Title (srp)

Identifikacija termičkih naprezanja disk kočnice za različite radne parametre kočenja

Author

Stojanović, Nadica, 1991-

Contributor

Glišović, Jasna, 1969-
Lukić, Jovanka, 1966-
Miloradović, Danijela, 1969-
Taranović, Dragan, 1956-
Dorić, Jovan, 1983-
Stojić, Boris, 1972-

Description (eng)

Thermal strains of disc brakes and their influences on the braking efficiency are representingone of the greatest problems during the vehicle exploitation. The cause of the brake heatingproblem is explained in PhD thesis, as well as its consequence on the braking systemfunctionality, and even on the traffic safety. Results of this PhD thesis are reflected in thedevelopment and realization of the specific test rig for investigation of disc brake’s thermalstresses, which was applied to obtain experimental results used in the analysis of the influenceof operating braking parameters on disc brakes. Experimental tests of the disc brake wereperformed according to the tests defined in the doctoral dissertation. According to the developedtests, various laboratory tests were performed, as well as determining which of theindependently (input) variables, such as the initial speed of the simulated vehicle, brakingpressure and vehicle mass quarter, has the greatest influence on the output parameters –temperature of the braking disc and braking pads, braking torque, friction coefficient andstopping time.In line with advances in technology and the numerical tools for solving various engineeringproblems, the ANSYS software package, Transient Structural module, was applied in PhDthesis in order to develop the model for the representation of disc brake’s thermal behaviour.The analysis on the thermal stresses was performed on a virtual model that dimensionally andaccording to the characteristics of the applied materials fully corresponds to the real model, andthe boundary conditions were the same as in the case of the laboratory experiment. Suchanalysis is used to determine the discrepancies between the results obtained experimentally andnumerically, as well as to determine whether the developed numerical model can besuccessfully applied for further research. The developed model had deviations within theallowed limits, so it was used for the analysis of two more disc brakes, which differed in theconstruction of the disc ribs. The rib shapes used in the brake disc are: radial, curved and pillar.Today, brake discs are expected to dissipate as much heat as possible into the environment, thatis, to have the capability to provide better cooling for a wide range of speeds. Through theanalysis performed in the ANSYS software package, using the Fluid Flow (Fluent) module, ithas shown that the shape of the ribs greatly affects the heat dissipation, as well as that the brakedisc with curved ribs heats up the least. Results of the analysis show that the brake disc withcurved ribs provides to the air to pass with high speed between ribs, and in that way, the greatamount of heat is dissipated into the environment. In order to predict the temperature values atthe most loaded part of the brake pad, a model with high-accuracy prediction was developed,in which the following factors were varied: vehicle mass, moving speed, braking pressure, andstopping time.Results of this PhD thesis, such as the realized test rig and numerical model, can be used bycompanies engaged in the production of brake discs and brake pads, with the aim to predicttheir behaviour in the exploitation. Also, the obtained experimental results can be used to createof virtual models for disc brake’s testing. The virtual model developed for the purposes of thisPhD thesis, can be used to develop/improve the brake disc and brake pads in order to reducedevelopment costs.

Description (srp)

Termička naprezanja disk kočnica i njihov uticaj na efikasnost kočenja predstavljajujedan od najvećih problema tokom eksploatacije vozila. U doktorskoj disertacijiobjašnjen je najpre uzrok nastanka problema zagrevanja kočnica, kao i njegove posledicena funkcionisanje kočnog sistema, pa čak i na bezbednost saobraćaja. Rezultati ovedoktorske disertacije ogledaju se u razvoju i realizaciji specifičnog probnog stola zaispitivanja termičkih naprezanja disk kočnica, koji je primenjen za dobijanjeeksperimentalnih rezultata korišćenih u analizi uticaja radnih parametara kočenjana disk kočnice. Eksperimentalna ispitivanja disk kočnice su vršena po testovimakoji su definisani u okviru doktorske disertacije. Prema razvijenim testovimaizvršena su i ispitivanja, kao i utvrđivanje koja od nezavisno promenljivih (ulaznih)veličina, kao što su početna brzina simuliranog vozila, kočni pritisak i masačetvrtine vozila, ima najveći uticaj na izlazne parametre – temperaturu kočnog diskai kočnih pločica, kočni moment, koeficijent trenja i vreme zaustavljanja.U skladu sa napretkom tehnologije i numeričkih alata za rešavanja različitihinženjerskih problema, u doktorskoj disertaciji je primenjen softverski paket ANSYS,modul Transient Structural, u cilju razvoja modela za prikazivanje termičkog ponašanjadisk kočnica. Izvršena je analiza termičkih naprezanja na virtuelnom modelu kojidimenziono i prema karakteristikama primenjenih materijala u potpunosti odgovararealnom modelu, pri čemu su granični uslovi bili isti kao u slučaju laboratorijskogeksperimenta. Analiza se koristi za određivanje odstupanja između rezultataeksperimentalnih i numeričkih ispitivanja, kao i za utvrđivanje da li se razvijeninumerički model može uspešno primenjivati za dalja istraživanja. Razvijeni model jeimao odstupanja u dozvoljenim granicama, pa je korišćen za analizu još dve diskkočnice, koje su se razlikovale po konstrukciji rebara diska. Primenjeni oblicirebara kod kočnog diska su: radijalni, zakrivljeni i stubičasti.Danas se od kočnih diskova očekuje da odvedu što veću količinu toplote u okolinu,odnosno, da imaju sposobnost da omoguće dobro hlađenje u širokom opsegu brzina. Krozanalizu koja je izvršena u softverskom paketu ANSYS, ali pomoću modula Fluid Flow(Fluent), pokazano je da oblik rebara utiče u velikoj meri na rasipanje toplote, kao i dase kočni disk sa zakrivljenim rebrima najmanje zagreva. Rezultati analize pokazuju dakočni disk sa zakrivljenim rebrima omogućava da vazduh velikom brzinom prođe izmeđurebara i da se na taj način velika količina toplote odvede u okolinu. U ciljupredviđanja vrednosti temperature na najopterećenijem delu kočne pločice, razvijen jemodel za predikciju temperature kočnih pločica visoke tačnosti, u kome su varirani:masa vozila, brzina kretanja, kočni pritisak i vreme zaustavljanja.Rezultati ove doktorske disertacije, kao što su realizovani probni sto i numeričkimodel, mogu poslužiti firmama koje se bave proizvodnjom kočnih diskova i kočnihpločica za predviđanje njihovog ponašanja u eksploataciji. Takođe, dobijenieksperimentalni rezultati mogu se koristiti za kreiranje virtuelnih modela zaispitivanje disk kočnice. Virtuelni model razvijen za potrebe ove doktorskedisertacije može se koristiti za razvoj/poboljšanje kočnog diska i kočnih pločica ucilju smanjenja troškova razvoja.

Description (srp)

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Object languages

Serbian

Date

2021

Rights

Creative Commons License
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CC BY-ND 3.0 AT - Creative Commons Attribution-NoDerivs 3.0 Austria License.

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