A damage constitutive model for sliding friction coupled to wear

Several new constitutive models are formulated for the planar interface of a soft body sliding on a rigid soil, describing stick-slip phenomena due to friction, and wear due to abrasion. Attention is focused on damage at the interface, by neglecting any interaction with damage of body and any propagation of damage inside the body. Models are formulated in the general framework of the Thermodynamics of the irreversible processes and account for suitable defined internal variables of phenomenological type, namely gap, isotropic friction hardening and wear. The main feature of the new presented models is that the formulation of the wear process at the interface is obtained in the contest of Damage Mechanics, and it is based on the formal analogy between abrasion of a soft body and ductile damage of an elastic-plastic material. By following this approach, a scalar wear field, an effective stress and appropriate state and dissipation potentials are defined, able to describe a tangential isotropic wear process due to stick-slip and to hardening mechanism. Both cases of linear and nonlinear friction hardening are formulated; moreover, wearable and no-wearable bodies are considered. Numerical results relevant to one-dimensional problems are illustrated for monotonic, forward-backward and cyclic displacement time-histories, showing evolution for stress, gap and wear. Results furnished by different models are compared and discussed.     

Evaluation of the morphology of particles produced by plasma-chemical synthesis of ceramic powders

A physicomathematical model of thermal and diffusion processes in a drop of a dilute metal salt solution during its heating in a plasma-chemical reactor for synthesizing metal oxide powders is presented. The results of numerical calculations are analyzed to assess the possible influence of the operation parameters of the reactor and the characteristics of the initial solution (precursor) on the morphology of the particles formed.     

A space monitoring system for powerful impulsive sources

The paper describes a space monitoring system for powerful impulsive sources designed for detecting storm fronts and lightning activity, predicting powerful magnetic storms, and analyzing the characteristics of faults in the Earth’s curst. It is shown that onboard apparatus can also be used to detect solar and Galactic ionizing-radiation activity, determine the total electron content in the ionosphere, etc. In conclusion, examples of social-economic problems that can be solved using the impulsive-source monitoring system are presented, and perspectives for the further development of this system are discussed.     

Synthesis and properties of isopropylamine borane i-C3H7NH2 · BH3

Isopropylamine borane i-C₃H₇NH₂ · BH₃ was synthesized by the reaction of sodium tetrahydroborate NaBH₄ with isopropylamine hydrochloride in tetrahydrofuran followed by extraction with diethyl ether. Its synthesis conditions were determined and optimized. The compound was characterized by chemical analysis, IR spectroscopy, and differential thermal analysis.     

Magnetic relaxation efficiency of gadolinium(III) and holmium(III) in 1-N-butyl-3-methylimidazolium chloride as probed by 35Cl/37Cl NMR

The magnetic relaxation efficiency of gadolilnium(III) and holmium(III) ions in 1-N-butyl-3-methylimidazolium chloride was investigated by the ³⁵Cl/³⁷Cl NMR method over the temperature range of 298?C393 K.     

Extraction of lanthanides(III) by phosphorylated naphthyridine ligands from carbonate solutions

The extraction capacities and selectivities of 1,8-naphthyridine-based neutral organophosphorus reagents in extracting trivalent lanthanides (Ln, Nd, Ho, Yb) from carbonate solutions were studied. The length and nature of the linker between the naphthyridine and phosphoryl moieties were found to have considerable influence on the efficiency and selectivity of lanthanide extraction.     

Thermochemistry of the silver(I) complexation with 18-crown-6 ether in binary acetonitrile—dimethylsulfoxide solvents

The effect of acetonitrile-dimethylsulfoxide solvents on the enthalpy of silver(I) complexation with 18-crown-6 ether is studied by means of calorimetry. It is found that an increase in the concentration of dimethylsulfoxide leads to an increase in the reaction exothermicity. It is shown that the determining factor in the change in the reaction enthalpy is the solvation effect of the ligand.