Straight Grain Research Articles

CARACTERIZACIÓN TECNOLÓGICA DE LA MADERA DE Juniperus flaccida VAR. POBLANA MARTÍNEZ

El presente estudio se realizó con la finalidad de conocer las características y propiedades tecnológicas de la madera de Juniperus flaccida var. poblana Martínez, para lo cual se utilizó la metodología del Laboratorio de Anatomía y Tecnología de la Madera de la División de Ciencias Forestales de la Universidad Autónoma Chapingo. Las propiedades físicas se determinaron según la norma NOM-EE-167-83 y las mecánicas de acuerdo a las normas ASTM 143-83 en el Campo Experimental San Martinito, del Instituto de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP). Los resultados con relación a las características anatómicas fueron los siguientes: la madera presenta un color castaño claro en el duramen y amarillo pálido en la albura, brillo medio, veteado suave, textura fina, hilo recto, sabor característico y olor aromático. Las traqueidas son largas, de diámetro tangencial mediano y paredes delgadas; presentan una hilera de puntuaciones areoladas seriadas, las puntuaciones de los campos de cruzamiento son tipo cupresoide y el parénquima axial es escaso. Los rayos de tipo uniseriados numerosos, muy bajos y muy angostos; los rayos y las células parenquimatosas axiales presentan aceites. La proporción de elementos fue 92 % de traqueidas, 7.72 de parénquima de rayo y 0.18 % de parénquima axial. La densidad básica fue de 0.50 g·cm-3, las contracciones totales fueron: volumétrica de 8.42 %, tangencial de 4.26 % y radial de 3.02 %; y los hinchamientos totales: volumétrico de 9.17 %, tangencial de 4.45 % y radial de 3.12 %. El punto de saturación de la fibra fue de 33 %; el coeficiente de hinchamiento 0.278 %, y la relación de anisotropía de 1.41. Los valores promedio de las propiedades mecánicas al 12 % de contenido de humedad (CH) y en condición verde, se clasificaron de medios a bajos en ambas condiciones de contenido de humedad. Considerando las características anatómicas y los valores de las propiedades físicas y mecánicas, esta madera puede ser empleada para elementos no estructurales como: molduras, peldaños de escaleras, pasamanos, lambrines, muebles, bastidores, mangos de herramientas de trabajo ligero y artesanías.

Technological Characterization of Cupressus spp. Wood

The objectives of the present study were to determine anatomical characteristics, mechanical properties and natural durability to two fungi types [Gloeophyllum trabeum (Persoon ex Fries) Murrill and Trametes versicolor (Linnaeus ex Fries)Pilat] for cypress wood (Cupressus spp.). The wood has straight grain, brown to white color, medium texture, and moderate luster. It also showed medium to low density, low shrinkage, and moderate dimensional stability. Lignin content was relatively high, whereas extractive content was low. Cupressus spp. showed static bending properties of 4.1 GPa for modulus of elasticity; 91.0 MPa for modulus of rupture; 1.8 MPa for internal bond; and 6357 and 4039 N for end and side Janka hardness, respectively. All mechanical properties, in air-dry condition, were similar to those described to cypresses and some Amazonian hardwood species. Cypress wood was ranked as highly resistant to the brown-rot fungus Gloeophyllum trabeum and to the white-rot fungus Trametes versicolor, making it suitable for interior and exterior uses and high humidity environment.

Microstructure, spallation and corrosion of plasma sprayed Al 2O 3–13%TiO 2 coatings

The electrochemical corrosion behaviours of the steel substrates coated with three different plasma sprayed Al 2O 3–13%TiO 2 coatings were studied in this paper. The three kinds of Al 2O 3–13%TiO 2 coatings were conventional ME coating, nanostructured NP coating and NS coating. There were micro cracks, laminar splats and straight columnar grains in ME coating. For the two nanostructured coatings, the laminar microstructure and columnar grains were not obvious. The NP coating had the highest hardness and spallation resistance. Electrochemical corrosion behaviour of the three coatings was mainly investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in aqueous Na 2SO 4 solution.

