Low Shear Strain Research Articles

Shear modulus from SPT N-values with different energy values

It is essential to determine low strain shear modulus (Gmax) to model dynamic soil response and estimate the site effects due to earthquakes. Several correlations have been developed between dynamic soil properties and soil penetration resistance values such as N-values from Standard Penetration Test (SPT). However, only a few of the established correlations are often used because of uncertainty over applied hammer energy (EH) and applicability in different regions. Hence, this study aims to signify the importance of EH in N-value corrections, its influence on Gmax estimation, to suggest modification factor for an existing correlation and validate with Downhole and Crosshole measurements. Different SPT corrections are studied besides the energy measurements in the analysis of the correlation between the N-value and Gmax. A previously proposed correlation between measured N-value and Gmax is improved to account for in-situ EH measurement, and the correction factors to account for different hammer energy ratios (ER) are suggested. Modified correlations compared well and agreed within the 95 % confidence bound with the freshly acquired seismic borehole tests data.

Tailoring of arteriovenous graft-to-vein anastomosis angle to attenuate pathological flow fields

Arteriovenous grafts are routinely placed to facilitate hemodialysis in patients with end stage renal disease. These grafts are conduits between higher pressure arteries and lower pressure veins. The connection on the vein end of the graft, known as the graft-to-vein anastomosis, fails frequently and chronically due to high rates of stenosis and thrombosis. These failures are widely believed to be associated with pathologically high and low flow shear strain rates at the graft-to-vein anastomosis. We hypothesized that consistent with pipe flow dynamics and prior work exploring vein-to-artery anastomosis angles in arteriovenous fistulas, altering the graft-to-vein anastomosis angle can reduce the incidence of pathological shear rate fields. We tested this via computational fluid dynamic simulations of idealized arteriovenous grafts, using the Bird-Carreau constitutive law for blood. We observed that low graft-to-vein anastomosis angles (<20^{circ }) led to increased incidence of pathologically low shear rates, and that high graft-to-vein anastomosis angles (>40^{circ }) led to increased incidence of pathologically high shear rates. Optimizations predicted that an intermediate (sim 30^circ) graft-to-anastomosis angle was optimal. Our study demonstrates that graft-to-vein anastomosis angles can significantly impact pathological flow fields, and can be optimized to substantially improve arteriovenous graft patency rates.

Analysis of slip-line model for serrated chip formation in orthogonal machining of AISI 304 stainless steel under various cooling/lubricating conditions

In the past, numerous slip-line models have been developed and presented for continuous chip formation. However the authors of this paper recently proposed a new slip-line model for serrated chip formation in machining with rounded cutting edge. In that model, Oxley’s predictive machining theory was integrated for machining of stainless steel material and the model was validated under dry cutting. The current study extends the previously developed slip-line model for orthogonal turning of AISI 304 austenitic stainless steel for various cooling/lubricating conditions. The orthogonal machining experiments were performed under dry, flood cooling, MQL (Minimum Quantity Lubrication) and cryogenic cooling conditions. Good correlations are observed between experimental work and predictions under various cooling/lubricating conditions for cutting force components and maximum and minimum chip thickness values. After achieving the good correlation, several important outputs such as the shear stress, flow stress, ploughing force, stagnation point angle, chip up-curl radius, which are difficult or impossible to measure experimentally were determined by solving the extension of the previously developed model. The lowest tool-chip frictional shear stress was achieved under MQL method whereas the highest was obtained in dry cutting. In addition, the minimum ploughing force was obtained in cryogenic cooling while the maximum value occurred in dry cutting. The stagnation point angle decreased when applying lubricant or coolant and increased with increasing cutting speed. The tool-chip contact length slightly decreased, the chip up-curl radius increased and the thickness of the primary shear zone reduced with increasing cutting speed. Additionally, lower tool-chip contact length, larger chip up-curl radius and larger primary shear zone thickness occurred while using lubricant or coolant. Higher cutting speed caused lower shear strain and flow stress and higher shear strain-rate. The highest and lowest flow stresses were obtained under cryogenic cooling and dry cutting, respectively.

