Academic literature on the topic 'Zero displacement method'
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Journal articles on the topic "Zero displacement method"
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DE BRUIN, H. A. R., and A. VERHOEF. "A NEW METHOD TO DETERMINE THE ZERO-PLANE DISPLACEMENT." Boundary-Layer Meteorology 82, no. 1 (1997): 159–64. http://dx.doi.org/10.1023/a:1000233230943.
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Namdar Zanganeh, M., S. I. I. Kam, T. C. C. LaForce, and W. R. R. Rossen. "The Method of Characteristics Applied to Oil Displacement by Foam." SPE Journal 16, no. 01 (2010): 8–23. http://dx.doi.org/10.2118/121580-pa.
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Summary Solutions obtained by the method of characteristics (MOC) provide key insights into complex foam enhanced-oil-recovery (EOR) displacements and the simulators that represent them. Most applications of the MOC to foam have excluded oil. We extend the MOC to foam flow with oil, where foam is weakened or destroyed by oil saturations above a critical oil saturation and/or weakened or destroyed at low water saturations, as seen in experiments and represented in foam simulators. Simulators account for the effects of oil and capillary pressure on foam using algorithms that bring foam strength to zero as a function of oil or water saturation, respectively. Different simulators use different algorithms to accomplish this. We examine SAG (surfactant-alternating-gas) and continuous foam-flood (coinjection of gas and surfactant solution) processes in one dimension, using both the MOC and numerical simulation. We find that the way simulators express the negative effect of oil or water saturation on foam can have a large effect on the calculated nature of the displacement. For instance, for gas injection in a SAG process, if foam collapses at the injection point because of infinite capillary pressure, foam has almost no effect on the displacement in the cases examined here. On the other hand, if foam maintains finite strength at the injection point in the gas-injection cycle of a SAG process, displacement leads to implied success in several cases. However, successful mobility control is always possible with continuous foam flood if the initial oil saturation in the reservoir is below the critical oil saturation above which foam collapses. The resulting displacements can be complex. One may observe, for instance, foam propagation predicted at residual water saturation, with zero flow of water. In other cases, the displacement jumps in a shock past the entire range of conditions in which foam forms. We examine the sensitivity of the displacement to initial oil and water saturations in the reservoir, the foam quality, the functional forms used to express foam sensitivity to oil and water saturations, and linear and nonlinear relative permeability models.
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Daniel, S. E., A. Aref, C. Rabbani, et al. "Three-dimensional visualization of stranded source migration following prostate brachytherapy." Journal of Clinical Oncology 29, no. 7_suppl (2011): 79. http://dx.doi.org/10.1200/jco.2011.29.7_suppl.79.
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79 Background: The use of radioactive seeds embedded in absorbable vicryl suture material has emerged as one preferred method for prostate cancer brachytherapy. However, it is unclear how strand displacement affects post-implant dosimetry. Our objective was to use CT imaging and 3D reconstruction to determine strand displacement between day zero and day 30 and to assess the dosimetric consequences of strand displacement. Methods: Between March 2006 and December 2009 there were 86 prostate brachytherapy patients with day zero and day 30 post-plan imaging. There was a mean of 18.24 strands per implant, 9.81 loose seeds per implant, and 69.08 total seeds per implant. Substantial strand displacement was identified by inspection. Migrated strands were identified on day zero and day 30 scans and the distance of displacement was measured using 3D fusion software. Results: Of 1550 strands placed, 23 were found to show substantial migration revealed by 3D imaging. These displacements occurred in 21 of the 86 cases. The estimated distance of strand displacement ranged from 0.5 cm to 2.5 cm with an average movement of 1.5 cm. The exact distance of strand displacement ranged from 0.31 m to 3.44 cm, with mean movement of 2.75 cm. Conclusions: 3D imaging reveals unexpected spatial instability in stranded brachytherapy sources. Significant movement may be expected to occur in approximately 1.48% of stranded sources and 24.42% of cases. Factors which predict for the migration of sources remain relatively undefined. Minimal dosimetric effects from strand displacement appear to be offset by resolution of prostate edema. [Table: see text] No significant financial relationships to disclose.
