Auswahl der wissenschaftlichen Literatur zum Thema „Wedge coupling“

Wedge waves (WW) are guided acoustic waves propagating along the tip of a wedge, with energy tightly confined near the apex. Like Lamb waves, wedge waves with displacement field anti-symmetric about the mid-apex-plane are called anti-symmetric flexural (ASF) modes. This study is focused on exploring the dispersion behaviors of ASF modes propagating along a bilinear wedge (BW). A BW is wedge with a cross section of two apex angles, compared with a linear wedge (LW) having a single apex angle. In the literature, many studies regarding to the dispersion behaviors of ASF modes are reported for LW, but not for BW. In this study, a laser ultrasonic technique and finite element simulations are used to investigate the dispersion behavior of BW-ASF modes. It is found out that a BW-ASF mode is a result of mode coupling between the two LW-ASF modes of the same order corresponding to the two apex angles of the BW.

A super wedge tip element for application to a bi-material wedge is develop utilizing the thermo-mechanical stress and displacement field solutions in which the singular parts are numerical solutions. Singular stresses near apex of an arbitrary bi-material wedge under mechanical and thermal loading can be obtained from the coupling between the super wedge tip element and conventional finite elements. The validity of this novel finite element method is established through existing asymptotic solutions and conventional detailed finite element analysis.

A new type of rigid-flexible coupling three degrees of freedom (3-DOF) micro-positioning platform with high positioning accuracy and high bearing capacity is developed, which consists of flexible drive mechanism and rigid platform. The flexible drive mechanism consists of three sets of symmetrical parallel round flexible hinge structures, each with a wedge structure in the middle of the symmetrical parallel flexible hinge. The rigid platform has an inclined plane with the same angle as the wedge, while the wedge structure is used to achieve the self-locking effect. The flexibility matrix method and ANSYS are used to analyze the statics of the flexible drive mechanism. The first four natural frequencies of the platform are obtained by dynamic simulation analysis. A symmetrical rigid flexible coupling micro-positioning platform experimental system is developed. Output characteristics, positioning accuracy, relationship between frequency and amplitude, and bearing performance of the micro-positioning platform are tested. These experimental results obviously show that the micro-positioning platform has good motion characteristics, high positioning accuracy, large movement distance, and large load bearing capacity performance.

Friction dampers are often used in turbine design to attenuate blade vibration to acceptable levels so as to prolong blades’ service life. A wedge damper, also called a self-centering, blade-to-blade damper, can provide more design flexibility to meet various needs in different operating conditions when compared with conventional platform dampers. However, direct coupling of the two inclined friction interfaces of the wedge damper often leads to very complex contact kinematics. In Part I of this two-part paper, a dual-interface friction force model is proposed to investigate the coupling contact kinematics. The key issue of the model formulation is to derive analytical criteria for the stick-slip transitions that can be used to precisely simulate the complex stick-slip motion and, thus, the induced friction force as well. When considering cyclic loading, the induced periodic friction forces can be obtained to determine the effective stiffness and damping of the interfaces over a cycle of motion. In Part II of this paper, the estimated stiffness and damping are then incorporated with the harmonic balance method to predict the forced response of a blade constrained by wedge dampers.