Experimental investigation and numerical modeling of piezoelectric bender element motion and wave propagation analysis in soils

The bender element (BE) test has been widely used for the dynamic characterization of soil specimens at low-shear strain levels. However, the actual behavior of the BE inside a soil specimen remains unknown. Thus, the current ASTM standard does not consider the interference of compressional and shear waves in BE testing, which can lead to significant errors in the evaluation of shear wave velocities. The main objective of this paper is to present a numerical model of the BE system to better understand the response of the BEs inside a soil sample. The model is calibrated, verified, and then used to demonstrate the importance of taking into consideration the interaction between compressional and shear waves for the correct interpretation of BE measurements. The model successfully captured the measured vibrations of the BE in air as well as inside transparent soils. More importantly, the numerical simulations provide a new understating of the significant interactions of P waves and S waves especially in clay soils. Thus, the proposed coupled piezoelectric and solid mechanics model can be used to study the soil–BE interaction so that sound recommendations can be given to improve the interpretation of BE tests in different soils.

Force Characteristic Analysis of Different Steel Deck Pavement under Temperature Load Coupling Situation

In order to investigate the force characteristic of different steel deck pavement under extreme temperature and load coupling situation, we established the three dimensional extreme high temperature and extreme low temperature field of simple supported beam bridge, the paving structure were double layered SMA, double layered epoxy concrete, SMA+GA, using material elastic modulus changing with temperature. Analysis indicated that the maximum value of high temperature normal stress occurred in the epoxy upper layer pavement, the maximum value of shear stress occurred in the epoxy lower layer pavement, the maximum value of high temperature strain occurred in the upper layer of double layered SMA pavement. The maximum value of low temperature stress occurred in the SMA+GA lower layer pavement, the maximum value of low temperature strain occurred in the SMA+GA upper layer pavement, the maximum value of shear strain occurred in the SMA lower layer pavement. The maximum value of high temperature stress usually occurred in the bottom of pavement layer, maximum strain usually occurred on top of pavement layer. The maximum value of low temperature shear stress and shear strain usually occurred in the bottom of pavement layer, normal strain occurred on top of pavement layer. The stress difference between the upper and lower layers in SMA+GA pavement structure is very large which adversely affected the structural force.

Shear modulus of conventional and auxetic open-cell foam

This work analyses shear moduli of conventional and auxetic open-cell polymer foams. Shear moduli are i) measured directly and ii) calculated by applying elasticity theory for isotropic solid materials, using Young's moduli and Poisson's ratios from compression tests. Zero and negative Poisson's ratio foams are fabricated from conventional foams using a thermo-mechanical process. Fabricated and conventional foams are compression tested in three orthogonal directions, up to densification at ~60% compression, with full-field strain measurements obtained using Digital Image Correlation. Compression testing is followed by shear testing. The measured shear moduli vary from 16±7 kPa for negative Poisson's ratio foams to 38±2 kPa for zero Poisson's ratio foams, with conventional foams in between with a mean value of 32±8 kPa. The calculated shear moduli are typically lower than the measured values. The results suggest that the application of elasticity theory to calculate the low strain shear modulus of open-cell foam from Young's modulus and Poisson's ratio measured in compression tests is appropriate if the foam is isotropic.

Site response analysis for deep and soft sedimentary deposits of Dhaka City, Bangladesh

The ground motion intensity of an earthquake is significantly changed when seismic waves propagate from the bedrock to the near-surface soft geological materials. The ground where the shear wave velocity (Vs) exists greater than 760 m/s is generally considered as bedrock. As a common practice in the last three decades, the surface ground motion of a soil site is estimated by multiplying the bedrock motion with the site coefficient that is empirically determined from the time-averaged shear wave velocity in the top 30 m (Vs30) of the site. The site coefficient is defined as the ratio of the ground motion intensity at the ground surface to that of the bedrock. If the bedrock of a site exists at a depth of greater than 30 m, the site effect from the depth of 30 m to the bedrock is not accounted in the Vs30-based site coefficient. In Dhaka City, the minimum depth of the bedrock is approximately 175 m. Therefore, the use of the Vs30-based site coefficient to estimate the surface ground motion is not appropriate for the soft and deep sedimentary deposits of this city. In this study, site response analysis using the Vs30-based site coefficient, linear, equivalent-linear, and nonlinear approaches has been performed to estimate the surface ground motion at different sites of Dhaka City and to compare the results of different approaches. It is observed that the surface ground motion is decreased with increasing the depth of the bedrock due to low shear strain and viscous damping in the soft sedimentary deposits.

