Analiza obrabljenosti kolesnega ležaja avtomobila

JELENKO, MATEVŽ (author), Geršak, Gregor (mentor), Ogorevc, Jaka (comentor)

Magistrska naloga zajema analizo kolesnega ležaja avtomobila. Ležaji so osnovni strojni elementi, ki omogočajo vodenje vrtečih strojnih delov in zagotavljajo najmanjše torno trenje in obrabo tornih površin. Kolesni ležaji, ki smo jih preverjali, spadajo v skupino radialnih kotalnih ležajev s krogličnimi ali stožčastimi kotalnimi telesi. Sedaj se v praksi preverja stanje kolesnih ležajev, tako, da mehanik, ko je vozilo na dvigalu, zavrti kolo in pozorno posluša, kakšne zvoke pri tem kolesni ležaj oddaja. Če presodi, da je ležaj obrabljen, se ga zamenja, v primeru pa, da ni popolnoma prepričan, se opravi še testna vožnja, kjer med vožnjo posluša, če nastajajo zvoki, ki so znak obrabljenega ležaja. Trenutna metoda je precej subjektivna, saj je odvisna od mehanikove sposobnosti poslušanja in njegove presoje, ki temelji na njegovih izkušnjah. Naloga je bila zastavljena tako, da smo del, kjer mehanik zavrti kolo in posluša zvok, zamenjali z meritvijo, ki smo jo opravili z mikrofonom, med testno vožnjo pa smo opravili še dodatno merjenje s pospeškometrom. Meritev s pospeškometrom je predstavljala referenčno metodo. Takšna metoda je tudi v skladu z metodo, ki jo podaja mednarodni standard za obrabo ležajev v industrijskem okolju. Merjenje z mikrofonom poteka na podoben način, kot poteka ocena stanja ležaja sedaj. Kolo še vedno zavrti mehanik, na mesto, kjer pa mehanik postavi uho in posluša zvok, ki ga oddaja ležaj, pa sedaj postavimo mikrofon. Zvok posnamemo in ga nato v programskem okolju DewesoftX dodatno obdelamo, da lahko ocenimo stanje ležaja. Če po obdelavi še vedno nismo popolnoma prepričani o stanju kolesnega ležaja, opravimo še meritev s pospeškometrom. Merjenje s pospeškometrom poteka med vožnjo. V bližino kolesnega ležaja, za katerega sumimo, da je obrabljen, namestimo pospeškometer. Nato med testno vožnjo opravimo meritev. Tako kot pri oceni stanja s pomočjo mikrofona tudi tukaj podatke meritev obdelamo v programskem okolju DewesoftX. Po opravljeni obdelavi lahko natančno analiziramo in ocenimo stanje ležaja. Pri obrabljenem ležaju lahko z uporabo kinematičnega modela ležaja določimo tudi, katera komponenta ležaja je uničena. Z mikrofonom smo opravili meritve na več kot 70 kolesnih ležajih. V večini primerov se je mehanikova ocena stanja kolesnega ležaja ujemala z oceno stanja na podlagi meritev opravljenih z mikrofonom. S pospeškometrom pa smo opravili več kot 15 meritev. V vseh primerih smo lahko jasno videli in ocenili stanje ležaja. S primerjavo ocen, ki smo jih podali na podlagi meritev, opravljenih z mikrofonom, in ocen, ki smo jih podali na podlagi meritev opravljenih s pospeškometrom, smo ugotovili, da ni bilo primera, da bi na podlagi meritve z mikrofonom ocenili stanje ležaja kot sprejemljivo, nato pa bi na podlagi meritve s pospeškometrom ocenili, da je ležaj obrabljen. Smo pa imeli primer, ko smo na podlagi meritve z mikrofonom ocenili kot obrabljen ležaj, nato pa na podlagi meritve s pospeškometrom ocenili ležaj kot sprejemljiv. Metoda nam je omogočila podrobno analizo okvare ležajev. Ugotovili smo, da bi v mehaničnih delavnicah in servisih lahko za oceno stanja kolesnega ležaja uporabljali mikrofon in pospeškometer. Ocenjevanje stanja kolesnega ležaja na podlagi meritve mikrofona in pospeškometra ima prednost, ker za ocenitev ne potrebujemo mehanika. Stanje ležaja lahko oceni nekdo brez izkušenj v mehanični delavnici. Slabost uvedbe mikrofona in pospeškometra je velika začetna investicija in časovna potratnost namestitve merilnega sistema. Kot možnost nadgradnje vidim preventivni merilni sistem integriran serijsko v vozilo. S takšnim merilnim sistemom bi bilo mogoče zaznati že zgodnjo fazo obrabe ležaja, poslati opozorilno obvestilo v nadzorni sistem vozila in se izogniti morebitnim nadaljnjim poškodbam na vozilu.

