scholarly journals Experimental Investigation of Energy Dissipation in Presliding Spherical Contacts Under Varying Normal and Tangential Loads

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Ahmet Deniz Usta ◽  
Sohan Shinde ◽  
Melih Eriten
Keyword(s):  
Energy Dissipation ◽  
Phase Difference ◽  
Tangential Force ◽  
Nonlinear Damping ◽  
Contact Interface ◽  
System Parameters ◽  
Elastic Mismatch ◽  
And Control ◽  
Frictional Slip ◽  
Phase Differences

Interfacial damping in assembled structures is difficult to predict and control since it depends on numerous system parameters such as elastic mismatch, roughness, contact geometry, and loading profiles. Most recently, phase difference between normal and tangential force oscillations has been shown to have a significant effect on interfacial damping. In this study, we conduct microscale (asperity-scale) experiments to investigate the influence of magnitude and phase difference of normal and tangential force oscillations on the energy dissipation in presliding spherical contacts. Our results show that energy dissipation increases with increasing normal preload fluctuations and phase difference. This increase is more prominent for higher tangential force fluctuations, thanks to larger frictional slip along the contact interface. We also show that the energy dissipation and tangential fluctuations are related through a power law. The power exponents we identify from the experiments reveal that contacts deliver a nonlinear damping for all normal preload fluctuation amplitudes and phase differences investigated. This is in line with the damping uncertainties and nonlinearities observed in structural dynamics community.

Frictional Energy Dissipation in Spherical Contacts Under Presliding: Effect of Elastic Mismatch, Plasticity and Phase Difference in Loading

2015 ◽  
Vol 82 (1) ◽  
Author(s):  
Deepak B. Patil ◽  
Melih Eriten
Keyword(s):  
Energy Dissipation ◽  
Phase Difference ◽  
Power Law ◽  
Normal Load ◽  
Material Interfaces ◽  
Tangential Load ◽  
Loading Cycle ◽  
Frictional Energy ◽  
Elastic Mismatch ◽  
Frictional Energy Dissipation

Behavior of friction at material interfaces is inherently nonlinear causing variations and uncertainties in interfacial energy dissipation. A finite element model (FEM) of an elastic–plastic spherical contact subjected to periodic normal and tangential loads is developed to study fundamental mechanisms contributing to the frictional energy dissipation. Particular attention is devoted to three mechanisms: the elastic mismatch between contacting pairs, plastic deformations, and phase difference between the normal and tangential fluctuations in loading. Small tangential loads simulating mild vibrational environments are applied to the model and resulting friction (hysteresis) loops are used to estimate the energy loss per loading cycle. The energy losses are then correlated against the maximum tangential load as a power-law where the exponents show the degree of nonlinearity. Exponents increase significantly with in-phase loading and increasing plasticity. Although increasing elastic mismatch facilitates more dissipation during normal load fluctuations, it has negligible influence on the power-law exponents in tangential loading. Among all the configurations considered, out-of-phase loading with minimal mismatch and no plasticity lead to the smallest power-law exponents; promising linear frictional dissipation. The duration the contact remains stuck during a loading cycle is found to have a predominant influence on the power-law exponents. Thus, controlling that duration enables tunable degree of nonlinearity and magnitude in frictional energy dissipation.

scholarly journals Combined Reduced Phase Dual-Directional Illumination Digital Holography and Speckle Displacements for Shape Measurement

2019 ◽  
Vol 2019 ◽  
pp. 1-6
Author(s):  
Davood Khodadad
Keyword(s):  
Phase Difference ◽  
Digital Holography ◽  
Relative Phase ◽  
Groove Depth ◽  
Phase Unwrapping ◽  
Shape Measurement ◽  
Phase Ambiguity ◽  
Holographic Method ◽  
Height Range ◽  
Phase Differences

We present a digital holographic method to increase height range measurement with a reduced phase ambiguity using a dual-directional illumination. Small changes in the angle of incident illumination introduce phase differences between the recorded complex fields. We decrease relative phase difference between the recorded complex fields 279 and 139 times by changing the angle of incident 0.5° and 1°, respectively. A two cent Euro coin edge groove is used to measure the shape. The groove depth is measured as ≈300  μm. Further, numerical refocusing and analysis of speckle displacements in two different planes are used to measure the depth without a use of phase unwrapping process.

scholarly journals Stochastic Inverse Identification of Nonlinear Roll Damping Moment of a Ship Moving at Nonzero-Forward Speeds

