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  • 51.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Tribo-condition monitoring for optimized performance and longer service life2017Konferansepaper (Annet vitenskapelig)
  • 52.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Wet clutch tribological performance optimization methods2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Wet clutches are used in a variety of machinery such as in vehicles where they are used to distribute torque in the drivetrains. Clutches can be located in automatic transmissions or in limited slip differentials. The frictional behavior of a clutch is of great importance for overall vehicle behavior and has to be thoroughly investigated when designing new wet clutch applications. Frictional behavior is normally studied in test rigs where whole friction discs or complete clutches are tested under similar working conditions to those pertaining to the clutches in the drivetrain of the vehicle. However, today clutch behavior may be simulated with regard to some clutch applications and design of the clutch system is not limited to testing. This is an advantage as it is possible to simulate behavior that may not be possible or suitable to study in a test rig. Another advantage is that the design process is faster and more cost efficient than that which is possible when all tests are carried out in a laboratory. The torque transferred by the clutch during engagement can roughly be divided into full film torque and boundary lubrication torque. Full film torque originates from the part of the engagement where the clutch discs are completely separated by a lubricant film and the friction surfaces are not in contact, whereas boundary lubrication torque occurs when the lubricant film is so thin that the surfaces of the clutch discs are in direct contact, only separated by a thin additive film. The distribution between full film torque transfer and boundary lubrication torque transfer differs for different types of wet clutch and for differing operating conditions. When the clutch works in full film regime it is possible to simulate the friction quite well. However, the friction in the boundary lubrication regime is much more difficult to model and simulate since it is very dependent on the additives. Wet clutches are most commonly used in automatic transmissions for vehicles. As a result, most research into wet clutch testing and most simulations concerns wet clutches suitable for such applications. In an automatic transmission the wet clutch is often used to brake a rotating shaft to stand still relative to another shaft and the total engagement has a duration of fractions of a second. During most of the engagement the clutch is working in full film lubrication. In this thesis the focus is on wet clutches working under limited slip conditions: in other words this thesis studies clutches that are working with a small amount of slip over a long period without reaching a state of lock-up. These clutch types can be found, for example, in limited slip differentials. During this type of engagement the clutch mainly works under boundary lubrication conditions and much heat can be generated. The optimum method of designing a new wet clutch would be to simulate the clutch performance without having to do any measurements in the laboratory. This, however, is not yet possible, but an efficient way to design clutches can be achieved by combining simple measurements with efficient computer simulations. In this thesis, simple measurement techniques for wet clutch materials are developed and combined with a temperature simulation of a wet clutch, where the lubricant cooling flow, which is dependent on the surface roughness and groove pattern, is simulated. This method makes it possible to optimize a wet clutch for given working conditions with regard to lubricant, friction material, surface roughness and groove pattern. The simulations are validated to measured data from a test rig in which torque behavior from whole friction discs are investigated. Good agreement between simulations and measurements is achieved.

  • 53.
    Marklund, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Almqvist, AndreasKassfeldt, Elisabet
    Nordtrib 2010: 14th Nordic Symposium on Tribology, Storforsen, Sweden2010Collection/Antologi (Annet vitenskapelig)
  • 54.
    Marklund, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Berglund, Kim
    Kassfeldt, Elisabet
    Baldos II, Sweden's most fuel efficient car: approved for street use2010Inngår i: SAE 2010 Powertrains, Fuels and Lubricants Meeting: October 25 - 27, 2010, San Diego, California, USA ; [papers], Warrendale, Pa: Society of Automotive Engineers, Incorporated , 2010Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Baldos II originates as an entry for the 2009 Shell Eco-marathon competition. It is built in cooperation between students from different fields of study, such as Mechanical Engineering, Industrial Design Engineering and Computer Science from Luleå University of Technology, Sweden. The car has been designed to meet the requirements set by Swedish authorities for legal street use. This includes wind screen wiper, 3-point seat belt, proper lighting, reverse gear and twin electric engines. Baldos II is tested and found to be Sweden's most fuel efficient car approved for street use.The internal combustion engine in the serial hybrid drive train is modified from an ordinary gasoline engine to run on pure ethanol. The fuel consumption of the vehicle corresponds to 0.065 litres ordinary gasoline/10 km, which results in a CO2 emission of 12 g/km. The car is design for one person only, and has room for a luggage in the size of an ordinary cabin bag. With full tank the total weight is 220 kg, and the total length is 2650 mm. The light weight has been achieve thorough an advanced monocoque chassis manufactured of carbon fiber sandwich construction.According to safety regulations the car is equipped with dual circuit hydraulic disc brakes. Today, the Team Baldos aims for defining a higher standard for street vehicles in Sweden.

