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Sample records for delamination front curvature

  1. Solitary Wave and Wave Front as Viewed From Curvature

    Institute of Scientific and Technical Information of China (English)

    LIU Shi-Kuo; FU Zun-Tao; LIU Shi-Da; LIANG Fu-Ming; XIN Guo-Jun

    2004-01-01

    The solitary wave and wave front are two important behaviors of nonlinear evolution equations. Geometri cally, solitary wave and wave front are all plane curve. In this paper, they can be represented in terms of curvature c(s), which varies with arc length s. For solitary wave when s →±∞, then its curvature c(s) approaches zero, and when s = 0, the curvature c(s) reaches its maximum. For wave front, when s →±∞, then its curvature c(s) approaches zero, and when s = 0, the curvature c(s) is still zero, but c'(s) ≠ 0. That is, s = 0 is a turning point. When c(s) is given, the variance at some point (x, y) in stream line with arc length s satisfies a 2-order linear variable-coefficient ordinary differential equation. From this equation, it can be determined qualitatively whether the given curvature is a solitary wave or wave front.

  2. Solitary Wave and Wave Front as Viewed From Curvature

    Institute of Scientific and Technical Information of China (English)

    LIUShi-Kuo; FUZun-Tao; LIUShi-Da; LIANGFu-Ming; XINGuo-Jun

    2004-01-01

    The solitary wave and wave front are two important behaviors of nonlinear evolution equations. Geometrically, solitary wave and wave front are all plane curve. In this paper, they can be represented in terms of curvature c(s),which varies with arc length s. For solitary wave when s→±∞, then its curvature c(s) approaches zero, and whens = 0, the curvature c(s) reaches its maximum. For wave front, when s→±∞, then its curvature c(s) approaches zero,and when s = 0, the curvature c(s) is still zero, but c'(s)≠0. That is, s = 0 is a turning point. When c(s) is given,the variance at some point (x, y) in stream line with arc length s satisfies a 2-order linear variable-coeffcient ordinary differential equation. From this equation, it can be determined qualitatively whether the given curvature is a solitary wave or wave front.

  3. Solvent-starved conditions in confinement cause chemical oscillations excited by passage of a cathodic delamination front.

    Science.gov (United States)

    Iqbal, Danish; Sarfraz, Adnan; Stratmann, Martin; Erbe, Andreas

    2015-11-18

    After passage of a delamination front at a polymer/zinc interface, pH oscillations and oscillations in the quantity of corrosion products are observed. The reason for these oscillations is the low quantity of water in the confined reaction volume, water consumption by oxygen reduction, and water regeneration after precipitation of ZnO.

  4. Prediction and control of front-end curvature in hot finish rolling process

    Directory of Open Access Journals (Sweden)

    Kyunghun Lee

    2015-11-01

    Full Text Available The purpose of this study is to predict the front-end curvature in hot strip finishing mills and to prevent it by controlling the rolling conditions. A theoretical model based on the slab method is developed for predicting the front-end curvature by taking into account the entrance angle of the strip, the friction condition and the back tension. To validate the developed theoretical model, the theoretically obtained curvature value is compared with the results of finite element analysis. Consequently, it is shown that the calculation results of the theoretical model are in good agreement with the measured results of the finite element analysis. Furthermore, a curvature control model based on geometrical and mathematical approaches that can reduce the front-end curvature by the control of the roll speed ratio of the upper to lower rolls is proposed. The proposed curvature control model is verified by finite element analysis, and it is shown that the front-end curvature can be reduced considerably using the proposed model. Therefore, it is concluded that the proposed control model for reducing the front-end curvature in a hot strip finishing mill can be used to improve the quality of the rolled product.

  5. Geometry-specific scaling of detonation parameters from front curvature

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, Scott I [Los Alamos National Laboratory; Short, Mark [Los Alamos National Laboratory

    2011-01-20

    It has previously been asserted that classical detonation curvature theory predicts that the critical diameter and the diameter-effect curve of a cylindrical high-explosive charge should scale with twice the thickness of an analogous two-dimensional explosive slab. The varied agreement of experimental results with this expectation have led some to question the ability of curvature-based concepts to predict detonation propagation in non-ideal explosives. This study addresses such claims by showing that the expected scaling relationship (hereafter referred to d = 2w) is not consistent with curvature-based Detonation Shock Dynamics (DSD) theory.

  6. CURVATURE RELATION OF WAVE FRONT AND WAVE CHANGING IN EXTERNAL FIELD

    Institute of Scientific and Technical Information of China (English)

    LIU Shen-quan; SONG Le

    2005-01-01

    The changing of wave structure in excitable media in external field is studied and the curvature relation of wave front is analyzed. Under external stimulus the normal velocity of wave front has linear relation with mean curvature of wave front, plane velocity and external field. The simulation methods have been used to analyze BarEiswirth model with external field and obtain the wave pattern of excitable media contained external stimulus. These theoretical analysis and simulation results are identical with experiments of BZ reaction. So the results here theoretically explain the BZ phenomenon under external field and the simulation results here have rich wave patterns.

  7. Controllable soliton propagation based on phase-front curvature in asymmetrical nonlocal media

    Science.gov (United States)

    Zhang, Huafeng; Lü, Hua; Luo, Jianghua; Sun, Lihui

    2016-08-01

    The influence of phase-front curvature on the dynamical behavior of the fundamental mode soliton during its transmission in asymmetrical nonlocal media is studied in detail and the phase-front curvature can be imposed on the fundamental mode soliton by reshaping or phase imprinting technologies. By changing the phase-front curvature or its imposed position, controllable soliton propagation in asymmetrical nonlocal media can be achieved. Project supported by the National Natural Science Foundation of China (Grants Nos. 11547007 and 11304024), the Innovation Personnel Training Plan for Excellent Youth of Guangdong University Project (Grant No. 2013LYM_0023), and the Yangtze Fund for Youth Teams of Science and Technology Innovation (Grant No. 2015cqt03).

  8. Accurate eikonal-curvature relation for wave fronts in locally anisotropic reaction-diffusion systems.

    Science.gov (United States)

    Dierckx, Hans; Bernus, Olivier; Verschelde, Henri

    2011-09-02

    The dependency of wave velocity in reaction-diffusion (RD) systems on the local front curvature determines not only the stability of wave propagation, but also the fundamental properties of other spatial configurations such as vortices. This Letter gives the first derivation of a covariant eikonal-curvature relation applicable to general RD systems with spatially varying anisotropic diffusion properties, such as cardiac tissue. The theoretical prediction that waves which seem planar can nevertheless possess a nonvanishing geometrical curvature induced by local anisotropy is confirmed by numerical simulations, which reveal deviations up to 20% from the nominal plane wave speed.

  9. Pulsar Polar Cap Heating and Surface Thermal X-Ray Emission I. Curvature Radiation Pair Fronts

    CERN Document Server

    Harding, A K; Harding, Alice K.; Muslimov, Alexander G.

    2001-01-01

    We investigate the effect of pulsar polar cap (PC) heating produced by positrons returning from the upper pair formation front. Our calculations are based on a self-consistent treatment of the pair dynamics and the effect of electric field screening by the returning positrons. We calculate the resultant X-ray luminosities, and discuss the dependence of the PC heating efficiencies on pulsar parameters, such as characteristic spin-down age, spin period, and surface magnetic field strength. In this study we concentrate on the regime where the pairs are produced in a magnetic field by curvature photons emitted by accelerating electrons. Our theoretical results are not in conflict with the available observational X-ray data and suggest that the effect of PC heating should significantly contribute to the thermal X-ray fluxes from middle-aged and old pulsars. The implications for current and future X-ray observations of pulsars are briefly outlined.

  10. Delamination tolerance studies in laminated composite panels

    Indian Academy of Sciences (India)

    K L Singh; B Dattaguru; T S Ramamurthy; P D Mangalgiri

    2000-08-01

    Determination of levels of tolerance in delaminated composite panels is an important issue in composite structures technology. The primary intention is to analyse delaminated composite panels and estimate Strain Energy Release Rate (SERR) parameters at the delamination front to feed into acceptability criteria. Large deformation analysis is necessary to cater for excessive rotational deformations in the delaminated sublaminate. Modified Virtual Crack Closure Integral (MVCCI) is used to estimate all the three SERR components at the delamination front from the finite element output containing displacements, strains and stresses. The applied loading conditions are particularly critical and compressive loading on the panel could lead to buckling of the delaminated sublaminate and consequent growth of delamination. Numerical results are presented for circular delamination of varioussizes and delamination at various interfaces (varying depth-wise location) between the base- and the sub-laminates. Numerical data are also presented on the effect of bi-axial loading and in particular on compressive loading in both directions. The results can be used to estimate delamination tolerance at various depths (or at various interfaces) in the laminate.

  11. Influence of substrate topography on cathodic delamination of anticorrosive coatings

    DEFF Research Database (Denmark)

    Sørensen, Per Aggerholm; Kiil, Søren; Dam-Johansen, Kim

    2009-01-01

    The cathodic delamination of a commercial magnesium silicate and titanium dioxide pigmented epoxy coating on abrasive cleaned cold rolled steel has been investigated. The rate of delamination was found to depend on interfacial transport from the artificial defect to the delamination front...... and thereby the substrate topography, whereas the coating thickness had little influence. The presence of a significant potential gradient between the anode and the cathode and the dependency of the delamination rate on the tortuosity of the steel surface suggests that cathodic delamination is controlled...... by migration of cations from the defect to the delamination front. This means that abrasive blasting, to some extent, can be applied to control and minimize the observed rate of cathodic delamination. The lifetime of the species causing disbondment suggested that sodium hydroxide or potassium hydroxide...

  12. Mode Mixity for Orthotropic Interface Delamination in Laminated Composites

    Institute of Scientific and Technical Information of China (English)

    FAN Xue-ling; SUN Qin; YUAN Mei-ni; Masanori Kikuchi

    2009-01-01

    The mode mixity is defined based on nonoscillatory strain energy release rate components of delamination between two different orthotropic materials to evaluate the delamination behavior of laminated composites.The result showes that the relative location of the delamination through the thickness influences the mode mixity in a relatively well-regulated way,and that the reinforcement directions of the adjacent plies along the delamination front have a more complicated impact on the mode mixity.This is caused by the bending/twist coupling and bending/bending coupling in the stress field at the crack tip for delamination between multidirectional plies,which completely modifies the stress and strain fields ahead of the crack tip.These kinds of couplings account for the non-uniform distribution of mode mixity values along the delamination front.Application of appropriate mode mixity values is necessary for accurate prediction of delamination growth.

  13. Buckling-driven Delamination in Layered Spherical Shells

    DEFF Research Database (Denmark)

    Sørensen, Kim Dalsten; Jensen, Henrik Myhre

    2008-01-01

    An analysis of buckling-driven delamination of a thin film on a spherical substrate has been carried out. The effects of the substrate having a double curvature compared to previous studies of delamination on cylindrical substrates turn out to be non-trivial: In addition to the effect of the shap...

  14. The Role of Lithospheric Delamination in the Evolution of Oroclinal Bending of Mountain Belts: Insights From Laboratory Experiments

    Science.gov (United States)

    Gogus, O. H.; Faccenna, C.; Houseman, G. A.

    2012-12-01

    In many geological settings, it has been suggested that lithospheric delamination - or any type of lithospheric removal - is associated with oroclinal bending of arcuate mountain belts, however the relationship between these two processes remain uncertain. In this work, we present a series of three-dimensional (3D) physical scaled laboratory experiments to investigate the link between these two processes. In these experiments, an idealized viscously deforming lithosphere-asthenosphere system is configured with silicone putty (representing lithospheric mantle and upper crust) and glucose syrup (representing the upper mantle and lower crust). Our primary focus was to investigate the role of the mantle flow in the physical development of oroclinal bending. Experiments without a crustal layer show that lateral mantle flow around a sinking slab is more vigorous in the center than on the lateral edges of the plate. Experiments that involve lower and upper crustal layers show a well-developed surface curvature of the upper crust when a weak lower crust permits decoupling (or delamination) of mantle lithosphere from crust and re-circulation of the mantle underneath the crust. We identified that the surface curvature of the delamination front is also dependent on the width ratio of crust to underlying mantle lithosphere layer. We present a scaling analysis of this relationship based on our experiments. Our results provide insights into the evolution of oroclinal bending/surface curvature which we relate to the collisional zones of the Mediterranean in cases where mantle lithosphere is thought to have been removed by such processes.

  15. Packaging issues: avoiding delamination.

    Science.gov (United States)

    Hall, R

    2005-10-01

    Manufacturers can minimise delamination occurrence by applying the appropriate packaging design and process features. The end user can minimise the impact of fibre tear and reduce subsequent delamination by careful package opening. The occasional inconvenient delamination is a small price to pay for the high level of sterility assurance that comes with the use of Tyvek.

  16. Development of a Benchmark Example for Delamination Fatigue Growth Prediction

    Science.gov (United States)

    Krueger, Ronald

    2010-01-01

    The development of a benchmark example for cyclic delamination growth prediction is presented and demonstrated for a commercial code. The example is based on a finite element model of a Double Cantilever Beam (DCB) specimen, which is independent of the analysis software used and allows the assessment of the delamination growth prediction capabilities in commercial finite element codes. First, the benchmark result was created for the specimen. Second, starting from an initially straight front, the delamination was allowed to grow under cyclic loading in a finite element model of a commercial code. The number of cycles to delamination onset and the number of cycles during stable delamination growth for each growth increment were obtained from the analysis. In general, good agreement between the results obtained from the growth analysis and the benchmark results could be achieved by selecting the appropriate input parameters. Overall, the results are encouraging but further assessment for mixed-mode delamination is required.

  17. Delamination of Composite Cylinders

    Science.gov (United States)

    Davies, Peter; Carlsson, Leif A.

    The delamination resistance of filament wound glass/epoxy cylinders has been characterized for a range of winding angles and fracture mode ratios using beam fracture specimens. The results reveal that the delamination fracture resistance increases with increasing winding angle and mode II (shear) fraction (GΠ/G). It was also found that interlaced fiber bundles in the filament wound cylinder wall acted as effective crack arresters in mode I loading. To examine the sensitivity of delamina-tion damage on the strength of the cylinders, external pressure tests were performed on filament-wound glass/epoxy composite cylinders with artificial defects and impact damage. The results revealed that the cylinder strength was insensitive to the presence of single delaminations but impact damage caused reductions in failure pressure. The insensitivity of the failure pressure to a single delamination is attributed to the absence of buckling of the delaminated sublaminates before the cylinder wall collapsed. The impacted cylinders contained multiple delaminations, which caused local reduction in the compressive load capability and reduction in failure pressure. The response of glass/epoxy cylinders was compared to impacted carbon reinforced cylinders. Carbon/epoxy is more sensitive to damage but retains higher implosion resistance while carbon/PEEK shows the opposite trend.

  18. Buckling-driven delamination in layered spherical shells

    Science.gov (United States)

    Sørensen, Kim D.; Jensen, Henrik M.

    An analysis of buckling-driven delamination of a layer in a spherical, layered shell has been carried out. The effects of the substrate having a double curvature compared to previous studies of delamination on cylindrical substrates turn out to be non-trivial in the sense that additional to the effect of the shape of the substrate, a new non-dimensional geometrical parameter enters the conditions for steady-state delamination. It is shown that this additional geometrical parameter in most cases of practical relevance has insignificant influence on the fracture mechanical parameters involved for the problem. The consequence is that solutions need to be mapped as a function of one rather than two dimensionless parameters. Furthermore, the shape of the substrate has profound influence especially on initiation of delamination growth.

  19. NUMERICAL ANALYSIS OF DELAMINATION GROWTH FOR STIFFENED COMPOSITE LAMINATED PLATES

    Institute of Scientific and Technical Information of China (English)

    白瑞祥; 陈浩然

    2004-01-01

    A study of postbuckling and delamination propagation behavior in delaminated stiffened composite plates was presented. A methodology was proposed for simulating the multi-failure responses, such as initial and postbuckling, delamination onset and propagation, etc. A finite element analysis was conducted on the basis of the Mindlin first order shear effect theory and the von-Krmn nonlinear deformation assumption. The total energy release rate used as the criteria of delamination growth was estimated with virtual crack closure technique (VCCT). A self-adaptive grid moving technology was adopted to model the delamination growth process. Moreover, the contact effect along delamination front was also considered during the numerical simulation process. By some numerical examples, the influence of distribution and location of stiffener, configuration and size of the delamination, boundary condition and contact effect upon the delamination growth behavior of the stiffened composite plates were investigated. The method and numerical conclusion provided should be of great value to engineers dealing with composite structures.

  20. Orogenic delamination - dynamics, effects, and geological expression

    Science.gov (United States)

    Ueda, Kosuke; Gerya, Taras

    2010-05-01

    collision rate, melting and hydration, the latter two incorporating the effects of sediment subduction and phase changes. The drag available for slab retreat scales with the age of the descending oceanic lithosphere; integrated strength of the lithosphere and activation volume for mantle creep additionally control angle and depth of the descent. Fully developed delamination is observed from between 10 to 15 Ma after collision ceases, with following trenchward migration of the delamination front. Consequently, the main maximum extension migrates, while local, partly intermittent compression can be observed on smaller scale. Across the orogen, extension thus has a strongly diachronous main component. We track common surface observables such as heat flow, partially melted rocks (domal migmatites), and predicted geo-/thermochronological ages over the evolving plate boundary. Geochemical projections of our observations confirm potential contamination of reservoirs - although the net delamination level follows the Moho, some crustal remnants along the old slab still sink through the 660-discontinuity. On the other hand, the base of the delaminated domain is not as plain a contact as in concept. Where the contact of asthenosphere with delaminated crust is the location of high-degree melting, also traces of original lithospheric mantle can be entangled. Our results do not fully support the conceptual distinction between convective thinning and blockwise delamination. While the foundering portion initially retains a fairly coherent, slab-like perimeter, the actual separation of layers in a limited process-zone occurs in smaller -scale eddies. Also, convection of the whole uprising asthenosphere wedge is dynamically not discernible from the latter and crucial for the removal of lithospheric mantle. The removed lithosphere does initially not convect, but subsequently shows an increasing tendency to drip down. In the presented case, extension in the axial zone of the orogen is not

  1. Fractography of composite delamination

    Science.gov (United States)

    Bascom, W. D.

    1990-01-01

    The microdamage that occurs for Mode 1 and Mode 2 delamination was examined by potting delaminated specimens in a clear epoxy, sectioning through the damage, polishing the cut sections and examining using light microscopy. For Mode 1 delamination of unidirectional carbon fiber reinforced plastic (CFRP) composites, the major observation was fiber bridging including large ligaments of fiber bundles. The Mode 2 delamination of unidirectional laminates revealed a very narrow crack opening with only occasional fiber bridging. Impact testing by repetitive impacts with increasing energy was studied and it was found that this technique does not discern changes in the type of damage with increasing cumulative impact energy. Instead, the changes in the impact response, notably stiffness, are the result of changes in the extent of damage. For laminates with a brittle thermoplastic matrix, 3501-6, there were distinct changes in stiffness that corresponded to the development of through the thickness damage and then to the extension of the damage to the specimen edges. For PEEK and polycarbonate, the changes in stiffness were not as abrupt as for the thermoset. None the less, the damage progressed in the same manner.

  2. STUDY ON FAILURE PROCESS OF DELAMINATED STIFFENED COMPOSITE PLATES UNDER COMPRESSION

    Institute of Scientific and Technical Information of China (English)

    陈浩然; 白瑞祥; 王蔓

    2003-01-01

    Failure behavior of the delaminated stiffened composite plates under compression is studied by the finite element method, based on a Global-Local variational model. A virtual crack closure technique and a self-adaptive grid moving scheme are proposed to predict the delamination growth process. The contact effect along the delamination front is considered. The numerical results show that the influences of the distribution and location of the stiffeners, the configuration and size of the delamination, the boundary condition and the contact upon the failure behavior of the plates are significant.

  3. Mirror with thermally controlled radius of curvature

    Science.gov (United States)

    Neil, George R.; Shinn, Michelle D.

    2010-06-22

    A radius of curvature controlled mirror for controlling precisely the focal point of a laser beam or other light beam. The radius of curvature controlled mirror provides nearly spherical distortion of the mirror in response to differential expansion between the front and rear surfaces of the mirror. The radius of curvature controlled mirror compensates for changes in other optical components due to heating or other physical changes. The radius of curvature controlled mirror includes an arrangement for adjusting the temperature of the front surface and separately adjusting the temperature of the rear surface to control the radius of curvature. The temperature adjustment arrangements can include cooling channels within the mirror body or convection of a gas upon the surface of the mirror. A control system controls the differential expansion between the front and rear surfaces to achieve the desired radius of curvature.

  4. Point Diffraction Interferometry to Measure Local Curvatures and Caustics of Noisy Wave Fronts: Application for Determining Optical Properties of Fish Lenses

    Science.gov (United States)

    Vallmitjana, S.; Ricart, I.; Bosch, S.; Gargallo, A.; Acosta, E.

    2015-02-01

    The study of caustics is important because they contain information about the image formation properties of optical systems. In this work we use the concept of caustic as a set of focal points, and we have developed a second order approach theory to determine local slopes and curvatures of a wavefront emerging from an optical system. The method is based on the use of a point diffraction interferometer, and the analysis of the interferograms allows us to compute the focal region. Experimental results obtained with a plano-convex lens demonstrate the accuracy of the combined theoretical-experimental method here developed. Application to noisy wavefronts such as those produced by biological samples, specifically in crystalline lenses of fish eyes, are also exposed.

  5. Impact Analysis of Embedded Delamination Location in Hybrid Curved Laminated Composite Stiffened Panel

    Science.gov (United States)

    Naini, Jeevan Kumar; P, Ramesh Babu

    2016-08-01

    Modern, aero structures are predominantly of curved construction characterized by a skin and stiffeners. The latest generation of large passenger aircraft also uses mostly composite material in their primary structure and there is trend towards the utilization of bonding of subcomponents. The presence of delamination is a major problem in composite laminated panels and so, it is of great concern to both the academic and aeronautical industrial worlds Indeed delamination can strongly affect the material strength and, sometimes, can cause their breaking up in service. A Pre-damaged configuration is loaded to study the delamination location and mode for delamination initiation and propagation. A parametric study is conducted to investigate the effect of the location of the delamination propagation when delamination is embedded inbetween plies of the skin-stiffener interface, with the cases i) delamination located at front and inbetween plies of the skin-stiffener interface ii) delamination located in middle and inbetween plies of the skin-stiffener interface iii) delamination located at the end and inbetween plies of the skin- stiffener interface. Further the influence of the location of the delamination on load carrying capacity of the panel is investigated. The effect of location of debonds on crack growth and collapse behavior is analyzed using analysis tool. An analysis tool is applied that includes an approach for predicting interlaminar damage initiation and interlaminar damage growth as well as in-plane damage mechanisms to predict the design of defect free panel.

  6. Development of Benchmark Examples for Delamination Onset and Fatigue Growth Prediction

    Science.gov (United States)

    Krueger, Ronald

    2011-01-01

    An approach for assessing the delamination propagation and growth capabilities in commercial finite element codes was developed and demonstrated for the Virtual Crack Closure Technique (VCCT) implementations in ABAQUS. The Double Cantilever Beam (DCB) specimen was chosen as an example. First, benchmark results to assess delamination propagation capabilities under static loading were created using models simulating specimens with different delamination lengths. For each delamination length modeled, the load and displacement at the load point were monitored. The mixed-mode strain energy release rate components were calculated along the delamination front across the width of the specimen. A failure index was calculated by correlating the results with the mixed-mode failure criterion of the graphite/epoxy material. The calculated critical loads and critical displacements for delamination onset for each delamination length modeled were used as a benchmark. The load/displacement relationship computed during automatic propagation should closely match the benchmark case. Second, starting from an initially straight front, the delamination was allowed to propagate based on the algorithms implemented in the commercial finite element software. The load-displacement relationship obtained from the propagation analysis results and the benchmark results were compared. Good agreements could be achieved by selecting the appropriate input parameters, which were determined in an iterative procedure.

  7. Characterization of Mode I and Mode II delamination growth and thresholds in AS4/PEEK composites

    Science.gov (United States)

    Martin, Roderick H.; Murri, Gretchen Bostaph

    1990-01-01

    Composite materials often fail by delamination. The onset and growth of delamination in AS4/PEEK, a tough thermoplastic matrix composite, was characterized for mode 1 and mode 2 loadings, using the Double Cantilever Beam (DCB) and the End Notched Flexure (ENF) test specimens. Delamination growth per fatigue cycle, da/dN, was related to strain energy release rate, G, by means of a power law. However, the exponents of these power laws were too large for them to be adequately used as a life prediction tool. A small error in the estimated applied loads could lead to large errors in the delamination growth rates. Hence strain energy release rate thresholds, G sub th, below which no delamination would occur were also measured. Mode 1 and 2 threshold G values for no delamination growth were found by monitoring the number of cycles to delamination onset in the DCB and ENF specimens. The maximum applied G for which no delamination growth had occurred until at least 1,000,000 cycles was considered the threshold strain energy release rate. Comments are given on how testing effects, facial interference or delamination front damage, may invalidate the experimental determination of the constants in the expression.

  8. Characterization of Mode 1 and Mode 2 delamination growth and thresholds in graphite/peek composites

    Science.gov (United States)

    Martin, Roderick H.; Murri, Gretchen B.

    1988-01-01

    Composite materials often fail by delamination. The onset and growth of delamination in AS4/PEEK, a tough thermoplastic matrix composite, was characterized for mode 1 and mode 2 loadings, using the Double Cantilever Beam (DCB) and the End Notched Flexure (ENF) test specimens. Delamination growth per fatigue cycle, da/dN, was related to strain energy release rate, G, by means of a power law. However, the exponents of these power laws were too large for them to be adequately used as a life prediction tool. A small error in the estimated applied loads could lead to large errors in the delamination growth rates. Hence strain energy release rate thresholds, G sub th, below which no delamination would occur were also measured. Mode 1 and 2 threshold G values for no delamination growth were found by monitoring the number of cycles to delamination onset in the DCB and ENF specimens. The maximum applied G for which no delamination growth had occurred until at least 1,000,000 cycles was considered the threshold strain energy release rate. Comments are given on how testing effects, facial interference or delamination front damage, may invalidate the experimental determination of the constants in the expression.

  9. Repair of prestressed concrete cylinder with localized delamination

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shen, E-mail: swang@bechtel.com; Munshi, Javeed A., E-mail: jamunshi@bechtel.com

    2015-12-15

    For prestressed concrete cylindrical structures such as nuclear containments, tanks and silos, the curvature effect of the tendons introduces radial tensile stresses in the concrete shell which are generally neglected in the design of such structures. For example, many prestressed concrete nuclear containments in US, especially those which were not designed following radial reinforcement requirement of ACI-359, are reinforced only in the circumferential (hoop) and meridional (vertical) directions but not in the radial direction. This leaves these structures vulnerable to potential laminar cracking and delamination, especially during post-tensioning and/or detensioning process. Should delamination occur, the structure needs to be repaired by either replacing cracked concrete or by “pinning” the delaminated concrete layers together by post-installed anchors. The latter option of post-installed anchors is less invasive from construction stand point and generally suitable for repairing small or localized delamination only. A comprehensive study is undertaken to explore various aspects and design consideration of post-installed anchors for prestressed concrete cylinders. The radial tension demand is first established by combining a mechanical based model with a detailed finite element analysis. With such design demand for post-installed anchors established, the next step aims at developing the tightness requirement of existing delamination cracks for effective use of post-installed anchors. A comprehensive literature search and evaluation is carried out for shear transfer capacity across cracks of various widths. The findings are used to develop specific recommendations for acceptable crack widths to ensure adequate in-plane shear transfer capacity for various design load conditions. A design process for post-installed anchors is proposed for repairing a delaminated prestressed concrete cylindrical structure at the end of the paper, supplemented by an illustrative

  10. The interplay of crack hopping, delamination and interface failure in drying nanoparticle films

    Science.gov (United States)

    Yang, Bin; Sharp, James S.; Smith, Mike I.

    2016-08-01

    Films formed through the drying of nanoparticle suspensions release the build-up of strain through a variety of different mechanisms including shear banding, crack formation and delamination. Here we show that important connections exist between these different phenomena: delamination depends on the dynamics of crack hopping, which in turn is influenced by the presence of shear bands. We also show that delamination does not occur uniformly across the film. As cracks hop they locally initiate the delamination of the film which warps with a timescale much longer than that associated with the hopping of cracks. The motion of a small region of the delamination front, where the shear component of interfacial crack propagation is believed to be enhanced, results in the deposition of a complex zig-zag pattern on the supporting substrate.

  11. Edge effects and delamination failures

    Science.gov (United States)

    Herakovich, C. T.

    1989-01-01

    The fundamental relationship between the morphology of a composite laminate and the resulting free edge effects is explored and related to delamination failures. Cross-ply, angle-ply, and quasi-isotropic laminates are discussed in detail. It is shown that the local mismatch in elastic properties of adjacent layers and the global stacking sequence of a laminate both have a significant influence on the interlaminar stresses and delamination failures.

  12. Dynamic fracture mechanics analysis for an edge delamination crack

    Science.gov (United States)

    Rizzi, Stephen A.; Doyle, James F.

    1994-01-01

    A global/local analysis is applied to the problem of a panel with an edge delamination crack subject to an impulse loading to ascertain the dynamic J integral. The approach uses the spectral element method to obtain the global dynamic response and local resultants to obtain the J integral. The variation of J integral along the crack front is shown. The crack behavior is mixed mode (Mode 2 and Mode 3), but is dominated by the Mode 2 behavior.

  13. Development and Application of Benchmark Examples for Mode II Static Delamination Propagation and Fatigue Growth Predictions

    Science.gov (United States)

    Krueger, Ronald

    2011-01-01

    The development of benchmark examples for static delamination propagation and cyclic delamination onset and growth prediction is presented and demonstrated for a commercial code. The example is based on a finite element model of an End-Notched Flexure (ENF) specimen. The example is independent of the analysis software used and allows the assessment of the automated delamination propagation, onset and growth prediction capabilities in commercial finite element codes based on the virtual crack closure technique (VCCT). First, static benchmark examples were created for the specimen. Second, based on the static results, benchmark examples for cyclic delamination growth were created. Third, the load-displacement relationship from a propagation analysis and the benchmark results were compared, and good agreement could be achieved by selecting the appropriate input parameters. Fourth, starting from an initially straight front, the delamination was allowed to grow under cyclic loading. The number of cycles to delamination onset and the number of cycles during delamination growth for each growth increment were obtained from the automated analysis and compared to the benchmark examples. Again, good agreement between the results obtained from the growth analysis and the benchmark results could be achieved by selecting the appropriate input parameters. The benchmarking procedure proved valuable by highlighting the issues associated with choosing the input parameters of the particular implementation. Selecting the appropriate input parameters, however, was not straightforward and often required an iterative procedure. Overall the results are encouraging, but further assessment for mixed-mode delamination is required.

  14. Development of Benchmark Examples for Quasi-Static Delamination Propagation and Fatigue Growth Predictions

    Science.gov (United States)

    Krueger, Ronald

    2012-01-01

    The development of benchmark examples for quasi-static delamination propagation and cyclic delamination onset and growth prediction is presented and demonstrated for Abaqus/Standard. The example is based on a finite element model of a Double-Cantilever Beam specimen. The example is independent of the analysis software used and allows the assessment of the automated delamination propagation, onset and growth prediction capabilities in commercial finite element codes based on the virtual crack closure technique (VCCT). First, a quasi-static benchmark example was created for the specimen. Second, based on the static results, benchmark examples for cyclic delamination growth were created. Third, the load-displacement relationship from a propagation analysis and the benchmark results were compared, and good agreement could be achieved by selecting the appropriate input parameters. Fourth, starting from an initially straight front, the delamination was allowed to grow under cyclic loading. The number of cycles to delamination onset and the number of cycles during delamination growth for each growth increment were obtained from the automated analysis and compared to the benchmark examples. Again, good agreement between the results obtained from the growth analysis and the benchmark results could be achieved by selecting the appropriate input parameters. The benchmarking procedure proved valuable by highlighting the issues associated with choosing the input parameters of the particular implementation. Selecting the appropriate input parameters, however, was not straightforward and often required an iterative procedure. Overall the results are encouraging, but further assessment for mixed-mode delamination is required.

  15. Development of Benchmark Examples for Static Delamination Propagation and Fatigue Growth Predictions

    Science.gov (United States)

    Kruger, Ronald

    2011-01-01

    The development of benchmark examples for static delamination propagation and cyclic delamination onset and growth prediction is presented and demonstrated for a commercial code. The example is based on a finite element model of an End-Notched Flexure (ENF) specimen. The example is independent of the analysis software used and allows the assessment of the automated delamination propagation, onset and growth prediction capabilities in commercial finite element codes based on the virtual crack closure technique (VCCT). First, static benchmark examples were created for the specimen. Second, based on the static results, benchmark examples for cyclic delamination growth were created. Third, the load-displacement relationship from a propagation analysis and the benchmark results were compared, and good agreement could be achieved by selecting the appropriate input parameters. Fourth, starting from an initially straight front, the delamination was allowed to grow under cyclic loading. The number of cycles to delamination onset and the number of cycles during stable delamination growth for each growth increment were obtained from the automated analysis and compared to the benchmark examples. Again, good agreement between the results obtained from the growth analysis and the benchmark results could be achieved by selecting the appropriate input parameters. The benchmarking procedure proved valuable by highlighting the issues associated with the input parameters of the particular implementation. Selecting the appropriate input parameters, however, was not straightforward and often required an iterative procedure. Overall, the results are encouraging but further assessment for mixed-mode delamination is required.

  16. Thermally induced delamination of multilayers

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Sarraute, S.; Jørgensen, O.

    1998-01-01

    Steady-state delamination of multilayered structures, caused by stresses arising during processing due to thermal expansion mismatch, is analyzed by a fracture mechanics model based on laminate theory. It is found that inserting just a few interlayers with intermediate thermal expansion coefficie...... coefficients may be an effective way of reducing the delamination energy release rate. Uneven layer thickness and increasing elastic mismatch are shown to raise the energy release rate. Experimental work confirms important trends of the model.......Steady-state delamination of multilayered structures, caused by stresses arising during processing due to thermal expansion mismatch, is analyzed by a fracture mechanics model based on laminate theory. It is found that inserting just a few interlayers with intermediate thermal expansion...

  17. The Delamination Theory of Wear

    Science.gov (United States)

    1974-09-01

    junctions, it is still based on the assumption that the deformation occurs at the asperities. Rabinowicz [14] advanced an adhesion theory of friction...shown that bronze particles were indeed bigger than steel particles. The compilation of wear particle sizes given by Rabinowicz [14] also indicates...Waterhouse [32] has shown that, in fact, fretting occurs by delamination. 6) Minimum Load for Loose Particle Formation Rabinowicz [14] found that no wear

  18. Detailed modelling of delamination buckling of thin films under global tension.

    Science.gov (United States)

    Toth, F; Rammerstorfer, F G; Cordill, M J; Fischer, F D

    2013-04-01

    Tensile specimens of metal films on compliant substrates are widely used for determining interfacial properties. These properties are identified by the comparison of experimentally observed delamination buckling and a mathematical model which contains the interface properties as parameters. The current two-dimensional models for delamination buckling are not able to capture the complex stress and deformation states arising in the considered uniaxial tension test in a satisfying way. Therefore, three-dimensional models are developed in a multi-scale approach. It is shown that, for the considered uniaxial tension test, the buckling and associated delamination process are initiated and driven by interfacial shear in addition to compressive stresses in the film. The proposed model is able to reproduce all important experimentally observed phenomena, like cracking stress of the film, film strip curvature and formation of triangular buckles. Combined with experimental data, the developed computational model is found to be effective in determining interface strength properties.

  19. Delaminated rotator cuff tear: extension of delamination and cuff integrity after arthroscopic rotator cuff repair.

    Science.gov (United States)

    Gwak, Heui-Chul; Kim, Chang-Wan; Kim, Jung-Han; Choo, Hye-Jeung; Sagong, Seung-Yeob; Shin, John

    2015-05-01

    The purpose of this study was to evaluate the extension of delamination and the cuff integrity after arthroscopic repair of delaminated rotator cuff tears. Sixty-five patients with delaminated rotator cuff tears were retrospectively reviewed. The delaminated tears were divided into full-thickness delaminated tears and partial-thickness delaminated tears. To evaluate the medial extension, we calculated the coronal size of the delaminated portion. To evaluate the posterior extension, we checked the tendon involved. Cuff integrity was evaluated by computed tomography arthrography. The mean medial extension in the full-thickness and partial-thickness delaminated tears was 18.1 ± 6.0 mm and 22.7 ± 6.3 mm, respectively (P = .0084). The posterior extension into the supraspinatus and the infraspinatus was 36.9% and 32.3%, respectively, in the full-thickness delaminated tears, and it was 27.7% and 3.1%, respectively, in the partial-thickness delaminated tears (P = .0043). With regard to cuff integrity, 35 cases of anatomic healing, 10 cases of partial healing defects, and 17 cases of retear were detected. Among the patients with retear and partial healing of the defect, all the partially healed defects showed delamination. Three retear patients showed delamination, and 14 retear patients did not show delamination; the difference was statistically significant (P = .0001). The full-thickness delaminated tears showed less medial extension and more posterior extension than the partial-thickness delaminated tears. Delamination did not develop in retear patients, but delamination was common in the patients with partially healed defects. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  20. Regional adaptive delaminating algorithm for rapid prototyping

    Institute of Scientific and Technical Information of China (English)

    CAI Daosheng; SHI Yusheng; HUANG Shuhuai

    2005-01-01

    With the development of rapid prototyping (RP) technology, the contradiction between fabricating speed and precision becomes more and more acute. In order to solve the contradiction, a regional effective adaptive delaminating algorithm is proposed in this paper. It is different from the traditional method that the regional adaptive delaminating method divides slicing contours into several regions and adaptively delaminates in respective region only according to the contours information. Namely, this method can not only adaptively delaminate at different height of CAD model but also adaptively delaminate different regions in one slicing layer. Furthermore, because the two-dimensional contour data adopted in this method are necessary for rapid prototyping system, this regional effective adaptive delaminating method is suitable for all RP systems. A comparative study is used to analyze the effectiveness of this method, which can demonstrate that this method can increase the fabricating speed and reduce the running cost under the condition of ensuring fabricating precision.

  1. The effect of coating/substrate interface curvature on fracture of Si-Al-N coatings subjected to mechanical loading

    Science.gov (United States)

    Shugurov, Artur

    2015-10-01

    The effect of curvature of the film/substrate interface on the fracture mechanisms of Si-Al-N coatings on Cu substrates subjected to uniaxial tension and alternating bending is studied. Local interface curvature due to substrate surface roughening caused by its plastic deformation in the course of the uniaxial tension is shown to have a profound effect on their delamination and buckling. Interface curvature induced by specimen bending promotes kinking of through-the-coating cracks at the interface that is followed by delamination and spalling of the coatings.

  2. Convective chemical fronts in a Poiseuille flow.

    Science.gov (United States)

    Vasquez, Desiderio A

    2007-11-01

    Autocatalytic reaction fronts propagating in a Poiseuille flow present a change of speed and curvature depending on the strength of the flow and on the direction of front propagation. These chemical fronts separate reacted and unreacted fluids of different densities, consequently convection will always be present due to the horizontal density gradient of the curved front. In this paper, we find the change of speed caused by gravity for fronts propagating in vertical tubes under a Poiseuille flow. For small density differences, we find axisymmetric fronts. Our theory predicts a transition to nonaxisymmetric fronts as the distance between the walls is increased. The transition depends on the average speed of the Poiseuille flow.

  3. Estimation of Local Delamination Buckling in Orthotropic Composite Plates Using Kirchhoff Plate Finite Elements

    Directory of Open Access Journals (Sweden)

    Zoltán Juhász

    2015-01-01

    Full Text Available We analyse the buckling process of composite plates with through-the-width delamination and straight crack front applying uniaxial compression. We are focusing on the mixed mode buckling case, where the non-uniform distribution of the in-plane forces controls the occurence of the buckling of the delaminated layers. For the analysis, semi-discrete finite elements will be derived based on the Lèvy-type method. The method of harmonic balance is used for taking into account the force distribution that is generally non uniform in-plane.

  4. Delamination of Compressed Thin Layers at Corners

    DEFF Research Database (Denmark)

    Sørensen, Kim D.; Jensen, Henrik Myhre; Clausen, Johan

    2008-01-01

    An analysis of delamination for a thin elastic layer under compression, attached to a substrate at a corner is carried out. The analysis is performed by combining results from interface fracture mechanics and the theory of thin shells. In contrast with earlier results for delamination on a flat...... layers, Fracture mechanics, Crack closure, Steady state crack propagation....

  5. Delamination of Compressed Thin Layers at Corners

    DEFF Research Database (Denmark)

    Sørensen, Kim Dalsten; Jensen, Henrik Myhre; Clausen, Johan

    2008-01-01

    An analysis of delamination for a thin elastic layer under compression, attached to a substrate at a corner is carried out. The analysis is performed by combining results from interface fracture mechanics and the theory of thin shells. In contrast with earlier results for delamination on a flat...

  6. Delamination Detection Using Guided Wave Phased Arrays

    Science.gov (United States)

    Tian, Zhenhua; Yu, Lingyu; Leckey, Cara

    2016-01-01

    This paper presents a method for detecting multiple delaminations in composite laminates using non-contact phased arrays. The phased arrays are implemented with a non-contact scanning laser Doppler vibrometer (SLDV). The array imaging algorithm is performed in the frequency domain where both the guided wave dispersion effect and direction dependent wave properties are considered. By using the non-contact SLDV array with a frequency domain imaging algorithm, an intensity image of the composite plate can be generated for delamination detection. For the proof of concept, a laboratory test is performed using a non-contact phased array to detect two delaminations (created through quasi-static impact test) at different locations in a composite plate. Using the non-contact phased array and frequency domain imaging, the two impact-induced delaminations are successfully detected. This study shows that the non-contact phased array method is a potentially effective method for rapid delamination inspection in large composite structures.

  7. Assembly induced delaminations in composite structures

    Science.gov (United States)

    Goering, J.; Bohlmann, R.; Wanthal, S.; Kautz, E.; Neri, Lawrence M.

    1992-01-01

    Experimental and analytical studies of the development of delaminations around fastener holes in composite structures are presented. This type of delamination is known to occur in composite skins that are mechanically fastened to a poorly mating substructure. Results of an experimental study to determine the resistance of laminates to the initiation of assembly induced delaminations and the residual strength of assembly damaged coupons are presented for AS4/3501-6, IM7/8551-7A, and AS4/PEEK material systems. A survey of existing analytical models for predicting the residual strength and stability of delaminations is presented, and the development of a new model for predicting the initiation of delaminations around a fastener hole is outlined. The fastener hole damage initiation model utilizes a finite element based Fourier series solution, and is validated through comparisons of analytical and experimental results.

  8. Extrinsic Curvature Embedding Diagrams

    CERN Document Server

    Lu, J L

    2003-01-01

    Embedding diagrams have been used extensively to visualize the properties of curved space in Relativity. We introduce a new kind of embedding diagram based on the {\\it extrinsic} curvature (instead of the intrinsic curvature). Such an extrinsic curvature embedding diagram, when used together with the usual kind of intrinsic curvature embedding diagram, carries the information of how a surface is {\\it embedded} in the higher dimensional curved space. Simple examples are given to illustrate the idea.

  9. Order Parameter Equations for Front Transitions Planar and Circular Fronts

    CERN Document Server

    Hagberg, A; Rubinstein, I; Zaltzman, B; Hagberg, Aric; Meron, Ehud

    1997-01-01

    Near a parity breaking front bifurcation, small perturbations may reverse the propagation direction of fronts. Often this results in nonsteady asymptotic motion such as breathing and domain breakup. Exploiting the time scale differences of an activator-inhibitor model and the proximity to the front bifurcation, we derive equations of motion for planar and circular fronts. The equations involve a translational degree of freedom and an order parameter describing transitions between left and right propagating fronts. Perturbations, such as a space dependent advective field or uniform curvature (axisymmetric spots), couple these two degrees of freedom. In both cases this leads to a transition from stationary to oscillating fronts as the parity breaking bifurcation is approached. For axisymmetric spots, two additional dynamic behaviors are found: rebound and collapse.

  10. Stability of Curvature Measures

    CERN Document Server

    Chazal, Frédéric; Lieutier, André; Thibert, Boris

    2008-01-01

    We address the problem of curvature estimation from sampled compact sets. The main contribution is a stability result: we show that the gaussian, mean or anisotropic curvature measures of the offset of a compact set K with positive $\\mu$-reach can be estimated by the same curvature measures of the offset of a compact set K' close to K in the Hausdorff sense. We show how these curvature measures can be computed for finite unions of balls. The curvature measures of the offset of a compact set with positive $\\mu$-reach can thus be approximated by the curvature measures of the offset of a point-cloud sample. These results can also be interpreted as a framework for an effective and robust notion of curvature.

  11. Detection and characterisation of delamination in PV modules by active infrared thermography

    Science.gov (United States)

    Sinha, A.; Sastry, O. S.; Gupta, R.

    2016-01-01

    The paper presents a fast and efficient method for the detection and characterisation of delamination in photovoltaic (PV) modules by using active infrared thermography approach. A discrete part of PV module was irradiated by step heating and its thermal image sequence was used to detect and analyse delamination. Different types of heating source for thermal excitation for this application have been studied. An electro-thermal model was developed to simulate the active thermography approach for the characterisation of delamination in PV module by equivalent resistance-capacitance (RC) network using a circuit simulator. This simulation approach was used to estimate the extent of delamination in the module and to determine the optimum parameters for the characterisation of delamination. Different applications based on front and backsides of heating the module were also proposed in this paper. The proposed method has the potential to be employed for the quality check of PV modules during inline production as well as for the predictive maintenance of outdoor PV plants.

  12. Characterization of delamination onset and growth in a composite laminate

    Science.gov (United States)

    Obrien, T. K.

    1981-01-01

    The onset and growth of delaminations in unnotched (+ or - 30/+ or - 30/90/90 bar) sub S graphite epoxy laminates is described quantitatively. These laminates, designed to delaminate at the edges under tensile loads, were tested and analyzed. Delamination growth and stiffness loss were monitored nondestructively. Laminate stiffness decreased linearly with delamination size. The strain energy release rate, G, associated with delamination growth, was calculated from two analyses. A critical G for delamination onset was determined, and then was used to predict the onset of delaminations in (+45 sub n/-45 sub n/o sub n/90 sub n) sub s (n=1,2,3) laminates. A delamination resistance curve (R curve) was developed to characterize the observed stable delamination growth under quasi static loading. A power law correlation between G and delamination growth rates in fatigue was established.

  13. Computational investigation of the delamination of polymer coatings during stent deployment.

    Science.gov (United States)

    Hopkins, C G; McHugh, P E; McGarry, J P

    2010-07-01

    Recent advances in angioplasty have involved the application of polymer coatings to stent surfaces for purposes of drug delivery. Given the high levels of deformation developed in the plastic hinge of a stent during deployment, the achievement of an intact bond between the coating and the stent presents a significant mechanical challenge. Problems with coating delamination have been reported in recent experimental studies. In this paper, a cohesive zone model of the stent-coating interface is implemented in order to investigate coating debonding during stent deployment. Simulations reveal that coatings debond from the stent surface in tensile regions of the plastic hinge during deployment. The critical parameters governing the initiation of delamination include the coating thickness and stiffness, the interface strength between the coating and stent surface, and the curvature of the plastic hinge. The coating is also computed to debond from the stent surface in compressive regions of the plastic hinge by a buckling mechanism. Computed patterns of coating delamination correlate very closely with experimental images. This study provides insight into the critical factors governing coating delamination during stent deployment and offers a predictive framework that can be used to improve the design of coated stents.

  14. Buckling and Delamination Growth Analysis of Composite Laminates Containing Embedded Delaminations

    Science.gov (United States)

    Hosseini-Toudeshky, H.; Hosseini, S.; Mohammadi, B.

    2010-04-01

    The objective of this work is to study the post buckling behavior of composite laminates, containing embedded delamination, under uniaxial compression loading. For this purpose, delamination initiation and propagation is modeled using the softening behavior of interface elements. The full layer-wise plate theory is also employed for approximating the displacement field of laminates and the interface elements are considered as a numerical layer between any two adjacent layers which delamination is expected to propagate. A finite element program was developed and the geometric non-linearity in the von karman sense is incorporated to the strain/displacement relations, to obtain the buckling behavior. It will be shown that, the buckling load, delamination growth process and buckling mode of the composite plates depends on the size of delamination and stacking sequence of the laminates.

  15. Curvature of the penis

    Science.gov (United States)

    ... curvature of the penis after surgery or radiation treatment for prostate cancer. Peyronie's disease is uncommon. It affects men ages 40 to 60 and older. Curvature of the penis can occur along with Dupuytren's contracture . This is a cord-like thickening across the ...

  16. The meaning of curvature

    DEFF Research Database (Denmark)

    diffusion to volume growth. We are e.g. interested in obtaining precise bounds for mean exit times for Brownian motions and for isoperimetric inequalities. One way to obtain such bounds are via curvature controlled comparison with corresponding values in constant curvature spaces and in other tailor-made so...

  17. Curvature-induced dissipation

    CERN Document Server

    Debus, J -D; Succi, S; Herrmann, H J

    2015-01-01

    By inspecting the effect of curvature on a moving fluid, we find that local sources of curvature not only exert inertial forces on the flow, but also generate viscous stresses as a result of the departure of streamlines from the idealized geodesic motion. The curvature-induced viscous forces are shown to cause an indirect and yet appreciable energy dissipation. As a consequence, the flow converges to a stationary equilibrium state solely by virtue of curvature-induced dissipation. In addition, we show that flow through randomly-curved media satisfies a non-linear transport law, resembling Darcy-Forchheimer's law, due to the viscous forces generated by the spatial curvature. It is further shown that the permeability can be characterized in terms of the average metric perturbation.

  18. Effect of Location of Delamination on Free Vibration of Cross-Ply Conical Shells

    Directory of Open Access Journals (Sweden)

    Sudip Dey

    2012-01-01

    Full Text Available Location of delamination is a triggering parameter for structural instability of laminated composites. In this paper, a finite element method is employed to determine the effects of location of delamination on free vibration characteristics of graphite-epoxy cross-ply composite pre-twisted shallow conical shells. The generalized dynamic equilibrium equation is derived from Lagrange's equation of motion neglecting Coriolis effect for moderate rotational speeds. The formulation is exercised by using an eight noded isoparametric plate bending element based on Mindlin's theory. Multi-point constraint algorithm is utilized to ensure the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. The standard eigen value problem is solved by applying the QR iteration algorithm. Finite element codes are developed to obtain the numerical results concerning the effects of location of delamination, twist angle and rotational speed on the natural frequencies of cross-ply composite shallow conical shells. The mode shapes are also depicted for a typical laminate configuration. Numerical results obtained from parametric studies of both symmetric and anti-symmetric cross-ply laminates are the first known non-dimensional natural frequencies for the type of analyses carried out here.

  19. Penile Curvature (Peyronie's Disease)

    Science.gov (United States)

    ... use mechanical traction and vacuum devices aimed at stretching or bending the penis to reduce curvature. Surgery ... Communication Programs FAQs About NIDDK Meet the Director Offices & Divisions Staff Directory Budget & Legislative Information Advisory & Coordinating ...

  20. Modeling Delamination in Postbuckled Composite Structures Under Static and Fatigue Loads

    Science.gov (United States)

    Bisagni, Chiara; Brambilla, Pietro; Bavila, Carlos G.

    2013-01-01

    The ability of the Abaqus progressive Virtual Crack Closure Technique (VCCT) to model delamination in composite structures was investigated for static, postbuckling, and fatigue loads. Preliminary evaluations were performed using simple Double Cantilever Beam (DCB) and Mixed-Mode Bending (MMB) specimens. The nodal release sequences that describe the propagation of the delamination front were investigated. The effect of using a sudden or a gradual nodal release was evaluated by considering meshes aligned with the crack front as well as misaligned meshes. Fatigue simulations were then performed using the Direct Cyclic Fatigue (DCF) algorithm. It was found that in specimens such as the DCB, which are characterized by a nearly linear response and a pure fracture mode, the algorithm correctly predicts the Paris Law rate of propagation. However, the Abaqus DCF algorithm does not consider different fatigue propagation laws in different fracture modes. Finally, skin/stiffener debonding was studied in an aircraft fuselage subcomponent in which debonding occurs deep into post-buckling deformation. VCCT was shown to be a robust tool for estimating the onset propagation. However, difficulties were found with the ability of the current implementation of the Abaqus progressive VCCT to predict delamination propagation within structures subjected to postbuckling deformations or fatigue loads.

  1. Delamination detection using methods of computational intelligence

    Science.gov (United States)

    Ihesiulor, Obinna K.; Shankar, Krishna; Zhang, Zhifang; Ray, Tapabrata

    2012-11-01

    Abstract Reliable delamination prediction scheme is indispensable in order to prevent potential risks of catastrophic failures in composite structures. The existence of delaminations changes the vibration characteristics of composite laminates and hence such indicators can be used to quantify the health characteristics of laminates. An approach for online health monitoring of in-service composite laminates is presented in this paper that relies on methods based on computational intelligence. Typical changes in the observed vibration characteristics (i.e. change in natural frequencies) are considered as inputs to identify the existence, location and magnitude of delaminations. The performance of the proposed approach is demonstrated using numerical models of composite laminates. Since this identification problem essentially involves the solution of an optimization problem, the use of finite element (FE) methods as the underlying tool for analysis turns out to be computationally expensive. A surrogate assisted optimization approach is hence introduced to contain the computational time within affordable limits. An artificial neural network (ANN) model with Bayesian regularization is used as the underlying approximation scheme while an improved rate of convergence is achieved using a memetic algorithm. However, building of ANN surrogate models usually requires large training datasets. K-means clustering is effectively employed to reduce the size of datasets. ANN is also used via inverse modeling to determine the position, size and location of delaminations using changes in measured natural frequencies. The results clearly highlight the efficiency and the robustness of the approach.

