Longitudinal Texture Research Articles

Texture Evolution and Plastic Deformation Mechanism of Cold-Drawn Co-Cr-Ni-Mo Alloy

The plastic deformation behavior and mechanisms of Co-Cr-Ni-Mo alloy were investigated. The wires were subjected to different reductions using a multi-pass drawing approach and the resulting microstructures were characterized by EBSD and TEM. It was found that the alloy cold-drawn from surface to center exhibited non-uniform radial strain, with decreasing strain from surface to center. As the strain increased, the transverse texture of the alloy evolved from the initial bimodal texture consisting of strong {100}<110> and weak {110}<001> components to bimodal texture with {110}<233> and {112}<111> components, with significant twinning and mirror orientation between twin and matrix. The longitudinal texture evolution of the alloy mainly occurred on the α-fiber line, and ultimately did not form a significant texture due to grain elongation and crystal rotation. The plastic deformation mechanism of the Co-Cr-Ni-Mo alloy was dominated by dislocation slip at lower strain levels, which gradually transitioned to a combination of dislocation slip and twinning at higher strain levels. The deformation twins were typically distributed in high-density dislocation regions, and the twin boundaries transformed into high-angle sub-grain boundaries, hindering the extension of dislocation slip and deformation twin. With the increase in strain, work hardening results in a significant increase in strength and microhardness.

Longitudinal changes in hippocampal texture from healthy aging to Alzheimer's disease.

Early detection of Alzheimer's disease is essential to develop preventive treatment strategies. Detectible change in brain volume emerges relatively late in the pathogenic progression of disease, but microstructural changes caused by early neuropathology may cause subtle changes in the MR signal, quantifiable using texture analysis. Texture analysis quantifies spatial patterns in an image, such as smoothness, randomness and heterogeneity. We investigated whether the MRI texture of the hippocampus, an early site of Alzheimer's disease pathology, is sensitive to changes in brain microstructure before the onset of cognitive impairment. We also explored the longitudinal trajectories of hippocampal texture across the Alzheimer's continuum in relation to hippocampal volume and other biomarkers. Finally, we assessed the ability of texture to predict future cognitive decline, over and above hippocampal volume. Data were acquired from the Alzheimer's Disease Neuroimaging Initiative. Texture was calculated for bilateral hippocampi on 3T T1-weighted MRI scans. Two hundred and ninety-three texture features were reduced to five principal components that described 88% of total variance within cognitively unimpaired participants. We assessed cross-sectional differences in these texture components and hippocampal volume between four diagnostic groups: cognitively unimpaired amyloid-β- (n = 406); cognitively unimpaired amyloid-β+ (n = 213); mild cognitive impairment amyloid-β+ (n = 347); and Alzheimer's disease dementia amyloid-β+ (n = 202). To assess longitudinal texture change across the Alzheimer's continuum, we used a multivariate mixed-effects spline model to calculate a 'disease time' for all timepoints based on amyloid PET and cognitive scores. This was used as a scale on which to compare the trajectories of biomarkers, including volume and texture of the hippocampus. The trajectories were modelled in a subset of the data: cognitively unimpaired amyloid-β- (n = 345); cognitively unimpaired amyloid-β+ (n = 173); mild cognitive impairment amyloid-β+ (n = 301); and Alzheimer's disease dementia amyloid-β+ (n = 161). We identified a difference in texture component 4 at the earliest stage of Alzheimer's disease, between cognitively unimpaired amyloid-β- and cognitively unimpaired amyloid-β+ older adults (Cohen's d = 0.23, Padj = 0.014). Differences in additional texture components and hippocampal volume emerged later in the disease continuum alongside the onset of cognitive impairment (d = 0.30-1.22, Padj < 0.002). Longitudinal modelling of the texture trajectories revealed that, while most elements of texture developed over the course of the disease, noise reduced sensitivity for tracking individual textural change over time. Critically, however, texture provided additional information than was provided by volume alone to more accurately predict future cognitive change (d = 0.32-0.63, Padj < 0.0001). Our results support the use of texture as a measure of brain health, sensitive to Alzheimer's disease pathology, at a time when therapeutic intervention may be most effective.

