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1
Mockutė, Agota, Enzo Marino, Claudio Lugni y Claudio Borri. "Comparison of Nonlinear Wave-Loading Models on Rigid Cylinders in Regular Waves". Energies 12, n.º 21 (23 de octubre de 2019): 4022. http://dx.doi.org/10.3390/en12214022.
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Monopiles able to support very large offshore wind turbines are slender structures susceptible to nonlinear resonant phenomena. With the aim to better understand and model the wave-loading on these structures in very steep waves where ringing occurs and the numerical wave-loading models tend to lose validity, this study investigates the distinct influences of nonlinearities in the wave kinematics and in the hydrodynamic loading models. Six wave kinematics from linear to fully nonlinear are modelled in combination with four hydrodynamic loading models from three theories, assessing the effects of both types of nonlinearities and the wave conditions where each type has stronger influence. The main findings include that the nonlinearities in the wave kinematics have stronger influence in the intermediate water depth, while the choice of the hydrodynamic loading model has larger influence in deep water. Moreover, finite-depth FNV theory captures the loading in the widest range of wave and cylinder conditions. The areas of worst prediction by the numerical models were found to be the largest steepness and wave numbers for second harmonic, as well as the vicinity of the wave-breaking limit, especially for the third harmonic. The main cause is the non-monotonic growth of the experimental loading with increasing steepness due to flow separation, which leads to increasing numerical overpredictions since the numerical wave-loading models increase monotonically.
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Jamieson, Wayne W., Etienne P. D. Mansard y Geoffrey R. Mogridge. "IRREGULAR WAVE LOADING ON A CONICAL STRUCTURE". Coastal Engineering Proceedings 1, n.º 21 (29 de enero de 1988): 167. http://dx.doi.org/10.9753/icce.v21.167.
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The horizontal forces, vertical forces and overturning moments exerted by waves on a fixed model of a 45" conical structure are presented. Irregular wave loading tests were conducted for a range of conditions described by base diameter on peak period wave length D/Lp from 0.31 to 1.76, water depth on peak period wave length h/Lp from 0.11 to 0.63, and significant wave height on peak period wave length Hm./Lp up to 0.07. Time series records, spectral densities and transfer functions for the irregular wave loading tests are used to illustrate the nonlinear nature of the measured wave loads. In most cases, similar trends in wave loading were observed for irregular and regular wave tests. For deep-water waves, the irregular and regular force measurements showed spectral peaks at the second harmonic of the wave frequency even though the waves themselves had relatively small second-order components. However, unlike the regular wave loading results, the fundamental spectral peak frequency for the irregular wave forces occurred at a frequency considerably lower than the peak frequency of the waves. Although linear diffraction theory provided a reasonable estimate of the wave forces for waves of low steepness, larger deviations were often present for higher wave steepness results. Comparison of theory and experiment for overturning moments was generally very poor for most wave conditions.
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Chen, L. F., J. Zang, P. H. Taylor, L. Sun, G. C. J. Morgan, J. Grice, J. Orszaghova y M. Tello Ruiz. "An experimental decomposition of nonlinear forces on a surface-piercing column: Stokes-type expansions of the force harmonics". Journal of Fluid Mechanics 848 (1 de junio de 2018): 42–77. http://dx.doi.org/10.1017/jfm.2018.339.
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Wave loading on marine structures is the major external force to be considered in the design of such structures. The accurate prediction of the nonlinear high-order components of the wave loading has been an unresolved challenging problem. In this paper, the nonlinear harmonic components of hydrodynamic forces on a bottom-mounted vertical cylinder are investigated experimentally. A large number of experiments were conducted in the Danish Hydraulic Institute shallow water wave basin on the cylinder, both on a flat bed and a sloping bed, as part of a European collaborative research project. High-quality data sets for focused wave groups have been collected for a wide range of wave conditions. The high-order harmonic force components are separated by applying the ‘phase-inversion’ method to the measured force time histories for a crest focused wave group and the same wave group inverted. This separation method is found to work well even for locally violent nearly-breaking waves formed from bidirectional wave pairs. It is also found that the $n$th-harmonic force scales with the $n$th power of the envelope of both the linear undisturbed free-surface elevation and the linear force component in both time variation and amplitude. This allows estimation of the higher-order harmonic shapes and time histories from knowledge of the linear component alone. The experiments also show that the harmonic structure of the wave loading on the cylinder is virtually unaltered by the introduction of a sloping bed, depending only on the local wave properties at the cylinder. Furthermore, our new experimental results reveal that for certain wave cases the linear loading is actually less than 40 % of the total wave loading and the high-order harmonics contribute more than 60 % of the loading. The significance of this striking new result is that it reveals the importance of high-order nonlinear wave loading on offshore structures and means that such loading should be considered in their design.
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Dudko, Olga V. y Alexandr A. Mantsybora. "Shock Loading of Heteromodular Elastic Materials under Plane-Strain Condition". Key Engineering Materials 887 (mayo de 2021): 634–39. http://dx.doi.org/10.4028/www.scientific.net/kem.887.634.
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The paper discusses the results of mathematical modeling the two-dimensional nonlinear dynamics of heteromodular elastic materials. The resistance of these materials under tension and compression is various. The deformation properties of the heteromodular medium are described within the framework of the isotropic elasticity theory with stress-dependent elastic moduli. In the plane strain case, it is shown that only two types of the nonlinear deformation waves can appear in the heteromodular elastic materials: a plane-polarized quasi-longitudinal wave and a plane-polarized quasi-transverse wave. Basing on obtained properties of the plane shock waves, two plane self-similar boundary value problems are formulated and solved.
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Erofeev, Vladimir I., Sergey I. Gerasimov y Alexey O. Malkhanov. "Nonlinear Spatial Localized Strain Waves". EPJ Web of Conferences 183 (2018): 02030. http://dx.doi.org/10.1051/epjconf/201818302030.
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A possible way of study of single waves in solids is discussed. The soliton is one of these waves without shape and parameters varying. Soliton deformation parameters are connected with the elastic moduli of the third order that allows defining values of these moduli by means of the measured solitondeformation parameters in various type waveguides made of the same material. The conditions under which a soliton can exist in a rod are analytically determined. For simultaneous excitation of loading in several wave guides two new energetic photosensitive structures (the mixtures are given) initiated by means of short light impulses of noncoherent light sources are proposed. Conditions of excitation of the waves on the basis of multipoint optical initiation loading impulses are described. As a technique for registration the shadowgraph visualization is proposed. It is discussed, how the problem connected to the use of energetic initiation structures consisting in the power background illumination can be solved. The shadow scheme with the use of a tiny dot explosive light source (Tbr ~41 kK) allows to carry out modelling experiments on research of slabbing actions, jet formations, fluffings, hydrodynamic instability during shock-wave loading of investigated samples, which makes it attractive for determination of parameters in equations-of-state for investigated materials, creation of numerical models and their validation. Some examples showing basic possibility of application of the declared techniques are included.
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Zhu, Bo y Jaesun Lee. "A Study on Fatigue State Evaluation of Rail by the Use of Ultrasonic Nonlinearity". Materials 12, n.º 17 (23 de agosto de 2019): 2698. http://dx.doi.org/10.3390/ma12172698.
