Napetosti v cementiranem in kaljenem zobniku z ravnimi zobmi

Gaberšček, Gregor (author), Nagode, Marko (mentor), Šeruga, Domen (comentor)

Cementacija in kaljenje omogočata, da ima zobnik žilavo jedro in trdo površino, zato imajo termično obdelani zobniki boljšo trdnost in obrabno odpornost v primerjavi s termično neobdelanimi. Postopek utrjevanja površine izboljša odpornost zobnika na sunkovite mehanske obremenitve in na obrabo. V tem delu smo se posvetili izključno obravnavi trdnosti zobnika. Primerjali smo, kakšen zobnik bolje prenaša statično mehansko obremenitev ter vzroke za to. Postopek termične obdelave smo simulirali v programu ANSYS z metalurškim paketom DANTE, s čimer smo predvideli porazdelitev zaostalih napetosti. To je bilo začetno stanje ob dodajanju mehanske obremenitve na zob zobnika. Za primerjavo smo simulirali enak zob, ki je bil deležen zgolj mehanske obremenitve. Tak primer smo tudi analitično preračunali. Pri iskanju vzrokov za nastalo stanje smo ugotovili, da se pri nastajanju martenzita povečajo tlačne napetosti. Te skupaj s krčenjem zaradi ohlajanja ustvarijo površinsko plast s tlačnimi napetostmi. Videli smo, da v vsakem primeru ta plast vpliva na boljše prenašanje mehanske obremenitve. Na koncu so analitični rezultati odstopali od numeričnih v vrednostih do 150 MPa. Ob upravičenih razlogih, kot so izbira robnih pogojev, mesta rezultatov in koeficienti v enačbah smo sklepali, da so pravilni. Potrdili in pojasnili smo, zakaj so termično obdelani zobniki boljši kot termično neobdelani.

• Language: Slovenian
• Keywords: zobniki, numerične analize, analitika, ogljičenje, kaljenje, zaostale napetosti
• Work type: Final paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FS - Faculty of Mechanical Engineering
• Place of publishing: Ljubljana
• Publisher: [G. Gaberšček]
• Year: 2021
• Number of pages: XII, 31 str.
• PID: 20.500.12556/RUL-129901
• UDC: 621.833:621.785.5:519.6(043.2)
• COBISS.SI-ID: 82835203
• Publication date in RUL: 09.09.2021

GABERŠČEK, Gregor, 2021, Napetosti v cementiranem in kaljenem zobniku z ravnimi zobmi [online]. Bachelor’s thesis. Ljubljana : G. Gaberšček. [Accessed 18 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=129901

Secondary language

• Language: English
• Title: Stresses in cemented and quenched spur gear

Abstract

Cementation and hardening allow the gear to have a tough core and a hard surface, so heat-treated gears have better strength and wear resistance compared to non heat-treated ones. The surface hardening process improves the resistance of the gear to shock mechanical loads and wear. In this paper, we have focused exclusively on dealing with gear strength. We compared which gear better withstands static mechanic load and the reasons for this. The heat treatment process was simulated in the ANSYS program with the DANTE metallurgical package, in order to be able to predict the distribution of residual stresses. This was the initial condition when adding mechanical load to the gear tooth. For comparison, we simulated the same tooth that received only a mechanical load. Such an example was also analytically recalculated. When searching for the causes of this condition, we found that the formation of martensite increases the compressive stresses and these, together with the shrinkage due to cooling, create a surface layer with compressive stresses. We have seen that in any case, this layer has an effect on better load tolerance. In the end, the analytical results deviated from numerical ones up to 150 MPa. Given the justified reasons, such as the chosen boundary conditions, the places of the results and the coefficients in the equations, we concluded that they were correct. We confirmed and explained why heat-treated gears are better than non heat-treated ones

• Keywords: spur gears, numerical analysis, analytics, carburising, quenching, residual stresses