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Ambient temperature produces great effects on battery state-of-charge (SOC) estimation, due to the unstable estimation algorithm, the weakened traceability of battery model, and variable model parameters at various temperatures, especially lower temperatures. The widely used method based on the equivalent circuit model (ECM) offline in using different algorithm, like current integral, the extended Kalman filter (EKF), or the unscented Kalman filter (UKF), can obtain an accurate SOC estimation at room temperature, but it is difficult to guarantee the high precision at lower temperatures. To address this problem, the battery model is investigated at different temperature, and an offset item is proposed to develop the observer equation in the estimated model. Then, the square root of the Sigma points Kalman filter (SR-UKF) is applied, and on the basis of the individual model parameter-temperature table and the developed model, the high accuracy of SOC estimation is achieved. Additionally, considering the burden of original parameter modification (all model parameters modified) at various temperature which will increase the product cost and computational complexity of the battery management system (BMS), the relationship between individual model parameter and the error of SOC estimation is built, which is helpful for the simplification of parameter modification. The results indicate that the proposed method based on the developed estimated model and the simplified parameter modification can achieve an accurate, stable, and efficient SOC estimation.

Locoweed is a poisonous plant that severely harms the development of grass-land and animal husbandry throughout the world. Oxytropis and Astragalus are the Latin names for the poisonous plants commonly known as locoweed. The main toxic substance in these plants is swainsonine. It is a strong inhibitor of lysosomal α-mannosidase I and Golgi body α-mannosidase II, resulting in the accumulation of oligosaccharides and glycoproteins in lysosomes, interfering with the molecular and cellular recognition of glycans, and causing tissue-cell vacuolar degeneration. Livestock shows a series of clinical and pathological symptoms, mainly for the decline of reproductive performance. The effects in dams are abortion, weak fetus, and fetal malformations. The key step in maintaining pregnancy in dams is early endometrial decidualization, because reproductive hormones, decidual cell apoptosis, endoplasmic reticulum (ER) stress, and other immune factors are negatively affected by swainsonine. This article addresses the modifications that occur through glycan processing and glycosylation resulting in the change of post-translational modification of the protein and the activity of the glycoprotein, and then direct and indirect mechanisms of ER stress, apoptosis, reproductive hormones, immune factors, and cell cycle and other pathways. Our aim is to find new methods of prevention and treatment of swainsonine poisoning in grassland animals.

Mechanical behavior of ultrafine-grained (UFG) materials is affected by many factors including “intrinsic” ones such as grain size, dislocation density and concentration of impurities, and “extrinsic” ones such as temperature, strain rate and strain. To evaluate those contributions to the yield and flow stress of commercial-purity titanium, compressive mechanical tests were conducted at strain rates from 10−4 to 3 × 103 s−1 and temperature from 77 to 473 K. Microstructure characterization was also carried out to pin-down the underlying mechanisms responsible for the observed mechanical behavior. Results show that the primary strengthening sources for coarse-grained (CG) titanium comes from interstitials, which contribute ∼64% of the yield stress. Grain boundary strengthening, dislocation interaction and interstitials contribute ∼38%, ∼32% and ∼30% of the yield stress of UFG-Ti, respectively. The flow stresses of both CG and UFG titanium depends positively on strain rate and negatively on temperature, but neither strain rate sensitivity (SRS) nor temperature sensitivity (TS) is constant over a wide range. The SRS of titanium is found to increase with increase in grain size and temperature.

The transforming growth factors β1 (TGF-β1) and TGF-β2, as two distinct homodimers of TGF-β superfamily, involve in chondrocyte growth and differentiation. Emerging evidence has implied that strontium (Sr) plays an important role in the bone formation and resorption, and has strong effects on stimulating human cartilage matrix formation in vitro. However, the direct effects of Sr on TGF-β1 and TGF-β2 expressions in chondrocytes are not entirely clear. The purpose of this study was to evaluate the influence of different Sr concentrations on the expression of TGF-β1 and TGF-β2 in rat chondrocytes in vitro. Chondrocytes were isolated from Wistar rat articular by enzymatic digestion. Strontium chloride hexahydrate (SrCl2·6H2O) was used as a Sr source in this study. Sr was added to the culture solution at final concentrations of 0, 0.5, 1.0, 2.0, 5.0, 20.0, and 100 μg/mL. After 72 h of continuous culture, TGF-β1 and TGF-β2 mRNA abundance and protein expression levels in the chondrocytes were determined by real-time polymerase chain reaction (real-time PCR) and Western blot, respectively. The results showed that TGF-β1 and TGF-β2 expressions in chondrocytes increased dose-dependently with Sr concentration. The mRNA abundance of TGF-β1 and TGF-β2 were markedly higher than those observed for control (P