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Nonlinear ultrasonic testing has been accepted as a promising manner for evaluating material integrity in an early stage. Stress fatigue is the main threats to train safety, railways examinations for stress fatigue are more significant and necessary. A series of ultrasonic nonlinear wave experiments are conducted for rail specimens extracted from railhead with different degree of fatigue produced by three-point bent loading condition. The nonlinear parameter is the indicator of nonlinear waves for expressing the degree the fatigue. The experimental results show that the sensitivity of a third harmonic longitudinal wave is higher than second harmonic longitudinal wave testing. As the same time, collinear wave mixing shows strong relative with fatigue damages than a second longitudinal wave nondestructive testing (NDT) method and provides more reliable results than third harmonic longitudinal waves nonlinear testing method.
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Liaw, Chih Young y Xiang Yuan Zheng. "Polynomial Approximations of Wave Loading and Superharmonic Responses of Fixed Structures". Journal of Offshore Mechanics and Arctic Engineering 125, n.º 3 (11 de julio de 2003): 161–67. http://dx.doi.org/10.1115/1.1576818.
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Besides the commonly considered drag force, inundation due to variable water surface is another important nonlinear effect of wave loading. Quadratic and quartic approximations of the inundation drag force are derived using the least squares method. Other nonlinear effects, including the second-order wave kinematics and nonlinear inertia wave forces, are also considered. Superharmonic forces and the corresponding structural responses due to different nonlinear effects are compared using a single mode representation of the fixed offshore structural system. The appropriate expressions that can serve as the basis for the Volterra series representation of the nonlinear wave forces are presented.
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Nekouzadeh, Ali, Guy M. Genin, Philip V. Bayly y Elliot L. Elson. "Wave motion in relaxation-testing of nonlinear elastic media". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 461, n.º 2058 (26 de abril de 2005): 1599–626. http://dx.doi.org/10.1098/rspa.2004.1437.
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Relaxation testing is a fundamental tool for mechanical characterization of viscoelastic materials. Inertial effects are usually neglected when analysing these tests. However, relaxation tests involve sudden stretching of specimens, which causes propagation of waves whose effects may be significant. We study wave motion in a nonlinear elastic model specimen and derive expressions for the conditions under which loading may be considered to be quasi-static. Additionally, we derive expressions for wave properties such as wave speed and the time needed to reach a steady-state wave pattern. These expressions can be used to deduce nonlinear elastic material properties from dynamic experiments.
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Li, Fu Cai, Zheng Hao Sun, Hong Guang Li y Li Min Zhou. "A Nonlinear Ultrasound Method for Fatigue Evaluation of Marine Structures". Materials Science Forum 813 (marzo de 2015): 116–23. http://dx.doi.org/10.4028/www.scientific.net/msf.813.116.
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Fatigue is a major cause of failure in marine structures resulting from random wave and wind loading. A nonlinear ultrasound method for fatigue evaluation which uses interaction of two non-collinear nonlinear ultrasonic waves with quadratic nonlinearity is investigated in this paper. A hyperbolic system of conservation laws is applied here and a semi-discrete central scheme is used to solve the numerical problem. The numerical results prove that a resonant wave can be generated by two primary waves with certain resonant conditions. Features of the resonant wave are analyzed both in the time and frequency domains, and several regularities are found on intensity distribution of the resonant wave in two-dimensional domain.
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Finn, Patrick J., Robert F. Beck, Armin W. Troesch y Yung Sup Shin. "Nonlinear Impact Loading in an Oblique Seaway". Journal of Offshore Mechanics and Arctic Engineering 125, n.º 3 (11 de julio de 2003): 190–97. http://dx.doi.org/10.1115/1.1578499.
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There is an increasing interest in developing direct calculation methods and procedures for determining extreme wave loads on ship girders (e.g. ISSC, 2000 [1]). Ships experiencing bottom and bow flare slamming have heightened the need for computational tools suitable to accurately predict motion and structural responses. The associated nonlinear impact problem is complicated by the complex free surface and body boundary conditions. This paper examines a “blended” linear–nonlinear method by which extreme loads due to bottom impact and flare slamming can be determined. Using a high-speed container ship as an example, comparisons of motions, shear and bending moments, and pressures are made in head and oblique bow-quartering waves. The time-domain computer program used in the comparison is based upon partially nonlinear models. The program, NSHIPMO, is an blended strip theory method using “impact” stations over the forward part of the ship and partially nonlinear stations over the rest. Body exact hydrostatics and Froude-Krylov excitation are used over the entire hull. The impact theory of Troesch and Kang [2] is employed to estimate the sectional nonlinear impact forces acting upon the specified nonlinear sections, while the linear theory of Salvesen et al. (STF) [3] is used to blend the remainder of the hydrodynamic forces, that is the radiation and diffraction components. Results from the simulation are presented with discussions of accuracy and time of computation. Several issues associated with the blended nonlinear time-domain simulation are presented, including modeling issues related to directional yaw-sway control and a vertical plane dynamic instability in long waves that has not previously been recognized.
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Mukhlas, Nurul 'Azizah, Noor Irza Mohd Zaki, Mohd Khairi Abu Husain y Gholamhossein Najafian. "Comparison of Extreme Surface Elevation for Linear and Nonlinear Random Wave Theory for Offshore Structures". MATEC Web of Conferences 203 (2018): 01021. http://dx.doi.org/10.1051/matecconf/201820301021.
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For offshore structural design, the load due to wind-generated random waves is usually the most important source of loading. While these structures can be designed by exposing them to extreme regular waves (100-year design wave), it is much more satisfactory to use a probabilistic approach to account for the inherent randomness of the wave loading. This method allows the statistical properties of the loads and structural responses to be determined, which is essential for the risk-based assessment of these structures. It has been recognized that the simplest wave generation is by using linear random wave theory. However, there is some limitation on its application as some of the nonlinearities cannot be explained when higher order terms are excluded and lead to underestimating of 100-year wave height. In this paper, the contribution of nonlinearities based on the second order wave theory was considered and being tested at a variety of sea state condition from low, moderate to high. Hence, it was proven that the contribution of nonlinearities gives significant impact the prediction of 100-year wave's design as it provides a higher prediction compared to linear wave theory.
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Wan, Xin Lin y Su Zhang. "Experimental Study of Time-Frequency Effect of Rocks". Applied Mechanics and Materials 204-208 (octubre de 2012): 755–60. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.755.
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Sine wave loading experiments are carried out on MTS for pump-oil saturated Nanjing sandstones and water saturated Dali marbles. The Young’s modulus and velocities of longitudinal wave and transverse wave increase with the frequency, and there are notable dispersions. The existence of micro defects in saturated rocks result in hysteresis at the sinusoidal loading experiments. The variation curves of instantaneous Young’s modulus with stress for loading and unloading intersect, and an “X” shape figure is obtained. As the frequency of the sinusoidal wave increases, the position of the intersection point moves to higher modulus area. Thus the modulus dispersion increases. Some physical mechanisms of nonlinear frequency response of rock are revealed. The results obtained are very important for nonlinear wave study, and the theoretical study and application of earthquake and engineering.
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Smit, P. B., T. T. Janssen y T. H. C. Herbers. "Nonlinear Wave Kinematics near the Ocean Surface". Journal of Physical Oceanography 47, n.º 7 (julio de 2017): 1657–73. http://dx.doi.org/10.1175/jpo-d-16-0281.1.
