Magnetorheological fluid-based nanotexturing of tool inserts for turning of duplex stainless steel

This paper deals with the study of the nanotexturing process of the cutting tool inserts with the influence of a magnetorheological fluid-based texturing method. The rake and flank surface of the cutting tool inserts were finished with a silicon carbide abrasive mixture of a magnetorheological fluid. Experimentation is conducted with input variables such as voltage, gap width, and polishing time to achieve the desired value of % reduction of surface roughness, polishing rate, andpolishing time. The surface roughness is found to be less than 40?nm for textured and 120?nm for non-textured inserts with a lesser polishing time. A higher polishing rate of the cutting tool inserts is achieved at a working voltage of 36?V and a gap width of 0.75?mm. The machinability characteristics of the nanotextured inserts are based on the cutting force; tool wear is studied for the turning operation of Duplex stainless steel. The tool flank wear is observed to be 0.63?mm, after 13th pass when turned with an unpolished insert and 0.612?mm after the 19th pass with a polished insert. From the results, it is found that the nanotextured inserts could achieve a tool life of 60% higher than the un-textured inserts in machining the duplex stainless steel.     

Virial equation of state and ideal-gas heat capacities of pentafluoro-dimethyl ether

A virial equation of state is presented for vapor-phase pentafluoro-dimethyl ether (CF₃−O−CF₂H), a candidate alternative refrigerant known as E125. The equation of state was determined from density measurements performed with a Burnett apparatus and from speed-of-sound measurements performed with an acoustical resonator. The speed-of-sound measurements spanned the ranges 260≤T≤400 K and 0.05≤P≤1.0 MPa. The Burnett measurements covered the ranges 283≤T≤373 K and 0.25≤P≤5.0 MPa. The speed-of-sound and Burnett measurements were first analyzed separately to produce two independent virial equations of state. The equation of state from the acoustical measurements reproduced the experimental sound speeds with a fractional RMS deviation of 0.0013%. The equation of state from the Burnett measurements reproduced the experimental pressures with a fractional RMS deviation of 0.012%. Finally, an equation of state was fit to both the speed-of-sound and the Burnett measurements simultaneously. The resulting equation of state reproduced the measured sound speeds with a fractional RMS deviation of 0.0018% and the measured Burnett densities with a fractional RMS deviation of 0.019%.     

Comparison of the results of modeling convective heat transfer in turbulent flows with experimental data

The results of simulation of natural turbulent convection in a square air cavity measuring 0.75 × 0.75 m and having isothermal vertical and highly heat-conducting horizontal walls are compared with the experimental data obtained for this cavity at a Rayleigh number equal to 1.58⋅10⁹. In carrying out numerical investigations, a two-dimensional, low-turbulence, two-parameter k–ε model known as the low-Reynolds-number k–ε turbulence model was used. The results of investigations are presented for the distributions of the velocity and temperature components, as well as local and average values of the Nusselt number. The model was also used in calculating forced turbulent convection in a low-velocity channel with a backward facing step. The results of modeling are compared with experimental data on heat transfer in a turbulent separation flow downstream of the step. In both cases, a satisfactory agreement of the measured values with those predicted by the k–ε turbulence model is obtained.     

Effect of crystallization parameters and presence of aqueous extract of Nigella Sativa on growth inhibition of calcium oxalate monohydrate particles

For the first time, nucleation kinetics, crystal growth and agglomeration of calcium oxalate monohydrate (COM) are studied as a crystal growth inhibitor with and without Nigella Sativa(NS) extract. The induction period was determined under different supersaturation ratios ranging from 1.63 to 4.51 at 37°C using the conductivity method. Based on the classical homogeneous nucleation theory; the critical nucleation parameters were evaluated at higher supersaturation ratio. The calculated surface energy was increased from 7.97?mJ/m² without additive to 10.31?mJ/m² with NS extract. However, the nucleation rate at a supersaturation ratio of 3.26 corresponding to 5.44 with the NS extract was decreased from 3.9?×?10²⁹ nuclei/cm³.s (without additive) to 1.3?×?10²⁹ nuclei/cm³.s with NS extract addition. The number of molecules required for the formation of a stable nucleus was calculated with and without NS extract at different supersaturation ratios. The crystallite sizes of the formed crystals without and with the additive are 93 and 51?nm, respectively. Scanning electron microscopy (SEM) photomicrographs show the formation of small crystals and less aggregated with the NS inhibitor compared with the baseline (without the inhibitor). This study can help us with a clear understanding of the inhibition mechanism of an aqueous NS extract on COM crystals.     

