scholarly journals Snapping of a Shallow Arch With Harmonic Excitation at One End

2007 ◽  
Vol 129 (4) ◽  
pp. 514-519 ◽  
Author(s):  
Jen-San Chen ◽  
Der-Wei Chang
Keyword(s):  
Natural Frequencies ◽  
Stable Equilibrium ◽  
Excitation Frequency ◽  
Longitudinal Direction ◽  
Harmonic Excitation ◽  
Small Distance ◽  
The Other ◽  
Base Line ◽  
Shallow Arch ◽  
Mechanical Shaker

In this paper we demonstrate both numerically and experimentally that it is possible to make a pinned-pinned shallow arch snap to and remain vibrating on the other side by harmonic excitation in the longitudinal direction at the end. One end of the arch is fixed in space, while the other end is attached to a mechanical shaker via a spring. The shaker-mount is first moved a small distance toward the arch to ensure that the arch assembly possesses two stable equilibrium positions, one on each side of the base line. The spring connecting the arch end and the mechanical shaker is carefully chosen such that a small shaker stroke can induce a large vibration amplitude in the arch. The natural frequencies of the two (initial and snapped, respectively) positions are measured first. By adjusting the excitation frequency of the mechanical shaker to the first natural frequency of either position of the arch, we demonstrate that the arch can be snapped to and remain vibrating on the other side when the magnitude of the electric current flowing through the shaker is properly chosen. The vibrant snapping action of the arch recorded in the experiment is confirmed by numerical simulation.

Experimental Observation of Amplitude- and Phase-Modulated Responses of Two Internally Coupled Oscillators to a Harmonic Excitation

1988 ◽  
Vol 55 (3) ◽  
pp. 706-710 ◽  
Author(s):  
A. H. Nayfeh ◽  
L. D. Zavodney
Keyword(s):  
Perturbation Theory ◽  
Qualitative Agreement ◽  
Coupled Oscillators ◽  
Natural Frequencies ◽  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Lower Mode ◽  
Quadratic Nonlinearities ◽  
Two Degree Of Freedom ◽  
Second Order Perturbation Theory

An experiment is performed on a two degree-of-freedom mechanical system having quadratic nonlinearities and linear natural frequencies ω1 and ω2 approximately in the ratio of two-to-one (i.e., ω2 ≈ 2ω1). When the lower mode is excited by a harmonic excitation whose frequency Ω is nearly equal to ω1, amplitude- and phase-modulated responses of the system have been observed for a range of the excitation frequency Ω, in qualitative agreement with the results of a second-order perturbation theory.

Vibro-Impact Dynamics of a Periodically Forced Beam

2000 ◽  
Vol 122 (2) ◽  
pp. 210-221 ◽  
Author(s):  
Jakob Knudsen ◽  
Ali R. Massih
Keyword(s):  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Unilateral Contact ◽  
Contact Forces ◽  
The Other ◽  
Impact Dynamics ◽  
Harmonic Loading ◽  
Model Calculations ◽  
Contact Sites ◽  
The Impact

The vibration and impact dynamics of a periodically forced loosely supported beam are analyzed. The wear work rates at impact points are evaluated. The considered beam is clamped at one end, and constrained against unilateral contact at contact sites, with or without friction, near the other end. In this work, the structure is modeled by a Bernoulli-type beam supported by springs using finite element method. Our model calculations are compared with measurements of contact forces and displacements made on a loosely supported rod that was subjected to harmonic loading. Furthermore, the dynamics of vibro-impacts are characterized by evaluating the impact velocity as a function of harmonic excitation frequency for two idealizations of the aforementioned structure. [S0094-9930(00)01002-7]

Nonlinear Vibrations of Elastic Structures Carrying Two Rectangular Liquid-Filled Tanks Under Horizontal Excitation

2005 ◽  
Author(s):  
Takashi Ikeda
Keyword(s):  
Internal Resonance ◽  
Nonlinear Vibrations ◽  
Natural Frequencies ◽  
Hydrodynamic Force ◽  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Response Curves ◽  
System Parameters ◽  
Chaotic Vibrations ◽  
Multi Mode

Nonlinear vibrations of an elastic structure carrying two liquid-filled tanks under horizontal harmonic excitation are investigated. When a 1:1:1 ratio of internal resonance is satisfied among the natural frequencies of the structure and sloshing in the two liquid tanks, modal equations are derived by using Galerkin’s method, taking into account the nonlinearity of the hydrodynamic force. Then, frequency response curves are calculated by using Andronov and Witt’s method. Peculiar vibrations, referred to as ‘multi-mode vibrations’, sometimes may appear depending on the values of the system parameters. They never occur in a structure carrying only one liquid-filled tank. In other words, even if the dimensions of the two tanks are identical, the sloshing which occurs in each tank differs depending on the excitation frequency. The multi-mode vibrations include constant amplitude vibrations and amplitude modulated motion as well as chaotic vibrations.