  • 55. Marklund, Pär
    et al.
    Berglund, Kim
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    The influence on boundary friction of the permeability of sintered bronze2008Inngår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 31, nr 1, s. 1-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Components made of sintered bronze are often used in tribological systems. Examples of applications are self lubricated bearings, wet clutches and brakes and synchromesh components for manual gearboxes. The bronze material in these applications is often porous and permeable. However, the required level of permeability i.e., the ability for a fluid to flow inside the material varies widely for different applications. This implies the need to investigate if the permeability can influence the properties of a tribological system. Various studies have been performed in order to investigate the permeability of different materials but a possible relationship between permeability and boundary lubrication performance has not yet been thoroughly investigated. In this article this relationship has been investigated in a pin-on-disk apparatus for test specimens with a permeability that is well-defined. Materials with three different permeabilities were investigated together with non-permeable test specimens. The results indicate that permeability has a small influence on the friction coefficient when the tribological system is operating with good lubrication of the contact. The function of the tribological system when working under starved conditions is also investigated and a very clear relationship between permeability and the ability to cope up with starved running conditions is shown. This is explained in terms of the varying ability of the materials' to store lubricant in pores. Non-porous test specimens were also tested as a comparison with the permeable test specimens in the investigation with starved running conditions . The results show that a material with high permeability works much better under starved running conditions than that with low permeability.

  • 56. Marklund, Pär
    et al.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Modeling and simulation of thermal effects in wet clutches operating under boundary lubrication conditions2009Inngår i: Svenska mekanikdagarna: Södertälje 2009, Stockholm: Svenska nationalkommittén för mekanik , 2009, s. 76-Konferansepaper (Annet vitenskapelig)
  • 57. Marklund, Pär
    et al.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Modeling and simulation of thermal effects in wet clutches operating under boundary lubrication conditions2008Inngår i: Tribology for tomorrow: iCAT 2008, 2nd International Conference on Advanced Tribology 2008 ; 3 - 5 December 2008, Singapore ; extended abstracts, Singapore, 2008, s. 518-520Konferansepaper (Annet vitenskapelig)
  • 58. Marklund, Pär
    et al.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Wet clutch friction characteristics obtained from simplified pin on disc test2006Inngår i: Nordtrib 2006, 12th Nordic Tribology Symposium, Denmark: [LO-skolen, Helsingør, Denmark, June 7 - 9 2006], Kongens Lyngby: Technical University of Denmark , 2006Konferansepaper (Fagfellevurdert)
  • 59. Marklund, Pär
    et al.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Wet clutch friction characteristics obtained from simplified pin on disc test2008Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 41, nr 9-10, s. 824-830Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The frictional behavior of wet clutches in vehicle drivetrains is critical for their overall behavior. During the development of new wet clutch systems there is a need to know this friction behavior. The transferred torque is normally investigated in test rigs where the friction in a sliding interface between a friction disc and separator disc is investigated. These test rigs can be designed differently, depending on the working conditions of the investigated clutch. However, it is possible today to simulate the clutch behavior and not limit ourselves to only using measurements from test rigs for the design of the wet clutch. The torque transferred by the clutch during engagement can be roughly divided into full film torque and boundary lubrication torque. The full film regime is possible to simulate quite well, whereas the friction in the boundary regime is much more difficult to simulate due to its strong additive dependency. To obtain a good prediction of the total engagement, friction measurements in the boundary lubrication regime are still needed. These measurements should be easy to perform and fast tests are preferable. Friction coefficients for the whole range of sliding speed, interface temperature and nominal surface pressure should be measured. To use these measurements in simulations and get a better understanding of the friction behavior, it is also preferable to conduct these measurements on a small test sample, for which the temperature and sliding speed can be regarded as constant.Here, the friction of a small sample of a wet clutch friction disc is investigated in a pin on disc test and the temperature is measured in the sample during the tests. Measurements are compared with measurements from a test rig for whole friction discs. A good correspondence between the frictional behaviors of the different measurement methods is achieved.

