Flow Strain Rate Research Articles

An enhanced method for analyzing flow number test data of asphalt mixtures

ABSTRACT This study aims to develop an enhanced method that eliminates the dependence of calculated flow number on the termination strain to allow for better analysis of flow number test data. The two-step secant method, the Francken model, and the double-tangent method are firstly evaluated. It is found that the flow number determined by the Francken model or the two-step secant method depends on the termination strain, as do the transition points identified by the double-tangent method. To address this issue, an enhanced two-step secant method is proposed based on the combined use of the secant method and the translation method. The idea behind the translation method is to specify a standardised criterion for flow number tests with different termination conditions, thereby avoiding the effect of the termination strain on the calculated flow number. The results show that the flow number obtained by the enhanced two-step secant method is no less than that obtained by the two-step secant method. It is also found that there is a unique relationship between flow number and strain rate during the secondary stage, which is independent of asphalt mixture type, stress level, and test temperature.

The long multiphase trunk–tributary surge history of the high-Arctic Chapman Glacier, 1959–2023

ABSTRACT Surge-type glaciers have been identified throughout the Canadian Arctic, but detailed surge behavior has been sparsely studied. Recent high spatiotemporal resolution satellite products enable such studies, allowing for better process-based understanding of surging in this region. Here, we present a multidecadal record (1999–2023) of flow velocities, strain rates, and elevation changes for Chapman Glacier, a 40-km-long land-terminating glacier on Umingmak Nuna (Ellesmere Island), using ITS_LIVE (Inter-mission Time Series of Land Ice Velocity and Elevation), Sentinel-1, and elevation time series data products. We further use historical remote sensing data to analyze surface morphology and displacement from 1959 to 2023. After an inferred century-long or longer quiescent phase, Chapman Glacier surged for at least twenty-two years in two successive phases. Phase 1 occurred from 2001 to 2012 and was spatially limited to the trunk, and Phase 2 started around 2012 and continues to 2024, impacting the main tributary and the lower part of the trunk. In each surge phase flow speeds increased from ~25 to >200 m a−1 over approximately ten years, propagated from up-glacier to down-glacier, and involved notable mass displacements. Our record of this high-Arctic surge and first account of a tributary–trunk surge in the Canadian Arctic contributes to the characterization of the spectrum of dynamic ice flow instabilities worldwide.

Normalization of hot deformation parameters for activation energy analysis in metallic alloys

Abstract Depending on melting point of a given alloy, the temperature range for
hot deformation of alloys varies widely. Consequently, the apparent activation energy
of hot deformation, Q, is greatly influenced by the temperature range as well as strain
rate applied during hot deformation. The purpose of this investigation is to normalize
hot deformation parameters – temperature and strain rate – to study their effects on
activation energy. Seventy published hot-deformation data sets were used to investigate
the effects of normalized hot-deformation variables on Arrhenius-type constitutive
model parameters. Flow stress, strain rate, and temperature from sample datasets
were normalized to the range [0, 1] and fitted with an Arrhenius-type model. The
results showed that, for normalized parameters, the activation energy has exponential
relationships with a partial derivative of flow stress with strain rate and temperature.

Hot Deformation Behavior and Processing Maps of Vapor-Phase-Grown Carbon Nanofiber Reinforced 7075Al Composites

The present study prepared 7075Al composites reinforced with vapor-phase-grown carbon nanofibers (VGCNFs) using the spark plasma sintering (SPS) method. Constitutive equations of the composites were calculated, and thermal processing maps were constructed by performing thermal compression tests on the VGCNF/7075Al composites at deformation temperatures ranging from 300 to 450 °C and strain rates from 0.01 to 1 s−1. This study analyzed the microstructural evolution of the VGCNF/7075Al composites during the thermomechanical processing. The experimental results demonstrated that dynamic recrystallization (DRX) primarily governed the softening mechanism of VGCNF/7075Al composites during thermomechanical processing. At high strain rates, a combination of dynamic recovery (DRV) and DRX contributed to the softening behavior. The incorporation of VGCNFs results in higher dislocation density and a larger orientation deviation within the 7075Al matrix during the thermomechanical deformation process, providing stored energy that facilitated DRX. The activation energy for deformation of VGCNF/7075Al composites was 175.98 kJ/mol. The constitutive equation of the flow stress showed that a hyperbolic sinusoidal form could effectively describe the relationship between flow stress, strain, strain rate, and temperature of VGCNF/7075Al composites. The optimal thermomechanical deformation parameters for VGCNF/7075Al composites were 400–450 °C and 0.01–0.1 s−1 when the strain ranged from 0.05 to 0.15. For strains between 0.25 and 0.35, the optimal thermomechanical parameters were 380–430 °C and 0.01–1 s−1.

