Theoretical-Experimental Method for Determining the Parameters of Damping Based on the Study of Damped Flexural Vibrations of Test Specimens. 3. Identification of the Characteristics of Internal Damping

Abstract

Keywords: flexural vibrations of plates, experimental investigation, theoretical-experimental method, internal damping, aerodynamic damping, identification of the parameters of internal dampingThe logarithmic decrement of damped vibrations of materials is determined using a theoretical-experimental method. The method is based on measuring the deflection amplitudes of flat cantilever test specimens during their damped vibrations according to the first resonance mode, on the description of internal viscous friction of materials by known models both in linear and nonlinear approximations, on theoretical determination of the aerodynamic constituent of damping, and on a theoretical investigation of damping vibrations of test specimens by employing equations of motion constructed with a corresponding degree of accuracy and pithiness. To determine the vibration decrement of a soft material in tension-compression, sandwich test specimens with a steel core and external layers made of the soft material were used, but in transverse shear -with a core made of the soft material and steel external layers. A considerable effect of external aerodynamic forces on the vibration decrement of the specimens is revealed. Two methods for identification of the parameters of internal damping are proposed on the basis of data of the experimental investigations performed.

Damping Oriented Design of Thin-Walled Mechanical Components by Means of Multi-Layer Coating Technology

“…Moreover, starting from the results of the present work, identification tools based on experimental dynamical measurements of simple specimens must also be developed to estimate most of the unknown layer parameters associated with the manufacturing technology, i.e., the ones related to inter-layer coupling, making it possible to extend the design optimization research stage. An experimental dynamical measurement test activity made on bi-layer specimens, mainly differing by means of the PVD, CVD, or hot melting deposition technology adopted, the substrate material, the surface finish texture, and the coating thickness, can be performed by properly designing an experimental test apparatus, following the indications reported in [27][28][29][30][31]. Test data can be used to evaluate the unknown interlaminar dissipation viscosity and thickness values by means of a robust, numerical identification technique, since only two unknown parameters have to be identified, following the approach developed by our research group in [11].…”

The Aerodynamic Component of the Damping of Cantilevered Test Specimens Oscillating Near a Rigid Shield

“…Это обусловлено множе-ством практических приложений, охватывающих разнооб-разные области знаний, включая атомную микроскопию [1,2], датчики и приводы головок на микромеханических генераторах [3], охлаждающие устройства [4], морскую и шельфовую технику [5,6]. Второе направление связано с развиваемым в последнее время подходом к определе-нию демпфирующих свойства материалов на основе ис-следования затухающих изгибных колебаний консольно-закрепленных плоских тест-образцов [7][8][9]. При этом тест-образцы находятся в воздухе, что приводит к необходимо-сти исключения аэродинамической составляющей демп-фирования с целью получения параметра внутреннего демпфирования тест-образца.…”

Identification of the Elasticity and Damping Characteristics of a Fiberglass Based on a Study of Dying Flexural Vibrations of Test Samples

“…, we took the experimental data[2,4] for the aerodynamic components of the LVD of St3 steel test samples of length L = 150, 200, and 300 mm, thickness h = 1 mm, and width b = 10 mm, according to which the coefficients d 1 and d 2 were derived for each test sample. Then, we calculated the dimensionless frequencies β of three test samples.…”