Average Orientation Factor Research Articles

Correlation between grain structures and tensile properties of Al–Li alloys

The correlation of grain structures (texture and grain shape) of some Al–Li alloys to their yield strength (YS) and elongation was investigated from a new perspective. The investigated materials include 2195, 2A96, 2A55 and 2050 Al–Li alloy sheets with 2 mm in thickness and plates with 5 and 10 mm in thickness as well as different layers in 2297-T87 and 2050-T83 Al–Li alloy thick plates with 80–85 mm in thickness. Higher YS in general corresponds to higher average orientation factor M () values, but there still exist some exceptions. As yielding occurs during tensile deformation, some grains just rotate, slip systems are not activated in all grains and the activated slip system number in different grains is also different. The value calculation therefore should be corrected and normalized excluding the grains in which slip system is not activated and considering the easiest activated slip systems. Meanwhile, the grain shape also plays an important role in YS. Although almost full recrystallization occurs, the higher grain aspect ratio tends to enhance the YS because of less grain rotating and more activated slip systems. Furthermore, the total equivalent slip system number and grain shape affect the elongation in that higher total equivalent slip system number and lower grain aspect ratio correspond to larger elongation.

Quantitative characterization of microstructures and elastic properties in plasma sprayed coatings based on “Ultrasonic – Elasticity – Microstructure” interaction mechanism

In plasma sprayed coatings, pores are the primary microstructure, and their features such as porosity, shape, and orientation significantly influence the thermal insulation and elastic properties of the coatings. Therefore, the ultrasonic characterization of pore feature parameters plays a crucial role in guiding the processing and predicting the lifespan of coatings. However, the coupling of multiple pore feature parameters leads to ill-posed problem and nonlinearity between these parameters and the ultrasonic feature signals, making it challenging to identify multiple pore feature parameters accurately. In this study, based on the “ultrasonic - elasticity - structure” interaction mechanism, a novel strategy for the ultrasonic quantitative identification of pore feature parameters and elastic constants in plasma sprayed coatings is proposed.Firstly, a random pore model (RPM) was developed to reveal the complex morphology of pores in plasma sprayed coatings. The porosity, average aspect ratio, orientation factor, and contour roughness factor were statistically analyzed for 15 sets of constructed RPMs, followed by ultrasonic finite element simulations. Then, a sensitivity matrix (SM) inversion method is developed for the “ultrasonic - elasticity” relationship by accurately measuring the elastic constants of the coatings through ultrasonic wave velocity inversion at multiple angles, yielding a relative error of only 0.57%. Lastly, a Multi-output Support Vector Regression machine learning model optimized by genetic algorithm (GA-MSVR) was proposed to establish the “elasticity - microstructure” relationship and identify multiple pore feature parameters based on elastic constants. The maximum relative errors for the four pore feature parameters are found to be 12.28%, 6.35%, 18.87%, and 7.62%, respectively, demonstrating the feasibility of the proposed strategy. Furthermore, the sensitivity matrix was employed to explain the cause for the larger relative error of the orientation factor.In summary, a challenging task of quantitatively identifying pore feature parameters in plasma sprayed coatings is addressed by proposing a novel solving strategy based on the “ultrasonic - elasticity - microstructure” interaction mechanism. The developed RPM, SM inversion method, and GA-MSVR model contribute to the accurate and comprehensive identification of pore feature parameters. The results obtained validate the feasibility of the proposed strategy.

Brush Printing Creates Polarized Green Fluorescence: 3D Orientation Mapping and Stochastic Analysis of Conductive Polymer Films.