The kinematics and architecture of orogenic systems may be heavily influenced by climate, but little research has focused on the long-term effects of glacial erosion on orogenesis. Low-temperature thermochronometry and subsidiary structural, earthquake relocation, and offshore seismic reflection data from the St. Elias orogen are the basis for a new architectural model and demonstrate an association between glacial denudation and orogenic evolution. These data show that exhumation and deformation within the St. Elias orogen are focused across a thin-skinned fold and thrust belt on the windward flank, whereas the leeward flank functions as a deformational backstop. A previously unrecognized structure beneath the Bagley ice field separates these domains with south-side-up motion. This structure is interpreted to be a backthrust, making the orogen doubly-vergent. Suggestive of accelerated fault motion in response to climate change, bedrock cooling rates within the hanging wall of the backthrust and across the entire subaerial wedge accelerated ~ten-fold coeval with the onset of intense glacial conditions. Within the orogenic wedge, the zone of highest Quaternary exhumation (5 km/myr (±25%)) is focused around a narrow zone where the glacial equilibrium line altitude (ELA) intersects mean topography. This zone of rapid exhumation, not present prior to the onset of intense glacial conditions, cuts across the structural trend of the orogen and is more narrowly focused than the zone of orographic precipitation. Augmented glacial erosion around glacial ELA also coincided with a regional shift in deformation away from prominent forethrusts including the North American-Yakutat terrane suture (Chugach St. Elias fault) and the seaward deformation front (Pamplona zone). Accelerated denudation across the subaerial wedge thus appears to have forced the redistribution of strain along the backthrust and a series of forethrusts that lie beneath the zone of highest glacial flux, which in turn are systematically truncated by the backthrust. In a cause and effect response, the expansion of glaciers therefore appears to have resulted in an orogen scale structural reorganization and a narrowing of the orogenic wedge to preserve topographic slope. The focusing of long-term erosion around glacial ELA and the structural response of the orogenic wedge to Cenozoic climate change have not previously been observed in a real-world orogenic system and imply a high degree of coupling between climate and tectonics in this glacially-dominated orogen.
Ph. D.

