution of that damage. In addition, we study the behaviour of particular natural earthquake faults and the spatial and temporal variation of GR scaling in those systems, in order to compare them with various damage cases from the simulations.

  14. On the Physical Basis of Rate Law Formulations for River Evolution, and their Applicability to the Simulation of Evolution after Earthquakes

    NASA Astrophysics Data System (ADS)

    An, C.; Parker, G.; Fu, X.

    2015-12-01

    River morphology evolves in response to trade-offs among a series of environmental forcing factors, and this evolution will be disturbed if such environmental factors change. One example of response to chronic disturbance is the intensive river evolution after earthquakes in southwest China's mountain areas. When simulating river morphological response to environmental disturbance, an exponential rate law with a specified characteristic response time is often regarded as a practical tool for quantification. As conceptual models, empirical rate law formulations can be used to describe broad brush morphological response, but their physically basis is not solid in that they do not consider the details of morphodynamic processes. Meanwhile, river evolution can also be simulated with physically-based morphodynamic models which conserve sediment via the Exner equation. Here we study the links between the rate law formalism and the Exner equation through solving the Exner equation mathematically and numerically. The results show that, when implementing a very simplified form of a relation for bedload transport, the Exner equation can be reduced to the diffusion equation, the solution of which is a Gaussian function. This solution coincides with the solution associated with rate laws, thus providing a physical basis for such formulations. However, when the complexities of a natural river are considered, the solution of the Exner equation will no longer be a simple Gaussian function. Under such circumstances, the rate law becomes invalid, and a full understanding of the response of rivers to earthquakes requires a complete morphodynamic model.

  15. Evolution of laser damage in indium antimonide(InSb) at 1.06-μm wavelength

    NASA Astrophysics Data System (ADS)

    Garg, Amit; Tripathi, K. N.; Kapoor, Avinashi; Bansal, S. K.

    2005-01-01

    Evolution of laser damage morphology has been studied in 112 oriented, mirror polished Indium Antimonide(InSb)samples as a function of increasing energy, pulse repetition rate and number of pulses using a Nd:Cr:GSGG laser of 1.06 μm wavelength having a pulse width of 20ns. Scanning Electron Microscope (SEM) investigations of the irradiated samples have been done to understand the evolution of damage morphology. Damage morphology is consistent with surface melting and solidification along with an evidence of subsurface overheating. Temperature profiles calculated at different fluence levels confirm substantial subsurface heating. Multiple pulse damage seen at 20Hz with increasing fluence levels is mainly thermal damage. Thermal modeling has been done to explain different morphological features.

  16. Implications Of Fault Damaged Bedrock To Tectonic and Landscape Evolution In Coastal Alaska

    NASA Astrophysics Data System (ADS)

    Boucher, A.; Koons, P. O.; Roy, S. G.; Birkel, S. D.; Kaluzienski, L. M.; Campbell, S. W.

    2015-12-01

    Bedrock material strength properties heavily impact erosion rates in temperate glacial environments. We focus on the influence of localized tectonic crustal weakening in southeast Alaska on modern glacial erosion rates, thereby quantifying a primary feedback in tectonic/climatic coupling. Southeast Alaska, with its coincident high strain rates, vigorous glacial erosion and rapid sedimentation rates, provides an excellent setting in which to evaluate this interaction. To characterize the relationship between fault damage and glacial incision, we collected data in transects across the strike-slip Fairweather Fault in Yakutat and Disenchantment Bays, in deglaciated valleys below the Mendenhall, Herbert, Ptarmigan, and Lemon Creek Glaciers on the perimeter of the Juneau Icefield, and on deglaciated nunataks on the Echo and Vaughan Lewis Glaciers in the interior of the Juneau Icefield. The mechanical properties of the bedrock are characterized by estimates of fault spacing and material cohesion. In structurally-controlled bedrock valleys exploited by glaciers, fracture spacing may vary by several orders of magnitude across fault damage zones, from more than 10 m to less than 0.1 m. Analysis of active and quiescent fault zones indicate that this variation approximates a power law relationship and correlates with a gradient in cohesive strength varying from greater than 50 MPa to less than 50 kPa between intact bedrock and the core of fault damage zones. The width and orientation of the damage zones is highly variable and we have chosen our field sites to sample zones of very large total displacement, up to kilometers along the Fairweather Fault, and substantially smaller displacements, down to centimeters for the Juneau Icefield locales. Using a Cordilleran Ice sheet model to extend our modern observations into last glacial maximum conditions, we predict both erosion rates and sediment provenance for a material strength pattern influenced by tectonically induced fault

  17. Detection of structural damage in multiwire cables by monitoring the entropy evolution of wavelet coefficients

    NASA Astrophysics Data System (ADS)

    Ibáñez, Flor; Baltazar, Arturo; Mijarez, Rito; Aranda, Jorge

    2015-03-01

    Multiwire cables are widely used in important civil structures. Since they are exposed to several dynamic and static loads, their structural health can be compromised. The cables can also be submitted to mechanical contact, tension and energy propagation in addition to changes in size and material within their wires. Due to the critical role played by multiwire cables, it is necessary to develop a non-destructive health monitoring method to maintain their structure and proper performance. Ultrasonic inspection using guided waves is a promising non-destructive damage monitoring technique for rods, single wires and multiwire cables. The propagated guided waves are composed by an infinite number of vibrational modes making their analysis difficult. In this work, an entropy-based method to identify small changes in non-stationary signals is proposed. A system to capture and post-process acoustic signals is implemented. The Discrete Wavelet Transform (DWT) is computed in order to obtain the reconstructed wavelet coefficients of the signals and to analyze the energy at different scales. The feasibility of using the concept of entropy evolution of non-stationary signals to detect damage in multiwire cables is evaluated. The results show that there is a high correlation between the entropy value and damage level of the cable. The proposed method has low sensitivity to noise and reduces the computational complexity found in a typical time-frequency analysis.

  18. Jurisdiction and applicable law in cases of damage from space in Europe—The advent of the most suitable choice—Rome II

    NASA Astrophysics Data System (ADS)

    Smith, Lesley Jane; Doldirina, Catherine

    2010-01-01

    Liability for space activities is a much discussed subject and the advent of commercial space operations has only added to its importance. Articles VI and VII Outer Space Treaty, together with Articles II and III Liability Convention, remain the main entry level for state liability for damage arising from private space activities. Few space-faring nations have introduced national space statutes that include a flow down of their international obligations. The European Union (EU) Regulation on the law applicable to non-contractual obligations—hereinafter Rome II Regulation—could harbour developments for liability law in the context of damage resulting from space operations. Space activities were not the main focus of the Regulation but may well turn out to be an interesting spin-off. The Regulation prescribes general rules that will determine the law applicable to damage scenarios where more than one legal system applies. It is important for trans-national tort cases in that it does not limit the rules of applicable law to EU Member States only. This paper focuses on the common rules applicable to damage actions based on torts or other non-contractual obligations as they apply to damage caused by space activities. After an assessment of the relevant international and national law norms, the impact of the Rome II Regulation will be addressed.

  19. Modeling study on the surface morphology evolution during removing the optics surface/subsurface damage using atmospheric pressure plasma processing

    NASA Astrophysics Data System (ADS)

    Xin, Qiang; Su, Xing; Wang, Bo

    2016-09-01

    Plasma processing has been widely reported as an effective tool in relieving or removing surface/subsurface damage induced by previous mechanical machining process. However, the surface morphology evolution during removing the damage using plasma processing is rarely reported. In this research, this procedure is studied based on experiments and robust numerical models developed on the basis of Level Set Method (LSM). Even if some unique properties of plasma etching are observed, such as particle redistribution, the dominant role of isotropic etching of plasma processing is verified based on experiments and 2D LSM simulations. With 2D LSM models, the damage removal process under various damage characteristics is explored in detail. Corresponding peak-to-valley roughness evolution is investigated as well. Study on morphology evolution is also conducted through the comparison between experiments and 3D LSM computations. The modeling results and experiments show good agreement with each other. The trends of simulated roughness evolution agree with the experiments as well. It is revealed that the plasma processing may end up with a planar surface depending on the damage characteristics. The planarization procedure can be divided into four parts: crack opening and pit formation; pit coalescing and shallow pits subsumed by deep ones; morphology duplicate etching; and finally a planar and damage free surface.

  20. Characterization and damaging law of CFC for high heat flux actively cooled plasma facing components

    NASA Astrophysics Data System (ADS)

    Chevet, G.; Martin, E.; Boscary, J.; Camus, G.; Herb, V.; Schlosser, J.; Escourbiac, F.; Missirlian, M.

    2011-10-01

    The carbon fiber reinforced carbon composite (CFC) Sepcarb N11 has been used in the Tore Supra (TS) tokamak (Cadarache, France) as armour material for the plasma facing components. For the fabrication of the Wendelstein 7-X (W7-X) divertor (Greifswald, Germany), the NB31 material was chosen. For the fabrication of the ITER divertor, two potential CFC candidates are the NB31 and NB41 materials. In the case of Tore Supra, defects such as microcracks or debonding were found at the interface between CFC tile and copper heat sink. A mechanical characterization of the behaviour of N11 and NB31 was undertaken, allowing the identification of a damage model and finite element calculations both for flat tiles (TS and W7-X) and monoblock (ITER) armours. The mechanical responses of these CFC materials were found almost linear under on-axis tensile tests but highly nonlinear under shear tests or off-axis tensile tests. As a consequence, damage develops within the high shear-stress zones.

  1. Characterization of damage evolution in an AM60 magnesium alloy by computed tomography

    SciTech Connect

    Waters, A.; Green, R.E.; Martz, H.; Dolan, K.; Horstemeyer, M.; Derrill, R.

    1999-06-16

    Lawrence Livermore National Lab and Sandia National Laboratories, CA are collaborating on the development of new techniques to study damage evolution and growth in material specimens subjected to mechanical loading. These techniques include metallography, radiography, computed tomography (CT) and modeling. The material specimens being studied include cast magnesium and aluminum alloys, and forged stainless steel. The authors concentrate on characterizing monotonically loaded Mg alloy specimens using CT. Several notched tensile specimens were uniaxially loaded to different percentages of the failure load. Specimens were initially characterized by radiography and computed tomography to determine the preloaded state. Subsequent CT scans were performed after the samples were loaded to different percentages of the load failure. The CT volumetric data are being used to measure void size, distribution and orientation in all three dimensions nondestructively to determine the effect of void growth on the mechanical behavior of the materials.

  2. Regional Distribution and Evolution of Gray Matter Damage in Different Populations of Multiple Sclerosis Patients

    PubMed Central

    Calabrese, Massimiliano; Reynolds, Richard; Magliozzi, Roberta; Castellaro, Marco; Morra, Aldo; Scalfari, Antonio; Farina, Gabriele; Romualdi, Chiara; Gajofatto, Alberto; Pitteri, Marco; Benedetti, Maria Donata; Monaco, Salvatore

    2015-01-01

    Background Both gray-matter (GM) atrophy and lesions occur from the earliest stages of Multiple Sclerosis (MS) and are one of the major determinants of long-term clinical outcomes. Nevertheless, the relationship between focal and diffuse GM damage has not been clarified yet. Here we investigate the regional distribution and temporal evolution of cortical thinning and how it is influenced by the local appearance of new GM lesions at different stages of the disease in different populations of MS patients. Methods We studied twenty MS patients with clinically isolated syndrome (CIS), 27 with early relapsing-remitting MS (RRMS, disease duration <5 years), 29 with late RRMS (disease duration ≥ 5 years) and 20 with secondary-progressive MS (SPMS). The distribution and evolution of regional cortical thickness and GM lesions were assessed during 5-year follow-up. Results The results showed that new lesions appeared more frequently in hippocampus and parahippocampal gyri (9.1%), insula (8.9%), cingulate cortex (8.3%), superior frontal gyrus (8.1%), and cerebellum (6.5%). The aforementioned regions showed the greatest reduction in thickness/volume, although (several) differences were observed across subgroups. The correlation between the appearance of new cortical lesions and cortical thinning was stronger in CIS (r2 = 50.0, p<0.001) and in early RRMS (r2 = 52.3, p<0.001), compared to late RRMS (r2 = 25.5, p<0.001) and SPMS (r2 = 6.3, p = 0.133). Conclusions We conclude that GM atrophy and lesions appear to be different signatures of cortical disease in MS having in common overlapping spatio-temporal distribution patterns. However, the correlation between focal and diffuse damage is only moderate and more evident in the early phase of the disease. PMID:26267665

  3. Fractal scaling and power-law landslide distribution in a micromodel of geomorphological evolution

    NASA Astrophysics Data System (ADS)

    Czirók, A.; Somfai, E.; Vicsek, T.

    Recent analyses of geographical data have shown that mountains can be well described in terms of fractals, which raises the fundamental question about the mechanisms producing fractal surfaces in geomorphological evolution. Because the formation of mountain ranges takes place over an extremely long period of time, direct observations of erosion mechanisms are hardly feasible. Therefore, we expect that model experiments on the erosion of mountain ridges taking place on a limited time scale should contribute significantly to our understanding of the emergence of fractal structures in geomorphological phenomena. During the watering of an initially smooth ridge made of a mixture of silica sand and earthy soil the surface evolves into a shape analogous to actual mountain profiles with self-affine geometry. For the exponents describing, respectively, the spatial and the temporal scaling of the surface width, α=0.78+/-0.05 and β=0.8+/-0.06 have been obtained. The former value is in a very good agreement with α=0.8+/-0.1 calculated for genuine transect profiles. The processes in our micromodel can be well described in terms of self-organized criticality: The system evolves into a critical state, where surface roughening takes place due to power-law distributed landslides.

  4. Whole cell tracking through the optimal control of geometric evolution laws

    NASA Astrophysics Data System (ADS)

    Blazakis, Konstantinos N.; Madzvamuse, Anotida; Reyes-Aldasoro, Constantino Carlos; Styles, Vanessa; Venkataraman, Chandrasekhar

    2015-09-01

    Cell tracking algorithms which automate and systematise the analysis of time lapse image data sets of cells are an indispensable tool in the modelling and understanding of cellular phenomena. In this study we present a theoretical framework and an algorithm for whole cell tracking. Within this work we consider that "tracking" is equivalent to a dynamic reconstruction of the whole cell data (morphologies) from static image data sets. The novelty of our work is that the tracking algorithm is driven by a model for the motion of the cell. This model may be regarded as a simplification of a recently developed physically meaningful model for cell motility. The resulting problem is the optimal control of a geometric evolution law and we discuss the formulation and numerical approximation of the optimal control problem. The overall goal of this work is to design a framework for cell tracking within which the recovered data reflects the physics of the forward model. A number of numerical simulations are presented that illustrate the applicability of our approach.

  5. Prediction of damage evolution in continuous fiber metal matrix composites subjected to fatigue loading

    SciTech Connect

    Allen, D.; Helms, K.; Lagoudas, D.

    1995-08-01

    A life prediction model is being developed by the authors for application to metal matrix composites (MMC`s). The systems under study are continuous silicon carbide fibers imbedded in titanium matrix. The model utilizes a computationally based framework based on thermodynamics and continuum mechanics, and accounts for matrix inelasticity, damage evolution, and environmental degradation due to oxidation. The computational model utilizes the finite element method, and an evolutionary analysis of a unit cell is accomplished via a time stepping algorithm. The computational scheme accounts for damage growth such as fiber-matrix debonding, surface cracking, and matrix cracking via the inclusion of cohesive zone elements in the unit cell. These elements are located based on experimental evidence also obtained by the authors. The current paper outlines the formulation utilized by the authors to solve this problem, and recent results are discussed. Specifically, results are given for a four-ply unidirectional composite subjected to cyclic fatigue loading at 650{degrees}C both in air and inert gas. The effects of oxidation on the life of the composite are predicted with the model, and the results are compared to limited experimental results.

  6. Proposed damage evolution model for large-scale finite element modeling of the dual coolant US-ITER TBM

    NASA Astrophysics Data System (ADS)

    Sharafat, S.; El-Awady, J.; Liu, S.; Diegele, E.; Ghoniem, N. M.

    2007-08-01

    Large-scale finite element modeling (FEM) of the US Dual Coolant Lead Lithium ITER Test Blanket Module including damage evolution is under development. A comprehensive rate-theory based radiation damage creep deformation code was integrated with the ABACUS FEM code. The advantage of this approach is that time-dependent in-reactor deformations and radiation damage can now be directly coupled with 'material properties' of FEM analyses. The coupled FEM-Creep damage model successfully simulated the simultaneous microstructure and stress evolution in small tensile test-bar structures. Applying the integrated Creep/FEM code to large structures is still computationally prohibitive. Instead, for thermo-structural analysis of the DCLL TBM structure the integrated FEM-creep damage model was used to develop true stress-strain behavior of F82H ferritic steel. Based on this integrated damage evolution-FEM approach it is proposed to use large-scale FEM analysis to identify and isolate critical stress areas for follow up analysis using detailed and fully integrated creep-FEM approach.

  7. Relating damage evolution of concrete cooled to cryogenic temperatures to permeability

    NASA Astrophysics Data System (ADS)

    Kogbara, Reginald B.; Iyengar, Srinath R.; Grasley, Zachary C.; Rahman, Syeda; Masad, Eyad A.; Zollinger, Dan G.

    2014-11-01

    Typically, 9% Ni steel is used for primary containment of liquefied natural gas (LNG). Utilization of concrete in place of 9% Ni steel for primary containment would lead to significant cost savings. Hence, this study investigates changes in the microstructure of concrete due to cryogenic freezing that would affect its relevant engineering properties for containment. The study also evaluates the effect of aggregate type on the damage potential of concrete subjected to cryogenic freezing. The aim is to investigate design methodologies to produce damage-resistant cryogenic concrete. The study employed four concrete mixture designs involving river sand as fine aggregate, and coarse aggregates with different coefficient of thermal expansion (CTE) values. Specifically, the coarse aggregates were limestone, sandstone, trap rock and lightweight aggregate. Concrete cubes were cured under water for at least 28 days and thereafter frozen from ambient (20 °C) to cryogenic temperature (-165 °C). Acoustic emission (AE) sensors were placed on the concrete cubes during freezing. X-ray computed tomography (XRCT) was employed to study the microstructure of concrete cores, before and after cryogenic freezing. The impact of the microstructural evolution thus obtained from AE and XRCT on relevant engineering properties was determined via water and chloride permeability tests. Microcrack propagation determined from AE correlated with changes in permeability. There were no observable cracks in majority of the concrete mixtures after freezing. This implies that microcracks detected via AE and increased permeability was very well distributed and smaller than the XRCT's resolution. Damage (microcracking) resistance of the concrete with different aggregates was in the order limestone ⩾ trap rock ≫ lightweight aggregate ⩾ sandstone.

  8. Damage evolution in uniaxial silicon carbide fiber-reinforced titanium matrix composites

    NASA Astrophysics Data System (ADS)

    Hanan, Jay Clarke

    Fiber fractures initiate damage zones ultimately determining the strength and lifetime of metal matrix composites (MMCs). The evolution of damage in a MMC comprising a row of unidirectional SiC fibers (32 vol.%) surrounded by a Ti matrix was examined using X-ray microdiffraction (gym beam size) and macrodiffraction (mm beam size). A comparison of high-energy X-ray diffraction (XRD) techniques including a powerful two-dimensional XRD method capable of obtaining powder averaged strains from a small number of grains is presented (HEmuXRD2). Using macrodiffraction, the bulk residual strain in the composite was determined against a true strain-free reference. In addition, the bulk in situ response of both the fiber reinforcement and the matrix to tensile stress was observed and compared to a three-dimensional finite element model. Using microdiffraction, multiple strain maps including both phases were collected in situ before, during, and after the application of tensile stress, providing an unprecedented detailed picture of the micromechanical behavior in the laminate metal matrix composite. Finally, the elastic axial strains were compared to predictions from a modified shear lag model, which unlike other shear lag models, considers the elastic response of both constituents. The strains showed excellent correlation with the model. The results confirmed, for the first time, both the need and validity of this new model specifically developed for large scale multifracture and damage evolution simulations of metal matrix composites. The results also provided unprecedented insight for the model, revealing the necessity of incorporating such factors as plasticity of the matrix, residual stress in the composite, and selection of the load sharing parameter. The irradiation of a small number of grains provided strain measurements comparable to a continuum mechanical state in the material. Along the fiber axes, thermal residual stresses of 740 MPa (fibers) and +350 MPa (matrix

  9. Damage Evolution in Composite Materials and Sandwich Structures Under Impulse Loading

    NASA Astrophysics Data System (ADS)

    Silva, Michael Lee

    Damage evolution in composite materials is a rather complex phenomenon. There are numerous failure modes in composite materials stemming from the interaction of the various constituent materials and the particular loading conditions. This thesis is concerned with investigating damage evolution in sandwich structures under repeated transient loading conditions associated with impulse loading due to hull slamming of high-speed marine craft. To fully understand the complex stress interactions, a full field technique to reveal stress or strain is required. Several full field techniques exist but are limited to materials with particular optical properties. A full field technique applicable to most materials is known as thermoelastic stress analysis (TSA) and reveals the variation in sum of principal stresses of a cyclically loaded sample by correlating the stresses to a small temperature change occurring at the loading frequency. Digital image correlation (DIC) is another noncontact full field technique that reveals the deformation field by tracking the motion of subsets of a random speckle pattern during the loading cycles. A novel experimental technique to aid in the study of damage progression that combines TSA and DIC simultaneously utilizing a single infrared camera is presented in this thesis. A technique to reliably perform DIC with an infrared (IR) camera is developed utilizing variable emissivity paint. The thermal data can then be corrected for rigid-body motion and deformation such that each pixel represents the same material point in all frames. TSA is then performed on this corrected data, reducing motion blur and increasing accuracy. This combined method with a single infrared camera has several advantages, including a straightforward experimental setup without the need to correct for geometric effects of two spatially separate cameras. Additionally, there is no need for external lighting in TSA as the measured electromagnetic radiation is emitted by the

  10. Information on the evolution of severe LWR fuel element damage obtained in the CORA program

    NASA Astrophysics Data System (ADS)

    Schanz, G.; Hagen, S.; Hofmann, P.; Schumacher, G.; Sepold, L.