The role of applied strain and volume percentage of components on mechanical properties and fracture toughness in multilayered Al/Mg composite fabricated by the accumulative roll bonding process

In this study, for the first time, the effect of applied strains and volume percentage of components of layered composite on the mechanical properties and fracture toughness of Al/Mg were investigated experimentally. The multilayered Al/Mg were produced by the accumulative roll bonding (ARB) process. For the investigation, three Al/Mg composites with different volume percentages (25%, 50%, and 66.6%Al) at different applied strains (0.8–3.2) were produced. The experimental evaluation included microscopic examination by optical microscope imaging, uniaxial tensile test, and plane strain fracture toughness. As the applied strain for all three composites increased, plastic instability in the magnesium reinforcement intensified, but due to the low thickness of the Al layers compared to the Mg layer, uniform structure of Mg distribution in Al for all three composite was not achieved. Also, by adding Al layers to the primary composite, a lower shear strain was applied to the magnesium reinforcement, and instability intensity in the reinforcement layer decreased. For this reason, as Al layers increased, plastic instability diminished. By raising the exerted strain, the values of tensile strength increased, and by adding Al layers, the elongation increased. The maximum amount of tensile strength and elongation for each composite was achieved in the same ARB pass (last pass) and the highest values of UTS and elongation were reached to 384.1 MPa and 1.95% for Al25%Mg, respectively. However, the highest amount of fracture toughness for each composite was obtained in the different exerted strains and the maximum value of 41.4 MPa·m1/2 was achieved for Al33.3% in the third pass. The present phenomena indicated that many factors such as higher Mg volume with higher energy absorption, plastic instability, thickness ratio, plastic instability, and value of applied strain affected the fracture toughness. In summary, the relationship between fracture toughness with applied strain and also with volume percent of Al was not always straightforward. It depends on other factors, such as how the reinforcement was distributed, the thickness of the layers, the workability, and the addition of aluminum. Also, the applied strain has a more significant effect on increasing fracture toughness in multilayered composite if they cause a uniform distribution of reinforcement particles in the field or continuity in the reinforcement layer.

A Conceptual Model and Evaluating Experiments for Studying the Effect of Soil Deformation on Its Permeability

Soil structure and void ratio are the major factors that control the permeability changes during soil deformation. In this research, we proposed and tested a conceptual model considering these two factors based on the concept of permeability anisotropy. This model, which is expressed as k(e) graph, determines the total k values that soil can achieve and shows that as deformation proceeds, soil permeability passes through a specific zone in the k(e) graph. Thus, by deforming a soil sample, measuring its permeability during deformation, and comparing the results using the k(e) graph, it might be possible to predict deformation effects on the permeability. To evaluate this conceptual model, we designed and built a special apparatus to carry out two sets of experiments. The first set was performed to achieve the k(e) graph during static compression based on the conceptual model; and the second set was conducted to investigate the permeability changes relative to k(e) graph during simple shear deformation in constant volume condition. Our results show that the theoretical k(e) graph agrees more with the measured k(e) graph in medium to dense samples that might have no macropore. In addition, particles’ preferential orientation and/or anisotropic permeability were not changed during shear deformation due to three possible causes: deformation done in constant volume deformation, relatively low shear strain, and shearing along particle orientation. Void ratio and particle orientation are associated with each other, and soil shearing with constant void ratio might cause the anisotropy of permeability to be relatively constant. Thus, it is needed to design and build a new complex apparatus or use a special method for testing how permeability changes within the k(e) graph zone during soil deformation.

Lattice distortion-enhanced superlubricity of (Mo, X)S2 (X = Al, Ti, Cr and V) with moiré superlattice.

