scholarly journals Prototype Test and Numerical Analysis of a Shallow Cable with Novel Viscous Inertial Damper

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Jing Liu ◽  
Dong Liang ◽  
Liu Yang ◽  
Lida Wang ◽  
Xiaowei Zhang
Keyword(s):  
Numerical Analysis ◽  
Theoretical Study ◽  
Damping Ratio ◽  
Future Research ◽  
Test Results ◽  
Stay Cables ◽  
Damping Characteristics ◽  
Prototype Test ◽  
Complex Valued ◽  
Symmetric And Antisymmetric Modes

As an essential component of offshore bridges, stay cables are prone to vibrations due to their low inherent damping characteristics. Various dampers have been used for cable vibration control; however, the experimental research and theoretical study of inertial dampers on real cables have not been conducted sufficiently. This study aims to investigate the damping performance of a novel viscous inertial damper (VID) and focuses on the frequency-dependent and displacement amplification phenomena of a cable-damper system. Tests were first conducted to verify the energy consumption capacity of a prototype damper. A shallow cable-VID system was established. Theoretically, complex-valued modes were analyzed to determine the influence of the inertial and viscous coefficients on the cable’s frequency and mode damping ratio. The test results and numerical analysis show that the VID has a good damping effect on the shallow cable. Considering multiple adjacent cable modes, the inertial and viscous coefficients can be optimized. After optimizing, the VID can simultaneously maximize both adjacent symmetric and antisymmetric modes’ damping ratios. The two frequencies are almost the same. The displacement amplification of the VID shows that a VID can overcome the shortcomings of displacement loss caused by traditional oil dampers. The implications of these findings of the VID on shallow cable are discussed, which will guide future research and applications of the VID or other inerter dampers.

scholarly journals Investigation on Damping Characteristics of Hydrostatic Bearing Film by Using Scale Method

2021 ◽  
Author(s):  
Sheng-Yen Hu ◽  
Wen-Chou Chen ◽  
Chien-Hsun Wang ◽  
Hsin-Ming Fu ◽  
Yuan Kang
Keyword(s):  
Damping Ratio ◽  
Resonant Peak ◽  
Test Results ◽  
Scaling Method ◽  
Single Degree Of Freedom ◽  
Hydrostatic Bearing ◽  
Damping Characteristics ◽  
Mass Spring ◽  
The Impact

Abstract The resonant peaks can be suppressed by damping, those effects is dependent on damping ratio of system. In this paper, we propose a scaling method to evaluate the damping ratio of hydrostatic bearings for the data from model test. This method fits specifically for the overdamping of all hydrostatic bearing. This is direct and the easiest method to obtain the damping characteristics of oil film for the lowest band before the first resonant peak. The frequency responses of acceleration per force for a single-degree-of-freedom mass-spring-damper model is used to generate the evaluation scales for the damping ratios of the modal test results of worktable mounting on hydrostatic bearing. The case study for experimental results of the impact response are evaluated for damping ratio of the hydrostatic film by these method. Furthermore, using this scaling method, the influences of three types of compensations on the damping ratio of a hydrostatic bearing are compared. The results reveal that the constant flow has the largest damping ratio, and the capillary restrictor has the smallest one.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

scholarly journals Multi-Scale Study of The Small-Strain Damping Ratio of Fiber-Sand Composites

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2476
Author(s):  
Haiwen Li ◽  
Sathwik S. Kasyap ◽  
Kostas Senetakis
Keyword(s):  
Dynamic Properties ◽  
Wide Spectrum ◽  
Damping Ratio ◽  
Polypropylene Fiber ◽  
Small Strain ◽  
Treatment Method ◽  
Fiber Content ◽  
Polypropylene Fibers ◽  
Test Results ◽  
Fiber Reinforced

The use of polypropylene fibers as a geosynthetic in infrastructures is a promising ground treatment method with applications in the enhancement of the bearing capacity of foundations, slope rehabilitation, strengthening of backfills, as well as the improvement of the seismic behavior of geo-systems. Despite the large number of studies published in the literature investigating the properties of fiber-reinforced soils, less attention has been given in the evaluation of the dynamic properties of these composites, especially in examining damping characteristics and the influence of fiber inclusion and content. In the present study, the effect of polypropylene fiber inclusion on the small-strain damping ratio of sands with different gradations and various particle shapes was investigated through resonant column (macroscopic) experiments. The macroscopic test results suggested that the damping ratio of the mixtures tended to increase with increasing fiber content. Accordingly, a new expression was proposed which considers the influence of fiber content in the estimation of the small-strain damping of polypropylene fiber-sand mixtures and it can be complementary of damping modeling from small-to-medium strains based on previously developed expressions in the regime of medium strains. Additional insights were attempted to be obtained on the energy dissipation and contribution of fibers of these composite materials by performing grain-scale tests which further supported the macroscopic experimental test results. It was also attempted to interpret, based on the grain-scale tests results, the influence of fiber inclusion in a wide spectrum of properties for fiber-reinforced sands providing some general inferences on the contribution of polypropylene fibers on the constitutive behavior of granular materials.