    1992-06-01

    In the CORA program a series of out-of-pile experiments on LWR severe accidental situations is being performed, in which test bundles of LWR typical components and arrangements (PWR, BWR) are exposed to temperature transients up to about 2400°C under flowing steam. The individual features of the facility, the test conduct, and the evaluation will be presented. In the frame of the international cooperation in severe fuel damage (SFD) programs the CORA tests are contributing confirmatory and complementary informations to the results from the limited number of in-pile tests. The identification of basic phenomena of the fuel element destruction, observed as a function of temperature, is supported by separate-effects test results. Most important mechanisms are the steam oxidation of the Zircaloy cladding, which determines the temperature escalation, the chemical interaction between UO 2 fuel and cladding, which dominates fuel liquefaction, relocation and resulting blockage formation, as well as chemical interactions with Inconel spacer grids and absorber units ((Ag, In, Cd) alloy or B 4C), which are leading to extensive low-temperature melt formation around 1200°C. Interrelations between those basic phenomena, resulting for example in cladding deformation ("flowering") and the dramatic hydrogen formation in response to the fast cooling of a hot bundle by cold water ("quenching") are determining the evolution paths of fuel element destruction, which are to be identified. A further important task is the abstraction from mechanistic and microstructural details in order to get a rough classification of damage regimes (temperature and extent), a practicable analytical treatment of the materials behaviour, and a basis for decisions in accident mitigation and management procedures.

  11. Fatigue crack initiation and damage evolution of unnotched titanium matrix composites

    NASA Astrophysics Data System (ADS)

    Her, Yung-Chiun

    Fatigue crack initiation, multiplication, matrix crack density evolution, and stiffness reduction of several unnotched SCS-6 silicon carbide fiber-reinforced titanium and titanium aluminide matrix composites have been investigated experimentally and analytically. The effects of the thickness of the interfacial reaction layer and fiber coating on fatigue crack initiation life, crack growth rate, and fatigue damage evolution of the composites were examined. Growth behavior of small fatigue cracks in TMCs was also studied carefully. It was found that fatigue crack initiation and multiplication of TMCs are strongly influenced by the thickness of the interfacial reaction layer. Fatigue crack will not develop from the micro-notches in the interfacial reaction layer until the thickness of the reaction layer exceeds a critical value. Matrix crack growth rate is affected by the applied stress level, however, it appears to be independent of the matrix material and heat treatment. The combined effects of fatigue crack multiplication and propagation result in stiffness degradation of the composites. The Ag/Ta duplex fiber coating significantly improves the transverse tensile and flexural creep resistance of the SCS-6/Ti-25-10 composite. However, the Ag/Ta-coated composite exhibits a shorter crack initiation life, higher number of matrix cracks, and higher crack growth rate than the uncoated composite. The embrittlement of the residual Ag/Ta layer suggests that Ag is not an effective diffusion barrier to prevent the interdiffusion of atomic species across the interface. The high interfacial cracking density and high interfacial bond strength in the Ag/Ta-coated SCS-6/Tisb3Al composite are believed to be responsible for its poor fatigue damage tolerance. For titanium alloys, the threshold intensity factor range, Delta Ksbth, for small fatigue cracks in the matrix alloys of TMCs has been determined to be between 0.9 ˜ 1.0 MPa*msp{1/2} which is much lower than that for long

  12. Surface damage and structure evolution of recrystallized tungsten exposed to ELM-like transient loads

    NASA Astrophysics Data System (ADS)

    Yuan, Y.; Du, J.; Wirtz, M.; Luo, G.-N.; Lu, G.-H.; Liu, W.

    2016-03-01

    Surface damage and structure evolution of the full tungsten ITER divertor under transient heat loads is a key concern for component lifetime and plasma operations. Recrystallization caused by transients and steady-state heat loads can lead to degradation of the material properties and is therefore one of the most serious issues for tungsten armor. In order to investigate the thermal response of the recrystallized tungsten under edge localized mode-like transient thermal loads, fully recrystallized tungsten samples with different average grain sizes are exposed to cyclic thermal shocks in the electron beam facility JUDITH 1. The results indicate that not only does the microstructure change due to recrystallization, but that the surface residual stress induced by mechanical polishing strongly influences the surface cracking behavior. The stress-free surface prepared by electro-polishing is shown to be more resistant to cracking than the mechanically polished one. The resulting surface roughness depends largely on the loading conditions instead of the recrystallized-grain size. As the base temperature increases from room temperature to 400 °C, surface roughening mainly due to the shear bands in each grain becomes more pronounced, and sub-grains (up to 3 μm) are simultaneously formed in the sub-surface. The directions of the shear bands exhibit strong grain-orientation dependence, and they are generally aligned with the traces of {1 1 2} twin habit planes. The results suggest that twinning deformation and dynamic recrystallization represent the predominant mechanism for surface roughening and related microstructure evolution.

  13. The discrepancies in multistep damage evolution of yttria-stabilized zirconia irradiated with different ions

    SciTech Connect

    Yang, Tengfei; Taylor, Caitlin A.; Kong, Shuyan; Wang, Chenxu; Zhang, Yanwen; Huang, Xuejun; Xue, Jianming; Yan, Sha; Wang, Yugang

    2013-01-01

    This paper reports a comprehensive investigation of structural damage in yttria-stabilized zirconia irradiated with different ions over a wide fluence range. A similar multistep damage accumulation exists for the irradiations of different ions, but the critical doses for occurrence of second damage step, characterized by a faster increase in damage fraction, and the maximum elastic strain at the first damage step are varied and depend on ion mass. For irradiations of heavier ions, the second damage step occurs at a higher dose with a lower critical elastic strain. Furthermore, larger extended defects were observed in the irradiations of heavy ions at the second damage step. Associated with other experiment results and multistep damage accumulation model, the distinct discrepancies in the damage buildup under irradiations of different ions were interpreted by the effects of electronic excitation, energy of primary knock-on atom and chemistry contributions of deposited ions.

  14. Power-law spectrum and small-world structure emerge from coupled evolution of neuronal activity and synaptic dynamics

    NASA Astrophysics Data System (ADS)

    Zeng, Hong-Li; Zhu, Chen-Ping; Guo, Yan-Dong; Teng, Ao; Jia, Jing; Kong, Hui; Zhou, Rui; Yang, Juan-Ping; Li, Su-Quan

    2015-04-01

    A co-evolutionary neuronal network model based on previous ones is proposed, and both functional and structural properties are numerically calculated. Recent experiments have revealed power-law behavior in electrocorticogram (ECoG) spectrum related with synaptic plasticity and reorganization. In the present neuronal network model, the network starts its evolution from the initial configuration of random network which is the least biased and without special structure, and the interaction rules among neurons are modified from both models by Bornholdt's and Arcangelis' groups to simulate the process of synaptic development and maturation. The system exhibits dynamic small-world structure which is the result of evolution instead of the assumption beforehand. Meanwhile, the power spectrum of electrical signals reproduces the power-law behavior with the exponent 2.0 just as what is experimentally measured in ECoG spectrum. Moreover, the power spectrum of the average degree per neuron over time also exhibits power-law behavior, with the exponent 2.0 again over more than 5 orders of magnitude. Different from previous results, our network exhibits assortative degree-degree correlation which is expected to be checked by experiments.

  15. Features in chemical kinetics. I. Signatures of self-emerging dimensional reduction from a general format of the evolution law

    NASA Astrophysics Data System (ADS)

    Nicolini, Paolo; Frezzato, Diego

    2013-06-01

    Simplification of chemical kinetics description through dimensional reduction is particularly important to achieve an accurate numerical treatment of complex reacting systems, especially when stiff kinetics are considered and a comprehensive picture of the evolving system is required. To this aim several tools have been proposed in the past decades, such as sensitivity analysis, lumping approaches, and exploitation of time scales separation. In addition, there are methods based on the existence of the so-called slow manifolds, which are hyper-surfaces of lower dimension than the one of the whole phase-space and in whose neighborhood the slow evolution occurs after an initial fast transient. On the other hand, all tools contain to some extent a degree of subjectivity which seems to be irremovable. With reference to macroscopic and spatially homogeneous reacting systems under isothermal conditions, in this work we shall adopt a phenomenological approach to let self-emerge the dimensional reduction from the mathematical structure of the evolution law. By transforming the original system of polynomial differential equations, which describes the chemical evolution, into a universal quadratic format, and making a direct inspection of the high-order time-derivatives of the new dynamic variables, we then formulate a conjecture which leads to the concept of an "attractiveness" region in the phase-space where a well-defined state-dependent rate function ω has the simple evolution dot{ω }= - ω ^2 along any trajectory up to the stationary state. This constitutes, by itself, a drastic dimensional reduction from a system of N-dimensional equations (being N the number of chemical species) to a one-dimensional and universal evolution law for such a characteristic rate. Step-by-step numerical inspections on model kinetic schemes are presented. In the companion paper [P. Nicolini and D. Frezzato, J. Chem. Phys. 138, 234102 (2013)], 10.1063/1.4809593 this outcome will be naturally

  16. Estimation of the Past and Future Infrastructure Damage Due the Permafrost Evolution Processes

    NASA Astrophysics Data System (ADS)

    Sergeev, D. O.; Chesnokova, I. V.; Morozova, A. V.

    2015-12-01

    The geocryological processes such as thermokarst, frost heaving and fracturing, icing, thermal erosion are the source of immediate danger for the structures. The economic losses during the construction procedures in the permafrost area are linked also with the other geological processes that have the specific character in cold regions. These processes are swamping, desertification, deflation, flooding, mudflows and landslides. Linear transport structures are most vulnerable component of regional and national economy. Because the high length the transport structures have to cross the landscapes with different permafrost conditions that have the different reaction to climate change. The climate warming is favorable for thermokarst and the frost heaving is linked with climate cooling. In result the structure falls in the circumstances that are not predicted in the construction project. Local engineering problems of structure exploitation lead to global risks of sustainable development of regions. Authors developed the database of geocryological damage cases for the last twelve years at the Russian territory. Spatial data have the attributive table that was filled by the published information from various permafrost conference proceedings. The preliminary GIS-analysis of gathered data showed the widespread territorial distribution of the cases of negative consequences of geocryological processes activity. The information about maximum effect from geocryological processes was validated by detailed field investigation along the railways in Yamal and Transbaicalia Regions. Authors expect the expanding of database by similar data from other sectors of Arctic. It is important for analyzing the regional, time and industrial tendencies of geocryological risk evolution. Obtained information could be used in insurance procedures and in information systems of decisions support in different management levels. The investigation was completed with financial support by Russian

  17. Off-fault damage and acoustic emission distributions during the evolution of structurally complex faults over series of stick-slip events

    NASA Astrophysics Data System (ADS)

    Goebel, T. H. W.; Becker, T. W.; Sammis, C. G.; Dresen, G.; Schorlemmer, D.

    2014-06-01

    Variations in fault structure, for example, surface roughness and deformation zone width, influence the location and dynamics of large earthquakes as well as the distribution of small seismic events. In nature, changes in fault roughness and seismicity characteristics can rarely be studied simultaneously, so that little is known about their interaction and evolution. Here, we investigate the connection between fault structure and near-fault distributions of seismic events over series of stick-slip cycles in the laboratory. We conducted a set of experiments on rough faults that developed from incipient fracture surfaces. We monitored stress and seismic activity which occurred in the form of acoustic emissions (AEs). We determined AE density distributions as a function of fault normal distance based on high-accuracy hypocentre locations during subsequent interslip periods. The characteristics of these distributions were closely connected to different structural units of the faults, that is, the fault core, off-fault and background damage zone. The core deformation zone was characterized by consistently high seismic activity, whereas the off-fault damage zone displayed a power-law decay of seismic activity with increasing distance from the fault core. The exponents of the power-law-distributed off-fault activity increased with successive stick-slip events so that later interslip periods showed a more rapid spatial decay of seismic activity from the fault. The increase in exponents was strongest during the first one to three interslip periods and reached approximately constant values thereafter. The relatively rapid spatial decay of AE events during later interslip periods is likely an expression of decreasing fault zone complexity and roughness. Our results indicate a close relationship between fault structure, stress and seismic off-fault activity. A more extensive mapping of seismic off-fault activity-decay has the potential to significantly advance the

  18. Padova Charter on personal injury and damage under civil-tort law : Medico-legal guidelines on methods of ascertainment and criteria of evaluation.

    PubMed

    Ferrara, Santo Davide; Baccino, Eric; Boscolo-Berto, Rafael; Comandè, Giovanni; Domenici, Ranieri; Hernandez-Cueto, Claudio; Gulmen, Mete Korkut; Mendelson, George; Montisci, Massimo; Norelli, Gian Aristide; Pinchi, Vilma; Ranavaya, Mohammed; Shokry, Dina A; Sterzik, Vera; Vermylen, Yvo; Vieira, Duarte Nuno; Viel, Guido; Zoja, Riccardo

    2016-01-01

    Compensation for personal damage, defined as any pecuniary or non-pecuniary loss causally related to a personal injury under civil-tort law, is strictly based on the local jurisdiction and therefore varies significantly across the world. This manuscript presents the first "International Guidelines on Medico-Legal Methods of Ascertainment and Criteria of Evaluation of Personal Injury and Damage under Civil-Tort Law". This consensus document, which includes a step-by-step illustrated explanation of flow charts articulated in eight sequential steps and a comprehensive description of the ascertainment methodology and the criteria of evaluation, has been developed by an International Working Group composed of juridical and medico-legal experts and adopted as Guidelines by the International Academy of Legal Medicine (IALM). PMID:26342285

  19. A methodology for determining the evolution law of gob permeability and its distributions in longwall coal mines

    NASA Astrophysics Data System (ADS)

    Zhang, Cun; Tu, Shihao; Zhang, Lei; Bai, Qingsheng; Yuan, Yong; Wang, Fangtian

    2016-04-01

    In order to understand the permeability evolution law of the gob by mining disturbances and obtain the permeability distribution of the fully compacted gob, comprehensive methods including theoretical analyses of monitoring data and numerical simulation are used to determine the permeability of gobs in the mining process. Based on current research, three zones of the vertical stress and permeability in the gob are introduced in this article, which are the caving rock mass accumulation zone, the gradually compacted zone and the fully compacted zone. A simple algorithm is written by using FISH language to be imported into the reservoir model. FISH language is an internal programming language in FLAC3D. It is possible to calculate the permeability at each zone with this algorithm in the mining process. Besides, we analyze the gas flow rates from seven gob gas ventholes (GGV) located on a longwall face operated in a mine of a Huainan coalfield in Huainan City, China. Combined with Darcy’s law, a calculation model of permeability around GGV in the gob is proposed. Using this model, the evolution law of permeability in the gob is deduced; the phases of permeability evolution are the decline stage and the stable stage. The result of the vertical stress monitoring data and good fitting effect of the permeability to the experimental data show that the permeability decline caused by the compaction of the gob is the principal reason for the decline stage. The stable stage indicates that the gob has been fully compacted, and the average period of full gob compaction is 47.75 d. The permeability in the middle of the compacted gob is much smaller than the permeability on the edge of the gob which presents an O shape trend. Besides, the little difference among the results of the numerical simulation, the permeability calculation model and other commonly used calculation models validate the correctness of the permeability calculation model and numerical simulation results.

  20. Study on Law of Groundwater Evolution under Natural and Artificial Forcing with Case study of Haihe River Basin

    NASA Astrophysics Data System (ADS)

    You, Jinjun; Gan, Hong; Wang, Lin; Bi, Xue; Du, Sisi

    2010-05-01

    The evolution of groundwater is one of the key problems of water cycle study. It is a result of joint effect of natural condition and human activities, but until now the driving forces of groundwater system evolution were not fully understood due to the complexity of groundwater system structures and the uncertainty of affecting factors. Geology, precipitation and human activity are the main factors affecting the groundwater system evolution and interact each other, but the influence of such three factors on groundwater system are not clarified clearly on a macroscopic scale. The precipitation changes the volume of water recharge and the groundwater pumping effect the discharge of groundwater. Another important factor influencing balance of groundwater storage is the underlaying that affects the renewablility of groundwater. The underlaying is decided mainly by geological attributes but also influenced by human activited. The macroscopic environment of groundwater evolves under the natural and anthropic factors. This paper study the general law of groundwater evolution among the factors based on the case study in Haihe River Basin, a typical area with dramatic groundwater change under natural precipitation attenuation and gradually increase of water suuply. Haihe River Basin is located in north-China, covers an area of 320,041 km2 with over 40% plain areas. The plain area of Haihe Basin is densely populated with many large and medium-sized cities, including metropolis of Beijing and Tianjin, and concentrated irrigated areas, playing important roles in China's economy and food production. It is the unique basin where groundwater occupies majority of total water supply in China. Long-term groundwater over-exploitation causes a series of ecological and environmental problems that threats the sustainable development. In this paper, the historical process of groundwater balance in Haihe Basin is divided into three phases by decrease of rainfall and increase of water

  1. Molecular dynamics study of radiation damage and microstructure evolution of zigzag single-walled carbon nanotubes under carbon ion incidence

    NASA Astrophysics Data System (ADS)

    Li, Huan; Tang, Xiaobin; Chen, Feida; Huang, Hai; Liu, Jian; Chen, Da

    2016-07-01

    The radiation damage and microstructure evolution of different zigzag single-walled carbon nanotubes (SWCNTs) were investigated under incident carbon ion by molecular dynamics (MD) simulations. The radiation damage of SWCNTs under incident carbon ion with energy ranging from 25 eV to 1 keV at 300 K showed many differences at different incident sites, and the defect production increased to the maximum value with the increase in incident ion energy, and slightly decreased but stayed fairly stable within the majority of the energy range. The maximum damage of SWCNTs appeared when the incident ion energy reached 200 eV and the level of damage was directly proportional to incident ion fluence. The radiation damage was also studied at 100 K and 700 K and the defect production decreased distinctly with rising temperature because radiation-induced defects would anneal and recombine by saturating dangling bonds and reconstructing carbon network at the higher temperature. Furthermore, the stability of a large-diameter tube surpassed that of a thin one under the same radiation environments.

  2. Menzerath-Altmann law in mammalian exons reflects the dynamics of gene structure evolution.

    PubMed

    Nikolaou, Christoforos

    2014-12-01

    Genomic sequences exhibit self-organization properties at various hierarchical levels. One such is the gene structure of higher eukaryotes with its complex exon/intron arrangement. Exon sizes and exon numbers in genes have been shown to conform to a law derived from statistical linguistics and formulated by Menzerath and Altmann, according to which the mean size of the constituents of an entity is inversely related to the number of these constituents. We herein perform a detailed analysis of this property in the complete exon set of the mouse genome in correlation to the sequence conservation of each exon and the transcriptional complexity of each gene locus. We show that extensive linear fits, representative of accordance to Menzerath-Altmann law are restricted to a particular subset of genes that are formed by exons under low or intermediate sequence constraints and have a small number of alternative transcripts. Based on this observation we propose a hypothesis for the law of Menzerath-Altmann in mammalian genes being predominantly due to genes that are more versatile in function and thus, more prone to undergo changes in their structure. To this end we demonstrate one test case where gene categories of different functionality also show differences in the extent of conformity to Menzerath-Altmann law. PMID:25155263

  3. Limitations on the Evolution of Quantum Coherences: Towards Fully Quantum Second Laws of Thermodynamics.

    PubMed

    Ćwikliński, Piotr; Studziński, Michał; Horodecki, Michał; Oppenheim, Jonathan

    2015-11-20

    The second law of thermodynamics places a limitation into which states a system can evolve into. For systems in contact with a heat bath, it can be combined with the law of energy conservation, and it says that a system can only evolve into another if the free energy goes down. Recently, it's been shown that there are actually many second laws, and that it is only for large macroscopic systems that they all become equivalent to the ordinary one. These additional second laws also hold for quantum systems, and are, in fact, often more relevant in this regime. They place a restriction on how the probabilities of energy levels can evolve. Here, we consider additional restrictions on how the coherences between energy levels can evolve. Coherences can only go down, and we provide a set of restrictions which limit the extent to which they can be maintained. We find that coherences over energy levels must decay at rates that are suitably adapted to the transition rates between energy levels. We show that the limitations are matched in the case of a single qubit, in which case we obtain the full characterization of state-to-state transformations. For higher dimensions, we conjecture that more severe constraints exist. We also introduce a new class of thermodynamical operations which allow for greater manipulation of coherences and study its power with respect to a class of operations known as thermal operations. PMID:26636834

  4. Limitations on the Evolution of Quantum Coherences: Towards Fully Quantum Second Laws of Thermodynamics

    NASA Astrophysics Data System (ADS)

    Ćwikliński, Piotr; Studziński, Michał; Horodecki, Michał; Oppenheim, Jonathan

    2015-11-01

    The second law of thermodynamics places a limitation into which states a system can evolve into. For systems in contact with a heat bath, it can be combined with the law of energy conservation, and it says that a system can only evolve into another if the free energy goes down. Recently, it's been shown that there are actually many second laws, and that it is only for large macroscopic systems that they all become equivalent to the ordinary one. These additional second laws also hold for quantum systems, and are, in fact, often more relevant in this regime. They place a restriction on how the probabilities of energy levels can evolve. Here, we consider additional restrictions on how the coherences between energy levels can evolve. Coherences can only go down, and we provide a set of restrictions which limit the extent to which they can be maintained. We find that coherences over energy levels must decay at rates that are suitably adapted to the transition rates between energy levels. We show that the limitations are matched in the case of a single qubit, in which case we obtain the full characterization of state-to-state transformations. For higher dimensions, we conjecture that more severe constraints exist. We also introduce a new class of thermodynamical operations which allow for greater manipulation of coherences and study its power with respect to a class of operations known as thermal operations.

  5. Evolution and Convergence of State Laws Governing Controlled Substance Prescription Monitoring Programs, 1998-2011

    PubMed Central

    Pierce, Matthew; Dasgupta, Nabarun

    2014-01-01

    Objectives. We sought to collect and characterize all laws governing the operation of prescription monitoring programs (PMPs), state-level databases that collect patient-specific prescription information, which have been suggested as a tool for reducing prescription drug overdose fatalities. Methods. We utilized a structured legal research protocol to systematically identify, review, and code all PMP statutes and regulations effective from 1998 through 2011. These laws were then abstracted along eleven domains, including reporting provisions, data sharing, and data access. Results. PMP characteristics vary greatly among states and across time. We observed an increase in the types and frequency of data required to be reported, the types of individuals permitted to access PMP data, and the percentage of PMPs authorized to proactively identify outlier prescribers and patients. As of 2011, 10 states required PMPs to report suspicious activity to law enforcement, while only 3 required reporting to the patient’s physician. None required linkage to drug treatment or required all prescribers to review PMP data before prescribing. Few explicitly address data retention. Conclusions. State PMP laws are heterogeneous and evolving. Future studies of PMP effectiveness should take these variations into account. PMID:24922132

  6. The effect of stress rate on crack damage evolution in polystyrene and PEEK. Ph.D. Thesis

    SciTech Connect

    Gregory, B.L.

