Deformation and fatigue behaviors of carburized automotive gear steel and predictions

The fatigue behavior of carburized components such as automotive transmission gears is very complex due to hardness and microstructure difference, residual stresses and multi-axial stress states developed between the case and the core. In addition, automotive gears in service, commonly used in helical type, are actually subjected to complex stress conditions such as bending, torsion, and contact stress states. This study presents experimental and analytical results on deformation behavior of carburized steels, widely used in automotive gears, under cyclic stress conditions including axial and torsion loadings. Axial fatigue tests and rotating bending fatigue tests are also included. Predictions of cyclic deformation and fatigue behaviors of the carburized steel with two-layer model are compared with experimental results. The carburized steel investigated in this study exhibited cyclic softening under both axial loading and torsional loading. Predicted results with simple two-layer model for the cyclic deformation and fatigue behaviors were comparatively similar to the experimental data

Cyclic deformation and fatigue behavior of carburized automotive gear steel and predictions including multiaxial stress states

The fatigue behavior of carburized components such as automotive transmission gears is very complex due to hardness and microstructure difference, residual stresses and multi-axial stress states developed between the case and the core and/or at stress concentrations. In addition, automotive gears in service, commonly used in helical type, are actually subjected to complex stress conditions such as bending, torsion, and contact stress states. This study presents experimental and analytical results on deformation behavior of carburized steels, widely used in automotive gears, under cyclic stress conditions including axial, torsional and combined axial-torsion loadings. Axial fatigue and rotating bending fatigue, as well as torsional fatigue and in-phase axial-torsional fatigue tests are also included. Predictions of cyclic deformation and fatigue behaviors of the carburized steel with two-layer model are compared with experimental results. Predicted results with simple two-layer model for the cyclic deformation and fatigue behaviors were comparatively similar to the experimental data

Photochemical Nitrogen Conversion to Ammonia in Ambient Conditions with FeMoS-Chalcogels

In nature, nitrogen fixation is one of the most important life processes and occurs primarily in microbial organisms containing enzymes called nitrogenases. These complex proteins contain two distinct subunits with different active sites, with the primary N₂ binding site being a FeMoS core cluster that can be reduced by other nearby iron–sulfur clusters. Although nitrogen reduction to ammonia in biology does not require the absorption of light, there is considerable interest in developing catalyst materials that could drive the formation of ammonia from nitrogen photochemically. Here, we report that chalcogels containing FeMoS inorganic clusters are capable of photochemically reducing N₂ to NH₃ under white light irradiation, in aqueous media, under ambient pressure and room temperature. The chalcogels are composed of [Mo₂Fe₆S₈(SPh)₃]³⁺ and [Sn₂S₆]^4– clusters in solution and have strong optical absorption, high surface area, and good aqueous stability. Our results demonstrate that light-driven nitrogen conversion to ammonia by MoFe sulfides is a viable process with implications in solar energy utilization and our understanding of primordial processes on earth