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Fibre reinforced concrete (FRC) exhibits complicated failure modes such as fibre breakage, mortar cracking, crushing and spalling, fibre-mortar interfacial debonding, depending on many material properties, geometric dimensions, boundary and loading conditions. Most existing numerical models are unable to reproduce these failure modes that may occur simultaneously or sequentially in a specimen, mainly due to difficulties in generating finite element meshes with a large number of randomly-oriented fibres. Herein we develop a discrete-continuum coupled finite element modelling approach for FRC materials capable of effectively simulating all the major failure modes. The continuum damaged plasticity model is used to simulate damage and fracture behaviour of the mortar, while debonding of fibre-mortar interfaces is modelled by nonlinear cohesive interfacial elements. Unique techniques are devised to generate conforming meshes between fibres and the surrounding mortar so that the randomly-oriented fibres are easily modelled. The modelling approach is validated by simulating single fibre pullout tests with different inclination angles, notched and non-notched direct tensile tests and three-point bending beam tests with randomly-distributed multiple fibres. [ABSTRACT FROM AUTHOR]

The dynamic damage and fracture behavior of concrete under compression with strain rate up to 100 s −1 is investigated by Monte Carlo simulations (MCSs) of realistic meso-scale models based on high-resolution micro-scale X-ray computed tomography (XCT) images, using the concrete damaged plasticity (CDP) model. For a given strain rate, 93 2D XCT images of a 37.2 mm concrete cube are simulated to obtain statistical results of macroscopic stress–strain curves. The predicted compressive dynamic increase factor (CDIF)–strain rate curve is in good agreement with existing experimental data and empirical curves. The effects of aggregate/void area fraction on dynamic compressive strength are also analyzed, and an augmented compressive strength-strain rate relation considering the void area fraction is proposed. A full 3D model is also simulated under various strain rates. It is found that the realistic XCT-image based meso-models with the CDP model are very promising in effectively elucidating the complicated and fundamental dynamic failure mechanisms of concrete. [ABSTRACT FROM AUTHOR]

We have studied the giant elastocaloric effect of directionally solidified Ni–Mn–In magnetic shape memory alloys (MSMAs) near room temperature. The textured microstructure significantly enhances the ductility of Ni–Mn-based MSMAs, which allows obtaining the martensitic transition characteristics of polycrystalline samples in a uniaxial stress field. A significant cooling level of about 4 K is measured when the stress is released. The experimentally measured temperature changes are found to be in good agreement with the theoretically calculated values. [ABSTRACT FROM AUTHOR]

Highlights: [•] The corrosion rate of BN-Al was less than that of CP-Al in 0.25mol/L HCl solution at room temperature. [•] The localized corrosion resistance of BN-Al was larger than that of CP-Al in 0.25mol/L HCl solution. [•] The work function of BN-Al was 0.23eV larger than that of CP-Al. [•] Al3+ and Cl− on BN-Al surface were more chemically stable than those on CP-Al surface. [•] The binding energies of BN-Al valence electrons were larger than those of the corresponding CP-Al valence electrons. [Copyright &y& Elsevier]

High-temperature pseudoelasticity was investigated in highly-oriented polycrystalline Ni52Fe17Ga27Co4 ferromagnetic shape memory alloy. The pseudoelastic behaviors and the kinetics of the martensitic transformation are significantly affected by the intersection angle between the loading direction and the grain boundaries. For the intersection angle of 0°, a complete pseudoelastic recovery of 5% is achieved at 348K. In contrast, only partial pseudoelastic recovery is observed for the intersection angle of 90°. At a constant pressure of 50MPa, the martensitic transformation starting temperature increases from 346K to 360K as the intersection angle changes from zero to 90°. [ABSTRACT FROM AUTHOR]