    1993-01-01

    The effects of stress rate on fatigue crack propagation (FCP) in polystyrene (PS) and polyetheretherketone (PEEK) were examined emphasizing damage evolution during fatigue fracture. Extruded and compression molded PS were studied. Craze distributions along trailing edges of successive process zone configurations in each material were self-similar. A core of dense crazing was observed in the extruded PS; no core was observed in the compression molded material. These results have important implications for the kinematics of process zone evolution in compression molded PS. Crack growth kinetics were treated as dl/dn and dl/dt. Consideration of the loading waveform and the load-time-area (LTA) revealed that LTA and rate effects couldn`t be decoupled. However, by treating the data as dl/dt the contribution of LTA constant, and the effect of stress rate was determined. Attempts were made to quantify the contributions of fatigue and creep LTA on total FCP kinetics by linear summation. While these failed, it was subsequently determined that two linear regimes separated by a characteristic period could approximate the data. The contributions of both stress rate and LTA varied above and below this characteristic period. From this analysis, the contributions of time and cycle reversal could be evaluated. Crack growth due to creep exhibited strong correlation with an exponential function compatible with stress-temperature activated processes. The crack damage evolution of PEEK as a function of stress rate during fatigue was also investigated. A brittle-ductile transition was observed characterized by a transformation at the crack tip from a rounded to a triangular (90 deg angle) crack front. The results showed that the damaged material ahead of the crack tip behaved as an elastic perfectly plastic material (plane stress conditions). This damage zone was further characterized as a volume of transformed material.

  7. Culture and the Constructal-Law evolution of the human and machine species. Comment on “An evolutionary framework for cultural change: Selectionism versus communal exchange” by L. Gabora

    NASA Astrophysics Data System (ADS)

    Bejan, Adrian

    2013-06-01

    Culture and the evolution of culture are manifestations of the physics phenomenon of design generation and evolution. The constructal law is the law of physics of the “design” phenomena in nature, including the evolution of culture. The evolutionary phenomena of creativity, science, technology, networks, hierarchy and communal exchange are features of the constructal design of nature.

  8. Penetration and induced damage evolution of concrete and granite when subjected to multiple projectile impacts

    NASA Astrophysics Data System (ADS)

    Gomez, Jason Thomas

    An experimental study was conducted to investigate the penetration process of multiple impacts into concrete targets. The concrete targets were subjected to repeated constant velocity impacts with an ogive nose projectile. The penetration and crater formation data were consistent with single impact penetration data from previous studies conducted at Sandia National Laboratories. In order to predict the depth of the multiple impact penetration, a single impact penetration model, developed by M. Forrestal at Sandia National Laboratories, was extended to account for the degradation of the target strength with each subsequent impact. The degradation of the target was determined empirically and included in the model as a strength-modifying factor. To further understand the multiple impact penetration process, a study was conducted to look at both the static and dynamic properties of concrete and granite as a function of induced damage. Both static and dynamic compression experiments were performed on concrete and granite specimens with various levels of induced damage. The static compressive strength of both materials decreased with increasing levels of damage due to the induced damage causing the activation and propagation of failure cracks in the specimens. In contrast, the dynamic compressive strength remained unchanged with increasing damage due to the inability of the fracture process zone to develop and relieve the strain energy before complete specimen failure. A series of dynamic and static tensile-splitting experiments were performed on concrete and granite specimens to investigate the effect of induced damage on their tensile strength. The experiments showed that the static splitting strength was highly dependent on the orientation of the induced damage with regard to the applied loading, however the dynamic tensile strength decreased with increasing damage with no apparent dependency on the random damage orientation. Photoelastic experiments have shown that

  9. Tracking composite material damage evolution using Bayesian filtering and flash thermography data

    NASA Astrophysics Data System (ADS)

    Gregory, Elizabeth D.; Holland, Steve D.

    2016-05-01

    We propose a method for tracking the condition of a composite part using Bayesian filtering of ash thermography data over the lifetime of the part. In this demonstration, composite panels were fabricated; impacted to induce subsurface delaminations; and loaded in compression over multiple time steps, causing the delaminations to grow in size. Flash thermography data was collected between each damage event to serve as a time history of the part. The ash thermography indicated some areas of damage but provided little additional information as to the exact nature or depth of the damage. Computed tomography (CT) data was also collected after each damage event and provided a high resolution volume model of damage that acted as truth. After each cycle, the condition estimate, from the ash thermography data and the Bayesian filter, was compared to 'ground truth'. The Bayesian process builds on the lifetime history of ash thermography scans and can give better estimates of material condition as compared to the most recent scan alone, which is common practice in the aerospace industry. Bayesian inference provides probabilistic estimates of damage condition that are updated as each new set of data becomes available. The method was tested on simulated data and then on an experimental data set.

  10. Numerical simulation of the damage evolution in the pelvic floor muscles during childbirth.

    PubMed

    Oliveira, Dulce A; Parente, Marco P L; Calvo, Begoña; Mascarenhas, Teresa; Natal Jorge, Renato M

    2016-02-29

    Several studies have shown that pelvic floor injuries during a vaginal delivery can be considered a significant factor in the development of pelvic floor dysfunction. Such disorders include a group of conditions affecting women like urinary incontinence, pelvic organ prolapse and fecal incontinence. Numerical simulations are valuable tools that are contributing to the clarification of the mechanisms behind pelvic floor disorders. The aim of this work is to propose a mechanical model implemented in the finite element method context to estimate the damage in the pelvic floor muscles by mechanical effects during a vaginal delivery of a fetus in vertex presentation and occipitoanterior position. The constitutive model adopted has already been successfully used in the simulation of childbirth and the structural damage model added has previously been applied to characterize the damage process in biological soft tissues undergoing finite deformations. The constitutive parameters were fit to experimental data available in the literature and the final proposed material model is suitable to estimate the mechanical damage in the pelvic floor muscle during a vaginal delivery. The computational model predicts that even an apparently uneventful vaginal delivery inflicts injuries to the pelvic floor muscles, particularly during the extension of the fetus head, having been obtained more than 10% of damaged fibers. As a clinical evidence, the present work allows to conclude that the puborectalis component of the levator ani muscle is the most prone to damage. PMID:26895779

  11. Investigation of surface characteristics evolution and laser damage performance of fused silica during ion-beam sputtering

    NASA Astrophysics Data System (ADS)

    Xu, Mingjin; Dai, Yifan; Zhou, Lin; Shi, Feng; Wan, Wen; Xie, Xuhui; Sui, Tingting

    2016-08-01

    Surface characteristics have great influence on the optical properties especially the laser radiation resistivity of optics. In this paper, the surface characteristics evolutions of fused silica during ion-beam sputtering and their effects on the laser damage performance were investigated. The results show that roughness change is strongly removal depth dependent and a super-smooth surface (0.25 nm RMS) can be obtained by the ion-induced smoothing effect. The concentration of metal impurities (especially Ce element) in subsurface can be effectively decreased after the removal of polishing re-deposition layer. During ion-beam sputtering process, the plastic scratches can be removed while the brittle cracks can be broadened and passivated without increase in the depth direction. Laser damage threshold of fused silica improved by 36% after ion-beam sputtering treatment. Research results have a guiding significance for ion-beam sputtering process technology of fused silica optics.

  12. Coda Wave Interferometry Method Applied in Structural Monitoring to Assess Damage Evolution in Masonry and Concrete Structures

    NASA Astrophysics Data System (ADS)

    Masera, D.; Bocca, P.; Grazzini, A.

    2011-07-01

    In this experimental program the main goal is to monitor the damage evolution in masonry and concrete structures by Acoustic Emission (AE) signal analysis applying a well-know seismic method. For this reason the concept of the coda wave interferometry is applied to AE signal recorded during the tests. Acoustic Emission (AE) are very effective non-destructive techniques applied to identify micro and macro-defects and their temporal evolution in several materials. This technique permits to estimate the velocity of ultrasound waves propagation and the amount of energy released during fracture propagation to obtain information on the criticality of the ongoing process. By means of AE monitoring, an experimental analysis on a set of reinforced masonry walls under variable amplitude loading and strengthening reinforced concrete (RC) beams under monotonic static load has been carried out. In the reinforced masonry wall, cyclic fatigue stress has been applied to accelerate the static creep and to forecast the corresponding creep behaviour of masonry under static long-time loading. During the tests, the evaluation of fracture growth is monitored by coda wave interferometry which represents a novel approach in structural monitoring based on AE relative change velocity of coda signal. In general, the sensitivity of coda waves has been used to estimate velocity changes in fault zones, in volcanoes, in a mining environment, and in ultrasound experiments. This method uses multiple scattered waves, which travelled through the material along numerous paths, to infer tiny temporal changes in the wave velocity. The applied method has the potential to be used as a "damage-gauge" for monitoring velocity changes as a sign of damage evolution into masonry and concrete structures.

  13. A coarse-grained model of thermally activated damage in heterogeneous media: Time evolution of the creep rate

    NASA Astrophysics Data System (ADS)

    Baxevanis, Th.

    2008-08-01

    A coarse-grained mean-field model is proposed where the damage enhanced creep of heterogeneous materials is described by the theory of absolute reaction rates. The dynamics of the proposed model, below a critical load, is characterized by an intensive precursor activity in the form of avalanches of microscopic breaking events that leads to a final catastrophic cascade occurring at a finite strain. Above the critical load, failure is instantaneous. The critical load is the static (elastic) fracture strength; thus the model is consistent with its time-independent analogue. Finally, the proposed model reproduces the experimental observations on the time evolution of the creep rate.

  14. Space Law

    NASA Astrophysics Data System (ADS)

    Hermida, Julian

    2006-01-01

    This chapter examines the salient characteristics of Space Law. It analyzes the origins and evolution of Space Law, its main international principles, and some current topics of interest to the scientific community: the delimitation of airspace and outer space, intellectual property, and criminal responsibility.

  15. Helicopter rotor blade frequency evolution with damage growth and signal processing

    NASA Astrophysics Data System (ADS)

    Roy, Niranjan; Ganguli, Ranjan

    2005-05-01

    Structural damage in materials evolves over time due to growth of fatigue cracks in homogenous materials and a complicated process of matrix cracking, delamination, fiber breakage and fiber matrix debonding in composite materials. In this study, a finite element model of the helicopter rotor blade is used to analyze the effect of damage growth on the modal frequencies in a qualitative manner. Phenomenological models of material degradation for homogenous and composite materials are used. Results show that damage can be detected by monitoring changes in lower as well as higher mode flap (out-of-plane bending), lag (in-plane bending) and torsion rotating frequencies, especially for composite materials where the onset of the last stage of damage of fiber breakage is most critical. Curve fits are also proposed for mathematical modeling of the relationship between rotating frequencies and cycles. Finally, since operational data are noisy and also contaminated with outliers, denoising algorithms based on recursive median filters and radial basis function neural networks and wavelets are studied and compared with a moving average filter using simulated data for improved health-monitoring application. A novel recursive median filter is designed using integer programming through genetic algorithm and is found to have comparable performance to neural networks with much less complexity and is better than wavelet denoising for outlier removal. This filter is proposed as a tool for denoising time series of damage indicators.

  16. Evolution of damage and plasticity in titanium-based, fiber-reinforced composites

    SciTech Connect

    Majumdar, B.S. ); Newaz, G.M. ); Ellis, J.R. . Fatigue and Failure Branch)

    1993-07-01

    The inelastic deformation mechanisms were evaluated for a model titanium-based, fiber-reinforced composite: a beta titanium alloy (Ti-15V-3Al-3Cr-3Sn) reinforced with SiC (SCS-6) fibers. The primary emphasis of this article is to illustrate the sequence in which damage and plasticity evolved for this system. The mechanical responses and the results of detailed microstructural evaluations for the [0][sub 8], [90][sub 8], and [[plus minus]45][sub 2s] laminates are provided. It is shown that the characteristics of the reaction zone around the fiber play a very important role in the way damage and plasticity evolve, particularly in the microyield regime of deformation, and must be included in any realistic constitutive model. Fiber-matrix debonding was a major damage mode for the off-axis systems. The tension test results are also compared with the predictions of a few constitutive models.

  17. Evolution of damage and plasticity in titanium-based, fiber-reinforced composites

    NASA Technical Reports Server (NTRS)

    Majumdar, B. S.; Newaz, G. M.; Ellis, J. R.

    1993-01-01

    The inelastic deformation mechanisms were evaluated for a model titanium-based, fiber-reinforced composite: a beta titanium alloy (Ti-15V-3Al-3Cr-3Sn) reinforced with SiC (SCS-6) fibers. The primary emphasis of this article is to illustrate the sequence in which damage and plasticity evolved for this system. The mechanical responses and the results of detailed microstructural evaluations for the 0(8), 90(8), and +/- 45(2s) line oriented laminates are provided. It is shown that the characteristics of the reaction zone around the fiber play a very important role in the way damage and plasticity evolve, particularly in the microyield regime of deformation, and must be included in any realistic constitutive model. Fiber-matrix debonding was a major damage mode for the off-axis systems. The tension test results are also compared with the predictions of a few constitutive models.

  18. From Migmatites to Plutons: Power Law Relationships in the Evolution of Magmatic Bodies

    NASA Astrophysics Data System (ADS)

    Soesoo, Alvar; Bons, Paul D.

    2015-07-01

    Magma is generated by partial melting from micrometre-scale droplets at the source and may accumulate to form >100 km-scale plutons. Magma accumulation thus spans well over ten orders of magnitude in scale. Here we provide measurements of migmatitic leucosomes and granitic veins in drill cores from the Estonian Proterozoic basement and outcrops at Masku in SW Finland and Montemor-o-Novo, central Portugal. Despite the differences in size and number of measured leucosomes and magmatic veins, differences in host rock types and metamorphic grades, the cumulative width distribution of the studied magmatic leucosomes/veins follows a power law with exponents usually between 0.7 and 1.8. Published maps of the SE Australian Lachlan Fold Belt were used to investigate the distribution of granitoid pluton sizes. The granites occupy ca. 22 % of the 2.6 × 105 km2 area. The cumulative pluton area distributions show good power law distributions with exponents between 0.6 and 0.8 depending on pluton area group. Using the self-affine nature of pluton shapes, it is possible to estimate the total volume of magma that was expelled from the source in the 2.6 × 105 km2 map area, giving an estimated 0.8 km3 of magma per km2. It has been suggested in the literature that magma batches in the source merge to form ever-bigger batches in a self-organized way. This leads to a power law for the cumulative distribution of magma volumes, with an exponent m V between 1 for inefficient melt extraction, and 2/3 for maximum accumulation efficiency as most of the volume resides in the largest batches that can escape from the source. If m V ≥ 1, the mass of the magma is dominated by small batches; in case m = 2/3, about 50 % of all magma in the system is placed in a single largest batch. Our observations support the model that the crust develops a self-organized critical state during magma generation. In this state, magma batches accumulate in a non-continuous, step-wise manner to form ever

  19. Topographic signatures and a general transport law for deep-seated landslides in a landscape evolution model

    NASA Astrophysics Data System (ADS)

    Booth, Adam M.; Roering, Josh J.; Rempel, Alan W.

    2013-06-01

    A fundamental goal of studying earth surface processes is to disentangle the complex web of interactions among baselevel, tectonics, climate, and rock properties that generate characteristic landforms. Mechanistic geomorphic transport laws can quantitatively address this goal, but no widely accepted law for landslides exists. Here we propose a transport law for deep-seated landslides in weathered bedrock and demonstrate its utility using a two-dimensional numerical landscape evolution model informed by study areas in the Waipaoa catchment, New Zealand, and the Eel River catchment, California. We define a non-dimensional landslide number, which is the ratio of the horizontal landslide flux to the vertical tectonic flux, that characterizes three distinct landscape types. One is dominated by stochastic landsliding, whereby discrete landslide events episodically erode material at rates exceeding the long-term uplift rate. Another is characterized by steady landsliding, in which the landslide flux at any location remains constant through time and is greatest at the steepest locations in the catchment. The third is not significantly affected by landsliding. In both the "stochastic landsliding" and "steady landsliding" regimes, increases in the non-dimensional landslide number systematically reduce catchment relief and widen valley spacing, producing long, low angle hillslopes despite high uplift rates. The stochastic landsliding regime captures the frequent observation that deep-seated landslides produce large sediment fluxes from small areal extents while being active only a fraction of the time. We suggest that this model is adaptable to a wide range of geologic settings and is useful for interpreting climate-driven changes in landslide behavior.

  20. Evolution of blood-brain barrier damage associated with changes in brain metabolites following acute ischemia.

    PubMed

    Yan, Gen; Xuan, Yinghua; Dai, Zhuozhi; Zhang, Guishan; Xu, Haiyun; Mikulis, David; Wu, Renhua

    2015-11-11

    Stroke is a serious medical condition that requires emergency care. In the case of ischemic stroke, ischemia may lead to damage to the blood-brain barrier (BBB); the damage in turn may exacerbate the condition. Therefore, noninvasive detection of BBB damage represents a challenge for experimental and clinical researchers. In this study, we assessed the onset of BBB disruption by means of T1-weighted images with administration of the contrast enhancement agent gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) and related BBB breakdown to brain metabolite changes in proton magnetic resonance spectrum (H-MRS) in the infarcted site following middle cerebral artery occlusion (MCAO) in rats. It was shown that MCAO for 30 min and 1.5 h caused no Gd-DTPA signal change in the T1-weighted images, whereas MCAO for 1 h significantly altered some of H-MRS brain metabolites, suggesting that brain metabolite changes occurred earlier than BBB damage after ischemic stroke. MCAO for 2 h caused BBB breakdown, which was related to changes in the levels of some brain metabolites detected by H-MRS. Between the second and the third hour after MCAO, brain metabolite changes continued as the result of BBB breakdown and the concurrent overperfusion to the infarcted site, which may ameliorate the metabolite changes, thus compensating for the functional failures of the brain after stroke. PMID:26366833

  1. Permeability of natural rock salt from the Waste Isolation Pilot Plant (WIPP) during damage evolution and healing

    SciTech Connect

    Pfeifle, T.W.

    1998-06-01

    The US Department of Energy has developed the Waste Isolation Pilot Plant (WIPP) in the bedded salt of southeastern New Mexico to demonstrate the safe disposal of radioactive transuranic wastes. Four vertical shafts provide access to the underground workings located at a depth of about 660 meters. These shafts connect the underground facility to the surface and potentially provide communication between lithologic units, so they will be sealed to limit both the release of hazardous waste from and fluid flow into the repository. The seal design must consider the potential for fluid flow through a disturbed rock zone (DRZ) that develops in the salt near the shafts. The DRZ, which forms initially during excavation and then evolves with time, is expected to have higher permeability than the native salt. The closure of the shaft openings (i.e., through salt creep) will compress the seals, thereby inducing a compressive back-stress on the DRZ. This back-stress is expected to arrest the evolution of the DRZ, and with time will promote healing of damage. This paper presents laboratory data from tertiary creep and hydrostatic compression tests designed to characterize damage evolution and healing in WIPP salt. Healing is quantified in terms of permanent reduction in permeability, and the data are used to estimate healing times based on considerations of first-order kinetics.

  2. Toward a mechanistic understanding of the damage evolution of SnAgCu solder joints in accelerated thermal cycling test

    NASA Astrophysics Data System (ADS)

    Mahin Shirazi, Sam

    Accelerated thermal cycling (ATC) tests are the most commonly used tests for the thermo-mechanical performance assessment of microelectronics assemblies. Currently used reliability models have failed to incorporate the microstructural dependency of lead free solder joint behavior and its microstructure evolution during cycling. Thus, it is essential to have a mechanistic understanding of the effect of cycling parameters on damage evolution and failure of lead free solder joints in ATC. Recrystallization has been identified as the damage rate controlling mechanism in ATC. Usually it takes 1/3 of life for completion of recrystallization regardless of cycling parameters. Thus, the life of the solder joints can be predicted by estimating global recrystallization. The objective of the first part of the study was to examine whether the damage scenario applies in service is the same as the harsh thermal cycling tests (i.e. 0/100 °C and -40/125 °C) commonly used in industry. Microstructure analysis results on a variety of lead free solder SnAgCu assemblies subjected to the both harsh (0/100 °C) and mild (20/80 °C) ATC confirmed similar failure mechanism under the both testing conditions. Sn grain morphology (interlaced versus beach ball) has a significant effect on the thermo-mechanical performance (and thus the model) of the lead free solder joints. The longer thermal cycling lifetime observed in the interlaced solder joints subjected to the ATC compared to the beach ball structure was correlated to the different initial microstructure and the microstructure evolution during cycling. For the modeling proposes, the present study was focused on Sn-Ag-Cu solder joints with either a single Sn grain or beach ball structure. Microstructural analysis results of the simulated thermal cycling experiment revealed that, the life can be approximated as determined by the accumulation of a certain amount of work during the high temperature dwells. Finally the effect of precipitates

  3. Deformation failure characteristics of coal body and mining induced stress evolution law.

    PubMed

    Wen, Zhijie; Qu, Guanglong; Wen, Jinhao; Shi, Yongkui; Jia, Chuanyang

    2014-01-01

    The results of the interaction between coal failure and mining pressure field evolution during mining are presented. Not only the mechanical model of stope and its relative structure division, but also the failure and behavior characteristic of coal body under different mining stages are built and demonstrated. Namely, the breaking arch and stress arch which influence the mining area are quantified calculated. A systematic method of stress field distribution is worked out. All this indicates that the pore distribution of coal body with different compressed volume has fractal character; it appears to be the linear relationship between propagation range of internal stress field and compressed volume of coal body and nonlinear relationship between the range of outburst coal mass and the number of pores which is influenced by mining pressure. The results provide theory reference for the research on the range of mining-induced stress and broken coal wall. PMID:24967438

  4. Deformation Failure Characteristics of Coal Body and Mining Induced Stress Evolution Law

    PubMed Central

    Wen, Zhijie; Wen, Jinhao; Shi, Yongkui; Jia, Chuanyang

    2014-01-01

    The results of the interaction between coal failure and mining pressure field evolution during mining are presented. Not only the mechanical model of stope and its relative structure division, but also the failure and behavior characteristic of coal body under different mining stages are built and demonstrated. Namely, the breaking arch and stress arch which influence the mining area are quantified calculated. A systematic method of stress field distribution is worked out. All this indicates that the pore distribution of coal body with different compressed volume has fractal character; it appears to be the linear relationship between propagation range of internal stress field and compressed volume of coal body and nonlinear relationship between the range of outburst coal mass and the number of pores which is influenced by mining pressure. The results provide theory reference for the research on the range of mining-induced stress and broken coal wall. PMID:24967438

  5. Analysis of the correlation between n-value and critical current in bent multifilamentary Bi2223 composite tape based on a damage evolution model

    NASA Astrophysics Data System (ADS)

    Ochiai, S.; Okuda, H.; Fujimoto, M.; Shin, J.-K.; Sugano, M.; Hojo, M.; Osamura, K.; Oh, S. S.; Ha, D. W.

