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Publications (10 of 88) Show all publications
Hultqvist, T., Vrček, A., Johannesson, T., Marklund, P. & Larsson, R. (2020). Analysis of Split Crankshaft Roller Bearings with Focus on Lubrication and Contact Stresses. In: : . Paper presented at 22nd International Colloquium Tribology: Industrial and Automotive Lubrication.
Open this publication in new window or tab >>Analysis of Split Crankshaft Roller Bearings with Focus on Lubrication and Contact Stresses
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2020 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-78735 (URN)978-3-943563-11-5 (ISBN)
Conference
22nd International Colloquium Tribology: Industrial and Automotive Lubrication
Funder
Swedish Energy Agency, 41215-1
Available from: 2020-04-30 Created: 2020-04-30 Last updated: 2020-04-30
Strömbergsson, D., Marklund, P., Berglund, K. & Larsson, P.-E. (2020). Bearing monitoring in the wind turbine drivetrain: A comparative study of the FFT and wavelet transforms. Wind Energy
Open this publication in new window or tab >>Bearing monitoring in the wind turbine drivetrain: A comparative study of the FFT and wavelet transforms
2020 (English)In: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824Article in journal (Refereed) Epub ahead of print
Abstract [en]

Wind turbines are often plagued by premature component failures, with drivetrain bearings being particularly subjected to these failures. To identify failing components, vibration condition monitoring has emerged and grown substantially. The fast Fourier transform (FFT) is the major signal processing method of vibrations. Recently, the wavelet transforms have been used more frequently in bearing vibration research, with one alternative being the discrete wavelet transform (DWT). Here, the low‐frequency component of the signal is repeatedly decomposed into approximative and detailed coefficients using a predefined mother wavelet. An extension to this is the wavelet packet transform (WPT), which decomposes the entire frequency domain and stores the wavelet coefficients in packets. How wavelet transforms and FFT compare regarding fault detection in wind turbine drivetrain bearings has been largely overlooked in literature when applied on field data, with non‐ideal placement of sensors and uncertain parameters influencing the measurements. This study consists of a comprehensive comparison of the FFT, a three‐level DWT, and the WPT when applied on enveloped vibration measurements from two 2.5‐MW wind turbine gearbox bearing failures. The frequency content is compared by calculating a robust condition indicator by summation of the harmonics and shaft speed sidebands of the bearing fault frequencies. Results show a higher performance of the WPT when used as a field vibration measurement analysis tool compared with the FFT as it detects one bearing failure earlier and more clearly, leading to a more stable alarm setting and avoidable, costly false alarms.

Place, publisher, year, edition, pages
John Wiley & Sons, 2020
Keywords
bearing failure, condition monitoring, discrete wavelet transform, wavelet packet transform, wind turbine gearbox bearings
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-77861 (URN)10.1002/we.2491 (DOI)000513910600001 ()2-s2.0-85079731480 (Scopus ID)
Available from: 2020-02-27 Created: 2020-02-27 Last updated: 2020-04-20
Hultqvist, T., Hansen, J., Björling, M., Marklund, P. & Larsson, R. (2020). On the Effects of Two-Sided Roughness in Rolling-Sliding EHL Contacts.. In: : . Paper presented at 22nd International Colloquium Tribology: Industrial and Automotive Lubrication.
Open this publication in new window or tab >>On the Effects of Two-Sided Roughness in Rolling-Sliding EHL Contacts.
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2020 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-77713 (URN)978-3-943563-11-5 (ISBN)
Conference
22nd International Colloquium Tribology: Industrial and Automotive Lubrication
Available from: 2020-02-14 Created: 2020-02-14 Last updated: 2020-04-28
Hultqvist, T., Vrček, A., Marklund, P., Prakash, B. & Larsson, R. (2020). Transient analysis of surface roughness features in thermal elastohydrodynamic contacts. Tribology International, 141, Article ID 105915.
Open this publication in new window or tab >>Transient analysis of surface roughness features in thermal elastohydrodynamic contacts
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2020 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 141, article id 105915Article in journal (Refereed) Published
Abstract [en]