  2. Delamination of Compressed thin Layers at Corners

    DEFF Research Database (Denmark)

    Clausen, Johan; Jensen, Henrik Myhre; Sørensen, Kim Dalsten

    2008-01-01

    An analysis of delamination for a thin elastic film, attached to a substrate with a corner, is carried out. The film is in compression and the analysis is performed by combining results from fracture mechanics and the theory of thin shells. The results show a very strong dependency of the angle...

  3. Failure and Delamination in Microelectronic Packages

    NARCIS (Netherlands)

    Sadeghinia, M.

    2013-01-01

    Thin layers of dissimilar materials are used in most microelectronic components in order to achieve special functional requirements. Generally, the interface between two adjacent materials forms a weak link, not only because of the relatively low delamination strength, but also because of the existi

  4. Bending strength of delaminated aerospace composites.

    Science.gov (United States)

    Kinawy, Moustafa; Butler, Richard; Hunt, Giles W

    2012-04-28

    Buckling-driven delamination is considered among the most critical failure modes in composite laminates. This paper examines the propagation of delaminations in a beam under pure bending. A pre-developed analytical model to predict the critical buckling moment of a thin sub-laminate is extended to account for propagation prediction, using mixed-mode fracture analysis. Fractography analysis is performed to distinguish between mode I and mode II contributions to the final failure of specimens. Comparison between experimental results and analysis shows agreement to within 5 per cent in static propagation moment for two different materials. It is concluded that static fracture is almost entirely driven by mode II effects. This result was unexpected because it arises from a buckling mode that opens the delamination. For this reason, and because of the excellent repeatability of the experiments, the method of testing may be a promising means of establishing the critical value of mode II fracture toughness, G(IIC), of the material. Fatigue testing on similar samples showed that buckled delamination resulted in a fatigue threshold that was over 80 per cent lower than the static propagation moment. Such an outcome highlights the significance of predicting snap-buckling moment and subsequent propagation for design purposes.

  5. Development and Application of Benchmark Examples for Mixed-Mode I/II Quasi-Static Delamination Propagation Predictions

    Science.gov (United States)

    Krueger, Ronald

    2012-01-01

    The development of benchmark examples for quasi-static delamination propagation prediction is presented. The example is based on a finite element model of the Mixed-Mode Bending (MMB) specimen for 50% mode II. The benchmarking is demonstrated for Abaqus/Standard, however, the example is independent of the analysis software used and allows the assessment of the automated delamination propagation prediction capability in commercial finite element codes based on the virtual crack closure technique (VCCT). First, a quasi-static benchmark example was created for the specimen. Second, starting from an initially straight front, the delamination was allowed to propagate under quasi-static loading. Third, the load-displacement as well as delamination length versus applied load/displacement relationships from a propagation analysis and the benchmark results were compared, and good agreement could be achieved by selecting the appropriate input parameters. The benchmarking procedure proved valuable by highlighting the issues associated with choosing the input parameters of the particular implementation. Overall, the results are encouraging, but further assessment for mixed-mode delamination fatigue onset and growth is required.

  6. Quantitative characterization of the interfacial adhesion of Ni thin film on steel substrate: A compression-induced buckling delamination test

    Science.gov (United States)

    Zhu, W.; Zhou, Y. C.; Guo, J. W.; Yang, L.; Lu, C.

    2015-01-01

    A compression-induced buckling delamination test is employed to quantitatively characterize the interfacial adhesion of Ni thin film on steel substrate. It is shown that buckles initiate from edge flaws and surface morphologies exhibit symmetric, half-penny shapes. Taking the elastoplasticity of film and substrate into account, a three-dimensional finite element model for an edge flaw with the finite size is established to simulate the evolution of energy release rates and phase angles in the process of interfacial buckling-driven delamination. The results show that delamination propagates along both the straight side and curved front. The mode II delamination plays a dominant role in the process with a straight side whilst the curved front experiences almost the pure mode I. Based on the results of finite element analysis, a numerical model is developed to evaluate the interfacial energy release rate, which is in the range of 250-315 J/m2 with the corresponding phase angle from -41° to -66°. These results are in agreement with the available values determined by other testing methods, which confirms the effectiveness of the numerical model.

  7. Spaces of constant curvature

    CERN Document Server

    Wolf, Joseph A

    2010-01-01

    This book is the sixth edition of the classic Spaces of Constant Curvature, first published in 1967, with the previous (fifth) edition published in 1984. It illustrates the high degree of interplay between group theory and geometry. The reader will benefit from the very concise treatments of riemannian and pseudo-riemannian manifolds and their curvatures, of the representation theory of finite groups, and of indications of recent progress in discrete subgroups of Lie groups. Part I is a brief introduction to differentiable manifolds, covering spaces, and riemannian and pseudo-riemannian geomet

  8. Middle Archean continent formation by crustal delamination

    Science.gov (United States)

    Zegers, Tanja E.; van Keken, Peter E.

    2001-12-01

    The processes that created the first large cratonic areas such as the Pilbara and the Kaapvaal remain poorly understood. Models based on the uniformitarian extrapolation of present-day arc volcanic processes to a hotter early Earth have not adequately explained the observations in these terranes. Here we propose an alternative mechanism for the formation of the earliest continental crust. The formation of continental crust may be achieved by delamination of the lower eclogitic part of an oceanic plateau like protocrust. Such delamination results in uplift, extension, and the production of tonalite, trondhjemite, and granodiorite (TTG) suites as recorded in Middle Archean cratons. The available geologic and geophysical observations in combination with model calculations permit this scenario as an alternative to subduction-based hypotheses.

  9. Investigating Delamination Migration in Composite Tape Laminates

    Science.gov (United States)

    Ratcliffe, James G.; DeCarvalho, Nelson V.

    2014-01-01

    A modification to a recently developed test specimen designed to investigate migration of a delamination between neighboring ply interfaces in tape laminates is presented. The specimen is a cross-ply laminated beam consisting of 40 plies with a polytetrafluoroethylene insert spanning part way along its length. The insert is located between a lower 0-degree ply (specimen length direction) and a stack of four 90-degree plies (specimen width direction). The modification involved a stacking sequence that promotes stable delamination growth prior to migration, and included a relocation of the insert from the specimen midplane to the interface between plies 14 and 15. Specimens were clamped at both ends onto a rigid baseplate and loaded on their upper surface via a piano hinge assembly, resulting in a predominantly flexural loading condition. Tests were conducted with the load-application point positioned at various locations along a specimen's span. This position affected the sequence of damage events during a test.

  10. Fiber Optic Thermal Detection of Composite Delaminations

    Science.gov (United States)

    Wu, Meng-Chou; Winfree, William P.

    2011-01-01

    A recently developed technique is presented for thermographic detection of delaminations in composites by performing temperature measurements with fiber optic Bragg gratings. A single optical fiber with multiple Bragg gratings employed as surface temperature sensors was bonded to the surface of a composite with subsurface defects. The investigated structure was a 10-ply composite specimen with prefabricated delaminations of various sizes and depths. Both during and following the application of a thermal heat flux to the surface, the individual Bragg grating sensors measured the temporal and spatial temperature variations. The data obtained from grating sensors were analyzed with thermal modeling techniques of conventional thermography to reveal particular characteristics of the interested areas. Results were compared and found to be consistent with the calculations using numerical simulation techniques. Also discussed are methods including various heating sources and patterns, and their limitations for performing in-situ structural health monitoring.

  11. Delamination-Indicating Thermal Barrier Coatings

    Science.gov (United States)

    Eldridge, Jeffrey I.

    2007-01-01

    The risk of premature failure of thermal barrier coatings (TBCs), typically composed of yttria-stabilized zirconia (YSZ), compromises the reliability of TBCs used to provide thermal protection for turbine engine components. Unfortunately, TBC delamination proceeds well beneath the TBC surface and cannot be monitored by visible inspection. Nondestructive diagnostic tools that could reliably probe the subsurface damage state of TBCs would alleviate the risk of TBC premature failure by indicating when the TBC needs to be replaced before the level of TBC damage threatens engine performance or safety. To meet this need, a new coating design for thermal barrier coatings (TBCs) that are self-indicating for delamination has been successfully implemented by incorporating a europium-doped luminescent sublayer at the base of a TBC composed of YSZ. The luminescent sublayer has the same YSZ composition as the rest of the TBC except for the addition of low-level europium doping and therefore does not alter TBC performance.

  12. DELAMINATION FORMATION AND DELAMINATION PROPAGATION OF COMPOSITE LAMINATES UNDER COMPRESSIVE FATIGUE LOADING

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Fatigue tests of the smooth composite laminates and the notched composite laminates under compressive cyclic loading have been carried out. The damage mechanism is discussed and analyzed. Damage evolution is monitored using stiffness decay. From these tests, it is found that the initial delamination occurs at the free boundary of smooth specimens, or the notch boundary of notched specimens, subjected to the compression-compression cyclic load. A point of view in relation to two-phases of compression fatigue delamination of composites is proposed, namely, compression-compression delamination consists of the delamination formation phase and the delamination propagation, and there is a "damage transition point" to separate this two-phases. Furthermore, an empirical modulus degradation formula and its parameters fitting method are presented. According to the test data handling results, it is shown that this formula is univocal and can fit the test data conveniently. In addition, two kinds of new anti-buckling devices are designed for these tests. At last, the E-N curves, the D-N curves and the S-N curve of the smooth carbon fiber reinforced composite laminates of T300/648C are determined to predict the fatigue life of the notched composite laminate. And the E-N curve of the notched specimens at the given load ratio R=10 and minimum load P min=-0.45 kN is also measured to verify the estimated result of fatigue life.

  13. The Spatial Curvature Endgame

    CERN Document Server

    Leonard, C Danielle; Allison, Rupert

    2016-01-01

    Current constraints on spatial curvature show that it is dynamically negligible: $|\\Omega_{\\rm K}| \\lesssim 5 \\times 10^{-3}$ (95% CL). Neglecting it as a cosmological parameter would be premature however, as more stringent constraints on $\\Omega_{\\rm K}$ at around the $10^{-4}$ level would offer valuable tests of eternal inflation models and probe novel large-scale structure phenomena. This precision also represents the "curvature floor", beyond which constraints cannot be meaningfully improved due to the cosmic variance of horizon-scale perturbations. In this paper, we discuss what future experiments will need to do in order to measure spatial curvature to this maximum accuracy. Our conservative forecasts show that the curvature floor is unreachable - by an order of magnitude - even with Stage IV experiments, unless strong assumptions are made about dark energy evolution and the optical depth to the CMB. We also discuss some of the novel problems that arise when attempting to constrain a global cosmological...

  14. Curvature calculations with GEOCALC

    Energy Technology Data Exchange (ETDEWEB)

    Moussiaux, A.; Tombal, P.

    1987-04-01

    A new method for calculating the curvature tensor has been recently proposed by D. Hestenes. This method is a particular application of geometric calculus, which has been implemented in an algebraic programming language on the form of a package called GEOCALC. They show how to apply this package to the Schwarzchild case and they discuss the different results.

  15. The curvature coordinate system

    DEFF Research Database (Denmark)

    Almegaard, Henrik

    2007-01-01

    hyperbolas. This means that when a plane orthogonal system of curves for which the vertices in a mesh always lie on a circle is mapped on a surface with positive Gaussian curvature using inverse mapping, and the mapped vertices are connected by straight lines, this network will form a faceted surface...

  16. Effect of graded interlayer on the mode I edge delamination by residual stresses in multilayer coating-based systems

    Science.gov (United States)

    Zhang, X. C.; Xu, B. S.; Wang, H. D.; Wu, Y. X.

    2008-01-01

    The mode I edge delamination could be initiated due to the presence of the interfacial peeling stresses near the edges of the multilayered systems due to the material mismatches between the adjacent layers. However, the exact peeling stress distributions could not be obtained by using the existing analytical and numerical models. It was proposed recently that the peeling moment resulting from the localized peeling stresses could be used to characterize mode I edge delamination. In this paper, the effect of the graded interlayer on the mode I edge delamination by thermal residual stresses in multilayer coating-based systems was investigated. Following the previous analysis approaches, the exact closed-form solutions for the peeling moments at individual interfaces and the curvatures for bilayer system, typical thermal barrier coating (TBC) system and TBC-based system with a graded interlayer inserted between the metallic layer and the ceramic layer were, respectively, derived. Case studies showed that the edge delamination by thermal stress could be impeded by properly selecting the coating materials and individual layer thicknesses. These studies may provide some important insights for developing fail-safe designing methodologies for multilayered systems.

  17. Compressive strength of delaminated aerospace composites.

    Science.gov (United States)

    Butler, Richard; Rhead, Andrew T; Liu, Wenli; Kontis, Nikolaos

    2012-04-28

    An efficient analytical model is described which predicts the value of compressive strain below which buckle-driven propagation of delaminations in aerospace composites will not occur. An extension of this efficient strip model which accounts for propagation transverse to the direction of applied compression is derived. In order to provide validation for the strip model a number of laminates were artificially delaminated producing a range of thin anisotropic sub-laminates made up of 0°, ±45° and 90° plies that displayed varied buckling and delamination propagation phenomena. These laminates were subsequently subject to experimental compression testing and nonlinear finite element analysis (FEA) using cohesive elements. Comparison of strip model results with those from experiments indicates that the model can conservatively predict the strain at which propagation occurs to within 10 per cent of experimental values provided (i) the thin-film assumption made in the modelling methodology holds and (ii) full elastic coupling effects do not play a significant role in the post-buckling of the sub-laminate. With such provision, the model was more accurate and produced fewer non-conservative results than FEA. The accuracy and efficiency of the model make it well suited to application in optimum ply-stacking algorithms to maximize laminate strength.

  18. Vibration of composite beams with two overlapping delaminations

    Institute of Scientific and Technical Information of China (English)

    Christian N. Della; Dongwei Shu; Yapu Zhao

    2005-01-01

    Delaminations in composite laminates may develop from small cracks due to fabrication and impact loading, or from places of high stress concentration. The locations of the delaminations are not determinate. In this research, an analytical solution for the free vibration of a composite beam with two overlapping delaminations is presented. The delaminated beam is analyzed as seven interconnected beams using the delaminations as their boundaries. The continuity and equilibrium conditions are satisfied between the adjoining regions of the beams. Classical beam theory is applied to each of the beams. Complex vibration behaviors emerge for different sizes and locations of the delaminations. Comparison with analytical results reported in the literature verifies the validity of the present solution.

  19. THE EFFECT OF SUPPORT PLATE ON DRILLING-INDUCED DELAMINATION

    Directory of Open Access Journals (Sweden)

    Navid Zarif Karimi

    2016-02-01

    Full Text Available Delamination is considered as a major problem in drilling of composite materials, which degrades the mechanical properties of these materials. The thrust force exerted by the drill is considered as the major cause of delamination; and one practical approach to reduce delamination is to use a back-up plate under the specimen. In this paper, the effect of exit support plate on delamination in twist drilling of glass fiber reinforced composites is studied. Firstly, two analytical models based on linear fracture mechanics and elastic bending theory of plates are described to find critical thrust forces at the beginning of crack growth for drilling with and without back-up plate. Secondly, two series of experiments are carried out on glass fiber reinforced composites to determine quantitatively the effect of drilling parameters on the amount of delamination. Experimental findings verify a large reduction in the amount of delaminated area when a back-up plate is placed under the specimen.

  20. Extended layerwise method for laminated composite plates with multiple delaminations and transverse cracks

    Science.gov (United States)

    Li, D. H.; Zhang, X.; Sze, K. Y.; Liu, Y.

    2016-10-01

    In this paper, the extended layerwise method (XLWM), which was developed for laminated composite beams with multiple delaminations and transverse cracks (Li et al. in Int J Numer Methods Eng 101:407-434, 2015), is extended to laminated composite plates. The strong and weak discontinuous functions along the thickness direction are adopted to simulate multiple delaminations and interlaminar interfaces, respectively, whilst transverse cracks are modeled by the extended finite element method (XFEM). The interaction integral method and maximum circumferential tensile criterion are used to calculate the stress intensity factor (SIF) and crack growth angle, respectively. The XLWM for laminated composite plates can accurately predicts the displacement and stress fields near the crack tips and delamination fronts. The thickness distribution of SIF and thus the crack growth angles in different layers can be obtained. These information cannot be predicted by using other existing shell elements enriched by XFEM. Several numerical examples are studied to demonstrate the capabilities of the XLWM in static response analyses, SIF calculations and crack growth predictions.

  1. Transient Dynamic Response of Delaminated Composite Rotating Shallow Shells Subjected to Impact

    Directory of Open Access Journals (Sweden)

    Amit Karmakar

    2006-01-01

    Full Text Available In this paper a transient dynamic finite element analysis is presented to study the response of delaminated composite pretwisted rotating shallow shells subjected to low velocity normal impact. Lagrange's equation of motion is used to derive the dynamic equilibrium equation and moderate rotational speeds are considered wherein the Coriolis effect is negligible. An eight noded isoparametric plate bending element is employed in the finite element formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin's theory. To satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front a multipoint constraint algorithm is incorporated which leads to unsymmetric stiffness matrices. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time dependent equations are solved by Newmark's time integration algorithm. Parametric studies are performed in respect of location of delamination, angle of twist and rotational speed for centrally impacted graphite-epoxy composite cylindrical shells.

  2. FINITE ELEMENT IMPLEMENTATION OF DELAMINATION IN COMPOSITE PLATES

    Directory of Open Access Journals (Sweden)

    Milan Žmindák

    2012-12-01

    Full Text Available Modelling of composite structures by finite element (FE codes to effectively model certain critical failure modes such as delamination is limited. Previous efforts to model delamination and debonding failure modes using FE codes have typically relied on ad hoc failure criteria and quasi-static fracture data. Improvements to these modelling procedures can be made by using an approach based on fracture mechanics. A study of modelling delamination using the finite element code ANSYS was conducted. This investigation demonstrates the modelling of composites through improved delamination modelling. Further developments to this approach may be improved.

  3. Subduction to Continental Delamination: Insights From Laboratory Experiments

    Science.gov (United States)

    Gogus, O. H.; Corbi, F.; Faccenna, C.; Pysklywec, R. N.

    2009-05-01

    The evolution of the lithosphere through subduction-collision and delamination and its surface/crustal response (topography/deformation) is investigated in this work. We present a series of lithosphere scale two dimensional (2-D) and three dimensional (3-D) laboratory experiments to better understand such processes. In these experiments, an idealized viscously deforming crust-mantle lithosphere-mantle system is configured with silicone putty (representing lithospheric mantle and upper crust) and glucose syrup (representing the upper mantle and lower crust). The initial focus was to investigate the physical development of delamination versus continental subduction without plate convergence. Experiments show that the delamination or continental subduction is strongly dependent on the density of the crust (both crust and mantle lithosphere subducts when crust has a higher density, instead of delamination), while in the investigated range, the viscosity of the weak layer does not have much influence on the process. In all the experiments, the topography is asymmetric with subsidence above the delaminating hinge due to the dynamic vertical pulling driven by the delaminating slab, and uplift above the delaminated region due to the buoyancy of asthenosphere. Our investigation on the oceanic subduction with a convergence rate of ~ 3cm/year plate velocity suggests that subduction -collision - delamination is well defined and at the end, the delaminating crust from the lithosphere is overthrusted on top of the overriding plate. Our results provide integrated insights on the Alpine-Himalayan type orogenies, in particular the neotectonic evolution of Eastern Anatolian plateau.

  4. Buckling-driven delamination of carbon nanotube forests

    Science.gov (United States)

    Pour Shahid Saeed Abadi, Parisa; Hutchens, Shelby B.; Greer, Julia R.; Cola, Baratunde A.; Graham, Samuel

    2013-06-01

    We report buckling-driven delamination of carbon nanotube (CNT) forests from their growth substrates when subjected to compression. Macroscale compression experiments reveal local delamination at the CNT forest-substrate interface. Results of microscale flat punch indentations indicate that enhanced CNT interlocking at the top surface of the forest accomplished by application of a metal coating causes delamination of the forest from the growth substrate, a phenomenon not observed in indentation of as-grown CNT forests. We postulate that the post-buckling tensile stresses that develop at the base of the CNT forests serve as the driving force for delamination.

  5. Sensing delamination in epoxy encapsulant systems with fiber Bragg gratings

    Science.gov (United States)

    Jones, Brad H.; Rohr, Garth D.; Kaczmarowski, Amy K.

    2016-05-01

    Fiber Bragg gratings (FBGs) are well-suited for embedded sensing of interfacial phenomena in materials systems, due to the sensitivity of their spectral response to locally non-uniform strain fields. Over the last 15 years, FBGs have been successfully employed to sense delamination at interfaces, with a clear emphasis on planar events induced by transverse cracks in fiber-reinforced plastic laminates. We have built upon this work by utilizing FBGs to detect circular delamination events at the interface between epoxy films and alumina substrates. Two different delamination processes are examined, based on stress relief induced by indentation of the epoxy film or by cooling to low temperature. We have characterized the spectral response pre- and post-delamination for both simple and chirped FBGs as a function of delamination size. We show that delamination is readily detected by the evolution of a non-uniform strain distribution along the fiber axis that persists after the stressing condition is removed. These residual strain distributions differ substantially between the delamination processes, with indentation and cooling producing predominantly tensile and compressive strain, respectively, that are well-captured by Gaussian profiles. More importantly, we observe a strong correlation between spectrally-derived measurements, such as spectral widths, and delamination size. Our results further highlight the unique capabilities of FBGs as diagnostic tools for sensing delamination in materials systems.

  6. Guided Wave Delamination Detection and Quantification With Wavefield Data Analysis

    Science.gov (United States)

    Tian, Zhenhua; Campbell Leckey, Cara A.; Seebo, Jeffrey P.; Yu, Lingyu

    2014-01-01

    Unexpected damage can occur in aerospace composites due to impact events or material stress during off-nominal loading events. In particular, laminated composites are susceptible to delamination damage due to weak transverse tensile and inter-laminar shear strengths. Developments of reliable and quantitative techniques to detect delamination damage in laminated composites are imperative for safe and functional optimally-designed next-generation composite structures. In this paper, we investigate guided wave interactions with delamination damage and develop quantification algorithms by using wavefield data analysis. The trapped guided waves in the delamination region are observed from the wavefield data and further quantitatively interpreted by using different wavenumber analysis methods. The frequency-wavenumber representation of the wavefield shows that new wavenumbers are present and correlate to trapped waves in the damage region. These new wavenumbers are used to detect and quantify the delamination damage through the wavenumber analysis, which can show how the wavenumber changes as a function of wave propagation distance. The location and spatial duration of the new wavenumbers can be identified, providing a useful means not only for detecting the presence of delamination damage but also allowing for estimation of the delamination size. Our method has been applied to detect and quantify real delamination damage with complex geometry (grown using a quasi-static indentation technique). The detection and quantification results show the location, size, and shape of the delamination damage.

  7. Forman curvature for complex networks

    Science.gov (United States)

    Sreejith, R. P.; Mohanraj, Karthikeyan; Jost, Jürgen; Saucan, Emil; Samal, Areejit

    2016-06-01

    We adapt Forman’s discretization of Ricci curvature to the case of undirected networks, both weighted and unweighted, and investigate the measure in a variety of model and real-world networks. We find that most nodes and edges in model and real networks have a negative curvature. Furthermore, the distribution of Forman curvature of nodes and edges is narrow in random and small-world networks, while the distribution is broad in scale-free and real-world networks. In most networks, Forman curvature is found to display significant negative correlation with degree and centrality measures. However, Forman curvature is uncorrelated with clustering coefficient in most networks. Importantly, we find that both model and real networks are vulnerable to targeted deletion of nodes with highly negative Forman curvature. Our results suggest that Forman curvature can be employed to gain novel insights on the organization of complex networks.

  8. Nanotube attachment for prevention of interfacial delamination

    Science.gov (United States)

    Mukhopadhyay, Sharmila M.; Karumuri, Anil K.

    2010-09-01

    A new approach to suppressing interfacial delamination in composites has been investigated. It involves growing strongly attached nanotubes on the surface of the core phase prior to matrix infiltration. Unusually durable interfaces between epoxy and graphite have been demonstrated using this technique. Two types of graphitic core materials have been studied: complex cellular foams having open-interconnected porosity and highly oriented pyrolitic graphite (HOPG) providing a model flat interface. When untreated foam is infiltrated with epoxy, the resulting composite is brittle, and shatters before 10% compression. However, when carbon nanotubes (CNTs) are grown on the foam prior to epoxy infiltration, the specimen becomes pliable, and visibly flattens out rather than fracturing. Model studies on a flat graphite-epoxy interface were performed by joining two HOPG specimens with a thin layer of epoxy, and testing the flexural response of the 'seam' using the three-point bend test. The untreated HOPG sandwich fails easily, whereas nanotube-attached HOPG sandwich shows an over three times increase in flexural load-carrying capacity, close to that of seamless monolithic graphite having identical dimensions. Microscopic evaluations of fractured interfaces indicate that, in all geometries, CNT grafting prevents delamination at the graphite-epoxy interface, and forces any crack(s) to propagate through the graphitic phase. This added inter-laminar strength and toughness can be related to the hierarchical morphology of the interface created by CNT attachment, and unprecedented composite structures can be envisioned.

  9. The Effect of Substrate Topography on Coating Cathodic Delamination

    DEFF Research Database (Denmark)

    Weinell, Claus E.; Sørensen, Per A.; Kiil, Søren

    2011-01-01

    This article describes the effect of steel substrate topography on coating cathodic delamination. The study showed that the surface preparation can be used to control and minimize the rate of cathodic delamination. The coating should have maximum wetting properties so that substrates with high...

  10. Gas permeation and temperature effects in laser-induced delamination

    NARCIS (Netherlands)

    Fedorov, Alexander; Vellinga, Willem-Pier; De Hosson, Jeff

    Laser-induced delamination (LID) is a technique aimed at measuring the work of adhesion of thin polymer coatings on metal substrates. A laser Pulse is used to create a blister that initiates delamination of the film under pressure. The stress fields in the blister wall and the work of adhesion of

  11. Curvature-Dependent Excitation Propagation in Cultured Cardiac Tissue.

    Science.gov (United States)

    Kadota, S; Kay, M W; Magome, N; Agladze, K

    2012-02-01

    The geometry of excitation wave front may play an important role on the propagation block and spiral wave formation. The wave front which is bent over the critical value due to interaction with the obstacles may partially cease to propagate and appearing wave breaks evolve into rotating waves or reentry. This scenario may explain how reentry spontaneously originates in a heart. We studied highly curved excitation wave fronts in the cardiac tissue culture and found that in the conditions of normal, non-inhibited excitability the curvature effects do not play essential role in the propagation. Neither narrow isthmuses nor sharp corners of the obstacles, being classical objects for production of extremely curved wave front, affect non-inhibited wave propagation. The curvature-related phenomena of the propagation block and wave detachment from the obstacle boundary were observed only after partial suppression of the sodium channels with Lidocaine. Computer simulations confirmed the experimental observations. The explanation of the observed phenomena refers to the fact that the heart tissue is made of finite size cells so that curvature radii smaller than the cardiomyocyte size loses sense, and in non-inhibited tissue the single cell is capable to transmit excitation to its neighbors.

  12. Volumetric characterization of delamination fields via angle longitudinal wave ultrasound

    Science.gov (United States)

    Wertz, John; Wallentine, Sarah; Welter, John; Dierken, Josiah; Aldrin, John

    2017-02-01

    The volumetric characterization of delaminations necessarily precedes rigorous composite damage progression modeling. Yet, inspection of composite structures for subsurface damage remains largely focused on detection, resulting in a capability gap. In response to this need, angle longitudinal wave ultrasound was employed to characterize a composite surrogate containing a simulated three-dimensional delamination field with distinct regions of occluded features (shadow regions). Simple analytical models of the specimen were developed to guide subsequent experimentation through identification of optimal scanning parameters. The ensuing experiments provided visual evidence of the complete delamination field, including indications of features within the shadow regions. The results of this study demonstrate proof-of-principle for the use of angle longitudinal wave ultrasonic inspection for volumetric characterization of three-dimensional delamination fields. Furthermore, the techniques developed herein form the foundation of succeeding efforts to characterize impact delaminations within inhomogeneous laminar materials such as polymer matrix composites.

  13. Experimental Vibration Study on the Healthy and Delaminated Composite Plates

    Energy Technology Data Exchange (ETDEWEB)

    Ullah, Israr; Sinha, Jyoti K, E-mail: Jyoti.Sinha@manchester.ac.uk [School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Manchester M13 9PL (United Kingdom)

    2011-07-19

    Vibration based damage, in particular delamination detection, in the composite structures is an active research area. The present study is also on the dynamics of the composite plates with and without delamination based on the experimental study. The test plate made of E-glass fibre and epoxy resins has been used here. A piezo-electric shaker has been used to excite the composite plate and the acceleration responses were measured using the number of accelerometers. The dynamics of the delaminated composite plates were then compared with a healthy composite plate when the vibration experiments have been conducted at the lower modes. The paper will discuss the observations made on the measured vibration responses from both the healthy and the delaminated plates and the possibility of the delamination detection from the experimental vibration data.

  14. Forman curvature for directed networks

    CERN Document Server

    Sreejith, R P; Saucan, Emil; Samal, Areejit

    2016-01-01

    A goal in network science is the geometrical characterization of complex networks. In this direction, we have recently introduced the Forman's discretization of Ricci curvature to the realm of undirected networks. Investigation of Forman curvature in diverse model and real-world undirected networks revealed that this measure captures several aspects of the organization of complex undirected networks. However, many important real-world networks are inherently directed in nature, and the Forman curvature for undirected networks is unsuitable for analysis of such directed networks. Hence, we here extend the Forman curvature for undirected networks to the case of directed networks. The simple mathematical formula for the Forman curvature in directed networks elegantly incorporates node weights, edge weights and edge direction. By applying the Forman curvature for directed networks to a variety of model and real-world directed networks, we show that the measure can be used to characterize the structure of complex ...

  15. Buckling-driven delamination growth in composite laminates: Guidelines for assessing the threat posed by interlaminar matrix delamination

    DEFF Research Database (Denmark)

    Bhushan, Karihaloo; Stang, Henrik

    2008-01-01

    This paper is concerned with development of a simple procedure to assess the threat posed by interlaminar matrix delaminations to the integrity of composite laminates when they are situated in a compressive stress field. Depending upon the size of the delamination, its location below the surface...

  16. On Gauss-Bonnet Curvatures

    Directory of Open Access Journals (Sweden)

    Mohammed Larbi Labbi

    2007-12-01

    Full Text Available The $(2k$-th Gauss-Bonnet curvature is a generalization to higher dimensions of the $(2k$-dimensional Gauss-Bonnet integrand, it coincides with the usual scalar curvature for $k = 1$. The Gauss-Bonnet curvatures are used in theoretical physics to describe gravity in higher dimensional space times where they are known as the Lagrangian of Lovelock gravity, Gauss-Bonnet Gravity and Lanczos gravity. In this paper we present various aspects of these curvature invariants and review their variational properties. In particular, we discuss natural generalizations of the Yamabe problem, Einstein metrics and minimal submanifolds.

  17. Compressive behavior of composite panels with deeply embedded delamination%Compressive behavior of composite panels with deeply embedded delamination

    Institute of Scientific and Technical Information of China (English)

    FU Hui-min; PENG Bo

    2012-01-01

    The compressive behavior of laminates with a deeply embedded circular delamination was studied numerically and experimentally.In the finite element analysis(FEA),virtual crack closure technique(VCCT) and B-K law were employed to simulate the delamination growth,and the contact of the two substrates was considered.The effect of the delamination size and through-thickness position on the compressive behavior of laminates with an artificially embedded circular delamination was discussed.It is found that the through-thickness position affects the buckling mode,which then strongly influences delamination growth speed and direction,as well as the dominant component energy release rate(ERR).The numerical results agreed well with the experimental results.

  18. Anisotropic cubic curvature couplings

    CERN Document Server

    Bailey, Quentin G

    2016-01-01

    To complement recent work on tests of spacetime symmetry in gravity, cubic curvature couplings are studied using an effective field theory description of spacetime-symmetry breaking. The associated mass dimension 8 coefficients for Lorentz violation studied do not result in any linearized gravity modifications and instead are revealed in the first nonlinear terms in an expansion of spacetime around a flat background. We consider effects on gravitational radiation through the energy loss of a binary system and we study two-body orbital perturbations using the post-Newtonian metric. Some effects depend on the internal structure of the source and test bodies, thereby breaking the Weak Equivalence Principle for self-gravitating bodies. These coefficients can be measured in solar-system tests, while binary-pulsar systems and short-range gravity tests are particularly sensitive.

  19. Rarefaction-undercompressive fronts in driven films

    Science.gov (United States)

    Münch, A.; Bertozzi, A. L.

    1999-10-01

    We consider experiments by Ludviksson and Lightfoot [AIChE J. 17, 1166 (1971)] on thin liquid films driven up a vertical plate by a thermally induced surface tension gradient with a counteracting gravitational force, and revisit their theoretical analysis, which neglects the effects of curvature, for predicting the climbing rate of the front. We present a new theory for the lubrication model with curvature effects, and get rising rates that depend on the microscopic length scale at the contact line. The predictions are, in general, in better agreement with the experiment.

  20. On Nonlinear Higher Spin Curvature

    OpenAIRE

    Manvelyan, Ruben(Yerevan Physics Institute, Alikhanian Br. St. 2, Yerevan, 0036, Armenia); Mkrtchyan, Karapet; Rühl, Werner; Tovmasyan, Murad

    2011-01-01

    We present the first nonlinear term of the higher spin curvature which is covariant with respect to deformed gauge transformations that are linear in the field. We consider in detail the case of spin 3 after presenting spin 2 as an example, and then construct the general spin s quadratic term of the deWit-Freedman curvature.

  1. On nonlinear higher spin curvature

    Energy Technology Data Exchange (ETDEWEB)

    Manvelyan, Ruben, E-mail: manvel@physik.uni-kl.d [Department of Physics, Erwin Schroedinger Strasse, Technical University of Kaiserslautern, Postfach 3049, 67653 Kaiserslautern (Germany); Yerevan Physics Institute, Alikhanian Br. Str. 2, 0036 Yerevan (Armenia); Mkrtchyan, Karapet, E-mail: karapet@yerphi.a [Department of Physics, Erwin Schroedinger Strasse, Technical University of Kaiserslautern, Postfach 3049, 67653 Kaiserslautern (Germany); Yerevan Physics Institute, Alikhanian Br. Str. 2, 0036 Yerevan (Armenia); Ruehl, Werner, E-mail: ruehl@physik.uni-kl.d [Department of Physics, Erwin Schroedinger Strasse, Technical University of Kaiserslautern, Postfach 3049, 67653 Kaiserslautern (Germany); Tovmasyan, Murad, E-mail: mtovmasyan@ysu.a [Yerevan Physics Institute, Alikhanian Br. Str. 2, 0036 Yerevan (Armenia)

    2011-05-09

    We present the first nonlinear term of the higher spin curvature which is covariant with respect to deformed gauge transformations that are linear in the field. We consider the case of spin 3 after presenting spin 2 as an example, and then construct the general spin s quadratic term of the de Wit-Freedman curvature.

  2. Environmental influences on DNA curvature

    DEFF Research Database (Denmark)

    Ussery, David; Higgins, C.F.; Bolshoy, A.

    1999-01-01

    DNA curvature plays an important role in many biological processes. To study environmentalinfluences on DNA curvature we compared the anomalous migration on polyacrylamide gels ofligation ladders of 11 specifically-designed oligonucleotides. At low temperatures (25 degreesC and below) most...... for DNAcurvature and for environmentally-sensitive DNA conformations in the regulation of geneexpression....

  3. Floating Carpets and the Delamination of Elastic Sheets

    KAUST Repository

    Wagner, Till J. W.

    2011-07-22

    We investigate the deformation of a thin elastic sheet floating on a liquid surface and subject to a uniaxial compression. We show that at a critical compression the sheet delaminates from the liquid over a finite region forming a delamination "blister." This blistering regime adds to the wrinkling and localized folding regimes that have been studied previously. The transition from wrinkled to blistered states occurs when delamination becomes energetically favorable compared with wrinkling. We determine the initial blister size and the evolution of blister size with continuing compression before verifying our theoretical results with experiments at a macroscopic scale. © 2011 American Physical Society.

  4. Microscale mechanics for metal thin film delamination along ceramic substrates

    Institute of Scientific and Technical Information of China (English)

    魏悦广

    2000-01-01

    The metal thin film delamination along metal/ceramic interface in the case of large scale yielding is studied by employing the strain gradient plasticity theory and the material microscale effects are considered. Two different f racture process models are used in this study to describe the nonlinear delamination phenomena for metal thin films. A set of experiments have been done on the mechanism of copper films delaminating from silica substrates, based on which the peak interface separation stress and the micro-length scale of material, as well as the dislocation-free zone size are predicted.

  5. Microscale mechanics for metal thin film delamination along ceramic substrates

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The metal thin film delamination along metal/ceramic interface in the case of large scale yielding is studied by employing the strain gradient plasticity theory and the material microscale effects are considered.Two different fracture process models are used in this study to describe the nonlinear delamination phenomena for metal thin films.A set of experiments have been done on the mechanism of copper films delaminating from silica substrates,based on which the peak interface separation stress and the micro-length scale of material,as well as the dislocation-free zone size are predicted.

  6. CURVATURE COMPUTATIONS OF 2-MANIFOLDS IN IRk

    Institute of Scientific and Technical Information of China (English)

    Guo-liang Xu; Chandrajit L. Bajaj

    2003-01-01

    In this paper, we provide simple and explicit formulas for computing Riemannian cur-vatures, mean curvature vectors, principal curvatures and principal directions for a 2-dimensional Riemannian manifold embedded in IRk with k ≥ 3.

  7. Lectures on mean curvature flows

    CERN Document Server

    Zhu, Xi-Ping

    2002-01-01

    "Mean curvature flow" is a term that is used to describe the evolution of a hypersurface whose normal velocity is given by the mean curvature. In the simplest case of a convex closed curve on the plane, the properties of the mean curvature flow are described by Gage-Hamilton's theorem. This theorem states that under the mean curvature flow, the curve collapses to a point, and if the flow is diluted so that the enclosed area equals \\pi, the curve tends to the unit circle. In this book, the author gives a comprehensive account of fundamental results on singularities and the asymptotic behavior of mean curvature flows in higher dimensions. Among other topics, he considers in detail Huisken's theorem (a generalization of Gage-Hamilton's theorem to higher dimension), evolution of non-convex curves and hypersurfaces, and the classification of singularities of the mean curvature flow. Because of the importance of the mean curvature flow and its numerous applications in differential geometry and partial differential ...

  8. Utilization of Large Cohesive Interface Elements for Delamination Simulation

    DEFF Research Database (Denmark)

    Bak, Brian Lau Verndal; Lund, Erik

    2012-01-01

    This paper describes the difficulties of utilizing large interface elements in delamination simulation. Solutions to increase the size of applicable interface elements are described and cover numerical integration of the element and modifications of the cohesive law.......This paper describes the difficulties of utilizing large interface elements in delamination simulation. Solutions to increase the size of applicable interface elements are described and cover numerical integration of the element and modifications of the cohesive law....

  9. EAU guidelines on penile curvature.

    Science.gov (United States)

    Hatzimouratidis, Konstantinos; Eardley, Ian; Giuliano, François; Hatzichristou, Dimitrios; Moncada, Ignacio; Salonia, Andrea; Vardi, Yoram; Wespes, Eric

    2012-09-01

    Penile curvature can be congenital or acquired. Acquired curvature is secondary due to La Peyronie (Peyronie's) disease. To provide clinical guidelines on the diagnosis and treatment of penile curvature. A systematic literature search on the epidemiology, diagnosis, and treatment of penile curvature was performed. Articles with the highest evidence available were selected and formed the basis for assigning levels of evidence and grades of recommendations. The pathogenesis of congenital penile curvature is unknown. Peyronie's disease is a poorly understood connective tissue disorder most commonly attributed to repetitive microvascular injury or trauma during intercourse. Diagnosis is based on medical and sexual histories, which are sufficient to establish the diagnosis. Physical examination includes assessment of palpable nodules and penile length. Curvature is best documented by a self-photograph or pharmacologically induced erection. The only treatment option for congenital penile curvature is surgery based on plication techniques. Conservative treatment for Peyronie's disease is associated with poor outcomes. Pharmacotherapy includes oral potassium para-aminobenzoate, intralesional treatment with verapamil, clostridial collagenase or interferon, topical verapamil gel, and iontophoresis with verapamil and dexamethasone. They can be efficacious in some patients, but none of these options carry a grade A recommendation. Steroids, vitamin E, and tamoxifen cannot be recommended. Extracorporeal shock wave treatment and penile traction devices may only be used to treat penile pain and reduce penile deformity, respectively. Surgery is indicated when Peyronie's disease is stable for at least 3 mo. Tunical shortening procedures, especially plication techniques, are the first treatment options. Tunical lengthening procedures are preferred in more severe curvatures or in complex deformities. Penile prosthesis implantation is recommended in patients with erectile dysfunction

  10. Sigma Models with Negative Curvature

    CERN Document Server

    Alonso, Rodrigo; Manohar, Aneesh V.

    2016-01-01

    We construct Higgs Effective Field Theory (HEFT) based on the scalar manifold H^n, which is a hyperbolic space of constant negative curvature. The Lagrangian has a non-compact O(n,1) global symmetry group, but it gives a unitary theory as long as only a compact subgroup of the global symmetry is gauged. Whether the HEFT manifold has positive or negative curvature can be tested by measuring the S-parameter, and the cross sections for longitudinal gauge boson and Higgs boson scattering, since the curvature (including its sign) determines deviations from Standard Model values.

  11. Integrated global digital image correlation for interface delamination characterization

    KAUST Repository

    Hoefnagels, Johan P.M.

    2013-07-23

    Interfacial delamination is a key reliability challenge in composites and micro-electronic systems due to (high-density) integration of dissimilar materials. Predictive finite element models are used to minimize delamination failures during design, but require accurate interface models to capture (irreversible) crack initiation and propagation behavior observed in experiments. Therefore, an Integrated Global Digital Image Correlation (I-GDIC) strategy is developed for accurate determination of mechanical interface behavior from in-situ delamination experiments. Recently, a novel miniature delamination setup was presented that enables in-situ microscopic characterization of interface delamination while sensitively measuring global load-displacement curves for all mode mixities. Nevertheless, extraction of detailed mechanical interface behavior from measured images is challenging, because deformations are tiny and measurement noise large. Therefore, an advanced I-GDIC methodology is developed which correlates the image patterns by only deforming the images using kinematically-admissible \\'eigenmodes\\' that correspond to the few parameters controlling the interface tractions in an analytic description of the crack tip deformation field, thereby greatly enhancing accuracy and robustness. This method is validated on virtual delamination experiments, simulated using a recently developed self-adaptive cohesive zone (CZ) finite element framework. © The Society for Experimental Mechanics, Inc. 2014.

  12. Solving higher curvature gravity theories

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, Sumanta [IUCAA, Pune (India); SenGupta, Soumitra [Indian Association for the Cultivation of Science, Theoretical Physics Department, Kolkata (India)

    2016-10-15

    Solving field equations in the context of higher curvature gravity theories is a formidable task. However, in many situations, e.g., in the context of f(R) theories, the higher curvature gravity action can be written as an Einstein-Hilbert action plus a scalar field action. We show that not only the action but the field equations derived from the action are also equivalent, provided the spacetime is regular. We also demonstrate that such an equivalence continues to hold even when the gravitational field equations are projected on a lower-dimensional hypersurface. We have further addressed explicit examples in which the solutions for Einstein-Hilbert and a scalar field system lead to solutions of the equivalent higher curvature theory. The same, but on the lower-dimensional hypersurface, has been illustrated in the reverse order as well. We conclude with a brief discussion on this technique of solving higher curvature field equations. (orig.)

  13. Effects of Curvature on Dynamics

    CERN Document Server

    Dutta, Gautam

    2010-01-01

    In this article we discuss the effect of curvature on dynamics when a physical system moves adiabatically in a curved space. These effects give a way to measure the curvature of the space intrinsically without referring to higher dimensional space. Two interesting examples, the Foucault Pendulum and the perihelion shift of planetary orbits, are presented in a simple geometric way. A paper model is presented to see the perihelion shift.

  14. Characterizing Delamination Migration in Carbon/Epoxy Tape Laminates

    Science.gov (United States)

    Ratcliffe, James G.; Czabaj, Michael W.; Obrien, Thomas K.

    2012-01-01

    A new test method is presented for the purpose of investigating migration of a delamination between neighboring ply interfaces in fiber-reinforced, polymer matrix tape laminates. The test is a single cantilever beam configuration consisting of a cross-ply laminate with a polytetrafluoroethylene (PTFE) insert implanted at the mid-plane and spanning part way along the length of the specimen. The insert is located between a 0-degree ply (specimen length direction) and a stack of four 90-degree plies (specimen width direction). The specimen is clamped at both ends onto a rigid baseplate and is loaded on its upper surface via a piano hinge. Tests were conducted with the load-application point located on the intact portion of the specimen in order to initiate delamination growth onset followed by migration of the delamination to a neighboring 90/0 ply interface by kinking through the 90- degree ply stack. Varying this position was found to affect the distance relative to the load-application point at which migration initiated. In each specimen, migration initiated by a gradual transition of the delamination at the 0/90 interface into the 90- degree ply stack. In contrast, transition of the kinked crack into the 90/0 interface was sudden. Fractography of the specimens indicated that delamination prior to migration was generally mixed mode-I/II. Inspection of the kink surface revealed mode-I fracture. In general, use of this test allows for the observation of the growth of a delamination followed by migration of the delamination to another ply interface, and should thus provide a means for validating analyses aimed at simulating migration.

  15. Spatial curvature endgame: Reaching the limit of curvature determination

    Science.gov (United States)

    Leonard, C. Danielle; Bull, Philip; Allison, Rupert

    2016-07-01

    Current constraints on spatial curvature show that it is dynamically negligible: |ΩK|≲5 ×10-3 (95% C.L.). Neglecting it as a cosmological parameter would be premature however, as more stringent constraints on ΩK at around the 10-4 level would offer valuable tests of eternal inflation models and probe novel large-scale structure phenomena. This precision also represents the "curvature floor," beyond which constraints cannot be meaningfully improved due to the cosmic variance of horizon-scale perturbations. In this paper, we discuss what future experiments will need to do in order to measure spatial curvature to this maximum accuracy. Our conservative forecasts show that the curvature floor is unreachable—by an order of magnitude—even with Stage IV experiments, unless strong assumptions are made about dark energy evolution and the Λ CDM parameter values. We also discuss some of the novel problems that arise when attempting to constrain a global cosmological parameter like ΩK with such high precision. Measuring curvature down to this level would be an important validation of systematics characterization in high-precision cosmological analyses.

  16. Discrete Curvature Theories and Applications

    KAUST Repository

    Sun, Xiang

    2016-08-25

    Discrete Di erential Geometry (DDG) concerns discrete counterparts of notions and methods in di erential geometry. This thesis deals with a core subject in DDG, discrete curvature theories on various types of polyhedral surfaces that are practically important for free-form architecture, sunlight-redirecting shading systems, and face recognition. Modeled as polyhedral surfaces, the shapes of free-form structures may have to satisfy di erent geometric or physical constraints. We study a combination of geometry and physics { the discrete surfaces that can stand on their own, as well as having proper shapes for the manufacture. These proper shapes, known as circular and conical meshes, are closely related to discrete principal curvatures. We study curvature theories that make such surfaces possible. Shading systems of freeform building skins are new types of energy-saving structures that can re-direct the sunlight. From these systems, discrete line congruences across polyhedral surfaces can be abstracted. We develop a new curvature theory for polyhedral surfaces equipped with normal congruences { a particular type of congruences de ned by linear interpolation of vertex normals. The main results are a discussion of various de nitions of normality, a detailed study of the geometry of such congruences, and a concept of curvatures and shape operators associated with the faces of a triangle mesh. These curvatures are compatible with both normal congruences and the Steiner formula. In addition to architecture, we consider the role of discrete curvatures in face recognition. We use geometric measure theory to introduce the notion of asymptotic cones associated with a singular subspace of a Riemannian manifold, which is an extension of the classical notion of asymptotic directions. We get a simple expression of these cones for polyhedral surfaces, as well as convergence and approximation theorems. We use the asymptotic cones as facial descriptors and demonstrate the

  17. MR imaging of delamination tears of the rotator cuff tendons

    Energy Technology Data Exchange (ETDEWEB)

    Walz, Daniel M.; Chen, Steven [North Shore University Hospital, Department of Radiology, Manhasset, NY (United States); Miller, Theodore T. [Hospital for Special Surgery, Department of Radiology and Imaging, New York, NY (United States); Hofman, Josh [Long Island Jewish Medical Center, New Hyde Park, NY (United States)

    2007-05-15

    The objective was to describe the imaging appearances and location of delamination tears of the rotator cuff tendons on non-contrast conventional MR imaging. This study was reviewed and approved by our Institutional Review Board. The reports of 548 consecutive MR examinations of the shoulder were reviewed, looking for mention or description of delamination tears of the rotator cuff. The images of the identified cases were then reviewed by two radiologists to confirm the findings. Correlation with surgical and arthroscopic information was then performed. Delamination tears were defined as horizontal retraction of either the bursal or articular surface of the tendon, manifest as thickening of the torn retracted edge, and/or interstitial splitting of the tendon, manifest as fluid-like high signal intensity on fat-suppressed T2-weighted oblique coronal images. Fourteen cases of delamination tears were identified in 13 patients. Ten of the cases involved the supraspinatus tendon, all with articular surface involvement. Nine of these supraspinatus cases were isolated tears and one occurred as part of a full thickness tear. All 10 of these supraspinatus cases showed medial retraction of the articular surface of the tendon, with thickening of the retracted edge, and 5 of the 10 had a demonstrable horizontal cleft in the interstitium. Four cases involved the subscapularis tendon, with articular surface disruption in three and pure interstitial delamination in one. Medial subluxation of the tendon of the long head of the biceps was present in all four cases. No delamination tears occurred on the bursal surface. Only three of the 14 shoulders underwent surgical repair with one confirmation of supraspinatus delamination, one confirmation of a subscapularis tear that had become a full thickness tear 10 months after initial imaging and another interstitial subscapularis delamination that was not identified arthroscopically. Delamination tears occur most often in the

  18. Microscopic mechanisms of graphene electrolytic delamination from metal substrates

    Science.gov (United States)

    Fisichella, G.; Di Franco, S.; Roccaforte, F.; Ravesi, S.; Giannazzo, F.

    2014-06-01

    In this paper, hydrogen bubbling delamination of graphene (Gr) from copper using a strong electrolyte (KOH) water solution was performed, focusing on the effect of the KOH concentration (CKOH) on the Gr delamination rate. A factor of ˜10 decrease in the time required for the complete Gr delamination from Cu cathodes with the same geometry was found increasing CKOH from ˜0.05 M to ˜0.60 M. After transfer of the separated Gr membranes to SiO2 substrates by a highly reproducible thermo-compression printing method, an accurate atomic force microscopy investigation of the changes in Gr morphology as a function of CKOH was performed. Supported by these analyses, a microscopic model of the delamination process has been proposed, where a key role is played by graphene wrinkles acting as nucleation sites for H2 bubbles at the cathode perimeter. With this approach, the H2 supersaturation generated at the electrode for different electrolyte concentrations was estimated and the inverse dependence of td on CKOH was quantitatively explained. Although developed in the case of Cu, this analysis is generally valid and can be applied to describe the electrolytic delamination of graphene from several metal substrates.

  19. EBSD and Nanoindentation-Correlated Study of Delamination Fracture in Al-Li Alloy 2090

    Science.gov (United States)

    Tayon, Wesley A.; Crooks, Roy E.; Domack, Marcia S.; Wagner, John A.; Elmustafa, A. A.

    2008-01-01

    Al-Li alloys offer attractive combinations of high strength and low density. However, a tendency for delamination fracture has limited their use. A better understanding of the delamination mechanisms may identify methods to control delaminations through processing modifications. A combination of new techniques has been used to evaluate delamination fracture in Al-Li alloys. Both high quality electron backscattered diffraction (EBSD) information and valid nanoindentation measurements were obtained from fractured test specimens. Correlations were drawn between nano-scale hardness variations and local texture along delaminating boundaries. Intriguing findings were observed for delamination fracture through the combined analysis of grain orientation, Taylor factor, and kernel average misorientation.

  20. Micromechanical models of delamination in aluminum-lithium alloys

    Science.gov (United States)

    Messner, Mark Christian

    Aluminum lithium (Al-Li) alloys are lighter, stiffer, and tougher than conventional aerospace aluminum alloys. Replacing conventional aluminums with Al-Li could substantially decrease the weight and cost of aerospace structures. However, Al-Li alloys often fracture intergranularly via a mechanism called delamination cracking. While secondary delamination cracks can improve the effective toughness of a component, no current model accurately predicts the initiation and growth of intergranular cracks. Since simulations cannot incorporate delamination into a structural model, designers cannot quantify the effect of delamination cracking on a particular component. This uncertainty limits the application of Al-Li alloys. Previous experiments identify microstructural features linked to delamination. Fractography of failed surfaces indicates plastic void growth triggers intergranular failure. Furthermore, certain types of soft/stiff grain boundaries tend to localize void growth and nucleate delamination cracks. This dissertation develops a mechanism for the initiation of delamination on the microscale that accounts for these experimental observations. Microscale simulations of grain boundaries near a long primary crack explore the delamination mechanism on the mesoscale. In these simulations, a physically-based crystal plasticity (CP) model represents the constitutive response of individual grains. This CP model incorporates plastic voriticity correction terms into a standard objective stress rate integration, to accurately account for the kinematics of lattice deformation. The CP model implements slip system hardening with a modular approach to facilitate quick testing and calibration of different theories of hardening. The microscale models reveal soft/stiff grain boundaries develop elevated mean stress and plastic strain as a consequence of the mechanics of the interface. These elevated stresses and strain drive plastic void growth. The results indicate plastic void

  1. Buckling induced delamination of graphene composites through hybrid molecular modeling

    Science.gov (United States)

    Cranford, Steven W.

