scholarly journals Dynamic Properties of Pretreated Rubberized Concrete under Incremental Loading

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2183
Author(s):  
Aijiu Chen ◽  
Xiaoyan Han ◽  
Zhihao Wang ◽  
Tengteng Guo
Keyword(s):  
Stress Level ◽  
Dynamic Properties ◽  
Dynamic Stiffness ◽  
Damping Ratio ◽  
Rubberized Concrete ◽  
Rubber Content ◽  
Rubber Particles ◽  
Energy Dissipation Capacity ◽  
Stiffness And Damping ◽  
Incremental Loading

Recycling scrap tyres as alternative aggregates of concrete is an innovative option. To clarify the dynamic properties of the pretreated rubberized concrete with some cumulative damage, the natural frequency, flexural dynamic stiffness, and damping ratio of the specimens under incremental stress level were investigated in this paper. The results indicated that the pretreatment of rubber particles improved the strength, ductility, and crack resistance of the rubberized concrete. The reduction of the flexural dynamic stiffness was clarified with the increase of concrete stress level. The addition of the pretreated rubber particles enhanced the concrete energy dissipation capacity during the destruction, and the specimen dissipated more energy with the increase of rubber content before its failure.

scholarly journals Identification of Dynamic Parameters of Pedestrian Walking Model Based on a Coupled Pedestrian–Structure System

2021 ◽  
Vol 11 (14) ◽  
pp. 6407
Author(s):  
Huiqi Liang ◽  
Wenbo Xie ◽  
Peizi Wei ◽  
Dehao Ai ◽  
Zhiqiang Zhang
Keyword(s):  
Negative Correlation ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Field Testing ◽  
The Body ◽  
Structural Vibration ◽  
Pedestrian Dynamics ◽  
Structure Interaction ◽  
Mass Spring ◽  
Stiffness And Damping

As human occupancy has an enormous effect on the dynamics of light, flexible, large-span, low-damping structures, which are sensitive to human-induced vibrations, it is essential to investigate the effects of pedestrian–structure interaction. The single-degree-of-freedom (SDOF) mass–spring–damping (MSD) model, the simplest dynamical model that considers how pedestrian mass, stiffness and damping impact the dynamic properties of structures, is widely used in civil engineering. With field testing methods and the SDOF MSD model, this study obtained pedestrian dynamics parameters from measured data of the properties of both empty structures and structures with pedestrian occupancy. The parameters identification procedure involved individuals at four walking frequencies. Body frequency is positively correlated to the walking frequency, while a negative correlation is observed between the body damping ratio and the walking frequency. The test results further show a negative correlation between the pedestrian’s frequency and his/her weight, but no significant correlation exists between one’s damping ratio and weight. The findings provide a reference for structural vibration serviceability assessments that would consider pedestrian–structure interaction effects.

Influence of Machine Tool Covers on Feed Drives

2011 ◽  
Author(s):  
Petr Kolar ◽  
Jan Masek ◽  
Jiri Sveda ◽  
Jan Hudec
Keyword(s):  
Machine Tool ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Reaction Force ◽  
Point Of View ◽  
Feed Drive ◽  
Feed Drives ◽  
Maximum Reaction ◽  
Stiffness And Damping ◽  
Multi Body

Machine tool covers are important parts of the machine. From the point of view of feed drives, a cover is an additional multi-body system that influences the dynamic properties of the feed drive and the positioning accuracy of the machine. The advantages of covers connected to the machine table with flexible elements are shown on simulation and experimental results. A mathematical model of the cover and its connection to the machine table is described. Optimization of the stiffness and damping ratio for the connection, using a model of the cover, is suggested. The optimal connection parameters cause decreasing of maximum reaction force acting from the cover to the feed drive. This phenomenon is presented on simulation example and also on the experiment results.

scholarly journals A Heuristic Approach to Dynamic Stiffness Control

2021 ◽  
Author(s):  
Farhad Fakour ◽  
M. Hossein Siadati
Keyword(s):  
Weight Reduction ◽  
Machine Tools ◽  
Dynamic Stiffness ◽  
Damping Ratio ◽  
Superior Performance ◽  
Dead Weight ◽  
Element Analysis ◽  
Areas Of Interest ◽  
Stiffness And Damping ◽  
Mass Participation

Abstract For appropriate and even superior performance yet cost reduction, this work was performed with the aim of weight reduction in the overall design and construction of possibly any machine tools. As far as our literature search is concerned, there does not seem to be much work published regarding successful weight reduction while maintaining performance using mass participation factor (MPF) in the areas of interest of the machine tools. In order to accomplish this task, we started with the ‘bed’ compartment of a CNC system and resorted to using the finite element analysis (FEA) software package and thoughtfully manipulated the available data/parameters until the desired results were obtained. The most important parameters were static stiffness, dynamic stiffness, and damping ratio. On the ‘bed’ of the machines’ compartment currently in production, it was so identified that there was unnecessary material (dead weight), and thus the FEA software was used in order to remove the unnecessary material by iteration. Finally, a new machine was built devoid of the unnecessary material, resulted in 9.3% weight reduction as predicted by the simulation, without sacrificing any accuracy and/or precision in performance.