  • 60.
    Marklund, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Wet clutch under limited slip conditions: simplified testing and simulation2007Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 221, nr 5, s. 545-551Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When designing new wet clutch systems, simulations and laboratory tests are important to obtain a functional system. An engineering tool is here developed to simulate wet clutches working under boundary lubrication conditions. Boundary lubrication friction is measured by a pin-on-disc test, and cooling oil flow is simulated by solving the Reynolds equation. Depending on the generated heat, the temperature in the clutch pack changes during engagement, affecting the transferred torque. With the developed method it is possible to easily and quickly investigate the behaviour of wet clutches with a variety of friction materials and groove patterns. The model is validated in a wet clutch test rig and the predicted torque agrees well with experimental data.

  • 61.
    Marklund, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Permeability of sinter bronze friction material for wet clutches2008Inngår i: Tribology & Lubrication Technology, ISSN 1545-858X, Vol. 64, nr 12, s. 34-41Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The characteristics of wet clutches are of great importance for the overall behavior of the drive trains of many modern vehicles. It is considered that the clutch characteristic is affected by the permeability of the friction material. The permeability is considered to influence both the time of engagement and the temperature in the clutch due to the lubricant flow in the permeable material. In this work, a permeability measurement method suitable for wet clutch friction materials is thus used to measure the permeability of a friction material made of sintered bronze. This friction material is suitable for applications such as limited slip differentials or other wet clutches that have to withstand high temperature and high torque transfer. The permeability is also investigated for friction materials with pressed groove patterns. Wet clutch friction material permeability is often accounted for in simulations but the method used to measure the permeability is seldom described. The permeability of the investigated friction material is shown to be so small that it hardly will affect the temperature in the material due to cooling oil flow inside the material. However, the engagement time can be influenced by the permeability. It is also shown that pressed groove patterns can seal the friction material so that it becomes almost impermeable.

  • 62. Marklund, Pär
    et al.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Permeability of sinter bronze friction material for wet clutches2007Inngår i: 62nd annual meeting of the Society of Tribologists and Lubrication Engineers 2007 : May 6 - 10, 2007, Philadelphia, Pennsylvania, USA, STLE , 2007Konferansepaper (Fagfellevurdert)
  • 63.
    Marklund, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Permeability of sinter bronze friction material for wet clutches2008Inngår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 51, nr 3, s. 303-309Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The characteristics of wet clutches are of great importance for the overall behavior of the drive trains of many modern vehicles. It is considered that the clutch characteristic is affected by the permeability of the friction material. The permeability is considered to influence both the time of engagement and the temperature in the clutch due to the lubricant flow in the permeable material. In this work, a permeability measurement method suitable for wet clutch friction materials is thus used to measure the permeability of a friction material made of sintered bronze. This friction material is suitable for application such as limited slip differentials or other wet clutches that have to withstand high temperature and high torque transfer. The permeability is also investigated for friction materials with pressed groove patterns. Wet clutch friction material permeability is often accounted for in simulations but the method used to measure the permeability is seldom described. The permeability of the investigated friction material is shown to be so small that it will hardly will affect the temperature in the material due to cooling oil flow inside the material. However, the engagement time can be influenced by the permeability. It is also shown that pressed groove patterns can seal the friction material so that it becomes almost impermeable.

