On the Nonlinear Response of Piping to Seismic Loads

2001 ◽  
Vol 123 (3) ◽  
pp. 324-331
Author(s):  
Luciano Lazzeri
Keyword(s):  
Complex Systems ◽  
Frequency Shift ◽  
Nonlinear Response ◽  
Experimental Tests ◽  
Piping System ◽  
Seismic Loads ◽  
Response Characteristics ◽  
Specific Geometry

The response of a piping system to extreme seismic conditions may be controlled and limited by yielding of the structure. The effect of yielding has been found to be decisive for individual components, but for complex systems, the effect of yielding may be either important or negligible, depending on the specific geometry. Analytical and experimental tests are reviewed. The L test is devised to give an indication of the response characteristics of the system. It has been found that a parameter related to the frequency shift is capable of reasonably predicting the effect of yielding.

Shooting With Deflation Algorithm-Based Nonlinear Response and Neimark-Sacker Bifurcation and Chaos in Floating Ring Bearing Systems

2016 ◽  
Vol 12 (3) ◽  
Author(s):  
Sitae Kim ◽  
Alan B. Palazzolo
Keyword(s):  
Nonlinear Response ◽  
Nonlinear Behavior ◽  
Rotor System ◽  
Operating Conditions ◽  
Fluid Film ◽  
Stable Limit ◽  
Bifurcation And Chaos ◽  
Chaotic Motions ◽  
Response Characteristics ◽  
Computation Efficiency

The double-sided fluid film force on the inner and outer ring surfaces of a floating ring bearing (FRB) creates strong nonlinear response characteristics such as coexistence of multiple orbits, Hopf bifurcation, Neimark-Sacker (N-S) bifurcation, and chaos in operations. An improved autonomous shooting with deflation algorithm is applied to a rigid rotor supported by FRBs for numerically analyzing its nonlinear behavior. The method enhances computation efficiency by avoiding previously found solutions in the numerical-based search. The solution manifold for phase state and period is obtained using arc-length continuation. It was determined that the FRB-rotor system has multiple response states near Hopf and N-S bifurcation points, and the bifurcation scenario depends on the ratio of floating ring length and diameter (L/D). Since multiple responses coexist under the same operating conditions, simulation of jumps between two stable limit cycles from potential disturbance such as sudden base excitation is demonstrated. In addition, this paper investigates chaotic motions in the FRB-rotor system, utilizing four different approaches, strange attractor, Lyapunov exponent, frequency spectrum, and bifurcation diagram. A numerical case study for quenching the large amplitude motion by adding unbalance force is provided and the result shows synchronization, i.e., subsynchronous frequency components are suppressed. In this research, the fluid film forces on the FRB are determined by applying the finite element method while prior work has utilized a short bearing approximation. Simulation response comparisons between the short bearing and finite bearing models are discussed.

Theoretical and Experimental Analysis of Nonlinear Dynamics in a Linear Compressor

2001 ◽  
Vol 124 (1) ◽  
pp. 152-154 ◽  
Author(s):  
Gyu-Sang Choe ◽  
Kwang-Joon Kim
Keyword(s):  
Steady State ◽  
Nonlinear Response ◽  
Dynamic Models ◽  
Steady State Response ◽  
Describing Function ◽  
Linear Compressor ◽  
Response Characteristics ◽  
State Response ◽  
Jump Phenomena ◽  
Method Effects

Steady-state nonlinear response characteristics of a linear compressor are investigated theoretically and experimentally. In the theoretical approach, motions of not only piston but also cylinder are considered and dynamic models for steady-state response predictions are formulated by applying the describing function method. Effects of piston mass on the jump phenomena are predicted by the derived models as an example of design parameter variation and compared with actual experimental results.

scholarly journals Nonlinear response characteristics of neural networks and single neurons undergoing optogenetic excitation