    2013-01-01

    The efficiency of graphene-based composites relies on mechanical stability and cooperativity, whereby separation of layers (i.e., delamination) can severely hinder performance. Here we study buckling induced delamination of mono- and bilayer graphene-based composites, utilizing a hybrid full atomistic and coarse-grained molecular dynamics approach. The coarse-grain model allows exploration of an idealized model material to facilitate parametric variation beyond any particular molecular structure. Through theoretical and simulation analyses, we show a critical delamination condition, where ΔD∝kL4, where ΔD is the change in bending stiffness (eV), k the stiffness of adhesion (eV/Å4), and L the length of the adhered section (Å).

  2. Equi-Gaussian Curvature Folding

    Indian Academy of Sciences (India)

    E M El-Kholy; El-Said R Lashin; Salama N Daoud

    2007-08-01

    In this paper we introduce a new type of folding called equi-Gaussian curvature folding of connected Riemannian 2-manifolds. We prove that the composition and the cartesian product of such foldings is again an equi-Gaussian curvature folding. In case of equi-Gaussian curvature foldings, $f:M→ P_n$, of an orientable surface onto a polygon $P_n$ we prove that (i) $f\\in\\mathcal{F}_{EG}(S^2)\\Leftrightarrow n=3$ (ii) $f\\in\\mathcal{F}_{EG}(T^2)\\Rightarrow n=4$ (iii) $f\\in\\mathcal{F}_{EG}(\\# 2T^2)\\Rightarrow n=5, 6$ and we generalize (iii) for $\\# nT^2$.

  3. Integral Menger curvature for surfaces

    OpenAIRE

    Strzelecki, Paweł; von der Mosel, Heiko

    2009-01-01

    We develop the concept of integral Menger curvature for a large class of nonsmooth surfaces. We prove uniform Ahlfors regularity and a $C^{1,\\lambda}$-a-priori bound for surfaces for which this functional is finite. In fact, it turns out that there is an explicit length scale $R>0$ which depends only on an upper bound $E$ for the integral Menger curvature $M_p(\\Sigma)$ and the integrability exponent $p$, and \\emph{not} on the surface $\\Sigma$ itself; below that scale, each surface with energy...

  4. Characterization of Multiple Delaminated Composite by Finite Element

    Directory of Open Access Journals (Sweden)

    SUDIP DEY

    2011-09-01

    Full Text Available In this paper, a finite element method is employed to investigate the natural frequencies of twisted rotating composite turbine blades subject to multiple delamination. The turbine blade is idealized as a shallow conical shell model with low aspect ratio. The formulation is based on Mindlin’s theory, QR iteration and multi-point constraint algorithm for moderate rotational speeds neglecting Coriolis effect. Computer codes are developed and the numerical results obtained for multiple delaminated graphite-epoxy cross-ply composite shallow conical shells are the first known non-dimensional frequencies for the type of analyses carried out here.

  5. Modeling Quasi-Static and Fatigue-Driven Delamination Migration

    Science.gov (United States)

    De Carvalho, N. V.; Ratcliffe, J. G.; Chen, B. Y.; Pinho, S. T.; Baiz, P. M.; Tay, T. E.

    2014-01-01

    An approach was proposed and assessed for the high-fidelity modeling of progressive damage and failure in composite materials. It combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. Delamination, matrix cracking, and migration were captured failure and migration criteria based on fracture mechanics. Quasi-static and fatigue loading were modeled within the same overall framework. The methodology proposed was illustrated by simulating the delamination migration test, showing good agreement with the available experimental data.

  6. Progressive delamination in polymer matrix composite laminates: A new approach

    Science.gov (United States)

    Chamis, C. C.; Murthy, P. L. N.; Minnetyan, L.

    1992-01-01

    A new approach independent of stress intensity factors and fracture toughness parameters has been developed and is described for the computational simulation of progressive delamination in polymer matrix composite laminates. The damage stages are quantified based on physics via composite mechanics while the degradation of the laminate behavior is quantified via the finite element method. The approach accounts for all types of composite behavior, laminate configuration, load conditions, and delamination processes starting from damage initiation, to unstable propagation, and to laminate fracture. Results of laminate fracture in composite beams, panels, plates, and shells are presented to demonstrate the effectiveness and versatility of this new approach.

  7. The postbuckling analysis of laminated circular plate with elliptic delamination

    Science.gov (United States)

    Chen, Deliang; Chen, Changping; Fu, Yiming

    2011-01-01

    Based on the Von Karman plate theory, considering the effect of transverse shear deformation, and using the method of the dissociated three regions, the postbuckling governing equations for the axisymmetric laminated circular plates with elliptical delamination are derived. By using the orthogonal point collocation method, the governing equations, boundary conditions and continuity conditions are transformed into a group of nonlinear algebraically equation and the equations are solved with the alternative method. In the numerical examples, the effects of various elliptical in shape, delamination depth and different material properties on buckling and postbuckling of the laminated circular plates are discussed and the numerical results are compared with available data.

  8. Probabilistic Delamination Diagnosis of Composite Materials Using a Novel Bayesian Imaging Method

    Data.gov (United States)

    National Aeronautics and Space Administration — In this paper, a probabilistic delamination location and size detection framework is proposed. The delamination probability image using Lamb wave-based damage...

  9. Surface meshing with curvature convergence

    KAUST Repository

    Li, Huibin

    2014-06-01

    Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.

  10. Environmental influences on DNA curvature

    DEFF Research Database (Denmark)

    Ussery, David; Higgins, C.F.; Bolshoy, A.

    1999-01-01

    of the sequences exhibited a degree of anomalous migration. Increasedtemperature had a significant effect on the anomalous migration (curvature) of some sequencesbut limited effects on others; at 50 degrees C only 1 sequence migrated anomalously. Mg2+ hada strong influence on the migration of certain sequences...

  11. The Effect of Strike Face Geometry on the Dynamic Delamination of Composite Back Plates

    Science.gov (United States)

    2015-01-01

    Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that...specimen allowed for capture of dynamic delamination images with high-speed photography . The projected delamination area was quantified using commercially...14 Fig. B-1 Delaminations outlined using tools in Image Pro Plus ..................................................22 Fig. B-2 Yellow

  12. Adhesion of polymer coatings studied by laser-induced delamination

    NARCIS (Netherlands)

    Fedorov, A; De Hosson, JTM

    2005-01-01

    This paper concentrates on the laser-induced delamination technique, aimed at measuring the practical work of adhesion of thin polymer coatings on metal substrates. In this technique an infrared laser-pulsed beam is used to create an initial blister. Upon increasing the pulse intensity, the size of

  13. Optimizing the delamination failure in bamboo fiber reinforced polyester composite

    Directory of Open Access Journals (Sweden)

    N. Abilash

    2016-01-01

    Full Text Available Delamination is represented to be the most prevalent failure in composite structures. The use of composites in the manufacturing sector plays a very important role in the industry in general. Moreover these materials have unique characteristics when analyzed separately from constituents which are a part of them. In this paper, a partially ecological composite was made, using natural fibers as reinforcement (bamboo fiber, in the polyester resin matrix to form a composite, seeking to improve the mechanical behavior among its class of materials. The characteristics of a composite material are determined by how it behaves while machining, Drilling is the most predominant machining process because of its cost effectiveness when compared with other processes. Obviously delamination is the major problem that is focused by many researchers while selecting drilling as the machining process in polymeric composites. This research mainly emphasizes on the critical parameters by varying its speed, feed, and diameter of the cutting tool, their contribution to delamination was analyzed. Reduced delaminations were identified by varying the speed and feed rate.

  14. Simulation of cusp formation in mode II delamination

    NARCIS (Netherlands)

    Sluys, L.J.; Van der Meer, F.P.

    2014-01-01

    On the microlevel, cusps are formed during delamination crack growth under mode II loading conditions. In this work, two different approaches to simulate this process are presented. Firstly a cohesive zone method where cohesive segments are introduced between a pair of neighbouring elements when the

  15. Modeling delamination due to thermal stress in optical storage media

    Science.gov (United States)

    Nkansah, M. A.; Evans, K. E.

    1990-04-01

    Finite element analysis is used to calculate the shape of blisters formed in bilayer optical storage media due to the buildup of thermal stresses during laser writing. It is shown that practically usable blisters may be expected to form in a time period of about 15 ns. Such a thermal stress delamination process may also precede melting in conventional pit formation processes.

  16. Delamination and debonding failure of laminated composite T-joints

    NARCIS (Netherlands)

    Cui, H.

    2014-01-01

    Composites are increasingly being used in aerospace, automotive and other industries. The T-joint (also named stringer stiffened skin) is a typical connection, broadly used in thin-walled structures, such as the wing and fuselage of aircraft. This thesis presents the analysis of the delamination and

  17. Ets-1 confers cranial features on neural crest delamination.

    Directory of Open Access Journals (Sweden)

    Eric Théveneau

    Full Text Available Neural crest cells (NCC have the particularity to invade the environment where they differentiate after separation from the neuroepithelium. This process, called delamination, is strikingly different between cranial and trunk NCCs. If signalings controlling slow trunk delamination start being deciphered, mechanisms leading to massive and rapid cranial outflow are poorly documented. Here, we show that the chick cranial NCCs delamination is the result of two events: a substantial cell mobilization and an epithelium to mesenchyme transition (EMT. We demonstrate that ets-1, a transcription factor specifically expressed in cranial NCCs, is responsible for the former event by recruiting massively cranial premigratory NCCs independently of the S-phase of the cell cycle and by leading the gathered cells to straddle the basal lamina. However, it does not promote the EMT process alone but can cooperate with snail-2 (previously called slug to this event. Altogether, these data lead us to propose that ets-1 plays a pivotal role in conferring specific cephalic characteristics on NCC delamination.

  18. Webbing and Delamination of Drug Eluting Stent Coatings.

    Science.gov (United States)

    Hopkins, C; Sweeney, C A; O'Connor, C; McHugh, P E; McGarry, J P

    2016-02-01

    The advancement of the drug-eluting stent technology raises the significant challenge of safe mechanical design of polymer coated stent systems. Experimental images of stent coatings undergoing significant damage during deployment have been reported; such coating damage and delamination can lead to complications such as restenosis and increased thrombogenicity. In the current study a cohesive zone modeling framework is developed to predict coating delamination and buckling due to hinge deformation during stent deployment. Models are then extended to analyze, for the first time, stent-coating damage due to webbing defects. Webbing defects occur when a bond forms between coating layers on adjacent struts, resulting in extensive delamination of the coating from the strut surfaces. The analyzes presented in this paper uncover the mechanical factors that govern webbing induced coating damage. Finally, an experimental fracture test of a commercially available stent coating material is performed and results demonstrate that the high cohesive strength of the coating material will prevent web fracture, resulting in significant coating delamination during stent deployment.

  19. Modeling the buckling and delamination of thin films

    Science.gov (United States)

    Jagla, E. A.

    2007-02-01

    I study numerically the problem of delamination of a thin film elastically attached to a rigid substrate. A nominally flat elastic thin film is modeled using a two-dimensional triangular mesh. Both compression and bending rigidities are included to simulate compression and bending of the film. The film can buckle (i.e., abandon its flat configuration) when enough compressive strain is applied. The buckled configurations of a piece of film with stripe geometry are investigated as a function of the compressive strain. It is found that the stable configuration depends strongly on the applied strain and the Poisson ratio of the film. Next, the film is considered to be attached to a rigid substrate by springs that can break when the detaching force exceeds a threshold value, producing partial delamination of the film. Delamination is induced by a mismatch of the relaxed configurations of film and substrate. The morphology of the delaminated film can be followed and compared with available experimental results as a function of model parameters. “Telephone-cord,” polygonal, and “brainlike” patterns qualitatively similar to experimentally observed configurations are obtained in different parameter regions. The main control parameters that select the different patterns are the strain mismatch between film and substrate and the degree of in-plane relaxation within the unbuckled regions.

  20. Influence of surface pretreatment of fiber posts on cement delamination

    NARCIS (Netherlands)

    Jongsma, L.A.; Kleverlaan, C.J.; Feilzer, A.J.

    2010-01-01

    Objectives To evaluate the influence of post surface pretreatment on the delamination strength of different cements from a prefabricated FRC post tested in a three-point bending test. Methods Three cements were tested; RelyX Unicem, DC Core Automix, and Panavia F2.0. Per cement, 40 posts (D.T. Light

  1. Impact Delamination and Fracture in Aluminum/Acrylic Sandwich Plates

    Science.gov (United States)

    Liaw, Benjamin; Zeichner, Glenn; Liu, Yanxiong; Bowles, Kenneth J. (Technical Monitor)

    2000-01-01

    Impact-induced delamination and fracture in 6061-T6 aluminum/cast acrylic sandwich plates adhered by epoxy were generated in an instrumented drop-weight impact machine. Although only a small dent was produced on the aluminum side when a hemispherical penetrator tup was dropped onto it from a couple of inches, a large ring of delamination at the interface was observed. The delamination damage was often accompanied by severe shattering in the acrylic substratum. Damage patterns in the acrylic layer include radial and ring cracks and, together with delamination at the interface, may cause peeling-off of acrylic material from the sandwich plate. Theory of stress-wave propagation can be used to explain these damage patterns. The impact tests were conducted at various temperatures. The results also show clearly that temperature effect is very important in impact damage. For pure cast acrylic nil-ductile transition (NDT) occurs between 185-195 F. Excessive impact energy was dissipated into fracture energy when tested at temperature below this range or through plastic deformation when tested at temperature above the NDT temperature. Results from this study will be used as baseline data for studying fiber-metal laminates, such as GLARE and ARALL for advanced aeronautical and astronautical applications.

  2. Stability of convective patterns in reaction fronts: a comparison of three models.

    Science.gov (United States)

    Vasquez, Desiderio A; Coroian, Dan I

    2010-09-01

    Autocatalytic reaction fronts generate density gradients that may lead to convection. Fronts propagating in vertical tubes can be flat, axisymmetric, or nonaxisymmetric, depending on the diameter of the tube. In this paper, we study the transitions to convection as well as the stability of different types of fronts. We analyze the stability of the convective reaction fronts using three different models for front propagation. We use a model based on a reaction-diffusion-advection equation coupled to the Navier-Stokes equations to account for fluid flow. A second model replaces the reaction-diffusion equation with a thin front approximation where the front speed depends on the front curvature. We also introduce a new low-dimensional model based on a finite mode truncation. This model allows a complete analysis of all stable and unstable fronts.

  3. On mean curvatures in submanifolds geometry

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    By using moving frame theory,first we introduce 2p-th mean curvatures and(2p+1)-th mean curvature vector fields for a submanifold.We then give an integral expression of them that characterizes them as mean values of symmetric functions of principle curvatures.Next we apply it to derive directly the celebrated Weyl-Gray tube formula in terms of integrals of the 2p-th mean curvatures and some Minkowski-type integral formulas.

  4. Test of a slow off-axis parabola at its center of curvature.

    Science.gov (United States)

    Parks, R E; Evans, C J; Shao, L

    1995-11-01

    We describe the interferometric testing of a slow (ƒ/16 at the center of curvature) off-axis parabola, intended for use in an x-ray spectrometer, that uses a spherical wave front matched to the mean radius of the asphere. We find the figure error in the off-axis mirror by removing the theoretical difference between the off-axis segment and the spherical reference from the measured wave-front error. This center of curvature test is easy to perform because the spherical reference wave front has no axis and thus alignment is trivial. We confirm that the test results are the same as the double-pass null test for a parabola that uses a plane autocollimating mirror. We also determine that the off-axis section apparently warped as the result of being cut from the symmetric parent part.

  5. Cosmological model with dynamical curvature

    CERN Document Server

    Stichel, Peter C

    2016-01-01

    We generalize the recently introduced relativistic Lagrangian darkon fluid model (EPJ C (2015) 75:9) by starting with a self-gravitating geodesic fluid whose energy-momentum tensor is dust-like with a nontrivial energy flow. The corresponding covariant propagation and constraint equations are considered in a shear-free nonrelativistic limit whose analytic solutions determine the 1st-order relativistic correction to the spatial curvature. This leads to a cosmological model where the accelerated expansion of the Universe is driven by a time-dependent spatial curvature without the need for introducing any kind of dark energy. We derive the differential equation to be satisfied by the area distance for this model.

  6. Quantum Complexity and Negative Curvature

    CERN Document Server

    Brown, Adam R; Zhao, Ying

    2016-01-01

    As time passes, once simple quantum states tend to become more complex. For strongly coupled k-local Hamiltonians, this growth of computational complexity has been conjectured to follow a distinctive and universal pattern. In this paper we show that the same pattern is exhibited by a much simpler system: classical geodesics on a compact two-dimensional geometry of uniform negative curvature. This striking parallel persists whether the system is allowed to evolve naturally or is perturbed from the outside.

  7. Substrate curvature regulates cell migration

    Science.gov (United States)

    He, Xiuxiu; Jiang, Yi

    2017-06-01

    Cell migration is essential in many aspects of biology. Many basic migration processes, including adhesion, membrane protrusion and tension, cytoskeletal polymerization, and contraction, have to act in concert to regulate cell migration. At the same time, substrate topography modulates these processes. In this work, we study how substrate curvature at micrometer scale regulates cell motility. We have developed a 3D mechanical model of single cell migration and simulated migration on curved substrates with different curvatures. The simulation results show that cell migration is more persistent on concave surfaces than on convex surfaces. We have further calculated analytically the cell shape and protrusion force for cells on curved substrates. We have shown that while cells spread out more on convex surfaces than on concave ones, the protrusion force magnitude in the direction of migration is larger on concave surfaces than on convex ones. These results offer a novel biomechanical explanation to substrate curvature regulation of cell migration: geometric constrains bias the direction of the protrusion force and facilitates persistent migration on concave surfaces.

  8. Effects of Delaminations on the Damped Dynamic Characteristics of Composite Laminates: Mechanics and Experiments

    Science.gov (United States)

    Saravanos, D. A.; Hopkins, D. A.

    1995-01-01

    Analytical and experimental work is presented on the damped free-vibration of delaminated laminates and beams. A laminate theory is developed where the unknown kinematic perturbations induced by a delamination crack are treated as additional degrees of freedom. The generalized stiffness, inertia and damping matrices of the laminate are formulated. An analytical solution is developed for the prediction of natural frequencies, modes and modal damping in composite beams with delamination cracks. Evaluations of the mechanics on various cantilever beams with a central delamination are performed. Experimental results for the modal frequencies and damping of composite beams with a single delamination are also presented and correlations between analytical predictions and measured data are shown. The effects of delamination vary based on crack size, laminate configuration, and mode order. The implications of the mechanics in developing delamination detection techniques are also discussed.

  9. The effect of delaminations on local buckling in wind turbine blades

    DEFF Research Database (Denmark)

    Haselbach, Philipp Ulrich; Bitsche, Robert; Branner, Kim

    2015-01-01

    was setup in Abaqus and cohesive elements were chosen for modelling delamination growth. For initial delaminations with a width of 30–50% of the cap width the study showed that delamination close to the surface started to grow in load ranges of normal operation conditions and led to local buckling modes....... The local buckling caused high strains and stresses in the surrounding of the delamination, which exceeded the material design properties and therefore should be considered as dangerous. Delaminations placed near the mid-surface of the cap did not have a significant effect on the blade response under normal...... operation conditions. In the simulations the static load exceeded the design load by more than 40% before delamination growth or cap buckling occurred. It could be concluded that delamination induced near-surface buckling modes have to be considered critical due to an onset of local sublaminate buckling...

  10. Mean curvature 1 surfaces in hyperbolic 3-space with low total curvature. I

    OpenAIRE

    Rossman, Wayne; Umehara, Masaaki; Yamada, Kotaro

    2004-01-01

    A complete surface of constant mean curvature 1 (CMC-1) in hyperbolic 3- space with constant curvature $-1$ has two natural notions of ‘‘total curvature’’—one is the total absolute curvature which is the integral over the surface of the absolute value of the Gaussian curvature, and the other is the dual total absolute curvature which is the total absolute curvature of the dual CMC-1 surface. In this paper, we completely classify CMC-1 surfaces with dual total absolute curvature...

  11. Finite elements modeling of delaminations in composite laminates

    DEFF Research Database (Denmark)

    Gaiotti, m.; Rizzo, C.M.; Branner, Kim;

    2011-01-01

    The application of composite materials in many structures poses to engineers the problem to create reliable and relatively simple methods, able to estimate the strength of multilayer composite structures. Multilayer composites, like other laminated materials, suffer from layer separation, i.e., d...... by finite elements using different techniques. Results obtained with different finite element models are compared and discussed.......The application of composite materials in many structures poses to engineers the problem to create reliable and relatively simple methods, able to estimate the strength of multilayer composite structures. Multilayer composites, like other laminated materials, suffer from layer separation, i...... of the buckling strength of composite laminates containing delaminations. Namely, non-linear buckling and post-buckling analyses are carried out to predict the critical buckling load of elementary composite laminates affected by rectangular delaminations of different sizes and locations, which are modelled...

  12. Fracture and Delamination of Chromium Thin Films on Polymer Substrates

    Science.gov (United States)

    Cordill, M. J.; Taylor, A.; Schalko, J.; Dehm, G.

    2010-04-01

    New emerging technologies in the field of flexible electronic devices require that metal films adhere well and flex with polymer substrates. Common thin film materials used for these applications include copper (Cu) with an adhesion interlayer of chromium (Cr). Copper can be quite ductile and easily move with the polymer substrate. However, Cr is more brittle and fractures at lower strains than Cu. This study aims to examine the fracture and subsequent buckling and delamination of strained Cr films on polyimide (PI). In-situ scanning electron microscope (SEM) straining is used to systematically study the influence of film thickness on fracture and buckling strains. Film fracture and delamination depend on film thickness, and increases in crack and buckle density with decreasing thickness are explored by a shear lag model.

  13. Free-edge delamination - Laminate width and loading conditions effects

    Science.gov (United States)

    Murthy, Pappu L. N.; Chamis, Christos C.

    1989-01-01

    The width and loading conditions effects on free-edge stress fields in composite laminates are investigated using a three-dimensional finite element analysis. This analysis includes a special free-edge region refinement or superelement with progressive substructuring (mesh refinement) and finite thickness interply layers. The different loading conditions include in-plane and out-of-plane bending, combined axial tension and in-plane shear, twisting, uniform temperature and uniform moisture. Results obtained indicate that: axial tension causes the smallest magnitude of interlaminar free edge stress compared to other loading conditions; free-edge delamination data obtained from laboratory specimens cannot be scaled to structural components; and composite structural components are not likely to delaminate.

  14. Free-edge delamination: Laminate width and loading conditions effects

    Science.gov (United States)

    Murthy, P. L. N.; Chamis, C. C.

    1987-01-01

    The width and loading conditions effects on free-edge stress fields in composite laminates are investigated using a three-dimensional finite element analysis. This analysis includes a special free-edge region refinement or superelement with progrssive substructuring (mesh refinement) and finite thickness interply layers. The different loading conditions include in-plane and out-of-plane bending, combined axial tension and in-plane shear, twisting, uniform temperature and uniform moisture. Results obtained indicate that: axial tension causes the smallest magnitude of interlaminar free edge stress compared to other loading conditions; free-edge delamination data obtained from laboratory specimens cannot be scaled to structural components; and composite structural components are not likely to delaminate.

  15. DETECTION OF DELAMINATION IN A COMPOSITE PLATE BY SEM

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A numerical method of integration of Green's functi ons of strip element method (SEM) is proposed. The response of ultrasonic sourc e generated by a transducer on the surface of a multi-ply composite plate conta ining a delamination is analyzed by the use of SEM. The numerical results show that the scanning features of the ultrasonic waves may be used to identify the d elamination inside the composite plate .

  16. Controlled delamination of metal films by hydrogen loading

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, Eugen

    2008-11-18

    n this work we quantitatively determine the adhesion energy between metal films and their substrates. Therefore a new controlled buckling technique is established, applying the strong compressive in-plane stress that results in thin films clamped on rigid substrates during hydrogen loading. When the elastic energy stored in the H-loaded thin film exceeds the adhesion energy between film and substrate, delamination occurs. At the onset of delamination, a critical hydrogen concentration, a critical stress value and a critical bending of the substrate are present, which are quantitative measures for the adhesion energy and permit its calculation. As the critical values are determined at the onset of delamination, plastic deformation is negligible, which denies the quantitative determination of adhesion energies in conventional test setups. In multilayer-systems, adhesion energies between substrates and films that hardly absorb hydrogen can be measured by the controlled buckling technique, when the films of interest are coated with hydrogen absorbing films (active layer). The measurements are performed easily and can be repeated under the same test conditions, while variables such as the thickness of the coating materials or the boundary surface structure can be varied and optimized. In this work the adhesion energies of different materials on polycarbonate and niobium on sapphire are investigated. (orig.)

  17. Guidelines and Parameter Selection for the Simulation of Progressive Delamination

    Science.gov (United States)

    Song, Kyongchan; Davila, Carlos G.; Rose, Cheryl A.

    2008-01-01

    Turon s methodology for determining optimal analysis parameters for the simulation of progressive delamination is reviewed. Recommended procedures for determining analysis parameters for efficient delamination growth predictions using the Abaqus/Standard cohesive element and relatively coarse meshes are provided for single and mixed-mode loading. The Abaqus cohesive element, COH3D8, and a user-defined cohesive element are used to develop finite element models of the double cantilever beam specimen, the end-notched flexure specimen, and the mixed-mode bending specimen to simulate progressive delamination growth in Mode I, Mode II, and mixed-mode fracture, respectively. The predicted responses are compared with their analytical solutions. The results show that for single-mode fracture, the predicted responses obtained with the Abaqus cohesive element correlate well with the analytical solutions. For mixed-mode fracture, it was found that the response predicted using COH3D8 elements depends on the damage evolution criterion that is used. The energy-based criterion overpredicts the peak loads and load-deflection response. The results predicted using a tabulated form of the BK criterion correlate well with the analytical solution and with the results predicted with the user-written element.

  18. Delamination toughness of ultra high molecular weight polyethylene (UHMWPE composites

    Directory of Open Access Journals (Sweden)

    Casas-Rodriguez J.P.

    2012-08-01

    Full Text Available Ultra high molecular weight polyethylene (UHMWPE fibre reinforced composites are an important group of material for armours solutions, where their unique combination of properties could be utilized. A commonly observed failure mode in this kind of unidirectional laminated composites under impact ballistic is delamination between the composite layers. In the present study, an investigation on the delamination toughness behaviour exhibited by UHMWPE composites laminated was made. The interlaminar Mode II critical strain energy release rates of (UHMWPE fibre reinforced composites were characterized using the End Notch Flexural (ENF test. Critical strain energy release rate was obtained from the load – deflection test data using the beam theory expression. It was found that the energy release rate of the composite exhibited a very low value of around 60J/m2 using a moulding pressure of approximately 1200 psi. In order to analyse the delamination resistance of composite, the effects of changing the manufacture process variables and the use of a thermoplastic adhesive film in the composites were investigated. The composite laminates were produced by hot compressing moulding using a film-stacking procedure. It was found that the damage resistance of the UHMWPE composite was influenced by the manufacture method, which affects the Mode II interlaminar fracture toughness and the ballistic response of composites.

  19. Prediction of the Critical Curvature for LX-17 with the Time of Arrival Data from DNS

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Jin [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Fried, Laurence E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Moss, William C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-01-10

    We extract the detonation shock front velocity, curvature and acceleration from time of arrival data measured at grid points from direct numerical simulations of a 50mm rate-stick lit by a disk-source, with the ignition and growth reaction model and a JWL equation of state calibrated for LX-17. We compute the quasi-steady (D, κ) relation based on the extracted properties and predicted the critical curvatures of LX-17. We also proposed an explicit formula that contains the failure turning point, obtained from optimization for the (D, κ) relation of LX-17.

  20. Wave front fragmentation due to ventricular geometry in a model of the rabbit heart

    Science.gov (United States)

    Rogers, Jack M.

    2002-09-01

    The role of the heart's complex shape in causing the fragmentation of activation wave fronts characteristic of ventricular fibrillation (VF) has not been well studied. We used a finite element model of cardiac propagation capable of simulating functional reentry on curved two-dimensional surfaces to test the hypothesis that uneven surface curvature can cause local propagation block leading to proliferation of reentrant wave fronts. We found that when reentry was induced on a flat sheet, it rotated in a repeatable meander pattern without breaking up. However, when a model of the rabbit ventricles was formed from the same medium, reentrant wave fronts followed complex, nonrepeating trajectories. Local propagation block often occurred when wave fronts propagated across regions where the Gaussian curvature of the surface changed rapidly. This type of block did not occur every time wave fronts crossed such a region; rather, it only occurred when the wave front was very close behind the previous wave in the cycle and was therefore propagating into relatively inexcitable tissue. Close wave front spacing resulted from nonstationary reentrant propagation. Thus, uneven surface curvature and nonstationary reentrant propagation worked in concert to produce wave front fragmentation and complex activation patterns. None of the factors previously thought to be necessary for local propagation block (e.g., heterogeneous refractory period, steep action potential duration restitution) were present. We conclude that the complex geometry of the heart may be an important determinant of VF activation patterns.

  1. The Cost of Bounded Curvature

    CERN Document Server

    Kim, Hyo-Sil

    2011-01-01

    We study the motion-planning problem for a car-like robot whose turning radius is bounded from below by one and which is allowed to move in the forward direction only (Dubins car). For two robot configurations $\\sigma, \\sigma'$, let $\\ell(\\sigma, \\sigma')$ be the shortest bounded-curvature path from $\\sigma$ to $\\sigma'$. For $d \\geq 0$, let $\\ell(d)$ be the supremum of $\\ell(\\sigma, \\sigma')$, over all pairs $(\\sigma, \\sigma')$ that are at Euclidean distance $d$. We study the function $\\dub(d) = \\ell(d) - d$, which expresses the difference between the bounded-curvature path length and the Euclidean distance of its endpoints. We show that $\\dub(d)$ decreases monotonically from $\\dub(0) = 7\\pi/3$ to $\\dub(\\ds) = 2\\pi$, and is constant for $d \\geq \\ds$. Here $\\ds \\approx 1.5874$. We describe pairs of configurations that exhibit the worst-case of $\\dub(d)$ for every distance $d$.

  2. Low-velocity Impact Damage Analysis of Composite Laminates Using Self-adapting Delamination Element Method

    Institute of Scientific and Technical Information of China (English)

    Wang Lipeng; Yan Ying; Wu Dafang; Wu Hao

    2008-01-01

    On the basis of a 2D 4-node Mindlin shell element method, a novel self-adapting delamination finite element method is presented,which is developed to model the delamination damage of composite laminates. In the method, the sublaminate elements are generated automatically when the delamination damage occurs or extends. Thus, the complex process and state of delamination damage can be simulated practically with high efficiency for both analysis and modeling. Based on the self-adapting delamination method, linear dynamic finite element damage analysis is performed to simulate the low-velocity impact damage process of three types of mixed woven composite laminates. Taking the frictional force among sublaminations during delaminating and the transverse normal stress into account,the analytical results ate consistent with those of the experimental data.

  3. Vibration of a delaminated beam-plate relative to buckled states

    Science.gov (United States)

    Yin, W.-L.; Jane, K. C.

    1992-07-01

    Free vibrations of delaminated beam-plates with respect to postbuckled referential states are studied. If the postbuckling deformation of the referential state is symmetric with respect to the mid-point, then the symmetric and antisymmetric vibration modes are uncoupled. Short delaminations which do not significantly degradate the overall stiffness of the beam-plate have little effect on the lowest modes of vibration and their frequencies, while the presence of a long delamination generally introduces additional vibration frequencies, the associated mode shapes of which show out-of-phase motions of the upper and lower delaminated layers. These new vibration modes and frequencies depend sensitively on the delamination length and location and on the magnitude of the postbuckling load. Hence their detection may indicate the presence and the nature of internal delamination damage.

  4. S-curvature of isotropic Berwald metrics

    Institute of Scientific and Technical Information of China (English)

    Akbar TAYEBI; Mehdi RAFIE-RAD

    2008-01-01

    Isotropic Berwald metrics are as a generalization of Berwald metrics. Shen proved that every Berwald metric is of vanishing S-curvature. In this paper, we generalize this fact and prove that every isotropic Berwald metric is of isotropic S-curvature. Let F = α + β be a Randers metric of isotropic Berwald curvature. Then it corresponds to a conformal vector field through navigation representation.

  5. A Stringy (Holographic) Pomeron with Extrinsic Curvature

    CERN Document Server

    Qian, Yachao

    2014-01-01

    We model the soft pomeron in QCD using a scalar Polyakov string with extrinsic curvature in the bottom-up approach of holographic QCD. The overall dipole-dipole scattering amplitude in the soft pomeron kinematics is shown to be sensitive to the extrinsic curvature of the string for finite momentum transfer. The characteristics of the diffractive peak in the differential elastic $pp$ scattering are affected by a small extrinsic curvature of the string.

  6. Curvature and bubble convergence of harmonic maps

    CERN Document Server

    Kokarev, Gerasim

    2010-01-01

    We explore geometric aspects of bubble convergence for harmonic maps. More precisely, we show that the formation of bubbles is characterised by the local excess of curvature on the target manifold. We give a universal estimate for curvature concentration masses at each bubble point and show that there is no curvature loss in the necks. Our principal hypothesis is that the target manifold is Kaehler.

  7. Curvatures for Parameter Subsets in Nonlinear Regression

    OpenAIRE

    1986-01-01

    The relative curvature measures of nonlinearity proposed by Bates and Watts (1980) are extended to an arbitrary subset of the parameters in a normal, nonlinear regression model. In particular, the subset curvatures proposed indicate the validity of linearization-based approximate confidence intervals for single parameters. The derivation produces the original Bates-Watts measures directly from the likelihood function. When the intrinsic curvature is negligible, the Bates-Watts parameter-effec...

  8. Retraction pattern of delaminated rotator cuff tears: dual-layer rotator cuff repair

    OpenAIRE

    Cha, Sang-Won; Lee, Choon-Key; Sugaya, Hiroyuki; Kim, Taegyun; Lee, Su-Chan

    2016-01-01

    Background There has been no report to date regarding retraction patterns of delaminated rotator cuff tears. The purpose of this study was to evaluate the incidence and tearing patterns of delamination and repair integrity after the dual-layer repair of delaminated cuff tears. Methods/design A consecutive series of 64 patients with posterosuperior rotator cuff tears underwent arthroscopic rotator cuff repair from August 2011 to September 2012. Among the patients, 53 who received either dual-l...

  9. Delamination Method In English Teaching Can Also Be Applicable In Senior Middle School

    Institute of Scientific and Technical Information of China (English)

    于淑兰; 滕越

    2015-01-01

    The paper makes a research on delamination method in English teaching in senior middle school—a dimension of English teaching.By applying theories of linguistics,the author analyzes the present situation of the application of delamination method in English teaching both in college school and in senior middle school and a conclusion is,then,drawn that delamination English teaching can also be applicable in senior middle school.

  10. Short review: Potential impact of delamination cracks on fracture toughness of structural materials

    Directory of Open Access Journals (Sweden)

    X.C. Arnoult

    2016-02-01

    Full Text Available The current energy policy envisages extended lifetime for the current nuclear power plants (GEN II NPP. This policy imposes a large research effort to understand the ageing of power plant components. In this goal, it is necessary to improve knowledge about safety, reliability and components’ integrity for more than forty years of operation. In Central and Eastern Europe, the majority of NPPs are VVER types, where some of the components are produced from austenitic steel 08Ch18N10T. Irradiated 08Ch18N10T may exhibit brittle behavior, namely delamination cracks are found in some cases on the fracture surface of irradiated 08Ch18N10T with elongated δ-ferrite. Delamination cracks have also been observed on the fracture surface of high-strength steels or aluminum-lithium alloys. This article presents a state-of-the art review to provide a detailed analysis of the influence of delamination cracks on the toughness of metal alloys. In general, the delamination cracks are present in metal alloys having a high texture and microstructure anisotropy. Three types of delamination cracks have been observed and are classified as crack arrester delamination, crack divider delamination and crack splitting delamination. The microscopy characterization, 3D fracture theories and computational studies explaining possible causes and effects of delamination cracks on the mechanical properties of metal alloys are presented.

  11. Higher curvature supergravity and cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Ferrara, Sergio [Th-Ph Department, CERN, Geneva (Switzerland); U.C.L.A., Los Angeles, CA (United States); INFN - LNF, Frascati (Italy); Sagnotti, Augusto [Scuola Normale Superiore, Pisa (Italy); INFN, Pisa (Italy)

    2016-04-15

    In this contribution we describe dual higher-derivative formulations of some cosmological models based on supergravity. Work in this direction started with the R + R{sup 2} Starobinsky model, whose supersymmetric extension was derived in the late 80's and was recently revived in view of new CMB data. Models dual to higher-derivative theories are subject to more restrictions than their bosonic counterparts or standard supergravity. The three sections are devoted to a brief description of R + R{sup 2} supergravity, to a scale invariant R{sup 2} supergravity and to theories with a nilpotent curvature, whose duals describe non-linear realizations (in the form of a Volkov-Akulov constrained superfield) coupled to supergravity. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. On the Ricci Curvature of a Randers Metric of Isotropic S-curvature

    Institute of Scientific and Technical Information of China (English)

    Xiao Huan MO; Chang Tao YU

    2008-01-01

    We derive the integral inequality of a Randers metric with isotropic S-curvature in terms of its navigation representation. Using the obtained inequality we give some rigidity results under the condition of Ricci curvature. In particular, we show the following result: Assume that an n-dimensional compact Randers manifold (M, F)hasconstantS-curvature c.Then(M, F) must be Riemannian ifits Ricci curvature satisfies that Ric < - (n - 1)c2.

  13. Modeling Delamination of Interfacial Corner Cracks in Multilayered Structures

    DEFF Research Database (Denmark)

    Veluri, Badrinath (Badri); Jensen, Henrik Myhre

    2013-01-01

    for steady-state propagation has been developed. The crack propagation is investigated by estimating the fracture mechanics parameters that include the strain energy release rate, crack front profiles and the three-dimensional mode-mixity along the crack front. The developed numerical approach...... for the calculation of fracture mechanical properties has been validated with threedimensional models for varying crack front shapes. A custom quantitative approach was formulated based on the finite element method with iterative adjustment of the crack front to estimate the critical delaminatio stress as a function...

  14. Laser detection of ultrasonic waves with concave portions of the wave fronts.

    Science.gov (United States)

    Korkh, Yulia; Perov, Dmitry; Rinkevich, Anatoly

    2012-10-01

    Special features of ultrasonic pulse wave field detection with concave regions of the wave fronts are investigated with the use of ultrasonic laser interferometry technique. Experimental proofs of the wave front with concave regions are obtained and it is found that the nonmonotonic wave front profiles are well described by the fourth-order even polynomial. The model proposed is applied to the investigation of the spatiotemporal structure of elastic wave fields on solid surfaces. The results obtained can be used for estimating the local wave front curvature.

  15. Complex patterns in reaction-diffusion systems a tale of two front instabilities

    CERN Document Server

    Hagberg, A; Aric Hagberg; Ehud Meron

    1994-01-01

    Two front instabilities in a reaction-diffusion system are shown to lead to the formation of complex patterns. The first is an instability to transverse modulations that drives the formation of labyrinthine patterns. The second is a Nonequilibrium Ising-Bloch (NIB) bifurcation that renders a stationary planar front unstable and gives rise to a pair of counterpropagating fronts. Near the NIB bifurcation the relation of the front velocity to curvature is highly nonlinear and transitions between counterpropagating fronts become feasible. Nonuniformly curved fronts may undergo local front transitions that nucleate spiral-vortex pairs. These nucleation events provide the ingredient needed to initiate spot splitting and spiral turbulence. Similar spatio-temporal processes have been observed recently in the ferrocyanide-iodate-sulfite reaction.

  16. Ductile film delamination from compliant substrates using hard overlayers

    Science.gov (United States)

    Cordill, M.J.; Marx, V.M.; Kirchlechner, C.

    2014-01-01

    Flexible electronic devices call for copper and gold metal films to adhere well to polymer substrates. Measuring the interfacial adhesion of these material systems is often challenging, requiring the formulation of different techniques and models. Presented here is a strategy to induce well defined areas of delamination to measure the adhesion of copper films on polyimide substrates. The technique utilizes a stressed overlayer and tensile straining to cause buckle formation. The described method allows one to examine the effects of thin adhesion layers used to improve the adhesion of flexible systems. PMID:25641995

  17. Undulatory delamination of thin polymer films on gold surfaces.

    Science.gov (United States)

    Chah, Soonwoo; Noolandi, Jaan; Zare, Richard N

    2005-10-20

    Using two-dimensional surface plasmon resonance measurements, we have observed the formation of traveling waves in the delamination of thin films of polydimethylsilane (PDMS) exposed to methanol. Films were spin-coated on a gold surface and the methanol was added to the top surface. The stress-induced instability caused by the swelling of the PDMS thin film when its edge is pinned to the gold surface leads to wrinkle formation and propagation at the interface. The periodic pattern is thought to be the result of an Asaro-Tiller-Grinfeld (ATG) instability.

  18. Lattice QCD simulation of the Berry curvature

    CERN Document Server

    Yamamoto, Arata

    2016-01-01

    The Berry curvature is a fundamental concept describing topological order of quantum systems. While it can be analytically tractable in non-interacting systems, numerical simulations are necessary in interacting systems. We present a formulation to calculate the Berry curvature in lattice QCD.

  19. BIFURCATION IN PRESCRIBED MEAN CURVATURE PROBLEM

    Institute of Scientific and Technical Information of China (English)

    马力

    2002-01-01

    This paper discusses the existence problem in the study of some partial differential equations. The author gets some bifurcation on the prescribed mean curvature problem on the unit ball, the scalar curvature problem on the n-sphere, and some field equations. The author gives some natural conditions such that the standard bifurcation or Thom-Mather theory can be used.

  20. Mean Curvature, Threshold Dynamics, and Phase Field Theory on Finite Graphs

    Science.gov (United States)

    2013-06-28

    BK91] Lia Bronsard and Robert V. Kohn, Motion by mean curvature as the singular limit of Ginzburg-Landau dynamics, J. Differential Equations 90 (1991...Proceedings of the IEEE 95 (2007), no. 1, 215–233. [Peg89] Robert L. Pego, Front migration in the nonlinear cahn-hilliard equation, Proceedings of the Royal...625. [SB10] Arthur Szlam and Xavier Bresson , Total variation and cheeger cuts, Proceedings of the 27th International Conference on Machine Learning

  1. Delamination growth behavior in cross-ply composites under compressive cyclic (fatigue) loading

    Science.gov (United States)

    Pelegri, Assimina A.

    A mode dependent fatigue delamination growth law for anisotropic composite plates is presented in this thesis. The novelty of the presented law lies in the mode dependency of the material and laminate constants m(Psi) and C(Psi). The model describing the mode dependent delamination growth law consists of an initial postbuckling solution accounting for general delaminated composites, i.e. with no restrictive assumptions on the delamination dimensions, and a fracture mechanics solution. A numerical code was developed for the implementation of the closed form solution which gives the loading and geometrical quantities as well as the energy release rates and the mode mixities. The computer code was especially designed for parametric studies. Parameters assigned in this particular investigation were: end conditions, delamination position (h/T), and applied strain. The effect of the end conditions, i.e. clamped-clamped versus simply-supported ends on the initial postbuckling and growth behavior of delaminated plates was also investigated. In conjunction with the previous analysis, a detailed experimental study was designed and carried out in order to validate the proposed model. The tests were designed so that the effect of certain parameters on the delamination growth behavior could be evaluated. The parameters included in the investigation were: initial delamination length, applied strain and delamination position (h/T). Compressive static, compressive fatigue (constant displacement amplitude), and double cantilever beam (DCB) tests were conducted. Data acquisition and analysis for these tests were performed. By comparing analytical and experimental results it is shown that a very good correlation exists, and the presented mode dependent fatigue delamination growth law can accurately predict fatigue lives of delaminated composite structures.

  2. Strong curvature effects in Neumann wave problems

    DEFF Research Database (Denmark)

    Willatzen, Morten; Pors, A.; Gravesen, Jens

    2012-01-01

    equation for a quantum-mechanical particle confined by infinite barriers relevant in semiconductor physics. With this in mind and the interest to tailor waveguides towards a desired spectrum and modal pattern structure in classical structures and nanostructures, it becomes increasingly important...... to understand the influence of curvature effects in waveguides. In this work, we demonstrate analytically strong curvature effects for the eigenvalue spectrum of the Helmholtz equation with Neumann boundary conditions in cases where the waveguide cross section is a circular sector. It is found that the linear......-in-curvature contribution originates from parity symmetry breaking of eigenstates in circular-sector tori and hence vanishes in a torus with a complete circular cross section. The same strong curvature effect is not present in waveguides subject to Dirichlet boundary conditions where curvature contributions contribute...

  3. Importance of plan curvature in watershed modeling

    Science.gov (United States)

    Boll, J.; Ribail, J.; Zhao, M.

    2016-12-01

    A hillslope's hydrologic response to precipitation events is largely controlled by the topographic features of a given hillslope, specifically the profile and plan curvature. Many models simplify hillslope topography and ignore the curvature properties, and some use alternate measures such as a topographic index or the hillslope width function. Models that ignore curvature properties may be calibrated to produce the statistically acceptable integrated response of runoff at a watershed outlet, but incorporating these properties is necessary to model accurately hydrologic processes such as surface flow, erosion, subsurface lateral flow, location of runoff generation and drainage response. In this study, we evaluated the sensitivity of rainfall-runoff modelling to profile and plan curvature in two models. In the first model, the Water Erosion Prediction Project (WEPP) model, hillslope uses a representative width to the hillslope by dividing the drainage area by the average surface channel length. Profile curvature is preserved with a limited spatial resolution due to the number of overland flow elements. In the second model, the distributed Soil Moisture Routing (SMR) model, the geographic information system uses the D8 algorithm to capture profile and plan curvature. Sensitivity to topographic features was tested for three profile curvatures (convex, concave, straight) combined with three plan curvatures (diverging, converging, uniform) resulting in a total of nine hillslopes. Each hillslope was subjected to different rainfall events to detect threshold behavior for when topographic features cannot be ignored. Our findings indicate that concave and convex plan curvature need to be included when subsurface flow processes are the dominant flow process for surface flow runoff generation. We present thresholds for acceptable cases when profile and plan curvature can be simplified in larger spatial hydrologic units.

  4. Integrating 3D seismic curvature and curvature gradient attributes for fracture characterization: Methodologies and interpretational implications

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Dengliang

    2013-03-01

    In 3D seismic interpretation, curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface; however, it provides only part of the solutions to subsurface structure analysis. This study extends the curvature algorithm to a new curvature gradient algorithm, and integrates both algorithms for fracture detection using a 3D seismic test data set over Teapot Dome (Wyoming). In fractured reservoirs at Teapot Dome known to be formed by tectonic folding and faulting, curvature helps define the crestal portion of the reservoirs that is associated with strong seismic amplitude and high oil productivity. In contrast, curvature gradient helps better define the regional northwest-trending and the cross-regional northeast-trending lineaments that are associated with weak seismic amplitude and low oil productivity. In concert with previous reports from image logs, cores, and outcrops, the current study based on an integrated seismic curvature and curvature gradient analysis suggests that curvature might help define areas of enhanced potential to form tensile fractures, whereas curvature gradient might help define zones of enhanced potential to develop shear fractures. In certain fractured reservoirs such as at Teapot Dome where faulting and fault-related folding contribute dominantly to the formation and evolution of fractures, curvature and curvature gradient attributes can be potentially applied to differentiate fracture mode, to predict fracture intensity and orientation, to detect fracture volume and connectivity, and to model fracture networks.

  5. 湿热载荷下含损伤夹层板分层扩展判定分析%Delamination Growth of Composite Sandwich under Hygrothermal and Mechanical Loads

    Institute of Scientific and Technical Information of China (English)

    张志民; 李向阳

    2001-01-01

    The local buckling may occur in composite sandwich with delamination induced by impact damage. This often causes delamination growth and structure failure. The delamiantion growth is studied by using the variational method of moving boundary, and the formulas of energy release rate G along the delamination front are obtained. By employing Rayleigh-Ritz method, the hygrothermal effect on buckling character of composite sandwich plates containing delamination between two faceplate laminae is studied.%含面板内分层损伤的复合材料夹层板在承受压缩载荷时,很容易发生局部屈曲,导致分层扩展和结构失效,恶劣的湿热环境更是使之加剧.利用可动边界变分问题对分层扩展进行了分析,导出了分层边界的逐点能量释放率表达式,采用Rayleigh-Ritz法研究了任意的湿热环境对含损伤的复合材料夹层板分层扩展性能的影响.

  6. Delamination behaviour in differently copper laminated REBCO coated conductor tapes under transverse loading

    Energy Technology Data Exchange (ETDEWEB)

    Gorospe, Alking [Department of Mechanical Design Engineering, Andong National University, 1375 Kyungdong-Ro, Andong 760-749 (Korea, Republic of); Department of Engineering, Aurora State College of Technology, Baler Aurora 3200 (Philippines); Nisay, Arman [Department of Mechanical Design Engineering, Andong National University, 1375 Kyungdong-Ro, Andong 760-749 (Korea, Republic of); Shin, Hyung-Seop, E-mail: hsshin@andong.ac.kr [Department of Mechanical Design Engineering, Andong National University, 1375 Kyungdong-Ro, Andong 760-749 (Korea, Republic of)

    2014-09-15

    Highlights: • I{sub c} degradation behavior under transverse tension loading in different CC tape structure. • Weibull distribution analysis applied on delamination mechanism of CC tape. • Delamination mechanism on CC tapes depending on copper lamination type. • SEM and WDS mapping analysis of delamination sites under transverse loading. - Abstract: Laminated HTS coated conductor (CC) tapes having a unique multi-layer structure made them vulnerable when exposed to transverse loading. Electromechanical transport properties of these CC tapes can be affected by excessive transverse stresses. Due to the coefficient of thermal expansion (CTE) mismatch and incompatibility among constituent materials used in coil applications, delamination among layers occurs and causes critical current, I{sub c} degradation in the CC tapes. In this study, the delamination behaviors in copper (Cu) solder-laminated CC tapes by soldering and surround Cu-stabilized ones by electroplating under transverse tension loading were investigated. Similarly to the surround Cu-stabilized CC tapes in our previous reports, the Cu solder-laminated CC tapes also showed an abrupt and gradual I{sub c} degradation behavior. However, the Cu solder-laminated CC tapes showed different delamination morphologies as compared to the surround Cu-stabilized CC tapes; the superconducting side and the substrate side of the Cu solder laminated CC tapes were totally separated by delamination. On the other hand, the brass laminate did not show any significant effect on the delamination strength when it is added upon the surround Cu-stabilized CC tapes.

  7. Numerical and experimental studies of delamination detection in short fiber reinforced composites using Lamb waves

    Science.gov (United States)

    Kudela, Pawel; Radzienski, Maciej; Ostachowicz, Wieslaw

    2016-04-01

    The aim of this paper is to present aspects of Lamb wave propagation in randomly oriented short fiber reinforce composites with delamination. Prediction of elastic constants is based on mechanics of composites, rule of mixture and total mass balance tailored to the spectral element mesh composed of 3D brick elements. Piezoelectric excitation as well as glue layer are taken into account. Complex full wave field includes multiple reflections at short fibers. This wave pattern is also obtained by the use of laser vibrometry confirming good quality of the model. Further studies are related to symmetrical and non-symmetrical delamination in respect to the thickness of the composite plate. Square delamination of the side length 10 mm is investigated. It has been found that reflections from delamination are mostly superimposed with reflections coming from short fibers. Hence, delamination detection by direct analysis of wave propagation pattern on the surface of the plate is ineffective. However, adaptive wavenumber filtering method overcome these difficulties and enables not only to detect the delamination but also is helpful for delamination size estimation. Moreover, the method is more effective if the full wavefield measurements are acquired on the surface of the plate which is closer to the delamination.

  8. Energy based study of quasi-static delamination as a low cycle fatigue process

    NARCIS (Netherlands)

    Amaral, L.; Yao, L.; Alderliesten, R.C.; Benedictus, R.

    2015-01-01

    This work proposes to treat quasi-static mode I delamination growth of CFRP as a low-cycle fatigue process. To this end, mode I quasi-static and fatigue delamination tests were performed. An average physical Strain Energy Release Rate (SERR), derived from an energy balance, is used to characterize t

  9. Cathodic delamination: Quantification of ionic transport rates along coating-steel interfaces

    DEFF Research Database (Denmark)

    Sørensen, P.A.; Dam-Johansen, Kim; Weinell, C.E.

    2010-01-01

    and Fick's second law, under the assumption of a transport-controlled mechanism, show qualitative agreement with the observed delamination rates in 0.5 M sodium chloride. This confirms that the rate-determining step of cathodic delamination is the transport of sodium ions along the coating-steel interface....

  10. Cathodic delamination: Quantification of ionic transport rates along coating-steel interfaces

    DEFF Research Database (Denmark)

    Sørensen, Per Aggerholm; Dam-Johansen, Kim; Erik Weinell, Claus

    2010-01-01

    and Fick's second law, under the assumption of a transport controlled mechanism, show qualitative agreement with the observed delamination rates in 0.5 M sodium chloride. This confirms that the rate-determining step of cathodic delamination is the transport of sodium ions along the coating-steel interface...