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Zhang, Hong-Sheng, and Soon-Ung Park. "Comments on 'a new Method to Determine the Zero-Plane Displacement'." Boundary-Layer Meteorology 91, no. 1 (1999): 135–39. http://dx.doi.org/10.1023/a:1001872128704.
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Shen, Yichang, Xiang Zhou, and Philip D. Cha. "Imposing points of zero displacement and zero slopes on a plate subjected to steady-state harmonic excitation." Journal of Vibration and Control 24, no. 20 (2017): 4904–20. http://dx.doi.org/10.1177/1077546317738616.
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In this paper, a simple and effective method to enforce fixed nodes, or points of zero displacement and zero slope, on an arbitrarily supported rectangular plate subjected to steady-state harmonic excitations is developed. This is achieved by attaching properly tuned translational and rotational oscillators at specified locations. The governing equations of the combined system are first derived using the assumed-modes method. By enforcing the conditions of zero displacements and zero slopes simultaneously, a set of constraint equations are formulated, from which the oscillator parameters can be determined. When the attachment locations coincide with the desired fixed node locations, it is always possible to select the oscillator parameters such that one or multiple fixed nodes are induced at any locations on the plate for any excitation frequency. When the attachment and the desired node locations are not collocated, it is only possible to induce nodes at certain locations on the plate. When the fixed node locations are judiciously chosen, a selected region of the plate can be made to remain nearly stationary. Thus, the proposed method provides a simple and yet effective means to passively control excessive vibrations.
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Hinneh, Perry, and Pi Hua Wen. "Displacement Correlation Technique for Interface Crack by FEM." Key Engineering Materials 713 (September 2016): 346–49. http://dx.doi.org/10.4028/www.scientific.net/kem.713.346.
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Interface crack is evaluated using modified quarter point crack tip displacement method. Quarter point elements around the crack tip were employed in the Finite Element (ABAQUS) analysis to determine the near crack tip grid point displacements. In this study, a technique is adopted in which the crack opening displacement of the near crack tip grid point is forced to satisfy a known constraint. The linear term in the distance around the crack tip is reduced to zero. The complex stress intensity factor for interface crack is determined using the quarter point and the displacement correlation technique. It is well observed that FEM produce a less reliable displacement approximation around interface crack tip. However, this report will show that the use of near crack tip open displacement as determined by the standard finite element method can be utilised to give satisfactory result for the interface stress intensity factors K1 and K2.
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Uozumi, Yosuke, Kouki Nagamune, Naoki Nakano, et al. "A Three-Dimensional Evaluation of EndoButton Displacement Direction After Anterior Cruciate Ligament Reconstruction in CT Image Using Tunnel Axis." Journal of Advanced Computational Intelligence and Intelligent Informatics 18, no. 5 (2014): 830–38. http://dx.doi.org/10.20965/jaciii.2014.p0830.
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The goal of this study was to propose a threedimensional evaluation of the EndoButton displacement direction after anterior cruciate ligament reconstruction in the multidetector-row computed tomography (MDCT) image by using the tunnel axis. The proposed method was applied experimentally to six subjects. The result of the simulated experiment revealed that the proposed method could analyze EndoButton displacement direction satisfactorily because the error was less than that of the MDCT image resolution. The clinical experiment results revealed displacement relative to the tunnel between time-zero and the followup point. We conclude that the proposed method can quantitatively evaluate the EndoButton displacement direction from the raw MDCT image after anterior cruciate ligament reconstruction; further, our findings suggest that the EndoButton was displaced relative to the tunnel between time-zero and the follow-up point.
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Xu, X., Z. Q. Zheng, Y. T. Gu, and G. R. Liu. "A Quasi-Conforming Point Interpolation Method (QC-PIM) for Elasticity Problems." International Journal of Computational Methods 13, no. 05 (2016): 1650026. http://dx.doi.org/10.1142/s0219876216500262.