2020 ◽  
Vol 4 (3) ◽  
pp. 852-870
Author(s):  
Jannik Luboeinski ◽  
Tatjana Tchumatchenko
Keyword(s):  
Neural Networks ◽  
Nonlinear Response ◽  
Pulse Frequency ◽  
Simulation Code ◽  
Response Characteristics ◽  
Optogenetic Stimulation ◽  
Spatial Response ◽  
Temporal And Spatial ◽  
Light Beams ◽  
Indirect Stimulation

Optogenetic stimulation has become the method of choice for investigating neural computation in populations of neurons. Optogenetic experiments often aim to elicit a network response by stimulating specific groups of neurons. However, this is complicated by the fact that optogenetic stimulation is nonlinear, more light does not always equal to more spikes, and neurons that are not directly but indirectly stimulated could have a major impact on how networks respond to optogenetic stimulation. To clarify how optogenetic excitation of some neurons alters the network dynamics, we studied the temporal and spatial response of individual neurons and recurrent neural networks. In individual neurons, we find that neurons show a monotonic, saturating rate response to increasing light intensity and a nonmonotonic rate response to increasing pulse frequency. At the network level, we find that Gaussian light beams elicit spatial firing rate responses that are substantially broader than the stimulus profile. In summary, our analysis and our network simulation code allow us to predict the outcome of an optogenetic experiment and to assess whether the observed effects can be attributed to direct or indirect stimulation of neurons.

The OECD-NEA Programme on Metallic Component Margins Under High Seismic Loads (MECOS)

2016 ◽  
Author(s):  
Pierre B. Labbé ◽  
G. R. Reddy ◽  
Cedric Mathon ◽  
François Moreau ◽  
Spyros A. Karamanos
Keyword(s):  
Seismic Analysis ◽  
Evaluation Criteria ◽  
Piping System ◽  
Seismic Loads ◽  
Metallic Component ◽  
Design Practices ◽  
Piping Systems ◽  
Current Design ◽  
New Criteria ◽  
Experimental Background

MECOS is Post-Fukushima OECD/NEA initiative, with the following main objectives: - To quantify the existing margins in seismic analysis of safety class components and assess the existing design practices within a benchmark activity. - To make proposals for new design/evaluation criteria of pressurized piping systems, accounting for their actual failure mode under strong input motions. The first part of MECOS consisted of gathering information on i) current design practices and ii) piping system experimentation carried out around the world that could be suitable for benchmarking. Part 2 is the benchmark itself and Part 3 proposals for new criteria. The purpose of the proposed paper is to present the experimental background and the benchmark exercise.

Numerical Analysis of Fracture Mechanics of SENB Specimens Prepared From HDPE Pipes

2014 ◽  
Author(s):  
Marco Gonzalez ◽  
Paulo Teixeira ◽  
Jeanette Gonzalez ◽  
Raul Machado
Keyword(s):  
Computational Study ◽  
Numerical Models ◽  
Low Cost ◽  
Pressure Fluctuations ◽  
Experimental Tests ◽  
External Pressure ◽  
Fracture Load ◽  
Two Dimensions ◽  
Mechanical Resistance ◽  
Piping System

High density polyethylene (HDPE) is commonly used in pipe fabrication for water and natural gas systems, due to its versatility, low cost and lightweight. A piping system is subject to service conditions such as impact and cyclic loads as a consequence of internal pressure or external pressure fluctuations, and the existence of discontinuities in the material. These conditions cause material damage, cracking and weakening, and have to be considered in the piping design. The Boundary Element Method (BEM) is a numerical method based on integral equations that consider only the contour of the solid (meaning an easier meshing). Crack modeling is one of the most important applications for the BEM, since it allows an accurate stress analysis around the crack tip. In this work, a computational study based on the BEM in two dimensions whose aim is to determine the stress intensity factors (SIFs) in order to evaluate the mechanical resistance to fracture of HDPE PE100 pipes and its comparison with the results obtained by previous experimental tests, is developed. Numerical simulations of specimens subject to three point bending loads (SENB specimens) using the characteristics of the linear elastic fracture mechanic (LEFM), are developed. As a first attempt, the numerical models of different SENB geometries are validated comparing the numerical solution versus the results given by a reference solution from literature. The results show that the BEM under the LEFM approach is valid for loads within the linear range of HDPE since LEFM gives an upper bound of the fracture load of HDPE specimens; however, an Elastic-Plastic fracture analysis could be required for loads in the plastic range of the material.

