Razvoj i usporedba algoritama za procjenu zamora uzrokovanog slučajnim vibracijama u vremenskoj i frekvencijskoj domeni

master's thesis

• Title (english): Development and comparison of algorithms for the assessment of fatigue induced by random vibrations in the time and frequency domains
• Author: Sara Večerić
• Mentor: Zvonimir Tomičević (mentor)
• Mentor: Damjan Čakmak (komentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2023-07-21, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Ovaj rad bavi se razvojem i usporedbom algoritama za procjenu zamora uzrokovanog
slučajnim vibracijama. Rezultati obje metode dobiveni su u vremenskoj i frekvencijskoj
domeni.
Na početku rada opisan je fenomen zamornog loma, S-N metoda i Palmgren-Minerovo
pravilo.
Detaljno je opisana Rainflow metoda brojanja ciklusa za ponavljajuću povijest naprezanja
u vremenskoj domeni prema ASTM E1049-85 normi. Rainflow metoda za ponavljajuću
povijest naprezanja je metoda kojom se pojednostavljuju složene povijesti naprezanja
promjenjivih amplituda u niz jednostavnih ciklusa naprezanja konstantnih amplituda.
S obzirom da proračun visokocikličkog zamora u vremenskoj domeni za dugu povijest
naprezanja postaje računalno zahtjevan, u svrhu pojednostavljenja, korištene su približne
spektralne teorije u frekvencijskoj domeni. U ovom radu korištena je i detaljno opisana Dirlikova spektralna teorija.
Opisane su sve formulacije potrebne za procjenu visokocikličkog zamora u vremenskoj
i frekvencijskoj domeni, na temelju kojih je odrađena analiza.
U zadnjem dijelu prikazan je sam tijek analize i rezultati analitičke i numeričke analize
za procjenu zamora. Rezultat analize je vrijeme do loma u vremenskoj i frekvencijskoj domeni.
Analitička analiza provedena je pomoću algoritma napisanog u programskog paketu MATLab
R2017b, a numerička analiza pomoću programskih paketa Abaqus i Fe-Safe.

Abstract (english)

This thesis deals with the development and comparison of algorithms for fatigue
assessment induced by random vibrations. The results obtained in both methods were obtained
in the time and frequency domains.
At the beginning, the phenomenon of fatigue fracture, the S-N method and the PalmgrenMiner rule are described.
The Rainflow cycle counting method for repetitive stress history in the time domain
according to the ASTM E1049-85 standard is described in detail. The Rainflow method for
repeating stress history is a method that simplifies complex stress histories of variable
amplitudes into a series of simple stress cycles of constant amplitudes. The calculation of this
method is in the time domain.
Since the calculation of high cycle fatigue in the time domain for a long stress history
becomes computationally demanding, for the purpose of simplification, approximate spectral
theories in the frequency domain are used. In this work, the Dirlik spectral theory is used and
described in detail.
All the formulations necessary for the assessment of high-cycle fatigue in the time and
frequency domain are described, based on which the analysis was performed.
In the last part, the analysis process and the results of the analytical and numerical
analysis for fatigue assessment are presented. The result of the analysis is the time to failure in
the time and frequency domains. The analytical analysis was performed using an algorithm
written in the MATLab R2017b software package, and the numerical analysis was performed
using the Abaqus and Fe-Safe software packages.

• Keywords: zamorni lom; uzbuda; odziv; Rainflow metoda; povijest naprezanja; akumulirano oštećenje; broj ciklusa do loma; Dirlik-ova spektralna teorija; frekvencijska domena
• Keywords (english): fatigue failure; excitation; response; Rainflow method; stress history; cumulative damage; number of cycles to failure; Dirlik spectral theory; frequency domain
• Language: croatian
• URN:NBN: urn:nbn:hr:235:509399
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2023-07-06 20:35:34