    2012-05-01

    The change in n-value and critical current with bending strain and the relation of n-value to critical current of bending-damaged Bi2223 composite tape were studied experimentally and analytically. The n-value of the bending-damaged Bi2223 filamentary composite tape decreased very slightly with increasing bending strain and with decreasing critical current, in comparison with that of tension-damaged tape. To describe the experimental result for bending-damaged tape, a damage evolution model was applied in which the steep tensile-strain variation in the thickness direction, the shape of the core into which the superconducting filaments are bundled and the damage strain parameters obtained from the analysis of the tensile stress-strain curve were incorporated. The measured change in n-value and critical current with bending strain and the relation of n-value to critical current under applied bending strain were described satisfactorily by the present approach.

  6. Perinatal hypoxic-ischemic brain damage: evolution of an animal model.

    PubMed

    Vannucci, Robert C; Vannucci, Susan J

    2005-01-01

    Early research in the Vannucci laboratory prior to 1981 focused largely on brain energy metabolism in the developing rat. At that time, there was no experimental model to study the effects of perinatal hypoxia-ischemia in the rodent, despite the tremendous need to investigate the pathophysiology of perinatal asphyxial brain damage in infants. Accordingly, we developed such a model in the postnatal day 7 rat, using a modification of the Levine preparation in the adult rat. Rat pups underwent unilateral common carotid artery ligation followed by exposure to systemic hypoxia (8% oxygen) at a constant temperature of 37 degrees C. Brain damage, seen histologically, was generally confined to the cerebral hemisphere ipsilateral to the arterial occlusion, and consisted of selective neuronal death or infarction, depending on the duration of the systemic hypoxia. Tissue injury was observed in the cerebral cortex, hippocampus, striatum, and thalamus. Subcortical and periventricular white matter injury was also observed. This model was originally described in the Annals of Neurology in 1981, and during the more than 20 years since that publication numerous investigations utilizing the model have been conducted in our laboratories as well as laboratories around the world. Cerebral blood flow and metabolic correlates have been fully characterized. Physiologic and pharmacologic manipulations have been applied to the model in search of neuroprotective strategies. More recently, molecular biologic alterations during and following the hypoxic-ischemic stress have been ascertained and the model has been adapted to the immature mouse for specific use in genetically altered animals. As predicted in the original article, the model has proven useful for the study of the short- and long-term effects of hypoxic-ischemic brain damage on motor activity, behavior, seizure incidence, and the process of maturation in the brain and other organ systems. PMID:16046840

  7. Damage evolution in acetabular replacements under long-term physiological loading conditions.

    PubMed

    Wang, J-Y; Heaton-Adegbile, P; New, A; Hussell, J G; Tong, J

    2009-05-29

    Damage development in cemented acetabular replacements has been studied in bovine pelvic bones under long-term physiological loading conditions, including normal walking, stair climbing and a combined block loading with representative routine activities. The physiological loading conditions were achieved using a specially designed hip simulator for fixation endurance testing. Damage was detected and monitored using micro-CT scanning at regular intervals of the experiments, and verified by microscopic studies post testing. The results show that debonding at the bone-cement interface defined the failure of cement fixation in all cases, and debondings initiated near the dome of the acetabulum in the superior-posterior quadrant, consistent with the high-stress region identified from the finite element analysis of implanted acetabular models Zant, N.P., Heaton-Adegbile, P., Hussell, J.G., Tong, J., 2008b. In-vitro fatigue failure of cemented acetabular replacements-a hip simulator study. Journal of Biomechanical Engineering, Transactions of the ASME, 130, 021019-1-9]; [Tong, J., Zant, N.P., Wang, J-Y., Heaton-Adegbile, P., Hussell, J.G., 2008. Fatigue in cemented acetabulum. International Journal of Fatigue, 30(8), 1366-1375]. PMID:19345357

  8. Dictyostelium discoideum, a lower eukaryote model for the study of DNA repair: Implications for the role of DNA-damaging chemicals in the evolution of repair proficient cells

    NASA Astrophysics Data System (ADS)

    Deering, R. A.

    1994-10-01

    The evolution of the ability of living cells to cope with stress is crucial for the maintenance of their genetic integrity. Yet low levels of mutation must remain to allow adaptation to environmental changes. The cellular slime mold D. discoideum is a good system for studying molecular aspects of the repair of lethal and mutagenic damage to DNA by radiation and chemicals. The wild-type strains of this soil microorganism are extremely resistant to DNA damaging agents. In nature the amoeboid cells in their replicative stage feed on soil bacteria and are exposed to numerous DNA-damaging chemicals produced by various soil microorganisms. It is probable that the evolution of repair systems in this organism and perhaps in others is a consequence of the necessity to cope with chemical damage which also confers resistance to radiation.

  9. Dictyostelium discoideum, a lower eukaryote model for the study of DNA repair: implications for the role of DNA-damaging chemicals in the evolution of repair proficient cells.

    PubMed

    Deering, R A

    1994-10-01

    The evolution of the ability of living cells to cope with stress is crucial for the maintenance of their genetic integrity. Yet low levels of mutation must remain to allow adaptation to environmental changes. The cellular slime mold D. discoideum is a good system for studying molecular aspects of the repair of lethal and mutagenic damage to DNA by radiation and chemicals. The wild-type strains of this soil microorganism are extremely resistant to DNA damaging agents. In nature the amoeboid cells in their replicative stage feed on soil bacteria and are exposed to numerous DNA-damaging chemicals produced by various soil microorganisms. It is probable that the evolution of repair systems in this organism and perhaps in others is a consequence of the necessity to cope with chemical damage which also confers resistance to radiation. PMID:11539974

  10. The effects of shockwave profile shape and shock obliquity on spallation in Cu and Ta: kinetic and stress-state effects on damage evolution(u)

    SciTech Connect

    Gray, George T

    2010-12-14

    Widespread research over the past five decades has provided a wealth of experimental data and insight concerning shock hardening and the spallation response of materials subjected to square-topped shock-wave loading profiles. Less quantitative data have been gathered on the effect of direct, in-contact, high explosive (HE)-driven Taylor wave (or triangular-wave) loading profile shock loading on the shock hardening, damage evolution, or spallation response of materials. Explosive loading induces an impulse dubbed a 'Taylor Wave'. This is a significantly different loading history than that achieved by a square-topped impulse in terms of both the pulse duration at a fixed peak pressure, and a different unloading strain rate from the peak Hugoniot state achieved. The goal of this research is to quantify the influence of shockwave obliquity on the spallation response of copper and tantalum by subjecting plates of each material to HE-driven sweeping detonation-wave loading and quantify both the wave propagation and the post-mortem damage evolution. This talk will summarize our current understanding of damage evolution during sweeping detonation-wave spallation loading in Cu and Ta and show comparisons to modeling simulations. The spallation responses of Cu and Ta are both shown to be critically dependent on the shockwave profile and the stress-state of the shock. Based on variations in the specifics of the shock drive (pulse shape, peak stress, shock obliquity) and sample geometry in Cu and Ta, 'spall strength' varies by over a factor of two and the details of the mechanisms of the damage evolution is seen to vary. Simplistic models of spallation, such as P{sub min} based on 1-D square-top shock data lack the physics to capture the influence of kinetics on damage evolution such as that operative during sweeping detonation loading. Such considerations are important for the development of predictive models of damage evolution and spallation in metals and alloys.

  11. Slip, Crystal Orientation, and Damage Evolution During Thermal Cycling in High-Strain Wafer-Level Chip-Scale Packages

    NASA Astrophysics Data System (ADS)

    Zhou, Bite; Zhou, Quan; Bieler, Thomas R.; Lee, Tae-kyu

    2015-03-01

    Wafer-level chip-scale package samples with pre-cross-sectioned edge rows were thermally cycled to study microstructure evolution and damage development. Electron backscattered diffraction (EBSD) and high-energy x-ray diffraction were used to obtain Sn grain orientations and the average coefficient of thermal expansion normal to the board in every joint of the package for samples in the as-fabricated and thermally cycled conditions. The results indicated a near-random distribution of joint orientation. Optical, scanning electron microscopy, and EBSD methods were used to characterize microstructure changes in pre-cross-sectioned samples due to thermal cycling. Slip trace analysis and Orientation Imaging Microscopy™ (OIM) show that slip systems with high Schmid factors (estimated global shear stress based on the package neutral point) are responsible for the observed microstructure evolution during thermal cycling, which provides information about slip systems that are more easily activated. Two joints were analyzed in detail to evaluate slip activity at different stages of their thermal history. The first case showed that a solidification twin grain boundary misorientation deviated from the twin relationship due to slip activity during thermal cycling, which can influence damage development and the path of crack propagation. The second case showed a new grain orientation developing due to gradual lattice rotation about the Sn [110] axis by a continuous recrystallization mechanism. This rotation was correlated with the operation of slip system . Small tin whiskers emerged from the initially polished chip interface and grew with increasing thermal cycles until a crack developed in the solder that relieved the stress. As the local stresses are not known experimentally, this analysis provides observations that can be compared with a crystal plasticity model simulation.

  12. On the correlation between primary damage and long-term nanostructural evolution in iron under irradiation

    NASA Astrophysics Data System (ADS)

    Souidi, A.; Hou, M.; Becquart, C. S.; Malerba, L.; Domain, C.; Stoller, R. E.

    2011-12-01

    Atomic displacement cascades in solids are complex phenomena, the outcome of which can be statistically characterised by properties such as their spatial extent, morphology and the spatial correlation of defects. Some properties scale in a simple way with parameters such as the cascade energy, others have limited variability with energy, for example point defect cluster size distributions. Taking advantage of the latter invariance, we use object kinetic Monte Carlo simulations to demonstrate that most properties of displacement cascade play no significant role in the evolution of point defect cluster size distributions after long enough time. It is suggested that reliable long-term predictions are possible, when using only the self-interstitial and vacancy cluster size distributions from low energy displacement cascades as building blocks to represent the complete spectrum of cascade energies obtained under neutron irradiation conditions. This is shown on the basis of recursive properties of displacement cascades evidenced for the first time and taking only approximately into account the average volumes in which vacancies and self-interstitial atoms are confined. The model has been successfully used to simulate the evolution of point defect clusters in iron for displacement rates in the range of 10 -6 dpa/s and doses of the order of 0.1 dpa. The applicability beyond this range and to more complex materials is discussed.

  13. Creep in Thermally Cracked Granite: Physical, Mechanical and Damage Properties Evolution

    NASA Astrophysics Data System (ADS)

    Wang, X.; Schubnel, A. J.; Fortin, J.; Gueguen, Y.; Ge, H.

    2011-12-01

    We investigate the effects of pervasive crack damage on the rupture processes of a fine-grained granite, under triaxial stress, in wet (H20) and dry (argon gas) saturated conditions, at room temperature. Eight samples of La Peyratte granite (a granodiorite with an average grain size of 200 microns) were cored with an initial porosity of <1%. Damage was introduced by heating four samples up to 700°C. These were then compared to the intact granite specimens. 4 samples were deformed at a constant strain rate of 2x10-6/s until brittle failure occurred. 4 other samples were deformed in creep conditions. During these 8 experiments, at each step, we recorded strains, elastic wave velocities and Acoustic Emissions (AE). Our main results are: 1. The brittle strength of the sample remained unchanged (approx. 500MPa deviatoric stress at 30MPa effective pressure), whether the sample was heat-treated or not. We did not observe any significant water weakening as well. However, the onset of dilatancy was observed at lower deviatoric stress in the heat-treated specimen than for the intact ones. 2. Acoustic emissions revealed useful in order to image the rupture processes. Indeed, AE locations and Focal mechanism were in good agreement with the post mortem analysis of sample. In intact specimen, failure occurred after a larger premonitory AE activity, while heat-treated specimen had a longer aftershocks activity. In creep conditions, we show that extreme damage localization is already initiated during the primary and secondary creep phases. 3. However, in all our experiments, we observed the development of an elastic fabric well before the onset of rupture. To be more precise, measuring the P wave velocities along two different horizontal travel paths - one perpendicular and one parallel to the eventual rupture plane, away from the nucleation zone - we showed that that both started to diverge as early as at 70% of the final rupture strength. This shows that quite early on during

  14. Damage Evolution in Al Wire Bonds Subjected to a Junction Temperature Fluctuation of 30 K

    NASA Astrophysics Data System (ADS)

    Agyakwa, Pearl A.; Yang, Li; Arjmand, Elaheh; Evans, Paul; Corfield, Martin R.; Johnson, C. Mark

    2016-07-01

    Ultrasonically bonded heavy Al wires subjected to a small junction temperature fluctuation under power cycling from 40°C to 70°C were investigated using a non-destructive three-dimensional (3-D) x-ray tomography evaluation approach. The occurrence of irreversible deformation of the microstructure and wear-out under such conditions were demonstrated. The observed microstructures consist of interfacial and inter-granular cracks concentrated in zones of stress intensity, i.e., near heels and emanating from interface precracks. Interfacial voids were also observed within the bond interior. Degradation rates of `first' and `stitch' bonds are compared and contrasted. A correlative microscopy study combining perspectives from optical microscopy with the x-ray tomography results clarifies the damage observed. An estimation of lifetime is made from the results and discussed in the light of existing predictions.

  15. Damage Evolution in Al Wire Bonds Subjected to a Junction Temperature Fluctuation of 30 K

    NASA Astrophysics Data System (ADS)

    Agyakwa, Pearl A.; Yang, Li; Arjmand, Elaheh; Evans, Paul; Corfield, Martin R.; Johnson, C. Mark

    2016-04-01

    Ultrasonically bonded heavy Al wires subjected to a small junction temperature fluctuation under power cycling from 40°C to 70°C were investigated using a non-destructive three-dimensional (3-D) x-ray tomography evaluation approach. The occurrence of irreversible deformation of the microstructure and wear-out under such conditions were demonstrated. The observed microstructures consist of interfacial and inter-granular cracks concentrated in zones of stress intensity, i.e., near heels and emanating from interface precracks. Interfacial voids were also observed within the bond interior. Degradation rates of `first' and `stitch' bonds are compared and contrasted. A correlative microscopy study combining perspectives from optical microscopy with the x-ray tomography results clarifies the damage observed. An estimation of lifetime is made from the results and discussed in the light of existing predictions.

  16. Strain Accumulation and Damage Evolution During Creep of SiCf/SiC Composites

    NASA Astrophysics Data System (ADS)

    Wilshire, Brian; Burt, Howard

    For many high-performance applications, worldwide research efforts continue to be focussed on ceramic-fibre-reinforced ceramic-matrix composites (CFCMCs), with numerous studies featuring SiC-fibre-reinforced SiC-matrix materials (termed SiCf/SiC type products). In particular, because these CFCMCs are being considered for components which must operate for long periods without failure under load in hostile high-temperature environments, special attention has then been directed to characterization of their creep and creep fracture behaviour. In turn, many of these studies have been concerned with clarification of the damage processes which cause creep failure, aiming to acquire the understanding needed for future product development and component design.

  17. Models for predicting damage evolution in metal matrix composites subjected to cyclic loading

    SciTech Connect

    Allen, D.H.; Hurtado, L.D.; Helms, K.L.E.

    1995-03-01

    A thermomechanical analysis of a continuous fiber metal matrix composite (MMC) subjected to cyclic loading is performed herein. The analysis includes the effects of processing induced residual thermal stresses, matrix inelasticity, and interface cracking. Due to these complexities, the analysis is performed computationally using the finite element method. Matrix inelasticity is modelled with a rate dependent viscoplasticity model. Interface fracture is modelled by the use of a nonlinear interface constitutive model. The problem formulation is summarized, and results are given for a four-ply unidirectional SCS-6/{beta}21S titanium composite under high temperature isothermal mechanical fatigue. Results indicate rate dependent viscoplasticity can be a significant mechanism for dissipating the energy available for damage propagation, thus contributing to improved ductility of the composite. Results also indicate that the model may be useful for inclusion in life prediction methodologies for MMC`s.

  18. An explicit finite element formulation for dynamic strain localization and damage evolution in metals

    SciTech Connect

    Mourad, Hashem M; Bronkhorst, Curt A; Addessio, Francis L

    2010-12-16

    An explicit finite element formulation, used to study the behavior and failure mechanisms of metallic materials under high strain rate loading, is presented. The formulation is based on the assumed-strain approach of Fish and Belytschko [1988], which allows localization bands to be embedded within an element, thereby alleviating mesh sensitivity and reducing the required computational effort. The behavior of the material outside localization bands (and of the virgin material prior to the onset of strain localization) is represented using a Gurson-type coupled plasticity-damage model based on the work of Johnson and Addessio [1988]. Assuming adiabatic conditions, the response of the localization band material is represented by a set of constitutive equations for large elasticviscoplastic deformations in metals at high strain rates and high homologous temperatures (see Brown et al. [1989]). Computational results are compared to experimental data for different metallic alloys to illustrate the advantages of the proposed modeling strategy.

  19. Civil Law Glossary.

    ERIC Educational Resources Information Center

    Update on Law-Related Education, 1997

    1997-01-01

    Presents a glossary of civil law terms originally compiled for journalists by the American Bar Association. Defines many essential civil law concepts and practices including compensatory damages, jurisdiction, motion to dismiss, discovery, and remedy. (MJP)

  20. A modified differential evolution algorithm for damage identification in submerged shell structures

    NASA Astrophysics Data System (ADS)

    Reed, H. M.; Nichols, J. M.; Earls, C. J.

    2013-08-01

    Obtaining good estimates of structural parameters from observed data is a particularly challenging task owing to the complex (often multi-modal) likelihood functions that often accompany such problems. As a result, sophisticated optimization routines are typically required to produce maximum likelihood estimates of the desired parameters. Evolutionary algorithms comprise one such approach, whereby nature-inspired mutation and crossover operations allow the sensible exploration of even multi-modal functions, in search of a global maximum. The challenge, of course, is to balance broad coverage in parameter space with the speed required to obtain such estimates. This work focuses directly on this problem by proposing a modified version of the Differential Evolution algorithm. The idea is to adjust both mutation and cross-over rates, during the optimization, in a manner that increases the convergence rate to the desired solution. Performance is demonstrated on the challenging problem of identifying imperfections in submerged shell structures.

  1. Acoustic and Ultrasonic Spectral Evolution in Pre- and Post-Damage Self-Healing Poly (Ethylene Co-Methacrylic Acid) Ionomer Samples

    NASA Astrophysics Data System (ADS)

    Buckley, Jonathan; Pestka, Kenneth, II; Kalista, Stephen

    We measured the pre- and post-damage resonant spectra of several self-healing ionomer samples composed of poly (ethylene co-methacrylic acid) (EMAA). The post-damage results indicate significant time-dependent variation in the acoustic and ultrasonic resonant spectral waveforms of these self-healing samples. These results are consistent with other recent experiments that demonstrate time evolution of resonant frequencies and associated quality factors within samples of post-damage EMAA ionomers. However, in our experiments it was found that, in some circumstances, the quality factors and associated resonant frequencies can exhibit time-dependent variation both before and after external damage. By quantifying time-dependent variations in the spectra of undamaged samples, including quality factor, resonant frequency and spectral waveform, we demonstrate a method to isolate changes in the resonant spectra that are present solely due to the post-damage healing behavior of these EMAA ionomers.

  2. THEORETICAL INVESTIGATION OF MICROSTRUCTURE EVOLUTION AND DEFORMATION OF ZIRCONIUM UNDER CASCADE DAMAGE CONDITIONS

    SciTech Connect

    Barashev, Alexander V; Golubov, Stanislav I; Stoller, Roger E

    2012-06-01

    This work is based on our reaction-diffusion model of radiation growth of Zr-based materials proposed recently in [1]. In [1], the equations for the strain rates in unloaded pure crystal under cascade damage conditions of, e.g., neutron or heavy-ion irradiation were derived as functions of dislocation densities, which include contributions from dislocation loops, and spatial distribution of their Burgers vectors. The model takes into account the intra-cascade clustering of self-interstitial atoms and their one-dimensional diffusion; explains the growth stages, including the break-away growth of pre-annealed samples; and accounts for some striking observations, such as of negative strain in prismatic direction, and co-existence of vacancy- and interstitial-type prismatic loops. In this report, the change of dislocation densities due to accumulation of sessile dislocation loops is taken into account explicitly to investigate the dose dependence of radiation growth. The dose dependence of climb rates of dislocations is calculated, which is important for the climb-induced glide model of radiation creep. The results of fitting the model to available experimental data and some numerical calculations of the strain behavior of Zr for different initial dislocation structures are presented and discussed. The computer code RIMD-ZR.V1 (Radiation Induced Microstructure and Deformation of Zr) developed is described and attached to this report.

  3. Dynamic Loading to Study Damage Evolution in Heterogeneous Microstructures using IMPULSE at the Advanced Photon Source

    NASA Astrophysics Data System (ADS)

    Yeager, John; Ramos, Kyle; Jensen, Brian; Graff Thompson, Darla; Iverson, Adam; Carlson, Carl; Fezzaa, Kamel; Hooks, Dan

    2013-06-01

    The performance, safety, and thermo-mechanical response of heterogeneous materials such as plastic-bonded explosives (PBXs) is inherently linked to microstructural phenomena. Experimental resolution of the physics and chemistry of the microstructure at appropriate length scales, both at ambient conditions and under dynamic loading, are highly desirable to develop new materials and models to predict their behavior. Here, the dynamic response of several heterogeneous materials is studied with real-time, in situ, spatially resolved measurements using the IMPULSE platform at the Advanced Photon Source (APS) at Argonne National Laboratory. Known PBX damage mechanisms such as void collapse, crack propagation, and plasticity or material flow are imaged at ultrafast speeds under shock loading conditions with simultaneous X-ray phase contrast imaging (PCI). PCI at APS beam line 32-ID is an improvement over radiography because it detects phase shifts in the transmitted X-ray beam, making PCI an ideal technique to image interfaces (i.e. heterogeneity) with high spatial resolution (2um) in-plane. IMPULSE experiments are compared with similar experiments at other length and time scales to discern relevant processing-structure-properties relationships for several PBX materials.

