► Plastic behavior of WBC is studied over wide temperature and strain rate ranges. ► Different micromechanisms are found in the evolution of microstructures. ► The interaction between the grains is ...the determining factor that cracks the grains. ► Different constitutive models are established, assessed by strain-rate-jump tests. ► The descriptive capabilities of the constitutive models are discussed separately.
Thermomechanical behavior of tungsten-based composite 93W–4.9Ni–2.1Fe is investigated systematically over strain rates ranging from 0.001 to 3000s−1, and temperatures ranging from 173 to 873K. Different micromechanisms are found in the evolution of microstructures between quasi-static and dynamic tests. The deformation of the tungsten particles is sensitive not only to strain rates, but also to plastic strain levels; the interaction between the grains is found to be the determining factor that cracks the grains, regardless of strain rates. Based on experimental results, two phenomenological and five physically-based constitutive models are established through a procedure of regression analysis and constrained optimization. Descriptive and predictive capabilities of these models are examined and compared. The performance of the models in characterization of work-hardening, temperature, and strain rate effects of the material is also investigated separately.
•Dynamic shear behaviors of copper are studied from 6000 s−1 to 45,000 s−1 at different temperatures.•The effects of stress state and strain rate have been decoupled successfully at high strain ...rates.•The stress state effect on the plastic behaviors of copper are clearly exhibited.•The shear constitutive model shows much better performance than the compression model.•The stress state should be considered in the selection of constitutive model for engineering computation.
A new double shear specimen (DSS) is used under the traditional Split Hopkinson pressure bar (SHPB) technique to study the constitutive behaviors of pure copper under dynamic shear loading. Shear stress-shear strain curves are obtained at 288–673 K and in a wide range of shear strain rates between 6000–45,000 s−1. A shear dominated stress state is obtained in the shear zone, in which the stress triaxiality and the Lode angle parameter are both very low. The influence of stress state on the plastic flow properties of the material is observed through comparison of the test results with the experimental data in compression. With the aid of finite element analysis (FEA), it's seen that the determined constitutive model JC1 can give much more precise prediction on the shear testing results than the compression-based model, JC2. The result implies that the commonly adopted compression or tension test data may not be suitable for description of shear dominated deformation conditions. In engineering application, the actual stress/strain state must be considered in the determination or selection of the constitutive models to obtain a precise computation result.
•Soy protein isolate (SPI) solution is treated under multiple freeze–thaw cycles.•The solubility of SPI is significantly reduced by freeze–thaw treatment.•The protein precipitation rate is upto ...55.79%.•The precipitated proteins have a higher antioxidant capacity.
Multiple freeze–thaw (F–T) treatments could change a protein structure and affect its physicochemical activities. In this work, soy protein isolate (SPI) was subjected to multiple F–T treatments, and the changes in its physicochemical and functional properties were investigated. The three-dimensional fluorescence spectroscopy indicated that F–T treatments changed the structure of SPI, including an increase in surface hydrophobicity. Fourier transform infrared spectroscopy showed that SPI underwent denaturation, unfolding and aggregation due to the interchange of sulfhydryl-disulfide bonds and the exposure of hydrophobic groups. Correspondingly, the particle size of SPI increased significantly and the protein precipitation rate also increased from 16.69%/25.33% to 52.52%/55.79% after nine F–T treatments. The F–T treated SPI had a higher antioxidant capacity. Results indicate that F–T treatments may be used as a strategy to ameliorate preparation methods and improve functional characteristics of SPI, and suggest that multiple F–T treatment is an alternative way to recover soy proteins.
Plastic behavior of 603 armor steel is studied at strain rates ranging from 0.001 s-1 to 4500 s-1, and temperature from 288 K to 873 K. Emphasis is placed on the effects of temperature, strain rate, ...and plastic strain on flow stress. Based on experimental results, the JC and the KHL models are used to simulate flow stress of this material. By comparing the model prediction and the experimental results of strain rate jump tests, the KHL model is shown to have a better prediction of plastic behavior under complex loading conditions for this material, especially in the dynamic region.
The objective of this paper is to propose a novel methodology for determining dynamic fracture toughness (DFT) of materials under mixed mode I/II impact loading. Previous experimental investigations ...on mixed mode fracture have been largely limited to qusi-static conditions, due to difficulties in the generation of mixed mode dynamic loading and the precise control of mode mixity at crack tip, in absence of sophisticated experimental techniques. In this study, a hybrid experimental–numerical approach is employed to measure mixed mode DFT of 40Cr high strength steel, with the aid of the split Hopkinson tension bar (SHTB) apparatus and finite element analysis (FEA). A fixture device and a series of tensile specimens with an inclined center crack are designed for the tests to generate the components of mode I and mode II dynamic stress intensity factors (DSIF). Through the change of the crack inclination angle
β (=90°, 60°, 45°, and 30°), the
K
II/
K
I ratio is successfully controlled in the range from 0 to 1.14. A mixed mode I/II dynamic fracture plane, which can also exhibit the information of crack inclination angle and loading rate at the same time, is obtained based on the experimental results. A safety zone is determined in this plane according to the characteristic line. Through observation of the fracture surfaces, different fracture mechanisms are found for pure mode I and mixed mode fractures.