  11. Work of adhesion in laser-induced delamination along polymer-metal interfaces

    NARCIS (Netherlands)

    Fedorov, A.; van Tijum, R.; Vellinga, W. P.; de Hosson, Jeff

    2007-01-01

    Laser-induced delamination is a recent technique aimed at characterizing adhesive strength of thin polymer coatings on metal substrates. A laser pulse is used to create a blister that initiates further delamination of the film under pressure. To process the experimental data a simple elastic model w

  12. Reliability at the Chip Interfaces: Delaminating the Silicon Die from Molding Compound

    NARCIS (Netherlands)

    Schlottig, G.

    2012-01-01

    This book describes a setup that allows to delaminate the Silicon-to-Molding Compound interface for obtaining interfacial fracture parameters: the Mixed Mode Chisel setup (MMC). With this device for the first time the delamination can be initiated and propagated, while preventing the occurrence of r

  13. Buckling of composite beams with two enveloped delaminations: Lower and upper bounds

    NARCIS (Netherlands)

    Parlapalli, M.S.R.; Shu, Dongwei; Chai, Gin B.

    2008-01-01

    Lower and upper bounds of the buckling load of a composite beam with two enveloped delaminations are obtained from newly developed analytical models. The characteristic equation, governing the delamination buckling is derived by using Euler–Bernoulli beam and classical lamination theory, performing

  14. Reliability at the Chip Interfaces: Delaminating the Silicon Die from Molding Compound

    NARCIS (Netherlands)

    Schlottig, G.

    2012-01-01

    This book describes a setup that allows to delaminate the Silicon-to-Molding Compound interface for obtaining interfacial fracture parameters: the Mixed Mode Chisel setup (MMC). With this device for the first time the delamination can be initiated and propagated, while preventing the occurrence of r

  15. Energy based study of quasi-static delamination as a low cycle fatigue process

    NARCIS (Netherlands)

    Amaral, L.; Yao, L.; Alderliesten, R.C.; Benedictus, R.

    2015-01-01

    This work proposes to treat quasi-static mode I delamination growth of CFRP as a low-cycle fatigue process. To this end, mode I quasi-static and fatigue delamination tests were performed. An average physical Strain Energy Release Rate (SERR), derived from an energy balance, is used to characterize

  16. Curvature function and coarse graining

    Science.gov (United States)

    Díaz-Marín, Homero; Zapata, José A.

    2010-12-01

    A classic theorem in the theory of connections on principal fiber bundles states that the evaluation of all holonomy functions gives enough information to characterize the bundle structure (among those sharing the same structure group and base manifold) and the connection up to a bundle equivalence map. This result and other important properties of holonomy functions have encouraged their use as the primary ingredient for the construction of families of quantum gauge theories. However, in these applications often the set of holonomy functions used is a discrete proper subset of the set of holonomy functions needed for the characterization theorem to hold. We show that the evaluation of a discrete set of holonomy functions does not characterize the bundle and does not constrain the connection modulo gauge appropriately. We exhibit a discrete set of functions of the connection and prove that in the abelian case their evaluation characterizes the bundle structure (up to equivalence), and constrains the connection modulo gauge up to "local details" ignored when working at a given scale. The main ingredient is the Lie algebra valued curvature function F_S (A) defined below. It covers the holonomy function in the sense that exp {F_S (A)} = Hol(l= partial S, A).

  17. Forced hyperbolic mean curvature flow

    CERN Document Server

    Mao, Jing

    2012-01-01

    In this paper, we investigate two hyperbolic flows obtained by adding forcing terms in direction of the position vector to the hyperbolic mean curvature flows in \\cite{klw,hdl}. For the first hyperbolic flow, as in \\cite{klw}, by using support function, we reduce it to a hyperbolic Monge-Amp$\\grave{\\rm{e}}$re equation successfully, leading to the short-time existence of the flow by the standard theory of hyperbolic partial differential equation. If the initial velocity is non-negative and the coefficient function of the forcing term is non-positive, we also show that there exists a class of initial velocities such that the solution of the flow exists only on a finite time interval $[0,T_{max})$, and the solution converges to a point or shocks and other propagating discontinuities are generated when $t\\rightarrow{T_{max}}$. These generalize the corresponding results in \\cite{klw}. For the second hyperbolic flow, as in \\cite{hdl}, we can prove the system of partial differential equations related to the flow is ...

  18. Magnetophoretic Induction of Root Curvature

    Science.gov (United States)

    Hasenstein, Karl H.

    1997-01-01

    The last year of the grant period concerned the consolidation of previous experiments to ascertain that the theoretical premise apply not just to root but also to shoots. In addition, we verified that high gradient magnetic fields do not interfere with regular cellular activities. Previous results have established that: (1) intracellular magnetophoresis is possible; and (2) HGMF lead to root curvature. In order to investigate whether HGMF affect the assembly and/or organization of structural proteins, we examined the arrangement of microtubules in roots exposed to HGMF. The cytoskeletal investigations were performed with fomaldehyde-fixed, nonembedded tissue segments that were cut with a vibratome. Microtubules (MTs) were stained with rat anti-yeast tubulin (YOL 1/34) and DTAF-labeled antibody against rat IgG. Microfilaments (MFs) were visualized by incubation in rhodamine-labeled phalloidin. The distribution and arrangement of both components of the cytoskeleton were examined with a confocal microscope. Measurements of growth rates and graviresponse were done using a video-digitizer. Since HGMF repel diamagnetic substances including starch-filled amyloplasts and most The second aspect of the work includes studies of the effect of cytoskeletal inhibitors on MTs and MFs. The analysis of the effect of micotubular inhibitors on the auxin transport in roots showed that there is very little effect of MT-depolymerizing or stabilizing drugs on auxin transport. This is in line with observations that application of such drugs is not immediately affecting the graviresponsiveness of roots.

  19. Programming curvature using origami tessellations

    Science.gov (United States)

    Dudte, Levi H.; Vouga, Etienne; Tachi, Tomohiro; Mahadevan, L.

    2016-05-01

    Origami describes rules for creating folded structures from patterns on a flat sheet, but does not prescribe how patterns can be designed to fit target shapes. Here, starting from the simplest periodic origami pattern that yields one-degree-of-freedom collapsible structures--we show that scale-independent elementary geometric constructions and constrained optimization algorithms can be used to determine spatially modulated patterns that yield approximations to given surfaces of constant or varying curvature. Paper models confirm the feasibility of our calculations. We also assess the difficulty of realizing these geometric structures by quantifying the energetic barrier that separates the metastable flat and folded states. Moreover, we characterize the trade-off between the accuracy to which the pattern conforms to the target surface, and the effort associated with creating finer folds. Our approach enables the tailoring of origami patterns to drape complex surfaces independent of absolute scale, as well as the quantification of the energetic and material cost of doing so.

  20. On different curvatures of spheres in Funk geometry

    CERN Document Server

    Olin, Eugeny A

    2011-01-01

    We compute the series expansions for the normal curvatures of hyperspheres, the Finsler and Rund curvatures of circles in Funk geometry as the radii tend to infinity. These three curvatures are different at infinity in Funk geometry.

  1. Study of multilayer packaging delamination mechanisms using different surface analysis techniques

    Energy Technology Data Exchange (ETDEWEB)

    Garrido-Lopez, Alvaro [Department of Chemistry, University of La Rioja, C/Madre de Dios 51, E-26006 Logrono, La Rioja (Spain); Tena, Maria Teresa, E-mail: maria-teresa.tena@unirioja.es [Department of Chemistry, University of La Rioja, C/Madre de Dios 51, E-26006 Logrono, La Rioja (Spain)

    2010-04-01

    Multilayer packaging, consisting of different layers joined by using an adhesive or an extrusion process, is widely used to promote different products, such as food, cosmetics, etc. The main disadvantage in using this form of packaging is the delamination process. In this work, different surface techniques (X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy) are used to analyse the delaminated surfaces in order to study the mechanisms that cause delamination of multilayer packaging. According to our results, the reaction of migrated molecules with adhesive-aluminium bonds is the main cause of the chemical delamination process. In contrast, the delamination of extruded materials would seem to be caused by the breaking of Van der Waals bonds.

  2. Assessment of Static Delamination Propagation Capabilities in Commercial Finite Element Codes Using Benchmark Analysis

    Science.gov (United States)

    Orifici, Adrian C.; Krueger, Ronald

    2010-01-01

    With capabilities for simulating delamination growth in composite materials becoming available, the need for benchmarking and assessing these capabilities is critical. In this study, benchmark analyses were performed to assess the delamination propagation simulation capabilities of the VCCT implementations in Marc TM and MD NastranTM. Benchmark delamination growth results for Double Cantilever Beam, Single Leg Bending and End Notched Flexure specimens were generated using a numerical approach. This numerical approach was developed previously, and involves comparing results from a series of analyses at different delamination lengths to a single analysis with automatic crack propagation. Specimens were analyzed with three-dimensional and two-dimensional models, and compared with previous analyses using Abaqus . The results demonstrated that the VCCT implementation in Marc TM and MD Nastran(TradeMark) was capable of accurately replicating the benchmark delamination growth results and that the use of the numerical benchmarks offers advantages over benchmarking using experimental and analytical results.

  3. Right thoracic curvature in the normal spine

    Directory of Open Access Journals (Sweden)

    Masuda Keigo

    2011-01-01

    Full Text Available Abstract Background Trunk asymmetry and vertebral rotation, at times observed in the normal spine, resemble the characteristics of adolescent idiopathic scoliosis (AIS. Right thoracic curvature has also been reported in the normal spine. If it is determined that the features of right thoracic side curvature in the normal spine are the same as those observed in AIS, these findings might provide a basis for elucidating the etiology of this condition. For this reason, we investigated right thoracic curvature in the normal spine. Methods For normal spinal measurements, 1,200 patients who underwent a posteroanterior chest radiographs were evaluated. These consisted of 400 children (ages 4-9, 400 adolescents (ages 10-19 and 400 adults (ages 20-29, with each group comprised of both genders. The exclusion criteria were obvious chest and spinal diseases. As side curvature is minimal in normal spines and the range at which curvature is measured is difficult to ascertain, first the typical curvature range in scoliosis patients was determined and then the Cobb angle in normal spines was measured using the same range as the scoliosis curve, from T5 to T12. Right thoracic curvature was given a positive value. The curve pattern was organized in each collective three groups: neutral (from -1 degree to 1 degree, right (> +1 degree, and left ( Results In child group, Cobb angle in left was 120, in neutral was 125 and in right was 155. In adolescent group, Cobb angle in left was 70, in neutral was 114 and in right was 216. In adult group, Cobb angle in left was 46, in neutral was 102 and in right was 252. The curvature pattern shifts to the right side in the adolescent group (p Conclusions Based on standing chest radiographic measurements, a right thoracic curvature was observed in normal spines after adolescence.

  4. Magnetic curvature effects on plasma interchange turbulence

    Science.gov (United States)

    Li, B.; Liao, X.; Sun, C. K.; Ou, W.; Liu, D.; Gui, G.; Wang, X. G.

    2016-06-01

    The magnetic curvature effects on plasma interchange turbulence and transport in the Z-pinch and dipole-like systems are explored with two-fluid global simulations. By comparing the transport levels in the systems with a different magnetic curvature, we show that the interchange-mode driven transport strongly depends on the magnetic geometry. For the system with large magnetic curvature, the pressure and density profiles are strongly peaked in a marginally stable state and the nonlinear evolution of interchange modes produces the global convective cells in the azimuthal direction, which lead to the low level of turbulent convective transport.

  5. Evaluation of Delamination Growth Characterization Methods Under Mode I Fatigue Loading

    Science.gov (United States)

    Murri, Gretchen B.

    2012-01-01

    Reliable delamination characterization data for laminated composites are needed for input to analytical models of structures to predict delamination. The double-cantilevered beam (DCB) specimen is used with laminated composites to measure fracture toughness, G(sub Ic), delamination onset strain energy release rate, and growth rate data under cyclic loading. In the current study, DCB specimens of IM7/8552 graphite/epoxy supplied by two different manufacturers were tested in static and fatigue to compare the measured characterization data from the two sources, and to evaluate a proposed ASTM standard for generating Paris Law equations. Static results were used to generate compliance calibration constants for the fatigue data, and a delamination resistance curve, G(sub IR), which was used to determine the effects of fiber-bridging on delamination growth. Specimens were tested in fatigue at a cyclic G(sub Imax) level equal to 50, 40 or 30% of G(sub Ic), to determine a delamination onset curve and delamination growth rate. The delamination onset curve equations had similar exponents and the same trends. Delamination growth rate was calculated by fitting a Paris Law to the da/dN versus G(sub Imax) data. Both a 2-point and a 7-point data reduction method were used and the Paris Law equations were compared. To determine the effects of fiber-bridging, growth rate results were normalized by the delamination resistance curve for each material and compared to the non-normalized results. Paris Law exponents were found to decrease by 31% to 37% due to normalizing the growth data. Normalizing the data also greatly reduced the amount of scatter between the different specimens. Visual data records from the fatigue testing were used to calculate individual compliance calibration constants from the fatigue data for some of the specimens. The resulting da/dN versus G(sub Imax) plots showed much improved repeatability between specimens. Gretchen

  6. Curvature constraints from Large Scale Structure

    CERN Document Server

    Di Dio, Enea; Raccanelli, Alvise; Durrer, Ruth; Kamionkowski, Marc; Lesgourgues, Julien

    2016-01-01

    We modified the CLASS code in order to include relativistic galaxy number counts in spatially curved geometries; we present the formalism and study the effect of relativistic corrections on spatial curvature. The new version of the code is now publicly available. Using a Fisher matrix analysis, we investigate how measurements of the spatial curvature parameter $\\Omega_K$ with future galaxy surveys are affected by relativistic effects, which influence observations of the large scale galaxy distribution. These effects include contributions from cosmic magnification, Doppler terms and terms involving the gravitational potential. As an application, we consider angle and redshift dependent power spectra, which are especially well suited for model independent cosmological constraints. We compute our results for a representative deep, wide and spectroscopic survey, and our results show the impact of relativistic corrections on the spatial curvature parameter estimation. We show that constraints on the curvature para...

  7. Generalized Strong Curvature Singularities and Cosmic Censorship

    CERN Document Server

    Rudnicki, W; Kondracki, W

    2002-01-01

    A new definition of a strong curvature singularity is proposed. This definition is motivated by the definitions given by Tipler and Krolak, but is significantly different and more general. All causal geodesics terminating at these new singularities, which we call generalized strong curvature singularities, are classified into three possible types; the classification is based on certain relations between the curvature strength of the singularities and the causal structure in their neighborhood. A cosmic censorship theorem is formulated and proved which shows that only one class of generalized strong curvature singularities, corresponding to a single type of geodesics according to our classification, can be naked. Implications of this result for the cosmic censorship hypothesis are indicated.

  8. Curvature of Indoor Sensor Network: Clustering Coefficient

    Directory of Open Access Journals (Sweden)

    2009-03-01

    Full Text Available We investigate the geometric properties of the communication graph in realistic low-power wireless networks. In particular, we explore the concept of the curvature of a wireless network via the clustering coefficient. Clustering coefficient analysis is a computationally simplified, semilocal approach, which nevertheless captures such a large-scale feature as congestion in the underlying network. The clustering coefficient concept is applied to three cases of indoor sensor networks, under varying thresholds on the link packet reception rate (PRR. A transition from positive curvature (“meshed” network to negative curvature (“core concentric” network is observed by increasing the threshold. Even though this paper deals with network curvature per se, we nevertheless expand on the underlying congestion motivation, propose several new concepts (network inertia and centroid, and finally we argue that greedy routing on a virtual positively curved network achieves load balancing on the physical network.

  9. Holomorphic curvature of complex Finsler submanifolds

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Let M be a complex n-dimensional manifold endowed with a strongly pseudoconvex complex Finsler metric F. Let M be a complex m-dimensional submanifold of M, which is endowed with the induced complex Finsler metric F. Let D be the complex Rund connection associated with (M, F). We prove that (a) the holomorphic curvature of the induced complex linear connection  on (M, F) and the holomorphic curvature of the intrinsic complex Rund connection ~* on (M, F) coincide; (b) the holomorphic curvature of ~* does not exceed the holomorphic curvature of D; (c) (M, F) is totally geodesic in (M, F) if and only if a suitable contraction of the second fundamental form B(·, ·) of (M, F) vanishes, i.e., B(χ, ι) = 0. Our proofs are mainly based on the Gauss, Codazzi and Ricci equations for (M, F).

  10. Modular Curvature for Noncommutative Two-Tori

    CERN Document Server

    Connes, Alain

    2011-01-01

    Starting from the description of the conformal geometry of noncommutative 2-tori in the framework of modular spectral triples, we explicitly compute the local curvature functionals determined by the value at zero of the zeta functions affiliated with these spectral triples. We give a closed formula for the Ray-Singer analytic torsion in terms of the Dirichlet quadratic form and the generating function for Bernoulli numbers applied to the modular operator. The gradient of the Ray-Singer analytic torsion is then expressed in terms of these functionals, and yields the analogue of scalar curvature. Computing this gradient in two ways elucidates the meaning of the complicated two variable functions occurring in the formula for the scalar curvature. Moreover, the corresponding evolution equation for the metric produces the appropriate analogue of Ricci curvature. We prove the analogue of the classical result which asserts that in every conformal class the maximum value of the determinant of the Laplacian on metrics...

  11. Cosmological Attractor Models and Higher Curvature Supergravity

    CERN Document Server

    Cecotti, Sergio

    2014-01-01

    We study cosmological $\\alpha$-attractors in superconformal/supergravity models, where $\\alpha$ is related to the geometry of the moduli space. For $\\alpha=1$ attractors \\cite{Kallosh:2013hoa} we present a generalization of the previously known manifestly superconformal higher curvature supergravity model \\cite{Cecotti:1987sa}. The relevant standard 2-derivative supergravity with a minimum of two chiral multiplets is shown to be dual to a 4-derivative higher curvature supergravity, where in general one of the chiral superfields is traded for a curvature superfield. There is a degenerate case when both matter superfields become non-dynamical and there is only a chiral curvature superfield, pure higher derivative supergravity. Generic $\\alpha$-models \\cite{Kallosh:2013yoa} interpolate between the attractor point at $\\alpha=0$ and generic chaotic inflation models at large $\\alpha$, in the limit when the inflaton moduli space becomes flat. They have higher derivative duals with the same number of matter fields as...

  12. Higher Curvature Supergravity, Supersymmetry Breaking and Inflation

    CERN Document Server

    Ferrara, Sergio

    2014-01-01

    In these lectures, after a short introduction to cosmology, we discuss the supergravity embedding of higher curvature models of inflation. The supergravity description of such models is presented for the two different formulations of minimal supergravity.

  13. The ‘Sticky Elastica’: delamination blisters beyond small deformations

    KAUST Repository

    Wagner, Till J. W.

    2013-01-01

    We consider the form of an elastic loop adhered to a rigid substrate: the \\'Sticky Elastica\\'. In contrast to previous studies of the shape of delamination \\'blisters\\', the theory developed accounts for deflections with large slope (i.e. geometrically nonlinear). Starting from the classical Euler Elastica we provide numerical results for the dimensions of such blisters for a variety of end-end confinements and develop asymptotic expressions that reproduce these results well, even up to the point of self-contact. Interestingly, we find that the width of such blisters does not grow monotonically with increased confinement. Our theoretical predictions are confirmed by simple desktop experiments and suggest a new method for the measurement of the elastocapillary length for deformations that cannot be considered small. We discuss the implications of our results for applications such as flexible electronics. © 2013 The Royal Society of Chemistry.

  14. Ductile film delamination from compliant substrates using hard overlayers

    Energy Technology Data Exchange (ETDEWEB)

    Cordill, M.J. [Erich Schmid Institute of Materials Science, Austrian Academy of Sciences (Austria); Marx, V.M.; Kirchlechner, C. [Max-Plank-Insitut für Eisenforschung GmbH, Düsseldorf (Germany)

    2014-11-28

    Flexible electronic devices call for copper and gold metal films to adhere well to polymer substrates. Measuring the interfacial adhesion of these material systems is often challenging, requiring the formulation of different techniques and models. Presented here is a strategy to induce well defined areas of delamination to measure the adhesion of copper films on polyimide substrates. The technique utilizes a stressed overlayer and tensile straining to cause buckle formation. The described method allows one to examine the effects of thin adhesion layers used to improve the adhesion of flexible systems. - Highlights: • Measuring the adhesion energies of ductile metal–polymer interfaces is difficult. • A Cu film would plastically deform under tensile strain without a Cr overlayer. • A Cr overlayer forces cracking and induces buckling between the crack fragments. • The adhesion energy of the metal–polymer interface can be measured.

  15. Curvature Gradient Driving Droplets in Fast Motion

    CERN Document Server

    Lv, Cunjing; Yin, Yajun; Tseng, Fan-gang; Zheng, Quanshui

    2011-01-01

    Earlier works found out spontaneous directional motion of liquid droplets on hydrophilic conical surfaces, however, not hydrophobic case. Here we show that droplets on any surface may take place spontaneous directional motion without considering contact angle property. The driving force is found to be proportional to the curvature gradient of the surface. Fast motion can be lead at surfaces with small curvature radii. The above discovery can help to create more effective transportation technology of droplets, and better understand some observed natural phenomena.

  16. GDP growth and the yield curvature

    DEFF Research Database (Denmark)

    Møller, Stig Vinther

    2014-01-01

    This paper examines the forecastability of GDP growth using information from the term structure of yields. In contrast to previous studies, the paper shows that the curvature of the yield curve contributes with much more forecasting power than the slope of yield curve. The yield curvature also...... predicts bond returns, implying a common element to time-variation in expected bond returns and expected GDP growth....

  17. Spherical gravitational curvature boundary-value problem

    Science.gov (United States)

    Šprlák, Michal; Novák, Pavel

    2016-08-01

    Values of scalar, vector and second-order tensor parameters of the Earth's gravitational field have been collected by various sensors in geodesy and geophysics. Such observables have been widely exploited in different parametrization methods for the gravitational field modelling. Moreover, theoretical aspects of these quantities have extensively been studied and well understood. On the other hand, new sensors for observing gravitational curvatures, i.e., components of the third-order gravitational tensor, are currently under development. As the gravitational curvatures represent new types of observables, their exploitation for modelling of the Earth's gravitational field is a subject of this study. Firstly, the gravitational curvature tensor is decomposed into six parts which are expanded in terms of third-order tensor spherical harmonics. Secondly, gravitational curvature boundary-value problems defined for four combinations of the gravitational curvatures are formulated and solved in spectral and spatial domains. Thirdly, properties of the corresponding sub-integral kernels are investigated. The presented mathematical formulations reveal some important properties of the gravitational curvatures and extend the so-called Meissl scheme, i.e., an important theoretical framework that relates various parameters of the Earth's gravitational field.

  18. Nonadditive Compositional Curvature Energetics of Lipid Bilayers

    Science.gov (United States)

    Sodt, A. J.; Venable, R. M.; Lyman, E.; Pastor, R. W.

    2016-09-01

    The unique properties of the individual lipids that compose biological membranes together determine the energetics of the surface. The energetics of the surface, in turn, govern the formation of membrane structures and membrane reshaping processes, and thus they will underlie cellular-scale models of viral fusion, vesicle-dependent transport, and lateral organization relevant to signaling. The spontaneous curvature, to the best of our knowledge, is always assumed to be additive. We describe observations from simulations of unexpected nonadditive compositional curvature energetics of two lipids essential to the plasma membrane: sphingomyelin and cholesterol. A model is developed that connects molecular interactions to curvature stress, and which explains the role of local composition. Cholesterol is shown to lower the number of effective Kuhn segments of saturated acyl chains, reducing lateral pressure below the neutral surface of bending and favoring positive curvature. The effect is not observed for unsaturated (flexible) acyl chains. Likewise, hydrogen bonding between sphingomyelin lipids leads to positive curvature, but only at sufficient concentration, below which the lipid prefers negative curvature.

  19. Total mean curvature, scalar curvature, and a variational analog of Brown-York mass

    CERN Document Server

    Mantoulidis, Christos

    2016-01-01

    Let $(\\Omega, g)$ be a compact Riemannian 3-manifold with nonnegative scalar curvature, and with a mean-convex boundary $\\Sigma$ which is topologically a 2-sphere. We demonstrate that the total mean curvature of $\\Sigma$ is bounded from above by a constant depending only on the induced metric on $\\Sigma$. As an application, we define a variational analog of the Brown-York quasi-local mass of $\\Sigma$ in $(\\Omega, g)$ without assuming that $\\Sigma$ has positive Gauss curvature. We also cast this discussion in the light of a natural variational problem on compact 3-manifolds with boundary and nonnegative scalar curvature.

  20. Evaluation of Delamination Onset and Growth Characterization Methods under Mode I Fatigue Loading

    Science.gov (United States)

    Murri, Gretchen B.

    2013-01-01

    Double-cantilevered beam specimens of IM7/8552 graphite/epoxy from two different manufacturers were tested in static and fatigue to compare the material characterization data and to evaluate a proposed ASTM standard for generating Paris Law equations for delamination growth. Static results were used to generate compliance calibration constants for reducing the fatigue data, and a delamination resistance curve, GIR, for each material. Specimens were tested in fatigue at different initial cyclic GImax levels to determine a delamination onset curve and the delamination growth rate. The delamination onset curve equations were similar for the two sources. Delamination growth rate was calculated by plotting da/dN versus GImax on a log-log scale and fitting a Paris Law. Two different data reduction methods were used to calculate da/dN. To determine the effects of fiber-bridging, growth results were normalized by the delamination resistance curves. Paris Law exponents decreased by 31% to 37% after normalizing the data. Visual data records from the fatigue tests were used to calculate individual compliance constants from the fatigue data. The resulting da/dN versus GImax plots showed improved repeatability for each source, compared to using averaged static data. The Paris Law expressions for the two sources showed the closest agreement using the individually fit compliance data.

  1. Monitoring Delamination of Thermal Barrier Coatings by Near-Infrared and Upconversion Luminescence Imaging

    Science.gov (United States)

    Eldridge, J. I.; Martin, R. E.; Singh, Jogender; Wolfe, Doug E.

    2008-01-01

    Previous work has demonstrated that TBC delamination can be monitored by incorporating a thin luminescent sublayer that produces greatly increased luminescence intensity from delaminated regions of the TBC. Initial efforts utilized visible-wavelength luminescence from either europium or erbium doped sublayers. This approach exhibited good sensitivity to delamination of electron-beam physical-vapor-deposited (EB-PVD) TBCs, but limited sensitivity to delamination of the more highly scattering plasma-sprayed TBCs due to stronger optical scattering and to interference by luminescence from rare-earth impurities. These difficulties have now been overcome by new strategies employing near-infrared (NIR) and upconversion luminescence imaging. NIR luminescence at 1550 nm was produced in an erbium plus ytterbium co-doped yttria-stabilized zirconia (YSZ) luminescent sublayer using 980-nm excitation. Compared to visible-wavelength luminescence, these NIR emission and excitation wavelengths are much more weakly scattered by the TBC and therefore show much improved depth-probing capabilities. In addition, two-photon upconversion luminescence excitation at 980 nm wavelength produces luminescence emission at 562 nm with near-zero fluorescence background and exceptional contrast for delamination indication. The ability to detect TBC delamination produced by Rockwell indentation and by furnace cycling is demonstrated for both EB-PVD and plasma-sprayed TBCs. The relative strengths of the NIR and upconversion luminescence methods for monitoring TBC delamination are discussed.

  2. Numerical simulation of behavior of gas bubbles using a 3-D front-tracking method

    NARCIS (Netherlands)

    Sint Annaland, van M.; Dijkhuizen, W.; Deen, N.G.; Kuipers, J.A.M.

    2005-01-01

    In this paper a three-dimensional (3-D) front-tracking (FT) model is presented featuring a new method to evaluate the surface force model that circumvents the explicit computation of the interface curvature. This method is based on a direct calculation of the net tensile forces acting on a different

  3. Mechanism of Electrochemical Delamination of Two-Dimensional Materials from Their Native Substrates by Bubbling

    Directory of Open Access Journals (Sweden)

    Jie Sun

    2015-12-01

    Full Text Available A capacitor-based circuit model is proposed to explain the electrochemical delamination of two-dimensional materials from their native substrates where produced gas bubbles squeeze into the interface. The delamination is actually the electric breakdown of the capacitor formed between the solution and substrate. To facilitate the procedure, the backside of the ubstrate has to be shielded so that the capacitor breakdown voltage can be reached. The screening effect can be induced either by nonreactive ions around the electrode or, more effectively, by an undetachable insulator. This mechanism serves as a guideline for the surface science and applications involving the bubbling delamination.

  4. Cdc42/N-WASP signaling links actin dynamics to pancreatic beta cell delamination and differentiation

    DEFF Research Database (Denmark)

    Kesavan, Gokul; Lieven, Oliver; Mamidi, Anant;

    2014-01-01

    to differentiation remains unknown. Using the developing mouse pancreas as a model system, we show that β cell delamination and differentiation are two independent events, which are controlled by Cdc42/N-WASP signaling. Specifically, we show that expression of constitutively active Cdc42 in β cells inhibits β cell......Delamination plays a pivotal role during normal development and cancer. Previous work has demonstrated that delamination and epithelial cell movement within the plane of an epithelium are associated with a change in cellular phenotype. However, how this positional change is linked...

  5. Corona Formation and Heat Loss on Venus by Coupled Upwelling and Delamination

    Science.gov (United States)

    Smrekar, Suzanne E.; Stofan, Ellen R.

    1997-01-01

    Coronae are volcanotectonic features that are unique to Venus and are interpreted to be small-scale upwellings. A model in which upwelling causes delamination at the edge of the plume head, along with deformation of a pre-existing depleted mantel Layer, can produce the full range of topographic forms of coronae. If half of the coronae are active, delamination of the lower lithosphere could account for about 10% of venus's heat loss, with another 15% due to upwelling. Delamination may occur in other geologic enviroment and could help account for 'Venus' heat loss 'deficit'.

  6. On the Through-the-Width Multiple Delamination, and Buckling and Postbuckling Behaviors of Symmetric and Unsymmetric Composite Laminates

    Science.gov (United States)

    Liu, P. F.; Zheng, J. Y.

    2013-12-01

    Multiple delamination causes severe degradation of the stiffness and strength of composites. Interactions between multiple delamination, and buckling and postbuckling under compressive loads add the complexity of mechanical properties of composites. In this paper, the buckling, postbuckling and through-the-width multiple delamination of symmetric and unsymmetric composite laminates are studied using 3D FEA, and the virtual crack closure technique with two delamination failure criteria: B-K law and power law is used to predict the delamination growth and to calculate the mixed-mode energy release rate. The compressive load-strain curves, load-central deflection curves and multiple delamination process for eight composite specimens with different initial delamination sizes and their distributions as well as two angle-ply configurations 04//(± θ)6//04 ( θ = 0° and 45°, and "//" denotes the delaminated interface) are comparatively studied. From numerical results, the unsymmetry decreases the local buckling load and initial delamination load, but does not affect the global buckling load compared with the symmetric laminates. Besides, the unsymmetry affects the unstable delamination and buckling behaviors of composite laminates largely when the initial multiple delamination sizes are relatively small.

  7. Strong curvature effects in Neumann wave problems

    Science.gov (United States)

    Willatzen, M.; Pors, A.; Gravesen, J.

    2012-08-01

    Waveguide phenomena play a major role in basic sciences and engineering. The Helmholtz equation is the governing equation for the electric field in electromagnetic wave propagation and the acoustic pressure in the study of pressure dynamics. The Schrödinger equation simplifies to the Helmholtz equation for a quantum-mechanical particle confined by infinite barriers relevant in semiconductor physics. With this in mind and the interest to tailor waveguides towards a desired spectrum and modal pattern structure in classical structures and nanostructures, it becomes increasingly important to understand the influence of curvature effects in waveguides. In this work, we demonstrate analytically strong curvature effects for the eigenvalue spectrum of the Helmholtz equation with Neumann boundary conditions in cases where the waveguide cross section is a circular sector. It is found that the linear-in-curvature contribution originates from parity symmetry breaking of eigenstates in circular-sector tori and hence vanishes in a torus with a complete circular cross section. The same strong curvature effect is not present in waveguides subject to Dirichlet boundary conditions where curvature contributions contribute to second-order in the curvature only. We demonstrate this finding by considering wave propagation in a circular-sector torus corresponding to Neumann and Dirichlet boundary conditions, respectively. Results for relative eigenfrequency shifts and modes are determined and compared with three-dimensional finite element method results. Good agreement is found between the present analytical method using a combination of differential geometry with perturbation theory and finite element results for a large range of curvature ratios.

  8. Strong curvature effects in Neumann wave problems

    Energy Technology Data Exchange (ETDEWEB)

    Willatzen, M.; Pors, A. [Mads Clausen Institute, University of Southern Denmark, Alsion 2, DK-6400 Sonderborg (Denmark); Gravesen, J. [Department of Mathematics, Technical University of Denmark, Matematiktorvet, DK-2800 Kgs. Lyngby (Denmark)

    2012-08-15

    Waveguide phenomena play a major role in basic sciences and engineering. The Helmholtz equation is the governing equation for the electric field in electromagnetic wave propagation and the acoustic pressure in the study of pressure dynamics. The Schroedinger equation simplifies to the Helmholtz equation for a quantum-mechanical particle confined by infinite barriers relevant in semiconductor physics. With this in mind and the interest to tailor waveguides towards a desired spectrum and modal pattern structure in classical structures and nanostructures, it becomes increasingly important to understand the influence of curvature effects in waveguides. In this work, we demonstrate analytically strong curvature effects for the eigenvalue spectrum of the Helmholtz equation with Neumann boundary conditions in cases where the waveguide cross section is a circular sector. It is found that the linear-in-curvature contribution originates from parity symmetry breaking of eigenstates in circular-sector tori and hence vanishes in a torus with a complete circular cross section. The same strong curvature effect is not present in waveguides subject to Dirichlet boundary conditions where curvature contributions contribute to second-order in the curvature only. We demonstrate this finding by considering wave propagation in a circular-sector torus corresponding to Neumann and Dirichlet boundary conditions, respectively. Results for relative eigenfrequency shifts and modes are determined and compared with three-dimensional finite element method results. Good agreement is found between the present analytical method using a combination of differential geometry with perturbation theory and finite element results for a large range of curvature ratios.

  9. Light-Front QCD

    CERN Document Server

    Brodsky, S J

    2004-01-01

    In these lectures, I survey a number of applications of light-front methods to hadron and nuclear physics phenomenology and dynamics, Light-front Fock-state wavefunctions provide a frame-independent representation of hadrons in terms of their fundamental quark and gluon degrees of freedom. Nonperturbative methods for computing LFWFs in QCD are discussed, including string/gauge duality which predicts the power-law fall-off at high momentum transfer of light-front Fock-state hadronic wavefunctions with an arbitrary number of constituents and orbital angular momentum. The AdS/CFT correspondence has important implications for hadron phenomenology in the conformal limit, including an all-orders derivation of counting rules for exclusive processes. One can also compute the hadronic spectrum of near-conformal QCD assuming a truncated AdS/CFT space. The quantum fluctuations represented by the light-front Fock expansion leads to novel QCD phenomena such as color transparency, intrinsic heavy quark distributions, diffr...

  10. Buckle Driven Delamination in Thin Hard Film Compliant Substrate Systems

    Directory of Open Access Journals (Sweden)

    Bahr D.F.

    2010-06-01

    Full Text Available Deformation and fracture of thin films on compliant substrates are key factors constraining the performance of emerging flexible substrate devices. [1-3] These systems often contain layers of thin polymer, ceramic and metallic films and stretchable interconnects where differing properties induce high normal and shear stresses. [4] As long as the films remain bonded to the substrates, they may deform far beyond their freestanding form. Once debonded, substrate constraint disappears leading to film failure. [3] Experimentally it is very difficult to measure properties in these systems at sub-micron and nanoscales. Theoretically it is very difficult to determine the contributions from the films, interfaces, and substrates. As a result our understanding of deformation and fracture behavior in compliant substrate systems is limited. This motivated a study of buckle driven delamination of thin hard tungsten films on pure PMMA substrates. The films were sputter deposited to thicknesses of 100 nm, 200 nm, and 400 nm with a residual compressive stress of 1.7 GPa. An aluminum oxide interlayer was added on several samples to alter interfacial composition. Buckles formed spontaneously on the PMMA substrates following film deposition. On films without the aluminum oxide interlayer, an extensive network of small telephone cord buckles formed following deposition, interspersed with regions of larger telephone cord buckles. (Figure 1 On films with an aluminum oxide interlayer, telephone cord buckles formed creating a uniform widely spaced pattern. Through-substrate optical observations revealed matching buckle patterns along the film-substrate interface indicating that delamination occurred for large and small buckles with and without an interlayer. The coexistence of large and small buckles on the same substrate led to two distinct behaviors as shown in Figure 2 where normalized buckle heights are plotted against normalized film stress. The behaviors deviate

  11. Buckle Driven Delamination in Thin Hard Film Compliant Substrate Systems

    Science.gov (United States)

    Moody, N. R.; Reedy, E. D.; Corona, E.; Adams, D. P.; Kennedy, M. S.; Cordill, M. J.; Bahr, D. F.

    2010-06-01

    Deformation and fracture of thin films on compliant substrates are key factors constraining the performance of emerging flexible substrate devices. [1-3] These systems often contain layers of thin polymer, ceramic and metallic films and stretchable interconnects where differing properties induce high normal and shear stresses. [4] As long as the films remain bonded to the substrates, they may deform far beyond their freestanding form. Once debonded, substrate constraint disappears leading to film failure. [3] Experimentally it is very difficult to measure properties in these systems at sub-micron and nanoscales. Theoretically it is very difficult to determine the contributions from the films, interfaces, and substrates. As a result our understanding of deformation and fracture behavior in compliant substrate systems is limited. This motivated a study of buckle driven delamination of thin hard tungsten films on pure PMMA substrates. The films were sputter deposited to thicknesses of 100 nm, 200 nm, and 400 nm with a residual compressive stress of 1.7 GPa. An aluminum oxide interlayer was added on several samples to alter interfacial composition. Buckles formed spontaneously on the PMMA substrates following film deposition. On films without the aluminum oxide interlayer, an extensive network of small telephone cord buckles formed following deposition, interspersed with regions of larger telephone cord buckles. (Figure 1) On films with an aluminum oxide interlayer, telephone cord buckles formed creating a uniform widely spaced pattern. Through-substrate optical observations revealed matching buckle patterns along the film-substrate interface indicating that delamination occurred for large and small buckles with and without an interlayer. The coexistence of large and small buckles on the same substrate led to two distinct behaviors as shown in Figure 2 where normalized buckle heights are plotted against normalized film stress. The behaviors deviate significantly from

  12. Measuring Berry curvature with quantum Monte Carlo

    CERN Document Server

    Kolodrubetz, Michael

    2014-01-01

    The Berry curvature and its descendant, the Berry phase, play an important role in quantum mechanics. They can be used to understand the Aharonov-Bohm effect, define topological Chern numbers, and generally to investigate the geometric properties of a quantum ground state manifold. While Berry curvature has been well-studied in the regimes of few-body physics and non-interacting particles, its use in the regime of strong interactions is hindered by the lack of numerical methods to solve it. In this paper we fill this gap by implementing a quantum Monte Carlo method to solve for the Berry curvature, based on interpreting Berry curvature as a leading correction to imaginary time ramps. We demonstrate our algorithm using the transverse-field Ising model in one and two dimensions, the latter of which is non-integrable. Despite the fact that the Berry curvature gives information about the phase of the wave function, we show that our algorithm has no sign or phase problem for standard sign-problem-free Hamiltonians...

  13. The Front Desks of Boston

    Directory of Open Access Journals (Sweden)

    Michael Oshins

    2013-04-01

    Full Text Available The role of hotel front desks has not changed significantly in more than a century. The activities of welcoming guests upon arrival, assisting guests during their stay, and settling accounts upon departure are still the mainstay of the front desk. Although the function of the front desk has remained static, its form has evolved. Front desks now differ widely in terms of aesthetics and, in some cases, even operational patterns. This article offers photographs of numerous hotel front desks in Boston and provides brief commentaries that provide insight about the changing nature of front desk design.

  14. Period problems for mean curvature one surfaces in H^3 (with application to surfaces of low total curvature)

    OpenAIRE

    Rossman, Wayne; Umehara, Masaaki; Yamada, Kotaro

    2001-01-01

    We survey our recent results on classifying complete constant mean curvature 1 (CMC-1) surfaces in hyperbolic 3-space with low total curvature. There are two natural notions of "total curvature"-- one is the total absolute curvature which is the integral over the surface of the absolute value of the Gaussian curvature, and the other is the dual total absolute curvature which is the total absolute curvature of the dual CMC-1 surface. Here we discuss results on both notions (proven in two other...

  15. DELAMINATION PREDICTION IN DRILLING OF CFRP COMPOSITES USING ARTIFICIAL NEURAL NETWORK

    Directory of Open Access Journals (Sweden)

    K. PALANIKUMAR

    2011-04-01

    Full Text Available Carbon fibre reinforced plastic (CFRP materials play a major role in the applications of aeronautic, aerospace, sporting and transportation industries. Machining is indispensible and hence drilling of CFRP materials is considered in this present study with respect to spindle speed in rpm, drill size in mm and feed in mm/min. Delamination is one of the major defects to be dealt with. The experiments are carried out using computer numerical control machine and the results are applied to an artificial neural network (ANN for the prediction of delamination factor at the exit plane of the CFRP material. It is found that ANN model predicts the delamination for any given set of machining parameters with a maximum error of 0.81% and a minimum error of 0.03%. Thus an ANN model is highly suitable for the prediction of delamination in CFRP materials.

  16. Failure analysis of multiple delaminated composite plates due to bending and impact

    Indian Academy of Sciences (India)

    P K Parhi; S K Bhattacharyya; P K Sinha

    2001-04-01

    The present work aims at the first ply failure analysis of laminated composite plates with arbitrarily located multiple delaminations subjected to transverse static load as well as impact. The theoretical formulation is based on a simple multiple delamination model. Conventional first order shear deformation is assumed using eight-noded isoparametric quadratic elements to develop the finite element analysis procedure. Composite plates are assumed to contain both single and multiple delaminations. For the case of impact, Newmark time integration algorithm is employed for solving the time dependent multiple equations of the plate and the impactor. Tsai-Wu failure criterion is used to check for failure of the laminate for both the cases. To investigate the first ply failure, parametric studies are made for different cases by varying the size and number of delaminations as well as the stacking sequences and boundary conditions.

  17. Mode I fatigue delamination growth in composite laminates with fibre bridging

    NARCIS (Netherlands)

    Yao, L.

    2015-01-01

    Advanced composite materials have been commonly used in aerospace engineering, because of their good mechanical properties and attractive potential for creating lightweight structures. Susceptibility to delamination is one of the most important issues in the applications of these materials. This

  18. Comparison of Nondestructive Testing Methods on Detection of Delaminations in Composites

    Directory of Open Access Journals (Sweden)

    Liang Cheng

    2012-01-01

    Full Text Available Delamination is one of the most common defects in carbon fibre reinforced plastic (CFRP components, such as those used in aircraft and wind turbine blades. To detect delaminations, different NDT methods such as ultrasonic (UT, eddy current (EC scanning, flash thermography, and recent developed pulsed-eddy-current-(PEC- simulated thermography are conducted for comparison and evaluation of the new developed PEC thermography system at Nanjing University of Aeronautics and Astronautics (NUAA, China through UK-China collaboration. A PEC-stimulated thermography system is built at NUAA, extended from previous joint work between Newcastle and Bath Universities. Using these NDT systems, man-made, dedicated delaminations with varied diameters and depths are investigated and studied. Through this comparison, PEC-stumilated and flash thermography show relatively good indications of the shape of delaminations. The joint studies also show that PEC-stimulated thermography has unique advantage for fibre orientation evaluation.

  19. Reduction of cathodic delamination rates of anticorrosive coatings using free radical scavengers

    DEFF Research Database (Denmark)

    Sørensen, Per Aggerholm; Weinell, C. E.; Dam-Johansen, Kim

    2010-01-01

    Cathodic delamination is one of the major modes of failure for anticorrosive coatings subjected to a physical damage and immersed in seawater. The cause of cathodic delamination has been reported to be the result of a chemical attack at the coating-steel interface by free radicals and peroxides...... formed as intermediates in the cathodic reaction during the corrosion process. In this study, antioxidants (i.e., free radical scavengers and peroxide decomposers) have been incorporated into various generic types of coatings to investigate the effect of antioxidants on the rate of cathodic delamination...... of epoxy coatings on cold rolled steel. The addition of cathodic delamination by up to 50% during seawater immersion, while peroxide decomposers had a limited effect. Testing using substrates prepared from stainless steel...

  20. Interaction of Guided Lamb Waves with Delaminations and Discontinuities in Composite Plate-Like Structures

    Science.gov (United States)

    Balasubramaniam, Krishnan; Ramadas, C.; Padiyar, Janardhan; Krishnamurthy, C. V.

    2011-06-01

    Delamination is one of the critical failure modes that laminated composites structures encounter during their fabrication and/or in-service. When guided Lamb wave (Ao) is employed for sizing of delamination, it is necessary to understand the wave interaction with the defect. Studies were carried out on the interaction of Ao mode with symmetric and asymmetric delaminations and transmission of turning modes in the sub-laminates. An attempt was also made to understand the propagation of Ao mode in composite structural T-joint. During the interaction of Ao mode with structural discontinuity in a T-joint, generation of a new mode, So, and propagation of turning modes were observed. Length and width of interface delamination in composite T-joint have been worked out using D-scan and B-scan respectively. All studied were carried out through numerical simulations and experimental verifications through Non- Contact Ultrasound (NCU) technique.

  1. Dynamic buckling analysis of delaminated composite plates using semi-analytical finite strip method

    Science.gov (United States)

    Ovesy, H. R.; Totounferoush, A.; Ghannadpour, S. A. M.

    2015-05-01

    The delamination phenomena can become of paramount importance when the design of the composite plates is concerned. In the current study, the effect of through-the-width delamination on dynamic buckling behavior of a composite plate is studied by implementing semi-analytical finite strip method. In this method, the energy and work integrations are computed analytically due to the implementation of trigonometric functions. Moreover, the method can lead to converged results with comparatively small number of degrees of freedom. These features have made the method quite efficient. To account for delamination effects, displacement field is enriched by adding appropriate terms. Also, the penetration of the delamination surfaces is prevented by incorporating an appropriate contact scheme into the time response analysis. Some selected results are validated against those available in the literature.

  2. Application of the Refined Zigzag Theory to the Modeling of Delaminations in Laminated Composites

    Science.gov (United States)

    Groh, Rainer M. J.; Weaver, Paul M.; Tessler, Alexander

    2015-01-01

    The Refined Zigzag Theory is applied to the modeling of delaminations in laminated composites. The commonly used cohesive zone approach is adapted for use within a continuum mechanics model, and then used to predict the onset and propagation of delamination in five cross-ply composite beams. The resin-rich area between individual composite plies is modeled explicitly using thin, discrete layers with isotropic material properties. A damage model is applied to these resin-rich layers to enable tracking of delamination propagation. The displacement jump across the damaged interfacial resin layer is captured using the zigzag function of the Refined Zigzag Theory. The overall model predicts the initiation of delamination to within 8% compared to experimental results and the load drop after propagation is represented accurately.

  3. Mixed-Mode Decohesion Finite Elements for the Simulation of Delamination in Composite Materials

    Science.gov (United States)

    Camanho, Pedro P.; Davila, Carlos G.

    2002-01-01

    A new decohesion element with mixed-mode capability is proposed and demonstrated. The element is used at the interface between solid finite elements to model the initiation and non-self-similar growth of delaminations. A single relative displacement-based damage parameter is applied in a softening law to track the damage state of the interface and to prevent the restoration of the cohesive state during unloading. The softening law for mixed-mode delamination propagation can be applied to any mode interaction criterion such as the two-parameter power law or the three-parameter Benzeggagh-Kenane criterion. To demonstrate the accuracy of the predictions and the irreversibility capability of the constitutive law, steady-state delamination growth is simulated for quasistatic loading-unloading cycles of various single mode and mixed-mode delamination test specimens.

  4. Discrete Spring Model for Predicting Delamination Growth in Z-Fiber Reinforced DCB Specimens

    Science.gov (United States)

    Ratcliffe, James G.; OBrien, T. Kevin

    2004-01-01

    Beam theory analysis was applied to predict delamination growth in Double Cantilever Beam (DCB) specimens reinforced in the thickness direction with pultruded pins, known as Z-fibers. The specimen arms were modeled as cantilever beams supported by discrete springs, which were included to represent the pins. A bi-linear, irreversible damage law was used to represent Z-fiber damage, the parameters of which were obtained from previous experiments. Closed-form solutions were developed for specimen compliance and displacements corresponding to Z-fiber row locations. A solution strategy was formulated to predict delamination growth, in which the parent laminate mode I critical strain energy release rate was used as the criterion for delamination growth. The solution procedure was coded into FORTRAN 90, giving a dedicated software tool for performing the delamination prediction. Comparison of analysis results with previous analysis and experiment showed good agreement, yielding an initial verification for the analytical procedure.

  5. Dark energy, curvature and cosmic coincidence

    CERN Document Server

    Franca, U

    2006-01-01

    The fact that the energy densities of dark energy and matter are similar currently, known as the coincidence problem, is one of the main unsolved problems of cosmology. We present here a phenomenological model in which a spatial curvature of the universe can lead to a transition in the present epoch from a matter dominated universe to a scaling dark energy dominance in a very natural way. In particular, we show that if the exponential potential of the dark energy field depends linearly on the spatial curvature density of a closed universe, the observed values of some cosmological parameters can be obtained assuming acceptable values for the present spatial curvature of the universe, and without fine tuning in the only parameter of the model. We also comment on possible variations of this model.

  6. On the curvature effect of thin membranes

    Science.gov (United States)

    Wang, Duo; Jiao, Xiangmin; Conley, Rebecca; Glimm, James

    2013-01-01

    We investigate the curvature effect of a thin, curved elastic interface that separates two subdomains and exerts a pressure due to a curvature effect. This pressure, which we refer to as interface pressure, is similar to the surface tension in fluid mechanics. It is important in some applications, such as the canopy of parachutes, biological membranes of cells, balloons, airbags, etc., as it partially balances a pressure jump between the two sides of an interface. In this paper, we show that the interface pressure is equal to the trace of the matrix product of the curvature tensor and the Cauchy stress tensor in the tangent plane. We derive the theory for interfaces in both 2-D and 3-D, and present numerical discretizations for computing the quality over triangulated surfaces.

  7. Total positive curvature of circular DNA

    DEFF Research Database (Denmark)

    Bohr, Jakob; Olsen, Kasper Wibeck

    2013-01-01

    molecules, e.g., plasmids, it is shown to have implications for the total positive curvature integral. For small circular micro-DNAs it follows as a consequence of Fenchel's inequality that there must exist a minimum length for the circular plasmids to be double stranded. It also follows that all circular...... micro-DNAs longer than the minimum length must be concave, a result that is consistent with typical atomic force microscopy images of plasmids. Predictions for the total positive curvature of circular micro-DNAs are given as a function of length, and comparisons with circular DNAs from the literature......The properties of double-stranded DNA and other chiral molecules depend on the local geometry, i.e., on curvature and torsion, yet the paths of closed chain molecules are globally restricted by topology. When both of these characteristics are to be incorporated in the description of circular chain...

  8. Extrinsic and intrinsic curvatures in thermodynamic geometry

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini Mansoori, Seyed Ali, E-mail: shossein@bu.edu [Department of Physics, Boston University, 590 Commonwealth Ave., Boston, MA 02215 (United States); Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Mirza, Behrouz, E-mail: b.mirza@cc.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Sharifian, Elham, E-mail: e.sharifian@ph.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2016-08-10

    We investigate the intrinsic and extrinsic curvatures of a certain hypersurface in thermodynamic geometry of a physical system and show that they contain useful thermodynamic information. For an anti-Reissner–Nordström-(A)de Sitter black hole (Phantom), the extrinsic curvature of a constant Q hypersurface has the same sign as the heat capacity around the phase transition points. The intrinsic curvature of the hypersurface can also be divergent at the critical points but has no information about the sign of the heat capacity. Our study explains the consistent relationship holding between the thermodynamic geometry of the KN-AdS black holes and those of the RN (J-zero hypersurface) and Kerr black holes (Q-zero hypersurface) ones [1]. This approach can easily be generalized to an arbitrary thermodynamic system.

  9. Gaussian Curvature on Hyperelliptic Riemann Surfaces

    Indian Academy of Sciences (India)

    Abel Castorena

    2014-05-01

    Let be a compact Riemann surface of genus $g ≥ 1, _1,\\ldots,_g$ be a basis of holomorphic 1-forms on and let $H=(h_{ij})^g_{i,j=1}$ be a positive definite Hermitian matrix. It is well known that the metric defined as $ds_H^2=\\sum^g_{i,j=1}h_{ij}_i\\otimes \\overline{_j}$ is a K\\"a hler metric on of non-positive curvature. Let $K_H:C→ \\mathbb{R}$ be the Gaussian curvature of this metric. When is hyperelliptic we show that the hyperelliptic Weierstrass points are non-degenerated critical points of $K_H$ of Morse index +2. In the particular case when is the × identity matrix, we give a criteria to find local minima for $K_H$ and we give examples of hyperelliptic curves where the curvature function $K_H$ is a Morse function.