Brush printing is a unique method used to obtain uniaxially oriented films, whereby a polymer solution is brushed onto a substrate. However, there have been only a few reports on the brush-printing method. Here, we report the preparation of a uniaxially oriented film of a green light-emitting conductive polymer, poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT). The fluorescence polarization ratio of the oriented F8BT films was as high as 11.3, and the average orientation factor reached 0.74 ± 0.06. The orientation factor and the torsion angle of F8BT were visualized by two mappings of fluorescence and Raman spectral measurements by confocal spectromicroscopy, respectively. These two x-y mapping data with many pixels (∼750 pixels) were evaluated by x-y-z mapping of the film thickness at a single position and were used to reveal the three-dimensional (3D) orientation mechanism from a stochastic approach. Polarized green fluorescence originates from polymer chains uniaxially oriented along the brush direction. The high orientation for a film thickness < 100 nm is established by shear stress, faster capillary flow, and flow-induced chain extension for a thin solution film on a substrate. The high orientation factor was also demonstrated by a high brushing speed, whereas an optimized brushing speed existed. We found that this optimization is attributed to the property of a non-Newtonian fluid. By applying this brush-printing method to the fabrication of an optoelectrical device, polarized green electroluminescence was preliminarily demonstrated by the OLED assembled from an oriented F8BT film.

Study on the Tensile Strength and Micromechanical Analysis of Alfa Fibers Reinforced High Density Polyethylene Composites

In the recent years, there has been a growing interest in eco-friendly composites, based on natural fiber reinforcements. In this work, Alfa fibers were obtained from Alfa grass (Stipa tenacissima) through an intensive cooking with sodium hydroxide and anthraquinone. These fibers, with contents ranging from 20 to 50 wt%, were used to reinforce a high density polyethylene. The composites were prepared in a kinetic mixer and later on tensile tested under standard conditions. The results showed that the tensile strength of the composites increased with the amount of fiber in the composite. Aditionally, a morphology and chemical composition analysis of the fibers surface were carried on, in order to further discuss the micromechanics analysis results. The average orientation factor and intrinsic tensile strength of the fibers were also determined during the micromechanics analysis.

Effect of different electrical stimulation waves on orientation and alignment of adipose derived mesenchymal stem cells

To investigate the effect of different electrical stimulation waves on orientation and alignment of adipose derived mesenchymal stem cells (ADSCs). ADSCs were isolated from 5-week-old Sprague Dawley rats (weight, 100-150 g) and cultivated. The cells at passages 3-5 were inoculated to prepare cell climbing slices, subsequently was exposed to direct-current electrical stimulations (ES) at electric field strengths of 1, 2, 3, 4, 5, and 6 V/cm on a homemade electric field bioreactor (groups A1, A2, A3, A4, A5, and A6); at electric field strength of 6 V/cm, at 50% duty cycle, and at frequency of 1 and 2 Hz (groups B1 and B2) of square wave ES; at electric field strength of 6 V/cm, at pulse width of 2 ms, and at frequency of 1 and 2 Hz (groups C1 and C2) of biphasic pulse wave ES; and no ES was given as a control (group D). The changes of cellular morphology affected by applied ES were evaluated by time-lapse micropho-tography via inverted microscope. The cell alignment was evaluated via average orientation factor ( OF). The cytoske-leton of electric field treated ADSCs was characterized by rhodamine-phalloidin staining. The cell survival rates were assessed via cell live/dead staining and intracellular calcium activities were detected by calcium ion fluorescent staining. The response of ADSCs to ES was related to the direct-current electric field intensity. The higher the direct-current electric field intensity was, the more cells aligned perpendicular to the direction of electric field. At each time point, there was no obvious cell alignment in groups B1, B2 and C1, C2. The average OF of groups A5 and A6 were significantly higher than that of group D ( P<0.05), but no significant difference was found between other groups and group D ( P>0.05). The cytoskeleton staining showed that the cells of groups A5 and A6 exhibited a compact fascicular structure of cytoskeleton, and tended to be perpendicular to the direction of the electric field vector. The cellular survival rate of groups A4, A5, and A6 were significantly lower than that of group D ( P<0.05), but no significant difference was found between other groups and group D ( P>0.05). Calcium fluorescence staining showed that the fluorescence intensity of calcium ions in groups A4, A5, and A6 was slightly higher than that in group D, and no significant difference was found between other groups and group D. The direct-current electric field stimulations with physiological electric field strength (5 V/cm and 6 V/cm) can induce the alignment of ADSCs, but no cell alignment is found under conditions of less than 5 V/cm direct-current electric field, square wave, and biphasic pulse wave stimulation. The cellular viability is negatively correlated with the electric field intensity.