Summary Negative energy balance is considered as the pathological basis of energy metabolic disorders in periparturient dairy cows. Serum non-esterified fatty acids (NEFA) are one of the most important indicators of energy balance status. Fibroblast growth factor 21 (FGF21) has been identified as a hepatokine involved in regulation of metabolic adaptations, such as promoting hepatic lipid oxidation and ketogenesis, during energy deprivation. However, the direct effects of NEFA on FGF21 expression and secretion in bovine hepatocytes are not entirely clear. The objective of this study was to investigate the effects of different NEFA concentrations on FGF21 expression and secretion in calf hepatocytes cultured in vitro. NEFA were added to the culture solution at final concentrations of 0.6, 1.2, 1.8 and 2.4 mmol/L. After 24 hr of continuous culture, FGF21 mRNA and protein expression levels in the hepatocytes were determined by real-time PCR and Western blot respectively. FGF21 secretion in the supernatant was determined by enzyme-linked immunosorbent assay (ELISA). The results showed that expression and secretion of FGF21 at 0.6 mmol/L NEFA-treated hepatocytes was higher than that of the control group (p

Monocrotaline (MCT) belongs to the category of Pyrrolizdine Alkaloids (PAs), which is one of important hepatotoxic alkaloid in Crotalaria Lin. Apoptosis is one mechanism of toxic responses induced by MCT. However, the underlying mechanism of liver apoptosis caused by MCT through Endoplasmic reticulum (ER) stress continues to be incompletely understood. In this study, we describe the role of ER stress in MCT induced hepatotoxicity in rats. 24 male rats were randomly divided into 3 groups: normal saline group, 45 mg/kg MCT group and 90 mg/kg MCT group. After 48 h of saline/MCT administration, the livers were collected for analysis of ER stress-related proteins by Western blotting. The expression of GRP78, p-IRE1α, ATF6 and caspase-12 showed a dose-dependent increase. PERK/eIF2α/ATF4/CHOP pathway is one of the major ER stress pathways which is required for cell survival. Therefore, through analyzing the effects of MCT on this pathway, we found the protein levels of p-PERK, p-eIF2α, ATF4 and CHOP were increase obviously. All these results indicate that MCT induces ER stress in rat liver. The PERK/eIF2α/ATF4/CHOP pathway is involved in the regulation of MCT-induced ER stress in the liver of rat.

In this work, the dynamic impact behavior and linked deformation mechanisms of a Cr26Mn20Fe20Co20Ni14 high-entropy alloy (HEA) with face-centered cubic structure were systematically explored. The HEA displays uniform plastic deformation without any adiabatic shear bands at a strain rate range from 1000 to 3000 s−1. Moreover, the yield strength exhibits a pronounced strain rate dependence, increasing by 28% from 282 MPa at 1000 s−1 to 360 MPa at 3000 s−1. The strain hardening exponent, strain rate sensitivity and temperature rise were calculated to be 0.899–0.95, 0.076 and 64.7 K, respectively, indicative of high strain and strain-rate hardening capabilities and strong resistance to thermal softening induced adiabatic shear localization. Detailed microstructural analyses decipher a transition of deformation mechanism from dislocation slip at 1000 s−1 to stacking faults (SFs) at 2000 s−1 and further to twinning at 3000 s−1, respectively. The strengthening mechanisms are delineated as manifold interactions between glide dislocations and SFs, SFs and SFs (i.e. the Lomer-Cottrell locks), and SFs and twins. Our work provides a comprehensive understanding on the dynamic impact behavior, deformation and strengthening mechanisms of Cr26Mn20Fe20Co20Ni14 high-entropy alloy.