Rhythms of the Agulhas Current Within the Framework of Energetic Anisotropy

AbstractThis study investigates the mechanisms driving the acceleration and meandering of the Agulhas Current (AC), focusing on the role of eddy‐mean flow interactions. The analysis revealed that anticyclones originating from the Mozambique Channel and south of Madagascar played pivotal roles in accelerating the AC. Simultaneously, when anticyclones collide with the AC, they undergo processes of rotating and elongating into ellipses. In addition to the previously suggested barotropic instability induced by anticyclones, this study revealed that the merging of cyclones with the AC plays a role in the generation of meanders. Upstream cyclones reduce the horizontal potential vorticity gradient, facilitating eddies to traverse the current. The AC envelops these cyclones and flows in meandering patterns. The places where these meanders form are not exclusive to the Natal Bight. In addition, we further diagnose the kinetic energy conversion to reveal the interaction between eddy anisotropy (i.e., eddy deformation and orientation) and mean flow strain (i.e., stretching and shearing). The results suggest that the anisotropy of anticyclonic and cyclonic eddies prompts downscale KE transfer and the growth of meanders, establishing a positive feedback loop. Contrary to the findings of previous hypotheses, the acceleration of AC in turn leads to a decrease in the mean flow strain rate, exerting negative feedback on energy conversion and inhibiting the development of meanders. These two feedback mechanisms work together to determine the fate of AC meandering. The energetic anisotropy diagnosis holds potential applicability to other western boundary current systems.

High strain rate behavior of polycaprolactone reinforced with aramid nanofiber for insight into dynamic behavior

Self-healing materials are repairable and extend product lifetimes but are limited in application due to their mechanical properties such as low yield strength. Here, we examined the dynamic mechanical performance of an elastomeric polymer composite containing aramid nanofibers. These studies provided an economically feasible foundation to understand the reinforcement concentration and resultant mechanical properties that would result should aramid nanofibers be used to reinforce a self-healing polymer that requires complex synthesis methods and expensive reactants. The elastomeric polymer used was polycaprolactone containing various weight percent aramid nanofibers. Dynamic mechanical testing of these samples was performed using a split-Hopkinson pressure bar system that enabled quantification of polymer softening and aramid nanofiber reinforcement. Dynamic flow stress and strain rates were also calculated with these data. Crystallinity and thermal softening effects of solvent dissolution of polycaprolactone are explored to further characterize the performance of aramid nanofibers as a fiber in composite materials.Graphical abstract

Experimental and numerical study of H[formula omitted] enrichment on swirl/bluff-body stabilized lean premixed n-butane/air flame

Experimental and numerical study of H[formula omitted] enrichment on swirl/bluff-body stabilized lean premixed n-butane/air flame

Research on Hot Deformation Rheological Stress of Al-Mg-Si-Mn-Sc Aluminium Alloy.

The hot compression simulation testing machine was utilized to conduct compression experiments on an Al-Mg-Si-Mn alloy containing the rare earth element Sc at a deformation temperature ranging from 450 to 550 °C and a strain rate of 0.01 to 10 s-1. The study focused on the hot deformation behavior of the aluminum alloy, resulting in the determination of the optimal range of deformation process parameters for the alloy. The relationship between material flow stress, deformation temperature, and strain rate was described using the Arrhenius relationship containing thermal activation energy based on the stress-strain curve of hot compression deformation of aluminum alloy. This led to calculations for structural factor A, stress index n, and stress level parameters as well as thermal deformation activation energy to establish a constitutive Formula for hot deformation rheological stress of aluminum alloy and calculate the power dissipation factor η. Through this process, an optimized range for the optimal deformation process parameter for aluminum alloy was determined (deformation temperature: 490~510 °C; strain rate: 0.05 s-1) and verified in combination with mechanical properties and microstructure through hot extrusion deformation trial production.