Joint refinement of FRET measurements using spectroscopic and computational tools

The variability of the orientation factor is a long-standing challenge in converting FRET efficiency measurements into donor-acceptor distances. We propose the use of molecular dynamics (MD) simulations to characterize orientation distributions and thus improve the accuracy of distance measurements. Here, we test this approach by comparing experimental and simulated FRET efficiencies for a model donor-acceptor pair of enhanced cyan and enhanced yellow FPs connected by a flexible linker. Several spectroscopic techniques were used to characterize FRET in solution. In addition, a series of atomistic MD simulations of a total length of 1.5 μs were carried out to calculate the distances and the orientation factor in the FRET-pair. The resulting MD-based and experimentally measured FRET efficiency histograms coincided with each other, allowing for direct comparison of distance distributions. Despite the fact that the calculated average orientation factor was close to 2/3, the application of the average κ2 to the entire histogram of FRET efficiencies resulted in a substantial artificial broadening of the calculated distribution of apparent donor-acceptor distances. By combining single pair-FRET measurements with computational tools, we demonstrate that accounting for the donor and acceptor orientation heterogeneity is critical for accurate representation of the donor-acceptor distance distribution from FRET measurements.

Tensile properties and micromechanical analysis of stone groundwood from softwood reinforced bio-based polyamide11 composites

Bio-polyamides (BioPA) reinforced with natural fibres are one of the most promising bio-based composites. However the principal challenge of polyamides (PA) is their high melting temperature close to the degradation temperature of the natural fibres. Polyamide 11 (PA11) is a 100% BioPA with a melting point lower than cellulose temperature degradation. Nonetheless, few researches about PA11 reinforced with natural fibres composites had been performed. In this work, PA11 was reinforced with stone groundwood fibres (SGW) ranging 20% up to 60% of fibre contents. The composites were prepared, extruded, injected moulded and their tensile properties were characterised. An enhancement of 66.8% was obtained for the tensile strength of the composites, besides the strain and the toughness decreased as expected. The significant enhancement of the tensile strength leads to consider a relatively good interface between the fibre and the polymer matrix which was determined in the micromechanical studies. Moreover a morphology analysis of the fibre and its chemical composition study at surface were carried on, in order to discuss the micromechanical analysis results. The average orientation factor and intrinsic tensile strength of the fibres were also determined in the micromechanical analysis.

Hall-Petch Relation in a Spheroidized Carbon Steel with Emphasis on the Effect of Intergranular Particles

The Hall-Petch relation in a spheroidized steel with bimodal cementite particle size distribution has been investigated in this study, with an emphasis on considering the effect of the large particles at ferrite grain boundaries and triple junctions. A medium carbon steel was processed by variable thermomechanical procedures to achieve spheroidized structures with different combinations of microstructrual parameters, but all exhibiting a bimodal particle size distribution, in which large intergranular particles and small intragranular particles coexisted in the ferrite matrix. A quantitative relationship between the Hall-Petch parameter ky and the volume fraction of the intergranular cementite particles is presented, by considering a composite model. The contribution of the large intergranular particles to grain boundary strengthening wa substantiated by the increment of the ky parameter, since the average orientation factor of the composite, is increased. After correction of the ky parameters based on the constants from literatures, the predicted stresses show good agreement with the experimental stresses. A linear fit between the experimental stresses and the reciprocal square root of grain sizes is performed, the slope constant ky derived agrees to within 11 % of the corrected ky parameters based on the constants from literatures.

The Impact of Microstructure on Yield Strength Anisotropy in Linepipe Steels

We describe here the effect of microstructure on the yield strength anisotropy in high-strength microalloyed linepipe steels. The anisotropy in steel with ferrite-bainite microstructure was lower compared to the steel with ferrite-pearlite microstructure and is attributed to the significant difference in their transformation texture components, {112}〈110〉 and {332}〈113〉. The yield strength anisotropy is discussed in terms of crystal plasticity concept involving estimation of average orientation factor and its relation to yield strength.

