The fabrication and the identification of damping properties of magnetorheological composites for energy dissipation

2018 ◽  
Vol 189 ◽  
pp. 177-183 ◽  
Author(s):  
Damian Bodniewicz ◽  
Jerzy Kaleta ◽  
Daniel Lewandowski
Keyword(s):  
Energy Dissipation ◽  
Damping Properties

scholarly journals Effect of Bottom Geometry on the Natural Sloshing Motion of Water Inside Tanks: An Experimental Analysis

2021 ◽  
Vol 11 (2) ◽  
pp. 605
Author(s):  
Antonio Agresta ◽  
Nicola Cavalagli ◽  
Chiara Biscarini ◽  
Filippo Ubertini
Keyword(s):  
Energy Dissipation ◽  
Water Depth ◽  
Shear Force ◽  
Experimental Tests ◽  
Shear Load ◽  
Damping Properties ◽  
Base Shear ◽  
Structure Interaction ◽  
Sloshing Phenomenon ◽  
Key Aspects

The present work aims at understanding and modelling some key aspects of the sloshing phenomenon, related to the motion of water inside a container and its effects on the substructure. In particular, the attention is focused on the effects of bottom shapes (flat, sloped and circular) and water depth ratio on the natural sloshing frequencies and damping properties of the inner fluid. To this aim, a series of experimental tests has been carried out on tanks characterised by different bottom shapes installed over a sliding table equipped with a shear load cell for the measurement of the dynamic base shear force. The results are useful for optimising the geometric characteristics of the tank and the fluid mass in order to obtain enhanced energy dissipation performances by exploiting fluid–structure interaction effects.

Damping Actions of the Neuromuscular System With Inertial Loads: Soleus Muscle of the Decerebrate Cat

2000 ◽  
Vol 83 (2) ◽  
pp. 652-658 ◽  
Author(s):  
David C. Lin ◽  
W. Zev Rymer
Keyword(s):  
Energy Dissipation ◽  
Linear System ◽  
Soleus Muscle ◽  
Stretch Reflex ◽  
Directional Asymmetry ◽  
Reflex Response ◽  
Neuromuscular System ◽  
Damping Properties ◽  
Kinetic Measurements ◽  
Decerebrate Cat

A transient perturbation applied to a limb held in a given posture can induce oscillations. To restore the initial posture, the neuromuscular system must provide damping, which is the dissipation of the mechanical energy imparted by such a perturbation. Despite their importance, damping properties of the neuromuscular system have been poorly characterized. Accordingly, this paper describes the damping characteristics of the neuromuscular system interacting with inertial loads. To quantitatively examine damping, we coupled simulated inertial loads to surgically isolated, reflexively active soleus muscles in decerebrate cats. A simulated force impulse was applied to the load, causing a muscle stretch, which elicited a reflex response. The resulting deviation from the initial position gave rise to oscillations, which decayed progressively. Damping provided by the neuromuscular system was then calculated from the load kinetics. To help interpret our experimental results, we compared our kinetic measurements with those of an analogous linear viscoelastic system and found that the experimental damping properties differed in two respects. First, the amount of damping was greater for large oscillation amplitudes than for small (damping is independent of amplitude in a linear system). Second, plots of force against length during the induced movements showed that damping was greater for shortening than lengthening movements, reflecting greater effective viscosity during shortening. This again is different from the behavior of a linear system, in which damping effects would be symmetrical. This asymmetric and nonlinear damping behavior appears to be related to both the intrinsic nonlinear mechanical properties of the soleus muscle and to stretch reflex properties. The muscle nonlinearities include a change in muscle force-generating capacity induced by forced lengthening, akin to muscle yield, and the nonlinear force-velocity property of muscle, which is different for lengthening versus shortening. Stretch reflex responses are also known to be asymmetric and amplitude dependent. The finding that damping is greater for larger amplitude motion represents a form of automatic gain adjustment to a larger perturbation. In contrast, because of reduced damping at small amplitudes, smaller oscillations would tend to persist, perhaps contributing to normal or “physiological” tremor. This lack of damping for small amplitudes may represent an acceptable compromise for postural regulation in that there is substantial damping for larger movements, where energy dissipation is more critical. Finally, the directional asymmetry in energy dissipation provided by muscle and reflex properties must be reflected in the neural mechanisms for a stable posture.