Longitudinal OCT texture analysis to assess the retinal changes in the triple‐transgenic mouse model of Alzheimer's disease

AbstractPurpose: This study aimed to investigate whether texture from optical coherence tomography (OCT) can address Alzheimer's disease (AD)‐related changes in the retina by evaluating differences to the wild‐type (WT) control group over time.Methods: The study included OCT data of WT mice and its age‐matched transgenic mice of AD (3xTg‐AD). Animals were imaged monthly from 1 month old up to 4 months old and at the ages of 8‐, 12‐, and 16 months old. Neuro‐retinal layers were analysed using various texture metrics, assuming that these could convey different views of unfolding changes. Two hundred forty texture metrics were computed from local binary patterns and some variants, local phase quantisation, wavelet features, and Gabor filters. The discriminative potential of the texture metrics was evaluated using the non‐parametric Mann–Whitney test with a 5% significance level at each age to determine the consistency in the texture difference between groups over time. The trajectories of the texture measurements of the WT and AD mice were compared to analyse the trends over time.Results: Texture metrics showing differences between the WT and AD groups from a time‐point onwards were found for all neuro‐retinal layers, with the retinal nerve fibre layer (RNFL) presenting the most significant number of metrics in these conditions. The most relevant differences between groups were found at 2 months old, while few metrics presented differences from 8 months old onwards. Consequently, this study demonstrated that texture metrics discriminate retinas of AD mice from the WT group based on OCT data. Furthermore, this study also demonstrated the parallel path of changes over time in both groups, with the vast majority of the metrics presenting the same type of variation with time.Conclusions: This study emphasizes the potential of the texture information in the OCT images to address AD‐related changes in the retina. We presented longitudinal texture analysis of WT and transgenic mice, where the texture differences were found at the youngest age of the study (1 month) and preserved the differences over the 16‐months study period. Those differences showed the same evolutionary trend for both groups.

Optimal Longitudinal Texture on Concrete Pavement to Reduce Lateral Vibration of Vehicles

Since the mid-2000 s, longitudinal tinning has been applied to concrete pavements of expressways to improve the comfort and safety of road vehicle users. However, in certain longitudinal tinning sections, lateral vibrations occur during driving, which poses a safety hazard. This paper analyzes the cause behind this problem and proposes a longitudinal texturing specification that can minimize lateral vibration. To perform this analysis, the accelerations of driving vehicles and the degree of lateral vibration transmitted to panels in the vehicles were evaluated for each longitudinal texture applied in South Korea. Structural analysis was also conducted for the lateral force and moment according to the tire tread profile and longitudinal texturing specifications using the finite element method. In addition, field investigation, indoor drivability evaluation, and field application were performed to evaluate the optimal longitudinal texturing specification. The results indicate that the texture designated as 2 × 3 × 19 mm is the optimal longitudinal texture on hardened concrete pavement. However, because this specification is difficult to apply to fresh concrete, 3 × 3 × 16 mm is proposed as the optimal longitudinal texture owing to its excellent performance in the panel survey and in structural analysis.

Macrotexture Assessments Using Line-Laser Technology

The Florida Department of Transportation (FDOT) State Materials Office measures statewide macrotexture in relation to mean profile depth (MPD). This is done using point-laser systems mounted along the driver-side wheel path of friction evaluation vehicles. Historically, point-lasers have been recognized by the FDOT to accurately measure MPD on flexible pavement. However, current point-laser technology is unable to measure the anisotropic texturing of rigid pavement, such as longitudinal diamond ground (LDG) concrete. For this reason, the FDOT purchased two LMI Technologies Gocator-2342-3B-12 line-laser systems, which have the capability of measuring longitudinal texture. As received, internal testing conducted by the FDOT had shown poor agreement between line-laser MPD and accepted reference values on both flexible and rigid pavement. Since then, a research-based approach in configuring the line-laser system to accurately assess pavement macrotexture has been completed. Results from the statewide testing showed that the updated line-laser system produced MPD values on flexible pavement with an average difference of ±5.2% when compared with the point-laser system. On rigid pavement, the updated line-laser system produced MPD values with an average difference of ±10.4% when compared with those produced by a circular track meter. Precision testing showed that the line-laser system produced repeatable results on all pavement types with an average repeatability limit, r, of 0.25 mm and reproducibility limit, R, of 0.30 mm, which was comparable to the precision results of the point-laser system.