ON "PLASTIC" WAVES IN SOLIDS

1959 ◽  
Vol 37 (9) ◽  
pp. 1017-1035 ◽  
Author(s):  
John M. Bowsher
Keyword(s):  
Theoretical Study ◽  
Short Review ◽  
Future Research ◽  
Past Work ◽  
The Past ◽  
Engineering Significance ◽  
The Subject

The study of the propagation of "plastic" waves in solids has reached a stage where it is necessary to consider which direction future research should take. In the past 90 or so years many experiments, mostly designed to elucidate certain points of engineering significance, and a few attempts at a theoretical study have cast some light on the subject and revealed it as one of formidable difficulty.Nearly all the experiments have of necessity relied on rather dubious theories for their interpretation, and part of the present paper will be devoted to a description of an apparatus which gives results capable of being interpreted with a very minimum of theory. The remainder of the paper is devoted to a short review of past work with particular emphasis on basic phenomena and to a brief discussion on the most pressing problems still remaining. The experiments described in the present paper bring to light a factor in the propagation of "plastic" waves that seems to have been overlooked in previous work.

Shear Modulus and Damping Ratio of Gravel Material

2011 ◽  
Vol 105-107 ◽  
pp. 1426-1432 ◽  
Author(s):  
De Gao Zou ◽  
Tao Gong ◽  
Jing Mao Liu ◽  
Xian Jing Kong
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Strain Amplitude ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Dynamic Shear Modulus ◽  
Test Results ◽  
Dynamic Shear ◽  
Data Points ◽  
Shear Strain Amplitude

Two of the most important parameters in dynamic analysis involving soils are the dynamic shear modulus and the damping ratio. In this study, a series of tests were performed on gravels. For comparison, some other tests carried out by other researchers were also collected. The test results show that normalized shear modulus and damping ratio vary with the shear strain amplitude, (1) normalized shear modulus decreases with the increase of dynamic shear strain amplitude, and as the confining pressure increases, the test data points move from the low end toward the high end; (2) damping ratio increases with the increase of shear strain amplitude, damping ratio is dependent on confining pressure where an increase in confining pressure decreased damping ratio. According to the test results, a reference formula is proposed to evaluate the maximum dynamic shear modulus, the best-fit curve and standard deviation bounds for the range of data points are also proposed.

Experimental and analytical investigation on the in-plane dynamic instability of arches owing to parametric resonance

2017 ◽  
Vol 24 (19) ◽  
pp. 4419-4432 ◽  
Author(s):  
Airong Liu ◽  
Zhicheng Yang ◽  
Hanwen Lu ◽  
Jiyang Fu ◽  
Yong-Lin Pi
Keyword(s):  
Parametric Resonance ◽  
Dynamic Instability ◽  
Damping Ratio ◽  
Analytical Investigation ◽  
Engineering Practice ◽  
Test Results ◽  
Periodic Load ◽  
Shallow Arches ◽  
Excitation Frequencies ◽  
Critical Regions

When an arch is subjected to a periodic load, it may lose in-plane stability dynamically owing to parametric resonance. Previous investigations have been concentrated on in-plane dynamic buckling of pin-ended shallow arches. However, in engineering practice, fixed arches with different rise-to-span ratios are often encountered. Little research on in-plane dynamic instability of deep fixed arches has been reported in the literature. This paper is concerned with experimental and analytical investigations for in-plane dynamic instability of fixed circular arches with rise-to-span ratios 1/8–1/2 under a central periodic load owing to parametric resonance. Experiments are carried out to determine the in-plane frequency and damping ratio of arches, to investigate critical regions of frequencies and amplitudes of the periodic load for in-plane dynamic instability of arches, and to explore effects of the rise-to-span ratio and additional weights on dynamic instability. The analytical method for determining the region of excitation frequencies and amplitudes of the periodic load causing in-plane instability of the arch is established using the Hamilton’s principle by accounting for effects of additional concentrated weights. Comparisons of analytical solutions with test results show that they agree with each other quite well. These results show that the rise-to-span ratio significantly influences the bandwidth of regions of critical excitation frequencies for in-plane dynamic instability of arches. The critical frequencies of the periodic load and their bandwidth increase with a decrease of the rise–span ratio of the arch, whereas the corresponding amplitude of the periodic load decreases at the same time. It is also found that the central concentrated weight influences in-plane dynamic instability of arches significantly. As the weight increases, the critical frequencies of excitation and their bandwidth for in-plane dynamic instability of arches decreases, whereas the corresponding amplitude of excitation increases.

