Numerical study of conditions for subsurface shear instability under contact interaction

Numerical modeling of nanostructuring burnishing has been carried out to reveal the limiting values of process parameters, which serve both to provide the appropriate surface quality and positive deformation-induced structural modification of the subsurface layers as well as to avoid shear instability in the subsurface layers of burnished metal. The effects of load, burnishing speed, tool pass number and tribological transfer on the burnished surface roughness have been elucidated by the example of quenched and tempered steels 20X (EN 20Cr4). It was shown that overloading results in quasi-viscous flow of the subsurface material, deterioration of the surface and ruining the positive effect of nanostructuring burnishing

Effect of adhesion transfer on the surface pattern regularity in nanostructuring burnishing

In the paper the influence of friction-induced adhesion of metal to the tool on the formation of surface topography under nanostructuring burnishing was studied. A comprehensive approach, including both experimental (optical microscopy and profilometry) and theoretical (computer-aided simulation) methods was used. The results showed a direct connection between values of adhesion strength of materials in contact with the workpiece surface pattern quality caused by the tool movement. Results of the experimental and theoretical study are in good agreement and allow us to identify the reason of regular profile forming during surface burnishing

Preparation of nano/micro-bimodal Ti/Al/(Mo, W, Cu) powders by simultaneous electrical explosion of dissimilar metal wires

Novel mixtures of micro- and nanoparticles have been obtained by simultaneous electrical explosion of three intertwisted wires (EEW). The possibility of obtaining of titanium‑aluminum micro- and nanoparticles alloyed with molybdenum, tungsten and copper by the electrical explosion of Ti/Al/(Mo, W, Cu – up to 6 at. %) wires has been shown. Spherical particle with sizes from 20 nm to 7 μm are formed under condition of introducing the electric energy at the level of 0.57–0.77 of the total sublimation energy. The mass content of particles with sizes less than 100 nm does not exceed 10%. The phase composition of powders includes double and triple intermetallic phases, titanium oxide (TiO) as well as phases of the initial metals. The study of the phase composition of bulk materials obtained by sintering powders Ti-Al-Mo, Ti-Al-W and Ti-Al-Cu for 2 h at 1000 °C showed the increase in the content of intermetallic phases, providing enhanced physical and mechanical properties of the titanium‑aluminum alloys. The results of the studies show that the obtained powders alloys can be used to produce feedstocks of TiAl alloys

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTIC‐HF: baseline characteristics and comparison with contemporary clinical trials

Aims: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC‐HF) trial. Here we describe the baseline characteristics of participants in GALACTIC‐HF and how these compare with other contemporary trials. Methods and Results: Adults with established HFrEF, New York Heart Association functional class (NYHA) ≥ II, EF ≤35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic‐guided dosing: 25, 37.5 or 50 mg bid). 8256 patients [male (79%), non‐white (22%), mean age 65 years] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NT‐proBNP 1971 pg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTIC‐HF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure < 100 mmHg (n = 1127), estimated glomerular filtration rate < 30 mL/min/1.73 m2 (n = 528), and treated with sacubitril‐valsartan at baseline (n = 1594). Conclusions: GALACTIC‐HF enrolled a well‐treated, high‐risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation

Numerical study of conditions for subsurface shear instability under contact interaction

Numerical modeling of nanostructuring burnishing has been carried out to reveal the limiting values of process parameters, which serve both to provide the appropriate surface quality and positive deformation-induced structural modification of the subsurface layers as well as to avoid shear instability in the subsurface layers of burnished metal. The effects of load, burnishing speed, tool pass number and tribological transfer on the burnished surface roughness have been elucidated by the example of quenched and tempered steels 20X (EN 20Cr4). It was shown that overloading results in quasi-viscous flow of the subsurface material, deterioration of the surface and ruining the positive effect of nanostructuring burnishing

Micron- and nanosized alloy particles made by electric explosion of W/Cu-Zn and W/Cu/Ni-Cr intertwined wires for 3D extrusion feedstock

A novel approach to electric explosion of intertwined wires to obtain homogeneous powder mixtures intended for preparing feedstock for extrusion 3D printing has been applied. The powder were composed of spherical micron- and nano-sized W/Cu particles in-situ alloyed by Zn and Ni during electric explosion of intertwined dissimilar metal wires is offered. The mean particle size measured by micron-sized particles was not more than 20 m. The average number size of these particles was 3 m and it was dependent on the energy input. The powders contained phases such as -W, -W/W3O as well as FCC -Cu(Zn) and -Cu(Ni) solid solutions with the crystalline lattice parameters 3.629 and 3.61 A, respectivel

Molecular dynamics study of the acoustic emission during nanoindentation of iron crystal

In the paper simulation of the indentation of iron crystal was carried out using the method of molecular dynamics. We investigated the effect of vibrations on the AE under the impact of a single element (indenter) with a certain amount of material. Fluctuations of the forces acting on the sensor, changing of the system energy and the formation of defects during loading were analyzed. The force signal showed the increase in its amplitude and power spectrum as well as the median frequency drop under loading by vibrating indenter. The rationale behind all these changes may be dependence between the vibration amplitude and full system energy

Subsurface structural evolution and wear lip formation on copper single crystals under unlubricated sliding conditions

The crystalline lattice reorientation in copper single crystals resulted from friction-induced subsurface deformation has been studied by means of electron back scattering diffraction as well as optical microscopy. The results have been compared to those obtained earlier in uniaxial compression. The copper single crystals oriented by their normal load forces either along [110] or [111] have been subjected to sliding tests during which the friction force direction was varied to assess the friction force orientation dependence on the crystalline lattice reorientation and segmentation. The results of dry sliding tests showed that the plastic deformation in copper single crystals depended on the crystal's orientation with respect to both normal and friction forces. Crystalline lattice reorientation in wear lip formation has been studied including reorientation by ridge-kink formations

Effect of adhesion transfer on the surface pattern regularity in nanostructuring burnishing

In the paper the influence of friction-induced adhesion of metal to the tool on the formation of surface topography under nanostructuring burnishing was studied. A comprehensive approach, including both experimental (optical microscopy and profilometry) and theoretical (computer-aided simulation) methods was used. The results showed a direct connection between values of adhesion strength of materials in contact with the workpiece surface pattern quality caused by the tool movement. Results of the experimental and theoretical study are in good agreement and allow us to identify the reason of regular profile forming during surface burnishing