Design on progressive corners of dies and macro textures of blank holders for S stamped parts

The shape dimensions of die corners and surface textures of blank holders are important in the effective control of twist springback. For predicting springback accurately, a mixed hardening model is presented for a thin-walled S beam made from TRIP780. Based on a proposed evaluation index for twist springback, the experiments of stamping and twist springback for TRIP780 are carried out. The twist springback angle is gauged by a three-coordinate measure instrument. A Response Surface Model (RSM) between the parameters of the mixed hardening model and the twist springback angles is established, and the parameters are inversed. The progressive die corners are designed for the twist springback compensation based on the stress distribution of the thin-walled S beam after stamping, and the die corner radius is optimized by the RSM and an Ant Colony Algorithm (ACA). Meanwhile, the macro textures of blank holders including longitudinal texture and transverse texture are designed. Based on the compensation analysis, a comprehensive compensation method which combined the progressive die corners with the longitudinal texture of the blank holder is proposed. The results show that the springback angle is reduced by 33.6%, proving the proposed comprehensive compensation method is effective.

Longitudinal T2 Mapping and Texture Feature Analysis in the Detection and Monitoring of Experimental Post-Traumatic Cartilage Degeneration.

Background: Traumatic cartilage injuries predispose articulating joints to focal cartilage defects and, eventually, posttraumatic osteoarthritis. Current clinical-standard imaging modalities such as morphologic MRI fail to reliably detect cartilage trauma and to monitor associated posttraumatic degenerative changes with oftentimes severe prognostic implications. Quantitative MRI techniques such as T2 mapping are promising in detecting and monitoring such changes yet lack sufficient validation in controlled basic research contexts. Material and Methods: 35 macroscopically intact cartilage samples obtained from total joint replacements were exposed to standardized injurious impaction with low (0.49 J, n = 14) or high (0.98 J, n = 14) energy levels and imaged before and immediately, 24 h, and 72 h after impaction by T2 mapping. Contrast, homogeneity, energy, and variance were quantified as features of texture on each T2 map. Unimpacted controls (n = 7) and histologic assessment served as reference. Results: As a function of impaction energy and time, absolute T2 values, contrast, and variance were significantly increased, while homogeneity and energy were significantly decreased. Conclusion: T2 mapping and texture feature analysis are sensitive diagnostic means to detect and monitor traumatic impaction injuries of cartilage and associated posttraumatic degenerative changes and may be used to assess cartilage after trauma to identify “cartilage at risk”.

Error analysis in 532 nm nanosecond laser cutting of solar glass

Laser cutting path is potentially important to glass nanosecond laser cutting accuracy and precision. Influence of cutting path error on surface quality was investigated in 532 nm nanosecond laser cutting of solar glass. 9 groups of experiments with different angles (5°, 10°, 15°, 20°, 25°, 30°, 35°,40°,45°, respectively) show that error distribution ranged between -0.12° and 0.07° with a random feature, and had no relationship with the cutting angle. Roughness at extreme corner positions is between 3.55 and 5.71 μm and randomly distributed. A negative effect on the kerf width can be observed using helix laser path. There is no obvious fillet on the inner glass of the intersection cutting curve, while a Φ 642.15 μm fillet can be observed under the example parameters on the outer glass of the curve. The diversity of fillets is caused by differences in the inner and outer sides of two helixes transition region. Textures with Δh under 30 μm are easier to appear when using low helix overlap rate under the condition with same width. Inclined texture will appear because of combination of transverse and longitudinal texture when each rise in height over a threshold.