This paper is focused on the determination of dynamic elastic modulus of polymer materials under high strain rate loading using the split Hopkinson pressure bar (SHPB) technique. Experiments conducted on the epoxy specimen by the traditional SHPB and the proposed vertical SHPB equipment demonstrates that the vertical SHPB can give more accurate measurements. The related factors, namely, the effect of stress inequilibrium in specimen, indentation in bars due to specimen and the tilt between specimen and bars, are extensively studied. It is concluded through theoretical analysis and numerical calculations that the influence of stress inequilibrium becomes negligible after two characteristic times. The numerical study on the indentation effect shows that the bar to specimen specific elastic modulus ratio and specific diameter ratio are critical to the level of influence on indentation. However, polymers with low elastic modulus values can still be accurately measured regardless of the indentation displayed. The numerical investigation on tilt effect indicates that the imperfect contact condition severely affects the accuracy of measured elastic modulus. This issue can be rectified by the newly proposed vertical SHPB. It can improve the contact conditions between bars and specimen significantly and offer acceptable accurate measurements for the dynamic elastic modulus of polymeric materials.

One of the most important issues related to adiabatic shear failure is the correlation among temperature elevation, adiabatic shear band (ASB) formation and the loss of load capacity of the material. Our experimental results show direct evidence that ASB forms several microseconds after stress collapse and temperature rise reaches its maximum about 30 μs after ASB formation. This observation indicates that temperature rise cannot be the cause of ASB. Rather, it might be the result of adiabatic shear localization. As such, the traditional well-accepted thermal-softening mechanism of ASB needs to be reconsidered.

Shear failure is frequently accompanied by the formation of an adiabatic shear band (ASB) under dynamic loading conditions. It was widely believed that both the thermal softening and stress state exert great influence on the initiation of the ASB. However, clear knowledge regarding the true mechanisms is still lacking and experimental research is especially needed. In this paper, a novel in-situ experimental setup was developed to observe the deformation localization and temperature evolution of the ASB simultaneously, by using the high-speed photography and high-speed infrared radiation (IR). The effect of the temperature increase on the initiation of the ASB was studied with the modified shear-compression specimens (SCS) of three different degrees. It is found that before the initiation of the ASB, the temperature of the deformed region in the SCS does not increase rapidly. Then, intense increment of temperature was found with the initiation and propagation of the ASB. The typical events—including the peak stress, the initiation of the ASB, and the maximum temperature—for adiabatic shear failure are ordered chronologically. It is proved that temperature increase may not the primary factor that triggers the initiation of the ASB.

Lipid peroxidation plays a crucial role in early brain injury (EBI) after subarachnoid hemorrhage (SAH), and cystine/glutamate antiporter system X

To investigate the effect of dietary copper on serum growth-related hormones levels and growth performance, a total of 60 weanling pigs were randomly assigned to six groups each containing 10 pigs, fed on basal diets supplemented with 0 (control), 100, 150, 200, 250, and 300 mg/kg copper sulfate for 80 days, respectively. The average daily gain (ADG), feed to gain ratio (F/G), feed intake and serum growth hormone (GH), insulin (INS), insulin-like growth factor 1 (IGF-1), and insulin-like growth factor-binding protein 3 (IGFBP-3) levels were detected at interval of 20 days. The results revealed that ADG, and serum GH, INS, IGF-1, and IGFBP-3 concentrations were increased significantly in the pigs fed on diets added with 100, 150, 200, 250, and 300 mg/kg copper sulfate. Meanwhile, in the pigs supplemented with 250 mg/kg copper sulfate, ADG was increased significantly from the 40th to the 60th day of the experiment (P

In this research, the thicknesses of Fe2Al5 sub-layer (lFe2Al5) in bead welds were roughly calculated according to the formula l = Kt1/2. The values of constant K and residence time t were obtained through recording welding pools temperature. Fe2Al5 sub-layers were also observed and their thicknesses were measured by SEM and EDS analysis. The calculated results were in close agreement with measured results, demonstrating the accuracy of these calculated Fe2Al5 sub-layer thicknesses.

In this work, a commercial magnesium alloy, AZ31B in hot-rolled condition, has been subjected to severe plastic deformation via four passes of equal channel angular pressing (ECAP) to modify its microstructure. Electron backscatter diffraction (EBSD) was used to characterize the microstructure of the as-received, ECAPed and mechanically loaded specimens. Mechanical properties of the specimens were evaluated under both compression and tension along the rolling/extrusion direction over a wide range of strain rates. The yield strength, ultimate strength and failure strain/elongation under compression and tension were compared in detail to sort out the effects of factors in terms of microstructure and loading conditions. The results show that both the as-received alloy and ECAPed alloy are nearly insensitive to strain rate under compression, and the stress–strain curves exhibit clear sigmoidal shape, pointing to dominance of mechanical twinning responsible for the plastic deformation under compression. All compressive samples fail prematurely via adiabatic shear banding followed by cracking. Significant grain size refinement is identified in the vicinity of the shear crack. Under tension, the yield strength is much higher, with strong rate dependence and much improved tensile ductility in the ECAPed specimens. Tensile ductility is even much larger than the malleability under compression. This supports the operation of 〈 c + a 〉 dislocations. However, ECAP lowers the yield and flow strengths of the alloy under tension. We attempted to employ a mechanistic model to provide an explanation for the experimental results of plastic deformation and failure, which is in accordance with the physical processes under tension and compression.