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It is well known that a high-order point interpolation method (PIM) based on the standard Galerkin formations is not conforming, and thus the solution may not always be convergent. This paper proposes a new interesting technique called quasi-conforming point interpolation method (QC-PIM) for solving elasticity problems, by devising a novel scheme that smears the discontinuity. In the QC-PIM, the problem domain is first discretized by a set of background cells (typically triangles that can be automatically generated), and the average displacements on the interfaces of the two neighboring cells are assumed to be equal. We prove that when the size of background cells approaches to zero, all the additional potential energy coming from the discontinuous displacement field becomes zero, which ensures the pass of the standard patch test and hence the convergence. Numerical experiments verify that QC-PIM can produce the convergent solutions with higher accuracy and convergent rate that is in between fully conforming linear and quadratic models.
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Shimizu, Hiroki, Ryousuke Yamashita, Takuya Hashiguchi, Tasuku Miyata, and Yuuma Tamaru. "Square Layout Four-Point Method for Two-Dimensional Profile Measurement and Self-Calibration Method of Zero-Adjustment Error." International Journal of Automation Technology 12, no. 5 (2018): 707–13. http://dx.doi.org/10.20965/ijat.2018.p0707.
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An on-machine measurement method, called the square-layout four-point (SLFP) method with angle compensation, for evaluating two-dimensional (2-D) profiles of flat machined surfaces is proposed. In this method, four displacement sensors are arranged in a square and mounted to the scanning table of a 2-D stage. For measuring the 2-D profile of a target plane, height data corresponding to all measuring points are acquired by means of the raster scanning motion. At the same time, pitching data of the first primary scan line and rolling data of the first subsidiary scan line are monitored by means of two auto-collimators to compensate for major profile errors that arise out of the posture error. Use of the SLFP method facilitates connection of the results of straightness-measurements results obtained for each scanning line by using two additional sensors and rolling data of the first subsidiary scan line. Specifically, the height of a measuring point is calculated by means of a recurrence equation using three predetermined height data for adjacent points in conjunction with data acquired by the four displacement sensors. Results of the numerical simulation performed in this study demonstrate higher efficiency of the SLFP method with angle compensation. During actual measurement, however, it is difficult to perfectly align inline the origin height of each displacement sensor. With regard to the SLFP method, zero-adjustment error is defined as the relative height of a sensor’s origin with respect to the plane comprising origins of the other three sensors. This error accumulates in proportion to number of times the recurrence equation is applied. Simulation results containing the zero-adjustment error demonstrate that accumulation of the said error results in unignorable distortion of measurement results. Therefore, a new self-calibration method for the zero-adjustment error has been proposed. During 2-D profile measurement, two different calculation paths – the raster scan path and orthogonal path – can be used to determine the height of a measurement point. Although heights determined through use of the two paths must ideally be equal, they are observed to be different because accumulated zero-adjustment errors for the two paths are different. In view of this result, the zero-adjustment error can be calculated backwards and calibrated. Validity of the calibration method has been confirmed via simulations and experiments.
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Yang, Jiao Jiao, Xin Chen, Guo Qing Ding, Li Hua Lei, and Yuan Li. "A Six-Probe Scanning Method for Guide Rail Straightness Measurement." Applied Mechanics and Materials 217-219 (November 2012): 2669–73. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.2669.
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Straightness error is the main profile error of guide rail. This paper studies a scanning six-probe system for measuring straightness of two guide rails. The system does not use angle sensors and consists of two probe-units, each having three displacement sensors. The two probe-units are moved by a scanning stage to scan the surface of two guide rails, then they are rotated 180 and scan guide rails again after the first scanning. The zero-differences of two probe-units before and after probe-units being rotated, as well as the straightness of the guide rails, can be accurately evaluated from the outputs of the displacement sensors in two scanning process. The effectiveness of this method is confirmed by computer simulation and experimental results in the case of two probe-units having different zero-differences before and after probe-units being rotated.
Dissertations / Theses on the topic "Zero displacement method"
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Filho, Carlos Augusto Moreira. "Análise estática não linear plana de pontes estaiadas e determinação das frequências naturais e modos de vibração." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-07042014-150248/.