  4. Evolution.

    ERIC Educational Resources Information Center

    Mayr, Ernst

    1978-01-01

    Traces the history of evolution theory from Lamarck and Darwin to the present. Discusses natural selection in detail. Suggests that, besides biological evolution, there is also a cultural evolution which is more rapid than the former. (MA)

  5. Brittle dynamic damage due to earthquake rupture

    NASA Astrophysics Data System (ADS)

    Bhat, Harsha; Thomas, Marion

    2016-04-01

    The micromechanical damage mechanics formulated by Ashby and Sammis, 1990, and generalized by Deshpande and Evans 2008 has been extended to allow for a more generalized stress state and to incorporate an experimentally motivated new crack growth (damage evolution) law that is valid over a wide range of loading rates. This law is sensitive to both the crack tip stress field and its time derivative. Incorporating this feature produces additional strain-rate sensitivity in the constitutive response. The model is also experimentally verified by predicting the failure strength of Dionysus-Pentelicon marble over wide range of strain rates. We then implement this constitutive response to understand the role of dynamic brittle off-fault damage on earthquake ruptures. We show that off-fault damage plays an important role in asymmetry of rupture propagation and is a source of high-frequency ground motion in the near source region.

  6. Damage-induced nonassociated inelastic flow in rock salt

    SciTech Connect

    Chan, K.S.; Bodner, S.R.; Brodsky, N.S.; Fossum, A.F.

    1993-06-01

    The multi-mechanism deformation coupled fracture model recently developed by CHAN, et al. (1992), for describing time-dependent, pressure-sensitive inelastic flow and damage evolution in crystalline solids was evaluated against triaxial creep experiments on rock salt. Guided by experimental observations, the kinetic equation and the flow law for damage-induced inelastic flow in the model were modified to account for the development of damage and inelastic dilatation in the transient creep regime. The revised model was then utilized to obtain the creep response and damage evolution in rock salt as a function of confining pressure and stress difference. Comparison between model calculation and experiment revealed that damage-induced inelastic flow is nonassociated, dilatational, and contributes significantly to the macroscopic strain rate observed in rock salt deformed at low confining pressures. The inelastic strain rate and volumetric strain due to damage decrease with increasing confining pressures, and all are suppressed at sufficiently high confining pressures.

  7. An investigation of the effects of history dependent damage in time dependent fracture mechanics: nano-scale studies of damage evolution

    SciTech Connect

    Brust, F.W. Jr; Mohan, R.; Yang, Y.P.; Oh, J.; Katsube, N.

    2002-12-01

    High-temperature operation of technical engineering systems is critical for system efficiency, and will be a key driver in the future US DOE energy policy. Developing an understanding of high-temperature creep and creep-fatigue failure processes is a key driver for the research work described here. The focus is on understanding the high-temperature deformation and damage development on the nano-scale (50 to 500 nm) level. The high-temperature damage development process, especially with regard to low and high cyclic loading, which has received little attention to date, is studied. Damage development under cyclic loading develops in a fashion quite different from the constant load situation. The development of analytical methodologies so that high-temperature management of new systems can be realized is the key goal of this work.

  8. A damage analysis for brittle materials using stochastic micro-structural information

    NASA Astrophysics Data System (ADS)

    Lin, Shih-Po; Chen, Jiun-Shyan; Liang, Shixue

    2016-03-01

    In this work, a micro-crack informed stochastic damage analysis is performed to consider the failures of material with stochastic microstructure. The derivation of the damage evolution law is based on the Helmholtz free energy equivalence between cracked microstructure and homogenized continuum. The damage model is constructed under the stochastic representative volume element (SRVE) framework. The characteristics of SRVE used in the construction of the stochastic damage model have been investigated based on the principle of the minimum potential energy. The mesh dependency issue has been addressed by introducing a scaling law into the damage evolution equation. The proposed methods are then validated through the comparison between numerical simulations and experimental observations of a high strength concrete. It is observed that the standard deviation of porosity in the microstructures has stronger effect on the damage states and the peak stresses than its effect on the Young's and shear moduli in the macro-scale responses.

  9. Investigating Damage Evolution at the Nanoscale: Molecular Dynamics Simulations of Nanovoid Growth in Single-Crystal Aluminum

    NASA Astrophysics Data System (ADS)

    Bhatia, M. A.; Solanki, K. N.; Moitra, A.; Tschopp, M. A.

    2013-02-01

    Nanovoid growth was investigated using molecular dynamics to reveal its dependence on void size, strain rate, crystallographic loading orientation, initial nanovoid volume fraction, and simulation cell size. A spherical nanovoid was embedded into a periodic face-centered cubic (fcc) Al lattice, and a remote uniaxial load was applied to elucidate dislocation nucleation and shear loop formation from the void surface as well as the subsequent void growth mechanisms. The nucleation stresses and void growth mechanisms were compared for four different strain rates (107 to 1010 seconds-1), five different simulation cell sizes (4-nm to 28-nm lengths), four different initial nanovoid volume fractions, and seven different tensile loading orientations representative of the variability within the stereographic triangle. The simulation results show an effect of the size scale, crystallographic loading orientation, initial void volume fraction, and strain rate on the incipient yield stress for simulations without a void (single-crystal bulk material). For instance, the crystallographic orientation dependence on yield stress was less pronounced for simulations containing a void. As expected, dislocations and shear loops nucleated on various slip systems for the different loading orientations, which included orientations favored for both single slip and multiple slip. The evolution of the nanovoid volume fraction with increasing strain is relatively insensitive to loading orientations, which suggests that the nanoscale plastic anisotropy caused by the initial lattice orientation has only a minor role in influencing the nanovoid growth rate. In contrast, a significant influence of the initial nanovoid volume fractions was observed on the yield stress, i.e., a ~35 pct decrease in yield stress was caused by introducing a 0.4 pct nanovoid volume fraction. Furthermore, a continuum-scale bridging parameter m—which is a material rate sensitivity parameter in continuum damage mechanics

  10. The effects of shockwave profile shape and shock obliquity on spallation : studies of kinetics and stress state effects on damage evolution

    SciTech Connect

    Gray, George T., III; Hull, Larry M; Faulkner, J R; Briggs, M E; Cerreta, E K; Addessio, F L; Bourne, N K

    2009-06-22

    Shock-loading of a material in contact with a high explosive (HE) experiences a 'Taylor wave' (triangular wave) loading profile in contrast to the square-wave loading profile imparted via the impact of a flyer plate. Detailed metallographic and mlcrotextural analysis of the damage evolution in spalled Cu samples as a function of square/triangle and sweeping detonation-wave loading is presented.

  11. Brittle Creep, Damage and Time to Failure in Rocks

    NASA Astrophysics Data System (ADS)

    Amitrano, D.; Helmstetter, A.

    2005-12-01

    We first review published data of time to failure, t_f, of rocks under creep conditions. We compare exponential and power-law relationship between t_f and the applied stress for tests performed on different types of rock and various environmental conditions. This data shows that the time to failure changes by several orders of magnitude when varying the confining pressure, the temperature or the water saturation. We then use this time-to-failure relation as input for a numerical model based on progressive damage. This model reproduces the primary and tertiary creep regimes observed experimentally for rocks. During primary creep, the strain rate, the energy rate, and the rate of damage events decay with time as a power-law with an exponent of 0.8. The tertiary creep is characterized by a power-law acceleration of damage with an exponent of 0.8 for the event rate, and 1.3 for strain and energy rates. We derive analytical solutions for a simplified version of the model, which explain qualitatively these results. The distribution of damage event sizes is a power law when integrated over all the simulation. The temporal evolution of this distribution shows an increase of the mean event size before failure. During primary creep, damage is relatively uniform in space. Damage localization occurs at the transition between primary and tertiary creep, when damage rate starts accelerating. The final state of the simulation shows highly damaged bands, similar to shear bands observed during laboratory experiments. The thickness and the orientation of these bands depend on the applied stress. This model shows that a complex global behavior (primary and tertiary creep regimes, power-law distribution of event sizes, and damage localization) can emerge from a simple elementary behavior, based on progressive damage and experimentally established time-to-failure law.

  12. Influence of sweeping detonation-wave loading on damage evolution during spallation loading of tantalum in both a planar and curved geometry

    SciTech Connect

    Gray, George Thompson III; Hull, Lawrence Mark; Livescu, Veronica; Faulkner, James; Briggs, Matthew E.; Meyer, Ross Keith; Andrews, Heather Lynn; Hare, Steven John; Jakulewicz, Micah Shawn; Shinas, Michael A.

    2015-03-30

    Widespread research over the past five decades has provided a wealth of experimental data and insight concerning the shock hardening, damage evolution, and the spallation response of materials subjected to square-topped shock-wave loading profiles. However, fewer quantitative studies have been conducted on the effect of direct, in-contact, high explosive (HE)-driven Taylor wave (unsupported shocks) loading on the shock hardening, damage evolution, or spallation response of materials. Systematic studies quantifying the effect of sweeping-detonation wave loading are yet sparser. In this study, the damage evolution and spallation response of Ta is shown to be critically dependent on the peak shock stress, the geometry of the sample (flat or curved plate geometry), and the shock obliquity during sweeping-detonation-wave shock loading. Sweepingwave loading in the flat-plate geometry is observed to: a) yield a lower spall strength than previously documented for 1-D supported-shock-wave loading, b) exhibit increased shock hardening as a function of increasing obliquity, and c) lead to an increased incidence of deformation twin formation with increasing shock obliquity. Sweeping-wave loading of a 10 cm radius curved Ta plate is observed to: a) lead to an increase in the shear stress as a function of increasing obliquity, b) display a more developed level of damage evolution, extensive voids and coalescence, and lower spall strength with obliquity in the curved plate than seen in the flat-plate sweeping-detonation wave loading for an equivalent HE loading, and c) no increased propensity for deformation twin formation with increasing obliquity as seen in the flat-plate geometry. The overall observations comparing and contrasting the flat versus curved sweeping-wave spall experiments with 1D loaded spallation behavior suggests a coupled influence of obliquity and geometry on dynamic shock-induced damage evolution and spall strength. Coupled experimental and modeling research

  13. Propagation of continuum damage in a viscoelastic ice bar

    SciTech Connect

    Shin, J.G. . Dept. of Naval Architecture and Ocean Engineering); Karr, D.G. . Dept. of Naval Architecture and Marine Engineering)

    1994-05-01

    An initial value problem of a semi-infinite nonlinear viscoelastic bar is solved with continuum damage evolution. The evolution law of the continuum damage for a viscoelastic material is used in order to explore the propagation of two crushing mechanisms: grain boundary cracking and transgranular cracking. Using the method of characteristics, the speed of propagation is found to be dependent on the continuum damage. On the wave front, the delayed elastic strain is zero, and only the continuum damage due to the transgranular cracking evolves. A finite difference method is developed to solve the governing equations on the obtained characteristic lines, and gives a stable solution for the propagation of the stress, strain, and damage. Numerical results are obtained and discussed using the material properties of polycrystalline ice.

  14. Development of a viscoelastic continuum damage model for cyclic loading

    NASA Astrophysics Data System (ADS)

    Sullivan, R. W.

    2008-12-01

    A previously developed spectrum model for linear viscoelastic behavior of solids is used to describe the rate-dependent damage growth of a time dependent material under cyclic loading. Through the use of the iterative solution of a special Volterra integral equation, the cyclic strain history is described. The spectrum-based model is generalized for any strain rate and any uniaxial load history to formulate the damage function. Damage evolution in the body is described through the use of a rate-type evolution law which uses a pseudo strain to express the viscoelastic constitutive equation with damage. The resulting damage function is used to formulate a residual strength model. The methodology presented is demonstrated by comparing the peak values of the computed cyclic strain history as well as the residual strength model predictions to the experimental data of a polymer matrix composite.

  15. Farmers, Ranchers, and the Railroad: The Evolution of Fence Law in the Great Plains, 1865-1900

    ERIC Educational Resources Information Center

    Kawashima, Yasuhide

    2010-01-01

    This article is divided into three parts. The first examines specific fencing policies in Kansas, Nebraska, and other Plains states, highlighting the transformation from the "fence-out" to "fence-in" (herd laws) policies. The second part discusses the coming of the railroads to the Great Plains and the farmers and the ranchers as beneficiaries who…

  16. Equilibrium configurations and stability of a damaged body under uniaxial tractions

    NASA Astrophysics Data System (ADS)

    Lanzoni, Luca; Tarantino, Angelo Marcello

    2015-02-01

    This paper deals with the equilibrium problem in nonlinear dissipative inelasticity of damaged bodies subject to uniaxial loading. To model the damage effects, a damage function, affecting the stored energy function, is defined. In the framework of the continuum thermodynamics theory, the constitutive law for damaged hyperelastic materials and an inequality for the energy release rate are derived. By means of an energy-based damage criterion, the irreversible evolution law for the damage function is obtained. After formulating the equilibrium boundary value problem, explicit expressions governing the global development of the equilibrium paths are written. Successively, the stability of the equilibrium solutions are assessed through the energy criterion. For a damaged body under uniaxial loading, seven inequalities are derived. These conditions, if fulfilled, ensure the stability of the solutions under each type of small perturbation. Finally, a number of applications for compressible neo-Hookean and Mooney-Rivlin materials are performed.

  17. Comparison of Tensile Damage Evolution in Ti6A14V Joints Between Laser Beam Welding and Gas Tungsten Arc Welding

    NASA Astrophysics Data System (ADS)

    Gao, Xiao-Long; Zhang, Lin-Jie; Liu, Jing; Zhang, Jian-Xun

    2014-12-01

    The present paper studied the evolution of tensile damage in joints welded using laser beam welding (LBW) and gas tungsten arc welding (TIG) under a uniaxial tensile load. The damage evolution in the LBW joints and TIG-welded joints was studied by using digital image correlation (DIC) technology and monitoring changes in Young's modulus during tensile testing. To study the mechanism of void nucleation and growth in the LBW joints and TIG-welded joints, test specimens with various amounts of plastic deformation were analyzed using a scanning electron microscope (SEM). Compared with TIG-welded joints, LBW-welded joints have a finer microstructure and higher microhardness in the fusion zone. The SEM analysis and DIC test results indicated that the critical strain of void nucleation was greater in the LBW-welded joints than in the TIG-welded joints, while the growth rate of voids was lower in the LBW-welded joints than in the TIG-welded joints. Thus, the damage ratio in the LBW joints was lower than that in the TIG-welded joints during tensile testing. This can be due to the coarser martensitic α' and the application of TC-1 welding rods in the TIG-welded joint.

  18. Comparison of Tensile Damage Evolution in Ti6A14V Joints Between Laser Beam Welding and Gas Tungsten Arc Welding

    NASA Astrophysics Data System (ADS)

    Gao, Xiao-Long; Zhang, Lin-Jie; Liu, Jing; Zhang, Jian-Xun

    2014-09-01

    The present paper studied the evolution of tensile damage in joints welded using laser beam welding (LBW) and gas tungsten arc welding (TIG) under a uniaxial tensile load. The damage evolution in the LBW joints and TIG-welded joints was studied by using digital image correlation (DIC) technology and monitoring changes in Young's modulus during tensile testing. To study the mechanism of void nucleation and growth in the LBW joints and TIG-welded joints, test specimens with various amounts of plastic deformation were analyzed using a scanning electron microscope (SEM). Compared with TIG-welded joints, LBW-welded joints have a finer microstructure and higher microhardness in the fusion zone. The SEM analysis and DIC test results indicated that the critical strain of void nucleation was greater in the LBW-welded joints than in the TIG-welded joints, while the growth rate of voids was lower in the LBW-welded joints than in the TIG-welded joints. Thus, the damage ratio in the LBW joints was lower than that in the TIG-welded joints during tensile testing. This can be due to the coarser martensitic α' and the application of TC-1 welding rods in the TIG-welded joint.

  19. Evolution of patients' complaints in a French university hospital: is there a contribution of a law regarding patients' rights?

    PubMed Central

    Giugliani, Camila; Gault, Nathalie; Fares, Valia; Jegu, Jérémie; Trolli, Sergio Eleni dit; Biga, Julie; Vidal-Trecan, Gwenaelle

    2009-01-01

    Background Legislative measures have been identified as one effective way of changing attitude or behaviour towards health care. The aim of this study was to describe trends in patients' complaints for medical issues; to evaluate the contribution of a law regarding patients' rights, and to identify factors associated to patients' perception of a medical error. Methods Patients with a complaint letter for medical issues in a French university hospital were included. Trends in complaint rates were analysed. Comparisons were made between a first (1998–2000) and a second (2001–2004) time period, before and after the diffusion of the law, and according to the perception of a medical error. Results Complaints for medical issues increased from 1998 to 2004. Of 164 complaints analysed, 66% were motivated by the perception of a medical error (47% during the first time period vs. 73% during the second time period; p = 0.001). Error or delay in diagnosis/treatment and surgical/medical complication were the main reasons for complaints. Surgical departments had the higher number of complaints. Second time period, substandard care, disability, and adverse effect of a health product were independently associated with the perception of a medical error, positively for the formers, and negatively for the latter. Conclusion This study revealed an increase with time in the number of complaints for medical issues in a university hospital, as well as an increase in the perception of a medical error after the passing of a law regarding patients' rights in France. PMID:19660131

  20. Lattice strain and damage evolution of 9-12/%Cr ferritic/martensitic steel during in situ tensile test by x-ray diffraction and small angle scattering.

    SciTech Connect

    Pan, X.; Wu, X.; Mo, K.; Chen, X,; Almer, J. D.; Ilavsky, J.; Haeffner, D. R.; Stubbins, J. F.; X-Ray Science Division; Univ. of Illinois

    2010-01-01

    In situ X-ray diffraction and small angle scattering measurements during tensile tests were performed on 9-12% Cr ferritic/martensitic steels. The lattice strains in both particle and matrix phases, along two principal directions, were directly measured. The load transfer between particle and matrix was calculated based on matrix/particle elastic mismatch, matrix plasticity and interface decohesion. In addition, the void or damage evolution during the test was measured using small angle X-ray scattering. By combining stress and void evolution during deformation, the critical interfacial strength for void nucleation was determined, and compared with pre-existing void nucleation criteria. These comparisons show that models overestimate the measured critical strength, and require a larger particle size than measured to match the X-ray observations.

  1. Evolution

    NASA Astrophysics Data System (ADS)

    Peter, Ulmschneider

    When we are looking for intelligent life outside the Earth, there is a fundamental question: Assuming that life has formed on an extraterrestrial planet, will it also develop toward intelligence? As this is hotly debated, we will now describe the development of life on Earth in more detail in order to show that there are good reasons why evolution should culminate in intelligent beings.

  2. Postbuckling Investigations of Piezoelectric Microdevices Considering Damage Effects

    PubMed Central

    Sun, Zhigang; Wang, Xianqiao

    2014-01-01

    Piezoelectric material has been emerging as a popular building block in MEMS devices owing to its unique mechanical and electrical material properties. However, the reliability of MEMS devices under buckling deformation environments remains elusive and needs to be further explored. Based on the Talreja's tensor valued internal state damage variables as well as the Helmhotlz free energy of piezoelectric material, a constitutive model of piezoelectric materials with damage is presented. The Kachanvo damage evolution law under in-plane compressive loads is employed. The model is applied to the specific case of the postbuckling analysis of the piezoelectric plate with damage. Then, adopting von Karman's plate theory, the nonlinear governing equations of the piezoelectric plates with initial geometric deflection including damage effects under in-plane compressive loads are established. By using the finite difference method and the Newmark scheme, the damage evolution for damage accumulation is developed and the finite difference procedure for postbuckling equilibrium path is simultaneously employed. Numerical results show the postbuckling behaviors of initial flat and deflected piezoelectric plates with damage or no damage under different sets of electrical loading conditions. The effects of applied voltage, aspect ratio of plate, thick-span ratio of plate, damage as well as initial geometric deflections on the postbuckling behaviors of the piezoelectric plate are discussed. PMID:24618774

  3. Spatial evolution of the helical behavior and the 2/3 power-law in single-square-grid-generated turbulence

    NASA Astrophysics Data System (ADS)

    Zhou, Yi; Nagata, Kouji; Sakai, Yasuhiko; Ito, Yasumasa; Hayase, Toshiyuki

    2016-04-01

    Direct numerical simulations are performed to investigate the helical properties of single-square-grid-generated turbulence. The streamwise evolution of the probability density functions of the relative helicity density h reveals the existence of a transition from a quasi-two-dimensional state to a three-dimensional state. The correlations between the helicity and the enstrophy level as well as the dissipation level are examined. When conditioned on a high level of dissipation or enstrophy, in the energy decay region the velocity and vorticity vectors in both instantaneous and fluctuating fields become more aligned. However, this correlation does not hold in the production region. We also study the second-order structure function and reveal that a well-defined 2/3 power-law can be found at a location quite close to the grid, where the turbulent flow is still in the transition state.

  4. Damage characterization for particles filled semi-crystalline polymer

    NASA Astrophysics Data System (ADS)

    Lauro, Franck; Balieu, Romain; Bennani, Bruno; Haugou, Gregory; Bourel, Benjamin; Chaari, Fahmi; Matsumoto, Tsukatada; Mottola, Ernesto

    2015-09-01

    Damage evolution and characterization in semi-crystalline polymer filled with particles under various loadings is still a challenge. A specific damage characterization method using Digital Image Correlation is proposed for a wide range of strain rates considering tensile tests with hydraulic jacks as well as Hopkinson's bars. This damage measurement is obtained by using and adapting the SEE method [1] which was developed to characterize the behaviour laws at constant strain rates of polymeric materials in dynamic. To validate the characterization process, various damage measurement techniques are used under quasi-static conditions before to apply the procedure in dynamic. So, the well-known damage characterization by loss of stiffness technique under quasi-static loading is applied to a polypropylene. In addition, an in-situ tensile test, carried out in a microtomograph, is used to observe the cavitation phenomenon in real time. A good correlation is obtained between all these techniques and consequently the proposed technique is supposed suitable for measuring the ductile damage observed in semi-crystalline polymers under dynamic loading. By applying it to the semi-crystalline polymer at moderate and high speed loadings, the damage evolution is measured and it is observed that the damage evolution is not strain rate dependent but the failure strain on the contrary is strain rate dependent.

  5. Selective neuronal vulnerability of human hippocampal CA1 neurons: lesion evolution, temporal course, and pattern of hippocampal damage in diffusion-weighted MR imaging.