Two-dimensional (2D) materials with the advantage of low interlayer shear strain are ultilized as lubricants in aerospace and precision manufacturing. Moiré superlattices (MSL), with attractive physical properties of electronic structures, interlayer hybridization and atomic forces, have been widely investigated in superlubricity, which is caused by elimination of interlayer lock-in by incommensurate atomic reconstruction. Although the foundations of superlubricity and the development of 2D lubricants via vanishing friction have been investigated, it is still important to comprehensively reveal the influence of MSL on the interlayer van der Waals (vdW) interactions of 2D lubricants. Here, the contributions of lattice distortions of solute-doped twisted bilayers (Mo, X)S2 (X = Al, Ti, V and Cr) to superlubricity are comprehensively investigated by high-throughput modelling and DFT-D2 calculations. It is revealed that the lattice distortion not only breaks the interlayer balance of repulsion and van der Waals interactions but also yields layer corrugation. These layer-corrugation-induced changes of the interlayer interactions and spacing distances are utilized to optimize lubricity, which matches with the experimental friction coefficients in the order of (Mo, Al)S2 > (Mo, Cr)S2 > MoS2 >(Mo, V)S2 >(Mo, Ti)S2. The evolutions of the band structures show an exponential relationship of the band edge width and layer deformations, paving a path to accelerate the development of advanced superlubricity materials via lattice distortions.

Relationship between microstructures and resistance in mafic assemblages that deform and transform

Abstract. Syn-kinematic mineral reactions play an important role for the mechanical properties of polymineralic rocks. Mineral reactions (i.e., nucleation of new phases) may lead to grain size reduction, producing fine-grained polymineralic mixtures, which have a strongly reduced viscosity because of the activation of grain-size-sensitive deformation processes. In order to study the effect of deformation–reaction feedback(s) on sample strength, we performed rock deformation experiments on “wet” assemblages of mafic compositions in a Griggs-type solid-medium deformation apparatus. Shear strain was applied at constant strain rate (10−5 s−1) and constant confining pressure (1 GPa) with temperatures ranging from 800 to 900 ∘C. At low shear strain, the assemblages that react faster are significantly weaker than the ones that react more slowly, demonstrating that reaction progress has a first-order control on rock strength. With increasing strain, we document two contrasting microstructural scenarios: (1) the development of a single throughgoing high-strain zone of well-mixed, fine-grained aggregates, associated with a significant weakening after peak stress, and (2) the development of partially connected, nearly monomineralic shear bands without major weakening. The lack of weakening is caused by the absence of interconnected well-mixed aggregates of fine-grained reaction products. The nature of the reaction products, and hence the intensity of the mechanical weakening, is controlled by the microstructures of the reaction products to a large extent, e.g., the amount of amphibole and the phase distribution of reaction products. The samples with the largest amount of amphibole exhibit a larger grain size and show less weakening. In addition to their implications for the deformation of natural shear zones, our findings demonstrate that the feedback between deformation and mineral reactions can lead to large differences in mechanical strength, even at relatively small initial differences in mineral composition.

Lattice Preferred Orientation and Deformation Microstructures of Glaucophane and Epidote in Experimentally Deformed Epidote Blueschist at High Pressure

To understand the lattice preferred orientation (LPO) and deformation microstructures at the top of a subducting slab in a warm subduction zone, deformation experiments of epidote blueschist were conducted in simple shear under high pressure (0.9–1.5 GPa) and temperature (400–500 °C). At low shear strain (γ ≤ 1), the [001] axes of glaucophane were in subparallel alignment with the shear direction, and the (010) poles were subnormally aligned with the shear plane. At high shear strain (γ &gt; 2), the [001] axes of glaucophane were in subparallel alignment with the shear direction, and the [100] axes were subnormally aligned with the shear plane. At a shear strain between 2&lt; γ &lt;4, the (010) poles of epidote were in subparallel alignment with the shear direction, and the [100] axes were subnormally aligned with the shear plane. At a shear strain where γ &gt; 4, the alignment of the (010) epidote poles had altered from subparallel to subnormal to the shear plane, while the [001] axes were in subparallel alignment with the shear direction. The experimental results indicate that the magnitude of shear strain and rheological contrast between component minerals plays an important role in the formation of LPOs for glaucophane and epidote.