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As pontes estaiadas são exemplos de estruturas esbeltas e flexíveis onde a capacidade de utilização dos materiais tem grande importância. Neste sentido, para garantir a melhor utilização dos materiais envolvidos (aço e concreto, por exemplo), é preciso determinar as forças de protensão aplicadas aos cabos. A melhor distribuição dos momentos fletores no tabuleiro de ponte é aquela obtida com uma viga contínua. Pontes estaiadas fornecem apoios elásticos ao tabuleiro. O presente trabalho emprega o método da anulação dos deslocamentos, MAD, para obter as forças axiais a que os cabos estarão submetidos de modo a aproximar o comportamento do tabuleiro ao de uma viga contínua. O método MAD. proporciona uma estrutura economicamente mais viável. O código computacional desenvolvido realiza análises estática e modal por meio do método dos elementos finitos, MEF. A análise estática utilizada é a não linear geométrica, considerando as não linearidades do efeito de catenária do cabo, e dos elementos submetidos à compressão. O material é assumido no campo do regime elástico linear. A ponte é modelada por elementos de treliça plana com módulo de elasticidade de Dischinger, para simular os cabos, e elementos de pórtico plano para os elementos do tabuleiro e da torre. O carregamento da estrutura considera a atuação apenas do peso-próprio dos elementos estruturais. O código computacional desenvolvido permite, também, a análise modal da estrutura a fim de determinar suas frequências naturais e modos de vibração. A análise modal pode ser realizada com a matriz de massa concentrada, ou consistente. Em relação à matriz de rigidez, a análise modal da estrutura pode utilizar a matriz de rigidez linear, para uma análise de vibrações livres, ou a matriz de rigidez tangente para as análises de vibração sob tensões iniciais. Exemplos encontrados na literatura são resolvidos com o código computacional desenvolvido para verificação e validação.<br>The cable-stayed bridges are examples of slender and flexible where the usability of the materials is very important structures. In this sense, to ensure the best use of the materials involved (steel and concrete, for example), one must determine the forces applied to the prestressing cables. A better distribution of the bending moments in the bridge deck is obtained with a continuous beam. Cable-stayed bridges provide elastic support to the deck. This work employs the zero displacement method, ZDM, to determine the axial forces that the cables will be subjected to in order to approximate the behavior of the deck to the one as a continuous beam. The ZDM method provides an economically viable structure. The computational code performs static and modal analysis, which are performed by using the finite element method, FEM. The static analysis is a nonlinear geometric analysis which considers the nonlinearities of the cable sag, and the compression effects on the elements. The material is assumed in the field of linear elastic regime. The bridge is modeled by elements of plane truss with Dischingers elasticity module, to simulate cables and plane frame elements for the deck and the tower elements. The structure is subjected to self-weight of the elements. The computer code developed also performs the modal analysis of the structure to determine their natural frequencies and mode shapes. The modal analysis can be carried out with the concentrated or consistent mass matrix. In relation to the stiffness matrix, modal analysis of the structure may use a linear stiffness matrix for analysis of free vibration analysis or the tangent stiffness matrix for the analysis of vibration under initial stress. Examples in the literature are solved with the computational code developed for verification and validation.
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Hakala, Tim. "Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse Control." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/1061.
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A new method of adaptive impulse control is developed to precisely and quickly control the position of machine components subject to friction. Friction dominates the forces affecting fine positioning dynamics. Friction can depend on payload, velocity, step size, path, initial position, temperature, and other variables. Control problems such as steady-state error and limit cycles often arise when applying conventional control techniques to the position control problem. Studies in the last few decades have shown that impulsive control can produce repeatable displacements as small as ten nanometers without limit cycles or steady-state error in machines subject to dry sliding friction. These displacements are achieved through the application of short duration, high intensity pulses. The relationship between pulse duration and displacement is seldom a simple function. The most dependable practical methods for control are self-tuning; they learn from online experience by adapting an internal control parameter until precise position control is achieved. To date, the best known adaptive pulse control methods adapt a single control parameter. While effective, the single parameter methods suffer from sub-optimal settling times and poor parameter convergence. To improve performance while maintaining the capacity for ultimate precision, a new control method referred to as Adaptive Impulse Control (AIC) has been developed. To better fit the nonlinear relationship between pulses and displacements, AIC adaptively tunes a set of parameters. Each parameter affects a different range of displacements. Online updates depend on the residual control error following each pulse, an estimate of pulse sensitivity, and a learning gain. After an update is calculated, it is distributed among the parameters that were used to calculate the most recent pulse. As the stored relationship converges to the actual relationship of the machine, pulses become more accurate and fewer pulses are needed to reach each desired destination. When fewer pulses are needed, settling time improves and efficiency increases. AIC is experimentally compared to conventional PID control and other adaptive pulse control methods on a rotary system with a position measurement resolution of 16000 encoder counts per revolution of the load wheel. The friction in the test system is nonlinear and irregular with a position dependent break-away torque that varies by a factor of more than 1.8 to 1. AIC is shown to improve settling times by as much as a factor of two when compared to other adaptive pulse control methods while maintaining precise control tolerances.