State of charge (SOC) is a key parameter for lithium-ion battery management systems. The square root cubature Kalman filter (SRCKF) algorithm has been developed to estimate the SOC of batteries. SRCKF calculates 2n points that have the same weights according to cubature transform to approximate the mean of state variables. After these points are propagated by nonlinear functions, the mean and the variance of the capture can achieve third-order precision of the real values of the nonlinear functions. SRCKF directly propagates and updates the square root of the state covariance matrix in the form of Cholesky decomposition, guarantees the nonnegative quality of the covariance matrix, and avoids the divergence of the filter. Simulink models and the test bench of extended Kalman filter (EKF), Unscented Kalman filter (UKF), cubature Kalman filter (CKF) and SRCKF are built. Three experiments have been carried out to evaluate the performances of the proposed methods. The results of the comparison of accuracy, robustness, and convergence rate with EKF, UKF, CKF and SRCKF are presented. Compared with the traditional EKF, UKF and CKF algorithms, the SRCKF algorithm is found to yield better SOC estimation accuracy, higher robustness and better convergence rate.

One of the most important issues related to dynamic shear localization is the correlation among the stress collapse, temperature elevation and adiabatic shear band (ASB) formation. In this work, the adiabatic shear failure process of pure titanium was investigated by dynamic shear-compression tests synchronically combined with high-speed photography and infrared temperature measurement. The time sequence of important events such as stress collapse, ASB initiation, temperature rise and crack formation was recorded. The key characteristics of ASB, such as width, critical strain, temperature, propagation speed and cooling rate were systematically studied. The maximum propagation velocity of ASB is found in this work to be about 1900 m/s, about 0.6Cs (Cs is the shear wave speed). The maximum temperature within ASB is in the range of 350–650 °C, while the material close to ASB is also heated. The cooling rate of ASB is on the order of 106 °C/s, indicating that it needs a few hundreds of microseconds for the ASB to cool down to the ambient temperature. One important observation is that the apparent temperature rise occurs after ASB initiation, which indicates that it might not be the causation but the consequences of ASB. Further efforts are called for confirmation of this notion because of its significance.

Shear failure is frequently accompanied with the formation of an adiabatic shear band (ASB) under dynamic loading condition. The results obtained by a previous study (Guo et al., 2019) indicate that temperature increase does not play a primary role in the formation of ASB. Moreover, the shear strain to ASB initiation is closely related to the stress state. In this paper, a hybrid experimental–numerical method is developed to evaluate quantitatively the effect of stress stare on the initiation of ASB within Ti–6Al–4V. A variety of geometries of specimens, including the modified shear-compression, shear-tension, and thin-walled tubular specimen are designed to create different stress states. Combined with high-speed photography, split Hopkinson bar systems are utilized to measure the mechanical response of these specimens. Critical shear strains of ASB initiation are acquired based on the high- speed photos. The stress state for each test condition is obtained by numerical simulation. A phenomenological model of ASB initiation considering stress triaxiality and Lode parameter is proposed. Compared to the experimental results, the proposed model can predict the initiation of ASB with good accuracy under the test condition of this work.

Nanoindentation is a powerful tool for characterizing the mechanical properties of materials at small length scales. Since the loading rate can be accurately recorded and controlled during a nanoindentation test, the strain rate dependence of these properties can also be determined. However, there are still a few problems that need to be addressed when it is applied to some special materials. High pressure torsion (HPT) processed metals are examples of these materials with non-uniform microstructures and mechanical properties. In this work, commercially pure niobium disks with diameter of ~10.0 mm and thickness of ~1.0 mm were processed by HPT. Grain sizes from a few nanometers to a few micrometers were generated due to a strong radial strain gradient in the disk. Instrumented nanoindentation tests were conducted at different radial locations of the HPT niobium disk. During each test, the loading rate was controlled so that the indentation strain rate was kept constant. Some key issues associated with the nanoindentation experiment, such as contact stiffness, contact area and the effect of pile-up or sink-in were evaluated and discussed carefully. The work-based method was used in data processing and it was compared with other approaches. The effects of indentation location, i.e., grain size, as well as indentation strain rate were characterized.