Preparation and Vibration Damping Characteristics of Wide Frequency Domain PVMQ/IIR Foam Materials

2012 ◽  
Vol 538-541 ◽  
pp. 2298-2303
Author(s):  
Shi Kai Luo ◽  
Guo Fang Ding ◽  
Jing Li Li ◽  
Yan Song Sha ◽  
Qing Min Cheng ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Wide Temperature Range ◽  
Damping Ratio ◽  
Vibration Damping ◽  
Simple Equation ◽  
Structural Damping ◽  
Damping Characteristics ◽  
Damping Materials ◽  
Foaming Technology ◽  
Isoprene Rubber

In this paper, we prepared foaming silicon rubber (PVMQ) /isobutylene-isoprene rubber (IIR) composites with chemical foaming technology. The DMA tests results showed that these foaming materials have effective damping characteristics in a wide temperature range. With the special vibrator, we found that the PVMQ/IIR foams that we prepared were the damping materials which has wide frequency domain, because they can keep high damping ratio in a wide frequency domain. When the preloading was between 1.0 mm and 1.7 mm, the structural damping did not change obviously. According to tests, we found that the damping ratio of these foams was fit to the simple equation .

Analysis of Beam-Like Structures With Displacement-Dependent Friction Forces: Part I — Single-Degree-of-Freedom Model

1995 ◽  
Author(s):  
Wayne E. Whiteman ◽  
Aldo A. Ferri
Keyword(s):  
Dry Friction ◽  
Damping Ratio ◽  
Strong Dependence ◽  
Time Integration ◽  
Single Mode ◽  
Stick Slip ◽  
Friction Forces ◽  
Equivalent Damping ◽  
Damping Characteristics ◽  
Parameter Values

Abstract The dynamic behavior of a beam-like structure undergoing transverse vibration and subjected to a displacement-dependent dry friction force is examined. In Part I, the beam is modeled by a single mode while Part II considers multi-mode representations. The displacement dependence in each case is caused by a ramp configuration that allows the normal force across the sliding interface to increase linearly with slip displacement. The system is studied first by using first-order harmonic balance and then by using a time integration method. The stick-slip behavior of the system is also studied. Even though the only source of damping is dry friction, the system is seen to exhibit “viscous-like” damping characteristics. A strong dependence of the equivalent natural frequency and damping ratio on the displacement amplitude is an interesting result. It is shown that for a given set of parameter values, an optimal ramp angle exists that maximizes the equivalent damping ratio. The appearance of two dynamic response solutions at certain system and forcing parameter values is also seen. Results suggest that the overall characteristics of mechanical systems may be improved by properly configuring frictional interfaces to allow normal forces to vary with displacement.

scholarly journals MS7001F Prototype Test Results

1989 ◽  
Author(s):  
D. E. Brandt
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Load Test ◽  
Test Results ◽  
Critical Temperatures ◽  
Prototype Test ◽  
Surge Margin ◽  
Pertinent Data ◽  
Post Test ◽  
Heavy Duty Gas Turbine

The MS7001F heavy–duty gas turbine has been designed utilizing advanced analytical methods and a substantial array of component tests. The integrity of the system required that the prototype unit, with its accessories, be rigorously tested under load. The factory load test was completed on May 18, 1988 after 387 hours and 134 start/stop cycles. The MS7001F prototype gas turbine was instrumented with more than 3000 pieces of instrumentation in order to record all critical temperatures, pressures, flows, strains, displacements, and other pertinent data. The load device was a modified MS7001E compressor, which also supplied the means by which the MS7001F prototype compressor’s pressure ratio was increased to provide for surge margin determination. Inlet throttling of the MS7001F compressor allowed for full firing temperature operation, at reduced load. The results of this factory prototype load test are reported in the paper as are observations made during post test teardown.

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