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Influence of gear surface roughness on the pitting and micropitting life
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).ORCID iD: 0000-0001-9346-7467
Department of Instrument Science and Technology, Beijing University of Technology, Beijing, China.
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).ORCID iD: 0000-0003-2489-0688
2020 (English)In: Proceedings of the Institution of mechanical engineers. Part C, journal of mechanical engineering science, ISSN 0954-4062, E-ISSN 2041-2983, Vol. 234, no 24, p. 4953-4961Article in journal (Refereed) Published
Abstract [en]

Pitting and micropitting are the two main gear rolling contact fatigue modes. It is widely accepted that micropitting will lead to pitting; however, the relationship between pitting and micropitting life needs further investigation. In this work, micropitting and pitting tests were performed on an FZG back-to-back test rig using standard FZG PT-C and GF-C gears. The gear tooth profile change due to micropitting and pitting damage was measured in situ in the gearbox using a profilometer after each test. The gear surface roughness parameters were calculated from the measured tooth profile. A Gaussian low pass filter with cut off length (Formula presented.) mm was applied to the measured tooth profile to obtain the waviness. The calculated roughness parameters and the obtained tooth profile with waviness for each test were imported into the KISSsoft software to calculate the contact stress and specific film thickness at the corresponding load stage. Experimental results show that smooth gear surface can reduce or even avoid micropitting damage, but could lead to a reduction in pitting life.

Place, publisher, year, edition, pages
SAGE Publications Ltd , 2020. Vol. 234, no 24, p. 4953-4961
Keywords [en]
FZG, micropitting, pitting, roughness, waviness, Low pass filters, Software testing, Surface roughness, Back-to-back tests, Contact Stress, Cut-off length, Pitting damage, Rolling contact fatigue, Roughness parameters, Specific film thickness, Surface roughness parameters, Gear teeth
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
URN: urn:nbn:se:kth:diva-287925DOI: 10.1177/0954406220931541ISI: 000539652700001Scopus ID: 2-s2.0-85086270569OAI: oai:DiVA.org:kth-287925DiVA, id: diva2:1513355
Note

QC 20201230

Available from: 2020-12-30 Created: 2020-12-30 Last updated: 2022-06-25Bibliographically approved
In thesis
1. A Comparative Investigation of Gear Performance BetweenWrought and Sintered Powder Metallurgical Steel: Utilizing In-situ Surface Profile Measurements to Investigate theInitiation and Evolution of Micropitting and Pitting Damage
Open this publication in new window or tab >>A Comparative Investigation of Gear Performance BetweenWrought and Sintered Powder Metallurgical Steel: Utilizing In-situ Surface Profile Measurements to Investigate theInitiation and Evolution of Micropitting and Pitting Damage
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Vehicle electrification is a strong trend that introduces new challenges, such as increased input speed of the transmission and increased power density. Alsothe noise emittance of the gearbox is of increasing importance, as the sound of the gearbox is no longer masked by the internal combustion engine. Pressed and sintered powder metallurgical steel could be an interesting alternative towrought steel; the internal porosity has a dampening effect on the noise, and gears can be made in a fast and efficient process. However, current manufacturing of powder metallurgical steel has significant performance limitations. The Nanotechnology Enhanced Sintered Steel Processing project aims to reduce the gap in performance between conventional steel and powder metallurgical steel. One of the potential benefits is that with the inclusion of nano-powder the density can be increased. To validate the new material, its performance needs to be compared to the performance of current generation powder metallurgical materials and also to wrought steel. It is therefor crucial to be able to test and evaluate different materials and gears. This thesis has developed methods for testing, comparing, and evaluating the performance of gears. Powder metallurgical steel has been tested and compared to wrought steel; the efficiency as well as pitting life have been investigated in an FZG test rig. Also the effects of different surface finishing operations have been evaluated. The gear flanks were measured in-situ in the gearbox using a stylus instrument; an optimisation routine was created to fit the measurements to the theoretical involute profile. This enabled an in-depth analysis of surface wear and presented an opportunity to investigate micropitting initiation. It was found that the damage mechanisms of wrought steel and powder metallurgical steel are similar and related to the surface finishing method. However, the powder metallurgical steel was also susceptible to sub-surface cracks. Superfinished gears can be negatively influenced by the lack of tip relief as cracks initiate in the surface layer of the root, rapidly destroying the tooth.

