Dynamics of High-Speed Cam-Driven Mechanisms—Part 2: Nonlinear System Models

1975 ◽  
Vol 97 (3) ◽  
pp. 777-781 ◽  
Author(s):  
F. Y. Chen ◽  
N. Polvanich
Keyword(s):  
Nonlinear System ◽  
High Speed ◽  
Phase Plane ◽  
Response Spectra ◽  
Equation Of Motion ◽  
Dynamic Responses ◽  
System Model ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Shock Response

The dynamic responses of the cam-driven mechanism are investigated, based on a non-linear lumped system model. The nonlinearity is an energy-dissipating element which consists of viscous, quadratic, Coulomb and static frictions combined. The nonlinear equation of motion of a single degree of freedom is first analyzed using a numerical method and the results of time responses are presented and characterized in the phase-plane. The primary and residual shock response spectra in nondimensional form for a number of typical cam input excitations are presented and compared with those of the associated linear cases.

Dynamics of High-Speed Cam-Driven Mechanisms—Part 1: Linear System Models

1975 ◽  
Vol 97 (3) ◽  
pp. 769-775 ◽  
Author(s):  
Fan Y. Chen ◽  
N. Polvanich
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Response Spectra ◽  
System Model ◽  
Single Degree Of Freedom ◽  
System Parameters ◽  
Response Characteristics ◽  
Single Degree ◽  
Design Charts ◽  
Driven System

The dynamic response of the cam-driven mechanism is investigated for a variety of cam motion profiles. Based on a linear, lumped system model of single degree of freedom, the results of the response characteristics of the follower are presented in the form of nondimensional primary and residual shock response spectra. These spectra are also recasted in four-coordinate log-log grid forms. The extension of this approach to treat the system model of two degrees of freedom is delineated. Furthermore, the analysis of a two-freedom model of the cam-driven system was also undertaken to clarify the effects of many system parameters and for obtaining an optimal design. Fundamental design charts are presented.

Effects of human-induced load models on tuned mass damper in reducing floor vibration

2019 ◽  
Vol 22 (11) ◽  
pp. 2449-2463
Author(s):  
Jun Chen ◽  
Ziping Han ◽  
Ruotian Xu
Keyword(s):  
Response Spectra ◽  
Tuned Mass Damper ◽  
Design Guidelines ◽  
Degree Of Freedom ◽  
Dynamic Responses ◽  
Single Degree Of Freedom ◽  
Load Model ◽  
Load Models ◽  
Single Degree ◽  
Mass Damper

Dozens of human-induced load models for individual walking and jumping have been proposed in the past decades by researchers and are recommended in various design guidelines. These models differ from each other in terms of function orders, coefficients, and phase angles. When designing structures subjected to human-induced loads, in many cases, a load model is subjectively selected by the design engineer. The effects of different models on prediction of structural responses and efficiency of vibration control devices such as a tuned mass damper, however, are not clear. This article investigates the influence of human-induced load models on performance of tuned mass damper in reducing floor vibrations. Extensive numerical simulations were conducted on a single-degree-of-freedom system with one tuned mass damper, whose dynamic responses to six walking and four jumping load models were calculated and compared. The results show a maximum three times difference in the acceleration responses among all load models. Acceleration response spectra of the single-degree-of-freedom system with and without a tuned mass damper were also computed and the response reduction coefficients were determined accordingly. Comparison shows that the reduction coefficient curves have nearly the same tendency for different load models and a tuned mass damper with 5% mass ratio is able to achieve 50%–75% response reduction when the structure’s natural frequency is in multiples of the walking or jumping frequency. All the results indicate that a proper load model is crucial for structural response calculation and consequently the design of tuned mass damper device.

Seismic Response Reduction Caused by Coupling Between Beam-Type and Oval-Type Vibrations of a Cylindrical Water Storage Tank Under Large Excitation

2007 ◽  
Author(s):  
Akira Maekawa ◽  
Katsuhisa Fujita ◽  
Michiaki Suzuki
Keyword(s):  
Seismic Response ◽  
Water Storage ◽  
Degree Of Freedom ◽  
Seismic Excitation ◽  
System Model ◽  
Single Degree Of Freedom ◽  
Water Storage Tank ◽  
Single Degree ◽  
Input Acceleration ◽  
Beam Type