An investigation into the compressive and tensile behavior of a carbon fiber reinforced resin matrix composite at high strain rates is carried out using a split Hopkinson bar. All the dynamic tests are performed under the condition of stress equilibrium and constant strain rate. The results of the compressive tests show that the failure strength and strain of the composite increase with the increase of strain rate. A plateau is observed in a typical stress–strain curve which prompts further study into the failure mechanism by monitoring the failure process with a high-speed camera. The three-phase failure mechanism of on-impact compression, crack-induced unloading, and crack deviation-caused further condensation, is found to have greatly increased the strength and toughness of the composite. In the tensile tests, an increase of strain rate produces a reduced fracture angle and extended crack path. In this process, more failure energy is absorbed, thus the failure strength and strain of the composite are improved. The Cowper–Symonds model of strain rate dependency indicates that the material has a higher tensile strength than compressive strength, and the strain rate sensitivity is more noticeable at high stain rates than quasi-static conditions.

Tensile deformation behavior of a copper bicrystal with a perpendicular grain boundary was investigated. The deformation distribution on specimen surface during test was obtained by using digital image correlation (DIC) method. Experimental results show that the specimen deforms in a ‘double-necking’ mode. Both the displacement and strain distributions on specimen surface are inhomogeneous, and strain level at the grain boundary is lower than that within the grains. The specimens always fracture at the interior of the grain with soft orientation. In situ tension tests by scanning electron microscopy (SEM) indicate that slip bands cannot pass through the grain boundary. The above results suggest that the tensile deformation behavior of copper bicrystal is determined by the orientation of each grain as well as the grain boundary property. Grain with soft orientation tends to deform plastically and fracture first. Large-angle grain boundary could impede slip bands and hence strengthen the material.

Modifications were made on the traditional split Hopkinson pressure bar (SHPB) system to conduct dynamic shear tests. The shear response of Ti-6Al-4V was acquired at a shear strain rate of 10 4 s −1 by using this modified apparatus. The geometry as well as the clamping mode of the double-notch specimen was optimized by commercial FEM software ABAQUS, and the feasibility of the experiment set-up was validated. A shear stress calibration coefficient of = 1.03 and a shear strain calibration coefficient of = 0.50 were obtained. We have employed highspeed photography to record the deformation process, especially the initiation and propagation of adiabatic shear band (ASB), during the dynamic shear test. The frames show that the time duration from ASB initiation to its completion is less than 2 μs, from which we can estimate that the propagation speed of ASB within Ti-6Al-4V is more than 1250 m/s under such loading conditions. The temperature rise within ASB is also estimated to be Δ T 2 ≈ 1460 °C based on energy balance. Such high temperature has led to softening of the material within the ASBs, and has intensified the shear localization and finally resulted in fracture of the material.

Adiabatic shear localization of viscoplastic materials has been an area of great interest in the past few decades. Many numerical and theoretical investigations have been performed, yet few have taken into account the influence of microstructure (e.g., texture, grain size) of the material. For instance, experimental evidence has suggested enhanced shear instability for some nanostructured metals compared to their coarse-grained counterparts. Recently, Joshi and Ramesh proposed a rotational diffusion mechanism for the quasi-static shear localization behavior of nanostructured materials. Since shear band formation is generally enhanced under dynamic loading where diffusive processes are no longer essential, the adiabatic shear localization behavior at high strain rates can be different. In this work, a geometry softening mechanism is presented to study the adiabatic shear instability of viscoplastic materials. We further use the analysis to study the adiabatic shear instability in nanostructured metals under dynamic loading. This mechanism is based on grain rotation and is directly related to the grain size of the material. The mechanism was implemented into the governing equations of adiabatic shear localization and a one-dimensional numerical model was employed by using the characteristic line method. The effects of strain rate hardening, strain hardening and initial microstructure condition have been studied numerically. Examples are given for some specific metals and the results are compared with those of experiments.