Book chapters on the topic "Zero displacement method"
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Bulatov, Vasily, and Wei Cai. "Case Study of Dynamic Simulation." In Computer Simulations of Dislocations. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780198526148.003.0008.
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The preceding chapter focused on the dislocation core structure at zero temperature obtained by energy minimization. In this chapter we will discuss a case study of dislocation motion at finite temperature by molecular dynamics (MD) simulations. MD simulations offer unique insights into the mechanistic and quantitative aspects of dislocation mobility because accurate measurements of dislocation velocity are generally difficult, and direct observations of dislocation motion in full atomistic detail are still impossible. The discussion of this case study is complete in terms of relevant details, including boundary and initial conditions, temperature and stress control, and, finally, visualization and data analysis. In Section 3.1 we discussed a method for introducing a dislocation into a simulation cell. It relies on the linear elasticity solutions for dislocation displacement fields. To expand our repertoire, let us try another method here. The idea is to create a planar misfit interface between two crystals, such that subsequent energy minimization would automatically lead to dislocation formation.
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Ammari, Habib, Elie Bretin, Josselin Garnier, Hyeonbae Kang, Hyundae Lee, and Abdul Wahab. "Boundary Perturbations due to the Presence of Small Cracks." In Mathematical Methods in Elasticity Imaging. Princeton University Press, 2015. http://dx.doi.org/10.23943/princeton/9780691165318.003.0005.
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This chapter considers the perturbations of the displacement (or traction) vector that are due to the presence of a small crack with homogeneous Neumann boundary conditions in an elastic medium. It derives an asymptotic formula for the boundary perturbations of the displacement as the length of the crack tends to zero. Using analytical results for the finite Hilbert transform, the chapter derives an asymptotic expansion of the effect of a small Neumann crack on the boundary values of the solution. It also derives the topological derivative of the elastic potential energy functional and proves a useful representation formula for the Kelvin matrix of the fundamental solutions of Lamé system. Finally, it gives an asymptotic formula for the effect of a small linear crack in the time-harmonic regime.
Conference papers on the topic "Zero displacement method"
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Myint, Shwe, Warit Wichakool, and Phonsit Santiprapan. "A Simple High Impedance Fault Detection Method based on Phase Displacement and Zero Sequence Current for Grounded Distribution Systems." In 2018 IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC). IEEE, 2018. http://dx.doi.org/10.1109/appeec.2018.8566323.
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Wilhelm, Shawn R., and James D. Van de Ven. "Synthesis of a Variable Displacement Linkage for a Hydraulic Transformer." In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47339.
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A hydraulic pump/motor with high efficiency at low displacements is required for a compressed air energy storage system that utilizes a liquid piston for near-isothermal compression. To meet this requirement, a variable displacement six-bar crank-rocker-slider mechanism, which goes to zero displacement with a constant top dead center position, has been designed. The synthesis technique presented in the paper develops the range of motion for the base four-bar crank-rocker, creates a method of synthesizing the output slider dyad, and analyzes the mechanisms performance in terms of transmission angles, slider stroke, mechanism footprint, and timing ratio. It is shown that slider transmission angles can be kept above 60 degrees and the base four-bar transmission angles can be controlled in order to improve overall efficiency. This synthesis procedure constructs a crank-rocker-slider mechanism for a variable displacement pump/motor that can be efficient throughout all displacements.
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Spears, R. E. "Unique Method for Generating Design Earthquake Time Histories." In ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61243.