A Yield Criterion of Porous Materials With Anisotropy Caused by Geometry or Distribution of Pores

1991 ◽  
Vol 113 (4) ◽  
pp. 425-429 ◽  
Author(s):  
T. Hisatsune ◽  
T. Tabata ◽  
S. Masaki
Keyword(s):  
Velocity Field ◽  
Porous Materials ◽  
Upper Bound ◽  
Volume Fraction ◽  
Yield Criterion ◽  
Longitudinal Direction ◽  
Axisymmetric Deformation ◽  
The Other ◽  
The Matrix ◽  
Spherical Cells

Axisymmetric deformation of anisotropic porous materials caused by geometry of pores or by distribution of pores is analyzed. Two models of the materials are proposed: one consists of spherical cells each of which has a concentric ellipsoidal pore; and the other consists of ellipsoidal cells each of which has a concentric spherical pore. The velocity field in the matrix is assumed and the upper bound approach is attempted. Yield criteria are expressed as ellipses on the σm σ3 plane which are longer in longitudinal direction with increasing anisotropy and smaller with increasing volume fraction of the pore. Furthermore, the axes rotate about the origin at an angle α from the σm-axis, while the axis for isotropic porous materials is on the σm-axis.

Effect of Specimen Geometry on the Predicted Mechanical Behavior of Polyethylene Pipe Material

2014 ◽  
Author(s):  
Tarek M. A. A. El-Bagory ◽  
Tawfeeq A. R. Alkanhal ◽  
Maher Y. A. Younan
Keyword(s):  
Mechanical Behavior ◽  
Longitudinal Direction ◽  
Primary Objective ◽  
The Other ◽  
Pipe Material ◽  
Ring Specimen ◽  
Design Data ◽  
Practical Applications ◽  
Other Hand ◽  
Gauge Section

The primary objective of the present paper is to depict the mechanical behavior of high density polyethylene, (HDPE), pipes under different loading conditions with different specimen geometries to provide the designer with reliable design data relevant to practical applications. Therefore, it is necessary to study the effect of strain rate, ring configuration, and grip or fixture type on the mechanical behavior of dumb-bell-shaped, (DBS), and ring specimens made from HDPE pipe material. DBS and ring specimens are cut from the pipe in longitudinally, and circumferential (transverse) direction respectively. On the other hand, the ring specimen configuration is classified into two types; full ring, (FR), and notched ring, (NR) (equal double notch from two sides of notched ring specimen) specimens according to ASTM D 2290-12 standard. Tensile tests are conducted on specimens cut out from the pipe with thickness 10 mm at different crosshead speeds (10–1000 mm/min), and ambient temperature, Ta = 20 °C to investigate the mechanical properties of DBS, and ring specimens. In the case of test specimens taken from longitudinal direction from the pipe a necking phenomenon before failure appears at different locations along the gauge section. On the other hand, the fracture of NR specimens occurs at one notched side. The results demonstrated that the NR specimen has higher yield stress than DBS, and FR specimens at all crosshead speeds. The present experimental work reveals that the crosshead speed has a significant effect on the mechanical behavior of both DBS, and ring specimens. The fixture type plays an important role in the mechanical behavior for both FR and NR specimens at all crosshead speeds.

Histologic Findings in Two Very Small Intracanalicular Solitary Schwannomas of the Eighth Nerve

1986 ◽  
Vol 95 (5) ◽  
pp. 460-465 ◽  
Author(s):  
J. Gail Neely ◽  
Jack Hough
Keyword(s):  
Nerve Fiber ◽  
Longitudinal Direction ◽  
Nerve Fibers ◽  
Vestibular Nerve ◽  
Cochlear Nerve ◽  
The Other ◽  
En Bloc ◽  
Hearing Conservation ◽  
Eighth Nerve ◽  
Conservation Surgery