  • 64. Marklund, Pär
    et al.
    Mäki, Rikard
    Larsson, Roland
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Khonsari, Michael. M.
    Louisiana State University.
    Jang, Joonyoung
    Louisiana State University.
    Ganemi, Bager
    Statoil Lubricants.
    Ohlsson, Richard
    Haldex Traction AB.
    Thermal influence on torque transfer of wet clutches in limited slip differential applications2005Inngår i: Proceedings of the World tribology congress III: presented at ..., September 12 - 16, 2005, Washington, DC, New York: American Society of Mechanical Engineers , 2005, s. 245-246Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Wet clutches operating under low velocity and high load are studied with the aim of obtaining reliable models for the torque transfer during boundary lubrication conditions.

  • 65.
    Marklund, Pär
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Mäki, Rikard
    Larsson, Roland
    Höglund, Erik
    Khonsari, M.M.
    Louisiana State University.
    Jang, Joonyoung
    Louisiana State University.
    Thermal influence on torque transfer of wet clutches in limited slip differential applications2007Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 40, nr 5, s. 876-884Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wet clutches operating under low velocity and high load are studied with the aim of obtaining reliable models for the torque transfer during boundary lubrication conditions. A friction model which takes temperature, speed and nominal pressure into account is developed and used with temperature calculations to be able to simulate behavior of a wet clutch working in boundary lubrication regime. Predicted torque and temperatures from the model agree well with experimental data.

  • 66. Marklund, Pär
    et al.
    Sahlin, Fredrik
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Modelling and simulation of thermal effects in wet clutches operating under boundary lubrication conditions2009Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 223, nr 8, s. 1129-1141Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wet clutches are frequently used in the drive trains of many modern vehicles. The behaviour of the clutches influences the behaviour of the whole drive train and therefore of the whole vehicle. The design of the clutch is very important because it operates in cooperation with the other parts of the drive train. The clutch also often has to work in the lubricant present in the transmission. To optimize the clutch for an application, properties such as disc geometry, materials, friction disc surface, and engagement axial force can be varied when designing the clutch. Today, the design process involves much testing, which is expensive and time consuming. There are no good hand-book solutions or engineering tools available, hence the designer has to be very experienced and often use trial and error methods in order to end up with a working clutch for an application.A simulation model is developed in this article, which in combination with a simple measurement technique for measuring the boundary lubrication friction coefficient is used to estimate temperature and torque transfer for a wet clutch working under limited slip conditions. The developed simulation model can be used as a design tool for wet clutches. The approach developed in this article can be used to investigate torque behaviour for wet clutches that have not been designed and is, therefore, suitable to use when optimizing the performance of a new clutch. The model includes fluid dynamics, contact mechanics, and temperature computations in the fluid film between the friction disc and the separator disc. Temperature computations in the clutch discs are also included in the model. The fluid dynamics calculations use homogenized flow factors to enable simulations of flow on a coarser grid and still include all surface roughness effects. The temperature distribution in the film in the sliding interface is approximated as a polynomial of the second order. The heat transfer in the grooves of the friction discs is solved by means of an equilibrium equation that includes radial cooling flow effects because of centrifugal flows. The temperature in the friction disc and separator disc is obtained from the solution of the full three-dimensional energy equation in polar cylindrical coordinates.The model is validated by measurements made in a test rig and good agreement between measurements and simulations is obtained, both with regard to temperature and transfered torque.The use of this model can reduce the time needed to develop a limited slip wet clutch application since the systematic way of finding the optimal clutch design will be more efficient than the often used Edisonian trial and error approach.