2012 ◽  
Vol 2012 ◽  
pp. 1-22 ◽  
Author(s):  
S. L. Han ◽  
Takeshi Kinoshita
Keyword(s):  
Nonlinear Damping ◽  
Rolling Motion ◽  
Forward Speed ◽  
Roll Damping ◽  
Nonparametric Approach ◽  
Nonlinear Responses ◽  
Different Types ◽  
Experimental Trials ◽  
And Control ◽  
Ship Rolling

The nonlinear responses of ship rolling motion characterized by a roll damping moment are of great interest to naval architects and ocean engineers. Modeling and identification of the nonlinear damping moment are essential to incorporate the inherent nonlinearity in design, analysis, and control of a ship. A stochastic nonparametric approach for identification of nonlinear damping in the general mechanical system has been presented in the literature (Han and Kinoshits 2012). The method has been also applied to identification of the nonlinear damping moment of a ship at zero-forward speed (Han and Kinoshits 2013). In the presence of forward speed, however, the characteristic of roll damping moment of a ship is significantly changed due to the lift effect. In this paper, the stochastic inverse method is applied to identification of the nonlinear damping moment of a ship moving at nonzero-forward speed. The workability and validity of the method are verified with laboratory tests under controlled conditions. In experimental trials, two different types of ship rolling motion are considered: time-dependent transient motion and frequency-dependent periodic motion. It is shown that this method enables the inherent nonlinearity in damping moment to be estimated, including its reliability analysis.

scholarly journals Multicriterial Evaluation of the Transport and Logistic System of the Moscow Region

2021 ◽  
Vol 334 ◽  
pp. 02029
Author(s):  
Vasily Demin ◽  
Alexey Terentyev
Keyword(s):  
Radio Frequency ◽  
Control Method ◽  
Complex Structure ◽  
Moscow Region ◽  
Logistics System ◽  
System Parameters ◽  
Complex Problems ◽  
Control Technologies ◽  
And Control

The article deals with the direction of solving complex problems of interaction between the elements of the transport and logistics system of the Moscow region as a complex structure of management methods in multi-criteria systems and technologies for monitoring the quality of processes. The control method should optimize the system parameters, and control technologies (radio frequency cargo identification) implement feedback in the system.

GENERATION AND CONTROL ANALYSIS OF A MULTISTATE INTERMITTENT SYSTEM

2010 ◽  
Vol 20 (11) ◽  
pp. 3663-3671 ◽  
Author(s):  
GUANGMING XIE ◽  
YIYANG YU
Keyword(s):  
Nonlinear System ◽  
Power Law ◽  
Complex Dynamics ◽  
Invariant Subspaces ◽  
Control Analysis ◽  
Power Law Distribution ◽  
System Parameters ◽  
And Control

In this paper, a Rössler-driving multistate intermittency is generated by a nonlinear system that contains controllable invariant subspaces. Intermittency-induced multiscroll attractor is found, and moreover, the control analysis is discussed, such as the number of attractors and the distance between laminar states can be easily adjusted by tuning some system parameters. The statistic behavior and power law distribution are also discussed, which reveal the regularities in the complex dynamics.

Research on Catenary Characteristics of FAST Tie-Down Cable and its Effect on Actuator and Joint

2014 ◽  
Vol 875-877 ◽  
pp. 664-670
Author(s):  
Jian Xing Xue ◽  
Xue Dong Gu ◽  
Li Qiang Song ◽  
Qi Ming Wang ◽  
Xue Bin Zhai ◽  
...  
Keyword(s):  
Tangential Force ◽  
Steel Cable ◽  
Initial Tension ◽  
Cable Length ◽  
Experimental Scheme ◽  
Reflector Surface ◽  
Equilibrium Differential Equation ◽  
And Control ◽  
Measurement And Control ◽  
Mechanics Characteristics

To study catenary characteristics of FAST (Five-hundred-meter Aperture Spherical radio Telescope) tie-down cable, this paper establishes tie-down cable equilibrium differential equation and cable length formula based on catenary theory, analyzes numerical simulation of multi-segment bar element method, and designs an experimental scheme. Taking 1×7 Ø12.7steel cable and Ø10 CFRP (Carbon Fiber Reinforced Polymer) cable for example, we can obtain three results respectively through manners mentioned above, and the agreement among them is excellent. Meanwhile, difference between results and elastic deformation of no-weight cable is not so big that catenary of two cables can be negligible. Further research shows that cable length is more sensitive to catenary than horizontal angle; cable longer deformation will benefit actuator to meet position precision effortlessly, however, stroke and velocity of actuator will increase and initial tension displacement of tie-down cable decrease correspondingly, this alteration should be compensated during reflector surface measuring and controlling; due to chord-tangent angle and tangential force is less than 1.28°and 241.4N, catenary effect on joint pose is weaker; generally speaking, CFRP cable has less catenary problem than steel cable, better mechanics characteristics, but bigger stroke and velocity for actuator and smaller initial tension displacement for tie-down cable. The research will provide references for design of tie-down cable, actuator, joint, and reflector measurement and control.

