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The crystallization behavior of amorphous Sm5Fe17 melt-spun ribbon was studied. The crystallized phases in annealed specimens were deeply dependent on both the annealing temperature and the heating rate. The optimally annealed Sm5Fe17 melt-spun ribbon consisted of Sm5Fe17 grains of around 50–100 nm in diameter and exhibited a remanence of 50 emu/g with a high coercivity of 40 kOe.

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Mixtures of powdered Sm5Fe17 melt-spun ribbon and Fe powder were consolidated into bulk magnets by the spark plasma sintering (SPS) method. Although these bulk magnets consisted of the hard magnetic Sm5Fe17 and soft magnetic α-Fe phases, they had a smooth hysteresis loop and exhibited coercivity. Among the magnets studied, the Sm5Fe17/Fe composite magnet with 30%Fe showed a remanence of 94 emu/g with a coercivity of 2.9 kOe.

<div class="section abstract"><div class="htmlview paragraph">A wet clutch couples or decouples gear elements to alter torque paths in an automatic transmission system. During the gear shifting event, the clutch torque is directly transmitted to the output shaft. Hence, clutch torque heavily influences the dynamics of the transmission. In order to evaluate the behavior of the transmission early and efficiently, the development process increasingly relies on high-fidelity transmission system simulations with added complexity. However, a wet clutch continues to be modeled using Coulomb’s friction in a typical shift simulation. Its linear framework does not physically represent non-linear hydrodynamic effects due to the presence of oil layer during clutch engagement. To make up the lack of physics, Coulomb’s clutch model often requires extensive tuning to match actual shift behaviors. Alternatively, a squeeze film based clutch model, coupled with an asperity contact model, can be employed to represent hydrodynamic behaviors and enable the broader use of dynamic simulation models in transmission development. However, while the squeeze film model has been extensively studied over the years, the asperity contact model remains largely unexamined. In this research, the contact behaviors of the asperities are empirically characterized for a wet clutch friction material. The results are compared against the base theory of Greenwood-Williamson asperity contact model (GW model) which is commonly accepted in wet clutch modeling. The analysis shows that the key assumptions of GW model, specifically the elastic deformation of spherical asperity tip and Gaussian distribution of their heights, do not hold for clutch friction materials. A new empirical asperity contact model is developed for wet friction material based on asperity roughness characterization and microscopic contact area measurements. The empirical model provides an accurate representation of asperity behaviors in wet clutch modeling, as an alternative to the conventional GW model, for high-fidelity transmission system simulations. The modeling framework is also applicable to a broad range of friction materials used in dry clutches, brakes and other applications that are characterized with hard constituents embedded in an elastic matrix.</div></div>