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AbstractEstimation of second-order, near-surface wave kinematics is important for interpretation of ocean surface remote sensing and surface-following instruments, determining loading on offshore structures, and understanding of upper-ocean transport processes. Unfortunately, conventional wave theories based on Stokes-type expansions do not consider fluid motions at levels above the unperturbed fluid level. The usual practice of extrapolating the fluid kinematics from the unperturbed free surface to higher points in the fluid is generally reasonable for narrowband waves, but for broadband ocean waves this results in dramatic (and nonphysical) overestimation of surface velocities. Consequently, practical approximations for random waves are at best empirical and are often only loosely constrained by physical principles. In the present work, the authors formulate the governing equations for water waves in an incompressible and inviscid fluid, using a boundary-fitted coordinate system (i.e., sigma or s coordinates) to derive expressions for near-surface kinematics in nonlinear random waves from first principles. Comparison to a numerical model valid for highly nonlinear waves shows that the new results 1) are consistent with second-order Stokes theory, 2) are similar to extrapolation methods in narrowband waves, and 3) greatly improve estimates of surface kinematics in random seas.
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Lv, Jian Gen y Jian Hui Qiu. "Analysis of Nonlinear Dynamic for Piles under Earthquake Loading". Applied Mechanics and Materials 275-277 (enero de 2013): 1326–29. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.1326.
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The nonlinear dynamic response of piles in uniform foundation under earthquake loading is investigated. Based on the established nonlinear equations of motion of piles under earthquake loading, the approximate solution of the pile for the case of the resonance is obtained by the method of multiple scales. The effects of major parameters on seismic force are studied, such as, frequency ratio, shear wave velocity, soil thickness. And the effects of the major parameters on the frequency response curves of the pile in single layer soil are studied. Comparing with the non-resonant response of the pile, the effect of the resonance on the actual dynamic response is analyzed. The results shows that shear wave velocity and soil thickness have significant effect on the seismic force in soft clay, which have little effect on the seismic force in the other soil layers; soil thickness has the most important influence on the nonlinear dynamic response of pile and it is followed by the earthquake coefficient, the shear wave velocity in the effects.
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Leng, Dingxin, Haiyan Xiao, Lei Sun, Guijie Liu, Xiaojie Wang y Lingyu Sun. "Study on a magnetorheological elastomer-base device for offshore platform vibration control". Journal of Intelligent Material Systems and Structures 30, n.º 2 (14 de noviembre de 2018): 243–55. http://dx.doi.org/10.1177/1045389x18808398.
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Wave loading is one of the leading factors contributing to fatigue damage of offshore platforms. Vibrations in marine platforms due to nonlinear hydrodynamic forces can reduce platform productivity, endanger safety, and affect serviceability. This article presents numerical evaluation of a magnetorheological elastomer device for wave-induced vibration reduction of offshore platform. Random wave loadings are estimated by wave spectrum analysis and Morison’s equations. By altering field-induced stiffness of magnetorheological elastomers and non-resonance control strategy, the wave-induced vibration of offshore platform is effectively reduced, and the magnetorheological elastomer device presents strong control robustness under various wave loadings. This work indicates that magnetorheological elastomer-base device may open a new insight for vibration mitigation of ocean structures.
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SHIBATA, H., Y. TANABE y S. ISHIHARA. "SIMULATION TECHNIQUE FOR ONE-DIMENSIONAL ELASTIC WAVE PROPAGATION". International Journal of Modern Physics B 22, n.º 09n11 (30 de abril de 2008): 1564–69. http://dx.doi.org/10.1142/s0217979208047080.
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The total stress in a structure changes dynamically by the stress multiplication phenomenon in the case of a fixed boundary condition. Therefore, it is important to evaluate the reflected stress waves under an impact loading in structures. In many problems, the method of the classical position-time diagram of wave fronts is effective to analyze the maximum stress in the structure under the impact loading and for a simple arrangement of members along the axis of the one-dimensional structure. In this study, stress analyses in one-dimensional structures based on the position-time diagram of stress wave fronts were realized as a computational method with and without attenuation of stress wave. This method was applied to the problem of stress analyses in a bone under an impact loading, and the stress states were compared with the experimental results.
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Abdel Raheem, Shehata E. y Elsayed M. A. Abdel Aal. "Finite Element Analysis for Structural Performance of Offshore Platforms under Environmental Loads". Key Engineering Materials 569-570 (julio de 2013): 159–66. http://dx.doi.org/10.4028/www.scientific.net/kem.569-570.159.
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Offshore structures for oil and gas exploitation are subjected to various ocean environmental phenomena which can cause highly nonlinear action effects. Offshore structures should be designed for severe environmental loads and strict requirements should set for the optimum performance. The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. The structure is discretized using the finite element method, wave force is determined according to linearized Morison equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixed offshore structure together with the distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme conditions, where the structure should keep production capability in conditions of the one year return period wave and must be able to survive the 100 year return period storm conditions. The results show that the nonlinear response analysis is quite crucial for safe design and operation of offshore platform. Fixed Jacket type offshore platforms under extreme wave loading conditions may exhibit significant nonlinear behavior. The effect of current with different angles when hitting the offshore structure with the wave and wind forces, is very important for calculate the stress, the response displacement and deformation shapes. As the current increase or decrease the effect of wave force according to the hitting angle of current.
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Liu, F., D. T. Brown y J. Fang. "Yawing of Turret-Moored Monohull Vessels in Response to Regular Waves". Journal of Ship Research 43, n.º 03 (1 de septiembre de 1999): 135–42. http://dx.doi.org/10.5957/jsr.1999.43.3.135.
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This paper considers the yawing behavior of a turret-moored floating production and storage vessel in regular waves. Experimental results are presented from regular wave tests performed on a model in a square wave basin indicating the vessel taking up yaw offsets of large amplitude in waves of specific frequency. The measured data are compared with results from second-order diffraction analysis and indicate that it is likely that the yawing behavior is caused by nonlinear potential loading.
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Hu, Sau‐Lon James. "Stochastic Dynamic Response to Nonlinear Wave Loading: Fourth‐Moment Analysis". Journal of Engineering Mechanics 116, n.º 1 (enero de 1990): 107–24. http://dx.doi.org/10.1061/(asce)0733-9399(1990)116:1(107).
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Luo, M. y W. Q. Zhu. "Nonlinear stochastic optimal control of offshore platforms under wave loading". Journal of Sound and Vibration 296, n.º 4-5 (octubre de 2006): 734–45. http://dx.doi.org/10.1016/j.jsv.2006.01.071.
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Park, Hun, Keejoo Lee, Sung W. Lee y Ki Kim. "Dynamic Analysis of Nonlinear Composite Structures under Pressure Wave Loading". Journal of Composite Materials 40, n.º 15 (25 de octubre de 2005): 1361–83. http://dx.doi.org/10.1177/0021998306059718.
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Wang, Lu, Amy Robertson, Jason Jonkman y Yi-Hsiang Yu. "Uncertainty Assessment of CFD Investigation of the Nonlinear Difference-Frequency Wave Loads on a Semisubmersible FOWT Platform". Sustainability 13, n.º 1 (23 de diciembre de 2020): 64. http://dx.doi.org/10.3390/su13010064.