scholarly journals Modeling and Dynamic Properties of a Four-Parameter Zener Model Vibration Isolator

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Wen-ku Shi ◽  
Chen Qian ◽  
Zhi-yong Chen ◽  
Yang Cao ◽  
Heng-hai Zhang
Keyword(s):  
High Performance ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Dynamic Stiffness ◽  
Installation Space ◽  
Structural Parameter ◽  
Channel Diameter ◽  
Zener Model ◽  
Isolation System ◽  
Stiffness And Damping

To install high-performance isolators in a limited installation space, a novel passive isolator based on the four-parameter Zener model is proposed. The proposed isolator consists of three major parts, namely, connecting structure, sealing construction, and upper and lower cavities, all of which are enclosed by four segments of metal bellows with the same diameter. The equivalent stiffness and damping model of the isolator are derived from the dynamic stiffness of the isolation system. Experiments are conducted, and the experiment error is analyzed. Test results verify the validity of the model. Theoretical analysis and numerical simulation reveal that the stiffness and damping of the isolator have multiple properties with different exciting amplitudes and structural parameters. In consideration of the design of the structural parameter, the effects of exciting amplitude, damp channel diameter, equivalent cylinder diameter of cavities, sum of the stiffness of the bellows at the end of the isolator, and length of damp channel on the dynamic properties of the isolator are discussed comprehensively. A design method based on the parameter sensitivity of the isolator’s design parameter is proposed. Thus, the novel isolator can be practically applied to engineering and provide a significant contribution in the field.

Effect of roundness error on the performance of novel gas foil conical bearings

2020 ◽  
Vol 72 (7) ◽  
pp. 895-904
Author(s):  
Hongyang Hu ◽  
Ming Feng ◽  
Tianming Ren
Keyword(s):  
Peer Review ◽  
Dynamic Properties ◽  
Load Capacity ◽  
Dynamic Stiffness ◽  
Friction Torque ◽  
Roundness Error ◽  
Content Type ◽  
Stiffness Model ◽  
Static Performance ◽  
Stiffness And Damping

Purpose The purpose of this paper is to study the effect law of roundness error on the properties of gas foil conical bearing (GFCB), and the performance of bearings with different non-circular sleeve shapes are calculated. Design/methodology/approach For the bump-type GFCB, the nonlinear bump foil stiffness model and 1-D beam top foil stiffness model are built. On this basis, the finite element method and finite difference method are used to solve the Reynolds equation and the film thickness equation coupled, and the static and dynamic properties of GFCB are calculated. The effect law of sleeve roundness error on the static performance under different conditions is obtained. Moreover, the dynamic stiffness and damping characteristics under different errors are also studied. Findings The roundness error will decrease the load capacity and friction torque of GFCB, and increase the attitude angle. The error effect is more dramatic when there is larger eccentric, small nominal clearance, larger error value and more error lobes, and the static performance exhibits a periodic change in the circumferential direction. The roundness error can also decrease the direct stiffness and cross-coupled damping of GFCB, while the cross-coupled stiffness increases largely, which will reduce the bearing stability. Originality/value The roundness error adversely affects the static and dynamic characteristics of GFCB, which should be concerned by bearing designers, researchers and academicians. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0019/

Eggshell Penetration of Various Types of Hens' Eggs by Salmonella enterica Serovar Enteritidis

2007 ◽  
Vol 70 (3) ◽  
pp. 623-628 ◽  
Author(s):  
WINY MESSENS ◽  
KOEN GRIJSPEERDT ◽  
KOEN DE REU ◽  
BART DE KETELAERE ◽  
KRISTOF MERTENS ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Dynamic Stiffness ◽  
Damping Ratio ◽  
Selective Medium ◽  
Housing System ◽  
Omega 3 ◽  
Salmonella Enterica Serovar Enteritidis ◽  
Membrane Complex ◽  
Highly Correlated ◽  
Stiffness And Damping

