Browsing by Author "Hartl, Martin"

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    Experimental investigation of friction in compliant contact: The effect of configuration, viscoelasticity and operating conditions
    (2022) Quinn, Cheney; Necas, David; Sperka, Petr; Marian, Max; Vrbka, Martin; Krupka, Ivan; Hartl, Martin
    This work investigates the effects of kinematic conditions, configuration, viscoelasticity, and lubricant viscosity on friction in lubricated compliant contacts. Experimental data were also used to develop a numerical simulation capable of predicting fluid friction in compliant contacts. Mini Traction Machine (MTM) in the ball-on-disc configuration was used to successfully gain insight into the behaviour of compliant contacts, allowing the investigation of the mentioned effects. The findings have confirmed that viscoelastic effects are present in all configurations, being soft-on-hard (S/H), hard-on-soft (H/S) and soft-on-soft (S/S), where they seem to be more profound in the configurations using compliant discs. The experimental data also suggest that the slide-to-roll ratio affects rolling friction in all configurations which is contrary to current literature
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    Frictional Behaviour and Surface Topography Evolution of DLC-Coated Biomedical Alloys
    (2025) Nečas, David; Gelnar, Adam; Rothammer, Benedict; Marian, Max; Ranuša, Matúš; Wartzack, Sandro; Vrbka, Martin; Křupka, Ivan; Hartl, Martin
    Advanced engineering coatings offer a promising solution to enhance the longevity and performance of medical biomaterials in orthopaedic implants. This study hypothesises that diamond-like carbon (DLC) coatings exhibit distinct frictional performance based on substrate and counterface material. Three different DLC coatings were tested using a pin-on-plate test in four material combinations. Virgin and DLC-coated CoCrMo and Ti6Al4V pins were tested under sliding against UHMWPE and glass plates with simulated body fluid lubrication. Results revealed that coating composition significantly impacts frictional performance, with silicon- and oxygen-doped coatings showing great potential to minimise friction. Surprisingly, reducing contact pressure had either a neutral or somewhat negative effect. Future investigations will focus on long-term testing and lubrication analyses of these material combinations.