Diameter-dependent bending modulus of individual multiwall boron nitride nanotubes.
Tanur, Adrienne E; Wang, Jiesheng; Reddy, Arava L M; Lamont, Daniel N; Yap, Yoke Khin; Walker, Gilbert C
2013-04-25
The mechanical properties of individual multiwall boron nitride nanotubes (MWBNNTs) synthesized by a growth-vapor-trapping chemical vapor deposition method are investigated by a three-point bending technique via atomic force microscopy. Multiple locations on suspended tubes are probed in order to determine the boundary conditions of the supported tube ends. The bending moduli (EB) calculated for 20 tubes with diameters ranging from 18 to 58 nm confirm the exceptional mechanical properties of MWBNNTs, with an average EB of 760 ± 30 GPa. For the first time, the bending moduli of MWBNNTs are observed to increase with decreasing diameter, ranging from 100 ± 20 GPa to as high as 1800 ± 300 GPa. This diameter dependence is evaluated by Timoshenko beam theory. The Young's modulus and shear modulus were determined to be 1800 ± 300 and 7 ± 1 GPa, respectively, for a trimmed data set of 16 tubes. The low shear modulus of MWBNNTs is the reason for the detected diameter-dependent bending modulus and is likely due to the presence of interwall shearing between the crystalline and faceted helical nanotube structures of MWBNNTs.
Plausible cloth animation using dynamic bending model
Chuan Zhou; Xiaogang Jin; Charlie C.L. Wang; Jieqing Feng
2008-01-01
Simulating the mechanical behavior of a cloth is a very challenging and important problem in computer animation. The models of bending in most existing cloth simulation approaches are taking the assumption that the cloth is little deformed from a plate shape.Therefore, based on the thin-plate theory, these bending models do not consider the condition that the current shape of the cloth under large deformations cannot be regarded as the approximation to that before deformation, which leads to an unreal static bending. [This paper introduces a dynamic bending model which is appropriate to describe large out-plane deformations such as cloth buckling and bending, and develops a compact implementation of the new model on spring-mass systems. Experimental results show that wrinkles and folds generated using this technique in cloth simulation, can appear and vanish in a more natural way than other approaches.
Tuncel, Eylul; Suzuki, Yasuhito; Iossifidis, Agathaggelos; Steinhart, Martin; Butt, Hans-Jurgen; Floudas, George; Duran, Hatice
Structure formation, thermodynamic stability, phase and dynamic behaviors of polypeptides are strongly affected by confinement. Since understanding the changes in these behaviors will allow their rational design as functional devices with tunable properties, herein we investigated Poly-Z-L-lysine (PZLL) and Poly-L-alanine (PAla) homopolypeptides confined in nanoporous alumina containing aligned cylindrical nanopores as a function of pore size by differential scanning calorimetry (DSC), Fourier Transform Infrared Spectroscopy, Solid-state NMR, X-ray diffraction, Dielectric spectroscopy(DS). Bulk PZLL exhibits a glass transition temperature (Tg) at about 301K while PZLL nanorods showed slightly lower Tg (294K). The dynamic investigation by DS also revealed a decrease (4K) in Tg between bulk and PZLL nanorods. DS is a very sensitive probe of the local and global secondary structure relaxation through the large dipole to study effect of confinement. The results revealed that the local segmental dynamics, associated with broken hydrogen bonds, and segmental dynamics speed-up on confinement.
Quasimolecular Dynamic Simulation for Bending Fracture of Laminar Composite Materials
无
2001-01-01
Recently, quasimolecular dynamics has been successfully used to simulate the deformation characteristics of actual size solid materials. In quasimolecular dynamics, which is an attempt to bridge the gap between atomistic and continuum simulations, molecules are aggregated into large units, called quasimolecules, to evaluate large scale material behavior. In this paper, a 2-dimensional numerical simulation using quasimolecular dynamics was performed to investigate laminar composite material fractures and crack propagation behavior in the uniform bending of laminar composite materials. It was verified that under bending deformation laminar composite materials deform quite differently from homogeneous materials
Dynamic Electromechanical Coupling of Piezoelectric Bending Actuators
Mostafa R. A. Nabawy
2016-01-01
Full Text Available Electromechanical coupling defines the ratio of electrical and mechanical energy exchanged during a flexure cycle of a piezoelectric actuator. This paper presents an analysis of the dynamic electromechanical coupling factor (dynamic EMCF for cantilever based piezoelectric actuators and provides for the first time explicit expressions for calculation of dynamic EMCF based on arrangement of passive and active layers, layer geometry, and active and passive materials selection. Three main cantilever layer configurations are considered: unimorph, dual layer bimorph and triple layer bimorph. The actuator is modeled using standard constitutive dynamic equations that relate deflection and charge to force and voltage. A mode shape formulation is used for the cantilever dynamics that allows the generalized mass to be the actual mass at the first resonant frequency, removing the need for numerical integration in the design process. Results are presented in the form of physical insight from the model structure and also numerical evaluations of the model to provide trends in dynamic EMCF with actuator design parameters. For given material properties of the active and passive layers and given system overall damping ratio, the triple layer bimorph topology is the best in terms of theoretically achievable dynamic EMCF, followed by the dual layer bimorph. For a damping ratio of 0.035, the dynamic EMCF for an example dual layer bimorph configuration is 9% better than for a unimorph configuration. For configurations with a passive layer, the ratio of thicknesses for the passive and active layers is the primary geometric design variable. Choice of passive layer stiffness (Young’s modulus relative to the stiffness of the material in the active layer is an important materials related design choice. For unimorph configurations, it is beneficial to use the highest stiffness possible passive material, whereas for triple layer bimorph configurations, the passive
The diameter-dependent photoelectrochemical performance of silicon nanowires.
Zhang, Bing-Chang; Wang, Hui; He, Le; Duan, Chun-Yang; Li, Fan; Ou, Xue-Mei; Sun, Bao-Quan; Zhang, Xiao-Hong
2016-01-25
We demonstrate the first systematic study of the diameter-dependent photoelectrochemical performance of single silicon nanowires within a broad size range from 200 to 2000 nm. SiNWs with a diameter of 1415 nm exhibit the highest solar energy conversion efficiency, which can be mainly traced to their diameter-dependent light absorption properties.
Diameter-dependent thermodynamic and elastic properties of metallic nanoparticles
Chandra, Jeewan; Kholiya, Kuldeep
2015-04-01
A simple theoretical model has been proposed to study the diameter-dependent properties of metallic nanoparticles, i.e. Ag, Au, Al, Ni, Pb, Cu and Fe. The diameter-dependent thermodynamic properties includes melting temperature, Debye temperature, evaporation temperature, melting enthapy and melting entropy. The model is also extended to study the diameter-dependent elastic properties including bulk modulus, Young's modulus and thermal expansion coefficient. On comparison with available experimental findings and other theoretical approaches, the results obtained with the present formulation depict a close agreement and demonstrate the validity of the method proposed in the present paper.
Bending dynamics of semi-flexible macromolecules in isotropic turbulence
Ali, Aamir; Vincenzi, Dario
2014-01-01
We study the Lagrangian dynamics of semi-flexible macromolecules in laminar as well as in homogeneous and isotropic turbulent flows by means of analytically solvable stochastic models and direct numerical simulations. The statistics of the bending angle is qualitatively different in laminar and turbulent flows and exhibits a strong dependence on the topology of the velocity field. In particular, in two-dimensional turbulence, particles are either found in a fully extended or in a fully folded configuration; in three dimensions, the predominant configuration is the fully extended one.
Diameter-dependent conductance of InAs nanowires
Scheffler, M.; Nadj-Perge, S.; Kouwenhoven, L.P.; Borgström, M.T.; Bakkers, E.P.A.M.
2009-01-01
Electrical conductance through InAs nanowires is relevant for electronic applications as well as for fundamental quantum experiments. Here, we employ nominally undoped, slightly tapered InAs nanowires to study the diameter dependence of their conductance. By contacting multiple sections of each wire
Dynamic conductance in double-bend silicene nanosystem
Sun, Yun-Lei; Zhu, Chun; Chen, Jian; Ye, En-Jia
2017-09-01
In this work, dynamic conductance transport properties are theoretically investigated in the zigzag silicene nanosystem with a double-bend structure. We numerically study the dc conductance and ac emittance in the nanosystem based on the tight-binding approach, Green's function method and ac transport theory, by considering the second-nearest-neighbor spin-orbit interaction (SOI) and external electric field. The numerical results suggest that the nanosystem undergoes a quantum phase transition driven by the relatively strong SOI, which results in a large dc conductance and a vanishing ac emittance around the Dirac point despite the interface scattering. The distribution of the local density of states in the real space reveals that the SOI induces the quantum edge state by establishing transport paths at the edge of the nanosystem. Further investigation indicates that the dynamic conductance related to the quantum edge state are topologically protected from the geometrical size change of the nanosystem. Finally, the nanosystem can be tuned to be a trivial band insulator without any dc or ac response by applying external electric field.
Dynamic Coupling among Protein Binding, Sliding, and DNA Bending Revealed by Molecular Dynamics.
Tan, Cheng; Terakawa, Tsuyoshi; Takada, Shoji
2016-07-13
Protein binding to DNA changes the DNA's structure, and altered DNA structure can, in turn, modulate the dynamics of protein binding. This mutual dependency is poorly understood. Here we investigated dynamic couplings among protein binding to DNA, protein sliding on DNA, and DNA bending by applying a coarse-grained simulation method to the bacterial architectural protein HU and 14 other DNA-binding proteins. First, we verified our method by showing that the simulated HU exhibits a weak preference for A/T-rich regions of DNA and a much higher affinity for gapped and nicked DNA, consistent with biochemical experiments. The high affinity was attributed to a local DNA bend, but not the specific chemical moiety of the gap/nick. The long-time dynamic analysis revealed that HU sliding is associated with the movement of the local DNA bending site. Deciphering single sliding steps, we found the coupling between HU sliding and DNA bending is akin to neither induced-fit nor population-shift; instead they moved concomitantly. This is reminiscent of a cation transfer on DNA and can be viewed as a protein version of polaron-like sliding. Interestingly, on shorter time scales, HU paused when the DNA was highly bent at the bound position and escaped from pauses once the DNA spontaneously returned to a less bent structure. The HU sliding is largely regulated by DNA bending dynamics. With 14 other proteins, we explored the generality and versatility of the dynamic coupling and found that 6 of the 15 assayed proteins exhibit the polaron-like sliding.
DYNAMIC BEHAVIOR OF BURIED BEND WITH THRUST RESTRAINT IN LIQUEFYING GROUND
Kawabata, Toshinori; Sawada, Yutaka; Mohri, Yoshiyuki; Ling, Hoe I.
In this study, a shaking table test was carried out in order to discuss the dynamic behavior for the bend of pressure pipeline with a concrete block and thrust restraints using geogrids or gravels in liquefying ground. As a result, it was revealed that the concrete block was largely moved and the relative displacement between the bend and the adjacent pipe became large. On the other hand, it was proved that geogrids and gravels were very effective for the lateral resistance in liquefying ground. In addition, the relative displacement was small because of the same difference between the bend and the adjacent pipe.
Elastoplastic dynamic analysis of strike-slip faults with bends using finite element method
Duan, B.; Day, S. M.
2006-12-01
Nonelastic off-fault response may play a role in rupture dynamics on geometrically complex faults, particularly in the vicinity of bends or other points of stress concentration. In this study, we have performed nonelastic dynamic analysis of strike-slip faults with bends by using a finite element method. The Coulomb yield criterion has been implemented in the code to model off-fault nonelastic response. We find that a smooth scheme (such as viscoplasticity) is required to regularize the numerical calculation of plastic yielding near a fault bend. The method is extensible to other material rheologies (e.g., damage mechanics models, tensile failure, etc), and amenable to parallel implementation. Compared with those from a calculation with elastic off-fault response, results from a calculation with nonelastic off-fault response show that (1) bends are locations of large plastic deformation; (2) stress near a bend is less heterogeneous; (3) less radiation is generated from a bend; (4) lower strong ground motion is produced.
Dynamic investigation of twist-bend coupling in a wind turbine blade
Luczak, M.; Manzato, S.; Peeters, B.;
2011-01-01
This paper presents some results and aspects of the multidisciplinary and interdisciplinary research oriented for the experimental and numerical study in static and dynamic domains on the bend-twist coupling in the full scale section of a wind turbine blade structure. The main goal of the conducted...... research is to confirm experimentally the numerical prediction of modification of the dynamic and static properties of a wind turbine blade. The bend-twist coupling was implemented by adding angled UD (UniDirectional) layers on the suction and pressure side of the blade. Static and dynamic tests were...... performed on a section of the full scale wind turbine blade provided by VestasWind Systems A/S. The results are presented and compared with the measurements of the original and modified blade. Comparison analysis confirmed that UD layers introduce measurable bend-twist couplings, which was not present...
Quasi-static and dynamical bending of a cantilever poroelastic beam
YANG Yi; LI Li; YANG Xiao
2009-01-01
Based on the theory of porous media, the quasi-static and dynamical bending of a cantilever poroelastic beam subjected to a step load at its free end is investigated, and the influences of its permeability on bending deformation is examined.The initial boundary value problems for dynamical and quasi-static responses are solved with the Laplace transform technique,and the deflections, the bending moments of the solid skeleton and the equivalent couples of the pore fluid pressure are shown in figures. It is shown that the dynamical and quasi-static behavior of the saturated poroelastic beam depends closely on the permeability conditions at the beam ends. Under the different permeability conditions, the deflections of the beam may oscillate or not. The Mandel-Cryer effect also exists in liquid-saturated poroelastic beams.
Dynamic investigation of twist-bend coupling in a wind turbine blade
Luczak, M.; Manzato, S.; Peeters, B.
2011-01-01
This paper presents some results and aspects of the multidisciplinary and interdisciplinary research oriented for the experimental and numerical study in static and dynamic domains on the bend-twist coupling in the full scale section of a wind turbine blade structure. The main goal of the conducted...... research is to confirm experimentally the numerical prediction of modification of the dynamic and static properties of a wind turbine blade. The bend-twist coupling was implemented by adding angled UD (UniDirectional) layers on the suction and pressure side of the blade. Static and dynamic tests were...... performed on a section of the full scale wind turbine blade provided by VestasWind Systems A/S. The results are presented and compared with the measurements of the original and modified blade. Comparison analysis confirmed that UD layers introduce measurable bend-twist couplings, which was not present...
无
2002-01-01
The nonlinear dynamic behavior of a rubbing rotor system was studied with a mathematical model established with the eccentricity and interaction between bending and torsional vibrations taken into consideration.The nonlinear vibrational response of a rubbing rotor was analyzed using numerical integral,spectroscopic analysis and Poince mapping method,which made it possible to have better understanding of the vibrational characteristics of partial rubbing and complete circular rubbing rotors.The numerical results reveal the response of torsional vibration mainly takes a form of suporchronous motion,and its frequency decreases as the rotational speed increases when partial rubbing occurs,and the response of torsional vibration is synchronous when complete circular rubbing occurs.The comparison of the dynamics of rubbing rotors with and without the interaction between bending and torsional vibrations shows the interaction between bending and torsional vibrations advances the rotational speed,at which the response of bending vibration changes from a synchronous motion into a quasi-periodic motion,and the interaction between bending and torsional vibrations reduces stability of the rubbing rotor.
Pseudo Slice Energy Spread in Dynamics of Electron Beams Moving through Magnetic Bends
Li, Rui
2014-01-01
In the previous canonical formulation of beam dynamics for an electron bunch moving ultrarelativistically through magnetic bending systems, we have shown that the transverse dynamics equation for a particle in the bunch has a driving term which behaves as the centrifugal force caused by the particle's initial potential energy due to collective particle interactions within the bunch. As a result, the initial potential energy at the entrance of a bending system, which we call pseudo (kinetic) energy, is indistinguishable from the usual kinetic energy offset from the design energy in its perturbation to particle optics through dispersion and momentum compaction. In this paper, in identifying this centrifugal force on particles as the remnant of the CSR cancellation effect in transverse particle dynamics, we show how the dynamics equation in terms of the canonical momentum for beam motion on a curved orbit is related to the Panofsky-Wenzel theorem for wakefields for beam motion on a straight path. It is shown tha...
Breather statics and dynamics in Klein-Gordon chains with a bend.
Cuevas, J; Kevrekidis, P G
2004-05-01
In this paper, we examine a nonlinear model with an impurity emulating a bend. We justify the geometric interpretation of the model and connect it with earlier work on models including geometric effects. We focus on both the bifurcation and stability analysis of the modes that emerge as a function of the strength of the bend angle, but we also examine dynamical effects including the scattering of mobile localized modes (discrete breathers) off of such a geometric structure. The potential outcomes of such numerical experiments (including transmission, trapping within the bend as well as reflection) are highlighted and qualitatively explained. Such models are of interest both theoretically in understanding the interplay of breathers with curvature, but also practically in simple models of photonic crystals or of bent chains of DNA.
A wake bending unsteady dynamic inflow model of tiltrotor in conversion flight of tiltrotor aircraft
YUE HaiLong; XIA PinQi
2009-01-01
The aerodynamics, dynamic responses and aeroelasticity of tiltrotor aircraft in the tilting of rotor i.e.In conversion flight are extraordinarily complicated.The traditional quasi-steady assumption model can not reflect the unsteady aerodynamic problems in the tilting of rotor.The CFD method based on the vortex theory can get better results, but it consumes a lot of computing resources.In this paper, a wake bending dynamic inflow model of tilting rotor was established firstly based on the Peters-He dynamic inflow model used in helicopter.Then combining with the ONERA unsteady aerodynamic model, a wake bending unsteady dynamic inflow model of tilting rotor in conversion flight of tiltrotor aircraft was es-tablished.The wake bending unsteady dynamic inflow model of tilting rotor was verified by using the experimental data of an isolated rotor model in large angle pitching up maneuver and was used to calculate the dynamic responses of tilting rotor in conversion flight of a tiltrotor aircraft model.The calculated results were analyzed to be physically reasonable.
A wake bending unsteady dynamic inflow model of tiltrotor in conversion flight of tiltrotor aircraft
无
2009-01-01
The aerodynamics, dynamic responses and aeroelasticity of tiltrotor aircraft in the tilting of rotor i.e. in conversion flight are extraordinarily complicated. The traditional quasi-steady assumption model can not reflect the unsteady aerodynamic problems in the tilting of rotor. The CFD method based on the vortex theory can get better results, but it consumes a lot of computing resources. In this paper, a wake bending dynamic inflow model of tilting rotor was established firstly based on the Peters-He dynamic inflow model used in helicopter. Then combining with the ONERA unsteady aerodynamic model, a wake bending unsteady dynamic inflow model of tilting rotor in conversion flight of tiltrotor aircraft was established. The wake bending unsteady dynamic inflow model of tilting rotor was verified by using the experimental data of an isolated rotor model in large angle pitching up maneuver and was used to calculate the dynamic responses of tilting rotor in conversion flight of a tiltrotor aircraft model. The calculated results were analyzed to be physically reasonable.
Monegaglia, Federico; Henshaw, Alex; Zolezzi, Guido; Tubino, Marco
2016-04-01
Planform development of evolving meander bends is a beautiful and complex dynamic phenomenon, controlled by the interplay among hydrodynamics, sediments and floodplain characteristics. In the past decades, morphodynamic models of river meandering have provided a thorough understanding of the unit physical processes interacting at the reach scale during meander planform evolution. On the other hand, recent years have seen advances in satellite geosciences able to provide data with increasing resolution and earth coverage, which are becoming an important tool for studying and managing river systems. Analysis of the planform development of meandering rivers through Landsat satellite imagery have been provided in very recent works. Methodologies for the objective and automatic extraction of key river development metrics from multi-temporal satellite images have been proposed though often limited to the extraction of channel centerlines, and not always able to yield quantitative data on channel width, migration rates and bed morphology. Overcoming such gap would make a major step forward to integrate morphodynamic theories, models and real-world data for an increased understanding of meandering river dynamics. In order to fulfill such gaps, a novel automatic procedure for extracting and analyzing the topography and planform dynamics of meandering rivers through time from satellite images is implemented. A robust algorithm able to compute channel centerline in complex contexts such as the presence of channel bifurcations and anabranching structures is used. As a case study, the procedure is applied to the Landsat database for a reach of the well-known case of Rio Beni, a large, suspended load dominated, tropical meandering river flowing through the Bolivian Amazon Basin. The reach-averaged evolution of single bends along Rio Beni over a 30 years period is analyzed, in terms of bend amplification rates computed according to the local centerline migration rate. A
Stretching and bending dynamics in triatomic ultralong-range Rydberg molecules
Fey, Christian; Schmelcher, Peter
2016-01-01
We investigate polyatomic ultralong-range Rydberg molecules consisting of three ground state atoms bound to a Rydberg atom via $s$- and $p$-wave interactions. By employing the finite basis set representation of the unperturbed Rydberg electron Green's function we reduce the computational effort to solve the electronic problem substantially. This method is subsequently applied to determine the potential energy surfaces of triatomic systems in electronic $s$- and $p$-Rydberg states. Their molecular geometry and resulting vibrational structure are analyzed within an adiabatic approach that separates the vibrational bending and stretching dynamics. This procedure yields information on the radial and angular arrangement of the nuclei and indicates in particular that kinetic couplings between bending and stretching modes induce a linear structure in triatomic $l=0$ ultralong-range Rydberg molecules.
Stretching and bending dynamics in triatomic ultralong-range Rydberg molecules
Fey, Christian; Kurz, Markus; Schmelcher, Peter
2016-07-01
We investigate polyatomic ultralong-range Rydberg molecules consisting of three ground-state atoms bound to a Rydberg atom via s - and p -wave interactions. By employing the finite basis set representation of the unperturbed Rydberg electron Green's function we reduce the computational effort to solve the electronic problem substantially. This method is subsequently applied to determine the potential energy surfaces of triatomic systems in electronic s - and p -Rydberg states. Their molecular geometry and resulting vibrational structure are analyzed within an adiabatic approach that separates the vibrational bending and stretching dynamics. This procedure yields information on the radial and angular arrangement of the nuclei and indicates in particular that kinetic couplings between bending and stretching modes induce a linear structure in triatomic l =0 ultralong-range Rydberg molecules.
Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Norman, R.; Yuan, Y. B.; Fritzer, J.; Schwaerz, M.; Zhang, K.
2015-01-01
We introduce a new dynamic statistical optimization algorithm to initialize ionosphere-corrected bending angles of Global Navigation Satellite System (GNSS) based radio occultation (RO) measurements. The new algorithm estimates background and observation error covariance matrices with geographically-varying uncertainty profiles and realistic global-mean correlation matrices. The error covariance matrices estimated by the new approach are more accurate and realistic than in simplified existing approaches and can therefore be used in statistical optimization to provide optimal bending angle profiles for high-altitude initialization of the subsequent Abel transform retrieval of refractivity. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.6 (OPSv5.6) algorithm, using simulated data on two test days from January and July 2008 and real observed CHAMP and COSMIC measurements from the complete months of January and July 2008. The following is achieved for the new method's performance compared to OPSv5.6: (1) significant reduction in random errors (standard deviations) of optimized bending angles down to about two-thirds of their size or more; (2) reduction of the systematic differences in optimized bending angles for simulated MetOp data; (3) improved retrieval of refractivity and temperature profiles; (4) produces realistically estimated global-mean correlation matrices and realistic uncertainty fields for the background and observations. Overall the results indicate high suitability for employing the new dynamic approach in the processing of long-term RO data into a reference climate record, leading to well characterized and high-quality atmospheric profiles over the entire stratosphere.
Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Norman, R.; Yuan, Y. B.; Fritzer, J.; Schwaerz, M.; Zhang, K.
2015-08-01
We introduce a new dynamic statistical optimization algorithm to initialize ionosphere-corrected bending angles of Global Navigation Satellite System (GNSS)-based radio occultation (RO) measurements. The new algorithm estimates background and observation error covariance matrices with geographically varying uncertainty profiles and realistic global-mean correlation matrices. The error covariance matrices estimated by the new approach are more accurate and realistic than in simplified existing approaches and can therefore be used in statistical optimization to provide optimal bending angle profiles for high-altitude initialization of the subsequent Abel transform retrieval of refractivity. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.6 (OPSv5.6) algorithm, using simulated data on two test days from January and July 2008 and real observed CHAllenging Minisatellite Payload (CHAMP) and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurements from the complete months of January and July 2008. The following is achieved for the new method's performance compared to OPSv5.6: (1) significant reduction of random errors (standard deviations) of optimized bending angles down to about half of their size or more; (2) reduction of the systematic differences in optimized bending angles for simulated MetOp data; (3) improved retrieval of refractivity and temperature profiles; and (4) realistically estimated global-mean correlation matrices and realistic uncertainty fields for the background and observations. Overall the results indicate high suitability for employing the new dynamic approach in the processing of long-term RO data into a reference climate record, leading to well-characterized and high-quality atmospheric profiles over the entire stratosphere.
Y. Li
2015-01-01
Full Text Available We introduce a new dynamic statistical optimization algorithm to initialize ionosphere-corrected bending angles of Global Navigation Satellite System (GNSS based radio occultation (RO measurements. The new algorithm estimates background and observation error covariance matrices with geographically-varying uncertainty profiles and realistic global-mean correlation matrices. The error covariance matrices estimated by the new approach are more accurate and realistic than in simplified existing approaches and can therefore be used in statistical optimization to provide optimal bending angle profiles for high-altitude initialization of the subsequent Abel transform retrieval of refractivity. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.6 (OPSv5.6 algorithm, using simulated data on two test days from January and July 2008 and real observed CHAMP and COSMIC measurements from the complete months of January and July 2008. The following is achieved for the new method's performance compared to OPSv5.6: (1 significant reduction in random errors (standard deviations of optimized bending angles down to about two-thirds of their size or more; (2 reduction of the systematic differences in optimized bending angles for simulated MetOp data; (3 improved retrieval of refractivity and temperature profiles; (4 produces realistically estimated global-mean correlation matrices and realistic uncertainty fields for the background and observations. Overall the results indicate high suitability for employing the new dynamic approach in the processing of long-term RO data into a reference climate record, leading to well characterized and high-quality atmospheric profiles over the entire stratosphere.
Bending Dynamics of Fluctuating Biopolymers Probed by Automated High-Resolution Filament Tracking
Brangwynne, Clifford P.; Koenderink, Gijsje H.; Barry, Ed; Dogic, Zvonimir; MacKintosh, Frederick C.; Weitz, David A.
2007-01-01
Microscope images of fluctuating biopolymers contain a wealth of information about their underlying mechanics and dynamics. However, successful extraction of this information requires precise localization of filament position and shape from thousands of noisy images. Here, we present careful measurements of the bending dynamics of filamentous (F-)actin and microtubules at thermal equilibrium with high spatial and temporal resolution using a new, simple but robust, automated image analysis algorithm with subpixel accuracy. We find that slender actin filaments have a persistence length of ∼17 μm, and display a q−4-dependent relaxation spectrum, as expected from viscous drag. Microtubules have a persistence length of several millimeters; interestingly, there is a small correlation between total microtubule length and rigidity, with shorter filaments appearing softer. However, we show that this correlation can arise, in principle, from intrinsic measurement noise that must be carefully considered. The dynamic behavior of the bending of microtubules also appears more complex than that of F-actin, reflecting their higher-order structure. These results emphasize both the power and limitations of light microscopy techniques for studying the mechanics and dynamics of biopolymers. PMID:17416612
Gabbasov Radek Fatykhovich
Full Text Available Bending plate is widely used in the construction of large-span structures. Its advantage is light weight, industrial production, low cost and easy installation. Implementing the algorithm for calculating bending plates in engineering practice is an important issue of the construction science. The generalized equations of finite difference method is a new trend in the calculation of building construction. FDM with generalized equation provides additional options for an engineer along with other methods (FEM. In the article the algorithm for dynamic calculation of thin bending plates basing on FDM was developed. The computer programs for dynamic calculation were created on the basis of the algorithm. The authors come to the conclusion that the more simple equations of FDM can be used in case of solving the impulse load problems in dynamic load calculation of thin bending plate.
Lei, Jingtao; Yu, Huangying; Wang, Tianmiao
2016-01-01
The body of quadruped robot is generally developed with the rigid structure. The mobility of quadruped robot depends on the mechanical properties of the body mechanism. It is difficult for quadruped robot with rigid structure to achieve better mobility walking or running in the unstructured environment. A kind of bionic flexible body mechanism for quadruped robot is proposed, which is composed of one bionic spine and four pneumatic artificial muscles(PAMs). This kind of body imitates the four-legged creatures' kinematical structure and physical properties, which has the characteristic of changeable stiffness, lightweight, flexible and better bionics. The kinematics of body bending is derived, and the coordinated movement between the flexible body and legs is analyzed. The relationship between the body bending angle and the PAM length is obtained. The dynamics of the body bending is derived by the floating coordinate method and Lagrangian method, and the driving force of PAM is determined. The experiment of body bending is conducted, and the dynamic bending characteristic of bionic flexible body is evaluated. Experimental results show that the bending angle of the bionic flexible body can reach 18°. An innovation body mechanism for quadruped robot is proposed, which has the characteristic of flexibility and achieve bending by changing gas pressure of PAMs. The coordinated movement of the body and legs can achieve spinning gait in order to improve the mobility of quadruped robot.
Kang An; Qijun Chen
2013-01-01
This paper presents a passive dynamic walking model based on knee-bend behaviour, which is inspired by the way human beings walk. The length and mass parameters of human beings are used in the walking model. The knee-bend mechanism of the stance leg is designed in the phase between knee-strike and heel- strike. q* which is the angular difference of the stance leg between the two events, knee-strike and knee-bend, is adjusted in order to find a stable walking motion. The results show that the ...
TIAN Ruijun; DU Xiuli; PENG Yijiang
2008-01-01
To study the bending strength of mass concrete under dynamic loading.the pure bending zone of three-graded concrete beam is considered as a three-phase composite composed of atrix.aggregate and interface between them on meso-level.Dynamic constitutive model considering strain-rate strengthening effect and damage softening effect is adopted to describe the cocrete and meso-element's damage.The failure mechanisms of beam under impact loading.triagle wave load.dynamic load coupling with initial static loading were sireulated by using displace-ment-controlled FEM.Furthermore.stress-strain curve of the specimens and their dynamic bending strength were obtained.The results obtained from numerical simulation agreed well with experimental data.
Dynamics of soft filaments that can stretch, shear, bend and twist
Gazzola, Mattia; McCormick, Andrew G; Mahadevan, L
2016-01-01
Soft slender structures are ubiquitous in natural and artificial systems and can be observed at scales that range from the nanometric to the kilometric, from polymers to space tethers. We present a general numerical approach to simulate the dynamics of filaments that, at every cross-section, can undergo all six possible modes of deformation, allowing the filament to bend, twist, shear and stretch, consistent with dynamics on the full Euclidean group SE(3). Additionally, we also account for the interaction of an active filament with itself and the environment via self-contact, surface friction and hydrodynamics. We examine the accuracy of our energy preserving and second order spatio-temporal method by means of a number of benchmark problems with known analytic solutions. Finally, we demonstrate the capabilities of our approach both on passive physical problems related to solenoid and plectoneme formation in twisted, stretched filaments, and active biophysical problems in the context of limbless locomotion on ...
Guo, Kai; Ma, Ying; Li, Huiqiao; Zhai, Tianyou
2016-02-24
Wire-shaped flexible supercapacitors (SCs) have aroused much attention due to their small size, light weight, high flexibility, and deformability. However, the previously reported wire-shaped SCs usually involve complex assembly processes, encounter potential structural instabilities, and the influence of dynamic bending on the electrochemical stability of wire-shaped SCs is also not clear. Here, a parallel double helix wire-shaped supercapacitor (PDWS) protocol has been developed with two symmetric titanium@MnO2 fiber electrodes winded on a flexible nylon fiber by a simple and reliable process. The PDWSs show an operate voltage of 0.8 V, a high capacitance of 15.6 mF cm(-2) and an energy density of 1.4 µWh cm(-2) . Due to rational structure design, the PDWSs demonstrate excellent mechanical and electrochemical stability under both static and dynamic deformations. Over 3500 bending cycles, 88.0% of the initial capacitance can still be retained. In terms of dynamic bending, it is found that the cyclic voltammetry curves show periodically fluctuations simultaneously with the bending frequency and the intensity of fluctuation increases with higher bending frequency, while the dynamic capacitance is almost not affected. With extraordinary mechanical flexibility and excellent electrochemical stability, the high performance PDWS is considered to be a promising power source for wearable electronics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Krishnamohan, G P; Olsen, R A; Kroes, G-J; Gatti, F; Woittequand, S
2010-10-14
Two-dimensional, three-dimensional, and four-dimensional quantum dynamic calculations are performed on the dissociative chemisorption of CH(4) on Ni(111) using the multiconfiguration time-dependent Hartree (MCTDH) method. The potential energy surface used for these calculations is 15-dimensional (15D) and was obtained with density functional theory for points which are concentrated in the region that is dynamically relevant to reaction. Many reduced dimensionality calculations were already performed on this system, but the molecule was generally treated as pseudodiatomic. The main improvement of our model is that we try to describe CH(4) as a polyatomic molecule by including a degree of freedom describing a bending vibration in our three-dimensional and four-dimensional models. Using a polyspherical coordinate system, a general expression for the 15D kinetic energy operator is derived, which discards all the singularities in the operator and includes rotational and Coriolis coupling. We use seven rigid constraints to fix the CH(3) umbrella of the molecule to its gas phase equilibrium geometry and to derive two-dimensional, three-dimensional, and four-dimensional Hamiltonians, which were used in the MCTDH method. Only four degrees of freedom evolve strongly along the 15D minimum energy path: the distance of the center of mass of the molecule to the surface, the dissociative C[Single Bond]H bond distance, the polar orientation of the molecule, and the bending angle between the dissociative C[Single Bond]H bond and the umbrella. A selection of these coordinates is included in each of our models. The polar rotation is found to be important in determining the mode selective behavior of the reaction. Furthermore, our calculations are in good agreement with the finding of Xiang et al. [J. Chem. Phys. 117, 7698 (2002)] in their reduced dimensional calculation that the helicopter motion of the umbrella symmetry axis is less efficient than its cartwheel motion for promoting
van Aalten, D.M.F.; Amadei, A; Linssen, A.B M; Eijsink, V.G.H.; Vriend, G.; Berendsen, H.J.C.
1995-01-01
Comparisons of the crystal structures of thermolysin and the thermolysin-like protease produced by B. cereus have recently led to the hypothesis that neutral proteases undergo a hinge-bending motion. We have investigated this hypothesis by analyzing molecular dynamics simulations of thermolysin in v
Bulacu, M; van der Giessen, E
2005-01-01
Extensive molecular-dynamics simulations have been performed to study the effect of chain conformational rigidity, controlled by bending and torsion potentials, on self-diffusion in polymer melts. The polymer model employs a novel torsion potential that avoids computational singularities without the
Diameter-dependent electronic transport properties of Au-catalyst/Ge-nanowire Schottky diodes
Picraux, S Thomas [Los Alamos National Laboratory; Leonard, Francois [SNL; Swartzentruber, Brian S [SNL; Talin, A Alee [SNL
2008-01-01
We present electronic transport measurements in individual Au-catalyst/Ge-nanowire interfaces demonstrating the presence of a Schottky barrier. Surprisingly, the small-bias conductance density increases with decreasing diameter. Theoretical calculations suggest that this effect arises because electron-hole recombination in the depletion region is the dominant charge transport mechanism, with a diameter dependence of both the depletion width and the electron-hole recombination time. The recombination time is dominated by surface contributions and depends linearly on the nanowire diameter.
Kang An
2013-10-01
Full Text Available This paper presents a passive dynamic walking model based on knee-bend behaviour, which is inspired by the way human beings walk. The length and mass parameters of human beings are used in the walking model. The knee-bend mechanism of the stance leg is designed in the phase between knee-strike and heel- strike. q* which is the angular difference of the stance leg between the two events, knee-strike and knee-bend, is adjusted in order to find a stable walking motion. The results show that the stable periodic walking motion on a slope of r <0.4 can be found by adjusting q*. Furthermore, with a particular q* in the range of 0.12
Kang An
2013-10-01
Full Text Available This paper presents a passive dynamic walking model based on knee-bend behaviour, which is inspired by the way human beings walk. The length and mass parameters of human beings are used in the walking model. The knee-bend mechanism of the stance leg is designed in the phase between knee-strike and heel-strike. q* which is the angular difference of the stance leg between the two events, knee-strike and knee-bend, is adjusted in order to find a stable walking motion. The results show that the stable periodic walking motion on a slope of r <0.4 can be found by adjusting q*. Furthermore, with a particular q* in the range of 0.12
Observation of diameter dependent carrier distribution in nanowire-based transistors
Schulze, A; Hantschel, T; Eyben, P; Verhulst, A S; Rooyackers, R; Vandooren, A; Mody, J; Nazir, A; Leonelli, D; Vandervorst, W, E-mail: Andreas.Schulze@imec.be [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)
2011-05-06
The successful implementation of nanowire (NW) based field-effect transistors (FET) critically depends on quantitative information about the carrier distribution inside such devices. Therefore, we have developed a method based on high-vacuum scanning spreading resistance microscopy (HV-SSRM) which allows two-dimensional (2D) quantitative carrier profiling of fully integrated silicon NW-based tunnel-FETs (TFETs) with 2 nm spatial resolution. The key elements of our characterization procedure are optimized NW cleaving and polishing steps, the use of in-house fabricated ultra-sharp diamond tips, measurements in high vacuum and a dedicated quantification procedure accounting for the Schottky-like tip-sample contact affected by surface states. In the case of the implanted TFET source regions we find a strong NW diameter dependence of conformality, junction abruptness and gate overlap, quantitatively in agreement with process simulations. In contrast, the arsenic doped drain regions reveal an unexpected NW diameter dependent dopant deactivation. The observed lower drain doping for smaller diameters is reflected in the device characteristics by lower TFET off-currents, as measured experimentally and confirmed by device simulations.
Jeng, Yeau-Ren; Tsai, Ping-Chi; Fang, Te-Hua
2005-06-08
This paper utilizes molecular-dynamics simulations to investigate the mechanical characteristics of a suspended (10, 10) single-walled carbon nanotube (SWCNT) during atomic force microscopy (AFM) nanoindentation at different temperatures. Spontaneous topological transition of the Stone-Wales (SW) defects is clearly observed in the indentation process. The present results indicate that under AFM-bending deformation, the mechanical properties of the SWCNT, e.g., the bending strength, are dependent on the wrapping angle. In addition, it is also found that the radial dependence of the reduced formation energy of the SW defects is reasonably insensitive only for the small tubes. However, for tube diameters greater than 2.4 nm [corresponding to the (18, 18) CNT], the SW defects tend to be more radius sensitive. The results indicate that the bending strength decreases significantly with increasing temperature. This study also investigates the variation in the mechanical properties of the nanotube with the density of C60 encapsulated within the nanotube at various temperatures. It is found that, at lower temperatures, the bending strength of the C60-filled nanotube increases with C60 density. However, the reverse tendency is observed at higher temperatures. Finally, the "sharpest tip" phenomena between the probe and the tube wall and the elastic recovery of the nanotube during the retraction process are also investigated.
Zhou, Yanguang; Zhang, Xiaoliang; Hu, Ming
2017-02-08
By carefully and systematically performing Green-Kubo equilibrium molecular dynamics simulations, we report that the thermal conductivity (κ) of Si nanowires (NWs) does not diverge but converges and increases steeply when NW diameter (D) becomes extremely small (dκ/dD < 0), a long debate of one-dimensional heat conduction in history. The κ of the thinnest possible Si NWs reaches a superhigh level that is as large as more than 1 order of magnitude higher than its bulk counterpart. The abnormality is explained in terms of the dominant normal (N) process (energy and momentum conservation) of low frequency acoustic phonons that induces hydrodynamic phonon flow in the Si NWs without being scattered. With D increasing, the downward shift of optical phonons triggers strong Umklapp (U) scattering with acoustic phonons and attenuates the N process, leading to the regime of phonon boundary scattering (dκ/dD < 0). The two competing mechanisms result in nonmonotonic diameter dependence of κ with minima at critical diameter of 2-3 nm. Our results unambiguously demonstrate the converged κ and the clear trend of κ ∼ D for extremely thin Si NWs by fully elucidating the competition between the hydrodynamic phonon flow and phonon boundary scattering.
Kawahara, Toshio, E-mail: toshi@isc.chubu.ac.jp [Center of Applied Superconductivity and Sustainable Energy Research, Chubu University, 1200, Matsumoto-cho, Kasugai-shi, Aichi 487-8501 (Japan); Yamaguchi, Satarou [Center of Applied Superconductivity and Sustainable Energy Research, Chubu University, 1200, Matsumoto-cho, Kasugai-shi, Aichi 487-8501 (Japan); Ohno, Yasuhide; Maehashi, Kenzo; Matsumoto, Kazuhiko [The Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Mizutani, Shin [NTT Communication Science Laboratories, 2-4, Hikaridai Seika-cho, Soraku-gun, Kyoto 619-0237 (Japan); Itaka, Kenji [North Japan Research Institute for Sustainable Energy, Hirosaki University, 2-1-3 Matsubara, Aomori 030-0813 (Japan)
2013-02-15
Carbon nanotubes (CNTs) have many interesting properties for nano devices such as high sensitive sensors or noise enhanced nonlinear devices. A field effect transistor (FET) structure is one of the key features for these applications, and the control of noise in FETs is important for the actual operation of the application. Several origins of noise have been proposed, and defects and/or surface adsorption of molecules seem to be dominant for the 1/f type noise in CNTs. To study the origins of noise, the diameter dependence of noise properties was studied. We analyzed the noise properties in CNTs using noise spectroscopy with different fabrication parameters or ambient environments. We observed the crossover of noise properties in CNTs, which involved transition between different origins of noise depending on their diameter. Additionally, noise spectroscopy was used to observe such crossover between air and vacuum environments. We can control noise intensity using the gate voltage, and noise properties can be controlled by the fabrication parameters. These phenomena are useful for the stochastic operation of CNT-FETs.
De-Deus, Gustavo; Leal Vieira, Victor Talarico; Nogueira da Silva, Emmanuel João; Lopes, Helio; Elias, Carlos Nelson; Moreira, Edson Jorge
2014-04-01
The aim of the present study was to evaluate the bending resistance and the dynamic and static cyclic fatigue life of Reciproc R40 and WaveOne large instruments. A sample of 68 nickel-titanium instruments (25 mm in length) for use under reciprocation movement (Reciproc and WaveOne) from 3 different lots was tested. Reciproc R40 and WaveOne Large files, both of which had a nominal size of 0.40 mm at D0, were selected. The bending resistance was performed in 10 instruments of each system by using a universal testing machine. Dynamic and static models for cyclic fatigue testing were performed by using a custom-made device. For these tests, an artificial canal measuring 1.4 mm in diameter and 19 mm total length was fabricated from a stainless steel tube. Scanning electron microscopy analysis was performed to determine the mode of fracture. Statistical analysis was performed by using parametric methods, 1-way analysis of variance. Post hoc pair-wise comparisons were performed by using Tukey test for multiple comparisons. WaveOne instruments presented significantly higher bending resistance than Reciproc (P < .05). Moreover, Reciproc revealed a significantly longer cyclic fatigue life (P < .05) in both static and dynamic tests (P < .05). Reciproc R40 instruments resisted dynamic and static cyclic fatigue significantly more than WaveOne Large instruments. Furthermore, WaveOne instruments presented significantly less flexibility than Reciproc. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.
Ping, Tan Ai; Hoe, Yeak Su [Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor Bahru, Johor Darul Takzim (Malaysia)
2014-07-10
Typically, short range potential only depends on neighbouring atoms and its parameters function can be categorized into bond stretching, angle bending and bond rotation potential. In this paper, we present our work called Angle Bending (AB) potential, whereas AB potential is the extension of our previous work namely Bond Stretching (BS) potential. Basically, potential will tend to zero after truncated region, potential in specific region can be represented by different piecewise polynomial. We proposed the AB piecewise potential which is possible to solve a system involving three atoms. AB potential able to handle the potential of covalent bonds for three atoms as well as two atoms cases due to its degeneracy properties. Continuity for the piecewise polynomial has been enforced by coupling with penalty methods. There are still plenty of improvement spaces for this AB potential. The improvement for three atoms AB potential will be studied and further modified into torsional potential which are the ongoing current research.
Kemper, Andrew R; McNally, Craig; Pullins, Clayton A; Freeman, Laura J; Duma, Stefan M; Rouhana, Stephen M
2007-10-01
The purpose of this study was to quantify both the tensile material properties and structural response of human ribs in order to determine which variables contribute to regional variation in the strength of human ribs. This was done by performing 94 matched tests on human rib specimens; 46 tension coupon tests, 48 three-point bending tests. Contralateral matched specimens were dissected from anterior and lateral regions of ribs 4 through 7 of six male fresh frozen post mortem human subjects ranging from 42 to 81 years of age. Tension coupons were taken from one side of the thorax, while three-point bending specimens were taken from the opposite side as the tension coupons at corresponding anatomical locations. The results of the tension coupon testing showed that there were no significant differences with respect to region or rib level: ultimate stress (p=0.90; p=0.53), ultimate strain (p=0.49; p=0.86), or modulus (p=0.72; p=0.81). In contrast, lateral three-point bending specimens were found to have a significantly higher peak bending moment (pbending specimens also had a significantly larger area moment of inertia (pradius of gyration (pradius of gyration (p=0.04) were found to be significantly different with respect to rib level. For lateral specimens, the area moment of inertia (pradius of gyration (p=0.03) were found to be significantly different with respect to rib level. These results clearly illustrate that there is variation in the structural response of human ribs with respect to anatomical region and rib level and this variation is due to changes in local geometry of each rib while the material properties remain constant.
DNA looping by FokI: the impact of twisting and bending rigidity on protein-induced looping dynamics
Laurens, Niels; Rusling, David A.; Pernstich, Christian; Brouwer, Ineke; Halford, Stephen E.; Wuite, Gijs J. L.
2012-01-01
Protein-induced DNA looping is crucial for many genetic processes such as transcription, gene regulation and DNA replication. Here, we use tethered-particle motion to examine the impact of DNA bending and twisting rigidity on loop capture and release, using the restriction endonuclease FokI as a test system. To cleave DNA efficiently, FokI bridges two copies of an asymmetric sequence, invariably aligning the sites in parallel. On account of the fixed alignment, the topology of the DNA loop is set by the orientation of the sites along the DNA. We show that both the separation of the FokI sites and their orientation, altering, respectively, the twisting and the bending of the DNA needed to juxtapose the sites, have profound effects on the dynamics of the looping interaction. Surprisingly, the presence of a nick within the loop does not affect the observed rigidity of the DNA. In contrast, the introduction of a 4-nt gap fully relaxes all of the torque present in the system but does not necessarily enhance loop stability. FokI therefore employs torque to stabilise its DNA-looping interaction by acting as a ‘torsional’ catch bond. PMID:22373924
Characterization and dynamic charge dependent modeling of conducting polymer trilayer bending
Farajollahi, Meisam; Sassani, Farrokh; Naserifar, Naser; Fannir, Adelyne; Plesse, Cédric; Nguyen, Giao T. M.; Vidal, Frédéric; Madden, John D. W.
2016-11-01
Trilayer bending actuators are charge driven devices that have the ability to function in air and provide large mechanical amplification. The electronic and mechanical properties of these actuators are known to be functions of their charge state making prediction of their responses more difficult when they operate over their full range of deformation. In this work, a combination of state space representation and a two-dimensional RC transmission line model are used to implement a nonlinear time variant model for conducting polymer-based trilayer actuators. Electrical conductivity and Young’s modulus of electromechanically active PEDOT conducting polymer containing films as a function of applied voltage were measured and incorporated into the model. A 16% drop in Young’s modulus and 24 times increase in conductivity are observed by oxidizing the PEDOT. A closed form formulation for radius of curvature of trilayer actuators considering asymmetric and location dependent Young’s modulus and conductivity in the conducting polymer layers is derived and implemented in the model. The nonlinear model shows the capability to predict the radius of curvature as a function of time and position with reasonable consistency (within 4%). The formulation is useful for general trilayer configurations to calculate the radius of curvature as a function of time. The proposed electrochemical modeling approach may also be useful for modeling energy storage devices.
Chen, Rong; Li, Kang; Xia, Kaiwen; Lin, Yuliang; Yao, Wei; Lu, Fangyun
2016-10-01
A dynamic load superposed on a static pre-load is a key problem in deep underground rock engineering projects. Based on a modified split Hopkinson pressure bar test system, the notched semi-circular bend (NSCB) method is selected to investigate the fracture initiation toughness of rocks subjected to pre-load. In this study, a two-dimensional ANSYS finite element simulation model is developed to calculate the dimensionless stress intensity factor. Three groups of NSCB specimen are tested under a pre-load of 0, 37 and 74 % of the maximum static load and with the loading rate ranging from 0 to 60 GPa m1/2 s-1. The results show that under a given pre-load, the fracture initiation toughness of rock increases with the loading rate, resembling the typical rate dependence of materials. Furthermore, the dynamic rock fracture toughness decreases with the static pre-load at a given loading rate. The total fracture toughness, defined as the sum of the dynamic fracture toughness and initial stress intensity factor calculated from the pre-load, increases with the pre-load at a given loading rate. An empirical equation is used to represent the effect of loading rate and pre-load force, and the results show that this equation can depict the trend of the experimental data.
Biophysically realistic filament bending dynamics in agent-based biological simulation.
Alberts, Jonathan B
2009-01-01
An appealing tool for study of the complex biological behaviors that can emerge from networks of simple molecular interactions is an agent-based, computational simulation that explicitly tracks small-scale local interactions--following thousands to millions of states through time. For many critical cell processes (e.g. cytokinetic furrow specification, nuclear centration, cytokinesis), the flexible nature of cytoskeletal filaments is likely to be critical. Any computer model that hopes to explain the complex emergent behaviors in these processes therefore needs to encode filament flexibility in a realistic manner. Here I present a numerically convenient and biophysically realistic method for modeling cytoskeletal filament flexibility in silico. Each cytoskeletal filament is represented by a series of rigid segments linked end-to-end in series with a variable attachment point for the translational elastic element. This connection scheme allows an empirically tuning, for a wide range of segment sizes, viscosities, and time-steps, that endows any filament species with the experimentally observed (or theoretically expected) static force deflection, relaxation time-constant, and thermal writhing motions. I additionally employ a unique pair of elastic elements--one representing the axial and the other the bending rigidity- that formulate the restoring force in terms of single time-step constraint resolution. This method is highly local -adjacent rigid segments of a filament only interact with one another through constraint forces-and is thus well-suited to simulations in which arbitrary additional forces (e.g. those representing interactions of a filament with other bodies or cross-links / entanglements between filaments) may be present. Implementation in code is straightforward; Java source code is available at www.celldynamics.org.
Biophysically realistic filament bending dynamics in agent-based biological simulation.
Jonathan B Alberts
Full Text Available An appealing tool for study of the complex biological behaviors that can emerge from networks of simple molecular interactions is an agent-based, computational simulation that explicitly tracks small-scale local interactions--following thousands to millions of states through time. For many critical cell processes (e.g. cytokinetic furrow specification, nuclear centration, cytokinesis, the flexible nature of cytoskeletal filaments is likely to be critical. Any computer model that hopes to explain the complex emergent behaviors in these processes therefore needs to encode filament flexibility in a realistic manner. Here I present a numerically convenient and biophysically realistic method for modeling cytoskeletal filament flexibility in silico. Each cytoskeletal filament is represented by a series of rigid segments linked end-to-end in series with a variable attachment point for the translational elastic element. This connection scheme allows an empirically tuning, for a wide range of segment sizes, viscosities, and time-steps, that endows any filament species with the experimentally observed (or theoretically expected static force deflection, relaxation time-constant, and thermal writhing motions. I additionally employ a unique pair of elastic elements--one representing the axial and the other the bending rigidity- that formulate the restoring force in terms of single time-step constraint resolution. This method is highly local -adjacent rigid segments of a filament only interact with one another through constraint forces-and is thus well-suited to simulations in which arbitrary additional forces (e.g. those representing interactions of a filament with other bodies or cross-links / entanglements between filaments may be present. Implementation in code is straightforward; Java source code is available at www.celldynamics.org.
