scholarly journals OVERVIEW OF THE KNITTED MATERIALS WITH VIBRATIONS DAMPING CAPACITY

2021 ◽  
Vol 2021 ◽  
pp. 342-347
Author(s):  
C. Grosu ◽  
M. Blaga
Keyword(s):  
Cyclic Stress ◽  
Free Vibrations ◽  
High Potential ◽  
Resonance Phenomenon ◽  
Impact Excitation ◽  
Damping Capacity ◽  
Textile Materials ◽  
Mechanical Field ◽  
Vibration Transmissibility ◽  
Two Phases

Textile materials are often subjected to different stresses, acting on them in two phases: during the knitting phase, when the yarns and the obtained structure are subjected to cyclic stress, but also during the use phase, when the knitted structures are subjected to various stresses. The dynamic behaviour of knitted fabrics in a vibrating environment is usually evaluated by standardized methods, such as the method using vibration exciters (e.g., ISO 10819:2013). However, in recent years, the authors' collective has carried out research to characterize the behaviour of knitted structures in a vibrating environment, using a well-known method for generating vibrations by impact excitation, which is specific to the mechanical field but also has a high potential for application in the textile field. This method refers to the determination of the free vibrations of an elastic system. Its measurement in the design phase of the system is considered a crucial step, since by knowing the frequency range of the system, the resonance phenomenon in the operational phase can be avoided. Similar results obtained by applying standardized methods for measuring vibration transmissibility and the currently adapted method from the field of mechanics to the field of textiles, represent a validation for this type of investigation process and also show the high potential of knitwear to be used in the vibration environment.

An Analytical and Experimental Evaluation of the Damping Capacity of Sandwich Beams With Viscoelastic Cores

1967 ◽  
Vol 89 (3) ◽  
pp. 438-443 ◽  
Author(s):  
I. W. Jones ◽  
V. L. Salerno ◽  
A. Savacchio
Keyword(s):  
Previous Investigation ◽  
Equations Of Motion ◽  
Free Vibrations ◽  
Vibration Damping ◽  
Damping Capacity ◽  
Sandwich Beams ◽  
Natural Boundary ◽  
Test Program ◽  
Test Procedures ◽  
Natural Boundary Conditions

A study is made of the free vibrations of sandwich beams with viscoelastic cores. The study, which is a generalization of a previous investigation by the authors [1] includes the equations of motion and natural boundary conditions, derivation of expressions for the modal distribution of damping based upon “small damping” assumptions, numerical examples, and a supporting test program. The generally high values calculated for beams of various materials indicate that this type of construction is efficient for vibration damping applications. It was found, however, that the calculated and test values were not in accord. This lack of agreement signifies the necessity for greater refinement in both analytical methods and test procedures.

Damping capacity in pseudo-elastic and ferro-elastic shape memory alloy-reinforced hybrid composite beam

2019 ◽  
Vol 38 (10) ◽  
pp. 467-477 ◽  
Author(s):  
Yahya Bayat ◽  
Hamid EkhteraeiToussi
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Composite Beam ◽  
Volume Fraction ◽  
Hysteresis Loops ◽  
Beam Theory ◽  
Material Model ◽  
Resonance Phenomenon ◽  
Damping Capacity ◽  
Concentrated Load

Reinforcing a composite beam with shape memory alloy wires may have several benefits such as reduction of buckling risks or elimination of unwanted oscillations. In this paper, the vibration damping of a typical shape memory alloy-reinforced composite or hybrid beam is explored. To formulate the thermo-mechanical behavior of embedded shape memory alloy wires, three-dimensional Panico–Brinson model is employed and tailored to one-dimensional model. This material model can simulate pseudo-elastic and ferro-elastic forms of martensite transformations which occurs in cyclic loadings. Besides, unlike the former studies which rely on classical beam theories, the first-order shear deformation beam theory is used to obtain more accurate estimations of shape memory alloy-wire hysteresis loops and their decaying characteristics. In order to explore the effects of a transient concentrated load applied in the middle of a beam, the governing equations are developed and discretized by differential quadrature–integral quadrature combined method. Incremental time marching solution of the problem is accomplished using the Newmark technique. Results are assessed by comparing with available literature. Considering different types of boundary conditions, the influence of pseudo-elastic and ferro-elastic hysteresis loops on the material damping effects, shape memory alloy volume fraction, and resonance phenomenon is studied in detail.

