Optimiziranje vibracijskog stanja u postupku obrade tokarenjem

Baričak, Viktor (2004) Optimiziranje vibracijskog stanja u postupku obrade tokarenjem. = Doctoral thesis , Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, UNSPECIFIED. Mentor: Stegić, Milenko.

[img]
Preview
Text
09_11_2007_Baricak_dr.pdf - Published Version Jezik dokumenta:Croatian

Download (2MB) | Preview

Abstract (Croatian)

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 (#61543; i #61632;r ) i optimalni tehnološki parametri obrade (f i ap) spram kriterija minimalne amplitude vibracija (A#61629;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 (#61543; i #61632;r ) i tehnološkim parametrima obrade (f i ap). Optimalne vrijednosti geometrijskih parametara oštrice alata (#61543; i #61632;r ) i tehnoloških parametara obrade (f i ap) dobijaju se po kriteriju da parametar Rz bude minimalan (Rz#61629;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, #61632;r i #61543;). 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, #61632;r i #61543;). Kao kriterij za optimiziranje parametara geometrije oštrice alata i tehnoloških parametara obrade uzete su minimalna vrijednost amplitude vibracija (A#61629;min) i minimalna vrijednost parametara kvalitete (Rz#61629;min). Optimalne vrijednosti geometrijskih parametara oštrice alata (#61543; i #61632;r ) i parametari obrade (f i ap) dobiveni po kriteriju A#61629;min i kriteriju Rz#61629;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

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 (g and Àr) 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 (g and Àr) and on machining conditions (f and ap). Optimal values of geometrical parameters of the cutting edges (g and Àr) 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, Àr and g ) 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, Àr and g). 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 (g and Àr) 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.

Item Type: Thesis (Doctoral thesis)
Uncontrolled Keywords: parametri obrade; geometrija alata; samouzbudne vibracije; kvaliteta površine; CNC strojevi; modeliranje; optimizacija
Keywords (Croatian): tools geometry; machining conditions; self-exciting vibrations; surface quality; CNC lathe; modelling and optimization
Divisions: 200 Department of Engineering Mechanics > 210 Chair of Mechanics and Strength of Materials
Date Deposited: 22 Sep 2014 18:00
Last Modified: 16 Oct 2015 13:19
URI: http://repozitorij.fsb.hr/id/eprint/215

Actions (login required)

View Item View Item

Downloads

Downloads per month over past year

Nema podataka za dohvacanje citata