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Current mid-fidelity modeling approaches for floating offshore wind turbines (FOWTs) have been found to underpredict the nonlinear, low-frequency wave excitation and the response of semisubmersible FOWTs. To examine the cause of this underprediction, the OC6 project is using computational fluid dynamics (CFD) tools to investigate the wave loads on the OC5-DeepCwind semisubmersible, with a focus on the nonlinear difference-frequency excitation. This paper focuses on assessing the uncertainty of the CFD predictions from simulations of the semisubmersible in a fixed condition under bichromatic wave loading and on establishing confidence in the results for use in improving mid-fidelity models. The uncertainty for the nonlinear wave excitation is found to be acceptable but larger than that for the wave-frequency excitation, with the spatial discretization error being the dominant contributor. Further, unwanted free waves at the difference frequency have been identified in the CFD solution. A wave-splitting and wave load-correction procedure are presented to remove the contamination from the free waves in the results. A preliminary comparison to second-order potential-flow theory shows that the CFD model predicted significantly higher difference-frequency wave excitations, especially in surge, suggesting that the CFD results can be used to better calibrate the mid-fidelity tools.
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Peake, N. y S. V. Sorokin. "A nonlinear model of the dynamics of a large elastic plate with heavy fluid loading". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 462, n.º 2072 (21 de febrero de 2006): 2205–24. http://dx.doi.org/10.1098/rspa.2006.1673.
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In this paper, we derive weakly nonlinear equations for the dynamics of a thin elastic plate of large extent under conditions of heavy fluid loading. Two situations are then considered. First, we consider the case in which transverse motion of the plate generates a weaker in-plane motion, which is in turn coupled back to the evolution of the transverse motion. This results in the familiar nonlinear Schrödinger equation for the amplitude of a transverse plane wave, and we show that solitary-wave solutions are possible over the range of (non-dimensional) frequencies ω > ω c , which depends on the material properties. Dimensional values of ω c are physically realizable for a typical composite material underwater. Second, we consider the case in which the amplitudes of the transverse and in-plane motion are of the same order of magnitude, possible at a single resonant frequency, which leads to an evolution equation of rather novel type. We find a range of travelling-wave solutions, including cases in which incident in-plane waves can generate localized regions of transverse displacement.
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Wang, Qiuzhe, Jiang Bian, Wenting Huang, Qingrui Lu, Kai Zhao y Zhaoyan Li. "Seabed Liquefaction around Pipeline with Backfilling Trench Subjected to Strong Earthquake Motions". Sustainability 14, n.º 19 (8 de octubre de 2022): 12825. http://dx.doi.org/10.3390/su141912825.
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As an indispensable part of the lifeline for the offshore gas and oil industry, submarine pipelines under long-term marine environmental loadings have historically been susceptible to earthquakes. This study investigates the impact of trench backfilling on the residual liquefaction around a pipeline and the induced uplift of a pipeline under the combined action of an earthquake, ocean wave and current loading. A fully coupled nonlinear effective stress analysis method, which can consider the nonlinear hysteresis and the large deformation after liquefaction of the seabed soil, is adopted to describe the interaction between the seabed soil and the submarine pipeline. Taking a typical borehole in the Bohai strait as the site condition, the nonlinear seismic response analysis of the submarine pipeline under the combined action of seismic loading and ocean wave and current is carried out. The numerical results show that trench backfilling has a significant impact on the seismic response of the pipeline. The existence of trench backfilling reduces the accumulation of the residual excess pore water pressure, so that the seabed liquefaction around the pipeline is mitigated and the uplift of the pipeline is also decreased.
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Sun, Shi Yan, Hai Long Chen y Gang Xu. "Water Entry of A Wedge Into Waves in Three Degrees Offreedom". Polish Maritime Research 26, n.º 1 (1 de marzo de 2019): 117–24. http://dx.doi.org/10.2478/pomr-2019-0013.
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Abstract The hydrodynamic problem of a two-dimensional wedge entering into a nonlinear wave in three degrees of freedom is investigated based on the incompressible velocity potential theory. The problem is solved through the boundary element method in the time domain. To avoid numerical difficulties due to an extremely small contact area at the initial stage, a stretched coordinate system is used based on the ratio of the Cartesian system in the physical space to the distance travelled by the wedge in the vertical direction. The mutual dependence of body motion and wave loading is decoupled by using the auxiliary function method. Detailed results about body accelerations, velocities and displacements at different Froude numbers or different waves are provided, and the mutual effect between body motion and wave loading is analysed in depth.
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Ragozina, Victoria E. y Yulia E. Ivanova. "Spherically Symmetric Shock Waves in Materials with a Nonlinear Stress-Strain Dependence". Materials Science Forum 945 (febrero de 2019): 807–12. http://dx.doi.org/10.4028/www.scientific.net/msf.945.807.
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The paper considers the dynamic deformation features of constructional materials with nonlinear stress-strain dependence. For the one-dimensional shock waves with nonzero curvature arising in constructions under dynamic loading the propagation regularities are studied on the basis of the matched asymptotic expansions method. In the nonstationary problem with the longitudinal spherical shock wave the relations for simultaneous consideration of dynamic properties in the outer and inner problem of the perturbation method are obtained. The solution in the front-line area is constructed on the basis of the evolution equation different from ones for a plane longitudinal wave. The need for a solving of an additional ODE system for matching outer and inner expansions is shown. It is obtained that the outer solution asymptotics in the spherically symmetric problem contains waves reflected from the leading front in contrast to the solution behavior behind the front of the plane shock wave.
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Шибецький, Владислав Юрійович. "Nonlinear oscillations of float suspension under the N-wave. Cyclic loading". Eastern-European Journal of Enterprise Technologies 6, n.º 9(66) (12 de diciembre de 2013): 22. http://dx.doi.org/10.15587/1729-4061.2013.19152.
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Bian, Xingwang, Min Miao, Zhensong Li y Xiaole Cui. "U-shaped meander-line slow-wave structure with stub-loading". Modern Physics Letters B 31, n.º 16 (junio de 2017): 1750173. http://dx.doi.org/10.1142/s0217984917501731.
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In this paper, a U-shaped meander-line slow-wave structure (SWS) with stub-loading is proposed for applications in Ka-band traveling-wave tube (TWT). This new slow-wave structure, loaded with a stub at the center of the U-turn section, has higher interaction impedance and lower phase velocity compared with conventional U-shaped meander-line SWSs, indicating that the devices based on this structure may have a lower operating voltage and higher output power. The dispersion characteristic, interaction impedance, transmission characteristics, and beam-wave interaction are simulated by utilizing simulation tool. The simulation result predicts that the millimeter-wave traveling-wave tube design based on this slow-wave structure is capable of delivering over 200 W with a gain of 33 dB and interaction efficiency 14.5% at the center frequency 34 GHz. This design, more compact and powerful in comparison with those based on more conventional vacuum electronic mechanisms, is demonstrated as a prospective option for integrated millimeter-wave power modules (MMPMs) empowering a broad spectrum of fields, from target detection, to imaging and telecommunications, among others.
