Numerical Phenomena of a Spatial Mechanism With Clearances

1994 ◽  
Author(s):  
Zhang Jianling ◽  
Li Zhe ◽  
Bai Shixian
Keyword(s):  
Differential Equation ◽  
Mechanical Model ◽  
Equation Of Motion ◽  
Numerical Results ◽  
Dynamic Responses ◽  
Spatial Mechanism ◽  
Spatial Mechanisms ◽  
Steady State Responses ◽  
Set Up ◽  
State Responses

Abstract The general mechanical model of C pair with clearances is set up and used to derive the differential equation of motion of a RSCR mechanism with clearance at C pair in this paper. The numerical results are analysed and compared with the dynamic responses of the nominal RSCR mechanism. Chaotic phenomena can be seen in the numerical results, which indicate that the steady state responses may not be achievable for spatial mechanisms with clearance connections.

Trigonometric Collocation for Computation of Steady State Responses of Cracked Structures

2012 ◽  
Author(s):  
Bakeer Bakeer ◽  
Oleg Shiryayev ◽  
Ammaar Tahir
Keyword(s):  
Steady State ◽  
Fatigue Cracks ◽  
Equations Of Motion ◽  
Dynamic Responses ◽  
Vibration Period ◽  
State Response ◽  
Trigonometric Collocation ◽  
Steady State Responses ◽  
Cracked Structures ◽  
State Responses

Development of vibration-based structural health monitoring techniques requires the use of various computational methods to predict dynamic responses of damaged structures. The method described in this work can be used for prediction of steady state harmonic responses for structures with fatigue cracks and may have several advantages over alternative techniques. The method appears to be relatively easy to implement and computationally inexpensive. The steady state response of the system at a given number of time points distributed over one vibration period is represented in terms of Fourier series containing higher frequency harmonics. Equations of motion are formulated in the form that allows for easy computation of Fourier coefficients for all terms in the series. Iterative procedure is used for determining the time of stiffness change in order to capture bilinear dynamic behavior. We present results of initial investigation by applying the method to a model of a cantilever beam with a crack.

Mechanical Model and Analysis on Movement of Rock Strata between Coal Seams in Pillar Upward Mining of Left-Over Coal

2011 ◽  
Vol 58-60 ◽  
pp. 393-398
Author(s):  
Guo Rui Feng ◽  
Jing Zheng ◽  
Ya Feng Ren ◽  
Cong Ming Zhong ◽  
Li Xun Kang
Keyword(s):  
Differential Equation ◽  
Mechanical Properties ◽  
Partial Differential Equation ◽  
Mechanical Model ◽  
Theoretical Foundation ◽  
Control Measures ◽  
Coal Seams ◽  
Set Up ◽  
Rock Strata ◽  
Upward Mining

Work out control measures for pillar upward mining of left-over coal, in view of coal floor movement, this paper analyzes theoretical foundation and mechanical properties of mechanical model on coal floor movement of rock strata between coal seams in pillar upward mining of left-over coal and presents a simplified corresponding mechanical condition. Taking into the relation between layer movement and time consideration, the PTh model is used to show its rheological properties. By using a two-dimension model, mechanical model of coal floor movement is set up and both ends of cantilever beam are fixed. Finally, subsiding partial differential equation is induced at different districts in pillar upward mining of left-over coal. After solving the equation, prediction model about law of coal floor movement at different districts is gotten in pillar upward mining of left-over coal, which provides a theory basis for further study on upward mining.

Influence of Hysteresis on the Dynamics of Cryogenic LNG Composite Hoses

2011 ◽  
Author(s):  
Niels Mallon ◽  
Gerard van der Weijde
Keyword(s):  
Steady State ◽  
Internal Friction ◽  
Dynamic Environments ◽  
Measurement Results ◽  
Steady State Responses ◽  
Friction Models ◽  
Set Up ◽  
State Responses ◽  
Frictional Effects ◽  
Bending Behaviour

In order to assess the influence of hysteretic bending behaviour of hoses used for LNG transfer in dynamic environments, a modelling strategy is set up. The modelling allows to include arbitrary internal frictional effects in the hose. After identifying the parameters for various friction models based on measurement results performed on the cryogenic hose, the model is exploited further to study other cases. For hose release events, inclusion of hysteresis accurately seems less important while for more slowly varying steady-state responses, the way how internal friction in the hose is included may have significant effects.