Adsorption of amino acids by fullerenes and fullerene nanowhiskers

We have investigated the adsorption of some amino acids and an oligopeptide by fullerene (C₆₀) and fullerene nanowhiskers (FNWs). C₆₀ and FNWs hardly adsorbed amino acids. Most of the amino acids used have a hydrophobic side chain. Ala and Val, with an alkyl chain, were not adsorbed by the C₆₀ or FNWs. Trp, Phe and Pro, with a cyclic structure, were not adsorbed by them either. The aromatic group of C₆₀ did not interact with the side chain. The carboxyl or amino group, with the frame structure of an amino acid, has a positive or negative charge in solution. It is likely that the C₆₀ and FNWs would not prefer the charged carboxyl or amino group. Tri-Ala was adsorbed slightly by the C₆₀ and FNWs. The carboxyl or amino group is not close to the center of the methyl group of Tri-Ala. One of the methyl groups in Tri-Ala would interact with the aromatic structure of the C₆₀ and FNWs. We compared our results with the theoretical interaction of 20 bio-amino acids with C₆₀. The theoretical simulations showed the bonding distance between C₆₀ and an amino acid and the dissociation energy. The dissociation energy was shown to increase in the order, Val < Phe < Pro < Asp < Ala < Trp < Tyr < Arg < Leu. However, the simulation was not consistent with our experimental results. The adsorption of albumin (a protein) by C₆₀ showed the effect on the side chains of Try and Trp. The structure of albumin was changed a little by C₆₀. In our study Try and Tyr were hardly adsorbed by C₆₀ and FNWs. These amino acids did not show a different adsorption behavior compared with other amino acids. The adsorptive behavior of mono-amino acids might be different from that of polypeptides.     

Instrumentation of a Kenwood Major Domestic-Type Mixer for Studies of Granulation

The mixer was reconstructed and equipped with a torque transducer consisting of a steel beam, with strain gauges in a full bridge circuit, which prevented the rotation of the bowl.

Repeated loadings of the separate steel beam with weights resulted in a relative standard deviation of less than 0.2%. However, tangential loading of the equipment with a dynamometer resulted in a relative standard deviation of 1.2% because of the inaccuracy of the dynamometer load. The smallest detectable load was about 98· 10^-3 N, corresponding to 1–2% sensitivity within the interesting part of the granulation curve.

The average torque was calculated.

The recording mixer was simple to handle and proved a suitable tool for granulation studies.     

Influence of microscopically distributed inhomogeneity and anisotropy of grains on high-temperature crack propagation properties of directionally solidified superalloy

The fluctuation of J-integral, during high-temperature fatigue crack propagation, due to the microscopic inclination of crack and elastic anisotropy of each grain, is investigated by means of a series of finite-element-analyses on a cracked body. The simulated material is a nickel-based directionally solidified (DS) superalloy, where the DS axis, load direction, and crack propagation axis are set to be perpendicular to each other. The magnitude of J is estimated using two-dimensional models simulated after an experimental test: (i) with the actual crack shape and grain arrangement, (ii) with the actual crack shape in a homogeneous body, and (iii) with a straight crack in a homogeneous body (averaged deformation behavior of the material). The microscopic inclination of crack propagation direction causes the sporadic drop of J at the point where the crack direction is largely inclined from the direction normal to the load axis. The anisotropy of grains causes the stepwise change in the a (crack length) vs. J relationship. Such changes in J due to the microscopic inhomogeneity directly relates to the change of the crack propagation rate in the transgranular cracking. Then, J, which takes into accounts the anisotropy of grains, correlates well with the crack propagation rate in the transgranular cracking. The grain-boundary cracking possesses fluctuated J, and shows weaker resistance to the propagation than the transgranular one.     