  • 67.
    Martin del Campo Barraza, Sergio
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Schnabel, Stephan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Sandin, Fredrik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Detection of particle contaminants in rolling element bearings with unsupervised acoustic emission feature learning2019Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 132, s. 30-38Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 68.
    Martin-del-Campo, Sergio
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Sandin, Fredrik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Schnabel, Stephan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Exploratory Analysis of Acoustic Emissions in Steel using Dictionary Learning2016Inngår i: IEEE Ultrasonics Symposium 2016, Tours France, September 18-21, 2016, Piscataway, NJ: IEEE conference proceedings, 2016, artikkel-id 7728825Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Analysis of acoustic emissions (AE) from steel deformation is a challenging condition monitoring problem due to the high frequencies and data rates involved, and the difficulty to separate signals from noise. The problem to characterize and identify different AE sources calls for methods that goes beyond conventional time and frequency domain analysis. Feature learning is common in the field of machine learning and is successfully used to approximate and classify other kinds of complex signals. Former studies show that AE classification results depend on the choice of predefined features that are extracted from the raw AE signal, but little is known about feature learning in this context. Here we use dictionary learning and sparse coding to optimize a set of shift-invariant features to the AE signal measured in a steel tensile strength test. The specimen undergoes elastic and plastic deformation and eventually cracks. We investigate the learned features and their repetition rates and use principal component analysis (PCA) to illustrate that the resulting sparse AE code is useful for classification of the three strain stages, without reference to the signal amplitude. Therefore, feature learning is a potentially useful approach to the AE analysis problem, which also opens up for further studies of automated methods for anomaly detection in AE.

  • 69.
    Sahlin, Fredrik
    et al.
    Siemens Industrial Turbomachinery AB.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Almqvist, Andreas
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Marklund, Pär
    A mixed lubrication model incorporating measured surface topography: Part 1: theory of flow factors2010Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 224, nr 4, s. 335-351Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mixed lubrication model that permits real three-dimensional surface topography as input is developed. The theory of computing flow factors within the model is presented, and with a following paper (Part 2) the method of measuring and adapting the surface roughness, and model validation through flow measurements and application to a bearing is shown. A contact mechanics model is used to calculate the elastoplastic displacement of a periodic topography signal. A method based on homogenization is used to calculate flow factors for all lubrication regimes. The flow factors are compared with the Patir and Cheng method. Results indicate that the two methods compare well for longitudinal roughness lay, but differ significantly for a cross-patterned surface roughness due to the more complete flow description of the current model.

  • 70.
    Sahlin, Fredrik
    et al.
    Siemens Industrial Turbomachinery AB.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Almqvist, Andreas
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    A mixed lubrication model incorporating measured surface topography: Part 2: roughness treatment, model validation, and simulation2010Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 224, nr 4, s. 353-365Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mixed lubrication flow factor model that permits real three-dimensional surface topography as input has been developed. Part 1 gives the theory of computing flow factors within the model. In this article, a method of adapting the measured surface topography signal to suit the numerical models is developed and presented in detail. The mixed lubrication model is validated through flow measurements for three different rough surface test specimens. Simulation of a hydrodynamic bearing was conducted and the results are presented in terms of pressure distributions and Stribeck curves covering all lubrication regimes. The results indicate that the model may be an efficient and accurate engineering design and research tool for tribological devices operating in all lubrication regimes.

  • 71.
    Schnabel, Stephan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Golling, Stefan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Absolute Measurement of Elastic Waves Excited by Hertzian Contacts in Boundary Restricted Systems2017Inngår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, nr 1, artikkel-id 7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In most applied monitoring investigations using acoustic emission, measurements are carried out relatively, even though that limits the use of the extracted information. The authors believe acoustic emission monitoring can be improved by instead using absolute measurements. However, knowledge about absolute measurement in boundary restricted systems is limited. This article evaluates a method for absolute calibration of acoustic emission transducers and evaluates its performance in a boundary restricted system. Absolute measured signals of Hertzian contact excited elastic waves in boundary restricted systems were studied with respect to contact time and excitation energy. Good agreement is shown between measured and calculated signals. For contact times short enough to avoid interaction between elastic waves and initiating forces, the signals contain both resonances and zero frequencies, whereas for longer contact times the signals exclusively contained resonances. For both cases, a Green’s function model and measured signals showed good agreement.