    PubMed

    Bartsch, Thorsten; Döhring, Juliane; Reuter, Sigrid; Finke, Carsten; Rohr, Axel; Brauer, Henriette; Deuschl, Günther; Jansen, Olav

    2015-11-01

    The CA1 (cornu ammonis) region of hippocampus is selectively vulnerable to a variety of metabolic and cytotoxic insults, which is mirrored in a delayed neuronal death of CA1 neurons. The basis and mechanisms of this regional susceptibility of CA1 neurons are poorly understood, and the correlates in human diseases affecting the hippocampus are not clear. Adopting a translational approach, the lesion evolution, temporal course, pattern of diffusion changes, and damage in hippocampal CA1 in acute neurologic disorders were studied using high-resolution magnetic resonance imaging. In patients with hippocampal ischemia (n=50), limbic encephalitis (n=30), after status epilepticus (n=17), and transient global amnesia (n=53), the CA1 region was selectively affected compared with other CA regions of the hippocampus. CA1 neurons exhibited a maximum decrease of apparent diffusion coefficient (ADC) 48 to 72 hours after the insult, irrespective of the nature of the insult. Hypoxic-ischemic insults led to a significant lower ADC suggesting that the ischemic insult results in a stronger impairment of cellular metabolism. The evolution of diffusion changes show that CA1 diffusion lesions mirror the delayed time course of the pathophysiologic cascade typically observed in animal models. Studying the imaging correlates of hippocampal damage in humans provides valuable insight into the pathophysiology and neurobiology of the hippocampus. PMID:26082014

  6. Self-similar bumps and wiggles: Isolating the evolution of the BAO peak with power-law initial conditions

    NASA Astrophysics Data System (ADS)

    Orban, Chris; Weinberg, David H.

    2011-09-01

    Motivated by cosmological surveys that demand accurate theoretical modeling of the baryon acoustic oscillation (BAO) feature in galaxy clustering, we analyze N-body simulations in which a BAO-like Gaussian bump modulates the linear theory correlation function ξL(r)=(r0/r)n+3 of an underlying self-similar model with initial power spectrum P(k)=Akn. These simulations test physical and analytic descriptions of BAO evolution far beyond the range of most studies, since we consider a range of underlying power spectra (n=-0.5, -1, -1.5) and evolve simulations to large effective correlation amplitudes (equivalent to σ8=4-12 for rbao=100h-1Mpc). In all cases, nonlinear evolution flattens and broadens the BAO bump in ξ(r) while approximately preserving its area. This evolution resembles a diffusion process in which the bump width σbao is the quadrature sum of the linear theory width and a length proportional to the rms relative displacement Σpair(rbao) of particle pairs separated by rbao. For n=-0.5 and n=-1, we find no detectable shift of the location of the BAO peak, but the peak in the n=-1.5 model shifts steadily to smaller scales, following rpeak/rbao=1-1.08(r0/rbao)1.5. The perturbation theory scheme of McDonald (2007) [P. McDonald, Phys. Rev. DPRVDAQ1550-7998 75, 043514 (2007).10.1103/PhysRevD.75.043514] and, to a lesser extent, standard 1-loop perturbation theory are fairly successful at explaining the nonlinear evolution of the Fourier power spectrum of our models. Analytic models also explain why the ξ(r) peak shifts much more for n=-1.5 than for n≥-1, though no ab initio model we have examined reproduces all of our numerical results. Simulations with Lbox=10rbao and Lbox=20rbao yield consistent results for ξ(r) at the BAO scale, provided one corrects for the integral constraint imposed by the uniform density box.

  7. Simultaneous Tomography and Diffraction Analysis of Creep Damage

    NASA Astrophysics Data System (ADS)

    Pyzalla, A.; Camin, B.; Buslaps, T.; Di Michiel, M.; Kaminski, H.; Kottar, A.; Pernack, A.; Reimers, W.

    2005-04-01

    Creep damage by void nucleation and growth limits the lifetime of components subjected to loading at high temperatures. We report a combined tomography and diffraction experiment using high-energy synchrotron radiation that permitted us to follow in situ void growth and microstructure development in bulk samples. The results reveal that void growth versus time follows an exponential growth law. The formation of large void volumes coincides with texture evolution and dislocation density, reaching a steady state. Creep damage during a large proportion of sample creep life is homogeneous before damage localization occurs, which leads to rapid failure. The in situ determination of void evolution in bulk samples should allow for the assessment of creep damage in metallic materials and subsequently for lifetime predictions about samples and components that are subject to high-temperature loading.

  8. 77 FR 31827 - Pipeline Safety: Pipeline Damage Prevention Programs

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-30

    ... Safety: Pipeline Damage Prevention Programs AGENCY: Pipeline and Hazardous Materials Safety... excavation damage prevention law enforcement programs; establish an administrative process for making... excavation damage prevention law enforcement programs; and establish the adjudication process...

  9. Investigation of a Novel NDE Method for Monitoring Thermomechanical Damage and Microstructure Evolution in Ferritic-Martensitic Steels for Generation IV Nuclear Energy Systems

    SciTech Connect

    Nagy, Peter

    2013-09-30

    The main goal of the proposed project is the development of validated nondestructive evaluation (NDE) techniques for in situ monitoring of ferritic-martensitic steels like Grade 91 9Cr-1Mo, which are candidate materials for Generation IV nuclear energy structural components operating at temperatures up to ~650{degree}C and for steam-generator tubing for sodium-cooled fast reactors. Full assessment of thermomechanical damage requires a clear separation between thermally activated microstructural evolution and creep damage caused by simultaneous mechanical stress. Creep damage can be classified as "negligible" creep without significant plastic strain and "ordinary" creep of the primary, secondary, and tertiary kind that is accompanied by significant plastic deformation and/or cavity nucleation and growth. Under negligible creep conditions of interest in this project, minimal or no plastic strain occurs, and the accumulation of creep damage does not significantly reduce the fatigue life of a structural component so that low-temperature design rules, such as the ASME Section III, Subsection NB, can be applied with confidence. The proposed research project will utilize a multifaceted approach in which the feasibility of electrical conductivity and thermo-electric monitoring methods is researched and coupled with detailed post-thermal/creep exposure characterization of microstructural changes and damage processes using state-of-the-art electron microscopy techniques, with the aim of establishing the most effective nondestructive materials evaluation technique for particular degradation modes in high-temperature alloys that are candidates for use in the Next Generation Nuclear Plant (NGNP) as well as providing the necessary mechanism-based underpinnings for relating the two. Only techniques suitable for practical application in situ will be considered. As the project evolves and results accumulate, we will also study the use of this technique for monitoring other GEN IV

  10. A model for predicting damage induced fatigue life of laminated composite structural components

    NASA Technical Reports Server (NTRS)

    Allen, David H.; Lo, David C.; Georgiou, Ioannis T.; Harris, Charles E.

    1990-01-01

    This paper presents a model for predicting the life of laminated composite structural components subjected to fatigue induced microstructural damage. The model uses the concept of continuum damage mechanics, wherein the effects of microcracks are incorporated into a damage dependent lamination theory instead of treating each crack as an internal boundary. Internal variables are formulated to account for the effects of both matrix cracks and internal delaminations. Evolution laws for determining the damage variables as functions of ply stresses are proposed, and comparisons of predicted damage evolution are made to experiment. In addition, predicted stiffness losses, as well as ply stresses are shown as functions of damage state for a variety of stacking sequences.

  11. Evaluation of damage evolution and material behavior in a sigma/Ti-6242 composite using nondestructive methods

    SciTech Connect

    Benson, D.; Karpur, P.; Stubbs, D.A.; Matikas, T.E.

    1997-12-31

    Correlations between damage, as it evolves under simulated service conditions, and the results produced from nondestructive evaluation (NDE) techniques are useful in establishing successful life prediction methodologies in metal-matrix composites. Traditional characterization techniques provide limited information on the failure mechanisms in metal-matrix composites because of the complexities caused by the inhomogeneous, anisotropic nature of these materials. In addition, the currently used destructive techniques yield only qualitative information on the internal damage of composites. Very little quantitative information exists correlating the internal damage with property changes in the material such as stiffness, elongation, and residual strength. This research effort correlated NDE results with the residual tensile strength of a six-ply, unidirectional BP Sigma-1240 SiC/Ti-6Al-2Sn-4Zr-2Mo composite after being isothermally fatigued. Information obtained from these tests was used to pinpoint load levels and interruption points for subsequent interrupted fatigue tests. The following nondestructive evaluation techniques were used to evaluate the test specimens before and after fatigue testing: (1) scanning acoustic microscopy, (2) oblique incidence shear wave scanning, (3) reflector plate ultrasonic scanning, (4) immersion surface wave scanning, (5) in situ surface and longitudinal waves and, (6) X-ray radiography. This paper presents the results from each of the NDE techniques and examines the correlation among the techniques, other destructive methods, and the residual tensile strength.

  12. Temperature activated absorption during laser-induced damage: The evolution of laser-supported solid-state absorption fronts

    SciTech Connect

    Carr, C W; Bude, J D; Shen, N; Demange, P

    2010-10-26

    Previously we have shown that the size of laser induced damage sites in both KDP and SiO{sub 2} is largely governed by the duration of the laser pulse which creates them. Here we present a model based on experiment and simulation that accounts for this behavior. Specifically, we show that solid-state laser-supported absorption fronts are generated during a damage event and that these fronts propagate at constant velocities for laser intensities up to 4 GW/cm{sup 2}. It is the constant absorption front velocity that leads to the dependence of laser damage site size on pulse duration. We show that these absorption fronts are driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport, and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. In addition to the practical application of selecting an optimal laser for pre-initiation of large aperture optics, this work serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

  13. Effects of processing history on the evolution of surface damage layer and dislocation substructure in large grain niobium cavities

    NASA Astrophysics Data System (ADS)

    Kang, D.; Bieler, T. R.; Compton, C.

    2015-12-01

    Large grain niobium (Nb) is being investigated for fabricating superconducting radiofrequency cavities as an alternative to the traditional approach using fine grain polycrystalline Nb sheets. Past studies have identified a surface damage layer on fine grain cavities due to deep drawing and demonstrated the necessity for chemical etching on the surface. However, the origin of and depth of the damage layer are not well understood, and similar exploration on large grain cavities is lacking. In this work, electron backscatter diffraction (EBSD) was used to examine the cross sections at the equator and iris of a half cell deep drawn from a large grain Nb ingot slice. The results indicate that the damage (identified by a high density of geometrically necessary dislocations) depends on crystal orientations, is different at the equator and iris, and is present through the full thickness of a half cell in some places. After electron backscatter diffraction, the specimens were heat treated at 800 °C or 1000 °C for two hours, and the same areas were reexamined. A more dramatic decrease in dislocation content was observed at the iris than the equator, where some regions exhibited no change. The specimens were then etched and examined again, to determine if the subsurface region behaved differently than the surface. Little change in the dislocation substructure was observed, suggesting that the large grain microstructure is retained with a normal furnace anneal.

  14. Do p+p Collisions Flow at RHIC? Understanding One-Particle Distributions, Multiplicity Evolution, and Conservation Laws

    NASA Astrophysics Data System (ADS)

    Chajęcki, Zbigniew; Lisa, Mike

    2009-11-01

    Collective, explosive flow in central heavy ion collisions manifests itself in the mass dependence of p distributions and femtoscopic length scales, measured in the soft sector (p≲1GeV/c). Measured p distributions from proton-proton collisions differ significantly from those from heavy ion collisions. This has been taken as evidence that p+p collisions generate little collective flow, a conclusion in line with naive expectations. We point out possible hazards of ignoring phase-space restrictions due to conservation laws when comparing high- and low-multiplicity final states. Already in two-particle correlation functions, we see clear signals of such phase-space restrictions in low-multiplicity collisions at RHIC. We discuss how these same effects, then, must appear in the single particle spectra. We argue that the effects of energy and momentum conservation actually dominate the observed systematics, and that p+p collisions may be much more similar to heavy ion collisions than generally thought.

  15. Evolution of different dual-use concepts in international and national law and its implications on research ethics and governance.

    PubMed

    Rath, Johannes; Ischi, Monique; Perkins, Dana

    2014-09-01

    This paper provides an overview of the various dual-use concepts applied in national and international non-proliferation and anti-terrorism legislation, such as the Biological and Toxin Weapons Convention, the Chemical Weapons Convention and United Nations Security Council Resolution 1540, and national export control legislation and in relevant codes of conduct. While there is a vast literature covering dual-use concepts in particular with regard to life sciences, this is the first paper that incorporates into such discussion the United Nations Security Council Resolution 1540. In addition, recent developments such as the extension of dual-use export control legislation in the area of human rights protection are also identified and reviewed. The discussion of dual-use concepts is hereby undertaken in the context of human- and/or national-security-based approaches to security. This paper discusses four main concepts of dual use as applied today in international and national law: civilian versus military, peaceful versus non-peaceful, legitimate versus illegitimate and benevolent versus malevolent. In addition, the usage of the term to describe positive technology spin-offs between civilian and military applications is also briefly addressed. Attention is also given to the roles civil society and research ethics may play in the governance of dual-use sciences and technologies. PMID:24497004

  16. Temporal Variation of Aerosol Properties at a Rural Continental Site and Study of Aerosol Evolution through Growth Law Analysis

    NASA Technical Reports Server (NTRS)

    Wang, Jian; Collins, Don; Covert, David; Elleman, Robert; Ferrare, Richard A.; Gasparini, Roberto; Jonsson, Haflidi; Ogren, John; Sheridan, Patrick; Tsay, Si-Chee

    2006-01-01

    Aerosol size distributions were measured by a Scanning Mobility Particle Sizer (SMPS) onboard the CIRPAS Twin Otter aircraft during 16 flights at the Southern Great Plains (SGP) site in northern central Oklahoma as part of the Aerosol Intensive Operation period in May, 2003. During the same period a second SMPS was deployed at a surface station and provided continuous measurements. Combined with trace gas measurements at the SGP site and back-trajectory analysis, the aerosol size distributions provided insights into the sources of aerosols observed at the SGP site. High particle concentrations, observed mostly during daytime, were well correlated with the sulfur dioxide (SO2) mixing ratios, suggesting nucleation involving sulfuric acid is likely the main source of newly formed particles at the SGP. Aerosols within plumes originating from wildfires in Central America were measured at the surface site. Vertically compact aerosol layers, which can be traced back to forest fires in East Asia, were intercepted at altitudes over 3000 meters. Analyses of size dependent particle growth rates for four periods during which high cloud coverage was observed indicate growth dominated by volume controlled reactions. Sulfate accounts for 50% to 72% of the increase in aerosol volume concentration; the rest of the volume concentration increase was likely due to secondary organic species. The growth law analyses and meteorological conditions indicate that the sulfate was produced mainly through aqueous oxidation of SO2 in clouds droplets and hydrated aerosol particles.

  17. Temporal variation of aerosol properties at a rural continental site and study of aerosol evolution through growth law analysis

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Collins, Don; Covert, David; Elleman, Robert; Ferrare, Richard A.; Gasparini, Roberto; Jonsson, Haflidi; Ogren, John; Sheridan, Patrick; Tsay, Si-Chee

    2006-09-01

    Aerosol size distributions were measured by a Scanning Mobility Particle Sizer (SMPS) on board the CIRPAS Twin Otter aircraft during 16 flights at the Southern Great Plains (SGP) site in northern central Oklahoma as part of the Aerosol Intensive Operation period in May 2003. During the same period a second SMPS was deployed at a surface station and provided continuous measurements. Combined with trace gas measurements at the SGP site and back trajectory analysis, the aerosol size distributions provided insights into the sources of aerosols observed at the SGP site. High particle concentrations, observed mostly during daytime, were well correlated with the sulfur dioxide (SO2) mixing ratios, suggesting nucleation involving sulfuric acid is likely the main source of newly formed particles at the SGP. Aerosols within plumes originating from wildfires in Central America were measured at the surface site. Vertically compact aerosol layers, which can be traced back to forest fires in East Asia, were intercepted at altitudes over 3000 m. Analyses of size-dependent particle growth rates for four periods during which high cloud coverage was observed indicate growth dominated by volume controlled reactions. Sulfate accounts for 50% to 72% of the increase in aerosol volume concentration; the rest of the volume concentration increase was likely due to secondary organic species. The growth law analyses and meteorological conditions indicate that the sulfate was produced mainly through aqueous oxidation of SO2 in clouds droplets and hydrated aerosol particles.

  18. Continuum damage model for ferroelectric materials and its application to multilayer actuators

    NASA Astrophysics Data System (ADS)

    Gellmann, Roman; Ricoeur, Andreas

    2016-05-01

    In this paper a micromechanical continuum damage model for ferroelectric materials is presented. As a constitutive law it is implemented into a finite element (FE) code. The model is based on micromechanical considerations of domain switching and its interaction with microcrack growth and coalescence. A FE analysis of a multilayer actuator is performed, showing the initiation of damage zones at the electrode tips during the poling process. Further, the influence of mechanical pre-stressing on damage evolution and actuating properties is investigated. The results provided in this work give useful information on the damage of advanced piezoelectric devices and their optimization.

  19. Evolution of Extra-Nigral Damage Predicts Behavioural Deficits in a Rat Proteasome Inhibitor Model of Parkinson's Disease

    PubMed Central

    Vernon, Anthony C.; Crum, William R.; Johansson, Saga M.; Modo, Michel

    2011-01-01

    Establishing the neurological basis of behavioural dysfunction is key to provide a better understanding of Parkinson's disease (PD) and facilitate development of effective novel therapies. For this, the relationships between longitudinal structural brain changes associated with motor behaviour were determined in a rat model of PD and validated by post-mortem immunohistochemistry. Rats bearing a nigrostriatal lesion induced by infusion of the proteasome inhibitor lactacystin into the left-medial forebrain bundle and saline-injected controls underwent magnetic resonance imaging (MRI) at baseline (prior to surgery) and 1, 3 and 5 weeks post-surgery with concomitant motor assessments consisting of forelimb grip strength, accelerating rotarod, and apormorphine-induced rotation. Lactacystin-injected rats developed early motor deficits alongside decreased ipsilateral cortical volumes, specifically thinning of the primary motor (M1) and somatosensory cortices and lateral ventricle hypertrophy (as determined by manual segmentation and deformation-based morphometry). Although sustained, motor dysfunction and nigrostriatal damage were maximal by 1 week post-surgery. Additional volume decreases in the ipsilateral ventral midbrain; corpus striatum and thalamus were only evident by week 3 and 5. Whilst cortical MRI volume changes best predicted the degree of motor impairment, post-mortem tyrosine hydroxylase immunoreactivity in the striatum was a better predictor of motor behaviour overall, with the notable exception of performance in the accelerating rotarod, in which, M1 cortical thickness remained the best predictor. These results highlight the importance of identifying extra-nigral regions of damage that impact on behavioural dysfunction from damage to the nigrostriatal system. PMID:21364887

  20. Preventing Persons Affected by Serious Mental Illnesses from Obtaining Firearms: The Evolution of Law, Policy, and Practice in Massachusetts.

    PubMed

    Silver, James; Fisher, William H; Silver, Emily

    2015-06-01

    A history of commitment to a mental health facility disqualifies applicants for gun licenses. Identifying such a history has become increasingly complex as the locus of confinement has become more diversified and privatized. In Massachusetts, prior to 2014, the databases used to identify individuals who would be disqualified on such grounds had not contemporaneously matched the evolution of the state's mental health systems. A survey of Massachusetts police chiefs, who, as in many jurisdictions, are charged with certifying qualification, indicates that some have broadened the scope of their background checks to include the experience of their officers with respect to certain applicants. The survey identifying these patterns, conducted in 2014, preceded by one month significant legislative reforms that mandate the modification of the reporting into a centralized database commitments to all types of mental health and substance use facilities, thus allowing identification of all commitments occurring in the state. The anticipated utilization of a different database mechanism, which has parallels in several other states, potentially streamlines the background check process, but raises numerous concerns that need to be addressed in developing and using such databases. PMID:25737302

  1. Mechanical Response of Stitched T300 Mat/Urethane 420 IMR Composite Laminates: Property/Orientation Dependence and Damage Evolution

    SciTech Connect

    Deng, S.; Weitsman, Y.J.

    2000-03-01

    This report presents experimental and analytical results of investigations on the mechanical response of stitched T300 mat/urethane 420 IMR composite laminates with three different lay-up configurations. Tensile tests and short-term creep and recovery tests were conducted on the laminate coupons at various orientations. The X-ray photographic technique was adopted to detect the internal damage due to external loading history. The tensile data of laminates with antisymmetric and symmetric lay-ups indicated that lay- up sequences of cross-ply laminates do not have much influence on their tensile properties. However, misalignments within the stitch-bonded plies disturb the symmetry of intended quasi-isotropic laminates and thereby cause the mechanical properties to exhibit a certain amount of angular dependence. Classic lamination theory was found to be able to provide a very good prediction of tensile properties for the stitched laminates within linear range. Creep and recovery response of laminate coupons is greatly dependent on loading angles and load levels. The internal damage of laminate coupons is also directly related to loading angles and load levels as well as loading history.

  2. Modeling Fatigue Damage in Long-Fiber Thermoplastics

    SciTech Connect

    Nguyen, Ba Nghiep; Kunc, Vlastimil; Bapanapalli, Satish K.

    2009-10-30

    This paper applies a fatigue damage model recently developed for injection-molded long-fiber thermoplastics (LFTs) to predict the modulus reduction and fatigue lifetime of glass/polyamide 6,6 (PA6,6) specimens. The fatigue model uses a multiscale mechanistic approach to describe fatigue damage accumulation in these materials subjected to cyclic loading. Micromechanical modeling using a modified Eshelby-Mori-Tanaka approach combined with averaging techniques for fiber length and orientation distributions is performed to establish the stiffness reduction relation for the composite as a function of the microcrack volume fraction. Next, continuum damage mechanics and a thermodynamic formulation are used to derive the constitutive relations and the damage evolution law. The fatigue damage model has been implemented in the ABAQUS finite element code and has been applied to analyze fatigue of the studied glass/PA6,6 specimens. The predictions agree well with the experimental results.

  3. A Global/Local Finite Element Approach for Predicting Interlaminar and Intralaminar Damage Evolution in Composite Stiffened Panels Under Compressive Load

    NASA Astrophysics Data System (ADS)

    Pietropaoli, Elisa; Riccio, Aniello

    2011-04-01

    This paper addresses the prediction of intralaminar and interlaminar damage onset and evolution in composite structures through the use of a finite element based procedure. This procedure joins methodologies whose credibility has been already assessed in literature such as the Virtual Crack Closure Technique (for delamination) and the ply discount approach (for matrix/fiber failures). In order to establish the reliability of the procedure developed, comparisons with literature experimental results on a stiffened panel with an embedded delamination are illustrated. The methodology proposed, implemented in ANSYS as post-processing routines, is combined with a finite element model of the panel, built by adopting both shell and solid elements within the frame of an embedded global/local approach to connect differently modelled substructures.

