Optimiziranje vibracijskog stanja u postupku obrade tokarenjem

doctoral thesis

• Author: Viktor Baričak; VIAF: 305473053
• Mentor: Milenko Stegić (mentor)
• Committee member: Nikola Šakić (predsjednik povjerenstva)
• Committee member: Milenko Stegić (član povjerenstva)
• Committee member: Sanjin Mahović (član povjerenstva)
• Committee member: Toma Udiljak (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2004-12-07, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering
• Universal decimal classification (UDC): 621 - Mechanical engineering. Nuclear technology. Machinery ; 53 - Physics

Abstract

Suvremeni pravci razvoja gospodarstva i tržišni uvjeti proizvodnje nameću potrebu
istraživanja procesa obrade materijala odvajanjem čestica. Pored razvijenih i verificiranih
metoda kojima se definira apsolutna obradivost, sve se više u proizvodnim uvjetima
primjenjuju brze metode za definiranje relativne obradivosti materijala, funkcionalnog
kvaliteta alata te kvaliteta izrade. Na ovim i sličnim istraživanjima radio je i radi čitav niz
istraživača, a istraživanja imaju veliki praktični i teorijski značaj.
Obrada odvajanjem čestica je složen proces, a ta složenost se očituje velikim
specifičnim tlakovima u zoni rezanja i visokim stupnjem zagrijanosti. Kao popratne pojave
tijekom procesa obrade odvajanjem čestica su: mehanička i toplinska opterećenja,
generiranje toplinske energije, trošenje i vibracije (samouzbudne). Analizom vibracija
utvrđena je ovisnost istih od intenziteta sila pri odvajanju čestica. Sile pri odvajanju čestica
su u funkcionalnoj ovisnosti od geometrije oštrice alata i tehnoloških parametara obrade.
Ovisnost vibracija i sila rezanja pri obradi odvajanjem čestica iskorištena je tako
da su definirani: optimalna geometrija oštrice alata (γ i ℵr ) i optimalni tehnološki
parametri obrade (f i ap) spram kriterija minimalne amplitude vibracija (A⏐min). Također je
pokazano (pokusima potvrđeno) da kvalitet obrađene površine kao zahtijevane izlazne
karakteristike koje se moraju ostvariti tijekom procesa odvajanja čestica ovisi o
geometrijskim parametrima oštrice alata (γ i ℵr ) i tehnološkim parametrima obrade (f i ap).
Optimalne vrijednosti geometrijskih parametara oštrice alata (γ i ℵr ) i tehnoloških
parametara obrade (f i ap) dobijaju se po kriteriju da parametar Rz bude minimalan
(Rz⏐min).
Ovisnost veličine amplitude vibracija o uvjetima obrade, geometrijskim
parametrima oštrice alata i tehnološkim parametrima obrade može se pisati u obliku
A=A(c, f, ap, ℵr i γ).
Ovisnost parametra kvalitete površine Rz o uvjetima obrade, geometrijskim
parametrima oštrice alata i tehnoloških parametara obrade može se pisati u obliku
Rz=Rz(c, f, ap, ℵr i γ).
Kao kriterij za optimiziranje parametara geometrije oštrice alata i tehnoloških
parametara obrade uzete su minimalna vrijednost amplitude vibracija (A⏐min) i minimalna
vrijednost parametara kvalitete (Rz⏐min).
Optimalne vrijednosti geometrijskih parametara oštrice alata (γ i ℵr ) i
parametari obrade (f i ap) dobiveni po kriteriju A⏐min i kriteriju Rz⏐min su podudarne.
Mjerenje parametara vibracija (amplitude) je relativno prosto, rezultati pouzdani,
a vrijeme mjerenja za potreban broj podataka relativno kratko (spram nekih drugih
mjerenja), i mogu se izvoditi ne prekidajući proizvodni proces.
Mogućnosti definiranja optimalne geometrije oštrice alata, optimalnih tehnoloških
parametara obrade, funkcionalnog kvaliteta alata te obradivosti s modelom za parametre
vibracija (amplitude) ima veliki praktični značaj te mogućnost implementacije tog načina u
laboratorijskim i proizvodnim uvjetima.

Abstract (english)

Contemporary directions of economic development and market conditions of
modern production processes impose the need for the research of metal cutting
processes. In addition to various well developed and verified methods which assess
machinability, short and fast methods for assessing relative machinability of materials,
functional quality of tools and machined parts quality are more and more used in real
production conditions. Such researches, which have significant practical and theoretical
experience, have been involving entire expert teams.
The metal cutting is a complex process, and its complexity is manifested in high
specific pressure in the cutting zone and in high heating level. During the metal cutting
process, various secondary effects occur, such as mechanical and thermal loads, tool
wear and vibration (self-exciting). Analysis of vibrations shows dependency of these
effects on intensity of the cutting forces. These forces functionally depend on cutting tool
geometry and of machining conditions.
Dependence of vibrations and cutting forces during the metal cutting process has
been used through definition of optimal cutting tool geomatry (γ and ℵr) and optimal
machining conditions (f and ap) versus criteria of minimal amplitude of vibrations (A|min). It
has also been proved (and practically explored) that the machined surface quality, in fact
the required output characteristics to be achieved during the metal cutting process,
depends on cuting tool geometry (γ and ℵr) and on machining conditions (f and ap).
Optimal values of geometrical parameters of the cutting edges (γ and ℵr) and of
machining conditions (f and ap) are obtained following the criteria that parameter Rz is
minimal (Rz|min).
Dependence of the vibration amplitudes on the machining conditions, cutting tool
geometry and cutting conditions could be formulated as A = A (c, f, ap, ℵr and γ )
Dependence of surface quality parameter Rz on the machining conditions,
cutting tool geometry and cutting conditions could be formulated as Rz = Rz (c,f, ap, ℵr and
γ).
As a criteria for optimization of parameters of cutting tool geometry and of
machining conditions, minimal values of the vibration amplitude (A|min) and minimal value
of machined surface parameters (Rz|min) are used.
Optimal values of geometrical parameters of cutting edges of the tools (γ and ℵr) and
machining conditions (f and ap), obtained according to the criteria A| min as and the criteria
Rz|min are identical.
Measurement of vibration parameters (amplitude) is relatively simple, results are
reliable, and duration of the measurement for obtaining required number of data is
relatively short (in comparison with some other measurements). These measurements
can be done without interrupting the production process.
Possibilities for defining optimal cutting tool geometry, optimal machining
conditions, functional quality of the tools, as well as machinability, by using the model of
vibration parameters (amplitude) has enormous practical importance and possibility for
implementation of such methodology in both laboratory and industrial conditions.

• Keywords: geometrija alata; parametri obrade; samouzbudne vibracije; kvalitet površine; CNC tokarilica; modeliranje i optimizacija
• Keywords (english): tools geometry; machining conditions; self-exciting vibrations; surface quality; CNC lathe; modelling and optimization
• Language: croatian
• URN:NBN: urn:nbn:hr:235:497859
• Study programme: Title: Mechanical Engineering and Naval Architecture; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje tehničkih znanosti (doktor/doktorica znanosti, područje tehničkih znanosti)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2020-11-30 13:47:33