The determination of the lifespan of polymer electric motor housing

Obravnavano je bilo obremenjevanje ohišja elektromotorja iz polimera. Polimeri izkazujejo viskoelastično obnašanje, zato se njihove mehanske lastnosti tekom življenjske dobe izdelka spreminjajo, kar lahko vpliva na funkcionalnost izdelka. Obravnavali smo časovno odvisno mehansko lastnost lezenja izbranega polimera. Ker se polimerom mehanske lastnosti spreminjajo tudi s temperaturo, smo se osredotočili na primernost materiala znotraj temperaturnega razpona delovanja elektromotorja. Glede na specifikacije elektromotorja so bili določeni pogoji, na podlagi katerih je bil izbran ustrezen polimer, PES. Upoštevajoč geometrijsko obliko polimernega ohišja, sta bili določeni kritični mesti, kjer se pojavita lezenje (ležajno mesto) ter relaksacija (vijačno mesto) polimera. Relaksacija je bila preprečena z uporabo tulk, medtem ko smo za napoved obnašanja materiala zaradi lezenja pod trajno obremenitvijo, izvedli meritve strižnega modula lezenja polimera PES. Glede na kriterij maksimalnih radialnih pomikov in predpisano življenjsko dobo je PES iz stališča lezenja materiala primeren do temperature 90 °C. Izvedena je bila mehanska analiza ohišja na osnovi metode končnih elementov, upoštevajoč temperaturni razpon delovanja elektromotorja. Ugotovljeno je bilo, da se napetosti nahajajo v elastičnem območju.This thesis discussed loading of electric motor polymer housing. Polymers are known for their high viscoelasticity, hence their mechanical properties change over the lifespan of a product, and this can modify product functionality. The observed property in our case was creep, a time-dependent mechanical property. Since the mechanical properties of polymers vary with temperature, too, the focus was on material suitability inside the temperature range of electric motor operation. According to electric motor specifications, conditions were determined, on the basis the poylmer PES was selected. According to the polymer housing starting model, two critical points where creep (bearing point) and relaxation (screw point) of the polymer were determined. Compression limiters can be used to prevent relaxation. We also predicted the way the material will react due to creep under permanent load by performing measurements of the creep shear modulus of PES. According to maximal radial extension and its set lifespan, PES is, from the point of view of creep, a suitable material up to 90 °C. A mechanical finite elements analysis in the temperature range of electric motor operation was conducted, showing that there are elastic stresses in the PES material