A new criterion for shear band formation in metallic glasses is proposed based on the shear plane criterion proposed by Packard and Schuh [1]. This modified shear plane (MSP) criterion suggests that a shear band is not initiated randomly throughout the entire material under stress but is initiated at the physical boundaries or defects and at locations where the highest normal stress modified maximum shear stress occurs. Moreover, the same as in the shear plan criterion, the shear stress all over the shear band should exceed the shear yield strength of the material. For a complete shear band to form, both requirements need to be fulfilled. The shear yield strength of the material is represented by the shear stress of the point at which the shear band stops. The new criterion agrees very well with experimental results in both the determination of the shear yield strength and the shear band path. (C) 2010 Elsevier B.V. All rights reserved.

Miniature tensile specimens, having various sizes and geometries, are often used to measure the mechanical properties of bulk nanostructured materials. However, these samples are generally too small for use with conventional extensometers so that the strains are usually calculated from the crosshead displacements. This study uses experimental results and finite element modeling (FEM) to critically evaluate the influence of the specimen dimensions and strain measurement methods on the tensile curves obtained from miniature specimens. Using coarse-grained Cu as a model material, the results demonstrate that the values of strain obtained from the crosshead displacement are critically influenced by the specimen dimensions such that the uniform elongation and the post-necking elongation both increase with decreasing gauge length and increasing specimen thickness. The results provide guidance on the optimum procedures for the tensile testing of miniature specimens of both coarse-grained and nanostructured materials.

A nanocrystalline (NC) NiFe alloy is presented, in which both highly improved plasticity and strength are achieved by the dynamic-loading-induced deformation mechanisms of de-twinning (that is, reduction of twin density) and significant grain coarsening (see figure). This work highlights potential ingenious avenues to exploit the superior behavior of NC materials under extreme conditions.

Recently, the size dependence of mechanical behaviors, particularly the yield strength and plastic deformation mode, of bulk metallic glasses (BMG) has created a great deal of interest. Contradicting conclusions have been drawn by different research groups, based on various experiments on different BMG systems. Based on in situ compression transmission electron microscopy (TEM) experiments on Zr41Ti14Cu12.5Ni10Be22.5 (Vit 1) nanopillars, this paper provides strong evidence that shear banding still prevails at specimen length scales as small as 150 nm in diameter. This is supported by in situ and ex situ images of shear bands, and by the carefully recorded displacement bursts under load control its well as load drops under displacement control. Finite element modeling of the stress state within the pillar shows that the unavoidable geometry constraints accompanying such experiments impart a strong effect on the experimental results, including non-uniform stress distributions and high level hydrostatic pressures. The seemingly improved compressive ductility is believed to be due to such geometry constraints. Observations underscore the notion that the mechanical behavior of metallic glasses, including strength and plastic deformation mode, is size independent at least in Vit 1. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Determination of the mechanical properties of materials under the combined effects of high-temperatures and high strain-rates has been an important and challenging issue. A strategy has been proposed and evaluated recently towards this purpose in which a heating cell with accurate temperature control is synchronized with the split Hopkinson pressure bar (SHPB) system. This strategy allows pre-heating the specimen to desired temperatures before arrival of the stress wave and provides an experimental technique for the measurement of dynamic mechanical properties of materials at high-temperatures. Since its advent, this method has gained increasing interest in the community of dynamic mechanical testing owing to its ease of manipulation. However, a couple of critical problems should be addressed to validate the experimental results. Among the problems, a crucial one is associated with the temperature change in the heated specimen upon its contact with the relatively cold bars. In this paper, experiments were designed to determine the influence of cold-contact-time (CCT) on the temperature variation within the specimen. The experiments were conducted on Ti700 alloy at strain-rates of ∼104 s−1 and at temperatures from 20 to 800 °C. The results show that the CCT does have a strong effect on the experimental results. Based on the experimental results and our analyses, we believe that the data can faithfully reflect the material behavior if CCT is shorter than 50 ms. While in most systems without the heating cell being synchronized with the SHPB system, the typical CCT is about 500 ms, and therefore the experimental data cannot be taken as representing the material behavior.