Two-Level Static Floatation Tool Used in Belt Grinding for Root Fillet of Titanium Alloy Blade

The root fillet of key components in aero-engines, such as the blade, blisk, and blade ring, is the most stress-concentrated area during thermodynamic interactions. The root fillet is constructed with a small curvature radius and variable curvature in different sections. Variable curvature is difficult to achieve with the integrated heat in the grinding process, and the surface quality of the root fillet is therefore greatly influenced. A “horseshoe nest”may be created in the high-temperature air environment, which would significantly affect the fatigue life of the key components. Therefore, to solve the problem of precision grinding for a variable-curvature root fillet, a two-level static floatation tool is proposed for belt grinding. First, the system design of the two-level static floatation tool is introduced, and the principle of the two-level static air floating is analyzed based on fluid dynamics. Second, the deformation and stress distribution of the two-level static floatation tool is analyzed when combined with the belt grinding process for a variable-curvature root fillet. Finally, an experiment performed on the root fillet of an aero-engine titanium alloy blade is described. The results show that the surface roughness is less than 0.4 μm, the profile precision errors are less than 5%, the transition is smooth between the plane and the fillet (blade surface to root fillet rabbet), and a longitudinal texture on the blade root fillet is formed.

Molecular modeling of the microstructure evolution during carbon fiber processing.

The rational design of carbon fibers with desired properties requires quantitative relationships between the processing conditions, microstructure, and resulting properties. We developed a molecular model that combines kinetic Monte Carlo and molecular dynamics techniques to predict the microstructure evolution during the processes of carbonization and graphitization of polyacrylonitrile (PAN)-based carbon fibers. The model accurately predicts the cross-sectional microstructure of the fibers with the molecular structure of the stabilized PAN fibers and physics-based chemical reaction rates as the only inputs. The resulting structures exhibit key features observed in electron microcopy studies such as curved graphitic sheets and hairpin structures. In addition, computed X-ray diffraction patterns are in good agreement with experiments. We predict the transverse moduli of the resulting fibers between 1 GPa and 5 GPa, in good agreement with experimental results for high modulus fibers and slightly lower than those of high-strength fibers. The transverse modulus is governed by sliding between graphitic sheets, and the relatively low value for the predicted microstructures can be attributed to their perfect longitudinal texture. Finally, the simulations provide insight into the relationships between chemical kinetics and the final microstructure; we observe that high reaction rates result in porous structures with lower moduli.

Formation mechanisms of periodic longitudinal microstructure and texture patterns in friction stir welded magnesium AZ80

Many studies of friction stir welding have shown that periodicity of metal flow around the tool pin may result in the formation of periodic differences in microstructure and texture in the weld nugget area correlated with the weld pitch. The current work investigates the periodicity of magnesium weld microtexture in the nugget region and its association with material flow using optical and electron microscopy. Two welds created in AZ80 at different processing conditions are presented in detail, one illustrating periodic longitudinal texture change, and one showing for the first time that periodic variations in texture, grain size, or composition are not defining features of periodic nugget flow. While nugget texture is dominated by shear deformation, it was found here to be affected to a lesser degree by compaction of material behind the welding tool, which led to reduction in intensity of the shear texture fiber. The decreased tendency for magnesium based alloys to form periodic patterns as compared to aluminum based alloys is explained with reference to the shear textures.

The formation of hysteretic magnetic properties in amorphous alloys of various classes upon thermomagmetic treatment in a transverse magnetic field

In this paper, we have studied the effects of the thermomagnetic treatment in a transverse magnetic field (TMaT⊥) on the permeability of the amorphous alloy Co69Fe3.7Cr3.8Si12.5B11 with such a low saturation magnetostriction (λs 10–7) that, in the ribbons of this alloy rolled into a toroid, a sharp longitudinal magnetic texture is observed (Ksq > 0.90). It has been revealed that the permeability μ4 (H = 4 mOe, f = 1 kHz) as a function of the annealing temperature or time of holding at a temperature is described by a curve with a maximum. This maximum is observed at a coefficient of the squareness of the hysteresis loop Ksq,m in the range of 0.2 ≤ Ksq,m ≤ 0.4. The regimes of the TMaT have been determined that provide optimum values of the permeability μ4 (15000) without a loss of the ductile state of the ribbons of this alloy. Based on the example of an iron-based alloy of composition Fe57Co31Si2.9B9.1 with λs = 35 × 10–6, it has been shown that the formation of the hysteretic magnetic properties upon the TMaT⊥ depends substantially on the magnitude of the magnetostriction and the Curie temperature of the amorphous alloys.