  10. Integrating curvature: from Umlaufsatz to J^+ invariant

    CERN Document Server

    Lanzat, Sergei

    2011-01-01

    Hopf's Umlaufsatz relates the total curvature of a closed immersed plane curve to its rotation number. While the curvature of a curve changes under local deformations, its integral over a closed curve is invariant under regular homotopies. A natural question is whether one can find some non-trivial densities on a curve, such that the corresponding integrals are (possibly after some corrections) also invariant under regular homotopies of the curve in the class of generic immersions. We construct a family of such densities using indices of points relative to the curve. This family depends on a formal parameter q and may be considered as a quantization of the total curvature. The linear term in the Taylor expansion at q=1 coincides, up to a normalization, with Arnold's J^+ invariant. This leads to an integral expression for J^+.

  11. Anisotropic membrane curvature sensing by antibacterial peptides

    CERN Document Server

    Gómez-Llobregat, Jordi; Lindén, Martin

    2014-01-01

    Many proteins and peptides have an intrinsic capacity to sense and induce membrane curvature, and play crucial roles for organizing and remodeling cell membranes. However, the molecular driving forces behind these processes are not well understood. Here, we describe a new approach to study curvature sensing, by simulating the direction-dependent interactions of single molecules with a buckled lipid bilayer. We analyze three antimicrobial peptides, a class of membrane-associated molecules that specifically target and destabilize bacterial membranes, and find qualitatively different sensing characteristics that would be difficult to resolve with other methods. These findings provide new insights into the microscopic mechanisms of antimicrobial peptides, which might aid the development of new antibiotics. Our approach is generally applicable to a wide range of curvature sensing molecules, and our results provide strong motivation to develop new experimental methods to track position and orientation of membrane p...

  12. Riemann curvature of a boosted spacetime geometry

    CERN Document Server

    Battista, Emmanuele; Scudellaro, Paolo; Tramontano, Francesco

    2014-01-01

    The ultrarelativistic boosting procedure had been applied in the literature to map the metric of Schwarzschild-de Sitter spacetime into a metric describing de Sitter spacetime plus a shock-wave singularity located on a null hypersurface. This paper evaluates the Riemann curvature tensor of the boosted Schwarzschild-de Sitter metric by means of numerical calculations, which make it possible to reach the ultrarelativistic regime gradually by letting the boost velocity approach the speed of light. Thus, for the first time in the literature, the singular limit of curvature through Dirac's delta distribution and its derivatives is numerically evaluated for this class of spacetimes. Eventually, the analysis of the Kteschmann invariant and the geodesic equation show that the spacetime possesses a scalar curvature singularity within a 3-sphere and it is possible to define what we here call boosted horizon, a sort of elastic wall where all particles are surprisingly pushed away, as numerical analysis demonstrates. Thi...

  13. Anomalous Coupling Between Topological Defects and Curvature

    Science.gov (United States)

    Vitelli, Vincenzo; Turner, Ari M.

    2004-11-01

    We investigate a counterintuitive geometric interaction between defects and curvature in thin layers of superfluids, superconductors, and liquid crystals deposited on curved surfaces. Each defect feels a geometric potential whose functional form is determined only by the shape of the surface, but whose sign and strength depend on the transformation properties of the order parameter. For superfluids and superconductors, the strength of this interaction is proportional to the square of the charge and causes all defects to be repelled (attracted) by regions of positive (negative) Gaussian curvature. For liquid crystals in the one elastic constant approximation, charges between 0 and 4π are attracted by regions of positive curvature while all other charges are repelled.

  14. Cosmic curvature from de Sitter equilibrium cosmology.

    Science.gov (United States)

    Albrecht, Andreas

    2011-10-01

    I show that the de Sitter equilibrium cosmology generically predicts observable levels of curvature in the Universe today. The predicted value of the curvature, Ω(k), depends only on the ratio of the density of nonrelativistic matter to cosmological constant density ρ(m)(0)/ρ(Λ) and the value of the curvature from the initial bubble that starts the inflation, Ω(k)(B). The result is independent of the scale of inflation, the shape of the potential during inflation, and many other details of the cosmology. Future cosmological measurements of ρ(m)(0)/ρ(Λ) and Ω(k) will open up a window on the very beginning of our Universe and offer an opportunity to support or falsify the de Sitter equilibrium cosmology.

  15. Debonding/Delamination of Composites (Le Decollement et le Delaminage des Materiaux Composites)

    Science.gov (United States)

    1992-12-01

    bouthS sides of the delamination. Fig 8a. Ithese cratcks coincide with the delamination length Linder conipressise loadingthe 1.1D-sublaminate buckles like...Scientific 115] R.O. Duda, PE. Hart , "Pattern classification and scene Research (NFWO) for its funding Considerable help was also analysis", John...unidirectional laminates were performed with the technology of differential 2 MATERIALS AND PREPARATIONS scanning calorimetry A Du Pont DSC system, model 910, was

  16. Detection of drilling-induced delamination in aeronautical composites by noncontact laser ultrasonic method.

    Science.gov (United States)

    Zhou, Zhenggan; Sun, Guangkai; Chen, Xiucheng; Wang, Jie

    2014-04-20

    A novel application of the laser ultrasonic technique for the detection of drilling-induced delamination in composite components of aircrafts is proposed. Numerous key components of aircrafts are made of composite materials, and drilling is often a final operation during assembly. Drilling-induced delamination significantly reduces the structural reliability, and it is rather difficult to be detected effectively and automatically. The laser ultrasonic technique is a promising method to solve the problem. This paper investigates the characterization of drilling-induced delamination in composites by a noncontact laser ultrasonic method. A carbon fiber reinforced plastic laminate with drilling holes is prepared as a specimen. The characterization of drilling-induced delamination with laser-generated ultrasonic waves is investigated theoretically and experimentally, and the morphology features of the delamination are obtained by laser ultrasonic C-scan testing. The results prove that the laser ultrasonic technique is effective for the detection of drilling-induced delamination in composite components, and it is a feasible solution for evaluating the drilling quality during assembly.

  17. Delamination detection in composite laminates using dispersion change based on mode conversion of Lamb waves

    Science.gov (United States)

    Okabe, Yoji; Fujibayashi, Keiji; Shimazaki, Mamoru; Soejima, Hideki; Ogisu, Toshimichi

    2010-11-01

    A new ultrasonic propagation system has been constructed using macrofiber composite (MFC) actuators and fiber Bragg grating (FBG) sensors. The MFCs and FBGs can be integrated into composite laminates because of their small size and high fracture strain. The developed system can send and receive broadband Lamb waves. In this research, this system was used to detect delamination damage in composite laminates. First, the multiple modes of Lamb waves in a carbon-fiber-reinforced plastic (CFRP) quasi-isotropic laminate were identified by transmitting and receiving the symmetric and antisymmetric modes separately. Then, the mode conversions at both tips of a delamination were investigated through an experiment and a two-dimensional finite element analysis (FEA). A new delamination detection method was proposed on the basis of the mode conversions, and experiments were carried out on laminates with an artificial delamination. When antisymmetric modes were excited, the frequency dispersion of the received A1 mode changed, depending on the delamination length owing to the mode conversion between the A1 mode and the S0 mode. This phenomenon was confirmed through the FEA and these results prove that this new method is effective in detecting a delamination in CFRP laminates.

  18. Scattering of the fundamental anti-symmetric Lamb wave at delaminations in composite laminates.

    Science.gov (United States)

    Ng, Ching-Tai; Veidt, Martin

    2011-03-01

    An analysis of the scattering characteristics of the fundamental anti-symmetric (A(0)) Lamb wave at a delamination in a quasi-isotropic composite laminate is presented. Analytical solutions for this problem do not exist due to the anisotropic nature and multilayer characteristics of composite laminates. This study uses a three-dimensional finite element (FE) method and experimental measurements to provide physical insight into the scattering phenomena. Good agreement is found between simulations and experimental measurements. The results show that the A(0) Lamb wave scattering at a delamination in composite laminates is much more complicated than the scattering at a defect in isotropic plates. Scatter amplitudes and scatter directivity distributions depend on the delamination size to wavelength ratio and the through-thickness location of the delamination damage. The study also investigates the feasibility of the common experimental practice of simulating delamination damage by bonding masses to the surface of composite laminates for guided wave damage detection and characterization methodologies verifications. The results suggest that care is required to use bonded masses to simulate delamination damage for verifying and optimizing damage characterization techniques. In summary, the results of the investigation help to further advance the use of the A(0) Lamb wave for damage detection and characterization.

  19. Mechanistic Study of Delamination Fracture in Al-Li Alloy C458 (2099)

    Science.gov (United States)

    Tayon, W. A.; Crooks, R. E.; Domack, M. S.; Wagner, J. A.; Beaudoin, A. J.; McDonald, R. J.

    2009-01-01

    Delamination fracture has limited the use of lightweight Al-Li alloys. In the present study, electron backscattered diffraction (EBSD) methods were used to characterize crack paths in Al-Li alloy C458 (2099). Secondary delamination cracks in fracture toughness samples showed a pronounced tendency for fracture between grain variants of the same deformation texture component. These results were analyzed by EBSD mapping methods and simulated with finite element analyses. Simulation procedures include a description of material anisotropy, local grain orientations, and fracture utilizing crystal plasticity and cohesive zone elements. Taylor factors computed for each grain orientation subjected to normal and shear stresses indicated that grain pairs with the largest Taylor factor differences were adjacent to boundaries that failed by delamination. Examination of matching delamination fracture surface pairs revealed pronounced slip bands in only one of the grains bordering the delamination. These results, along with EBSD studies, plasticity simulations, and Auger electron spectroscopy observations support a hypothesis that delamination fracture occurs due to poor slip accommodation along boundaries between grains with greatly differing plastic response.

  20. Numerical investigation of nonlinear interactions between multimodal guided waves and delamination in composite structures

    Science.gov (United States)

    Shen, Yanfeng

    2017-04-01

    This paper presents a numerical investigation of the nonlinear interactions between multimodal guided waves and delamination in composite structures. The elastodynamic wave equations for anisotropic composite laminate were formulated using an explicit Local Interaction Simulation Approach (LISA). The contact dynamics was modeled using the penalty method. In order to capture the stick-slip contact motion, a Coulomb friction law was integrated into the computation procedure. A random gap function was defined for the contact pairs to model distributed initial closures or openings to approximate the nature of rough delamination interfaces. The LISA procedure was coded using the Compute Unified Device Architecture (CUDA), which enables the highly parallelized computation on powerful graphic cards. Several guided wave modes centered at various frequencies were investigated as the incident wave. Numerical case studies of different delamination locations across the thickness were carried out. The capability of different wave modes at various frequencies to trigger the Contact Acoustic Nonlinearity (CAN) was studied. The correlation between the delamination size and the signal nonlinearity was also investigated. Furthermore, the influence from the roughness of the delamination interfaces was discussed as well. The numerical investigation shows that the nonlinear features of wave delamination interactions can enhance the evaluation capability of guided wave Structural Health Monitoring (SHM) system. This paper finishes with discussion, concluding remarks, and suggestions for future work.

  1. Cdc42/N-WASP signaling links actin dynamics to pancreatic β cell delamination and differentiation

    Science.gov (United States)

    Kesavan, Gokul; Lieven, Oliver; Mamidi, Anant; Öhlin, Zarah Löf; Johansson, Jenny Kristina; Li, Wan-Chun; Lommel, Silvia; Greiner, Thomas Uwe; Semb, Henrik

    2014-01-01

    Delamination plays a pivotal role during normal development and cancer. Previous work has demonstrated that delamination and epithelial cell movement within the plane of an epithelium are associated with a change in cellular phenotype. However, how this positional change is linked to differentiation remains unknown. Using the developing mouse pancreas as a model system, we show that β cell delamination and differentiation are two independent events, which are controlled by Cdc42/N-WASP signaling. Specifically, we show that expression of constitutively active Cdc42 in β cells inhibits β cell delamination and differentiation. These processes are normally associated with junctional actin and cell-cell junction disassembly and the expression of fate-determining transcription factors, such as Isl1 and MafA. Mechanistically, we demonstrate that genetic ablation of N-WASP in β cells expressing constitutively active Cdc42 partially restores both delamination and β cell differentiation. These findings elucidate how junctional actin dynamics via Cdc42/N-WASP signaling cell-autonomously control not only epithelial delamination but also cell differentiation during mammalian organogenesis. PMID:24449844

  2. Combined effect of matrix cracking and stress-free edge on delamination

    Science.gov (United States)

    Salpekar, S. A.; Obrien, T. K.

    1990-01-01

    The effect of the stress-free edge on the growth of local delaminations initiating from a matrix crack in (0 sub 2/90 sub 4) sub s and (+ or - 45.90 sub 4) sub s glass epoxy laminates is investigated using 3-D finite element analysis. The presence of high interlaminar normal stresses at the intersection (corner) of the matrix crack with the stress-free edge, suggests that a mode I delamination may initiate at the corners. The strain energy release rates (G) were calculated by modeling a uniform through-width delamination and two inclined delaminations at 10.6 deg and 45 deg to the matrix crack. All components of G have high values near the free edges. The mode I component of G is high at small delamination length and becomes zero for a delamination length of one-ply thickness. The total G values near the free edge agreed well with previously derived closed form solution. The quasi-3D solutions agreed well with the 3-D interior solutions.

  3. Clay-polymer nanocomposite material from the delamination of kaolinite in the presence of sodium polyacrylate.

    Science.gov (United States)

    Letaief, Sadok; Detellier, Christian

    2009-09-15

    A chemical route for the delamination of kaolinite in a polymeric matrix is reported in this work. The strategy that was used is based on mixing polyelectrolytes of opposite charges, an organic polyanion, polyacrylate, with an inorganic polycation resulting from the modification of the internal surfaces of kaolinite. The delamination was carried out by the reaction of sodium polyacrylate (PANa) with kaolinite whose internal aluminol surfaces were previously grafted with triethanolamine and subsequently quaternized with iodomethane (TOIM-K) to form an extended lamellar inorganic polycation. X-ray diffraction as well as scanning electron microscopy (SEM) confirmed the complete delamination of the kaolinite particles. 13C CP/MAS NMR showed the removal of the ammonium groups resulting from hydrolysis of the internal surfaces once exposed, and 29Si CP/MAS NMR spectra were in agreement with the retention of the 1:1 aluminosilicate kaolinite layers structures. From the thermogravimetry (TG) data, the respective percentages in mass of PA and kaolinite in the delaminated nanocomposite could be estimated to be 61% and 39%, respectively, in the conditions of the particular experiment. The procedure was repeated several times to show the reproducibility of the delamination. The interlayer functionalization of kaolinite was crucial for the success of the delamination procedure. SEM pictures show that some individual kaolinite platelets fold and form curved structures.

  4. Buckling delamination induced microchannel: Flow regulation in microfluidic devices

    Science.gov (United States)

    Kang, Jingtian; Wang, Changguo; Xue, Zhiming; Liu, Mengxiong; Tan, Huifeng

    2016-09-01

    The buckling delamination induced microchannel is employed to regulate fluid flow as a microvalve which can be utilized in microfluidic devices. This microvalve consists of a soft substrate and a stiff thin film, between which there is a pre-set small imperfection. Two critical strain values, namely, on-off strain and failure strain, have been proposed to determine the working strain interval using analytical predictions. Within this interval, the cross-sectional area of the microchannel can be controlled and predicted by different compressive strains of the film/substrate system. The fluid flow rate within this microchannel can be then estimated by both analytical and numerical simulations and adjusted to satisfy different values by alternating the compressive strain. In addition, a demonstrative experiment has been taken to verify the feasibility of this approach. This flexible microvalve has potential in the application where the use of traditional rigid microvalves is improper in flexible microfluidic devices. The method and approach of this paper can provide a general guide for flow rate control in microfluidic devices.

  5. Hypersurfaces of constant curvature in Hyperbolic space

    CERN Document Server

    Guan, Bo

    2010-01-01

    We show that for a very general and natural class of curvature functions, the problem of finding a complete strictly convex hypersurface satisfying f({\\kappa}) = {\\sigma} over (0,1) with a prescribed asymptotic boundary {\\Gamma} at infinity has at least one solution which is a "vertical graph" over the interior (or the exterior) of {\\Gamma}. There is uniqueness for a certain subclass of these curvature functions and as {\\sigma} varies between 0 and 1, these hypersurfaces foliate the two components of the complement of the hyperbolic convex hull of {\\Gamma}.

  6. Fingerprint Feature Extraction Based on Macroscopic Curvature

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiong; He Gui-ming; Zhang Yun

    2003-01-01

    In the Automatic Fingerprint Identification System (AFIS), extracting the feature of fingerprint is very important. The local curvature of ridges of fingerprint is irregular, so people have the barrier to effectively extract the fingerprint curve features to describe fingerprint. This article proposes a novel algorithm; it embraces information of few nearby fingerprint ridges to extract a new characteristic which can describe the curvature feature of fingerprint. Experimental results show the algorithm is feasible, and the characteristics extracted by it can clearly show the inner macroscopic curve properties of fingerprint. The result also shows that this kind of characteristic is robust to noise and pollution.

  7. Fingerprint Feature Extraction Based on Macroscopic Curvature

    Institute of Scientific and Technical Information of China (English)

    Zhang; Xiong; He; Gui-Ming; 等

    2003-01-01

    In the Automatic Fingerprint Identification System(AFIS), extracting the feature of fingerprint is very important. The local curvature of ridges of fingerprint is irregular, so people have the barrier to effectively extract the fingerprint curve features to describe fingerprint. This article proposes a novel algorithm; it embraces information of few nearby fingerprint ridges to extract a new characterstic which can describe the curvature feature of fingerprint. Experimental results show the algorithm is feasible, and the characteristics extracted by it can clearly show the inner macroscopic curve properties of fingerprint. The result also shows that this kind of characteristic is robust to noise and pollution.

  8. Dynamics of curved fronts

    CERN Document Server

    Pelce, Pierre

    1989-01-01

    In recent years, much progress has been made in the understanding of interface dynamics of various systems: hydrodynamics, crystal growth, chemical reactions, and combustion. Dynamics of Curved Fronts is an important contribution to this field and will be an indispensable reference work for researchers and graduate students in physics, applied mathematics, and chemical engineering. The book consist of a 100 page introduction by the editor and 33 seminal articles from various disciplines.

  9. Radiative thermal conduction fronts

    Science.gov (United States)

    Borkowski, Kazimierz J.; Balbus, Steven A.; Fristrom, Carl C.

    1990-01-01

    The discovery of the O VI interstellar absorption lines in our Galaxy by the Copernicus observatory was a turning point in our understanding of the Interstellar Medium (ISM). It implied the presence of widespread hot (approx. 10 to the 6th power K) gas in disk galaxies. The detection of highly ionized species in quasi-stellar objects' absorption spectra may be the first indirect observation of this hot phase in external disk galaxies. Previous efforts to understand extensive O VI absorption line data from our Galaxy were not very successful in locating the regions where this absorption originates. The location at interfaces between evaporating ISM clouds and hot gas was favored, but recent studies of steady-state conduction fronts in spherical clouds by Ballet, Arnaud, and Rothenflug (1986) and Bohringer and Hartquist (1987) rejected evaporative fronts as the absorption sites. Researchers report here on time-dependent nonequilibrium calculations of planar conductive fronts whose properties match well with observations, and suggest reasons for the difference between the researchers' results and the above. They included magnetic fields in additional models, not reported here, and the conclusions are not affected by their presence.

  10. Timelike Constant Mean Curvature Surfaces with Singularities

    DEFF Research Database (Denmark)

    Brander, David; Svensson, Martin

    2014-01-01

    We use integrable systems techniques to study the singularities of timelike non-minimal constant mean curvature (CMC) surfaces in the Lorentz–Minkowski 3-space. The singularities arise at the boundary of the Birkhoff big cell of the loop group involved. We examine the behavior of the surfaces at ...

  11. Timelike Constant Mean Curvature Surfaces with Singularities

    DEFF Research Database (Denmark)

    Brander, David; Svensson, Martin

    2014-01-01

    We use integrable systems techniques to study the singularities of timelike non-minimal constant mean curvature (CMC) surfaces in the Lorentz–Minkowski 3-space. The singularities arise at the boundary of the Birkhoff big cell of the loop group involved. We examine the behavior of the surfaces...

  12. Geometrical Constraint on Curvature with BAO experiments

    CERN Document Server

    Takada, Masahiro

    2015-01-01

    The spatial curvature ($K$ or $\\Omega_K$) is one of the most fundamental parameters of isotropic and homogeneous universe and has a close link to the physics of early universe. Combining the radial and angular diameter distances measured via the baryon acoustic oscillation (BAO) experiments allows us to unambiguously constrain the curvature. The method is primarily based on the metric theory, but not much on the theory of structure formation other than the existence of BAO scale and is free of any model of dark energy. In this paper, we estimate a best-achievable accuracy of constraining the curvature with the BAO experiments. We show that an all-sky, cosmic-variance-limited galaxy survey covering the universe up to $z>4$ enables a precise determination of the curvature to an accuracy of $\\sigma(\\Omega_K)\\simeq 10^{-3}$. When we assume a model of dark energy, either the cosmological constraint or the $(w_0,w_a)$-model, it can achieve a precision of $\\sigma(\\Omega_K)\\simeq \\mbox{a few}\\times 10^{-4}$. These fo...

  13. Spinal curvature measurement by tracked ultrasound snapshots.

    Science.gov (United States)

    Ungi, Tamas; King, Franklin; Kempston, Michael; Keri, Zsuzsanna; Lasso, Andras; Mousavi, Parvin; Rudan, John; Borschneck, Daniel P; Fichtinger, Gabor

    2014-02-01

    Monitoring spinal curvature in adolescent kyphoscoliosis requires regular radiographic examinations; however, the applied ionizing radiation increases the risk of cancer. Ultrasound imaging is favored over radiography because it does not emit ionizing radiation. Therefore, we tested an ultrasound system for spinal curvature measurement, with the help of spatial tracking of the ultrasound transducer. Tracked ultrasound was used to localize vertebral transverse processes as landmarks along the spine to measure curvature angles. The method was tested in two scoliotic spine models by localizing the same landmarks using both ultrasound and radiographic imaging and comparing the angles obtained. A close correlation was found between tracked ultrasound and radiographic curvature measurements. Differences between results of the two methods were 1.27 ± 0.84° (average ± SD) in an adult model and 0.96 ± 0.87° in a pediatric model. Our results suggest that tracked ultrasound may become a more tolerable and more accessible alternative to radiographic spine monitoring in adolescent kyphoscoliosis.

  14. Geodesic curvature driven surface microdomain formation.

    Science.gov (United States)

    Adkins, Melissa R; Zhou, Y C

    2017-09-15

    Lipid bilayer membranes are not uniform and clusters of lipids in a more ordered state exist within the generally disorder lipid milieu of the membrane. These clusters of ordered lipids microdomains are now referred to as lipid rafts. Recent reports attribute the formation of these microdomains to the geometrical and molecular mechanical mismatch of lipids of different species on the boundary. Here we introduce the geodesic curvature to characterize the geometry of the domain boundary, and develop a geodesic curvature energy model to describe the formation of these microdomains as a result of energy minimization. Our model accepts the intrinsic geodesic curvature of any binary lipid mixture as an input, and will produce microdomains of the given geodesic curvature as demonstrated by three sets of numerical simulations. Our results are in contrast to the surface phase separation predicted by the classical surface Cahn-Hilliard equation, which tends to generate large domains as a result of the minimizing line tension. Our model provides a direct and quantified description of the structure inhomogeneity of lipid bilayer membrane, and can be coupled to the investigations of biological processes on membranes for which such inhomogeneity plays essential roles.

  15. Local surface orientation dominates haptic curvature discrimination

    NARCIS (Netherlands)

    Wijntjes, M.W.A.; Sato, A.; Hayward, V.; Kappers, A.M.L.

    2009-01-01

    Prior studies have shown that local surface orientation is a dominant source of information for haptic curvature perception in static conditions. We show that this dominance holds for dynamic touch, just as was shown earlier for static touch. Using an apparatus specifically developed for this purpos

  16. Einstein Hermitian Metrics of Positive Sectional Curvature

    CERN Document Server

    Koca, Caner

    2011-01-01

    In this paper we will prove that the only compact 4-manifold M with an Einstein metric of positive sectional curvature which is also hermitian with respect to some complex structure on M, is the complex projective plane CP^2, with its Fubini-Study metric.

  17. Curvature controlled wetting in two dimensions

    DEFF Research Database (Denmark)

    Gil, Tamir; Mikheev, Lev V.

    1995-01-01

    . As the radius of the substrate r0→∞, the leading effect of the curvature is adding the Laplace pressure ΠL∝r0-1 to the pressure balance in the film. At temperatures and pressures under which the wetting is complete in planar geometry, Laplace pressure suppresses divergence of the mean thickness of the wetting...

  18. Riemann curvature of a boosted spacetime geometry

    Science.gov (United States)

    Battista, Emmanuele; Esposito, Giampiero; Scudellaro, Paolo; Tramontano, Francesco

    2016-10-01

    The ultrarelativistic boosting procedure had been applied in the literature to map the metric of Schwarzschild-de Sitter spacetime into a metric describing de Sitter spacetime plus a shock-wave singularity located on a null hypersurface. This paper evaluates the Riemann curvature tensor of the boosted Schwarzschild-de Sitter metric by means of numerical calculations, which make it possible to reach the ultrarelativistic regime gradually by letting the boost velocity approach the speed of light. Thus, for the first time in the literature, the singular limit of curvature, through Dirac’s δ distribution and its derivatives, is numerically evaluated for this class of spacetimes. Moreover, the analysis of the Kretschmann invariant and the geodesic equation shows that the spacetime possesses a “scalar curvature singularity” within a 3-sphere and it is possible to define what we here call “boosted horizon”, a sort of elastic wall where all particles are surprisingly pushed away, as numerical analysis demonstrates. This seems to suggest that such “boosted geometries” are ruled by a sort of “antigravity effect” since all geodesics seem to refuse to enter the “boosted horizon” and are “reflected” by it, even though their initial conditions are aimed at driving the particles toward the “boosted horizon” itself. Eventually, the equivalence with the coordinate shift method is invoked in order to demonstrate that all δ2 terms appearing in the Riemann curvature tensor give vanishing contribution in distributional sense.

  19. Resolving curvature singularities in holomorphic gravity

    NARCIS (Netherlands)

    Mantz, C.L.M.; Prokopec, T.

    2011-01-01

    We formulate a holomorphic theory of gravity and study how the holomorphy symmetry alters the two most important singular solutions of general relativity: black holes and cosmology. We show that typical observers (freely) falling into a holomorphic black hole do not encounter a curvature singularity

  20. Geodesic curvature driven surface microdomain formation

    Science.gov (United States)

    Adkins, Melissa R.; Zhou, Y. C.

    2017-09-01

    Lipid bilayer membranes are not uniform and clusters of lipids in a more ordered state exist within the generally disorder lipid milieu of the membrane. These clusters of ordered lipids microdomains are now referred to as lipid rafts. Recent reports attribute the formation of these microdomains to the geometrical and molecular mechanical mismatch of lipids of different species on the boundary. Here we introduce the geodesic curvature to characterize the geometry of the domain boundary, and develop a geodesic curvature energy model to describe the formation of these microdomains as a result of energy minimization. Our model accepts the intrinsic geodesic curvature of any binary lipid mixture as an input, and will produce microdomains of the given geodesic curvature as demonstrated by three sets of numerical simulations. Our results are in contrast to the surface phase separation predicted by the classical surface Cahn-Hilliard equation, which tends to generate large domains as a result of the minimizing line tension. Our model provides a direct and quantified description of the structure inhomogeneity of lipid bilayer membrane, and can be coupled to the investigations of biological processes on membranes for which such inhomogeneity plays essential roles.

  1. Change in corneal curvature induced by surgery

    NARCIS (Netherlands)

    G. van Rij (Gabriel)

    1987-01-01

    textabstractThe first section deals with the mechanisms by which sutures, incisions and intracorneal contact lenses produce a change in corneal curvature. To clarify the mechanisms by which incisions and sutures produce astigmatism, we made incisions and placed sutures in the corneoscleral limbus of

  2. Level-Slope-Curvature - Fact or Artefact?

    NARCIS (Netherlands)

    R. Lord (Roger); A.A.J. Pelsser (Antoon)

    2005-01-01

    textabstractThe first three factors resulting from a principal components analysis of term structure data are in the literature typically interpreted as driving the level, slope and curvature of the term structure. Using slight generalisations of theorems from total positivity, we present sufficient

  3. Improving Polyp Detection Algorithms for CT Colonography: Pareto Front Approach.

    Science.gov (United States)

    Huang, Adam; Li, Jiang; Summers, Ronald M; Petrick, Nicholas; Hara, Amy K

    2010-03-21

    We investigated a Pareto front approach to improving polyp detection algorithms for CT colonography (CTC). A dataset of 56 CTC colon surfaces with 87 proven positive detections of 53 polyps sized 4 to 60 mm was used to evaluate the performance of a one-step and a two-step curvature-based region growing algorithm. The algorithmic performance was statistically evaluated and compared based on the Pareto optimal solutions from 20 experiments by evolutionary algorithms. The false positive rate was lower (pPareto optimization process can effectively help in fine-tuning and redesigning polyp detection algorithms.

  4. Fronts under arrest: Nonlocal boundary dynamics in biology.

    Science.gov (United States)

    McCalla, Scott G; von Brecht, James H

    2016-12-01

    We introduce a minimal geometric partial differential equation framework to understand pattern formation from interacting, counterpropagating fronts. Our approach concentrates on the interfaces between different states in a system, and relies on both nonlocal interactions and mean-curvature flow to track their evolution. As an illustration, we use this approach to describe a phenomenon in bacterial colony formation wherein sibling colonies can arrest each other's growth. This arrested motion leads to static separations between healthy, growing colonies. As our minimal model faithfully recovers the geometry of these competing colonies, it captures and elucidates the key leading-order mechanisms responsible for such patterned growth.

  5. Delamination behaviour of GdBCO coated conductor tapes under transverse tension

    Energy Technology Data Exchange (ETDEWEB)

    Gorospe, A. [Department of Mechanical Design Engineering, Andong National University, Andong 760-749 (Korea, Republic of); Department of Engineering, Aurora State College of Technology, Baler 3200 (Philippines); Nisay, A. [Department of Mechanical Design Engineering, Andong National University, Andong 760-749 (Korea, Republic of); Dizon, J.R. [Department of Mechanical Design Engineering, Andong National University, Andong 760-749 (Korea, Republic of); College of Engineering and Architecture, Bataan Peninsula State University, Balanga 2100 (Philippines); Shin, H.S., E-mail: hsshin@andong.ac.kr [Department of Mechanical Design Engineering, Andong National University, Andong 760-749 (Korea, Republic of)

    2013-11-15

    Highlights: •Installation of a test frame which gives precisely aligned transverse load. •Investigation of I{sub c} degradation behaviour depending on the type of sample delamination. •Inhomogeneity of the CC tapes caused large variation on delamination strength. •SEM and EDS analysis of delamination sites under transverse loading. -- Abstract: The electromechanical property behaviour of 2G coated conductor (CC) tapes fabricated by multi-layer deposition process both in the in-plane and transverse direction should be understood. The CC tapes are used in the fabrication of epoxy resin-impregnated coils. In such case, the Lorentz force due to the high magnetic field applied as well as the thermal stress due to the difference in coefficient of thermal expansion (CTE) among constituent layers during cooling to cryogenic temperature will induce transversely applied load to the surface of CC tapes in coils. Hence, the CC tape should have a good mechanical property in the transverse direction in order to maintain its superior performance under magnetic field. In this study, a test frame which gives precisely aligned transverse load was devised. Using the fixture, the delamination behaviours including the delamination strength of the GdBCO CC tapes under transverse tensile loading were investigated. Large variation on the delamination strength of the CC tapes was recorded and might have resulted from the slit edge effect and the inhomogeneity of the CC tapes. The I{sub c} degradation behaviour under transverse load was related to the location where delamination occurred in the sample.

  6. Detection of Delamination in Composite Beams Using Broadband Acoustic Emission Signatures

    Science.gov (United States)

    Okafor, A. C.; Chandrashekhara, K.; Jiang, Y. P.

    1996-01-01

    Delamination in composite structure may be caused by imperfections introduced during the manufacturing process or by impact loads by foreign objects during the operational life. There are some nondestructive evaluation methods to detect delamination in composite structures such as x-radiography, ultrasonic testing, and thermal/infrared inspection. These methods are expensive and hard to use for on line detection. Acoustic emission testing can monitor the material under test even under the presence of noise generated under load. It has been used extensively in proof-testing of fiberglass pressure vessels and beams. In the present work, experimental studies are conducted to investigate the use of broadband acoustic emission signatures to detect delaminations in composite beams. Glass/epoxy beam specimens with full width, prescribed delamination sizes of 2 inches and 4 inches are investigated. The prescribed delamination is produced by inserting Teflon film between laminae during the fabrication of composite laminate. The objectives of this research is to develop a method for predicting delamination size and location in laminated composite beams by combining smart materials concept and broadband AE analysis techniques. More specifically, a piezoceramic (PZT) patch is bonded on the surface of composite beams and used as a pulser. The piezoceramic patch simulates the AE wave source as a 3 cycles, 50KHz, burst sine wave. One broadband AE sensor is fixed near the PZT patch to measure the AE wave near the AE source. A second broadband AE sensor, which is used as a receiver, is scanned along the composite beams at 0.25 inch step to measure propagation of AE wave along the composite beams. The acquired AE waveform is digitized and processed. Signal strength, signal energy, cross-correlation of AE waveforms, and tracking of specific cycle of AE waveforms are used to detect delamination size and location.

  7. A Test for Characterizing Delamination Migration in Carbon/Epoxy Tape Laminates

    Science.gov (United States)

    Ratcliffe, James G.; Czabaj, Michael W.; O'Brien, Thomas K.

    2013-01-01

    A new test method is presented for the purpose of investigating migration of a delamination between neighboring ply interfaces in fiber-reinforced, polymer matrix tape laminates. The test is a single cantilever beam configuration consisting of a cross-ply laminate with a polytetrafluoroethylene insert implanted at the mid-plane and spanning part way along the length of the specimen. The insert is located between a 0- degree ply (specimen length direction) and a stack of four 90-degree plies (specimen width direction). The specimen is clamped at both ends onto a rigid baseplate and is loaded on its upper surface via a piano hinge. Tests were conducted with the load-application point located on the intact portion of the specimen in order to initiate delamination growth onset followed by migration of the delamination to a neighboring 90/0 ply interface by kinking through the 90-degree ply stack. Varying this position was found to affect the distance relative to the load-application point at which migration initiated. In each specimen, migration initiated by a gradual transition of the delamination at the 0/90 interface into the 90-degree ply stack. In contrast, transition of the kinked crack into the 90/0 interface was sudden. Fractography of the specimens indicated that delamination prior to migration was generally mixed mode-I/II. Inspection of the kink surface revealed mode-I fracture. In general, use of this test allows for the observation of the growth of a delamination followed by migration of the delamination to another ply interface, and should thus provide a means for validating analyses aimed at simulating migration.

  8. Cyclic delamination behavior of plasma-sprayed hydroxyapatite coating on Ti-6Al-4V substrates in simulated body fluid.

    Science.gov (United States)

    Otsuka, Yuichi; Kawaguchi, Hayato; Mutoh, Yoshiharu

    2016-10-01

    This study aimed to clarify the effect of a simulated body fluid (SBF) on the cyclic delamination behavior of a plasma-sprayed hydroxapatite (HAp) coating. A HAp coating is deposited on the surfaces of surgical metallic materials in order to enhance the bond between human bone and such surfaces. However, the HAp coating is susceptible to delamination by cyclic loading from the patient's gait. Although hip joints are subjected to both positive and negative moments, only the effects of tensile bending stresses on vertical crack propagation behavior have been investigated. Thus, the cyclic delamination behavior of a HAp coating was observed at the stress ratio R=-1 in order to determine the effects of tensile/compressive loading on the delamination behavior. The delamination growth rate increased with SBF immersion, which decreased the delamination life. Raman spectroscopy analysis revealed that the selective phase dissolution in the HAp coating was promoted at interfaces. Finite element analysis revealed that the energy release rate Gmax showed a positive value even in cases with compressive loading, which is a driving force for the delamination of a HAp coating. A prediction model for the delamination growth life was developed that combines a fracture mechanics parameter with the assumed stress-dependent dissolution rate. The predicted delamination life matched the experimental data well in cases of lower stress amplitudes with SBF. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. New Front End Technology

    Energy Technology Data Exchange (ETDEWEB)

    Pennington, D; Jovanovic, I; Comaskey, B J

    2001-02-01

    The next generation of Petawatt class lasers will require the development of new laser technology. Optical parametric chirped pulse amplification (OPCPA) holds a potential to increase the peak power level to >10 PW with existing grating technology through ultrashort pulses. Furthermore, by utilizing a new type of front-end system based on optical parametric amplification, pulses can be produced with substantially higher contrast than with Ti:sapphire regenerative amplifier technology. We performed extensive study of OPCPA using a single crystal-based OPA. We developed a replacement for Ti:sapphire regenerative amplifier for high peak power lasers based on OPCPA, with an output of 30 mJ, at 10 Hz repetition rate and 16.5 nm spectral bandwidth. We developed a 3D numerical model for OPCPA and we performed a theoretical study of influences of pump laser beam quality on optical parametric amplification. Our results indicate that OPCPA represents a valid replacement for Ti:sapphire in the front end of high energy short pulse lasers.

  10. Methods for Assessing Curvature and Interaction in Mixture Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Piepel, Gregory F.(BATTELLE (PACIFIC NW LAB)); Hicks, Ruel D.(ASSOC WESTERN UNIVERSITY); Szychowski, Jeffrey M.(ASSOC WESTERN UNIVERSITY); Loeppky, Jason L.(ASSOC WESTERN UNIVERSITY)

    2002-05-01

    The terms curvature and interaction traditionally are not defined or used in the context of mixture experiments because curvature and interaction effects are partially confounded due to the mixture constrain that the component proportions sum to 1.

  11. Photoevaporation Flows in Blister HII Regions: I. Smooth Ionization Fronts and Application to the Orion Nebula

    CERN Document Server

    Henney, W J; Garcia-Diaz, M T; Garcia-Diaz, Ma. T.

    2005-01-01

    We present hydrodynamical simulations of the photoevaporation of a cloud with large-scale density gradients, giving rise to an ionized, photoevaporation flow. The flow is found to be approximately steady during the large part of its evolution, during which it can resemble a "champagne flow" or a "globule flow" depending on the curvature of the ionization front. The distance from source to ionization front and the front curvature uniquely determine the structure of the flow, with the curvature depending on the steepness of the lateral density gradient in the neutral cloud. We compare these simulations with both new and existing observations of the Orion nebula and find that a model with a mildly convex ionization front can reproduce the profiles of emission measure, electron density, and mean line velocity for a variety of emitting ions on scales of 10^{17} to 10^{18} cm. The principal failure of our model is that we cannot explain the large observed widths of the [O I] 6300 Angstrom line that forms at the ion...

  12. From the front

    Energy Technology Data Exchange (ETDEWEB)

    Price, Stephen [Los Alamos National Laboratory

    2009-01-01

    The causes of recent dynamic thinning of Greenland's outlet glaciers have been debated. Realistic simulations suggest that changes at the marine fronts of these glaciers are to blame, implying that dynamic thinning will cease once the glaciers retreat to higher ground. For the last decade, many outlet glaciers in Greenland that terminate in the ocean have accelerated, thinned, and retreated. To explain these dynamic changes, two hypotheses have been discussed. Atmospheric warming has increased surface melting and may also have increased the amount of meltwater reaching the glacier bed, increasing lubrication at the base and hence the rate of glacier sliding. Alternatively, a change in the delicate balance of forces where the glacier fronts meet the ocean could trigger the changes. Faezeh Nick and colleagues5 present ice-sheet modeling experiments that mimic the observations on Helheim glacier, East Greenland, and suggest that the dynamic behaviour of outlet glaciers follows from perturbations at their marine fronts. Greenland's ice sheet loses mass partly through surface melting and partly through fast flowing outlet glaciers that connect the vast plateau of inland ice with the ocean. Earlier ice sheet models have failed to reproduce the dynamic variability exhibited by ice sheets over time. It has therefore not been possible to distinguish with confidence between basal lubrication from surface meltwater and changes at the glaciers' marine fronts as causes for the observed changes on Greenland's outlet glaciers. But this distinction bears directly on future sea-level rise, the raison d'etre of much of modern-day glaciology: If the recent dynamic mass loss Greenland's outlet glaciers is linked to changing atmospheric temperatures, it may continue for as long as temperatures continue to increase. On the other hand, if the source of the dynamic mass loss is a perturbation at the ice-ocean boundary, these glaciers will lose contact with

  13. Laser triangulation measurements of scoliotic spine curvatures.

    Science.gov (United States)

    Čelan, Dušan; Jesenšek Papež, Breda; Poredoš, Primož; Možina, Janez

    2015-01-01

    The main purpose of this research was to develop a new method for differentiating between scoliotic and healthy subjects by analysing the curvatures of their spines in the cranio-caudal view. The study included 247 subjects with physiological curvatures of the spine and 28 subjects with clinically confirmed scoliosis. The curvature of the spine was determined by a computer analysis of the surface of the back, measured with a non-invasive, 3D, laser-triangulation system. The determined spinal curve was represented in the transversal plane, which is perpendicular to the line segment that was defined by the initial point and the end point of the spinal curve. This was achieved using a rotation matrix. The distances between the extreme points in the antero-posterior (AP) and left-right (LR) views were calculated in relation to the length of the spine as well as the quotient of these two values LR/AP. All the measured parameters were compared between the scoliotic and control groups using the Student's t-Test in case of normal data and Kruskal-Wallis test in case of non-normal data. Besides, a comprehensive diagram representing the distances between the extreme points in the AP and LR views was introduced, which clearly demonstrated the direction and the size of the thoracic and lumbar spinal curvatures for each individual subject. While the distances between the extreme points of the spine in the AP view were found to differ only slightly between the groups (p = 0.1), the distances between the LR extreme points were found to be significantly greater in the scoliosis group, compared to the control group (p < 0.001). The quotient LR/AP was statistically significantly different in both groups (p < 0.001). The main innovation of the presented method is the ability to differentiate a scoliotic subject from a healthy subject by assessing the curvature of the spine in the cranio-caudal view. Therefore, the proposed method could be useful for human posture

  14. Exact and Approximate Quadratures for Curvature Tensor Estimation

    OpenAIRE

    Langer, Torsten; Belyaev, Alexander; Seidel, Hans-Peter; Greiner, Günther; Hornegger, Joachim; Niemann, Heinrich; Stamminger, Marc

    2005-01-01

    Accurate estimations of geometric properties of a surface from its discrete approximation are important for many computer graphics and geometric modeling applications. In this paper, we derive exact quadrature formulae for mean curvature, Gaussian curvature, and the Taubin integral representation of the curvature tensor. The exact quadratures are then used to obtain reliable estimates of the curvature tensor of a smooth surface approximated by a dense triangle me...

  15. Preliminary study on occurrence of composite material delamination processed by abrasive water jet cutting

    Directory of Open Access Journals (Sweden)

    Popan Ioan Alexandru

    2017-01-01

    Full Text Available The paper presents a preliminary experimental study on processing composite materials (CFRP using abrasive water jet cutting (AWJC process, analysing the possibilities of occurrence of material delamination. AWJC is a proper solution for cutting CFRP because of reduced interface temperature, high flexibility, low mechanical loading and reduced cutting forces. Cutting CFRP using AWJC involves several challenges like material delamination due to the high velocity impact of the jet. To understand the delamination, three experimental tests were made: in the first test the cutting and the drilling was made with high water pressure (350 MPa, in the second test the cutting was made with high water pressure and for drilling was used low water pressure (200 MPa and in last test a pre-drilled hole was used. Within those experiments was observed the CFRP delamination appears just during the drilling, not during the cutting. By decreasing the water jet pressure, the jet energy is decreased and in this way the delamination decrease.

  16. The Effect of Delamination on Damage Path and Failure Load Prediction for Notched Composite Laminates

    Science.gov (United States)

    Satyanarayana, Arunkumar; Bogert, Philip B.; Chunchu, Prasad B.

    2007-01-01

    The influence of delamination on the progressing damage path and initial failure load in composite laminates is investigated. Results are presented from a numerical and an experimental study of center-notched tensile-loaded coupons. The numerical study includes two approaches. The first approach considers only intralaminar (fiber breakage and matrix cracking) damage modes in calculating the progression of the damage path. In the second approach, the model is extended to consider the effect of interlaminar (delamination) damage modes in addition to the intralaminar damage modes. The intralaminar damage is modeled using progressive damage analysis (PDA) methodology implemented with the VUMAT subroutine in the ABAQUS finite element code. The interlaminar damage mode has been simulated using cohesive elements in ABAQUS. In the experimental study, 2-3 specimens each of two different stacking sequences of center-notched laminates are tensile loaded. The numerical results from the two different modeling approaches are compared with each other and the experimentally observed results for both laminate types. The comparisons reveal that the second modeling approach, where the delamination damage mode is included together with the intralaminar damage modes, better simulates the experimentally observed damage modes and damage paths, which were characterized by splitting failures perpendicular to the notch tips in one or more layers. Additionally, the inclusion of the delamination mode resulted in a better prediction of the loads at which the failure took place, which were higher than those predicted by the first modeling approach which did not include delaminations.

  17. Hierarchical fiber-optic delamination detection system for carbon fiber reinforced plastic structures

    Science.gov (United States)

    Minakuchi, Shu; Banshoya, Hidehiko; Shingo, Ii; Takeda, Nobuo

    2012-10-01

    This study develops a delamination detection system by extending our previous approach for monitoring surface cracks in a large-scale composite structure. In the new system, numerous thin glass capillaries are embedded into a composite structure, and internal pressure in the built-in capillary sensors, based on comparative vacuum monitoring (CVM), is maintained as a vacuum. When delamination is induced, the capillary sensors located within the delaminated area are breached, and atmospheric air flows into the capillaries. The consequent pressure change within the capillaries is then converted into axial strain in a surface-mounted optical fiber through a transducing mechanism, which is connected to the capillaries. By monitoring the strain distribution along the optical fiber, it is possible to identify a transducing mechanism in which the pressure change occurred and thus to specify the location of the delamination. This study begins by establishing a novel sensor embedding/extracting method. The airflow characteristic in the capillary sensors is then comprehensively evaluated, determining the basic performance of the new system. The proposed detection technique is validated by taking a step-by-step approach, and finally the hierarchical fiber-optic delamination detection system is demonstrated. A further advance to be combined with a self-healing concept is also discussed.

  18. In situ infrared spectroscopic study of cubic boron nitride thin film delamination

    Institute of Scientific and Technical Information of China (English)

    Yang Hang-Sheng; Zhang Jian-Ying; Nie An-Min; Zhang Xiao-Bin

    2008-01-01

    This paper investigates the procedure of cubic boron nitride(cBN)thin film delamination by Fourier-transform infrared(IR)spectroscopy.It finds that the apparent IR absorption peak area near 1380 cm-1 and 1073 cm-1 attributed to the B-N stretching vibration of sp2-bonded BN and the transverse optical phonon of cBN,respectively,increased up to 195% and 175% of the original peak area after film delamination induced compressive stress relaxation.The increase of IR absorption of sp2-bonded BN is found to be non-linear and hysteretic to film delamination,which suggests that the relaxation of the turbostratic BN(tBN)layer from the compressed condition is also hysteretic to film delamination.Moreover,cross-sectional transmission electron microscopic observations revealed that cBN film delamination is possible from near the aBN(amorphons BN)/tBN interface at least for films prepared by plasma-enhanced chemical vapour deposition.

  19. Collineations of the curvature tensor in general relativity

    Indian Academy of Sciences (India)

    Rishi Kumar Tiwari

    2005-07-01

    Curvature collineations for the curvature tensor, constructed from a fundamental Bianchi Type-V metric, are studied. We are concerned with a symmetry property of space-time which is called curvature collineation, and we briefly discuss the physical and kinematical properties of the models.

  20. Self-Dual Manifolds with Positive Ricci Curvature

    OpenAIRE

    Lebrun, Claude; Nayatani, Shin; Nitta, Takashi

    1994-01-01

    We prove that the connected sums CP_2 # CP_2 and CP_2 # CP_2 # CP_2 admit self-dual metrics with positive Ricci curvature. Moreover, every self-dual metric of positive scalar curvature on CP_2 # CP_2 is conformal to a metric with positive Ricci curvature.

  1. On a curvature-statistics theorem

    Energy Technology Data Exchange (ETDEWEB)

    Calixto, M [Departamento de Matematica Aplicada y Estadistica, Universidad Politecnica de Cartagena, Paseo Alfonso XIII 56, 30203 Cartagena (Spain); Aldaya, V [Instituto de Astrofisica de Andalucia, Apartado Postal 3004, 18080 Granada (Spain)], E-mail: Manuel.Calixto@upct.es

    2008-08-15

    The spin-statistics theorem in quantum field theory relates the spin of a particle to the statistics obeyed by that particle. Here we investigate an interesting correspondence or connection between curvature ({kappa} = {+-}1) and quantum statistics (Fermi-Dirac and Bose-Einstein, respectively). The interrelation between both concepts is established through vacuum coherent configurations of zero modes in quantum field theory on the compact O(3) and noncompact O(2; 1) (spatial) isometry subgroups of de Sitter and Anti de Sitter spaces, respectively. The high frequency limit, is retrieved as a (zero curvature) group contraction to the Newton-Hooke (harmonic oscillator) group. We also make some comments on the physical significance of the vacuum energy density and the cosmological constant problem.

  2. Discrete Curvatures and Discrete Minimal Surfaces

    KAUST Repository

    Sun, Xiang

    2012-06-01

    This thesis presents an overview of some approaches to compute Gaussian and mean curvature on discrete surfaces and discusses discrete minimal surfaces. The variety of applications of differential geometry in visualization and shape design leads to great interest in studying discrete surfaces. With the rich smooth surface theory in hand, one would hope that this elegant theory can still be applied to the discrete counter part. Such a generalization, however, is not always successful. While discrete surfaces have the advantage of being finite dimensional, thus easier to treat, their geometric properties such as curvatures are not well defined in the classical sense. Furthermore, the powerful calculus tool can hardly be applied. The methods in this thesis, including angular defect formula, cotangent formula, parallel meshes, relative geometry etc. are approaches based on offset meshes or generalized offset meshes. As an important application, we discuss discrete minimal surfaces and discrete Koenigs meshes.

  3. Scalar Curvature for the Noncommutative Two Torus

    CERN Document Server

    Fathizadeh, Farzad

    2011-01-01

    We give a local expression for the {\\it scalar curvature} of the noncommutative two torus $ A_{\\theta} = C(\\mathbb{T}_{\\theta}^2)$ equipped with an arbitrary translation invariant complex structure and Weyl factor. This is achieved by evaluating the value of the (analytic continuation of the) {\\it spectral zeta functional} $\\zeta_a(s): = \\text{Trace}(a \\triangle^{-s})$ at $s=0$ as a linear functional in $a \\in C^{\\infty}(\\mathbb{T}_{\\theta}^2)$. A new, purely noncommutative, feature here is the appearance of the {\\it modular automorphism group} from the theory of type III factors and quantum statistical mechanics in the final formula for the curvature. This formula coincides with the formula that was recently obtained independently by Connes and Moscovici in their recent paper.

  4. Space-time curvature and cosmology

    Science.gov (United States)

    Nurgaliev, I. S.; Ponomarev, V. N.

    1982-10-01

    The possibility is considered of obtaining a steady-state cosmological solution in the framework of the Einstein-Cartan theory. It is found that the Einstein-Cartan equations without the cosmological constant admit a solution in the form of the static de Sitter metric for a specific value of the spin-spin gravitational interaction constant, whose introduction is required by gauge theory. It is shown that the steady-state solution might serve as a model for the pre-Friedmann stage of the expansion of the universe, when the spin-curvature interaction was comparable to the interaction between space-time curvature and energy-momentum. A value of about 10 to the -20th is obtained for the spin-spin interaction constant in the case where the de Sitter stage occurs at quantum densities (10 to the 94th g/cu cm).

  5. Effect of intrinsic curvature on semiflexible polymers

    Science.gov (United States)

    Ghosh, Surya K.; Singh, Kulveer; Sain, Anirban

    2009-11-01

    Recently many important biopolymers have been found to possess intrinsic curvature. Tubulin protofilaments in animal cells, FtsZ filaments in bacteria and double stranded DNA are examples. We examine how intrinsic curvature influences the conformational statistics of such polymers. We give exact results for the tangent-tangent spatial correlation function C(r)=⟨t̂(s).t̂(s+r)⟩ , both in two and three dimensions. Contrary to expectation, C(r) does not show any oscillatory behavior, rather decays exponentially and the effective persistence length has strong length dependence for short polymers. We also compute the distribution function P(R) of the end to end distance R and show how curved chains can be distinguished from wormlike chains using loop formation probability.

  6. Measuring Intrinsic Curvature of Space with Electromagnetism

    Science.gov (United States)

    Mabin, Mason; Becker, Maria; Batelaan, Herman

    2016-10-01

    The concept of curved space is not readily observable in everyday life. The educational movie "Sphereland" attempts to illuminate the idea. The main character, a hexagon, has to go to great lengths to prove that her world is in fact curved. We present an experiment that demonstrates a new way to determine if a two-dimensional surface, the 2-sphere, is curved. The behavior of an electric field, placed on a spherical surface, is shown to be related to the intrinsic Gaussian curvature. This approach allows students to gain some understanding of Einstein's theory of general relativity, which relates the curvature of spacetime to the presence of mass and energy. Additionally, an opportunity is provided to investigate the dimensionality of Gauss's law.

