Razvoj brezdotične dinamske metode za določanje frekvenčno odvisnega elastičnega modula polimernih materialov

Varšek, Lucija (author), Čepon, Gregor (mentor), Boltežar, Miha (co-mentor)

Za karakterizacijo frekvenčno in temperaturno odvisnega elastičnega modula polimernih materialov se uporablja metodo dinamske mehanske analize DMA (ang. Dynamic Mechanical Analysis). V sklopu analize DMA se preko sinusnega preleta aplicira obremenitev vzorca ter sočasno meri odziv sistema, kar omogoča določitev frekvenčno odvisnega elastičnega modula. Navadno se uporablja upogibno obremenjevanje epruvete, pri čemer metoda predvideva različne načine podprtja/vpenjanja vzorcev. Samo podprtje ima razmeroma velik vpliv na identificiran elastični modul materiala, kar je posledica vpliva neidealnih robnih pogojev na mestu vpetja. V nalogi je predstavljen nov način dinamske mehanske analize polimernih vzorcev za identifikacijo elastičnega modula materiala. Metoda omogoča brezdotično vzbujanje vzorca ter brezdotičen zajem njegovega odziva. Vzorec je med testiranjem vpet prosto-prosto, saj ta način vpetja najlažje repliciramo pri dejanski izvedbi meritve. Cilj novo razvite brezdotične DMA analize je identifikacija elastičnega modula materiala. Postopek identifikacije temelji na eksperimentalni določitvi lastnih frekvenc v povezavi z metodo modalnega posodabljanja ekvivalentnega numeričnega modela. Z razvito metodo je bil določen elastični modul za 17 različnih polimernih materialov, pri čemer je bilo razvidno dobro ujemanje z rezultati, objavljenimi v dostopni literaturi.

• Language: Slovenian
• Keywords: brezdotična metoda, polimerni materiali, elastični moduli, temperaturna odvisnost, frekvenčna odvisnost, dinamska mehanska analiza
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FS - Faculty of Mechanical Engineering
• Place of publishing: Ljubljana
• Publisher: [L. Varšek]
• Year: 2019
• Number of pages: XXIII, 70 str.
• PID: 20.500.12556/RUL-107892
• UDC: 620.174.22:678.7(043.2)
• COBISS.SI-ID: 16658203
• Publication date in RUL: 02.06.2019

Secondary language

• Language: English
• Title: Development of a non-contact dynamic method for identification of frequency dependent elastic modulus of polymers

Abstract

Dynamic mechanical analysis DMA is used for characterization of frequency and temperature dependent elastic modulus of polymer materials. The excitations are applied to the sample with a sinusoidal signal. The system response is measured simultaneously, and serves for the identification of frequency dependent elastic modulus. The test sample is usually loaded in a bending mode with different mounting clamps being available. Usually, the fixation of a sample is not ideal and does not meet the theoretical boundary conditions. That results in fixation-dependent natural oscillations of the sample. Thus, a new way of dynamic mechanical analysis for identification of elastic modulus will be presented. The new method enables a non-contact application of force on the sample and a non-contact acquisition of its response. During the measurements, the free-free boundary condition is proposed, as it can be effectively replicated in the experiment. The goal of the newly developed non-contact DMA method is the identification of elastic modulus of the material. The procedure of identification is based on the experimental determination of natural frequencies in conjunction with a method of modal updating of an equivalent numerical model. With the developed method elastic modulus of 17 tested samples was determined. The closeness of the agreement between the results, obtained by measurements, and the results from accessible literature, are displayed.

• Keywords: non-contact method, polymers, elastic modules, temperature dependency, frequency dependency, dynamic mechanical analysis