In this work, we have processed commercial purity tungsten (W) via different routes of equal-channel angular extrusion (ECAE) at temperatures as low as 600 °C. We have systematically evaluated the quasi-static and dynamic compressive behaviors of the processed W. Quasi-static compression tests were performed using an MTS hydro-servo system at room temperature. It is observed that samples ECAE processed at 800 °C show higher yield and flow stresses than those processed at other temperatures; no obvious strain hardening is observed in the quasi-static stress–strain curves. Quasi-static strain rate jump tests show that the strain rate sensitivity of ECAE W is in the range of 0.02 to 0.03, smaller than that of coarse-grained W. Uni-axial dynamic compressive tests were performed using the Kolsky bar (or split-Hopkinson pressure bar, SHPB) system. Post-loading SEM observations revealed that under dynamic compression, the competition between cracking at pre-existing extrinsic surface defects, grain boundaries, and uniform plastic deformation of the individual grains control the overall plastic deformation of the ECAE W. The existence of flow softening under dynamic loading has been established for all of the ECAE W specimens.

Miniature dog-bone specimens with different sizes and geometries are frequently used to measure the tensile behaviors of nanostructured materials. Here we report a significant specimen dimensions influence on the tensile behavior of ultrafine-grained Cu: the elongation to failure, post-necking elongation and strain hardening rate all increase with increasing thickness or decreasing gauge length. The thickness effect is caused by the necking geometry and the effect of gauge length originates from the strain definition.

The aim of this study was to investigate the surface characterization of ultrafine-grain pure titanium (UFG-Ti) after sandblasting and acid-etching (SLA) and to evaluate its biocompatibility as dental implant material in vitro and in vivo. UFG-Ti was produced by equal channel angular pressing (ECAP) using commercially pure titanium (CP-Ti). Microstructure and yield strength were investigated. The morphology, wettability and roughness of the specimens were analyzed after they were modified by SLA. MC3T3-E1 osteoblasts were seeded onto the specimens to evaluate its biocompatibility in vitro. For the in vivo study, UFG-Ti implants after SLA were embedded into the femurs of New Zealand rabbits. Osseointegration was investigated though micro-CT analysis, histological assessment and pull-out test. The control group was CP-Ti. UFG-Ti with enhanced mechanical properties was produced by four passes of ECAP in BC route at room temperature. After SLA modification, the hierarchical porous structure on its surface exhibited excellent wettability. The adhesion, proliferation and viability of cells cultured on the UFG-Ti were superior to that of CP-Ti. In the in vivo study, favorable osseointegration occurred between the implant and bone in CP and UFG-Ti groups. The combination intensity of UF- Ti with bone was higher according to the pull-out test. This study supports the claim that UFG-Ti has grain refinement with outstanding mechanical properties and, with its excellent biocompatibility, has potential for use as dental implant material.

The quasi-static and dynamic characteristics of SiO2–epoxy nanocomposites with SiO2 nanoparticle weight contents of 0, 3 and 7% under uniaxial compression at different loading rates (10−4 to 104 s−1) are experimentally studied by means of a universal testing machine and desktop split Hopkinson pressure bar (SHPB), respectively. Results show that strain-rate hardening plays a dominate role in the stress–strain behavior of the composites and the effect of strain-hardening plays a secondary role. The performance of the composite is dependent on loading rate and nanoparticle dispersion. The compressive strength of the composites is higher than that of pure epoxy at high strain-rates, whereas there is no obvious trend between the compressive strength and the particle contents at low loading rate.

In this paper, a 3D finite element model is used to analyse the deformation heterogeneity during a single pass of equal channel angular pressing (ECAP). The equivalent plastic strains in three perpendicular planes of the billet are predicted and the influence of the friction between billet and channel on the equivalent plastic strain is determined. The results show that the equivalent plastic strains are not uniform in three directions. The deformation inhomogeneity indexes and the location of maximum equivalent plastic strain are varied with the increasing friction coefficient. The numerical predictions have a good agreement with theoretical and experimental results. This indicates that the proposed 3D finite element model can perfectly simulate the deformation distribution during ECAP process.

Ultrafine-grained (UFG) materials have extensive prospects for engineering application due to their excellent mechanical properties. However, the grain size decrease reduces their strain hardening ability and makes UFG materials more susceptible to deformation instability such as shear localization. In most cases, critical shear strain is taken as the criterion for formation of shear localization under impact loading or adiabatic shear band (ASB). Recently, some researchers found that the formation of ASB was determined only by the dynamic loading process and had nothing to do with its static loading history. They proposed for coarse-grained metals a dynamic stored energy-based criterion for ASB and verified it by some experiments. In this study, we will focus on the shear localization behavior of UFG metals such as UFG titanium and magnesium alloy AZ31. Quasi-static loading and dynamic loading will be applied on the same specimen alternately. The shear localization behavior will be analyzed and the criterion of its formation will be evaluated.