  7. Scaling up the curvature of mammalian metabolism

    Directory of Open Access Journals (Sweden)

    Juan eBueno

    2014-10-01

    Full Text Available A curvilinear relationship between mammalian metabolic rate and body size on a log-log scale has been adopted in lieu of thelongstanding concept of a 3/4 allometric relationship (Kolokotrones et al. 2010. The central tenet of Metabolic Ecology (ME states that metabolism at the individual level scales-up to drive the ecology of populations, communities and ecosystems. If this tenet is correct, the curvature of metabolism should be perceived in other ecological traits. By analyzing the size scaling allometry of eight different mammalian traits including basal and field metabolic rate, offspring biomass production, ingestion rate, costs of locomotion, life span, population growth rate and population density we show that the curvature affects most ecological rates and

  8. On the curvature of the real amoeba

    CERN Document Server

    Passare, Mikael

    2011-01-01

    For a real smooth algebraic curve $A \\subset (\\mathhbb{C}^*)^2$, the amoeba $\\mathcal{A} \\subset \\mathbb{R}^2$ is the image of $A$ under the map Log : $(x,y) \\mapsto (\\log |x|, \\log | y |)$. We describe an universal bound for the total curvature of the real amoeba $\\mathcal{A}_{\\mathbb{R} A}$ and we prove that this bound is reached if and only if the curve $A$ is a simple Harnack curve in the sense of Mikhalkin.

  9. Curvature Could Give Fish Fins Their Strength

    National Research Council Canada - National Science Library

    2017-01-01

    ... maneuverable is by having the ability to generate varying amounts of force on the water when flapping a fin,” said Shreyas Mandre, an assistant professor in Brown’s School of Engineering and a co-author of the research. “We think that fish modulate curvature at the base of the fin to make it stiffer or softer, which alters the force they gene...

  10. Transformation optics, curvature and beyond (Conference Presentation)

    Science.gov (United States)

    McCall, Martin W.

    2016-04-01

    Although the transformation algorithm is very well established and implemented, some intriguing questions remain unanswered. 1) In what precise mathematical sense is the transformation optics algorithm `exact'? The invariance of Maxwell's equations is well understood, but in what sense does the same principle not apply to acoustics (say)? 2) Even if the fields are transformed in a way that apparently mimic vacuum perfectly, it is easy to construct very simple examples where the impedance of the transformed medium is no longer isotropic and homogeneous. This would seem to imply a fundamental shortcoming in any claim that electromagnetic cloaking has been reduced to technology. 3) Transformations are known to exist that introduce a discrepancy between the Poynting vector and the wave-vector. Does this distinction carry any physical significance? We have worked extensively on understanding a commonality between transformation theories that operates at the level of rays - being interpreted as geodesics of an appropriate manifold. At this level we now understand that the *key* problem underlying all attempts to unify the transformational approach to disparate areas of physics is how to relate the transformation of the base metric (be it Euclidean for spatial transformation optics, or Minkowskian for spacetime transformation optics) to the medium parameters of a given physical domain (e.g. constitutive parameters for electromagnetism, bulk modulus and mass density for acoustics, diffusion constant and number density for diffusion physics). Another misconception we will seek to address is the notion of the relationship between transformation optics and curvature. Many have indicated that transformation optics evinces similarities with Einstein's curvature of spacetime. Here we will show emphatically that transformation optics cannot induce curvature. Inducing curvature in an electromagnetic medium requires the equivalent of a gravitational source. We will propose a scheme

  11. Menger curvature and rectifiability in metric spaces

    OpenAIRE

    2012-01-01

    We show that for any metric space $X$ the condition \\[ \\int_X\\int_X\\int_X c(z_1,z_2,z_3)^2\\, d\\Hm z_1\\, d\\Hm z_2\\, d\\Hm z_3 < \\infty, \\] where $c(z_1,z_2,z_3)$ is the Menger curvature of the triple $(z_1,z_2,z_3)$, guarantees that $X$ is rectifiable.

  12. Gravitational curvature an introduction to Einstein's theory

    CERN Document Server

    Frankel, Theodore

    2011-01-01

    This classic text and reference monograph applies modern differential geometry to general relativity. A brief mathematical introduction to gravitational curvature, it emphasizes the subject's geometric essence, replacing the often-tedious analytical computations with geometric arguments. Clearly presented and physically motivated derivations express the deflection of light, Schwarzchild's exterior and interior solutions, and the Oppenheimer-Volkoff equations. A perfect choice for advanced students of mathematics, this volume will also appeal to mathematicians interested in physics. It stresses

  13. Curvature of spacetime: A simple student activity

    Science.gov (United States)

    Wood, Monika; Smith, Warren; Jackson, Matthew

    2016-12-01

    The following is a description of an inexpensive and simple student experiment for measuring the differences between the three types of spacetime topology—Euclidean (flat), Riemann (spherical), and Lobachevskian (saddle) curvatures. It makes use of commonly available tools and materials, and requires only a small amount of construction. The experiment applies to astronomical topics such as gravity, spacetime, general relativity, as well as geometry and mathematics.

  14. Ultrafast Drop Movements Arising from Curvature Gradient

    CERN Document Server

    Lv, Cunjing; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Zheng, Quanshui

    2011-01-01

    We report experimental observation of a kind of fast spontaneous movements of water drops on surfaces of cones with diameters from 0.1 to 1.5 mm. The observed maximum speed (0.22 m/s) under ambient conditions were at least two orders of magnitude higher than that resulting from any known single spontaneous movement mechanism, for example, Marangoni effect due to gradient of surface tension. We trapped even higher spontaneous movement speeds (up to 125 m/s) in virtual experiments for drops on nanoscale cones by using molecular dynamics simulations. The underlying mechanism is found to be universally effective - drops on any surface either hydrophilic or hydrophobic with varying mean curvature are subject to driving forces toward the gradient direction of the mean curvature. The larger the mean curvature of the surface and the lower the contact angle of the liquid are, the stronger the driving force will be. This discovery can lead to more effective techniques for transporting droplets.

  15. Intrinsically disordered proteins drive membrane curvature

    Science.gov (United States)

    Busch, David J.; Houser, Justin R.; Hayden, Carl C.; Sherman, Michael B.; Lafer, Eileen M.; Stachowiak, Jeanne C.

    2015-07-01

    Assembly of highly curved membrane structures is essential to cellular physiology. The prevailing view has been that proteins with curvature-promoting structural motifs, such as wedge-like amphipathic helices and crescent-shaped BAR domains, are required for bending membranes. Here we report that intrinsically disordered domains of the endocytic adaptor proteins, Epsin1 and AP180 are highly potent drivers of membrane curvature. This result is unexpected since intrinsically disordered domains lack a well-defined three-dimensional structure. However, in vitro measurements of membrane curvature and protein diffusivity demonstrate that the large hydrodynamic radii of these domains generate steric pressure that drives membrane bending. When disordered adaptor domains are expressed as transmembrane cargo in mammalian cells, they are excluded from clathrin-coated pits. We propose that a balance of steric pressure on the two surfaces of the membrane drives this exclusion. These results provide quantitative evidence for the influence of steric pressure on the content and assembly of curved cellular membrane structures.

  16. Biological Activity at Oceanic Fronts.

    Science.gov (United States)

    1985-12-01

    and/or phytoplankton concentrations between the adjacent areas. High particle concentrations are associated with a front east of the Galapagos Islands...yeTlowfin, albacore, and bluefin tunas, mackerel, salmon, and some whales (Uda, 1938, 1952,. 9.=, 1973; Uda and Ishino, 1958). Behavioral responses of...Marine mammals ,Gaskin, 1976) also utilize tidal fronts. Minke whales were observed to feed on herring or capelin collected in fronts and fin whales fed

  17. Characterization of Delaminations and Transverse Matrix Cracks in Composite Laminates Using Multiple-Angle Ultrasonic Inspection

    Science.gov (United States)

    Johnston, Patrick H.; Appleget, Chelsea D.; Odarczenko, Michael T.

    2012-01-01

    Delaminations and transverse matrix cracks often appear concurrently in composite laminates. Normal-incidence ultrasound is excellent at detecting delaminations, but is not optimum for matrix cracks. Non-normal incidence, or polar backscattering, has been shown to optimally detect matrix cracks oriented perpendicular to the ultrasonic plane of incidence. In this work, a series of six composite laminates containing slots were loaded in tension to achieve various levels of delamination and ply cracking. Ultrasonic backscattering was measured over a range of incident polar and azimuthal angles, in order to characterize the relative degree of damage of the two types. Sweptpolar- angle measurements were taken with a curved phased array, as a step toward an array-based approach to simultaneous measurement of combined flaws.

  18. A hybrid method based upon nonlinear Lamb wave response for locating a delamination in composite laminates.

    Science.gov (United States)

    Yelve, Nitesh P; Mitra, Mira; Mujumdar, P M; Ramadas, C

    2016-08-01

    A new hybrid method based upon nonlinear Lamb wave response in time and frequency domains is introduced to locate a delamination in composite laminates. In Lamb wave based nonlinear method, the presence of damage is shown by the appearance of higher harmonics in the Lamb wave response. The proposed method not only uses this spectral information but also the corresponding temporal response data, for locating the delamination. Thus, the method is termed as a hybrid method. The paper includes formulation of the method and its application to locate a Barely Visible Impact Damage (BVID) induced delamination in a Carbon Fiber Reinforced Polymer (CFRP) laminate. The method gives the damage location fairly well. It is a baseline free method, as it does not need data from the pristine specimen.

  19. A Damage Model for the Simulation of Delamination in Advanced Composites under Variable-Mode Loading

    Science.gov (United States)

    Turon, A.; Camanho, P. P.; Costa, J.; Davila, C. G.

    2006-01-01

    A thermodynamically consistent damage model is proposed for the simulation of progressive delamination in composite materials under variable-mode ratio. The model is formulated in the context of Damage Mechanics. A novel constitutive equation is developed to model the initiation and propagation of delamination. A delamination initiation criterion is proposed to assure that the formulation can account for changes in the loading mode in a thermodynamically consistent way. The formulation accounts for crack closure effects to avoid interfacial penetration of two adjacent layers after complete decohesion. The model is implemented in a finite element formulation, and the numerical predictions are compared with experimental results obtained in both composite test specimens and structural components.

  20. Dynamic behavior of a rotating delaminated composite beam including rotary inertia and shear deformation effects

    Directory of Open Access Journals (Sweden)

    Ramazan-Ali Jafari-Talookolaei

    2015-09-01

    Full Text Available A finite element (FE model is developed to study the free vibration of a rotating laminated composite beam with a single delamination. The rotary inertia and shear deformation effects, as well as the bending–extension, bending–twist and extension–twist coupling terms are taken into account in the FE model. Comparison between the numerical results of the present model and the results published in the literature verifies the validity of the present model. Furthermore, the effects of various parameters, such as delamination size and location, fiber orientation, hub radius, material anisotropy and rotating speed, on the vibration of the beam are studied in detail. These results provide useful information in the study of the free vibration of rotating delaminated composite beams.

  1. On a multiscale strategy and its optimization for the simulation of combined delamination and buckling

    CERN Document Server

    Saavedra, Karin; Gosselet, Pierre; 10.1002/nme.4305

    2012-01-01

    This paper investigates a computational strategy for studying the interactions between multiple through-the-width delaminations and global or local buckling in composite laminates taking into account possible contact between the delaminated surfaces. In order to achieve an accurate prediction of the quasi-static response, a very refined discretization of the structure is required, leading to the resolution of very large and highly nonlinear numerical problems. In this paper, a nonlinear finite element formulation along with a parallel iterative scheme based on a multiscale domain decomposition are used for the computation of 3D mesoscale models. Previous works by the authors already dealt with the simulation of multiscale delamination assuming small perturbations. This paper presents the formulation used to include geometric nonlinearities into this existing multiscale framework and discusses the adaptations that need to be made to the iterative process in order to ensure the rapid convergence and the scalabi...

  2. Optical Evaluation on Delamination Buckling of Composite Laminate with Impact Damage

    Directory of Open Access Journals (Sweden)

    J. T. Ruan

    2014-01-01

    Full Text Available The delamination buckling and growth behaviors of a cross-ply composite laminate with damage induced by low velocity impact are investigated optically using three-dimensional digital image correlation (3D-DIC method. For the 3D deformation measurement, the 3D-DIC setup comprised of two CCD cameras was adopted. The rectangle specimen was impacted under the impact energy of 7.0 J using a drop-weight testing machine, and the impact damage was detected by means of X-ray nondestructive evaluation (NDE technique. The 3D deformation field measured with the optical system clearly reveals that the delamination buckling characteristic of the specimen mainly appears local deformation mode under compression after impact test. Moreover, the behavior of delamination growth evaluated by the 3D-DIC optical method reasonably agrees with the NDE observed damage result after compression.

  3. Numerical optimization approach to modelling delamination and buckling of geometrically constrained structures.

    Science.gov (United States)

    Mullineux, G; Hicks, B J; Berry, C

    2012-04-28

    Understanding what happens in terms of delamination during buckling of laminate materials is of importance across a range of engineering sectors. Normally concern is that the strength of the material is not significantly impaired. Carton-board is a material with a laminate structure and, in the initial creation of carton nets, the board is creased in order to weaken the structure. This means that when the carton is eventually folded into its three-dimensional form, correct folding occurs along the weakened crease lines. Understanding what happens during creasing and folding is made difficult by the nonlinear nature of the material properties. This paper considers a simplified approach which extends the idea of minimizing internal energy so that the effects of delamination can be handled. This allows a simulation which reproduces the form of buckling-delamination observed in practice and the form of the torque-rotation relation.

  4. Mechanisms governing the interfacial delamination of thermal barrier coating system with double ceramic layers

    Science.gov (United States)

    Xu, Rong; Fan, Xueling; Wang, T. J.

    2016-05-01

    A systematic study of factors affecting the interfacial delamination of thermal barrier coating system (TBCs) with double ceramic layers (DCL) is presented. Crack driving forces for delaminations at two weak interfaces are examined. The results show that a thicker outermost ceramic layer can induce dramatic increase in crack driving force and make the interface between two ceramic coatings become more prone to delamination. The behavior is shown to be more prominent in TBCs with stiffer outmost coating. The thickness ratio of two ceramic layers is an important parameter for controlling the failure mechanisms and determining the lifetime of DCL TBCs under inservice condition. By accounting for the influences of thickness ratio of two ceramic layers and interfacial fracture toughnesses of two involved interfaces, the fracture mechanism map of DCL TBCs has been constructed, in which different failure mechanisms are identified. The results quanlitatively agree with the aviliable experimental data.

  5. Non-destructive evaluation of delamination growth in glass fiber composites using optical coherence tomography

    Science.gov (United States)

    Liu, Ping; Groves, Roger M.; Benedictus, Rinze

    2014-03-01

    Based on low coherence interferometry, a robust optical coherence tomography (OCT) system has been built. The system was used to monitor the growth of a delamination between the middle layers of a glass fiber composite under a static loading. Firstly specimens of the material used for the spar webs in wind turbines were prepared with an interlaminar crack from free edges. Then they were statically loaded by a customized tensile test stage to extend the delamination length and simultaneously scanned by the OCT system. To process the acquired data, an optimized signal processing algorithm was developed. The cross-sectional images clearly show the microstructure and the crack within the specimen. The 3D crack profiles show the application of OCT to determine the evolution of the crack structure inside the composite material during the propagation of the delamination, for the first time to the best of our knowledge.

  6. Photoionization effects in ionization fronts

    Energy Technology Data Exchange (ETDEWEB)

    Arrayas, Manuel [Departamento de Electromagnetismo, Universidad Rey Juan Carlos, Tulipan s/n, 28933 Mostoles, Madrid (Spain); Fontelos, Marco A [Departamento de Matematicas, Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones CientIficas, C/Serrano 123, 28006 Madrid (Spain); Trueba, Jose L [Departamento de Electromagnetismo, Universidad Rey Juan Carlos, Tulipan s/n, 28933 Mostoles, Madrid (Spain)

    2006-12-21

    In this paper we study the effects of photoionization processes on the propagation of both negative and positive ionization fronts in streamer discharge. We show that negative fronts accelerate in the presence of photoionization events. The appearance and propagation of positive ionization fronts travelling with constant velocity is explained as the result of the combined effects of photoionization and electron diffusion. The photoionization range plays an important role in the selection of the velocity of the ionization front as we show in this work.

  7. Distributed mean curvature on a discrete manifold for Regge calculus

    CERN Document Server

    Conboye, Rory; Ray, Shannon

    2015-01-01

    The integrated mean curvature of a simplicial manifold is well understood in both Regge Calculus and Discrete Differential Geometry. However, a well motivated pointwise definition of curvature requires a careful choice of volume over which to uniformly distribute the local integrated curvature. We show that hybrid cells formed using both the simplicial lattice and its circumcentric dual emerge as a remarkably natural structure for the distribution of this local integrated curvature. These hybrid cells form a complete tessellation of the simplicial manifold, contain a geometric orthonormal basis, and are also shown to give a pointwise mean curvature with a natural interpretation as a fractional rate of change of the normal vector.

  8. Free-streaming radiation in cosmological models with spatial curvature

    Science.gov (United States)

    Wilson, M. L.

    1982-01-01

    The effects of spatial curvature on radiation anisotropy are examined for the standard Friedmann-Robertson-Walker model universes. The effect of curvature is found to be very important when considering fluctuations with wavelengths comparable to the horizon. It is concluded that the behavior of radiation fluctuations in models with spatial curvature is quite different from that in spatially flat models, and that models with negative curvature are most strikingly different. It is therefore necessary to take the curvature into account in careful studies of the anisotropy of the microwave background.

  9. A curvature theory for discrete surfaces based on mesh parallelity

    KAUST Repository

    Bobenko, Alexander Ivanovich

    2009-12-18

    We consider a general theory of curvatures of discrete surfaces equipped with edgewise parallel Gauss images, and where mean and Gaussian curvatures of faces are derived from the faces\\' areas and mixed areas. Remarkably these notions are capable of unifying notable previously defined classes of surfaces, such as discrete isothermic minimal surfaces and surfaces of constant mean curvature. We discuss various types of natural Gauss images, the existence of principal curvatures, constant curvature surfaces, Christoffel duality, Koenigs nets, contact element nets, s-isothermic nets, and interesting special cases such as discrete Delaunay surfaces derived from elliptic billiards. © 2009 Springer-Verlag.

  10. Coupled flexural-longitudinal vibration of delaminated composite beams with local stability analysis

    Science.gov (United States)

    Szekrényes, András

    2014-09-01

    A novel analytical model is developed to solve the problem of free vibration of delaminated composite beams. The beam with a single delamination was modelled by six equivalent single layers by establishing the kinematic continuity in the undelaminated portion of the system. In the delaminated region the layers were captured by the traditional theories. First, Timoshenko beam theory is applied to solve the problem, then by reducing the model, the corresponding Euler-Bernoulli solution is presented. Both the free and constrained models were considered. The most important aspect of the present analysis is that the beams of the delaminated region are subjected to normal forces, as well. That is the essential reason for leading to a coupled flexural-longitudinal vibration problem. It is also concluded that delamination buckling can take place if the normal force is compressive in one of the half-periods of the vibration and reaches a critical value. The problem was also investigated experimentally by modal hammer and sweep excitation tests on beams made of E-glass/polyester in order to measure the natural frequencies and mode shapes. The comparison of the analytical and experimental results indicates the importance of the independent rotations provided by Timoshenko beams over the simple beam theory. The delamination buckling of the beams was captured based on the static stability analysis in the first step. Further results show that the problem is more complex than it was thought before, e.g., some nonlinearity, time-dependent stiffness as well as parametric excitation aspects were discovered during the present analysis.

  11. Monitoring Delamination of Plasma-Sprayed Thermal Barrier Coatings by Reflectance-Enhanced Luminescence

    Science.gov (United States)

    Eldridge, Jeffrey I.; Bencic, Timothy J.

    2006-01-01

    Highly scattering plasma-sprayed thermal barrier coatings (TBCs) present a challenge for optical diagnostic methods to monitor TBC delamination because scattering attenuates light transmitted through the TBC and usually degrades contrast between attached and delaminated regions of the TBC. This paper presents a new approach where reflectance-enhanced luminescence from a luminescent sublayer incorporated along the bottom of the TBC is used to identify regions of TBC delamination. Because of the higher survival rate of luminescence reflecting off the back surface of a delaminated TBC, the strong scattering exhibited by plasma-sprayed TBCs actually accentuates contrast between attached and delaminated regions by making it more likely that multiple reflections of luminescence off the back surface occur before exiting the top surface of the TBC. A freestanding coating containing sections designed to model an attached or delaminated TBC was prepared by depositing a luminescent Eu-doped or Er-doped yttria-stabilized zirconia (YSZ) luminescent layer below a plasma-sprayed undoped YSZ layer and utilizing a NiCr backing layer to represent an attached substrate. For specimens with a Eu-doped YSZ luminescent sublayer, luminescence intensity maps showed excellent contrast between unbacked and NiCr-backed sections even at a plasma-sprayed overlayer thickness of 300 m. Discernable contrast between unbacked and NiCr-backed sections was not observed for specimens with a Er-doped YSZ luminescent sublayer because luminescence from Er impurities in the undoped YSZ layer overwhelmed luminescence originating form the Er-doped YSZ sublayer.

  12. Floating Node Method and Virtual Crack Closure Technique for Modeling Matrix Cracking-Delamination Interaction

    Science.gov (United States)

    DeCarvalho, N. V.; Chen, B. Y.; Pinho, S. T.; Baiz, P. M.; Ratcliffe, J. G.; Tay, T. E.

    2013-01-01

    A novel approach is proposed for high-fidelity modeling of progressive damage and failure in composite materials that combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. In this study, the approach is applied to the modeling of delamination migration in cross-ply tape laminates. Delamination, matrix cracking, and migration are all modeled using fracture mechanics based failure and migration criteria. The methodology proposed shows very good qualitative and quantitative agreement with experiments.

  13. Floating Node Method and Virtual Crack Closure Technique for Modeling Matrix Cracking-Delamination Migration

    Science.gov (United States)

    DeCarvalho, Nelson V.; Chen, B. Y.; Pinho, Silvestre T.; Baiz, P. M.; Ratcliffe, James G.; Tay, T. E.

    2013-01-01

    A novel approach is proposed for high-fidelity modeling of progressive damage and failure in composite materials that combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. In this study, the approach is applied to the modeling of delamination migration in cross-ply tape laminates. Delamination, matrix cracking, and migration are all modeled using fracture mechanics based failure and migration criteria. The methodology proposed shows very good qualitative and quantitative agreement with experiments.

  14. Buckling and Delamination of Ti/Cu/Si Thin Film During Annealing

    Science.gov (United States)

    Lin, Qijing; Yang, Shuming; Jing, Weixuan; Li, Changsheng; Wang, Chenying; Jiang, Zhuangde; Jiang, Kely

    2014-09-01

    In this paper, the formation of buckling and delamination of sandwiched stacking of Ti/Cu/Si thin film are investigated. The crystallization structures, the composition of the Cu/Ti thin films, and the surface morphology are measured during annealing. The results show that the solid-phase reaction between Cu and Ti occurs at the interface. Buckling is initiated in the thin film annealed at 600°C. The volume expansion promotes the buckling and further produces microcracks. With increasing volume expansion, there are cavities formed in the middle layer when the annealing temperature is up to 700°C. Finally, thin film is delaminated from the substrate.

  15. Problem of Delamination in RC Beams Strengthened by FRP with Rheological Model of Adhesive Leyer

    Science.gov (United States)

    Kula, Krzysztof; Socha, Tomasz

    2016-12-01

    This paper deals with one of the most dangerous failure modes in layered structures, namely delamination. The strengthening layer is modelled by a solid-shell finite element. The mechanical modelling of delamination onset and propagation is based upon a cohesive zone model implemented into a cohesive element located between adhesive layer and a concrete structure. The long time behavior of epoxy adhesive layer is modelled with the five-parameter rheological model. The numerical simulations are accomplished within the commercial software package Abaqus by the implementation of a user-written finite element and user-written material.

  16. On the Riemann Curvature Operators in Randers Spaces

    Science.gov (United States)

    Rafie-Rad, M.

    2013-05-01

    The Riemann curvature in Riemann-Finsler geometry can be regarded as a collection of linear operators on the tangent spaces. The algebraic properties of these operators may be linked to the geometry and the topology of the underlying space. The principal curvatures of a Finsler space (M, F) at a point x are the eigenvalues of the Riemann curvature operator at x. They are real functions κ on the slit tangent manifold TM0. A principal curvature κ(x, y) is said to be isotropic (respectively, quadratic) if κ(x, y)/F(x, y) is a function of x only (respectively, κ(x, y) is quadratic with respect to y). On the other hand, the Randers metrics are the most popular and prominent metrics in pure and applied disciplines. Here, it is proved that if a Randers metric admits an isotropic principal curvature, then F is of isotropic S-curvature. The same result is also established for F to admit a quadratic principal curvature. These results extend Shen's verbal results about Randers metrics of scalar flag curvature K = K(x) as well as those Randers metrics with quadratic Riemann curvature operator. The Riemann curvature Rik may be broken into two operators Rik and Jik. The isotropic and quadratic principal curvature are characterized in terms of the eigenvalues of R and J.

  17. Fiber Fabry-Perot interferometer for curvature sensing

    Science.gov (United States)

    Monteiro, Catarina S.; Ferreira, Marta S.; Silva, Susana O.; Kobelke, Jens; Schuster, Kay; Bierlich, Jörg; Frazão, Orlando

    2016-07-01

    A curvature sensor based on an Fabry-Perot (FP) interferometer was proposed. A capillary silica tube was fusion spliced between two single mode fibers, producing an FP cavity. Two FP sensors with different cavity lengths were developed and subjected to curvature and temperature. The FP sensor with longer cavity showed three distinct operating regions for the curvature measurement. Namely, a linear response was shown for an intermediate curvature radius range, presenting a maximum sensitivity of 68.52 pm/m-1. When subjected to temperature, the sensing head produced a similar response for different curvature radii, with a sensitivity varying from 0.84 pm/°C to 0.89 pm/°C, which resulted in a small cross-sensitivity to temperature when the FP sensor was subjected to curvature. The FP cavity with shorter length presented low sensitivity to curvature.

  18. All unitary cubic curvature gravities in D dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Sisman, Tahsin Cagri; Guellue, Ibrahim; Tekin, Bayram, E-mail: sisman@metu.edu.tr, E-mail: e075555@metu.edu.tr, E-mail: btekin@metu.edu.tr [Department of Physics, Middle East Technical University, 06531 Ankara (Turkey)

    2011-10-07

    We construct all the unitary cubic curvature gravity theories built on the contractions of the Riemann tensor in D-dimensional (anti)-de Sitter spacetimes. Our construction is based on finding the equivalent quadratic action for the general cubic curvature theory and imposing ghost and tachyon freedom, which greatly simplifies the highly complicated problem of finding the propagator of cubic curvature theories in constant curvature backgrounds. To carry out the procedure we have also classified all the unitary quadratic models. We use our general results to study the recently found cubic curvature theories using different techniques and the string generated cubic curvature gravity model. We also study the scattering in critical gravity and give its cubic curvature extensions.

  19. Fiber Fabry-Perot interferometer for curvature sensing

    Science.gov (United States)

    Monteiro, Catarina S.; Ferreira, Marta S.; Silva, Susana O.; Kobelke, Jens; Schuster, Kay; Bierlich, Jörg; Frazão, Orlando

    2016-12-01

    A curvature sensor based on an Fabry-Perot (FP) interferometer was proposed. A capillary silica tube was fusion spliced between two single mode fibers, producing an FP cavity. Two FP sensors with different cavity lengths were developed and subjected to curvature and temperature. The FP sensor with longer cavity showed three distinct operating regions for the curvature measurement. Namely, a linear response was shown for an intermediate curvature radius range, presenting a maximum sensitivity of 68.52 pm/m-1. When subjected to temperature, the sensing head produced a similar response for different curvature radii, with a sensitivity varying from 0.84 pm/°C to 0.89 pm/°C, which resulted in a small cross-sensitivity to temperature when the FP sensor was subjected to curvature. The FP cavity with shorter length presented low sensitivity to curvature.

  20. Computation of interface curvature in modelling of solidification by the method of cellular automaton

    Directory of Open Access Journals (Sweden)

    Burbelko A. A.

    2007-01-01

    Full Text Available Modelling of solidification process by the method of cellular automaton (CA requires determination of geometrical characteristics of the interface, i.e. of its direction and curvature. In previous studies the authors proposed a method to reduce the well-known effect of an artificial symmetry of the simulation results caused by the anisotropy of the CA computation grid (e.g. a preferred growth of the main dendrite arms along the grid lines or at an angle of 45° in the case of grids with square cells. The aim was achieved by application of the developed methods of computation of the transformation rate and front direction. In this study the authors examined the problem of an accuracy of the computations of an interface curvature. The obtained results show us that the error of the curvature computation introduced by some well-known methods exceeds by 100% a nominal value of this parameter. A method to estimate the accuracy of the applied solution has been proposed. Practical application of the proposed tests enables selection of a best solution, including the authors' own solutions, thus considerably improving an accuracy of the solidification modelling by the method of CA.

  1. THE INFLUENCE OF THE TOOL POINT ANGLE AND FEED RATE ON THE DELAMINATION AT DRILLING OF PRE-LAMINATED PARTICLEBOARD

    Directory of Open Access Journals (Sweden)

    Mihai ISPAS

    2015-12-01

    Full Text Available Pre-laminated particleboard is a wood based composite extensively used in the furniture industry. Drilling is the most common machining process which prepares the panels for joining using twist/helical drills in the absolute majority of cases. The point angle of the drill bit and the feed speed during drilling play a major role in gaining a good surface quality and minimizing the delamination tendency of the pre-laminated particleboard. The objective of this study was to measure and analyze the influence of the two above-mentioned factors on the processing quality, evaluated by de size of delaminations, both, at the entrance side and the exit side of the drill bit. To assess the defect, two parameters were used: the delamination factor and the effective area of delamination. The results showed that, in general, the combination of small point angle with low feed rate minimizes the delamination of pre-laminated particleboard panels at drilling.

  2. Active learning of Pareto fronts.

    Science.gov (United States)

    Campigotto, Paolo; Passerini, Andrea; Battiti, Roberto

    2014-03-01

    This paper introduces the active learning of Pareto fronts (ALP) algorithm, a novel approach to recover the Pareto front of a multiobjective optimization problem. ALP casts the identification of the Pareto front into a supervised machine learning task. This approach enables an analytical model of the Pareto front to be built. The computational effort in generating the supervised information is reduced by an active learning strategy. In particular, the model is learned from a set of informative training objective vectors. The training objective vectors are approximated Pareto-optimal vectors obtained by solving different scalarized problem instances. The experimental results show that ALP achieves an accurate Pareto front approximation with a lower computational effort than state-of-the-art estimation of distribution algorithms and widely known genetic techniques.

  3. Light Front Boson Model Propagation

    Institute of Scientific and Technical Information of China (English)

    Jorge Henrique Sales; Alfredo Takashi Suzuki

    2011-01-01

    stract The scope and aim of this work is to describe the two-body interaction mediated by a particle (either the scalar or the gauge boson) within the light-front formulation. To do this, first of all we point out the importance of propagators and Green functions in Quantum Mechanics. Then we project the covariant quantum propagator onto the light front time to get the propagator for scalar particles in these coordinates. This operator propagates the wave function from x+ = 0 to x+ > O. It corresponds to the definition of the time ordering operation in the light front time x+. We calculate the light-front Green's function for 2 interacting bosons propagating forward in x+. We also show how to write down the light front Green's function from the Feynman propagator and finally make a generalization to N bosons.

  4. Extrinsic curvature induced 2-d gravity

    CERN Document Server

    Viswanathan, K S

    1993-01-01

    Abtract: 2-dimensional fermions are coupled to extrinsic geometry of a conformally immersed surface in ${\\bf R}^3$ through gauge coupling. By integrating out the fermions, we obtain a WZNW action involving extrinsic curvature of the surface. Restricting the resulting effective action to surfaces of $h\\sqrt g=1$, an explicit form of the action invariant under Virasaro symmetry is obtained. This action is a sum of the geometric action for the Virasaro group and the light-cone action of 2-d gravity plus an interaction term. The central charges of the theory in both the left and right sectors are calculated.

  5. Variational formulas of higher order mean curvatures

    CERN Document Server

    Xu, Ling

    2011-01-01

    In this paper, we establish the first variational formula and its Euler-Lagrange equation for the total $2p$-th mean curvature functional $\\mathcal {M}_{2p}$ of a submanifold $M^n$ in a general Riemannian manifold $N^{n+m}$ for $p=0,1,...,[\\frac{n}{2}]$. As an example, we prove that closed complex submanifolds in complex projective spaces are critical points of the functional $\\mathcal {M}_{2p}$, called relatively $2p$-minimal submanifolds, for all $p$. At last, we discuss the relations between relatively $2p$-minimal submanifolds and austere submanifolds in real space forms, as well as a special variational problem.

  6. Scalar Curvature and Intrinsic Flat Convergence

    CERN Document Server

    Sormani, Christina

    2016-01-01

    Herein we present open problems and survey examples and theorems concerning sequences of Riemannian manifolds with uniform lower bounds on scalar curvature and their limit spaces. Examples of Gromov and of Ilmanen which naturally ought to have certain limit spaces do not converge with respect to smooth or Gromov-Hausdorff convergence. Thus we focus here on the notion of Intrinsic Flat convergence, developed jointly with Wenger. This notion has been applied successfully to study sequences that arise in General Relativity. Gromov has suggested it should be applied in other settings as well. We first review intrinsic flat convergence, its properties, and its compactness theorems, before presenting the applications and the open problems.

  7. Curvature and shape determination of growing bacteria

    Science.gov (United States)

    Mukhopadhyay, Ranjan; Wingreen, Ned S.

    2009-12-01

    Bacterial cells come in a variety of shapes, determined by the stress-bearing cell wall. Though many molecular details about the cell wall are known, our understanding of how a particular shape is produced during cell growth is at its infancy. Experiments on curved Escherichia coli grown in microtraps, and on naturally curved Caulobacter crescentus, reveal different modes of growth: one preserving arc length and the other preserving radius of curvature. We present a simple model for curved cell growth that relates these two growth modes to distinct but related growth rules—“hooplike growth” and “self-similar growth”—and discuss the implications for microscopic growth mechanisms.

  8. Curvature, zero modes and quantum statistics

    Energy Technology Data Exchange (ETDEWEB)

    Calixto, M [Departamento de Matematica Aplicada y EstadIstica, Universidad Politecnica de Cartagena, Paseo Alfonso XIII 56, 30203 Cartagena (Spain); Aldaya, V [Instituto de AstrofIsica de AndalucIa, Apartado Postal 3004, 18080 Granada (Spain)

    2006-08-18

    We explore an intriguing connection between the Fermi-Dirac and Bose-Einstein statistics and the thermal baths obtained from a vacuum radiation of coherent states of zero modes in a second quantized (many-particle) theory on the compact O(3) and noncompact O(2, 1) isometry subgroups of the de Sitter and anti-de Sitter spaces, respectively. The high frequency limit is retrieved as a (zero-curvature) group contraction to the Newton-Hooke (harmonic oscillator) group. We also make some comments on the vacuum energy density and the cosmological constant problem. (letter to the editor)

  9. Double curvature mirrors for linear concentrators

    Science.gov (United States)

    Lance, Tamir; Ackler, Harold; Finot, Marc

    2012-10-01

    Skyline Solar's medium concentration photovoltaic system uses quasi-parabolic mirrors and one axis tracking. Improvements in levelized cost of energy can be achieved by effective management of non-uniformity of the flux line on the panels. To reduce non uniformity of the flux line due to mirror to mirror gaps, Skyline developed a dual curvature mirror that stretches the flux line along the panel. Extensive modeling and experiments have been conducted to analyze the impact of this new design and to optimize the design.

  10. Amplification of curvature perturbations in cyclic cosmology

    Science.gov (United States)

    Zhang, Jun; Liu, Zhi-Guo; Piao, Yun-Song

    2010-12-01

    We analytically and numerically show that through the cycles with nonsingular bounce, the amplitude of curvature perturbation on a large scale will be amplified and the power spectrum will redden. In some sense, this amplification will eventually destroy the homogeneity of the background, which will lead to the ultimate end of cycles of the global universe. We argue that for the model with increasing cycles, it might be possible that a fissiparous multiverse will emerge after one or several cycles, in which the cycles will continue only at corresponding local regions.

  11. Curvature sensor for ocular wavefront measurement.

    Science.gov (United States)

    Díaz-Doutón, Fernando; Pujol, Jaume; Arjona, Montserrat; Luque, Sergio O

    2006-08-01

    We describe a new wavefront sensor for ocular aberration determination, based on the curvature sensing principle, which adapts the classical system used in astronomy for the living eye's measurements. The actual experimental setup is presented and designed following a process guided by computer simulations to adjust the design parameters for optimal performance. We present results for artificial and real young eyes, compared with the Hartmann-Shack estimations. Both methods show a similar performance for these cases. This system will allow for the measurement of higher order aberrations than the currently used wavefront sensors in situations in which they are supposed to be significant, such as postsurgery eyes.

  12. Scalar Curvature of a Causal Set

    Science.gov (United States)

    Benincasa, Dionigi M. T.; Dowker, Fay

    2010-05-01

    A one parameter family of retarded linear operators on scalar fields on causal sets is introduced. When the causal set is well approximated by 4 dimensional Minkowski spacetime, the operators are Lorentz invariant but nonlocal, are parametrized by the scale of the nonlocality, and approximate the continuum scalar D’Alembertian □ when acting on fields that vary slowly on the nonlocality scale. The same operators can be applied to scalar fields on causal sets which are well approximated by curved spacetimes in which case they approximate □-(1)/(2)R where R is the Ricci scalar curvature. This can used to define an approximately local action functional for causal sets.

  13. Challenges in Modelling of Lightning-Induced Delamination; Effect of Temperature-Dependent Interfacial Properties

    Science.gov (United States)

    Naghipour, P.; Pineda, E. J.; Arnold, S.

    2014-01-01

    Lightning is a major cause of damage in laminated composite aerospace structures during flight. Due to the dielectric nature of Carbon fiber reinforced polymers (CFRPs), the high energy induced by lightning strike transforms into extreme, localized surface temperature accompanied with a high-pressure shockwave resulting in extensive damage. It is crucial to develop a numerical tool capable of predicting the damage induced from a lightning strike to supplement extremely expensive lightning experiments. Delamination is one of the most significant failure modes resulting from a lightning strike. It can be extended well beyond the visible damage zone, and requires sophisticated techniques and equipment to detect. A popular technique used to model delamination is the cohesive zone approach. Since the loading induced from a lightning strike event is assumed to consist of extreme localized heating, the cohesive zone formulation should additionally account for temperature effects. However, the sensitivity to this dependency remains unknown. Therefore, the major focus point of this work is to investigate the importance of this dependency via defining various temperature dependency profiles for the cohesive zone properties, and analyzing the corresponding delamination area. Thus, a detailed numerical model consisting of multidirectional composite plies with temperature-dependent cohesive elements in between is subjected to lightning (excessive amount of heat and pressure) and delamination/damage expansion is studied under specified conditions.

  14. Fatigue Crack and Delamination Growth in Fibre Metal Laminates under Variable Amplitude Loading

    NARCIS (Netherlands)

    Khan, S.

    2013-01-01

    This thesis presents the investigation into the fatigue propagation and delamination growth of Fibre Metal Laminates under variable amplitude loading. As explained in the first chapter, the motivation of the research is twofold: first, to obtain a clear understanding and detailed characterization of

  15. Hierarchical system for autonomous sensing-healing of delamination in large-scale composite structures

    Science.gov (United States)

    Minakuchi, Shu; Sun, Denghao; Takeda, Nobuo

    2014-10-01

    This study combines our hierarchical fiber-optic-based delamination detection system with a microvascular self-healing material to develop the first autonomous sensing-healing system applicable to large-scale composite structures. In this combined system, embedded vascular modules are connected through check valves to a surface-mounted supply tube of a pressurized healing agent while fiber-optic-based sensors monitor the internal pressure of these vascular modules. When delamination occurs, the healing agent flows into the vascular modules breached by the delamination and infiltrates the damage for healing. At the same time, the pressure sensors identify the damaged modules by detecting internal pressure changes. This paper begins by describing the basic concept of the combined system and by discussing the advantages that arise from its hierarchical nature. The feasibility of the system is then confirmed through delamination infiltration tests. Finally, the hierarchical system is validated in a plate specimen by focusing on the detection and infiltration of the damage. Its self-diagnostic function is also demonstrated.

  16. Finite element modeling of guided wave scattering at delaminations in composite panels

    Science.gov (United States)

    Murat, B. I. S.; Fromme, P.

    2016-04-01

    Carbon fiber laminate composites, consisting of layers of polymer matrix reinforced with high strength carbon fibers, are increasingly employed for aerospace structures. They offer advantages for aerospace applications, e.g., good strength to weight ratio. However, impact during the operation and servicing of the aircraft can lead to barely visible and difficult to detect damage. Depending on the severity of the impact, delaminations can occur, reducing the load carrying capacity of the structure. Efficient structural health monitoring of composite panels can be achieved using guided ultrasonic waves propagating along the structure. The guided ultrasonic wave (A0 Lamb wave mode) scattering at delaminations was modelled using full three-dimensional Finite Element (FE) simulations. The influence of the delamination size was systematically investigated from a parameter study. The angular dependency of the scattered guided wave amplitude was calculated using a baseline subtraction method. A significant influence of the delamination width on the guided wave scattering was found. The sensitivity of guided waves for the detection of barely visible impact damage in composite panels has been predicted.

  17. Methods for the prediction of fatigue delamination growth in composites and adhesive bonds: A critical review

    NARCIS (Netherlands)

    Pascoe, J.A.; Alderliesten, R.C.; Benedictus, R.

    2013-01-01

    An overview is given of the development of methods for the prediction of fatigue driven delamination growth over the past 40 years. Four categories of methods are identified: stress/strain-based models, fracture mechanics based models, cohesive-zone models, and models using the extended finite eleme

  18. BEM solution of delamination problems using an interface damage and plasticity model

    CERN Document Server

    Panagiotopoulos, C G; Roubicek, T

    2012-01-01

    The problem of quasistatic and rate-independent evolution of elastic-plastic-brittle delamination at small strains is considered. Delamination processes for linear elastic bodies glued by an adhesive to each other or to a rigid outer surface are studied. The energy amounts dissipated in fracture Mode I (opening) and Mode II (shear) at an interface may be different. A concept of internal parameters is used here on the delaminating interfaces, involving a couple of scalar damage variable and a plastic tangential slip with kinematic-type hardening. The so-called energetic solution concept is employed. An inelastic process at an interface is devised in such a way that the dissipated energy depends only on the rates of internal parameters and therefore the model is associative. A fully implicit time discretization is combined with a spatial discretization of elastic bodies by the BEM to solve the delamination problem. The BEM is used in the solution of the respective boundary value problems, for each subdomain sep...

  19. Interaction between cracking, delamination and buckling in brittle elastic thin films

    NARCIS (Netherlands)

    Vellinga, W. P.; Van den Bosch, M.; Geers, M. G. D.

    2008-01-01

    A discrete lattice based model for the interaction of cracking, delamination and buckling of brittle elastic coatings is presented. The model is unique in its simultaneous incorporation of the coating and of disorder in the interface and material properties, leading to realistic 3D bending (and buck

  20. On a multiscale strategy and its optimization for the simulation of combined delamination and buckling

    Science.gov (United States)

    Saavedra, K.; Allix, O.; Gosselet, P.

    2012-08-01

    This paper investigates a computational strategy for studying the interactions between multiple through-the-width delaminations and global or local buckling in composite laminates taking into account possible contact between the delaminated surfaces. In order to achieve an accurate prediction of the quasi-static response, a very refined discretization of the structure is required, leading to the resolution of very large and highly nonlinear numerical problems. In this paper, a nonlinear finite element formulation along with a parallel iterative scheme based on a multiscale domain decomposition are used for the computation of 3D mesoscale models. Previous works by the authors already dealt with the simulation of multiscale delamination assuming small perturbations. This paper presents the formulation used to include geometric nonlinearities into this existing multiscale framework and discusses the adaptations that need to be made to the iterative process in order to ensure the rapid convergence and the scalability of the method in the presence of buckling and delamination. These various adaptations are illustrated by simulations involving large numbers of DOFs.

  1. The Mexican hat effect on the delamination buckling of a compressed thin film

    Science.gov (United States)

    Zhang, Yin; Liu, Yun

    2014-12-01

    Because of the interaction between film and substrate, the film buckling stress can vary significantly, depending on the delamination geometry, the film and substrate mechanical properties. The Mexican hat effect indicates such interaction. An analytical method is presented, and related dimensional analysis shows that a single dimensionless parameter can effectively evaluate the effect.

  2. Cracking and delamination of metal organic vapour deposited alumina and silica films

    NARCIS (Netherlands)

    Haanappel, V.A.C.; Haanappel, V.A.C.; van Corbach, H.D.; Fransen, T.; Gellings, P.J.

    1993-01-01

    Amorphous alumina and silica films were deposited on AISI by thermal decomposition at atmospheric pressure of aluminium-tri-sec-butoxide and di-acetoxy-di-tertiary-butoxided-silane respectively. Above a critical coating thickness of the oxide films, cracking and delamination occurred during the

  3. The concept of fatigue fracture toughness in fatigue delamination growth behavior

    NARCIS (Netherlands)

    Yao, L.; Alderliesten, R.C.; Benedictus, R.

    2015-01-01

    This paper provides a study on mode I fatigue delamination growth in composite laminates using energy principles. Experimental data has been obtained from fatigue tests conducted on Double Cantilever Beam (DCB) specimens at various stress ratios. A concept of fatigue fracture toughness is proposed t

  4. Delamination of a strong film from a ductile substrate during indentation unloading

    NARCIS (Netherlands)

    Abdul-Baqi, A.; van der Giessen, E.

    2001-01-01

    In this work, a finite element method was performed to simulate the spherical indentation of a ductile substrate coated by a strong thin film. Our objective was to study indentation-induced delamination of the film from the substrate. The film was assumed to be linear elastic, the substrate was elas

  5. Mode I fatigue delamination growth in composite laminates with fibre bridging

    NARCIS (Netherlands)

    Yao, L.

    2015-01-01

    Advanced composite materials have been commonly used in aerospace engineering, because of their good mechanical properties and attractive potential for creating lightweight structures. Susceptibility to delamination is one of the most important issues in the applications of these materials. This dis

  6. Effect of oxidation on delamination of ultrahigh-molecular-weight polyethylene tibial components.

    Science.gov (United States)

    Bell, C J; Walker, P S; Abeysundera, M R; Simmons, J M; King, P M; Blunn, G W

    1998-04-01

    Whether oxidation of ultrahigh-molecular-weight polyethylene (UHMWPE) causes delamination of the plastic in total knee arthroplasties (TKAs) was investigated. Examination of retrieved TKAs has shown that oxidation of UHMWPE can be caused by postirradiation damage leading to a subsurface band or, to a lesser extent, by mechanical forces during use leading to surface oxidation. Delamination cracks propagated through the subsurface oxidized band. In wear tests, delamination occurred in artificially aged UHMWPE where only subsurface oxidized bands had formed. Increased surface wear predominated where oxidation was associated with the surface of the plastic. Similarly, in tensile and fatigue tests of oxidized UHMWPE, there was a significant reduction in the ultimate tensile strength and in the fatigue resistance of specimens that had developed a subsurface band. Oxidation increased fatigue crack growth rate. It was observed that UHMWPE from different manufacturers varied in its resistance to oxidation. This study demonstrates that the effect of oxidation, which results in the development of a subsurface white band, combined with high subsurface shear forces observed in TKAs, is to enhance delamination wear.

  7. Development and Applications of Benchmark Examples for Static Delamination Propagation Predictions

    Science.gov (United States)

    Krueger, Ronald

    2013-01-01

    The development and application of benchmark examples for the assessment of quasistatic delamination propagation capabilities was demonstrated for ANSYS (TradeMark) and Abaqus/Standard (TradeMark). The examples selected were based on finite element models of Double Cantilever Beam (DCB) and Mixed-Mode Bending (MMB) specimens. First, quasi-static benchmark results were created based on an approach developed previously. Second, the delamination was allowed to propagate under quasi-static loading from its initial location using the automated procedure implemented in ANSYS (TradeMark) and Abaqus/Standard (TradeMark). Input control parameters were varied to study the effect on the computed delamination propagation. Overall, the benchmarking procedure proved valuable by highlighting the issues associated with choosing the appropriate input parameters for the VCCT implementations in ANSYS® and Abaqus/Standard®. However, further assessment for mixed-mode delamination fatigue onset and growth is required. Additionally studies should include the assessment of the propagation capabilities in more complex specimens and on a structural level.

  8. Simulation of Thermographic Responses of Delaminations in Composites with Quadrupole Method

    Science.gov (United States)

    Winfree, William P.; Zalameda, Joseph N.; Howell, Patricia A.; Cramer, K. Elliott

    2016-01-01

    The application of the quadrupole method for simulating thermal responses of delaminations in carbon fiber reinforced epoxy composites materials is presented. The method solves for the flux at the interface containing the delamination. From the interface flux, the temperature at the surface is calculated. While the results presented are for single sided measurements, with ash heating, expansion of the technique to arbitrary temporal flux heating or through transmission measurements is simple. The quadrupole method is shown to have two distinct advantages relative to finite element or finite difference techniques. First, it is straight forward to incorporate arbitrary shaped delaminations into the simulation. Second, the quadrupole method enables calculation of the thermal response at only the times of interest. This, combined with a significant reduction in the number of degrees of freedom for the same simulation quality, results in a reduction of the computation time by at least an order of magnitude. Therefore, it is a more viable technique for model based inversion of thermographic data. Results for simulations of delaminations in composites are presented and compared to measurements and finite element method results.

  9. Cathodic delamination of seawater-immersed anticorrosive coatings: Mapping of parameters affecting the rate

    DEFF Research Database (Denmark)

    Sørensen, Per Aggerholm; Dam-Johansen, Kim; Weinell, C. E.

    2010-01-01

    -steel interface, where solid iron is oxidized to ferrous ions and oxygen is reduced to hydroxyl ions. In this work, the effects of various parameters on cathodic delamination have been investigated. The parameters are: permeability of the coating, concentration of dissolved oxygen and cations, polarization...

  10. The arc delaminate: a geochemical reservoir twice the size of the continental crust

    Science.gov (United States)

    Jagoutz, O.; Schmidt, M. W.

    2012-12-01

    Most primitive melts in arcs are basaltic in composition but the continental crust or arc average is andesitic. To evolve from a primitive basalt to an andesitic composition, cumulates have to be fractionated and, if gravitationally unstable, can be delaminated. Such lower crustal cumulates are exposed in the Kohistan arc (N Pakistan) in a 10 km section through dunites, wehrlites, websterites, cpx-bearing garnetites and hornblendites, and garnet gabbros. We have compiled primitive melts for nine island arcs from the literature and fitted these with the bulk Kohistan arc [1] or average bulk continental crust [2] and the Kohistan cumulates. By average, ~15 wt% wehrlite + ~20% garnet hornblendite + ~35% garnet gabbro complement ~30% arc or continental crust and explain very well (r2~2) the evolution from a tholeiitic/calc-alkaline primitive high-Mg basalt to the continental crust. The bulk delaminate has 44-48 wt% SiO2, total alkalis of 1.1-1.4 wt% and an XMg of 0.67-0.69. Mass fractions derived from major elements were employed to compare trace elements: cumulates+crust deviate on average only by 25-30% from primitive melts, with the biggest deviations on the subduction-added traces. Relative to the continental or arc crust, the delaminate mass results to 1.8-2.5 times that of the continental crust. The delaminates have rho=3.2-3.5 g/cm3 and VP=7.9-8.2. At the base of the crust, they are thus difficult to distinguish seismically. Once reaching a critical thickness, they may sink into the deeper mantle where they form a geochemical reservoir twice the size of the continental crust. With respect to primitive mantle, the delaminate is enriched in Ba, K, Sr, and P and REE with LREEdelaminate reservoir would develop highly unradiogenic Pb over time and would counterbalance the radiogenic MORB and OIB reservoirs. Delamination of twice as much material as remains in the arc crust increases the flux of primitive melt in arcs threefold. This places the magma

  11. Spacetime curvature induced corrections to Lamb shift

    CERN Document Server

    Zhou, Wenting

    2012-01-01

    The Lamb shift results from the coupling of an atom with vacuum fluctuations of quantum fields, so corrections are expected to arise when the spacetime is curved since the vacuum fluctuations are modified by the presence of spacetime curvature. Here, we calculate the curvature-induced correction to the Lamb shift outside a spherically symmetric object and demonstrate that this correction can be remarkably significant outside a compact massive astrophysical body. For instance, for a neutron star or a stellar mass black hole, the correction is $\\sim$ 25% at a radial distance of $4GM/c^2$, $\\sim$ 16% at $10GM/c^2$ and as large as $\\sim$ 1.6% even at $100GM/c^2$, where $M$ is the mass of the object, $G$ the Newtonian constant, and $c$ the speed of light. In principle, we can look at the spectra from a distant compact supper-massive body to find such corrections. Therefore, our results suggest a possible way of detecting fundamental quantum effects in astronomical observations.

  12. Emergent gravity in spaces of constant curvature

    Science.gov (United States)

    Alvarez, Orlando; Haddad, Matthew

    2017-03-01

    In physical theories where the energy (action) is localized near a submanifold of a constant curvature space, there is a universal expression for the energy (or the action). We derive a multipole expansion for the energy that has a finite number of terms, and depends on intrinsic geometric invariants of the submanifold and extrinsic invariants of the embedding of the submanifold. This is the second of a pair of articles in which we try to develop a theory of emergent gravity arising from the embedding of a submanifold into an ambient space equipped with a quantum field theory. Our theoretical method requires a generalization of a formula due to by Hermann Weyl. While the first paper discussed the framework in Euclidean (Minkowski) space, here we discuss how this framework generalizes to spaces of constant sectional curvature. We focus primarily on anti de Sitter space. We then discuss how such a theory can give rise to a cosmological constant and Planck mass that are within reasonable bounds of the experimental values.

