RESUMO
To further exert the technical advantages of face gears, high-end equipment puts forward the need for the long-life mass-machining of face gears. However, the commonly used technique of hard honing is more sensitive to installation errors and impact loads, and soft honing has insufficient removal ability to the margin, so the quality of the gear's life is difficult to guarantee. To solve this contradiction, this paper introduces a damper to honing and proposes a flexible honing method for face gears. First, to reveal the flexible honing mechanism, the tooth-surface model of face-gear honing is derived, and the mathematical model for face-gear flexible honing is established. Second, to clarify the influence of flexible honing parameters on the quality of the tooth surface, a roughness model of the honing surface is established, and the influence of flexible honing parameters on roughness is analyzed. Third, by analyzing the influence of roughness under the action of honing parameters on the stress of the tooth surface, the parameters for flexible honing are determined. Finally, the effectiveness of the method is verified by flexible honing machining and testing.
RESUMO
Struvite is a chemically bonded ceramic product in the pipeline of a sewage treatment plant. In order to explore the fire extinguishing potential of struvite, a new type of struvite ultrafine dry powder with excellent performance was prepared by a simple process, and its fire extinguishing performance and mechanism were analyzed in depth. Under the same process conditions, the refinement degree (D50 = 5.132 µm) and the specific surface area (BET = 25.72 m2/g) of ultrafine struvite were larger than those of NH4H2PO4 (D50 = 8.961 µm, BET = 13.64 m2/g), making struvite more suitable for fire extinguishing. Besides, the pyrolysis process of struvite was relatively concentrated and absorbed more heat in a short time. Its heat absorption (458.4 J/mg) was higher than that of NH4H2PO4 (156.4 J/mg). Water, ammonia, and PO· were released during the pyrolysis of struvite, which effectively reduced fire temperature, diluted oxygen concentrations and captured free radicals. At the same time, the final products were magnesium orthophosphate and magnesium pyrophosphate, which formed a dense flame-retardant ceramic layer with good thermal insulation and environmental protection functions. In these cases, the fire extinguishing mechanism of struvite was determined to have three stages: the cooling effect, the asphyxiation effect, and the chemical effect. Correspondingly, the fire extinguishing time of struvite was three seconds faster than that of ammonium phosphate under 0.2 MPa based on the local oil basin test.