Two very small intracanalicular tumors, resected en bloc with the complete eighth nerve, were serially sectioned in order to study the relationship between the tumors and the nerves of origin. Both cases met the size criteria for hearing conservation surgery; however, the patient with the smaller tumor and the better hearing had no recognizable cochlear nerve fibers passing the tumor. The cochlear nerve in the patient with poorer hearing was completely free of tumor. The tumor with the infiltrated cochlear nerve seemed to originate from the inferior vestibular nerve. The other tumor seemed to arise from the superior vestibular nerve. Proximally, the tumors occupied a more central location in the involved nerves, but they abruptly became eccentric and exophytic as they proceeded laterally. Nerve fibers remaining about the tumors were displaced to the periphery. These nerve fiber aggregates became quite thin and attenuated, frequently separating into smaller aggregates which, ultimately, were incorporated into the tumors. As fibers came closer to the tumors, they tended to change from their longitudinal direction toward a more circumferential orientation about the surface of the tumors. The tumor-nerve fiber interfaces were quite variable throughout the course of the tumor, ranging from large aggregates of nerve fibers distinctly separate from the tumors to aggregates separate but tightly applied to the tumors without a tissue plane between, to aggregates partially incorporated within the periphery of the tumors, to aggregates completely incorporated into the periphery of the tumors. Frequently several types of interfaces were seen in the same section. These findings showed that in one case the cochlear nerve could have been surgically separated from the acoustic tumor; in the other specimen, it could not have been separated. It was impossible to predict between the two. In these two very small tumors, the gross specimen observation correlated reasonably well with the histology, thus suggesting that intraoperative observation may be a predictor in hearing conservation surgery; however, previous studies in slightly larger tumors make this an extremely guarded concept.

scholarly journals INFORMATION TECHNOLOGY PLAN AS AN IT GOVERNANCE MATURITY DRIVER

2012 ◽  
Vol 5 (1) ◽  
pp. 50
Author(s):  
Budi Yuwono ◽  
Rein Nusa Triputra ◽  
Muhammad Nasri
Keyword(s):  
Information Technology ◽  
It Governance ◽  
The Other ◽  
Base Line ◽  
Maturity Level ◽  
Governance Mechanisms ◽  
Technology Plan ◽  
Government Institutions ◽  
Other Hand

Having an information technology (IT) plan is a minimum baseline for optimal IT governance. But, creating a plan is only one problem, executing it poses even more challenging problems. In this research, we investigate the correlation between an organization’s IT plan and the organization’s IT governance maturity level. We show that, on one hand, executing an IT plan requires a certain IT governance maturity level, on the other hand, the experience of executing an IT plan drives the organization IT governance maturity level. We compare the situations in two government institutions and found indications that the organization with an ambitious IT plan has more mature IT governance than the other whose IT plan is relatively modest. The results suggest that an effective IT plan should include plans for the development of IT governance mechanisms relevant to the goals that the plan is intended to achieve, and the plan’s implementation schedule, also known as the IT roadmap, should take into consideration the growth of the IT governance mechanisms’ maturity levels. Memiliki rencana untuk teknologi informasi (TI) adalah base line untuk tata kelola TI yang optimal. Tapi, membuat rencana hanyalah satu masalah, melaksanakannya akan menciptakan masalah baru yang lebih menantang. Dalam penelitian ini, kami menyelidiki korelasi antara rencana TI suatu organisasi dengan tingkat maturity tata kelola TI-nya. Kami menunjukkan bahwa, di satu sisi, untuk melaksanakan rencana TI memerlukan tingkat kematangan tata kelola TI tertentu, di sisi lain, pengalaman dalam menjalankan rencana TI mendorong organisasi dalam meningkatkan tata kelola TI. Kami membandingkan situasi di dua lembaga pemerintah dan menemukan indikasi bahwa organisasi dengan rencana TI yang ambisius memiliki tata kelola TI lebih matang dari organisasi yang rencana TI-nya relatif sederhana. Hasil penelitian menunjukkan bahwa perencanaan TI yang efektif harus mencakup rencana untuk pengembangan mekanisme tata kelola TI yang relevan dengan tujuan yang ingin dicapai, dan jadwal pelaksanaan rencana atau roadmap TI, harus mempertimbangkan pertumbuhan tingkat mekanisme tata kelola TI.

scholarly journals On the elementary structure of muscular fibre of animal and organic life

1837 ◽  
Vol 3 ◽  
pp. 462-463
Keyword(s):  
Longitudinal Direction ◽  
Average Diameter ◽  
The Other ◽  
Arterial System ◽  
Muscular Fibre ◽  
Exact Nature ◽  
Animal Life ◽  
Partial Separation ◽  
Organic Life