Understanding the influence of surface roughness in elastohydrodynamically lubricated (EHL) contacts is essential to improve durability and friction performance of machine elements employing non-conformal contacting surfaces. In this work, the transient event of a surface feature passing through a thermal EHL line contact operating under different sliding conditions is investigated with the purpose of providing a deeper understanding of surface roughness influence. This is achieved by solving the EHL problem in space and time. It was seen that sliding influences the temperature rise in the contact significantly, especially in the vicinity of the asperity. However, due to the characteristic behaviour of EHL contacts, the local temperature rise mainly influence the film thickness during exiting of inlet perturbations and the asperity.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Thermal elastohydrodynamic lubrication, Transient conditions, Surface features, Numerical modelling
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-75817 (URN)10.1016/j.triboint.2019.105915 (DOI)000505271400031 ()2-s2.0-85071778495 (Scopus ID)
Funder
Swedish Energy Agency, 41215-1
Note

Validerad;2019;Nivå 2;2019-09-10 (johcin)

Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2020-05-15Bibliographically approved
Hultqvist, T., Vrček, A., Johannesson, T., Marklund, P. & Larsson, R. (2020). Transient plasto-elastohydrodynamic lubrication concerning surface features with application to split roller bearings. Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology
Open this publication in new window or tab >>Transient plasto-elastohydrodynamic lubrication concerning surface features with application to split roller bearings
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2020 (English)In: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305XArticle in journal (Refereed) Accepted
Keywords
Split roller bearings, Plasto-elastohydrodynamic lubrication, Elastohydrodynamic lubrication, Transient conditions, Numerical modelling
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-78887 (URN)
Funder
Swedish Energy Agency, P41215-1
Available from: 2020-05-15 Created: 2020-05-15 Last updated: 2020-05-15
Björling, M., Habchi, W., Bair, S., Larsson, R. & Marklund, P. (2019). Corrigendum to “Towards the true prediction of EHL friction” [tribol. Int. 66 (2013) 19–26] (ed.) [Letter to the editor]. Tribology International, 133, 297-297
Open this publication in new window or tab >>Corrigendum to “Towards the true prediction of EHL friction” [tribol. Int. 66 (2013) 19–26]
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2019 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 133, p. 297-297Article in journal, Letter (Other academic) Published
Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73121 (URN)10.1016/j.triboint.2018.10.018 (DOI)
Note

Erratum in: Tribology International, vol. 66, p.19-26, DOI:10.1016/j.triboint.2013.04.008

Available from: 2019-03-06 Created: 2019-03-06 Last updated: 2020-05-07Bibliographically approved
Martin del Campo Barraza, S., Schnabel, S., Sandin, F. & Marklund, P. (2019). Detection of particle contaminants in rolling element bearings with unsupervised acoustic emission feature learning. Tribology International, 132, 30-38
Open this publication in new window or tab >>Detection of particle contaminants in rolling element bearings with unsupervised acoustic emission feature learning
2019 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 132, p. 30-38Article in journal (Refereed) Published
Abstract [en]

The detection of contaminants in the lubricant of rolling element bearings using acoustic emission signals is a challenging problem, in particular at high rotational speeds. This problem calls for new analysis methods beyond the conventional amplitude- and frequency-based methods. Feature learning is successfully used in the machine learning field to characterize complex signals. Here we use an unsupervised feature learning approach to distinguish acoustic emission signals. We investigate the repetition rates of features identified with shift-invariant dictionary learning and find that the signature of contaminated lubricant is significantly stronger than the effect on conventional condition indicators like the RMS and the enveloped RMS at rotational speeds above 300 rpm and up to 3000 rpm.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Acoustic emission, Contamination, Dictionary learning, Unsupervised feature learning
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Machine Elements; Industrial Electronics
Identifiers
urn:nbn:se:ltu:diva-63112 (URN)10.1016/j.triboint.2018.12.007 (DOI)000456758700004 ()2-s2.0-85058395512 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-01-03 (svasva)

Available from: 2017-04-21 Created: 2017-04-21 Last updated: 2019-05-14Bibliographically approved
Hultqvist, T., Vrček, A., Prakash, B., Marklund, P. & Larsson, R. (2019). Influence of lubricant pressure response on sub-surface stress in elastohydrodynamically lubricated finite line contacts. Journal of tribology, 141(3), Article ID 031502.
Open this publication in new window or tab >>Influence of lubricant pressure response on sub-surface stress in elastohydrodynamically lubricated finite line contacts
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2019 (English)In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 141, no 3, article id 031502Article in journal (Refereed) Published
Abstract [en]