Effect of tool rotational speeds on material flow and strain rates during friction stir butt welding of AA2219-T87 plates

ABSTRACT Friction stir welding (FSW) process is widely used for joining Al-Cu alloy (AA2219-T87) plates because of its high joint efficiency and low residual stresses in contrast to fusion-based joining techniques. A two-way coupled, 3D thermal-material flow model has been developed in COMSOL software, and the effect of tool rotational speeds on thermal and material flow fields, strain rates, thermal histories, and size of weld zones are being studied. The non-uniform net heat generation during the FSW process is due to the friction between workpiece and tool materials and the deformation energy of plasticized material flow sheared by the rotating tool. An approximate range of temperatures for the weld zones has been proposed and found to be appropriate because the predicted sizes are in good agreement with the experiments. Furthermore, the authors suggested that a quality FSW joint must have the nugget zone smaller and the heat-affected zone larger than the tool shoulder diameter.

Three-dimensional fluid-thermal–mechanical coupling numerical modeling of elastocaloric cooler for electronic chip

Three-dimensional fluid-thermal–mechanical coupling numerical modeling of elastocaloric cooler for electronic chip

A little mica goes a long way: Impact of phyllosilicates on quartz deformation fabrics in naturally deformed rocks

Quartz deformation fabrics reflect stress and strain conditions in mylonites, and their interpretation has become a mainstay of kinematic and structural analysis. Quantification of grain size and shape and interpretation of textures reflecting deformation mechanisms can provide estimates of flow stress, strain rate, kinematic vorticity, and deformation temperatures. Empirical calibration and determination of quartz flow laws is based on laboratory experiments of pure samples; however, pure quartzite mylonites are relatively uncommon. In particular, phyllosilicates may localize and partition strain that can inhibit or enhance different deformation mechanisms. Experimental results demonstrate that even minor phyllosilicate content (<15 vol%) can dramatically alter the strain behavior of quartz; however, few field studies have demonstrated these effects in a natural setting. To investigate the role of phyllosilicates on quartz strain fabrics, we quantify phyllosilicate content and distribution in quartzite mylonites from the Miocene Raft River detachment shear zone (NW Utah, USA). We use microstructural analysis and electron backscatter diffraction to quantify quartz deformation fabrics and muscovite spatial distribution, and X-ray computed tomography to quantify muscovite content in samples with varying amounts of muscovite collected across the detachment shear zone. Phyllosilicate content has a direct control on quartz deformation mechanisms, and application of piezometers and flow laws based on quartz deformation fabrics yield strain rates and flow stresses that vary by up to two orders of magnitude across our samples. These findings have important implications for the application of flow laws in quartzite mylonites and strain localization mechanisms in mid-crustal shear zones.

Experimental study on the structure and propagation of the stretched hydrogen-rich turbulent premixed flames in the thin-reaction-zone regime

Experimental study on the structure and propagation of the stretched hydrogen-rich turbulent premixed flames in the thin-reaction-zone regime

An experimental study of localized flow pattern, strain rate and turbulence kinetic energy dissipation rate of in-line teethed high shear mixer with different rotor and stator structures

An experimental study of localized flow pattern, strain rate and turbulence kinetic energy dissipation rate of in-line teethed high shear mixer with different rotor and stator structures

Non-monotonic plasticity and fracture in DP1000: Stress-state, strain-rate and temperature influence

Non-monotonic plasticity and fracture in DP1000: Stress-state, strain-rate and temperature influence

Application value of ultrasound elastography for screening of early pregnancy cervical insufficiency: a retrospective case-control study.

This study aimed to investigate changes in the cervical strain rate (SR), cervical length (CL), and uterine artery blood flow parameters during early pregnancy in women with cervical insufficiency and evaluate the clinical efficacy of these markers for screening of cervical insufficiency in early pregnancy. This retrospective study in 60 pregnant women with cervical insufficiency and 100 normal pregnant women was conducted between September 2021 and January 2023 and measured ultrasound parameters of the cervix during early pregnancy. The cervical SR, CL, and uterine artery resistance index (RI) were measured in both groups at 11-14 weeks of gestation. Strain elastography represented by the SR was used to assess the hardness of the internal and external cervical openings. During early pregnancy, the SR at the internal and external cervical openings were significantly higher in the cervical insufficiency group than those in the normal pregnancy group (SR I: 0.19 ± 0.018% vs. 0.16 ± 0.014%; SR E: 0.26 ± 0.028% vs. 0.24 ± 0.025%; p < .001). The CL was significantly shorter in the cervical insufficiency group than that measured in the normal pregnancy group (34.3 ± 2.9 mm vs. 35.2 ± 1.99 mm; p = .036), while cervical blood perfusion was also poorer in the cervical insufficiency group than that in the normal pregnancy group (uterine artery RI: 0.76 ± 0.07 vs. 0.74 ± 0.05; p = .048). Receiver operating characteristic (ROC) curve analysis showed that the optimal critical values for diagnosing cervical insufficiency were 0.17% for SR I, 0.25% for SR E, 33.8 mm for CL, and 0.78 for uterine artery RI. Of these parameters, the ROC curve for SR I had the largest area under the curve [AUC = 0.89 (p < .001)], with the highest sensitivity (78%) and specificity (82%). Multivariate logistic regression analysis demonstrated that the SR at the internal cervical opening (OR 17.47, 95% confidence interval (CI) 5.08-60.08; p < .001) and CL (OR 5.05, 95% CI 1.66-15.32; p = .004) still showed significant differences between the two groups. Cervical elastography is an effective tool for screening early pregnancy cervical insufficiency. The SR at the internal cervical opening is a valuable indicator for screening cervical insufficiency and has superior clinical efficacy for screening for this condition compared to that of CL and the uterine artery blood flow index.

