A simplified method for the evaluation of fatigue crack front shapes under mode I loading

Two-dimensional elastic or elasto-plastic models dominate the current fatigue crack growth assessment and life prediction procedures for plate components with through-the-thickness cracks. However, as demonstrated in many theoretical and experimental papers, the stress field near the crack tip is always three-dimensional and, as a result, the fatigue crack front is not straight. It is normally curved towards the plate faces. Over the past few years there were a number of very careful numerical studies focusing on the evaluation of fatigue crack front shapes. However, the application of the direct numerical techniques to fatigue phenomena is a very tedious and time consuming process and, sometimes, it is quite ambiguous. In the current paper we develop a simplified method for the evaluation of the front shapes of through-the-thickness fatigue cracks. Further, we validate the developed method against experimental results, investigate the influence of various parameters on the crack front shapes at stable (steady-state) propagation and analyse the differences in the results of fatigue crack growth evaluation obtained with two- and three-dimensional approaches.     

Optical and electrical characterization of a gold nanoparticle dispersion in a chiral liquid crystal matrix

We report on the effect of gold nanoparticle (Au NP) dispersion in a chiral nematic liquid crystal (LC). Polarized optical microscopy and X-ray diffraction measurements evidence the insurgence of an order change in the LC host. Moreover, a comparative analysis based on dielectric and voltammetric spectroscopies performed on pure LC and on Au NP-doped LC shows that Au NP’s presence besides affecting LC order influences its electric properties: ion conductivity results importantly reduced, and beyond a threshold value of the applied field electrophoresis phenomena are induced.     

Effect of P2O5 on the Structural and Magnetic Properties of Magnetite‐Based Glass‐Ceramics

The specific morphology and magnetic properties of magnetite‐based glass‐ceramics obtained by crystallization of Fe‐containing borosilicate glassmelts in the presence of P₂O₅ as nucleating agent are investigated. We found that the distribution of the tiny nanoparticles of magnetite determines the low temperature response to magnetic field. The observed effects are discussed with respect to the following factors: (1) the existence of a multimodal size distribution of the tiny grains as revealed by Mössbauer spectroscopy, magnetometry, and high‐resolution electron microscopy; (2) the existence of a disordered layer at the grain surface which is driven by field in a magnetically ordered state; and (3) the interplay between the relaxation mechanisms in different temperature ranges.     

Hydrocracking of vegetable oil on boron-containing catalysts: Effect of the nature and content of a hydrogenation component

Catalysts based on metals (Pt, Pd) and metal oxides (NiO, Co₃O₄, MoO₃, WO₃), supported on the surface of borate-containing aluminum oxide (B₂O₃–Al₂O₃), in the hydrocracking of sunflower oil at a temperature of 400°C, a pressure 4.0 MPa and a mass hourly space velocity MHSV 5.0 h^–1 are compared. H₂ TPR and IR spectroscopy of adsorbed CO and ESDR show that the hydrogenation catalyst components are Pt⁰ and Pd⁰, a mixture of Ni²⁺ + Ni⁰, Co²⁺ + Co⁰, or a mixture of the highest and partially reduced oxides of Mo and W. It is established that catalysts containing Pt, Pd, NiO and Co₃O₄, ensure complete oil hydrodeoxygenation. The main oxygen removal reactions in Ptand Pd-systems are decarboxylation and hydrodecarbonylation. For catalysts with NiO and Co₃O₄, characteristic reactions are reduction and methanation. The highest yield of the diesel fraction was obtained on Pt/B₂O₃-Al₂O₃ catalysts with metal contents of 0.3–1.0 wt %. Along with n-alkanes, the diesel fractions obtained on these catalysts include cycloalkanes and iso-alkanes (up to around 40 wt %) and aromatic hydrocarbons present in trace amounts. Hydrocracking on the Pt system at 400°C for 20 h with MHSV of 1.0 h^–1 produces a diesel fraction with a yield of at least 82.0 wt % and the content of iso-alkanes at least 76.1 wt %.     

State and Properties of a Carbon Sorbent Modified with a Bioactive Substance

Protection of Metals and Physical Chemistry of Surfaces - A method for introducing small amounts of betulin (up to 1 wt %) into a mesoporous carbon material with a preset specific surface area of...     

Effect of Heat Treatment on Dendritic Segregation and High-Temperature Strength of Single Crystals of Ni3Al-Base Rhenium-Alloyed Intermetallic Alloys

Metal Science and Heat Treatment - The nature of stability of dendritic microsegregation of rhenium in single crystals of intermetallic (γ′ + γ) alloys based on γ′-Ni3Al...     

Molecularly imprinted poly(acrylonitrile‐co‐acrylic acid) matrix with sclareol

There are presented results regarding a new set of molecularly imprinted polymers (MIPs) based on acrylonitrile:acrylic acid (AN:AA) copolymer matrix. As template, it was used sclareol, an important anticancer bioactive compound, never used before for molecular imprinting. An emerging and insufficient studied MIP preparation method, namely the phase inversion, was used to prepare 0.8 mm spherical sclareol MIPs (S‐MIPs). Three AN:AA copolymers, having the initial monomer ratios 90:10, 80:20, and 70:30, were synthesized by radical copolymerization in emulsion, without emulsifier. After that, each copolymer was dissolved in the presence of the template (sclareol) in dimethylformamide. The imprinting and the morphology of these new materials were analyzed by rheology, elemental analysis, infrared spectroscopy, size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry, batch rebinding tests, and Scatchard analysis. The conclusion was that the AN:AA‐80:20 matrix proved to be the optimized solution between high rigidity (given by the AN segments) and high affinity for the template (given by AA segments), the average imprinting factor for this system being 2.67. POLYM. ENG. SCI., 54:1484–1494, 2014. © 2013 Society of Plastics Engineers     

Positional‐Species Composition of Triacylglycerols from the Arils of Mature Euonymus Fruits

Positional‐species composition (PSC) of 1,2,3‐triacyl‐sn‐glycerols (TAG) from the arils of mature fruits of 13 species of Euonymus L. genus was established. The residues of six major fatty acids (FA), palmitic, stearic, hexadecenoic (H), octadecenoic (O), linoleic (L), and linolenic, were present in the TAG. PSC of TAG was determined by their partial lipase hydrolysis. By using hierarchical cluster and principal component analyses, it was definitely demonstrated that separate taxonomic units forming this genus were significantly distinguished as regards PSC of TAG. In particular, the Euonymus subgenus greatly exceeded the Kalonymus subgenus in both total content of L in TAG and in the rate of its incorporation into their mid‐position, while TAG of Kalonymus were marked by a prevalence of O‐TAG and sn‐2‐O isomers. Thus, these subgenera were significantly distinct in the rate of incorporation of O and L residues in the sn‐2 position of TAG molecules. Meanwhile, the TAG from the Euonymus section species were marked by an enhanced concentration of H and the incorporation of H in UUU TAG was much more active than in other TAG types. As for positional‐type composition of TAG, saturated FA were always virtually absent in the sn‐2 position of Euonymus aril TAG.