Optimization of mechanical systems: On strategy of non-linear first-order approximation

The paper presents an extended approach to non-linear first-order approximation of non-linear programming problems and it explains how to transform an approximate problem into a strictly convex one. The essence of the proposed approximation technique is to rewrite each given function h_j as a composite g_j ^o Ψ^j. The function Ψ^j has to be chosen—the paper explains how to do this—while g_j is linear approximated with g_j. The approximation of h_j is then obtained as g_j ^o Ψ^j. This approach enables one to obtain approximate functions with variable conservativeness, which implies an adjustable approximate problem. A solution procedure, which replaces the original problem with a sequence of approximate problems, can therefore adjust each succeeding approximate problem to improve the convergence properties. The theory is illustrated with a three parameters controlled approximation. This technique represents, together with an optimality criteria based solution procedure, a powerful and economic tool for solving nonlinear programming problems. The three parameters, which influence to a great extent the conservativeness of the approximate functions, are under full control of the optimizer. They are varied automatically during the process of optimization to speed-up the convergence or to prevent oscillations. The benefits gained from the proposed approach are demonstrated on several numerical examples involving structures and a dynamic multibody system.     

A computer simulation of four-point bending fatigue of a rear axle assembly

The bending fatigue test of a rear axle assembly is simulated by using a FE-integrated fatigue analysis methodology. The presented technique is based on local stress–strain approach in conjunction with two critical plane damage parameters. The stress–strain response at a material point is computed with a cyclic plasticity model coupled with a notch stress–strain approximation scheme. Linear elastic FE stress analyses are used in the calculation of local fatigue loading. All computational modules are implemented into the software tool and used in the four-point bending fatigue test simulation of rear axles made of a high-strength alloy steel. In fatigue models, proportional loadings with a static preload are considered, and the effects of residual stresses are neglected. The fatigue test cycles and crack initiation locations are predicted using Smith–Watson–Topper and Fatemi–Socie fatigue damage parameters. Both damage parameters provided conservative test cycle estimates for the test conditions simulated. It is also observed that von Mises stress distributions cannot be used to predict fatigue crack initiation locations while Smith–Watson–Topper critical plane parameter estimated the cracking location suitably. Comparisons with the prototype tests showed the applicability of the proposed approach.     

Effects of vapor- growth conditions and ionizing radiation on the structure of black zinc diphosphide

The effects of growth conditions and various types of irradiation on the structure of black zinc diphosphide were studied. The results demonstrate that the great diversity in the growth habits of black ZnP₂ is due to twinning on a scale on the order of a few lattice parameters (30 Å). Neutron irradiation with a dose of 3 × 10¹⁸ cm^-2 induces a displacive phase transition (D_2h-C_2h). The associated structural changes, correlated with changes in the excitonic spectrum, occur with participation of defects in the phosphorus sublattice.     

A study of the compaction process and the properties of tablets made of a new co-processed starch excipient

This article deals with the study of the energetic relationships during compaction and the properties of tablets produced from a co-processed excipient based on starch and called StarCap1500^®. This article compares it with the substance Starch1500^®. The study also includes the mixtures of StarCap 1500^® and the granulated directly compressible lactose Pharmatose DCL^®15. The tablet properties tested included tensile strength and disintegration time, examined in dependence on compression force, and also a 0.4% addition of magnesium stearate. The results show a better compressibility of StarCap 1500 in comparison with Starch 1500 and a lower elastic component of energy. The tablets were stronger and disintegrated more rapidly, but the substance possessed a higher sensitivity to an addition of a lubricant than Starch 1500. Increasing portions of StarCap 1500 in the mixtures with Pharmatose DCL 15 increased the tensile strength of tablets, disintegration period as well as the sensitivity to an addition of a lubricant. From the energetic viewpoint, energy for friction was decreasing, while the energy accumulated by the tablet during compaction and the elastic component of energy were increased.     