  13. Multidimensional integrable vacuum cosmology with two curvatures

    CERN Document Server

    Gavrilov, V R; Melnikov, V N

    1996-01-01

    The vacuum cosmological model on the manifold R \\times M_1 \\times \\ldots \\times M_n describing the evolution of n Einstein spaces of non-zero curvatures is considered. For n = 2 the Einstein equations are reduced to the Abel (ordinary differential) equation and solved, when (N_1 = dim M_1, N_2 = dim M_2) = (6,3), (5,5), (8,2). The Kasner-like behaviour of the solutions near the singularity t_s \\to +0 is considered (t_s is synchronous time). The exceptional ("Milne-type") solutions are obtained for arbitrary n. For n=2 these solutions are attractors for other ones, when t_s \\to + \\infty. For dim M = 10, 11 and 3 \\leq n \\leq 5 certain two-parametric families of solutions are obtained from n=2 ones using "curvature-splitting" trick. In the case n=2, (N_1, N_2)= (6,3) a family of non-singular solutions with the topology R^7 \\times M_2 is found.

  14. Suppressing Super-Horizon Curvature Perturbations

    CERN Document Server

    Sloth, M S

    2006-01-01

    We consider the possibility of suppressing superhorizon curvature perturbations after the end of the ordinary slow-roll inflationary stage. This is the opposite of the curvaton limit. We assume that large curvature perturbations are created by the inflaton and investigate to which extent they can be diluted or suppressed by a second very homogeneous field which starts to dominate the energy density of the universe shortly after the end of inflation. The suppression is non-trivial to achieve, but we demonstrate two examples where it works. The mechanism is shown to work if the decay rate of the second field has a certain time-dependence leading to an intrinsic non-adiabatic energy transfer or if the second field is an axion field with a very non-linear periodic potential leading to a non-vanishing intrinsic non-adiabatic pressure perturbation. This opens the possibility of having much larger inflaton perturbations created during inflation than normally allowed by the COBE bound. It relaxes the upper bound on t...

  15. Delamination-Debond Behaviour of Composite T- Joints in Wind Turbine Blades

    Science.gov (United States)

    Gulasik, H.; Coker, D.

    2014-06-01

    Wind turbine industry utilizes composite materials in turbine blade structural designs because of their high strength/stiffness to weight ratio. T-joint is one of the design configurations of composite wind turbine blades. T-joints consist of a skin panel and a stiffener co-bonded or co-cured together with a filler material between them. T-joints are prone to delaminations between skin/stiffener plies and debonds between skin-stiffener-filler interfaces. In this study, delamination/debond behavior of a co-bonded composite T-joint is investigated under 0° pull load condition by 2D finite element method. Using Abaqus® commercial FE software, zero-thickness cohesive elements are used to simulate delamination/debond in ply interfaces and bonding lines. Pulling load at 0° is applied and load-displacement behavior and failure scenario are observed. The failure sequence consists of debonding of filler/stringer interface during one load drop followed by a second drop in which the 2nd filler/stringer debonds, filler/skin debonding and skin delamination leading to total loss of load carrying capacity. This type of failure initiation has been observed widely in the literature. When the debond strength is increased 30%, failure pattern is found to change in addition to increasing the load capacity by 200% before total loss of loading carrying capacity occurs. Failure initiation and propagation behavior, initial and max failure loads and stress fields are affected by the property change. In all cases mixed-mode crack tip loading is observed in the failure initiation and propagation stages. In this paper, the detailed delamination/debonding history in T-joints is predicted with cohesive elements for the first time.

  16. Engineering curvature in graphene ribbons using ultrathin polymer films.

    Science.gov (United States)

    Li, Chunyu; Koslowski, Marisol; Strachan, Alejandro

    2014-12-10

    We propose a method to induce curvature in graphene nanoribbons in a controlled manner using an ultrathin thermoset polymer in a bimaterial strip setup and test it via molecular dynamics (MD) simulations. Continuum mechanics shows that curvature develops to release the residual stress caused by the chemical and thermal shrinkage of the polymer during processing and that this curvature increases with decreasing film thickness; however, significant deformation is only achieved for ultrathin polymer films. Quite surprisingly, explicit MD simulations of the curing and annealing processes show that the predicted trend not just continues down to film thicknesses of 1-2 nm but that the curvature development is enhanced significantly in such ultrathin films due to surface tension effects. This combination of effects leads to very large curvatures of over 0.14 nm(-1) that can be tuned via film thickness. This provides a new avenue to engineer curvature and, thus, electromagnetic properties of graphene.

  17. Timelike surfaces with zero mean curvature in Minkowski 4-space

    CERN Document Server

    Ganchev, Georgi

    2011-01-01

    On any timelike surface with zero mean curvature in the four-dimensional Minkowski space we introduce special geometric (canonical) parameters and prove that the Gauss curvature and the normal curvature of the surface satisfy a system of two natural partial differential equations. Conversely, any two solutions to this system determine a unique (up to a motion) timelike surface with zero mean curvature so that the given parameters are canonical. We find all timelike surfaces with zero mean curvature in the class of rotational surfaces of Moore type. These examples give rise to a one-parameter family of solutions to the system of natural partial differential equations describing timelike surfaces with zero mean curvature.

  18. Ricci Curvature on Polyhedral Surfaces via Optimal Transportation

    Directory of Open Access Journals (Sweden)

    Benoît Loisel

    2014-03-01

    Full Text Available The problem of correctly defining geometric objects, such as the curvature, is a hard one in discrete geometry. In 2009, Ollivier defined a notion of curvature applicable to a wide category of measured metric spaces, in particular to graphs. He named it coarse Ricci curvature because it coincides, up to some given factor, with the classical Ricci curvature, when the space is a smooth manifold. Lin, Lu and Yau and Jost and Liu have used and extended this notion for graphs, giving estimates for the curvature and, hence, the diameter, in terms of the combinatorics. In this paper, we describe a method for computing the coarse Ricci curvature and give sharper results, in the specific, but crucial case of polyhedral surfaces.

  19. Geometric and spectral consequences of curvature bounds on tessellations

    OpenAIRE

    Keller, Matthias

    2016-01-01

    This is a chapter of a forthcoming Lecture Notes in Mathematics "Modern Approaches to Discrete Curvature" edited by L. Najman and P. Romon. It provides a survey on geometric and spectral consequences of curvature bounds. The geometric setting are tessellations of surfaces with finite and vanishing genus. We consider a curvature arising as an angular defect. Several of the results presented here have analogues in Riemannian geometry. In some cases one can go even beyond the Riemannian results ...

  20. Operation principle of a novel curvature plastic fiber optic sensor

    Institute of Scientific and Technical Information of China (English)

    Fu Yili; Liu Renqiang; Wang Shuguo

    2005-01-01

    The operation principle of a new type of intensity modulate macrobend curvature optical fiber senor was presented based on surface light scattering theory. Sensor's static and dynamic performance was investigated. This type of sensor can distinguish between positive and negative bending directions. When curvature radius is larger than 50mm, the sensor will keep good linearity. Two-dimensional shape measurement experiments using curvature sensors have been implemented.

  1. Incidence of penile curvature in various forms of hypospadias

    OpenAIRE

    2009-01-01

    Introduction. Hypospadias is a congenital anomaly of the penis, characterised by ectopically positioned urethral meatus and associated anomalies (cryptorchidism, inguinal hernia, penile curvature). Proximal forms of hypospadias, as severe cases, are particularly accompanied by penile curvature (chordee). Distal types are considered to be mild degrees. Objective. To determine the incidence of congenital curvature within various forms of hypospadias in order to signify preoperative and intraope...

  2. An $\\varepsilon$-regularity Theorem For The Mean Curvature Flow

    OpenAIRE

    Han, Xiaoli; Sun, Jun

    2011-01-01

    In this paper, we will derive a small energy regularity theorem for the mean curvature flow of arbitrary dimension and codimension. It says that if the parabolic integral of $|A|^2$ around a point in space-time is small, then the mean curvature flow cannot develop singularity at this point. As an application, we can prove that the 2-dimensional Hausdorff measure of the singular set of the mean curvature flow from a surface to a Riemannian manifold must be zero.

  3. Sectional and Ricci Curvature for Three-Dimensional Lie Groups

    Directory of Open Access Journals (Sweden)

    Gerard Thompson

    2016-01-01

    Full Text Available Formulas for the Riemann and Ricci curvature tensors of an invariant metric on a Lie group are determined. The results are applied to a systematic study of the curvature properties of invariant metrics on three-dimensional Lie groups. In each case the metric is reduced by using the automorphism group of the associated Lie algebra. In particular, the maximum and minimum values of the sectional curvature function are determined.

  4. "Front" hotshet izvinitsja / Aleksandr Ikonnikov

    Index Scriptorium Estoniae

    Ikonnikov, Aleksandr

    2003-01-01

    Põhiliselt vene rahvusest noori ühendava liikumise "Front" esindajad kavatsevad kohtuda USA suursaadikuga Eestis ja vabandada kevadel suursaatkonna ees vägivallatsemisega lõppenud meeleavalduse pärast

  5. On the curvature of the present-day universe

    Energy Technology Data Exchange (ETDEWEB)

    Buchert, Thomas [Universite Lyon 1, Centre de Recherche Astrophysique de Lyon, CNRS UMR 5574, 9 avenue Charles Andre, F-69230 Saint-Genis-Laval (France); Carfora, Mauro [Dipartimento di Fisica Nucleare e Teorica, Universita degli Studi di Pavia, via A. Bassi 6, I-27100 Pavia (Italy)], E-mail: buchert@obs.univ-lyon1.fr, E-mail: mauro.carfora@pv.infn.it

    2008-10-07

    We discuss the effect of curvature and matter inhomogeneities on the averaged scalar curvature of the present-day universe. Motivated by studies of averaged inhomogeneous cosmologies, we contemplate on the question of whether it is sensible to assume that curvature averages out on some scale of homogeneity, as implied by the standard concordance model of cosmology, or whether the averaged scalar curvature can be largely negative today, as required for an explanation of dark energy from inhomogeneities. We confront both conjectures with a detailed analysis of the kinematical backreaction term and estimate its strength for a multi-scale inhomogeneous matter and curvature distribution. Our main result is a formula for the spatially averaged scalar curvature involving quantities that are all measurable on regional (i.e. up to 100 Mpc) scales. We propose strategies to quantitatively evaluate the formula, and pinpoint the assumptions implied by the conjecture of a small or zero averaged curvature. We reach the conclusion that the standard concordance model needs fine tuning in the sense of an assumed equipartition law for curvature in order to reconcile it with the estimated properties of the averaged physical space, whereas a negative averaged curvature is favoured, independent of the prior on the value of the cosmological constant.

  6. Spine curve modeling for quantitative analysis of spinal curvature.

    Science.gov (United States)

    Hay, Ori; Hershkovitz, Israel; Rivlin, Ehud

    2009-01-01

    Spine curvature and posture are important to sustain healthy back. Incorrect spine configuration can add strain to muscles and put stress on the spine, leading to low back pain (LBP). We propose new method for analyzing spine curvature in 3D, using CT imaging. The proposed method is based on two novel concepts: the spine curvature is derived from spinal canal centerline, and evaluation of the curve is carried out against a model based on healthy individuals. We show results of curvature analysis of healthy population, pathological (scoliosis) patients, and patients having nonspecific chronic LBP.

  7. Evolution of the curvature perturbations during warm inflation

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, Tomohiro, E-mail: matsuda@sit.ac.jp [Laboratory of Physics, Saitama Institute of Technology, Fusaiji, Okabe-machi, Saitama 369-0293 (Japan)

    2009-06-15

    This paper considers warm inflation as an interesting application of multi-field inflation. Delta-N formalism is used for the calculation of the evolution of the curvature perturbations during warm inflation. Although the perturbations considered in this paper are decaying after the horizon exit, the corrections to the curvature perturbations sourced by these perturbations can remain and dominate the curvature perturbations at large scales. In addition to the typical evolution of the curvature perturbations, inhomogeneous diffusion rate is considered for warm inflation, which may lead to significant non-Gaussianity of the spectrum.

  8. 3D face recognition with asymptotic cones based principal curvatures

    KAUST Repository

    Tang, Yinhang

    2015-05-01

    The classical curvatures of smooth surfaces (Gaussian, mean and principal curvatures) have been widely used in 3D face recognition (FR). However, facial surfaces resulting from 3D sensors are discrete meshes. In this paper, we present a general framework and define three principal curvatures on discrete surfaces for the purpose of 3D FR. These principal curvatures are derived from the construction of asymptotic cones associated to any Borel subset of the discrete surface. They describe the local geometry of the underlying mesh. First two of them correspond to the classical principal curvatures in the smooth case. We isolate the third principal curvature that carries out meaningful geometric shape information. The three principal curvatures in different Borel subsets scales give multi-scale local facial surface descriptors. We combine the proposed principal curvatures with the LNP-based facial descriptor and SRC for recognition. The identification and verification experiments demonstrate the practicability and accuracy of the third principal curvature and the fusion of multi-scale Borel subset descriptors on 3D face from FRGC v2.0.

  9. Evolving extrinsic curvature and the cosmological constant problem

    Science.gov (United States)

    Capistrano, Abraão J. S.; Cabral, Luis A.

    2016-10-01

    The concept of smooth deformation of Riemannian manifolds associated with the extrinsic curvature is explained and applied to the Friedmann-Lemaître-Robertson-Walker cosmology. We show that such deformation can be derived from the Einstein-Hilbert-like dynamical principle may produce an observable effect in the sense of Noether. As a result, we show how the extrinsic curvature compensates both quantitative and qualitative differences between the cosmological constant Λ and the vacuum energy {ρ }{vac} obtaining the observed upper bound for the cosmological constant problem at electroweak scale. The topological characteristics of the extrinsic curvature are discussed showing that the produced extrinsic scalar curvature is an evolving dynamical quantity.

  10. Evolution of the curvature perturbations during warm inflation

    Science.gov (United States)

    Matsuda, Tomohiro

    2009-06-01

    This paper considers warm inflation as an interesting application of multi-field inflation. Delta-N formalism is used for the calculation of the evolution of the curvature perturbations during warm inflation. Although the perturbations considered in this paper are decaying after the horizon exit, the corrections to the curvature perturbations sourced by these perturbations can remain and dominate the curvature perturbations at large scales. In addition to the typical evolution of the curvature perturbations, inhomogeneous diffusion rate is considered for warm inflation, which may lead to significant non-Gaussianity of the spectrum.

  11. Curvature optical fiber sensor by using bend enhanced method

    Institute of Scientific and Technical Information of China (English)

    Jianrong ZHANG; Hairong LIU; Xinkun WU

    2009-01-01

    Deflection curvature measurement can offer a number of advantages compared with the well-established strain measurement alternative. It is able to measure thin structure; fiber has no resistance with force, which leads to a high precision. There are many kinds of curvature gauges with different operation principles. A low-cost curvature optical fiber sensor using bend enhanced method to improve its curvature measurement sensitivity was devel-oped in recent years. This sensor can distinguish between convex bending and concave bending and has a good linearity in measuring large curvature deformation. Whisper gallery ray theory and Monte Carlo simulation are new achievements by computer experiment. The operation mechanism of this curvature optical fiber sensor is presented based on light scattering theory. The attenuation is ascribed to the transmission mode changing by the curvature of the fiber, which affects the attenuation of the surface scattering. The mathematical model of relationship among light loss, bending curvature, surface roughness, and parameters of the fiber's configuration is also presented. We design different kinds of shapes of sensitive zones; each zone has different parameters. Through detecting their output optical attenuations in different curvatures and fitting the results by exponential decaying functions, the proposed model is demonstrated by experimental results. Also, we compare the experi-mental results with the theoretical analysis and discuss the sensitivity dependence on bending direction.

  12. Stability of oblique shock front

    Institute of Scientific and Technical Information of China (English)

    CHEN; Shuxing(陈恕行)

    2002-01-01

    The stability of the weak planar oblique shock front with respect to the perturbation of the wall is discussed. By the analysis of the formation and the global construction of shock and its asymptotic behaviour for stationary supersonic flow along a smooth rigid wall we obtain the stability of the solution containing a weak planar shock front. The stability can be used to single out a physically reasonable solution together with the entropy condition.

  13. Radiative magnetized thermal conduction fronts

    Science.gov (United States)

    Borkowski, Kazimierz J.; Balbus, Steven A.; Fristrom, Carl C.

    1990-01-01

    The evolution of plane-parallel magnetized thermal conduction fronts in the interstellar medium (ISM) was studied. Separating the coronal ISM phase and interstellar clouds, these fronts have been thought to be the site of the intermediate-temperature regions whose presence was inferred from O VI absorption-line studies. The front evolution was followed numerically, starting from the initial discontinuous temperature distribution between the hot and cold medium, and ending in the final cooling stage of the hot medium. It was found that, for the typical ISM pressure of 4000 K/cu cm and the hot medium temperature of 10 to the 6th K, the transition from evaporation to condensation in a nonmagnetized front occurs when the front thickness is 15 pc. This thickness is a factor of 5 smaller than previously estimated. The O VI column densities in both evaporative and condensation stages agree with observations if the initial hot medium temperature Th exceeds 750,000 K. Condensing conduction fronts give better agreement with observed O VI line profiles because of lower gas temperatures.

  14. Differential geometry connections, curvature, and characteristic classes

    CERN Document Server

    Tu, Loring W

    2017-01-01

    This text presents a graduate-level introduction to differential geometry for mathematics and physics students. The exposition follows the historical development of the concepts of connection and curvature with the goal of explaining the Chern–Weil theory of characteristic classes on a principal bundle. Along the way we encounter some of the high points in the history of differential geometry, for example, Gauss' Theorema Egregium and the Gauss–Bonnet theorem. Exercises throughout the book test the reader’s understanding of the material and sometimes illustrate extensions of the theory. Initially, the prerequisites for the reader include a passing familiarity with manifolds. After the first chapter, it becomes necessary to understand and manipulate differential forms. A knowledge of de Rham cohomology is required for the last third of the text. Prerequisite material is contained in author's text An Introduction to Manifolds, and can be learned in one semester. For the benefit of the reader and to establ...

  15. Curvature effects in thin magnetic shells.

    Science.gov (United States)

    Gaididei, Yuri; Kravchuk, Volodymyr P; Sheka, Denis D

    2014-06-27

    A magnetic energy functional is derived for an arbitrary curved thin shell on the assumption that the magnetostatic effects can be reduced to an effective easy-surface anisotropy; it can be used for solving both static and dynamic problems. General static solutions are obtained in the limit of a strong anisotropy of both signs (easy-surface and easy-normal cases). It is shown that the effect of the curvature can be treated as the appearance of an effective magnetic field, which is aligned along the surface normal for the case of easy-surface anisotropy and is tangential to the surface for the case of easy-normal anisotropy. In general, the existence of such a field excludes the solutions that are strictly tangential or strictly normal to the surface. As an example, we consider static equilibrium solutions for a cone surface magnetization.

  16. Coarse-grained Modeling of DNA Curvature

    CERN Document Server

    Freeman, Gordon S; Lequieu, Joshua P; Whitmer, Jonathan K; de Pablo, Juan J

    2014-01-01

    Modeling of DNA-protein interactions is a complex process involving many important time and length scales. This can be facilitated through the use of coarse-grained models which reduce the number of degrees of freedom and allow efficient exploration of binding configurations. It is known that the local structure of DNA can significantly affect its protein-binding properties (i.e. intrinsic curvature in DNA-histone complexes). In a step towards comprehensive DNA-protein modeling, we expand the 3SPN.2 coarse-grained model to include intrinsic shape, and validate the refined model against experimental data including melting temperature, local flexibility, persistence length, and minor groove width profile.

  17. Natural curvature for manifest T-duality

    Energy Technology Data Exchange (ETDEWEB)

    Poláček, Martin; Siegel, Warren [C. N. Yang Institute for Theoretical PhysicsState University of New York, Stony Brook, NY 11794-3840 (United States)

    2014-01-08

    We reformulate the manifestly T-dual description of the massless sector of the closed bosonic string, directly from the geometry associated with the (left and right) affine Lie algebra of the coset space Poincaré/Lorentz. This construction initially doubles not only the (spacetime) coordinates for translations but also those for Lorentz transformations (and their “dual”). As a result, the Lorentz connection couples directly to the string (as does the vielbein), rather than being introduced ad hoc to the covariant derivative as previously. This not only reproduces the old definition of T-dual torsion, but automatically gives a general, covariant definition of T-dual curvature (but still with some undetermined connections)

  18. Polarized Curvature Radiation in Pulsar Magnetosphere

    CERN Document Server

    Wang, P F; Han, J L

    2014-01-01

    The propagation of polarized emission in pulsar magnetosphere is investigated in this paper. The polarized waves are generated through curvature radiation from the relativistic particles streaming along curved magnetic field lines and co-rotating with the pulsar magnetosphere. Within the 1/{\\deg} emission cone, the waves can be divided into two natural wave mode components, the ordinary (O) mode and the extraord nary (X) mode, with comparable intensities. Both components propagate separately in magnetosphere, and are aligned within the cone by adiabatic walking. The refraction of O-mode makes the two components separated and incoherent. The detectable emission at a given height and a given rotation phase consists of incoherent X-mode and O-mode components coming from discrete emission regions. For four particle-density models in the form of uniformity, cone, core and patches, we calculate the intensities for each mode numerically within the entire pulsar beam. If the co-rotation of relativistic particles with...

  19. Natural curvature for manifest T-duality

    CERN Document Server

    Polacek, Martin

    2013-01-01

    We reformulate the manifestly T-dual description of the massless sector of the closed bosonic string, directly from the geometry associated with the (left and right) affine Lie algebra of the coset space Poincare/Lorentz. This construction initially doubles not only the (spacetime) coordinates for translations but also those for Lorentz transformations (and their dual). As a result, the Lorentz connection couples directly to the string (as does the vielbein), rather than being introduced ad hoc to the covariant derivative as previously. This not only reproduces the old definition of T-dual torsion, but automatically gives a general, covariant definition of T-dual curvature (but still with some undetermined connections).

  20. Band geometry, Berry curvature, and superfluid weight

    Science.gov (United States)

    Liang, Long; Vanhala, Tuomas I.; Peotta, Sebastiano; Siro, Topi; Harju, Ari; Törmä, Päivi

    2017-01-01

    We present a theory of the superfluid weight in multiband attractive Hubbard models within the Bardeen-Cooper-Schrieffer (BCS) mean-field framework. We show how to separate the geometric contribution to the superfluid weight from the conventional one, and that the geometric contribution is associated with the interband matrix elements of the current operator. Our theory can be applied to systems with or without time-reversal symmetry. In both cases the geometric superfluid weight can be related to the quantum metric of the corresponding noninteracting systems. This leads to a lower bound on the superfluid weight given by the absolute value of the Berry curvature. We apply our theory to the attractive Kane-Mele-Hubbard and Haldane-Hubbard models, which can be realized in ultracold atom gases. Quantitative comparisons are made to state of the art dynamical mean-field theory and exact diagonalization results.

  1. Apparent surface curvature affects lightness perception.

    Science.gov (United States)

    Knill, D C; Kersten, D

    1991-05-16

    The human visual system has the remarkable capacity to perceive accurately the lightness, or relative reflectance, of surfaces, even though much of the variation in image luminance may be caused by other scene attributes, such as shape and illumination. Most physiological, and computational models of lightness perception invoke early sensory mechanisms that act independently of, or before, the estimation of other scene attributes. In contrast to the modularity of lightness perception assumed in these models are experiments that show that supposedly 'higher-order' percepts of planar surface attributes, such as orientation, depth and transparency, can influence perceived lightness. Here we show that perceived surface curvature can also affect perceived lightness. The results of the earlier experiments indicate that perceiving luminance edges as changes in surface attributes other than reflectance can influence lightness. These results suggest that the interpretation of smooth variations in luminance can also affect lightness percepts.

  2. A Field Theory with Curvature and Anticurvature

    Directory of Open Access Journals (Sweden)

    M. I. Wanas

    2014-01-01

    Full Text Available The present work is an attempt to construct a unified field theory in a space with curvature and anticurvature, the PAP-space. The theory is derived from an action principle and a Lagrangian density using a symmetric linear parameterized connection. Three different methods are used to explore physical contents of the theory obtained. Poisson’s equations for both material and charge distributions are obtained, as special cases, from the field equations of the theory. The theory is a pure geometric one in the sense that material distribution, charge distribution, gravitational and electromagnetic potentials, and other physical quantities are defined in terms of pure geometric objects of the structure used. In the case of pure gravity in free space, the spherical symmetric solution of the field equations gives the Schwarzschild exterior field. The weak equivalence principle is respected only in the case of pure gravity in free space; otherwise it is violated.

  3. Quantum Gravity and Higher Curvature Actions

    CERN Document Server

    Bojowald, M; Bojowald, Martin; Skirzewski, Aureliano

    2006-01-01

    Effective equations are often useful to extract physical information from quantum theories without having to face all technical and conceptual difficulties. One can then describe aspects of the quantum system by equations of classical type, which correct the classical equations by modified coefficients and higher derivative terms. In gravity, for instance, one expects terms with higher powers of curvature. Such higher derivative formulations are discussed here with an emphasis on the role of degrees of freedom and on differences between Lagrangian and Hamiltonian treatments. A general scheme is then provided which allows one to compute effective equations perturbatively in a Hamiltonian formalism. Here, one can expand effective equations around any quantum state and not just a perturbative vacuum. This is particularly useful in situations of quantum gravity or cosmology where perturbations only around vacuum states would be too restrictive. The discussion also demonstrates the number of free parameters expect...

  4. Domain wall brane in squared curvature gravity

    CERN Document Server

    Liu, Yu-Xiao; Zhao, Zhen-Hua; Li, Hai-Tao

    2011-01-01

    We suggest a thick braneworld model in the squared curvature gravity theory. Despite the appearance of higher order derivatives, the localization of gravity and various bulk matter fields is shown to be possible. The existence of the normalizable gravitational zero mode indicates that our four-dimensional gravity is reproduced. In order to localize the chiral fermions on the brane, two types of coupling between the fermions and the brane forming scalar is introduced. The first coupling leads us to a Schr\\"odinger equation with a volcano potential, and the other a P\\"oschl-Teller potential. In both cases, the zero mode exists only for the left-hand fermions. Several massive KK states of the fermions can be trapped on the brane, either as resonant states or as bound states.

  5. The Scalar Curvature of a Causal Set

    CERN Document Server

    Benincasa, Dionigi M T

    2010-01-01

    A one parameter family of retarded linear operators on scalar fields on causal sets is introduced. When the causal set is well-approximated by 4 dimensional Minkowski spacetime, the operators are Lorentz invariant but nonlocal, are parametrised by the scale of the nonlocality and approximate the continuum scalar D'Alembertian, $\\Box$, when acting on fields that vary slowly on the nonlocality scale. The same operators can be applied to scalar fields on causal sets which are well-approximated by curved spacetimes in which case they approximate $\\Box - {{1/2}}R$ where $R$ is the Ricci scalar curvature. This can used to define an approximately local action functional for causal sets.

  6. Streamline curvature and bed resistance in shallow water flow

    NARCIS (Netherlands)

    De Vriend, H.J.

    1979-01-01

    The relationship between streamline curvature and bed resistance in shallow water flow with little side constraint, as derived in 1970 by H.J. Schoemaker, is reconsidered. Schoemaker concluded that the bed resistance causes the curvature of a free streamline to grow exponentially with the distance a

  7. Constant mean curvature surfaces via integrable dynamical system

    CERN Document Server

    Konopelchenko, B G

    1995-01-01

    It is shown that the equation which describes constant mean curvature surface via the generalized Weierstrass-Enneper inducing has Hamiltonian form. Its simplest finite-dimensional reduction has two degrees of freedom, integrable and its trajectories correspond to well-known Delaunay and do Carmo-Dajzcer surfaces (i.e., helicoidal constant mean curvature surfaces).

  8. Effect of Rolling Parameters on Plate Curvature during Snake Rolling

    Institute of Scientific and Technical Information of China (English)

    FU Yao; XIE Shuisheng; XIONG Baiqing; HUANG Guojie; CHENG Lei

    2012-01-01

    In order to predict the plate curvature during snake rolling,FE model was constructed based on plane strain assumption.The accuracy of the FE model was verified by the comparison between the plate curvature conducted by FE model and experiment respectively.By using FE model,the effect of offset distance,speed ratio,reduction,roll radius and initial plate thickness on the plate curvature during snake rolling was investigated.The experimental results show that,a proper offsetting distance can efficiently decrease plate curvature,however an excessive offsetting distance will increase plate curvature.A larger speed ratio,reduction will cause a large plate curvature,however a larger roll radius has effect to reduce plate curvature.Plate which undergoes a larger reduction and plate with a larger initial thickness always need a larger offset distance to keep the plate the minimum plate curvature,but for a larger roll radius a smaller offset distance is needed.

  9. Systematic evaluation of a new combinatorial curvature for complex networks

    CERN Document Server

    Sreejith, R P; Saucan, Emil; Samal, Areejit

    2016-01-01

    We have recently introduced Forman's discretization of Ricci curvature to the realm of complex networks. Forman curvature is an edge-based measure whose mathematical definition elegantly encapsulates the weights of nodes and edges in a complex network. In this contribution, we perform a comparative analysis of Forman curvature with other edge-based measures such as edge betweenness, embeddedness and dispersion in diverse model and real networks. We find that Forman curvature in comparison to embeddedness or dispersion is a better indicator of the importance of an edge for the large-scale connectivity of complex networks. Based on the definition of the Forman curvature of edges, there are two natural ways to define the Forman curvature of nodes in a network. In this contribution, we also examine these two possible definitions of Forman curvature of nodes in diverse model and real networks. Based on our empirical analysis, we find that in practice the unnormalized definition of the Forman curvature of nodes wit...

  10. Intramanual and intermanual transfer of the curvature aftereffect

    NARCIS (Netherlands)

    van der Horst, B.J.; Duijndam, M.J.A.; Ketels, M.F.M.; Wilbers, M.T.J.M.; Zwijsen, S.A.; Kappers, A.M.L.

    2008-01-01

    The existence and transfer of a haptic curvature aftereffect was investigated to obtain a greater insight into neural representation of shape. The haptic curvature aftereffect is the phenomenon whereby a flat surface is judged concave if the preceding touched stimulus was convex and vice versa. Sing

  11. On the total mean curvature of non-rigid surfaces

    OpenAIRE

    Alexandrov, Victor

    2008-01-01

    Using Green's theorem we reduce the variation of the total mean curvature of a smooth surface in the Euclidean 3-space to a line integral of a special vector field and obtain the following well-known theorem as an immediate consequence: the total mean curvature of a closed smooth surface in the Euclidean 3-space is stationary under an infinitesimal flex.

  12. On complete submanifolds with parallel mean curvature in product spaces

    CERN Document Server

    Fetcu, Dorel

    2011-01-01

    We prove a Simons type formula for submanifolds with parallel mean curvature vector field in product spaces of type $M^n(c)\\times\\mathbb{R}$, where $M^n(c)$ is a space form with constant sectional curvature $c$, and then we use it to characterize some of these submanifolds.

  13. A Simons type formula for surfaces with parallel mean curvature

    CERN Document Server

    Fetcu, Dorel

    2011-01-01

    We prove a Simons type equation for non-minimal surfaces with parallel mean curvature vector (pmc surfaces) in $M^n(c)\\times\\mathbb{R}$, where $M^n(c)$ is an $n$-dimensional space form. Then, we use this equation in order to characterize complete non-minimal pmc surfaces with non-negative Gaussian curvature.

  14. How to obtain Transience from Bounded Radial Mean Curvature

    DEFF Research Database (Denmark)

    Markvorsen, Steen; Palmer, Vicente

    2005-01-01

    We show that Brownian motion on any unbounded submanifold P in an ambient manifold N with a pole P is transient if the following conditions are satisfied: The p-radial mean curvatures of P are sufficiently small outsidea compact set and the p-radial sectional curvatures of N are sufficiently nega...

  15. The scalar curvature problem on the four dimensional half sphere

    CERN Document Server

    Ben-Ayed, M; El-Mehdi, K

    2003-01-01

    In this paper, we consider the problem of prescribing the scalar curvature under minimal boundary conditions on the standard four dimensional half sphere. We provide an Euler-Hopf type criterion for a given function to be a scalar curvature for some metric conformal to the standard one. Our proof involves the study of critical points at infinity of the associated variational problem.

  16. Generalised functions and distributional curvature of cosmic strings

    CERN Document Server

    Clarke, C J S; Wilson, J P

    1996-01-01

    A new method is presented for assigning distributional curvature, in an invariant manner, to a space-time of low differentiability, using the techniques of Colombeau's `new generalised functions'. The method is applied to show that curvature of a cone is equivalent to a delta function. The same is true under small enough perturbations.

  17. Dynamics and Control of Adaptive Shells with Curvature Transformations

    OpenAIRE

    1995-01-01

    Adaptive structures with controllable geometries and shapes are rather useful in many engineering applications, such as adaptive wings, variable focus mirrors, adaptive machines, micro-electromechanical systems, etc. Dynamics and feedback control effectiveness of adaptive shells whose curvatures are actively controlled and continuously changed are evaluated. An adaptive piezoelectric laminated cylindrical shell composite with continuous curvature changes is studied, and its natural frequencie...

  18. Detonative propagation and accelerative expansion of the Crab Nebula shock front.

    Science.gov (United States)

    Gao, Yang; Law, Chung K

    2011-10-21

    The accelerative expansion of the Crab Nebula's outer envelope is a mystery in dynamics, as a conventional expanding blast wave decelerates when bumping into the surrounding interstellar medium. Here we show that the strong relativistic pulsar wind bumping into its surrounding nebula induces energy-generating processes and initiates a detonation wave that propagates outward to form the current outer edge, namely, the shock front, of the nebula. The resulting detonation wave, with a reactive downstream, then provides the needed power to maintain propagation of the shock front. Furthermore, relaxation of the curvature-induced reduction of the propagation velocity from the initial state of formation to the asymptotic, planar state of Chapman-Jouguet propagation explains the observed accelerative expansion. Potential richness in incorporating reactive fronts in the description of various astronomical phenomena is expected.

  19. Detonative Propagation and Accelerative Expansion of the Crab Nebula Shock Front

    CERN Document Server

    Gao, Yang

    2011-01-01

    The accelerative expansion of the Crab nebula's outer envelope is a mystery in dynamics as a conventional expanding blast wave decelerates when bumping into the surrounding interstellar medium. Here we show that the strong relativistic pulsar wind bumping into its surrounding nebula induces energy-generating processes and initiates a detonation wave that propagates outward to form the current outer edge, namely the shock front, of the nebula. The resulting detonation wave, with a reactive downstream, then provides the needed power to maintain propagation of the shock front. Furthermore, relaxation of the curvature-induced reduction of the propagation velocity from the initial state of formation to the asymptotic, planar state of Chapman-Jouguet propagation explains the observed accelerative expansion. The essential role of detonative propagation in the structure and dynamics of the Crab nebula offers potential richness in incorporating reactive fronts in the description of various astronomical phenomena.

  20. Effect of tool geometry and cutting parameters on delamination and thrust forces in drilling CFRP/Al-Li

    Science.gov (United States)

    El Bouami, Souhail; Habak, Malek; Franz, Gérald; Velasco, Raphaël; Vantomme, Pascal

    2016-10-01

    Composite materials are increasingly used for structural parts in the aeronautic industries. Carbon Fiber-Reinforced Plastics (CFRP) are often used in combination with metallic materials, mostly aluminium alloys. This raises new problems in aircraft assembly. Delamination is one of these problems. In this study, CFRP/Al-Li stacks is used as experimental material for investigation effect of interaction of cutting parameters (cutting speed and feed rate) and tool geometry on delamination and thrust forces in drilling operation. A plan of experiments, based on Taguchi design method, was employed to investigate the influence of tool geometry and in particular the point angle and cutting parameters on delamination and axial effort. The experimental results demonstrate that the feed rate is the major parameter and the importance of tool point angle in delamination and thrust forces in the stacks were shown.

  1. Wave Propagation Analysis in Composite Laminates Containing a Delamination Using a Three-Dimensional Spectral Element Method

    Directory of Open Access Journals (Sweden)

    Fucai Li

    2012-01-01

    Full Text Available A three-dimensional spectral element method (SEM was developed for analysis of Lamb wave propagation in composite laminates containing a delamination. SEM is more efficient in simulating wave propagation in structures than conventional finite element method (FEM because of its unique diagonal form of the mass matrix. Three types of composite laminates, namely, unidirectional-ply laminates, cross-ply laminates, and angle-ply laminates are modeled using three-dimensional spectral finite elements. Wave propagation characteristics in intact composite laminates are investigated, and the effectiveness of the method is validated by comparison of the simulation results with analytical solutions based on transfer matrix method. Different Lamb wave mode interactions with delamination are evaluated, and it is demonstrated that symmetric Lamb wave mode may be insensitive to delamination at certain interfaces of laminates while the antisymmetric mode is more suited for identification of delamination in composite structures.

  2. Internal-Notched Flexure Test for Measurement of Mode II Delamination Resistance of Fibre-Reinforced Polymers

    Directory of Open Access Journals (Sweden)

    Chengye Fan

    2013-01-01

    Full Text Available This paper introduces a new test, method, named internal-notched flexure (INF test, that is designed to measure the critical energy release rate of fibre-reinforced polymers for delamination growth in shear mode (mode II. The INF test generates stable delamination growth, with a monotonic increase of load and displacement in a nearly linear fashion. Values of the mode II delamination toughness were deduced using experimental compliance fitting method. Good repeatability of the results was obtained. Compared with the end-notched flexure (ENF test using the same material, the INF test yielded higher delamination resistance, possibly due to the bridging fibres found between fracture surfaces of the INF test specimens.

  3. Effects of Iris Surface Curvature on Iris Recognition

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Joseph T [ORNL; Flynn, Patrick J [ORNL; Bowyer, Kevin W [University of Notre Dame, IN; Santos-Villalobos, Hector J [ORNL

    2013-01-01

    To focus on objects at various distances, the lens of the eye must change shape to adjust its refractive power. This change in lens shape causes a change in the shape of the iris surface which can be measured by examining the curvature of the iris. This work isolates the variable of iris curvature in the recognition process and shows that differences in iris curvature degrade matching ability. To our knowledge, no other work has examined the effects of varying iris curvature on matching ability. To examine this degradation, we conduct a matching experiment across pairs of images with varying degrees of iris curvature differences. The results show a statistically signi cant degradation in matching ability. Finally, the real world impact of these ndings is discussed

  4. Dynamics and Control of Adaptive Shells with Curvature Transformations

    Directory of Open Access Journals (Sweden)

    H.S. Tzou

    1995-01-01

    Full Text Available Adaptive structures with controllable geometries and shapes are rather useful in many engineering applications, such as adaptive wings, variable focus mirrors, adaptive machines, micro-electromechanical systems, etc. Dynamics and feedback control effectiveness of adaptive shells whose curvatures are actively controlled and continuously changed are evaluated. An adaptive piezoelectric laminated cylindrical shell composite with continuous curvature changes is studied, and its natural frequencies and controlled damping ratios are evaluated. The curvature change of the adaptive shell starts from an open shallow shell (30° and ends with a deep cylindrical shell (360°. Dynamic characteristics and control effectiveness (via the proportional velocity feedback of this series of shells are investigated and compared at every 30° curvature change. Analytical solutions suggest that the lower modes are sensitive to curvature changes and the higher modes are relatively insensitive.

  5. Curvature sensor based on a Fabry-Perot interferometer

    Science.gov (United States)

    Monteiro, Catarina; Ferreira, Marta S.; Kobelke, Jens; Schuster, Kay; Bierlich, Jörg; Frazão, Orlando

    2016-05-01

    A curvature sensor based on a Fabry-Perot interferometer is proposed. A capillary tube of silica is fusion spliced between two single mode fibers, producing a Fabry-Perot cavity. The light propagates in air, when passing through the capillary tube. Two different cavities are subjected to curvature and temperature. The cavity with shorter length shows insensitivity to both measurands. The larger cavity shows two operating regions for curvature measurement, where a linear response is shown, with a maximum sensitivity of 18.77pm/m-1 for the high curvature radius range. When subjected to temperature, the sensing head produces a similar response for different curvature radius, with a sensitivity of 0.87pm/°C.

  6. Effect of Material Property of Interply Film on the Delamination in Laminated Composites 8

    Institute of Scientific and Technical Information of China (English)

    WeiFENG; QiaoHUANG

    1999-01-01

    The delamination is one of the main failure modes in laminated composites.In order to suppress and /or delay it,considerable research has been devoted to the reduction of the interlaminar stresses at the interfaces between two different plies.This paper studies the effect of isotropic layers placed at ply interface on the interlaminar behaviour of the angle-ply laminated composites.The results of the experiment and numerical analysis show that the material properties of interply film have strong influence on the interlaminar behaviour of laminated composites.In order to suppress delamination,the material of interply film has to been selected carefully due to the fact that different matrials have different results .SOme materials may increase the stress values at the interfaces.Some materials may reduce the stress concertration.

  7. Ag-Coated Heterostructures of ZnO-TiO2/Delaminated Montmorillonite as Solar Photocatalysts

    Science.gov (United States)

    Hinojosa, Mariana; Tobajas, Montserrat; Alvarez, Maria Ariadna; Rodríguez-González, Vicente; Rodriguez, Juan Jose

    2017-01-01

    Heterostructures based on ZnO-TiO2/delaminated montmorillonite coated with Ag have been prepared by sol–gel and photoreduction procedures, varying the Ag and ZnO contents. They have been thoroughly characterized by XRD, WDXRF, UV–Vis, and XPS spectroscopies, and N2 adsorption, SEM, and TEM. In all cases, the montmorillonite was effectively delaminated with the formation of TiO2 anatase particles anchored on the clay layer’s surface, yielding porous materials with high surface areas. The structural and textural properties of the heterostructures synthesized were unaffected by the ZnO incorporated. The photoreduction led to solids with Ag nanoparticles decorating the surface. These materials were tested as photocatalysts for the degradation of several emerging contaminants with different nitrogen-bearing chemical structures under solar light. The catalysts yielded high rates of disappearance of the starting pollutants and showed quite stable performance upon successive applications. PMID:28817106

  8. Segmenting delaminations in carbon fiber reinforced polymer composite CT using convolutional neural networks

    Science.gov (United States)

    Sammons, Daniel; Winfree, William P.; Burke, Eric; Ji, Shuiwang

    2016-02-01

    Nondestructive evaluation (NDE) utilizes a variety of techniques to inspect various materials for defects without causing changes to the material. X-ray computed tomography (CT) produces large volumes of three dimensional image data. Using the task of identifying delaminations in carbon fiber reinforced polymer (CFRP) composite CT, this work shows that it is possible to automate the analysis of these large volumes of CT data using a machine learning model known as a convolutional neural network (CNN). Further, tests on simulated data sets show that with a robust set of experimental data, it may be possible to go beyond just identification and instead accurately characterize the size and shape of the delaminations with CNNs.

  9. The Use of Sprint Interface Element Delamination Simulation of Sandwich Composite Beam

    Science.gov (United States)

    Xu, Geng; Yan, Renjun

    2016-12-01

    Sandwich composite beams have been more and more used in various industries because of their excellent mechanical properties. However, the mismatched performance between face sheet and foam core always lead to such as cracks and damages in the core or face/core interface during the processes of manufacturing or service. Delamination damage at the adhesive interface is the most dangerous and could be one main source that the mechanical capability of the structure is serous degenerated. In this paper, a simple and natural model to evaluate the stiffness of the spring interface elements, which is based on the physics and the geometry of the adhesive layers, is proposed. In order to validate the model, cantilever beam bending test were conducted for marine sandwich composite I-beam. A good comparison has been found between predictions and experimental results, and results indicate that the spring interface element can provide an efficient model for the delamination simulation of sandwich composite structures.

  10. Analysis of vibration for regions above rectangular delamination defects in solids

    Science.gov (United States)

    Oh, Taekeun; Popovics, John S.; Sim, Sung-Han

    2013-04-01

    We propose a semi-analytical approach to predict the natural flexural vibration frequencies of the material overlying a near-surface delamination defect in a solid. The formulation accommodates arbitrary length to depth ratio of the defect and higher-order modes of vibration. The material above the defect is modeled as a semi-clamped rectangular plate, where the dynamic edge effect factors, as deduced by Bolotin's asymptotic method, are estimated. The formulation results are evaluated through comparison to 3-D finite element (FE) simulation and experimental results obtained from impact resonance tests on concrete samples with controlled delamination defects. Good agreement with both experimental and 3-D FE results confirms the accuracy of the formulation in all cases.

  11. A subregional model for delamination prediction of rubber composite under fatigue loading

    Institute of Scientific and Technical Information of China (English)

    TIAN Zhen-hui; TAN Hui-feng

    2005-01-01

    Results from fatigue experiments of cross-laminated steel cord-rubber composites (SCRC) indicate that fatigue damage life can be categorized into three regimes. In terms of fatigue modes, a subregional fatigue model is developed to describe the damages evolution of SCRC under fatigue loads. Firstly, finite element analysis is introduced to determine interply stress distribution of the specimen. Then, based on the experimental fatigue data, subregional models are introduced to simulate relations between maximum strain, effective stiffness,delamination shear stress and fatigue cycles. Relations between crack density, delamination length growth rate,macro crack density and cycles are modeled by two semi-empirical models. A reasonable prediction result was achieved by the current model, where model parameters can be determined by basic outputs of fatigue testing.

  12. Ag-Coated Heterostructures of ZnO-TiO2/Delaminated Montmorillonite as Solar Photocatalysts

    Directory of Open Access Journals (Sweden)

    Carolina Belver

    2017-08-01

    Full Text Available Heterostructures based on ZnO-TiO2/delaminated montmorillonite coated with Ag have been prepared by sol–gel and photoreduction procedures, varying the Ag and ZnO contents. They have been thoroughly characterized by XRD, WDXRF, UV–Vis, and XPS spectroscopies, and N2 adsorption, SEM, and TEM. In all cases, the montmorillonite was effectively delaminated with the formation of TiO2 anatase particles anchored on the clay layer’s surface, yielding porous materials with high surface areas. The structural and textural properties of the heterostructures synthesized were unaffected by the ZnO incorporated. The photoreduction led to solids with Ag nanoparticles decorating the surface. These materials were tested as photocatalysts for the degradation of several emerging contaminants with different nitrogen-bearing chemical structures under solar light. The catalysts yielded high rates of disappearance of the starting pollutants and showed quite stable performance upon successive applications.

  13. Enhancement of delamination strength in Cu-stabilized coated conductor tapes through additional treatments under transverse tension at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Hyung Seop; Bautista, Zhierwinjay [Andong National University, Andong (Korea, Republic of); Moon, Seung Hyun; Lee, Jae Hun; Mean, Byoung Jean [SuNAM Co Ltd., Anseong (Korea, Republic of)

    2017-06-15

    In superconducting coil applications particularly in wet wound coils, coated conductor (CC) tapes are subjected to different type of stresses that could affect its electromechanical transport property. These include hoop stress acting along the length of the CC tape and the Lorentz force acting perpendicular to the CC tape’s surface. Since the latter is commonly associated with the delamination problem of multi-layered REBCO CC tapes, more understanding and attention on the delamination phenomena induced in the case of coil applications are needed. Difference on the coefficient of thermal expansion (CTE) of each constituent layer of the CC tape, the bobbin, and the impregnating materials is the main causes of delamination in CC tapes when subjected to thermal and mechanical cycling. In the design of degradation-free superconducting coils, therefore, characterization of the delamination behaviors including mechanism and strength in the multi-layered REBCO CC tapes becomes a critical issue. Various trials to increase the delamination strength by improving interface characteristics at interlayers have been performed. In this study, in order to investigate the influences of laser cleaning and Ag annealing treated at the substrate side surface, transverse tensile tests were conducted under different sample configurations using 4.5mm x 8 mm upper anvil. The mechanical delamination strength of differently processed CC samples was examined at room temperature (RT). As a result, the Sample 1 with the additional laser cleaning and Ag annealing processes and the Sample 2 with additional Ag annealing process only showed higher mechanical delamination strength as compared to the Sample 3 without such additional treatments. Sample 3 showed quite different behavior when the loading direction is to the substrate side where the delamination strength much lower as compared to other cases.

  14. Delamination of sub-crustal lithosphere beneath the Isthmus of Tehuantepec, Mexico

    Science.gov (United States)

    Manea, Marina; Constantin Manea, Vlad; Ferrari, Luca; Orozco-Esquivel, Maria Teresa

    2015-04-01

    Recent seismic data from a dense seismic array (VEOX), as well as from the permanent broadband network of the Mexican National Seismological Service (SSN), revealed several anomalous structures in the Isthmus of Tehuantepec. Seismic tomography imaged a high velocity body dipping ~30° from the Gulf of Mexico southward. Analysis of seismic noise detected a large well-defined low-velocity anomaly on top of this structure in the vicinity of the Late Miocene-Quaternary Los Tuxtlas volcanic field. The current interpretation of these observations propose the presence of a southward dipping slab resulting from the subduction of oceanic lithosphere prior to the collision of the Yucatán Block with Mexico ~12 Ma ago. However this interpretation contradicts many aspects of well-established models of Caribbean tectonics. Additionally such model does not explain how the southward dipping structure remained at a relatively low dipping angle (~30°) over the last 12 Ma, and why it is not seismically active. We propose an alternative model that reconciles the seismic observations with the tectonic evolution of the region. The south dipping seismic structure is the result of lithospheric delamination produced by a thermal anomaly that migrated upwards through a slab gap in the Cocos slab located at ~200 km depth. Using high-resolution two-dimensional coupled petrological-thermomechanical numerical simulations of subduction, we show that hot and buoyant asthenospheric material flowing through a slab gap in the Cocos plate may have produced a rapid delamination of the lithosphere once it reached its base. The model geometry of the delaminated lithosphere is similar to the observed seismic anomaly, and the hot material from the plume impact is consistent with the low-velocity anomaly located at the north of the Isthmus of Tehuantepec, which feeds the Los Tuxtla volcanic field. Additionally our simulations show that the temperature of the delaminated lithosphere is above 700

  15. Cracking and delamination behaviors of photovoltaic backsheet after accelerated laboratory weathering

    Science.gov (United States)

    Lin, Chiao-Chi; Lyu, Yadong; Hunston, Donald L.; Kim, Jae Hyun; Wan, Kai-Tak; Stanley, Deborah L.; Gu, Xiaohong

    2015-09-01

    The channel crack and delamination phenomena that occurred during tensile tests were utilized to study surface cracking and delamination properties of a multilayered backsheet. A model sample of commercial PPE (polyethylene terephthalate (PET)/PET/ethylene vinyl acetate (EVA)) backsheet was studied. Fragmentation testing was performed after accelerated aging with and without ultraviolet (UV) irradiation in two relative humidity (RH) levels (5 % RH and 60 % RH) at elevated temperature (85 °C) conditions for 11 days and 22 days. Results suggest that the embrittled surface layer resulting from the UV photo-degradation is responsible for surface cracking when the strain applied on the sample is far below the yielding strain (2.2 %) of the PPE sample. There was no surface cracking observed on the un-aged sample and samples aged without UV irradiation. According to the fragmentation testing results, the calculated fracture toughness (KIC) values of the embrittled surface layer are as low as 0.027 MPa·m1/2 to 0.104 MPa·m1/2, depending on the humidity levels and aging times. Surface analysis using attenuated total reflectance Fourier transform infrared and atomic force microscopy shows the degradation mechanism of the embrittled surface layer is a combination of the photodegradation within a certain degradation depth and the moisture erosion effect depending on the moisture levels. Specifically, UV irradiation provides a chemical degradation effect while moisture plays a synergistic effect on surface erosion, which influences surface roughness after aging. Finally, there was no delamination observed during tensile testing in this study, suggesting the surface cracking problem is more significant than the delamination for the PPE backsheet material and conditions tested here.

  16. Lamb wave sensing using fiber Bragg grating sensors for delamination detection in composite laminates

    Science.gov (United States)

    Takeda, N.; Okabe, Y.; Kuwahara, J.; Kojima, S.

    2005-05-01

    The authors are constructing a damage detection system using ultrasonic waves. In this system, a piezo-ceramic actuator generates Lamb waves in a CFRP laminate. After the waves propagate in the laminate, transmitted waves are received by a fiber Bragg grating (FBG) sensor attached on the laminate using a newly developed high-speed optical wavelength interrogation system. At first, the optimal gauge length of the FBG to detect ultrasonic waves was investigated through theoretical simulations and experiments. Then, the directional sensitivity of the FBG to ultrasonic waves was evaluated experimentally. On the basis of the above results, the 1mm FBG sensors were applied to the detection of Lamb waves propagated in carbon fiber reinforced plastic (CFRP) cross-ply laminates. The piezo-actuator was put on the laminate about 50mm away from the FBG sensor glued on the laminate, and three-cycle sine waves of 300kHz were excited repeatedly. The waveforms obtained by the FBG showed that S0 and A0 modes could be detected appropriately. Then, artificial delamination was made in the laminate by removing of a Teflon sheet embedded in the 0/90 interface after the manufacturing. When the Lamb waves passed through the delamination, the amplitude decreased and a new wave mode appeared. These phenomena could be well simulated using a finite element method. Furthermore, since the amplitude and the velocity of the new mode increased with an increase in the delamination length, this system has a potential to evaluate the interlaminar delamination length quantitatively.