THERMAL AND HYDRODYNAMIC ANALYSIS OF NANOFLUID FLOW IN A CIRCULAR PIPE USING EULER-GRANULAR MIXTURE MODEL

THERMAL AND HYDRODYNAMIC ANALYSIS OF NANOFLUID FLOW IN A CIRCULAR PIPE USING EULER-GRANULAR MIXTURE MODEL

High-temperature compression deformation behavior of the high Nb-containing TiAl alloys doped with Sn

High-temperature compression deformation behavior of the high Nb-containing TiAl alloys doped with Sn

Hot deformation characteristics and microstructure evolution of Al20Co36Cr4Fe4Ni36 eutectic high entropy alloy

Hot deformation characteristics and microstructure evolution of Al20Co36Cr4Fe4Ni36 eutectic high entropy alloy

Grain Size Distribution of DP 600 Steel Using Single-Pass Asymmetrical Wedge Test

Grain size distribution after the completion of a phase transformation was studied through the laboratory-controlled hot-plastic deformation of dual phase 600 (DP 600) steel using a specially prepared asymmetric single-pass hot-rolling wedge test with a refined reheating grain size instead of the usual coarse-grained starting microstructure observed in practice. The experiment was performed to reduce generally needed experimental trials to observe the microstructure development at elevated temperatures, where stable and unstable conditions could be observed as in the industrial hot-rolling practice. For this purpose, experimental stress–strain curves and softening behaviors were used concerning FEM simulations to reproduce in situ hot-rolling conditions to interpret the grain size distribution. The presented study revealed that the usual approach found in the literature for microstructure investigation and evolution with a hot-rolling wedge test was deficient concerning the observed field of interest. The degree of potential error concerning the implemented deformation per notch position, as well as the stress–strain rate and related mean flow stresses, were highly related to the geometry of the specimen and the material behavior itself, which could be defined by the actual hardening and softening kinetics (recrystallization and grain growth at elevated temperatures and longer interpass times). The grain size distribution at 1100–1070 °C was observed up to a 3.45 s−1 strain rate and, based on its stable forming behavior according to the FEM simulations and the optimal refined grain size, the optimal deformation was positioned between e = 0.2 and e = 0.5.

Effects of Mn addition on mechanical properties, fracture surface, and electrochemical corrosion resistance of CoCrFeNiAl high-entropy alloys

High-entropy alloys consisting of CoCrFeNiAl as the major elements and 2–5 at% Mn as the minor element were prepared using a vacuum arc melting method. The crystalline structures of the prepared alloys were identified by x-ray diffraction. Moreover, the mechanical properties of the alloys were examined under quasi-static (10−1, 10−2 and 10−3 s−1) and dynamic (3000, 4000, and 5000 s−1) loading conditions using a universal testing machine and split-Hopkinson pressure bar system, respectively. The experimental results showed that, for all of the HEA alloys, the flow stress and strain rate sensitivity coefficient increased with increasing strain rate. Among all the alloys, that with 3 at% Mn exhibited the best mechanical properties. A significant loss in plasticity was observed as the Mn content increased to 5 at%. The scanning electron microscope observations showed that the favorable mechanical properties of the alloy with 3 at% Mn were the result of a compact dimple structure, which enhanced the toughness. The HEA with 5 at% Mn showed the best electrochemical corrosion resistance among all the alloys due to the formation of dendritic structures at the grain boundaries.