Wyniki wyszukiwania - BazTech

1

Experimental investigation of damping properties of unidirectionally and fabric reinforced plastics by the free decay method

Romano M., Micklitz M., Olbrich F., Bierl R., Ehrlich I., Gebbeken N.

Journal of Achievements in Materials and Manufacturing Engineering

|

2014

|

Vol. 63, nr 2

65--80

EN

Purpose: of this paper is experimental investigation of damping properties of unidirectionally and fabric reinforced plastics by the free decay method. Design/methodology/approach: For the evaluation of the presumed effect experimental structural dynamic investigations comparing unidirectionally and fabric reinforced plastics are carried out. In detail the free decay behaviour of flat beamlike specimens under fixed-free boundary conditions and relatively constant and reproducible displacement excitation is investigated. Findings: The vibrating structure has been measured by a laser scanning vibrometer PSV 400 from POLYTEC. In both cases evaluation of the results yields enhanced damping properties of the specimens with fabric reinforcement compared to the unidirectionally reinforced specimens. The results justify the presumed acting of a mesomechanic kinematic. Research limitations/implications: The results show that in either case the material damping in terms of the logarithmic decrement of the fabric reinforced material is higher than the material damping in of the unidirectionally reinforced material. Additionally, when the fabric reinforced specimens are addressed, in each case the plain weave reinforced specimens exhibited higher values of the material damping as the twill weave 2/2 reinforced ones. Originality/value: Ondulations in fabrics as a textile semi-finished product are caused by the alternating crossing of warp and fill yarns. In the mesoscopic scale the acting of a mesomechanic kinematic is presumed to enhance the damping properties under cyclic elastic deformation. For the evaluation of the presumed effect experimental structural dynamic investigations comparing unidirectionally and fabric reinforced plastics are carried out.

2

New Concept of Using Coherence Function in Digital Signal Analysis

Dąbrowski Z., Dziurdź J.

Machine Dynamics Problems

|

2007

|

Vol. 31, No. 3

25-31

EN

Quick progress in development of digital computational techniques has also been reflected in signal analysis. However, faster and more accurate arithmetic calculations are far from being a cure-all for all the problems conditioned by physical properties of phenomena. Limitations resulting from nature of the Fourier transformant or other features of non-linear relationships do not disappear. Therefore, it seems crucial that new interpretations methods are applied in order to bypass these limitations. On the other hand, many forms of description used to be of quite restricted use because of limited computing power, and the situation has changed only recently. According to the Authors, high capacity of digital analysis opens new possibilities of applying the coherence analysis. The paper considers an idea of using the coherence function for two tasks: identification of non-linear analytic model and improvement of accuracy narrow-band analysis.

3

Studies on propagation of vibroacoustic energy and its influence on structure vibration in a large-size object

Dąbrowski Z., Dziurdź J., Klekot G.

Archives of Acoustics

|

2007

|

Vol. 32, No. 2

231-240

EN

Large-size spaces of general use are usually characterized by atypical acoustic features. The Great Lecture Hall of Warsaw Technical University can be an example, as its maximum crosswise dimension is comparable with its height. When powerful amplification equipment is used for special events, the question that arises is possible negative influence of acoustic signal energy on the building's structure, especially the skylight. The paper presents selected results of studies on acoustically induced vibrations of construction elements and tries to answer the above formulated question.

4

A class of electro-mechanical systems: linear and nonlinear dynamics

Dell'Isola F., Vestroni F., Vidoli S.

Journal of Theoretical and Applied Mechanics

|

2002

|

Vol. 40 nr 1

47-71

EN

The linear and nonlinear problems of dynamics of some electro-mechanical systems, characterized by a gyroscopic internal coupling, are analyzed. Since the technical importance of this system lies in the possibility of damping and controlling structural vibrations, the interest is focused on the energy exchanges between the mechanical and electric components. In order to maximize these energy transformations, the optimal values of the system parameters and their modifications in the nonlinear case are investigated.

PL

Klasa układów elektromechanicznych: dynamika liniowa i nieliniowa. W pracy przedstawiono analizę liniowego i nieliniowego zagadnienia dynamiki układów elektromechanicznych, charakteryzujących się wewnętrznym sprzężeniem żyroskopowym. Ze względu na techniczną wartość problemu tłumienia i sterowania drganiami, główny nacisk położono na procesy wymiany energii między podzespołami mechanicznymi i elektrycznymi. W celu zmaksymalizowania przepływu i transformacji energii określono optymalne parametry układu i ich modyfikacje w przypadkku nieliniowym.

5

Simulation examination of active and semiactive damping of structural vibrations

Tylikowski A.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

|

1999

|

z. 52 [174]

357-362

EN

The aim of the paper is to present a review of problems related to active and semiactive control of structural vibrations with special emphasis put on the role of simulation. Depending on criteria of interest the problems of smart (intelligent, adaptive) structures can be divided into different categories to include fundamental research on the one hand, and simulations of quite sophisticated systems on the other.