Enhancement of the coercivity of electrodeposited nickel nanowire arrays

In the present study, the single-crystal Ni nanowire arrays with a preferred growth along the [110] direction have been prepared by the deposition of Ni into the alumina template with nanopores at a current density of 2.0 mA/cm². The single-crystal Ni nanowire arrays show a magnetic anisotropy with the easy axis parallel to the nanowires and an enhanced coercivity as compared with the polycrystalline Ni nanowire arrays. A large coercivity of 1110 Oe together with a high remanence M_r = 0.92M_s is observed for 15-nm diameter single-crystal Ni nanowire arrays. The preferred growth mechanism of the single-crystal nanowires is briefly discussed.     

Biofiltration of wastewater lift station emissions: evaluation of VOC removal in the presence of H2S

The capacity of biofilter systems to remove volatile organic compounds in the presence of high concentrations of hydrogen sulfide was investigated for applications in wastewater lift stations. The treatment system was an enclosed unit composed of a biotrickling filter coupled with a biofilter. The biofilter media were plastic hollow spherical balls filled with a compost mixture; and the biotrickling filter media was a structured plastic packing. The gases from the pumping station wet well were a mixture of H₂S and low concentration aliphatic and aromatic VOCs, toluene being the most significant in concentrations of 41 ppb. The H₂S concentration was 314 ppm with fluctuations of 100 ppm resulting from pumping cycles at the station. No inhibition effect was detected from the simultaneous biological removal of VOCs and H₂S: toluene removal efficiency was 91% with the two sections contributing approximately equally to the pollutant removal; and the average removal of H₂S was 74%. A traditional open-in-ground biofilter filled with wood chips and compost, existing in the site, attained similar removal efficiencies for toluene, but the elimination capacity of the biotrickling/biofilter system was 3.3-times higher than the open biofilter.     

Nature of inclusions in steel weld metals and their influence on formation of acicular ferrite

Abstract

The chemistry and structure of weld metal inclusions has been studied. Four submerged arc welds which utilized plate and consumables to cover a range of oxygen and deoxidant contents were examined. Analysis of the inclusions was carried out on carbon extraction replicas in a Philips 400T scanning transmission electron microscope, fitted with an energy dispersive analyser. Two major types of inclusion were found. With weld metal aluminium approaching the stoichiometric ratio with oxygen, the inclusions were crystalline and had a spinel structure at the centre with a discontinuous, polycrystalline, titanium-rich phase on the surface. With weld metal oxygen high compared with the stoichiometric ratio with aluminium, inclusions were glassy and essentially manganese silicate in composition, again with areas of a polycrystalline, titanium-rich phase on the surface. The interinclusion spacing varied little with weld metal oxygen content in the range 0·0268–0·0858 wt-%. The spacing was found to be of a similar order to the acicular ferrite grain size. The titanium-rich surface phase in all the welds was of fcc structure with a lattice parameter of 0·42 nm, which suggests a mixture of TiO and TiN, possibly rich in TiO. The spinel phase was also fcc and had a composition between galaxite (Al₂O₃MnO) and γ-alumina. Both these phases have a low lattice misfit with ferrite. A low lattice misfit of the inclusion surface layers with ferrite coupled with closely spaced inclusions would seem to be key factors in the development of an acicular ferrite weld metal microstructure.

MST/543     

Computational analysis of the regimes of solidification and cooling of a continuous casting with a circular cross section

The nonlinear problem on heat conduction with discontinuity coefficients was solved by the finite-difference method with the use of a grid irregular in time and space. The calculations were carried out using difference schemes with a “weight,” making it possible to control the calculation accuracy. The computational experiment has been performed for a steel of standard quality. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 3–8, March–April, 2007.     