Effect of Crystallographic Texture on Anisotropy of Yield Strength in X100 Pipeline Steel

The anisotropy of microstructures and mechanical properties in commercial American Petroleum Institute (API) X100 pipeline steel was systematically investigated by experimental measurements. The experimental results show that anisotropy of yield strength could be observed considerably, which should be attributed to the crystallographic textures due to deformation and transformation of texture components. This is because the effect of the inhomogencity of microstructure in different directions on the mechanical properties could be reasonably neglected based on the experimental investigation of grain size distribution. The effect of crystallographic texture on the anisotropy of yield strength was interpreted theoretically based on the relationship between yield strength and average orientation factor.

Effect of crystallographic texture on the anisotropy of Charpy impact behavior in pipeline steel

The current study systematically investigated the anisotropy of fracture behavior in commercial API X100 pipeline steel. The experimental results showed that the temperature for transition from ductile to brittle fracture was significantly different in samples with different orientations, defined as anisotropy of fracture behavior in this paper. The inhomogeneity distribution of microstructure (grain size) and the crystallographic texture were systematically analyzed. The difference in grain size of the samples with different orientations can be reasonably ignored in this study. Therefore, the anisotropy of fracture behavior is attributed to the crystallographic textures in which the deformation and transformation texture components were included. The effect of crystallographic texture on the anisotropy of ductile to brittle fracture transition temperature was theoretically interpreted based on the relationship among yield strength, fracture strength, and their average orientation factor.

Fracture Characteristic of a Mg-Gd-Y Alloy Compressed at High Strain Rate and Sub-Zero Temperature

In this paper, an as-extruded Mg-10Gd-2Y-0.5Zr alloy was compressed at 3265 s-1and -20 °C using a split Hopkinson pressure bar (SHPB) machine. Details about the initial texture and the lattice parameters of the as-extruded alloy were obtained by pole figures combined by orientation distribution function (ODF) and X-ray diffraction (XRD) Rietveld refinement method, respectively. It can be obtained that the maximum average orientation factor being 0.297 can be obtained at 45oangled to the extruded direction that is the force axis, resulting in the fracture of the impact compressed sample along a plane orientated at an angle of ~45oto the compression axis. Analysis of the fracture reveals that the fracture forms near the periphery of one face of the specimen and then penetrates into the bulk material subsequently meet near the other face. Even though the local shear deformation exists in the compressed sample, the fracture of the as-extruded Mg-10Gd-2Y-0.5Zr alloy compressed at 3265 s-1and -20 °C is not caused by forming the adiabatic shear band (ASB).

Simple tools for fiber orientation prediction in industrial practice

In this paper, the two origins of the preferred orientation of fibers are first reviewed. We then propose a definition of what to call an oriented fiber from a practical point of view in the cementitious material field. Considering typical industrial flows and materials, we identify the dominant phenomena and orientation characteristic time involved in the fiber orientation process in the construction industry. We show that shear induced fiber orientation is almost instantaneous at the time scale of a typical casting process. We moreover emphasize the fact that shear induced orientation is far stronger in the case of fluid materials such as self compacting concretes. The proposed approach is validated on experimental measurements in a simple channel flow. Finally, a semi-empirical relation allowing for the prediction of the average orientation factor in a section as a function of the rheological behavior, the length of the fibers and the geometry of the element to be cast is proposed.

Taylor factors in materials with many deformation modes

A Taylor factor (M) is frequently used to express a flow stress {sigma} measured in a polycrystal in terms of the critical resolved shear stress (CRSS) {tau} in the constituent single crystals. It is an average orientation factor which depends on the texture of the material and on the crystallographic nature of the assumed slip systems. When stress strain curves are analyzed, this Taylor factor is also commonly used to express the macroscopic strain in terms of the algebraic sum of crystallographic shears. As a result, the polycrystals strain hardening slope is proportional to M{sup 2}, and therefore rather sensitive to the assumed value of M. The strain hardening rate in single crystals, obtained by dividing the polycrystal value by M{sup 2}, provides useful information on the deformation mechanism and on constitutive relations to be used in polycrystal simulations.

