Numerical modelling and evaluation of the temperature distribution in an Earthmover Tyre: establishing a safe operating envelope.

Marais, Jeannette (2017-03)

Thesis (MEng)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: The explosion of haul truck tyres due to internal heat generation during operation can lead to loss of life and severe damage to the vehicle and the surroundings. This thesis describes the development of a finite element model for the numerical modelling of a 23.5R25 earthmover tyre using MSC.Marc/Mentat. The numerical model is subjected to different combinations of inflation pressures, loads and rolling velocities to obtain a working knowledge of the heat generation in the tyre cross-section as a function of these conditions. This function is used to give an indication to the maximum temperature in the tyre's cross-section during steady-state heat transfer conditions. As a result, this function can be used to ensure that maximum temperature in the tyre cross-section remains within a safe operating envelope to prevent the explosion of these tyres. The static tyre deformation obtained from the numerical analysis was compared to experimental data provided by the manufacturer to evaluate the accuracy of the proposed numerical model. From the results obtained it was concluded that the numerical tyre results were consistent with the experimental data within a maximum percentage difference of 3.9 %, 2.5 %, 3.4 % and 9.7 % for the vertical tyre deflection, the overall tyre width, the tyre's contact width and the tyre's contact length, respectively. Thus, it was concluded that the numerical model represented the deformation of the actual tyre to an acceptable extent. The thermal results could not be experimentally verified and therefore its accuracy could not be determined explicitly. However, from the theoretical description of the method used to simulate the heat generation rate in numerical models, it was evident that the heat generation rate will ultimately be a function of the tyre's deformation and its rolling velocity. Thus, the assumption was made that the accuracy of the static tyre behaviour could be used to provide some measure of verification of the thermal results. Furthermore, thermal results were consistent with the expected temperatures observed in industry when the tyre is subjected to similar conditions. Thus, the thermal results were used to establish an equation that predicted the expected maximum temperature in the tyre's cross-section as a function of the tyre's vertical deflection, its velocity and the ambient temperature of the surroundings. This equation could in turn be used to maintain allowable temperature conditions in the tyre during operation. Furthermore, it was concluded that the rolling velocity of the tyre will have the most significant effect on the heat generation in the tyre and therefore should be managed accordingly.

AFRIKAANSE OPSOMMING: Die ontploffng van myntrok-bande as gevolg van die interne hitte wat in die deursnit van die band gegenereer word kan lei tot die verlies van lewe en ernstige skade aan die voertuig en die omgewing. Hierdie tesis beskryf die ontwikkeling van 'n eindige element model van 'n 23.5R25 grondverskuiwingsband met behulp van MSC.Marc/- Mentat. Die numeriese model word onderwerp aan verskillende kombinasies van inflasiedrukke, laste en snelhede om die hitte-generasie in die deursnit van die band te evalueer as 'n funksie van hierdie toestande. Hierdie funksie word dan gebruik om 'n aanduiding van die maksimum temperatuur in die band se deursnit tydens ewewigstoestand te voorspel. Gevolglik kan hierdie funksie gebruik word om te verseker dat die maksimum temperatuur in die deursnit van die band binne 'n veilige werkstoestand bly om die ontploffing van hierdie bande te voorkom. Die statiese band se vervorming is met eksperimentele data soos verskaf deur die vervaardiger vergelyk om die akkuraatheid van die voorgestelde numeriese model te bepaal. Op grond van hierdie resultate was dit duidelik dat die numeriese resultate in ooreenstemming met die gemete data is met 'n maksimum persentasie verskil van 3.9 %, 2.5 %, 3.4 % en 9.7 % vir die vertikale band defleksie, die algehele bandwydte, die kontak breedte van die band en die kontak lengte van die band, onderskeidelik. Dus is die gevolgtrekking gemaak dat die vervorming van die numeriese model die werklike vervorming van die band tot 'n aanvaarbare mate voorstel. Die termiese resultate kon nie met eksperimentele resultate vergelyk word om die akkuraatheid daarvan te bepaal nie. Vanuit die teoretiese beskrywing van die metode wat gebruik is om die hitte-generasie in numeriese modelle te bepaal, was dit duidelik dat die hitte-generasie in die band 'n funksie van die band se vervorming en snelheid is. Dus is die aanname gemaak dat die akkuraatheid van die statiese analise gebruik kan word om 'n mate van verifikasie van die termiese resultate te verskaf. Verder was dit ook duidelik die termiese resultate in ooreenstemming was met die verwagte temperature in industrie indien die bande onderwerp is aan soortgelyke omstandighede. Dus is die termiese resultate gebruik om 'n vergelyking te ontwikkel wat die verwagte maksimum temperatuur in die deursnit van die band voorspel as 'n funksie van die band se vertikale defleksie, snelheid en die omgewingstemperatuur. Hierdie vergelyking kon dan op sy beurt gebruik word om toelaatbare temperatuur kondisies in the band tydens werking te handhaaf. Vanuit hierdie beskrywing is dit duidelik dat die band se snelheid die mees beduidende invloed op die hitte-generasie in die band sal hê en daarom moet dit ooreenstemmend beheer word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101073
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