A Method Research to Obtain Quickly the Vibration Transmissibility of Cushioning Packaging Materials

2012 ◽  
Vol 542-543 ◽  
pp. 87-90
Author(s):  
Yi Hua Wang ◽  
Lin Bao ◽  
Hai Ming Jin
Keyword(s):  
Frequency Domain ◽  
Transmission Rate ◽  
Impact Excitation ◽  
Interference Signal ◽  
Transient Vibration ◽  
Time Domain Signal ◽  
Spectrum Density ◽  
Vibration Transmissibility ◽  
The Time Domain ◽  
Material Power

Through the data acquisition system of drop impact test impact excitation pulse and in response to a pulse, to reduce or eliminate the experimental process generated interference signal brought influence, the excitation and response signals are Fourier transform (FFT), get the cushing material power spectrum and cross spectrum density value, the time domain signal into frequency domain signal, realize the effective filtering, the frequency domain signal in each frequency through the transfer rate calculation formula of cushing packaging material transient vibration transmitting rate, the transmission rate of the way the process of obtaining description and theoretical analysis.

scholarly journals Effect of Aging Treatment on the Damping Capacity and Mechanical Properties of Mg-6Al-1Zn Alloy

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Abdel-Wahab El-Morsy ◽  
Ahmed I. Z. Farahat
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
Damping Ratio ◽  
Aging Treatment ◽  
Peak Level ◽  
Free Vibrations ◽  
Logarithmic Decrement ◽  
Damping Capacity ◽  
Damping Characteristics ◽  
Heat Treated

The damping capacity and mechanical properties of Mg-6Al-1Zn alloy after heat treatment were investigated. The damping characteristics of un-heat-treated, solution treated, and aged Mg-6Al-1Zn specimens were determined by measuring the damping ratio and the logarithmic decrement of free vibrations of a bending beam clamped at one side. The microstructural evaluations confirmed that theβ-Mg17Al12phase was reprecipitated after aging and increased with an increase in aging time. The peak level of damping ratio and logarithmic decrement was obtained after 34 hr of aging time, over which the damping capacity declined according to increasing amount of strong pining points.

Evaluation of Own Pulses in the Event of Free Vibrations of a Multiparker Type Parking Machine Lifting Machine

2019 ◽  
Vol 34 ◽  
pp. 137-142
Author(s):  
Carmen Elisabeta Radu ◽  
Edward Rășchitor ◽  
Iosif Tempea
Keyword(s):  
Free Vibrations ◽  
Resonance Phenomenon ◽  
Parking Lot ◽  
Common Unit

To study the vibrations of a Multiparker lift lift model, use various models for the lifting mechanism. Calculate the first pulsation using the Dunkerley method. Behavior of the elevator to the action of an explosive task. We intend to evaluate the own pulsations in case of free vibrations of a lifting mechanism at an elevator within a multiparker parking lot. IT is absolutely necessary that the wave pulsation is different from the own pulsation of the studied system so as to avoid the resonance phenomenon leading to the system’s destruction. We shall establish a work algorithm using several models of the system as following: the model of the system with an autonomy degree; the calculation of the first own pulsations is used by the Dunkerley method; the model of the continuous system.A model is executed for the lifting mechanism of the Multiparker parking lot, considered as being composed of a continuous and homogeneous bar, embedded at the base, becoming a common unit with the mass M of the elevator. The own pulsations are determined in case of free vibrations for this bar.

Recent Radiative and Collisional Atomic Data of Astrophysical Interest

1988 ◽  
Vol 102 ◽  
pp. 129-132
Author(s):  
K.L. Baluja ◽  
K. Butler ◽  
J. Le Bourlot ◽  
C.J. Zeippen
Keyword(s):  
Mass Production ◽  
Bound States ◽  
Physical Models ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Atomic Data ◽  
Isoelectronic Sequence ◽  
Astrophysical Interest ◽  
Radiative Transitions ◽  
Forbidden Transitions

SummaryUsing sophisticated computer programs and elaborate physical models, accurate radiative and collisional atomic data of astrophysical interest have been or are being calculated. The cases treated include radiative transitions between bound states in the 2p4and 2s2p5configurations of many ions in the oxygen isoelectronic sequence, the photoionisation of the ground state of neutral iron, the electron impact excitation of the fine-structure forbidden transitions within the 3p3ground configuration of CℓIII, Ar IV and K V, and the mass-production of radiative data for ions in the oxygen and fluorine isoelectronic sequences, as part of the international Opacity Project.

