Vpliv jeklenih vlaken v kompozitnem tornem materialu : diplomsko delo

Miladinovska, Julija (author), Nagode, Aleš (mentor), Čurila, Sven (co-mentor)

Torni materiali za zavorne sisteme običajno vsebujejo kovinske sestavine za izboljšanje njihove odpornosti proti obrabi, toplotne prevodnosti in trdnosti. Različne kovine, kot so baker, jeklo, železo, med, bron in aluminij, se v tornih materialih uporabljajo v obliki vlaken ali delcev. Na trenje in obrabo tornih materialov vplivajo vrsta, morfologija in trdota kovinskih sestavin. Trenutno se v industriji tornih materialov veliko uporabljajo jeklena vlakna, saj zagotavljajo dobro odpornost proti obrabi in ohranjajo učinkovitost trenja pri povišani temperaturi. Vendar pa lahko jeklena vlakna povzročijo čezmerno obrabo zavornega diska, zaradi česar nastanejo v zavornem disku velike razlike v debelini, kar je glavni vzrok za tresenje ali vibriranje zavor. Vzrok je v visoki trdoti in dobrem kovinskem oprijemu jeklenih vlaken v tornem materialu. Koeficient trenja, dobljen iz čistega stika med kovino in kovino, pa se pogosto razlikuje od koeficienta trenja kompozita, ki vsebuje kovine in drsi ob kovinsko površino; neskladje je posledica vpliva drugih sestavin v kompozitu. O vlogi kovinskih vlaken v tornih materialih in interakcij različnih sestavin tornih materialov na drsnem vmesniku pri zavornem delovanju ni veliko znanega. V diplomskem delu smo obravnavali vpliv armaturnih delcev v kompozitnem tornem materialu. Raziskovali smo učinek različnih vsebnosti jeklenih vlaken na trenje in obrabo različnih tornih parov zavor. Namen naloge je bil preučevati lastnosti tornega materiala glede na njegove mehanske lastnosti, kot so obraba, strižna trdnost in tribološke lastnosti v prisotnosti armaturnih vlaken. Za izvedbo testov so bile izdelane štiri različne mešanice kompozitnih tornih materialov z različno vsebnostjo jeklenih vlaken. Eksperimentalno delo je obsegalo pripravo zmesi, toplo stiskanje vzorcev in toplotno obdelavo. Poleg tega pa še izdelavo namenskega orodja za epruvete strižnega preizkusa. Za testiranje obrabne odpornosti in merjenja koeficienta trenja smo uporabili Kraussov test ter strižni test. Za karakterizacijo mikrostrukture tornih materialov smo uporabili svetlobni in vrstični elektronski mikroskop (SEM) z energijsko disperzijsko spektroskopijo rentgenskih žarkov (EDS).

• Language: Slovenian
• Keywords: torni material, jeklena vlakna, kompozit, obraba, strižna trdnost, mikroskopija.
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Place of publishing: Ljubljana
• Publisher: J. Miladinovska
• Year: 2023
• Number of pages: XII, 38 str.
• PID: 20.500.12556/RUL-150809
• UDC: 669
• COBISS.SI-ID: 168504323
• Publication date in RUL: 23.09.2023

Secondary language

• Language: English
• Title: Effect of steel fibers in composite friction material : diploma work

Abstract

Friction materials for brake systems typically contain metallic components to improve their wear resistance, thermal conductivity and strength. Various metals such as copper, steel, iron, brass, bronze, and aluminum are used in friction materials the form of fibers or particles. Friction and wear of friction materials are affected by the type, morphology, and hardness of the metallic components. Steel fibers are currently used in the friction materials industry as they provide good wear resistance and maintain frictional performance at elevated temperature. However, steel fibers can cause excessive wear on the disc, resulting in large thickness variations in the disc, which is the main cause of brake shaking or vibration. The reason is the high hardness and good metal adhesion of the steel fibers to the friction material. The friction coefficient obtained from pure metal-to-metal contact, however, is often different from the friction coefficient of a composite containing metal sliding against a metal surface; the discrepancy is due to the influence of other components in the composite. Not much is known about the role of metal fibers in friction materials in braking performance due to the interactions of different components of friction materials at the sliding interface. In the thesis, we discussed the influence of reinforcement particles in composite friction material. We investigated the effect of different contents of steel fibers on the friction and wear of different brake friction pairs. The purpose of the assignment was to investigate the properties of the friction material in terms of its mechanical properties such as wear, shear strength and tribological properties in the presence of reinforcing fibers. Four different mixtures of composite friction materials with different content of steel fibers were produced for the tests. The experimental work included the preparation of the mixture, hot pressing of the samples and heat treatment. In addition, the manufacture of a dedicated tool for shear test tubes. To test wear resistance and measure the friction coefficient, we used the Krauss test and the shear test. Light and scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS) was used to characterize the microstructure of friction materials.

• Keywords: friction material, steel fibers, composite, wear, shear strength, microscopy.