Sevanje zvoka iz ravne aluminijaste plošče z različnimi prevlekami za dušenje vibracij

Strmole, Lan (author), Prezelj, Jurij (mentor)

Zaključna naloga obravnava vpliv prevleke za dušenje vibracij na nihajne lastnosti prosto vpete ravne pravokotne aluminijaste plošče. S poznavanjem vpliva dušenja na lastne frekvence in oblike nihajočih sistemov in z ustrezno izbiro dušilne prevleke lahko vplivamo na nihajne lastnosti obravnavanega sistema ter tako dosežemo, da ne pride do resonance sistema s katero od vzbujevalnih sil. Tako preprečimo dinamsko ojačenje odziva sistema, kar naredi konstrukcijo tišjo in varnejšo. Z zaključno nalogo smo želeli pridobiti znanje, potrebno za načrtovanje zmanjševanja hrupa strojev in naprav, ki se kot posledica vibracij generira pri njihovem delovanju. Analiza je bila izvedena s pomočjo numeričnih simulacij in z meritvami zvočnega tlaka v bližnjem polju plošče ter hitrosti plošče pri nihanju. Ugotovili smo, da nanos prevleke iz poliuretanske pene zniža lastne frekvence plošče, nihajni načini pa ostanejo enaki, vendar se zniža frekvenca, pri kateri se določen nihajni način pojavi. Dušenje vpliva tudi na amplitudo nihanja plošče pri posamezni lastni frekvenci. Pri nekaterih frekvencah se amplituda poveča, pri drugih pa zmanjša. Z numeričnimi izračuni in eksperimentom smo prišli do rezultatov, ki so se zelo dobro ujemali, s čimer smo pokazali tudi, da je merjenje zvočnega tlaka v bližnjem polju lahko ustrezna metoda pri analizi vibracijskih lastnosti mehanskih sistemov.

• Language: Slovenian
• Keywords: vibracije, plošče, dušenje, lastne oblike, lastne frekvence, metoda končnih elementov, simulacije
• Work type: Final paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FS - Faculty of Mechanical Engineering
• Place of publishing: Ljubljana
• Publisher: [L. Strmole]
• Year: 2020
• Number of pages: XV, 49 f.
• PID: 20.500.12556/RUL-119359
• UDC: 534.83:519.61(043.2)
• COBISS.SI-ID: 28833795
• Publication date in RUL: 08.09.2020

Secondary language

• Language: English
• Title: Influence of different vibration damping layers on sound radiation from aluminium plate

Abstract

The thesis deals with the influence of the vibration damping coating on the vibrational properties of a freely supported flat rectangular aluminum plate. By knowing the effects of damping on the natural frequencies and the mode shapes of the oscillating systems and with the right choice of damping coating we can affect the vibrational properties of the system and prevent resonance. That reduces noise emission from vibrating surfaces which makes the machine safer and quieter. The analysis was carried out with the help of numerical simulations and measurements of the sound pressure in the very near field of the plate along with the velocity of the vibration. We have noted that the coating made of polyurethane foam lowers the natural frequencies of the plate, while the mode shapes remain the same. However, the frequency at which a certain mode shape appears lowers. Damping also affects the amplitude of the oscillation. At some frequencies damping even increases the vibration amplitude. The results of numerical calculations are very well correlated with those of the experiment, which means that it is possible to analyse the vibrational properties of mechanical systems by measuring the sound pressure in the very near field.

• Keywords: vibrations, plates, damping, natural modes, natural frequencies, finite element method, simulations