Dynamic NVH Numerical Analysis of Power Steering in the Presence of Lubricant in the System.

The ongoing shift towards hybrid and electric vehicles has a strong impact on noise and vibration engineering. New, complex dynamic phenomena are brought to vehicle user attention due to the absence of internal combustion engines and the significant role in vehicle and drive feel perception. This paper presents an FEM (Finite Element Method) dynamic simulation model of an automotive Electric Power Steering assembly. Preliminary modal simulations and experiments as well as field data replication techniques were implemented to identify the phenomena and prepare and validate model components. A full dynamic model of an Electric Power Steering was presented, and fine-tuned including the presence of lubrication at the gear mesh interface. Experimental investigations were conducted alongside FEM simulations for various model setups. Linear and nonlinear contact stiffness models were implemented, as well as contact damping, and simulated at chosen assembly interfaces. The results indicated that in the case of NVH (Noise Vibration and Harshness) analysis of shock/impact originating problems, contact parameters used for static, quasi-static, and low velocity analyses were not applicable. Nonlinear and damped contact stiffness provided better results in such a case.

Finite Volume Method Modeling of Heat Transfer in Acoustic Enclosure for Machinery.

This paper deals with the problem of heat accumulation in acoustic enclosures. Increased noise levels at production sites or manufacturing lines force the application of acoustic enclosures. Effective noise reduction due to enclosures often comes with the additional thermal insulation of the device, which in many cases causes a strong increase in the device operation temperature. This paper presents the methodology of thermal phenomena numerical modeling based on the potential influence of acoustic enclosures on the increase in device operation temperature. The proposed model consists of an original acoustic enclosure concept design, and the numerical modeling is based on the computational fluid dynamics FVM (finite volume method) conducted in Ansys Fluent. The research comprised a set of simulations at different air flow rates of 52.5 m3/h, 105 m3/h, 210 m3/h and 420 m3/h at the enclosure inlet. The analysis carried out on the basis of flow paths and temperature distribution plots inside the enclosure led to the conclusion that the expected, analytically calculated minimum volumetric flow rate is not sufficient to effectively cool the investigated device to the required temperature of 26 °C, and higher air flow rates should be applied. Simulation results indicated that the numerical tools can be useful in the prediction of the heat exchange process, as well as in the selection of an appropriate source and location of cooling.

Synergistic effect of methylene blue and biogenic gold nanoparticles against Enterococcus faecalis.

This study reports successful photodynamic inactivation of planktonic and biofilm cells of Enterococcus faecalis using Methylene Blue (MB) in combination with gold nanoparticles synthesized using the cell-free filtrate obtained from 3-day biomass of Trichoderma asperellum strain. Monodispersed colloidal gold nanoparticles were characterized by UV-vis absorption, TEM and DLS to be 13 ±â€¯3 nm spheres. Diode lasers with the peak-power wavelength ʎ = 660 nm (output power of 21, 41 and 68 mW; power density of 55, 108 and 179 mW∙cm-2, respectively, were used as a light source to study the effects of MB alone, the gold nanoparticles alone (AuNPs) and the MB + AuNPs mixture on the viability of E. faecalis cells. The lethal effect of planktonic cells was achieved for MB after 30 min of laser irradiation with energy fluence of 322 J∙cm-2. When MB + AuNPs mixture was used as photosensitizer, the lethal effect was achieved with energy fluence of 292 J∙cm-2. The biofilm culture was more resistant to photo-inactivation and the best bactericidal effect of MB as photosensitizer was found after light dose of 483 J∙cm-2. The bacterial cell viability was reduced by 99.92%. It was proved that MB + AuNPs mixture synergistically enhances the kill of the studied microorganism as the same light dose resulted in 99.991% kill.