•The SAFs/PUL electrospun films showed improved hydrophobicity.•The SAFs/PUL electrospun films showed enhanced mechanical properties.•The SAFs/PUL electrospun films exhibits a favorable antibacterial ...performance.•The SAFs/PUL electrospun films possesses potential oral applications.
Electrospun films (ESF) are gaining attention for active delivery due to their biocompatibility and biodegradability. This study investigated the impact of adding soy protein amyloid fibrils (SAFs) to ESF. Functional ESF based on SAFs/pullulan were successfully fabricated, with SAFs clearly observed entangled in the electrospun fibers using fluorescence microscopy. The addition of SAFs improved the mechanical strength of the ESF threefold and increased its surface hydrophobicity from 24.8° to 49.9°. Moreover, the ESF demonstrated antibacterial properties against Escherichia coli and Staphylococcus aureus. In simulated oral disintegration tests, almost 100% of epigallocatechin gallate (EGCG) dissolved within 4 min from the ESF. In summary, the incorporation of SAFs into ESF improved their mechanical strength, hydrophobicity, and enabled them to exhibit antibacterial properties, making them promising candidates for active delivery applications in food systems. Additionally, the ESF showed efficient release of EGCG, indicating their potential for controlled release of bioactive compounds.
The layer-directional compressive properties of 2D-C/SiC composites were investigated at strain rates ranging from 10
−4 to 2.8
×
10
3
s
−1. The quasi-static experiments were performed using the ...electronic universal testing machine, and the dynamic experiments were conducted by the split Hopkinson pressure bar system. The results show that the dynamic compressive stress–strain curves are non-linear. The failure strength and the elasticity modulus vary linearly to the logarithm of the strain rate, and the failure strain reduces with an increasing strain rate. Scatter of dynamic compressive failure strength obeys Weibull distribution and the Weibull parameter
m is 5.27. The damage angle of dynamic compression is larger than that of static loading. Observed on SEM, the ruptured surface is smooth at high loading rate and more cracked fibers appear in the specimens than at lower strain rate. Based on the experimental results, a new constitutive model is proposed in this paper.
Applicabilities of several well-known constitutive models for BCC metals have been reviewed in detail previously (Modelling Simul. Mater. Sci. Eng. 20 (2012) 015005; Acta Mech. Solid. Sin. 2012, ...25(6): 598–608; Int. J. Plasticity, 2013, 40: 163–184). In this paper, descriptive and predictive capabilities of the same models for FCC metals are investigated and compared systematically, in characterizing plastic behavior of cold-worked pure copper at temperatures ranging from 93 K to 873 K, and strain rates ranging from 0.001 s−1 to 8000 s−1. Validities of the established models are checked by strain rate jump tests that were performed under different loading conditions. Flexibilities of the models in describing the effects of work hardening, temperature, and strain rate are also analyzed separately. The results show that these models have various capabilities in the characterization of different aspects of material behaviors, but the precision of prediction relies largely on that of description. Different models should be selected considering the specific details of material behaviors to obtain better performance in the engineering application.
•Experimental research is performed systematically on cold-worked pure copper.•Different constitutive models have been established based on the test results.•Descriptive and predictive capabilities of these models are investigated.•Description of work-hardening, temperature, and strain rate effects is compared.
Protein extraction from soybeans is a vital part of the soy industry. Traditionally, the extraction of soy protein has been done by alkaline extraction and isoelectric precipitation. With the ...advancement of technology, more extraction techniques have been developed, and are superior to this traditional method. In this review, the composition and classification of soy protein are summarized. Next, the current emerging technologies for soy protein extraction are highlighted. Three extraction technologies, namely reverse micellar, enzyme‐assisted and membrane ultrafiltration, are reviewed in detail. Finally, the research prospects and trends of soy protein extraction technology are also summarized.
•Uniaxial compression, uniaxial tension, and new double shear experimental methods are used to study the effect of stress state on mechanical behaviors of Ti6Al4V.•The effects of the strain rate and ...stress state on mechanical response are investigated.•The microscopic failure mechanisms under different loading conditions are revealed.
Uniaxial compression, uniaxial tension, and new double shear experimental methods are used to study the effect of stress state on the mechanical behaviors of Ti-6Al-4V over a wide range of strain rates (0.001-6500s−1). The experimental results show that strain rate and stress state both have strong influences on the plastic flow and failure properties of the material. With an increasing strain rate, the work-hardening rate increases under uniaxial compression loading, but decreases under uniaxial tension and shear. Moreover, with the increase of strain rates, the initial failure strain increases under uniaxial tension, but decreases under the uniaxial compression conditions. Based on the experimental results, the Johnson-Cook (JC) hardening laws are used in finite element analysis (FEA) to simulate the mechanical responses of the material. It shows that the simulated results and the experimental data are in good agreement. The results indicate that the effects of strain rate and stress state should be considered in the constitutive model. Fractographic examinations are also conducted under different loading conditions. The failure processes of the material are controlled by different micro-mechanisms.
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