Influence of notch radius and microstructure on the fracture behavior of Al–Zn–Mg–Cu alloys of different purity

The influence of notch radius on the fracture behavior of two high-strength Al–Zn–Mg–Cu alloys with different Fe content in the T73 condition was investigated. The fracture toughness tests were performed on non-fatigue-precracked notched bending specimens with different notch radii ranged from 0.15 mm to 1.0 mm. The obtained data were interpreted using the concept of Notch Fracture Mechanics combined with finite-element method (FEM) calculations. It was found that both alloys are very sensitive to the notch radius. The fracture toughness increases with increasing notch radius. For a given notch radii, the increase in fracture toughness is more significant for the more pure alloy. The fracture behavior of investigated alloys with respect to microstructural features and their relation with the fracture micromechanisms were analyzed.     

Comparison of the products of Kombucha fermentation on sucrose and molasses

Fermentation of 1.5 g/L of Indian black tea, sweetened either with 70 g/L of sucrose or an adequate quantity of three kinds of molasses, was conducted by domestic Kombucha (Acetobacter strains in symbiosis with Saccharomycodes ludwigii, Saccharomyces cerevisiae, Saccharomyces bisporus, Torulopsis sp. and Zygosaccharomyces sp.). Inoculation was performed with 10% of fermentation broth from the previous process. The fermentation in cylindrical vessels containing 2 L of liquid phase, was carried out at 22 ± 1 °C for 14 days, with periodical sampling to measure pH, content of acids (total, acetic and l-lactic), content of remaining sucrose and the yield of biomass at the end of fermentation. Significance of the differences of the results obtained in the fermentations on different substrates was analyzed by applying Duncan’s multiple range test. The molasses that yielded the beverage richest in l-lactic acid was suggested for Kombucha fermentation.     

PM6 and DFT study of free radical scavenging activity of morin

Flavonoids have long been recognised for their general health-promoting properties, of which their antioxidant activity may play an important role. In this work, we have studied the properties of flavonoid morin using semiempirical and density functional theory (DFT) methods in order to validate the application of the recently developed parametric method 6 (PM6). Reaction enthalpies related to mechanisms of free radical scavenging by flavonoid morin were calculated by DFT and PM6 methods in gas-phase, water, DMSO and benzene. It has been shown that fast semiempirical PM6 method can mimic results obtained by means of more accurate time consuming DFT calculations. Thermodynamically favoured mechanism depends on reaction medium: SPLET (sequential proton loss electron transfer) is preferred in water and DMSO, and HAT (hydrogen atom transfer) is predominant in gas-phase. In benzene these two mechanisms are competitive.     

Comparative cavitation erosion test on steels produced by ESR and AOD refining

Cavitation erosion studies of steels produced by Electroslag Refining (ESR) and Argon Oxygen Decarburization (AOD refining) have been carried out. The experiments were conducted using the modified ultrasonically induced cavitation test method. Erosion rates were measured and the morphology of damages under cavitation action was studied by scanning electron microscopy and optical microscopy techniques. The present work is aimed at understanding the cavitation erosion behaviour of electroslag refined steel (ESR) compared with the steel produced by Argon Oxygen Decarburization (AOD refining), commonly used in the production of hydraulic machinery parts (Pelton blades). The results exhibited lower cavitation rate of ESR steel compared with AOD steel, as a consequence of its better mechanical properties and homogeneous and fine-grained microstructure.     

An end-quality assessment system for electronically commutated motors based on evidential reasoning

Automatic end-quality assessment is a mean that helps reaching zero-fault products at the end of the manufacturing process. In this paper we present a system for assessing the quality of electronically commutated motors. The system consists of two major parts: feature extraction and overall quality assessment. The feature extraction part consists of signal processing algorithms tailored for mechanical fault detection. The quality assessment part, aimed for fault isolation and final quality decision, employs evidential reasoning for multi-attribute decision analysis. A prototype version of the system is validated on a test batch of 130 electronically commutated motors, demonstrating high diagnostic resolution and accuracy.     

Conservation laws in nonlocal elasticity

Summary In this paper Noether's theorem is formulated for the nonlocal field together with the appropriate general conservation law. Then using the Euclidean group of transformation, the equivalence between the conservation law and the Euclidean invariance is demonstrated. As a consequence a novel result for the conservation law in nonlocal elastodynamics has been obtained.