Structural Damping Enhancement of Nanocomposites With Engineered Vapor Grown Carbon Nanofiber Paper

2006 ◽  
Author(s):  
Jihua Gou ◽  
Haichang Gu ◽  
Gangbing Song
Keyword(s):  
Carbon Nanotubes ◽  
Energy Dissipation ◽  
Carbon Nanofibers ◽  
Composite Laminates ◽  
Carbon Nanofiber ◽  
Glass Fibers ◽  
Hybrid Nanocomposites ◽  
Structural Vibration ◽  
Damping Properties ◽  
Structural Damping

Due to their nanometer size and low density, the surface area to mass ratio of carbon nanotubes and carbon nanofibers is extremely large. In addition, the large aspect ratio and high elastic modulus of carbon nanotubes and carbon nanofibers allow for large differences in strain between the constituents in the nanocomposites, which could enhance the interfacial energy dissipation ability. While there are many reported benefits of carbon nanotubes and carbon nanofibers in the nanocomposites, the potential of carbon nanotubes and carbon nanofibers to enhance the structural damping properties of nanocomposites has not been fully explored. This paper presents a novel process to manufacture multifunctional and cost-effective hybrid nanocomposites through integrating engineered carbon nanofiber paper into traditional fiber reinforced composites to improve the structural damping properties. The vacuum-assisted resin transfer molding (VARTM) process was employed to fabricate the nanocomposites by using engineered carbon nanofiber papers as inter-layers or surface layers of traditional composite laminates. To characterize the structural damping properties, the influence of frequency dependence was analyzed through the experiments conducted using the nanocomposite beams. It was found that there is up to 200–700% increase of the damping ratios at higher frequencies. It was found that the connectivities between carbon nanofibers and short glass fibers within the carbon nanofiber paper were responsible for the significant energy dissipation in the nanocomposites during structural vibration applications.

Vibration Damping Properties of Nanotube-Reinforced Materials

2006 ◽  
Vol 50 ◽  
pp. 31-36 ◽  
Author(s):  
Maksim Kireitseu
Keyword(s):  
Energy Dissipation ◽  
Vibration Damping ◽  
Damping Properties ◽  
Engineering Applications ◽  
Preliminary Results ◽  
Damping Behavior ◽  
Polymeric Structures ◽  
Nanoscale Level ◽  
Reinforced Materials

Energy dissipation (damping) in structures/materials at the nanoscale level, the damping/ dynamics of materials require investigations before they will come to advanced engineering applications. By invoking the properties of nanostructures, it may be possible to enhance the energy dissipation. The paper therefore presents some preliminary results on the topic providing route map to the nanotechnology-based vibration damping solutions and comparison of some experimental damping behavior of nanoparticle-reinforced polymeric structures.

scholarly journals Frictional damping in hollow beam structures joined by bolts, rivets, and adhesive

2021 ◽  
pp. 146442072199430
Author(s):  
RD Adams ◽  
T Brearley ◽  
E Nehammer ◽  
E Rouse ◽  
D Vaughan
Keyword(s):  
Energy Dissipation ◽  
Cross Section ◽  
Adhesive Bonding ◽  
Flexural Vibration ◽  
Relative Displacement ◽  
Damping Properties ◽  
Hollow Beam ◽  
Frictional Damping ◽  
Mechanical Fastening ◽  
Shaped Cross Section

The objective of this work was to investigate how different joining techniques affect the level of damping in structures. Beams were constructed from four different joining techniques, bolting, riveting, adhesive bonding, and brazing by joining two lengths of steel each with a ‘U’-shaped cross-section. They were joined such that the edges of the ‘U’ overlapped to form a tube. The damping of each beam was determined by flexural vibration. The bolted beam had a series of bolts along its length. The effect of removing bolts was investigated. It was found that removing bolts increased damping. When bolts were removed successively from holes at the end of the beam, the damping increased more than when bolts were removed from holes in the middle of the beam. A further objective of this project was to investigate the effect of introducing penetrant between two surfaces. WD-40 was introduced between the contacting surfaces for the beams joined by mechanical fastening. The penetrant had the effect of increasing damping. This may be because the penetrant has the effect of increasing the relative displacement between the two beams, leading to greater energy dissipation. Introducing penetrant also changed the order of which beam had the greatest damping, with the bolted beam now having greater damping than the riveted beam. The effect of increasing bolt tension on the bolted beam was also investigated. When the beams were dry, increasing bolt tension reduced the damping, but when penetrant was introduced increasing the bolt tension increased the damping. A comparison between the damping properties from different joining techniques was made. The conclusions could be applied in industry by engineers constructing beams of a similar fashion.

Damping Properties of Li6La2SrBi2O12 Ceramic Particulates Reinforced Cement Composites

2012 ◽  
Vol 512-515 ◽  
pp. 1873-1876
Author(s):  
Wei Guo Wang ◽  
Gang Ling Hao ◽  
Xin Cheng Ren ◽  
Lei Lv
Keyword(s):  
Composite Materials ◽  
Energy Dissipation ◽  
Room Temperature ◽  
Cement Composite ◽  
Vibration Energy ◽  
Damping Capacity ◽  
Cement Composites ◽  
Damping Properties ◽  
Cement Sample ◽  
Reinforced Cement

The higher damping capacity and hardness Li6La2SrBi2O12ceramic particles at room temperature were added into the cement to form the composite materials. The maximum damping capacity of the 25 wt% Li6La2SrBi2O12ceramic/cement composites is as high as 0.015 at 310 K and 9 Hz, corresponding to a vibration energy dissipation of about 10% in each vibration cycle. The flexural strength of the the 10 wt% Li6La2SrBi2O12ceramic/cement composite is about 50% higher than that of the pure cement sample

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