Model Lengkung Bentuk Batang (Taper Curve) Pohon Jati (Tectona Grandis)

Model of Taper Curve of Teak Stem (Tectona grandis)Detailed information on tree volume for fancy wood, such as teak, is important to estimate its financial value. Therefore, a method of estimating stem volume in portion wise is developed. The objective of this study was to apply a parabolic taper curve in various tree strata. Data of stem diameter at any relative height were collected from selected felled-tree samples according to stem quality both in the state and community forests by section wise measurement. Regression analysis was applied to estimate parameter and to test the suitability level of the parabolic taper model. The results showed that parabolic taper model could be used to describe the stem curve of clear bole stem in state forest and the stem curve up to tree height with minimum diameter of ca. 10 cm. In the state forest, the parabolic taper model was fit to medium and large diameter classes or in the intermediate and dominant strata. For small diameter class or in suppressed stratum, the model was not sufficiently fit. On the other hand, the parabolic taper model was fit to all samples from community forests because the samples comprised the stem of best quality from the stand. The parabolic taper model was suitable to apply on high quality stems which were characterized with healthy, cylindrical, and straight stem, high clear bole, and straight grain.

Playback Performance of Facing Targets Sputtered Tape Media on Moving Tape Substrate with a High Speed

Playback performances and microstructures of facing targets sputtered (FTS) longitudinal recording tape media on moving tape substrates were investigated at a fast (100 cm/min) and a slow (5.8 cm/min) moving speed. CoPtCr-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> granular magnetic layers were deposited on Ru underlayer on moving 4.5 mum thick Aramid films by a FTS system at room temperature. Coercivity over 300 kA/m and grain structures with average diameter of 8 nm were achieved on very thin plastic film. Moving speed does not affect microstructure grown by FTS. The magnetic grains are physically isolated by segregation of silicon and chromium to grain boundaries. This was observed by transmission electron microscopy (TEM) and spot energy-dispersive X-ray spectroscopy (EDS). Cross-sectional TEM images show that straight columnar magnetic grains were grown and unaffected by the moving direction of the substrate. In playback tests, it was shown that both samples had over 8 dB higher SNR than commercial particulate tape media of 0.5 Gb/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> areal density.

Thermal stress in the Apuan marbles: Relationship between microstructure and petrophysical characteristics

Apuan marbles originating from different zones of the Apuan Metamorphic Complex have been characterized from the chemical, petrographical, microstructural and physical points of view. All samples were subjected to accelerated ageing by thermal cycling and their petrophysical parameters evaluated. After accelerated ageing, all samples show an increase in total open porosity and/or porosity evaluated with Hg porosimeter in the range of pore sizes between 0.0037 and 150 μm. The greatest variations were recorded in the coarse and fine-grained marbles with straight grain boundaries. Two trends were observed in variation of the ratio of Hg-porosity to total open porosity after thermal cycling: either an increase in total open porosity not followed by a proportional increase in Hg-porosity or an increase in Hg-porosity proportional to an increase in total open porosity. During total immersion tests, an increase of the water absorption was observed for those samples characterised by a high ratio Hg-porosity/total open porosity with a unimodal distribution of Hg-porosity. In the case of water absorption through capillarity, the samples that suffer a higher increase are those characterised by a bimodal pore size distribution, even if they possess low Hg-porosity. This behaviour underlines that in the aged samples, subjected to the two different mechanisms of water absorption, the pore size distribution plays an important role.

Study on the Modelling of Microstructure for Polycrystalline Materials

Microstructure plays a significant role in the evolution of short fatigue cracks. The modelling procedure of microstructure for polycrystalline materials is presented in this paper. The factors that effect on the modelling of microstructure are discussed in detail. Firstly, the 2D microstructure of LZ 50 steel with straight grain boundary is simulated with the help of Voronoi tessellation. To validate the modelling results of the microstructure, two load cases are intentionally designed to verify the microstructure for the view of comparing the results with homogeneous material under the same load cases. The whole process is carried out with the application of FEM. From the comparison of mechanical properties generated by the simulated microstructure with anisotropic material property to the ones showed by macrostructure with homogeneous material property, the validity and convenience of the modelling process is shown. The simulated microstructure for polycrystalline materials can be used for the further research on the initiation and growth of short fatigue cracks.

Thermal and salt crystallization effects on marble deterioration: Examples from Western Anatolia, Turkey

Six commercially available and extensively used Turkish marbles having different textural properties were subjected to ageing tests in order to assess their resistance against salt crystallization with thermal effect. The change in physico-mechanical properties of the marbles including weight, dry unit weight, effective porosity, water absorption, dry and saturated sonic velocities, uniaxial compressive strength (UCS), indirect (brazilian) tensile strength, flexural strength, abrasion value, and impact resistance has been determined for various stages of the ageing tests. The results are evaluated in terms of the grain size, grain boundary, and grain size distribution of the marbles. Based on the test results, the physico-mechanical properties of the marbles are not uniformly affected from the ageing tests. The water absorption, effective porosity, UCS, sonic velocity and abrasion value of the marbles are found to be good parameters to assess the deterioration and quality of the marbles, whereas the weight loss, unit weight, brazilian tensile strength and impact resistance of the marbles are not. The marbles having small grain size, dominant grain size distribution in a narrow range, and irregular grain boundary are more resistant against the ageing tests than the ones with large grain size, grain size distribution in a wide range, and straight grain boundary.