Abstract: Two of the current challenges facing producers of Ni–Mn–In alloys are the achievement of small hysteresis and good ductility. Here, we present a dual-phase (β-Ni51.8Mn31.4In16.8 and γ-Ni62.4Mn32.5In5.1) Ni52Mn32In16 alloy prepared by the zone melting liquid metal cooling directional solidification method, which simultaneously shows small hysteresis (ΔT <10K) and good ductility (6.6%). In addition, and more importantly, an inter-martensitic transition with a large magnetization jump occurs in this alloy. This is expected to further broaden the working temperature range of actuators and sensors that use this magnetic shape memory alloy. The sequence of the martensitic transformation can be shown by in situ X-ray diffraction to be austenite→10M→14M. Additionally, the second (γ) phase dramatically enhances the entropy change of these structural transformations and shifts them to higher temperatures. During the directional solidification, a novel banded-like microstructure, consisting of two layers, one of the β single phase and the other of the two phases coupled, forms at the low growth rate. A qualitative model is presented to explain the experimental observation, taking into account both the competitive nucleation and the growth of the phases. Experimental and theoretical analysis in the present work shows a linear relationship between the maximum spacing of the β single phase layer and the growth rate. [Copyright &y& Elsevier]

The tensile behavior of TiZrNiCuBe metallic glass was studied using synchrotron X-ray diffraction and scanning electron microscopy. Shear band formation was carefully controlled by the introduction of a stress gradient due to a semi-circular notch. Micro- and atomic-level strains were calculated by the Q-space method and pair distribution function analysis, respectively. The atomic-pair strains for the area near the notch increase exponentially at the final deformation stage. This can be directly linked to the shear-induced dilatation resulting from the shear band formation. [Copyright &y& Elsevier]

Abstract: The porous Ti-based metallic glassy/nanocrystalline composites were synthesized using powder metallurgy route. The sintered samples with different porosities can be obtained at sintering temperatures below glass transition temperature. The properties of the samples directly depend on the porosities and the sintered porous samples combine mechanical and acoustic properties of the porous crystalline material and the metallic glass, e.g. high strength, strong wave and energy absorption ability. Furthermore, the fundamental electrical behavior for this kind of novel porous material was also studied based on the percolation theory model, which helps to design and fabricate porous composites with unique electrical property. Our results suggest that the sintered porous composites have potentials for structural and functional applications. [Copyright &y& Elsevier]

Abstract: Joints with fully amorphous structure can be obtained by selecting proper friction time and rotational speed. The optimum strength of the joint is close to that of the base bulk metallic glass (BMG), demonstrating a perfect bonding. Based on the analysis of the temperature distribution during the friction welding, an equation mentioning the critical friction time for retaining amorphous structure has been established. The experimental results prove the validity of the equation. Moreover, the temperature distribution in the friction interface has been studied by numerical simulation, aiming to provide a better understanding of the friction welding process and the microstructure in the interface. The simulation results further confirm the availability of the calculation results, thus can be helpful for designing the process parameters using other BMG systems. [Copyright &y& Elsevier]

Abstract: Ti60Cu30Ni10− x Co x (x =0, 2, and 4) alloys with high fracture strength and large compressive plasticity have been investigated. The microstructure and fracture morphologies have been studied by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The largest compressive fracture plastic strain of 32.5% with the fracture strength of 2480MPa is achieved for Ti60Cu30Ni10Co4 alloy composite. The enhanced plasticity is attributed to the addition of Co element having a positive heat of mixing with Cu element, and the retardment for the shear band propagation resulted from the dendrites, which are homogeneously distributed in the matrix. The high fracture strength of the alloys is resulted from work hardening character due to a series of dislocations in the dendrites and the unique microstructure of the Ti60Cu30Ni10Co4 alloy, i.e., the coexistence of amorphous phase, nanocrystals, and micron-scale dendrites. [Copyright &y& Elsevier]

Abstract: In this study, the hypervelocity impact experiments were performed on Zr51Ti5Ni10Cu25Al9 bulk metallic glass using a two-stage light gas gun. The morphologies of the bullet holes exhibit three different regions: melting area, vein-pattern area, and radiating core feature area, suggesting that various regions experience different stress states during the hypervelocity impact. For the post-impact samples, the nano-hardness increases and plastic deformability decreases both with the increase in the distance from the bullet hole and with the decrease in the impact velocity, which is discussed by means of spherical stress wave theory and free-volume model. [Copyright &y& Elsevier]