[ES] En la actualidad, una gran cantidad de infraestructuras están compuestas de forma parcial o total de materiales cementicios, siendo el hormigón uno de los materiales cementicios más antiguos y utilizados en la construcción debido a su bajo coste, durabilidad y características mecánicas y estructurales. Pese a sus características, estos materiales están expuestos a diversas condiciones adversas del entorno y sufren procesos de deterioro que afectan a su integridad y seguridad. El reconocimiento de la integridad y seguridad en las estructuras cementicias ha implicado una extensa investigación y el desarrollo de diversas pruebas para verificar su calidad y estado. Mediante la destrucción de una muestra extraída de la estructura, en el caso de los ensayos destructivos (ED), o mediante la inspección de la estructura sin necesidad de dañarla o alterar sus propiedades, en el caso de los ensayos no destructivos (END). Existen multitud de técnicas END que tratan de caracterizar estas estructuras sin dañarlas, siendo la inspección mediante ultrasonidos una de las más utilizadas en materiales cementicios. Tradicionalmente estas técnicas ultrasónicas se basan en el estudio de las ondas longitudinales (P) y transversales (S), que permiten caracterizar una estructura mediante la realización de múltiples medidas. Sin embargo, existe otro tipo de ondas, formadas por la superposición de los desplazamientos de las partículas de las ondas P y S denominadas ondas guiadas, las cuales permiten inspeccionar una estructura de forma global a partir de una única medida, además de ser capaces de propagarse a grandes distancias manteniendo una buena relación señal-a-ruido en comparación a las ondas P y S. Dentro de las ondas guiadas más utilizadas para inspeccionar materiales cementicios, se encuentran las ondas de Rayleigh y las ondas de Lamb. Las ondas de Rayleigh se propagan en estructuras de gran espesor, mientras que las ondas de Lamb se propagan en placas. Las ondas de Lamb presentan una naturaleza dispersiva y multimodal. Su naturaleza dispersiva implica que las velocidades de fase y grupo de estas ondas depende de la frecuencia, mientras que la naturaleza multimodal implica que existen cada vez más modos de propagación conforme aumenta la frecuencia de excitación. Se pueden excitar y detectar selectivamente los distintos modos de Lamb mediante la incidencia oblicua, es decir, variando la inclinación del transmisor y el receptor. Para ello, existen distintas técnicas de acoplamiento que permiten la incidencia oblicua, como el acoplamiento por cuñas sólidas, el acoplamiento por agua y el acoplamiento por aire. La presente tesis se ha centrado en el estudio de nuevas técnicas de END basadas en ondas guiadas para caracterizar diferentes tipos de daño en los materiales cementicios. Para ello, se han llevado a cabo un número considerable de medidas experimentales basadas en distintas técnicas de acoplamiento para la generación y captación de ondas guiadas. Inicialmente se han analizado materiales homogéneos como los metales, para, posteriormente, utilizar el conocimiento adquirido en dichos materiales y estudiar materiales más heterogéneos como los cementicios. Se han evaluado diferentes tipos de técnicas de acoplamiento junto con diferentes tipos de transductores. Los materiales cementicios se han inspeccionado mediante ondas guiadas ultrasónicas con dos tipos de daño: la carbonatación, estudiando el efecto con probetas de dos capas de mortero, y el envejecimiento de fibras en placas de cemento reforzado con fibra de vidrio (GRC). Se ha demostrado que las ondas guiadas son sensibles a estos daños, obteniendo resultados esperanzadores. Concretamente, las ondas de Rayleigh se han utilizado en el daño por carbonatación debido a su sensibilidad a capas superficiales de degradación, mientras que en el envejecimiento de fibras se han utilizado las ondas de Lamb, por su sensibilidad a defectos a lo largo
[CA] En l'actualitat, una gran quantitat d'infraestructures estan formades totalment o parcialment de materials cementants. El formigó és un dels materials cementants més antics i utilitzats en la construcció degut al seu preu, la seua durabilitat i les seues característiques mecàniques i estructurals. Malgrat la seua durabilitat i característiques, aquests materials estan exposats a diverses condicions adverses de l'entorn i pateixen processos de deterioració que afecten la seua integritat i seguretat. El reconeixement de la integritat i seguretat en les estructures cementants ha implicat una extensa investigació i el desenvolupament de diverses proves per a verificar la seua qualitat i estat. Mitjançant la destrucció d'una mostra de l'estructura en el cas dels assajos destructius, o mitjançant la inspecció de l'estructura sense danyar-la o alterar les seues propietats en el cas dels assajos no destructius. Existeixen multitud de tècniques d'inspecció no destructiva que tracten de caracteritzar aquestes estructures sense danyar-les. La inspecció mitjançant ultrasons és un dels assajos no destructius més utilitzats en materials cementants. Tradicionalment, aquestes tècniques ultrasòniques estan basades en l'estudi de les ones longitudinals (P) i transversals (S), que permeten caracteritzar una estructura mitjançant la realització de múltiples mesures en l'estructura. No obstant, existeixen altres tipus d'ones, formades per la superposició dels desplaçaments de les partícules de les ones P i S, denominades ones guiades, les quals permeten inspeccionar una estructura de manera global a partir d'una única mesura, a més de poder propagar-se a grans distàncies mantenint una bona relació senyal-soroll en comparació a les ones P i S. Dins de les ones guiades més utilitzades per a inspeccionar materials cementants, es troben les ones de Rayleigh i les ones de Lamb. Les ones de Rayleigh es propaguen en estructures de gran grossària, mentre que les ones de Lamb es propaguen en plaques. Les ones de Lamb presenten una naturalesa dispersiva i multimodal. La seua naturalesa dispersiva implica que les velocitats de fase i grup d'aquestes ones depenen de la