Experimental investigation of the ignition process in a separated dual-swirl spray flame

Centrally staged lean premixed pre-evaporation combustion technology has been used in aero engines for its capability in effectively reducing NOx emissions while still providing stable flames. Previous work has shown the “ignition delay” phenomenon in the forced ignition process, revealing that the burner ignition process is complex and needs further exploration. In this work, the spark ignition and flame kernel propagation in a centrally staged optical model combustor are experimentally investigated to further illustrate the interaction between random kernel motion and flow statistics from the perspective of timescales and kernel propagations. Stochasticity involved in each individual phases of the whole ignition is obtained via repeated high-speed imaging tests. Timescales of the successful ignition processes are analyzed in a statistical method, revealing the time randomness of ignition phases. Spatial probability of the flame kernel propagation in turbulent sprays is calculated and analyzed with the combination of time-averaged flow and spray distribution. The flame projected area evolutions show that the burner ignition phase can be further divided into three phases: flame propagation, flame residence and flame growth. Three modes of ignition failure are identified during the burner ignition phase. The flame residence phase features a special period of spark ignition with low light emissions from the highly wrinkled flame kernel in the center, which is the “ignition delay” before the growth of flame. Timescales of ignition stages involve stochasticity and the flame growth phase has a higher proportion in the whole process. Statistical analysis of the flame kernel spatial position shows that in turbulent spray the flame kernel has a greater probability of propagating to the region with low axial velocity, low shear strain rate, and appropriate spray concentration.

Inverse Simulation for Extracting the Flow Characteristics of Artificial Snow Avalanches Based on Computation Fluid Dynamics

Many numerical analysis methods for predicting the motion of soil or snow avalanches may set the characteristics of the dynamic friction obtained from field tests, such as the measurement of real avalanche and model slope tests. However, the friction characteristics of the actual flow of objects are influenced by changes in the velocity and density of the flowing objects and are not necessarily constant. In addition, determining the shear strain rate dependence of the frictional properties at low shear strain rates is important for accurately predicting the avalanche reach distance. In this research, model tests using a rotating drum device were carried out, and an artificial snow avalanche was generated. Then, the flow velocity distribution of the flow was extracted by organizing the motion of the artificial snow avalanche flowing in the drum device using the Digital Image Correlation method. Moreover, the changing characteristics of the viscosity coefficient of the pseudo flow were estimated using an inverse simulation. For the results, it was suggested that the method of estimating flow characteristics and friction characteristics from the artificial avalanche generated by the rotating drum and the time inverse analysis proposed in this study was effective, but it is necessary to confirm the issue of the need for a similar analysis using real scale. If it is found to be applicable to real scales in the future, it will contribute to the development of this field because it will expand the range of methods for analyzing avalanches using model experiments.

Strain-Induced Fabric Transition of Chlorite and Implications for Seismic Anisotropy in Subduction Zones

Seismic anisotropy of S-wave, trench-parallel or trench-normal polarization direction of fast S-wave, has been observed in the fore-arc and back-arc regions of subduction zones. Lattice preferred orientation (LPO) of elastically anisotropic chlorite has been suggested as one of the major causes of seismic anisotropy in subduction zones. However, there are two different LPOs of chlorite reported based on the previous studies of natural chlorite peridotites, which can produce different expression of seismic anisotropy. The mechanism for causing the two different LPOs of chlorite is not known. Therefore, we conducted deformation experiments of chlorite peridotite under high pressure–temperature conditions (P = 0.5–2.5 GPa, T = 540–720 °C). We found that two different chlorite LPOs were developed depending on the magnitude of shear strain. The type-1 chlorite LPO is characterized by the [001] axes aligned subnormal to the shear plane, and the type-2 chlorite LPO is characterized by a girdle distribution of the [001] axes subnormal to the shear direction. The type-1 chlorite LPO developed under low shear strain (γ ≤ 3.1 ± 0.3), producing trench-parallel seismic anisotropy. The type-2 chlorite LPO developed under high shear strain (γ ≥ 5.1 ± 1.5), producing trench-normal seismic anisotropy. The anisotropy of S-wave velocity (AVs) of chlorite was very strong up to AVs = 48.7% so that anomalous seismic anisotropy in subduction zones can be influenced by the chlorite LPOs.