Salau Tajudeen A.O.
2014-01-01
Full Text Available This study reported a simulation approach to the understanding of the interactions between a buried pipe and the soil system by computing the bending stress variation of harmonically-excited buried pipes. The established principles of linear dynamics theory and simple beam theory were utilised in the analysis of the problem of buried pipe bending stress accumulation and its dynamics. With regards to the parameters that influence the bending stress variations, the most important are the isolation factor, uniform external load, and the corresponding limiting conditions. The simulated mathematical expressions, containing static and dynamic parameters of the buried pipe and earth, were coded in Fortran programming language and applied in the simulation experiment. The results obtained showed that harmonically-excited buried thick-walled pipe became stable and effective when the ratio of the natural frequency of vibration to the forced frequency is greater than 2.0, whenever the damped factor is used as the control parameter for the maximum bending stress. The mirror image of the stress variation produces variation in the location of the maximum bending stress in quantitative terms. The acceptable pipe materials for the simulated cases must have yield strength in bending greater than or equal to 13.95 MPa. The results obtained in this work fill a gap in the literature and will be useful to pipeline engineers and designers, as well as to environmental scientists in initialising and controlling environmental issues and policy formulation concerning the influence of buried pipe on the soil and water in the environment.
无
2000-01-01
A new kind of bend sensor is introduced.It can be used to detect the bend angle of an object or inclination between two objects.It has characteristics of small size, lightweight, high reliability, fine flexibility and plasticity.When this bend sensor is used with a proper converting circuit, it can implement dynamic measuring the bend angle of an object conveniently.The application of the bend sensor in dataglove is also described.
High frequency dynamic bending response of piezoresistive GaN microcantilevers
Talukdar, Abdul; Qazi, Muhammad; Koley, Goutam
2012-12-01
Static and dynamic ac responses of piezoresistive GaN microcantilevers, with integrated AlGaN/GaN heterostructure field effect transistors as highly sensitive deflection transducers, have been investigated. Very high gauge factor exceeding 3500 was exhibited by the microcantilevers, with quality factor determined from electronically transduced ac response exceeding 200 in air and 4500 at low pressure. The gauge factor reduced at resonance frequency of the cantilevers, possibly due to reduced charge exchange with surface donor and trap states. Ultrasonic waves generated in air by a piezochip, and in the Si substrate through photoacoustic effect, could be detected by the cantilevers with high sensitivity.
Huang, Xiaohu
2013-01-01
Understanding and measuring the size-dependent surface strain of nanowires are essential to their applications in various emerging devices. Here, we report on the diameter-dependent surface strain and Young\\'s modulus of single-crystalline Co nanowires investigated by in situ X-ray diffraction measurements. Diameter-dependent initial longitudinal elongation of the nanowires is observed and ascribed to the anisotropic surface stress due to the Poisson effect, which serves as the basis for mechanical measurements. As the nanowire diameter decreases, a transition from the "smaller is softer" regime to the "smaller is tougher" regime is observed in the Young\\'s modulus of the nanowires, which is attributed to the competition between the elongation softening and the surface stiffening effects. Our work demonstrates a new nondestructive method capable of measuring the initial surface strain and estimating the Young\\'s modulus of single crystalline nanowires, and provides new insights on the size effect. © 2013 The Royal Society of Chemistry.
Xu, Y.; Dai, F.; Xu, N. W.; Zhao, T.
2016-03-01
The International Society for Rock Mechanics (ISRM) has suggested a notched semi-circular bend technique in split Hopkinson pressure bar (SHPB) testing to determine the dynamic mode I fracture toughness of rock. Due to the transient nature of dynamic loading and limited experimental techniques, the dynamic fracture process associated with energy partitions remains far from being fully understood. In this study, the dynamic fracturing of the notched semi-circular bend rock specimen in SHPB testing is numerically simulated for the first time by the discrete element method (DEM) and evaluated in both microlevel and energy points of view. The results confirm the validity of this DEM model to reproduce the dynamic fracturing and the feasibility to simultaneously measure key dynamic rock fracture parameters, including initiation fracture toughness, fracture energy, and propagation fracture toughness. In particular, the force equilibrium of the specimen can be effectively achieved by virtue of a ramped incident pulse, and the fracture onset in the vicinity of the crack tip is found to synchronize with the peak force, both of which guarantee the quasistatic data reduction method employed to determine the dynamic fracture toughness. Moreover, the energy partition analysis indicates that simplifications, including friction energy neglect, can cause an overestimation of the propagation fracture toughness, especially under a higher loading rate.
Juan Yang; Yu Liu; Daqi Zhang; Xiao Wang; Ruoming Li; Yan Li
2015-01-01
Owing to the unique conjugated structure, the chemical-reaction selectivity of single-walled carbon nanotubes （SWNTs） has attracted great attention. By utilizing the radial deformation of SWNTs caused by the strong interactions with the quartz lattice, we achieve an anomalous diameter-dependent reaction selectivity of quartz lattice-oriented SWNTs in treatment with iodine vapor; this is distinctly different from the widely reported and well accepted higher reaction activity in small-diameter tubes compared to large-diameter tubes. The radial deformation of SWNTs on quartz substrate is verified by detailed Raman spectroscopy and mappings in both G-band and radial breathing mode. Due to the strong interaction between SWNTs and the quartz lattice, large-diameter tubes present a larger degree of radial deformation and more delocalized partial electrons are distributed at certain sidewall sites with high local curvature. It is thus easier for the carbon--carbon bonds at these high-curvature sites on large-diameter tubes to break down during reaction. This anomalous reaction activity offers a novel approach for selective removal of small-band~aD large-diameter tubes.
Al-Qahtani, Saad Mubarak; Abdullah, Abdulmuin Mostafa A.; Nishat, Md. Rezaul Karim; Ahmed, Shaikh S.
2017-03-01
A multiscale computational study is performed to investigate how electronic structure, optical transitions, and terminal characteristics of nanostructured ZnO/MgO disk-in-wire emitters are governed by an intricate coupling of size-quantization, atomicity, and built-in structural and polarization fields. As for the models, an 8-band sp3 (with spin) atomistic tight-binding basis set was used to construct the Hamiltonian of the device in wurtzite crystal symmetry. Strain and the associated distortions of bond directions and bond lengths were modeled via the valence force-field (VFF) molecular mechanics framework. Specifically, in this work, a recently proposed ab initio based diameter-dependent model for the piezoelectric fields was implemented, which, as compared to the conventional diameter-independent model, was found to curb the influence of spontaneous (pyroelectric) polarization significantly. This particular finding is further illustrated through the calculation of electronic bandgap and localization of wavefunctions, optical emission characteristics, and the internal quantum efficiency of the device.
Sivak, David Alexander
with even finer resolution models through the calculation of coarse-grained bending potentials from molecular dynamics simulations.
Collings, D. A.; Winter, H.; Wyatt, S. E.; Allen, N. S.; Davies, E. (Principal Investigator)
1998-01-01
Characterization of gravitropic bending in the maize stem pulvinus, a tissue that functions specifically in gravity responses, demonstrates that the pulvinus is an ideal system for studying gravitropism. Gravistimulation during the second of three developmental phases of the pulvinus induces a gradient of cell elongation across the non-growing cells of the pulvinus, with the most elongation occurring on the lower side. This cell elongation is spatially and temporally separated from normal internodal cell elongation. The three characterized growth phases in the pulvinus correspond closely to a specialized developmental sequence in which structural features typical of cells not fully matured are retained while cell maturation occurs in surrounding internodal and nodal tissue. For example, the lignification of supporting tissue and rearrangement of transverse microtubules to oblique that occur in the internode when cell elongation ceases are delayed for up to 10 d in the adjacent cells of the pulvinus, and only occurs as a pulvinus loses its capacity to respond to gravistimulation. Gravistimulation does not modify this developmental sequence. Neither wall lignification nor rearrangement of transverse microtubules occurs in the rapidly elongating lower side or non-responsive upper side of the pulvinus until the pulvinus loses the capacity to bend further. Gravistimulation does, however, lead to the formation of putative pit fields within the expanding cells of the pulvinus.
具有屈膝行为的双足被动行走模型%Passive dynamic walking model with knee-bend behavior
安康; 陈启军
2013-01-01
参考人类下坡行走运动特点,提出一种具有屈膝行为的双足被动行走模型.采用5质点4杆被动行走模型,设计支撑腿在行走过程中弯曲,通过对支撑腿膝关节弯曲时刻的调整,求解得到模型在不同斜面上的稳定周期行走步态.仿真结果表明,模型实现了在坡度范围小于0.39 rad的斜面上稳定行走步态.与传统步态相比,稳定行走的坡度范围显著提高,在较大坡度上也具有很好的稳定性.%With the inspiration from human walking pattern during going down slope, we developed a passive dynamic walking model with particular knee-bend behavior. A five-mass-point and four-stick model is used, and the knee-bend mechanism is designed in the phase from knee-strike event to heel-strike event in one walking cycle. The stable periodic walking motion on the slope with different slope angle is found by means of adjusting the bending time of the stance knee. The simulation results show that the walking motion is stable on the slope of γ < 0.39 rad. Compared with conventional walking gait, the proposed gait can achieve stable walking motion with a much wider range of slope angle.
A Numerical Study of the Spring-Back Phenomenon in Bending with a Rebar Bending Machine
Chang Hwan Choi
2014-10-01
Full Text Available Recently, the rebar bending methodology started to change from field processing to utilizing rebar bending machines at plant sites prior to transport to the construction locations. Computerized control of rebar plant bending machines provides more accurate and faster bending of rebars than the low quality inefficient field processing alternative. The bending process involves plastic deformation of rebars, where bending stress beyond the yield point of the material is applied. When the bending stress is removed, spring back is caused by the elastic restoring stress. Therefore, an accurate numerical analysis of the spring-back process is required to reduce the bending process errors. The most sensitive factors affecting the spring-back process are the bending radius, the bending angle, the diameter of the rebar, the friction coefficient, and the yielding strength of material. In this paper, we suggest a numerical modeling method using these factors. The finite element modeling of the dynamic mechanical behavior of the material during bending is performed using a commercial dynamic analysis program “DAFUL.” We use the least squares approach to derive the spring-back deflection as a function of the rebar bending parameters.
J.Sadowski
2008-10-01
Full Text Available The increase of quality and durability of produced casting alloys can be evaluated on the base of material tests performed on a high level. One of such modern test methods are tests of the dynamic damage process of materials and the evaluation on the base of obtained courses F(f, F(t of parameters of dynamic cracking resistance KId, JId, performed with the usage of instrumented Charpy pendulums. In the paper there was presented the evaluation of dynamic cracking resistance parameters of casting alloys such as: AK12 aluminum alloy, L20G cast steel and spheroid cast iron. The methodology of the evaluation of that parameters was described and their change as well, for the AK12 alloy with the cold work different level, L20G cast steel cooled from different temperatures in the range +20oC -60oC, and for the spheroid cast iron in different stages of treatment i.e. raw state, after normalization, spheroid annealing and graphitizing annealing.Obtained parameters of dynamic cracking resistance KId, JId of tested casting alloys enabled to define the critical value of the ad defect that can be tolerated by tested castings in different work conditions with impact loadings.
Glor, FP; Westenberg, JJM; Vierendeels, J; Danilouchkine, M; Verdonck, P
2002-01-01
Magnetic resonance imaging (MRI) can be used in vivo in combination with computational fluid dynamics (CFD) to derive velocity profiles in space and time and accordingly, pressure drop and wall shear stress distribution in natural or artificial vessel segments. These hemodynamic data are difficult o
2002-01-01
A Japanese team has found a way to bend and shape silicon substrates by growing a thin layer of diamond on top. The technique has been proposed as an alternative to mechanical bending, which is currently used to make reflective lenses for X-ray systems and particle physics systems (2 paragraphs).
Occipital bending in schizophrenia.
Maller, Jerome J; Anderson, Rodney J; Thomson, Richard H; Daskalakis, Zafiris J; Rosenfeld, Jeffrey V; Fitzgerald, Paul B
2017-01-01
To investigate the prevalence of occipital bending (an occipital lobe crossing or twisting across the midline) in subjects with schizophrenia and matched healthy controls. Occipital bending prevalence was investigated in 37 patients with schizophrenia and 44 healthy controls. Ratings showed that prevalence was nearly three times higher among schizophrenia patients (13/37 [35.1%]) than in control subjects (6/44 [13.6%]). Furthermore, those with schizophrenia had greater normalized gray matter volume but less white matter volume and had larger brain-to-cranial ratio. The results suggest that occipital bending is more prevalent among schizophrenia patients than healthy subjects and that schizophrenia patients have different gray matter-white matter proportions. Although the cause and clinical ramifications of occipital bending are unclear, the results infer that occipital bending may be a marker of psychiatric illness.
A transparent bending-insensitive pressure sensor
Lee, Sungwon; Reuveny, Amir; Reeder, Jonathan; Lee, Sunghoon; Jin, Hanbit; Liu, Qihan; Yokota, Tomoyuki; Sekitani, Tsuyoshi; Isoyama, Takashi; Abe, Yusuke; Suo, Zhigang; Someya, Takao
2016-05-01
Measuring small normal pressures is essential to accurately evaluate external stimuli in curvilinear and dynamic surfaces such as natural tissues. Usually, sensitive and spatially accurate pressure sensors are achieved through conformal contact with the surface; however, this also makes them sensitive to mechanical deformation (bending). Indeed, when a soft object is pressed by another soft object, the normal pressure cannot be measured independently from the mechanical stress. Here, we show a pressure sensor that measures only the normal pressure, even under extreme bending conditions. To reduce the bending sensitivity, we use composite nanofibres of carbon nanotubes and graphene. Our simulations show that these fibres change their relative alignment to accommodate bending deformation, thus reducing the strain in individual fibres. Pressure sensitivity is maintained down to a bending radius of 80 μm. To test the suitability of our sensor for soft robotics and medical applications, we fabricated an integrated sensor matrix that is only 2 μm thick. We show real-time (response time of ∼20 ms), large-area, normal pressure monitoring under different, complex bending conditions.
A transparent bending-insensitive pressure sensor.
Lee, Sungwon; Reuveny, Amir; Reeder, Jonathan; Lee, Sunghoon; Jin, Hanbit; Liu, Qihan; Yokota, Tomoyuki; Sekitani, Tsuyoshi; Isoyama, Takashi; Abe, Yusuke; Suo, Zhigang; Someya, Takao
2016-05-01
Measuring small normal pressures is essential to accurately evaluate external stimuli in curvilinear and dynamic surfaces such as natural tissues. Usually, sensitive and spatially accurate pressure sensors are achieved through conformal contact with the surface; however, this also makes them sensitive to mechanical deformation (bending). Indeed, when a soft object is pressed by another soft object, the normal pressure cannot be measured independently from the mechanical stress. Here, we show a pressure sensor that measures only the normal pressure, even under extreme bending conditions. To reduce the bending sensitivity, we use composite nanofibres of carbon nanotubes and graphene. Our simulations show that these fibres change their relative alignment to accommodate bending deformation, thus reducing the strain in individual fibres. Pressure sensitivity is maintained down to a bending radius of 80 μm. To test the suitability of our sensor for soft robotics and medical applications, we fabricated an integrated sensor matrix that is only 2 μm thick. We show real-time (response time of ∼20 ms), large-area, normal pressure monitoring under different, complex bending conditions.
Finger-jointed beams in bending
Andreasen, Lotte; Hoffmeyer, Preben
1997-01-01
An investigation of the dynamic and static fatique of finger-jointed beams in bending was carried out. Results were obtained for five different frequencies from static loading to a load cycle period of two minutes. A total of seven series were long-term tested and five series were short-term tested...
CERN PhotoLab
1981-01-01
During 1981, the PS South-Hall, no longer used for physics experiments, was cleared for the installation of the Low Energy Antiproton Ring, LEAR. In October 1981, 3 of the 4 bending magnet quadrants were in place, this is one of them.
Anharmonic bend-stretch coupling in neat liquid water
Lindner, Joerg; Cringus, Dan; Pshenichnikov, Maxim S.; Voehringer, Peter
2007-01-01
Femtosecond mid-IR spectroscopy is used to study the vibrational relaxation dynamics in neat liquid water. By exciting the bending vibration and probing the stretching mode, it is possible to reliably determine the bending and librational lifetimes of water. The anharmonic coupling between the bendi
A multipurpose tissue bending machine.
Vesely, I; Boughner, D R
1985-01-01
A unique tissue bending machine was developed to test the bending properties of normal and bioprosthetic heart valve material. It can be operated in air or in a tissue bath and can measure bending torques with an accuracy in excess of 1.0 microN m. Three contrasting substances were tested to compare their stiffness and to demonstrate the machine.
Peeling, sliding, pulling and bending
Lister, John; Peng, Gunnar
2016-11-01
The peeling of an elastic sheet away from thin layer of viscous fluid is a simply-stated and generic problem, that involves complex interactions between the flow and elastic deformation on a range of length scales. Consider an analogue of capillary spreading, where a blister of injected viscous fluid spreads due to tension in the overlying elastic sheet. Here the tension is coupled to the deformation of the sheet, and thus varies in time and space. A key question is whether or not viscous shear stresses ahead of the blister are sufficient to prevent the sheet sliding inwards and relieving the tension. Our asymptotic analysis reveals a dichotomy between fast and slow spreading, and between two-dimensional and axisymmetric spreading. In combination with bending stresses and gravity, which may dominate parts of the flow but not others, there is a plethora of dynamical regimes.
Bending response of single layer MoS2.
Xiong, Si; Cao, Guoxin
2016-03-11
Using molecular mechanics (or dynamics) simulations, three different approaches, including the targeted molecular mechanics, four-point bending and nanotube methods, are employed to investigate the bending response of single layer MoS2 (SLMoS2), among which four-point bending is the most accurate approach to determine the bending stiffness according to the continuum theory. It is found that when the bending curvature radius is large enough (e.g. >4 nm), three approaches will give the same bending stiffness of SLMoS2 and the bending behavior is isotropic for SLMoS2, whereas the nanotube method with small tubes (e.g. bending stiffness. Compared with the reported result from the MoS2 nanotube calculated by density functional theory, the revised Stillinger-Weber (SW) and reactive empirical bond-order (REBO) potentials can give the reasonable bending stiffness of SLMoS2 (8.7-13.4 eV) as well as the effective deformed conformation. In addition, since the Mo-S bond deformation of SLMoS2 under bending is similar to that under in-plane tension/compression, the continuum bending theory can quite accurately predict the bending stiffness of SLMoS2 if a reasonable thickness of SLMoS2 is given. For SLMoS2, the reasonable thickness should be larger than the distance between its two S atomic planes and lower than the distance between two Mo atomic planes of bulk MoS2 crystal, e.g. 0.375-0.445 nm.
Bending response of single layer MoS2
Xiong, Si; Cao, Guoxin
2016-03-01
Using molecular mechanics (or dynamics) simulations, three different approaches, including the targeted molecular mechanics, four-point bending and nanotube methods, are employed to investigate the bending response of single layer MoS2 (SLMoS2), among which four-point bending is the most accurate approach to determine the bending stiffness according to the continuum theory. It is found that when the bending curvature radius is large enough (e.g. >4 nm), three approaches will give the same bending stiffness of SLMoS2 and the bending behavior is isotropic for SLMoS2, whereas the nanotube method with small tubes (e.g. <4 nm) cannot give the correct bending stiffness. Compared with the reported result from the MoS2 nanotube calculated by density functional theory, the revised Stillinger-Weber (SW) and reactive empirical bond-order (REBO) potentials can give the reasonable bending stiffness of SLMoS2 (8.7-13.4 eV) as well as the effective deformed conformation. In addition, since the Mo-S bond deformation of SLMoS2 under bending is similar to that under in-plane tension/compression, the continuum bending theory can quite accurately predict the bending stiffness of SLMoS2 if a reasonable thickness of SLMoS2 is given. For SLMoS2, the reasonable thickness should be larger than the distance between its two S atomic planes and lower than the distance between two Mo atomic planes of bulk MoS2 crystal, e.g. 0.375-0.445 nm.
Giorgio Serchi, F.; Peakall, J.; Ingham, D. B.; Burns, A. D.
2011-06-01
A numerical model of saline density currents across a triple-bend sinuous submerged channel enclosed by vertical sidewalls is developed. The unsteady, non-Boussinesq, turbulent form of the Reynolds Averaged Navier-Stokes equations is employed to study the flow structure in a quasi-steady state. Recursive tests are performed with axial slopes of 0.08°, 0.43°, 1.5°, and 2.5°. For each numerical experiment, the downstream and vertical components of the fluid velocity, density, and turbulent kinetic energy are presented at four distinct locations within the channel cross section. It is observed that a crucial change in the flow pattern at the channel bends is observed as the axial slope is increased. At low values of the axial slope a typical river-like pattern is found. At an inclination of 1.5°a transition starts to occur. When the numerical test is repeated with an axial slope of 2.5°, a clearly visible river-reversed secondary circulation is achieved. The change in the cross-sectional flow pattern appears to be associated with the spatial displacement of the core of the maximum downstream fluid velocity. Therefore, the axial slope in this series of experiments is linked to the velocity structure of the currents, with the height of the velocity maximum decreasing as a function of increasing slope. As such, the axial slope should be regarded also as a surrogate for flows with enhanced density or sediment stratification and higher Froude numbers. The work unifies the apparently paradoxical experimental and numerical results on secondary circulation in submarine channels.
Kekalo, I. B.; Mogil'nikov, P. S.
2015-07-01
When studying the amorphous alloy Co69Fe3.7Cr3.8Si12.5B11 with a near-zero magnetostriction (|λs| ≤ 10-7), uncommon (anomalous) effects of bending stresses (of the diameter D of toroidal samples) on the hysteretic magnetic properties ( H c, μ5) measured in a dynamic regime at frequencies f of the ac magnetic field from 0.1 to 20 kHz have been revealed. At low frequencies ( f < 1 kHz), the coercive force H c of the alloy is almost independent of D. The permeability μ5 ( H = 5 mOe) is independent of D at high frequencies and depends on D at low frequencies. In samples subjected to high-temperature annealing (390°C) with subsequent water quenching, uncommon regularities are observed; the permeability μ5 increases with decreasing radius of the toroidal samples, i.e., with increasing bending stresses.
Revisit the anomalous bending elasticity of sharply bent DNA
Cong, Peiwen; Chen, Hu; van der Maarel, Johan R C; Doyle, Patrick S; Yan, Jie
2015-01-01
Several recent experiments have suggested that sharply bent DNA has a surprisingly high bending flexibility, but the cause is poorly understood. It has been demonstrated that excitation of flexible defects can explain the results; while whether such defects can be excited under the level of DNA bending in those experiments has remained unclear and been debated. Interestingly, due to experimental design DNA contained pre-existing nicks in nearly all those experiments, while the potential effect of nicks have never been considered. Here, using full-atom molecular dynamics (MD) simulations, we show that nicks promote DNA basepair disruption at the nicked sites which drastically reduced DNA bending energy. In the absence of nicks, basepair disruption can also occur, but it requires a higher level of DNA bending. Overall, our results challenge the interpretations of previous sharp DNA bending experiments and highlight that the micromechanics of sharply bent DNA still remains an open question.
Fuzzy model for Laser Assisted Bending Process
Giannini Oliviero
2016-01-01
Full Text Available In the present study, a fuzzy model was developed to predict the residual bending in a conventional metal bending process assisted by a high power diode laser. The study was focused on AA6082T6 aluminium thin sheets. In most dynamic sheet metal forming operations, the highly nonlinear deformation processes cause large amounts of elastic strain energy stored in the formed material. The novel hybrid forming process was thus aimed at inducing the local heating of the mechanically bent workpiece in order to decrease or eliminate the related springback phenomena. In particular, the influence on the extent of springback phenomena of laser process parameters such as source power, scan speed and starting elastic deformation of mechanically bent sheets, was experimentally assessed. Consistent trends in experimental response according to operational parameters were found. Accordingly, 3D process maps of the extent of the springback phenomena according to operational parameters were constructed. The effect of the inherent uncertainties on the predicted residual bending caused by the approximation in the model parameters was evaluated. In particular, a fuzzy-logic based approach was used to describe the model uncertainties and the transformation method was applied to propagate their effect on the residual bending.
Aerosol deposition in bends with turbulent flow
McFarland, A.R.; Gong, H.; Wente, W.B. [Texas A& M Univ., College Station, TX (United States)] [and others
1997-08-01
The losses of aerosol particles in bends were determined numerically for a broad range of design and operational conditions. Experimental data were used to check the validity of the numerical model, where the latter employs a commercially available computational fluid dynamics code for characterizing the fluid flow field and Lagrangian particle tracking technique for characterizing aerosol losses. Physical experiments have been conducted to examine the effect of curvature ratio and distortion of the cross section of bends. If it curvature ratio ({delta} = R/a) is greater than about 4, it has little effect on deposition, which is in contrast with the recommendation given in ANSI N13.1-1969 for a minimum curvature ratio of 10. Also, experimental results show that if the tube cross section is flattened by 25% or less, the flattening also has little effect on deposition. Results of numerical tests have been used to develop a correlation of aerosol penetration through a bend as a function of Stokes number (Stk), curvature ratio ({delta}) and the bend angle ({theta}). 17 refs., 10 figs., 2 tabs.
Bending elastic moduli of lipid bilayers : modulation by solutes
Duwe, H.P.; Kaes, J.; Sackmann, E.
1990-01-01
We present high precision measurements of the bending elastic moduli for bilayers of a variety of different lipids and of modifications of the flexural rigidity by solutes. The measurements are based on the Fourier analysis of thermally excited membrane undulations (vesicle shape fluctuations) using a recently developed dynamic image processing method. Measurements of the bending modulus as a function of the undulation wave vector provide information on the limitation of the excitations by th...
Vortex breakdown in simple pipe bends
Ault, Jesse; Shin, Sangwoo; Stone, Howard
2016-11-01
Pipe bends and elbows are one of the most common fluid mechanics elements that exists. However, despite their ubiquity and the extensive amount of research related to these common, simple geometries, unexpected complexities still remain. We show that for a range of geometries and flow conditions, these simple flows experience unexpected fluid dynamical bifurcations resembling the bubble-type vortex breakdown phenomenon. Specifically, we show with simulations and experiments that recirculation zones develop within the bends under certain conditions. As a consequence, fluid and particles can remain trapped within these structures for unexpectedly-long time scales. We also present simple techniques to mitigate this recirculation effect which can potentially have impact across industries ranging from biomedical and chemical processing to food and health sciences.
Reinhard, Bjorn; Sheikholeslami, Sassan; Mastroianni, Alexander; Alivisatos, A. Paul; Liphardt, Jan
2006-09-06
Pairs of Au nanoparticles have recently been proposed asplasmon rulers based on the dependence of their light scattering on theinterparticle distance. Preliminary work has suggested that plasmonrulers can be used to measure and monitor dynamic distance changes overthe 1 to 100nm length scale in biology. Here, we substantiate thatplasmon rulers can be used to effectively measure dynamical biophysicalprocesses by applying the ruler to a system that has been investigatedextensively using ensemble kinetic measurements: the cleavage of DNA bythe restriction enzyme EcoRV. Temporal resolutions of up to 240 Hz wereobtained, and the end-to-end extension of up to 1000 individual dsDNAenzyme substrates could be monitored in parallel for hours. The singlemolecule cleavage trajectories acquired here agree well with valuesobtained in bulk through other methods, and confirm well-known featuresof the cleavage process, such as the fact that the DNA is bent prior tocleavage. New dynamical information is revealed as well, for instance,the degree of softening of the DNA just prior to cleavage. The unlimitedlife time, high temporal resolution, and high signal/noise make theplasmon ruler an excellent tool for studying macromolecular assembliesand conformational changes at the single molecule level.
Sheet Bending using Soft Tools
Sinke, J.
2011-05-01
Sheet bending is usually performed by air bending and V-die bending processes. Both processes apply rigid tools. These solid tools facilitate the generation of software for the numerical control of those processes. When the lower rigid die is replaced with a soft or rubber tool, the numerical control becomes much more difficult, since the soft tool deforms too. Compared to other bending processes the rubber backed bending process has some distinct advantages, like large radius-to-thickness ratios, applicability to materials with topcoats, well defined radii, and the feasibility of forming details (ridges, beads). These advantages may give the process exclusive benefits over conventional bending processes, not only for industries related to mechanical engineering and sheet metal forming, but also for other disciplines like Architecture and Industrial Design The largest disadvantage is that also the soft (rubber) tool deforms. Although the tool deformation is elastic and recovers after each process cycle, the applied force during bending is related to the deformation of the metal sheet and the deformation of the rubber. The deformation of the rubber interacts with the process but also with sheet parameters. This makes the numerical control of the process much more complicated. This paper presents a model for the bending of sheet materials using a rubber lower die. This model can be implemented in software in order to control the bending process numerically. The model itself is based on numerical and experimental research. In this research a number of variables related to the tooling and the material have been evaluated. The numerical part of the research was used to investigate the influence of the features of the soft lower tool, like the hardness and dimensions, and the influence of the sheet thickness, which also interacts with the soft tool deformation. The experimental research was focused on the relation between the machine control parameters and the most
A Numerical Study of the Spring-Back Phenomenon in Bending with a Rebar Bending Machine
Chang Hwan Choi; Lawrence Kulinsky; Joon Soo Jun; Jin Ho Kim
2014-01-01
Recently, the rebar bending methodology started to change from field processing to utilizing rebar bending machines at plant sites prior to transport to the construction locations. Computerized control of rebar plant bending machines provides more accurate and faster bending of rebars than the low quality inefficient field processing alternative. The bending process involves plastic deformation of rebars, where bending stress beyond the yield point of the material is applied. When the bending...
Bending fracture in carbon nanotubes.
Kuo, Wen-Shyong; Lu, Hsin-Fang
2008-12-10
A novel approach was adopted to incur bending fracture in carbon nanotubes (CNTs). Expanded graphite (EG) was made by intercalating and exfoliating natural graphite flakes. The EG was deposited with nickel particles, from which CNTs were grown by chemical vapor deposition. The CNTs were tip-grown, and their roots were fixed on the EG flakes. The EG flakes were compressed, and many CNTs on the surface were fragmented due to the compression-induced bending. Two major modes of the bending fracture were observed: cone-shaped and shear-cut. High-resolution scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the crack growth within the graphene layers. The bending fracture is characterized by two-region crack growth. An opening crack first appears around the outer-tube due to the bending-induced tensile stress. The crack then branches to grow along an inclined direction toward the inner-tube due to the presence of the shear stress in between graphene layers. An inner-tube pullout with inclined side surface is formed. The onset and development of the crack in these two regions are discussed.
Tube bending on the roll machine
Nepershin, Rostislav I.
2013-10-01
Computer simulation of the elastic-plastic tube bending by pushing on three-roll machine with work hardening effect consideration is presented. Non-steady tube bending process for specified curvature is simulated with axis of bending roll displacement, followed by transfer to the steady-state bending process. Estimation of curvature, constrained by tube section elliptical distortion modeled by plastic hinge mechanism is given. Elastic-plastic bending moment versus curvature and critical curvature estimation reasonably correlated with experiments.
Design of an impedance matching acoustic bend
Yang, Yuzhen; Jia, Han; Lu, Wenjia; Sun, Zhaoyong; Yang, Jun
2017-01-01
We propose the design of an impedance matching acoustic bend in this article. The bending structure is composed of sub-wavelength unit cells with perforated plates and side pipes, whose mass density and bulk modulus can be tuned simultaneously. So the refraction index and the impedance of the acoustic bend can be modulated simultaneously to guarantee both the bending effect and the high transmission. The simulation results of sound pressure field distribution show that the bending effect of t...
Bending characteristics of resin concretes
Ribeiro Maria Cristina Santos
2003-01-01
Full Text Available In this research work the influence of composition and curing conditions in bending strength of polyester and epoxy concrete is analyzed. Various mixtures of resin and aggregates were considered in view of an optimal combination. The Taguchi methodology was applied in order to reduce the number of tests, and in order to evaluate the influence of various parameters in concrete properties. This methodology is very useful for the planning of experiments. Test results, analyzed by this methodology, shown that the most significant factors affecting bending strength properties of resin concretes are the type of resin, resin content and charge content. An optimal formulation leading to a maximum bending strength was achieved in terms of material parameters.
无
2006-01-01
The torsional oscillation characteristics on the bending and torsion coupled vibration of rotary shaft system were investigated using the elasto-dynamic theory and other mathematic methods, such as difference approach, Fourier transform, and wavelet transform. It is concluded that mass eccentricity and other exciting modalities affect the bending and torsion coupled vibration of rotary shafts. Torsional vibration caused by bending vibration features linearity along with the change of amplitude of bending vibration. Meanwhile, energy spectrum concentrates on high frequency area with the wavelet analysis.
Bending behavior of lapped plastic ehv cables
Morgan, G H; Muller, A C
1980-01-01
One of the factors delaying the development of lapped polymeric cables has been their reputed poor bending characteristics. Complementary programs were begun at BNL several years ago to mathematically model the bending of synthetic tape cables and to develop novel plastic tapes designed to have moduli more favorable to bending. A series of bend tests was recently completed to evaluate the bending performance of several tapes developed for use in experimental superconducting cables. The program is discussed and the results of the bend tests are summarized.
Hormonal regulation of gravitropic bending
Hu, X.; Cui, D.; Xu, X.; Hu, L.; Cai, W.
Gravitropic bending is an important subject in the research of plant Recent data support the basics of the Cholodny-Went hypothesis indicating that differential growth in gravitropism is due to redistribution of auxin to the lower sides of gravistimulated roots but little is known regarding the molecular details of such effects So we carried a series of work surround the signals induced by auxin end center We found the endogenous signaling molecules nitric oxide NO and cGMP mediate responses to gravistimulation in primary roots of soybean Glycine max Horizontal orientation of soybean roots caused the accumulation of both NO and cGMP in the primary root tip Fluorescence confocal microcopy revealed that the accumulation of NO was asymmetric with NO concentrating in the lower side of the root Auxin induced NO accumulation in root protoplasts and asymmetric NO accumulation in root tips Gravistimulation NO and auxin also induced the accumulation of cGMP a response inhibited by removal of NO or by inhibitors of guanylyl cyclase compounds that also reduced gravitropic bending Asymmetric NO accumulation and gravitropic bending were both inhibited by an auxin transport inhibitor and the inhibition of bending was overcome by treatment with NO or 8-bromo-cGMP a cell-permeable analog of cGMP These data indicate that auxin-induced NO and cGMP mediate gravitropic curvature in soybean roots From Hu et al Plant Physiol 2005 137 663-670 The asymmetric distribution of auxin plays a fundamental role in plant gravitropic bending
Moderate bending strain induced semiconductor to metal transition in Si nanowires
Rabbani, M. Golam; Patil, Sunil R.; Anantram, M. P.
2016-12-01
A moderate amount of bending strains, ∼3% is found to be enough to induce the semiconductor-metal transition in Si nanowires of ∼4 nm diameter. The influence of bending on silicon nanowires of 1 nm to 4.3 nm diameter is investigated using molecular dynamics and quantum transport simulations. Local strains in nanowires are analyzed along with the effect of bending strain and nanowire diameter on electronic transport and the transmission energy gap. Interestingly, relatively wider nanowires are found to undergo semiconductor-metal transition at relatively lower bending strains. The effect of bending strain on electronic properties is then compared with the conventional way of straining, i.e. uniaxial, which shows that bending is a much more efficient way of straining to enhance the electronic transport and also to induce the semiconductor-metal transition in experimentally realizable Si nanowires.
Effect of Bend Radius on Magnitude and Location of Erosion in S-Bend
Quamrul H. Mazumder
2015-01-01
Full Text Available Solid particle erosion is a mechanical process that removes material by the impact of solid particles entrained in the flow. Erosion is a leading cause of failure of oil and gas pipelines and fittings in fluid handling industries. Different approaches have been used to control or minimize damage caused by erosion in particulated gas-solid or liquid-solid flows. S-bend geometry is widely used in different fluid handling equipment that may be susceptible to erosion damage. The results of a computational fluid dynamic (CFD simulation of diluted gas-solid and liquid-solid flows in an S-bend are presented in this paper. In addition to particle impact velocity, the bend radius may have significant influence on the magnitude and the location of erosion. CFD analysis was performed at three different air velocities (15.24 m/s–45.72 m/s and three different water velocities (0.1 m/s–10 m/s with entrained solid particles. The particle sizes used in the analysis range between 50 and 300 microns. Maximum erosion was observed in water with 10 m/s, 250-micron particle size, and a ratio of 3.5. The location of maximum erosion was observed in water with 10 m/s, 300-micron particle size, and a ratio of 3.5. Comparison of CFD results with available literature data showed reasonable and good agreement.
FFAG lattice without opposite bends
Trbojevic, Dejan; Courant, Ernest D.; Garren, Al
2000-08-01
A future "neutrino factory" or Muon Collider requires fast muon acceleration before the storage ring. Several alternatives for fast muon acceleration have previously been considered. One of them is the FFAG (Fixed Field Alternating Gradient) synchrotron. The FFAG concept was developed in 1952 by K. R. Symon (ref. 1). The advantages of this design are the fixed magnetic field, large range of particle energy, simple RF; power supplies are simple, and there is no transition energy. But a drawback is that reverse bending magnets are included in the configuration; this increases the size and cost of the ring. Recently some modified FFAG lattice designs have been described where the amount of opposite bending was significantly reduced (ref. 2, ref. 3).
FFAG lattice without opposite bends
Trbojevic, D; Garren, A
2000-01-01
A future 'neutrino factory' or Muon Collider requires fast muon acceleration before the storage ring. Several alternatives for fast muon acceleration have previously been considered. One of them is the FFAG (Fixed Field Alternating Gradient) synchrotron. The FFAG concept was developed in 1952 by K. R. Symon (ref. 1). The advantages of this design are the fixed magnetic field, large range of particle energy, simple RF; power supplies are simple, and there is no transition energy. But a drawback is that reverse bending magnets are included in the configuration; this increases the size and cost of the ring. Recently some modified FFAG lattice designs have been described where the amount of opposite bending was significantly reduced (ref. 2, ref. 3).
Design Study: ELENA Bending Magnet Prototype
Schoerling, D
2013-01-01
The ELENA bending magnet prototype shall prove that the proposed design meets the requirements set by the ELENA beam dynamics. The following points will be discussed in detail: (i) production process of a magnetic yoke diluted with stainless steel plates, (ii) the stability and repeatability of the field homogeneity of such a yoke over the full working range, (iii) choice of soft magnetic steel, (iv) hysteresis effects, (v) mechanical deformations, (vi) thermal insulation to intercept heat load from baking for activation of NEG coating in the vacuum chamber, (vii) end shim design. In order to verify these points the following measurements will be performed: (i) Hall probe scanning, (ii) integrated field homogeneity measurement (DC), (iii) integrated field homogeneity measurement (AC).
Nonlinear Optimization of CLIC DRS New Design with Variable Bends and High Field Wigglers
Ghasem, H.; Alabau-Gonzalvo, J.; Papadopoulou, S.; Papaphilippou, Y.
2016-01-01
The new design of CLIC damping rings is based on longitudinal variable bends and high field superconducting wiggler magnets. It provides an ultra-low horizontal normalised emittance of 412 nm-rad at 2.86 GeV. In this paper, nonlinear beam dynamics of the new design of the damping ring (DR) with trapezium field profile bending magnets have been investigated in detail. Effects of the misalignment errors have been studied in the closed orbit and dynamic aperture.
Fuzzy Control System of Hydraulic Roll Bending Based on Genetic Neural Network
JIA Chun-yu; LIU Hong-min; ZHOU Hui-feng
2005-01-01
For nonlinear hydraulic roll bending control, a new fuzzy intelligent control method was proposed based on the genetic neural network. The method taking account of dynamic and static characteristics of control system has settled the problems of recognizing and controlling the unknown, uncertain and nonlinear system successfully,and has been applied to hydraulic roll bending control. The simulation results indicate that the system has good performance and strong robustness, and is better than traditional PID and neural-fuzzy control. The method is an effective tool to control roll bending force with increased dynamic response speed of control system and enhanced tracking accuracy.
Bending and stretching of plates
Mansfield, E H; Hemp, W S
1964-01-01
The Bending and Stretching of Plates deals with elastic plate theory, particularly on small- and large-deflexion theory. Small-deflexion theory concerns derivation of basic equations, rectangular plates, plates of various shapes, plates whose boundaries are amenable to conformal transformation, plates with variable rigidity, and approximate methods. Large-deflexion theory includes general equations and some exact solutions, approximate methods in large-deflexion theory, asymptotic large-deflexion theories for very thin plates. Asymptotic theories covers membrane theory, tension field theory, a
Particle deposition in industrial duct bends.
Peters, Thomas M; Leith, David
2004-07-01
A study of particle deposition in industrial duct bends is presented. Particle deposition by size was measured by comparing particle size distributions upstream and downstream of bends that had geometries and flow conditions similar to those used in industrial ventilation. As the interior surface of the duct bend was greased to prevent particle bounce, the results are applicable to liquid drops and solid particles where duct walls are sticky. Factors investigated were: (i) flow Reynolds number (Re = 203 000, 36 000); (ii) particle Reynolds number (10 vertical); and (vii) construction technique (smooth, gored, segmented). Measured deposition was compared with models developed for bends in small diameter sampling lines (Re 20 microm, deposition was slightly greater in the horizontal-to-horizontal orientation than in the horizontal-to-vertical orientation due to gravitational settling. Penetration was not a multiplicative function of bend angle as theory predicts, due to the developing nature of turbulent flow in bends. Deposition in a smooth bend was similar to that in a gored bend; however, a tight radius segmented bend (R0 = 1.7) exhibited much lower deposition. For more gradual bends (3 < R0 < 12), curvature ratio had negligible effect on deposition.
Garment-Integrated Bend Sensor
Guido Gioberto
2014-09-01
Full Text Available Garment-integrated sensors equip clothes with a smart sensing capability, while preserving the comfort of the user. However, this benefit can be to the detriment of sensing accuracy due to the unpredictability of garment movement (which affects sensor positioning and textile folds (which can affect sensor orientation. However, sensors integrated directly into garments or fabric structures can also be used to detect the movement of the garment during wearing. Specifically, a textile bend sensor could be used to sense folds in the garment. We tested a garment-integrated stitched sensor for five types of folds, stitched on five different weights of un-stretchable denim fabric and analyzed the effects of fold complexity and fabric stiffness, under un-insulated and insulated conditions. Results show that insulation improves the linearity and repeatability of the sensor response, particularly for higher fold complexity. Stiffer fabrics show greater sensitivity, but less linearity. Sensor response amplitude is larger for more complex fold geometries. The utility of a linear bending response (insulated and a binary shorting response (un-insulated is discussed. Overall, the sensor exhibits excellent repeatability and accuracy, particularly for a fiber-based, textile-integrated sensor.
Isotope effect in normal-to-local transition of acetylene bending modes.
Ma, Jianyi; Xu, Dingguo; Guo, Hua; Tyng, Vivian; Kellman, Michael E
2012-01-07
The normal-to-local transition for the bending modes of acetylene is considered a prelude to its isomerization to vinylidene. Here, such a transition in fully deuterated acetylene is investigated using a full-dimensional quantum model. It is found that the local benders emerge at much lower energies and bending quantum numbers than in the hydrogen isotopomer HCCH. This is accompanied by a transition to a second kind of bending mode called counter-rotator, again at lower energies and quantum numbers than in HCCH. These transitions are also investigated using bifurcation analysis of two empirical spectroscopic fitting Hamiltonians for pure bending modes, which helps to understand the origin of the transitions semiclassically as branchings or bifurcations out of the trans- and cis-normal bend modes when the latter become dynamically unstable. The results of the quantum model and the empirical bifurcation analysis are in very good agreement.
FACTORS INFLUENCING BENDING RIGIDITY OF SUBMERGED VEGETATION
WU Long-hua; YANG Xiao-li
2011-01-01
The bending rigidity of submerged vegetation is closely related with vegetative drag force.This work aims at determining the effects of flow conditions and characteristics of vegetation on the bending rigidity of submerged vegetation.Based on the dimensional analysis method,the factors influencing the bending rigidity of individual submerged vegetation were analyzed.The relationship between the relative bending rigidity and its influencing factors was investigated by experimental observation,and a relative bending rigidity expression for submerged vegetation was obtained by means of multiple linear regression method.The results show that the submerged vegetation has three states under different inflow conditions,and the each critical relative bending rigidity of individual submerged vegetation was determined for the different states of submerged vegetation.
Elastic bending modulus of monolayer graphene
Lu Qiang; Huang Rui [Department of Aerospace Engineering and Engineering Mechanics, University of Texas, Austin, TX 78712 (United States); Arroyo, Marino [Department of Applied Mathematics 3, LaCaN, Universitat Politecnica de Catalunya (UPC), Barcelona 08034 (Spain)
2009-05-21
An analytic formula is derived for the elastic bending modulus of monolayer graphene based on an empirical potential for solid-state carbon atoms. Two physical origins are identified for the non-vanishing bending stiffness of the atomically thin graphene sheet, one due to the bond-angle effect and the other resulting from the bond-order term associated with the dihedral angles. The analytical prediction compares closely with ab initio energy calculations. Pure bending of graphene monolayers into cylindrical tubes is simulated by a molecular mechanics approach, showing slight nonlinearity and anisotropy in the tangent bending modulus as the bending curvature increases. An intrinsic coupling between bending and in-plane strain is noted for graphene monolayers rolled into carbon nanotubes. (fast track communication)
New triangular and quadrilateral plate-bending finite elements
Narayanaswami, R.
1974-01-01
A nonconforming plate-bending finite element of triangular shape and associated quadrilateral elements are developed. The transverse displacement is approximated within the element by a quintic polynomial. The formulation takes into account the effects of transverse shear deformation. Results of the static and dynamic analysis of a square plate, with edges simply supported or clamped, are compared with exact solutions. Good accuracy is obtained in all calculations.
Ovalization of Tubes Under Bending and Compression
Demer, L J; Kavanaugh, E S
1944-01-01
An empirical equation has been developed that gives the approximate amount of ovalization for tubes under bending loads. Tests were made on tubes in the d/t range from 6 to 14, the latter d/t ratio being in the normal landing gear range. Within the range of the series of tests conducted, the increase in ovalization due to a compression load in combination with a bending load was very small. The bending load, being the principal factor in producing the ovalization, is a rather complex function of the bending moment, d/t ratio, cantilever length, and distance between opposite bearing faces. (author)
Bending Angle Prediction Model Based on BPNN-Spline in Air Bending Springback Process
Zhefeng Guo; Wencheng Tang
2017-01-01
In order to rapidly and accurately predict the springback bending angle in V-die air bending process, a springback bending angle prediction model on the combination of error back propagation neural network and spline function (BPNN-Spline) is presented in this study. An orthogonal experimental sample set for training BPNN-Spline is obtained by finite element simulation. Through the analysis of network structure, the BPNN-Spline black box function of bending angle prediction is established, an...
Waveguiding and bending modes in a plasma photonic crystal bandgap device
B. Wang
2016-06-01
Full Text Available Waveguiding and bending modes are investigated in a fully tunable plasma photonic crystal. The plasma device actively controls the propagation of free space electromagnetic waves in the S to X band of the microwave spectrum. An array of discharge plasma tubes form a square crystal lattice exhibiting a well-defined bandgap, with individual active switching of the plasma elements to allow for waveguiding and bending modes to be generated dynamically. We show, through simulations and experiments, the existence of transverse electric (TE mode waveguiding and bending modes.
STUDY ON INFLUENCE OF BENDING-TORSION COUPLING IN AN IMPACTING-RUB ROTOR SYSTEM
孙政策; 徐健学; 周桐; 谭宁
2003-01-01
A mathematical model of an impacting-rub rotor system with bending-torsion coupling was established. It was compared with the model without bending-torsion coupling through the nodern nonlinear dynamic theory. It is observed that periodical, chaotic,period adding phenomena in them and the two models have a similar bifurcation process in their bifurcation figures. But the influence of bending-torsion on the dynmaic characteristics of the system is not neglected. The results have considerable meanings to analyze and improve the characteristics of an impacting-rub rotor system.
Discontinious Galerkin formulations for thin bending problems
Nguyen, T.D.
2008-01-01
A structural thin bending problem is essentially associated with a fourth-order partial differential equation. Within the finite element framework, the numerical solution of thin bending problems demands the use of C^1 continuous shape functions. Elements using these functions are challenging and di
Restorying the Self: Bending toward Textual Justice
Thomas, Ebony Elizabeth; Stornaiuolo, Amy
2016-01-01
In this essay, Ebony Elizabeth Thomas and Amy Stornaiuolo explore new trends in reader response for a digital age, particularly the phenomenon of bending texts using social media. They argue that bending is one form of "restorying," a process by which people reshape narratives to represent a diversity of perspectives and experiences that…
Anharmonic Bend-Stretch Coupling in Water
Lindner, Jörg; Vöhringer, Peter; Pshenichnikov, Maxim S.; Cringus, Dan; Wiersma, Douwe A.; Corkum, Paul; Jonas, David M.; Miller, R.J. Dwayne.; Weiner, Andrew M.
2006-01-01
Following excitation of the H-O-H bending mode of water molecules in solution the stretching mode region is monitored over its entire width. The anharmonic coupling between the two modes results in a substantial change of the transient stretch absorption that decays with the bend depopulation time.
Bandwidth engineering of photonic crystal waveguide bends
Borel, Peter Ingo; Frandsen, Lars Hagedorn; Harpøth, Anders;
2004-01-01
An effective design principle has been applied to photonic crystal waveguide bends fabricated in silicon-on-insulator material using deep UV lithography resulting in a large increase in the low-loss bandwidth of the bends. Furthermore, it is experimentally demonstrated that the absolute bandwidth...
Bends and splitters in graphene nanoribbon waveguides
Zhu, Xiaolong; Yan, Wei; Mortensen, N. Asger
2013-01-01
We investigate the performance of bends and splitters in graphene nanoribbon waveguides. Although the graphene waveguides are lossy themselves, we show that bends and splitters do not induce any additional loss provided that the nanoribbon width is sub-wavelength. We use transmission line theory...
Millett, A. U.
1977-01-01
Combination protractor and scale for measuring tube bends has novel pivot that allows tube to remain in contact with scale arms for all bend angles. Device permits rapid and accurate scribing and measurement of mockup fluid lines to obtain production data.
Wire and Cable Cold Bending Test
Colozza, Anthony
2010-01-01
One of the factors in assessing the applicability of wire or cable on the lunar surface is its flexibility under extreme cold conditions. Existing wire specifications did not address their mechanical behavior under cold, cryogenic temperature conditions. Therefore tests were performed to provide this information. To assess this characteristic 35 different insulated wire and cable pieces were cold soaked in liquid nitrogen. The segments were then subjected to bending and the force was recorded. Any failure of the insulation or jacketing was also documented for each sample tested. The bending force tests were performed at room temperature to provide a comparison to the change in force needed to bend the samples due to the low temperature conditions. The results from the bending tests were plotted and showed how various types of insulated wire and cable responded to bending under cold conditions. These results were then used to estimate the torque needed to unroll the wire under these low temperature conditions.
49 CFR 195.212 - Bending of pipe.
2010-10-01
... 49 Transportation 3 2010-10-01 2010-10-01 false Bending of pipe. 195.212 Section 195.212... PIPELINE Construction § 195.212 Bending of pipe. (a) Pipe must not have a wrinkle bend. (b) Each field bend must comply with the following: (1) A bend must not impair the serviceability of the pipe. (2) Each...
A derivation of the generalized model of strains during bending of metal tubes at bending machines
Śloderbach Z.
2014-01-01
According to the postulate concerning a local change of the “actual active radius” with a bending angle in the bend zone, a generalized model of strain during metal tube bending was derived. The tubes should be subjected to bending at tube bending machines by the method of wrapping at the rotating template and with the use of a lubricated steel mandrel. The model is represented by three components of strain in the analytic form, including displacement of the neutral axis. Generalization of th...
Mechanism and elimination of bending effect in femtosecond laser deep-hole drilling.