  • 72.
    Schnabel, Stephan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Golling, Stefan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    The influence of contact time and event frequency on acoustic emission signals2017Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 231, nr 10, s. 1341-1349Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies of acoustic emissions (AE) of rotating machine elements is often performed under a constant speed. There are few investigations on speed and contact time dependency of acoustic emission signals, even though some investigations have reported difficulties at elevated rotational speeds. Simplified experiments are, therefore, presented in this article to increase the understanding of the time dependency of acoustic emission signals. Hertzian impacts and tensile tests are used to study contact time, the time duration of an event and offset time, the time between events and accordingly the event frequency. The results of these model experiments indicate an indirect quadratic proportionality of acoustic emission amplitudes and contact time (umax∝1/(tc2)">u max ∝1/(t 2 c ) umax∝1/(tc2) ), as well as a proportional relationship between the root mean square and event frequency (RMS∝fevent∝1/toffset">RMS∝f event ∝1/t offset  RMS∝fevent∝1/toffset ). The relationship between contact time and the root mean square of acoustic emission signals is strongly dependent on the damping of the system

  • 73.
    Schnabel, Stephan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Contact resistance measurements as a monitoring tool for running in processes of point contacts2013Konferansepaper (Fagfellevurdert)
  • 74.
    Schnabel, Stephan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Elastic Waves of a Single Elasto-Hydrodynamically Lubricated Contact2017Inngår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, nr 1, artikkel-id 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Elastic waves are widely used for condition monitoring of rolling element bearings through vibration or acoustic emission measurements . While vibration signals are understood to a high degree due to many scientific investigations as well as a long history of usage in the field, acoustic emission signals of rolling element bearings are poorly understood. Therefore, this investigation presents simulation studies and measurements of a single elasto-hydrodynamically lubricated (EHL) contact. In this investigation the EHL contact is a ball bouncing on a lubricated plate. The simulation based on Green’s function and the measurements based on a accelerometer to some extent agree. A shift of zero frequencies towards higher frequencies when compared to Hertzian reference measurements was determined for an infinite plate setup. Taking boundary restrictions into account, elastic waves of a Hertzian contact and an EHL contact only differ by a damping of higher resonances which is most likely caused by the EHL film.

  • 75.
    Schnabel, Stephan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Study of the short term effect of Fe3O4 particles in rolling element bearings: Observation of vibration, friction and change of surface topography of contaminated angular contact ball bearings2013Konferansepaper (Fagfellevurdert)
  • 76.
    Schnabel, Stephan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Study of the short-term effect of Fe3O4 particles in rolling element bearings: Observation of vibration, friction and change of surface topography of contaminated angular contact ball bearings2014Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 228, nr 10, s. 1063-1070Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The harsh environment rolling element bearings are exposed to in iron-mining industries is replicated in a laboratory scale in this work. Bearings (SKF 7204BEP) were tested both with and without magnetite oxide (Fe3O4) contamination. In order to study the interaction between contaminants and extreme pressure additives, the rolling element bearings were lubricated with two different greases: Grease without extreme pressure and grease containing sulphur-based extreme pressure additives. Further, the effect of the contamination–additive interaction on rolling bearing performance and monitoring signals (vibration and acoustic emission) was investigated. The obtained results indicate an advantage of extreme pressure additive in case of the investigated operating conditions. Furthermore, the use of extreme pressure additives decreased wear, surface roughness, vibration and acoustic emission for both test durations of 24 h and 168 h. The decrease of the acoustic emissions and the surface roughness parameter Rq in case of the tests with a duration of 168 h as high as 70% and 60%, respectively using extreme pressure additives in comparison with the plain grease was observed. The major cause for this reduction seems to be the interaction between contaminants and extreme pressure additives.