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Joseph, Anitha, V. G. Idichandy y S. K. Bhattacharyya. "Experimental and Numerical Study of Coupled Dynamic Response of a Mini Tension Leg Platform". Journal of Offshore Mechanics and Arctic Engineering 126, n.º 4 (1 de noviembre de 2004): 318–30. http://dx.doi.org/10.1115/1.1833358.
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Role of mini tension leg platforms (TLP) in oil exploration and production in marginal deepwater fields is becoming increasingly important. Mini TLP combines the simplicity of a spar and favorable response features of a TLP. In this paper, the results of a detailed experimental and numerical investigation of the coupled dynamic behavior of a mini TLP are reported with special attention to hull-tether coupling. The experimental study has been carried out using a scaled model in wave flume with specially designed tethers whose first two “string” natural frequencies are excited by waves, thus achieving strong hull-tether coupling. The numerical study has been carried out using a nonlinear time domain finite element method specifically addressed to compliant offshore platforms using a combination of potential theory based wave loading and Morison-type wave loading. Extensive comparisons between numerical and experimental results have been made both for platform motions and deflected shapes of the tethers and conclusions drawn.
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Saedi Daryan, Amir, Sahman Soleimani y Hesam Ketabdari. "A modal nonlinear static analysis method for assessment of structures under blast loading". Journal of Vibration and Control 24, n.º 16 (16 de mayo de 2017): 3631–40. http://dx.doi.org/10.1177/1077546317708517.
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Modal pushover analysis (MPA) has been developed in previous studies to analyze the response of structures subjected to seismic excitation. Although this method has already been extended for diverse systems of buildings and bridges, its application is currently restricted to earthquake loading. This study is intended to extend this approach for the analysis of structures subjected to other probable loading patterns, such as blast waves and wind loads. For the analysis of structures under seismic excitation, an acceleration is applied to the structure’s base; however, in the case of a blast wave or wind load, the external load is directly applied to the building with an unexpected load pattern. Based on these differences, a new formulation for the modal analysis of structures is developed in this study. To evaluate the method, a shear wall structure is used as a case study, and the impact of a blast wave is considered as an imposed lateral load. The results obtained by the proposed method, called MPA-B, are compared to those of nonlinear dynamic analysis as a benchmark solution. The structural demands that are used as the comparison criteria are story displacement, story drifts and hinge rotations. The results of this evaluation show that the accuracy of the MPA-B method in the analysis of structures under a blast load is similar to the accuracy of the MPA method in the analysis of structures under earthquake loading.
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Chen, Wei, Xingyu Du, Bao-Lin Zhang, Zhihui Cai y Zhongqiang Zheng. "Near-Optimal Control for Offshore Structures with Nonlinear Energy Sink Mechanisms". Journal of Marine Science and Engineering 10, n.º 6 (14 de junio de 2022): 817. http://dx.doi.org/10.3390/jmse10060817.
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To improve the safety and reliability of offshore structures subject to wave loading, the active vibration control problem is always one of significant issues in the field of ocean engineering. This paper deals with the near–optimal control problem of offshore structures with a nonlinear energy sink (NES) mechanism. By taking the dominant vibration mode of the offshore structure with the NES into account, a nonlinear dynamic model of the steel–jacket structure subject to wave loading is presented first. Then, using the parameter perturbation approach to solve a nonlinear two–point boundary value problem, an NES–based optimal controller with the form of infinite series sum is presented to suppress the vibration of the offshore structure. Third, an iteration algorithm is provided to obtain the near–optimal controller. Simulation results demonstrate that the NES–based near–optimal controller can mitigate the oscillation amplitude of offshore structures significantly. Moreover, the NES–based optimal controller outperforms the one based on active tuned mass damper.
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Wu, Yanling. "Numerical tools to predict the environmental loads for offshore structures under extreme weather conditions". Modern Physics Letters B 32, n.º 12n13 (10 de mayo de 2018): 1840039. http://dx.doi.org/10.1142/s0217984918400390.
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In this paper, the extreme waves were generated using the open source computational fluid dynamic (CFD) tools — OpenFOAM and Waves2FOAM — using linear and nonlinear NewWave input. They were used to conduct the numerical simulation of the wave impact process. Numerical tools based on first-order (with and without stretching) and second-order NewWave are investigated. The simulation to predict force loading for the offshore platform under the extreme weather condition is implemented and compared.
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Tuty, Suhartodjo, Mark J. Cassidy y Beverley F. Ronalds. "Investigation of Shallow Water Kinematics and Local Loading Effects on Reliability of Minimum Structures". Journal of Offshore Mechanics and Arctic Engineering 124, n.º 1 (11 de agosto de 2001): 41–47. http://dx.doi.org/10.1115/1.1423910.
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In shallow water, and specifically for minimum structures, the critical wave height exponent α has been shown to vary significantly with structural configuration. Because of the strong relationship to the wave kinematics, α is also sensitive to the wave theory chosen. The North West Shelf offshore Australia has numerous minimum structures located in relatively shallow water, which requires non-linear wave theory. In the near-breaking condition, estimation of the wave crest kinematics is difficult, with Stream Function theory being the most widely used. However, various other wave theories and nonlinear numerical techniques have been developed to predict wave kinematics for shallow water conditions. The following wave theories are compared: regular Stream Function theory, Cnoidal wave theory, Stokes’ theory, NewWave theory, and a second-order correction to NewWave theory. Kinematics, loads and α results are presented for a cylinder in three different water depths.
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Fatt, Michelle S. Hoo. "Shock-Wave Damage of Ring-Stiffened Cylindrical Shells". Journal of Ship Research 38, n.º 03 (1 de septiembre de 1994): 245–52. http://dx.doi.org/10.5957/jsr.1994.38.3.245.
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A solution methodology for the nonlinear plastic response of the central bay of a ring-stiffened cylindrical shell subject to shock-wave loading is presented. The solution is based on a simple structural model that uses an analogy between a cylindrical shell and a string-on foundation in which ring stiffeners are modeled as lumped masses and springs. By requiring dynamic equilibrium within the central bay of the shell, one may reduce the problem to solving an inhomogeneous wave equation for which the motion of the ring stiffener is introduced into one of the boundary conditions of the string. The initial-boundary-value problem is solved by using a modified Galerkin approximation. The mode shape used to describe the local or bay deformation in the Galerkin approximation is determined from the experimental profile of an actual damaged shell. A Galerkin approximation not only yields a simple solution for the transient deformations of the shell, but it also has an advantage over an exact solution in that it can be easily extended to shells subject to asymmetric pressure loading with arbitrary time variation. The Galerkin solution is shown to approach two extreme cases of dynamic loading for the exponentially decaying pressure load: impulsive loading and static loading. A final deformed profile of the shell is obtained by using the concept of plastic unloading waves. The solution for the transient deflection is a stepping stone to the evaluation of strains and is therefore important in establishing a failure criterion for the shell. The analytical results presented herein may therefore be instrumental in establishing design criteria for prevention of failure of the ring-stiffened shell.
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Lee, Sang-Moon y Woo-Young Jung. "Evaluation of anchorage performance of the switchboard cabinet under seismic loading condition". Advances in Mechanical Engineering 12, n.º 5 (mayo de 2020): 168781402092630. http://dx.doi.org/10.1177/1687814020926309.