Xia, Bo; Jiang, Lan; Li, Xiaowei; Yan, Xueliang; Lu, Yongfeng
2015-10-19
In this work, a comprehensive study of the bending effect, which remains one of the most critical challenges during deep-hole drilling, was conducted. The experimental statistics indicate that polarization is not the main factor in bending, but the deviation of the hole tends to be perpendicular to the polarization direction. Also, the dynamic ablated material/plasma was studied. Straight microholes were obtained by extending the interval between laser pulses to avoid dynamic ablated material existing in the millisecond time domain. Therefore, we speculated that the disturbance of the laser beam at the dynamic ablated aerosol, which have not sufficiently dispersed in the millisecond domain, is the main mechanism of bending. However, to more efficiently reduce the disturbance factor, a rough vacuum environment was applied; and the bending effect was also eliminated. The critical pressure for eliminating bending was about 2 × 10(4) Pa that is about one order of magnitude lower than the atmosphere. The fabricated high-quality microhole arrays without bending show that the proposed drilling method is convenient and efficient with high repeatability and controllability.
Transfer matrices of dipoles with bending radius variation
无
2011-01-01
With the increasing demand of high brightness in light source, the uniform dipole can not meet the needs of low emittance, and thus the dipole with bending radius variation is introduced in this paper. The transfer matrix of a non-uniform dipole whose bending radius is linearly changed is chosen as an example and a very simple calculation formula of non-uniform dipole transfer matrices is given. The transfer matrices of some common profile non-uniform dipoles are also listed. The comparison of these transfer matrices and the matrices calculated with slices method verifies the numerical accuracy of this formula. This method can make the non-uniform beam dynamic problem simpler, very helpful for emittance research and lattice design with non-uniform dipoles.
The bending of cell sheets - from folding to rolling
Keller Ray
2011-12-01
Full Text Available Abstract The bending of cell sheets plays a major role in multicellular embryonic morphogenesis. Recent advances are leading to a deeper understanding of how the biophysical properties and the force-producing behaviors of cells are regulated, and how these forces are integrated across cell sheets during bending. We review work that shows that the dynamic balance of apical versus basolateral cortical tension controls specific aspects of invagination of epithelial sheets, and recent evidence that tissue expansion by growth contributes to neural retinal invagination in a stem cell-derived, self-organizing system. Of special interest is the detailed analysis of the type B inversion in Volvox reported in BMC Biology by Höhn and Hallmann, as this is a system that promises to be particularly instructive in understanding morphogenesis of any monolayered spheroid system. See research article: http://www.biomedcentral.com/1741-7007/9/89
Low Loss S-Bend Structure With Tapered Curved Waveguides
无
2003-01-01
A novel S-bend with tapered curved waveguides is proposed. The normalized transmitted power is greater than the conventional bend with weakly guided waveguides. Small size and low loss can be reached by the proposed S-bend.
Springback of thin-walled tube NC precision bending and its numerical simulation
GU Rui-jie; YANG He; ZHAN Mei; LI Heng
2006-01-01
The springback is one of the key factors which affect the forming quality of thin-walled tube NC precision bending. The elastic-plastic finite element method was proposed to study the springback process of thin-walled tube NC precision bending and the combination of dynamic explicit algorithm and the static implicit algorithm was proposed to solve the whole process of thin-walled tube NC precision bending. Then,the 3D elastic-plastic finite element model was established based on the DYNAFORM platform,and the model was verified to be reasonable. At last,the springback rule of thin-walled tube NC precision bending and the effect of geometry and material parameters on the springback rule of thin-walled tube NC precision bending were studied,which is useful to controlling the springback of thin-walled tube NC precision bending,and the numerical simulation method can be used to study other effect of parameters on the forming quality of thin-walled tube NC precision bending.
Bending stresses in Facetted Glass Shells
Bagger, Anne; Jönsson, Jeppe; Almegaard, Henrik
2008-01-01
A shell structure of glass combines a highly effective structural principle with a material of optimal permeability to light. A facetted shell structure has a piecewise plane geometry, and together the facets form an approximation to a curved surface. A distributed load on a plane-based facetted...... structure will locally cause bending moments in the loaded facets. The bending stresses are dependent on the stiffness of the joints. Approximate solutions are developed to estimate the magnitude of the bending stresses. A FE-model of a facetted glass shell structure is used to validate the expressions...
Bidirectional bending splitter of designer surface plasmons
Jin Zhou, Yong; Jiang, Quan; Jun Cui, Tie
2011-09-01
We propose and experimentally verify a bidirectional bending splitter of designer surface plasmons which is composed of two metallic gratings of trapezoid grooves. A metal wire is used to excite the designer surface plasmons propagating along the gratings. A full-wave numerical method has been used to simulate the performance of the bending splitter. The experimental verifications in the microwave frequencies have excellent agreements to the simulations. It is demonstrated that the splitter can not only split the electromagnetic waves at different frequencies, but also guide the electromagnetic waves effectively for large-angle bending.
EFFECT OF CHANNEL BENDS ON TRANSVERSE MIXING
user
1986-09-01
Sep 1, 1986 ... The first study of transverse mixing in bends of turbulent open channel flows ... Rozovskii's transverse velocity distribution for fully developed turbulent flow ... Yotsukura et al (3) employed a simulation procedure to predict the.
Bending artificial muscle from nylon filaments
Mirvakili, Seyed M.; Hunter, Ian W.
2016-04-01
Highly oriented nylon and polyethylene fibers shrink in length and expand in diameter when heated. Using this property, in this work, for the first time we are introducing a type of bending artificial muscle from nylon filaments such as fishing line. Reversible radius of curvature of 0.23 mm-1 was achieved with maximum reversible bending amplitude of 115 mm for the nylon bending actuator. Peak force of up to 2040 mN was measured with a catch-state force of up to 40% of the active force. A 3 dB roll-off frequency of around 0.7 Hz was observed in the frequency response of the bending actuator in water.
Interferometric fiber-optic bending / nano-displacement sensor using plastic dual-core fiber
Qu, H; Skorobogatiy, M
2014-01-01
We demonstrate an interferometric fiber-optic bending/micro-displacement sensor based on a plastic dual-core fiber with one end coated with a silver mirror. The two fiber cores are first excited with the same laser beam, the light in each core is then back-reflected at the mirror-coated fiber-end, and, finally, the light from the two cores is made to interfere at the coupling end. Bending of the fiber leads to shifting interference fringes that can be interrogated with a slit and a single photodetector. We find experimentally that the resolution of our bending sensor is ~3x10-4 m-1 for sensing of bending curvature, as well as ~70 nm for sensing of displacement of the fiber tip. We demonstrate operation of our sensor using two examples. One is weighting of the individual micro-crystals of salt, while the other one is monitoring dynamics of isopropanol evaporation.
This is a slice of a LEP dipole bending magnet, made as a concrete and iron sandwich The bending field needed in LEP is small (about 1000 Gauss), equivalent to two of the magnets people stick on fridge doors. Because it is very difficult to keep a low field steady, a high field was used in iron plates embedded in concrete. A CERN breakthrough in magnet design, LEP dipoles can be tuned easily and are cheaper than conventional magnets.
This is a slice of a LEP dipole bending magnet, made as a concrete and iron sandwich. The bending field needed in LEP is small (about 1000 Gauss), equivalent to two of the magnets people stick on fridge doors. Because it is very difficult to keep a low field steady, a high field was used in iron plates embedded in concrete. A CERN breakthrough in magnet design, LEP dipoles can be tuned easily and are cheaper than conventional magnets.
Pipes under internal pressure and bending
Catinaccio, A
2009-01-01
This article covers the general behaviour of a straight uniform pipe, with built-in open ends, subject to internal pressure and in plane bending or curvature. It is intended as a summary of the basic equations driving the unintuitive phenomena of bending and instability of pipes under internal pressure. The analysis covers in addition the investigation of opposite pressure stabilisation effects that can be observed in some orthotropic material pipes like composite pressure hoses.
Bending sound in graphene: Origin and manifestation
Adamyan, V.M., E-mail: vadamyan@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Bondarev, V.N., E-mail: bondvic@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Zavalniuk, V.V., E-mail: vzavalnyuk@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Department of Fundamental Sciences, Odessa Military Academy, 10 Fontanska Road, Odessa 65009 (Ukraine)
2016-11-11
Highlights: • The origin of sound-like dispersion of graphene bending mode is disclosed. • The speed of graphene bending sound is determined. • The renormalized graphene bending rigidity is derived. • The intrinsic corrugations of graphene are estimated. - Abstract: It is proved that the acoustic-type dispersion of bending mode in graphene is generated by the fluctuation interaction between in-plane and out-of-plane terms in the free energy arising with account of non-linear components in the graphene strain tensor. In doing so we use an original adiabatic approximation based on the alleged (confirmed a posteriori) significant difference of sound speeds for in-plane and bending modes. The explicit expression for the bending sound speed depending only on the graphene mass density, in-plane elastic constants and temperature is deduced as well as the characteristics of the microscopic corrugations of graphene. The obtained results are in good quantitative agreement with the data of real experiments and computer simulations.
Multiphase forces on bend structures
Nennie, E.D.; Belfroid, S.P.C.
2016-01-01
Piping structures are generally subjected to high dynamic loading due to multiphase forces. In particular subsea structures are very vulnerable as large flexibility is required to cope for instance with thermal stresses. The forces due to multiphase flow are characterized by a broadband spectrum wit
Multiphase forces on bend structures
Nennie, E.D.; Belfroid, S.P.C.
2016-01-01
Piping structures are generally subjected to high dynamic loading due to multiphase forces. In particular subsea structures are very vulnerable as large flexibility is required to cope for instance with thermal stresses. The forces due to multiphase flow are characterized by a broadband spectrum wit
Forming characteristics of thin-walled tube bending process with small bending radius
LI Heng; YANG He; ZHAN Mei; GU Rui-Jie
2006-01-01
Currently requirements of thin-walled tube with small bending radius cause the defects such as wrinkling,overthinning and cross-section distortion more prone to occur in bending process. Based on the analysis of the forming characteristics by analytical and experimental methods,a complete 3D elastic-plastic FEM model of the process was developed using ABAQUS/Explicit code,including bending process,balls retracting and unloading process,and thus the plastic deformation characteristics with small bending radius were investigated. The main results show that: 1) The utmost deformation feature of the NC bending process is its continuous progressive deformation. 2) The occurring conditions of the defects such as wrinkling and tension instability in the process are obtained. The wrinkling is traditional on the double compressive stresses state and the tension instability is on the double tension stresses state. 3) The enhanced non-uniform deformation in thin-walled tube with small bending radius is demonstrated by comparing the stress/ strains distributions under the 1.5D and 1D bending conditions. 4) For 1D small bending process,a new method-"stepped mandrel retraction" is proposed to improve the bending quality in experiment according to the FE simulation. The simulation results are verified by experiment.
New Equation for Bending Development of Arbitrary Rods and Application to Palm Fronds Bending
Abdullah, Mikrajuddin
2016-01-01
A new general equation to explain bending of arbitrary rods (from arbitrary materials, cross sections, densities, strengthnesses, bending angles, etc) was proposed. This equation can solve several problems found in classical equations, which have many limitations such as only applies for small bending angles or must be solved using very complex schemes. Experiments were also conducted to confirm the theoretical predictions. The equation might be used to explain bending of palm fronds in a very simple way. The proposed equation may be used to obtain solution of several problems which are usually obtain with iteration procedures.
The quantitative check-measure of the bend strain parameters of the rotating components
李文华; 乔中涛
2002-01-01
Based on the principle of the electric-magnetic check-measure, this paper puts forward a new technology and method that use the magnetic marks to check and measure the dynamic physical parameters such as angle speed, bending strain,stress and bending moment. The principles of the check-measure and the dealing and exchanging technology about signals have been demonstrated and the rotating components have been made up. The timely and quantitative check-measure of the dynamic physical parameters during the component in working has been realized by using computer control.
Stereotypical reaching movements of the octopus involve both bend propagation and arm elongation.
Hanassy, S; Botvinnik, A; Flash, T; Hochner, B
2015-05-13
The bend propagation involved in the stereotypical reaching movement of the octopus arm has been extensively studied. While these studies have analyzed the kinematics of bend propagation along the arm during its extension, possible length changes have been ignored. Here, the elongation profiles of the reaching movements of Octopus vulgaris were assessed using three-dimensional reconstructions. The analysis revealed that, in addition to bend propagation, arm extension movements involve elongation of the proximal part of the arm, i.e., the section from the base of the arm to the propagating bend. The elongations are quite substantial and highly variable, ranging from an average strain along the arm of -0.12 (i.e. shortening) up to 1.8 at the end of the movement (0.57 ± 0.41, n = 64 movements, four animals). Less variability was discovered in an additional set of experiments on reaching movements (0.64 ± 0.28, n = 30 movements, two animals), where target and octopus positions were kept more stationary. Visual observation and subsequent kinematic analysis suggest that the reaching movements can be broadly segregated into two groups. The first group involves bend propagation beginning at the base of the arm and propagating towards the arm tip. In the second, the bend is formed or present more distally and reaching is achieved mainly by elongation and straightening of the segment proximal to the bend. Only in the second type of movements is elongation significantly positively correlated with the distance of the bend from the target. We suggest that reaching towards a target is generated by a combination of both propagation of a bend along the arm and arm elongation. These two motor primitives may be combined to create a broad spectrum of reaching movements. The dynamical model, which recapitulates the biomechanics of the octopus muscular hydrostatic arm, suggests that achieving the observed elongation requires an extremely low ratio of longitudinal to transverse muscle
Bend-insensitive optical fibers for FTTH applications
Li, Ming-Jun
2009-01-01
This paper reviews recent development in bend-insensitive fibers for fiber-to-the-home (FTTH) applications. First, requirements for bend-insensitive fibers are discussed. Then different design approaches for reducing fiber bending loss are described and compared. A new bend-insensitive fiber using the nano-engineered ring design is presented in detail.
The Effect of First-Order Bending Resonance of Wheelset at High Speed on Wheel-Rail Contact Behavior
Shuoqiao Zhong
2013-01-01
Full Text Available The first-order bending deformation of wheelset is considered in the modeling vehicle/track coupling dynamic system to investigate its effect on wheel/rail contact behavior. In considering the effect of the first-order bending resonance on the rolling contact of wheel/rail, a new wheel/rail contact model is derived in detail in the modeling vehicle/track coupling dynamic system, in which the many intermediate coordinate systems and complex coordinate system transformations are used. The bending mode shape and its corresponding frequency of the wheelset are obtained through the modal analysis by using commercial software ANSYS. The modal superposition method is used to solve the differential equations of wheelset motion considering its flexible deformation due to the first-order bending resonance. In order to verify the present model and clarify the influence of the first-order bending deformation of wheelset on wheel/track contact behavior, a harmonic track irregularity with a fixed wavelength and a white-noise roughness are, respectively used as the excitations in the two models of vehicle-rail coupling dynamic system, one considers the effect of wheelset bending deformation, and the other does not. The numerical results indicate that the wheelset first-order bending deformation has an influence on wheel/rail rolling contact behavior and is easily excited under wheel/rail roughness excitation.
王丹; 陈予恕; 曹庆杰; 熊冶平
2014-01-01
针对涡轮旋转机械的叶片所处的高温、高压及复杂多场环境，建立其弯曲和扭转两自由度耦合的截面模型，研究了来流速度对振幅的影响。利用平均法和能量法原理，得到了系统在发生临界颤振时的幅频关系以及在能量输入输出情况下系统的稳定性关系，避免了颤振发生引起的气动弹性设计失效问题，从而对叶片的优化设计提供理论依据。%Blades of turbines and compressors are important components to produce power.They works often in a complicated condition with high pressure,high temperature and three dimensional fluid flows as well.The aeroelastic problem such as blade flutter may occur during different working states.Flow-induced vibration of a blade with coupling of bending and torsion was investigated to reveal the mechanism of a flutter.Averaging method and power flow approach were used to demonstrate flutter behaviors of the interaction between an isolated blade and a quasi-steady flow.The relation between amplitudes and frequencies of blade vibration was obtained to predict flutters.The results provided a theoretical basis for aeroelastic optimal design of blades.
Finite Element Simulation of Magnesium Alloy AZ31 Tube Bending
Wu Wenyun
2016-01-01
Full Text Available A finite element method based model has been developed for magnesium alloy AZ31 tube bending process simulation, using the tensile (for bend outer radius and compressive (for bend inner radius properties of the AZ31 alloy at the bending temperature of 150°C. The results shown that very high compressive stresses are developed in the bend inner radius, limiting the minimum bend radius for the AZ31 tube. The simulation results suggest the minimum centerline bend radius to the tube outer diameter ratio is 1.5 to 2. The maximum diameter to thickness ratio is 30.
Tunable thermoelectric properties in bended graphene nanoribbons
Chang-Ning, Pan; Jun, He; Mao-Fa, Fang
2016-07-01
The ballistic thermoelectric properties in bended graphene nanoribbons (GNRs) are systematically investigated by using atomistic simulation of electron and phonon transport. We find that the electron resonant tunneling effect occurs in the metallic-semiconducting linked ZZ-GNRs (the bended GNRs with zigzag edge leads). The electron-wave quantum interference effect occurs in the metallic-metallic linked AA-GNRs (the bended GNRs with armchair edge leads). These different physical mechanisms lead to the large Seebeck coefficient S and high electron conductance in bended ZZ-GNRs/AA-GNRs. Combined with the reduced lattice thermal conduction, the significant enhancement of the figure of merit ZT is predicted. Moreover, we find that the ZTmax (the maximum peak of ZT) is sensitive to the structural parameters. It can be conveniently tuned by changing the interbend length of bended GNRs. The magnitude of ZT ranges from the 0.15 to 0.72. Geometry-controlled ballistic thermoelectric effect offers an effective way to design thermoelectric devices such as thermocouples based on graphene. Project supported by the National Natural Science Foundation of China (Grant No. 61401153) and the Natural Science Foundation of Hunan Province, China (Grant Nos. 2015JJ2050 and 14JJ3126).
Pure plate bending in couple stress theories
Hadjesfandiari, Ali R; Dargush, Gary F
2016-01-01
In this paper, we examine the pure bending of plates within the framework of modified couple stress theory (M-CST) and consistent couple stress theory (C-CST). In this development, it is demonstrated that M-CST does not describe pure bending of a plate properly. Particularly, M-CST predicts no couple-stresses and no size effect for the pure bending of the plate into a spherical shell. This contradicts our expectation that couple stress theory should predict some size effect for such a deformation pattern. Therefore, this result clearly demonstrates another inconsistency of indeterminate symmetric modified couple stress theory (M-CST), which is based on considering the symmetric torsion tensor as the curvature tensor. On the other hand, the fully determinate skew-symmetric consistent couple stress theory (C-CST) predicts results for pure plate bending that tend to agree with mechanics intuition and experimental evidence. Particularly, C-CST predicts couple-stresses and size effects for the pure bending of the ...
Tunable thermoelectric properties in bended graphene nanoribbons
潘长宁; 何军; 方卯发
2016-01-01
The ballistic thermoelectric properties in bended graphene nanoribbons (GNRs) are systematically investigated by using atomistic simulation of electron and phonon transport. We find that the electron resonant tunneling effect occurs in the metallic–semiconducting linked ZZ-GNRs (the bended GNRs with zigzag edge leads). The electron-wave quan-tum interference effect occurs in the metallic–metallic linked AA-GNRs (the bended GNRs with armchair edge leads). These different physical mechanisms lead to the large Seebeck coefficient S and high electron conductance in bended ZZ-GNRs/AA-GNRs. Combined with the reduced lattice thermal conduction, the significant enhancement of the figure of merit ZT is predicted. Moreover, we find that the ZTmax (the maximum peak of ZT) is sensitive to the structural parameters. It can be conveniently tuned by changing the interbend length of bended GNRs. The magnitude of ZT ranges from the 0.15 to 0.72. Geometry-controlled ballistic thermoelectric effect offers an effective way to design thermoelectric devices such as thermocouples based on graphene.
Influence of High Pressure on the Bending Rigidity of Model Membranes.
Purushothaman, Sowmya; Cicuta, Pietro; Ces, Oscar; Brooks, Nicholas J
2015-07-30
Curvature is a fundamental lipid membrane property that influences many membrane-mediated biological processes and dynamic soft materials. One of the key parameters that determines the energetics of curvature change is the membrane bending rigidity. Understanding the intrinsic effect of pressure on membrane bending is critical to understanding the adaptation and structural behavior of biomembranes in deep-sea organisms as well as soft material processing. However, it has not previously been possible to measure the influence of high hydrostatic pressure on membrane bending energetics, and this bottleneck has primarily been due to a lack of technology platforms for performing such measurements. We have developed a new high-pressure microscopy cell which, combined with vesicle fluctuation analysis, has allowed us to make the first measurements of membrane bending rigidity as a function of pressure. Our results show a significant increase in bending rigidity at pressures up to 40 MPa. Above 40 MPa, the membrane mechanics become more complex. Corresponding small and wide-angle X-ray diffraction shows an increase in density and thickness of the bilayer with increasing pressure which correlates with the micromechanical measurements. These results are consistent with recent theoretical predictions of the bending rigidity as a function of hydrocarbon chain density. This technology has the potential to transform our quantitative understanding of the role of pressure in soft material processing, the structural behavior of biomembranes, and the adaptation mechanisms employed by deep-sea organisms.
Suzuki, Toshiya; Mochizuki, Takashi; Ushimizu, Hidetaka; Miyazawa, Shinya; Tsurui, Nobuhiro; Masuda, Kohji
2017-07-01
Although we have already experimented on the bending of a thin catheter with acoustic radiation force using a single transducer, it is necessary to develop a method of bending a catheter in an arbitrary direction because the installation position of ultrasound transducers on a body surface is limited for application to various shapes of in vivo blood vessels. Therefore, we examined the bending of a thin catheter in the direction perpendicular to ultrasound propagation using a two-dimensional array transducer (1 MHz), which realizes not only the temporospatial design but also the dynamic variation of acoustic fields. Forming two focal points with opposite phases, where the amplitudes of the two points instantaneously have the positive and negative relationship, we confirmed the bending of a thin catheter in the direction perpendicular to ultrasound propagation. We used a thin catheter (diameter, 200 µm length, 50 mm) to obtain the maximum displacement of 220 µm, where the displacement was proportional to the square of the maximum sound pressure and the duty ratio. From these results, the acoustic energy densities observed in front of and behind the catheter are dominant for the bending of the thin catheter independent of ultrasound propagation. We also found that the distance between two focal points may improve the bending performance without requiring a precise position setting.
2010-11-24
... Forest Service Bend/Ft. Rock Ranger District; Deschutes National Forest; Deschutes County, OR; West Bend... Jeffries, District Ranger, Bend-Fort Rock Ranger District, Red Oaks Square, 1230 NE. Third Street, Suite A...-Fort Rock Ranger District, Red Oaks Square, 1230 NE. Third Street, Suite A-262, Bend, Oregon 97701...
Bending Angle Prediction Model Based on BPNN-Spline in Air Bending Springback Process
Zhefeng Guo
2017-01-01
Full Text Available In order to rapidly and accurately predict the springback bending angle in V-die air bending process, a springback bending angle prediction model on the combination of error back propagation neural network and spline function (BPNN-Spline is presented in this study. An orthogonal experimental sample set for training BPNN-Spline is obtained by finite element simulation. Through the analysis of network structure, the BPNN-Spline black box function of bending angle prediction is established, and the advantage of BPNN-Spline is discussed in comparison with traditional BPNN. The results show a close agreement with simulated and experimental results by application examples, which means that the BPNN-Spline model in this study has higher prediction accuracy and better applicable ability. Therefore, it could be adopted in a numerical control bending machine system.
Robotic Arm Comprising Two Bending Segments
Mehling, Joshua S.; Difler, Myron A.; Ambrose, Robert O.; Chu, Mars W.; Valvo, Michael C.
2010-01-01
The figure shows several aspects of an experimental robotic manipulator that includes a housing from which protrudes a tendril- or tentacle-like arm 1 cm thick and 1 m long. The arm consists of two collinear segments, each of which can be bent independently of the other, and the two segments can be bent simultaneously in different planes. The arm can be retracted to a minimum length or extended by any desired amount up to its full length. The arm can also be made to rotate about its own longitudinal axis. Some prior experimental robotic manipulators include single-segment bendable arms. Those arms are thicker and shorter than the present one. The present robotic manipulator serves as a prototype of future manipulators that, by virtue of the slenderness and multiple- bending capability of their arms, are expected to have sufficient dexterity for operation within spaces that would otherwise be inaccessible. Such manipulators could be especially well suited as means of minimally invasive inspection during construction and maintenance activities. Each of the two collinear bending arm segments is further subdivided into a series of collinear extension- and compression-type helical springs joined by threaded links. The extension springs occupy the majority of the length of the arm and engage passively in bending. The compression springs are used for actively controlled bending. Bending is effected by means of pairs of antagonistic tendons in the form of spectra gel spun polymer lines that are attached at specific threaded links and run the entire length of the arm inside the spring helix from the attachment links to motor-driven pulleys inside the housing. Two pairs of tendons, mounted in orthogonal planes that intersect along the longitudinal axis, are used to effect bending of each segment. The tendons for actuating the distal bending segment are in planes offset by an angle of 45 from those of the proximal bending segment: This configuration makes it possible to
Tubular lining material for pipelines having bends
Moringa, A.; Sakaguchi, Y.; Hyodo, M.; Yagi, I.
1987-03-24
A tubular lining material for pipelines having bends or curved portions comprises a tubular textile jacket made of warps and wefts woven in a tubular form overlaid with a coating of a flexible synthetic resin. It is applicable onto the inner surface of a pipeline having bends or curved portions in such manner that the tubular lining material with a binder onto the inner surface thereof is inserted into the pipeline and allowed to advance within the pipeline, with or without the aid of a leading rope-like elongated element, while turning the tubular lining material inside out under fluid pressure. In this manner the tubular lining material is applied onto the inner surface of the pipeline with the binder being interposed between the pipeline and the tubular lining material. The lining material is characterized in that a part of all of the warps are comprised of an elastic yarn around which, over the full length thereof, a synthetic fiber yarn or yarns have been left-and/or right-handedly coiled. This tubular lining material is particularly suitable for lining a pipeline having an inner diameter of 25-200 mm and a plurality of bends, such as gas service pipelines or house pipelines, without occurrence of wrinkles in the lining material in a bend.
RELIABILITY ANALYSIS OF BENDING ELIABILITY ANALYSIS OF ...
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performance of any structural system be eva ... by the Joint crete slabs, bending, shear, deflection, reliability, design codes. ement such as ... could be sensitive to this distribution. Table 1: ..... Ang, A. H-S and Tang, W. H. Probability Concepts in.
Monitoring the Bending Stiffness of DNA
Yuan, Chongli; Lou, Xiongwen; Rhoades, Elizabeth; Chen, Huimin; Archer, Lynden
2007-03-01
In eukaryotic cells, the accessibility of genomic sequences provides an inherent regulation mechanism for gene expression through variations in bending stiffness encoded by the nucleic acid sequence. Cyclization of dsDNA is the prevailing method for determining DNA bending stiffness. Recent cyclization data for short dsDNA raises several fundamental questions about the soundness of the cyclization method, particularly in cases where the probability of highly bent DNA conformations is low. We herein evaluate the role of T4 DNA ligase in the cyclization reaction by inserting an environmental sensitive base analogue, 2-amino purine, to the DNA molecule. By monitoring the 2-AP fluorescence under standard cyclization conditions, it is found that in addition to trapping highly-bent cyclic DNA conformations, T4 DNA ligase enhances the apparent base pair flip out rate, thus exaggerating the measured flexibility. This result is further confirmed using fluorescence anisotropy experiments. We show that fluorescence resonance energy transfer (FRET) measurements on suitably labeled dsDNA provides an alternative approach for quantifying the bending stiffness of short fragments. DNA bending stiffness results obtained using FRET are compared with literature values.
Demonstration model of LEP bending magnet
CERN PhotoLab
1981-01-01
To save iron and raise the flux density, the LEP bending magnet laminations were separated by spacers and the space between the laminations was filled with concrete. This is a demonstration model, part of it with the spaced laminations only, the other part filled with concrete.
A process model for air bending
de Vin, L.J.; de Vin, L.J.; Streppel, A.H.; Singh, U.P.; Kals, H.J.J.
1996-01-01
A so called `three-section¿ model for air bending is presented. It is assumed that a state of plane strain exists and that Bernoulli's law is valid. The material behaviour is described with Swift's equation, and the change of Young's modulus under deformation is addressed. As compared with other
Design of a hydraulic bending machine
Steven G. Hankel; Marshall Begel
2004-01-01
To keep pace with customer demands while phasing out old and unserviceable test equipment, the staff of the Engineering Mechanics Laboratory (EML) at the USDA Forest Service, Forest Products Laboratory, designed and assembled a hydraulic bending test machine. The EML built this machine to test dimension lumber, nominal 2 in. thick and up to 12 in. deep, at spans up to...
Spring-back deformation in tube bending
Da-xin E; Hua-hui He; Xiao-yi Liu; Ru-xin Ning
2009-01-01
The spring-back of a bending metal tube was studied through extensive experiments and finite element method (FEM) analysis. An approximate equation for the spring-back angle of bending was deduced. It is noted that the mechanical properties of the material (in a tubular form) are quite different from those found in the standard tensile tests (when the materials are in bar forms). This is one of the major reasons that result in the discrepancies in the outcomes of experimental study, FEM calculations, and spring-back analysis. It is therefore of crucial importance to study the mechanical properties of the materials in their tubular forms. The experiments and FEM simulations prove that the spring-back angle is significantly affected by the mechanical properties of the materials. The angle decreases accordingly with plastic modulus, but changes inversely with the hardening index and elastic modulus. The spring-back angle is also affected by the conditions of tube deformation: it increases accordingly with the relative bending radius but changes inversely with the relative wall thickness. In addition, the spring-back angle increases nonlinearly with the bending an-gle.
Inelastic Deformation Analysis of Aluminum Bending Members
CHENG Ming; SHI Yongjiu; WANG Yuanqing
2006-01-01
Aluminum alloys are typical nonlinear materials, and consequently bending members made of this material exhibit a nonlinear behavior. Most design codes do not pay much attention to such deformations and adopt a simple linear analysis for the calculation of deflections. This paper presents an investigation of the nonlinear deformation of aluminum bending members using the finite-element analysis (FEA). The plastic adaptation coefficient, which can be used to limit the residual deflection, is introduced, and the influence of residual deflection is investigated. A method for evaluating the plastic adoption coefficient is proposed. This paper also shows the load-deflection curve of aluminum bending members and the influence of several parameters. A semi-empirical formula is derived, and some numerical examples are given by FEA. The coefficients of the semi-empirical formula are modified by the FEA results using the nonlinear fitting method. Based on these results, two improved design methods for strength and deformation of aluminum bending members are proposed. Through the comparison with test data, these methods are proved to be suitable for structural design.
Probing the elastic limit of DNA bending
Le, Tung T
2014-01-01
Many structures inside the cell such as nucleosomes and protein-mediated DNA loops contain sharply bent double-stranded (ds) DNA. Therefore, the energetics of strong dsDNA bending constitutes an essential part of cellular thermodynamics. Although the thermomechanical behavior of long dsDNA is well described by the worm-like chain (WLC) model, the length limit of such elastic behavior remains controversial. To investigate the energetics of strong dsDNA bending, we measured the opening rate of small dsDNA loops with contour lengths of 40-200 bp using Fluorescence Resonance Energy Transfer (FRET). From the measured relationship of loop stability to loop size, we observed a transition between two separate bending regimes at a critical loop size below 100 bp. Above this loop size, the loop lifetime decreased with decreasing loop size in a manner consistent with an elastic bending stress. Below the critical loop size, however, the loop lifetime became less sensitive to loop size, indicative of softening of the doub...
Head movements while steering around bends
Erp, J.B.F. van; Oving, A.B.
2012-01-01
In this study, the determinants of head motions (rotations) when driving around bends were investigated when drivers viewed the scene through a head-mounted display. The scene camera was either fixed or coupled to head motions along 2 or 3 axes of rotation. Eight participants drove around a
Experimental Characterization of Stretch-Bending Formability of AHSS Sheets
Kitting, Daniela; Ofenheimer, Aldo; Pauli, Heinrich; Till, Edwin T.
2011-05-01
Deformation conditions of combined stretching and bending are known to enhance material formability compared to forming conditions without bending (e.g. in-plane stretching). These phenomena can be observed for most conventional steel grades but is even more pronounced for Advanced High Strength Steel (AHSS) sheets. Consequently, there is an urgent need in industry to quantify the phenomena of enhanced material formability due to bending effects. In this work new stretch-bend test setups are presented which can be used in addition to the conventional Angular Stretch Bend Test to systematically investigate the influence of various stretch-bending deformation conditions on the formability of AHSS sheets.
Bending effects on lasing action of semiconductor nanowires.
Yang, Weisong; Ma, Yaoguang; Wang, Yipei; Meng, Chao; Wu, Xiaoqin; Ye, Yu; Dai, Lun; Tong, Limin; Liu, Xu; Yang, Qing
2013-01-28
High flexibility has been one of advantages for one-dimensional semiconductor nanowires (NWs) in wide application of nanoscale integrated circuits. We investigate the bending effects on lasing action of CdSe NWs. Threshold increases and differential efficiency decreases gradually when we decrease the bending radius step by step. Red shift and mode reduction in the output spectra are also observed. The bending loss of laser oscillation is considerably larger than that of photoluminescence (PL), and both show the exponential relationship with the bending radius. Diameter and mode dependent bending losses are investigated. Furthermore, the polarizations of output can be modulated linearly by bending the NWs into different angles continuously.
Subrahmanyam, K. B.; Kaza, K. R. V.; Brown, G. V.; Lawrence, C.
1986-01-01
The coupled bending-bending-torsional equations of dynamic motion of rotating, linearly pretwisted blades are derived including large precone, second degree geometric nonlinearities and Coriolis effects. The equations are solved by the Galerkin method and a linear perturbation technique. Accuracy of the present method is verified by comparisons of predicted frequencies and steady state deflections with those from MSC/NASTRAN and from experiments. Parametric results are generated to establish where inclusion of only the second degree geometric nonlinearities is adequate. The nonlinear terms causing torsional divergence in thin blades are identified. The effects of Coriolis terms and several other structurally nonlinear terms are studied, and their relative importance is examined.
A comparison of two reciprocating instruments using bending stress and cyclic fatigue tests
Pantaleo SCELZA
2015-01-01
Full Text Available The aim of this study was to comparatively evaluate the bending resistance at 45º, the static and dynamic cyclic fatigue life, and the fracture type of the WaveOne (Dentsply Maillefer, Ballaigues, Switzerland 25-08 and Reciproc (VDW, Munich, Germany 25-08 instruments. A total of 60 nickel-titanium (NiTi instruments (30 Reciproc and 30 WaveOne from three different lots, each of which was 25 mm in length, were tested. The bending resistance was evaluated through the results of a cantilever-bending test conducted using a universal testing machine. Static and dynamic cyclic fatigue testing was conducted using a custom-made device. For the static and dynamic tests, a cast Ni-Cr-Mo-Ti alloy metal block with an artificial canal measuring 1.77 mm in diameter and 20.00 mm in total length was used. A scanning electron microscope was used to determine the type of fracture. Statistical analyses were performed on the results. The WaveOne instrument was less flexible than the Reciproc (p < 0.05. The Reciproc instrument showed better resistance in the static and dynamic cyclic fatigue tests (p < 0.05. The transverse cross-section and geometry of the instruments were important factors in their resistance to bending and cyclic fracture. Both of the instruments showed ductile-type fracture characteristics. It can be concluded that the Reciproc 25-08 instrument was more resistant to static and dynamic cyclic fatigue than the WaveOne 25-08 instrument, while the WaveOne 25-08 instrument was less flexible. Bending and resistance to cyclic fracture were influenced by the instruments’ geometries and transverse cross-sections. Both of the instruments showed ductile-type fracture characteristics.
The Dependency of Nematic and Twist-bend Mesophase Formation on Bend Angle
Mandle, Richard J.; Archbold, Craig T.; Sarju, Julia P.; Andrews, Jessica L.; Goodby, John W.
2016-11-01
We have prepared and studied a family of cyanobiphenyl dimers with varying linking groups with a view to exploring how molecular structure dictates the stability of the nematic and twist-bend nematic mesophases. Using molecular modelling and 1D 1H NOESY NMR spectroscopy, we determine the angle between the two aromatic core units for each dimer and find a strong dependency of the stability of both the nematic and twist-bend mesophases upon this angle, thereby satisfying earlier theoretical models.
Design of a multi-bend achromat lattice for 3 GeV synchrotron light source
Kim, Eun-San
2016-03-01
We present a lattice design for a low-emittance and high-brilliance 3 GeV synchrotron light source that has been widely investigated in the world. We show the design results for a MBA (Multi-Bend Achromat) lattice with an emittance of 1.3 nm and 282.4 m circumference. Each cell has 5 bending magnets that consist of outer two with bending angle of 4.5° and inner three with bending angle of 7°. The lattice is designed to be flexible and consists of 12 straight sections in which one straight section has a length of 5.9 m. We have studied the dynamic aperture in the lattice with machine errors. It is shown that the designed low-emittance lattice provides sufficient dynamic aperture after COD correction. We present the results of variations of emittance, energy spread and dynamic aperture due to in-vacuum undulators in the straight sections. We performed particle tracking after the beam injection to investigate the efficiency of the injection scheme. We show the designed results of an injection scheme that shows the space allocation in injection section and the particle motions of injected beam. Our designed lattice provides a good optimization in terms of the emittance and brilliance as a light source for 3 GeV energy and circumference of 28 m.
Twist-Bend Coupling and the Torsional Response of Double-Stranded DNA
Nomidis, Stefanos K.; Kriegel, Franziska; Vanderlinden, Willem; Lipfert, Jan; Carlon, Enrico
2017-05-01
Recent magnetic tweezers experiments have reported systematic deviations of the twist response of double-stranded DNA from the predictions of the twistable wormlike chain model. Here we show, by means of analytical results and computer simulations, that these discrepancies can be resolved if a coupling between twist and bend is introduced. We obtain an estimate of 40 ±10 nm for the twist-bend coupling constant. Our simulations are in good agreement with high-resolution, magnetic-tweezers torque data. Although the existence of twist-bend coupling was predicted long ago [J. Marko and E. Siggia, Macromolecules 27, 981 (1994), 10.1021/ma00082a015], its effects on the mechanical properties of DNA have been so far largely unexplored. We expect that this coupling plays an important role in several aspects of DNA statics and dynamics.
Study of double triple bend achromat (DTBA) lattice for a 3GeV light source
Alekou, Androula; Carmignani, Nicola; Liuzzo, Simone Maria; Raimondi, Pantaleo; Pulampong, Thapakron; Walker, Richard
2017-01-01
Starting from the concepts of the Hybrid Multi Bend Achromat (HMBA) lattice developed at ESRF and of the Double-Double Bend Achromat(DDBA) lattice developed at Diamond, we present a new cell tha tincludes all the advantages of the two designs. The resulting Double Triple Bend Achromat(DTBA) cel lallows for a natural horizontal emittance of less than 100pm with a large dynamic aperture and lifetime. It includes two straight sections, for insertion devices, ﬁve and three meters long. The lattice is consistent with the engineering design developed for the ESRF-EBS lattice and the layout and user requirements of Diamond. The characteristics of the cell are presented together with the results of the optimisation process.
The Worm-Like Chain Theory And Bending Of Short DNA
Mazur, Alexey K
2007-01-01
The probability distributions for bending angles in double helical DNA obtained in all-atom molecular dynamics simulations are compared with theoretical predictions. The computed distributions remarkably agree with the worm-like chain theory for double helices of one helical turn and longer, and qualitatively differ from predictions of the semi-elastic chain model. The computed data exhibit only small anomalies in the apparent flexibility of short DNA and cannot account for the recently reported AFM data (Wiggins et al, Nature nanotechnology 1, 137 (2006)). It is possible that the current atomistic DNA models miss some essential mechanisms of DNA bending on intermediate length scales. Analysis of bent DNA structures reveals, however, that the bending motion is structurally heterogeneous and directionally anisotropic on the intermediate length scales where the experimental anomalies were detected. These effects are essential for interpretation of the experimental data and they also can be responsible for the a...
Severity of the Bend and Its Effect on the Subsequent Hydroforming Process for Aluminum Alloy Tube
Gholipour, J.; Worswick, M. J.; Oliveira, D. A.; Khodayari, G.
2004-06-01
The interaction between pre-bending and subsequent hydroforming of AlMg3.5Mn aluminum tubes is examined in this paper. Pre-bending induces large strains and strain gradients in the tube, which reduce the available formability for the subsequent hydroforming process. Corner fill hydroforming operations were performed on straight tubes (R/D=∞) and pre-bent tubes with R/D=2.5, representing a transition from low severity to moderate severity bending conditions. An Eagle EPT-75 instrumented mandrel-rotary draw tube bender was used for the pre-bending stage, which records all process parameters. The experiments were modeled using an explicit dynamic finite element code, LS-DYNA. An in-house Gurson-Tvergaard-Needleman (GTN) constitutive softening model, incorporated within LS-DYNA, has been considered to predict damage and formability. Based on these results, the formability of a tube bent at an R/D=2.0 is predicted as a higher severity bend condition.
Bending induced electrical response variations in ultra-thin flexible chips and device modeling
Heidari, Hadi; Wacker, Nicoleta; Dahiya, Ravinder
2017-09-01
Electronics that conform to 3D surfaces are attracting wider attention from both academia and industry. The research in the field has, thus far, focused primarily on showcasing the efficacy of various materials and fabrication methods for electronic/sensing devices on flexible substrates. As the device response changes are bound to change with stresses induced by bending, the next step will be to develop the capacity to predict the response of flexible systems under various bending conditions. This paper comprehensively reviews the effects of bending on the response of devices on ultra-thin chips in terms of variations in electrical parameters such as mobility, threshold voltage, and device performance (static and dynamic). The discussion also includes variations in the device response due to crystal orientation, applied mechanics, band structure, and fabrication processes. Further, strategies for compensating or minimizing these bending-induced variations have been presented. Following the in-depth analysis, this paper proposes new mathematical relations to simulate and predict the device response under various bending conditions. These mathematical relations have also been used to develop new compact models that have been verified by comparing simulation results with the experimental values reported in the recent literature. These advances will enable next generation computer-aided-design tools to meet the future design needs in flexible electronics.
A comparison of two reciprocating instruments using bending stress and cyclic fatigue tests.
Scelza, Pantaleo; Harry, Davidowicz; Silva, Licinio Esmeraldo da; Barbosa, Igor Bastos; Scelza, Miriam Zaccaro
2015-01-01
The aim of this study was to comparatively evaluate the bending resistance at 45º, the static and dynamic cyclic fatigue life, and the fracture type of the WaveOne (Dentsply Maillefer, Ballaigues, Switzerland) 25-08 and Reciproc (VDW, Munich, Germany) 25-08 instruments. A total of 60 nickel-titanium (NiTi) instruments (30 Reciproc and 30 WaveOne) from three different lots, each of which was 25 mm in length, were tested. The bending resistance was evaluated through the results of a cantilever-bending test conducted using a universal testing machine. Static and dynamic cyclic fatigue testing was conducted using a custom-made device. For the static and dynamic tests, a cast Ni-Cr-Mo-Ti alloy metal block with an artificial canal measuring 1.77 mm in diameter and 20.00 mm in total length was used. A scanning electron microscope was used to determine the type of fracture. Statistical analyses were performed on the results. The WaveOne instrument was less flexible than the Reciproc (p bending and cyclic fracture. Both of the instruments showed ductile-type fracture characteristics. It can be concluded that the Reciproc 25-08 instrument was more resistant to static and dynamic cyclic fatigue than the WaveOne 25-08 instrument, while the WaveOne 25-08 instrument was less flexible. Bending and resistance to cyclic fracture were influenced by the instruments' geometries and transverse cross-sections. Both of the instruments showed ductile-type fracture characteristics.
Oide Effect and Radiation in Bending Magnets
Blanco, Oscar; Bambade, Philip
2014-01-01
Including radiation effects during lattice design optimization is crucial in high energy accelerators. Oide effect and radiation in bending magnets are reviewed aiming to include them in the optical design process to minimize the IP beam size. The Oide double integral is expressed in simpler terms in order to speed up calculations, concluding in how longer quadrupoles with lower gradients may help reducing the Oide effect. Radiation in bending magnets is reviewed for linear lattices, generalizing to the case when the final dispersion is different from zero and making comparisons with theoretical results and particle tracking. An agreement between the theory, the implemented approximation included in MAPCLASS2 and the six-dimensional tracking in PLACET has been found.
Rock bending creep and disturbance effects
付志亮; 郑颖人; 刘元雪
2008-01-01
The bending creep and its disturbance effects of red sandstone rock beam and oil shale rock beam were studied by adopting the self-developed gravitation level style rock creep test machine and bending creep test system,and the constitutive equations were established.It is found that fracture morphology of rock beams under no disturbance load is regular,cracking position of fractures is on part of loading concentration,the crack starts from a neutral plane.However,fracture morphology of rock beams under disturbance load is irregular,cracking position of fractures deviates from a neutral plane.Delayed instability of rock beam occurs for some time under constant disturbance load.When disturbance load is beyond a certain range,suddenly instability of occurs rock beam in a certain time.The results show that there is a guiding significance for creep stability in the geotechnical engineering fields.
Ultrasonic fatigue testing device under biaxial bending
C. Brugger
2016-07-01
Full Text Available A new fatigue testing device has been developed to test specimens under biaxial loading at 20 kHz. A flat smooth specimen with a disc geometry is placed on a torus frame and cyclically loaded at the center of its upper face. Disc bending generates a biaxial proportional stress state at the center of the lower face. Any positive loading ratio can be applied. A cast aluminum alloy (used to produce cylinder heads has been tested under biaxial bending using this device in order to determine its fatigue strength at 109 cycles under high hydrostatic pressure. Self-heating is moderate but macroscopic fatigue cracks after testing are very long. First results in VHCF regime are consistent with literature results obtained under similar stress state but in HCF regime and at 20 Hz.
Thermal Analysis of Bending Under Tension Test
Ceron, Ermanno; Martins, Paulo A.F.; Bay, Niels
2014-01-01
The tribological conditions in deep drawing can be simulated in the Bending Under Tension test to evaluate the performance of new lubricants, tool materials, etc. Deep drawing production with automatic handling runs normally at high rate. This implies considerable heating of the tools, which...... sometimes can cause lubricant film breakdown and galling. In order to replicate the production conditions in bending under tension testing it is thus important to control the tool/workpiece interface temperature. This can be done by pre-heating the tool, but it is essential that the interface temperature...... during testing is similar to the one in the production tool. A universal sheet tribo-tester has been developed, which can run multiple tests automatically from coil. This allows emulating the temperature increase as in production. The present work performs finite element analysis of the evolution...
Parallel monostrand stay cable bending fatigue
Winkler, Jan Pawel
of damage and replacement of bridge stay cables due to wind and traffic-induced fatigue. The understanding of fatigue mechanisms in most steel structures is well established. However, in the case of cables composed of steel strands, many important aspects related with bending fatigue remain to be clarified......This dissertation investigates the bending fatigue response of high-strength steel monostrands and multistrand stay cables to cyclic transverse deformations. Increasing bridge stock numbers and a push for longer cable-supported span lengths have led to an increased number of reported incidents...... associated with variable loading, and different testing procedures. As most of the contemporary stay cables are comprised of a number of individual highstrength steel monostrands, the research study started with an extensive experimental work on the fatigue response of a single monostrand to cyclic flexural...
Approach to hot bending process simulation
Carmignani, B.; Daneri, A.; Toselli, G. [ENEA, Bologna (Italy). Centro Ricerche Energia `E. Clementel` - Area Energia e Innovazione
1995-06-01
An approach to the simulation of the thermal shaping or bending of large steel sheets, by ABAQUS/Standard code, will be presented. A thermal source representation, which can produce a temperature distribution, adequate to the processes which must be considered, has been set up. Some problems connected with the hot sheet shaping or bending process simulation have been approached and calculations have been executed in order to single out how to perform the sheet heating, so that the required sheet shape may be obtained. The results for one reference model for different source situations and one heating line, object of the first phase of the analyses performed, will be presented and discussed. The work will be presented at the 8th International Abaqus Users` Conference at Paris, 31 May - 2 June 1995.
Holey fibers for low bend loss
Nakajima, Kazuhide; Saito, Kotaro; Yamada, Yusuke; Kurokawa, Kenji; Shimizu, Tomoya; Fukai, Chisato; Matsui, Takashi
2013-12-01
Bending-loss insensitive fiber (BIF) has proved an essential medium for constructing the current fiber to the home (FTTH) network. By contrast, the progress that has been made on holey fiber (HF) technologies provides us with novel possibilities including non-telecom applications. In this paper, we review recent progress on hole-assisted type BIF. A simple design consideration is overviewed. We then describe some of the properties of HAF including its mechanical reliability. Finally, we introduce some applications of HAF including to high power transmission. We show that HAF with a low bending loss has the potential for use in various future optical technologies as well as in the optical communication network.
Cyclic stretch-bending: mechanics, stability and formability
Emmens, W.C.; van den Boogaard, Antonius H.
2011-01-01
Cyclic stretch-bending has been studied using the so-called Continuous-Bending-under-Tension (CBT) test. This is a modified tensile test where the specimen is subjected to repetitive bending at the same time. A wide variety of materials have been tested this way. A simple mechanical model is
EXPERIMENTAL STUDY ON CRACK CURVING PROPAGATION IN BENDING BEAMS UNDER IMPULSIVE LOAD
Fang Jing; Yao Xuefeng; Xiong Chunyang
2000-01-01
Dynamic fracture behaviour of crack curving in bent beams has been investigated.In order to understand the propagation mechanism of such cracks under impact,an experimental method is used that combines dynamic photoelasticity with dynamic caustics to study the interaction of the flexural waves and the crack.From the state change of the transient stresses in polymer specimen,the curving fracture in the impulsively loaded beams is analyzed.The dynamic responses of crack tips are evaluated by the stress intensity factors for the cracks running in varying curvature paths under bending stress wave.
Wooden Model of Wide AA Bending Magnet
1978-01-01
The very particular lattice of the AA required 2 types of dipoles (bending magnets: BLG, long and narrow; BST, short and wide). The wide ones had a steel length of 2.71 m, a "good field" width of 0.564 m, and a weight of about 75 t. Here we see a wooden model, built in 1978, to gain dimensional experience with such a monster.
Electron cooling device without bending magnets
Sharapa, A. N.; Shemyakin, A. V.
1993-11-01
The scheme of an axisymmetric electron cooling device without bending magnets is proposed. Solutions for the most important elements, i.e., a gun and a recuperator, are considered. The main characteristics of the recuperator of the Faraday cup type having a reflector and a gun with a ring emitter are explored. In the gun, the beam is formed, the diameter of which is 40 mm and the dimension of a disturbance region is several millimeters.
AA, assembly of wide bending magnet
1980-01-01
The very particular lattice of the AA required 2 types of dipoles (bending magnets; BST, short and wide; BLG, long and narrow). The wide ones had a steel length of 2.71 m, a "good field" width of 0.564 m, and a weight of about 75 t. Here we see the copper coils being hoisted onto the lower half of a BST. See also 7811105, 8006050. For a BLG, see 8001044.
Drag Reduction, from Bending to Pruning
Lopez, Diego; Michelin, Sébastien; de Langre, Emmanuel
2013-01-01
Most plants and benthic organisms have evolved efficient reconfiguration mechanisms to resist flow-induced loads. These mechanisms can be divided into bending, in which plants reduce their sail area through elastic deformation, and pruning, in which the loads are decreased through partial breakage of the structure. In this work, we show by using idealized models that these two mechanisms or, in fact, any combination of the two, are equally efficient to reduce the drag experienced by terrestrial and aquatic vegetation.
Big Bend National Park, TX, USA, Mexico
1991-01-01
The Sierra del Carmen of Mexico, across the Rio Grande River from Big Bend National Park, TX, (28.5N, 104.0W) is centered in this photo. The Rio Grande River bisects the scene; Mexico to the east, USA to the west. The thousand ft. Boquillas limestone cliff on the Mexican side of the river changes colors from white to pink to lavender at sunset. This severely eroded sedimentary landscape was once an ancient seabed later overlaid with volcanic activity.