freqüència, mentre que la naturalesa multimodal implica que apareguen més modes de propagació a l'augmentar la freqüència d'excitació. Es poden excitar i detectar selectivament els diferents modes de Lamb mitjançant la incidència obliqua, és a dir, variant la inclinació del transmissor i el receptor. Existeixen diferents tècniques d'acoblament que permeten la incidència obliqua, com l'acoblament per metacrilat, l'acoblament per aigua i l'acoblament per aire. Aquesta tesi s'ha enfocat en l'estudi de noves tècniques d'assajos no destructius basades en ones guiades (ones de Rayleigh i ones de Lamb) per a caracteritzar diferents tipus de dany en els materials cementants. S'han realitzat un nombre considerable de mesures experimentals basades en diferents tècniques d'acoblament per a la generació i captació d'ones guiades. Inicialment s'han analitzat materials homogenis com els metalls per a, posteriorment, utilitzar el coneixement adquirit en aquests materials i estudiar d'altres més heterogenis com els cementants. Concretament, s'han avaluat diferents tipus de tècniques d'acoblament i diferents tipus de transductors. Els materials cementants s'han inspeccionat mitjançant ones guiades ultrasòniques amb dos tipus de dany o degradació: la carbonatació, estudiant el seu efecte amb provetes de dues capes de morter, i l'envelliment de fibres en plaques de ciment reforçat amb fibra de vidre (GRC). S'ha demostrat que les ones guiades són sensibles a aquests danys, obtenint resultats esperançadors. Concretament, les ones de Rayleigh s'han utilitzat en el dany per carbonatació a causa de la seua sensibilitat a capes superficials de degradació, mentre que en l'envelliment de fibres s'han utilitzat les ones de Lamb, per la seua sensibilitat a defe
[EN] Nowadays, a large number of infrastructures are partially or wholly built with cementitious materials. Concrete is one of the oldest and most popular cementitious materials due to its low cost, durability and remarkable mechanical and structural characteristics. However, if these materials are exposed to different environments and harsh conditions, they suffer damaging processes that affect their integrity and safety. To verify their state and quality, extensive research has been conducted and several tests have been developed, such as destructive testing and non-destructive testing. Destructive testing (DT) requires a sample of the inspected structure while non-destructive testing (NDT) allows the inspection of the structure without altering its properties and without damaging it. There are several NDT techniques that characterize cementitious structures without harming them, such as ultrasonic testing, which is one of the most widely used. This technique is based on the study of longitudinal (P) and shear (S) waves, which enable the characterization of a structure by a point-by-point scan. However, there are another kind of waves, called guided waves, which are composed of the superposition of the P and S wave particle displacements. Unlike P and S waves, guided waves allow a global inspection of a structure from a single transducer position and they are able to propagate over long distances with a good signal-to-noise ratio. Rayleigh and Lamb waves are the most frequently used guided waves in NDT of cementitious materials. Rayleigh waves propagate in thick structures while Lamb waves propagate in plate-like structures. Lamb waves are dispersive (their phase and group velocities depend on frequency) and multimodal (as frequency increases, many propagation modes with different velocities exist in the received signal). Lamb wave modes can be selectively excited and detected by means of oblique incidence, i.e., by varying the inclination of the transmitting and receiving transducers. Different coupling techniques can be used to change the inclination of the transducers, such as the contact technique with angle beam wedge transducers, water coupling and air coupling. This thesis has been focused in the study of new NDT techniques based on guided waves (Rayleigh and Lamb waves) to characterize different types of damage of cementitious materials. For this goal, a significant number of experimental arrangements based on different coupling techniques have been carried out. Firstly, homogeneous materials as metals have been analized, because they are a reference in guided wave testing. After performing different experiments in metals, the acquired knowledge has been used to inspect heterogeneous materials as cementitious ones. Different coupling techniques (variable angle wedges, immersion testing, fixed angle wedges, ...) with different types of transducers (contact transducers, immersion transducers and air-coupled transducers) have been employed. Cementitious materials with two damaging processes have been inspected by means of guided waves: two-layered mortar specimens to study carbonation and glass-fibre reinforced cement (GRC) plates to study fiber ageing. This thesis demonstrates that guided waves are sensitive to these damaging processes and the obtained results are encouraging. Specifically, Rayleigh waves have been used to detect carbonation due to its sensitivity to surface layers, while Lamb waves have been used to detect fiber ageing due to its sensitivity to defects along the thickness of the GRC plates.
La investigación realizadaen esta tesis se ha financiado con las siguientes ayudas y proyectos concedidos por el gobierno español: Ayudas para contratos predoctorales para la formación de doctores 2015 (BES-2015-071958); Nuevas aplicaciones de ensayos no destructivos basados en ondas mecánicas para la evaluación de la degradación en materiales cementantes (BIA2014-55311-C2-2-P); Desarrollo y aplicación de ensayos no destructivos basados en ondas mecánicas para la evaluación y monitorización de reología y autosanación en materiales cementantes (BIA2017-87573-C2)
Vázquez Martínez, S. (2021). Nuevas técnicas de ensayos no destructivos basadas en ondas mecánicas para la valoración del daño en materiales cementicios [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/165531
TESIS