Partial high‐pressure aragonitization of micritic limestones in an accretionary complex, Tavşanlı Zone, NW Turkey

AbstractPelagic micritic limestones within an upper Cretaceous accretionary complex in the Tavşanlı Zone, NW Turkey, preserve textures indicating incomplete prograde transformation of micritic calcite to aragonite, representing the only known example of this type. Aragonitization starts at the central parts of the micritic limestone beds and advances towards the lower and upper parts of the layers at the expense of micrite. Micrite is very fine grained (&lt;0.003 mm) and contains radiolaria, foraminifera and thin shell fragments. Aragonite forms large crystals, up to 3 cm across, with straight grain boundaries and c‐axis mostly subparallel to the carbonate beds. Relict micritic portions are devoid of any aragonite grain. Stylolites characterized by the accumulation of clay minerals, Fe‐Mn‐hydroxides and quartz are concentrated in the upper and lower parts of the beds. Stylolite formation precedes aragonitization. Conditions of aragonitization are estimated as 200 ± 50 °C and 0.45–0.65 GPa, based on metamorphic mineral assemblages observed in associated basalts. Several features such as (i) constant composition of micritic calcite (98–99 mol.% CaCO3) throughout individual beds, (ii) enormous grain size difference between micritic calcite and aragonite (up to 1200 times), and (iii) absence of any aragonite grains within the relict micritic portions suggest that kinetic rather than thermodynamic factors controlled selective aragonite formation in the central portions of carbonate layers.

Effect of Recrystallization on Low-Cycle Fatigue Behavior of DZ4 Directionally-Solidified Superalloy

Effect of recrystallization on DZ4 directionally-solidified nickel-base superalloy was investigated both at room temperature and high temperature of 673K. In-situ SEM surface observation were performed. Experimental results reveal that the material performance is strongly influenced by surface recrystallization layer. All specimens were prepared under conditions of shot peening and 4h 1220°C high temperature annealing. Different shot peening pressure specimens have different recrystallization states. High shot penning pressure specimens have clear and straight grain boundaries and the grain size appears to be a little bit larger. Recrystallization state seems not only affect the fatigue life, but also the crack initiation pattern and crack initiation life. Low shot peening pressure specimens have much lower fatigue life which is around 8-10% of virgin one, and SEM Real-time observation reveals that channeling cracks initiated at the early stage of fatigue life. High shot peening pressure specimens have higher fatigue life comparing to low shot peening pressure specimens, although it’s almost half lower than the virgin one, and cracks initiated not until middle or latter stage of fatigue life. Crack initiation life is also much longer than those of low shot peening pressure. Low shot peening pressure specimens seems not fully recrystallized, and its grain boundaries are much fragile which is responsible for high density microcracks initiation, and finally leads to the failure. Further nano-indention experiments on surface recrystallized layers show that higher shot peening recrystallized layers have much lower elastic module, which may explain the longer crack initiation life.

Grain boundary ridge formation during initial high temperature oxidation of Mn/Al TRIP steel

Confocal scanning laser microscopy (CSLM) was used in real-time observation of alloy element oxidation of a Mn/Al TRIP steel in an Ar–O2 atmosphere. CSLM images reveal a marked role of grain boundaries in the overall initial oxidation kinetics of the alloy, and consequently in the morphology of the initial surface oxide. The oxidation on the alloy surface is dominated by the formation of Mn-rich oxide ridges along grain boundary traces on the surface. Oxide ridge formation kinetics was quantified by measurements on images extracted from real-time recordings of surface oxide evolution. Oxide ridge growth was found to take place at a constant rate. Scanning electron microscopy (SEM) images of the oxidized surfaces showed homogenous oxide ridges along straight grain boundary traces and heterogeneous oxide ridges along non-straight grain boundary traces. A transport mechanism of Mn to the surface is proposed, which relies on grain boundary segregation of Mn and on a relationship between grain boundary diffusivity and grain boundary character. It is suggested that when regarding alloys with significant grain boundary segregation of a solute, separate Wagner balances for internal vs. external oxidation is required for the grain lattices and the grain boundaries, respectively.