Nonlinear Response Characteristics of a Cracked Rotor in Maneuvering Aircraft

2003 ◽  
Author(s):  
Fu-Sheng Lin ◽  
Guang Meng ◽  
Eric Hahn
Keyword(s):  
Fault Diagnosis ◽  
Constant Velocity ◽  
Nonlinear Response ◽  
Nonlinear Behavior ◽  
Rotor System ◽  
Parameter Range ◽  
Cracked Rotor ◽  
Periodic Response ◽  
Response Characteristics ◽  
Cracked Rotor System

This paper investigates numerically the nonlinear response of a simple cracked rotor in moving supports, as may occur in aircraft rotors when the aircraft is maneuvering with constant velocity or acceleration. Of particular interest is the influence of the aircraft climb angle. Results show that the climb angle can markedly affect the parameter range for which the system is stable; and over which there results bifurcation, quasi-periodic response or chaotic response. It is shown that aircraft acceleration can also significantly affect the nonlinear behavior of the cracked rotor system, illustrating the possibility for online rotor crack fault diagnosis.

Response Characteristics of Piping System Supported by Visco-Elastic and Elasto-Plastic Dampers

1990 ◽  
Vol 112 (1) ◽  
pp. 34-38 ◽  
Author(s):  
T. Chiba ◽  
H. Kobayashi
Keyword(s):  
Energy Dissipation ◽  
Seismic Design ◽  
Damping Ratio ◽  
The Other ◽  
Piping System ◽  
Response Level ◽  
Response Characteristics ◽  
Damping Effect ◽  
Component Test ◽  
Piping Systems

Improving the reliability of the piping systems can be achieved by eliminating the mechanical snubber and by reducing the response of the piping. In the seismic design of piping system, damping is one of the important parameters to reduce the seismic response. It is reported that the energy dissipation at piping supports contributes to increasing the damping ratio of piping system. Visco-elastic damper (VED) and elasto-plastic damper (EPD) were developed as more reliable, high-damping piping supports. The dynamic characteristics of these dampers were studied by the component test and the full-scale piping model test. Damping effect of VED is independent of the piping response and VED can be modeled as a complex spring in the dynamic analysis. On the other hand, damping ratio of piping system supported by EPD increases with the piping response level. So, these dampers are helpful to increase the damping ratio and to reduce the dynamic response of piping system.

scholarly journals Nonlinear tuning of microresonators for dynamic range enhancement

2015 ◽  
Vol 471 (2179) ◽  
pp. 20140969 ◽  
Author(s):  
M. Saghafi ◽  
H. Dankowicz ◽  
W. Lacarbonara
Keyword(s):  
Nonlinear Response ◽  
Dynamic Range ◽  
Multiple Scales ◽  
Method Of Multiple Scales ◽  
Equations Of Motion ◽  
Path Following ◽  
Critical Amplitude ◽  
Inertia Effects ◽  
Response Characteristics ◽  
The Galerkin Method

This paper investigates the development of a novel framework and its implementation for the nonlinear tuning of nano/microresonators. Using geometrically exact mechanical formulations, a nonlinear model is obtained that governs the transverse and longitudinal dynamics of multilayer microbeams, and also takes into account rotary inertia effects. The partial differential equations of motion are discretized, according to the Galerkin method, after being reformulated into a mixed form. A zeroth-order shift as well as a hardening effect are observed in the frequency response of the beam. These results are confirmed by a higher order perturbation analysis using the method of multiple scales. An inverse problem is then proposed for the continuation of the critical amplitude at which the transition to nonlinear response characteristics occurs. Path-following techniques are employed to explore the dependence on the system parameters, as well as on the geometry of bilayer microbeams, of the magnitude of the dynamic range in nano/microresonators.

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