The transport or the separation of solid particles or droplets suspended in a fluid flow is a common task in mechanical and process engineering. To improve machinery and physical processes (e.g. for coal combustion, reduction of NO_x and soot) an optimization of complex phenomena by simulation applying the fundamental conservation equations is required. Fluid-particle flows are characterized by the ratio of density of the two phases gamma=rho_P/rho_F, by the Stokes number St=tau_P/tau_F and by the loading in terms of void and mass fraction. Those numbers (Stokes number, gamma) define the flow regime and which relevant forces are acting on the particle. Dependent on the geometrical configuration the particle-wall interaction might have a heavy impact on the mean flow structure. The occurrence of particle-particle collisions becomes also more and more important with the increase of the local void fraction of the particulate phase. With increase of the particle loading the interaction with the fluid phase can not been neglected and 2-way or even 4-way coupling between the continous and disperse phases has to be taken into account. For dilute to moderate dense particle flows the Euler-Lagrange method is capable to resolve the main flow mechanism. An accurate computation needs unfortunately a high number of numerical particles (1,...,10^7) to get the reliable statistics for the underlying modelling correlations. Due to the fact that a Lagrangian algorithm cannot be vectorized for complex meshes the only way to finish those simulations in a reasonable time is the parallization applying the message passing paradigma. Frank et al. describes the basic ideas for a parallel Eulererian-Lagrangian solver, which uses multigrid for acceleration of the flow equations. The performance figures are quite good, though only steady problems are tackled. The presented paper is aimed to the numerical prediction of time-dependend fluid-particle flows using the simultanous particle tracking approach based on the Eulerian-Lagrangian and the particle-source-in-cell (PSI-Cell) approach. It is shown in the paper that for the unsteady flow prediction efficiency and load balancing of the parallel numerical simulation is an even more pronounced problem in comparison with the steady flow calculations, because the time steps for the time integration along one particle trajectory are very small per one time step of fluid flow integration and so the floating point workload on a single processor node is usualy rather low. Much time is spent for communication and waiting time of the processors, because for cold flow particle convection not very extensive calculations are necessary. One remedy might be a highspeed switch like Myrinet or Dolphin PCI/SCI (500 MByte/s), which could balance the relative high floating point performance of INTEL PIII processors and the weak capacity of the Fast-Ethernet communication network (100 Mbit/s) of the Chemnitz Linux Cluster (CLIC) used for the presented calculations. Corresponding to the discussed examples calculation times and parallel performance will be presented. Another point is the communication of many small packages, which should be summed up to bigger messages, because each message requires a startup time independently of its size. Summarising the potential of such a parallel algorithm, it will be shown that a Beowulf-type cluster computer is a highly competitve alternative to the classical main frame computer for the investigated Eulerian-Lagrangian simultanous particle tracking approach.