Relative fatigue life prediction of high-speed and heavy-load ball bearing based on surface texture

In this paper, a new calculation method of relative fatigue life considering surface texture on high-speed and heavy-load ball bearing is presented. Rolling bearing quasi-dynamics, micro-TEHL analysis, non-Gaussian surface simulating technique and stress analysis with FEM are combined to obtain the relative fatigue life. The maximum subsurface stress with the new method are compared with data in inference, the relative error is 3.9%, which caused by decreasing surface stress under high speed. The non-Gaussian surface textures effect on surface pressure and shear stress are studied, which show transverse texture perpendicular to entrainment direction is helpful to form film because of the increasing hydrodynamic effect, and decrease the pressure and shear stress, but longitudinal texture has an opposite effect. Non-Gaussian parameters effects on relative fatigue life are researched, which display relative fatigue life increase with the increase of transverse texture, and decrease with the increasing longitudinal texture. The increasing skewness and curtosis can bring the decrease of relative fatigue life, but the relative fatigue life is beneficial as skewness is negative and curtosis is small, which is helpful for bearing life. Finally, the whole relative fatigue life of inner race and balls are given.

Electro-Optics of Nematic/Gold Nanoparticles Composites: The Effect from Dopants

We studied the change of electro-optic properties of room-temperature nematic pentylcyanobiphenyl (5CB) when this liquid crystal is mixed with a small amount (∼ 0.5 wt.%) of polymer-capped gold nanoparticles (AuNPs). The AuNPs were spherical-shaped, with a diameter of about 12 nm, the size of the polymer-capped AuNPs was ca. 25 nm. Instead of well pronounced stationary longitudinal domains observed in planar 5CB nematic layers upon static electric field, hybrid longitudinal texture pattern oriented along the rubbing of the cells takes place in this case in identical cells of 5CB doped with AuNPs. The micro-periodic-modulated morphology is reflected on the electro-optic response of AuNPs/5CB nanocomposites. The effect from the nano-dopants is elucidated by detailed investigation (optical, thermo-optical, electrical and electro-optical macroscopic measurements).

Electro-optically responsive composites of gold nanospheres in 5CB liquid crystal under direct current and alternating current joint action

Direct current (DC) electro-optical (EO) control of transmitted laser beam intensity based on EO controlled coherent light scattering and diffraction by stationary longitudinal texture pattern (LTP) is achieved in planar-oriented cells with a composite mixture of polymer-coated gold spherical nanoparticles (Au-NPs) with a mean diameter of about 12 nm and the room-temperature nematic pentylcyanobiphenyl (5CB). At relatively low DC voltage of about 5 V, the effective scattering/diffraction by Au-NPs/5CB composites leads to a spatial spreading of transmitted coherent light from a low-power continuous wave laser beam, resulting in a drastic reduction of its local intensity. The effect is polarization dependent and is strongest when the polarization of the input laser beam is along the LTP. The EO response of Au-NPs/5CB mixtures is studied under DC and alternating current (AC) joint action with the aim of the potential use of these composite materials as EO controlled diffusers. The specific V-shaped sharp dip in the DC voltage-dependent coherent light transmittance of Au-NPs/5CB planar films, as well as the possibility for erasing the scattering/diffractive LTP in the films by joint low AC voltage, can be useful for EO applications in the field of process control and for detection of weak dynamic electric fields.