  17. Contribution to interplay between a delamination test and a sensory analysis of mid-range lipsticks.

    Science.gov (United States)

    Richard, C; Tillé-Salmon, B; Mofid, Y

    2016-02-01

    Lipstick is currently one of the most sold products of cosmetics industry, and the competition between the various manufacturers is significant. Customers mainly seek products with high spreadability, especially long-lasting or long wear on the lips. Evaluation tests of cosmetics are usually performed by sensory analysis. This can then represent a considerable cost. The object of this study was to develop a fast and simple test of delamination (objective method with calibrated instruments) and to interplay the obtained results with those of a discriminative sensory analysis (subjective method) in order to show the relevance of the instrumental test. Three mid-range lipsticks were randomly chosen and were tested. They were made of compositions as described by the International Nomenclature of Cosmetic Ingredients (INCI). Instrumental characterization was performed by texture profile analysis and by a special delamination test. The sensory analysis was voluntarily conducted with an untrained panel as blind test to confirm or reverse the possible interplay. The two approaches or methods gave the same type of classification. The high-fat lipstick had the worst behaviour with the delamination test and the worst notation of the intensity of descriptors with the sensory analysis. There is a high correlation between the sensory analysis and the instrumental measurements in this study. The delamination test carried out should permit to quickly determine the lasting (screening test) and in consequence optimize the basic formula of lipsticks. © 2015 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  18. Analytical Solution for the Free Vibration Analysis of Delaminated Timoshenko Beams

    OpenAIRE

    2014-01-01

    This work presents a method to find the exact solutions for the free vibration analysis of a delaminated beam based on the Timoshenko type with different boundary conditions. The solutions are obtained by the method of Lagrange multipliers in which the free vibration problem is posed as a constrained variational problem. The Legendre orthogonal polynomials are used as the beam eigenfunctions. Natural frequencies and mode shapes of various Timoshenko beams are presented to demonstrate the effi...

  19. Analytical solution for the free vibration analysis of delaminated Timoshenko beams.

    Science.gov (United States)

    Jafari-Talookolaei, Ramazan-Ali; Abedi, Maryam

    2014-01-01

    This work presents a method to find the exact solutions for the free vibration analysis of a delaminated beam based on the Timoshenko type with different boundary conditions. The solutions are obtained by the method of Lagrange multipliers in which the free vibration problem is posed as a constrained variational problem. The Legendre orthogonal polynomials are used as the beam eigenfunctions. Natural frequencies and mode shapes of various Timoshenko beams are presented to demonstrate the efficiency of the methodology.

  20. On the Signal-Image Intensity-Curvature Content

    Directory of Open Access Journals (Sweden)

    Carlo Ciulla

    2013-04-01

    Full Text Available The biomedical engineering problem addressed in this work is the one of finding a novel signal-image content measure called intensity-curvature functional making use of all of the second order derivatives of the model function fitted to the data. Given a signal-image made of a sequel of discrete samples and given a model function which embeds the property of second order differentiability, it is possible to quantify the content of the signal-image through a novel approach based on both of the intensity and of the total curvature of the signal-image. The signal-image is fitted with the model function. The total curvature can be calculated through the sum of all of the second order derivatives of the Hessian of the model function fitted to the data. The intensity-curvature functional is defined as the ratio between: (i the integral of the multiplication between the value of the signal modeled through an interpolation function and the total curvature of the signal-image; both of them at the temporal-spatial location of its sampling (the grid nodes and, (ii the integral of the value of the multiplication between the signal modeled through an interpolation function and the total curvature of the signal-image; both of them at any given temporal-spatial location of its re-sampling (intra-pixel location. This manuscript shows both of the formulae and the qualitative results of: the intensity-curvature functional and the intensity-curvature measures which are conceptually linked to the intensity-curvature functional. The formulations here presented make the engineering innovation. The intensity-curvature functional depends on both of the model function fitting the signal-image and the magnitude of re-sampling employed to calculate the second order derivatives of the Hessian of the model function.

  1. Haptic perception of object curvature in Parkinson's disease.

    Directory of Open Access Journals (Sweden)

    Jürgen Konczak

    Full Text Available BACKGROUND: The haptic perception of the curvature of an object is essential for adequate object manipulation and critical for our guidance of actions. This study investigated how the ability to perceive the curvature of an object is altered by Parkinson's disease (PD. METHODOLOGY/PRINCIPAL FINDINGS: Eight healthy subjects and 11 patients with mild to moderate PD had to judge, without vision, the curvature of a virtual "box" created by a robotic manipulandum. Their hands were either moved passively along a defined curved path or they actively explored the curved curvature of a virtual wall. The curvature was either concave or convex (bulging to the left or right and was judged in two locations of the hand workspace--a left workspace location, where the curved hand path was associated with curved shoulder and elbow joint paths, and a right workspace location in which these joint paths were nearly linear. After exploring the curvature of the virtual object, subjects had to judge whether the curvature was concave or convex. Based on these data, thresholds for curvature sensitivity were established. The main findings of the study are: First, 9 out 11 PD patients (82% showed elevated thresholds for detecting convex curvatures in at least one test condition. The respective median threshold for the PD group was increased by 343% when compared to the control group. Second, when distal hand paths became less associated with proximal joint paths (right workspace, haptic acuity was reduced substantially in both groups. Third, sensitivity to hand trajectory curvature was not improved during active exploration in either group. CONCLUSION/SIGNIFICANCE: Our data demonstrate that PD is associated with a decreased acuity of the haptic sense, which may occur already at an early stage of the disease.

  2. Comprehensively simulating the mixed-mode progressive delamination in composite laminates

    Science.gov (United States)

    Gao, Zhenyuan

    Delamination, or interlaminar debonding, is a commonly observed failure mechanism in composite laminates. It is of great significance to comprehensively simulate the mixed-mode progressive delamination in composite structures because by doing this, people can save a lot of effort in evaluating the safe load which a composite structure can endure. The objective of this thesis is to develop a numerical approach to simulating double-cantilever beam (DCB) and mixed-mode bending (MMB) tests and also of specifying/validating various cohesive models. A finite element framework, which consists of properly selecting time integration scheme (explicit dynamic), viscosity, load rate and mass scaling, is developed to yield converged and accurate results. Two illustrative cohesive laws (linear and power-law) are programmed with a user- defined material subroutine for ABAQUS/Explicit, VUMAT, and implemented into the finite element framework. Parameters defined in cohesive laws are studied to evaluate their effects on the predicted load-displacement curves. The finite element model, together with the predetermined model parameters, is found to be capable of producing converged and accurate results. The finite element framework, embedded with the illustrative cohesive laws, is found to be capable of handling various interfacial models. The present approach is concluded to be useful in simulating delamination with more sophisticated material models. Together with the method for determining model parameters, it can be used by computer codes other than ABAQUS.

  3. Comparison Study on the Effect of Interlayer Hydration and Solvation on Montmorillonite Delamination

    Science.gov (United States)

    Li, Hongliang; Song, Shaoxian; Zhao, Yunliang; Nahmad, Yuri; Chen, Tianxing

    2016-11-01

    The effect of water and isopropanol intercalation on montmorillonite (MMT) delamination was investigated in order to compare the roles of hydration and solvation in the delamination. Transmittance results showed that water has a significant effect on the delamination of MMT compared with isopropanol. This observation was attributed to the difference of the intercalation of water and isopropanol. Thermogravimetric (TG) results illustrate that the intercalation mass of water was greater than that of isopropanol when the pressure remained constant. Weighing test results show that the intercalation mass of water was smaller than that of isopropanol when the volume of MMT remained constant. Molecule dynamic simulation results show that the water and isopropanol molecules were interacting with Na+ and siloxane surface of MMT, respectively. It was demonstrated that the hydration of the MMT interlayer followed two steps: in step 1, the Na+ in the interlayer was hydrated, thereby expanding the interlayer spacing; in step 2, additional water molecules were absorbed into the expanded interlayer space. It was found that step 2 could not be actuated until the completion of step 1. For the solvation of the MMT interlayer with isopropanol, however, only one step was required, in which isopropanol was absorbed onto the siloxane sites of the interlayer while maintaining the interlayer spacing.

  4. Delaminated graphene at silicon carbide facets: atomic scale imaging and spectroscopy.

    Science.gov (United States)

    Nicotra, Giuseppe; Ramasse, Quentin M; Deretzis, Ioannis; La Magna, Antonino; Spinella, Corrado; Giannazzo, Filippo

    2013-04-23

    Atomic-resolution structural and spectroscopic characterization techniques (scanning transmission electron microscopy and electron energy loss spectroscopy) are combined with nanoscale electrical measurements (conductive atomic force microscopy) to study at the atomic scale the properties of graphene grown epitaxially through the controlled graphitization of a hexagonal SiC(0001) substrate by high temperature annealing. This growth technique is known to result in a pronounced electron-doping (∼10(13) cm(-2)) of graphene, which is thought to originate from an interface carbon buffer layer strongly bound to the substrate. The scanning transmission electron microscopy analysis, carried out at an energy below the knock-on threshold for carbon to ensure no damage is imparted to the film by the electron beam, demonstrates that the buffer layer present on the planar SiC(0001) face delaminates from it on the (112n) facets of SiC surface steps. In addition, electron energy loss spectroscopy reveals that the delaminated layer has a similar electronic configuration to purely sp2-hybridized graphene. These observations are used to explain the local increase of the graphene sheet resistance measured around the surface steps by conductive atomic force microscopy, which we suggest is due to significantly lower substrate-induced doping and a resonant scattering mechanism at the step regions. A first-principles-calibrated theoretical model is proposed to explain the structural instability of the buffer layer on the SiC facets and the resulting delamination.

  5. Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations Under Flexure Loads

    Science.gov (United States)

    Nordendale, Nikolas A.; Goyal, Vinay K.; Lundgren, Eric C.; Patel, Dhruv N.; Farrokh, Babak; Jones, Justin; Fischetti, Grace; Segal, Kenneth N.

    2015-01-01

    An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and face-sheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. A building block approach using fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a small strength reduction due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

  6. Detecting Thermal Barrier Coating Delamination Using Visible and Near-Infrared Luminescence from Erbium-Doped Sublayers

    Science.gov (United States)

    Eldridge, J. I.; Bencic, T. J.; Martin, R. E.; Singh, J.; Wolfe, D. E.

    2007-01-01

    Nondestructive diagnostic tools are needed to monitor early stages of delamination progression in thermal barrier coatings (TBCs) because the risk of delamination induced coating failure will compromise engine performance and safety. Previous work has demonstrated that for TBCs composed of yttria-stabilized zirconia (YSZ), luminescence from a buried europium-doped sublayer can be utilized to identify the location of TBC delamination from the substantially higher luminescence intensity observed from the delaminated regions of the TBC. Luminescence measurements from buried europium-doped layers depend on sufficient transmittance of the 532 nm excitation and 606 nm emission wavelengths through the attenuating undoped YSZ overlayer to produce easily detected luminescence. In the present work, improved delamination indication is demonstrated using erbium-doped YSZ sublayers. For visible-wavelength luminescence, the erbium-doped sublayer offers the advantage of a very strong excitation peak at 517 nm that can be conveniently excited a 514 nm Ar ion laser. More importantly, the erbium-doped sublayer also produces near-infrared luminescence at 1550 nm that is effectively excited by a 980 nm laser diode. Both the 980 nm excitation and the 1550 nm emission are transmitted through the TBC with much less attenuation than visible wavelengths and therefore show great promise for delamination monitoring through thicker or more highly scattering TBCs. The application of this approach for both electron beam physical vapor deposited (EB-PVD) and plasma-sprayed TBCs is discussed.

  7. A modeling study of convection initiation prior to the merger of a sea-breeze front and a gust front

    Science.gov (United States)

    Abulikemu, Abuduwaili; Xu, Xin; Wang, Yuan; Ding, Jinfeng; Zhang, Shushi; Shen, Wenqiang

    2016-12-01

    Convection initiation (CI) prior to the merger of a sea-breeze front (SBF) with a gust front (GF) in North China is investigated using a real-data Weather Research and Forecasting (WRF) simulation with a high resolution of 444.4 m. The overall evolution of the GF and SBF is well reproduced by the simulation. The GF was produced by the decaying convective storm over northern Beijing, while the SBF came from the Bohai Sea. Several convective cells were generated between the two fronts even though they were still about 25-30 km far away from each other. During the development of these cells, the low-level convergence and conditional instability averaged within the intermediate area between the two fronts were enhanced significantly, both of which favored the initiation of convection. Vertical momentum budgets were conducted in the intermediate area as well as along the backward trajectories of parcels within a selected convective cell. The vertical acceleration was decomposed into dynamic and buoyant components, respectively. The diagnostic results showed that the dynamic acceleration dominated in the low level, while buoyant acceleration became evident only when the parcel reached a high altitude above 2 km. Therefore the dynamic forcing appeared to be more relevant to CI. The dynamic acceleration was further decomposed into four terms based on anelastic approximation. The positive dynamic acceleration was mainly caused by fluid extension associated with the low-level convergence, while fluid twisting in the vertical contributed negatively to the dynamic acceleration. The other two terms related to horizontal curvature and height variation of density were negligibly small.

  8. Slow axis collimation lens with variable curvature radius for semiconductor laser bars

    Science.gov (United States)

    Xiong, Ling-Ling; Cai, Lei; Zheng, Yan-Fang; Liu, Hui; Zhang, Pu; Nie, Zhi-Qiang; Liu, Xing-Sheng

    2016-03-01

    Based on Snell's law and the constant phase in the front of optical field, a design method of the slow axis collimation lens with variable curvature radius is proposed for semiconductor laser bars. Variable radius of the collimator is designed by the transmission angle, and it is demonstrated that the collimator has good beam collimation ability by material with low refractive index. Resorting to the design thought of finite element method, the surface of the collimator has been divided, and it is feasible to be fabricated. This method is applied as an example in collimation of a 976 nm semiconductor laser bar. 6 mrad divergence angle of collimated beam at slow axis is realized by the designed collimation lens with refraction index of 1.51.

  9. Accelerated Observers, Thermal Entropy, and Spacetime Curvature

    CERN Document Server

    Kothawala, Dawood

    2016-01-01

    Assuming that an accelerated observer with four-velocity ${\\bf u}_{\\rm R}$ in a curved spacetime attributes the standard Bekenstein-Hawking entropy and Unruh temperature to his "local Rindler horizon", we show that the $\\rm \\it change$ in horizon area under parametric displacements of the horizon has a very specific thermodynamic structure. Specifically, it entails information about the time-time component of the Einstein tensor: $\\bf G({\\bf u}_{\\rm R}, {\\bf u}_{\\rm R})$. Demanding that the result holds for all accelerated observers, this actually becomes a statement about the full Einstein tensor, $\\rm \\bf G$. We also present some perspectives on the free fall with four-velocity ${\\bf u}_{\\rm ff}$ across the horizon that leads to such a loss of entropy for an accelerated observer. Motivated by results for some simple quantum systems at finite temperature $T$, we conjecture that at high temperatures, there exists a universal, system-independent curvature correction to partition function and thermal entropy of...

  10. Berry curvature and various thermal Hall effects

    Science.gov (United States)

    Zhang, Lifa

    2016-10-01

    Applying the approach of semiclassical wave packet dynamics, we study various thermal Hall effects where carriers can be electron, phonon, magnon, etc. A general formula of thermal Hall conductivity is obtained to provide an essential physics for various thermal Hall effects, where the Berry phase effect manifests naturally. All the formulas of electron thermal Hall effect, phonon Hall effect, and magnon Hall effect can be directly reproduced from the general formula. It is also found that the Strěda formula can not be directly applied to the thermal Hall effects, where only the edge magnetization contributes to the Hall effects. Furthermore, we obtain a combined formula for anomalous Hall conductivity, thermal Hall electronic conductivity and thermal Hall conductivity for electron systems, where the Berry curvature is weighted by a different function. Finally, we discuss particle magnetization and its relation to angular momentum of the carrier, change of which could induce a mechanical rotation; and possible experiments for thermal Hall effect associated with a mechanical rotation are also proposed.

  11. Characterizing repulsive gravity with curvature eigenvalues

    Science.gov (United States)

    Luongo, Orlando; Quevedo, Hernando

    2014-10-01

    Repulsive gravity has been investigated in several scenarios near compact objects by using different intuitive approaches. Here, we propose an invariant method to characterize regions of repulsive gravity, associated to black holes and naked singularities. Our method is based upon the behavior of the curvature tensor eigenvalues, and leads to an invariant definition of a repulsion radius. The repulsion radius determines a physical region, which can be interpreted as a repulsion sphere, where the effects due to repulsive gravity naturally arise. Further, we show that the use of effective masses to characterize repulsion regions can lead to coordinate-dependent results whereas, in our approach, repulsion emerges as a consequence of the spacetime geometry in a completely invariant way. Our definition is tested in the spacetime of an electrically charged Kerr naked singularity and in all its limiting cases. We show that a positive mass can generate repulsive gravity if it is equipped with an electric charge or an angular momentum. We obtain reasonable results for the spacetime regions contained inside the repulsion sphere whose size and shape depend on the value of the mass, charge and angular momentum. Consequently, we define repulsive gravity as a classical relativistic effect by using the geometry of spacetime only.

  12. Programming curvature using origami tessellations.

    Science.gov (United States)

    Dudte, Levi H; Vouga, Etienne; Tachi, Tomohiro; Mahadevan, L

    2016-05-01

    Origami describes rules for creating folded structures from patterns on a flat sheet, but does not prescribe how patterns can be designed to fit target shapes. Here, starting from the simplest periodic origami pattern that yields one-degree-of-freedom collapsible structures-we show that scale-independent elementary geometric constructions and constrained optimization algorithms can be used to determine spatially modulated patterns that yield approximations to given surfaces of constant or varying curvature. Paper models confirm the feasibility of our calculations. We also assess the difficulty of realizing these geometric structures by quantifying the energetic barrier that separates the metastable flat and folded states. Moreover, we characterize the trade-off between the accuracy to which the pattern conforms to the target surface, and the effort associated with creating finer folds. Our approach enables the tailoring of origami patterns to drape complex surfaces independent of absolute scale, as well as the quantification of the energetic and material cost of doing so.

  13. Cosmic acceleration from matter-curvature coupling

    Science.gov (United States)

    Zaregonbadi, Raziyeh; Farhoudi, Mehrdad

    2016-10-01

    We consider f( {R,T} ) modified theory of gravity in which, in general, the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor. We indicate that in this type of the theory, the coupling energy-momentum tensor is not conserved. However, we mainly focus on a particular model that matter is minimally coupled to the geometry in the metric formalism and wherein, its coupling energy-momentum tensor is also conserved. We obtain the corresponding Raychaudhuri dynamical equation that presents the evolution of the kinematic quantities. Then for the chosen model, we derive the behavior of the deceleration parameter, and show that the coupling term can lead to an acceleration phase after the matter dominated phase. On the other hand, the curvature of the universe corresponds with the deviation from parallelism in the geodesic motion. Thus, we also scrutinize the motion of the free test particles on their geodesics, and derive the geodesic deviation equation in this modified theory to study the accelerating universe within the spatially flat FLRW background. Actually, this equation gives the relative accelerations of adjacent particles as a measurable physical quantity, and provides an elegant tool to investigate the timelike and the null structures of spacetime geometries. Then, through the null deviation vector, we find the observer area-distance as a function of the redshift for the chosen model, and compare the results with the corresponding results obtained in the literature.

  14. Active optics: variable curvature mirrors for ELT laser guide star refocusing systems

    Science.gov (United States)

    Challita, Zalpha; Hugot, Emmanuel; Madec, Fabrice; Ferrari, Marc; Le Mignant, David; Vivès, Sébastien; Cuby, Jean-Gabriel

    2011-10-01

    The future generation of Extremely Large Telescopes will require a complex combination of technologies for adaptive optics (AO) systems assisted by laser guide stars (LGS). In this context, the distance from the LGS spot to the telescope pupil ranges from about 80 to 200 km, depending on the Sodium layer altitude and the elevation of the telescope. This variation leads to a defocusing effect on the LGS wave-front sensor which needs to be compensated. We propose an active mirror able to compensate for this variation, based on an original optical design including this active optics component. This LGS Variable Curvature Mirror (LGS-VCM) is a 120 mm spherical active mirror able to achieve 820 μm deflection sag with an optical quality better than 150 nm RMS, allowing the radius of curvature variation from F/12 to F/2. Based on elasticity theory, the deformation of the metallic mirror is provided by an air pressure applied on a thin meniscus with a variable thickness distribution. In this article, we detail the analytical development leading to the specific geometry of the active component, the results of finite element analysis and the expected performances in terms of surface error versus the range of refocalisation. Three prototypes have been manufactured to compare the real behavior of the mirror and the simulations data. Results obtained on the prototypes are detailed, showing that the deformation of the VCM is very close to the simulation, and leads to a realistic active concept.

  15. Axial dispersion in segmented gas-liquid flow: Effects of alternating channel curvature

    Science.gov (United States)

    Muradoglu, Metin

    2010-12-01

    The effects of channel curvature on the axial dispersion in segmented gas-liquid flows are studied computationally in a two-dimensional setting using a finite-volume/front-tracking method. Passive tracer particles are used to visualize and quantify the axial dispersion. The molecular diffusion is modeled by random walk of tracer particles. It is found that there is significant axial dispersion in serpentine channels even in the absence of molecular diffusion. The lubricating thin liquid layer that persists on the wall of a straight channel is periodically broken in the serpentine channel leading to enhanced axial dispersion. It is also found that the axial dispersion is always larger in the serpentine channel than that in the straight channel but the effects of channel curvature are more pronounced at high Peclet numbers, i.e., Pe>104. A model is proposed based on the difference between the liquid film thicknesses on the inner and outer side of the bend in the limit as Pe→∞. Good agreement is found between the computational results and the model when the liquid slug is well mixed by the chaotic advection.

  16. Axial Dispersion in Segmented Gas-Liquid Flow: Effects of the Channel Curvature

    Science.gov (United States)

    Muradoglu, Metin

    2009-11-01

    The effects of channel curvature on the axial dispersion in segmented gas-liquid flows have been studied computationally in a two-dimensional setting using a front-tracking/finite-volume method. Passive tracer particles are used to visualize and quantify the axial dispersion. The molecular diffusion is modeled by random walk of tracer particles. It is found that there is significant axial dispersion in serpentine channels even in the absence of molecular diffusion and dispersion increases with channel curvature. It is known that there is no dispersion in straight channels since a lubricating thin liquid layer persists on the wall. However this lubricating liquid layer is periodically broken in the curved channel case leading to enhanced axial dispersion. It is found that the dispersion increases as the Peclet number (Pe) decreases both in straight and curved channels. Difference between the straight and curved channel decreases continuously as the Peclet number decreases and virtually disappears at low Peclet numbers, i.e., Pestudy. A model is proposed based on the difference between the liquid film thicknesses on the inner and outer side of the bend in the limit as Pe->∞. Good agreement is found between the computational results and the model when the liquid slug is well mixed by the chaotic advection.

  17. Profile Curvature Derivative Surface used to characterize the complexity of the seafloor around St. John, USVI

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Profile curvature was calculated from the bathymetry surface for each raster cell using the ArcGIS 3D Analyst "Curvature" Tool. Profile curvature describes the rate...

  18. Curvature Derivative Surface used to characterize the complexity of the seafloor around St. John, USVI

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Curvature was calculated from the bathymetry surface for each raster cell using the ArcGIS 3D Analyst "Curvature" Tool. Curvature describes the rate of change of...

  19. Plan Curvature Derivative Surface used to characterize the complexity of the seafloor around St. John, USVI

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Plan curvature was calculated from the bathymetry surface for each raster cell using the ArcGIS 3D Analyst "Curvature" Tool. Plan curvature describes the rate of...

  20. 3D curvature of muscle fascicles in triceps surae.

    Science.gov (United States)

    Rana, Manku; Hamarneh, Ghassan; Wakeling, James M

    2014-12-01

    Muscle fascicles curve along their length, with the curvatures occurring around regions of high intramuscular pressure, and are necessary for mechanical stability. Fascicles are typically considered to lie in fascicle planes that are the planes visualized during dissection or two-dimensional (2D) ultrasound scans. However, it has previously been predicted that fascicles must curve in three-dimensional (3D) and thus the fascicle planes may actually exist as 3D sheets. 3D fascicle curvatures have not been explored in human musculature. Furthermore, if the fascicles do not lie in 2D planes, then this has implications for architectural measures that are derived from 2D ultrasound scans. The purpose of this study was to quantify the 3D curvatures of the muscle fascicles and fascicle sheets within the triceps surae muscles and to test whether these curvatures varied among different contraction levels, muscle length, and regions within the muscle. Six male subjects were tested for three torque levels (0, 30, and 60% maximal voluntary contraction) and four ankle angles (-15, 0, 15, and 30° plantar flexion), and fascicles were imaged using 3D ultrasound techniques. The fascicle curvatures significantly increased at higher ankle torques and shorter muscle lengths. The fascicle sheet curvatures were of similar magnitude to the fascicle curvatures but did not vary between contractions. Fascicle curvatures were regionalized within each muscle with the curvature facing the deeper aponeuroses, and this indicates a greater intramuscular pressure in the deeper layers of muscles. Muscle architectural measures may be in error when using 2D images for complex geometries such as the soleus.

  1. Influence of Coanda surface curvature on performance of bladeless fan

    Science.gov (United States)

    Li, Guoqi; Hu, Yongjun; Jin, Yingzi; Setoguchi, Toshiaki; Kim, Heuy Dong

    2014-10-01

    The unique Coanda surface has a great influence on the performance of bladeless fan. However, there is few studies to explain the relationship between the performance and Coanda surface curvature at present. In order to gain a qualitative understanding of effect of the curvature on the performance of bladeless fan, numerical studies are performed in this paper. Firstly, three-dimensional numerical simulation is done by Fluent software. For the purpose to obtain detailed information of the flow field around the Coanda surface, two-dimensional numerical simulation is also conducted. Five types of Coanda surfaces with different curvature are designed, and the flow behaviour and the performance of them are analyzed and compared with those of the prototype. The analysis indicates that the curvature of Coanda surface is strongly related to blowing performance, It is found that there is an optimal curvature of Coanda surfaces among the studied models. Simulation result shows that there is a special low pressure region. With increasing curvature in Y direction, several low pressure regions gradually enlarged, then begin to merge slowly, and finally form a large area of low pressure. From the analyses of streamlines and velocity angle, it is found that the magnitude of the curvature affects the flow direction and reasonable curvature can induce fluid flow close to the wall. Thus, it leads to that the curvature of the streamlines is consistent with that of Coanda surface. Meanwhile, it also causes the fluid movement towards the most suitable direction. This study will provide useful information to performance improvements of bladeless fans.

  2. Align the Front End First.

    Science.gov (United States)

    Perry, Jim

    1995-01-01

    Discussion of management styles and front-end analysis focuses on a review of Douglas McGregor's theories. Topics include Theories X, Y, and Z; leadership skills; motivational needs of employees; intrinsic and extrinsic rewards; and faulty implementation of instructional systems design processes. (LRW)

  3. Multiple WH-Fronting Constructions.

    Science.gov (United States)

    Rudin, Catherine

    The unique position of WH words in Slavic languages is discussed, with specific reference to Bulgarian and Serbo-Croatian. The multiple fronting characteristics of Bulgarian and Serbo-Croatian differ in terms of the following positions and behaviors: extraction from embedded questions; clitic placement and other indications of constituent status;…

  4. The Light-Front Vacuum

    CERN Document Server

    Herrmann, Marc

    2015-01-01

    Background: The vacuum in the light-front representation of quantum field theory is trivial while vacuum in the equivalent canonical representation of the same theory is non-trivial. Purpose: Understand the relation between the vacuum in light-front and canonical representations of quantum field theory and the role of zero-modes in this relation. Method: Vacuua are defined as linear functionals on an algebra of field operators. The role of the algebra in the definition of the vacuum is exploited to understand this relation. Results: The vacuum functional can be extended from the light-front Fock algebra to an algebra of local observables. The extension to the algebra of local observables is responsible for the inequivalence. The extension defines a unitary mapping between the physical representation of the local algebra and a sub-algebra of the light-front Fock algebra. Conclusion: There is a unitary mapping from the physical representation of the algebra of local observables to a sub-algebra of the light-fro...

  5. Align the Front End First.

    Science.gov (United States)

    Perry, Jim

    1995-01-01

    Discussion of management styles and front-end analysis focuses on a review of Douglas McGregor's theories. Topics include Theories X, Y, and Z; leadership skills; motivational needs of employees; intrinsic and extrinsic rewards; and faulty implementation of instructional systems design processes. (LRW)

  6. Light Front Fermion Model Propagation

    Institute of Scientific and Technical Information of China (English)

    Jorge Henrique Sales; Alfredo Takashi Suzuki

    2013-01-01

    In this work we consider the propagation of two fermion fields interacting with each other by the exchange of intermediate scalar bosons in the light front.We obtain the corrections up to fourth order in the coupling constant using hierarchical equations in order to obtain the bound state equation (Bethe-Salpeter equation).

  7. FAZIA front-end electronics

    OpenAIRE

    Salomon F.; Edelbruck P.; Brulin G.; Boiano A.; Tortone G.; Ordine A.; Bini M.; Barlini S.; Valdré S.

    2015-01-01

    FAZIA is a multi-detector specifically designed to optimize ion identification in heavy-ion experiments. Its electronic is fully digital; it was designed in the laboratories of the collaboration. This paper presents the front-end part of this electronic.

  8. FAZIA front-end electronics

    Directory of Open Access Journals (Sweden)

    Salomon F.

    2015-01-01

    Full Text Available FAZIA is a multi-detector specifically designed to optimize ion identification in heavy-ion experiments. Its electronic is fully digital; it was designed in the laboratories of the collaboration. This paper presents the front-end part of this electronic.

  9. Spacetime Curvature in terms of Scalar Field Propagators

    CERN Document Server

    Saravani, Mehdi; Kempf, Achim

    2015-01-01

    We show how quantum fields can be used to measure the curvature of spacetime. In particular, we find that knowledge of the imprint that spacetime curvature leaves in the correlators of quantum fields suffices, in principle, to reconstruct the metric. We then consider the possibility that the quantum fields obey a natural ultraviolet cutoff, for example, at the Planck scale. We investigate how such a cutoff limits the spatial resolution with which curvature can be deduced from the properties of quantum fields. We find that the metric deduced from the quantum correlator exhibits a peculiar scaling behavior as the scale of the natural UV cutoff is approached.

  10. Numerical studies of transverse curvature effects on transonic flow stability

    Science.gov (United States)

    Macaraeg, M. G.; Daudpota, Q. I.

    1992-01-01

    A numerical study of transverse curvature effects on compressible flow temporal stability for transonic to low supersonic Mach numbers is presented for axisymmetric modes. The mean flows studied include a similar boundary-layer profile and a nonsimilar axisymmetric boundary-layer solution. The effect of neglecting curvature in the mean flow produces only small quantitative changes in the disturbance growth rate. For transonic Mach numbers (1-1.4) and aerodynamically relevant Reynolds numbers (5000-10,000 based on displacement thickness), the maximum growth rate is found to increase with curvature - the maximum occurring at a nondimensional radius (based on displacement thickness) between 30 and 100.

  11. 3-manifolds with(out) metrics of nonpositive curvature

    CERN Document Server

    Leeb, B

    1994-01-01

    In the context of Thurstons geometrisation program we address the question which compact aspherical 3-manifolds admit Riemannian metrics of nonpositive curvature. We show that non-geometric Haken manifolds generically, but not always, admit such metrics. More precisely, we prove that a Haken manifold with, possibly empty, boundary of zero Euler characteristic admits metrics of nonpositive curvature if the boundary is non-empty or if at least one atoroidal component occurs in its canonical topological decomposition. Our arguments are based on Thurstons Hyperbolisation Theorem. We give examples of closed graph-manifolds with linear gluing graph and arbitrarily many Seifert components which do not admit metrics of nonpositive curvature.

  12. On Hypersurfaces with two Distinct Principal Curvatures in Space Forms

    Indian Academy of Sciences (India)

    Bing Ye Wu

    2011-11-01

    We investigate the immersed hypersurfaces in space forms $\\mathbb{N}^{n+1}(c),n≥ 4$ with two distinct non-simple principal curvatures without the assumption that the (high order) mean curvature is constant. We prove that any immersed hypersurface in space forms with two distinct non-simple principal curvatures is locally conformal to the Riemannian product of two constant curved manifolds. We also obtain some characterizations for the Clifford hypersurfaces in terms of the trace free part of the second fundamental form.

  13. Motion on constant curvature spaces and quantization using Noether symmetries.

    Science.gov (United States)

    Bracken, Paul

    2014-12-01

    A general approach is presented for quantizing a metric nonlinear system on a manifold of constant curvature. It makes use of a curvature dependent procedure which relies on determining Noether symmetries from the metric. The curvature of the space functions as a constant parameter. For a specific metric which defines the manifold, Lie differentiation of the metric gives these symmetries. A metric is used such that the resulting Schrödinger equation can be solved in terms of hypergeometric functions. This permits the investigation of both the energy spectrum and wave functions exactly for this system.

  14. Effect of membrane curvature on lateral distribution of membrane proteins

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Several membrane proteins exhibit interesting shapes that increases their preference for certain membrane curvatures. Both peripheral and transmembrane proteins are tested with respect to their affinity for a spectrum of high membrane curvatures. We generate high membrane curvatures by pulling...... membrane tubes out of Giant Unilamellar lipid Vesicles (GUVs). The tube diameter can be tuned by aspirating the GUV into a micropipette for controlling the membrane tension. By using fluorescently labled proteins we have shown that sorting of proteins like e.g. FBAR onto tubes is significantly increased...

  15. Surfaces with parallel mean curvature vector in complex space forms

    CERN Document Server

    Fetcu, Dorel

    2010-01-01

    We consider a quadratic form defined on the surfaces with parallel mean curvature vector of an any dimensional complex space form and prove that its $(2,0)$-part is holomorphic. When the complex dimension of the ambient space is equal to $2$ we define a second quadratic form with the same property and then determine those surfaces with parallel mean curvature vector on which the $(2,0)$-parts of both of them vanish. We also provide a reduction of codimension theorem and prove a non-existence result for $2$-spheres with parallel mean curvature vector.

  16. Correlation between thoracolumbar curvatures and respiratory function in older adults

    Directory of Open Access Journals (Sweden)

    Rahman NNAA

    2017-03-01

    Full Text Available Nor Najwatul Akmal Ab Rahman,1 Devinder Kaur Ajit Singh,1 Raymond Lee2 1Physiotherapy Programme, School of Rehabilitation Sciences, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, Kuala Lumpur, Malaysia; 2School of Applied Sciences, London South Bank University, London, UK Abstract: Aging is associated with alterations in thoracolumbar curvatures and respiratory function. Research information regarding the correlation between thoracolumbar curvatures and a comprehensive examination of respiratory function parameters in older adults is limited. The aim of the present study was to examine the correlation between thoracolumbar curvatures and respiratory function in community-dwelling older adults. Thoracolumbar curvatures (thoracic and lumbar were measured using a motion tracker. Respiratory function parameters such as lung function, respiratory rate, respiratory muscle strength and respiratory muscle thickness (diaphragm and intercostal were measured using a spirometer, triaxial accelerometer, respiratory pressure meter and ultrasound imaging, respectively. Sixty-eight community-dwelling older males and females from Kuala Lumpur, Malaysia, with mean (standard deviation age of 66.63 (5.16 years participated in this cross-sectional study. The results showed that mean (standard deviation thoracic curvature angle and lumbar curvature angles were -46.30° (14.66° and 14.10° (10.58°, respectively. There was a significant negative correlation between thoracic curvature angle and lung function (forced expiratory volume in 1 second: r=-0.23, P<0.05; forced vital capacity: r=-0.32, P<0.05, quiet expiration intercostal thickness (r=-0.22, P<0.05 and deep expiration diaphragm muscle thickness (r=-0.21, P<0.05. The lumbar curvature angle had a significant negative correlation with respiratory muscle strength (r=-0.29, P<0.05 and diaphragm muscle thickness at deep inspiration (r=-0.22, P<0.05. However, respiratory rate

  17. Holomorphic Bisectional Curvatures, Supersymmetry Breaking, and Affleck-Dine Baryogenesis

    CERN Document Server

    Dutta, Bhaskar

    2012-01-01

    Working in $D=4, N=1$ supergravity, we utilize relations between holomorphic sectional and bisectional curvatures of Kahler manifolds to constrain Affleck-Dine baryogenesis. We show the following No-Go result: Affleck-Dine baryogenesis cannot be performed if the holomorphic sectional curvature at the origin is isotropic in tangent space; as a special case, this rules out spaces of constant holomorphic sectional curvature (defined in the above sense) and in particular maximally symmetric coset spaces. We also investigate scenarios where inflationary supersymmetry breaking is identified with the supersymmetry breaking responsible for mass splitting in the visible sector, using conditions of sequestering to constrain manifolds where inflation can be performed.

  18. Engineering Curvature-Induced Anisotropy in Thin Ferromagnetic Films

    Science.gov (United States)

    Tretiakov, Oleg A.; Morini, Massimiliano; Vasylkevych, Sergiy; Slastikov, Valeriy

    2017-08-01

    We investigate the effect of large curvature and dipolar energy in thin ferromagnetic films with periodically modulated top and bottom surfaces on magnetization behavior. We predict that the dipolar interaction and surface curvature can produce perpendicular anisotropy which can be controlled by engineering special types of periodic surface structures. Similar effects can be achieved by a significant surface roughness in the film. We demonstrate that, in general, the anisotropy can point in an arbitrary direction depending on the surface curvature. Furthermore, we provide simple examples of these periodic surface structures to show how to engineer particular anisotropies in thin films.

  19. Curvature-driven assembly in soft matter.

    Science.gov (United States)

    Liu, Iris B; Sharifi-Mood, Nima; Stebe, Kathleen J

    2016-07-28

    Control over the spatial arrangement of colloids in soft matter hosts implies control over a wide variety of properties, ranging from the system's rheology, optics, and catalytic activity. In directed assembly, colloids are typically manipulated using external fields to form well-defined structures at given locations. We have been developing alternative strategies based on fields that arise when a colloid is placed within soft matter to form an inclusion that generates a potential field. Such potential fields allow particles to interact with each other. If the soft matter host is deformed in some way, the potential allows the particles to interact with the global system distortion. One important example is capillary assembly of colloids on curved fluid interfaces. Upon attaching, the particle distorts that interface, with an associated energy field, given by the product of its interfacial area and the surface tension. The particle's capillary energy depends on the local interface curvature. We explore this coupling in experiment and theory. There are important analogies in liquid crystals. Colloids in liquid crystals elicit an elastic energy response. When director fields are moulded by confinement, the imposed elastic energy field can couple to that of the colloid to define particle paths and sites for assembly. By improving our understanding of these and related systems, we seek to develop new, parallelizable routes for particle assembly to form reconfigurable systems in soft matter that go far beyond the usual close-packed colloidal structures.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.

  20. Frontal dynamics in a California Current System shallow front: 1. Frontal processes and tracer structure

    Science.gov (United States)

    Pallã S-Sanz, E.; Johnston, T. M. S.; Rudnick, D. L.

    2010-12-01

    The three-dimensional dynamics in a shallow front are examined using density and current data from two surveys 100 km offshore of Monterey Bay, California. Survey 1 is forced by down-front winds, and both surveys have considerable cross-front density gradients and flow curvature. The maximum Rossby numbers on the dense side reached maxima of +0.60 in survey 1 and +0.45 in survey 2. Downwelling occurs in regions of confluence (frontogenesis) associated with potential vorticity (PV) change and thermal wind imbalance. Streamers of particulate matter and PV are advected southeastward by the frontal jet and downward. Nonlinear Ekman currents advect dense water over light water in the presence of down-front winds, which leads to upwelling along the front and downwelling on the light side of the front. At sites of active ageostrophic secondary circulation (ASC), induced by frontogenesis or Ekman effects, the observed cross-front ageostrophic velocity is consistent with the diagnosed vertical velocity. Furthermore, in survey 2, ageostrophic divergence may play an important role at the curved front, presumably counteracting quasi-geostrophic frontogenesis due to isopycnal confluence. Downward frictional vertical PV flux below the surface extracts PV from the pycnocline and reinforces the frontogenetic vertical PV flux. PV destruction at the surface is inferred from a low PV anomaly below the mixed layer in survey 2. Since the magnitude of the frontogenetic ASC is only twice the magnitude of Ekman suction, external forcing may have a considerable impact on the vertical heat and PV fluxes.

  1. Monitoring Delamination of Thermal Barrier Coatings During Interrupted High-Heat-Flux Laser Testing using Luminescence Imaging

    Science.gov (United States)

    Eldridge, Jeffrey I.; Zhu, Dongming; Wolfe, Douglas E.

    2011-01-01

    This presentation showed progress made in extending luminescence-base delamination monitoring to TBCs exposed to high heat fluxes, which is an environment that much better simulates actual turbine engine conditions. This was done by performing upconversion luminescence imaging during interruptions in laser testing, where a high-power CO2 laser was employed to create the desired heat flux. Upconverison luminescence refers to luminescence where the emission is at a higher energy (shorter wavelength) than the excitation. Since there will be negligible background emission at higher energies than the excitation, this methods produces superb contrast. Delamination contrast is produced because both the excitation and emission wavelengths are reflected at delamination cracks so that substantially higher luminescence intensity is observed in regions containing delamination cracks. Erbium was selected as the dopant for luminescence specifically because it exhibits upconversion luminescence. The high power CO2 10.6 micron wavelength laser facility at NASA GRC was used to produce the heat flux in combination with forced air backside cooling. Testing was performed at a lower (95 W/sq cm) and higher (125 W/sq cm) heat flux as well as furnace cycling at 1163C for comparison. The lower heat flux showed the same general behavior as furnace cycling, a gradual, "spotty" increase in luminescence associated with debond progression; however, a significant difference was a pronounced incubation period followed by acceleration delamination progression. These results indicate that extrapolating behavior from furnace cycling measurements will grossly overestimate remaining life under high heat flux conditions. The higher heat flux results were not only accelerated, but much different in character. Extreme bond coat rumpling occurred, and delamination propagation extended over much larger areas before precipitating macroscopic TBC failure. This indicates that under the higher heat flux (and

  2. A mean curvature estimate for cylindrically bounded submanifolds

    CERN Document Server

    Alias, Luis J

    2010-01-01

    We extend the estimate obtained in [1] for the mean curvature of a cylindrically bounded proper submanifold in a product manifold with an Euclidean space as one factor to a general product ambient space endowed with a warped product structure.

  3. Comment on "On curvature coupling and quintessence fine-tuning"

    CERN Document Server

    Franca, U

    2005-01-01

    In this comment, we show explicitly that the phenomenological model in which the quintessence field depends linearly on the energy density of the spatial curvature can provide acceleration for the universe, contrary to recent claims it could not.

  4. Inverse lyotropic phases of lipids and membrane curvature

    Energy Technology Data Exchange (ETDEWEB)

    Shearman, G C; Ces, O; Templer, R H; Seddon, J M [Department of Chemistry, Imperial College London, SW7 2AZ (United Kingdom)

    2006-07-19

    In recent years it has become evident that many biological functions and processes are associated with the adoption by cellular membranes of complex geometries, at least locally. In this paper, we initially discuss the range of self-assembled structures that lipids, the building blocks of biological membranes, may form, focusing specifically on the inverse lyotropic phases of negative interfacial mean curvature. We describe the roles of curvature elasticity and packing frustration in controlling the stability of these inverse phases, and the experimental determination of the spontaneous curvature and the curvature elastic parameters. We discuss how the lyotropic phase behaviour can be tuned by the addition of compounds such as long-chain alkanes, which can relieve packing frustration. The latter section of the paper elaborates further on the structure, geometric properties, and stability of the inverse bicontinuous cubic phases.

  5. Curvature-based Hyperbolic Systems for General Relativity

    CERN Document Server

    Choquet-Bruhat, Y; Anderson, A; Choquet-Bruhat, Yvonne; York, James W.; Anderson, Arlen

    1998-01-01

    We review curvature-based hyperbolic forms of the evolution part of the Cauchy problem of General Relativity that we have obtained recently. We emphasize first order symmetrizable hyperbolic systems possessing only physical characteristics.

  6. Abnormalities of penile curvature: chordee and penile torsion.

    Science.gov (United States)

    Montag, Sylvia; Palmer, Lane S

    2011-07-28

    Congenital chordee and penile torsion are commonly observed in the presence of hypospadias, but can also be seen in boys with the meatus in its orthotopic position. Varying degrees of penile curvature are observed in 4-10% of males in the absence of hypospadias. Penile torsion can be observed at birth or in older boys who were circumcised at birth. Surgical management of congenital curvature without hypospadias can present a challenge to the pediatric urologist. The most widely used surgical techniques include penile degloving and dorsal plication. This paper will review the current theories for the etiology of penile curvature, discuss the spectrum of severity of congenital chordee and penile torsion, and present varying surgical techniques for the correction of penile curvature in the absence of hypospadias.

  7. Bacterial cell curvature through mechanical control of cell growth

    DEFF Research Database (Denmark)

    Cabeen, M.; Charbon, Godefroid; Vollmer, W.

    2009-01-01

    The cytoskeleton is a key regulator of cell morphogenesis. Crescentin, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus and localizes to the inner cell curvature. Here, we show that crescentin forms a single filamentous structure...... that collapses into a helix when detached from the cell membrane, suggesting that it is normally maintained in a stretched configuration. Crescentin causes an elongation rate gradient around the circumference of the sidewall, creating a longitudinal cell length differential and hence curvature. Such curvature...... can be produced by physical force alone when cells are grown in circular microchambers. Production of crescentin in Escherichia coli is sufficient to generate cell curvature. Our data argue for a model in which physical strain borne by the crescentin structure anisotropically alters the kinetics...

  8. Abnormalities of Penile Curvature: Chordee and Penile Torsion

    Directory of Open Access Journals (Sweden)

    Sylvia Montag

    2011-01-01

    Full Text Available Congenital chordee and penile torsion are commonly observed in the presence of hypospadias, but can also be seen in boys with the meatus in its orthotopic position. Varying degrees of penile curvature are observed in 4–10% of males in the absence of hypospadias. Penile torsion can be observed at birth or in older boys who were circumcised at birth. Surgical management of congenital curvature without hypospadias can present a challenge to the pediatric urologist. The most widely used surgical techniques include penile degloving and dorsal plication. This paper will review the current theories for the etiology of penile curvature, discuss the spectrum of severity of congenital chordee and penile torsion, and present varying surgical techniques for the correction of penile curvature in the absence of hypospadias.

  9. Quasi-Maxwell interpretation of the spin-curvature coupling

    CERN Document Server

    Natario, J

    2007-01-01

    We write the Mathisson-Papapetrou equations of motion for a spinning particle in a stationary spacetime using the quasi-Maxwell formalism and give an interpretation of the coupling between spin and curvature.

  10. Changes on the corneal thickness and curvature after orthokeratology

    Science.gov (United States)

    Mitsui, Iwane; Yamada, Yoshiya

    2004-07-01

    To evaluate the corneal thickness and curvature changes after Orthokeratology contact lens wear, using the ORBSCAN II corneal topography system, corneal thickness and corneal curvature were measured on one hundred and twenty eyes of sixty patients before and after wearing the custom rigid gas permeable contact lenses for Orthokeratology. The contact lenses were specially designed for each eye. The subjects wore the orthokeratology lenses for approximately Four hours with their eyes closed. The corneal thickness of the subjects was increased on fifty-five eyes at not only the peripheral zone but also the center of the cornea. The average increase of central and peripheral corneal thickness was 18 micrometer and 22micrometer, respectively. The mean anterior curvature of corneal surface changed 1.25D. The mean posterior curvature of corneal endothelium side changed 0.75D.

  11. A compactness theorem for surfaces with Bounded Integral Curvature

    OpenAIRE

    Debin, Clément

    2016-01-01

    We prove a compactness theorem for metrics with Bounded Integral Curvature on a fixed closed surface $\\Sigma$. As a corollary, we obtain a compactification of the space of Riemannian metrics with conical singularities, where an accumulation of singularities is allowed.

  12. A Method for Wavefront Curvature Ranging of Speech Sources ...

    African Journals Online (AJOL)

    A Method for Wavefront Curvature Ranging of Speech Sources. ... A new approach for estimating the location of a speech source in a reverberant environment is presented. The approach ... EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT

  13. Curvature-induced stiffening of a fish fin

    CERN Document Server

    Nguyen, Khoi; Bandi, Mahesh M; Venkadesan, Madhusudhan; Mandre, Shreyas

    2016-01-01

    Fish behaviour and its ecological niche require modulation of its fin stiffness. Using mathematical analyses of rayed fish fins, we show that curvature transverse to the rays is central to fin stiffness. We model the fin as rays with anisotropic bending that are connected by an elastic membrane. For fins with transverse curvature, external loads that bend the rays also splay them apart, which stretches the membrane. This coupling, between ray bending and membrane stretching, underlies the curvature-induced stiffness. A fin that appears flat may still exhibit bending-stretching coupling if the principal bending axes of adjacent rays are misaligned by virtue of intrinsic geometry, i.e. morphologically flat yet functionally curved. Analysis of the pectoral fin of a mackerel shows such functional curvature. Furthermore, as identified by our analyses, the mackerel's fin morphology endows it with the potential to modulate stiffness over a wide range.

  14. The probability equation for the cosmological comoving curvature perturbation

    Energy Technology Data Exchange (ETDEWEB)

    Riotto, Antonio; Sloth, Martin S., E-mail: antonio.riotto@pd.infn.it, E-mail: sloth@cern.ch [CERN, PH-TH Division, CH-1211, Genève 23 (Switzerland)

    2011-10-01

    Fluctuations of the comoving curvature perturbation with wavelengths larger than the horizon length are governed by a Langevin equation whose stochastic noise arise from the quantum fluctuations that are assumed to become classical at horizon crossing. The infrared part of the curvature perturbation performs a random walk under the action of the stochastic noise and, at the same time, it suffers a classical force caused by its self-interaction. By a path-interal approach and, alternatively, by the standard procedure in random walk analysis of adiabatic elimination of fast variables, we derive the corresponding Kramers-Moyal equation which describes how the probability distribution of the comoving curvature perturbation at a given spatial point evolves in time and is a generalization of the Fokker-Planck equation. This approach offers an alternative way to study the late time behaviour of the correlators of the curvature perturbation from infrared effects.

  15. Curvature-Squared Cosmology In The First-Order Formalism

    Science.gov (United States)

    Shahid-Saless, Bahman

    1993-01-01

    Paper presents theoretical study of some of general-relativistic ramifications of gravitational-field energy density proportional to R - alpha R(exp 2) (where R is local scalar curvature of space-time and alpha is a constant).

  16. Curvature Control of Silicon Microlens for THz Dielectric Antenna

    Science.gov (United States)

    Lee, Choonsup; Chattopadhyay, Goutam; Cooper, Ken; Mehdi, Imran

    2012-01-01

    We have controlled the curvature of silicon microlens by changing the amount of photoresist in order to microfabricate hemispherical silicon microlens which can improve the directivity and reduce substrate mode losses.

  17. Facial landmark localization by curvature maps and profile analysis

    National Research Council Canada - National Science Library

    Lippold, Carsten; Liu, Xiang; Wangdo, Kim; Drerup, Burkhard; Schreiber, Kristina; Kirschneck, Christian; Moiseenko, Tatjana; Danesh, Gholamreza

    2014-01-01

    .... This study wants to evaluate and present an objective method for measuring selected facial landmarks based on an analysis of curvature maps and of sagittal profile obtained by a laser-scanning method...

  18. Springback prediction of three-dimensional variable curvature tube bending

    National Research Council Canada - National Science Library

    Zhang, Shen; Wu, Jianjun

    2016-01-01

    .... The springback prediction of three-dimensional variable curvature bent tube is projected on each discrete osculating and rectifying plane, and then the three-dimensional problem can be transformed into two dimensions...

  19. Curvature Control of Silicon Microlens for THz Dielectric Antenna

    Science.gov (United States)

    Lee, Choonsup; Chattopadhyay, Goutam; Cooper, Ken; Mehdi, Imran

    2012-01-01

    We have controlled the curvature of silicon microlens by changing the amount of photoresist in order to microfabricate hemispherical silicon microlens which can improve the directivity and reduce substrate mode losses.

  20. Waves, instabilities and turbulence properties in Depolarisation Fronts

    Science.gov (United States)

    Lapenta, Giovanni; Goldman, Martin; Newman, David L.; Olshevskyi, Vyacheslav; Eastwood, Jonathan; Divin, Andrey; Pucci, Francesco

    2016-04-01

    The new mission MMS is currently focusing on the magnetopause but we need to be ready for the study of the tail. An aspect of great importance there are the Dipolarization fronts (DF), formed by reconnection outflows interacting with the pre-existing environment. These regions are host of important energy and wave phenomena [1-3]. Our recent work has investigated these regions via fully kinetic 3D simulations [4-5]. As reported recently on Nature Physics [3], based on 3D fully kinetic simulations started with a well defined x-line, we observe that in the DF reconnection transitions towards a more chaotic regime. In the fronts an instability develops caused by the local gradients of the density and by the unfavourable acceleration and field line curvature. The consequence is the break up of the fronts in a fashion similar to the classical fluid Rayleigh-Taylor instability and the onset of waves and secondary instabilities, transitioning towards a turbulent state. We investigate here especially the wave signatures that are observed in fully 3D simulations, looking for signatures of interchange-type lower hybrid waves [8], of whistler waves [7]. The end result present a vast array of waves and it is best analysed relying on concepts mutated by the turbulence theory. The end result of these waves and particle flows [2,6] are energy exchanges. We evaluate the different terms of the energy exchanges (energy deposition, J.E, and energy fluxes) and evaluate their relative improtance. The results presented are contrasted against existing results [1,9] and will provided useful guidance in analysis of future MMS data. [1] Hamrin, Maria, et al. "The evolution of flux pileup regions in the plasma sheet: Cluster observations." Journal of Geophysical Research: Space Physics 118.10 (2013): 6279-6290. [2] Angelopoulos, V., et al. "Electromagnetic energy conversion at reconnection fronts." Science 341.6153 (2013): 1478-1482. [3] Zhou, Meng, et al. "THEMIS observation of multiple