Hydroelastic effects during slamming of high-speed marine vehicles affect the development of the pressure along their bottom. The aim of this study is to investigate coupling process of a novel CFD method and a FEM structural solver for simulation of hydroelastic slamming. As slamming is characterised by violent and strongly nonlinear fluid–structure interaction, the flow solver is based on a Lagrangian, volume–conservative, second–order accurate method, meshless FDM. Rhoxyz fluid solver is coupled to CalculiX structural solver, through a partitioned bidirectional coupling tool, preCICE. After the validation of coupling using a dam break experiment, the effect of hydroelasticity in slamming is studied by analysing the pressure and deformations of the structure during water entries of a deformable symmetrical wedge with low angle of deadrise.

Alcohols are usually protected as alkyl or silyl ethers. Michael P. Jennings of the University of Alabama found (Tetrahedron Lett. 2008, 49, 5175) that pyridinium tribromide can selectively remove the TBS (or TES) protection from the primary alcohol of a protected primary-secondary alcohol such as 1. Propargyl ethers are useful because they are stable, but can be selectively removed in the presence of other protecting groups. Shino Manabe and Yukishige Ito at RIKEN showed (Tetrahedron Lett. 2008, 49, 5159) that SmI2 could reductively remove a propargyl group in the presence of acetonides (illustrated, 3), MOM, benzyl and TBS ethers. Hisanaka Ito of the Tokyo University of Pharmacy and Life Sciences took advantage (Organic Lett. 2008, 10, 3873) of the reducing power of Cp2Zr to selectively remove the allyl ethers from 5, to give 6. These conditions might also remove propargyl ethers. Esters can also be useful protecting groups. Naoki Asao of Tohoku University developed (Tetrahedron Lett . 2008, 49, 7046) the o-alkynyl ester 7. Au catalyst in EtOH removed the ester, leaving benzoates, acetates, OTBS and OTHP intact. Alternatively, an o-iodobenzoate can be removed by Sonogashira coupling followed by the Au hydrolysis. N-Formylation is usually accomplished using mixed anhydrides. Weige Zhang and Maosheng Chang of Shenyang Pharmaceutical University put forward ( Chem. Commun. 2008 , 5429) an intriguing alternative, heating a secondary amine 9 with KCN in the presence of dimethyl malonate to give 10. Many of the current methods for amination that have been developed deliver the aryl amine. John F. Hartwig of the University of Illinois established (J. Am. Chem. Soc. 2008, 130, 12220) that exposure of the amine 11 to Boc2O followed by CAN led to the protected, dearylated amine 12. Adam McCluskey of The University of Newcastle observed (Tetrahedron Lett. 2008, 49, 6962) that microwave heating removed Boc protecting groups when there was a free carboxylic acid elsewhere in the molecule. Michael Lefenfeld of SiGNa Chemistry and James E. Jackson of Michigan State University used (Organic Lett. 2008, 10, 5441) easilyhandled Na/silica gel to remove primary and secondary sulfonamides (e.g. 15 → 16). Methanesulfonamides were also removed under these conditions.

Abstract Polyethylene pipe has been used widely in gas transportation and nuclear safety-related cooling water applications due to its exceptional resistance to corrosion and erosion. Butt fusion joint is one of the main welding forms for polyethylene pipes. Ultrasonic technique is a typical nondestructive examination technique. To overcome the coupling problems when inspecting butt fusion structures, an inspection technique of ultrasonic phased array using water wedge is proposed to solve the coupling matching and to increase the ultrasound amplitudes. The influences on the imaging of the parameters (such as the angle and height of the water wedge), the array element specifications, and the aperture, were investigated via simulations. The parameter optimization was conducted to establish a suitable detection process. After that, the related probe and a simulated water wedge were designed based on the results and manufactured, in which the simulated wedge as a specific probe holder could adjust its own incident angle and array height. Meanwhile, a typical DN315 pipe of PE 100 was made with some typical artificial defects in it. Experiments were conducted, and the results showed that the proposed water-wedged ultrasonic phased array technique is suitable for butt fusion joint inspection.

This paper presents a study of fluid structure interaction during the impact of a ship on a water surface. The analysis combines the assumption of small displacements for the ideal fluid and the solid with an asymptotic formulation for accurate pressure evaluation on the wet surface boundary. A fluid-heat analogy is used to obtain the regular displacement, velocity and pressure fields in the fluid domain with ABAQUS/Standard finite element code. PYTHON and FORTRAN languages are also employed to connect fluid and structure data. Two methods are developed. The first method employs a weak fluid-structure coupling. The average discrepancy between our numerical results and experiments was 22% for the peak pressures for conical shell structures. The wet surface velocity was well predicted. The second method (implicit fluid-structure coupling using a convergence criterion) is more accurate. Recent results with an improved, numerical hydrodynamic model based on CFD are also presented.

The purpose of this paper is to study and compare two finite element coupling methods to simulate the problem of a body penetrating a free surface. The hydrodynamic impact problem concerns industrial designers in shipbuilding domain. In rough seas, sometimes ships suffer local damages from large water impact loads called slamming impacts. In the framework of a collaboration with a french research company in shipbuilding (Principia Marine) a numerical prediction of the local impulse load on a wedge striking a free surface is investigated by using two methods: penalty and Lagrange multiplier formulations. These methods of coupling, which makes it possible to transmit the efforts in pressure from the Eulerian formulation to the Lagrangian formulation and conversely are relatively recent algorithmic developments. The Euler/Lagrange penalty method was successfully used in many scientific and industrial applications: the modeling of the attack of birds on the fuselage of a Jet for the Boeing Corporation, the underwater explosion shaking the oil platforms, the airbag simulation... The explicit coupling based on multiplier approach is a new development, which is compared to the penalty method. For both methods, a parametric study of the local pressure peak is investigated for impact angles from 0 to 30 degrees.