The author concludes, from his microscopic examinations of the structure of muscular fibres, that those subservient to the functions of animal life have, in man, an average diameter of one 400dth of an inch, and are surrounded by transverse circular striae varying in thickness, and in the number contained in a given space. He describes these striae as constituted by actual elevations on the surface of the fibre, with intermediate depressions, considerably narrower than the diameter of a globule of the blood. Each of these muscular fibres, of which the diameter is one 400dth of an inch, is divisible into bands or fibrillae, each of which is again subdivisible into about one hundred tubular filaments, arranged parallel to one another, in a longitudinal direction, around the axis of the tubular fibre which they compose, and which contains in its centre a soluble gluten. The partial separation of the fibrillae gives rise to the appearance of broken or interrupted circular striae, which are occasionally seen. The diameter of each filament is one 16,000dth of an inch, or about a third part of that of a globule of the blood. On the other hand, the muscles of organic life are composed, not of fibres similar to those above described, but of filaments only ; these filaments being interwoven with each other in irregularly disposed lines of various thickness; having for the most part a longitudinal direction, but forming a kind of untraceable network. They are readily distinguishable from tendinous fibres, by the filaments of the latter being uniform in their size, and pursuing individually one unvarying course, in lines parallel to each other. The fibres of the heart appear to possess a somewhat compound character of texture. The muscles of the pharynx exhibit the character of animal life; while those of the oesophagus, the stomach, the intestines, and the arterial system, possess that of inorganic life. The determination of the exact nature of the muscular fibres of the iris presented considerable difficulties, which the author has not yet been able satisfactorily to overcome.

Nonlinear Combination Resonances in Cantilever Composite Plates

1995 ◽  
Author(s):  
Kyoyul Oh ◽  
Ali H. Nayfeh
Keyword(s):  
Natural Frequencies ◽  
Excitation Frequency ◽  
Power Spectra ◽  
Low Frequency ◽  
Composite Plates ◽  
High Amplitude ◽  
Mode Shapes ◽  
Laser Vibrometer ◽  
Combination Resonance ◽  
Response Curves

Abstract We experimentally investigated nonlinear combination resonances in a graphite-epoxy cantilever plate having the configuration (–75/75/75/ – 75/75/ – 75)s. As a first step, we compared the natural frequencies and mode shapes obtained from the finite-element and experimental modal analyses. The largest difference in the obtained frequencies was 2.6%. Then, we transversely excited the plate and obtained force-response and frequency-response curves, which were used to characterize the plate dynamics. We acquired time-domain data for specific input conditions using an A/D card and used them to generate time traces, power spectra, pseudo-state portraits, and Poincaré maps. The data were obtained with an accelerometer monitoring the excitation and a laser vibrometer monitoring the plate response. We observed the external combination resonance Ω≈12(ω2+ω5) and the internal combination resonance Ω≈ω8≈12(ω2+ω13), where the ωi are the natural frequencies of the plate and Ω is the excitation frequency. The results show that a low-amplitude high-frequency excitation can produce a high-amplitude low-frequency motion.

Torsional Vibration Analysis of Shafts With Sections of Tapered Diameter

1993 ◽  
Author(s):  
John R. Baker ◽  
Keith E. Rouch
Keyword(s):  
Torsional Vibration ◽  
Vibration Analysis ◽  
Natural Frequencies ◽  
Displacement Function ◽  
The Other ◽  
Mode Shapes ◽  
Axial Distance ◽  
Rotational Degree ◽  
Rotor Systems ◽  
Constant Diameter

Abstract This paper presents the development of two tapered finite elements for use in torsional vibration analysis of rotor systems. These elements are particularly useful in analysis of systems that have shaft sections with linearly varying diameters. Both elements are defined by two end nodes, and inertia matrices are derived based on a consistent mass formulation. One element assumes a cubic displacement function and has two degrees of freedom at each node: rotation about the shaft’s axis and change in angle of rotation with respect to the axial distance along the shaft. The other element assumes a linear displacement function and has one rotational degree of freedom at each node. The elements are implemented in a computer program. Calculated natural frequencies and mode shapes are compared for both tapered shaft sections and constant diameter sections. These results are compared with results from an available constant diameter element. It is shown that the element derived assuming a cubic displacement function offers much better convergence characteristics in terms of calculated natural frequencies, both for tapered sections and constant diameter sections, than either of the other two elements. The finite element code that was developed for implementation of these elements is specifically designed for torsional vibration analysis of rotor systems. Lumped inertia, lumped stiffness, and gear connection elements necessary for rotor system analysis are also discussed, as well as calculation of natural frequencies, mode shapes, and amplitudes of response due to a harmonic torque input.

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