TEM Studies of Grain Boundary Structure in a Cast Polycrystalline Silicon

Cast polycrystalline silicon for solar cell contains mostly straight twin boundaries which are thought to have little effect on the electrical activity. There are, however, some complicated grain boundaries in it. One of these boundaries consists of slightly curved and straight parts. The structure of this boundary was analyzed to investigate the difference of these two types of boundaries. The conventional transmission electron microscopy (TEM) found that this slightly curved boundary was the zigzag shaped boundary made by (11 _ ,2) and ( _ ,211) planes. High resolution electron microscopy (HREM) confirmed that (11 _ ,2) plane was the boundary of {112} Σ3 twin boundary which formed a straight grain boundary at the other end of the analyzed grain boundary, and also confirmed that ( _ ,2 11) plane was also the boundary of {112} Σ3 twin boundary which intersected with the former twin boundary at an angle of 120 [deg].

TEM Observations of Singular Grain Boundaries and their Roughening Transition in TiO2-Excess BaTiO3

Abstract When BaTiO3 powder compacts with 0.2 mol% excess TiO2 are sintered in air at 1250°C, below the eutectic temperature, some grains grow abnormally to very large sizes with double twins in the 〈111〉 directions at their centers. The abnormal grains, elongated in the 〈111〉 directions, form mostly straight grain boundaries, lying on their {111} planes with the fine matrix grains. Some grain boundaries between the nearly (111) face of an abnormal grain and the matrix grains are faceted with some facet planes lying on either the (111) plane of the abnormal grain or (210) plane of the matrix grain. These flat grain boundaries, as observed by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), must be singular, corresponding to cusps in the polar plots of the grain boundary energy against the boundary normal. A schematic analysis with the capillarity vectors shows that the straight {111} grain boundaries across the triple junctions with the matrix grains are...

Improvement of Creep-Fatigue Life by the Modification of Carbide Characteristics through Grain Boundary Serration in an AISI 304 Stainless Steel

The modification of carbide characteristics through grain boundary serration and its subsequent effect on the creep-fatigue property at 873 K have been investigated, using an AISI 304 stainless steel. It was found that the grain boundaries are considerably serrated when a specimen is furnace-cooled. The grain boundary serration leads to a change in the carbide characteristics as well as grain boundary configuration, i.e., morphology of carbide from an acute triangular to a planar form and a lowered density. Additionally, an array of carbide particles is changed from a consistent to zigzag pattern, in terms of their preference to one grain to share the coherency. Planar carbides on serrated grain boundaries have a lower interfacial energy than that of triangular carbides on straight grain boundaries. It is suggested that the modification of carbide characteristics through the grain boundary serration has a remarkable influence on the improvement of creep-fatigue resistance.

Grain-boundary sliding in elongated microstructures during diffusion creep

In diffusion creep, the contribution of grain-boundary sliding to the overall strain os can be evaluated in arbitrary polycrystals, if the angular distribution of grain boundaries is known. A os value of 0.5 is obtained for two-dimensional (2D) equiaxed microstructures consisting of regular hexagonal grains, equiaxed grains grown from a Voronoi structure or grains having a circular distribution of grain-boundary angles. The os value is also evaluated for uniaxially deformed 2D microstructures, both diffusionally and uniformly deformed. For the former, the deformed microstructure is obtained by the simulation of microstructural evolution in polycrystals with straight grain boundaries. The os value increases gradually with increasing or decreasing strain and is larger in the diffusionally deformed microstructures than in the uniformly deformed microstructures for a given grain aspect ratio. The os value for three-dimensional (3D) polycrystalline microstructures is also obtained from an ellipsoidal distribution of grain-boundary angles. The resultant os value is 0.60 for 3D equiaxed polycrystals and increases gradually with increasing strain.

On Structure, production, and market of bamboo-based panels in China

Since bamboo has the advantages of straight grain, beautiful color, high strength and toughness, and excellent abrasion resistance, bamboo-based panels have been widely used in the fields of vehicle, construction, ship building, furniture, and decoration to partly take the place of wood, steel, plastic etc in China. This paper briefly described the basic component units, including strip, sliver, and particle, of bamboo-based panel and pointed out that to design the structure of bamboo-based panels should follow the principle of symmetric structure, surface foming method, and structuring principle of equalizing stress. According to the processing methods and formation of component units, the authors classified the bamboo-based panels in China into 13 types and presented the manufacturing technique and uses of the bamboo products, such as plybamboo, bamboo flooring, and bamboo-wood composite products in detail. In the last part of the paper, much information were offered on the output, market, and selling prospect of each type of bamboo-based panels.