The use of the isotropic orientation factor in fluorescence resonance energy transfer (FRET) studies of the actin filament

A Dale-Eisinger style analysis (R. E. Daleet al., Biophys. J. 26, 161, 1979) is used to produce three-dimensional plots that display the limits on the average orientation factor [Symbol: see text]K (2)[Symbol: see text] that is required to calculate molecular distances in F-actin from fluorescence resonance energy transfer measurements. Maxima and minima plots are generated for the transfer of energy from a donor to a single acceptor and for transfer to multiple acceptors that are related by F-actin helical symmetry. The analysis is performed in terms of dipole cone half-angles rather than depolarization factors, in order to facilitate the modeling of the multiple acceptor problem. Calculations are carried out under the restrictive condition of a single electric dipole moment per fluorophore. In addition, both surface and volume averaging of the donor and acceptor dipoles are considered. Comparisons between the plots show that for the multiple acceptor cases with F-actin symmetry, there is a great reduction in the range for maxima and minima limits on [Symbol: see text]K (2)[Symbol: see text]. The calculations also suggest guidelines for the choice of fluorescence label that will result in an average orientation factor occurring within acceptable limits, i.e., inside the limits for which [Symbol: see text]K (2)[Symbol: see text]=2/3 may be employed. Thus, without having detailed knowledge of the mean donor or acceptor dipole relative orientations, the use of [Symbol: see text]K (2)[Symbol: see text]=2/3 in radial coordinate studies of F-actin is more than reasonable and is fairly assured of being correct.

The tensile properties of a textured Ti 65Al 25Nb 10 alloy

The α 2 alloy Ti 65Al 25Nb 10 can form a sharp (001) basal plane texture following a two-step hot rolling procedure and subsequently heat treatment. A tensile test has been conducted on this textured alloy. The elongation in the rolling direction and the reduction in the width direction are both found to increase significantly compared with the Ti 3Al alloys, but the reduction in thickness is similar to that in the Ti 3Al alloys. The yield stress of the textured alloy is below that of the Ti 3Al alloys. It is proposed that the type «aå and type « c + a a ̊ dislocation slippings are related to the reductions in witdh and thickness respectively. It is suggested that the improvement in elongation in this textured alloy results from the lower average orientation factor M̄ and from the smaller grain boundary angles present in the textured alloy. Both factors contribute a lower blocking energy of the grain boundaries for dislocation slipping.

Wide angle X‐ray diffraction investigations of orientation of chopped fibers in fabricated thermoplastic parts

AbstractA method of determining fiber orientation in composites using wide angle X‐ray diffraction (WAXD) is described. This approach is based upon examining the alignment of the highly oriented crystalline fibers. X‐ray studies were carried out using Kevlar [poly(p‐phenylene terephthalamide) (PPTA)] fibers suspended at a 0.31 volume fraction loading in a polycarbonate matrix. A pole figure device was used to determine the orientation distribution and average orientation factor of the PPTA crystallographic chain axes relative to reference axes located in the test specimen. We prepared ideally oriented uniaxial and bioaxial composites as reference specimens using a compression molding machine. The fiber orientations in capillary extrudates, slit die extrudates, cold rolled sheets, and injection‐molded specimens were examined by WAXD. The capillary extrudates showed uniaxial orientation but the slit die extrudates and cold rolled sheets exhibited biaxial orientation. Injection‐molded specimens contained complex states of fiber orientation.