This study describes the response reduction caused by coupling between the beam-type and the oval-type vibrations of a cylindrical water storage tank under seismic excitation. In this study, the seismic response experiment is performed by using a 1/10 reduced scale model of an actual tank and then numerical simulation is performed by the simplified model. The authors conducted the sinusoidal response experiment for the tank and reported that the coupling between the beam-type and the oval-type vibrations causes the resonance frequency of the beam-type vibration to shift to the lower frequency and the response in the beam-type vibration (the response of the tank) to reduce. The seismic response experiment of the tank model filled with water up to 95% is performed by a shaking table. The El Centro 1940 NS and the improved standard seismic wave for Japanese LWR are used as the input seismic wave. The experimental results show that the maximum response acceleration does not enlarge linearly as the maximum input acceleration increases. The dominant resonance frequency slightly shifts to the lower frequency as the maximum input acceleration increases. It is concluded that the coupling between the beam-type and the oval-type vibrations make an influence on the beam-type vibration in seismic excitation. In the meantime, the authors propose the nonlinear single-degree-of-freedom system model to explain that the vibration response of the tank reduces. This model is based on geometric nonlinearity due to the out-of-plane deformation of the side-wall of the tank caused by the oval-type vibration. The numerical simulation of the seismic response is conducted using the nonlinear single-degree-of-freedom system model proposed by the authors. The analytical results agree with the experimental results as a general trend. Therefore, it is concluded that the response reduction of the tank is generated by coupling between the beam-type and the oval-type vibrations in the seismic excitation as well as the sinusoidal excitation. In addition, the response reduction rate of the tank under much larger seismic excitation can be estimated by using the nonlinear single-degree-of-freedom system model.

scholarly journals Blast Simulator Testing of Structures: Methodology and Validation

2011 ◽  
Vol 18 (4) ◽  
pp. 579-592 ◽  
Author(s):  
T. Rodriguez-Nikl ◽  
G.A. Hegemier ◽  
F. Seible
Keyword(s):  
High Speed ◽  
Field Tests ◽  
Detailed Model ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Explosive Materials ◽  
Blast Effects ◽  
Resistance Function ◽  
The University ◽  
Good Agreement

The blast simulator at the University of California, San Diego is a unique tool for conducting full-scale testing of blast effects on structures without the use of explosive materials. This blast simulator uses high speed hydraulic actuators to launch specially designed modules toward the specimen, thereby imparting impulse in a blast-like manner. This method of testing offers numerous advantages over field tests with actual explosives, including cost, turn-around time, repeatability, and a clear view of the progression of damage in the specimen. The viability of this method is established by comparing results obtained in the blast simulator with results obtained with actual explosives. The process by which the impulse is imparted to the specimen is then described by a detailed model based on the equivalent single degree of freedom method. Impulse calculated by the model is found to be in good agreement with the experimentally recorded values. Calculated impulse is found to be relatively insensitive to assumptions made about the specimen's resistance function (often not well known before a test) implying that the model can be used with confidence in designing an experimental study.

A Computationally Efficient Numerical Algorithm for the Transient Response of High-Speed Elastic Linkages

1979 ◽  
Vol 101 (1) ◽  
pp. 138-148 ◽  
Author(s):  
A. Midha ◽  
A. G. Erdman ◽  
D. A. Frohrib
Keyword(s):  
Transient Response ◽  
Numerical Algorithm ◽  
High Speed ◽  
Relative Size ◽  
Degree Of Freedom ◽  
Time Dependent ◽  
Computationally Efficient ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Forcing Function

A new numerical algorithm, easily adaptable for computer simulation, is developed to approximate the transient response of a single degree-of-freedom vibrating system; governing differential equation is linear and second order with time-dependent and periodic coefficients. This is accomplished by first solving the classical linear single degree-of-freedom problem with constant coefficients. The system is excited by a periodic forcing function possessing a certain degree of smoothness. The integration terms in the solution are systematically expanded into two groups of terms: one consists of non-integral terms while the other contains only integral terms. The final integral terms are bounded. For certain combinations of frequency and damping, within the sub-resonant frequency range, the relative size of the integral terms are demonstrated to be small. The algebraic expansion (non-integral) terms then approximate the solution. The solution to a single degree-of-freedom system with time-dependent and periodic parameters is made possible by discretizing the forcing period into a number of intervals and assuming the system parameters as constant over each interval. The numerical algorithm is then employed to solve an elastic linkage problem via modal superposition. Convergence of the solution is verified by refining the number of intervals of discretization.