Multiculturalism, Gender and Bend it Like Beckham
Gamal Abdel-Shehid
2015-06-01
Full Text Available In this article, we explore the efficacy of sport as an instrument for social inclusion through an analysis of the film Bend it Like Beckham. The film argues for the potential of sport to foster a more inclusive society in terms of multiculturalism and gender equity by showing how a hybrid culture can be forged through the microcosm of an English young women’s football club, while simultaneously challenging assumptions about traditional masculinities and femininities. Yet, despite appearances, Bend it Like Beckham does little to challenge the structure of English society. Ultimately, the version of multiculturalism offered by the film is one of assimilation to a utopian English norm. This conception appears progressive in its availability to all Britons regardless of ethnicity, but falls short of conceptions of hybrid identity that do not privilege one hegemonic culture over others. Likewise, although the film presents a feminist veneer, underneath lurks a troubling reassertion of the value of chastity, masculinity, and patriarchy. Bend it Like Beckham thus provides an instructive case study for the potential of sport as a site of social inclusion because it reveals how seductive it is to imagine that structural inequalities can be overcome through involvement in teams.
SYMPLECTIC SOLUTION SYSTEM FOR REISSNER PLATE BENDING
姚伟岸; 隋永枫
2004-01-01
Based on the Hellinger-Reissner variatonal principle for Reissner plate bending and introducing dual variables, Hamiltonian dual equations for Reissner plate bending were presented. Therefore Hamiltonian solution system can also be applied to Reissner plate bending problem, and the transformation from Euclidian space to symplectic space and from Lagrangian system to Hamiltonian system was realized. So in the symplectic space which consists of the original variables and their dual variables, the problem can be solved via effective mathematical physics methods such as the method of separation of variables and eigenfunction-vector expansion. All the eigensolutions and Jordan canonical form eigensolutions for zero eigenvalue of the Hamiltonian operator matrix are solved in detail,and their physical meanings are showed clearly. The adjoint symplectic orthonormal relation of the eigenfunction vectors for zero eigenvalue are formed. It is showed that the all eigensolutions for zero eigenvalue are basic solutions of the Saint-Venant problem and they form a perfect symplectic subspace for zero eigenvalue. And the eigensolutions for nonzero eigenvalue are covered by the Saint-Venant theorem. The symplectic solution method is not the same as the classical semi- inverse method and breaks through the limit of the traditional semi-inverse solution. The symplectic solution method will have vast application.
Da, Lin-Tai
2016-04-19
The dynamics of the RNA polymerase II (Pol II) backtracking process is poorly understood. We built a Markov State Model from extensive molecular dynamics simulations to identify metastable intermediate states and the dynamics of backtracking at atomistic detail. Our results reveal that Pol II backtracking occurs in a stepwise mode where two intermediate states are involved. We find that the continuous bending motion of the Bridge helix (BH) serves as a critical checkpoint, using the highly conserved BH residue T831 as a sensing probe for the 3′-terminal base paring of RNA:DNA hybrid. If the base pair is mismatched, BH bending can promote the RNA 3′-end nucleotide into a frayed state that further leads to the backtracked state. These computational observations are validated by site-directed mutagenesis and transcript cleavage assays, and provide insights into the key factors that regulate the preferences of the backward translocation.
2012-06-15
... COMMISSION PPL Bell Bend, LLC; Bell Bend Nuclear Power Plant Combined License Application; Notice of Intent... its Bell Bend Nuclear Power Plant (BBNPP) site, located west of the existing Susquehanna Steam... by relocating the power block footprint and other plant components. For purposes of developing...
2013-01-22
... COMMISSION PPL Bell Bend, LLC; Combined License Application for Bell Bend Nuclear Power Plant; Exemption 1.0... Approvals for Nuclear Power Plants.'' This reactor is to be identified as Bell Bend Nuclear Power Plant... (RCOL) application for UniStar's Calvert Cliffs Nuclear Power Plant, Unit 3 (CCNPP3). The......
2011-12-29
... COMMISSION PPL Bell Bend, LLC; Combined License Application for Bell Bend Nuclear Power Plant; Exemption 1.0..., Certifications, and Approvals for Nuclear Power Plants.'' This reactor is to be identified as Bell Bend Nuclear Power Plant (BBNPP), in Salem County, Pennsylvania. The BBNPP COL application incorporates by...
Tunable waveguide bends with graphene-based anisotropic metamaterials
Chen, Zhao-xian
2016-01-15
We design tunable waveguide bends filled with graphene-based anisotropic metamaterials to achieve a nearly perfect bending effect. The anisotropic properties of the metamaterials can be described by the effective medium theory. The nearly perfect bending effect is demonstrated by finite element simulations of various structures with different bending curvatures and shapes. This effect is attributed to zero effective permittivity along the direction of propagation and matched effective impedance at the interfaces between the bending part and the dielectric waveguides. We envisage that the design will be applicable in the far-infrared and terahertz frequency ranges owing to the tunable dielectric responses of graphene.
Permanent bending and alignment of ZnO nanowires.
Borschel, Christian; Spindler, Susann; Lerose, Damiana; Bochmann, Arne; Christiansen, Silke H; Nietzsche, Sandor; Oertel, Michael; Ronning, Carsten
2011-05-06
Ion beams can be used to permanently bend and re-align nanowires after growth. We have irradiated ZnO nanowires with energetic ions, achieving bending and alignment in different directions. Not only the bending of single nanowires is studied in detail, but also the simultaneous alignment of large ensembles of ZnO nanowires. Computer simulations reveal how the bending is initiated by ion beam induced damage. Detailed structural characterization identifies dislocations to relax stresses and make the bending and alignment permanent, even surviving annealing procedures.
Permanent bending and alignment of ZnO nanowires
Borschel, Christian; Spindler, Susann; Oertel, Michael; Ronning, Carsten [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Lerose, Damiana [MPI fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle/Saale (Germany); Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Bochmann, Arne [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Christiansen, Silke H. [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); MPI fuer die Physik des Lichts, Guenther-Scharowsky-Str. 1, 91058 Erlangen (Germany); Nietzsche, Sandor [Zentrum fuer Elektronenmikroskopie, Friedrich-Schiller-Universitaet Jena, Ziegelmuehlenweg 1, 07743 Jena (Germany)
2011-07-01
Ion beams can be used to bend or re-align nanowires permanently, after they have been grown. We have irradiated ZnO nanowires with ions of different species and energy, achieving bending and alignment in various directions. We study the bending of single nanowires as well as the simultaneous alignment of large ensembles of ZnO nanowires in detail. Computer simulations show that the bending is initiated by ion beam induced damage. Dislocations are identified to relax stresses and make the bending and alignment permanent and resistant against annealing procedures.
Tunable waveguide bends with graphene-based anisotropic metamaterials
Chen, Zhao-xian; Chen, Ze-guo; Ming, Yang; Wu, Ying; Lu, Yan-qing
2016-02-01
We design tunable waveguide bends filled with graphene-based anisotropic metamaterials to achieve a nearly perfect bending effect. The anisotropic properties of the metamaterials can be described by the effective medium theory. The nearly perfect bending effect is demonstrated by finite element simulations of various structures with different bending curvatures and shapes. This effect is attributed to zero effective permittivity along the direction of propagation and matched effective impedance at the interfaces between the bending part and the dielectric waveguides. We envisage that the design will be applicable in the far-infrared and terahertz frequency ranges owing to the tunable dielectric responses of graphene.
Parameter prediction in laser bending of aluminum alloy sheet
Xuyue WANG; Weixing XU; Hua CHEN; Jinsong WANG
2008-01-01
Based on the basic platform of BP neural net-works, a BP network model is established to predict the bending angle in the laser bending process of an aluminum alloy sheet (1-2 mm in thickness) and to optimize laser bending parameters for bending control. The sample experimental data is used to train the BP network. The nonlinear regularities of sample data are fitted through the trained BP network; the predicted results include laser bending angles and parameters. Experimental results indi-cate that the prediction allowance is controlled less than 5%-8% and can provide a theoretical and experimental basis for industry purpose.
Diameter dependence of thermoelectric power of semiconducting carbon nanotubes
Hung, Nguyen T.; Nugraha, Ahmad R. T.; Hasdeo, Eddwi H.; Dresselhaus, Mildred S.; Saito, Riichiro
2015-10-01
We calculate the thermoelectric power (or thermopower) of many semiconducting single wall carbon nanotubes (s-SWNTs) within a diameter range 0.5 -1.5 nm by using the Boltzmann transport formalism combined with an extended tight-binding model. We find that the thermopower of s-SWNTs increases as the tube diameter decreases. For some s-SWNTs with diameters less than 0.6 nm , the thermopower can reach a value larger than 2000 μ V /K at room temperature, which is about 6 to 10 times larger than that found in commonly used thermoelectric materials. The large thermopower values may be attributed to the one dimensionality of the nanotubes and to the presence of large band gaps of the small-diameter s-SWNTs. We derive an analytical formula to reproduce the numerical calculation of the thermopower and we find that the thermopower of a given s-SWNT is directly related with its band gap. The formula also explains the shape of the thermopower as a function of tube diameter, which looks similar to the shape of the so-called Kataura plot of the band gap dependence on tube diameter.
Recent developments in bend-insensitive and ultra-bend-insensitive fibers
Boivin, David; de Montmorillon, Louis-Anne; Provost, Lionel; Montaigne, Nelly; Gooijer, Frans; Aldea, Eugen; Jensma, Jaap; Sillard, Pierre
2010-02-01
Designed to overcome the limitations in case of extreme bending conditions, Bend- and Ultra-Bend-Insensitive Fibers (BIFs and UBIFs) appear as ideal solutions for use in FTTH networks and in components, pigtails or patch-cords for ever demanding applications such as military or sensing. Recently, however, questions have been raised concerning the Multi-Path-Interference (MPI) levels in these fibers. Indeed, they are potentially subject to interferences between the fundamental mode and the higher-order mode that is also bend resistant. This MPI is generated because of discrete discontinuities such as staples, bends and splices/connections that occur on distance scales that become comparable to the laser coherent length. In this paper, we will demonstrate the high MPI tolerance of all-solid single-trench-assisted BIFs and UBIFs. We will present the first comprehensive study combining theoretical and experimental points of view to quantify the impact of fusion splices on coherent MPI. To be complete, results for mechanical splices will also be reported. Finally, we will show how the single-trench- assisted concept combined with the versatile PCVD process allows to tightly control the distributions of fibers characteristics. Such controls are needed to massively produce BIFs and to meet the more stringent specifications of the UBIFs.
Standard test methods for bend testing of material for ductility
American Society for Testing and Materials. Philadelphia
2009-01-01
1.1 These test methods cover bend testing for ductility of materials. Included in the procedures are four conditions of constraint on the bent portion of the specimen; a guided-bend test using a mandrel or plunger of defined dimensions to force the mid-length of the specimen between two supports separated by a defined space; a semi-guided bend test in which the specimen is bent, while in contact with a mandrel, through a specified angle or to a specified inside radius (r) of curvature, measured while under the bending force; a free-bend test in which the ends of the specimen are brought toward each other, but in which no transverse force is applied to the bend itself and there is no contact of the concave inside surface of the bend with other material; a bend and flatten test, in which a transverse force is applied to the bend such that the legs make contact with each other over the length of the specimen. 1.2 After bending, the convex surface of the bend is examined for evidence of a crack or surface irregu...
Wininger, Fred A; Kapatkin, Amy S; Radin, Alex; Shofer, Frances S; Smith, Gail K
2007-12-01
To compare failure mode and bending moment of a canine pancarpal arthrodesis construct using either a 2.7 mm/3.5 mm hybrid dynamic compression plate (HDCP) or a 3.5 mm dynamic compression plate (DCP). Paired in vitro biomechanical testing of canine pancarpal arthrodesis constructs stabilized with either a 2.7/3.5 HDCP or 3.5 DCP. Paired cadaveric canine antebrachii (n=5). Pancarpal arthrodesis constructs were loaded to failure (point of maximum load) in 4-point bending using a materials-testing machine. Using this point of failure, bending moments were calculated from system variables for each construct and the 2 plating systems compared using a paired t-test. To examine the relationship between metacarpal diameter and screw diameter failure loads, linear regression was used and Pearson' correlation coefficient was calculated. Significance was set at Pbending strength. There was a significant linear correlation r=0.74 (P-slope=.014) and 0.8 (P-slope=.006) between metacarpal diameter and failure loads for the HDCP and 3.5 DCP, respectively. There was a small but significant difference between bending moment at failure between 2.7/3.5 HDCP and 3.5 DCP constructs; however, the difference may not be clinically evident in all patients. The 2.7/3.5 HDCP has physical and mechanical properties making it a more desirable plate for pancarpal arthrodesis.
On the Simulation of Floods in a Narrow Bending Valley: The Malpasset Dam Break Case Study
Chiara Biscarini
2016-11-01
Full Text Available In this paper, we investigate the performance of three-dimensional (3D hydraulic modeling when dealing with river sinuosity and meander bends. In river bends, the flow is dominated by a secondary current, which has a key role on the flow redistribution. The secondary flow induces transverse components of the bed shear stress and increases the velocity in outward direction, thus generating local erosion and riverbed modifications. When in river bends, the 3D processes prevail, and a 3D computational fluid dynamics (CFD model is required to correctly predict the flow structure. An accurate description of the different hydrodynamic processes in mildly and sharply curved bends find a relevant application in meanders migration modeling. The mechanisms that drive the velocity redistribution in meandering channels depend on the river’s roughness, the flow depth (H, the radius curvature (R, the width (B and the bathymetric variations. Here, the hydro-geomorphic characterization of sharp and mild meanders is performed by means of the ratios R/B, B/H, and R/H, and of the sinuosity index. As a case study, we selected the Malpasset dam break on the Reyran River Valley (FR, as it is perfectly suited for investigating performances and issues of a 3D model in simulating the inundation dynamics in a river channel with a varying curvature radius.
A study on springback of bending linear flow split profiles
Mahajan, P.; Taplick, C.; Özel, M.; Groche, P.
2016-11-01
The bending of linear flow split profiles made up of high strength materials involves high bending loads leading to high springback and geometrical defects. In addition, the linear flow split profiles are made stronger due to the high plastic deformation applied by the process itself. The bending method proposed in this paper combines the linear flow splitting process with a movable bending tool. The aim of the research was to investigate the effect of superimposed stresses exerted by the linear flow splitting process on bending load and springback of the profile by using a finite element model. The latter was validated by means of experimental results. The results show that the bending loads and the springback were reduced by increasing the superposition of stress applied by the linear flow splitting process. The reduction in the bending loads leads to a reduction in the cross-sectional distortion. Furthermore, the springback was compensated by controlling the amount of superimposed stress.
Cricket antennae shorten when bending (Acheta domesticus L.
Catherine eLoudon
2014-06-01
Full Text Available Insect antennae are important mechanosensory and chemosensory organs. Insect appendages, such as antennae, are encased in a cuticular exoskeleton and are thought to bend only between segments or subsegments where the cuticle is thinner, more flexible, or bent into a fold. There is a growing appreciation of the dominating influence of folds in the mechanical behavior of a structure, and the bending of cricket antennae was considered in this context. Antennae will bend or deflect in response to forces, and the resulting bending behavior will affect the sensory input of the antennae. In some cricket antennae, such as in those of Acheta domesticus, there are a large number (>100 of subsegments (flagellomeres that vary in their length. We evaluated whether these antennae bend only at the joints between flagellomeres, which has always been assumed but not tested. In addition we questioned whether an antenna undergoes a length change as it bends, which would result from some patterns of joint deformation. Measurements using light microscopy and SEM were conducted on both male and female adult crickets (Acheta domesticus with bending in four different directions: dorsal, ventral, medial and lateral. Bending occurred only at the joints between flagellomeres, and antennae shortened a comparable amount during bending, regardless of sex or bending direction. The cuticular folds separating antennal flagellomeres are not very deep, and therefore as an antenna bends, the convex side (in tension does not have a lot of slack cuticle to unfold and does not lengthen during bending. Simultaneously on the other side of the antenna, on the concave side in compression, there is an increasing overlap in the folded cuticle of the joints during bending. Antennal shortening during bending would prevent stretching of antennal nerves and may promote hemolymph exchange between the antenna and head.
Rahmah, Fitri; Sekartedjo, Sekartedjo; Hatta, Agus Muhamad
2016-11-01
Modelling of load effect on macro-bend losses for a singlemode-multimode-singlemode (SMS) fiber structure with small bend radius is presented. Load effect on macro-bend losses for the SMS fiber structure placed between two high-density polyethylene (HDPE) boards are investigated theoretically and experimentally. A model on macro-bend losses for SMS fiber structure is constructed by using the light transmission formula in a straight SMS fiber structure and taking into account the effective number of guided modes due to the macrobending. In the experimental, a mandrel with a diameter of 0.8 mm is used to induce the bend. When the loads are applied on the system, the mandrel will affect the bend losses for the SMS fiber structure. It is shown numerically and experimentally that the bend-loss of SMS fiber structure strongly depends on the applied loads and the multimode fiber (MMF) lengths.
Sydney Abrão Haje; Davi de Podestá Haje; Gustavo Eduardo Vieira Martins; Mariana Gonçalves Ferrer
2011-01-01
OBJECTIVE:To investigate a concomitant orthotic treatment for coexisting scoliosis and pectus deformities. No detailed study on such concomitancy was found in literature. METHODS: A spine bending brace for use day and night, and dynamic chest compressor orthoses for use four hours a day, along with one hour of exercises, were prescribed. From 638 adolescents, 25 met the inclusion criteria for a retrospective study. Two groups of patients were identified: A (15 compliant patients) and B (10 no...
Swie, Y W; Sakamoto, K; Shimizu, Y
2005-01-01
The present study aims to perform further investigation on muscular activity during forward bending posture by applying a nonlinear dynamic (chaotic) analysis method. The objective is to determine the characteristics of the low back and lower limb muscle electromyography (EMG) signal under chaotic analysis while maintaining a certain posture. Twelve subjects were asked to maintain postures of six stages in bending angles from 0 to 180 degrees, and the EMG signals of erector spinae (ES) at L1 and L5 levels, hamstrings, and gastrocnemius were recorded. Two important concepts to characterize deterministic chaos, Correlation Dimension (D2) and Lyapunov Exponents (lambda, LE), were applied to observe the chaotic characteristic of the EMG signals, and the results were also compared to the FFT based total power value. The EMG signals in all observed muscles during bending posture showed results of positive LE and high D2 at 5.5 to 7.5, which led us to classify EMG as a high dimension chaotic signal. The result obtained showed that the correlation dimension could be used as a reliable method to compare the EMG signal in various postures (or muscle contraction conditions). However, Lyapunov exponents did not show a significant difference of comparison result thus leading to the conclusion that LE could not be a reliable measure for high dimension chaotic system, such as an EMG signal. It was also shown that in both light and deep bending, the EMG signal of the low back muscles was of the same complexity level due to the D2 result. It was evident that somehow the low back muscle remained loaded in all bending stages which was contrary to the hypothesis that the low back muscle was less active during the deep bending, as was the case in most of the previous studies. The reason of such phenomenon was elucidated with use of the theory of muscular functional differentiation, including corticalization and spinalization.
Light bending in $f(T)$ gravity
Ruggiero, Matteo Luca
2016-01-01
In the framework of $f(T)$ gravity, we focus on a weak-field and spherically symmetric solution for the Lagrangian $f(T)=T+\\alpha T^{2}$, where $\\alpha$ is a small constant which parameterizes the departure from General Relativity. In particular, we study the propagation of light and obtain the correction to the general relativistic bending angle. Moreover, we discuss the impact of this correction on some gravitational lensing observables, and evaluate the possibility of constraining the theory parameter $\\alpha$ by means of observations.
Anomalous bending effect in photonic crystal fibers.
Tu, Haohua; Jiang, Zhi; Marks, Daniel L; Boppart, Stephen A
2008-04-14
An unexpected transmission loss up to 50% occurs to intense femtosecond pulses propagating along an endlessly single-mode photonic crystal fiber over a length of 1 m. A specific leaky-fiber mode gains amplification along the fiber at the expense of the fundamental fiber mode through stimulated four-wave mixing and Raman scattering, leading to this transmission loss. Bending near the fiber entrance dissipates the propagating seed of this leaky mode, preventing the leaky mode amplification and therefore enhancing the transmission of these pulses.
Thermoelastic bending of locally heated orthotropic shells
Shevchenko, V. P.; Gol'tsev, A. S.
2007-03-01
The thermoelastic bending of locally heated orthotropic shells is studied using the classical theory of thermoelasticity of thin shallow orthotropic shells and the method of fundamental solutions. Linear distribution of temperature over thickness and the Newton's law of cooling are assumed. Numerical analysis is carried out for orthotropic shells of arbitrary Gaussian curvature made of a strongly anisotropic material. The behavior of thermal forces and moments near the zone of local heating is studied for two areas of thermal effect: along a coordinate axis and along a circle of unit radius. Generalized conclusions are drawn
Extension versus Bending for Continuum Robots
George Grimes
2008-11-01
Full Text Available In this paper, we analyze the capabilities of a novel class of continuous-backbone ("continuum" robots. These robots are inspired by biological "trunks, and tentacles". However, the capabilities of established continuum robot designs, which feature controlled bending but not extension, fall short of those of their biological counterparts. In this paper, we argue that the addition of controlled extension provides dual and complementary functionality, and correspondingly enhanced performance, in continuum robots. We present an interval-based analysis to show how the inclusion of controllable extension significantly enhances the workspace and capabilities of continuum robots.
Wooden Model of Wide AA Bending Magnet
1978-01-01
The very particular lattice of the AA required 2 types of dipoles (bending magnets: BLG, long and narrow; BST, short and wide). A wide one had a steel length of 2.71 m, a "good field" width of 0.564 m, and a weight of about 75 t. A wooden model was build in 1978, to gain dimensional experience. Here, Peter Zettwoch, one of the largest men at CERN at that time, is putting a hand in the mouth of the wooden BST monster.
Clinical bending of nickel titanium wires
Stephen Chain
2015-01-01
Full Text Available Since the evolution and the involvement of Nickel Titanium wires in the field of Orthodontics. The treatment plan has evolved with the use of low force Nickel Titanium wires. Because of their high springback, low stiffness, they are the key initial wires in leveling and alignment but have poor formability. Since poor formability limits its ability to create variable arch forms thus; limits the form of treatment. We have devised a method to bend the Nickel Titanium wires to help in our inventory but also customized the wire according to the treatment.
Bendix, Pól Martin
2015-01-01
Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...... for the lateral organization of membranes as wells as for physical properties like bending, permeability and elasticity...
Effect of pH and Ibuprofen on Phopholipid Bilayer Bending Modulus
Boggara, Mohan; Faraone, Antonio; Krishnamoorti, Ramanan
2010-03-01
Non-steroidal anti-inflammatory drugs (NSAIDs) e.g. Aspirin and Ibuprofen, are known to cause gastrointestinal (GI) toxicity with chronic usage. However, NSAIDs pre-associated with phospholipids has been experimentally shown to reduce the GI toxicity and increase the therapeutic efficacy. In this study, using neutron spin-echo the effect of ibuprofen on the phospholipid membrane bending modulus is studied as a function of pH and temperature. Ibuprofen was found to lower the bending modulus at all pH values. We further present molecular insights into the observed effect on membrane dynamics based on structural studies using molecular dynamics simulations and small angle neutron scattering data as well as changes in zwitterionic headgroup electrostatics due to pH and addition of ibuprofen. This study is expected to help towards effective design of drug delivery nanoparticles based on variety of soft condensed matter such as lipids or polymers.
Design study of a low-emittance lattice with a five-bend achromat
Liu, Hao-Lin; Kim, Eun-San
2016-04-01
The multi-bend achromat (MBA) lattice, which can provide a small horizontal emittance in the subnanometer range, shows promise for future storage-ring-based light-source facilities. We present the linear and the nonlinear properties of an optical design and the results of its optimization. The MBA lattice is designed as a five-bend achromat, and an emittance of 0.270 nm rad is achieved. The energy and the circumference of the designed ring are 3 GeV and 499.3 m, respectively. We investigated an injection system with a single-pulsed sextupole magnet in the storage ring. We describe the space allocation in the injection section and the particle dynamics of the injected beam. The investigation shows that our design exhibits a very low emittance and a sufficient dynamic aperture, and provides a suitable injection scheme for a 3-GeV light source.
Bending strain tolerance of MgB2 superconducting wires
Kováč, P.; Hušek, I.; Melišek, T.; Kulich, M.; Kopera, L.
2016-04-01
This work describes the strain tolerance of MgB2 superconductors subjected to variable bending stresses. Bending of MgB2 wire was done at room temperature in different modes: (i) direct bending of straight annealed samples to variable diameters and by (ii) indirect bending by straightening of bent and annealed samples. I c-bending strain characteristics of samples made by in situ PIT and by the internal magnesium diffusion (IMD) process were measured at 4.2 K. The results show a good agreement between the direct and indirect bending mode, which allows easier estimation of limits important for the winding process of MgB2 superconductors with brittle filaments. A comparison of MgB2 wires made by in situ PIT and IMD processes showed improved strain tolerance for IMD due to better grain connectivity the low annealing temperature, which does not appear to reduce the mechanical strength of sheath material.
Flexible bending of aluminum profiles with polyurethane pad
HE Zhu-bin; LIU Gang; WANG Zhong-ren
2006-01-01
The high flexibility of profile bending with hyperelastic pad enables it to be a promising method for small lot or single part production, especially for space frame and roof-rail parts in automotive and aerospace industries. Bending of two aluminum profiles with different sections was carried out to investigate the effect of main process parameters on the bending process. Results show that the shape of the cross-section and its relative thickness and section modulus in bending are the main factors that determine the bending properties of the profiles. Roller stroke, properties of polyurethane pad and constraints on profiles are key factors that determine the bending radius and section deformation of bent profiles. Failures and quality problems met in experiments were also analyzed.
Reduction Bending of Thin Crystalline Silicon Solar Cells
SHEN Lan-xian; LIU Zu-ming; LIAO Hua; TU Jie-lei; DENG Shu-kang
2009-01-01
Reported are the results of reduction the bending of thin crystalline silicon solar ceils after printing and sintering of back electrode by changing the back electrode paste and adjusting the screen printing parameters without effecting the electrical properties of the cell. Theory and experiments showed that the bending of the cell is changed with its thickness of suhstrate, the thinner cell, the more serious bending. The bending of the cell is decreased with the thickness decrease of the back contact paste. The substrate with the thickness of 190μm printing with sheet aluminum paste shows a relatively lower bend compared with that of the substrate printing with ordinary aluminum paste, and the minimum bend is 0.55 mm which is reduced by52%.
INVESTIGATION INTO THE SPRINGBACK OF PIPE BENDING USING INDUCTION HEATING
1998-01-01
Stresses and deformation states of pipe bending are investigated under loading or unloading with various pipe materials, size, bending radius and deformation temperature. A theorem of springback of large diameter pipe bending is presented. The experiments are carried out with pipe materials of 20, 10CrMo910 and 12Cr1MoV steel. Results of computations are in good agreement with experiments.
BEND3 mediates transcriptional repression and heterochromatin organization.
Khan, Abid; Prasanth, Supriya G
2015-01-01
Transcription repression plays a central role in gene regulation. Transcription repressors utilize diverse strategies to mediate transcriptional repression. We have recently demonstrated that BEND3 (BANP, E5R and Nac1 domain) protein represses rDNA transcription by stabilizing a NoRC component. We discuss the role of BEND3 as a global regulator of gene expression and propose a model whereby BEND3 associates with chromatin remodeling complexes to modulate gene expression and heterochromatin organization.
Multiple-cladding fibers with reduced bend loss
Tomljenovic-Hanic, Snjezana; Bulla, Douglas A. P.; Ankiewicz, Adrian; Love, John D.; Bailey, Ron
2007-04-01
We demonstrate that a highly bend-resistant fiber can be realized. It is shown theoretically that, by introducing both depressed and elevated rings into the cladding, bending loss can be reduced significantly. A fiber based on this design has been fabricated and characterized as a first step toward achieving this goal. The results show that a multiple-cladding fiber is highly bend resistant when compared with the standard telecom single-mode fiber.
49 CFR 192.315 - Wrinkle bends in steel pipe.
2010-10-01
... 49 Transportation 3 2010-10-01 2010-10-01 false Wrinkle bends in steel pipe. 192.315 Section 192... Transmission Lines and Mains § 192.315 Wrinkle bends in steel pipe. (a) A wrinkle bend may not be made on steel pipe to be operated at a pressure that produces a hoop stress of 30 percent, or more, of SMYS. (b) Each...
Viscous control of peeling an elastic sheet by bending and pulling.
Lister, John R; Peng, Gunnar G; Neufeld, Jerome A
2013-10-11
Propagation of a viscous fluid beneath an elastic sheet is controlled by local dynamics at the peeling front, in close analogy with the capillary-driven spreading of drops over a precursor film. Here we identify propagation laws for a generic elastic peeling problem in the distinct limits of peeling by bending and peeling by pulling, and apply our results to the radial spread of a fluid blister over a thin prewetting film. For the case of small deformations relative to the sheet thickness, peeling is driven by bending, leading to radial growth as t(7/22). Experimental results reproduce both the spreading behavior and the bending wave at the front. For large deformations relative to the sheet thickness, stretching of the blister cap and the consequent tension can drive peeling either by bending or by pulling at the front, both leading to radial growth as t(3/8). In this regime, detailed predictions give excellent agreement and explanation of previous experimental measurements of spread in the pulling regime in an elastic Hele-Shaw cell.
Viscous control of peeling an elastic sheet by bending and pulling
Lister, John R; Neufeld, Jerome A
2013-01-01
Propagation of a viscous fluid beneath an elastic sheet is controlled by local dynamics at the peeling front, in close analogy with the capillary-driven spreading of drops over a precursor film. Here we identify propagation laws for a generic elastic peeling problem in the distinct limits of peeling by bending and peeling by pulling, and apply our results to the radial spread of a fluid blister over a thin pre-wetting film. For the case of small deformations relative to the sheet thickness, peeling is driven by bending, leading to radial growth as $t^{7/22}$. Experimental results reproduce both the spreading behaviour and the bending wave at the front. For large deformations relative to the sheet thickness, stretching of the blister cap and the consequent tension can drive peeling either by bending or by pulling at the front, both leading to radial growth as $t^{3/8}$. In this regime, detailed predictions give excellent agreement and explanation of previous experimental measurements of spread in the pulling r...
Disk heating and bending instability in galaxies with counterrotation
Khoperskov, Sergey
2016-01-01
With the help of high-resolution long-slit and integral-field spectroscopy observations, the number of confirmed cases of galaxies with counterrotation is increasing rapidly. The evolution of such counterrotating galaxies remains far from being well understood. In this paper we study the dynamics of counterrotating collisionless stellar disks by means of $N$-body simulations. We show that, in the presence of counterrotation, an otherwise gravitationally stable disk can naturally generate bending waves accompanied by strong disk heating across the disk plane, that is in the vertical direction. Such conclusion is found to hold even for dynamically warm systems with typical values of the initial vertical-to-radial velocity dispersion ratio $\\sigma_{\\rm R}/\\sigma_{\\rm z} \\approx 0.5$, for which the role of pressure anisotropy should be unimportant. We note that, during evolution, the $\\sigma_{\\rm R}/\\sigma_{\\rm z}$ ratio tends to rise up to values close to unity in the case of locally Jeans-stable disks, whereas ...
Hot bending with a fiber coupled solid state laser
Bammer, F.; Schumi, T.; Schuöcker, D.
2010-09-01
For bending of brittle materials it is necessary to heat up the forming zone. This can be done with a fiber coupled solid state laser, whose beam is evenly distributed on the bending line with a beam splitter installed in the lower tool (die) of a bending press. With polarization optics the laser beam is divided there into partial beams that are evenly distributed on the bending line with lenses and prisms. A setup for a bending length of 200mm heated by a fiber-coupled 3kW Nd:YAG-laser shows the feasibility of the concept. Successful operation was shown for the Mg-alloy AZ31, which breaks during forming at room temperature, but can be well formed at temperatures in the range of 200-300°C. Other materials benefiting from this method are Ti-alloys, high-strength-Al-alloys, and high-strength-steels. Typical heating times are in the range of up to 5s and much of the heat input is generated during the bending operation where the laser continues to work. Laser Assisted Bending with a fiber coupled solid state laser is a straightforward way to perform the bending of brittle materials in a process as simple as cold bending.
A preliminary bending fatigue spectrum for steel monostrand cables
Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.;
2011-01-01
This paper presents the results of the experimental study on the bending fatigue resistance of high-strength steel monostrand cables. From the conducted fatigue tests in the high-stress, low-cycle region, a preliminary bending fatigue spectrum is derived for the estimation of monostrand cable...... service life expectancy. The presented preliminary bending fatigue spectrum of high-strength monostrands is currently unavailable in the published literature. The presented results provide relevant information on the bending mechanism and fatigue characteristics of monostrand steel cables in tension...
PERMEABILITY OF SALTSTONE MEASUREMENT BY BEAM BENDING
Harbour, J; Tommy Edwards, T; Vickie Williams, V
2008-01-30
One of the goals of the Saltstone variability study is to identify (and, quantify the impact of) the operational and compositional variables that control or influence the important processing and performance properties of Saltstone mixes. A performance property for Saltstone mixes that is important but not routinely measured is the liquid permeability or saturated hydraulic conductivity of the cured Saltstone mix. The value for the saturated hydraulic conductivity is an input into the Performance Assessment for the SRS Z-Area vaults. Therefore, it is important to have a method available that allows for an accurate and reproducible measurement of permeability quickly and inexpensively. One such method that could potentially meet these requirements for the measurement of saturated hydraulic conductivity is the technique of beam bending, developed by Professor George Scherer at Princeton University. In order to determine the feasibility of this technique for Saltstone mixes, a summer student, David Feliciano, was hired to work at Princeton under the direction of George Scherer. This report details the results of this study which demonstrated the feasibility and applicability of the beam bending method to measurement of permeability of Saltstone samples. This research effort used samples made at Princeton from a Modular Caustic side solvent extraction Unit based simulant (MCU) and premix at a water to premix ratio of 0.60. The saturated hydraulic conductivities for these mixes were measured by the beam bending technique and the values determined were of the order of 1.4 to 3.4 x 10{sup -9} cm/sec. These values of hydraulic conductivity are consistent with independently measured values of this property on similar MCU based mixes by Dixon and Phifer. These values are also consistent with the hydraulic conductivity of a generic Saltstone mix measured by Langton in 1985. The high water to premix ratio used for Saltstone along with the relatively low degree of hydration for
佐々木, 善教; 大津, 雅亮; 松村, 正三; 森下, 和幸; 田中, 大樹; 八木, 秀樹; 関根, 雄一郎; 浅川, 基男
2015-01-01
In forming of glasses frame, bending and inverse bending of rim wires with 4 rolls are usually employed. Only an inverse bending roll, the 4th roll, can change the position to control the curvature of the rim wire. A deriving method of inverse bending roll position is proposed in this study. The proposed method requires not the computational simulations but only some simple steady inverse bending experiments to obtain a relationship between inverse bending roll position and bent curvature whi...
On the gravitational seesaw and light bending
Accioly, Antonio; Shapiro, Ilya L
2016-01-01
Local gravitational theories with more than four derivatives are superrenormalizable, and also may be unitary in the Lee-Wick sense. It makes sense to study low-energy properties of these theories, e.g., identify observables which might be useful for experimental detection of higher derivatives. Using an analogy with neutrino Physics, we explore the possibility of a gravitational seesaw mechanism, in which several dimensional parameters of the same order of magnitude produce a hierarchy in the masses of propagating particles and make a relatively light degree of freedom detectable by frequency dependence in the gravitational light bending. It turns out that such a seesaw mechanism in the six- and more-derivative theories is unable to reduce the lightest mass more than in the simplest four-derivative model. Adding more derivatives can only make heavier masses even larger. This fact may be favorable for protecting the theory from instabilities, but makes experimental detection of higher derivatives more difficu...
Secondary turbulent flow in an infinte bend
Christensen, H. Bo; Gislason, Kjartan; Fredsøe, Jørgen
1999-01-01
The flow in an infinite circular bend is inverstigated in both the laminar and fully turbulent flow case, by use of laminar flow solver, a k-e turbulence model, and a fully Reynolds stress turbulence model. The topic of the analysis is to investigate whether a counter-rotating secondary flow cell...... is formed near the surface at the outer bank. This cell might help to stabilise the bank and hereby be an important factor for the morphology in a meandering river. In the laminar runs stability criterion related to a Dean number was estabilshed. In the simulations with the k-e model and the Reynolds stress...... model, the influence of the curvature ratio and cross section geometry on the vortex pattern is investigated. Furthermore, it is demonstrated that an-isotropy of turbulence plays an important role for the structure of flow pattern and existence of an extra flow cell....
Bend-insensitive fiber based vibration sensor
Xu, Yanping; Lu, Ping; Baset, Farhana; Bhardwaj, Vedula Ravi; Bao, Xiaoyi
2014-05-01
We report two novel fiber-optic vibration sensors based on standard telecom bend-insensitive fiber (BIF). A tapered BIF forming a fiber Mach-Zehnder interferometer could measure continuous and damped vibration from 1 Hz up to 500 kHz. An enclosed microcantilever is fabricated inside the BIF by chemical etching and fusion spliced with a readout singlemode fiber that exhibits a frequency range from 5 Hz to 10 kHz with high signal-to-noise ratio (SNR) up to 68 dB. The unique double cladding structure of the BIF ensures both sensors with advantages of compactness, high resistance to the external disturbance and stronger mechanical strength.
Bending of pipes with inconel cladding
Nachpitz, Leonardo; Menezes, Carlos Eduardo B.; Vieira, Carlos R. Tavares [Primus Processamento de Tubos S.A. (PROTUBO), Macae, RJ (Brazil)
2009-07-01
The high-frequency induction bending process, using API pipes coated with Inconel 625 reconciled to a mechanical transformation for a higher degree of resistance, was developed through a careful specification and control of the manufacturing parameters and inherent heat treatments. The effects of this technology were investigated by a qualification process consisting of a sequence of tests and acceptance criteria typically required by the offshore industry, and through the obtained results was proved the effectiveness of this entire manufacturing process, without causing interference in the properties and the quality of the inconel cladding, adding a gain of resistance to the base material, guaranteed by the requirements of the API 5L Standard. (author)
A Study on Residual Stress of U-Bending Heat Transfer Tube using Rotary Draw Bending Processing
Kwak, Ok Gyu; Jang, Kye Hwan; Kim, Won Seok [BHI Co., Haman (Korea, Republic of); Ku, Tae Wan [Pusan National University, Busan (Korea, Republic of)
2016-05-15
The heat transfer tubes can be considered a kind of heat exchange boundary that is direct heat exchange from inside the steam generator. The heat transfer tubes of the steam generator have various bending radius. The heat transfer tubes have the U-shape and L-shape, depending on installed location and arrangement. The forming of the heat transfer tubes can be applied to process of rotary draw bending, roll bending, ram bending and etc. The rotary draw bending process is mainly used, when the bending radius is small. Recently, Alloy 600 or Alloy 690 tubes have been used as material for the heat transfer tubes of the steam generator. The purpose of this study is to evaluate the residual stress of the heat transfer row-1 tubes for deriving the remaining residual stress after U-Bending processing, as a primary study. In this study, the samples of U-Bending tube were made using Rotary Draw Bending Machine by Alloy690 straight tube. This study was measured Residual Stresses of the Row-1 Heat Transfer Tube in Steam Generator. The measurement methods are used two type of the analytical method (FEM) and experimental method (HDM). It was confirmed that the correlation of the measurement of the FEM and HDM methods. The FEM and HDM both methods showed compressive residual stresses. In numerical terms, the HDM is shown that higher value than the FEM.
Coupled-Mode Flutter of Bending-Bending Type in Highly-Flexible Uniform Airfoils
Pourazarm, Pariya; Modarres-Sadeghi, Yahya
2016-11-01
We study the behavior of a highly flexible uniform airfoil placed in wind both numerically and experimentally. It is shown that for a non-rotating highly-flexible cantilevered airfoil, placed at very small angles of attack (less than 1 degree), the airfoil loses its stability by buckling. For slightly higher angles of attack (more than 1 degree) a coupled-mode flutter in which the first and the second flapwise modes coalesce toward a flutter mode is observed, and thus the observed flutter has a bending-bending nature. The flutter onset and frequency found experimentally matched the numerical predictions. If the same airfoil is forced to rotate about its fixed end, the static deflection decreases and the observed couple-mode flutter becomes of flapwise-torsional type, same as what has already been observed for flutter of rotating wind turbine blades. The support provided by the National Science Foundation, CBET-1437988, is greatly acknowledged.
Bending the Curve: Sensitivity to Bending of Curved Paths and Application in Room-Scale VR.
Langbehn, Eike; Lubos, Paul; Bruder, Gerd; Steinicke, Frank
2017-04-01
Redirected walking (RDW) promises to allow near-natural walking in an infinitely large virtual environment (VE) by subtle manipulations of the virtual camera. Previous experiments analyzed the human sensitivity to RDW manipulations by focusing on the worst-case scenario, in which users walk perfectly straight ahead in the VE, whereas they are redirected on a circular path in the real world. The results showed that a physical radius of at least 22 meters is required for undetectable RDW. However, users do not always walk exactly straight in a VE. So far, it has not been investigated how much a physical path can be bent in situations in which users walk a virtual curved path instead of a straight one. Such curved walking paths can be often observed, for example, when users walk on virtual trails, through bent corridors, or when circling around obstacles. In such situations the question is not, whether or not the physical path can be bent, but how much the bending of the physical path may vary from the bending of the virtual path. In this article, we analyze this question and present redirection by means of bending gains that describe the discrepancy between the bending of curved paths in the real and virtual environment. Furthermore, we report the psychophysical experiments in which we analyzed the human sensitivity to these gains. The results reveal encouragingly wider detection thresholds than for straightforward walking. Based on our findings, we discuss the potential of curved walking and present a first approach to leverage bent paths in a way that can provide undetectable RDW manipulations even in room-scale VR.
YANG He; LI Heng; ZHAN Mei; GU Rui-jie
2006-01-01
The wrinkling has become the main defect in the thin-walled tube NC bending process. In the study, a dynamic explicit FE model for aluminum alloy thin-walled tube NC bending process is developed to predict the wrinkling by using FE code ABAQUS/Explicit. Attention was paid to the influences of mass scaling, loading rate scaling, mesh density and element type on accurate wrinkling prediction. So the wrinkling modes and mechanism are revealed based on the reliable FE model. Then a two step strategy is proposed to capture the critical bifurcation point for the optimal design process. The results show: 1) The boundary conditions determine the tube materials response greatly so that the frequency analysis is meaningless to the simulation. It is the contact conditions that make the effect of the mass scaling and loading rate less significant.2) There are two wrinkling modes in the tube bending process. One refers to that local ripples occur initially in the straight regions contacted with wiper die and mandrel; the other refers to that local wrinkles occur in the curved regions due to the relative slipping between tube and clamp die. 3) Both the difference of the in-plane compressive stresses and the relative slipping distance are chosen to be the quantitative indexes to represent the critical point and wrinkling tendency. The experiment of aluminum alloy (5052 O) tube bending was carried out to verify whether the above wrinkle modes exist and the indexes proposed are reasonable to catch the critical bifurcation point. The results may help better understanding of the wrinkling mechanism and the process optimization of the tube bending.
Representation of horizontal strain due to tidal bending by observation and modeling
Rack, Wolfgang; King, Matt; Marsh, Oliver; Wild, Christian; Floricioiu, Dana
2017-04-01
An important control of ice sheet mass balance is the ice dynamics in the grounding zones around Antarctica. On many outflow glaciers a large temporal variability in ice flow has been observed, which is at least partly related to tides. Here we investigate the tide induced short term ice deformation in an ice shelf grounding zone and the related bending stresses and strain. We make use of the arguably most precise measurement method, differential SAR interferometry, in combination with ground based measurements and model assumptions for tidal bending. Ground validation and satellite data have been acquired within a dedicated field campaign. The Southern McMurdo Ice Shelf in the Western Ross Ice Shelf region was chosen as the experiment site. This area is optimal for the data interpretation because of a simple grounding line configuration, small ice flux, and favourable satellite imaging geometry. It is also a safe area which allowed the installation of tiltmeters and GPS stations, and glaciological measurements such as ice thickness and snow accumulation. From November 2014 to January 2015 the tidal movement was recorded over a period of 2.5 months. TerrSAR-X radar images have been acquired over the same period as a basis to derive ice shelf flexure maps. Despite the viscoelastic effects in ice shelf bending a simple elastic bending model for a beam of finite ice thickness can largely explain the GPS-observed surface strain. Using the same model and taking into account the viewing geometry of the satellite radar, it is now possible to separate horizontal and vertical displacement components in the satellite data. As a result we can obtain more realistic ice shelf flexure profiles from the interferometric SAR measurement. The newly derived flexure profiles are therefore more suitable to recover viscoelastic effects of tidal bending in grounding zones of ice shelves and outlet glaciers. These effects would have otherwise remained unnoticed.
36 CFR 7.41 - Big Bend National Park.
2010-07-01
... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Big Bend National Park. 7.41 Section 7.41 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.41 Big Bend National Park. (a) Fishing; closed...
Rule bending by morally disengaged detectives : an ethnographic study
Loyens, Kim
2014-01-01
Rule bending is a well-known practice in policing worldwide, often linked to 'noble cause corruption'. This ethnographic study shows how police detectives sometimes consider to creatively bend rules when rule abidance would lead to other values being jeopardized. This paper illustrates that the theo
On the Bending Problem for Large Scale Mapping
Esteban, I.; Booij, O.; Dijk, J.; Groen, F.
2010-01-01
During Simultaneous Localization And Mapping, geometrical constraints are established between map features. These constraints, introduced through measurements and motion prediction, produce a bending effect in the event of closing a large loop. In this paper we present a discussion of the bending pr
On the bending problem for large scale mapping
I. Esteban; O. Booij; J. Dijk; F. Groen
2009-01-01
During Simultaneous Localization And Mapping, geometrical constraints are established between map features. These constraints, introduced through measurements and motion prediction, produce a bending effect in the event of closing a large loop. In this paper we present a discussion of the bending pr
Bending Resistance of Steel Plate-Reinforced Concrete Beam
TIAN Zhimin; CHEN Jie
2006-01-01
The formulas for calculating bending-resistant capacity of a steel plate-reinforced concrete composite beam are derived.To validate the formulas,experiments of the composite beam under three-point bending are carried out.Calculated results based on the formulas are in good agreement with experimental results.
On the bending problem for large scale mapping
Esteban, I.; Booij, O.; Dijk, J.; Groen, F.
2009-01-01
During Simultaneous Localization And Mapping, geometrical constraints are established between map features. These constraints, introduced through measurements and motion prediction, produce a bending effect in the event of closing a large loop. In this paper we present a discussion of the bending
APPLICABILITY OF THE BEND DEVELOPMENT THEORY IN NATURAL ALLUVIAL RIVERS
M.M.RAHMAN; M.A.HAQUE; M.M.HOQUE
2002-01-01
The theoretical conditions for the bend development or attenuation have been reviewed and tested for a study reach of the Meghna river.The field observations in the natural alluvial meander do not support the theories developed for bend development.The limitations of the theory to apply in the natural meandering river are discussed.
Flexible DNA bending in HU-DNA cocrystal structures.
Swinger, Kerren K; Lemberg, Kathryn M; Zhang, Ying; Rice, Phoebe A
2003-07-15
HU and IHF are members of a family of prokaryotic proteins that interact with the DNA minor groove in a sequence-specific (IHF) or non-specific (HU) manner to induce and/or stabilize DNA bending. HU plays architectural roles in replication initiation, transcription regulation and site-specific recombination, and is associated with bacterial nucleoids. Cocrystal structures of Anabaena HU bound to DNA (1P71, 1P78, 1P51) reveal that while underlying proline intercalation and asymmetric charge neutralization mechanisms of DNA bending are similar for IHF and HU, HU stabilizes different DNA bend angles ( approximately 105-140 degrees ). The two bend angles within a single HU complex are not coplanar, and the resulting dihedral angle is consistent with negative supercoiling. Comparison of HU-DNA and IHF-DNA structures suggests that sharper bending is correlated with longer DNA binding sites and smaller dihedral angles. An HU-induced bend may be better modeled as a hinge, not a rigid bend. The ability to induce or stabilize varying bend angles is consistent with HU's role as an architectural cofactor in many different systems that may require differing geometries.
Atmospheric Refractive Electromagnetic Wave Bending and Propagation Delay
Mangum, Jeffrey G
2014-01-01
In this tutorial we summarize the physics and mathematics behind refractive electromagnetic wave bending and delay. Refractive bending and delay through the Earth's atmosphere at both radio/millimetric and optical/IR wavelengths are discussed, but with most emphasis on the former, and with Atacama Large Millimeter Array (ALMA) applications in mind. As modern astronomical measurements often require sub-arcsecond position accuracy, care is required when selecting refractive bending and delay algorithms. For the spherically-uniform model atmospheres generally used for all refractive bending and delay algorithms, positional accuracies $\\lesssim 1^{\\prime\\prime}$ are achievable when observing at zenith angles $\\lesssim 75^\\circ$. A number of computationally economical approximate methods for atmospheric refractive bending and delay calculation are presented, appropriate for astronomical observations under these conditions. For observations under more realistic atmospheric conditions, for zenith angles $\\gtrsim 75^...
Sorting of bending magnets for the SSRF booster
HOU Jie; LIU Gui-Min; LI Hao-Hu; ZHANG Man-Zhou
2008-01-01
The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.
Sorting of bending magnets for the SSRF booster
Hou, Jie; Liu, Gui-Min; Li, Hao-Hu; Zhang, Man-Zhou
2008-04-01
The Shanghai Synchrotron Radiation Facility (SSRF)booster ring, a full energy injector for the storage ring, is deigned to accelerate the electron beam energy from 150 MeV to 3.5 GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping. Closed orbit distortion (COD) caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting. Considering the affections of random errors in measurement, both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5 is given as the final installation sequence of the booster bending magnets in this paper. Supported by SSRF Project
Role of xyloglucan in gravitropic bending of azuki bean epicotyl.
Ikushima, Toshimitsu; Soga, Kouichi; Hoson, Takayuki; Shimmen, Teruo
2008-04-01
The mechanism of the gravitropic bending was studied in azuki bean epicotyls. The cell wall extensibility of the lower side became higher than that of the upper side in the epicotyl bending upward. The contents of matrix polysaccharides of the cell wall (pectin and xyloglucan in hemicellulose-II) in the lower side became smaller than those in the upper side. The molecular mass of xyloglucans in the lower side decreased. After an epicotyl was fixed to a metal rod to prevent the bending, gravistimulation was applied. Fundamentally the same results were obtained with respect to rheological and chemical characteristics of the cell wall as those of epicotyls showing gravitropic bending. The present results suggested that the initial gravitropic bending was caused by the increase in extensibility of the lower side and the decrease in extensibility of the upper side via the change of the cell wall matrix, especially xyloglucans.
Simulation and prediction in laser bending of silicon sheet
WANG Xu-yue; XU Wei-xing; XU Wen-ji; HU Ya-feng; LIANG Yan-de; WANG Lian-ji
2011-01-01
The laser bending of single-crystal silicon sheet (0.2 mm in thickness) was investigated with JK701 Nd:YAG laser. The models were developed to describe the beam characteristics of pulsed laser. In order to simulate the process of laser bending, the FEM softvare ANSYS was used to predict the heat temperature and stress-strain fields. The periodic transformation of temperature field and stress-strain distribution was analyzed during pulsed laser scanning silicon sheet. The results indicate that the mechanism of pulsed laser bending silicon is a hybrid mechanism in silicon bending, rather than a simple mechanism of TGM or BM. This work also gets silicon sheet bent after scanning 6 times with pulsed laser, and its bending angle is up to 6.5°. The simulation and prediction results reach well agreement with the verifying experiments.
