Wyniki wyszukiwania - BazTech

1

Influence of material distribution and damping on the dynamic stability of Bernoulli-Euler beams

Garus Sebastian, Garus Justyna, Sochacki Wojciech, Nabiałek Marcin, Petru Jana, Borek Wojciech, Šofer Michal, Kwiatoń Paweł

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2023

|

Vol. 71, nr 4

art. no. e145567

EN

The study analyzed the influence of materials and different types of damping on the dynamic stability of the Bernoulli-Euler beam. Using the mode summation method and applying an orthogonal condition of eigenfunctions and describing the analyzed system with the Mathieu equation, the problem of dynamic stability was solved. By examining the influence of internal and external damping and damping in the beam supports, their influence on the regions of stability and instability of the solution to the Mathieu equation was determined.

2

Optimization of a Bandgap in the Ultrasonic Phononic Coating

Garus Sebastian, Sochacki Wojciech, Garus Justyna, Sandu Andrei Victor

Archives of Metallurgy and Materials

|

2021

|

Vol. 66, iss. 2

537--542

EN

This work concerns the study of the coatings for the ultrasound frequency range as a quasi one-dimensional phononic crystal structure protecting a sea object against high resolution active sonar in the frequency range most commonly found for this type of equipment. The topology of the examined structure was optimized to obtain a band gap in the 2.2-2.3 MHz frequency band. For this purpose, a genetic algorithm was used, which allows for optimal distribution of individual elements of the ultrasound multilayer composite. By optimal distribution is meant to achieve a structure that will allow minimal reflectance in a given frequency range without height reflectance peaks with a small half width. Analysis of the wave propagation was made using the Transfer Matrix Method (TMM). As part of the research, 15 and 20-layer structures with reflectance at the level of 0.23% and 0.18%, respectively, were obtained. increasing the number of layers in the analyzed structures resulted in finding such a distribution in which a narrow band of low reflectance was obtained, such distributions could also be used as bandpass filters. The use of a genetic algorithm for designing allows to obtain modern coatings, the characteristics of which result from the structure.

3

Influence of Material Defects on the Dynamic Stability of the Bernoulli-Euler Beam

Sochacki Wojciech, Garus Sebastian, Garus Justyna

Archives of Metallurgy and Materials

|

2021

|

Vol. 66, iss. 2

519--522

EN

The paper presents the results of tests on dynamic stability of Bernoulli-Euler beam with damages. Damages (cracks) were modeled using three rotational springs. An analysis of the influence of crack depth and their position relative to the beam ends on dynamic stability of the beam was carried out. The problem of dynamic stability was solved by applying the mode summation method. Applying an orthogonal condition of eigenfunctions, the dynamic of the system was described with the use of the Mathieu equation. The obtained equation allowed the dynamic stability of the tested system to be analyzed. Stable and unstable solutions were analyzed using the Strutt card.