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  • 1.
    Gåård, Anders
    et al.
    Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Karlstads universitet, Karlstad, Sweden.
    Karlsson, Patrik
    Örebro University, School of Science and Technology.
    Krakhmalev, Pavel
    Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Karlstads universitet, Karlstad, Sweden.
    Broitman, Esteban
    Tunnfilmsfysik, Linköpings universitet, Linköping, Sweden.
    Nano-scale friction of multi-phase powder metallurgy tool steels2015In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 1119, p. 70-74Article in journal (Refereed)
    Abstract [en]

    Friction is a fundamental phenomenon in tribology involving complex mechanisms between thecontacting surfaces. Measurements of friction are often made using devices with substantially largercontact area than dimensions corresponding to microstructural features of the materials. Hence, for multi-phase materials,influence of particular microstructural constituents is not resolved. In the present work, a tribometerwith a contact area in the nano-scale range was used to map friction for different types of tool steelswith different chemical- and phase composition. Owing to the small tip radius, frictionalcharacteristics of primary carbides and the steel matrix were measured and compared. Dependingon chemical composition, a difference was observed where the coefficient of friction wasapproximately twice higher for the steel possessing highest coefficient of friction, including bothcarbides and the steel matrix.

  • 2.
    Karlsson, Patrik
    et al.
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Gåård, Anders
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Krakhmalev, Pavel
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Berhe-Larsson, Johanna
    Department of Mechanical and Materials Engineering, Karlstad University, Karlstad, Sweden.
    Influence of tool steel hard phase orientation and shape on galling2014In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 966-96, p. 249-258Article in journal (Refereed)
    Abstract [en]

    Conventionally manufactured cold work tool steel is often used in sheet metal forming as die material. Due to the forging process, the as-cast network structure of carbides is broken into elongated particles. Depending on the tool cross-section, the orientation and shape of carbides in the active tool surface is different. In the present research, the influence of tool steel hard phase orientation and shape on galling was investigated. D2 type tool steel was cut in three different orientations and tested in lubricated sliding conditions against AISI 304 austenitic stainless steel. Tests were performed using a Slider-On-Flat-Surface and galling was detected by changes in friction and post-test microscopy. The lubricant was Castrol FST8 using 5 g/m2 sheet material. Results showed a strong correlation between sliding distance to galling and tool steel hard phase orientation and shape at low loads, whereas high load contact resulted in early galling in all cases. Material transfer was observed mainly to the tool steel matrix. The worst performance was observed for specimens cut so that the tool steel hard phase, M7C3 carbides in the D2 steel, were oriented along the sliding direction, which resulted in longer open tool matrix areas contacting the sheet material.

  • 3.
    Ranjbar, Parivash
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Örebro University, School of Science and Technology.
    Signal Processing Methods for Improvement of Environmental Perception of Persons with Deafblindness2014In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 902, p. 398-404Article in journal (Refereed)
    Abstract [en]

    Environmental perception is a functional area that is severely limited in persons with  deafblindness (DB) who belong a category of people with severe disabilities. Monitor is a vibratory aid developed with the aim to improve environmental perception of persons with DB. The aid consists of a mobile phone with an application connected to a microphone and vibrator. Monitor picks up the sounds produced by events by microphone, processes the sound using an algorithm programmed as an application in the mobile phone and then presents the signal via the vibrator to the persons with DB to be sensed and interpreted. In previous laboratory studies, four algorithms (AM, AMMC, TR, and TRHA) were developed based on modulating, and transposing principles.

    The algorithms were tested by persons with normal hearing/hearing impairment and selected as good candidates to improve vibratory identification of environmental sounds. In this on-going the algorithms are tested by 13 persons with congenital D and five persons with DB using Monitor in a realistic environment, living room, kitchen or office. Forty five recorded environmental sounds were used as test stimuli.

    The subjects tested the algorithms two times, Test and Retest each including a test session

    initiated by a training session. The four algorithms were tested in four days at Test and four days at Retest in total eight test days. Each test day began with a training session where a sound was presented as vibrations to be sensed by the person with the aim to remember its pattern and identity.

    The 45 sounds were grouped in four groups where an specific algorithm was chosen to process an specific sound group in a specific day. At the test session a sound was presented and the person was given 5 randomly chosen sound alternatives to choose the one as represented sound. The algorithms were different for different sound groups during four different test days so all algorithms were used to process all sounds. The algorithms were tested a second time, Retest, in same way as in Test.

    The mean value of identification of environmental sounds varied between 74.6% and 84.0% at Test and between 86.9% and 90.4% at Retest. The identification results at Retest were

    significantly improved (p<0.01) for all algorithms after a relatively short time of training indicating a good learning effect. At Test the algorithm AM was significantly better than the algorithms AMMC and TRHA (p< 0.01) and the algorithm TR was better than TRHA (p<0.01).

    The algorithms AM, AMMC, and TR were selected as good candidates to be implemented in the Monitor to improve environmental perception.

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