scholarly journals Frequency‐dependent dynamic properties of rubber materials with a random distribution of voids

1983 ◽  
Vol 73 (S1) ◽  
pp. S90-S90 ◽  
Author(s):  
V. K. Varadan ◽  
V. V. Varadan ◽  
Y. Ma
Keyword(s):  
Random Distribution ◽  
Dynamic Properties ◽  
Frequency Dependent

Dynamic Analysis of NPP Piping Systems and Components With Viscoelastic Dampers Subjected to Severe Earthquake Motions

2016 ◽  
Author(s):  
Ichiro Tamura ◽  
Masashi Kuramasu ◽  
Frank Barutzki ◽  
Daniel Fischer ◽  
Victor Kostarev ◽  
...  
Keyword(s):  
Dynamic Analysis ◽  
Dynamic Characteristics ◽  
Seismic Analysis ◽  
Dynamic Properties ◽  
Maxwell Model ◽  
Shaking Table ◽  
Nonlinear Dependence ◽  
Piping System ◽  
Frequency Dependent ◽  
Viscoelastic Dampers

In Shimane nuclear power plant of Chugoku Electric Power Co., a number of safety improvements are planned to be implemented aiming for the highest level of safety in the world to be achieved. One of the new safety measures is the application of viscoelastic dampers for seismic protection of safety related piping system and components. High performance of viscoelastic dampers has been confirmed by direct testing of the piping natural scale model at the shaking table subjected to severe seismic accelerations up to 20 m/s2. However, viscoelastic dampers as a dynamic protection device have frequency-dependent dynamic characteristics, which are difficult to reproduce in the frame of conventional seismic analysis based typically on the use of response spectrum method. For example, the dynamic properties of viscoelastic dampers exhibit nonlinear dependence on dissipation energy, shear rate of viscous fluid, and temperature. Method for Seismic analysis of systems with viscoelastic dampers (SAVD-Method) is one of the analytical approaches capable of considering the dynamic properties and nonlinear behavior of viscoelastic dampers. The SAVD-Method is a comparatively simple but reliable approach for dynamic analysis of a piping system and components with viscoelastic dampers. Frequency-dependent dynamic characteristics of the viscoelastic dampers are able to be modeled by a four-parameter Maxwell model. To consider the nonlinearity of the dynamic properties of viscoelastic dampers, the Maxwell model parameters were determined for different usage conditions in conjunction with the adjustment dependent on the energy dissipation criteria. Direct comparison of the shaking table measurements and analysis according to SAVD-method shows good matching of results for all controlled parameters and levels of seismic excitation.

Influence of the temperature- and frequency-dependent dynamic properties of rail pads on the vibration characteristics of rails at low temperature

2020 ◽  
pp. 095440972091376
Author(s):  
Wang Ping ◽  
Dou Yinling ◽  
Wang Shaohua ◽  
Wang Feng ◽  
Kai Wei
Keyword(s):  
Decay Rate ◽  
Dynamic Properties ◽  
Temperature Dependent ◽  
Frequency Dependent ◽  
First Order ◽  
Railway Tracks ◽  
System Vibration ◽  
Temperature Dependent Properties ◽  
Rolling Noise ◽  
Attenuation Characteristics

The dynamic properties of railway tracks and rail pads are significant for accurately predicting both the wheel–rail system vibration and rolling noise. The effect that the dynamic properties of rail pads have on the dynamic characteristics of railway tracks at extremely low temperatures was not adequately studied in previous research. In order to better predict the attenuation of the rail vibration, the viscoelastic dynamic properties of rail pads varying nonlinearly with temperature and frequency were first tested, in a wide temperature range (−60 ℃ to 20 ℃), and represented by the fractional derivative Zener model. Then, rail vibration and its attenuation characteristics were investigated by accounting for the frequency-dependent, temperature-dependent and frequency- and temperature-dependent properties, respectively. To be more specific, the frequency and amplitude of the rail first-order bending resonance and pinned–pinned resonance, as well as the rail decay rate were analyzed for the three cases. In conclusion, the study shows that the temperature/frequency-dependent properties of the rail pad have a significant effect on the first-order bending resonance of the rail, but no influence on the pinned–pinned resonance frequency. The rail decay rate indicates a clear increasing trend in the entire frequency domain with the decrease of temperature (especially below about −20 ℃). The frequency dependence mainly affects the vibration and its attenuation characteristics of the rail below about 400 Hz, which should not be ignored in the track dynamics modelling. Therefore, when the analyzed environmental temperature is below −20 ℃, the temperature dependence of rail pads should be considered.

Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. I. Frequency-specific recovery of horizontal VOR after inactivation of the lateral semicircular canals

1996 ◽  
Vol 76 (5) ◽  
pp. 2941-2953 ◽  
Author(s):  
D. E. Angelaki ◽  
B. J. Hess ◽  
Y. Arai ◽  
J. Suzuki
Keyword(s):  
Dynamic Properties ◽  
Semicircular Canals ◽  
Adaptive Plasticity ◽  
Slow Phase ◽  
Vestibuloocular Reflex ◽  
Frequency Dependent ◽  
Lateral Canal ◽  
Large Phase ◽  
Torsional Component ◽  
Eye Velocity

1. The adaptive plasticity of the vestibuloocular reflex (VOR) following a selective lesion of the peripheral vestibular organs was investigated in rhesus monkeys whose lateral semicircular canals were inactivated by plugging of the canal lumen in both ears. Gain and phase of horizontal, vertical, and torsional slow-phase eye velocity were determined from three-dimensional eye movement recordings obtained acutely after the plugging operation, as well as in regular intervals up to 10 mo later. 2. Acutely after plugging, horizontal VOR was minimal during yaw rotation with gains of < 0.1 at all frequencies. Horizontal VOR gain gradually increased over time, reaching gains of 0.4–0.5 for yaw oscillations at 1.1 Hz approximately 5 mo after lateral canal inactivation. This response recovery was strongly frequency dependent: horizontal VOR gains were largest at the highest frequency tested and progressively decreased for lower frequencies. Below approximately 0.1 Hz, no consistent horizontal VOR could be elicited even 10 mo after plugging. 3. The frequency-dependent changes in gain paralleled changes in horizontal VOR phase. Below approximately 0.1–0.05 Hz large phase leads were present, similarly as in semicircular canal primary afferents. Smaller phase leads were also present at higher frequencies, particularly at 1.1 Hz (the highest frequency tested). 4. Consistent with the afferent-like dynamics of the adapted horizontal VOR, per- and postrotatory horizontal responses to constant-velocity yaw rotations were short lasting. Time constants of the slow-phase eye velocity envelope of the horizontal postrotatory nystagmus were approximately 2 s. Nonetheless, a consistent horizontal optokinetic afternystagmus was evoked in plugged animals. 5. A torsional component that was absent in intact animals was consistently present during yaw rotation acutely after lateral canal inactivation and remained approximately constant thereafter. The frequency response characteristics of this torsional component resembled those of the adapted horizontal slow-phase responses: gain decreased and large phase leads were introduced at frequencies below approximately 0.05–0.1 Hz. Torsional responses elicited by roll oscillations in supine position, on the other hand, were indistinguishable in their dynamics from intact animals. No consistent vertical nystagmus was elicited during yaw rotation. 6. Our results show that there is a slow, frequency-specific recovery of horizontal VOR after selective inactivation of the lateral semicircular canals. Both the spatial organization and the dynamic properties of the adapted VOR responses are distinctly different from responses in intact animals, suggesting complex changes in the underlying vestibuloocular circuitry.

Dynamic properties of elastomers containing a random distribution of nonspherical inclusions

1985 ◽  
Vol 77 (S1) ◽  
pp. S79-S80
Author(s):  
V. K. Varadan ◽  
V. V. Varadan ◽  
Y. Ma ◽  
W. M. Madigosky ◽  
K. P. Scharnhorst
Keyword(s):  
Random Distribution ◽  
Dynamic Properties
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