Study on the Friction Characteristics of Double Reciprocating Elements and Micro Surface Textures

A new test device has been designed and manufactured on trial in order to investigate into reducing total friction in the system where double mechanical elements, like a piston ring-package, slide simultaneously. The test device has much simpler structure than others because of having shear force sensors to measure friction and coil springs to load the double elements. Using the test device, the effects of the micro surface textures of mated materials, oil supply flow and position to the sliding parts and others on the total friction have been examined in detail. Under oil fully flooded condition, the total friction of double elements was smaller in case of transverse texture which is perpendicular to the sliding direction than the ones in cases of longitudinal and cross textures. Under oil starved condition, that was smaller in case of longitudinal texture due to easy oil transportation than the other two textures. Oil supply position on the outer side far from the crankshaft gave larger friction than the one on the inner side. This seemed to be caused by the difference of element velocity around both dead centers. Double elements gave larger friction than the sum of friction of each single element. The phenomenon is mainly attributed to the sliding area and the small oil flow with the upstream element. These experimental results were simply analyzed with a theoretical model of mixed lubrication with consideration of surface roughness and oil starvation.

Research on the Fabric Defect Detection Method based on Improved PSO and NN Algorithm

This paper can reasonably identify the connection weight and threshold of NN and improve capability of true problem solution. This paper also applies PSO-BP NN model into classification of fabric flaws, decomposes the fabric image at single layer and extract the sub-image in horizontal and vertical direction to represent longitudinal and latitudinal texture by using orthogonal wavelet transform method and finally computes the feature values such as longitudinal and latitudinal energy, variance and entropy as the input of NN. By comparing the results of PSO-BP NN with the results of the BP NN, the results indicate that the PSO-BP NN can obtain a better effect.

Longitudinal analysis of MRI T2 knee cartilage laminar organization in a subset of patients from the osteoarthritis initiative: A texture approach

Cartilage magnetic resonance imaging T(2) relaxation time is sensitive to hydration, collagen content, and tissue anisotropy, and a potential imaging-based biomarker for knee osteoarthritis. This longitudinal pilot study presents an improved cartilage flattening technique that facilitates texture analysis using gray-level co-occurrence matrices parallel and perpendicular to the cartilage layers, and the application of this technique to the knee cartilage of 13 subjects of the osteoarthritis initiative at baseline, 1-year follow-up, and 2-year follow-up. Cartilage flattening showed minimum distortion (∼ 0.5 ms) of mean T(2) values between nonflattened and flattened T(2) maps. Gray-level co-occurrence matrices texture analysis of flattened T(2) maps detected a cartilage laminar organization at baseline, 1-year follow-up, and 2-year follow-up by yielding significant (P < 0.05) differences between texture parameters perpendicular and parallel to the cartilage layers. Tendencies showed higher contrast, dissimilarity, angular second moment, and energy perpendicular to the cartilage layers; and higher homogeneity, entropy, variance, and correlation parallel to them. Significant (P < 0.05) longitudinal texture changes were also detected reflecting subtle signs of a laminar disruption. Tendencies showed decreasing contrast, dissimilarity, and entropy; and increasing homogeneity, energy, and correlation. Results of this study warrant further investigation to complete the assessment of the usefulness of the presented methodology in the study of knee osteoarthritis.

Fundamentals of Surface Mechanics with Applications, Second Edition. Mechanical Engineering Series

Fundamentals of Surface Mechanics with Applications, Second Edition. Mechanical Engineering Series

Inorganic particle toughening I: micro-mechanical deformations in the fracture of glass bead filled epoxies

General characteristics of micro-mechanical deformations found in the fracture of various glass bead filled epoxies are investigated. Among the various types of step features on fracture surfaces, the basic longitudinal texture is not influenced by the existence of glass beads, but most other steps formed are significantly affected. Various microscopic investigations show that microcracking does not extensively occur in the fracture of glass bead filled epoxies. Microcracking other than debonding of glass beads is seldom observed, and furthermore, debonding is found to occur only on and near the fracture surface. Micro-shear bands are clearly identified and distinguished from microcracks found in unnotched tensile specimens. Based on examination of micro-mechanical deformations, three types of fracture processes are proposed for glass bead filled epoxies having different glass bead contents and interfacial strengths.