Development and optimization of aluminum nanocomposites for production of tribological elements

Rezime: Pri razvoju i proizvodnji novih materijala i elemenata eksperiment ima značajnu ulogu. Pristup eksperimentalnom istraživanju ne može se zamisliti bez upotrebe dizajna eksperimenta čijom primenom se pristupa sistematskom načinu planiranja eksperimenta, izvođenju i interpretaciji rezultata eksperimenata. Za potrebe ovog rada su razvijeni, a u radu su analizirani novi nanokompoziti sa A356 osnovom ojačani SiC i Al2O3 nanočesticama različitih veličina i sadržaja. U okviru ispitivanja određene su i prikazane fizičke i mehaničke karakteristike nanokompozita. U radu su sprovedena tribološka ispitivanja primenom dizajna eksperimenta za prvu seriju materijala koji do trenutka proizvodnje nisu bili predmet ranijih istraživanja. Nanokompoziti su proizvedeni sa malim masenim sadržajem ojačavajućih nanočestica primenom modifikovanog kompokasting procesa. Ostvareni eksperimentalni rezultati prvom serijom materijala ukazali su na pravac i tok razvoja nanokompozita sa novim sadržajem ojačavača. Druga faza istraživanja nanokompozita je usmerena na tribološka ispitivanja jer se prvom serijom materijala dokazalo da nije ostvareno značajno poboljšanje u mehaničkim i tribološkim karakteristikama nanokompozita. Izvršena je analiza pohabanih površina nanokompozita što je od velikog značaja za praktičnu primenu ovih materijala. Primenom optimizacionih metoda izvršena je višekriterijumska optimizacija i određena optimalna kombinacija faktora kojom se postižu najbolje karakteristike nanokompozita. Na osnovu eksperimentalnih istraživanja ostvarenih u ovoj disertaciji može se zaključiti da su ostvarena poboljšanja u mehaničkim i tribološkim karakteristikama nanokompozita u poređenju sa osnovnom legurom. Područje primene aluminijumskih nanokompozita neprekidno se širi s obzirom na kombinaciju svojstava koja se mogu postići dodavanjem različitih ojačavača. Dobijene karakteristike razvijenih nanokompozita omogućavaju njihovo korišćenje pri modeliranju i naponsku analizu različitih mašinskih elemenata u CAD softveru. Izvršena je numerička analiza zupčastih parova i ustanovljeno je da se maksimalne vrednosti ekvivalentnog napona javljaju u podnožju zubaca spregnutih zupčanika. Primenom nanokompozita za izradu zupčastog para može se postići veći prenos snage u odnosu na zupčasti par izrađen od osnovne legure, zatim smanjuje se pojava inicijalnih prslina, masa prenosnika, i nivo buke i vibracije u zupčastim prenosnicima manjih snaga, a povećava se njihova otpornost na habanje.Abstract: The experiment has a significant role in the development and production of new materials and machine elements. An approach to experimental research cannot be imagined without design of experiment usage, which repesents a systematic way of planning an experiment, performing and interpreting the experiments results. For the purposes of this thesis, new nanocomposites with A356 base reinforced with SiC and Al2O3 nanoparticles of different sizes and contents were developed and analyzed. Within this research, the physical and mechanical characteristics of nanocomposites were determined and presented. Tribological tests were performed using the design of experiment for the first series of materials that were not the subject of previous research, in today’s literature sources, until the time of production. Nanocomposites were produced with a low mass content of reinforcing nanoparticles using a modified compocasting process. The achieved experimental results with the first series of materials indicated the direction and course of development of nanocomposites with a new content of reinforcements. The second phase of nanocomposite research is focused on tribological tests because the first series of materials didn’t proved the significant improvement in the mechanical and tribological characteristics of nanocomposites is achieved. The analysis of worn surfaces of nanocomposites was performed, which is of great importance for the practical application of these materials. By applying optimization methods, multicriteria optimization was performed and the optimal combination of factors was determined for which gives the nanocomposites of the best characteristics. Based on the experimental research achieved in this dissertation, it can be concluded that improvements have been made both in the mechanical and tribological characteristics of nanocomposites compared to the base alloy. Application field of aluminum nanocomposites is constantly expanding due to the combination of properties that can be achieved by adding different reinforcements. The obtained characteristics of the developed nanocomposites enable their usage in modeling and stress analysis of various machine elements in CAD software. Stress analysis of gear pairs was performed and it was concluded that the maximum values of equivalent stress occur at the base of the teeth of the coupled gears. The use of nanocomposites for the production of gear pair can achieve a higher power transmission compared to the gear pair made of base alloy, then reduces the occurrence of initial cracks, gear mass, and noise and vibration levels in gears of lower power, and increases their wear resistance