  • 77.
    Schnabel, Stephan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Golling, Stefan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    The Detection of Plastic Deformation in Rolling Element Bearings by Acoustic Emission2017Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 110, s. 209-215Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The detection of plastic deformation caused by particle contamination in rolling element bearings using acoustic emission is reliable at low speeds as shown in several studies. However, there are no studies at greater speeds of the detection of plastic deformation by acoustic emission in rolling element bearings. The acoustic emission signals of rolling element bearings have, however, been shown to be dominated by transient force signals which are elastic waves caused by transient forces acting at the raceway surface. The results of the test showed a dominance of transient force signals at elevated speeds, which masks signals caused by plastic deformation and prohibits the detection of particle contamination, while at low rotational speed plastic deformation is detected by acoustic emission.

  • 78.
    Schnabel, Stephan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Minami, Ichiro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Monitoring of Running-in of an EHL contact using Contact Impedance2016Inngår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 63, nr 3, artikkel-id 35Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Running-in is an important process for elasto-hydrodynamic lubricated contacts, which affect both service life and operating performance. However, the possibilities of monitoring running-in are still poor. Therefore, the properties of electrical contact impedance as a monitoring tool were studied by using an in-house made ball on disc apparatus. The contact impedance was monitored during run-in experiments with different initial surface roughness of the discs, different slide-to-roll ratios and with pure or additive containing paraffinic oil. The relationship between surface roughness parameters, contact resistance and contact capacitance was investigated. While the contact resistance seems to be affected by the parameter Rz, the contact capacitance seems more dependent on Rq. In addition, the experiments showed that surface active additives do not necessarily need to influence the contact impedance.

  • 79.
    Strömbergsson, Daniel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Berglund, Kim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Bearing faults in the wind turbine drivetrain: Comparative study of monitoring with FFT and the Discrete Wavelet Transform2017Konferansepaper (Fagfellevurdert)
  • 80.
    Strömbergsson, Daniel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Berglund, Kim
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Saari, Juhamatti
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Thomson, Allan
    Industrial Digitalisation & Solutions, Livingston, Scotland.
    Mother wavelet selection in the discrete wavelet transform for condition monitoring of wind turbine drivetrain bearings2019Inngår i: Wind Energy, ISSN 1095-4244, E-ISSN 1099-1824, Vol. 22, nr 11, s. 1581-1592Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although the discrete wavelet transform has been used for diagnosing bearing faults for two decades, most work in this field has been done with test rig data. Since field data starts to be made more available, there is a need to shift into application studies.

    The choice of mother wavelet, ie, the predefined shape used to analyse the signal, has previously been investigated with simulated and test rig data without consensus of optimal choice in literature. Common between these investigations is the use of the wavelet coefficients' Shannon entropy to find which mother wavelet can yield the most useful features for condition monitoring.

    This study attempts to find the optimal mother wavelet selection using the discrete wavelet transform. Datasets from wind turbine gearbox accelerometers, consisting of enveloped vibration measurements monitoring both healthy and faulty bearings, have been analysed. The bearing fault frequencies' excitation level has been analysed with 130 different mother wavelets, yielding a definitive measure on their performance. Also, the applicability of Shannon entropy as a ranking method of mother wavelets has been investigated.

    The results show the discrete wavelet transforms ability to identify faults regardless of mother wavelet used, with the excitation level varying no more than 4%. By analysing the Shannon entropy, broad predictions to the excitation level could be drawn within the mother wavelet families but no direct correlation to the main results. Also, the high computational effort of high order Symlet wavelets, without increased performance, makes them unsuitable.

  • 81.
    Strömbergsson, Daniel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Edin, Emil
    Applied Nano Surfaces Sweden AB.
    Zeman, Frida
    Applied Nano Surfaces Sweden AB.
    Acoustic emission monitoring of a mechanochemical surface finishing process2017Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 112, s. 129-136Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Acoustic emission monitoring of cutting machining operations is an established researched area, though monitoring non-removal finishing processes is less studied.