  4. A model for time-independent and time-dependent damage evolution and their influence on creep of multidirectional polymer composite laminates

    NASA Astrophysics Data System (ADS)

    Asadi, Amir

    Application of polymer matrix composites in engineering structures has been steadily increasing over the past five decades. Multidirectional polymer composites are one class of continuous fiber reinforced polymer matrix composites used in aerospace structures, where the desired mechanical performance outweighs the cost. Their modulus and strength degrade with time (known as creep and creep rupture) during the service, owing to the viscos-elasticity of the polymer matrix. Additional contribution to this degradation comes from various damage modes developed in the plies of the composite with time and identified in this thesis as TDD (Time Dependent Damage). These damage modes may also develop due to process-induced residual stresses, and during loading to the service load, identified as TID (Time Independent Damage). TID influences the TDD, the creep and the creep rupture. The objective of this thesis is to develop a model to predict the evolution of TID and TDD in multiple plies of a laminate and their influence on creep. The predominant damage mode, transverse cracking, is modeled in this study. The model consists of four modules, PIS, QSL, SL, and VA. The PIS, QSL, and SL moduli predict changes in ply stresses for incremental change in temperature, stress, and time respectively, using lamination theory and assuming linear elastic behavior of the plies during an incremental step. In parallel, each module predicts the stored elastic energy in each ply after each incremental step and compares it with a critical stored elastic energy criterion to determine if a ply would crack. If fracture is predicted, the VA module based on variational analysis, is invoked to determine the crack density and the perturbation in ply stresses due to cracking. The perturbation stresses are used by the module that invoked the VA module to determine the ply stresses after cracking during the current incremental step. The model predictions for a [+/-45/90]s laminate, at two test

  5. A Dynamic Damage Mechanics Source Model for Explosions in Crystalline Rock

    NASA Astrophysics Data System (ADS)

    Mihaly, J. M.; Bhat, H. S.; Sammis, C. G.; Rosakis, A.

    2011-12-01

    The micromechanical damage mechanics formulated by Ashby and Sammis [PAGEOPH, 1990] and generalized by Deshpande and Evans [J. Mech. Phys. Solids, 2008] has been extended to allow for a more generalized stress state and to incorporate an experimentally motivated crack growth (damage evolution) law that is valid over a wide range of loading rates. This law is sensitive to both the crack tip stress field and its time derivative, and thus produces strain-rate sensitivity in the constitutive response. The model is experimentally verified by predicting the failure strength of Dionysus-Pentelicon marble over strain rates ranging from to . This rate-dependent damage mechanics has been implemented in the ABAQUS dynamic finite element code and used to explore the effects of burn rate (loading rate) and lithostatic stress on the spatial extent of fracture damage and S waves generated by explosions in crystalline rock. Slower rise times and longer pressure pulses produce more damage and stronger S waves.

  6. A SMALL-SCALE DAMAGE APPROACH TO PREDICT FATIGUE CRACK GROWTH IN CERAMIC MATERIALS

    SciTech Connect

    Nguyen, Ba Nghiep; Koeppel, Brian J.; Khaleel, Mohammad A.

    2006-05-19

    This paper proposes a small-scale damage modeling approach to predict fatigue crack growth in ceramic materials. A fatigue damage model is formulated that uses two variables. One variable is the scalar damage variable governing the reduction of stiffness, and the other is the number of cycles. The damage evolution law is obtained based on thermodynamics of continuous media and a damage criterion containing a damage threshold function that depends on the damage variable and the cyclic loading parameters. The model has been implemented into the ABAQUS finite element code via user-subroutines and has been used in a modified boundary layer (MBL) modeling approach to analyze fatigue crack growth in a small fracture process zone situated at an initial crack tip. The model application is illustrated through an analysis of fatigue crack growth in an yttria-stabilized tetragonal zirconia material.

  7. Defect interactions with stepped CeO₂/SrTiO₃ interfaces: implications for radiation damage evolution and fast ion conduction.

    PubMed

    Dholabhai, Pratik P; Aguiar, Jeffery A; Misra, Amit; Uberuaga, Blas P

    2014-05-21

    Due to reduced dimensions and increased interfacial content, nanocomposite oxides offer improved functionalities in a wide variety of advanced technological applications, including their potential use as radiation tolerant materials. To better understand the role of interface structures in influencing the radiation damage tolerance of oxides, we have conducted atomistic calculations to elucidate the behavior of radiation-induced point defects (vacancies and interstitials) at interface steps in a model CeO2/SrTiO3 system. We find that atomic-scale steps at the interface have substantial influence on the defect behavior, which ultimately dictate the material performance in hostile irradiation environments. Distinctive steps react dissimilarly to cation and anion defects, effectively becoming biased sinks for different types of defects. Steps also attract cation interstitials, leaving behind an excess of immobile vacancies. Further, defects introduce significant structural and chemical distortions primarily at the steps. These two factors are plausible origins for the enhanced amorphization at steps seen in our recent experiments. The present work indicates that comprehensive examination of the interaction of radiation-induced point defects with the atomic-scale topology and defect structure of heterointerfaces is essential to evaluate the radiation tolerance of nanocomposites. Finally, our results have implications for other applications, such as fast ion conduction. PMID:24852551

  8. Damage evolution of bi-body model composed of weakly cemented soft rock and coal considering different interface effect.

    PubMed

    Zhao, Zenghui; Lv, Xianzhou; Wang, Weiming; Tan, Yunliang

    2016-01-01

    Considering the structure effect of tunnel stability in western mining of China, three typical kinds of numerical model were respectively built as follows based on the strain softening constitutive model and linear elastic-perfectly plastic model for soft rock and interface: R-M, R-C(s)-M and R-C(w)-M. Calculation results revealed that the stress-strain relation and failure characteristics of the three models vary between each other. The combination model without interface or with a strong interface presented continuous failure, while weak interface exhibited 'cut off' effect. Thus, conceptual models of bi-material model and bi-body model were established. Then numerical experiments of tri-axial compression were carried out for the two models. The relationships between stress evolution, failure zone and deformation rate fluctuations as well as the displacement of interface were detailed analyzed. Results show that two breakaway points of deformation rate actually demonstrate the starting and penetration of the main rupture, respectively. It is distinguishable due to the large fluctuation. The bi-material model shows general continuous failure while bi-body model shows 'V' type shear zone in weak body and failure in strong body near the interface due to the interface effect. With the increasing of confining pressure, the 'cut off' effect of weak interface is not obvious. These conclusions lay the theoretical foundation for further development of constitutive model for soft rock-coal combination body. PMID:27066329

  9. International law and law enforcement firearms.

    PubMed

    Jussila, Jorma; Normia, Pertti

    2004-01-01

    Several international agreements set constraints on the legitimate use of firearms as representing lethal force. Their meaning in terms of weapons technology must take into account their operational frame of reference, and legitimate warfare can be regarded as a law enforcement operation with similar principles on the use of force. Changes in weapons technology, such as new types of ammunition, transforming firearms into weapons with less-lethal and even humanitarian options, require new interpretations of the legislation. A division into lethal and non-lethal weapons is an oversimplification and the separation of international humanitarian law into military and law enforcement provisions can be questioned from the technical aspect. The type of technology acceptable for law enforcement use of firearms should be defined. An assessment for weapon injury should not be based on lethality, but rather on the potential for tissue damage and its reversibility. PMID:15015547

  10. Evolution of target organ damage and haemodynamic parameters over 4 years in patients with increased insulin resistance: the LOD-DIABETES prospective observational study

    PubMed Central

    Gómez-Marcos, Manuel Ángel; Recio-Rodríguez, José Ignacio; Patino-Alonso, María Carmen; Agudo-Conde, Cristina; Rodríguez-Sanchez, Emiliano; Maderuelo-Fernandez, Jose Angel; Gómez-Sánchez, Leticia; Gomez-Sanchez, Marta; García-Ortiz, Luís

    2016-01-01

    Objectives We prospectively examined the impact of type 2 diabetes compared with metabolic syndrome (MetS) on the development of vascular disease over 4 years as determined by anatomic and functional markers of vascular disease. By comparing the vascular outcomes of the 2 disorders, we seek to determine the independent effect of elevated glucose levels on vascular disease. Setting 2 primary care centres in Salamanca, Spain. Participants We performed a prospective observational study involving 112 patients (68 with type 2 diabetes and 44 with MetS) who were followed for 4 years. Primary and secondary outcome measures Measurements included blood pressure, blood glucose, lipids, smoking, body mass index, waist circumference, Homeostasis Model Assessment Insulin Resistance (HOMA-IR), hs-c-reactive protein and fibrinogen levels. We also evaluated vascular, carotid intima media thickness (IMT), pulse wave velocity (PWV) and ankle/brachial index, heart and renal target organ damage (TOD). The haemodynamic parameters were central (CAIx) and peripheral (PAIx) augmentation indices. Results In year 4, participants with type 2 diabetes had increased IMT thickness. These patients had more plaques and an IMT>0.90 mm. In participants with MetS, we only found an increase in the number of plaques. We found no changes in PWV, CAIx and PAIx. The patients with diabetes had a greater frequency of vascular TOD. There were no differences neither in renal nor cardiac percentage of TOD in the patients with MetS or diabetes mellitus type 2. Conclusions This prospective study showed that the evolution of vascular TOD is different in participants with type 2 diabetes compared with those with MetS. While IMT and PWV increased in type 2 diabetes, these were not modified in MetS. The renal and cardiac TOD evolution, as well as the PAIx and CAIx, did not change in either group. Trial registration number NCT01065155; Results. PMID:27251684

  11. Computer simulation of creep damage at crack tip in short fibre composites

    NASA Astrophysics Data System (ADS)

    Shuangyin, Zhang; Tsai, L. W.

    1994-08-01

    Creep damage at crack tip in short fibre composites has been simulated by using the finite element method (FEM). The well-known Schapery non-linear viscoelastic constitutive relationship was used to characterize time-dependent behaviour of the material. A modified recurrence equation was adopted to accelerate the iteration. Kachanov-Rabotnov's damage evolution law was employed. The growth of the damage zone with time around the crack tip was calculated and the results were shown with the so-called “digit photo”, which was produced by the printer.

  12. In-situ luminescence monitoring of ion-induced damage evolution in SiO2 and Al2O3

    DOE PAGESBeta

    Crespillo, Miguel L.; Graham, Joseph T.; Zhang, Yanwen; Weber, William J.

    2015-12-17

    Real-time, in-situ ionoluminescence measurements provide information of evolution of emission bands with ion fluence, and thereby establish a correlation between point defect kinetics and phase stability. Using fast light ions (2 MeV H and 3.5 He MeV) and medium mass-high energy ions (8 MeV O, E=0.5 MeV/amu), scintillation materials of a-SiO2, crystalline quartz, and Al2O3 are comparatively investigated at room temperature with the aim of obtaining a further insight on the structural defects induced by ion irradiation and understand the role of electronic energy loss on the damage processes. For more energetic heavy ions, the electronic energy deposition pattern offersmore » higher rates of excitation deeper into the material and allows to evaluate the competing mechanisms between the radiative and non-radiative de-excitation processes. Irradiations with 8 MeV O ions have been selected corresponding to the electronic stopping regime, where the electronic stopping power is dominant, and above the critical amorphization threshold for quartz. Lastly, the usefulness of IBIL and its specific capabilities as a sensitive tool to investigate the material characterization and evaluation of radiation effects are demonstrated.« less

  13. 43 CFR 8365.1-7 - State and local laws.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... and local laws. Except as otherwise provided by Federal law or regulation, State and local laws and..., or destruction or damage to property; (e) Air and water pollution; (f) Littering; (g) Sanitation;...

  14. 43 CFR 8365.1-7 - State and local laws.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... and local laws. Except as otherwise provided by Federal law or regulation, State and local laws and..., or destruction or damage to property; (e) Air and water pollution; (f) Littering; (g) Sanitation;...

  15. 43 CFR 8365.1-7 - State and local laws.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... and local laws. Except as otherwise provided by Federal law or regulation, State and local laws and..., or destruction or damage to property; (e) Air and water pollution; (f) Littering; (g) Sanitation;...

  16. 43 CFR 8365.1-7 - State and local laws.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... and local laws. Except as otherwise provided by Federal law or regulation, State and local laws and..., or destruction or damage to property; (e) Air and water pollution; (f) Littering; (g) Sanitation;...

  17. Water, law, science

    SciTech Connect

    Narasimhan, T.N.

    2007-10-17

    In a world with water resources severely impacted bytechnology, science must actively contribute to water law. To this end,this paper is an earth scientist s attempt to comprehend essentialelements of water law, and to examine their connections to science.Science and law share a common logical framework of starting with apriori prescribed tenets, and drawing consistent inferences. In science,observationally established physical laws constitute the tenets, while inlaw, they stem from social values. The foundations of modern water law inEurope and the New World were formulated nearly two thousand years ago byRoman jurists who were inspired by Greek philosophy of reason.Recognizing that vital natural elements such as water, air, and the seawere governed by immutable natural laws, they reasoned that theseelements belonged to all humans, and therefore cannot be owned as privateproperty. Legally, such public property was to be governed by jusgentium, the law of all people or the law of all nations. In contrast,jus civile or civil law governed private property. Remarkably, jusgentium continues to be relevant in our contemporary society in whichscience plays a pivotal role in exploiting vital resources common to all.This paper examines the historical roots of modern water law, followstheir evolution through the centuries, and examines how the spirit ofscience inherent in jus gentium is profoundly influencing evolving waterand environmental laws in Europe, the United States and elsewhere. In atechnological world, scientific knowledge has to lie at the core of waterlaw. Yet, science cannot formulate law. It is hoped that a philosophicalunderstanding of the relationships between science and law willcontribute to their constructively coming together in the service ofsociety.

  18. Prediction Of Formability In Sheet Metal Forming Processes Using A Local Damage Model

    SciTech Connect

    Teixeira, P.; Santos, Abel; Cesar Sa, J.; Andrade Pires, F.; Barata da Rocha, A.

    2007-05-17

    The formability in sheet metal forming processes is mainly conditioned by ductile fracture resulting from geometric instabilities due to necking and strain localization. The macroscopic collapse associated with ductile failure is a result of internal degradation described throughout metallographic observations by the nucleation, growth and coalescence of voids and micro-cracks. Damage influences and is influenced by plastic deformation and therefore these two dissipative phenomena should be coupled at the constitutive level. In this contribution, Lemaitre's ductile damage model is coupled with Hill's orthotropic plasticity criterion. The coupling between damaging and material behavior is accounted for within the framework of Continuum Damage Mechanics (CDM). The resulting constitutive equations are implemented in the Abaqus/Explicit code, for the prediction of fracture onset in sheet metal forming processes. The damage evolution law takes into account the important effect of micro-crack closure, which dramatically decreases the rate of damage growth under compressive paths.

  19. Cumulative creep damage for polycarbonate and polysulfone

    NASA Technical Reports Server (NTRS)

    Zhang, M.; Brinson, H. F.

    1985-01-01

    The literature for creep to failure cumulative damage laws are reviewed. Creep to failure tests performed on polycarbonate and polysulfone under single and two step loadings are discussed. A cumulative damage law or modified time fraction rule is developed using a power law for transient creep response as the starting point. Experimental results are approximated well by the new rule. Damage and failure mechanisms associated with the two materials are suggested.

  20. 32 CFR 750.33 - Damages.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 32 National Defense 5 2013-07-01 2013-07-01 false Damages. 750.33 Section 750.33 National Defense... Claims Act § 750.33 Damages. (a) Generally. The measure of damages is determined by the law of the place... for interest prior to judgment or for punitive damages. In a death case, if the place where the act...

  1. 32 CFR 750.33 - Damages.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 5 2011-07-01 2011-07-01 false Damages. 750.33 Section 750.33 National Defense... Claims Act § 750.33 Damages. (a) Generally. The measure of damages is determined by the law of the place... for interest prior to judgment or for punitive damages. In a death case, if the place where the act...

  2. 32 CFR 750.33 - Damages.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 5 2012-07-01 2012-07-01 false Damages. 750.33 Section 750.33 National Defense... Claims Act § 750.33 Damages. (a) Generally. The measure of damages is determined by the law of the place... for interest prior to judgment or for punitive damages. In a death case, if the place where the act...

  3. 32 CFR 750.33 - Damages.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 32 National Defense 5 2014-07-01 2014-07-01 false Damages. 750.33 Section 750.33 National Defense... Claims Act § 750.33 Damages. (a) Generally. The measure of damages is determined by the law of the place... for interest prior to judgment or for punitive damages. In a death case, if the place where the act...

  4. 32 CFR 750.33 - Damages.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 5 2010-07-01 2010-07-01 false Damages. 750.33 Section 750.33 National Defense... Claims Act § 750.33 Damages. (a) Generally. The measure of damages is determined by the law of the place... for interest prior to judgment or for punitive damages. In a death case, if the place where the act...

  5. Limit laws for Zipf's law

    NASA Astrophysics Data System (ADS)

    Eliazar, Iddo

    2011-01-01

    In this communication we establish stochastic limit laws leading from Zipf's law to Pareto's and Heaps' laws. We consider finite ensembles governed by Zipf's law and study their asymptotic statistics as the ensemble size tends to infinity. A Lorenz-curve analysis establishes three types of limit laws for the ensembles' statistical structure: 'communist', 'monarchic', and Paretian. Further considering a dynamic setting in which the ensembles grow stochastically in time, a functional central limit theorem analysis establishes a Gaussian approximation for the ensembles' stochastic growth. The Gaussian approximation provides a generalized and corrected formulation of Heaps' law.

  6. Courtside: A Damaging Lesson

    ERIC Educational Resources Information Center

    Zirkel, Perry A.

    2004-01-01

    This case presents a costly lesson for teachers and for districts that include a liquidated, or stipulated, damages clause in their teacher employment contracts. Although the court enforced the clause in this case, in this well-reasoned recent decision and in most of the much older, canvassed case law from other jurisdictions, the answer to the…

  7. Micro-Macro Analysis and Phenomenological Modelling of Salt Viscous Damage and Application to Salt Caverns

    NASA Astrophysics Data System (ADS)

    Zhu, Cheng; Pouya, Ahmad; Arson, Chloé

    2015-11-01

    This paper aims to gain fundamental understanding of the microscopic mechanisms that control the transition between secondary and tertiary creep around salt caverns in typical geological storage conditions. We use a self-consistent inclusion-matrix model to homogenize the viscoplastic deformation of halite polycrystals and predict the number of broken grains in a Representative Elementary Volume of salt. We use this micro-macro modeling framework to simulate creep tests under various axial stresses, which gives us the critical viscoplastic strain at which grain breakage (i.e., tertiary creep) is expected to occur. The comparison of simulation results for short-term and long-term creep indicates that the initiation of tertiary creep depends on the stress and the viscoplastic strain. We use the critical viscoplastic deformation as a yield criterion to control the transition between secondary and tertiary creep in a phenomenological viscoplastic model, which we implement into the Finite Element Method program POROFIS. We model a 850-m-deep salt cavern of irregular shape, in axis-symmetric conditions. Simulations of cavern depressurization indicate that a strain-dependent damage evolution law is more suitable than a stress-dependent damage evolution law, because it avoids high damage concentrations and allows capturing the formation of a damaged zone around the cavity. The modeling framework explained in this paper is expected to provide new insights to link grain breakage to phenomenological damage variables used in Continuum Damage Mechanics.

  8. MULTI-WAVELENGTH OBSERVATIONS OF THE SPATIO-TEMPORAL EVOLUTION OF SOLAR FLARES WITH AIA/SDO. II. HYDRODYNAMIC SCALING LAWS AND THERMAL ENERGIES

    SciTech Connect

    Aschwanden, Markus J.; Shimizu, Toshifumi E-mail: shimizu.toshifumi@isas.jaxa.jp

    2013-10-20

    In this study we measure physical parameters of the same set of 155 M- and X-class solar flares observed with AIA/SDO as analyzed in Paper I, by performing a differential emission measure analysis to determine the flare peak emission measure EM{sub p} , peak temperature T{sub p} , electron density n{sub p} , and thermal energy E{sub th}, in addition to the spatial scales L, areas A, and volumes V measured in Paper I. The parameter ranges for M- and X-class flares are log (EM{sub p}) = 47.0-50.5, T{sub p} = 5.0-17.8 MK, n{sub p} = 4 × 10{sup 9}-9 × 10{sup 11} cm{sup –3}, and thermal energies of E{sub th} = 1.6 × 10{sup 28}-1.1 × 10{sup 32} erg. We find that these parameters obey the Rosner-Tucker-Vaiana (RTV) scaling law T{sub p}{sup 2}∝n{sub p} L and H∝T {sup 7/2} L {sup –2} during the peak time t{sub p} of the flare density n{sub p} , when energy balance between the heating rate H and the conductive and radiative loss rates is achieved for a short instant and thus enables the applicability of the RTV scaling law. The application of the RTV scaling law predicts power-law distributions for all physical parameters, which we demonstrate with numerical Monte Carlo simulations as well as with analytical calculations. A consequence of the RTV law is also that we can retrieve the size distribution of heating rates, for which we find N(H)∝H {sup –1.8}, which is consistent with the magnetic flux distribution N(Φ)∝Φ{sup –1.85} observed by Parnell et al. and the heating flux scaling law F{sub H} ∝HL∝B/L of Schrijver et al.. The fractal-diffusive self-organized criticality model in conjunction with the RTV scaling law reproduces the observed power-law distributions and their slopes for all geometrical and physical parameters and can be used to predict the size distributions for other flare data sets, instruments, and detection algorithms.

  9. Continuum Damage Modeling of Short-Fiber Composites Subject to Matrix Cracking

    SciTech Connect

    Nguyen, Ba Nghiep; Ahn, Byung K.; Khaleel, Mohammad A.

    2002-09-01

    In this paper, a continuum damage mechanics approach proposed by Renard et al. for continuous fiber composites subject to matrix cracking is extended to misoriented short-fiber composites. First, the associated damage variable is defined as a measure of the crack density, then the model by Laws et al. is used to determine the stiffness reduction of an aligned short-fiber composite. Considering moderate microcrack densities and assuming completely random and planar orientations of microcracks and fibers, the stiffness of a cracked misoriented fiber layer is obtained by averaging that of a cracked aligned fiber composite over all possible orientations and weighted by an orientation distribution function. The damage evolution law is obtained using the concepts of thermodynamics of continuum media.