Analysis and Simulation of Adiabatic Bend Transitions in Optical Fibers
YAO Lei; LOU Shu-Qin; JIAN Shui-Sheng
2009-01-01
A low-loss criterion for bend transitions in optical fibers is proposed. An optical fiber can be tightly bent with low loss to be adiabatic for the fundamental mode, provided that an approximate upper bound on the rate of change of bend curvature for a given bend curvature is satisfied. Two typical adiabatic bend transition paths, the optimum profile and linear profile, are analyzed and studied numerically. A realizable adiabatic transition with an Archimedean spiral profile is introduced for low bend loss in tightly bent optical fibers. Design of the transitions is based on modeling of the propagation and coupling characteristics of the core and cladding modes,which clearly illustrate the physical processes involved.
Bend-Induced Distortion in Large Mode Area Holey Fibre
TAN Xiao-Ling; GENG You-Fu; ZHANG Tie-Li; WANG Wei-Neng; WANG Peng; YAO Jian-Quan
2008-01-01
A simplified scheme of bend-induced mode distortion is introduced into bent holey fibres,the distorted mode distribution and mode effective area reduction are investigated using the finite difference method.Numerical results show that the modes of bent holey fibres with small bend radius shift away from the core and are deformed greatly,and the mode areas drop significantly as the bend radius decreases,which severely affects the fibre laser performance.The propagation characteristics of bent holey fibres at given wavelength are determined by fill factor and normalized bend radius.Finally,the transition normalized bend radius that represents the location of the mode area beginning to fall off is obtained.
String theory--the physics of string-bending and other electric guitar techniques.
Grimes, David Robert
2014-01-01
Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed.
String Theory - The Physics of String-Bending and Other Electric Guitar Techniques
Grimes, David Robert
2014-01-01
Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed. PMID:25054880
String theory--the physics of string-bending and other electric guitar techniques.
David Robert Grimes
Full Text Available Electric guitar playing is ubiquitous in practically all modern music genres. In the hands of an experienced player, electric guitars can sound as expressive and distinct as a human voice. Unlike other more quantised instruments where pitch is a discrete function, guitarists can incorporate micro-tonality and, as a result, vibrato and sting-bending are idiosyncratic hallmarks of a player. Similarly, a wide variety of techniques unique to the electric guitar have emerged. While the mechano-acoustics of stringed instruments and vibrating strings are well studied, there has been comparatively little work dedicated to the underlying physics of unique electric guitar techniques and strings, nor the mechanical factors influencing vibrato, string-bending, fretting force and whammy-bar dynamics. In this work, models for these processes are derived and the implications for guitar and string design discussed. The string-bending model is experimentally validated using a variety of strings and vibrato dynamics are simulated. The implications of these findings on the configuration and design of guitars is also discussed.
Narayanaswami, R.
1973-01-01
A new higher order triangular plate-bending finite element is presented which possesses high accuracy for practical mesh subdivisions and which uses only translations and rotations as grid point degrees of freedom. The element has 18 degrees of freedom, the transverse displacement and two rotations at the vertices and mid-side grid points of the triangle. The transverse displacement within the element is approximated by a quintic polynomial; the bending strains thus vary cubically within the element. Transverse shear flexibility is taken into account in the stiffness formulation. Two examples of static and dynamic analysis are included to show the behavior of the element.
A. M. Zenkour
2009-01-01
Full Text Available The quasistatic bending response is presented for a simply supported functionally graded rectangular plate subjected to a through-the-thickness temperature field under the effect of various theories of generalized thermoelasticity, namely, classical dynamical coupled theory, Lord and Shulman's theory with one relaxation time, and Green and Lindsay's theory with two relaxation times. The generalized shear deformation theory obtained by the first author is used. Material properties of the plate are assumed to be graded in the thickness direction according to a simple exponential law distribution in terms of the volume fractions of the constituents. The numerical illustrations concern quasistatic bending response of functionally graded square plates with two constituent materials are studied using the different theories of generalized thermoelasticity
The gearing function of running shoe longitudinal bending stiffness.
Willwacher, Steffen; König, Manuel; Braunstein, Björn; Goldmann, Jan-Peter; Brüggemann, Gert-Peter
2014-07-01
The purpose of the present study was to investigate whether altered longitudinal bending stiffness (LBS) levels of the midsole of a running shoe lead to a systematic change in lower extremity joint lever arms of the ground reaction force (GRF). Joint moments and GRF lever arms in the sagittal plane were determined from 19 male subjects running at 3.5 m/s using inverse dynamics procedures. LBS was manipulated using carbon fiber insoles of 1.9 mm and 3.2 mm thickness. Increasing LBS led to a significant shift of joint lever arms to a more anterior position. Effects were more pronounced at distal joints. Ankle joint moments were not significantly increased in the presence of higher GRF lever arms when averaged over all subjects. Still, two individual strategies (1: increase ankle joint moments while keeping push-off times almost constant, 2: decrease ankle joint moments and increase push-off times) could be identified in response to increased ankle joint lever arms that might reflect individual differences between subjects with respect to strength capacities or anthropometric characteristics. The results of the present study indicate that LBS systematically influences GRF lever arms of lower extremity joints during the push-off phase in running. Further, individual responses to altered LBS levels could be identified that could aid in finding optimum LBS values for a given individual. Copyright © 2014 Elsevier B.V. All rights reserved.
ZERODUR: bending strength data for etched surfaces
Hartmann, Peter; Leys, Antoine; Carré, Antoine; Kerz, Franca; Westerhoff, Thomas
2014-07-01
In a continuous effort since 2007 a considerable amount of new data and information has been gathered on the bending strength of the extremely low thermal expansion glass ceramic ZERODUR®. By fitting a three parameter Weibull distribution to the data it could be shown that for homogenously ground surfaces minimum breakage stresses exist lying much higher than the previously applied design limits. In order to achieve even higher allowable stress values diamond grain ground surfaces have been acid etched, a procedure widely accepted as strength increasing measure. If surfaces are etched taking off layers with thickness which are comparable to the maximum micro crack depth of the preceding grinding process they also show statistical distributions compatible with a three parameter Weibull distribution. SCHOTT has performed additional measurement series with etch solutions with variable composition testing the applicability of this distribution and the possibility to achieve further increase of the minimum breakage stress. For long term loading applications strength change with time and environmental media are important. The parameter needed for prediction calculations which is combining these influences is the stress corrosion constant. Results from the past differ significantly from each other. On the basis of new investigations better information will be provided for choosing the best value for the given application conditions.
Bending strength of delaminated aerospace composites.
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.
2014 land cover land use horseshoe bend
Hanson, Jenny L.; Hoy, Erin E.; Robinson, Larry R.
2016-01-01
This collection of conservation areas consists of the floodplain of the combined streams of the Iowa River and the Cedar River. The study area begins just southeast of Wapello, IA, and continues southeast until the Horseshoe Bend Division, Port Louisa NWR. The area is currently managed to maintain meadow or grassland habitat which requires intensive management due to vegetative succession. In addition, this floodplain area contains a high proportion of managed lands and private lands in the Wetland Reserve Program and is a high priority area for cooperative conservation actions. This project provides a late-summer baseline vegetation inventory to assess future management actions in an adaptive process. Changes in levees, in addition to increased water flows and flood events due to climate change and land use practices, make restoration of floodplain processes more complex. Predictive models could help determine more efficient and effective restoration and management techniques. Successful GIS tools developed for this project would be applicable to other floodplain refuges and conservation areas.
Equilibria and Free Vibration of a Two-Pulley Belt-Driven System with Belt Bending Stiffness
Jieyu Ding
2014-01-01
Full Text Available Nonlinear equilibrium curvatures and free vibration characteristics of a two-pulley belt-driven system with belt bending stiffness and a one-way clutch are investigated. With nonlinear dynamical tension, the transverse vibrations of the translating belt spans and the rotation motions of the pulleys and the accessory shaft are coupled. Therefore, nonlinear piecewise discrete-continuous governing equations are established. Considering the bending stiffness of the translating belt spans, the belt spans are modeled as axially moving beams. The pattern of equilibria is a nontrivial solution. Furthermore, the nontrivial equilibriums of the dynamical system are numerically determined by using two different approaches. The governing equations of the vibration near the equilibrium solutions are derived by introducing a coordinate transform. The natural frequencies of the dynamical systems are studied by using the Galerkin method with various truncations and the differential and integral quadrature methods. Moreover, the convergence of the Galerkin truncation is investigated. Numerical results reveal that the study needs 16 terms after truncation in order to determine the free vibration characteristics of the pulley-belt system with the belt bending stiffness. Furthermore, the first five natural frequencies are very sensitive to the bending stiffness of the translating belt.
PROGRESS IN STUDIES ON ICE ACCUMULATION IN RIVER BENDS
WANG Jun; CHEN Pang-pang; SUI Jue-yi
2011-01-01
River ice is an important hydraulic element in temperate and polar environments and would affect hydrodynamic conditions of rivers through changes both in the boundary conditions and the thermal regime.The river bend has been reported as the common location for the initiation of ice jams because the water flow along a river bend is markedly affected by the channel curvature.In this article,the experimental studies about the ice accumulation in a river bend are reviewed.Based on experiments conducted so far,the criteria for the formation of ice jams in the river bend,the mechanisms of the ice accumulation in the river bend and the thickness profile of the ice accumulation in the river bend are discussed.The k- ε two-equation turbulence model is used to simulate the ice accumulation under an ice cover along a river bend.A formula is proposed for describing the deformation of the ice jam bottom.Our results indicate that all simulated thickness of the ice accumulation agrees reasonably well with the measured thickness of the ice accumulation in the laboratory.
Fixed bending current for Elekta SL25 linear accelerators.
Kok, J G
2001-01-01
In a medical linear accelerator a bending magnet is used to bend the electron beam produced by the accelerator tube, in the treatment direction. For each electron energy the strength of the magnetic field has to be set to a specific level. Changing the magnetic field strength is done by changing the electric current through the bending magnet. When electron energy and magnetic field strength are not matched, performance of the linac can be affected. As electron energy, magneticfield strength and electrical current through the bending magnet are related to each other, it is reasonable to assume that for each electron energy the correct bending current can be predetermined. This calculated bending current reduces the number of variable parameters used to set up a treatment beam. Predetermining a variable simplifies the tuning procedures. It also prevents a deviation of the electron beam energy being compensated by variation of the bending current. Preventing false machine settings can contribute to increase linac performance and reduce down time and cost of ownership.
Guo, Y.; Keller, J.; LaCava, W.
2012-09-01
This computational work investigates planetary gear load sharing of three-mount suspension wind turbine gearboxes. A three dimensional multibody dynamic model is established, including gravity, bending moments, fluctuating mesh stiffness, nonlinear tooth contact, and bearing clearance. A flexible main shaft, planetary carrier, housing, and gear shafts are modeled using reduced degrees-of-freedom through modal compensation. This drivetrain model is validated against the experimental data of Gearbox Reliability Collaborative for gearbox internal loads. Planet load sharing is a combined effect of gravity, bending moment, bearing clearance, and input torque. Influences of each of these parameters and their combined effects on the resulting planet load sharing are investigated. Bending moments and gravity induce fundamental excitations in the rotating carrier frame, which can increase gearbox internal loads and disturb load sharing. Clearance in carrier bearings reduces the bearing load carrying capacity and thus the bending moment from the rotor can be transmitted into gear meshes. With bearing clearance, the bending moment can cause tooth micropitting and can induce planet bearing fatigue, leading to reduced gearbox life. Planet bearings are susceptible to skidding at low input torque.
Mathieson, Haley Aaron
This thesis investigates experimentally and analytically the structural performance of sandwich panels composed of glass fibre reinforced polymer (GFRP) skins and a soft polyurethane foam core, with or without thin GFRP ribs connecting skins. The study includes three main components: (a) out-of-plane bending fatigue, (b) axial compression loading, and (c) in-plane bending of sandwich beams. Fatigue studies included 28 specimens and looked into establishing service life (S-N) curves of sandwich panels without ribs, governed by soft core shear failure and also ribbed panels governed by failure at the rib-skin junction. Additionally, the study compared fatigue life curves of sandwich panels loaded under fully reversed bending conditions (R=-1) with panels cyclically loaded in one direction only (R=0) and established the stiffness degradation characteristics throughout their fatigue life. Mathematical models expressing fatigue life and stiffness degradation curves were calibrated and expanded forms for various loading ratios were developed. Approximate fatigue thresholds of 37% and 23% were determined for non-ribbed panels loaded at R=0 and -1, respectively. Digital imaging techniques showed significant shear contribution significantly (90%) to deflections if no ribs used. Axial loading work included 51 specimens and examined the behavior of panels of various lengths (slenderness ratios), skin thicknesses, and also panels of similar length with various rib configurations. Observed failure modes governing were global buckling, skin wrinkling or skin crushing. In-plane bending involved testing 18 sandwich beams of various shear span-to-depth ratios and skin thicknesses, which failed by skin wrinkling at the compression side. The analytical modeling components of axially loaded panels include; a simple design-oriented analytical failure model and a robust non-linear model capable of predicting the full load-displacement response of axially loaded slender sandwich panels
Four point bending setup for characterization of semiconductor piezoresistance
Richter, Jacob; Arnoldus, Morten Berg; Hansen, Ole
2008-01-01
We present a four point bending setup suitable for high precision characterization of piezoresistance in semiconductors. The compact setup has a total size of 635 cm3. Thermal stability is ensured by an aluminum housing wherein the actual four point bending fixture is located. The four point...... bending fixture is manufactured in polyetheretherketon and a dedicated silicon chip with embedded piezoresistors fits in the fixture. The fixture is actuated by a microstepper actuator and a high sensitivity force sensor measures the applied force on the fixture and chip. The setup includes heaters...
Stored Energy of Plastic Deformation in Tube Bending Processes
Śloderbach, Z.; Pająk, J.
2013-03-01
The paper presents an aproximate analytic method for determination of the stored energy of plastic deformation during cold bending of metal tubes at bending machines. Calculations were performed for outer points of the tube layers subjected to tension and compression (the points of maximum strains). The percentage of stored energy related to the plastic strain work was determined and the results were presented in graphs. The influence and importance of the stored energy of plastic deformation on the service life of pipeline bends are discussed.
Hamiltonian system for orthotropic plate bending based on analogy theory
无
2001-01-01
Based on analogy between plane elasticity and plate bending as well as variational principles of mixed energy, Hamiltonian system is further led to orthotropic plate bending problems in this paper. Thus many effective methods of mathematical physics such as separation of variables and eigenfunction expansion can be employed in orthotropic plate bending problems as they are used in plane elasticity. Analytical solutions of rectangular plate are presented directly, which expands the range of analytical solutions. There is an essential distinction between this method and traditional semi-inverse method. Numerical results of orthotropic plate with two lateral sides fixed are included to demonstrate the effectiveness and accuracy of this method.
Bends in nanotubes allow electric spin control and coupling
Flensberg, Karsten; Marcus, Charles Masamed
2010-01-01
We investigate combined effects of spin-orbit coupling and magnetic field in carbon nanotubes containing one or more bends along their length. We show how bends can be used to provide electrical control of confined spins, while spins confined in straight segments remain insensitive to electric...... fields. Device geometries that allow general rotation of single spins are presented and analyzed. In addition, capacitive coupling along bends provides coherent spin-spin interaction, including between otherwise disconnected nanotubes, completing a universal set of one- and two-qubit gates....
Buffers affect the bending rigidity of model lipid membranes.
Bouvrais, Hélène; Duelund, Lars; Ipsen, John H
2014-01-14
In biophysical and biochemical studies of lipid bilayers the influence of the used buffer is often ignored or assumed to be negligible on membrane structure, elasticity, or physical properties. However, we here present experimental evidence, through bending rigidity measurements performed on giant vesicles, of a more complex behavior, where the buffering molecules may considerably affect the bending rigidity of phosphatidylcholine bilayers. Furthermore, a synergistic effect on the bending modulus is observed in the presence of both salt and buffer molecules, which serves as a warning to experimentalists in the data interpretation of their studies, since typical lipid bilayer studies contain buffer and ion molecules.
Influence of plywood grain direction on sandwich panel bending properties
Jaroslav Kljak; Mladen Brezović; Alan Antonović
2009-01-01
This paper investigates the influence of plywood grain direction on bending properties of a sandwich panel, as well as on stress distribution in each layer. Experimental sandwich panels (tnom= 29 mm) were made of two three-ply plywood panels and a rigid PVC core between them. Grain directions of plywood panels were between 0° and 90°, continuously raised by 15°. Seven models of sandwich panels were made. Bending properties of a sandwich panel was determined by three point bending method and s...
Damage Analysis of Rectangular Section Composite Beam under Pure Bending
Liu, Yiping; Xiao, Fan; Liu, Zejia; Tang, Liqun; Fang, Daining
2013-02-01
Laminated composite beams are commonly used in engineering applications involving macro to nano structures. Based on the assumption that plain sections remain plain after deformation, this paper analyzes stress distributions in cross-ply laminated composite beams with rectangular cross-sections, and formulates the basic damage equations through Kachanov's damage definition and Janson's failure criterion. The location of the neutral axis and the ultimate bending moment are obtained for pure bending cases. The effect of the elastic modulus of the two layers on the damage evolution is analyzed; a reasonable damage composite beam model is proposed to predict the ultimate bending moment.
"Bending the cost curve" in gastroenterology.
Slattery, E; Harewood, G C; Murray, F; Patchett, S
2013-12-01
Increasing attention is being focused on reigning in escalating costs of healthcare, i.e. trying to 'bend the cost curve'. In gastroenterology (GI), inpatient hospital care represents a major component of overall costs. This study aimed to characterize the trend in cost of care for GI-related hospitalizations in recent years and to identify the most costly diagnostic groups. All hospital inpatients admitted between January 2008 and December 2009 with a primary diagnosis of one of the six most common GI-related Diagnosis Related Groups (DRGs) in this hospital system were identified; all DRGs contained at least 40 patients during the study period. Patient Level Costing (PLC) was used to express the total cost of hospital care for each patient; PLC comprised a weighted daily bed cost plus cost of all medical services provided (e.g., radiology, pathology tests) calculated according to an activity-based costing approach; cost of medications were excluded. All costs were discounted to 2009 values. Mean length of stay (LOS) was also calculated for each DRG. Over 2 years, 470 patients were admitted with one of the six most common GI DRGs. Mean cost of care increased from 2008 to 2009 for all six DRGs with the steepest increases seen in 'GI hemorrhage (non-complex)' (31 % increase) and 'Cirrhosis/Alcoholic hepatitis (non-complex)' (45 % increase). No differences in readmission rates were observed over time. There was a strong correlation between year-to-year change in costs and change in mean LOS, r = 0.93. The cost of GI-related inpatient care appears to be increasing in recent years with the steepest increases observed in non-complex GI hemorrhage and non-complex Cirrhosis/Alcoholic hepatitis. Efforts to control the increasing costs should focus on these diagnostic categories.
Advantages of customer/supplier involvement in the upgrade of River Bend`s IST program
Womack, R.L.; Addison, J.A.
1996-12-01
At River Bend Station, IST testing had problems. Operations could not perform the test with the required repeatability; engineering could not reliably trend test data to detect degradation; licensing was heavily burdened with regulatory concerns; and maintenance could not do preventative maintenance because of poor prediction of system health status. Using Energy`s Total Quality principles, it was determined that the causes were: lack of ownership, inadequate test equipment usage, lack of adequate procedures, and lack of program maintenance. After identifying the customers and suppliers of the IST program data, Energy management put together an upgrade team to address these concerns. These customers and suppliers made up the IST upgrade team. The team`s mission was to supply River Bend with a reliable, functional, industry correct and user friendly IST program. The IST program in place went through a verification process that identified and corrected over 400 individual program discrepancies. Over 200 components were identified for improved testing methods. An IST basis document was developed. The operations department was trained on ASME Section XI testing. All IST tests have been simplified and shortened, due to heavy involvement by operations in the procedure development process. This significantly reduced testing time, resulting in lower cost, less dose and greater system availability.
Monitoring Composites under Bending Tests with Infrared Thermography
Carosena Meola
2012-01-01
Full Text Available The attention of the present paper is focused on the use of an infrared imaging device to monitor the thermal response of composite materials under cyclic bending. Three types of composites are considered including an epoxy matrix reinforced with either carbon fibres (CFRP or glass fibres (GFRP and a hybrid composite involving glass fibres and aluminium layers (FRML. The specimen surface, under bending, displays temperature variations pursuing the load variations with cooling down under tension and warming up under compression; such temperature variations are in agreement with the bending moment. It has been observed that the amplitude of temperature variations over the specimen surface depends on the material characteristics. In particular, the presence of a defect inside the material affects the temperature distribution with deviation from the usual bending moment trend.
Turbulent flow computation in a circular U-Bend
Miloud Abdelkrim
2014-03-01
Full Text Available Turbulent flows through a circular 180° curved bend with a curvature ratio of 3.375, defined as the the bend mean radius to pipe diameter is investigated numerically for a Reynolds number of 4.45×104. The computation is performed for a U-Bend with full long pipes at the entrance and at the exit. The commercial ANSYS FLUENT is used to solve the steady Reynolds–Averaged Navier–Stokes (RANS equations. The performances of standard k-ε and the second moment closure RSM models are evaluated by comparing their numerical results against experimental data and testing their capabilities to capture the formation and extend this turbulence driven vortex. It is found that the secondary flows occur in the cross-stream half-plane of such configurations and primarily induced by high anisotropy of the cross-stream turbulent normal stresses near the outer bend.
Fishery Manangement Plan : Holla Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This plan describes fishery management for Holla Bend National Wildlife Refuge in 1990. The plan outlines goals, objectives for fishery management for the benefit of...
Holla Bend National Wildlife Refuge: Comprehensive Conservation Plan
US Fish and Wildlife Service, Department of the Interior — This Comprehensive Conservation Plan (CCP) was written to guide management on Holla Bend NWR for the next 15 years. This plan outlines the Refuge vision and purpose...
Novel boundary element method for resolving plate bending problems
陈颂英; 王乐勤; 焦磊
2003-01-01
This paper discusses the application of the boundary contour method for resolving plate bending problems. The exploitation of the integrand divergence free property of the plate bending boundary integral equation based on the Kirchhoff hypothesis and a very useful application of Stokes' Theorem are presented to convert surface integrals on boundary elements to the computation of bending potential functions on the discretized boundary points, even for curved surface elements of arbitrary shape. Singularity and treatment of the discontinued corner point are not needed at all. The evaluation of the physics variant at internal points is also shown in this article. Numerical results are presented for some plate bending problems and compared against analytical and previous solutions.
Low Cycle Fatigue of Steel in Strain Controled Cyclic Bending
Kulesa Anna
2016-03-01
Full Text Available The paper presents a comparison of the fatigue life curves based on test of 15Mo3 steel under cyclic, pendulum bending and tension-compression. These studies were analyzed in terms of a large and small number of cycles where strain amplitude is dependent on the fatigue life. It has been shown that commonly used Manson-Coffin-Basquin model cannot be used for tests under cyclic bending due to the impossibility of separating elastic and plastic strains. For this purpose, some well-known models of Langer and Kandil and one new model of authors, where strain amplitude is dependent on the number of cycles, were proposed. Comparing the results of bending with tension-compression it was shown that for smaller strain amplitudes the fatigue life for both test methods were similar, for higher strain amplitudes fatigue life for bending tests was greater than for tension-compression.
Gender differences in variability patterns of forward bending
Villumsen, Morten; Madeleine, Pascal; Jørgensen, Marie Birk
2016-01-01
The variability pattern is highly relevant in the analysis of occupational physical exposures. It is hypothesized that gender differences exist in the variability pattern of forward bending between work and leisure....
1984 Deer Harvest Summary for Holla Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This memo summarizes the 1984 deer harvest for Holla Bend National Wildlife Refuge. Tables summarize numerical findings, including bucks, does, and points.
Narrative report 1968: U. L. Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This annual narrative report for Ul Bend NWR outlines Refuge accomplishments during the 1968 calendar year. The report begins by summarizing the weather conditions,...
Wildlife Inventory Plan : Holla Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This plan describes wildlife inventory in Holla Bend National Wildlife Refuge in 1983. This plan helps achieve refuge objectives by detailing the plan, purpose, and...
Magnetically Assisted Bilayer Composites for Soft Bending Actuators
Sung-Hwan Jang
2017-06-01
Full Text Available This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically distributed them by applying a strong non-uniform magnetic field to one side of the mold during the curing process. The biased magnetic field induces sedimentation of the ferromagnetic particles toward one side of the structure. The nonhomogeneous distribution of the particles induces bending of the structure when inflated, as a result of asymmetric stiffness of the composite. The bilayer composites were then characterized with a scanning electron microscopy and thermogravimetric analysis. The bending performance and the axial expansion of the actuator were discussed for manipulation applications in soft robotics and bioengineering. The magnetically assisted manufacturing process for the soft bending actuator is a promising technique for various applications in soft robotics.
Active vibration control of structures undergoing bending vibrations
Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor)
1995-01-01
An active vibration control subassembly for a structure (such as a jet engine duct or a washing machine panel) undergoing bending vibrations caused by a source (such as the clothes agitator of the washing machine) independent of the subassembly. A piezoceramic actuator plate is vibratable by an applied electric AC signal. The plate is connected to the structure such that vibrations in the plate induced by the AC signal cause canceling bending vibrations in the structure and such that the plate is compressively pre-stressed along the structure when the structure is free of any bending vibrations. The compressive prestressing increases the amplitude of the canceling bending vibrations before the critical tensile stress level of the plate is reached. Preferably, a positive electric DC bias is also applied to the plate in its poling direction.
Preliminary Project Investigation : Holla Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This report covers the proposed expansion of Holla Bend National Wildlife Refuge to increase the quantity and quality of wintering habitat primarily for mallards and...
Energy Dissipation Analysis of Bended SMA Bar in Isothermal State
PENG Gang; LI Li; TAN Jia-xiang
2004-01-01
The theory calculation formula is deduced about stress distribution in cross section and changes in Martensite percentages with the section height of random section shape bar under the action of the bending moment according to the Brinson's Constitutive Relation.The bar's energy dissipation capability under circulation of bending moment was analyzed and the calculation theory was set up. By using MATLAB program and the numerical calculation for uniform rectangle cross section bar, the relationships among the maximal stress and strain on cross section edge with bend load, the stress and Martensite percent's with cross section height, the energy dissipation capability with cross section height, and the energy dissipation capability with maximal strain on cross section edge are gained, also those curves are discused. It is put forward that the SMA material can be used for passive structure vibration control to dissipate energy of bend load.
Tidal bending of glaciers: a linear viscoelastic approach
Reeh, Niels; Christensen, Erik Lintz; Mayer, Christoph;
2003-01-01
In theoretical treatments of tidal bending of floating glaciers, the glacier is usually modelled as an elastic beam with uniform thickness, resting on an elastic foundation. With a few exceptions, values of the elastic (Young's) modulus E of ice derived from tidal deflection records of floating...... glaciers are in the range 0.9-3 GPa. It has therefore been suggested that the elastic-beam model with a single value of E approximate to 1 GPa adequately describes tidal bending of glaciers.In contrast, laboratory experiments with ice give E =93 GPa, i.e. 3-10 times higher than the glacier-derived values....... This suggests that ice creep may have a significant influence on tidal bending of glaciers. Moreover, detailed tidal-deflection and tilt data from Nioghalvfjerdsfjorden glacier, northeast Greenland, cannot be explained by elastic-beam theory. We present a theory of tidal bending of glaciers based on linear...
1984 Deer Harvest Summary for Holla Bend National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — This memo summarizes the 1985 deer harvest for Holla Bend National Wildlife Refuge. Tables summarize numerical findings, including bucks, does, and points.
Computational Strategies for the Architectural Design of Bending Active Structures
Tamke, Martin; Nicholas, Paul
2013-01-01
Active bending introduces a new level of integration into the design of architectural structures, and opens up new complexities for the architectural design process. In particular, the introduction of material variation reconfigures the design space. Through the precise specification...... of their stiffness, it is possible to control and pre-calibrate the bending behaviour of a composite element. This material capacity challenges architecture’s existing methods for design, specification and prediction. In this paper, we demonstrate how architects might connect the designed nature of composites...... with the design of bending-active structures, through computational strategies. We report three built structures that develop architecturally oriented design methods for bending-active systems using composite materials. These projects demonstrate the application and limits of the introduction of advanced...
Curvature-Induced Bunch Self-Interaction for an Energy-Chirped Bunch in Magnetic Bends
Li, Rui
2008-02-01
Within the realm of classical electrodynamics, the curvature-induced bunch collective interaction in magnetic bends can be studied using effective forces in the canonical formulation of the coherent synchrotron radiation (CSR) effect. As an application of this canonical formulation, in this paper, for an electron distribution moving ultrarelativistically in a bending system, the dynamics of the particles in the distribution is derived from the Hamiltonian of the particles in terms of the bunch internal coordinates. The consequent Vlasov equation manifests explicitly how the phase-space distribution is perturbed by the effective CSR forces. In particular, we study the impact of an initial linear energy chirp of the bunch on the behavior of the effective longitudinal CSR force, which arises due to the modification of the retardation relation as a result of the energy-chirping- induced longitudinal-horizontal correlation of the bunch distribution (bunch tilt) in dispersive regions. Our study demonstrates clearly the time delay (or retardation) of the behavior of the effective longitudinal CSR force on a bunch in responding to the change of the bunch length in a magnetic bend. Our result also shows that the effective longitudinal CSR force for a bunch under full compression can have sensitive dependence on the transverse position of the test particle in the bunch for certain parameter regimes.
Hongjun Zhu
2014-01-01
Full Text Available Accurate prediction of erosion thickness is essential for pipe engineering. The objective of the present paper is to study the temperature distribution in an eroded bend pipe and find a new method to predict the erosion reduced thickness. Computational fluid dynamic (CFD simulations with FLUENT software are carried out to investigate the temperature field. And effects of oil inlet rate, oil inlet temperature, and erosion reduced thickness are examined. The presence of erosion pit brings about the obvious fluctuation of temperature drop along the extrados of bend. And the minimum temperature drop presents at the most severe erosion point. Small inlet temperature or large inlet velocity can lead to small temperature drop, while shallow erosion pit causes great temperature drop. The dimensionless minimum temperature drop is analyzed and the fitting formula is obtained. Using the formula we can calculate the erosion reduced thickness, which is only needed to monitor the outer surface temperature of bend pipe. This new method can provide useful guidance for pipeline monitoring and replacement.
Estimating the bending modulus of a FtsZ bacterial-division protein filament
Cytrynbaum, Eric N.; Li, Yongnan Devin; Allard, Jun F.; Mehrabian, Hadi
2012-01-01
FtsZ, a cytoskeletal protein homologous to tubulin, is the principle constituent of the division ring in bacterial cells. It is known to have force-generating capacity in vitro and has been conjectured to be the source of the constriction force in vivo. Several models have been proposed to explain the generation of force by the Z ring. Here we re-examine data from in vitro experiments in which Z rings formed and constricted inside tubular liposomes, and we carry out image analysis on previously published data with which to better estimate important model parameters that have proven difficult to measure by direct means. We introduce a membrane-energy-based model for the dynamics of multiple Z rings moving and colliding inside a tubular liposome and a fluid model for the drag of a Z ring as it moves through the tube. Using this model, we estimate an effective membrane bending modulus of 500-700 pNnm. If we assume that FtsZ force generation is driven by hydrolysis into a highly curved conformation, we estimate the FtsZ filament bending modulus to be 310-390 pNnm2. If we assume instead that force is generated by the non-hydrolysis-dependent intermediate curvature conformation, we find that Bf>1400pNnm2. The former value sits at the lower end of the range of previously estimated values and, if correct, may raise challenges for models that rely on filament bending to generate force.
An Analysis of Elasto-Plastic Bending of Rectangular Plate
Matsuda, Hiroshi; Sakiyama, Takeshi
1988-01-01
In this paper, a discrete method for analyzing the problem of elasto-plastic bending of a rectangular plate is proposed. The solutions for partial differential equation of rectangular plate are obtained in discrete forms by applying numerical integnltion. An incremental variable elasticity procedure has been used for the clasta-plastic analysis of the rectangular plate. As the applications of the proposed method, clasta-plastic bending of rectangular plate with four types of boundary conditio...
Stress Analysis of a Secondary-Bending Specimen
1993-11-01
Control Office Ansett Airlines of Australia, Library 0 Qantas Airways Limited Hawker de Havilland Aust Pty Ltd, Victoria, Library Hawker de Havilland...MELBOURNE, VICTORIA Technical Note 58 STRESS ANALYSIS OF A SECONDARY-BENDING SPECIMEN 0 by R.L. EVANS M. HELLER Approved for public release C) COMMONWEALTH...AND TECHNOLOGY ORGANISATION AERONAUTICAL RESEARCH LABORATORY Technical Note 58 0 STRESS ANALYSIS OF A SECONDARY-BENDING SPECIMEN by R.L. EVANS 0 M
NUMERICAL SIMULATION FOR LASER BENDING OF SHEET METAL
1998-01-01
The new flexible forming technique of sheet metal-laser bending process is numerically simulated by using finite element method of large elastic-plastic deformation. The temperature fields and stress-strain distribution in deformation area are calculated, forming process is described and relationship between bend angle and width of sheet is discussed. It is shown that the calculated values are in good accordance with the experiments.
Localized bending fatigue behavior of high-strength steel monostrands
Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.
2012-01-01
In this paper, the localized bending fatigue behavior of pretensioned high strength steel monostrands is investigated. Furthermore, a new methodology using an optical photogrammetry system, which can quantify surface deformations on the strand is presented. The system allows measurement of the st......In this paper, the localized bending fatigue behavior of pretensioned high strength steel monostrands is investigated. Furthermore, a new methodology using an optical photogrammetry system, which can quantify surface deformations on the strand is presented. The system allows measurement...
A cylindrical standing wave ultrasonic motor using bending vibration transducer.
Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun
2011-07-01
A cylindrical standing wave ultrasonic motor using bending vibration transducer was proposed in this paper. The proposed stator contains a cylinder and a bending vibration transducer. The two combining sites between the cylinder and the transducer locate at the adjacent wave loops of bending vibration of the transducer and have a distance that equal to the half wave length of bending standing wave excited in the cylinder. Thus, the bending mode of the cylinder can be excited by the bending vibration of the transducer. Two circular cone type rotors are pressed in contact to the end rims of the teeth, and the preload between the rotors and stator is accomplished by a spring and nut system. The working principle of the proposed motor was analyzed. The motion trajectories of teeth were deduced. The stator was designed and analyzed with FEM. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 165rpm and maximum torque of 0.45Nm at an exciting voltage of 200V(rms).
Tunable characteristics of bending resonance frequency in magnetoelectric laminated composites
Chen Lei; Li Ping; Wen Yu-Mei; Zhu Yong
2013-01-01
As the magnetoelectric (ME) effect in piezoelectric/magnetostrictive laminated composites is mediated by mechanical deformation,the ME effect is significantly enhanced in the vicinity of resonance frequency.The bending resonance frequency (fr) of bilayered Terfenol-D/PZT (MP) laminated composites is studied,and our analysis predicts that (i) the bending resonance frequency of an MP laminated composite can be tuned by an applied dc magnetic bias (Hdc) due to the △E effect; (ii) the bending resonance frequency of the MP laminated composite can be controlled by incorporating FeCuNbSiB layers with different thicknesses.The experimental results show that with Hdc increasing from 0Oe (1 Oe=79.5775 A/m)to 700 Oe,the bending resonance frequency can be shifted in a range of 32.68 kHz ≤ fr ≤ 33.96 kHz.In addition,with the thickness of the FeCuNbSiB layer increasing from 0 μm to 90 μm,the bending resonance frequency of the MP laminated composite gradually increases from 33.66 kHz to 39.18 kHz.This study offers a method of adjusting the strength of dc magnetic bias or the thicknesses of the FeCuNbSiB layer to tune the bending resonance frequency for ME composite,which plays a guiding role in the ME composite design for real applications.
Optimal Orthogonal Graph Drawing with Convex Bend Costs
Bläsius, Thomas; Wagner, Dorothea
2012-01-01
Traditionally, the quality of orthogonal planar drawings is quantified by either the total number of bends, or the maximum number of bends per edge. However, this neglects that in typical applications, edges have varying importance. Moreover, as bend minimization over all planar embeddings is NP-hard, most approaches focus on a fixed planar embedding. We consider the problem OptimalFlexDraw that is defined as follows. Given a planar graph G on n vertices with maximum degree 4 and for each edge e a cost function cost_e : N_0 --> R defining costs depending on the number of bends on e, compute an orthogonal drawing of G of minimum cost. Note that this optimizes over all planar embeddings of the input graphs, and the cost functions allow fine-grained control on the bends of edges. In this generality OptimalFlexDraw is NP-hard. We show that it can be solved efficiently if 1) the cost function of each edge is convex and 2) the first bend on each edge does not cause any cost (which is a condition similar to the posi...
Safdar, Shakeel; Li, Lin; Sheikh, M. A.; Zhu Liu
2007-09-01
Laser forming has received considerable attention in recent years. Within laser forming, tube bending is an important industrial activity, with applications in critical engineering systems like micro-machines, heat exchangers, hydraulic systems, boilers, etc. Laser tube bending utilizes the thermal stresses generated during laser scanning to achieve the desired bends. The parameters to control the process are usually laser power, beam diameter, scanning velocity and number of scans. Recently axial scanning has been used for tube bending instead of commonly used circumferential scans. However the comparison between the scanning schemes has involved dissimilar laser beam geometries with circular beam used for circumferential scanning and a rectangular beam for the axial scan. Thermal stresses generated during laser scanning are strongly dependent upon laser beam geometry and scanning direction and hence it is difficult to isolate the contribution made by these two variables. It has recently been established at the Corrosion and Protection Centre, University of Manchester, that corrosion properties of material during laser forming are affected by the number of laser passes. Depending on the material, the corrosion behaviour is either adversely or favourably affected by number of passes. Thus it is of great importance to know how different scanning schemes would affect laser tube bending. Moreover, any scanning scheme which results in greater bending angle would eliminate the need for higher number of passes, making the process faster. However, it is not only the bending angle which is critical, distortions in other planes are also extremely important. Depending on the use of the final product, unwanted distortions may be the final selection criteria. This paper investigates the effect of scanning direction on laser tube bending. Finite-element modelling has been used for the study of the process with some results also validated by experiments.
Improving Bending Moment Measurements on Wind Turbine Blades
Post, Nathan L.
2016-03-15
Full-scale fatigue testing of wind turbine blades is conducted using resonance test techniques where the blade plus additional masses is excited at its first resonance frequency to achieve the target loading amplitude. Because there is not a direct relationship between the force applied by an actuator and the bending moment, the blade is instrumented with strain gauges that are calibrated under static loading conditions to determine the sensitivity or relationship between strain and applied moment. Then, during dynamic loading the applied moment is calculated using the strain response of the structure. A similar procedure is also used in the field to measure in-service loads on turbine blades. Because wind turbine blades are complex twisted structures and the deflections are large, there is often significant cross-talk coupling in the sensitivity of strain gauges placed on the structure. Recent work has shown that a sensitivity matrix with nonzero cross terms must be employed to find constant results when a blade is subjected to both flap and lead-lag loading. However, even under controlled laboratory conditions, potential for errors of 3 percent or more in the measured moment exist when using the typical cross-talk matrix approach due to neglecting the influence of large deformations and torsion. This is particularly critical when considering a biaxial load as would be applied on the turbine or during a biaxial fatigue test. This presentation describes these results demonstrating errors made when performing current loads measurement practices on wind turbine blades in the lab and evaluating potential improvements using enhanced cross-talk matrix approaches and calibration procedures.
Fretting fatigue behavior of high-strength steel monostrands under bending load
Winkler, Jan; Georgakis, Christos T.; Fischer, Gregor
2015-01-01
In this paper, the fretting fatigue behavior of pretensioned high-strength steel monostrands is investigated. To measure the local deformations on the strands, a novel method based on the digital image correlation (DIC) technique was used to quantify the relative movement between individual wires...... along the length of the monostrand. Information about the monostrand bending stiffness and the extent of relative displacement between core and outer wires of a monostrand undergoing flexural deformations is provided. From the series of dynamic fatigue tests, a fretting fatigue spectrum is derived...
How lidocaine influences the bilayer thickness and bending elasticity of biomembranes
Zheng Yi; Nagao, Michihiro; Bossev, Dobrin P, E-mail: zhyi@indiana.edu
2010-11-01
We have studied how local anesthetics influence the structural and dynamical properties of model bio-membranes. The measurements of small-angle neutron scattering have been performed on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) unilamellar vesicles with different concentrations of lidocaine in D{sub 2}O to determine the bilayer thickness as a function of the lidocaine concentration. The neutron-spin echo spectroscopy (NSE) has been used to study the influence of lidocaine on the bending elasticity of DMPC bilayers in fluid crystal phase (L{sub {alpha}}) and the ripple gel (P{sub {beta}}') phase.
LI Heng; YANG He
2011-01-01
Thin-walled tube numerical control (NC) bending is a tri-nonlinear physical process with multi-defect and multi-die constraints. The clearance on each contact interface is the major factor to indicate the contact conditions. A three-dimensional-finite element (3D-FE) model is established to consider the realistic dynamic boundary conditions of multiple dies under ABAQUS/Explicit platform. Combined with experiment, numerical study on bending behavior and bendability under different clearance between tube and various dies is conducted in terms of wrinkling, wall thinning and cross section deformation. The results show that (1)with smaller clearance of tube-wiper die and tube-mandrel, the wrinkling can be restrained while the wall thinning It and cross-section deformation Id increase; while excessive small clearance blocks tube materials to flow past tangent point and causes piles up, the onset of wrinkling enhances It and Id. (2)Both It and Id decrease with smaller clearance of tube-pressure die; the wrinkling possibility rises with larger clearance on this interface if the mandrel's freedom along Y-axis is opened; smaller clearance of tube-bend die prevents wrinkling while increases It, and the clearance on this interface has little effect on Id. (3)A modified Yoshida buckling test (YBT) is used to address the wrinkling mechanisms under normal constraints in tube bending: the smaller clearance may restrain wrinkling efficiently; the smaller wall thickness, the less critical clearance needed; the critical clearance for tube bending 38 mm× 1 mm×57 mm (tube outer diameter×wall thickness×centerline bending radius) equals about 20％ of initial wall thickness.
Improving bending stress in spur gears using asymmetric gears and shape optimization
Pedersen, Niels Leergaard
2010-01-01
Bending stress plays a significant role in gear design wherein its magnitude is controlled by the nominal bending stress and the stress concentration due to the geometrical shape. The bending stress is indirectly related to shape changes made to the cutting tool. This work shows that the bending...
Advances and Trends on Tube Bending Forming Technologies
YANG He; LI Heng; ZHANG Zhiyong; ZHAN Mei; LIU Jing; LI Guangjun
2012-01-01
As one kind of key components with enormous quantities and diversities,the bent tube parts satisfy the increasing needs for lightweight and high-strength product from both materials and structure aspects.The bent tubes have been widely used in many high-end industries such as aviation,aerospaee,shipbuilding,automobile,energy and health care.The tube bending has become one of the key manufacturing technologies for lightweight product forming.Via the analysis of bending characteristics and multiple defects,advances on exploring the common issues in tube bending are summarized regarding wrinkling instability at the intrados,wall thinning (cracking) at the extrados,springback phenomenon,cross-section deformation,forming limit and process/tooling design/optimization.Some currently developed bending techniques are reviewed in terms of their advantages and limitations.Finally,in view of the urgent requirements of high-performance complex bent tube components with difficult-to-deform and lightweight materials in aviation and aerospace fields,the development trends and corresponding challenges are presented for realizing the precise and high-efficiency tube bending deformation.
Hysteresis of the resonance frequency of magnetostrictive bending cantilevers
Löffler, Michael; Kremer, Ramona; Sutor, Alexander; Lerch, Reinhard
2015-05-01
Magnetostrictive bending cantilevers are applicable for wirelessly measuring physical quantities such as pressure and strain. Exploiting the ΔE-effect, the resonance frequency of the cantilevers is shifted because of a change in the magnetic biasing field. The biasing field, in turn, depends on the applied pressure or strain, respectively. With a view to the application as a reliable sensor, maximum sensitivity but minimum hysteresis in the biasing field/resonance frequency dependence is preferred. In this contribution, monomorph bending cantilevers fabricated using magnetostrictive Fe49Co49V2 and Metglas 2605SA1 are investigated regarding their applicability for future sensors. For this purpose, the biasing field-dependent polarization of the magnetostrictive materials and bending of the cantilevers are determined. Furthermore, a setup to magnetically bias the cantilevers and determine the bending resonance frequency is presented. Here, the resonance frequency is identified by measuring the impulse response employing a laser Doppler vibrometer. The measurement results reveal that cantilevers made of Fe49Co49V2 possess a distinct hysteretic behaviour at low magnetic biasing field magnitudes. This is ascribed to the polarization and bending hysteresis. Cantilevers fabricated using Metglas 2605SA1 feature a lower resonance frequency shift compared to cantilevers with Fe49Co49V2, which would result in a lower sensitivity of the sensor. However, their resonance frequency hysteresis is almost negligible.
Investigation of span-chordwise bending anisotropy of honeybee forewings
JianGuo Ning
2017-05-01
Full Text Available In this study, the spanwise and chordwise bending stiffness EI of honeybee forewings were measured by a cantilevered bending test. The test results indicate that the spanwise EI of the forewing is two orders of magnitude larger than the chordwise EI. Three structural aspects result in this span-chordwise bending anisotropy: the distribution of resilin patches, the corrugation along the span and the leading edge vein of the venation. It was found that flexion lines formed by resilin patches revealed through fluorescence microscopy promoted the chordwise bending of the forewing during flapping flight. Furthermore, the corrugation of the wing and leading edge veins of the venation, revealed by micro-computed tomography, determines the relatively greater spanwise EI of the forewing. The span-chordwise anisotropy exerts positive structural and aerodynamic influences on the wing. In summary, this study potentially assists researchers in understanding the bending characteristics of insect wings and might be an important reference for the design and manufacture of bio-inspired wings for flapping micro aerial vehicles.
Bending moment of galvanized iron glass fiber sandwich panel
Gurustal Somnath Swamy
2016-05-01
Full Text Available The main objective of this project is to prepare a laminated with Galvanized iron thickness fractions, fiber volume fractions and orientation in the layers of GF were fabricated by hand lay-up method and evaluated for their bending moment properties of the sandwich panel using universal testing machine. This paper theoretically calculates the bending behavior of sandwich panel. The recent need to develop a new range of materials has resulted in the development of high performance lightweight composites with excellent properties. Metal– composite systems consist of alternating layers of metal and fiber-reinforced polymer composites which are bonded by an adhesive. Sandwich beams were tested under Air Bending. Stress-strain and stress-displacement were recorded by using AIMIL UTM. The beam face sheets exhibited a softening non-linearity on the bending side. Experimental results were in good agreement with predictions from simple models. On an overall basis, the sandwich panel exhibited better bending moment performance than the monolithic galvanized iron
Photomechanical Energy Conversion of Photoresponsive Fibers Exhibiting Bending Behavior
Kazuya Nakata
2012-01-01
Full Text Available Photoresponsive fibers based on poly(acrylamide (PAA with methylene blue (MB dye were prepared. All semicircular fibers show bending towards the direction of the flat surface of the fiber when illuminated. The fibers recover their initial shape when the illumination stops. The fiber is heated upon illumination and cooled to room temperature once the illumination is stopped. The fiber also is sensitive to humidity, showing bending behavior towards the direction of the flat surface of the fiber upon changing the humidity. The mechanical energy of the PAA/MB fiber is approximately 0.6 mN for the bending direction when it is illuminated. A possible mechanism for the bending behavior is as follow: (1 the fiber is heated upon illumination because of the photothermal effect, (2 the fiber loses water molecules, (3 the fiber shrinks; bending towards the direction of the flat surface of the fiber occurs because of a difference in the shrinkage for the flat surface and the other side of the fiber. Finally, we demonstrated that a PP ball (1.5 mg can be moved by the mechanical energy produced by the changing shape of the fiber upon illumination.
Curvature optical fiber sensor by using bend enhanced method
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.
Elina Kasvi
2017-02-01
Full Text Available The fluvio-geomorphological processes in meander bends are spatially uneven in distribution. Typically, higher velocities and erosion take place near the outer bank beyond the bend apex, while the inner bend point bar grows laterally towards the outer bank, increasing the bend amplitude. These dynamics maintain the meander evolution. Even though this development is found in meandering rivers independent of soil or environmental characteristics, each river still seems to behave unpredictably. The special mechanisms that determine the rate and occasion of morphological changes remain unclear. The aim of this study is to offer new insights regarding flow-induced morphological changes in meander using a novel study approach. We focused on short-term and small-spatial-scale changes by conducting a spatially and temporally (daily intensive survey during a flood (a period of nine days with an ADCP attached to a remotely controlled mini-boat. Based on our analysis, the flood duration and the rate of discharge increase and decrease seems to play key roles in determining channel changes by controlling the flow velocities and depth and the backwater effect may have notable influence on the morphological processes. We discuss themes such as the interaction of inner and outer bend processes and the longer-term development of meander bends.
Chen, X.; Le, T.; Ewing, D.; Ching, C. Y.
2016-12-01
The mass transfer to turbulent flow through back-to-back pipe bends arranged in a 180° configuration with different lengths of pipe between the bends was measured using a dissolving gypsum test section in water. The measurements were performed for bends with a radius of curvature of 1.5 times the pipe diameter ( D) at a Reynolds numbers of 70,000 and Schmidt number of 1280. The maximum mass transfer in the bends decreased from approximately 1.8 times the mass transfer in the upstream pipe when there was no separation distance between the bends to 1.7 times when there was a 1 D or 5 D length of pipe between the bends. The location of the maximum mass transfer was on the inner sidewall downstream of the second bend when there was no separation distance between the bends. This location changed to the inner wall at the beginning of the second bend when there was a 1 D long pipe between the bends, and to the inner sidewall at the end of the first bend when there was a 5 D long pipe between the bends.
Chen, L.-T.; Dugundji, J.
1979-01-01
A preliminary study conducted by Kerrebrock et al. (1976) has shown that the torsional rigidity of untwisted thin blades of a transonic compressor can be reduced significantly by transient thermal stresses. The aerodynamic loads have various effects on blade vibration. One effect is that gas bending loads may result in a bending-torsion coupling which may change the characteristics of the torsion and bending vibration of the blade. For a general study of transient-temperature distribution within a rotor stage, a finite-element heat-conduction analysis was developed. The blade and shroud are divided into annular elements. With a temperature distribution obtained from the heat-conduction analysis and a prescribed gas bending load distribution along the blade span, the static deformation and moment distributions of the blade can be solved iteratively using the finite-element method. The reduction of the torsional rigidity of pretwisted blades caused by the thermal stress effect is then computed. The dynamic behavior of the blade is studied by a modified Galerkin's method.
Chen, L.-T.; Dugundji, J.
1979-01-01
A preliminary study conducted by Kerrebrock et al. (1976) has shown that the torsional rigidity of untwisted thin blades of a transonic compressor can be reduced significantly by transient thermal stresses. The aerodynamic loads have various effects on blade vibration. One effect is that gas bending loads may result in a bending-torsion coupling which may change the characteristics of the torsion and bending vibration of the blade. For a general study of transient-temperature distribution within a rotor stage, a finite-element heat-conduction analysis was developed. The blade and shroud are divided into annular elements. With a temperature distribution obtained from the heat-conduction analysis and a prescribed gas bending load distribution along the blade span, the static deformation and moment distributions of the blade can be solved iteratively using the finite-element method. The reduction of the torsional rigidity of pretwisted blades caused by the thermal stress effect is then computed. The dynamic behavior of the blade is studied by a modified Galerkin's method.
Photomechanical Bending of Azobenzene-Based Photochromic Molecular Fibers
Riku Matsui
2013-03-01
Full Text Available Microfibers composed of azobenzene-based photochromic amorphous molecular materials, namely low molecular-mass photochromic materials with a glass-forming property, could be fabricated. These fibers were found to exhibit mechanical bending motion upon irradiation with a laser beam. In addition, the bending direction could be controlled by altering the polarization direction of the irradiated light without changing the position of the light source or the wavelength of the light. In-situ fluorescence observation of mass transport induced at the surface of the fiber doped with CdSe quantum dots suggested that the bending motions were related with the photoinduced mass transport taking place near the irradiated surface of the fiber.