Effects of Lumped Masses on the Stability of Fluid Conveying Tubes

1970 ◽  
Vol 37 (2) ◽  
pp. 494-497 ◽  
Author(s):  
J. L. Hill ◽  
C. P. Swanson
Keyword(s):  
Differential Equation ◽  
Partial Differential Equation ◽  
Fluid Flow ◽  
Flow Velocity ◽  
Equation Of Motion ◽  
Numerical Results ◽  
Fluid Flow Velocity ◽  
The Stability ◽  
The Masses ◽  
Lumped Masses

The effects of adding lumped masses to fluid conveying tubes are studied. The addition of the masses is accounted for by a discontinuous mass distribution. Solutions of the partial differential equation of motion with the discontinuous coefficient are sought approximately using Galerkin’s method. Numerical results are presented for the destabilizing fluid-flow velocity for a cantilevered tube. The numerical results compare favorably with experimental results.

Dynamic Responses of Two Parallel Circular Cylinders in a Liquid

1975 ◽  
Vol 97 (2) ◽  
pp. 78-83 ◽  
Author(s):  
Shoei-Sheng Chen
Keyword(s):  
Approximate Solution ◽  
Equations Of Motion ◽  
Closed Form Solution ◽  
Added Mass ◽  
Form Solution ◽  
Dynamic Responses ◽  
Circular Cylinders ◽  
Steady State Responses ◽  
Fluid Coupling ◽  
State Responses

The problem of two parallel circular cylinders vibrating in a liquid is studied analytically. First, the equations of motion including fluid coupling are derived using the added mass concept. Then, a closed form solution and an approximate solution are obtained for free vibration. Finally, the steady-state responses of two cylinders subjected to harmonic excitations are presented. The results of this study illustrate the significance of the interaction of two structures in a liquid.

scholarly journals Vibration characteristics of triple-gear-rotor system in compressed air energy storage under variable torque load

2021 ◽  
Vol 104 (1) ◽  
pp. 003685042098705
Author(s):  
Xinran Wang ◽  
Yangli Zhu ◽  
Wen Li ◽  
Dongxu Hu ◽  
Xuehui Zhang ◽  
...  
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Element Model ◽  
Rotor System ◽  
Dynamic Responses ◽  
System Response ◽  
Rotating Speed ◽  
Torque Load ◽  
Set Up ◽  
Two Stages

This paper focuses on the effects of the off-design operation of CAES on the dynamic characteristics of the triple-gear-rotor system. A finite element model of the system is set up with unbalanced excitations, torque load excitations, and backlash which lead to variations of tooth contact status. An experiment is carried out to verify the accuracy of the mathematical model. The results show that when the system is subjected to large-scale torque load lifting at a high rotating speed, it has two stages of relatively strong periodicity when the torque load is light, and of chaotic when the torque load is heavy, with the transition between the two states being relatively quick and violent. The analysis of the three-dimensional acceleration spectrum and the meshing force shows that the variation in the meshing state and the fluctuation of the meshing force is the basic reasons for the variation in the system response with the torque load. In addition, the three rotors in the triple-gear-rotor system studied show a strong similarity in the meshing states and meshing force fluctuations, which result in the similarity in the dynamic responses of the three rotors.

Estimating the Audiogram Using Multiple Auditory Steady-State Responses

2002 ◽  
Vol 13 (04) ◽  
pp. 205-224 ◽  
Author(s):  
Andrew Dimitrijevic ◽  
Sasha M. John ◽  
Patricia Van Roon ◽  
David W. Purcell ◽  
Julija Adamonis ◽  
...  
Keyword(s):  
Steady State ◽  
Correlation Coefficients ◽  
Behavioral Threshold ◽  
Behavioral Thresholds ◽  
Sensorineural Hearing Impairment ◽  
Steady State Responses ◽  
Auditory Steady State Responses ◽  
Tonal Stimuli ◽  
Conductive Hearing ◽  
State Responses

Multiple auditory steady-state responses were evoked by eight tonal stimuli (four per ear), with each stimulus simultaneously modulated in both amplitude and frequency. The modulation frequencies varied from 80 to 95 Hz and the carrier frequencies were 500, 1000, 2000, and 4000 Hz. For air conduction, the differences between physiologic thresholds for these mixed-modulation (MM) stimuli and behavioral thresholds for pure tones in 31 adult subjects with a sensorineural hearing impairment and 14 adult subjects with normal hearing were 14 ± 11, 5 ± 9, 5 ± 9, and 9 ± 10 dB (correlation coefficients .85, .94, .95, and .95) for the 500-, 1000-, 2000-, and 4000-Hz carrier frequencies, respectively. Similar results were obtained in subjects with simulated conductive hearing losses. Responses to stimuli presented through a forehead bone conductor showed physiologic-behavioral threshold differences of 22 ± 8, 14 ± 5, 5 ± 8, and 5 ± 10 dB for the 500-, 1000-, 2000-, and 4000-Hz carrier frequencies, respectively. These responses were attenuated by white noise presented concurrently through the bone conductor.

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