Creep of polycrystalline sodium chloride containing a dispersion of alumina

The creep of polycrystalline NaCl contaning a fine dispersion of Al₂O₃ particles is analysed in terms of dependence on stress, temperature, volume fraction and size of dispersion, and grain size of samples. Compressive creep experiments around 0.8 Tm show that the dispersion inhibits diffusive creep. The creep is characterized by a threshold stress above which the creep rate increased linearly with applied stress. The threshold stress decreases with increasing temperature and is proportional to the volume fraction of the dispersion in agreement with a model proposed by Burton. The activation energy corrected for the temperature dependence of the threshold stress falls within a narrow range consistent with grain-boundary diffusion of chlorine in sodium chloride. The grain-size dependence is not consistent with a modified diffusive creep model but it is suggested that it may be controlled by inhibited grain-boundary sliding according to a new model.     

Effect of Mo on microstructure and mechanical properties of bulk nanocrystalline Fe3Al materials prepared by aluminothermic reaction

Abstract

Bulk nanocrystalline Fe₃Al based materials with 5, 10 and 15 wt-%Mo were prepared by aluminothermic reaction. The microstructure and mechanical properties of the materials were investigated. It was shown that the materials consisted of a nanocrystalline matrix phase that was composed of Fe, Al and Mo and a little Al₂O₃ contamination phase. The nanocrystalline phase had a disordered bcc crystal structure. Average grain sizes of the nanocrystalline phase of the materials with 5, 10 and 15 wt-%Mo were 19, 31 and 24 nm respectively and that of the material with 5 wt-%Mo was the smallest. The materials with 10 and 15 wt-%Mo exhibited brittle behaviour in compression, whereas the material with 5 wt-%Mo had a large plastic deformation. The material with 5 wt-%Mo had the highest bending strength and the lowest compressive yield strength.     

Transport properties of SnTe interpreted by means of a two valence band model

Electrical conductivity, thermoelectric power and Hall coefficient of SnTe have been measured between 300 K and 160 K. The temperature variation of thermoelectric power and the carrier concentration estimated from the Hall coefficient have been explained with a two valence band model. The variation of mobility with temperature has been calculated from the above measurements. The mobility of holes in the upper valence band is found to follow the usual $\text{T}{}^{\mathrm{<mtext>-3</mtext><mtext>2</mtext>}}$ law, whereas the mobility in the lower valence band increases with temperature in a peculiar manner which cannot be explained with the help of a parabolic band.     

Characteristics of a magnetron cold cathode gauge

The discharge characteristics of a cold-cathode gauge of the non-inverted magnetron type were studied in ultra-high vacuum. The experimental magnetron cell of length 56 mm and diameter 32 mm was made of stainless steel. The cathode with a diameter of 6 mm was placed along the anode axis. The diameter of the anode was 25 mm and the length was 50 mm. Discharge current versus voltage and magnetic field was measured in the pressure range between 1×10⁻⁸ and 1×10⁻⁶ mbar. It was found that the current at first slowly increased with increasing voltage, reached a maximum at a certain voltage, and decreased rapidly with further increase of the voltage. The voltage, at which the current reached the maximum, depended on the magnetic field density and slightly on the pressure. A novel type of a cold cathode gauge with a self-adjusting power supply is suggested.     

Effect of thermal treatments on the structure of MoNxOy thin films

MoN_xO_y films were deposited on steel substrates by dc reactive magnetron sputtering. The depositions were carried out from a pure molybdenum target, varying the flow rate of reactive gases. X-ray diffraction (XRD) results revealed the occurrence of cubic MoN_x and hexagonal (δ-MoN) phases for the films with high nitrogen flow rates. The increase of oxygen content induces the decrease of the grain size of the molybdenum nitride crystallites. The thermal stability of a set of samples was studied in vacuum, for an annealing time of 1 h, for temperatures ranging from 500 to 800 °C in 100 °C steps. The results showed that pure molybdenum nitride films changed their structure from a meta-stable cubic MoN to hexagonal δ-MoN and cubic γ-Mo₂N-type structures with increasing annealing temperatures. The samples with molybdenum nitride films evidenced a good thermal stability, but those with molybdenum oxynitride coatings showed a tendency to detach with the increase of the annealing temperature.