Flow resistance of ice slurry in bends and elbow pipes
Niezgoda-Żelasko, B.; Żelasko, J.
2014-08-01
The present paper covers the flow of ice slurry made of a 10.6% ethanol solution through small-radius bends and elbow pipes. The paper presents the results of experimental research on the flow resistances of Bingham-fluid ice slurry in bends and elbows. The research, performed for three pipe diameters and a relative bend radius of 1<=D/di<=2, has made it possible to take into consideration the influence of friction resistances as well the of the flow geometry on the total local resistance coefficients. The study attempts to make the local resistance coefficient dependent on the Dean number defined for a generalized Reynolds number according to Metzner-Reade
Platonic scattering cancellation for bending waves in a thin plate
Farhat, Mohamed
2014-04-10
We propose an ultra-thin elastic cloak to control the scattering of bending waves in isotropic heterogeneous thin plates. The cloak design makes use of the scattering cancellation technique applied, for the first time, to the biharmonic operator describing the propagation of bending waves in thin plates. We first analyze scattering from hard and soft cylindrical objects in the quasistatic limit, then we prove that the scattering of bending waves from an object in the near and far-field regions can be suppressed significantly by covering it with a suitably designed coating. Beyond camouflaging, these findings may have potential applications in protection of buildings from earthquakes and isolating structures from vibrations in the motor vehicle industry.
Segmental Bridges under Combined Torsion, Bending and Shear
黄真; 刘西拉
2003-01-01
Segmental bridges with unbonded prestressed tendons have some advantages, such as the weather independence and the corrosion protection of prestressing tendons. This paper analyzed the behavior of a prestressed segmental bridge with unbonded tendons under combined loading of torsion, bending and shear. According to the experiment research, a modified skew bending model was developed to calculate the bearing capacity of segmental bridges subjected to combined bending, shear and torsion. The finite element method was used to investigate the deflection behaviors of such structure, also to check the theoretical model. The theoretical and FEM research resuits were compared favorably with the test results from Technical University of Braunschweig, Germany. Finally, suggestion for the design and construction of segmental bridges with external prestressing was made.
Longitudinal-bending mode micromotor using multilayer piezoelectric actuator.
Yao, K; Koc, B; Uchino, K
2001-07-01
Longitudinal-bending mode ultrasonic motors with a diameter of 3 mm were fabricated using stacked multilayer piezoelectric actuators, which were self-developed from hard lead zirconate titanate (PZT) ceramic. A bending vibration was converted from a longitudinal vibration with a longitudinal-bending coupler. The motors could be bidirectionally operated by changing driving frequency. Their starting and braking torque were analyzed based on the transient velocity response. With a load of moment of inertia 2.5 x 10(-7) kgm2, the motor showed a maximum starting torque of 127.5 microNm. The braking torque proved to be a constant independent on the motor's driving conditions and was roughly equivalent to the maximum starting torque achievable with our micromotors.
Strain localization and damage development in 2060 alloy during bending
Xiao Jin; Bao-qin Fu; Cheng-lu Zhang; Wei Liu
2015-01-01
The microstructure evolution and damage development of the third-generation Al–Li alloy 2060 (T8) were studied using in situ bending tests. Specimens were loaded with a series of punches of different radii, and the microstructure evolution was studied by scanning electron microscopy, electron backscatter diffraction, and digital image correlation (DIC) methods. The evolution of the microscopic fracture strain distribution and microstructure in 2060 alloy during bending was characterized, where the dispersion distribution of precipitates was recorded by backscattered electron imaging and later inputted into a DIC system for strain calculations. The experimental results showed that strain localization in the free surface of bent specimens induced damage to the microstructure. The region of crack initiation lies on the free surface with maximum strain, and the shear crack propagates along the macro-shear band in the early stages of bending. Crack propagation in the later stages was interpreted on the basis of the conventional mechanism of ductile fracture.
Bend-twist coupling potential of wind turbine blades
Fedorov, Vladimir; Berggreen, Christian
2014-01-01
In the present study an evaluation of the potential for bend-twist coupling effects in wind turbine blades is addressed. A method for evaluation of the coupling magnitude based on the results of finite element modeling and full-field displacement measurements obtained by experiments is developed...... and tested on small-scale coupled composite beams. In the proposed method the coupling coefficient for a generic beam is introduced based on the Euler-Bernoulli beam formulation. By applying the developed method for analysis of a commercial wind turbine blade structure it is demonstrated that a bend......-twist coupling magnitude of up to 0.2 is feasible to achieve in the baseline blade structure made of glass-fiber reinforced plastics. Further, by substituting the glass-fibers with carbon-fibers the coupling effect can be increased to 0.4. Additionally, the effect of introduction of bend-twist coupling...
Demonstration of acoustic waveguiding and tight bending in phononic crystals
Ghasemi Baboly, M.; Raza, A.; Brady, J.; Reinke, C. M.; Leseman, Z. C.; El-Kady, I.
2016-10-01
The systematic design, fabrication, and characterization of an isolated, single-mode, 90° bend phononic crystal (PnC) waveguide are presented. A PnC consisting of a 2D square array of circular air holes in an aluminum substrate is used, and waveguides are created by introducing a line defect in the PnC lattice. A high transmission coefficient is observed (-1 dB) for the straight sections of the waveguide, and an overall 2.3 dB transmission loss is observed (a transmission coefficient of 76%) for the 90° bend. Further optimization of the structure may yield higher transmission efficiencies. This manuscript shows the complete design process for an engineered 90° bend PnC waveguide from inception to experimental demonstration.
Elastocapillary instability under partial wetting conditions: bending versus buckling
Andreotti, Bruno; Das, Siddhartha; Snoeijer, Jacco H
2011-01-01
The elastocapillary instability of a flexible plate plunged in a liquid bath is analysed theoretically. We show that the plate can bend due to two separate destabilizing mechanisms, when the liquid is partially wetting the solid. For contact angles $\\theta_e > \\pi/2$, the capillary forces acting tangential to the surface are compressing the plate and can induce a classical buckling instability. However, a second mechanism appears due to capillary forces normal to surface. These induce a destabilizing torque that tends to bend the plate for any value of the contact angle $\\theta_e > 0$. We denote these mechanisms as "buckling" and "bending" respectively and identify the two corresponding dimensionless parameters that govern the elastocapillary stability. The onset of instability is determined analytically and the different bifurcation scenarios are worked out for experimentally relevant conditions.
Goodman, Lawrence E
2001-01-01
Beginning text presents complete theoretical treatment of mechanical model systems and deals with technological applications. Topics include introduction to calculus of vectors, particle motion, dynamics of particle systems and plane rigid bodies, technical applications in plane motions, theory of mechanical vibrations, and more. Exercises and answers appear in each chapter.
Renato, Lemus; María del Mar, Estezez-Fregozo
2017-06-01
An approach to connect the su(3) dynamical group- used to describe the bending modes of linear molecules- with configuration space is discussed. The SU(3) group may be seen as a consequence of adding a scalar boson to the SU(2) space of two degenerate harmonic oscillators. The resulting SU(3) group becomes the dynamical group for the bending degrees of freedom of linear molecules, but the connection to configuration space is not obvious. This work aims at providing this connection. Our approach is based on the basis of establishing a mapping between the algebraic and configuration states. An arbitrary operator in configuration space is then expanded in terms of generators of the dynamical algebra. The coefficients are determined through a minimization procedure and given in terms of matrix elements defined in configuration space. As an application we consider the vibrational description of the bending modes of the acetylene molecule, where the force constants are estimated in the framework of the U(3) × U(3) model.
Modulated liquid-crystal phases induced by polarity: Twist-bend, splay-bend, and blue phases
Selinger, Jonathan; Shamid, Shaikh; Allender, David
2014-03-01
Nematic liquid crystals exhibit flexoelectric couplings between polar order and gradients in the director field. When the couplings become strong enough, the uniform nematic phase can become unstable to the formation of a modulated polar phase. The question is then: What is the structure of the modulated polar phase? Classic work by Meyer and further studies by Dozov predicted two possible structures, known as twist-bend and splay-bend. One of these predictions, the twist-bend phase, has recently been identified in experiments on bent-core liquid crystals. Here, we investigate modulated polar phases through a combination of Landau theory and lattice simulations. We find a range of possibilities, including the twist-bend and splay-bend phases as well as polar blue phases, with 2D or 3D modulations of the director field and the polar order. We compare these polar blue phases with chiral blue phases, and discuss opportunities for observing them experimentally. Supported by NSF DMR-1106014.
Sasidharan, Sumesh; Arunachalam, Veerappan; Subramaniam, Shanmugam [Dept. of Mechanical Engineering, National Institute of Technology, Tiruchirappalli (India)
2017-02-15
Finite-element analysis based on elastic-perfectly plastic material was conducted to examine the influence of structural deformations on collapse loads of circumferential through-wall critically cracked 90 .deg. pipe bends undergoing in-plane closing bending and internal pressure. The critical crack is defined for a through-wall circumferential crack at the extrados with a subtended angle below which there is no weakening effect on collapse moment of elbows subjected to in-plane closing bending. Elliptical and semioval cross sections were postulated at the bend regions and compared. Twice-elastic-slope method was utilized to obtain the collapse loads. Structural deformations, namely, ovality and thinning, were each varied from 0% to 20% in steps of 5% and the normalized internal pressure was varied from 0.2 to 0.6. Results indicate that elliptic cross sections were suitable for pipe ratios 5 and 10, whereas for pipe ratio 20, semioval cross sections gave satisfactory solutions. The effect of ovality on collapse loads is significant, although it cancelled out at a certain value of applied internal pressure. Thinning had a negligible effect on collapse loads of bends with crack geometries considered.
Bending of the looping heart: differential growth revisited.
Shi, Yunfei; Yao, Jiang; Xu, Gang; Taber, Larry A
2014-08-01
In the early embryo, the primitive heart tube (HT) undergoes the morphogenetic process of c-looping as it bends and twists into a c-shaped tube. Despite intensive study for nearly a century, the physical forces that drive looping remain poorly understood. This is especially true for the bending component, which is the focus of this paper. For decades, experimental measurements of mitotic rates had seemingly eliminated differential growth as the cause of HT bending, as it has commonly been thought that the heart grows almost exclusively via hyperplasia before birth and hypertrophy after birth. Recently published data, however, suggests that hypertrophic growth may play a role in looping. To test this idea, we developed finite-element models that include regionally measured changes in myocardial volume over the HT. First, models based on idealized cylindrical geometry were used to simulate the bending process in isolated hearts, which bend without the complicating effects of external loads. With the number of free parameters in the model reduced to the extent possible, stress and strain distributions were compared to those measured in embryonic chick hearts that were isolated and cultured for 24 h. The results show that differential growth alone yields results that agree reasonably well with the trends in our data, but adding active changes in myocardial cell shape provides closer quantitative agreement with stress measurements. Next, the estimated parameters were extrapolated to a model based on realistic 3D geometry reconstructed from images of an actual chick heart. This model yields similar results and captures quite well the basic morphology of the looped heart. Overall, our study suggests that differential hypertrophic growth in the myocardium (MY) is the primary cause of the bending component of c-looping, with other mechanisms possibly playing lesser roles.
Proteomic Analysis of Fruit Bending in Cucumber (Cucumis sativus L.)
WANG Li-li; ZHANG Peng; QIN Zhi-wei; ZHOU Xiu-yan
2014-01-01
In cucumber, fruit shape is an important quality criterion, and fruit bending is known to limit growth, yield, and taste. To investigate the post-transcriptional changes that regulate fruit bending and to better understand the underlying molecular mechanisms, we generated a proteomic proifle of the abdomen and back of cucumber bending fruit. Two-dimensional gel electrophoresis (2-DE) allowed the detection of approximately 900 distinct protein spots in each gel, 32 of which were differentially expressed in the abdomen and back of bending cucumber fruit. Ten of the differentially expressed proteins were analyzed using matrix-assisted laser ionization time of lfight mass spectrometry (MALDI-TOF/MS). A search of primary databases showed that the identiifed proteins are involved in various metabolic processes and cellular responses, including photosynthesis metabolism, energy metabolism, defense and stress response, and regulation. The identiifed proteins included large subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase, which are involved in photosynthesis and photorespiratory metabolism, and isocitrate dehydrogenase, which is involved in the tricarboxylic acid cycle. It is possible that imbalances in catabolic and anabolic processes directly affect the bending of cucumber fruit. The predicted function of the cobalamin-independent methionine synthase isozyme is closely related to ethylene biosynthesis; fruit bending may be regulated by ethylene, or by ethylene signaling crosstalk during fruit development. The 14-3-3 protein is usually considered to be a regulation-related protein, which plays a role in regulating cell hyperplasia, cell differentiation during growth, and apoptosis during senescence. Involvement of guanosine triphosphate (GTP)-binding proteins in signal transmission is known to regulate the development of cells in cucumber fruits and to play a role in fruit shape variation. Patterns of protein expression showed high repeatability. We hypothesize
Enhanced resolution of long-period grating bend sensor
Glavind, Lars; Gao, S; Cook, K
2013-01-01
We present an optical fiber bend sensor with enhanced resolution based on the principle of a Mach-Zehnder interferometer in transmission. The sensor is based on two identical Long-Period Gratings separated by approximately 100 mm in a D-shaped single-mode optical fiber. The sensor provides a narr...... resonance bandwidth compared to a typical resonance from a Long-Period Grating. The sensor was recoated with low refractive index polyimide and embedded on a fiber-glass base plate before it was characterized as a bending sensor....
Bending Mechanical Behavior of Polyester Matrix Reinforced with Fique Fiber
Altoé, Giulio Rodrigues; Netto, Pedro Amoy; Barcelos, Mariana; Gomes, André; Margem, Frederico Muylaert; Monteiro, Sergio Neves
Environmentally correct composites, made from natural fibers, are among the most investigated and applied today. In this paper, we investigate the mechanical behavior of polyester matrix composites reinforced with continuous fique fibers, through bending tensile tests. Specimens containing 0, 10, 20 and 30% in volume of fique fiber were aligned along the entire length of a mold to create plates of these composites, those plates were cut following the ASTM standard to obtained bending tests specimens. The test was conducted in a Instron Machine and the fractured specimens were analyzed by SEM, the results showed the increase in the materials tensile properties with the increase of fiber amount.
Elastostatic bending of a bimaterial plate with a circular interface
Ogbonna, Nkem
2015-08-01
The elastostatic bending of an arbitrarily loaded bimaterial plate with a circular interface is analysed. It is shown that the deflections in the composite solid are directly related to the deflection in the corresponding homogeneous material by integral and differential operators. It is further shown that, by a simple transformation of elastic constants, the Airy stress function induced in the composite by a stretching singularity can be deduced from the deflection induced by a bending singularity. This result is significant for reduction of mathematical labour and for systematic construction of solutions for more complex structures with circular geometry.
Effects of rim thickness on spur gear bending stress
Bibel, G. D.; Reddy, S. K.; Savage, M.; Handschuh, R. F.
1991-01-01
Thin rim gears find application in high-power, light-weight aircraft transmissions. Bending stresses in thin rim spur gear tooth fillets and root areas differ from the stresses in solid gears due to rim deformations. Rim thickness is a significant design parameter for these gears. To study this parameter, a finite element analysis was conducted on a segment of a thin rim gear. The rim thickness was varied and the location and magnitude of the maximum bending stresses reported. Design limits are discussed and compared with the results of other researchers.
Origin of bending in uncoated microcantilever - Surface topography?
Lakshmoji, K.; Prabakar, K.; Tripura Sundari, S., E-mail: sundari@igcar.gov.in; Jayapandian, J.; Tyagi, A. K.; Sundar, C. S. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)
2014-01-27
We provide direct experimental evidence to show that difference in surface topography on opposite sides of an uncoated microcantilever induces bending, upon exposure to water molecules. Examination on opposite sides of the microcantilever by atomic force microscopy reveals the presence of localized surface features on one side, which renders the induced stress non-uniform. Further, the root mean square inclination angle characterizing the surface topography shows a difference of 73° between the opposite sides. The absence of deflection in another uncoated microcantilever having similar surface topography confirms that in former microcantilever bending is indeed induced by differences in surface topography.
Flagella bending affects macroscopic properties of bacterial suspensions
Potomkin, M.; Tournus, M.; Berlyand, L. V.; Aranson, I. S.
2017-05-01
To survive in harsh conditions, motile bacteria swim in complex environments and respond to the surrounding flow. Here, we develop a mathematical model describing how flagella bending affects macroscopic properties of bacterial suspensions. First, we show how the flagella bending contributes to the decrease in the effective viscosity observed in dilute suspension. Our results do not impose tumbling (random reorientation) as was previously done to explain the viscosity reduction. Second, we demonstrate how a bacterium escapes from wall entrapment due to the self-induced buckling of flagella. Our results shed light on the role of flexible bacterial flagella in interactions of bacteria with shear flow and walls or obstacles.
Numerical manifold method for the forced vibration of thin plates during bending.
Jun, Ding; Song, Chen; Wei-Bin, Wen; Shao-Ming, Luo; Xia, Huang
2014-01-01
A novel numerical manifold method was derived from the cubic B-spline basis function. The new interpolation function is characterized by high-order coordination at the boundary of a manifold element. The linear elastic-dynamic equation used to solve the bending vibration of thin plates was derived according to the principle of minimum instantaneous potential energy. The method for the initialization of the dynamic equation and its solution process were provided. Moreover, the analysis showed that the calculated stiffness matrix exhibited favorable performance. Numerical results showed that the generalized degrees of freedom were significantly fewer and that the calculation accuracy was higher for the manifold method than for the conventional finite element method.
Numerical Manifold Method for the Forced Vibration of Thin Plates during Bending
Ding Jun
2014-01-01
Full Text Available A novel numerical manifold method was derived from the cubic B-spline basis function. The new interpolation function is characterized by high-order coordination at the boundary of a manifold element. The linear elastic-dynamic equation used to solve the bending vibration of thin plates was derived according to the principle of minimum instantaneous potential energy. The method for the initialization of the dynamic equation and its solution process were provided. Moreover, the analysis showed that the calculated stiffness matrix exhibited favorable performance. Numerical results showed that the generalized degrees of freedom were significantly fewer and that the calculation accuracy was higher for the manifold method than for the conventional finite element method.
Bending-induced mode non-degeneracy and coupling in chalcogenide negative curvature fibers.
Wei, Chengli; Menyuk, Curtis R; Hu, Jonathan
2016-05-30
We study bend loss in chalcogenide negative curvature fibers with different polarizations, different tube wall thicknesses, and different bend directions relative to the mode polarization. The coupling between the core mode and tube modes induces bend loss peaks in the two non-degenerate modes at the same bend radius. There is as much as a factor of 28 difference between the losses of the two polarization modes. The fiber with a larger tube wall thickness, corresponding to a smaller inner tube diameter, can sustain a smaller bend radius. The bend loss is sensitive to the bend direction when coupling occurs between the core mode and tube modes. A bend loss of 0.2 dB/m at a bend radius of 16 cm, corresponding to 0.2 dB/turn, can be achieved in a chalcogenide negative curvature fiber.
Thin-walled aluminum alloy tube NC precision bending based on finite element simulation
GU Rui-jie; YANG He; ZHAN Mei; LI Heng
2006-01-01
Elongation and springback are the bottleneck problems of thin-walled aluminum alloy tube NC precision bending. So thin-walled aluminum alloy tube NC precision bending based on finite element simulation is put forward. The finite element model of thin-walled aluminum alloy tube NC bending is established based on the DYNAFORM platform. The process of thin-walled aluminum alloy tube NC precision bending is simulated with the model and the elongation and springback of tube bending can be is put forward and the computing equations of bending angle, bending radius, blanking length and initial bending section based on elongation and springback angle are derived. The bending angle, bending radius, blanking length and initial bending section of tube bending can be gained with these equations based on the elongation and springback angle from the simulation. The study can be used to control the quality of thin-walled aluminum alloy tube NC bending so that precision bending without redundance can be realized.
汤任基; 汤昕燕
2001-01-01
Using the single crack solution and the regular solution of plane harmonic function, the problem of Saint-Venant bending of a cracked cylinder by a transverse force was reduced to solving two sets of integral equations and its general solution was then obtained. Based on the obtained solution, a method to calculate the bending center and the stress intensity factors of the cracked cylinger whose cross-section is not thin-walled, but of small torsion rigidity is proposed. Some numerical examples are given.
Electrical Emissions from Concrete under Three-point Bending Tests
LIU Qingping; SUN Mingqing; LI Zhuoqiu; LI Guoqiang
2005-01-01
Electrical emission(EM) signals, which are generated from the concrete specimens under three-point bending tests, were conducted. It is shown that electrical emission phenomena are related to cracking of the specimens, cohesive failure, contact-separation etc. The simultaneous appearance of electric emission signals and visible cracks during the flexure loading of beams was also observed.
Secondary flow in sharp open-channel bends
Blanckaert, K.; De Vriend, H.J.
2004-01-01
Secondary currents are a characteristic feature of flow in open-channel bends. Besides the classical helical motion (centre-region cell), a weaker and smaller counter-rotating circulation cell (outer-bank cell) is often observed near the outer bank, which is believed to play an important role in ban
Photoacoustic elastic bending in thin film—Substrate system
Todorović, D. M., E-mail: dmtodor@imsi.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, P.O. Box 33, 11030 Belgrade (Serbia); Rabasović, M. D.; Markushev, D. D. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade-Zemun (Serbia)
2013-12-07
Theoretical model for optically excited two-layer elastic plate, which includes plasmaelastic, thermoelastic, and thermodiffusion mechanisms, is given in order to study the dependence of the photoacoustic (PA) elastic bending signal on the optical, thermal, and elastic properties of thin film—substrate system. Thin film-semiconductor sample (in our case Silicon) is modeled by simultaneous analysis of the plasma, thermal, and elastic wave equations. Multireflection effects in thin film are included in theoretical model and analyzed. Relations for the amplitude and phase of electronic and thermal elastic bending in the optically excited two-layer mechanically-supported circular plate are derived. Theoretical analysis of the thermodiffusion, plasmaelastic, and thermoelastic effects in a sample-gas-microphone photoacoustic detection configuration is given. Two normalization procedures of the photoacoustic elastic bending signal in function of the modulation frequency of the optical excitation are established. Given theoretical model can be used for various photoacoustic detection configurations, for example, in the study of optical, thermal, and elastic properties of the dielectric-semiconductor or metal-semiconductor structure, etc., Theoretical analysis shows that it is possible to develop new noncontact and nondestructive experimental method—PA elastic bending method for thin film study, with possibility to obtain the optical, thermal, and elastic parameters of the film thinner than 1 μm.
A Novel Rotary Piezoelectric Motor Using First Bending Hybrid Transducers
Yingxiang Liu
2015-08-01
Full Text Available We report a novel rotary piezoelectric motor using bending transducers in this work. Three transducers are used to drive a disk-shaped rotor together by the elliptical movements of their driving tips; these motions are produced by the hybrid of two first bending vibration modes. The proposed piezoelectric transducer has a simple structure as it only contains an aluminum alloy beam and four pieces of PZT plates. Symmetrical structure is the only necessary condition in the design process as it will ensure the resonance frequencies of the two orthogonal first bending modes are equal. Transducers with first bending resonance frequency of about 53 kHz were fabricated and assembled into a rotary motor. The proposed motor exhibits good performance on speed and torque control. Under a working frequency of 53.2 kHz, the maximum no-load speed and the maximum torque of the prototype are tested to be 53.3 rpm and of 27 mN·m.
Optimization of bandwidth in 60^o photonic crystal waveguide bends
Xing, P. F.; Borel, Peter Ingo; Frandsen, Lars Hagedorn;
2005-01-01
A systematic scheme utilizing 2D and 3D finite-difference time-domain calculations to design 60^o photonic crystal waveguide bends is presented. The method results in an improved transmission bandwidth from 70 to 160 nm in 2D simulations, and from 50 to 100 nm in 3D simulations. The design...
Tidal bending of glaciers: a linear viscoelastic approach
Reeh, Niels; Christensen, Erik Lintz; Mayer, Christoph
2003-01-01
glaciers are in the range 0.9-3 GPa. It has therefore been suggested that the elastic-beam model with a single value of E approximate to 1 GPa adequately describes tidal bending of glaciers.In contrast, laboratory experiments with ice give E =93 GPa, i.e. 3-10 times higher than the glacier-derived values...
Varmebesparelser ved løbende bygningsrenovering frem til 2050
Wittchen, Kim Bjarne; Kragh, Jesper
Som noget relativt nyt er der i bygningsreglementet indført krav til efterisolering af bygningsdele i forbindelse med den løbende renovering, som fx udskiftning af en tagbelægning. Hvor meget påvirker det netto-varmeforbruget frem til 2050, hvis der fortsættes med de gældende regler, og hvilken e...
Water-rich bending faults at the Middle America Trench
Naif, Samer; Key, Kerry; Constable, Steven; Evans, Rob L.
2015-09-01
The portion of the Central American margin that encompasses Nicaragua is considered to represent an end-member system where multiple lines of evidence point to a substantial flux of subducted fluids. The seafloor spreading fabric of the incoming Cocos plate is oriented parallel to the trench such that flexural bending at the outer rise optimally reactivates a dense network of normal faults that extend several kilometers into the upper mantle. Bending faults are thought to provide fluid pathways that lead to serpentinization of the upper mantle. While geophysical anomalies detected beneath the outer rise have been interpreted as broad crustal and upper mantle hydration, no observational evidence exists to confirm that bending faults behave as fluid pathways. Here we use seafloor electromagnetic data collected across the Middle America Trench (MAT) offshore of Nicaragua to create a comprehensive electrical resistivity image that illuminates the infiltration of seawater along bending faults. We quantify porosity from the resistivity with Archie's law and find that our estimates for the abyssal plain oceanic crust are in good agreement with independent observations. As the Cocos crust traverses the outer rise, the porosity of the dikes and gabbros progressively increase from 2.7% and 0.7% to 4.8% and 1.7%, peaking within 20 km of the trench axis. We conclude that the intrusive crust subducts twice as much pore water as previously thought, significantly raising the flux of fluid to the seismogenic zone and the mantle wedge.
Finite element analysis of damage in pipeline bends
Swart, A.E.; Karamanos, S.A.; Scarpas, A.; Blaauwendraad, J.
2010-01-01
The present paper describes a numerical formulation for the analysis of damage in steel pipeline bends. In particular, the numerical implementation of Gurson plasticity model is described in the framework of a special element, referred to as “tube element”. This is a three-node element, which simula
Effect of train carbody's parameters on vertical bending stiffness performance
Yang, Guangwu; Wang, Changke; Xiang, Futeng; Xiao, Shoune
2016-10-01
Finite element analysis(FEA) and modal test are main methods to give the first-order vertical bending vibration frequency of train carbody at present, but they are inefficiency and waste plenty of time. Based on Timoshenko beam theory, the bending deformation, moment of inertia and shear deformation are considered. Carbody is divided into some parts with the same length, and it's stiffness is calculated with series principle, it's cross section area, moment of inertia and shear shape coefficient is equivalent by segment length, and the fimal corrected first-order vertical bending vibration frequency analytical formula is deduced. There are 6 simple carbodies and 1 real carbody as examples to test the formula, all analysis frequencies are very close to their FEA frequencies, and especially for the real carbody, the error between analysis and experiment frequency is 0.75%. Based on the analytic formula, sensitivity analysis of the real carbody's design parameters is done, and some main parameters are found. The series principle of carbody stiffness is introduced into Timoshenko beam theory to deduce a formula, which can estimate the first-order vertical bending vibration frequency of carbody quickly without traditional FEA method and provide a reference to design engineers.
Predicting bending stiffness of randomly oriented hybrid panels
Laura Moya; William T.Y. Tze; Jerrold E. Winandy
2010-01-01
This study was conducted to develop a simple model to predict the bending modulus of elasticity (MOE) of randomly oriented hybrid panels. The modeling process involved three modules: the behavior of a single layer was computed by applying micromechanics equations, layer properties were adjusted for densification effects, and the entire panel was modeled as a three-...
Electrical Reliability of a Film-Type Connection during Bending
Ryosuke Mitsui
2015-10-01
Full Text Available With the escalating demands for downsizing and functionalizing mobile electronics, flexible electronics have become an important aspect of future technologies. To address limitations concerning junction deformation, we developed a new connection method using a film-type connector that is less than 0.1 mm thick. The film-type connector is composed of an organic film substrate, a UV-curable adhesive that deforms elastically under pressure, and electrodes that are arranged on the adhesive. The film-type connection relies on a plate-to-plate contact, which ensures a sufficient contact area. The electrical reliability of the film-type connection was investigated based on changes in the resistance during bending at curvature radii of 70, 50, 25, 10, 5, and 2.5 mm. The connection was bent 1000 times to investigate the reproducibility of the connector’s bending properties. The tests showed that no disconnections occurred due to bending in the vertical direction of the electrode, but disconnections were observed due to bending in the parallel direction at curvature radii of 10, 5, and 2.5 mm. In addition, the maximum average change in resistance was less than 70 milliohms unless a disconnection was generated. These results support the application of the new film-type connection in future flexible devices.
A Second Look at Brian Simon's "Bending the Rules"
Cox, Sue
2016-01-01
In this article the author revisits an important book: Brian Simon's "Bending the Rules: the Baker reform of education." Written by a key figure in the history of the journal FORUM as well as in the history of education, Simon's book documented the features of the Education Reform Bill of 1987 (the precursor to the Education Reform Act…
Band bending and electrical transport at chemically modified silicon surfaces
Lopinski, Greg; Ward, Tim; Hul'Ko, Oleksa; Boukherroub, Rabah
2002-03-01
High resolution electron energy loss spectroscopy (HREELS) and electrical transport measurements have been used to investigate how various chemical modifications give rise to band bending and alter the conductivity of Si(111) surfaces. HREELS is a sensitive probe of band bending through observations of the low frequency free carrier plasmon mode. For hydrogen terminated surfaces, prepared by the standard etch in ammonium flouride, HREELS measurements on both n and n+ substrates are consistent with nearly flat bands. Chlorination of these surfaces results in substantial upward band bending due to the strong electron withdrawing nature of the chlorine, driving the surface into inversion. The presence of this inversion layer on high resistivity n-type samples is observed through a substantial enhancement of the surface conductivity (relative to the H-terminated surface), as well as through broadening of the quasi-elastic peak in the HREELS measurements. We have also begun to examine organically modified silicon surfaces, prepared by various wet chemical reactions with the H-terminated surface. Decyl modified Si(111) surfaces are seen to exhibit a small degree of band bending, attributed to extrinsic defect states cause by a small degree of oxidation accompanying the modification reaction. The prospects of using conductivity as an in-situ monitor of the rate of these reactions will be discussed.
The Clinch Bend Regional Industrial Site and economic development opportunities
NONE
1995-12-31
This effort focuses initially on the Clinch Bend site. Other sites and developable tracts of land are identified with the assistance of communities in proximity to Oak Ridge, the State of Tennessee, and others, and compared with the projected site requirements for large industrial facilities.
A COMBINED HYBRID FINITE ELEMENT METHOD FOR PLATE BENDING PROBLEMS
Tian-xiao Zhou; Xiao-ping Xie
2003-01-01
In this paper, a combined hybrid method is applied to finite element discretization ofplate bending problems. It is shown that the resultant schemes are stabilized, i.e., theconvergence of the schemes is independent of inf-sup conditions and any other patch test.Based on this, two new series of plate elements are proposed.
Multiphase fluid structure interaction in bends and T-joints
Cargnelutti, M.F.; Belfroid, S.P.C.; Schiferli, W.; Osch, M.M.E. van
2010-01-01
Air-water experiments were carried out in a horizontal 1" pipe system to measure the magnitude of the forces induced by the multiphase flow. Forces and accelerations were measured on a number of bends and T-joint configurations for a wide range of operating conditions. Five different configurations
Multiphase fluid structure interaction in bends and T-joints
Cargnelutti, M.F.; Belfroid, S.P.C.; Schiferli, W.; Osch, M.M.E. van
2010-01-01
Air-water experiments were carried out in a horizontal 1" pipe system to measure the magnitude of the forces induced by the multiphase flow. Forces and accelerations were measured on a number of bends and T-joint configurations for a wide range of operating conditions. Five different configurations
Elastocapillary instability under partial wetting conditions: Bending versus buckling
Andreotti, Bruno; Marchand, Antonin; Das, Siddhartha; Snoeijer, Jacco H.
2011-01-01
The elastocapillary instability of a flexible plate plunged in a liquid bath is analyzed theoretically. We show that the plate can bend due to two separate destabilizing mechanisms, when the liquid is partially wetting the solid. For contact angles θe>π/2, the capillary forces acting tangential to t
High precision optical fiber alignment using tube laser bending
Folkersma, Ger; Römer, Gerardus Richardus, Bernardus, Engelina; Brouwer, Dannis Michel; Herder, Justus Laurens
2016-01-01
In this paper, we present a method to align optical fibers within 0.2 μm of the optimal position, using tube laser bending and in situ measuring of the coupling efficiency. For near-UV wavelengths, passive alignment of the fibers with respect to the waveguides on photonic integrated circuit chips
Springback prediction of three-dimensional variable curvature tube bending
Shen Zhang
2016-03-01
Full Text Available The springback phenomenon of tube bending occurs consequentially after unloading, which will affect the manufacturing accuracy and processing efficiency of the tubular products. In this article, the bending and springback processes of minor-diameter thick-walled tube are simulated by ABAQUS to reveal the springback laws. 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. The mathematic relationship of the radius before and after springback in the plane is built by approximate pure bending springback experiments. The springback on such planes is transformed into three dimensions. The tube axes are merged by first-order geometric (G1 continuity and then compensated with the modified function according to the axis complexity, so as to establish mathematic analytic model for springback prediction of three-dimensional variable curvature tube bending. Finally, the feasibility, reliability, and accuracy of the model are verified by finite element method and experiments.
Hydraulically controlled flexible arm can bend in any direction
Griffin, F. D.
1966-01-01
Arm assembly consisting of four flexible tubes controlled by a four-way hydraulic or pneumatic valve can bend in any direction. The flexible arm could be used for probing areas that cannot be reached by ordinary tools, handling hazardous materials, and for graph recording.
Bend-twist coupling potential of wind turbine blades
Fedorov, V.; Berggreen, C.
2014-06-01
In the present study an evaluation of the potential for bend-twist coupling effects in wind turbine blades is addressed. A method for evaluation of the coupling magnitude based on the results of finite element modeling and full-field displacement measurements obtained by experiments is developed and tested on small-scale coupled composite beams. In the proposed method the coupling coefficient for a generic beam is introduced based on the Euler-Bernoulli beam formulation. By applying the developed method for analysis of a commercial wind turbine blade structure it is demonstrated that a bend-twist coupling magnitude of up to 0.2 is feasible to achieve in the baseline blade structure made of glass-fiber reinforced plastics. Further, by substituting the glass-fibers with carbon-fibers the coupling effect can be increased to 0.4. Additionally, the effect of introduction of bend-twist coupling into a blade on such important blade structural properties as bending and torsional stiffness is demonstrated.
Teaching Cultural Geography with "Bend It like Beckham"
Algeo, Katie
2007-01-01
The British film "Bend It Like Beckham" (2002) is pedagogically useful in the cultural geography classroom for engaging students with core concepts, such as ethnicity, migration, acculturation, and assimilation, and with more advanced modes of analysis, such as the social construction of identity. Although the film depicts a particular…
Ultrathin 90-degree sharp bends for spoof surface plasmon polaritons
Yang, Yihao; Chen, Hongsheng; Xiao, Sanshui;
2015-01-01
surface plasmons around 90-degree sharp bends on ultrathin metallic films in the microwave regime. We demonstrate that by judiciously engineering the structure, the dispersion relation can be designed to reduce the scattering. Furthermore, the reflection can be suppressed by proper structural decoration...
Photoelastic stress analysis in mitred bend under internal pressure
Sawa, Yoshiaki
1987-12-01
The stress analysis and stress relaxation in mitred bend subjected to internal pressure have been studied by means of the photoelastic stress freezing method. The experimental results show that stress concentration occurs in the wedge tip of the intersectional plane and it is considerably influenced by the bent angle. Then, the stress relaxation was obtained by planing the wedge tip.
Schmidt, Hendrik; Heuer, Frank; Wilke, Hans-Joachim
2009-01-01
Dynamic stabilization devices have been introduced to clinics as an alternative to rigid fixation. The stiffness of these devices varies widely, whereas the optimal stiffness, achieving a predefined stabilization of the spine, is unknown. This study was focused on the determination of stiffness values for posterior stabilization devices achieving a flexible, semi-flexible or rigid connection between two vertebrae. An extensively validated finite element model of a lumbar spinal segment L4-5 with an implanted posterior fixation device was used in this study. The model was exposed to pure moments of 7.5 and 20Nm around the three principal anatomical directions, simulating flexion, extension, lateral bending and axial rotation. In parametrical studies, the influence of the axial and bending fixator stiffness on the spinal range of motion was investigated. In order to examine the validity of the computed results, an in-vitro study was carried out. In this, the influence of two posterior stabilization devices (DSS and rigidly internal fixator) on the segmental stabilization was investigated. The finite element (FE)-model predicted that each load direction caused a pairing of stiffness relations between axial and bending stiffness. In flexion and extension, however, the bending stiffness had a neglectable effect on the segmental stabilization, compared to the axial stiffness. In contrast, lateral bending and axial rotation were influenced by both stiffness parameters. Except in axial rotation, the model predictions were in a good agreement with the determined in-vitro data. In axial rotation, the FE-model predicted a stiffer segmental behavior than it was determined in the in-vitro study. It is usually expected that high stiffness values are required for a posterior stabilization device to stiffen a spinal segment. We found that already small stiffness values were sufficient to cause a stiffening. Using these data, it may possible to develop implants for certain clinical
Direct observation of T4 lysozyme hinge-bending motion by fluorescence correlation spectroscopy.
Yirdaw, Robel B; McHaourab, Hassane S
2012-10-01
Bacteriophage T4 Lysozyme (T4L) catalyzes the hydrolysis of the peptidoglycan layer of the bacterial cell wall late in the infection cycle. It has long been postulated that equilibrium dynamics enable substrate access to the active site located at the interface between the N- and C-terminal domains. Crystal structures of WT-T4L and point mutants captured a range of conformations that differ by the hinge-bending angle between the two domains. Evidence of equilibrium between open and closed conformations in solution was gleaned from distance measurements between the two domains but the nature of the equilibrium and the timescale of the underlying motion have not been investigated. Here, we used fluorescence fluctuation spectroscopy to directly detect T4L equilibrium conformational fluctuations in solution. For this purpose, Tetramethylrhodamine probes were introduced at pairs of cysteines in regions of the molecule that undergo relative displacement upon transition from open to closed conformations. Correlation analysis of Tetramethylrhodamine intensity fluctuations reveals hinge-bending motion that changes the relative distance and orientation of the N- and C-terminal domains with ≅ 15 μs relaxation time. That this motion involves interconversion between open and closed conformations was further confirmed by the dampening of its amplitude upon covalent substrate trapping. In contrast to the prevalent two-state model of T4L equilibrium, molecular brightness and number of particles obtained from cumulant analysis suggest that T4L populates multiple intermediate states, consistent with the wide range of hinge-bending angles trapped in the crystal structure of T4L mutants.
Binding by TRBP-dsRBD2 Does Not Induce Bending of Double-Stranded RNA.
Acevedo, Roderico; Evans, Declan; Penrod, Katheryn A; Showalter, Scott A
2016-06-21
Protein-nucleic acid interactions are central to a variety of biological processes, many of which involve large-scale conformational changes that lead to bending of the nucleic acid helix. Here, we focus on the nonsequence-specific protein TRBP, whose double-stranded RNA-binding domains (dsRBDs) interact with the A-form geometry of double-stranded RNA (dsRNA). Crystal structures of dsRBD-dsRNA interactions suggest that the dsRNA helix must bend in such a way that its major groove expands to conform to the dsRBD's binding surface. We show through isothermal titration calorimetry experiments that dsRBD2 of TRBP binds dsRNA with a temperature-independent observed binding affinity (KD ∼500 nM). Furthermore, a near-zero observed heat capacity change (ΔCp = 70 ± 40 cal·mol(-1)·K(-1)) suggests that large-scale conformational changes do not occur upon binding. This result is bolstered by molecular-dynamics simulations in which dsRBD-dsRNA interactions generate only modest bending of the RNA along its helical axis. Overall, these results suggest that this particular dsRBD-dsRNA interaction produces little to no change in the A-form geometry of dsRNA in solution. These results further support our previous hypothesis, based on extensive gel-shift assays, that TRBP preferentially binds to sites of nearly ideal A-form structure while being excluded from sites of local deformation in the RNA helical structure. The implications of this mechanism for efficient micro-RNA processing will be discussed.
Estimating the bending modulus of a FtsZ bacterial-division protein filament.
Cytrynbaum, Eric N; Li, Yongnan Devin; Allard, Jun F; Mehrabian, Hadi
2012-01-01
FtsZ, a cytoskeletal protein homologous to tubulin, is the principle constituent of the division ring in bacterial cells. It is known to have force-generating capacity in vitro and has been conjectured to be the source of the constriction force in vivo. Several models have been proposed to explain the generation of force by the Z ring. Here we re-examine data from in vitro experiments in which Z rings formed and constricted inside tubular liposomes, and we carry out image analysis on previously published data with which to better estimate important model parameters that have proven difficult to measure by direct means. We introduce a membrane-energy-based model for the dynamics of multiple Z rings moving and colliding inside a tubular liposome and a fluid model for the drag of a Z ring as it moves through the tube. Using this model, we estimate an effective membrane bending modulus of 500-700 pN nm. If we assume that FtsZ force generation is driven by hydrolysis into a highly curved conformation, we estimate the FtsZ filament bending modulus to be 310-390 pN nm(2). If we assume instead that force is generated by the non-hydrolysis-dependent intermediate curvature conformation, we find that B(f)>1400 pN nm(2). The former value sits at the lower end of the range of previously estimated values and, if correct, may raise challenges for models that rely on filament bending to generate force. © 2012 American Physical Society
Nitric oxide mediates gravitropic bending in soybean roots.
Hu, Xiangyang; Neill, Steven J; Tang, Zhangcheng; Cai, Weiming
2005-02-01
Plant roots are gravitropic, detecting and responding to changes in orientation via differential growth that results in bending and reestablishment of downward growth. Recent data support the basics of the Cholodny-Went hypothesis, indicating that differential growth is due to redistribution of auxin to the lower sides of gravistimulated roots, but little is known regarding the molecular details of such effects. Here, we investigate auxin and gravity signal transduction by demonstrating that the endogenous signaling molecules nitric oxide (NO) and cGMP mediate responses to gravistimulation in primary roots of soybean (Glycine max). Horizontal orientation of soybean roots caused the accumulation of both NO and cGMP in the primary root tip. Fluorescence confocal microcopy revealed that the accumulation of NO was asymmetric, with NO concentrating in the lower side of the root. Removal of NO with an NO scavenger or inhibition of NO synthesis via NO synthase inhibitors or an inhibitor of nitrate reductase reduced both NO accumulation and gravitropic bending, indicating that NO synthesis was required for the gravitropic responses and that both NO synthase and nitrate reductase may contribute to the synthesis of the NO required. Auxin induced NO accumulation in root protoplasts and asymmetric NO accumulation in root tips. Gravistimulation, NO, and auxin also induced the accumulation of cGMP, a response inhibited by removal of NO or by inhibitors of guanylyl cyclase, compounds that also reduced gravitropic bending. Asymmetric NO accumulation and gravitropic bending were both inhibited by an auxin transport inhibitor, and the inhibition of bending was overcome by treatment with NO or 8-bromo-cGMP, a cell-permeable analog of cGMP. These data indicate that auxin-induced NO and cGMP mediate gravitropic curvature in soybean roots.
Theory and algorithms to compute Helfrich bending forces: a review
Guckenberger, Achim; Gekle, Stephan
2017-05-01
Cell membranes are vital to shield a cell’s interior from the environment. At the same time they determine to a large extent the cell’s mechanical resistance to external forces. In recent years there has been considerable interest in the accurate computational modeling of such membranes, driven mainly by the amazing variety of shapes that red blood cells and model systems such as vesicles can assume in external flows. Given that the typical height of a membrane is only a few nanometers while the surface of the cell extends over many micrometers, physical modeling approaches mostly consider the interface as a two-dimensional elastic continuum. Here we review recent modeling efforts focusing on one of the computationally most intricate components, namely the membrane’s bending resistance. We start with a short background on the most widely used bending model due to Helfrich. While the Helfrich bending energy by itself is an extremely simple model equation, the computation of the resulting forces is far from trivial. At the heart of these difficulties lies the fact that the forces involve second order derivatives of the local surface curvature which by itself is the second derivative of the membrane geometry. We systematically derive and compare the different routes to obtain bending forces from the Helfrich energy, namely the variational approach and the thin-shell theory. While both routes lead to mathematically identical expressions, so-called linear bending models are shown to reproduce only the leading order term while higher orders differ. The main part of the review contains a description of various computational strategies which we classify into three categories: the force, the strong and the weak formulation. We finally give some examples for the application of these strategies in actual simulations.
Statistical analysis of the V-tool bending process parameters in the bending of HC260Y steel
J. Cumin
2016-04-01
Full Text Available This paper presents statistical analysis of the parameters in the V-tool bending process of the HC260Y steel. Assessment of the mathematical model and analysis of variance (ANOVA were performed within the design of experiments. The hydraulic testing machine Amsler and the developed V-tool were used in the experiments.
Ligament rupture and unstable burst behaviors of axial flaws in steam generator U-bends
Bahn, Chi Bum, E-mail: bahn@pusan.ac.kr [Pusan National University, 2 Busandaehak-ro 63 beon-gil, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Oh, Young-Jin [KEPCO Engineering & Construction Co. Inc., Seongnam 463-870 (Korea, Republic of); Majumdar, Saurin [Argonne National Laboratory, Lemont, IL 60439 (United States)
2015-11-15
Highlights: • Ligament rupture and unstable burst pressure tests were conducted with U-bends. • In general, U-bends showed higher ligament rupture and burst pressures than straight tubes. • U-bend test data was bounded by 90% lower limit of the probabilistic models for straight tubes. • Prediction models for straight tubes could be conservatively applied to U-bends. - Abstract: Incidents of U-bend cracking in steam generator (SG) tubes have been reported, some of which have led to tube rupture. Experimental and analytical modeling efforts to determine the failure criteria of flawed SG U-bends are limited. To evaluate structural integrity of flawed U-bends, ligament rupture and unstable burst pressure tests were conducted on 57 and 152 mm bend radius U-bends with axial electrical discharge machining notches. In general, the ligament rupture and burst pressures of the U-bends were higher than those of straight tubes with similar notches. To quantitatively address the test data scatter issue, probabilistic models were introduced. All ligament rupture and burst pressures of U-bends were bounded by 90% lower limits of the probabilistic models for straight tubes. It was concluded that the prediction models for straight tubes could be applied to U-bends to conservatively evaluate the ligament rupture and burst pressures of U-bends with axial flaws.
Molecular Dynamics of Lipid Bilayers
1989-08-09
The aim of this work is to study, by molecular dynamics simulations, the properties of lipid bilayers. We have applied the vectorizable, order-N...fast angle-dependent force/potential algorithms to treat angle bending and torsion. Keywords: Molecular dynamics , Lipid bilayers.
Numerical analysis of stress state during single point bending in DMTA examinations
A. Gnatowski
2008-05-01
Full Text Available Purpose: Determination of stresses at the change of Young′s modulus values in temperature function for samples made of PA 6.6 filled with glass fibre, by DMTA method, was the aim of work.Design/methodology/approach: Investigations were carried out for samples subjected to the one-axial bending. The change in the value of the dynamic Young modulus and the mechanical loss tangent in function of temperature and oscillation frequency by the DMTA method was determined. The computer simulations of changes of the stress and strain distribution within the range of elastic strains and the glass transition phase were done.Findings: Examinations made possible the determination of dynamic mechanical proprieties PA 6.6 filled with glass fibre and changes in the stress distribution during the dynamic loading of the sample in function of temperature. Higher values of the Young modulus were observed within the range of elasticity and the glass transition phase. The stress increased with the increase in Young′s modulus, at the strain generated from push rot oscillation.Research limitations/implications: The accuracy of used approximate method for computer simulations was not sufficient to indicate the Bielajew point.Practical implications: Investigated polymeric composite is characterized by viscoelastic properties, so all indicators of the physical and chemical properties depend on not only the time but and also the temperature.Originality/value: To characterize properties of investigated composite and to estimate the composite usage in particular conditions, dependences of the storage module and the mechanical losses tangent was determined in function of temperature at the one-axial bending.
The analysis of the bending stiffness and intensity of cylindrical tubes
SONG YuQuan; GUAN ZhiPing; NIE YuQin; GUAN XiaoFang
2007-01-01
Based on the mechanics of material, the bending stiffness and intensity of cylindrical bar and tube are analyzed. By comparing the cylindrical tube whose ratio of outside diameter to internal diameter is 0.7 with the cylindrical bar, it is concluded that when both of them have the same mass, the section stiffness of the cylindrical tube is three times that of the cylindrical bar; when both of them have the same external diameter, the mass of the cylindrical tube is only 1/2 that of the cylindrical bar, but the section stiffness of the cylindrical tube is 3/4 that of the cylindrical bar.By virtue of the elemental elastic-plastic theory, the yield stress of the liquid-filled cylindrical tube is investigated. Due to the incompressibility of liquid and the strain hardening effect of material, the yield stress of the liquid-filled tube is enlarged compared with the hollow tube, thus raising its bending intensity. Under the dynamic load, compared with the hollow tube, the impact resistance of the liquid-filled tube is also raised due to elastic recovery. Because the hydraulic pressures perpendicular to the inner surface are identical everywhere, the local stress concentration resulting from the ovalisation of the tube would be decreased, and the resistance to buckling would be improved.
The analysis of the bending stiffness and intensity of cylindrical tubes
2007-01-01
Based on the mechanics of material,the bending stiffness and intensity of cylin-drical bar and tube are analyzed. By comparing the cylindrical tube whose ratio of outside diameter to internal diameter is 0.7 with the cylindrical bar,it is concluded that when both of them have the same mass,the section stiffness of the cylindrical tube is three times that of the cylindrical bar;when both of them have the same external diameter,the mass of the cylindrical tube is only 1/2 that of the cylindrical bar,but the section stiffness of the cylindrical tube is 3/4 that of the cylindrical bar. By virtue of the elemental elastic-plastic theory,the yield stress of the liquid-filled cylindrical tube is investigated. Due to the incompressibility of liquid and the strain hardening effect of material,the yield stress of the liquid-filled tube is enlarged compared with the hollow tube,thus raising its bending intensity. Under the dy-namic load,compared with the hollow tube,the impact resistance of the liquid-filled tube is also raised due to elastic recovery. Because the hydraulic pressures per-pendicular to the inner surface are identical everywhere,the local stress concen-tration resulting from the ovalisation of the tube would be decreased,and the re-sistance to buckling would be improved.
Effect of Turbulence on Power for Bend-Twist Coupled Blades
Stäblein, Alexander R.; Hansen, Morten H.
2016-09-01
Bend-twist coupling of wind turbine blades reduces the structural loads of the turbine but it also results in a decrease of the annual energy production. The main part of the power loss can be mitigated by pretwisting the blade, but some power loss remains and previous studies indicate that it might be related to the dynamic response of bend-twist coupled blades in turbulent flow. This paper contains estimations of the power curve from nonlinear time simulations, a linear frequency domain based method and a normal distribution weighted average method. It is shown that the frequency domain based estimation is highly dependant on the validity of the linearized model, thus estimations are poor for operational points close to rated wind speed. The weighted average method gives good results if an appropriate standard deviation is known a priori. The nonlinear time simulations show that changes in power due to turbulence are similar for coupled and uncoupled blades. Power gains at low wind speeds are related to the curvature of the steady state power curve. Losses around rated wind speed are caused by the effects of controller switching between partial and full power operation.