2825 高純度 cBN 多結晶体の微細構造と切削性能

High-purity Polycrystalline cBN can be synthesized from hBN by the direct conversion method under HPHT condition without additives or catalyst. Such polycrystalline cBNs under various conditions were prepared and investigated to clarify the effect of impurities and microstructure on cutting performance of the materials. When the amount of the compressed hBN exceeded 0.5%, the cutting performance was found to deteriorate rapidly in high-speed interrupted cutting test of gray cast iron. The tool life of polycrystalline cBN of coarse grade (1-5μm) was found to be shorter than that of fine grade (<0.5μm) by the breakage of the tool edge. From TEM observation, it was found that coarse cBN grains have crystal defects and straight grain boundaries, which are thought to weaken the mechanical strength. It was confirmed that the reduction of remaining compressed hBN (<0.5%) and the suppression of coarsening of cBN grain (<1μ1) are necessary for polycrystalline cBN having excellent performance.

Automated Image Processing and Analysis of Fracture Surface Patterns Formed during Creep Crack Growth in Austenitic Heat-Resisting Steels with Different Microstructures.

A computer program of automated image processing was developed for fractal analysis of creep fracture surface profiles in this study. Change in the creep fracture surface patterns during crack growth was examined by the computer-aided image processing and analysis. Fractal analysis was then made using software on the processed images. Creep crack growth experiments were carried out on the surface notched specimens of the austenitic 21Cr-4Ni-9Mn steel at 973 K. Creep crack growth rate was lower in the specimens with serrated grain boundaries than in those with straight grain boundaries. The fractal dimension of the grain-boundary fracture surface profiles was larger in the former specimens than in the latter ones. The fractal dimension was larger in the specimens tested under the lower stress, and decreased with increasing distance from notch root. Effects of grain-boundary microstructures and stress on the fracture patterns were correlated to the microstructure and stress dependence of the density of grain-boundary microcracks linked to the fracture surface. Quantitative evaluation of fracture surface patterns may give an important information about the fracture origin or crack growth direction.

Synthesis of feldspar bicrystals by direct bonding

We have produced synthetic feldspar bicrystals using a direct bonding technique. A gem-quality orthoclase crystal from Itrongay, Madagascar, was used for the bonding experiments. Microprobe analysis shows only minor concentrations of iron and sodium. Orthoclase single crystal plates oriented parallel (0 0 1) were cut and chemomechanically polished with silica slurry. From interferometry, final roughness of the square crystal plates was about 0.34 nm. Specimens were wet-chemically cleaned using deionised water. The bonding procedure produced an orthoclase bicrystal with an optically straight grain boundary-oriented parallel (0 0 1), which was investigated by HREM. Along the interface no amorphous layer was observed between lattice fringes of both crystals. We suggest that the bicrystals formed by initial hydrogen bonding and subsequent water loss and polymerisation of silanol and aluminol groups at elevated temperatures.

インバー合金の溶接に関する検討 ２ インバー合金の溶接金属割れ防止機構に関する検討

The effects of alloyed elements on ductility dip cracking susceptibility in multi-pass weld metal of Fe-36%Ni alloy (Invar alloy) was investigated to obtain the proper chemical compositions for preventing the ductility dip cracking and to clarify its mechanism. The tests were carried out using the Fe-36%Ni plates containing various contents of manganese, titanium, calcium, carbon and niobium. The ductility dip cracking susceptibility was evaluated by double bead longitudinal Varestraint test and restraint weld cracking test using gas tungsten arc welding (GTAW). The ductility dip cracking susceptibility decreased with the addition of both carbon and niobium. By the addition of these elements, the micro structure of weld metal was changed from the cellular structure with straight grain boundary to the cellular dendritic structure with grain boundary like saw teeth. Additionally, in the weld metal containing both niobium and carbon, the eutectic microstructure, with the niobium carbide, was produced. From these results, the prevention of ductility dip cracking in weld metal, with the addition of both niobium and carbon, is thought to be due to: (1) the decrease of sulfur concentration in the grain boundary by formation of eutectic structure with niobium carbide; and (2) the locking of the intergranular slip by the anchoring effect of the cellular dendritic structure with grain boundary like saw teeth.