In order to adapt to increasingly stringent CO2 regulations, the automotive industry must develop and evaluate low cost, low emission solutions in the powertrain technology. This often implies increased power density and the use of low viscosity oils, leading to additional challenges related to the durability of various machine elements. Therefore, an increased understanding of lubricated contacts becomes important where oil viscosity-pressure and compressibility-pressure behaviour have been shown to influence the film thickness and pressure distribution in EHL contacts, further influencing the durability. In this work, a finite line EHL contact is analysed with focus on the oil compressibility- and viscositypressure response, comparing two oils with relatively different behaviour and its influence on subsurface stress concentrations in the contacting bodies. Results indicate that increased pressure gradients and pressure spikes, and therefore increased localized stress concentrations, can be expected for stiffer, less compressible oils, which under transient loading conditions not only affect the outlet but also the edges of the roller

Place, publisher, year, edition, pages
ASME Press, 2019
Keywords
Elastohydrodynamic lubrication, Finite line contacts, Sub-surface stress, Transient loading
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-71551 (URN)10.1115/1.4041733 (DOI)000457029800007 ()2-s2.0-85057759100 (Scopus ID)
Funder
Swedish Energy Agency, 41215-1
Note

Validerad;2018;Nivå 2;2018-12-07 (johcin)

Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2020-05-15Bibliographically approved
Vrček, A., Hultqvist, T., Baubet, Y., Björling, M., Marklund, P. & Larsson, R. (2019). Micro-pitting and wear assessment of engine oils operating under boundary lubrication conditions. Tribology International, 129, 338-346
Open this publication in new window or tab >>Micro-pitting and wear assessment of engine oils operating under boundary lubrication conditions
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2019 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 129, p. 338-346Article in journal (Refereed) Published
Abstract [en]

Current state-of-the-art engine oils tend to enhance micro-pitting damage in rolling contacts under certain operating conditions. ZDDP anti-wear additive was shown to promote such behavior. However, in order to optimize an engine oil formulation for rolling contacts, further studies are needed to assess engine oils in terms of micro-pitting and wear damage. This investigation studies the micro-pitting and wear performance of a number of engine oils for rolling contacts in a ball-on-disc configuration under conditions prevalent in crankshaft roller bearing applications. Based on the results it was concluded that an engine oil containing higher blend of PAO base oil compared to the oil mixture of Group III and PAO has a lower tendency towards micro-pitting and wear.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-70731 (URN)10.1016/j.triboint.2018.08.032 (DOI)000447575600028 ()2-s2.0-85052642062 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-09-24 (inah)

Available from: 2018-09-03 Created: 2018-09-03 Last updated: 2020-05-26Bibliographically approved
Vrček, A., Hultqvist, T., Baubet, Y., Björling, M., Marklund, P. & Larsson, R. (2019). Micro-Pitting and Wear Assessment of PAO vs Mineral-Based Engine Oil Operating under Mixed Lubrication Conditions: Effects of Lambda, Roughness Lay and Sliding Direction. Lubricants, 7(5), Article ID 42.
Open this publication in new window or tab >>Micro-Pitting and Wear Assessment of PAO vs Mineral-Based Engine Oil Operating under Mixed Lubrication Conditions: Effects of Lambda, Roughness Lay and Sliding Direction
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2019 (English)In: Lubricants, E-ISSN 2075-4442, Vol. 7, no 5, article id 42Article in journal (Refereed) Published
Abstract [en]

Under certain operating conditions, rolling contacts have been shown to experience some challenges when lubricated with engine oils containing zinc dialkyldithophosphate (ZDDP) anti-wear additive. In order to better understand the main damage mechanisms during various operating conditions, further studies are needed. This article studies micro-pitting and wear damages of bearing steel surfaces under mixed lubrication conditions in a ball-on-disc setup, lubricated with different engine oils. Based on the results, micro-pitting and wear damage is shown to be highly case-dependent. In general, PAO-based engine oil tends to eliminate micro-pitting damage compared to mineral-based engine oil at less severe lubricating conditions. Moreover, a critical lambda was found for both oils, where the highest micro-pitting damage was observed. 

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
micro-pitting, ZDDP, mild wear, surface-initiated fatigue
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-75059 (URN)10.3390/lubricants7050042 (DOI)000470959700003 ()2-s2.0-85066431252 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-27 (johcin)

Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2020-05-26Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3157-4632

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