Lee, Young Joon; Park, Jong Yeon; Kim, Kun Il; Sol, Chang Hyo; Kim, Byung Soo [Pusan National University College of Medicine, Pusan (Korea, Republic of)
1993-07-15
There are considerable discrepancies between clinical symptoms and imaging diagnosis in the localization of the responsible rediculopathy. The purpose of this study are to analyze the dynamic alteration of contrast filling of the spinal nerve sleeves during positional changes and determine how the abnormalities of nerve sleeves on lateral bending A-P views correlate with sciatica. The criteria indicating the root abnormality in functional myelography were (1) bad filling of ipsolateral root to sciatica and (2) good filling of contralateral root compared with those in neutral A-P view. Of total 77 patients, 67 had radiculopathy and 10 had no radiculopathy. In 23 (34.3%) of 67 patients with radiculopathy and 6 (60%) of 10 patients with no radiculopathy, their clinical symptoms well correlated with conventional myelographic findings. However, in 35 (52.2%) of 67 patients with radiculopathy and 6 (60%) of 10 patients with no radiculopathy, their symptoms well correlated with functional myelographic findings. This study suggest that the functional myelography using both lateral bending A-P views can be used as a complementary tool in the evaluation of the radiculopathy.
Competition between Bending and Internal Pressure Governs the Mechanics of Fluid Nanovesicles.
Vorselen, Daan; MacKintosh, Fred C; Roos, Wouter H; Wuite, Gijs J L
2017-03-28
Nanovesicles (∼100 nm) are ubiquitous in cell biology and an important vector for drug delivery. Mechanical properties of vesicles are known to influence cellular uptake, but the mechanism by which deformation dynamics affect internalization is poorly understood. This is partly due to the fact that experimental studies of the mechanics of such vesicles remain challenging, particularly at the nanometer scale where appropriate theoretical models have also been lacking. Here, we probe the mechanical properties of nanoscale liposomes using atomic force microscopy (AFM) indentation. The mechanical response of the nanovesicles shows initial linear behavior and subsequent flattening corresponding to inward tether formation. We derive a quantitative model, including the competing effects of internal pressure and membrane bending, that corresponds well to these experimental observations. Our results are consistent with a bending modulus of the lipid bilayer of ∼14kbT. Surprisingly, we find that vesicle stiffness is pressure dominated for adherent vesicles under physiological conditions. Our experimental method and quantitative theory represents a robust approach to study the mechanics of nanoscale vesicles, which are abundant in biology, as well as being of interest for the rational design of liposomal vectors for drug delivery.
Three-point bending test simulation on implant fpds with a bio-faithful model.
Vertucci, V; Montani, M; Arcuri, C; Cardelli, P
2017-01-01
It is well known by previous important studies that mandible flexes during different jaw movements. According to this assumption it is very important to know how implant supported fixed partial dentures could restrict mandibular movements and, could lead to excess strain accumulation that could modify the resolution of implant treatment. The aim of our project is to create a bio-faithful model able to recreate mandibular movements, during three point bending test methods of (FIXED -PARTIAL -DENTURES) FPDs, to avoid a not flexible metal base, where models' properties doesn't allow to obtain a bio-faithful simulation during testing phases. 2 implants (premium Sweden and Martina®) were embedded in mandible resin section to mimic osteointegrated implants in premolar and molar areas, in order to recreate a Kennedy Class II configuration. Our mandible test simulator was creating according to the measurement obtained according to the study of Schwartz-Dabney and Dechow (2002). Sample so created is tested with testing machine (Instron 5566(®), UK) adopting the three point bending mechanical tests configuration. We can admit that oral cavity is a bio-dynamic system, where different variables incurr, so it's very important that experimental conditions simulate clinical environment. Experimentation should be based on the correlation between the failure mechanisms exhibited for in vitro samples and those observed in fractured clinical prostheses made of the same composition and processing conditions. A bio-faithful model could reduce this wide range between in vitro and in vivo study experimentation.
Song Cen; Xiangrong Fu; Yuqiu Long; Hongguang Li; Zhenhan Yao
2007-01-01
Recently, some new quadrilateral finite elements were successfully developed by the Quadrilateral Area Coordinate (QAC) method. Compared with those traditional models using isoparametric coordinates, these new models are less sensitive to mesh distortion. In this paper, a new displacement-based, 4-node 20-DOF (5-DOF per node)quadrilateral bending element based on the first-order shear deformation theory for analysis of arbitrary laminated composite plates is presented. Its bending part is based on the element AC-MQ4, a recent-developed high-performance Mindlin-Reissner plate element formulated by QAC method and the generalized conforming condition method; and its in-plane displacement fields are interpolated by bilinear shape functions in isoparametric coordinates. Furthermore,the hybrid post-processing procedure, which was firstly proposed by the authors, is employed again to improve the stress solutions, especially for the transverse shear stresses. The resulting element, denoted as AC-MQ4-LC, exhibits excellent performance in all linear static and dynamic numerical examples. It demonstrates again that the QAC method, the generalized conforming condition method, and the hybrid post-processing procedure are efficient tools for developing simple, effective and reliable finite element models.
Flow visualization study of inverted U-bend two-phase flow
Ishii, M.; Kim, S.B.; Lee, R.
1986-12-01
A hot-leg U-bend experiment was performed. The experimental condition simulated the two-phase flow in a B and W primary loop during a small break loss of coolant accident or during some other abnormal transients. The loop design was based on the scaling criteria developed previously and the loop was operated either in a natural circulation mode or in a forced circulation mode using nitrogen gas and water. The two-phase flow regimes at the hot-leg were identified on the basis of visual observation. The phase separation at the top of the inverted U-bend was observed at low gas flow rate. The void fractions were measured using differential pressure transducers and compared with the prediction from the drift-flux model. The natural circulation flow interruption occurred in two different modes, namely, quasi-periodic and semi-permanent modes. This phenomenon is mainly dependent on the difference in the hydrostatic head in the riser and downcomer, and the flow regime at hot-leg. Besides this flow interruption phenomenon, dynamic flow instabilities of considerable amplitudes have been observed.
Numerical Investigation of Bending-Body Projectile Aerodynamics for Maneuver Control
Youn, Eric; Silton, Sidra
2015-11-01
Precision munitions are an active area of research for the U.S. Army. Canard-control actuators have historically been the primary mechanism used to maneuver fin-stabilized, gun-launched munitions. Canards are small, fin-like control surfaces mounted at the forward section of the munition to provide the pitching moment necessary to rotate the body in the freestream flow. The additional lift force due to the rotated body and the canards then alters the flight path toward the intended target. As velocity and maneuverability requirements continue to increase, investigation of other maneuver mechanisms becomes necessary. One option for a projectile with a large length-to-diameter ratio (L/D) is a bending-body design, which imparts a curvature to the projectile body along its axis. This investigation uses full Navier-Stokes computational fluid dynamics simulations to evaluate the effectiveness of an 8-degree bent nose tip on an 8-degree bent forward section of an L/D =10 projectile. The aerodynamic control effectiveness of the bending-body concept is compared to that of a standard L/D =10 straight-body projectile as well as that of the same projectile with traditional canards. All simulations were performed at supersonic velocities between Mach 2-4.
Nowroozi, B N; Brainerd, E L
2012-10-07
Unlike mammalian, disc-shaped intervertebral joints (IVJs), the IVJs in fishes are biconid structures, filled with fluid and thought to act as hydrostatic hinge joints during swimming. However, it remains unclear which IVJ structures are dominant in mechanical resistance to forces in fishes, and whether variation in these tissues might impact the function of the vertebral column along its length. Here, we measured the dynamic mechanical behaviour of IVJs from striped bass, Morone saxatilis. During lateral bending, angular stiffness was significantly lower in the caudal and cervical regions, relative to the abdominal region. The neutral zone, defined as the range of motion (ROM) at bending moments less than 0.001 Nm, was longer in the caudal relative to the abdominal IVJs. Hysteresis was 30-40% in all regions, suggesting that IVJs may play a role in energy dissipation during swimming. Cutting the vertical septum had no statistically significant effect, but cutting the encapsulating tissues caused a sharp decline in angular stiffness and a substantial increase in ROM and hysteresis. We conclude that stiffness decreases and ROM increases from cranial to caudal in striped bass, and that the encapsulating tissues play a prominent role in mechanical variation along the length of the vertebral column.
EPA Regional Administrator Highlights the Benefits of Reducing Food Waste in South Bend
(SOUTH BEND, IND. - November 5, 2015) U.S. Environmental Protection Agency Regional Administrator Susan Hedman joined South Bend Mayor Pete Buttigieg today at Ivy Tech Community College's culinary school to highlight the benefits of diverting food waste fr
Novel low-loss 60° bends in photonic crystal waveguides
Thorhauge, Morten; Frandsen, Lars Hagedorn; Borel, Peter Ingo;
2004-01-01
A novel type of 60 degree photonic crystal waveguide bend has been designed, simulated and fabricated in silicon-on-insulator material utilizing deep ultraviolet lithography. Loss-free bending has been observed in certain wavelength regions....
Hargittai, Magdolna; Veszprémi, Tamás; Pasinzki, Tibor
1994-09-01
All geometrical parameters, including bond lengths, are influenced by large-amplitude vibrations. The magnitude of this effect was examined for metal dihalides performing large-amplitude bending motions, using CaCl 2 as an example. By using quantum chemical calculations it was shown that the effect of bending on the bond length is very sensitive to the choice of basis set. A dynamic electron diffraction analysis, augmented with quantum chemical calculations, revealed that the effect of bending on the bond length is of moderate magnitude within experimental error. This fact contrasts with the consequences of other motions, in particular stretching, that must always be accounted for in any meaningful comparison of experimental and computed structures.
Analysis of flagellar bending in hamster spermatozoa: characterization of an effective stroke.
Kinukawa, Masashi; Ohmuro, Junko; Baba, Shoji A; Murashige, Sunao; Okuno, Makoto; Nagata, Masao; Aoki, Fugaku
2005-12-01
The mechanism by which flagella generate the propulsive force for movement of hamster spermatozoa was analyzed quantitatively. Tracing points positioned 30, 60, 90, and 120 microm from the head-midpiece junction on the flagellum revealed that they all had zigzag trajectories. These points departed from and returned to the line that crossed the direction of progression. They moved along the concave side (but not the convex side) of the flagellar envelope that was drawn by tracing the trajectory of the entire flagellum. To clarify this asymmetry, the bending rate was analyzed by measuring the curvatures of points 30, 60, 90, and 120 microm from the head-midpiece junction. The bending rate was not constant through the cycle of flagellar bending. The rate was higher when bending was in the direction described by the curve of the hook-shaped head (defined as a principal bend [P-bend]) to the opposite side (R-bend). We measured a lower bending rate in the principal direction (R-bend to P-bend). To identify the point at which the propulsive force is generated efficiently within the cycle of flagellar bending, we calculated the propulsive force generated at each point on the flagellum. The value of the propulsive force was positive whenever the flagellum bent from an R-bend to a P-bend (when the bending rate was lowest). By contrast, the propulsive force value was zero or negative when the flagellum bent in the other direction (when the bending rate was higher). These results indicate that flagellar bending in hamster spermatozoa produces alternate effective and ineffective strokes during propulsion.
The Strength of PIN-PMN-PT Single Crystals under Bending with a Longitudinal Electric Field
2011-04-06
The strength of PIN– PMN – PT single crystals under bending with a longitudinal electric field This article has been downloaded from IOPscience. Please...COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE The Strength Of PIN- PMN - PT Single Crystals Under Bending With A Longitudinal Electric Field... PMN ? PT ) single crystals was measured using a four point bending apparatus with a longitudinal electric field applied to the bar during bending. The
Jui-Chang Lin; Kingsun Lee
2015-01-01
The three-dimensional tube (or pipe) is manufactured by CNC tube bending machine. The key techniques are determined by tube diameter, wall thickness, material, and bending radius. The obtained technique through experience and the trial and error method is unreliable. Finite element method (FEM) simulation for the tube bending process before production can avoid wasting manpower and raw materials. The computer-aided engineering (CAE) software ABAQUS 6.12 is applied to simulate bending characte...
A new strain based brick element for plate bending
L. Belounar
2014-03-01
Full Text Available This paper presents the development of a new three-dimensional brick finite element by the use of the strain based approach for the linear analysis of plate bending. The developed element has the three essential external degrees of freedom (U, V and W at each of the eight corner nodes as well as at the centroidal node. The displacement field of the developed element is based on assumed functions for the various strains satisfying the compatibility equations and the static condensation technique is used for the internal node. The performance of this element is evaluated on several problems related to thick and thin plate bending in linear analysis. The obtained results show the good performances and accuracy of the present element.
Flow resistance in a compound gravel-bed bend
Hossein Afzalimehr; Manouchehr Heidarpour; Alireza Salimi
2006-12-01
In this paper, the effect of a gravel-bed in a compound bend (similar to sinusoidal top view) of a natural river (Zayandehrud River ﬂowing through Isfahan, Iran) has been investigated for ﬂow resistance analysis, measuring the velocity with a micro current meter. The data were analysed and the following observations were made. In a compound bend, the law of the wall can be valid for up to 66% of the ﬂow depth from the bed. The parabolic law is the most effective method for the determination of shear velocity. Based on the existing criteria for verifying the equilibrium boundary layer, the ﬂow cannot be in equilibrium. The shear stress distribution and the sediment transport parameters have considerable inﬂuence on resistance to ﬂow. Froude number and the ﬂow depth relative to the representative gravel size have little effect on the ﬂow resistance estimation.
An analytic solution to asymmetrical bending problem of diaphragm coupling
无
2008-01-01
Because rigidity of either hub or rim of diaphragm coupling is much greater than that of the disk, and asymmetrical bending is under the condition of high speed revolution, an assumption is made that each circle in the middle plane before deforma-tion keeps its radius unchanged after deformation, but the plane on which the circle lies has a varying deflecting angle. Based on this assumption, and according to the principle of energy variation, the corresponding Euler's equation can be obtained, which has the primary integral. By neglecting some subsidiary factors, an analytic solution is obtained. Applying these formulas to a hyperbolic model of diaphragm, the results show that the octahedral shear stress varies less along either radial or thickness direction, but fluctu-ates greatly and periodically along circumferential direction. Thus asymmetrical bending significantly affects the material's fatigue.
A Low Frequency FBG Accelerometer with Symmetrical Bended Spring Plates
Fufei Liu
2017-01-01
Full Text Available To meet the requirements for low-frequency vibration monitoring, a new type of FBG (fiber Bragg grating accelerometer with a bended spring plate is proposed. Two symmetrical bended spring plates are used as elastic elements, which drive the FBG to produce axial strains equal in magnitude but opposite in direction when exciting vibrations exist, leading to doubling the wavelength shift of the FBG. The mechanics model and a numerical method are presented in this paper, with which the influence of the structural parameters on the sensitivity and the eigenfrequency are discussed. The test results show that the sensitivity of the accelerometer is more than 1000 pm/g when the frequency is within the 0.7–20 Hz range.
Elasticity solutions for functionally graded plates in cylindrical bending
YANG Bo; DING Hao-jiang; CHEN Wei-qiu
2008-01-01
The plate theory of functionally graded materials suggested by Mian and Spencer is extended to analyze the cylindrical bending problem of a functionally graded rectangular plate subject to uniform load. The expansion formula for displacements is adopted. While keeping the assumption that the material parameters can vary along the thickness direction in an arbitrary fashion, this paper considers orthotropic materials rather than isotropic materials. In addition, the traction-free condition on the top surface is replaced with the condition of uniform load applied on the top surface. The plate theory for the particular case of cylindrical bending is presented by considering an infinite extent in the y-direction. Effects of boundary conditions and material inhomogeneity on the static response of functionally graded plates are investigated through a numerical example.
Bending and buckling behavior analysis of foamed metal circular plate.
Fan, Jian Ling; Ma, Lian Sheng; Zhang, Lu; De Su, Hou
2016-07-04
This paper establishes a density gradient model along the thickness direction of a circular plate made of foamed material. Based on the first shear deformation plate theory, the result is deduced that the foamed metal circular plate with graded density along thickness direction yields axisymmetric bending problem under the action of uniformly distributed load, and the analytical solution is obtained by solving the governing equation directly. The analyses on two constraint conditions of edge radial clamping and simply supported show that the density gradient index and external load may affect the axisymmetric bending behavior of the plate. Then, based on the classical plate theory, the paper analyzes the behavior of axisymmetric buckling under radial pressure applied on the circular plate. Shooting method is used to obtain the critical load, and the effects of gradient nature of material properties and boundary conditions on the critical load of the plate are analyzed.
Bending characteristic of a cantilevered magnetostrictive film-substrate system
B.; Narsu
2007-01-01
The bending problem of a film-substrate cantilever with arbitrary film-to-substrate thickness ratio is solved exactly by employing the force equilibrium equation, and then the optimization and application of the bending characteristic of the magne-tostrictive cantilever is discussed. Furthermore, the influence of geometrical and physical parameters of the two cantilever components on the maximum free-end deflection of the cantilever is addressed. The results indicate that as the substrate thickness is kept constant, the greater film-to-substrate stiffness ratio will induce a larger deflection, while for the case of fixed total cantilever thickness, the optimal cantilever deflection is independent of the physical parameters of the materials such as Young’s modulus and Poisson’s ratio.
Bending characteristic of a cantilevered magnetostrictive film-substrate system
B. Narsu; YUN GuoHong
2007-01-01
The bending problem of a film-substrate cantilever with arbitrary film-to-substrate thickness ratio is solved exactly by employing the force equilibrium equation, and then the optimization and application of the bending characteristic of the magnetostrictive cantilever is discussed. Furthermore, the influence of geometrical and physical parameters of the two cantilever components on the maximum free-end deflection of the cantilever is addressed. The results indicate that as the substrate thickness is kept constant, the greater film-to-substrate stiffness ratio will induce a larger deflection, while for the case of fixed total cantilever thickness, the optimal cantilever deflection is independent of the physical parameters of the materials such as Young's modulus and Poisson's ratio.
Elastoswellability: Will it bend or will it buckle?
Holmes, Douglas; Pandey, Anupam
2013-03-01
Soft mechanical structures such as biological tissues and gels exhibit motion, instabilities, and large morphological changes when subjected to external stimuli. Swelling is a robust approach for inducing structural change as it occurs naturally in humid environments and can be easily adapted for industrial design. Small volumes of fluid that interact favorably with a material can cause large, dramatic, and geometrically nonlinear deformations including beam bending, plate buckling, and surface wrinkling. In this talk we address an overarching question regarding swelling-induced deformations: will the structural change occur globally, or will it be confined to the material's surface? We introduce a materials and geometry defined transition point that describes a fluid-structure's characteristic ``elastoswellability'' lengthscale. By locally swelling unconstrained slender beams and plates with solvents of varying solubility, we identify a transition between local surface wrinkling and global structural bending.
Bending and rotational behaviour of semi-continuous composite beams
2008-01-01
Stresses and deflections were measured in various semi-continuous composite beams.The bending and rotational capacities of the composite connections were measured in terms of beam curvatures and deflections by using two full-scale semi-rigid composite frames with monotonic loadings.The effect of semi-rigid connections on the performance of composite beams with various loadings was compared with predictions and codes.The tests show that the semi-continuous composite beams are more economic and effective than the simple or continuous composite beams.The semi-rigid connections affect the bending capacities and beam deflections,so the connection behavior should be considered in the design of composite beams.Yielding analysis of the steel beam bottom flange has some influence on the deflection calculation of composite beams.
A Topological Approach to Bend-Twist Maps with Applications
Anna Pascoletti
2011-01-01
Full Text Available In this paper we reconsider, in a purely topological framework, the concept of bend-twist map previously studied in the analytic setting by Tongren Ding in (2007. We obtain some results about the existence and multiplicity of fixed points which are related to the classical Poincaré-Birkhoff twist theorem for area-preserving maps of the annulus; however, in our approach, like in Ding (2007, we do not require measure-preserving conditions. This makes our theorems in principle applicable to nonconservative planar systems. Some of our results are also stable for small perturbations. Possible applications of the fixed point theorems for topological bend-twist maps are outlined in the last section.
Influence of bending test configuration on cracking behavior of FRC
Finazzi, Silvia; Paegle, Ieva; Fischer, Gregor;
2014-01-01
This paper describes an investigation of the influence of the testing configuration for Fiber Reinforced Concrete in bending and aims at evaluating the influence of the test configuration details on the characterization of the material. Two different types of FRC, Steel Fiber Reinforced Concrete...... (SFRC) and Engineered Cementitious Composites (ECC), were tested and are described in this study. The materials were chosen so that one of them would be strain hardening (ECC) and the other tension softening (SFRC). Notched and un-notched three- and four-point bending tests were carried out to determine...... the flexural load-deformation response of FRC. This research focuses particularly on the influence of the appearance and depth of the notch on the cracking behavior of FRC. For this purpose, several specimens, both un-notched and notched with different depths of the notch (25 mm and 45 mm), were tested...
Negative bending mode curvature via Robin boundary conditions
Adams, Samuel D. M.; Craster, Richard V.; Guenneau, Sébastien
2009-06-01
We examine the band spectrum, and associated Floquet-Bloch eigensolutions, arising in straight walled acoustic waveguides that have periodic structure along the guide. Homogeneous impedance (Robin) conditions are imposed along the guide walls and we find that in certain circumstances, negative curvature of the lowest (bending) mode can be achieved. This is unexpected, and has not been observed in a variety of physical situations examined by other authors. Further unexpected properties include the existence of the bending mode only on a subset of the Brillouin zone, as well as permitting otherwise unobtainable velocities of energy transmission. We conclude with a discussion of how such boundary conditions might be physically reproduced using effective conditions and homogenization theory, although the methodology to achieve these effective conditions is an open problem. To cite this article: S.D.M. Adams et al., C. R. Physique 10 (2009).
A Low Frequency FBG Accelerometer with Symmetrical Bended Spring Plates
Liu, Fufei; Dai, Yutang; Karanja, Joseph Muna; Yang, Minghong
2017-01-01
To meet the requirements for low-frequency vibration monitoring, a new type of FBG (fiber Bragg grating) accelerometer with a bended spring plate is proposed. Two symmetrical bended spring plates are used as elastic elements, which drive the FBG to produce axial strains equal in magnitude but opposite in direction when exciting vibrations exist, leading to doubling the wavelength shift of the FBG. The mechanics model and a numerical method are presented in this paper, with which the influence of the structural parameters on the sensitivity and the eigenfrequency are discussed. The test results show that the sensitivity of the accelerometer is more than 1000 pm/g when the frequency is within the 0.7–20 Hz range. PMID:28117740
Bending properties of different REBCO coated conductor tapes and Roebel cables at T = 77 K
Otten, Simon; Kario, Anna; Kling, Andrea; Goldacker, Wilfried
2016-12-01
Application of REBCO coated conductors in coils or cables involves deformation of the conductor in different modes, such as in-plane bending, out-of-plane bending and torsion. For example, the dipole magnet designs in the EuCARD-2 project require bending radii as low as 7.5 mm, inducing significant bending strain in the REBCO layer. In this paper, we investigate the effect of out-of-plane bending on the current-carrying properties of coated conductors from different manufacturers. The samples are manipulated by means of a Goldacker-type bending rig, which allows continuous bending at T = 77 K. By reversal to R=∞ after each bending step, the reversible strain effect is separated from irreversible degradation. All tested conductors are found to tolerate compressive bending to a radius of 6 mm with less than 5% irreversible degradation of the critical current. The magnitude of the reversible strain effect shows a large variation among the samples. The effect of out-of-plane bending on Roebel cables is investigated as well, and the results are compared to the bending characteristic of single conductors. The results show no detrimental effect of the cable assembly on the bending properties within the constraints of the test.
Advanced System Identification for High-rise Building Using Shear-Bending Model
Kohei Fujita
2016-11-01
Full Text Available In order to identify physical model parameters of a high-rise building, a new story stiffness identification method is presented based on a shear-bending model and the identification function. Although a shear building model may be the simplest conventional model for representing tall buildings, the system identification (SI method using that model is not necessarily appropriate. This is because the influence of bending deformation is predominant in such high-rise buildings. For this reason, a shear-bending model is used where the shear and bending stiffnesses are unknown. In the previous researches using the shear-bending model, it was difficult to identify the bending stiffnesses stably and reliably. In this paper, to overcome such instability of bending stiffness identification of the shear-bending model, a new SI algorithm using both the shear model and the shear-bending model is presented. The proposed SI algorithm is based on the observation that the fundamental-mode shape of the identified shear model is similar to that of the shear-bending model identified in the previous SI method. In order to verify the advanced SI method, two different 20-story building models are investigated in the numerical simulations. From the results of the simulations, both the shear and bending stiffnesses of the shear-bending model are identified reliably and stably in the proposed SI method.
Rotating Square-Ended U-Bend Using Low-Reynolds-Number Models
Konstantinos-Stephen P. Nikas
2005-01-01
bend is better reproduced by the low-Re models. Turbulence levels within the rotating U-bend are underpredicted, but DSM models produce a more realistic distribution. Along the leading side, all models overpredict heat transfer levels just after the bend. Along the trailing side, the heat transfer predictions of the low-Re DSM with the NYap, are close to the measurements.
Requirements for Bend Insensitive Fiber in Millimeter-Wave Fronthaul Systems
Rommel, Simon; Cavalcante, Lucas Costa Pereira; Vegas Olmos, Juan José;
2015-01-01
The impact of fiber bending on mm-wave radioover-fiber transmission is investigated and the need for bend insensitive fiber for front-haul installation confirmed. A 70m Wband hybrid photonic-wireless link including bend insensitive fiber is demonstrated with BER
A new set of bending Td symmetry coordinates for MX4 molecules.
Schmidling, David
2013-12-15
The conventional set of Td symmetry coordinates for the bending modes of MX4 molecules can lead to ambiguous geometries when displacements from equilibrium are large. It is proposed here to use internal coordinates that are haversines of the bending angles divided by their sum. The A1 representation becomes a constant, enabling recovery of the bending angles unambiguously, analytically, and without approximation.
Topology design and fabrication of an efficient double 90° photonic crystal waveguide bend
Jensen, Jakob Søndergaard; Sigmund, Ole; Frandsen, Lars Hagedorn
2005-01-01
We have designed and fabricated a novel 90 bend in a photonic crystal waveguide. The design was obtained using topology optimization and the fabricated waveguide displays a bend loss for transverse-electric-polarized light of less than 1 dB per bend in a 200-nm wavelength range....
Wooden models of an AA quadrupole between bending magnets
1978-01-01
At two points in the AA lattice, a quadrupole (QDN, defocusing, narrow) was tightly wedged between two bending magnets (BST, short, wide). This picture of wooden models lets one imagine the strong interaction between their magnetic fields. There was no way one could calculate with the necessary accuracy the magnetic effects and their consequences for the machine optics. The necessary corrections were made after measurements with a circulating beam, in a tedious iterative procedure, with corrrection coils and shims.
Designing CNC Knit for Hybrid Membrane And Bending Active Structures
Tamke, Martin; Holden Deleuran, Anders; Gengnagel, Christoph
2015-01-01
Recent advances in computation allow for the integration of design and simulation of highly interrelated systems, such as hybrids of structural membranes and bending active elements. The engaged complexities of forces and logistics can be mediated through the development of materials with project...... means to design, specify, make and test CNC knit as material for hybrid structures in architectural scale. This paper shares the developed process, identifies challenges, potentials and future work...
Influence of Whipping on Long term Vertical Bending Moment
Baarholm, G. S.; Jensen, Jørgen Juncher
2004-01-01
This paper is concerned with estimating the response value corresponding to a long return period, say a twenty years. Time domain simulation is required to obtain the nonlinear response, and long time series are required to limit the statistical uncertainty in the simulations. It is crucial to in......). Results are presented for the S-175 container ship, (15th & 16th ITTC Seakeeping Committee 1983). The analysis shoes that whipping increases the vertical bending moment and that the correlation is significant...
Bending rigid molecular rods: formation of oligoproline macrocycles.
Scully, Conor C G; Rai, Vishal; Poda, Gennadiy; Zaretsky, Serge; Burns, Darcy C; Houliston, R Scott; Lou, Tiantong; Yudin, Andrei K
2012-12-01
Bent but not broken: cyclic oligoprolines are accessed in a reaction that effectively bends rigid oligoproline peptides (see scheme; TBDMS=tert-butyldimethylsilyl). The stitching is accomplished during macrocyclization enabled by aziridine aldehydes and isocyanides. Molecular modeling studies suggest that electrostatic attraction between the termini of the linear peptide is pivotal for macrocyclization. The macrocycles were studied by circular dichroism with a polyproline II structure being observed in larger macrocycles.
Springback of thick sheet AHSS subject to bending under tension
Chalal, Hocine; RACZ, Sever-Gabriel; BALAN, Tudor
2012-01-01
http://www.sciencedirect.com/science/article/pii/S0020740312000677; International audience; The springback behavior of four advanced high-strength sheet steels (Dual-Phase, TRIP, ferrite-bainite) with thicknesses ranging from 1.2 to 4 mm was investigated by means of the bending-under-tension (BUT) test. The applicability of several guidelines from the literature was investigated experimentally and numerically. The monotonic decrease of springback as back force increased was confirmed for this...
Bending and Focusing with Plasmas and Crystals - Potential and Challenges
Zimmermann, F
2013-01-01
This talk review the potential of plasmas and crystals for focusing and bending high-energy charged particle beams. It covers topics like plasma lenses, plasma wigglers, plasma dipoles, crystal channeling & reflection, radiation in crystals, crystal accelerators, crystalline beams and ultimate limitations. Past, ongoing or required R&D efforts are highlighted. Invited presentation at EuCARD'13 "Visions for the Future of Particle Accelerators," CERN, 11 June 2013.
Bending light on demand by holographic sculpturing its wavefront
Latychevskaia, Tatiana
2015-01-01
A classical light beam propagates along a straight line and does not bend unless in a medium of variable refractive index. It is well known that by modifying the wavefront in a certain manner, the light intensity can be turned into a certain shape. Examples are optical lenses or Fresnel Zone Plates for focusing an incident wave to a point at the focal plane. Another example are Airy beams created by modifying the phase distribution of the wavefront into an Airy function resulting in a bending of the light intensity while propagating. A further example is holography, where the phase of the wavefront passing through a hologram is changed to mimic the object wavefront, thus providing the illusion that the original object is present in space. However, all these known techniques allow for limited light modifications: either focusing within a limited region in space2 or shaping a certain class of parametric curves along the optical axis or creating a bend in a quadratic-dependent declination as in the case of Airy ...
Bending rigidity of type I collagen homotrimer fibrils
Han, Sejin; Leikin, Sergey; Losert, Wolfgang
2009-03-01
Normal type I collagen is an α1(I)2α2(I) heterotrimeric triple helix, but α1(I)3 homotrimers are also found in fetal tissues and various pathological conditions, e.g., causing bone fragility and reducing tendon tensile strength. It remains unclear whether homotrimers alter mechanical properties of individual fibrils or affect tissues by altering their organization at a higher level. To address this question, we investigated how homotrimers affect fibril bending rigidity. Homotrimer fibrils have been shown to be more loosely packed so that we expected them to be more susceptible to bending. However, homotrimer fibrils were more rigid despite being thinner and more hydrated. To quantify fibril rigidity, we analyzed their shape by Fourier decomposition, determined the correlation function for the direction along each fibril, and calculated the distribution of local fibril curvature. The estimated persistence length of homotrimer fibrils was 3 ˜ 10 times longer than for heterotrimer fibrils, indicating much higher bending rigidity of homotrimer fibrils.
Brightness of synchrotron radiation from undulators and bending magnets
Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2014-07-15
We consider the maximum of the Wigner distribution (WD) of synchrotron radiation (SR) fields as a possible definition of SR source brightness. Such figure of merit was originally introduced in the SR community by Kim. The brightness defined in this way is always positive and, in the geometrical optics limit, can be interpreted as maximum density of photon flux in phase space. For undulator and bending magnet radiation from a single electron, the WD function can be explicitly calculated. In the case of an electron beam with a finite emittance the brightness is given by the maximum of the convolution of a single electron WD function and the probability distribution of the electrons in phase space. In the particular case when both electron beam size and electron beam divergence dominate over the diffraction size and the diffraction angle, one can use a geometrical optics approach. However, there are intermediate regimes when only the electron beam size or the electron beam divergence dominate. In this asymptotic cases the geometrical optics approach is still applicable, and the brightness definition used here yields back once more the maximum photon flux density in phase space. In these intermediate regimes we find a significant numerical disagreement between exact calculations and the approximation for undulator brightness currently used in literature. We extend the WD formalism to a satisfactory theory for the brightness of a bending magnet. We find that in the intermediate regimes the usually accepted approximation for bending magnet brightness turns out to be inconsistent even parametrically.
Electro-active material (EAM) based bend sensors
LaComb, Ronald; LaComb, Julie
2010-04-01
The capability to accurately estimate strain and orientation of cables in an undersea environment is important for a multitude of applications. One way to estimate the positional location of a submersed cable is to utilize a network of distributed bend sensors providing inputs to a curve fitting algorithm. In this work commercially available bend sensors are characterized for small deflections. In addition proto-type devices are presented which can potentially improve device sensitivity. Commercially available bend sensors are based upon electro-active materials and variable resistance materials. Electro-active materials (EAM) are known for their actuator functionality but certain EAMs are capable of sensing as well. New advances in materials such as Ionic Polymer Metal Composites (IPMC) are proving suitable for quasi-static sensor applications. These sensors are low power, conformal and produce directionally dependent output voltages which are linearly proportional to deflection, with voltage polarity representative of the deflection direction. IPMCs are capable of being morphed for increased sensitivity. Variable resistivity sensors are based on smart epoxy polymer and carbon loaded inks. These sensors are inexpensive and conformal and unlike EAMs provide static measurements.
On-line fuzzy logic control of tube bending
Lieh, Junghsen; Li, Wei Jie
2005-11-01
This paper describes the simulation and on-line fuzzy logic control of tube bending. By combining elasticity and plasticity theories, a conventional model was developed. The results from simulation were compared with those obtained from testing. The experimental data reveal that there exists certain level of uncertainty and nonlinearity in tube bending, and its variation could be significant. To overcome this, a on-line fuzzy logic controller with self-tuning capabilities was designed. The advantages of this on-line system are (1) its computational requirement is simple in comparison with more algorithmic-based controllers, and (2) the system does not need prior knowledge of material characteristics. The device includes an AC motor, a servo controller, a forming mechanism, a 3D optical sensor, and a microprocessor. This automated bending machine adopts primary and secondary errors between the actual response and desired output to conduct on-line rule reasoning. Results from testing show that the spring back angle can be effectively compensated by the self- tuning fuzzy system in a real-time fashion.
Bending strength and holding power of tibial locking screws.
Lin, J; Lin, S J; Chiang, H; Hou, S M
2001-04-01
The bending strength and holding power of two types of specially designed tibial locking devices, a both-ends-threaded screw and an unthreaded bolt, were studied and compared with four types of commercially available tibial interlocking screws: Synthes, Howmedica, Richards, and Osteo AG. To test bending strength, the devices were inserted into a high molecular weight polyethylene tube and loaded at their midpoint by a materials testing machine to simulate a three point bending test. Single loading yielding strength and cyclic loading fatigue life were measured. To test holding power, the devices were inserted into tubes made of polyurethane foam, and their tips were loaded axially to measure pushout strength. The devices were tested with two different densities of foam materials and two different sizes of pilot holes. Insertion torque and stripping torque of the screws were measured first. Pushout tests were performed with each screw inserted with a tightness equal to 60% of its stripping torque. Test results showed that the yielding strength and the fatigue life were related closely to the inner diameter of the screws. The stripping torque predicted the pushout strength more reliably than did the insertion torque. All tested devices showed greater holding power in the foam with the higher density and with the smaller pilot holes. The both-ends-threaded screw had the highest pushout strength and a satisfactory fatigue strength. The unthreaded bolt had the highest fatigue strength but only fair holding power. Clinical studies of the use of these two types of locking devices are worthwhile.
Ethnic Differences in Bending Stiffness of the Ulna and Tibia
Arnaud, S. B.; Liang, M. T. C.; Bassin, S.; Braun, W.; Dutto, D.; Plesums, K.; Huvnh, H. T.; Cooper, D.; Wong, N.
2004-01-01
There is considerable information about the variations in bone mass associated with different opportunity to compare a mechanical property of bone in young college women of Caucasian, Hispanic and Asian descent who gave informed consent to participate in an exercise study. The subjects were sedentary, in good health, eumenorrheic, non-smokers and had body mass indices (BMI) less than 30. Measurements acquired were body weight, kg, and height, cm, calcaneal and wrist bone density, g/square cm (PIXI, Lunar GE) and bending stiffness (EI, Nm(exp 2)) in the ulna and tibia. E1 was determined non-invasively with an instrument called the Mechanical Response Tissue Analyzer (MRTA) that delivers a vibratory stimulus to the center of the ulna or tibia and analyzes the response curve based on the equation E1 = k(sub b) L(exp 3)/48 where k, is lateral bending stiffness, L is the length of the bone, E is Young's modulus of elasticity and I, the bending moment of inertia. The error of the test (CV) based on measurements of an aluminum rod with a known E1 was 4.8%, of calcaneal BMD, 0.54%, and of wrist bone density, 3.45%.
Bending instability in galactic discs. Advocacy of the linear theory
Rodionov, S A
2013-01-01
We demonstrate that in N-body simulations of isolated disc galaxies there is numerical vertical heating which slowly increases the vertical velocity dispersion and the disc thickness. Even for models with over a million particles in a disc, this heating can be significant. Such an effect is just the same as in numerical experiments by Sellwood (2013). We also show that in a stellar disc, outside a boxy/peanut bulge, if it presents, the saturation level of the bending instability is rather close to the value predicted by the linear theory. We pay attention to the fact that the bending instability develops and decays very fast, so it couldn't play any role in secular vertical heating. However the bending instability defines the minimal value of the ratio between the vertical and radial velocity dispersions $\\sigma_z / \\sigma_R \\approx 0.3$ (so indirectly the minimal thickness) which could have stellar discs in real galaxies. We demonstrate that observations confirm last statement.
Performance of a novel VUV bending magnet beamline
Song, Y F; Hsieh, T F; Huang, L R; Chung, S C; Cheng, N F; Hsiung, G Y; Wang, D J; Chen, C T; Tsang, K L
2001-01-01
A novel high resolution, high flux bending magnet beamline with an energy range from 5 to 40 eV has been constructed at SRRC. This Dragon-like beamline, which horizontally collects 50 mrad of synchrotron radiation from a bending magnet source, uses four cylindrical gratings with an included angle of 140 deg. and a movable curved exit slit. The average photon flux with an energy resolving power of 1000 is about 2x10 sup 1 sup 2 photons/s, which is among the highest of all existing VUV bending magnet beamlines. An energy resolving power of 24,000 at 6.8 eV has been obtained from the Schumann-Runge bands (B sup 3 limit construction operator in a limit construction/sum L: summation operator operator End lower limit of a limit construction u lower limit End limit End sup - /leftarrow/gets A: =leftward arrow X sup 3 limit construction operator in a limit construction/sum L: summation operator operator End lower limit of a limit construction g lower limit End limit End sup -) absorption spectra of O sub 2 gas. A pho...
Obstructive parotitis secondary to an acute masseteric bend.
Reddy, Ryan; White, David R; Gillespie, M Boyd
2012-01-01
To investigate 3 cases of chronic parotitis secondary to an acute bend in Stensen's duct caused by an enlargement of the masseteric space. Three female patients presented with symptoms consistent with obstructive parotitis including glandular swelling and tenderness during meals. A 10-year-old patient had unilateral facial swelling with enlargement of the masseter muscle and mandible later diagnosed as fibrous dysplasia. Salivary endoscopy showed an acute bend in Stensen's duct secondary to a mass effect. The patient's parotid swelling resolved following debulking of the mandibular mass and sialendoscopy with irrigation. Two adult patients with bilateral parotid involvement presented with bilateral masseteric hypertrophy and dental wear facets consistent with bruxism. Salivary endoscopy revealed bilateral kinking of Stensen's duct with jaw closure. Both patients improved symptomatically following nightly bite guard use and ultrasound-guided Botox injections of the masseter muscle and parotid. Obstructive parotitis is rarely caused by an acute masseteric bend. Diagnosis of a kinking Stensen's duct is aided with salivary endoscopy and imaging to determine the precipitating pathology. In the case of masseteric hypertrophy, symptomatic improvement can be achieved with Botox-induced atrophy of masseteric hypertrophy or with surgical reduction for associated fibrous dysplasia. Copyright © 2011 S. Karger AG, Basel.
Cylindrical Bending of Deformable Textile Rectangular Patch Antennas
Freek Boeykens
2012-01-01
Full Text Available Textile patch antennas are well known as basic components for wearable systems that allow communication between a human body and the external world. Due to their flexibility, textile antennas are subjected to bending when worn, causing a variation in resonance frequency and radiation pattern with respect to the flat state in which their nominal design is performed. Hence, it is important for textile antenna engineers to be able to predict these performance parameters as a function of the bending radius. Therefore, we propose a comprehensive analytical model that extends the cylindrical cavity model for conformal rigid patch antennas by incorporating the effects of patch stretching and substrate compression. It allows to predict the resonance frequency and the radiation pattern as a function of the bending radius. Its validity has been verified experimentally. Unlike previous contributions, which concerned only qualitative studies by means of measurements and numerical full-wave simulations, the proposed model offers advantages in terms of physical insight, accuracy, speed, and cost.
How two-dimensional bending can extraordinarily stiffen thin sheets
Pini, V.; Ruz, J. J.; Kosaka, P. M.; Malvar, O.; Calleja, M.; Tamayo, J.
2016-07-01
Curved thin sheets are ubiquitously found in nature and manmade structures from macro- to nanoscale. Within the framework of classical thin plate theory, the stiffness of thin sheets is independent of its bending state for small deflections. This assumption, however, goes against intuition. Simple experiments with a cantilever sheet made of paper show that the cantilever stiffness largely increases with small amounts of transversal curvature. We here demonstrate by using simple geometric arguments that thin sheets subject to two-dimensional bending necessarily develop internal stresses. The coupling between the internal stresses and the bending moments can increase the stiffness of the plate by several times. We develop a theory that describes the stiffness of curved thin sheets with simple equations in terms of the longitudinal and transversal curvatures. The theory predicts experimental results with a macroscopic cantilever sheet as well as numerical simulations by the finite element method. The results shed new light on plant and insect wing biomechanics and provide an easy route to engineer micro- and nanomechanical structures based on thin materials with extraordinary stiffness tunability.
Mechanosensing of DNA bending in a single specific protein-DNA complex
Le, Shimin; Chen, Hu; Cong, Peiwen; Lin, Jie; Dröge, Peter; Yan, Jie
2013-12-01
Many crucial biological processes are regulated by mechanical stimuli. Here, we report new findings that pico-Newton forces can drastically affect the stability of the site-specific DNA binding of a single transcription factor, the E. coli integration host factor (IHF), by stretching a short ~150 nm DNA containing a single IHF binding site. Dynamic binding and unbinding of single IHF were recorded and analyzed for the force-dependent stability of the IHF-DNA complex. Our results demonstrate that the IHF-DNA interaction is fine tuned by force in different salt concentration and temperature over physiological ranges, indicating that, besides other physiological factors, force may play equally important role in transcription regulation. These findings have broad implications with regard to general mechanosensitivity of site-specific DNA bending proteins.
Modal disturbance investigation of rod-shaped ultrasonic motor using bending vibrations
Jiantao ZHANG; Hua ZHU; Chunsheng ZHAO
2008-01-01
Modal disturbance of a rod-shaped ultrasonic motor using bending vibrations can cause problems such as low motor efficiency, instability, and poor control. In this paper, a dynamic analysis model of a stator is cre-ated on the basis of the finite element method (FEM) and Hamilton principle. The modal frequency sensitiv-ities of the stator to the structure parameters are inves-tigated by modal analysis. Accordingly, the structure parameters of the stator are modified to separate working modes from disturbance modes. A rod-shaped ultrasonic motor stator is fabricated, and the experi-mental results of its amplitude frequency response char-acteristics show that the purpose of modal separation is achieved. The frequency separation between working modes and disturbance modes is more than 2 kHz. The validity of the method is verified.
Lower Emittance Lattice for the Advanced Photon Source Upgrade Using Reverse Bending Magnets
Borland, M.; Berenc, T.; Sun, Y.; Sajaev, V.
2017-06-01
The Advanced Photon Source (APS) is pursuing an upgrade to the storage ring to a hybrid seven-bend-achromat design [1]. The nominal design provides a natural emittance of 67 pm [2]. By adding reverse dipole fields to several quadrupoles [3, 4] we can reduce the natural emittance to 41 pm while simultaneously providing more optimal beta functions in the insertion devices and increasing the dispersion function at the chromaticity sextupole magnets. The improved emittance results from a combination of increased energy loss per turn and a change in the damping partition. At the same time, the nonlinear dynamics performance is very similar, thanks in part to increased dispersion in the sextupoles. This paper describes the properties, optimization, and performance of the new lattice.
The perihelion of Mercury advance and the light bending calculated in (enhanced) Newton's theory
Abramowicz, M A; Wielgus, M
2013-01-01
We show that results of a simple dynamical gedanken experiment interpreted according to standard Newton's gravitational theory, may reveal that three-dimensional space is curved. The experiment may be used to reconstruct the curved geometry of space, i.e. its non-Euclidean metric. The perihelion of Mercury advance and the light bending calculated from the Poisson equation and the equation of motion in the curved geometry have the correct (observed) values. Independently, we also show that Newtonian gravity theory may be enhanced to incorporate the curvature of three dimensional space by adding an extra equation which links the Ricci scalar with the density of matter. Like in Einstein's general relativity, matter is the source of curvature. In the spherically symmetric (vacuum) case, the metric of space 3gik that follows from this extra equation agrees, to the expected accuracy, with the metric measured by the Newtonian gedanken experiment mentioned above.
A New High-Speed, High-Cycle, Gear-Tooth Bending Fatigue Test Capability
Stringer, David B.; Dykas, Brian D.; LaBerge, Kelsen E.; Zakrajsek, Andrew J.; Handschuh, Robert F.
2011-01-01
A new high-speed test capability for determining the high cycle bending-fatigue characteristics of gear teeth has been developed. Experiments were performed in the test facility using a standard spur gear test specimens designed for use in NASA Glenn s drive system test facilities. These tests varied in load condition and cycle-rate. The cycle-rate varied from 50 to 1000 Hz. The loads varied from high-stress, low-cycle loads to near infinite life conditions. Over 100 tests were conducted using AISI 9310 steel spur gear specimen. These results were then compared to previous data in the literature for correlation. Additionally, a cycle-rate sensitivity analysis was conducted by grouping the results according to cycle-rate and comparing the data sets. Methods used to study and verify load-path and facility dynamics are also discussed.
Dislocation-Mediated Deformation in Solid Langmuir Monolayers: Plastic Bending and Tilt Boundary.
Hatta, E
2015-09-08
The shear response of three types of textures (mosaic, striation, and stripe) in 10,12-pentacosadiynoic acid solid Langmuir monolayers has been investigated with Brewster angle microscopy. Low temperature mosaic textures respond to an applied stress elastically. Upon the application of shear the change of contrast appears in the form of propagation of fronts roughly perpendicularly to the shear direction within a single domain reversibly, while the domain shape keeps constant since it is presumably frozen kinetically. The striation and stripe textures at high temperatures show a viscoplastic behavior (plastic bending) in its rheological response, being consistent with the formation of a dislocation wall (tilt boundary) through dislocation dynamics (dislocation glide and climb). The stress-induced formation of a tilt boundary provides a manifestation of the collective motion of a number of dislocations.
Bending elasticity of charged surfactant layers: the effect of mixing.
Bergström, L Magnus
2006-08-01
Expressions have been derived from which the spontaneous curvature (H(0)), bending rigidity (k(c)), and saddle-splay constant (k(c)) of mixed monolayers and bilayers may be calculated from molecular and solution properties as well as experimentally available quantities such as the macroscopic hydrophobic-hydrophilic interfacial tension. Three different cases of binary surfactant mixtures have been treated in detail: (i) mixtures of an ionic and a nonionic surfactant, (ii) mixtures of two oppositely charged surfactants, and (iii) mixtures of two ionic surfactants with identical headgroups but different tail volumes. It is demonstrated that k(c)H(0), k(c), and k(c) for mixtures of surfactants with flexible tails may be subdivided into one contribution that is due to bending properties of an infinitely thin surface as calculated from the Poisson-Boltzmann mean field theory and one contribution appearing as a result of the surfactant film having a finite thickness with the surface of charge located somewhat outside the hydrophobic-hydrophilic interface. As a matter of fact, the picture becomes completely different as finite layer thickness effects are taken into account, and as a result, the spontaneous curvature is extensively lowered whereas the bending rigidity is raised. Furthermore, an additional contribution to k(c) is present for surfactant mixtures but is absent for k(c)H(0) and k(c). This contribution appears as a consequence of the minimization of the free energy with respect to the composition of a surfactant layer that is open in the thermodynamic sense and must always be negative (i.e., k(c) is generally found to be brought down by the process of mixing two or more surfactants). The magnitude of the reduction of k(c) increases with increasing asymmetry between two surfactants with respect to headgroup charge number and tail volume. As a consequence, the bending rigidity assumes the lowest values for layers formed in mixtures of two oppositely charged
Transition to coarsening for confined one-dimensional interfaces with bending rigidity
Le Goff, Thomas; Politi, Paolo; Pierre-Louis, Olivier
2015-08-01
We discuss the nonlinear dynamics and fluctuations of interfaces with bending rigidity under the competing attractions of two walls with arbitrary permeabilities. This system mimics the dynamics of confined membranes. We use a two-dimensional hydrodynamic model, where membranes are effectively one-dimensional objects. In a previous work [T. Le Goff et al., Phys. Rev. E 90, 032114 (2014), 10.1103/PhysRevE.90.032114], we have shown that this model predicts frozen states caused by bending rigidity-induced oscillatory interactions between kinks (or domain walls). We here demonstrate that in the presence of tension, potential asymmetry, or thermal noise, there is a finite threshold above which frozen states disappear, and perpetual coarsening is restored. Depending on the driving force, the transition to coarsening exhibits different scenarios. First, for membranes under tension, small tensions can only lead to transient coarsening or partial disordering, while above a finite threshold, membrane oscillations disappear and perpetual coarsening is found. Second, potential asymmetry is relevant in the nonconserved case only, i.e., for permeable walls, where it induces a drift force on the kinks, leading to a fast coarsening process via kink-antikink annihilation. However, below some threshold, the drift force can be balanced by the oscillatory interactions between kinks, and frozen adhesion patches can still be observed. Finally, at long times, noise restores coarsening with standard exponents depending on the permeability of the walls. However, the typical time for the appearance of coarsening exhibits an Arrhenius form. As a consequence, a finite noise amplitude is needed in order to observe coarsening in observable time.
Improving formability of tube bending for a copper material using finite element simulation
Nguyen, Duc Toan; Nnuyen, Dinh Thanh [Hungyen University of Technology and Education, Hungyen (Viet Nam); Kim, Young Suk [Kyungpook National University, Daegu (Korea, Republic of)
2015-10-15
Bending tubes are key products in many industries. The geometric parameters of the bending process are considered according to Taguchi's orthogonal array and then coupled with finite element simulation to predict and improve the formability of the tube bending process for copper JIS25A material. Three parameters, namely, mandrel diameter, distance between mandrel rings, and distance from the tip of the mandrel bar to the center of the base die, are selected to study their effects on the quality of the bending process. The variance analysis shows that the effect distribution of each parameter to bending quality is determined, and optimal conditions are adopted to conduct experiments.
Control of Prestressing Force in Rod for Reducing Bending in Beams
Wong, M. B.
2010-05-01
This paper presents a method to determine the prestressing force required in a rod for reducing the bending effects in a beam. The rod is positioned underneath the beam such that the prestressing force is counteracting the effects of beam bending. It has been found that the prestressing force may also increase the bending as a result of P-δ effect. Therefore, the choice of both the prestressing force and the rod eccentricity from the beam axis is important in determining the appropriate actions to resist the bending of the beam. Over-prestressing the rod may even induce bending or buckling failure in the beam in the reverse direction.