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In this study, the seismic response of the anchorage used for switchboard cabinets at a power plant was presented based on the results of an experiment and numerical simulations. In the experimental study, shaking table tests were performed to investigate the overall structural behavior of switchboard cabinets. The finite element modeling was conducted using the ABAQUS program, and in order to validate the proposed finite element model, the natural frequency, stress, and displacement were compared with the experimental results. A slight difference was found in the results due to the problem cup-like deformation at the anchorage of the bottom, but it showed reasonable agreement when considering the results for all behaviors. Using the proven model, nonlinear dynamic analysis was performed using three types of a period waves. The maximum stress on the anchorage occurred when a long-period wave was applied, and the horizontal maximum displacement of the cabinet was approximately 10 times greater than when an ultra-short-period wave was applied. It is expected that the flexibility of the cabinet stiffness resulted in more structural weakness, especially under a long-period wave, and that is recommended to focus on displacement rather than stress when establishing seismic design guidelines for switchboard cabinets.
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Faltinsen, O. M., M. Greco y M. Landrini. "Green Water Loading on a FPSO". Journal of Offshore Mechanics and Arctic Engineering 124, n.º 2 (11 de abril de 2002): 97–103. http://dx.doi.org/10.1115/1.1464128.
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Green Water Loading in the bow region of a Floating Production Storage and Offloading unit (FPSO) in head sea waves is studied by numerical means. A 2-D method satisfying the exact nonlinear free-surface conditions within potential-flow theory has been developed as a step towards a fully 3-D method. The flow is assumed 2-D in a plane containing the ship’s centerplane. The method is partly validated by model tests. The importance of environmental conditions, 3-D flow effects, ship motions, and hull parameters are summarized. The wave steepness of the incident waves causes important nonlinear effects. The local flow at the bow is, in general, important to account for. It has become popular to use a dam-breaking model to study the propagation of water on the deck. However, the numerical studies show the importance of accounting for the coupled flow between the deck and outside the ship. When the water is propagating on the deck, a suitable distance from the bow can be found from where shallow-water equations can be used. Impact between green water on deck and a vertical deck-house side in the bow area is studied in details. A similarity solution for impact between a wedge-formed water front and a vertical rigid wall is used. Simplified solutions for an impacting fluid wedge with small and large interior angles are developed, both to support the numerical computations and to provide simpler formulas of practical use. It is demonstrated how the local design of the deck house can reduce the slamming loads. The importance of hydroelasticity during the impact is discussed by using realistic structural dimensions of a deck house. This indicates that hydroelasticity is insignificant. On the contrary, first results from an ongoing experimental investigation document blunt impacts against the deck during the initial stage of water shipping, which deserve a dedicated hydroelastic analysis.
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KangGu, Xue y Torgeir Moan. "Long-Term Fatigue Damage of Ship Structures Under Nonlinear Wave Loads". Marine Technology and SNAME News 39, n.º 02 (1 de abril de 2002): 95–104. http://dx.doi.org/10.5957/mt1.2002.39.2.95.
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Fatigue is a principal mode of failure in ship structures, especially when high tensile steels are applied. Although significant efforts have been made to predict fatigue damage, there are still uncertainties existing, e.g., in the stress histories that cause fatigue. This paper addresses estimation of fatigue damage in ships under wave loads, with an emphasis on containerships, which have large bow flare and low hull girder rigidity. Linear and nonlinear wave-induced loads as well as dynamic effects due to hull flexibility, i.e., whipping, are researched. With the direct analysis method of fatigue, the nature of the wave loading, hull rigidity, structural damping, stress range counting algorithm and SN curve on structural fatigue damage are investigated. In long-term fatigue damage estimates, the influence of different sea environments is numerically analyzed. The importance of nonlinearity of wave loads and especially the whipping on the structural fatigue damage is demonstrated by calculation for a large container vessel with large flare and lowest natural frequency of 0.749 Hz. Depending upon sea environments and SN curves used in long-term predictions, the fatigue damage based on nonlinear wave loads (excluding whipping) is 10–100% larger than that due to linear wave loads; the fatigue damage based on nonlinear combined loads (including whipping) may be 1–9 times larger than that of steady-state nonlinear wave loads.
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Kalateh, Farhoud y Ali Koosheh. "Finite Element Analysis of Flexible Structure and Cavitating Nonlinear Acoustic Fluid Interaction under Shock Wave Loading". International Journal of Nonlinear Sciences and Numerical Simulation 19, n.º 5 (26 de julio de 2018): 459–73. http://dx.doi.org/10.1515/ijnsns-2016-0135.
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AbstractThis paper describes a numerical model and its finite element implementation that used to compute the cavitation effects on nonlinear acoustic fluid and adjacent flexible structure interaction. The system is composed of two sub-systems, namely, the fluid and the flexible flat plate. A fully coupled approach using iterative implicit partitioned scheme was implemented in the present work which can account for the effects associated whit a mutual interaction. This approach included a compressible nonlinear acoustic fluid Eulerian solver and a Lagrangian solver for the flexible structure both in finite element formulation. A novel implementation of acoustic cavitation was made possible with the introduction of a simplified one-fluid cavitation model. The element-by-element PCG (Preconditioned Conjugate Gradient) solver together with diagonal preconditioning is used to solve the large equation system resulting from the finite element discretization of the governing equation of fluid domain. The capability of three different cavitation model, as the cut-off model, Modified Schmidt model and developed model are compared with each other in the evaluation of plate vibration response. Simulation results are presented on a large size shock tube, in which planar shock waves were impacting in “face on” configuration flat plates mounted at tube's end. Results are presented to demonstrate the capability of proposed solver in simulating cavitating nonlinear acoustic fluid. Obtained results show that impact forces caused impinging shock wave and reloading by cavitating region collapse have a considerable effect on the dynamic response of flexible plate.
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Mahmoud Hosseini, Seyed. "Elastic wave propagation and time history analysis in FG nanocomposite cylinders reinforced by carbon nanotubes using a hybrid mesh-free method". Engineering Computations 31, n.º 7 (30 de septiembre de 2014): 1261–82. http://dx.doi.org/10.1108/ec-12-2012-0312.
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Purpose – The purpose of this paper is to propose a hybrid mesh-free method based on generalized finite difference (GFD) and Newmark finite difference methods to study the elastic wave propagation in functionally graded nanocomposite reinforced by carbon nanotubes (FGNRCN). The presented hybrid mesh-free method is applied for a thick hollow cylinder, which is made of FGNRCN and excited by various mechanical shock loadings. Design/methodology/approach – The FG nanocomposite cylinder is assumed to be under shock loading. The elastic wave propagation is obtained and studied for various nonlinear grading patterns and distributions of the aligned carbon nanotubes. The distribution of carbon naotubes in FG nanocomposite are considered to vary as nonlinear function of radius, which varies with various nonlinear grading patterns continuously through radial direction. The effective material properties of functionally graded carbon nanotube are estimated using a micro-mechanical model. Findings – The mechanical shock analysis of FGNRCN thick hollow cylinder is carried out and the dynamic behavior of displacement field and the time history of radial displacement are obtained for various grading patterns. An effective hybrid mesh-free method based on GFD and Newmark finite difference methods is presented to calculate the average velocity of elastic wave propagation in FGNRCN. The average velocity of elastic wave propagation is obtained for various grading patterns and various kinds of volume fraction. The effects of some parameters on average velocity of elastic wave propagation are obtained and studied in detail. Originality/value – The calculation of elastic radial wave propagation in a FGNRCN thick hollow cylinder is presented using a hybrid mesh-free method. The effects of some parameters on wave propagation such as various grading patterns of distribution of carbon nanotubes are studied in details.
