Specific damping capacity for high‐loss materials.

1996 ◽  
Vol 99 (4) ◽  
pp. 2520-2520
Author(s):  
Gilbert F. Lee ◽  
Bruce Hartmann
Keyword(s):  
Damping Capacity ◽  
High Loss ◽  
Specific Damping Capacity

Assessment of Internal Damping in Uniaxially Stressed Metals: Exponential and Autoregressive Methods

1998 ◽  
Vol 120 (2) ◽  
pp. 177-184 ◽  
Author(s):  
A. L. Audenino ◽  
E. M. Zanetti ◽  
P. M. Calderale
Keyword(s):  
Nonlinear Behavior ◽  
Least Square ◽  
Dissipated Energy ◽  
Exponential Fitting ◽  
Damping Capacity ◽  
Test Machine ◽  
Internal Damping ◽  
Cast Irons ◽  
Decay Signal ◽  
Specific Damping Capacity

When a metallic material is highly stressed, its internal specific damping capacity increases showing a nonlinear behavior. In spite of this, the most part of experimental methods employ nonhomogeneous stress fields measuring only a volumetric average, often called structural damping. To overcome this problem the procedure herein presented extends the applicability of the plain traction or compression methods to higher frequency range (up to 300 Hz). The introduced methodology corrects for elastic energy and dissipated energy relative to the test machine and to the fixtures. The experimental procedure is based on the acquisition of a decay signal when the test machine excitation force has been removed. Two different methods to extract the pattern of internal damping versus material strain have been compared: one is based on least square exponential fitting while the other employs an autoregressive model. Best results have been obtained combining the two techniques taking into account also the variation of Young’s modulus with strain. The resulting curves of the loss factor as a function of strain amplitude for three steels and two cast irons are presented.

Identification of Material Damping of a Carbon Composite Bar and Study of Its Effect on Attenuation of Its Transient Lateral Vibrations

2015 ◽  
Vol 07 (06) ◽  
pp. 1550081 ◽  
Author(s):  
Jaroslav Zapoměl ◽  
Vladimír Dekýš ◽  
Petr Ferfecki ◽  
Alžbeta Sapietová ◽  
Milan Sága ◽  
...  
Keyword(s):  
Composite Material ◽  
Carbon Composite ◽  
Damping Capacity ◽  
Internal Damping ◽  
Material Damping ◽  
Damping Coefficients ◽  
Lateral Vibrations ◽  
Carbon Composite Material ◽  
Frequency Independent ◽  
Specific Damping Capacity

Reduction of noise and vibrations is one of the major requirements put on operation of modern machines. It can be achieved by application of new materials. The ability to utilize them properly requires learning more about their mechanical properties. Vibration attenuation depends on material damping as an important factor. This paper presents the results of research in a carbon composite material focusing on its internal damping, on the measurement of the damping coefficients and on its implementation into mathematical models. The obtained results were used for investigation of suppressing lateral vibrations of a long homogeneous carbon composite bar oscillating in the resonance area. During the transient period and due to nonlinear effects, the harmonic time-varying loading excites the bar response consisting of a number of harmonic components. The specific damping capacity referred to several oscillation frequencies determined by measurement. The results were evaluated from the point of view of two simple damping theories — viscous and hysteretic. The experiments showed that internal damping of the investigated material could be considered as frequency independent. Therefore, in order to carry out simulations, the bar was represented in the computational model by an Euler beam constituted of Maxwell–Weichert theoretical material. A suitable setting of material constants enabled reaching a constant value of the damping parameters in the required frequency range. The investigated bar vibration is governed by the motion equation in which the internal damping forces depend not only on instantaneous magnitudes of the system’s kinematic parameters but also on their past history. Solution of the equations of motion was performed after its transformation into the state space in the time domain. Results of the computational simulations showed that material damping significantly reduced amplitude of the bar vibrations in the resonance area. The producers of composite materials usually provide material parameters allowing to solve various stationary problems (density, modulus of elasticity, yielding point, strength, etc.), but there is only little or almost no information concerning the data needed for carrying out dynamical or other time-dependent analyses such as internal damping coefficients, fatigue limit, etc. Therefore, determination of the hysteretic character of material damping of the investigated carbon composite material, measurement of its specific damping capacity and implementation of the frequency-independent damping into the computational model are the principal contributions of this article.