Effect of Sand Fouling on the Dynamic Properties and Volume Change of Gravel During Cyclic Loadings

Understanding the factors that influence the dynamic behavior of granular soils during cyclic loading is critical to infrastructure design. Previous research has lacked quantitative study of the effects of fouling index (FI), mean effective confining pressure, relative density, shear strain level and anisotropic consolidation, especially when the effective vertical stress is lower than the effective horizontal stress on the dynamic behavior of gravelly soils. The objective of the present study was to evaluate the dynamic behavior and volume change of both clean and fouled specimens for practical applications. To this end, cyclic triaxial tests with local strain measurements under both isotropic and anisotropic confining conditions were conducted. It is found that the fouled specimen with 50 % sand (i.e. the specimen which contains 50 % gravel and 50 % sand) has the highest shear modulus at low shear strain levels and the largest volume reduction and damping ratio at large shear strain levels. The results of tests indicate that the effect of fouling index on the shear modulus is reduced at large shear strain levels. Volumetric contraction due to the increase in mean effective confining pressure is more significant at large shear strain levels. The results also indicate that the stiffness of the specimens under anisotropic compression mode are larger than those in extension or isotropic mode.

Shear controllable synthesis of barium sulfate particles using lobed inner cylinder Taylor-Couette flow reactor

A novel lobed inner cylinder assembled in Taylor-Couette flow reactor (LTC) has been adopted to synthesize barium sulfate particles. The fluid dynamics that affects synthesis of particles using both the LTC and the classical Taylor-Couette flow reactor (CTC) was investigated through CFD modelling and experiments. The results have demonstrated that the Taylor vortices and turbulence induced shear rate distribution in the reactors have a significant influence on the final particle size distribution. The narrower shear rate distribution in the LTC is beneficial to the synthesis of particles with smaller size. The local turbulence intensification in the intra-Taylor vortices in the LTC effectively reduces the low shear strain regions. A strong correlation between the synthesized particle size and the local turbulent dissipation rate is existing. Shear induced by small turbulent eddies can inhibit particle growth. The LTC can be used for effectively shear controllable synthesis of particles.

1178 High coronary wall shear strain developed more vulnerable plaque compared to low shear strain: a systematic review and meta-analysis

Abstract Background and Aim Arterial wall strain has been proposed to impact the features of developed plaques. The aim of this meta-analysis is to assess the impact of different types of wall shear strain (WSS) on the changes of vulnerable plaque in coronary artery disease (CAD). Methods We systematically searched PubMed-Medline, EMBASE, Scopus, Google Scholar and the Cochrane Central Registry, from 1989 up to May 2019 in order to select clinical trials and observational studies, which assessed the relationship between WSS measured by intravascular ultrasound (IVUS) and morphology of plaque in CAD. Results In 7 studies, a total of 724 patients with 32,083 segments were recruited, with mean follow up 8.4 months. The pooled analysis showed that low WSS was associated with larger baseline lumen area WMD 2.55 [1.34 to 3.76, p &amp;lt; 0.001], smaller plaque area WMD -1.16 [-0.1.84 to -0.49, p = 0007] and necrotic core area WMD -0.45 [-0.78 to 0.14, p = 0.004], dense calcium score WMD -0.18 [-0.46 to 0.10, p = 0.01], and fibrous area WMD -0.79 [-1.84 to 0.30, p = 0.02] as well as smaller fibro-fatty area WMD -0.22 [-0.57 to 0.13, p = 0.02] compared to high WSS. At follow-up, the high WSS had regression of fibrous area, WMD -0.12 [-0.22 to -0.02, p = 0.02] and fibro-fatty area WMD -0.11 [-0.23 to -0.01, p = 0.04], reduction of plaque area WMD -0.09 [-0.17 to -0.02, p = 0.01] and increased dense calcium WMD 0.08 [0.02 to 0.14, p = 0.006] and necrotic core area WMD 0.07 [0.01 to 0.13, p = 0.03] compared to low WSS (Figure 1). The high WSS developed more profound remodeling compared to low WSS (40 vs. 18%, p &amp;lt; 0.05) with more constructive remodelling with low WSS (78%vs. 40 %, p &amp;lt; 0.01). Conclusions. Baseline high WSS is associated with higher necrotic core, calcium, fibrous and fibro-fatty area compared with low WSS, and during follow up the high WSS resulted in the development of more profound remodeling compared with low WSS. These findings highlighted the role of IVUS in detecting the vulnerable plaque in CAD. Abstract 1178 Figure 1. Mean change of plaque morpholo