    This work presents an initial investigation on Acoustic emissions potential of an mechanochemical superfinishing process. Conclusions are drawn from the monitoring signal regarding the resulting surface friction characteristics, composition and possible runnability issues.

    Monitoring data was collected from tests performed at Applied Nano Surfaces' testing laboratory. Test series with varying parameters enabled a correlation analysis between the monitoring data, surface friction characteristics and tribofilm formation. Increasing tool wear tests were monitored to find early runnability warning.

    Results shows Acoustic emissions indication potential when the finishing process has achieved the intended friction reduction, tribofilm deposition as well as runnability issues identification.

  • 82.
    Söderfjäll, Markus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Almqvist, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Texture-induced effects causing reduction of friction in mixed lubrication for twin land oil control rings2018Inngår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology, ISSN 1350-6501, E-ISSN 2041-305X, Vol. 232, nr 2, s. 166-178Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Piston rings are responsible for a major part of the frictional losses in a heavy-duty diesel engine. Such losses can be reduced by applying texture, such as dimples, on the cylinder liner surface. This paper investigates the effect of such texture on the friction between a land of the oil control ring and a textured cylinder liner via numerical simulation. A simulation model considering inertia and mixed lubrication together with a mass-conserving cavitation model is developed. The model is used to determine the dimple parameters that yield the lowest amount of friction for a specific oil control ring of a heavy-duty diesel engine

  • 83.
    Vrček, Aleks
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hultqvist, Tobias
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Baubet, Yannick
    SKF, Nieuwegein.
    Björling, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Micro-pitting and wear assessment of engine oils operating under boundary lubrication conditions2019Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 129, s. 338-346Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 84.
    Vrček, Aleks
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hultqvist, Tobias
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Baubet, Yannick
    SKF Engineering & Research Centre, Nieuwegein, The Netherlands.
    Björling, Marcus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Micro-Pitting and Wear Assessment of PAO vs Mineral-Based Engine Oil Operating under Mixed Lubrication Conditions: Effects of Lambda, Roughness Lay and Sliding Direction2019Inngår i: Lubricants, E-ISSN 2075-4442, Vol. 7, nr 5, artikkel-id 42Artikkel i tidsskrift (Fagfellevurdert)
    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. 

  • 85.
    Vrček, Aleks
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hultqvist, Tobias
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Baubet, Yannick
    SKF Research and Technology Development, Nieuwegein, Netherlands.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Larsson, Roland
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Micro-pitting Damage of Bearing Steel Surfaces under Mixed Lubrication Conditions: Effects of Roughness, Hardness and ZDDP Additive2019Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 138, s. 239-249Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Micro-pitting presents a failure of the rolling/sliding contact metal asperities operating under boundary/mixed lubrication conditions. The studies have shown that micro-pitting failure competes with mild wear and that lubricant additives can have either detrimental or beneficial effects on micro-pitting evolution. This article describes a methodology to investigate micro-pitting damage on bearing steels using a twin-disc machine to better represent mechanical components, i.e. bearings, crankshafts, etc. In addition, effects of roughness, hardness and the ZDDP additive are presented and discussed. A sufficient hardness difference can completely eliminate micro-pitting damage mode. Furthermore, the presence of ZDDP anti-wear additive in fully formulated engine oil was shown to protect rougher surfaces and promote wear on smoother surfaces, thus completely eliminating the micro-pitting damage mode.

  • 86.
    Westin, Per-Oskar
    et al.
    Institute of Applied Hydraulics.
    Marklund, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Sandström, Jon
    Institute of Applied Hydraulics.
    Wear detection by monitoring hydraulic oil contamination: an experimental comparison between on-line and off-line measurements2013Konferansepaper (Fagfellevurdert)
12 51 - 86 of 86
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