A conventional thermo-mechanical process is developed to increase strength and provide good ductility for an Al–Cu–Mg alloy. After the aging treatment, the elongation to failure reaches ∼12%, which is higher by a factor of ∼2.6 than that of conventional T8 heat-treated alloys, and there is also a notable increase of ∼40MPa in the yield strength in comparison to T8 heat-treated alloys. [Copyright &y& Elsevier]

The crystallization behavior of Ti-based metallic glassy powders was systematically investigated. The results show a novel metastable nanocrystallization process, i.e. the glassy powders exhibit multi-step phase transition behavior. For the first exothermic event, the entire glassy phase crystallized into metastable nanocrystals, then a face-centered cubic structured Ni2SnZr and a monoclinic structured TiNi0.8Cu0.2 phases formed by a solid state transition (the second exothermic event). These crystallizations are believed to be driven by the synergetic effect of thermodynamics and kinetics. [Copyright &y& Elsevier]

Abstract: In this study, the room temperature creep behavior of Fe41Co7Cr15Mo14C15B6Y2 bulk metallic glass was investigated using nanoindentation technique with the maximum applied load ranging from 1mN to 100mN under different loading rates (0.01–2.5mNs−1). The creep stress exponent was derived from the recorded displacement–holding time curve. It was found that the stress exponent increases rapidly from 2.87 to 6.37 with increasing indentation size, i.e. exhibiting a positive indentation size dependence. Furthermore, as the indentation loading rate increases from 0.01mNs−1 to 2.5mNs−1, the stress exponent decreases gradually from 4.93 to 0.94. The deformation mechanism causing the nanoindentation creep is discussed in the light of the “shear transformation zone” (STZ) which provides qualitative explanation for the observed plasticity in amorphous alloy. [Copyright &y& Elsevier]

Abstract: Platinum–hydrogen tungsten bronze (Pt–H x WO3) was prepared on glass carbon electrode by potentiostat in 0.1mM H2PtCl6 +4mM Na2WO4 +2M H2SO4. Its surface morphology, structure and activity toward oxygen reduction reaction were studied with scan electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and linear sweeping voltammetry. It is found that platinum and hydrogen tungsten bronze can be co-deposited together on glassy carbon and the activity of platinum toward oxygen reduction can be improved significantly by H x WO3. Furthermore, the activity of Pt–H x WO3 toward oxygen reduction is hardly influenced by methanol. [Copyright &y& Elsevier]

• CHF data in a vertical tube with an inner diameter of 6.0 mm under oscillatory flow conditions were obtained. • The effect of flow oscillation on periodic and continuous dryout was analyzed. • CHF data were compared with predictions calculated by previous correlations. Experimental investigations on single-phase convection and critical heat flux in a vertical tube with an inner diameter of 6.0 mm under inlet flow oscillation conditions were carried out for the following range: 255 ≤ G av ≤ 455 kg·m−2·s−1, 0.5 ≤ P ≤ 3.0 MPa, 0 < Δ G / G av ≤ 3.0 and 0 < τ (period of flow oscillation) ≤ 10.6 s. Single-phase convective results show that the fluctuation amplitude of single-phase pressure drop decreases with an increasing τ. Besides, there may be a critical value τ c. The average value of wall temperature under steady state condition is smaller than that under oscillatory flow condition when τ > τ c while the former is larger than the latter when τ < τ c. With respect to two-phase results, the effect of flow oscillation on fluctuation amplitude of wall temperatures under flow boiling conditions is quite small. In addition, flow oscillation deteriorates flow boiling heat transfer in vertical tubes to some extent when 1.04 ≤ τ ≤ 10.6 s. The normalized periodic CHF (F p) decreases with an increasing average mass velocity, especially for short periods of flow oscillation. In addition, the declining rate of F p as a function of Δ G / G av was decayed with an increasing period of flow oscillation. In a general, 2006 CHF lookup-table and Kim et al. correlation are recommended to calculate CHF under steady state condition and periodic dryout heat flux under inlet flow sinusoidal oscillation condition, respectively. [ABSTRACT FROM AUTHOR]