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A method has been developed which takes a seed earthquake time history and modifies it to produce given design response spectra. It is a multi-step process with an initial scaling step and then multiple refinement steps. It is unique in the fact that both the acceleration and displacement response spectra are considered when performing the fit (which primarily improves the low frequency acceleration response spectrum accuracy). Additionally, no matrix inversion is needed. The features include encouraging the code acceleration, velocity, and displacement ratios and attempting to fit the pseudo velocity response spectrum. Also, “smoothing” is done to transition the modified time history to the seed time history at its start and end. This is done in the time history regions below a cumulative energy of 5% and above a cumulative energy of 95%. Finally, the modified acceleration, velocity, and displacement time histories are adjusted to start and end with an amplitude of zero (using Fourier transform techniques for integration).
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Azadi, Mohammad, and Mehrnoosh Damircheli. "Nonlinear Thermoelastic Stress Analysis of the Rotating FGM Disk With Variable Thickness and Temperature-Dependent Material Properties Using Finite Element Method." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12204.
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In this paper, nonlinear radial and hoop thermoelastic stress analysis of rotating disk made of functionally graded material (FGM) with variable thickness is carried out by using the finite element method. In this method, one-dimensional second order elements with three nodes have been used. The geometrical and boundary conditions are in the shape of nonexistence of the pressure (zero radial stress) in both external and internal layers and zero displacement at the internal layer of rotating disk. Furthermore, it’s assumed that heat distribution is as second order curve while material properties such as elasticity modulus, Poisson’s ratio and thermal expansion coefficient vary by using a power law versus radius of the disk and also vary with the temperature. In a numerical example, the displacements and stresses for various powers (N) and the angular velocities have been calculated in according to the radius. It’s obvious that by increasing the values of the power (N) and the angular velocity, the value of displacements and stresses will be increased consequently. Finally, the effect of varying the thickness and the dependency and in-dependency of the material properties on the temperature has been considered.
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Ma, Rujian, Guixi Li, and Dong Zhao. "Nonlinear Analysis of a Simple Pendulum With Large Displacement." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42792.
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The vibration of simple pendulum with large displacement is a kind of nonlinear system. The relationship between spectra of response and excitation is established by nonlinear analysis method under the assumption of the displacement response being a zero-mean Gaussian process, which is proved to be true by numerical simulation. The numerical computation is used to investigate the amplitude-frequency characteristics of the system. The results show that the value of amplitude-frequency characteristics decreases significantly with the increase of natural frequency and damping ratio near the point of frequency ratio being one, and the changes become less notable when the frequency ratio is greater than two.
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Liu, Lilan, Hongzhao Liu, Ziying Wu, and Daning Yuan. "A New Method for the Identification of Coulomb and Viscous Friction." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-79043.
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In this paper, a new method for simultaneously estimating Coulomb and viscous friction parameters from the free vibration of a damped oscillator is put forward. In the method, the nonlinear vibration equation with Coulomb and viscous friction is transformed into a linear procedure with equivalent viscous damping which is a function of velocity. The proposed method works well with both the displacement and velocity response data, while the case of zero velocity is not considered. From the displacement decaying curve, the equivalent viscous damping ratios are obtained by means of the local exponential fitting method, and different velocities corresponding to the equivalent viscous damping ratios are also obtained from the velocity decaying curve. Then, according to the relationship between the equivalent viscous damping ratio and the velocity, the Coulomb friction and the viscous damping are achieved using the least square method. The validity and accuracy of the proposed method are demonstrated through good simulation results.
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AlSahlani, Assaad, Frank B. Mathis, and Ranjan Mukherjee. "Vibration Control of a String Using Zero-Displacement Constraint at a Point Near One Boundary: Theory and Experiment." In ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/detc2012-71128.
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A new method for vibration control of a string is proposed in which a zero displacement constraint is sequentially applied and released at a point near one boundary. When the constraint is applied, the string is partitioned into two vibrating strings, one of them is much shorter in length than the other. The vibration in the shorter segment of the string decays out much faster than the longer segment due to higher frequency. After the vibration in the shorter segment has decayed, the constraint is removed and the string is allowed to vibrate in its full length. The total energy is now redistributed over the full length, and this provides the scope for application of the constraint again for further reduction of energy. Vibration suppression is achieved through sequential application and removal of the constraint and this is simulated using a linear damped model of the string. Experiments were conducted and the experimental results were found to match well with simulation results.