An investigation of the SH 1-SH 2 and SH 1-ATPase distances in myosin subfragment-1 by resonance energy transfer using nanosecond fluorimetry

The separation between the two reactive thiols SH 1 (Cys-704) and SH 2 (Cys-694) and that between SH 1 and the active site of myosin subfragment-1 were further investigated by Förster energy transfer techniques. The SH 1-SH 2 distance was determined with the probe 5[[2-[(iodoacetyl)amino]ethyl]amino]naphthalene-1-sulfonic acid (AEDANS) attached to SH 1 as the energy donor and 5-(iodoacetamido)fluorescein (IAF) attached to SH 2 as energy acceptor. The results derived from measurements of donor lifetimes yielded a donor-acceptor separation in the range 26–52Å, with the distance R(2/3) based on rapid and isotropic probe motions being 40 Å. These parameters were not sensitive to added MgADP, in agreement with previous results obtained by using the steady-state method. The SH 1-SH 2 distance was also determined with AEDANS attached to SH 1 and N-(4-dimethylamino-3,5-dinitrophenyl)maleimide (DDPM) attached to SH 2. The range in R for the AEDANS/DDPM pair was 12–36 Å, with R(2/3) equal to 27 Å. The transfer efficiency between these two probes increased by an average of 38% upon addition of MgADP. These results are in agreement with those previously reported (Dalbey, R.E.; Weiel, J.; Yount, R.G. (1983) Biochemistry 22, 4696–4706), but the uncertainty in choosing an appropriate value of the orientation factor to describe the AEDANS-DDPM separation does not allow a unique interpretation of the observed increase in energy transfer because it could reflect either an increase in the average orientation factor or a decrease in the donor-acceptor separation. Nevertheless, the results are consistent with the notion that nucleotide binding induces structural perturbations that can be sensed by SH 1 and SH 2. The distance between SH 1 and the ATPase site was determined with AEDANS linked to SH 1 and the nucleotide analogue 2′(3′)- O-(2,4,6,-trinitrophenyl)adenosine 5′-diphosphate (TNP-ADP) noncovalently bound to the active site as energy acceptor. The bound TNP-ADP was highly immobilized, with a depolarization factor approaching unity. The sepration between AEDANS at SH 1 and TNP-ADP at the active site was in the range 15–44 Å. The actual minimal separation between SH 1 and the active site is probably less than 15 Å, which suggests that direct interaction between the two sites cannot be ruled out from energy transfer results.

Pattern analysis of irregularly shaped particles

Methodical considerations are presented on the application of a commercial pattern-recognition instrument like the Quantimet 720 for the computer-supported analysis of irregularly shaped particles. To discriminate between particles of different shape on the basis of some simple geometrical models proposed, effective analytical criteria are suggested and adequate expressions are derived for the numerical calculation of length and width of particles irrespective of their actual shape as well as for such properties as convexity, clustering or eccentricity. A slightly enhanced k-factor compared to that in common use is discussed. Based on the results so far obtained with single particles, formulae for the determination of an average orientation factor and an autocorrelation function are provided. All considerations were extensively tested by the numerical evaluation of proper drawing models.

The orientational freedom of molecular probes. The orientation factor in intramolecular energy transfer

The measurement of the efficiency of Förster long-range resonance energy transfer between donor (D) and acceptor (A) luminophores attached to the same macromolecular substrate can be used to estimate the D-A separation, R. If the D and A transition dipoles sample all orientations with respect to the substrate (the isotropic condition) in a time short compared with the transfer time (the dynamic averaging condition), the average orientation factor less than K2 greater than is 2/3. If the isotropic condition is not satisfied but the dynamic averaging condition is, upper and lower bounds for less than K2 greater than, and thus R, may be obtained from observed D and A depolarizations, and these limits may be further narrowed if the transfer depolarization is also known. This paper offers experimental protocols for obtaining this reorientational information and presents contour plots of less than K2 greater than min and less than K2 greater than max as functions of generally observable depolarizations. This permits an uncertainty to be assigned to the determined value of R. The details of the D and A reoreintational process need not be known, but the orientational distributions are assumed to have at least approximate axial symmetry with respect to a stationary substrate. Average depolarization factors are derived for various orientational distribution functions that demonstrate the effects of various mechanisms for reorientation of the luminophores. It is shown that in general the static averaging regime does not lend itself to determinations of R.