Design Approach Based on UAFR Spectra for Structures with Displacement-Dependent Dissipating Elements

2007 ◽  
Vol 23 (2) ◽  
pp. 417-439 ◽  
Author(s):  
J. Luz Rivera ◽  
Sonia E. Ruiz
Keyword(s):  
Seismic Response ◽  
Response Spectra ◽  
Design Criterion ◽  
Limit States ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Mdof Systems ◽  
Concrete Building ◽  
Hazard Curves ◽  
Ultimate Limit

In the first part of this paper an algorithm is proposed to obtain demand hazard curves and, from them, seismic-response spectra with uniform annual failure rates for single-degree-of-freedom (SDOF) systems with energy-dissipating devices (EDDs). In the second part, a performance-based dual-level approach is proposed for the design of buildings with EDDs. The criterion establishes acceptance conditions (related to serviceability—and to ultimate limit-states) that correspond to the main system and to the dissipating elements. The uncertainties implicit in the transformation between the response of SDOF and MDOF systems with EDDs are taken into account by means of their demand hazard curves. The reliability-based dual-level design criterion proposed is illustrated by means of a ten-story reinforced concrete building rehabilitated with steel energy-dissipating devices.

Estimation of Ship Roll Parameters in Random Waves

1992 ◽  
Vol 114 (2) ◽  
pp. 114-121 ◽  
Author(s):  
J. B. Roberts ◽  
J. F. Dunne ◽  
A. Debonos
Keyword(s):  
Markov Property ◽  
Simulated Data ◽  
Wide Band ◽  
Equation Of Motion ◽  
Roll Motion ◽  
Random Waves ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Ship Roll ◽  
Stochastic Input

The problem of estimating the parameters in an equation of roll motion from roll measurements only, taken in an irregular sea, is discussed. A single degree of freedom equation of motion is assumed, with a wide-band stochastic input and with a linear-in-the-parameters representation of both the damping and restoration terms. A method based on the Markov property of the energy envelope process, associated with the roll motion, is developed which enables all the relevant parameters to be estimated. The method is validated by applying it to some simulated data, for which the true parameters are known.

scholarly journals Miura-ori, Basics for Designing its Folding Machines

2019 ◽  
Vol 2 ◽  
pp. 1-5
Author(s):  
Koryo Miura
Keyword(s):  
Basic Concept ◽  
High Speed ◽  
Geometric Property ◽  
Unique Property ◽  
Degree Of Freedom ◽  
Design Parameters ◽  
Geometric Properties ◽  
Single Degree Of Freedom ◽  
Single Degree

<p><strong>Abstract.</strong> The unique property of the Miura-ori map is due to the geometric property of “the single degree of freedom”. With this, one can open a map with a single pull motion. However, due to this property, the high-speed folding machine is difficult to realized. In this presentation, author investigates the natural geometric properties of Miura-ori in detail and proposes a basic concept for designing its folding machine. Though, the result does not provide a draft of a folding machine, the basics for the design parameters is beneficial for future works.</p>

Numerical and experimental analysis of rubbing–misalignment mixed fault in a dual-rotor system

2020 ◽  
pp. 095440622096858
Author(s):  
Wenzhen Xie ◽  
Chao Liu ◽  
Nanfei Wang ◽  
Dongxiang Jiang
Keyword(s):  
High Speed ◽  
Experimental Tests ◽  
Rotor System ◽  
Dynamic Responses ◽  
System Model ◽  
Speed Ratio ◽  
Rotor Systems ◽  
Frequency Components ◽  
Aero Engines ◽  
Misalignment Fault

Dual-rotor systems are widely used in aero-engines, in which rubbing–misalignment mixed faults are essential, as both are frequently observed and can occur simultaneously due to the harsh working conditions of high temperature, high pressure, and high speed. To analyze the vibration characteristics of such faults, a dual-rotor system model is established and dynamic responses under varying parameters of the dual-rotor system with rubbing–misalignment mixed fault are investigated. Through numerical simulation, the effects of speed ratio, rubbing clearance, and rubbing stiffness on the dual-rotor system with rubbing–misalignment fault are revealed. Meanwhile, experimental tests are conducted for validation, the main findings of which are that the characteristic frequency components could benefit the diagnosis of mixed faults in dual-rotor systems.

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