THE EFFECT OF NONLINEAR DAMPING ON THE UNIVERSAL ESCAPE OSCILLATOR

1999 ◽  
Vol 09 (04) ◽  
pp. 735-744 ◽  
Author(s):  
MIGUEL A. F. SANJUÁN
Keyword(s):  
Energy Dissipation ◽  
Period Doubling ◽  
Nonlinear Damping ◽  
Basins Of Attraction ◽  
Period Doubling Bifurcation ◽  
Damping Coefficient ◽  
Nonlinear Dissipation ◽  
Fractal Basin Boundaries ◽  
Basin Boundaries

This paper analyzes the role of nonlinear dissipation on the universal escape oscillator. Nonlinear damping terms proportional to the power of the velocity are assumed and an investigation on its effects on the dynamics of the oscillator, such as the threshold of period-doubling bifurcation, fractal basin boundaries and how the basins of attraction are destroyed, is carried out. The results suggest that increasing the power of the nonlinear damping, has similar effects as of decreasing the damping coefficient for a linearly damped case, showing the very importance of the level or amount of energy dissipation.

scholarly journals Design, Analysis, and Verification of an Electro- Hydrostatic Actuator for Distributed Actuation System

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 634 ◽  
Author(s):  
Yang Li ◽  
Zongxia Jiao ◽  
Zimeng Wang
Keyword(s):  
Phase Difference ◽  
Dynamic Characteristics ◽  
High Efficiency ◽  
Control Method ◽  
Low Cost ◽  
Detailed Structure ◽  
Actuation System ◽  
And Control ◽  
Valve Control ◽  
Direct Pump

In order to provide a simplified and low-cost solution of the terminal for a distributed actuation system, this paper proposes an electro-hydrostatic actuator (EHA) based on the linear drive principle. The proposed actuator is directly driven by a linear pump with a collaborative rectification mechanism, whose performance relies on the collaboration of the internal two units. A pair of linear oscillating motors are employed to drive the two pump units respectively. The control of the actuator is based on the modulation of the oscillating amplitude, frequency, and phase difference of the two motors. The advantage of this actuator is that no more valve control is needed to rectify the linear pump besides the high efficiency of the direct pump drive. In this paper, both schematic and detailed structure of the actuator is presented. The kinematic and dynamic characteristics are analyzed and modeled, based on which the control method is proposed. The experiments verify the validity of the actuator structure and control.

Interaural Phase Disparity of Stutterers and Nonstutterers

1972 ◽  
Vol 15 (4) ◽  
pp. 771-780 ◽  
Author(s):  
Courtney Stromsta
Keyword(s):  
Control System ◽  
Phase Shift ◽  
Phase Difference ◽  
Auditory Feedback ◽  
Laryngeal Function ◽  
Interaural Phase ◽  
Frequency Criterion ◽  
Interaural Phase Difference ◽  
The Mean ◽  
Phase Differences

Stutterers and nonstutterers cancelled the auditory sensation evoked by bone-conducted sinusoidal signals. They accomplished this by appropriate phase and amplitude adjustments of simultaneously presented bilateral air-conducted signals of the same frequency. Criterion measures of interaural phase difference at the point of cancellation were obtained for seven frequencies. The mean interaural phase differences obtained by stutterers were consistently greater than those of the nonstutterers. Based on time-equivalent values of the mean interaural phase differences, the values for stutterers were approximately twice as great as for nonstutterers at 150, 300, and 1200 Hz. The mean interaural phase difference found to exist for stutterers at 150 Hz approximates the magnitude of phase shift of normally delayed air-conducted auditory feedback of speech sounds that serves to induce experimental blockage of phonation. This relationship, in view of other findings, offers credence to the idea that disturbance of laryngeal function effected by an anomalous audition-phonation control system could be a causative agent in stuttering.

Sign in / Sign up

Export Citation Format

Share Document