EXPERIMENTAL STUDY ON BED SCOUR IN A 90°CHANNEL BEND
Masoud GHODSIAN; S. Kamal MOUSAVI
2006-01-01
The special feature of bend flow leads to scouring of the bed and bank. Various parameters like flow depth, flow velocity or discharge, geometry of bend and characteristics of bed material may affect the scour process. Experiments were carried out to study the effect of some important parameters on bend scour under clear water condition. Experiments were conducted in a 0.6m wide and 0.7m high flume with 90 degree bend. The lateral variations of bed slope were studied. The maximum depth of scour was correlated to densimetric Froude number, relative bend radius and relative depth of flow.
Kohno, Hideo, E-mail: kohno.hideo@kochi-tech.ac.jp [School of Environmental Science and Engineering, Kochi University of Technology, Kami, Kochi 782-8502 (Japan); Masuda, Yusuke [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)
2015-05-11
When the direction of flattening of a carbon nanotube changes during growth mediated by a metal nanoparticle, a carbon nanotetrahedron is formed in the middle of the carbon nanoribbon. We report the bending properties of the carbon nanotetrahedron/nanoribbon structure using a micro-manipulator system in a transmission electron microscope. In many cases, bending occurs at an edge of the carbon nanotetrahedron. No significant change is observed in the tetrahedron's shape during bending, and the bending is reversible and repeatable. Our results show that the carbon nanotetrahedron/nanoribbon structure has good durability against mechanical bending.
Hamid Ahmadi
2015-01-01
Full Text Available Fatigue life of tubular joints in offshore structures is significantly influenced by the degree of bending (DoB. The DoB exhibits considerable scatter calling for greater emphasis in accurate determination of its governing probability distribution which is a key input for the fatigue reliability analysis of a tubular joint. Although the tubular X-joints are commonly found in offshore jacket structures, as far as the authors are aware, no comprehensive research has been carried out on the probability distribution of the DoB in tubular X-joints. In the present paper, results of parametric equations available for the calculation of the DoB have been used to develop probability distribution models for the DoB in the chord member of tubular X-joints subjected to four types of bending loads. Based on a parametric study, a set of samples was prepared and density histograms were generated for these samples using Freedman-Diaconis method. Twelve different probability density functions (PDFs were fitted to these histograms. In each case, Kolmogorov-Smirnov test was used to evaluate the goodness of fit. Finally, after substituting the values of estimated parameters for each distribution, a set of fully defined PDFs have been proposed for the DoB in tubular X-joints subjected to bending loads.
Hasanyan, D.; Gao, J.; Wang, Y.; Viswan, R.; Li, M.; Shen, Y.; Li, J.; Viehland, D.
2012-07-01
In this paper, we discuss a theoretical model with experimental verification for the resonance enhancement of magnetoelectric (ME) interactions at frequencies corresponding to bending-tension oscillations. A dynamic theory of arbitrary laminated magneto-elasto-electric bars was constructed. The model included bending and longitudinal vibration effects for predicting ME coefficients in laminate bar composite structures consisting of magnetostrictive, piezoelectric, and pure elastic layers. The thickness dependence of stress, strain, and magnetic and electric fields within a sample are taken into account, as such the bending deformations should be considered in an applied magnetic or electric field. The frequency dependence of the ME voltage coefficients has obtained by solving electrostatic, magnetostatic, and elastodynamic equations. We consider boundary conditions corresponding to free vibrations at both ends. As a demonstration, our theory for multilayer ME composites was then applied to ferromagnetic-ferroelectric bilayers, specifically Metglas-PZT ones. A theoretical model is presented for static (low-frequency) ME effects in such bilayers. We also performed experiments for these Metglas-PZT bilayers and analyzed the influence of Metglas geometry (length and thickness) and Metglas/PZT volume fraction on the ME coefficient. The frequency dependence of the ME coefficient is also presented for different geometries (length, thickness) of Metglas. The theory shows good agreement with experimental data, even near the resonance frequency.
Rahmanseresht, Sheema; Gamari, Ben D; Goldner, Lori S
2014-01-01
We report on the observation of a change in the bend angle of an RNA kissing complex upon Rop binding using single-molecular-pair FRET. The angular relationship between the dyes, rather than the distance between them, is shown to be responsible for the observed change in energy transfer. It has long been thought that Rop increases the bend angle of the R1inv-R2inv complex upon binding, but this has never been directly observed. In contrast, we find an increase in FRET upon the addition of Rop that is shown via modeling to be consistent with a decrease in the bend angle of the complex of $-15^{\\circ}\\pm7^{\\circ}$. The model predicts FRET from dye trajectories generated using molecular dynamics simulations of Cy3 and Cy5 attached to $5'$ terminal cytosine or guanosine on RNA. While FRET is commonly used to observe global changes in molecular structure attributed to changes in the distance between dyes, it is rarely, if ever, used to elucidate angular changes. Subtle global changes in molecular structure upon bi...
Dresig, Hans
2010-01-01
Dynamic loads and disturbing oscillations increase with higher speed of the machines and more lightweight constructions. Industrial safety standards require better oscillation reduction and noise control. The book by Dresig/Holzweissig deals with these topics. It presents the classical areas of modeling, dynamics of rigid bodies, balancing, torsional and bending vibrations, problems of vibration isolation and the dynamic behavior of complex vibrating systems. Typical dynamic effects, i.e., the gyroscopic effect, the damping of oscillations, resonances of k-th order, subharmonic and nonlinear f
Optimal r/b ratio of bend channel in centrifugal compressor
Suping WEN; Xiaowen HU; Yong ZHANG; Jun WANG; Tingbin LI
2008-01-01
A numerical investigation on the flow in a bend channel by coupling the impeller with the vaneless diffuser in a centrifugal compressor with different r/b ratios (bend radius r to bend channel width b) is presented. The jet-wake effect of the impeller outlet is considered and flow pattern in the bend channel and the performance of the centrifugal compressor stage are investigated. The results indicate that there is an optimal r/b ratio for increasing the stage efficiency to the highest for a specific compressor stage. The change in r/b ratio significantly affects the flow angle of the bend chan-nel outlet. The prime reason for the total pressure loss in the bend channel is the wall friction in the bend channel.
Influence of Characteristics on Bending Strength of Layered Steel Fiber Reinforced Concrete
DAI Shao-bin; SONG Ming-hai; HUANG Jun
2005-01-01
The influence of two main characteristics of steel fiber, the aspect ratio (Df) and volume fraction (pf), on the bending strength of Layered Steel Fiber Reinforced Concrete (LSFRC) is investigated by using orthogonal test. Via the variance analysis on the experimental results and trend analysis on the two characteristics, Df is found significantly related to the bending strength of LSFRC. The influence ratio is 63.3%. The bending strength of LSFRC increases if Df increases, makes better when Df reaches 100. ρf has ordinary influence on the bending strength of LSFRC. The influence ratio is 29.2%. Other characteristics, such as the shape of steel fiber and the mix proportion, have less influence. The best ρf contributing to the bending strength of LSFRC is 1.5 %. If pf is greater than 1.5 %, it has negative influence on the bending strength of LSFRC. So, pf makes a limited contribution to the bending strength of LSFRC.
Brightness of synchrotron radiation from undulators and bending magnets.
Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni
2015-03-01
The maximum of the Wigner distribution (WD) of synchrotron radiation (SR) fields is considered as a possible definition of SR source brightness. Such a figure of merit was originally introduced in the SR community by Kim [(1986), Nucl. Instrum. Methods Phys. Res. A, 246, 71-76]. The brightness defined in this way is always positive and, in the geometrical optics limit, can be interpreted as the maximum density of photon flux in phase space. For undulator and bending magnet radiation from a single electron, the WD function can be explicitly calculated. In the case of an electron beam with a finite emittance the brightness is given by the maximum of the convolution of a single electron WD function and the probability distribution of the electrons in phase space. In the particular case when both electron beam size and electron beam divergence dominate over the diffraction size and the diffraction angle, one can use a geometrical optics approach. However, there are intermediate regimes when only the electron beam size or the electron beam divergence dominate. In these asymptotic cases the geometrical optics approach is still applicable, and the brightness definition used here yields back once more to the maximum photon flux density in phase space. In these intermediate regimes a significant numerical disagreement is found between exact calculations and the approximation for undulator brightness currently used in the literature. The WD formalism is extended to a satisfactory theory for the brightness of a bending magnet. It is found that in the intermediate regimes the usually accepted approximation for bending magnet brightness turns out to be inconsistent even parametrically.
On the bending algorithms for soft objects in flows
Guckenberger, Achim; Schraml, Marcel P.; Chen, Paul G.; Leonetti, Marc; Gekle, Stephan
2016-10-01
One of the most challenging aspects in the accurate simulation of three-dimensional soft objects such as vesicles or biological cells is the computation of membrane bending forces. The origin of this difficulty stems from the need to numerically evaluate a fourth order derivative on the discretized surface geometry. Here we investigate six different algorithms to compute membrane bending forces, including regularly used methods as well as novel ones. All are based on the same physical model (due to Canham and Helfrich) and start from a surface discretization with flat triangles. At the same time, they differ substantially in their numerical approach. We start by comparing the numerically obtained mean curvature, the Laplace-Beltrami operator of the mean curvature and finally the surface force density to analytical results for the discocyte resting shape of a red blood cell. We find that none of the considered algorithms converges to zero error at all nodes and that for some algorithms the error even diverges. There is furthermore a pronounced influence of the mesh structure: Discretizations with more irregular triangles and node connectivity present serious difficulties for most investigated methods. To assess the behavior of the algorithms in a realistic physical application, we investigate the deformation of an initially spherical capsule in a linear shear flow at small Reynolds numbers. To exclude any influence of the flow solver, two conceptually very different solvers are employed: the Lattice-Boltzmann and the Boundary Integral Method. Despite the largely different quality of the bending algorithms when applied to the static red blood cell, we find that in the actual flow situation most algorithms give consistent results for both hydrodynamic solvers. Even so, a short review of earlier works reveals a wide scattering of reported results for, e.g., the Taylor deformation parameter. Besides the presented application to biofluidic systems, the investigated
Geologic map of Big Bend National Park, Texas
Turner, Kenzie J.; Berry, Margaret E.; Page, William R.; Lehman, Thomas M.; Bohannon, Robert G.; Scott, Robert B.; Miggins, Daniel P.; Budahn, James R.; Cooper, Roger W.; Drenth, Benjamin J.; Anderson, Eric D.; Williams, Van S.
2011-01-01
The purpose of this map is to provide the National Park Service and the public with an updated digital geologic map of Big Bend National Park (BBNP). The geologic map report of Maxwell and others (1967) provides a fully comprehensive account of the important volcanic, structural, geomorphological, and paleontological features that define BBNP. However, the map is on a geographically distorted planimetric base and lacks topography, which has caused difficulty in conducting GIS-based data analyses and georeferencing the many geologic features investigated and depicted on the map. In addition, the map is outdated, excluding significant data from numerous studies that have been carried out since its publication more than 40 years ago. This report includes a modern digital geologic map that can be utilized with standard GIS applications to aid BBNP researchers in geologic data analysis, natural resource and ecosystem management, monitoring, assessment, inventory activities, and educational and recreational uses. The digital map incorporates new data, many revisions, and greater detail than the original map. Although some geologic issues remain unresolved for BBNP, the updated map serves as a foundation for addressing those issues. Funding for the Big Bend National Park geologic map was provided by the United States Geological Survey (USGS) National Cooperative Geologic Mapping Program and the National Park Service. The Big Bend mapping project was administered by staff in the USGS Geology and Environmental Change Science Center, Denver, Colo. Members of the USGS Mineral and Environmental Resources Science Center completed investigations in parallel with the geologic mapping project. Results of these investigations addressed some significant current issues in BBNP and the U.S.-Mexico border region, including contaminants and human health, ecosystems, and water resources. Funding for the high-resolution aeromagnetic survey in BBNP, and associated data analyses and
2013-01-01
When a DNA molecule is stretched, the zero-force correlation length for its bending fluctuations – the persistence length A – bifurcates into two different correlation lengths - the shorter “longitudinal” correlation length ξ‖(f) and the longer “transverse” correlation length ξ⊥(f). In the high-force limit, ξ‖(f)=ξ⊥(f)/2=kBTA/f/2. When DNA-bending proteins bind to the DNA molecule, there is an effective interaction between the protein-generated bends mediated by DNA elasticity and bending fluctuations. Surprisingly, the range of this interaction is not the longest correlation length associated with transverse fluctuations of the tangent vector along the polymer, but instead is the second longest longitudinal correlation length ξ‖ (f, μ). The effect arises from the protein-bend contribution to the Hamiltonian having an axial rotational symmetry which eliminates its coupling to the transverse fluctuations. PMID:23368394
Design Analysis of the Mixed Mode Bending Sandwich Specimen
Quispitupa, Amilcar; Berggreen, Christian; Carlsson, Leif A.
2010-01-01
A design analysis of the mixed mode bending (MMB) sandwich specimen for face–core interface fracture characterization is presented. An analysis of the competing failure modes in the foam cored sandwich specimens is performed in order to achieve face–core debond fracture prior to other failure modes....... The analysis facilitates selection of the appropriate geometry for the MMB sandwich specimen to promote debond failure. An experimental study is performed using MMB sandwich specimens with a H100 PVC foam core and E-glass–polyester faces. The results reveal that debond propagation is successfully achieved...... for the chosen geometries and mixed mode loading conditions....
Wake-induced bending of two-dimensional plasma crystals
Röcker, T. B., E-mail: tbr@mpe.mpg.de; Ivlev, A. V., E-mail: ivlev@mpe.mpg.de; Zhdanov, S. K.; Morfill, G. E. [Max Planck Institute for Extraterrestrial Physics, 85741 Garching (Germany); Couëdel, L. [CNRS, Aix-Marseille-Université, Laboratoire de Physique des Interactions Ioniques et Moléculaires, UMR 7345, 13397 Marseille Cedex 20 (France)
2014-07-15
It is shown that the wake-mediated interactions between microparticles in a two-dimensional plasma crystal affect the shape of the monolayer, making it non-flat. The equilibrium shape is calculated for various distributions of the particle number density in the monolayer. For typical experimental conditions, the levitation height of particles in the center of the crystal can be noticeably smaller than at the periphery. It is suggested that the effect of wake-induced bending can be utilized in experiments, to deduce important characteristics of the interparticle interaction.
Wake-induced bending of two-dimensional plasma crystals
Röcker, T B; Zhdanov, S K; Couëdel, L; Morfill, G E
2014-01-01
It is shown that the wake-mediated interactions between microparticles in a two-dimensional plasma crystal affect the shape of the monolayer, making it non-flat. The equilibrium shape is calculated for various distributions of the particle number density in the monolayer. For typical experimental conditions, the levitation height of particles in the center of the crystal can be noticeably smaller than at the periphery. It is suggested that the effect of wake-induced bending can be utilized in experiments, to deduce important characteristics of the interparticle interaction.
NONLINEAR BENDING THEORY OF DIAGONAL SQUARE PYRAMID RETICULATED SHALLOW SHELLS
肖潭; 刘人怀
2001-01-01
Double-deck reticulated shells are a main form of large space structures. One of the shells is the diagonal square pyramid reticulated shallow shell, whose its upper and lower faces bear most of the load but its core is comparatively flexible. According to its geometrical and mechanical characteristics, the diagonal square pyramid reticulated shallow shell is treated as a shallow sandwich shell on the basis of three basic assumptions. Its constitutive relations are analyzed from the point of view of energy and internal force equivalence. Basic equations of the geometrically nonlinear bending theory of the diagonal square pyramid reticulated shallow shell are established by means of the virtual work principle .
Tensile and bending fatigue of the adhesive interface to dentin.
Belli, Renan; Baratieri, Luiz Narciso; Braem, Marc; Petschelt, Anselm; Lohbauer, Ulrich
2010-12-01
The aim of this study was to evaluate the fatigue limits of the dentin-composite interfaces established either with an etch-and-rinse or an one-step self-etch adhesive systems under tensile and bending configurations. Flat specimens (1.2 mm×5 mm×35 mm) were prepared using a plexiglass mold where dentin sections from human third molars were bonded to a resin composite, exhibiting the interface centrally located. Syntac Classic and G-Bond were used as adhesives and applied according to the manufacturer's instructions. The fluorochrome Rhodamine B was added to the adhesives to allow for fractographic evaluation. Tensile strength was measured in an universal testing machine and the bending strength (n=15) in a Flex machine (Flex, University of Antwerp, Belgium), respectively. Tensile (TFL) and bending fatigue limits (BFL) (n=25) were determined under wet conditions for 10(4) cycles following a staircase approach. Interface morphology and fracture mechanisms were observed using light, confocal laser scanning and scanning electron microscopy. Statistical analysis was performed using three-way ANOVA (mod LSD test, pbending characteristic strengths at 63.2% failure probability for Syntac were 23.8 MPa and 71.5 MPa, and 24.7 MPa and 72.3 MPa for G-Bond, respectively. Regarding the applied methods, no significant differences were detected between adhesives. However, fatigue limits for G-Bond (TFL=5.9 MPa; BFL=36.2 MPa) were significantly reduced when compared to Syntac (TFL=12.6 MPa; BFL=49.7 MPa). Fracture modes of Syntac were generally of adhesive nature, between the adhesive resin and dentin, while G-Bond showed fracture planes involving the adhesive-dentin interface and the adhesive resin. Cyclic loading under tensile and bending configurations led to a significant strength degradation, with a more pronounced fatigue limit decrease for G-Bond. The greater decrease in fracture strength was observed in the tensile configuration. Copyright © 2010 Academy of Dental
Experimental Study Regarding of Bending Behaviour of Stabilizator Link
Cofaru, Nicolae; Roman, Lucian; Pascu, Adrian; Oleksik, Valentin
2016-12-01
This paper presents an experimental study of the behavior of anti-roll power link subjected to bending, power link coming from an Opel Astra G. The power link is made of PA66 GF30 polyamide. For this study, there were used a universal testing machine (Instron 5587) and a real-time strain measurement optical system (Aramis). The results showed are those obtained in the case of a compression force of 1,000 [N] namely: major Strain ɛ1, minor strain ɛ2, equivalent von Mises strain, displacement on X axis, displacement on Y axis (compression force direction), displacement on Z axis.
Analyzing refractive index changes and differential bending in microcantilever arrays
Huber, François; Lang, Hans Peter; Hegner, Martin; Despont, Michel; Drechsler, Ute; Gerber, Christoph
2008-08-01
A new microcantilever array design is investigated comprising eight flexible microcantilevers introducing two solid bars, enabling to subtract contributions from differences in refractive index in an optical laser read out system. Changes in the refractive index do not contribute undesirably to bending signals at picomolar to micromolar DNA or protein concentrations. However, measurements of samples with high salt concentrations or serum are affected, requiring corrections for refractive index artifacts. Moreover, to obtain a deeper understanding of molecular stress formation, the differential curvature of cantilevers is analyzed by positioning the laser spots along the surface of the levers during pH experiments.
Transverse bending waves and the breaking broomstick demonstration
Vandegrift, Guy
1997-06-01
When a broomstick is supported at both ends by two wine glasses, a strong downward blow to the center will break the stick, leaving the wine glasses undisturbed, provided care is taken to cushion the wine glasses against an initial and brief downward motion of the ends of the broomstick. This downward motion is analyzed and estimated to be about 1 mm in magnitude. Qualitative experimental evidence of this motion is easily obtained using a force probe to monitor a light and nondestructive tap to a 2-m measuring stick. The method of analysis developed here leads to a simple derivation of the dispersion relation for transverse bending waves on a long rod.
Reflection of bending Waves from Border of the Plate
Belubekyan M.V.
2010-03-01
Full Text Available To problems of the reflection of the bending waves from flat border of the ambience dedicated to the multiple studies. Relatively little works are connected with questions of the reflection curved waves from flat edge of the thin plate. In this work happen to the decisions of the problem of the plate under different border condition. For partial case of the free edge, as limiting case of the absence of the reflected wave, is got decision of the problem localized curved variations.
TRAPEZOIDAL PLATE BENDING ELEMENT WITH DOUBLE SET PARAMETERS
Shao-chun Chen; Dong-yang Shi; I chiro Hagiwara
2003-01-01
Using double set parameter method, a 12-parameter trapezoidal plate bending element is presented. The first set of degrees of freedom, which make the element convergent, are the values at the four vertices and the middle points of the four sides together with the mean values of the outer normal derivatives along four sides. The second set of degree of freedom, which make the number of unknowns in the resulting discrete system small and computation convenient are values and the first derivatives at the four vertices of the element. The convergence of the element is proved.
Bending Under Tension Test with Direct Friction Measurement
Andreasen, Jan Lasson; Olsson, David Dam; Chodnikiewicz, K.
2006-01-01
A special Bending-Under-Tension (BUT) transducer has been developed in which friction around the tool radius can be directly measured when drawing a plane sheet strip around a cylindrical tool-pin under constant back tension. The front tension, back tension and torque on the tool-pin are all...... measured directly, thus enabling accurate measurement of friction and direct determination of lubricant film breakdown for varying normal pressure, sliding speed, tool radius and tool preheat temperature. The transducer is applied in an experimental investigation focusing on limits of lubrication...... in drawing of stainless steel showing the influence of varying process conditions and the performance of different lubricants....
Mechano sorptive behaviour of notched beams in bending
Jensen, Signe Kamp; Hoffmeyer, Preben
1996-01-01
Short term bending tests with end-notched beams at constant or varying moisture content have shown an apparent contradictory dependency between moisture content and strength. The higher the moisture content the higher the strength. Varying moisture results in particularly significant differences...... and by neglecting deformation due to shear. Compression stresses perpendicular to grain in excess of 6 MPa were found in the vicinity of the notch following a period of adsorption. Similarly, small tension stresses of the order 1 MPa were registered in this area when the specimens were at their most dry condition...
Tilted bending magnet for SPS target area TCC2
1976-01-01
A slow-extracted proton beam from the SPS goes to the underground target zone TCC2. The part of the primary beam which traverses target T4 is recuperated and transported over some 800 m, for further use in the North Area High Intensity facility (NAHIF). The curved and sloped trajectory required 4 of the bending magnets to be tilted. Here we see one of them being attended by Gilbert Françon in hall 867, ready for installation in TCC2.
Silva, Danilo Machado L. da; Rodrigues, Marcos V. [Det Norske Veritas (DNV), Rio de Janeiro, RJ (Brazil); Venaas, Asle [Det Norske Veritas (DNV), Oslo (Norway); Medeiros, Antonio Roberto de [Subsea 7 (Brazil)
2009-12-19
Bending is a primary loading experienced by pipelines during installation and operation. Significant bending in the presence of tension is experienced during installation by the S-lay method, as the pipe conforms to the curvature of the stinger and beyond in the over bend region. Bending in the presence of external pressure is experienced in the sag bend of all major installation methods (e.g., reeling, J-lay, S-lay) as well as in free-spans on the sea floor. Bending is also experienced by pipelines during installation by horizontal directional drilling. HDD procedures are increasingly being utilized around the world not only for crossings of rivers and other obstacles but also for shore approach of offshore pipelines. During installation the pipeline experience a combination of tensile, bending, and compressive stresses. The magnitude of these stresses is a function of the approach angle, bending radius, pipe diameter, length of the borehole, and the soil properties at the site. The objective of this paper is to present an overview of some aspects related to bending of the product pipe during HDD operations, which is closely related to the borehole path as the pipeline conforms to the curvature of the hole. An overview of the aspects related to tensile forces is also presented. The combined effect of bending and tensile forces during the pullback operation is discussed. (author)
A Novel Low-Cost, Large Curvature Bend Sensor Based on a Bowden-Cable.
Jeong, Useok; Cho, Kyu-Jin
2016-06-24
Bend sensors have been developed based on conductive ink, optical fiber, and electronic textiles. Each type has advantages and disadvantages in terms of performance, ease of use, and cost. This study proposes a new and low-cost bend sensor that can measure a wide range of accumulated bend angles with large curvatures. This bend sensor utilizes a Bowden-cable, which consists of a coil sheath and an inner wire. Displacement changes of the Bowden-cable's inner wire, when the shape of the sheath changes, have been considered to be a position error in previous studies. However, this study takes advantage of this position error to detect the bend angle of the sheath. The bend angle of the sensor can be calculated from the displacement measurement of the sensing wire using a Hall-effect sensor or a potentiometer. Simulations and experiments have shown that the accumulated bend angle of the sensor is linearly related to the sensor signal, with an R-square value up to 0.9969 and a root mean square error of 2% of the full sensing range. The proposed sensor is not affected by a bend curvature of up to 80.0 m(-1), unlike previous bend sensors. The proposed sensor is expected to be useful for various applications, including motion capture devices, wearable robots, surgical devices, or generally any device that requires an affordable and low-cost bend sensor.
Numberical Investigation of a New Method for Reducing Bends Erosion from Particles Impacts
YAOJun; FANJianren; 等
2002-01-01
The present paper intends to introduce a new method for reducing bends erosion from particles impacts: the ribbed bend erosion protection method. Ribs are evenly fixed in the range of 20°-80° on the inner-wall of inside 90° bend and the bend (including ribs) is made of medium carbon steel. Three-dimensional numerical work is performed and the result shows satisfactory agreement with the experimental measurement. Numerical simulation studies the characteristics of axial gas flow along the bend and secondary flow at cross section. Detailed analyses involving the impact velocity and incidence angle of particle-metal (either particle-rib or particle-duct) impact unveil the mechanism of the anti-erosion effect. As a result, predications achieve that the average erosion rate of the ribbed bends is only a third of the bare bend under test conditions and rectangle ribs possess higher anti-erosion effect than square ribs, while the wear distribution pattern remains unchanged after adding ribs onto the bend. All results confirm that the ribbed bend erosion protection method is a simple and effective method for reducing bends erosion from particles impacts.
Bending continuous structures with SMAs: a novel robotic fish design.
Rossi, C; Colorado, J; Coral, W; Barrientos, A
2011-12-01
In this paper, we describe our research on bio-inspired locomotion systems using deformable structures and smart materials, concretely shape memory alloys (SMAs). These types of materials allow us to explore the possibility of building motor-less and gear-less robots. A swimming underwater fish-like robot has been developed whose movements are generated using SMAs. These actuators are suitable for bending the continuous backbone of the fish, which in turn causes a change in the curvature of the body. This type of structural arrangement is inspired by fish red muscles, which are mainly recruited during steady swimming for the bending of a flexible but nearly incompressible structure such as the fishbone. This paper reviews the design process of these bio-inspired structures, from the motivations and physiological inspiration to the mechatronics design, control and simulations, leading to actual experimental trials and results. The focus of this work is to present the mechanisms by which standard swimming patterns can be reproduced with the proposed design. Moreover, the performance of the SMA-based actuators' control in terms of actuation speed and position accuracy is also addressed.
Pressure and bending tests on fibreglass augmented steel technology pipes
Chen, Qishi; Ozkan, Istemi F. [C-FER Technologies, Edmonton, Alberta, (Canada); Salama, Mamdouh M. [ConocoPhillips Company, Houston, Texas, (United States)
2010-07-01
The economic manufacture of large diameter high pressure pipelines is a challenge. The FAST-PipeTM concept is fabricated from a steel liner hoop-wound with non-impregnated fibreglass stands. This report presents the qualification results of the FAST-PipeTM concept. The qualification testing program studied the effects of external environment (frozen/thawed cycle), load duration and the wrap thickness on the burst and bending capacity of the FAST-PipeTM concept. Burst and pressure-bend tests were performed under different conditions and for different thickness of fibreglass. The values obtained were compared to those from unwrapped pipes. It also established FAST-PipeTM behaviour in several loading scenarios using the FEA model. The burst tests results showed that freezing temperatures do not have an impact on the pressure capacity of FAST-PipeTM. The results of the tests showed the effectiveness of dry fibreglass wrap in increasing the internal pressure capacity of the pipe.
How Does The Bone Shaft Geometry Affect its Bending Properties?
Kaveh P. Saffar
2009-01-01
Full Text Available In this research, ten fresh specimens of sheep tibiae were provided from slaughtered animals. Whole bone specimens were loaded in three-point bending according to standard wet bone test protocols. Mechanical properties were determined and compared with the results which were obtained from two dry bone tests. The results showed that fracture bending moment and bone extrinsic stiffness had significant relations with fracture cross-section dependent parameters (i.e., cross-section area and area moment of inertia. Where, fracture energy and ultimate strength did not have such a relation with these parameters. Finite element modeling of bone shaft was made with simplified geometry (neglecting cross-section variations along bone shaft in two steps: First, by elliptical cross-section and second, by circular cross-section, assuming linear elastic and isotropic properties for the specimens. Elastic (Youngs modulus and fracture load, evaluated from curves obtained from tests, were applied to the finite element model and close results of maximum stress in both test specimen and first (elliptical cross-section model showed up. There was an average difference of about 2% between ultimate strength of wet bone specimens and maximum (tensile stress occurred in the elliptical models. However, this value for circular models was about 16%.
Relativity for everyone how space-time bends
Fischer, Kurt
2015-01-01
This book, now in a revised and updated second edition, explains the theory of special and general relativity in detail without approaching Einstein's life or the historical background. The text is formulated in such a way that the reader will be able to understand the essence intuitively, and new sections have been added on time machines, the twin paradoxes, and tensors. The first part of the book focuses on the essentials of special relativity. It explains the famous equivalence between mass and energy and tells why Einstein was able to use the theory of electrodynamics as a template for his "electrodynamics of moving bodies". General relativity is then addressed, mainly with the help of thought experiments. Reference is made to the previously introduced special relativity and the equivalence principle and, using many figures, it is explained how space-time is bending under gravity. The climax of the book is the Einstein equation of gravity, which describes the way in which matter bends space-time. The read...
Optical guiding and beam bending in free-electron lasers
Scharlemann, E.T.
1987-01-01
The electron beam in a free-electron laser (FEL) can act as an optical fiber, guiding or bending the optical beam. The refractive and gain effects of the bunched electron beam can compensate for diffraction, making possible wigglers that are many Rayleigh ranges (i.e., characteristic diffraction lengths) long. The origin of optical guiding can be understood by examining gain and refractive guiding in a fiber with a complex index of refraction, providing a mathematical description applicable also to the FEL, with some extensions. In the exponential gain regime of the FEL, the electron equations of motion must be included, but a self-consistent description of exponential gain with diffraction fully included becomes possible. The origin of the effective index of refraction of an FEL is illustrated with a simple example of bunched, radiating dipoles. Some of the properties of the index of refraction are described. The limited experimental evidence for optical beam bending is summarized. The evidence does not yet provide conclusive proof of the existence of optical guiding, but supports the idea. Finally, the importance of refractive guiding for the performance of a high-gain tapered-wiggler FEL amplifier is illustrated with numerical simulations.
Composite failure prediction of π-joint structures under bending
HUANG Hong-me; YUAN Shen-fang
2012-01-01
In this article,the composite π-joint is investigated under bending loads.The "L" preform is the critical component regarding composite π-joint failure.The study is presented in the failure detection of a carbon fiber composite π-joint structure under bending loads using fiber Bragg grating (FBG) sensor.Firstly,based on the general finite element method (FEM)software,the 3-D finite element (FE) model of composite π-joint is established,and the failure process and every lamina failure load of composite π-joint are investigated by maximum stress criteria.Then,strain distributions along the length of FBG are extracted,and the reflection spectra of FBG are calculated according to the strain distribution.Finally,to verify the numerical results,a test scheme is performed and the experimental spectra of FBG are recorded.The experimental results indicate that the failure sequence and the corresponding critical loads of failure are consistent with the numerical predictions,and the computational error of failure load is less than 6.4％.Furthermore,it also verifies the feasibility of the damage detection system.
Radio occultation bending angle anomalies during tropical cyclones
R. Biondi
2011-02-01
Full Text Available The tropical deep convection affects the radiation balance of the atmosphere changing the water vapor mixing ratio and the temperature of the upper troposphere lower stratosphere. The aim of this work is to better understand these processes and to investigate if severe storms leave a significant signature in radio occultation profiles in the tropical tropopause layer. Using tropical cyclone best track database and data from different GPS radio occultation missions (COSMIC, GRACE, CHAMP, SACC and GPSMET, we selected 1194 profiles in a time window of 3 h and a space window of 300 km from the eye of the cyclone. We show that the bending angle anomaly of a GPS radio occultation signal is typically larger than the climatology in the upper troposphere and lower stratosphere and that a double tropopause during deep convection can easily be detected using this technique. Comparisons with co-located radiosondes, climatology of tropopause altitudes and GOES analyses are also shown to support the hypothesis that the bending angle anomaly can be used as an indicator of convective towers. The results are discussed in connection to the GPS radio occultation receiver which will be part of the Atomic Clock Ensemble in Space (ACES payload on the International Space Station.
Xyloglucan for Generating Tensile Stress to Bend Tree Stem
Kei'ichi Baba; Yong Woo Park; Tomomi Kaku; Rumi Kaida; Miyuki Takeuchi; Masato Yoshida; Yoshihiro Hosoo; Yasuhisa Ojio; Takashi Okuyama; Toru Taniguchi; Yasunori Ohmiya; Teiji Kondo; Ziv Shani; Oded Shoseyov; Tatsuya Awano; Satoshi Serada; Naoko Norioka; Shigemi Norioka; Takahisa Hayashi
2009-01-01
In response to environmental variation, angiosperm trees bend their stems by forming tension wood, which consists of a cellulose-rich G (gelatinous)-Iayer in the walls of fiber cells and generates abnormal tensile stress in the sec-ondary xylem. We produced transgenic poplar plants overexpressing several endoglycanases to reduce each specific poly-saccharide in the cell wall, as the secondary xylem consists of primary and secondary wall layers. When placed horizontally, the basal regions of stems of transgenic poplars overexpressing xyloglucanase alone could not bend upward due to low strain in the tension side of the xylem. In the wild-type plants, xyloglucan was found in the inner surface of G-layers during multiple layering. In situ xyloglucan endotransglucosylase (XET) activity showed that the incorporation of whole xylo-glucan, potentially for wall tightening, began at the inner surface layers S1 and S2 and was retained throughout G-layer development, while the incorporation of xyloglucan heptasaccharide (XXXG) for wall loosening occurred in the primary wall of the expanding zone. We propose that the xyloglucan network is reinforced by XET to form a further connection between wall-bound and secreted xyloglucans in order to withstand the tensile stress created within the cellulose G-layer microfibrils.
The first ANDES elements: 9-DOF plate bending triangles
Militello, Carmelo; Felippa, Carlos A.
1991-01-01
New elements are derived to validate and assess the assumed natural deviatoric strain (ANDES) formulation. This is a brand new variant of the assumed natural strain (ANS) formulation of finite elements, which has recently attracted attention as an effective method for constructing high-performance elements for linear and nonlinear analysis. The ANDES formulation is based on an extended parametrized variational principle developed in recent publications. The key concept is that only the deviatoric part of the strains is assumed over the element whereas the mean strain part is discarded in favor of a constant stress assumption. Unlike conventional ANS elements, ANDES elements satisfy the individual element test (a stringent form of the patch test) a priori while retaining the favorable distortion-insensitivity properties of ANS elements. The first application of this formulation is the development of several Kirchhoff plate bending triangular elements with the standard nine degrees of freedom. Linear curvature variations are sampled along the three sides with the corners as gage reading points. These sample values are interpolated over the triangle using three schemes. Two schemes merge back to conventional ANS elements, one being identical to the Discrete Kirchhoff Triangle (DKT), whereas the third one produces two new ANDES elements. Numerical experiments indicate that one of the ANDES element is relatively insensitive to distortion compared to previously derived high-performance plate-bending elements, while retaining accuracy for nondistorted elements.
Electrical Bending and Mechanical Buckling Instabilities in Electrospinning Jets
Han, Tao; Reneker, Darrell H.
2007-03-01
The electrospinning jet was a continuous fluid flow ejected from the surface of a fluid when the applied electrical force overcomes the surface tension. The jet moved straight away from the tip and then became unstable and bent into coils. This phenomenon is the electrical bending instability [1]. When the distance between the tip and collector was reduced to less than the maximal straight segment length, the electrical bending instability did not occur. The periodic buckling of a fluid jet incident onto a surface is a striking fluid mechanical instability [2]. When axial compressive stress along the jet reached a sufficient value, it produced the fluid mechanics analogue to the buckling of a slender solid column. In the electrospinning, the buckling instability occurred just above the collector where the jet was compressed as it encountered the collector. The buckling frequencies of these jets are in the range of 10^4 to 10^5 Hz. The buckling lengths of these jets are in the range of 10 to 100μm. *Reneker,D.H.; Yarin, A. L.; Fong, H.; Koombhongse, S., Journal of Applied Physics, 87, 4531, 2000 *Tchavdarov B.; Yarin, A. L.; Radev S., Journal of Fluid Mechanics; 253, 593,1993
Finite element simulations of the bending of the IPMC sheet
Pugal, D.; Kasemägi, H.; Kim, K. J.; Kruusmaa, M.; Aabloo, A.
2007-04-01
This paper presents a electro-mechanical model of an IPMC sheet. The model is developed using Finite Element method. The physical bending of an IPMC sheet due to the drift of counter-ions (e.g Na+) and water in applied electric field are simulated. Our model establishes a cause-effect relationship between the charge imbalance of the counter-ions and the mechanical bending of the IPMC sheet. The model takes into account the mechanical properties of the Nafion polymer as well as the platinum coating. As the simulations are time dependent, a transient model is used and some additional parameters, such as damping coefficients, are included. In addition to electro-mechanical model, electrochemical reactions are introduced. Equations describing periodic adsorption and desorption of CO and OH on a platinum electrode of an IPMC muscle immersed into formaldehyde solution are coupled to mechanical properties of the proposed model. This permits us to simulate self-oscillatory behavious of an IPMC sheet. The simulation results are compared to experimental data.
Torsional and Bending Vibration Measurement on Rotors Using Laser Technology
MILES, T. J.; LUCAS, M.; HALLIWELL, N. A.; ROTHBERG, S. J.
1999-09-01
Based on the principles of laser Doppler velocimetry, the laser torsional vibrometer (LTV) was developed for non-contact measurement of torsional oscillation of rotating shafts, offering significant advantages over conventional techniques. This paper describes comprehensive theory to account for the sensitivity of the LTV's measurements to shaft motion in all degrees of freedom. The optical geometry of the LTV offers inherent immunity to translational motion of the target shaft, either axial or radial. However, its measurements are sensitive to angular lateral vibration of the shaft. The significance of this sensitivity is compared with the instrument noise floor and typical torsional and lateral vibration levels. Optimum alignments of the instrument are then specified to ensure effective immunity to all lateral motion in typical applications. To overcome this problem more reliably, a new technique is proposed permitting unambiguous measurement of pure torsional vibration in situations where use of a single LTV demonstrates unacceptable sensitivity to angular lateral vibrations. Practical application of this technology is demonstrated with torsional vibration measurements from a diesel engine crankshaft. Simultaneously, previously unattained measurements of shaft bending vibration measurements are made. The first bending mode of the crankshaft was identified and its vibration amplitude and damping estimated. This application of laser vibrometry for non-contact measurements of shaft vibration represents a further step forward in the use of this technology for machinery diagnostics.
Bending mechanics of the red-eared slider turtle carapace.
Achrai, Ben; Bar-On, Benny; Wagner, H Daniel
2014-02-01
The turtle shell is a natural shield that possesses complex hierarchical structure, giving rise to superior mechanical properties. The keratin-covered boney top (dorsal) part of the shell, termed carapace, is composed of rigid sandwich-like ribs made of a central foam-like interior flanked by two external cortices. The ribs are attached to one another in a 3-D interdigitated manner at soft unmineralized collagenous sutures. This unique structural combination promotes sophisticated mechanical response upon predator attacks. In the present study mechanical bending tests were performed to examine the static behavior of the red-eared slider turtle carapace, in different orientations and from various locations, as well as from whole-rib and sub-layer regions. In addition, the suture properties were evaluated as well and compared with those of the rib. A simplified classical analysis was used here to rationalize the experimental results of the whole rib viewed as a laminated composite. The measured strength (~300MPa) and bending modulus (~7-8.5GPa) of the rib were found to be of the same order of magnitude as the strength and modulus of the cortices. The theoretical prediction of the ribs' moduli, predicted in terms of the individual sub-layers moduli, agreed well with the experimental results. The suture regions were found to be more compliant and weaker than the ribs, but comparatively tough, likely due to the interlocking design of the boney zigzag elements. © 2013 Elsevier Ltd. All rights reserved.
Overall Thermal Performance of Flexible Piping Under Simulated Bending Conditions
Fesmire, James E.; Augustynowicz, S. D.; Demko, J. A.; Thompson, Karen (Technical Monitor)
2001-01-01
Flexible, vacuum-insulated transfer lines for low-temperature applications have higher thermal losses than comparable rigid lines. Typical flexible piping construction uses corrugated tubes, inner and outer, with a multilayer insulation (MLI) system in the annular space. Experiments on vacuum insulation systems in a flexible geometry were conducted at the Cryogenics Test Laboratory of NASA Kennedy Space Center. The effects of bending were simulated by causing the inner tube to be eccentric with the outer tube. The effects of spacers were simulated in a controlled way by inserting spacer tubes for the length of the cylindrical test articles. Two material systems, standard MLI and a layered composite insulation (LCI), were tested under the full range of vacuum levels using a liquid nitrogen boiloff calorimeter to determine the apparent thermal conductivity (k-value). The results indicate that the flexible piping under simulated bending conditions significantly degrades the thermal performance of the insulation system. These data are compared to standard MLI for both straight and flexible piping configurations. The definition of an overall k-value for actual field installations (k(sub oafi)) is described for use in design and analysis of cryogenic piping systems.
Sensor enabled closed-loop bending control of soft beams
Case, Jennifer C.; White, Edward L.; Kramer, Rebecca K.
2016-04-01
Control of soft-bodied systems is challenging, as the absence of rigidity typically implies distributed deformations and infinite degrees-of-freedom. In this paper, we demonstrate closed-loop control of three elastomer beams that vary in bending stiffness. The most stiff beam is comprised of a single prismatic structure made from a single elastomer. In the next beam, increased flexibility is introduced via an indentation in the elastomer, forming a joint. The most flexible beam uses a softer elastomer in the joint section, along with an indentation. An antagonistic pair of actuators bend the joint while a pair of liquid-metal-embedded strain sensors provide angle feedback to a control loop. We were able to achieve control of the system with a proportional-integral-derivative control algorithm. The procedure we demonstrate in this work is not dependent on actuator and sensor choice and could be applied to to other hardware systems, as well as more complex multi-joint robotic structures in the future.
Thermal fluctuations and bending rigidity of bilayer membranes.
Tarazona, Pedro; Chacón, Enrique; Bresme, Fernando
2013-09-07
We present a new scheme to estimate the elastic properties of biological membranes in computer simulations. The method analyzes the thermal fluctuations in terms of a coupled undulatory mode, which disentangle the mixing of the mesoscopic undulations and the high-q protrusions. This approach makes possible the accurate estimation of the bending modulus both for membranes under stress and in tensionless conditions; it also extends the applicability of the fluctuation analysis to the small membrane areas normally used in atomistic simulations. Also we clarify the difference between the surface tension imposed in simulations through a pressure coupling barostat, and the surface tension that can be extracted from the analysis of the low wave vector dependence of the coupled undulatory fluctuation spectrum. The physical analysis of the peristaltic mode is also refined, by separating the bulk and protrusions contributions. We illustrate the procedure by analyzing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine bilayers. The bending moduli obtained from our analysis, shows good agreement with available experiments.
Bending characteristics of dual-hole PM-PCF based on LP01 and LP11 modal interference
Guo, Xuan; Liu, Feng; Gao, Meng-yuan; Tan, Ai-ling; Fu, Xing-hu; Bi, Wei-hong
2016-03-01
The bending characteristics of dual-hole polarization maintaining photonic crystal fiber (PM-PCF) are demonstrated in this paper. The modal interference is induced by the LP01 mode and LP11 mode propagating in a single PM-PCF with the same polarization direction. Simulation results demonstrate that the bending radius induces the phase difference between LP01 mode and LP11 mode, which leads to the change of light interference intensity on the fiber output facet. The relationship between bending radius and normalized interference intensity with three different bending angles is discussed, where the bending angle is defined as the angle between hole axis and the x axis. The bending sensitivity is obtained to be about -188.78/m around the bending radius of 1.5 cm with the bending angle of 90°. The bending characteristics can contribute for online bending detection in widespread areas.
Abdelkefi, A.; Najar, F.; Nayfeh, A. H.; Ben Ayed, S.
2011-11-01
Recently, piezoelectric cantilevered beams have received considerable attention for vibration-to-electric energy conversion. Generally, researchers have investigated a classical piezoelectric cantilever beam with or without a tip mass. In this paper, we propose the use of a unimorph cantilever beam undergoing bending-torsion vibrations as a new piezoelectric energy harvester. The proposed design consists of a single piezoelectric layer and a couple of asymmetric tip masses; the latter convert part of the base excitation force into a torsion moment. This structure can be tuned to be a broader band energy harvester by adjusting the first two global natural frequencies to be relatively close to each other. We develop a distributed-parameter model of the harvester by using the Euler-beam theory and Hamilton's principle, thereby obtaining the governing equations of motion and associated boundary conditions. Then, we calculate the exact eigenvalues and associated mode shapes and validate them with a finite element (FE) model. We use these mode shapes in a Galerkin procedure to develop a reduced-order model of the harvester, which we use in turn to obtain closed-form expressions for the displacement, twisting angle, voltage output, and harvested electrical power. These expressions are used to conduct a parametric study for the dynamics of the system to determine the appropriate set of geometric properties that maximizes the harvested electrical power. The results show that, as the asymmetry is increased, the harvester's performance improves. We found a 30% increase in the harvested power with this design compared to the case of beams undergoing bending only. We also show that the locations of the two masses can be chosen to bring the lowest two global natural frequencies closer to each other, thereby allowing the harvesting of electrical power from multi-frequency excitations.
Experimental Determination of Bending Resonances of Millimeter Size PVF2 Cantilevers
David F. Thompson
2003-07-01
Full Text Available The polymer piezoelectric polvinylidene fluoride has found widespread use in sensors and actuators. The bending mode of piezoelectricity offers very high sensitivities and low mechanical input impedance, but has not been studied in as much detail for sensor applications. We report the dynamic electromechanical properties of millimeter size cantilevers made from electroded films of PVF2. All devices tested had a single polymer layer. Several resonances are found below 1 kHz and the experimentally observed resonance frequency dependence on cantilever thickness and length are seen to agree well with published models which take the properties of the electrodes into account. It is found that bending resonances are also modulated by the width of the cantilever. Therefore, though the length and thickness control the resonance frequency most strongly, the actual realized value can be fine-tuned by changing cantilever width and the electrode material and its thickness. Further, all resonances display high piezoelectric coupling coefficients (keff, ranging between 0.2 - 0.35. The data presented here will be extremely useful in the design of sensors and actuators for a number of applications, since the combination of millimeter size scales and high piezoelectric sensitivities in the low audio range can be realized with this marriage of polymeric materials and cantilever geometries. Such an array of sensors can be used in cochlear implant applications, and when integrated with a resonance interrogation circuit can be used for the detection of low frequency vibrations of large structures. If appropriate mass/elasticity sensitive layers are coated on the electrodes, such a sensor can be used for the detection of a wide range of chemicals and biochemicals.
Fu, Y. B.; Liu, J. L.; Francisco, G. S.
2016-05-01
We study localized bulging of a cylindrical hyperelastic tube of arbitrary thickness when it is subjected to the combined action of inflation and axial extension. It is shown that with the internal pressure P and resultant axial force F viewed as functions of the azimuthal stretch on the inner surface and the axial stretch, the bifurcation condition for the initiation of a localized bulge is that the Jacobian of the vector function (P , F) should vanish. This is established using the dynamical systems theory by first computing the eigenvalues of a certain eigenvalue problem governing incremental deformations, and then deriving the bifurcation condition explicitly. The bifurcation condition is valid for all loading conditions, and in the special case of fixed resultant axial force it gives the expected result that the initiation pressure for localized bulging is precisely the maximum pressure in uniform inflation. It is shown that even if localized bulging cannot take place when the axial force is fixed, it is still possible if the axial stretch is fixed instead. The explicit bifurcation condition also provides a means to quantify precisely the effect of bending stiffness on the initiation pressure. It is shown that the (approximate) membrane theory gives good predictions for the initiation pressure, with a relative error less than 5%, for thickness/radius ratios up to 0.67. A two-term asymptotic bifurcation condition for localized bulging that incorporates the effect of bending stiffness is proposed, and is shown to be capable of giving extremely accurate predictions for the initiation pressure for thickness/radius ratios up to as large as 1.2.
Damage mechanisms of Ti-Al intermetallics in three point ultrasonic bending fatigue
E. Bayraktar
2007-09-01
Full Text Available Purpose: Damage mechanisms of two phases (α2−Ti3Al and γ−Ti-Al intermetallics alloy are investigated at room temperature in a new developed resonance type 3- point (3P fatigue bending test device at a frequency of 20 kHz.Design/methodology/approach: Manufacturing and analysis of composition of this alloy were carried out in advanced materials laboratory by collaborating with aircraft design engineering department for non-ferrous metal research centre in China. All of the 3P- fatigue bending were carried out at the stress ratios of R=0.1, R=0.5, R=0.7 mainly in gigacycle regime.Findings: Damage mechanisms were compared in static and dynamic test conditions. The geometries of static tensile test and ultrasonic fatigue test specimens have been calculated by analytical or numerical method as discussed in detail formerly. This paper gives further results and more complicate discussion on this study particularly on the crack formation and the role of the different parameters on the damage mechanisms of this alloy. Damage analysis was made by means of optical (OM and Scanning Electron Microscopies (SEM.Research limitations/implications: Paper gives results and more complicate discussion on the crack formation and the role of the different parameters on the damage mechanisms of this alloy.Originality/value: This study proposes a new methodology for fatigue design and a new idea on the criterion for the damage under very high cycle fatigue regime. The results are well comparables for the specimens under real service conditions. This type of study gives many facilities for the sake of simplicity in industrial application.
Wire-bending test as a predictor of preclinical performance by dental students.
Kao, E C; Ngan, P W; Wilson, S; Kunovich, R
1990-10-01
Traditional Dental Aptitude Test and academic grade point average have been shown to be poor predictors of clinical performance by dental students. To refine predictors of psychomotor skills, a wire-bending test was given to 105 freshmen at the beginning of their dental education. Grades from seven restorative preclinical courses in their freshman and sophomore years were compared to scores on wire bending and the three traditional predictors: GPA, academic aptitude, and perceptual aptitude scores. Wire-bending scores correlated significantly with six out of seven preclinical restorative courses. The predictive power for preclinical performance was doubled when wire bending was added to traditional predictors in stepwise multiple regression analysis. Wire-bending scores identified students of low performance. These preliminary results suggest that the wire-bending test shows some potential as a screening test for identifying students who may hae psychomotor difficulties, early in their dental education.
Jui-Chang Lin
2015-01-01
Full Text Available The three-dimensional tube (or pipe is manufactured by CNC tube bending machine. The key techniques are determined by tube diameter, wall thickness, material, and bending radius. The obtained technique through experience and the trial and error method is unreliable. Finite element method (FEM simulation for the tube bending process before production can avoid wasting manpower and raw materials. The computer-aided engineering (CAE software ABAQUS 6.12 is applied to simulate bending characteristics and to explore the maximum stress and strain conditions. The Taguchi method is used to find the optimal parameters of bending. The confirmation experiment is performed according to optimal parameters. Results indicate that the strain error between CAE simulation and bending experiments is within 6.39%.
Theoretical analysis on shear-bending deflection of a ring-shape piezoelectric plate
Zejun Yu
2016-02-01
Full Text Available In this paper, the electromechanical coupling field in shear-bending mode for a ring-shape piezoelectric plate was theoretically established. According to the classical small bending elastic plate theory and piezoelectric constitutive equations, the analytical solution to the bending deformation of the piezo-actuator under electric field and a concentrated or uniformly distributed mechanical load was achieved. The mechanism for generating bending deformation is attributed to axisymmetric shear strain, which further induces the bending deformation of the single ring-shape piezoelectric plate. This mechanism is significant different from that of piezoelectric bimorph or unimorph actuators reported before. Our analysis offers guidance for the optimum design of a ring-shape shear-bending piezo-actuator.