A New AID for Interpolating and Assessing Collision Strengths and Rate Coefficients

1988 ◽  
Vol 102 ◽  
pp. 107-110
Author(s):  
A. Burgess ◽  
H.E. Mason ◽  
J.A. Tully
Keyword(s):  
Significant Loss ◽  
Impact Excitation ◽  
Rate Coefficients ◽  
Electron Impact Excitation ◽  
Graphical Display ◽  
Practical Procedure ◽  
Positive Ions ◽  
Allowed Transition ◽  
Computational Errors ◽  
Existing Data

AbstractA new way of critically assessing and compacting data for electron impact excitation of positive ions is proposed. This method allows one (i) to detect possible printing and computational errors in the published tables, (ii) to interpolate and extrapolate the existing data as a function of energy or temperature, and (iii) to simplify considerably the storage and transfer of data without significant loss of information. Theoretical or experimental collision strengths Ω(E) are scaled and then plotted as functions of the colliding electron energy, the entire range of which is conveniently mapped onto the interval (0,1). For a given transition the scaled Ω can be accurately represented - usually to within a fraction of a percent - by a 5 point least squares spline. Further details are given in (2). Similar techniques enable thermally averaged collision strengths upsilon (T) to be obtained at arbitrary temperatures in the interval 0 < T < ∞. Application of the method is possible by means of an interactive program with graphical display (2). To illustrate this practical procedure we use the program to treat Ω for the optically allowed transition 2s → 2p in ArXVI.

Precipitation of NiHfsi phase in NiAl single crystals containing Hf

1995 ◽  
Vol 53 ◽  
pp. 532-533
Author(s):  
A. Garg ◽  
R. D. Noebe ◽  
R. Darolia
Keyword(s):  
High Temperature ◽  
Single Crystals ◽  
High Temperature Strength ◽  
Bridgman Technique ◽  
Shell Mold ◽  
Third Phase ◽  
Unknown Phase ◽  
Transmission Electron ◽  
Two Phases ◽  
Nial Matrix

Small additions of Hf to NiAl produce a significant increase in the high-temperature strength of single crystals. Hf has a very limited solubility in NiAl and in the presence of Si, results in a high density of G-phase (Ni16Hf6Si7) cuboidal precipitates and some G-platelets in a NiAl matrix. These precipitates have a F.C.C structure and nucleate on {100}NiAl planes with almost perfect coherency and a cube-on-cube orientation-relationship (O.R.). However, G-phase is metastable and after prolonged aging at high temperature dissolves at the expense of a more stable Heusler (β'-Ni2AlHf) phase. In addition to these two phases, a third phase was shown to be present in a NiAl-0.3at. % Hf alloy, but was not previously identified (Fig. 4 of ref. 2 ). In this work, we report the morphology, crystal-structure, O.R., and stability of this unknown phase, which were determined using conventional and analytical transmission electron microscopy (TEM).Single crystals of NiAl containing 0.5at. % Hf were grown by a Bridgman technique. Chemical analysis indicated that these crystals also contained Si, which was not an intentional alloying addition but was picked up from the shell mold during directional solidification.

Imaging of Al-Li-Cu alloys with a Scanning Ion Microprobe

1990 ◽  
Vol 48 (2) ◽  
pp. 314-315
Author(s):  
K.K. Soni ◽  
D.B. Williams ◽  
J.M. Chabala ◽  
R. Levi-Setti ◽  
D.E. Newbury
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Equilibrium Phase ◽  
Icosahedral Symmetry ◽  
Ion Microprobe ◽  
X Ray ◽  
Cu Alloys ◽  
Two Phases ◽  
The University ◽  
Secondary Ion

In contrast to the inability of x-ray microanalysis to detect Li, secondary ion mass spectrometry (SIMS) generates a very strong Li+ signal. The latter’s potential was recently exploited by Williams et al. in the study of binary Al-Li alloys. The present study of Al-Li-Cu was done using the high resolution scanning ion microprobe (SIM) at the University of Chicago (UC). The UC SIM employs a 40 keV, ∼70 nm diameter Ga+ probe extracted from a liquid Ga source, which is scanned over areas smaller than 160×160 μm2 using a 512×512 raster. During this experiment, the sample was held at 2 × 10-8 torr.In the Al-Li-Cu system, two phases of major importance are T1 and T2, with nominal compositions of Al2LiCu and Al6Li3Cu respectively. In commercial alloys, T1 develops a plate-like structure with a thickness <∼2 nm and is therefore inaccessible to conventional microanalytical techniques. T2 is the equilibrium phase with apparent icosahedral symmetry and its presence is undesirable in industrial alloys.

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