doktorska disertacija
Povzetek
Metalurgija prahov je že dodobra uveljavljen proizvodni proces v industrijah z velikoserijsko proizvodnjo. V avtomobilski industriji so tako izdelani npr. različni manjši nosilci kompleksnih oblik, zobniki oljnih črpalk in njihova ohišja. Napredek tehnologije in materialov pa že nakazuje prodor kovinskih prahov tudi v bolj obremenjene avtomobilske dele; npr. ojnice in zobniki v menjalniku.
Predlagan računski model izračuna upogibne trdnosti sintranih zobnikov temelji na dobrem poznavanju materialnih parametrov in geometrije obravnavanega zobnika. S klasičnim kvazistatičnim nateznim preizkusom so ugotovljene osnovne mehanske lastnosti materiala. Dinamičen odziv je ugotovljen glede na parametre Basquinove enačbe, ki so izračunani iz rezultatov testiranj pri utripni obremenitvi. Zaradi velike verjetnosti nastanka razpok med proizvodnim procesom je analiziran vpliv prisotnosti razpoke tako, da so določeni parametri Parisove enačbe, prag širjenja razpoke in lomna žilavost. Rezultati so pokazali izjemno pomembnost preprečevanja nastanka plastnih razpok, saj le-te kritično vplivajo na nosilnost sintranega izdelka. Tako kot običajno jeklo, se lahko tudi sintrano jeklo po sintranju še dodatno toplotno obdela z različnimi toplotnimi obdelavami, zato je vpliv poboljšanja, ki se navzven vidi kot sprememba mehanskih lastnosti materiala, preučen v analizi mikrostrukture.
Računski model je predstavljen na primeru, ki implementira izmerjene materialne parametre in poznano geometrijo zobnika. Napetostno stanje v korenu zoba je z numeričnimi postopki ugotovljeno na podlagi geometrije in materialnih parametrov in se nato oplemeniti z izračunanimi parametri Basquinove enačbe do verjetnostne napovedi intervala, v katerem se pričakuje zlom zoba sintranega zobnika. Testiranje sintranih zobnikov na modificiranem FZG preizkuševališču pokaže, da predstavljen računski model ob znani geometriji in materialnih parametrih z natančnostjo velikostnega razreda napove dobo trajanja sintranega zobnika.
Ključne besede
metalurgija prahov;utrujanje;upogibna trdnost;sintrani zobniki;
Podatki
Jezik: |
Slovenski jezik |
Leto izida: |
2015 |
Tipologija: |
2.08 - Doktorska disertacija |
Organizacija: |
UM FERI - Fakulteta za elektrotehniko, računalništvo in informatiko |
Založnik: |
[M. Šori] |
UDK: |
621.833:669.14-138(043.3) |
COBISS: |
280410368
|
Št. ogledov: |
2027 |
Št. prenosov: |
234 |
Ocena: |
0 (0 glasov) |
Metapodatki: |
|
Ostali podatki
Sekundarni jezik: |
Angleški jezik |
Sekundarni naslov: |
Computational model for bending strength determination of sintered gears |
Sekundarni povzetek: |
Powder metallurgy is a well-established production process in large-series production industries. Many parts in automotive industry, such as small complex brackets, oil pump gears and housings, are made with this technology. Its quick development and improvement of metal powders show a great potential to be used as a favorable process also in more demanding car parts, e.g. connecting rods and transmission gears.
Proposed computational model for bending strength determination of sintered gears is based on well-known material properties and geometry of treated gear. Classical quasi-static pull test is used to determine basic mechanical properties. Dynamic response of material is based on Basquin`s equation parameters, which are calculated from dynamic tests, performed at pulsating load. Due to high probability of layer cracks formation during production process, effect of crack presence is analyzed with determined Paris equation parameters, crack formation threshold and fracture toughness. Results showed prevention of layer cracks has extreme importance, as they significantly affect the load capacity of a sintered part. As well as conventional steel, sintered steel can also undergo an additional heat treatment with different procedures. Therefore, hardening effects are studied as change in mechanical properties as well as in microstructure analysis.
Computational model, that implements measured material properties and known geometry of a gear, is presented on a particular case for better understanding. Numerical procedures are used to determine gear tooth root stress field, which is then complemented with calculated parameters of Basquin expression to prediction of an interval, in which gear tooth brakeage is expected with known probability. Tests of sintered gears on modified FZG rig showed that presented model yields fatigue lifetime predictions within one size class for a sintered gear with known geometry and material properties. |
Sekundarne ključne besede: |
powder metallurgy;fatigue;bending strength;sintered gears;Zobniki;Disertacije;Trdnost;Računski modeli; |
URN: |
URN:SI:UM: |
Vrsta dela (COBISS): |
Doktorska disertacija |
Komentar na gradivo: |
Univ. v Mariboru, Fak. za strojništvo |
Strani: |
XX, 117 str. |
ID: |
8740353 |