Browsing by Author "Kalifa, Mohamed"

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    Analyzing frictional noise for wear monitoring under dry and lubrication condition: experimental modelling with pin-on-disc tribometer
    (Trans Tech Publications Ltd, 2025-01-06) Kalifa, Mohamed; Starr, Andrew; Khan, Muhammad
    In industrial settings, the use of frictional noise to improve wear monitoring is highly promising. It enables the identification of changes in friction and wear conditions, the assessment of different phases of wear, and the examination of the impact of wear on machine performance. By analysing acoustic signatures, it is conceivable to continuously monitor the wear characteristics and surface conditions. This helps in predicting wear and detecting aberrant wear regimes in real-time. The data demonstrate that in dry conditions, the aluminum disc has higher coefficients of friction relative to cast iron and mild steel, likely due to the absence of graphite flakes in aluminum. Under lubricated conditions, a layer of lube significantly decreases the coefficient of friction, with no apparent deviations across the materials, demonstrating that complete lubrication avoids direct metal contact. In lubrication-starved applications, oily depictions nevertheless help minimize friction, though less efficiently than complete lubrication. In dry conditions, frictional sound levels for mild steel are higher due to direct surface hits, while lubrication reduces noise by eliminating metal-on-metal contact. As a result, monitoring noise levels is a helpful indicator of lubrication difficulties, aiding in maintenance and repairs.
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    Current research and challenges in modelling wear, friction, and noise in mechanical contacts
    (SAGE, 2025-12-31) Kalifa, Mohamed; Starr, Andrew; Khan, Muhammad
    In recent years, the investigation of friction noise which using to predict the wear has gained increasing attention within the field of tribology. In a wide variety of industries, the wear of mechanical components is a matter of major concern, as it directly affects the working life of machinery and equipment such as brake systems and high-speed running machines. Numerous earlier studies, using mathematical, analytical, and finite element methods (FEM), have proposed various hypotheses concerning contact dynamics and friction surface characteristics with the goal of modeling the contact mechanisms. Modelling mechanical contact with rough surfaces poses significant challenges. This study emphasizes the need for advanced modelling techniques by revealing the limitations of existing models in accurately predicting wear, friction, and frictional noise. The analysis highlights the importance of linking friction, wear, and noise in both dry and lubricated conditions, and underscores the necessity of addressing current gaps to develop more precise wear prediction methods based on noise generation in industrial applications. This paper is to review prominent existing models, exploring their approaches to noise generation from friction and its subsequent effect on surface wear. The paper aims to identify key limitations and challenges in accurately modelling these interdependencies. While previous research has often focused on wear caused by friction between surfaces, there is a notable gap in understanding the relationships between frictional noise, friction coefficient, surface roughness, and wear under sliding contact. Current models still face limitations, such as the influence of lubricants.
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    Interplay between wear and thermal expansion in 6082 aluminum: a simulation and experimental study
    (MDPI, 2024-11-23) Tian, Yang; Kalifa, Mohamed; Khan, Muhammad; Yang, Yifan
    This study investigates how wear and thermal expansion interact in 6082 aluminum, utilizing a pin-on-disc tribometer and finite element analysis under diverse mechanical conditions. The findings show that thermal expansion reduces contact area by forming a protrusion at the contact interface. This interaction between wear and thermal expansion causes dynamic shifts in the contact region and pressure distribution, affecting the disc center and altering wear progression and temperature patterns. High thermal expansion shifts maximum wear from the contact center to outer regions, especially at higher speeds and loads. Without thermal expansion, wear-only conditions overestimate friction dissipation, resulting in a higher peak temperature. These results highlight the critical role of thermal expansion in shaping wear patterns and contact behavior in sliding applications. This research offers insights for optimizing tribological performance in 6082 aluminum, with potential applications in other materials.