Damage evolution in braided composite tubes under torsion studied by in-situ X-ray computed tomography

Here we present the first real-time three dimensional (3D) observations of damage evolution in a carbon fibre reinforced polymer (CFRP) composite tube under torsion. An in-situ torsion test of 1/1 45° (diamond) braided carbon fibre-epoxy circular composite tube was performed and the damage process was characterised by synchrotron X-ray computed tomography (CT). A number of damage modes and their damage sequence has been identified and monitored globally and in more detail within a representative region of interest. In particular, intra-tow cracks and inter-tow debonding have been found to occur almost simultaneously at low shear strains (1.5%). It is noteworthy that inter-tow debonding was initially constrained within repeated braid units before propagating and connecting with other damage modes in 3D. The area fraction of inter-tow debonds was quantified at different stages and it was found to dramatically increase with increasing shear strain beyond 1.5%. The total volume fraction of the observed intra-tow cracks of various forms was seen to grow rapidly beyond shear strain of 2.0%. Beyond the peak shear stress (at a shear strain of 2.5%), fibre micro-buckling and kink bands occur in the tows subjected to torsion induced axial compression at crimped regions close to tow crossovers. Tow crossovers control many aspects of damage propagation under torsion, positively by localising inter-tow debonds and negatively by initiating fibre micro-buckling.

Effects of ultrasonicated methylcellulose coating on French fries during deep frying process

AbstractUltrasonic treatment (UT) effects on methylcellulose (MC) for the food coating purpose prior to deep‐fat frying process of potato strips were demonstrated. Different concentration of MC (0.5–2.0 wt/vol%) solutions were subjected to UT at 20 W to evaluate the effect of UT treated coatings on rheological behavior of the coated samples and their efficiency in minimizing the oil uptake. Application of UT to methylcellulose (UTMC) clearly showed a phase transition from fluid‐ to gel‐like between 20 and 65°C with the increasing in the oscillatory frequency and temperature ramp test of UTMC showed the sol–gel transition occurrence is lower than non‐UTMC at 20 and 29°C, respectively, within the linear viscoelastic region. When the MC concentrations were varied, the most effective concentration was noticed to occur at 1.0 (wt/vol%) UTMC whereby the relative variation of water retention and oil uptake were reduced to about 49.9 and 31.0%, respectively, as compared to 1.0 wt/vol% non‐UTMC formulation. Experimental results affirm that UTMC coating application can be used successively to improve rheological properties of MC by minimizing oil uptake on fried food.Practical ApplicationUltrasonic treatment (UT) application to methylcellulose (MC) solutions with varied concentration (0.5–2.0 wt/vol%) clearly showed a phase transition from fluid‐to‐gel like with the increasing in the oscillatory frequency (10−1 to 102 rad/s) and temperature ramp test (65–10°C) at low shear strains compared to non‐UTMC. The gelation of UTMC was faster than non‐UTMC when coated onto the substrate at the ambient conditions thus allowed the transformation of green coating layer to form the gel layer instantaneously. Application of MC was successfully in minimizing oil uptake on fried potato strips whereby the most effective layer was noticed to occur at 1.0 wt/vol% UTMC. Introducing UT to polysaccharide coating, that is, MC benefit the food coating industries by increasing the food coating process efficiency so that the coated layer can be fully utilized to increase the function of the coated substrate.