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Wendt, Nielsen, Yu, Bingham, Eskilsson, Kramer, Babarit et al. "Ocean Energy Systems Wave Energy Modelling Task: Modelling, Verification and Validation of Wave Energy Converters". Journal of Marine Science and Engineering 7, n.º 11 (25 de octubre de 2019): 379. http://dx.doi.org/10.3390/jmse7110379.
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The International Energy Agency Technology Collaboration Programme for Ocean Energy Systems (OES) initiated the OES Wave Energy Conversion Modelling Task, which focused on the verification and validation of numerical models for simulating wave energy converters (WECs). The long-term goal is to assess the accuracy of and establish confidence in the use of numerical models used in design as well as power performance assessment of WECs. To establish this confidence, the authors used different existing computational modelling tools to simulate given tasks to identify uncertainties related to simulation methodologies: (i) linear potential flow methods; (ii) weakly nonlinear Froude–Krylov methods; and (iii) fully nonlinear methods (fully nonlinear potential flow and Navier–Stokes models). This article summarizes the code-to-code task and code-to-experiment task that have been performed so far in this project, with a focus on investigating the impact of different levels of nonlinearities in the numerical models. Two different WECs were studied and simulated. The first was a heaving semi-submerged sphere, where free-decay tests and both regular and irregular wave cases were investigated in a code-to-code comparison. The second case was a heaving float corresponding to a physical model tested in a wave tank. We considered radiation, diffraction, and regular wave cases and compared quantities, such as the WEC motion, power output and hydrodynamic loading.
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Chaplin, John R. "Orbital flow around a circular cylinder. Part 1. Steady streaming in non-uniform conditions". Journal of Fluid Mechanics 237 (abril de 1992): 395–411. http://dx.doi.org/10.1017/s002211209200346x.
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This work is concerned with the source of an important component of nonlinear loading on a horizontal cylinder beneath waves that is not present in conventional diffraction calculations. Earlier measurements (Chaplin 1984b) have suggested that circulation induced by steady streaming around the cylinder may be responsible for loading which in some cases reduces the perceived inertia force by 50%. The present work is aimed at studying the steady streaming around a cylinder in general non-uniform orbital flow, and determining whether in the particular case of wave-induced flow it could be related quantitatively to the loading.The steady outer flow has been obtained numerically for cases where the steady streaming does not have a reversal, and for cases where a weak reversal is compatible with a uniform outer circulation. It is found that the outer circulation is closely related to the mean streaming velocity around the cylinder at the outer edge of the shear-wave layer. Results for conditions corresponding to previous measurements of force on a horizontal cylinder beneath waves suggest that separation, turbulence, transient effects and organized three-dimensional instabilities should also be considered.
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KRYLOV, VICTOR V. "PROPAGATION OF LOCALIZED VIBRATION MODES ALONG EDGES OF IMMERSED WEDGE-LIKE STRUCTURES: GEOMETRICAL-ACOUSTICS APPROACH". Journal of Computational Acoustics 07, n.º 01 (marzo de 1999): 59–70. http://dx.doi.org/10.1142/s0218396x99000060.
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The theory of antisymmetric localized elastic modes propagating along edges of immersed wedge-like structures is developed using the geometrical-acoustics approach to the description of flexural waves in elastic plates of variable thickness. The velocities of these modes, often called wedge acoustic waves, are calculated using solutions of the dispersion equation of the Bohr-Sommerfeld type following from the geometrical-acoustics description of localized wedge modes. In a subsonic regime of wave propagation, i.e. for wedge modes slower than sound in liquid, the influence of liquid loading results in significant decrease of wedge wave velocities in comparison with their values in vacuum. This decrease is a nonlinear function of a wedge apex angle θ and is more pronounced for small values of θ. In a supersonic regime of wedge wave propagation, a smaller decrease in velocities takes place and the waves travel with the attenuation due to radiation of sound into the surrounding liquid. The comparison is given with the recent experimental investigations of wedge waves carried out by independent researchers.
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Shokouhi, P., A. Zoëga y H. Wiggenhauser. "Nondestructive Investigation of Stress-Induced Damage in Concrete". Advances in Civil Engineering 2010 (2010): 1–9. http://dx.doi.org/10.1155/2010/740189.
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The changes in the sonic surface wave velocity of concrete under stress were investigated in this paper. Surface wave velocities at sonic frequency range were measured on a prismatic concrete specimen undergoing several cycles of uniaxial compression. The loading was applied (or removed) gradually in predefined small steps (stress-controlled). The surface wave velocity was measured at every load step during both loading and unloading phases. Acoustic Emission (AE) test was conducted simultaneously to monitor the microcracking activities at different levels of loading. It was found that the sonic surface wave velocity is highly stress dependent and the velocity-stress relationship follows a particular trend. The observed trend could be explained by a combination of acoustoelasticity and microcracking theories, each valid over a certain range of applied stresses. Having measured the velocities while unloading, when the material suffers no further damage, the effect of stress and damage could be differentiated. The slope of the velocity-stress curves over the elastic region was calculated for different load cycles. This quantity was normalized to yield a dimensionless nonlinear parameter. This parameter generally increases with the level of induced damage in concrete.
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Ren, Hui Lan y Ping Li. "A Dynamic Damage Model for Uniaxial Compressive Response of AD90 Alumina". Key Engineering Materials 340-341 (junio de 2007): 289–94. http://dx.doi.org/10.4028/www.scientific.net/kem.340-341.289.
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The dynamic response of polycrystalline alumina were investigated in the pressure range of 0-13Gpa by planar impact experiments. Manganin gauges were employed to obtain the stress-time histories. From the free surface particle velocity profiles indicate the dispersion of the “plastic” wave for alumina. Using path line principle of Lagrange Analysis the dynamic mechanical behaviors for alumina under impact loading are analyzed, such as nonlinear, strain rate dependence, dispersion and declination of shock wave in the material. A damage model applicable to ceramics subjected to dynamic compressive loading is developed. The model is based on the damage micromechanics and established on wing crack nucleation and growth. The results of the dynamic damage evolution model are compared to the experimental results and a good correlation is obtained.
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Li, Sheng, Ziming Xiong, Pengxian Fan, Haozhe Xing y Kaidi Xie. "The Attenuation Ability of Saturated Joints Filled with Granular Materials under High-Amplitude Stress Wave Loading". Geofluids 2022 (26 de octubre de 2022): 1–20. http://dx.doi.org/10.1155/2022/2124392.