Abstract [sv]

Den pågående elektrifieringen ställer nya krav på transmissioner och kugghjul. För att minska förluster bör elmotorn användas vid höga varvtal, dessutomär ljudnivån allt mer viktig då förbränningsmotorns ljud inte längre döljer det vinande ljudet från transmissionen. Pressade och sintrade komponenter av pulvermetall är ett intressant alternativ till konventionellt stål, då processen ärsnabb och effektiv, dessutom dämpar porerna inne i materialet ljud då ljudvågorinte kan propagera lika fritt genom gas som genom solidt stål. Dagens pulver-metallurgiskamaterial har dock vissa begränsningar, så som lägre styrka. SSF projektet Nanotechnology Enhanced Sintered Steel Processing jobbar mot att förbättra dagens pulvermetall material. Genom att blanda in nano-partiklar så kan densiteten ökas och därmed förbättras materialets egenskaper. För att kunna utvärdera nya kugghjul och materialkombinationer så behöver prestandan kartläggas för dagens material. Det är därmed viktigt att hitta en metod för att kunna testa och göra relevanta jämförelser. Denna avhandling presenterar metoder för att testa samt utvärdera prestandan för olika material och därmed generera underlag för att kunna jämförade olika materialen. Genom att genomföra effektivitets samt pittingprov i en FZG testrig, har prestandan för dagens pulvermetallmaterial kunnat jämföras mot konventionellt stål, utöver materialskillnader har ett antal olika slutbearbetningsmetorder har också utvärderats. Kuggflankerna har mätts på plats i växellådan fortlöpande under testningen med ett släpnålsinstrument, en metod för att optimera positionen av de mätta profilerna mot den teoretiska kuggpro-filen har också utvecklats. Genom denna metod är det möjligt att direkt jämföraolika mätningar för att se hur slitage påverkar profilen. Därmed kan man studera hur mikropitting initieras och även förstå hur skademekanismerna påverkas av material och slutbearbetningsmetod. Vid samma slutbearbetningsmetod så uppvisade pulvermetallmaterialen liknande ytinitierade skademekanismer som konventionellt stål. En skillnad är att pulvermetallmaterialet även uppvisade skador som initierats inuti materialet. Kugghjul med superfinerad yta uppvisadetidigt omfattande skador i pittingtesten. Detta är kopplat till avsaknaden avtoppavlättning (en parameter som modifierar kuggprofilens utseende) på kuggprofilen, kraftiga slag ger sprickbildning i roten och när tillräcklig mängd sprickor ansamlats så börjar kuggflanken flagna, därefter propagerar skadan snabbt mot toppen av tanden.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2021. p. 50
Series
TRITA-ITM-AVL ; 2021:13
Keywords
Gear testing, Micropitting, Pitting, Efficiency, Surface transformation, Kugghjulstestning, Micropitting, Pitting, Effektivitetsmätning, Yttransformationer
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Design
Identifiers
urn:nbn:se:kth:diva-293324 (URN)978-91-7873-821-2 (ISBN)
Public defence
2021-06-04, https://kth-se.zoom.us/j/68966894832, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research , GMT14-0045
Available from: 2021-05-04 Created: 2021-04-30 Last updated: 2022-06-25Bibliographically approved

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Bergstedt, EdwinOlofsson, Ulf

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Proceedings of the Institution of mechanical engineers. Part C, journal of mechanical engineering science
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)

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