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Sharma, Sheshadri, and Richard Rodrigues Jettappa. "A Method to Determine the Exact Time Period of Oscillations of a Bifilar Pendulum." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23531.
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A novel method to determine the exact time period of oscillations of a class of non-linear systems is presented. Taking the bifilar pendulum as an example, and employing the conservation of total energy concept, the free oscillations of the system is studied. The governing equation of motion of a bifilar pendulum is non-linear. The integration of this equation to obtain the time period of oscillation is highly complicated and only numerical solution is available. This is because the integral is singular at the extremities of the motion where the velocity will be zero. But, what cannot be achieved by integral calculus can be obtained easily by employing the definition of velocity taught in the high school curriculum. By employing this simple mathematical trick, this intractable equation is recast in a different but exact form. This leads to the identification of what is called the “Geometric Inertia” in bifilar pendulums. This Geometric Inertia is the additional inertia displayed by the system due to the constraint imposed by the two filaments as a result of the geometry of the pendulum. In the proposed method, the total displacement of the system is considered and divided into small equal segments. At the end points of each such segment, the corresponding velocity is calculated from the energy equation. Noting that the velocities are zero at the extremities of the system, an average velocity to each segment is calculated, and this average velocity is positive in each segment. The “delta” time spent by the system in each segment is now calculated by dividing the segment length by the average velocity of that segment. (From, time = displacement/velocity). The linear sum of such “delta” times gives the time period of oscillation. As the number of segments is increased, thereby reducing the segment length, the estimate becomes increasingly accurate. The proposed approach avoids a direct integration of complex, and often singular expressions that complicate the determination of time periods of oscillations of non-linear systems.
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Ghayesh, Mergen H., Michael P. Païdoussis, and Marco Amabili. "Nonlinear Planar Dynamics of Fluid-Conveying Cantilevered Extensible Pipes." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65785.
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This paper for the first time investigates the nonlinear planar dynamics of a cantilevered extensible pipe conveying fluid; the centreline of the pipe is considered to be extensible resulting in coupled longitudinal and transverse equations of motion; specifically, the kinetic and potential energies are obtained in terms of longitudinal and transverse displacements and then the extended version of the Lagrange equations for systems containing non-material volumes is employed to derive the equations of motion. Direct time integration along with the pseudo-arclength continuation method are employed to solve the discretized equations of motion. Bifurcation diagrams of the system are constructed as the flow velocity is increased as the bifurcation parameter. As opposed to the case of an inextensible pipe, an extensible pipe elongates in the axial direction as the flow velocity is increased from zero. At the critical flow velocity, the stability of the system is lost via a supercritical Hopf bifurcation, emerging from the trivial solution for the transverse displacement and non-trivial solution for the longitudinal displacement and leading to a flutter.
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Wang, Guoqing, Liming Dai, and Diankui Liu. "The Scattering Field of SH-Wave in Half-Space With a Semi-Cylindrical Hill and a Horizontal Circular Tunnel." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80117.
Full textAbstract:
The scattering field of SH-wave in a half-space with a semi-cylindrical hill and a subsurface horizontal hole is studied in the present research by utilizing a complex function and the moving-coordinate method. Based on the concept of ‘conjunction,’ the domain considered is divided into two subdomains. The first subdomain is a cylindrical one which includes the surface of the hill, while the rest is the second subdomain. In the cylindrical subdomain, a standing wave function is constructed which automatically satisfies the zero-stress condition at the hill surface and arbitrary-stress condition at the other part of the circular subdomain. For the second subdomain, which contains a semi-cylindrical canyon and a subsurface hole, a scattering wave function is assumed, which satisfies the zero-stress condition on the horizontal surface. By employing the moving-coordinate method, the solutions of the mathematical model established for the SH-wave can be obtained with the satisfaction of the continuous conditions of stress and displacement across the junction interface together with the zero-stress condition at the surface of the tunnel. The solutions such obtained consist of a series of infinite linear algebraic equations, which can be solved numerically with consideration of the first finite terms corresponding to the frequencies of the wave. For demonstrating the application of the model developed, the displacements of the horizontal and semi-cylindrical hill surfaces are quantified with different properties of wave and geometry parameters.