  10. An anisotropic thermomechanical damage model for concrete at transient elevated temperatures.

    PubMed

    Baker, Graham; de Borst, René

    2005-11-15

    The behaviour of concrete at elevated temperatures is important for an assessment of integrity (strength and durability) of structures exposed to a high-temperature environment, in applications such as fire exposure, smelting plants and nuclear installations. In modelling terms, a coupled thermomechanical analysis represents a generalization of the computational mechanics of fracture and damage. Here, we develop a fully coupled anisotropic thermomechanical damage model for concrete under high stress and transient temperature, with emphasis on the adherence of the model to the laws of thermodynamics. Specific analytical results are given, deduced from thermodynamics, of a novel interpretation on specific heat, evolution of entropy and the identification of the complete anisotropic, thermomechanical damage surface. The model is also shown to be stable in a computational sense, and to satisfy the laws of thermodynamics. PMID:16243703

  11. Cumulative creep damage for polycarbonate and polysulfone

    NASA Technical Reports Server (NTRS)

    Zhang, M. J.; Straight, M. R.; Brinson, H. F.

    1985-01-01

    Creep to failure tests performed on polycarbonate and polysulfone under single and two step loadings are discussed. A cumulative damage law or modified time fraction rule is developed using a power law for transient creep response as the starting point. Experimental results are approximated well by the new rule. Damage and failure mechanisms associated with the two materials are suggested.

  12. A model for high temperature creep of single crystal superalloys based on nonlocal damage and viscoplastic material behavior

    NASA Astrophysics Data System (ADS)

    Trinh, B. T.; Hackl, K.

    2014-07-01

    A model for high temperature creep of single crystal superalloys is developed, which includes constitutive laws for nonlocal damage and viscoplasticity. It is based on a variational formulation, employing potentials for free energy, and dissipation originating from plasticity and damage. Evolution equations for plastic strain and damage variables are derived from the well-established minimum principle for the dissipation potential. The model is capable of describing the different stages of creep in a unified way. Plastic deformation in superalloys incorporates the evolution of dislocation densities of the different phases present. It results in a time dependence of the creep rate in primary and secondary creep. Tertiary creep is taken into account by introducing local and nonlocal damage. Herein, the nonlocal one is included in order to model strain localization as well as to remove mesh dependence of finite element calculations. Numerical results and comparisons with experimental data of the single crystal superalloy LEK94 are shown.

  13. Damage evolution analysis in mortar, during compressive loading using acoustic emission and X-ray tomography: Effects of the sand/cement ratio

    SciTech Connect

    Elaqra, H.; Godin, N.; Peix, G.; R'Mili, M. . E-mail: Mohamed.Rmili@insa-lyon.fr; Fantozzi, G.

    2007-05-15

    This paper explores the use of acoustic emission (AE) and X-ray tomography to identify the mechanisms of damage and the fracture process during compressive loading on concrete specimens. Three-dimensional (3D) X-ray tomography image analysis was used to observe defects of virgin mortar specimen under different compressive loads. Cumulative AE events were used to evaluate damage process in real time according to the sand/cement ratio. This work shows that AE and X-ray tomography are complementary nondestructive methods to measure, characterise and locate damage sites in mortar. The effect of the sand proportion on damage and fracture behaviour is studied, in relation with the microstructure of the material.

  14. Partition coefficients for REE between garnets and liquids - Implications of non-Henry's Law behaviour for models of basalt origin and evolution

    NASA Technical Reports Server (NTRS)

    Harrison, W. J.

    1981-01-01

    An experimental investigation of Ce, Sm and Tm rare earth element (REE) partition coefficients between coexisting garnets (both natural and synthetic) and hydrous liquids shows that Henry's Law may not be obeyed over a range of REE concentrations of geological relevance. Systematic differences between the three REE and the two garnet compositions may be explained in terms of the differences between REE ionic radii and those of the dodecahedral site into which they substitute, substantiating the Harrison and Wood (1980) model of altervalent substitution. Model calculations demonstrate that significant variation can occur in the rare earth contents of melts produced from a garnet lherzolite, if Henry's Law partition coefficients do not apply for the garnet phase.

  15. Limits of imagination: the 150th Anniversary of Mendel's Laws, and why Mendel failed to see the importance of his discovery for Darwin's theory of evolution.

    PubMed

    Singh, Rama S

    2015-09-01

    Mendel is credited for discovering Laws of Heredity, but his work has come under criticism on three grounds: for possible falsification of data to fit his expectations, for getting undue credit for the laws of heredity without having ideas of segregation and independent assortment, and for being interested in the development of hybrids rather than in the laws of heredity. I present a brief review of these criticisms and conclude that Mendel deserved to be called the father of genetics even if he may not, and most likely did not, have clear ideas of segregation and particulate determiners as we know them now. I argue that neither Mendel understood the evolutionary significance of his findings for the problem of genetic variation, nor would Darwin have understood their significance had he read Mendel's paper. I argue that the limits to imagination, in both cases, came from their mental framework being shaped by existing paradigms-blending inheritance in the case of Darwin, hybrid development in the case of Mendel. Like Einstein, Darwin's natural selection was deterministic; like Niels Bohr, Mendel's Laws were probabilistic-based on random segregation of trait-determining "factors". Unlike Einstein who understood quantum mechanics, Darwin would have been at a loss with Mendel's paper with no guide to turn to. Geniuses in their imaginations are like heat-seeking missiles locked-in with their targets of deep interests and they generally see things in one dimension only. Imagination has limits; unaided imagination is like a bird without wings--it goes nowhere. PMID:26372894

  16. Law 302.

    ERIC Educational Resources Information Center

    Manitoba Dept. of Education, Winnipeg.

    This publication outlines a law course intended as part of a business education program in the secondary schools of Manitoba, Canada. The one credit course of study should be taught over a period of 110-120 hours of instruction. It provides students with an introduction to the principles, practices, and consequences of law with regard to torts,…

  17. Interacting damage models mapped onto ising and percolation models

    SciTech Connect

    Toussaint, Renaud; Pride, Steven R.

    2004-03-23

    The authors introduce a class of damage models on regular lattices with isotropic interactions between the broken cells of the lattice. Quasistatic fiber bundles are an example. The interactions are assumed to be weak, in the sense that the stress perturbation from a broken cell is much smaller than the mean stress in the system. The system starts intact with a surface-energy threshold required to break any cell sampled from an uncorrelated quenched-disorder distribution. The evolution of this heterogeneous system is ruled by Griffith's principle which states that a cell breaks when the release in potential (elastic) energy in the system exceeds the surface-energy barrier necessary to break the cell. By direct integration over all possible realizations of the quenched disorder, they obtain the probability distribution of each damage configuration at any level of the imposed external deformation. They demonstrate an isomorphism between the distributions so obtained and standard generalized Ising models, in which the coupling constants and effective temperature in the Ising model are functions of the nature of the quenched-disorder distribution and the extent of accumulated damage. In particular, they show that damage models with global load sharing are isomorphic to standard percolation theory, that damage models with local load sharing rule are isomorphic to the standard ising model, and draw consequences thereof for the universality class and behavior of the autocorrelation length of the breakdown transitions corresponding to these models. they also treat damage models having more general power-law interactions, and classify the breakdown process as a function of the power-law interaction exponent. Last, they also show that the probability distribution over configurations is a maximum of Shannon's entropy under some specific constraints related to the energetic balance of the fracture process, which firmly relates this type of quenched-disorder based damage model

  18. Interacting damage models mapped onto Ising and percolation models.

    PubMed

    Toussaint, Renaud; Pride, Steven R

    2005-04-01

    We introduce a class of damage models on regular lattices with isotropic interactions between the broken cells of the lattice. Quasi-static fiber bundles are an example. The interactions are assumed to be weak, in the sense that the stress perturbation from a broken cell is much smaller than the mean stress in the system. The system starts intact with a surface-energy threshold required to break any cell sampled from an uncorrelated quenched-disorder distribution. The evolution of this heterogeneous system is ruled by Griffith's principle which states that a cell breaks when the release in potential (elastic) energy in the system exceeds the surface-energy barrier necessary to break the cell. By direct integration over all possible realizations of the quenched disorder, we obtain the probability distribution of each damage configuration at any level of the imposed external deformation. We demonstrate an isomorphism between the distributions so obtained and standard generalized Ising models, in which the coupling constants and effective temperature in the Ising model are functions of the nature of the quenched-disorder distribution and the extent of accumulated damage. In particular, we show that damage models with global load sharing are isomorphic to standard percolation theory and that damage models with a local load sharing rule are isomorphic to the standard Ising model, and draw consequences thereof for the universality class and behavior of the autocorrelation length of the breakdown transitions corresponding to these models. We also treat damage models having more general power-law interactions, and classify the breakdown process as a function of the power-law interaction exponent. Last, we also show that the probability distribution over configurations is a maximum of Shannon's entropy under some specific constraints related to the energetic balance of the fracture process, which firmly relates this type of quenched-disorder based damage model to standard

  19. Constitutive modeling of solid propellant materials with evolving microstructural damage

    NASA Astrophysics Data System (ADS)

    Xu, F.; Aravas, N.; Sofronis, P.

    Solid propellants are composite materials with complex microstructure. In a generic form, the material consists of polymeric binder, crystal oxidizer (e.g., ammonium perchlorate), and fuel particles (e.g., aluminum). Severe stressing and extreme temperatures induce damage which is manifested in particle cracking, dewetting along particle/polymer interfaces, void nucleation and growth. Damage complicates the overall constitutive response of a solid propellant over and above the complexities associated with the differing constitutive properties of the particle and binder phases. Using rigorous homogenization theory for composite materials, we propose a general 3-D nonlinear macroscopic constitutive law that models microstructural damage evolution upon straining through continuous void formation and growth. The law addresses the viscous deformation rate within the framework of additive decomposition of the deformation rate and the concept of back stress is used to improve the model performance in stress relaxation. No restriction is placed on the magnitude of the strains. Experimental data from the standard relaxation and uniaxial tension tests are used to calibrate the model parameters in the case of a high elongation solid propellant. It is emphasized that the model parameters are descriptors of individual phase constitutive response and criticality conditions for particle decohesion which can systematically be determined through experiment. The model is used to predict the response of the material under more complex loading paths and to investigate the effect of crack tip damage on the mechanical behavior of a compact tension fracture specimen.

  20. Irreversible entropy model for damage diagnosis in resistors

    SciTech Connect

    Cuadras, Angel Crisóstomo, Javier; Ovejas, Victoria J.; Quilez, Marcos

    2015-10-28

    We propose a method to characterize electrical resistor damage based on entropy measurements. Irreversible entropy and the rate at which it is generated are more convenient parameters than resistance for describing damage because they are essentially positive in virtue of the second law of thermodynamics, whereas resistance may increase or decrease depending on the degradation mechanism. Commercial resistors were tested in order to characterize the damage induced by power surges. Resistors were biased with constant and pulsed voltage signals, leading to power dissipation in the range of 4–8 W, which is well above the 0.25 W nominal power to initiate failure. Entropy was inferred from the added power and temperature evolution. A model is proposed to understand the relationship among resistance, entropy, and damage. The power surge dissipates into heat (Joule effect) and damages the resistor. The results show a correlation between entropy generation rate and resistor failure. We conclude that damage can be conveniently assessed from irreversible entropy generation. Our results for resistors can be easily extrapolated to other systems or machines that can be modeled based on their resistance.

  1. 3D Progressive Damage Modeling for Laminated Composite Based on Crack Band Theory and Continuum Damage Mechanics

    NASA Technical Reports Server (NTRS)

    Wang, John T.; Pineda, Evan J.; Ranatunga, Vipul; Smeltzer, Stanley S.

    2015-01-01

    A simple continuum damage mechanics (CDM) based 3D progressive damage analysis (PDA) tool for laminated composites was developed and implemented as a user defined material subroutine to link with a commercially available explicit finite element code. This PDA tool uses linear lamina properties from standard tests, predicts damage initiation with an easy-to-implement Hashin-Rotem failure criteria, and in the damage evolution phase, evaluates the degradation of material properties based on the crack band theory and traction-separation cohesive laws. It follows Matzenmiller et al.'s formulation to incorporate the degrading material properties into the damaged stiffness matrix. Since nonlinear shear and matrix stress-strain relations are not implemented, correction factors are used for slowing the reduction of the damaged shear stiffness terms to reflect the effect of these nonlinearities on the laminate strength predictions. This CDM based PDA tool is implemented as a user defined material (VUMAT) to link with the Abaqus/Explicit code. Strength predictions obtained, using this VUMAT, are correlated with test data for a set of notched specimens under tension and compression loads.

  2. Ductile Damage Evolution Assessment in High Purity Copper and Stainless Steel Subjected to Different Shock-Loading Profiles Using Cohesive Modeling

    NASA Astrophysics Data System (ADS)

    Ruggiero, A.; Bonora, N.; Esposito, L.; Gray, G. T.

    2009-12-01

    The calculated energy dissipation associated with the pull-back signal amplitude in plate impact experiment is usually larger than that obtained by accounting the contributions of the estimated plastic work at continuum scale and that due to ductile damage. As a possible explanation, it is proposed that the drop in the stress triaxiality, due to the formation of free surfaces as a result of the first appearance of the damage in form of voids, allows the matrix material to exhibit much larger plastic deformation. In order to verify this proposition, a numerical investigation based on the use of cohesive finite elements has been performed. The proposed numerical model has been used to predict the damage development and the rear pressure profile in a flyer plate impact test on 99.99% Cu and 316 L SS under flat top and triangular pressure wave profile.

  3. EFFECT OF CREVICE FORMER ON CORROSION DAMAGE PROPAGATION

    SciTech Connect

    J.H. Payer; U. Landau; X. Shan; A.S. Agarwal

    2006-03-01

    The objectives of this report are: (1) To determine the effect of the crevice former on the localized corrosion damage propagation; (2) FOCUS on post initiation stage, crevice propagation and arrest processes; (3) Determine the evolution of damage--severity, shape, location/distribution, damage profile; and (4) Model of crevice corrosion propagation, i.e. the evolution of the crevice corrosion damage profile.

  4. A damage mechanics based general purpose interface/contact element

    NASA Astrophysics Data System (ADS)

    Yan, Chengyong

    Most of the microelectronics packaging structures consist of layered substrates connected with bonding materials, such as solder or epoxy. Predicting the thermomechanical behavior of these multilayered structures is a challenging task in electronic packaging engineering. In a layered structure the most complex part is always the interfaces between the strates. Simulating the thermo-mechanical behavior of such interfaces, is the main theme of this dissertation. The most commonly used solder material, Pb-Sn alloy, has a very low melting temperature 180sp°C, so that the material demonstrates a highly viscous behavior. And, creep usually dominates the failure mechanism. Hence, the theory of viscoplasticity is adapted to describe the constitutive behavior. In a multilayered assembly each layer has a different coefficient of thermal expansion. Under thermal cycling, due to heat dissipated from circuits, interfaces and interconnects experience low cycle fatigue. Presently, the state-of-the art damage mechanics model used for fatigue life predictions is based on Kachanov (1986) continuum damage model. This model uses plastic strain as a damage criterion. Since plastic strain is a stress path dependent value, the criterion does not yield unique damage values for the same state of stress. In this dissertation a new damage evolution equation based on the second law of thermodynamic is proposed. The new criterion is based on the entropy of the system and it yields unique damage values for all stress paths to the final state of stress. In the electronics industry, there is a strong desire to develop fatigue free interconnections. The proposed interface/contact element can also simulate the behavior of the fatigue free Z-direction thin film interconnections as well as traditional layered interconnects. The proposed interface element can simulate behavior of a bonded interface or unbonded sliding interface, also called contact element. The proposed element was verified against

  5. Progressive Damage Analysis of Laminated Composite (PDALC)-A Computational Model Implemented in the NASA COMET Finite Element Code

    NASA Technical Reports Server (NTRS)

    Lo, David C.; Coats, Timothy W.; Harris, Charles E.; Allen, David H.

    1996-01-01

    A method for analysis of progressive failure in the Computational Structural Mechanics Testbed is presented in this report. The relationship employed in this analysis describes the matrix crack damage and fiber fracture via kinematics-based volume-averaged variables. Damage accumulation during monotonic and cyclic loads is predicted by damage evolution laws for tensile load conditions. The implementation of this damage model required the development of two testbed processors. While this report concentrates on the theory and usage of these processors, a complete list of all testbed processors and inputs that are required for this analysis are included. Sample calculations for laminates subjected to monotonic and cyclic loads were performed to illustrate the damage accumulation, stress redistribution, and changes to the global response that occur during the load history. Residual strength predictions made with this information compared favorably with experimental measurements.

  6. MULTI-WAVELENGTH OBSERVATIONS OF THE SPATIO-TEMPORAL EVOLUTION OF SOLAR FLARES WITH AIA/SDO. I. UNIVERSAL SCALING LAWS OF SPACE AND TIME PARAMETERS

    SciTech Connect

    Aschwanden, Markus J.; Zhang, Jie; Liu, Kai E-mail: jzhang7@gmu.edu

    2013-09-20

    We extend a previous statistical solar flare study of 155 GOES M- and X-class flares observed with AIA/SDO to all seven coronal wavelengths (94, 131, 171, 193, 211, 304, and 335 Å) to test the wavelength dependence of scaling laws and statistical distributions. Except for the 171 and 193 Å wavelengths, which are affected by EUV dimming caused by coronal mass ejections (CMEs), we find near-identical size distributions of geometric (lengths L, flare areas A, volumes V, and fractal dimension D{sub 2}), temporal (flare durations T), and spatio-temporal parameters (diffusion coefficient κ, spreading exponent β, and maximum expansion velocities v{sub max}) in different wavelengths, which are consistent with the universal predictions of the fractal-diffusive avalanche model of a slowly driven, self-organized criticality (FD-SOC) system, i.e., N(L)∝L {sup –3}, N(A)∝A {sup –2}, N(V)∝V {sup –5/3}, N(T)∝T {sup –2}, and D{sub 2} = 3/2, for a Euclidean dimension d = 3. Empirically, we find also a new strong correlation κ∝L {sup 0.94±0.01} and the three-parameter scaling law L∝κ T {sup 0.1}, which is more consistent with the logistic-growth model than with classical diffusion. The findings suggest long-range correlation lengths in the FD-SOC system that operate in the vicinity of a critical state, which could be used for predictions of individual extreme events. We find also that eruptive flares (with accompanying CMEs) have larger volumes V, longer flare durations T, higher EUV and soft X-ray fluxes, and somewhat larger diffusion coefficients κ than confined flares (without CMEs)

  7. Progressive Damage Analysis of Laminated Composite (PDALC) (A Computational Model Implemented in the NASA COMET Finite Element Code). 2.0

    NASA Technical Reports Server (NTRS)

    Coats, Timothy W.; Harris, Charles E.; Lo, David C.; Allen, David H.

    1998-01-01

    A method for analysis of progressive failure in the Computational Structural Mechanics Testbed is presented in this report. The relationship employed in this analysis describes the matrix crack damage and fiber fracture via kinematics-based volume-averaged damage variables. Damage accumulation during monotonic and cyclic loads is predicted by damage evolution laws for tensile load conditions. The implementation of this damage model required the development of two testbed processors. While this report concentrates on the theory and usage of these processors, a complete listing of all testbed processors and inputs that are required for this analysis are included. Sample calculations for laminates subjected to monotonic and cyclic loads were performed to illustrate the damage accumulation, stress redistribution, and changes to the global response that occurs during the loading history. Residual strength predictions made with this information compared favorably with experimental measurements.

  8. [The concept of loss of chance: A major evolution in the definition of damage or how to prevent litigation for loss of chance?].

    PubMed

    Nguyen, T-D

    2016-07-01

    The concept of medical error in responsibility litigation was based until the past last years on a necessary direct and definite causal link between fault and injury. In France, since the 1960s and increasingly during the last decade, the idea of loss of chance arose, considered as a new and genuine prejudice (practically, a fixable damage); it became the subject of several legal precedents from the Cour de cassation and the Conseil d'État. Thus, plaintiffs may currently demand a compensation for a loss of chance even though a doubt exists on the causal link between the fault and the observed damage. The most frequent litigation circumstances implying a loss of chance are lack of information, lack or delay in diagnosis, delay in action, and default in medical assessment. Based on practical cases, the author presents the most propitious situations where litigation for loss of chance may occur and discusses possible preventive measures. PMID:27342945

  9. Cumulative fatigue damage models

    NASA Technical Reports Server (NTRS)

    Mcgaw, Michael A.

    1988-01-01

    The problem of calculating expected component life under fatigue loading conditions is complicated by the fact that component loading histories contain, in many cases, cyclic loads of widely varying amplitudes. In such a case a cumulative damage model is required, in addition to a fatigue damage criterion, or life relationship, in order to compute the expected fatigue life. The traditional cumulative damage model used in design is the linear damage rule. This model, while being simple to use, can yield grossly unconservative results under certain loading conditions. Research at the NASA Lewis Research Center has led to the development of a nonlinear cumulative damage model, named the double damage curve approach (DDCA), that has greatly improved predictive capability. This model, which considers the life (or loading) level dependence of damage evolution, was applied successfully to two polycrystalline materials, 316 stainless steel and Haynes 188. The cumulative fatigue behavior of the PWA 1480 single-crystal material is currently being measured to determine the applicability of the DDCA for this material.

  10. Effects of multiaxial stress state and saltwater on fatigue damage and failure of glass/epoxy composite

    NASA Astrophysics Data System (ADS)

    Wang, Feng

    2007-12-01

    Fiber composites used in advanced mechanical systems are generally subjected to cyclic loading with multiaxial stress state. Thus multiaxial fatigue is a subject of major importance in design and evaluation of long-term performance of composite structures and components. Theoretical work was initially performed to address the fundamental issues of damage evolution and material degradation in glass/epoxy composites subject to multiaxial cyclic stresses. A continuum damage mechanics formulation based on irreversible thermodynamics was used to construct multiaxial cyclic constitutive equations of the composite. With coupling of damage anisotropy and multiaxial stress state and using Gibb's free energy function, damage driving force was determined. Based on the second principle of thermodynamics, evolution equations were also obtained to describe the change of the damage state in the composite under multiaxial fatigue loading. A newly introduced failure-life theory was employed for the fiber composite, based on anisotropic nature of composite strength property and distinct mechanisms of microcrack formation and growth under different multiaxial cyclic stresses. A driving force for fatigue failure was formulated with a governing function, involving combined cyclic shear and transverse tensile stresses along the weakest principal material plane of the composite. Multiaxial fatigue life of the composite was related to the forcing function using a power-law. A formulation of thermomechanical response of a fiber composite based on the general thermodynamics theory was proposed to establish a model that can couple water sorption, applied stress and damage in the composite. Starting from general Gibbs free energy, constitutive equations, which describe the relationships between state variables and corresponding driving forces, were derived. The evolution laws that describe relationships of damage driving force-damage evolution and chemical potential gradient-water flux were