• Language: Slovenian
• Keywords: kolesni ležaj, obraba, merjenje, mikrofon, pospeškometer, Dewesoft
• Work type: Master's thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2023
• PID: 20.500.12556/RUL-144946
• COBISS.SI-ID: 148096515
• Publication date in RUL: 24.03.2023

Secondary language

• Language: English
• Title: Car wheel bearing failure analysis

Abstract

The master's thesis covers the analysis of a car wheel bearing. Bearings are basic machine elements that enable the guidance of rotating machine parts and ensure minimum friction and wear of friction surfaces. The wheel bearings we analyzed were ball bearing and tapered roller bearings. In practice the condition of the wheel bearings is checked by lifting the vehicle, then mechanic turns the wheel and listens carefully to what sounds the wheel bearing makes. If he judges that the bearing is worn, it is replaced, but if he is not completely sure, a test drive is carried out, where he listens while driving for sounds that are a sign of a worn bearing. The current method is quite subjective as it depends on the mechanic's ability to listen and his judgment based on his experience. The task was set in such a way that we replaced the part where the mechanic turns the wheel and listens to the sound with a measurement made with a microphone, and during the test drive we made an additional measurement with an accelerometer. The accelerometer measurement was the reference method. Such a method is also in accordance with the method given by the international standard for mechanical vibration in an industrial environment. The measurement with a microphone is carried out in a similar way to the assessment of the condition of the bearing now. The wheel is still turned by the mechanic, but in the place where mechanic places his ear and listens to the sound emitted by the bearing, we now place a microphone. We record the sound and then further process it in the DewesoftX software so that we can assess the state of the bearing. If, after analysis, we are still not completely sure about the condition of the wheel bearing, we also measure it with an accelerometer. Accelerometer measurement takes place while driving. We place an accelerometer near the wheel bearing that we suspect is worn. Then we take a measurement during the test drive. Data is analyzed in the same software environment as measurement we made with a microphone. After processing, we can accurately analyze and assess the condition of the bearing. In the case of a worn bearing, the kinematic model of the bearing can also be used to determine which component of the bearing is destroyed. We performed measurements on more than 70 wheel bearings with a microphone. In most cases, the mechanic's assessment of the condition of the wheel bearing matched the assessment of the condition based on the measurements made with the microphone. We made more than 15 measurements with the accelerometer. In all cases, we could clearly see and assess the condition of the bearing. By comparing the ratings given based on the measurements made with the microphone and the ratings given based on the measurements made with the accelerometer, we found that there was no case in which the condition of the bearing was assessed as acceptable based on the measurements made with the microphone, and then, based on the measurement with the accelerometer, we would estimate that the bearing is worn. However, we had a case where, based on a measurement with a microphone, we assessed the bearing as worn, and then, based on a measurement with an accelerometer, the bearing was assessed as acceptable. We found that a microphone and an accelerometer could be used in mechanical workshops and repair shops to assess the condition of the wheel bearing. Evaluating the condition of the wheel bearing based on the microphone and accelerometer measurements has the advantage that a mechanic is not needed for the evaluation, as the condition of the bearing can be evaluated by someone without experience in a mechanic's workshop. The disadvantage of introducing a microphone and accelerometer is the large initial investment and the time-consuming installation of the measurement system. As an upgrade option, I see a preventive measurement system integrated as standard in the vehicle. With such a measuring system, it would be possible to detect the early stage of bearing wear, send a warning message to the vehicle's control system and avoid possible further damage to the vehicle.

• Keywords: wheel bearing, wear, measurement, microphone, accelerometer, Dewesoft