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Existing experimental evidence shows that the propagation of explosive waves in the free fields of soils is remarkably affected by the degree of saturation. In the surrounding rocks of underground protective structures, the underground water is normally unavoidable, which is supposed to reduce the isolation efficiency of a passive antiblast barrier. To investigate the effect of water saturation on the stress wave attenuation ability of infilled joints, impact tests were carried out on artificial joints filled with dry and saturated granular materials using a split Hopkinson pressure bar (SHPB). The test results revealed that under the same conditions, the stress and energy transmission coefficients of the waves crossing saturated sand-filled joints were about 3.16–4.13 times and 9.75–11.4 times those of joints filled with dry sand, respectively. The dynamic stress-strain relationship of the filling layer during the impact process and the crushing index of the infill were analyzed. The results showed that the compressibility and the granular crushing index of the dry sand were much greater than that of the saturated sand, and the dynamic stress-strain relationship of the dry sand exhibited three-stage nonlinear characteristics. The experimental results quantitatively uncovered the serious adverse effect of water on the wave absorption properties and markedly diminished the potential of the filled joints as a wave elimination barrier, which should be a matter of great concern in the design of underground protective structures.
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Melnikov, Boris y Artem Semenov. "Fatigue Damage Accumulation under the Complex Varying Loading". Applied Mechanics and Materials 617 (agosto de 2014): 187–92. http://dx.doi.org/10.4028/www.scientific.net/amm.617.187.
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Fatigue analysis of steel parts of structures, which are subjected to complex irregular loading programs caused by wind, thermal, wave loads, earthquakes and combined imposed actions, requires in some cases using special methods of stress-strain evaluation. The model of the low cycle fatigue nonlinear damage accumulation is developed with taking into account the history of the deformation process. The damage is defined on the base of considering the quasi-static accumulation of maximal strain (stress) and hysteresis loops. The identification of material constants of the model is discussed. Application of the damage model for fatigue analysis of the antennas, pipelines, basements and fasteners units is considered and a comparison with experiments is given.
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Galaz Donoso, Belfor A., Siva Avudaiappan y Erick I. Saavedra Flores. "Feasibility of Using Shear Wave Ultrasonic Probes as Pump-Wave Sources in Concrete Microcrack Detection and Monitoring by Nonlinear Ultrasonic Coda Wave Interferometry". Sensors 22, n.º 6 (9 de marzo de 2022): 2105. http://dx.doi.org/10.3390/s22062105.
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This paper represents a first attempt to study the feasibility of using shear wave (SW) ultrasonic probes as pump-wave sources in concrete microcrack detection and monitoring by Nonlinear Ultrasonic Coda Wave Interferometry (NCWI). The premise behind our study is that the nonlinear elastic hysteretic behavior at microcracks may depend on their orientation with respect to the stationary wave-field induced by the pump-wave source. In this context, the use of a SW probe as a pump-wave source may induce the nonlinear elastic behavior of microcracks oriented in directions not typically detected by a conventional longitudinal pump-wave source. To date, this premise is hard to address by current experimental and numerical methods, however, the feasibility of using SW probes as a pump-wave source can be experimentally tested. This idea is the main focus of the present work. Under laboratory conditions, we exploit the high sensitivity of the CWI technique to capture the transient weakening behaviour induced by the SW pump-wave source in concrete samples subjected to loading and unloading cycles. Our results show that after reaching a load level of 40% of the ultimate stress, the material weakening increases as a consequence of microcrack proliferation, which is consistent with previous studies. Despite the lack of exhaustive experimental studies, we believe that our work is the first step in the formulation of strategies that involve an appropriate selection and placement of pump-wave sources to improve the NCWI technique. These improvements may be relevant to convert the NCWI technique into a more suitable non-destructive testing technique for the inspection of microcracking evolution in concrete structures and the assessment of their structural integrity.
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TANABE, Y., T. UCHIYAMA, H. YAMAOKA y H. OHASHI. "LOAD TRANSMISSION THROUGH ARTIFICIAL HIP JOINTS DUE TO STRESS WAVE LOADING". International Journal of Modern Physics B 22, n.º 09n11 (30 de abril de 2008): 1789–94. http://dx.doi.org/10.1142/s0217979208047420.
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Since wear of the polyethylene (Ultra High Molecular Weight Polyethylene or UHMWPE) acetabular cup is considered to be the main cause of loosening of the artificial hip joint, the cross-linked UHMWPE with high durability to wear has been developed. This paper deals with impact load transmission through the complex of an artificial hip joint consisting of a UHMWPE acetabular cup (or liner), a metallic femoral head and stem. Impact compressive tests on the complex were performed using the split-Hopkinson pressure bar apparatus. To investigate the effects of material (conventional or cross-linked UHMWPE), size and setting angle of the liner, and test temperature on force transmission, the impact load transmission ratio (ILTR) was experimentally determined. The ILTR decreased with an increase of the setting angle independent of material and size of the liner, and test temperature. The ILTR values at 37°C were larger than those at 24 °C and 60°C. The ILTR also appeared to be affected by the type of material as well as size of the liner.
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Cai, Hua-Lin, Yi Yang, Yi-Han Zhang, Chang-Jian Zhou, Cang-Ran Guo, Jing Liu y Tian-Ling Ren. "A high sensitivity wireless mass-loading surface acoustic wave DNA biosensor". Modern Physics Letters B 28, n.º 07 (13 de marzo de 2014): 1450056. http://dx.doi.org/10.1142/s0217984914500560.
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In this paper, a surface acoustic wave (SAW) biosensor with gold delay area on LiNbO 3 substrate detecting DNA sequences is proposed. By well-designed device parameters of the SAW sensor, it achieves a high performance for highly sensitive detection of target DNA. In addition, an effective biological treatment method for DNA immobilization and abundant experimental verification of the sensing effect have made it a reliable device in DNA detection. The loading mass of the probe and target DNA sequences is obtained from the frequency shifts, which are big enough in this work due to an effective biological treatment. The experimental results show that the biosensor has a high sensitivity of 1.2 pg/ml/Hz and high selectivity characteristic is also verified by the few responses of other substances. In combination with wireless transceiver, we develop a wireless receiving and processing system that can directly display the detection results.
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Islam, A. B. M. Saiful, Mohammed Jameel, Suhail Ahmad, Mohd Zamin Jumaat y V. John Kurian. "STRUCTURAL BEHAVIOUR OF FULLY COUPLED SPAR–MOORING SYSTEM UNDER EXTREME WAVE LOADING". Journal of Civil Engineering and Management 19, Supplement_1 (9 de enero de 2014): S69—S77. http://dx.doi.org/10.3846/13923730.2013.801899.
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Floating spar platform has been proven to be an economical and efficient type of offshore oil and gas exploration structure in deep and ultra-deep seas. Associated nonlinearities, coupled action, damping effect and extreme sea environments may modify its structural responses. In this study, fully coupled spar–mooring system is modelled integrating mooring lines with the cylindrical spar hull. Rigid beam element simulates large cylindrical spar hull and catenary mooring lines are configured by hybrid beam elements. Nonlinear finite element analysis is performed under extreme wave loading at severe deep sea. Morison's equation has been used to calculate the wave forces. Spar responses and mooring line tensions have been evaluated. Though the maximum mooring line tensions are larger at severe sea-state, it becomes regular after one hour of wave loading. The response time histories in surge, heave, pitch and the maximum mooring tension gradually decreases even after attaining steady state. It is because of damping due to heavier and longer mooring lines in coupled spar–mooring system under deep water conditions. The relatively lesser values of response time histories in surge, heave, pitch and the maximum mooring tension under extreme wave loading shows the suitability of a spar platform for deep water harsh and uncertain environmental conditions.