Specific Properties of Industrial High-Damping Fe-Al Steels

2006 ◽  
Vol 115 ◽  
pp. 57-62
Author(s):  
V.A. Udovenko ◽  
I.B. Chudakov
Keyword(s):  
Mechanical Properties ◽  
Magnetic Structure ◽  
Elastic Energy ◽  
Damping Capacity ◽  
Damping Properties ◽  
Metallic System ◽  
Internal Dissipation ◽  
High Level ◽  
Specific Damping Capacity ◽  
Very High

It is shown that industrial high damping steels based on the Fe-Al metallic system are characterized by a very high level of internal dissipation of elastic energy. The specific damping capacity of industrial steels exceeds 40 % and their damping properties are close to those of highpurity damping alloys based on the Fe-Al system. Mechanical properties of damping steels are similar to those of conventional construction steels. High level of properties of damping steels can be explained by their specific crystalline and magnetic structure.

scholarly journals Analytical model for flexural damping responses of CFRP cantilever beams in the low-frequency vibration

2018 ◽  
Vol 37 (4) ◽  
pp. 669-681 ◽  
Author(s):  
Mo Yang ◽  
Yefa Hu ◽  
Jinguang Zhang ◽  
Guoping Ding ◽  
Chunsheng Song
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Natural Frequency ◽  
Analytical Model ◽  
Flexural Vibration ◽  
Maximum Error ◽  
Damping Capacity ◽  
Element Analysis ◽  
First Order ◽  
Specific Damping Capacity

In this paper, an analytical model for the flexural vibration damping of Carbon Fiber Reinforced Plastics (CFRP) cantilever beams was proposed, which is based on the Lamination Theory and Euler–Bernoulli Beam Theory. By using a finite element analysis and an analytical model, four sets of specific damping capacity with different pavement schemes were predicted, and flexural vibration test and damping analysis were carried out. Comparing the analytical model, finite element analysis, and test results, it could be found that the analytical model had relatively good accuracy in predicting the first-order natural frequency and specific damping capacity of the bending vibration of CFRP beams. The maximum error of the first-order natural frequency between the analysis result and the experimental result was 7.05%; the maximum specific damping capacity error was only 5.65%. Comparing the finite element analysis method and the experiment results, the maximum error of the first-order natural frequency was 7.8%, the error of the specific damping capacity was bigger, and the [±30°]5S specimen was as high as 18.7%. However, there was a significant error when the analytical model was used to predict the second-order natural frequency and the specific damping capacity of CFRP beam’s flexural vibration.

SPECIFIC DAMPING CAPACITY FOR ARBITRARY LOSS ANGLE

1998 ◽  
Vol 211 (2) ◽  
pp. 265-272 ◽  
Author(s):  
G.F. Lee ◽  
B. Hartmann
Keyword(s):  
Damping Capacity ◽  
Loss Angle ◽  
Specific Damping Capacity

scholarly journals Detection of Friction Stir Welding Defects of AA1060 Aluminum Alloy Using Specific Damping Capacity

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2437 ◽  
Author(s):  
Waheed AbuShanab ◽  
Essam Moustafa
Keyword(s):  
Finite Element ◽  
Friction Stir Welding ◽  
Natural Frequency ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Impact Testing ◽  
Damping Capacity ◽  
Element Analysis ◽  
Friction Stir ◽  
Specific Damping Capacity

The demand for nondestructive testing has increased, especially in welding testing. In the current study, AA1060 aluminum plates were jointed using the friction stir welding (FSW) process. The fabricated joints were subjected to free vibration impact testing in order to investigate the dynamic properties of the welded joint. Damping capacity and dynamic modulus were used in the new prediction method to detect FSW defects. The data acquired were processed and analyzed using a dynamic pulse analyzer lab shop and ME’Scope’s post-processing software, respectively. A finite element analysis using ANSYS software was conducted on different types of designed defects to predict the natural frequency. The results revealed that defective welded joints significantly affect the specific damping capacity. As the damping ratio increased, so did the indication of opportunities to increase the presence of defects. The finite element simulation model was consistent with experimental work. It was therefore revealed that natural frequency was insufficient to predict smaller defects.

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