Egg weight, shell thickness, number of pores, cuticle deposition, eggshell strength (dynamic stiffness and damping ratio), and the ability of Salmonella enterica serovar Enteritidis (SE) to penetrate the eggshell were determined. Penetration was assessed by filling the eggs with a selective medium that allowed viewing of Salmonella growth on the inside of the shell and membrane complex. After inoculation of each shell with on average 2.71 log CFU, the eggs were stored for up to 14 days at 20°C and 60% relative humidity. Commercially available eggs were used. At 14 days of storage, only 6.0% of the eggs from free-range hens and 16.0% of the generic (i.e., eggs from hens in conventional battery cages that were given standard feed) white eggs were penetrated. The generic brown, organic, and omega-3–enriched eggs were penetrated at a frequency of 30 to 34%. In a second experiment it was shown that the layer strains of the hen (ISA-Brown Warren versus Bovans Goldline), which were kept in furnished cages, did not affect eggshell penetration by SE. For Bovans Goldline hens, the housing system (furnished cage versus aviary) did not affect penetration, while a trend was visible toward a higher fraction of penetrated eggshells when hens were fed corncob mix rather than standard feed. Eggshell penetration was observed more frequently in the absence of cuticle spots and for eggs having lower dynamic stiffness values. Shell contamination at the end of storage was highly correlated with SE penetration.

Study on Dynamic Properties of Semi-Active Seism Isolator for Building

2012 ◽  
Vol 598 ◽  
pp. 299-302
Author(s):  
Wei Xiong Yu ◽  
Sheng Chun Yang
Keyword(s):  
Dynamic Properties ◽  
Dynamic Stiffness ◽  
Damping Ratio ◽  
Magnetorheological Elastomers

The dynamic properties of semi-active seism isolator for building made of magnetorheological elastomers (MRE) were studied. Semi-active seism isolators were designed with MRE, and their dynamic properties at different amplitudes, frequencies, preloads or currents were tested. The results show that the dynamic stiffness decreases with the increase of amplitude or preload, but increases with the rise of frequency or current; the damping ratio ascends with the increase of amplitude, but declines with the rise of preload.

Study of Dynamic Properties of Automotive Hydrobushing

2000 ◽  
Author(s):  
Min Lu ◽  
Judah Ari-Gur
Keyword(s):  
Mathematical Model ◽  
Resonant Frequency ◽  
Dynamic Properties ◽  
Dynamic Stiffness ◽  
Damping Ratio ◽  
Minimal Effect ◽  
Stiffness Ratio ◽  
Loss Angle ◽  
High Frequencies ◽  
Maximum Loss

Abstract The objective of this research is to understand the dynamic properties of the hydrobushing. By means of a proposed mathematical model, it is found that the dynamic stiffness and loss angle of a hydrobushing are related to the rubber property and the effectiveness of the fluid in the inertia track. At high frequencies, however, the fluid in the inertia track becomes inefficient so that it may be ignored. It is also concluded that the rubber damping has minimal effect on the hydrobushing dynamic properties and may be neglected. The maximum loss angle of a hydrobushing, which corresponds to the maximum damping coefficient, occurs at a frequency close to the fluid resonant frequency. The degree of its closeness depends on the damping ratio and dynamic stiffness ratio.

scholarly journals Evaluation of Dynamic Properties of Sodium-Alginate-Reinforced Soil Using A Resonant-Column Test

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2743
Author(s):  
Seongnoh Ahn ◽  
Jae-Eun Ryou ◽  
Kwangkuk Ahn ◽  
Changho Lee ◽  
Jun-Dae Lee ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Sodium Alginate ◽  
Shear Failure ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Reinforced Soil ◽  
Resonant Column ◽  
Column Test ◽  
Alginate Solution ◽  
Resonant Column Test

Ground reinforcement is a method used to reduce the damage caused by earthquakes. Usually, cement-based reinforcement methods are used because they are inexpensive and show excellent performance. Recently, however, reinforcement methods using eco-friendly materials have been proposed due to environmental issues. In this study, the cement reinforcement method and the biopolymer reinforcement method using sodium alginate were compared. The dynamic properties of the reinforced ground, including shear modulus and damping ratio, were measured through a resonant-column test. Also, the viscosity of sodium alginate solution, which is a non-Newtonian fluid, was also explored and found to increase with concentration. The maximum shear modulus and minimum damping ratio increased, and the linear range of the shear modulus curve decreased, when cement and sodium alginate solution were mixed. Addition of biopolymer showed similar reinforcing effect in a lesser amount of additive compared to the cement-reinforced ground, but the effect decreased above a certain viscosity because the biopolymer solution was not homogeneously distributed. This was examined through a shear-failure-mode test.

Dynamic properties of the mucky clay improved with the steel slag and the rubber particles

2021 ◽  
Vol 294 ◽  
pp. 123489
Author(s):  
Liyan Wang ◽  
Xing Xiao ◽  
Wenwei Ji ◽  
Aimable Ishimwe ◽  
Binghui Wang ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Steel Slag ◽  
Rubber Particles ◽  
Mucky Clay
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