An analytical model for predicting the freeze–thaw durability of wood–fiber composites

The development and validation of an analytical model that predicts the onset of frost-induced damage in wood–plastic composites (WPCs) is presented in this work. The mathematical model is based on the mechanics of a hollow cylinder subjected to an internal pressure caused by the expansion of freezing moisture bound in the wood–fiber reinforcement. The model is substantiated using experimental data from several published studies. Using a stochastic approach, the model is implemented to analyze the effect of wood fiber specie, fiber volume fraction, and matrix material properties on the frost resistance of fully and partially saturated WPCs. Results show that WPCs with high fiber contents, high moisture contents, and low polymer tensile strengths are most susceptible to frost-induced damage. Data also suggest that the use of softwood fibers (e.g., pine, spruce) and polymers with low moduli and high tensile strengths enhances the frost-resistance of WPCs.     

Electrochemical investigation of the P2–NaxCoO2 phase diagram

Sodium layered oxides NaxCoO2 form one of the most fascinating low-dimensional and strongly correlated systems; in particular P2–NaxCoO2 exhibits various single-phase domains with different Na+/vacancy patterns depending on the sodium concentration. Here we used sodium batteries to clearly depict the P2–NaxCoO2 phase diagram for x≥0.50. By coupling the electrochemical process with an in situ X-ray diffraction experiment, we identified the succession of single-phase or two-phase domains appearing on sodium intercalation with a rather good accuracy compared with previous studies. We reported new single-phase domains and we underlined the thermal instability of some ordered phases from an electrochemical study at various temperatures. As each phase is characterized by the position of its Fermi level versus the Na+/Na couple, we showed that the synthesis of each material, even in large amounts, can be carried out electrochemically. The physical properties of the as-prepared Na1/2CoO2 and Na2/3CoO2 ordered phases were characterized and compared. Electrochemical processes are confirmed to be an accurate route to precisely investigate in a continuous way such a complex system and provide a new way to synthesize materials with a very narrow existence range.     

Experimental investigation and thermodynamic description of the Mg–Y–Zr system

The Mg–Y–Zr system was studied via experimental investigation and thermodynamic modeling. Four diffusion couples and four key alloys of the Mg–Y–Zr system at 500 °C were prepared. The phase relations of the Mg–Y–Zr system were investigated by means of X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. No ternary compound was found at 500 °C. The solubility of (αZr) in the Mg–Y intermetallics, i.e., Mg₂₄Y₅, Mg₂Y and MgY, was determined to be negligible. The differential scanning calorimetry measurement was performed on the Mg–Y–Zr alloys to obtain the phase transition temperature. The present thermodynamic calculations of the Mg–Y–Zr system matched well with the experimental data. The presently established Mg–Y–Zr phase diagram can offer a better understanding of the recent processing technique of creep-resistant magnesium alloys.     

Experimental investigation and thermodynamic prediction of the Bi–Sb–Zn phase diagram

Phase diagram of the ternary Bi–Sb–Zn system was investigated experimentally by DTA and SEM-EDS methods and analytically by CALPHAD method. The liquidus projection, invariant equilibria, several vertical sections and isothermal section at 300 °C were predicted using COST 531 thermodynamic database. Phase transition temperatures of alloys along three predicted vertical sections of the Bi–Sb–Zn ternary system with molar ratio Bi:Sb = 1, Bi:Zn = 1 and Sb:Zn = 1, were measured by differential thermal analysis (DTA). Predicted isothermal section at 300 °C was compared with the results of the scanning electron microscope (SEM) with energy dispersive spectrometry (EDS) analysis from this work.     

Synthesis of an integrated biorefinery via the C–H–O ternary diagram

An integrated biorefinery is designed to handle a wide variety of feedstocks (mainly biomass) and can produce a broad range of products (e.g., biofuel, biochemicals, etc.) via multiple conversion pathways and technologies. Gasification is recognized as one of the most promising technologies for initial processing of biomass. It uses thermal energy to convert the biomass feedstock into a gaseous mixture, which is also known as syngas, consisting mainly of carbon dioxide (CO₂), steam (H₂O), methane (CH₄), carbon monoxide (CO) and hydrogen (H₂). It is noted that the composition of syngas, especially the ratio of H₂ to CO, is crucial when the syngas is further converted to liquid fuels and chemicals. In this work, a graphical targeting approach for the evaluation of gas phase equilibrium composition of biomass gasification is proposed. Based on the targeted composition, a conceptual design of an integrated biorefinery can be systematically developed.     

Wetting transition of grain boundaries in the Sn-rich part of the Sn–Bi phase diagram

The microstructural evolution of tin-rich Sn–Bi alloys after the grain boundary wetting phase transition in the (liquid + β-Sn) two-phase region of the Sn–Bi phase diagram was investigated. Three Sn–Bi alloys with 30.6, 23, and 10 wt% Bi were annealed between 139 and 215 °C for 24 h. The micrographs of Sn–Bi alloys reveal that the small amount of liquid phase prevented the grain boundary wetting transition to occur during annealing close to the solidus line. The melted area of the grain boundary triple junctions and grain boundaries increased with increasing the annealing temperature. When the amount of liquid phase exceeded 34 wt% during annealing, increasing temperature has not affected the wetting behavior of grain boundaries noticeably and led only to the increase of the amount of liquid phase among solid grains in the microstructure. The XRD results show that the phase structure and crystallinity remained unchanged after quenching from various annealing temperatures.     

Thermodynamic calculation of the phase diagram of the Si–C system up to 8 GPa

The isobaric sections of the phase diagram of the silicon–carbon system at 8 GPa has been calculated using the phenomenological thermodynamics models with parameters of the interaction that have been defined based on the experimental data on the phase equilibria at high pressures and temperatures.     

An analytical approach and experimental confirmation of dislocation–twin boundary interactions in titanium

The morphology of $ \{ 10\overline{1} 2\} \left\langle {\overline{1} 011} \right\rangle $ { 10 1 ¯ 2 } 〈 1 ¯ 011 〉 deformation twins formed in commercial purity titanium during an initial pass of equal-channel angular pressing was studied by transmission electron microscopy (TEM). The corresponding diffraction patterns show a symmetry line splitting of $ (10\overline{1} 2) $ ( 10 1 ¯ 2 ) twin boundaries (TB) which is related to the presence of interfacial defects. A simple modeling for the interaction between non-screw a-slip lattice dislocations (Burgers vector b =  $ \frac{1}{3}[\overline{1} \overline{1} 20] $ 1 3 [ 1 ¯ 1 ¯ 20 ] ) and the $ (10\overline{1} 2) $ ( 10 1 ¯ 2 ) twin plane is used according to crystallographic geometry and vector conservation. The results show that dislocation dissociation into different Frank partial dislocations on the interfacial plane is more favorable than its transmission to the other side of the interface. The formation of the Frank partials at the TB can produce a small change in the TB misorientation angle and this is consistent with the symmetry line splitting of the $ (10\overline{1} 2) $ ( 10 1 ¯ 2 ) twin boundaries observed by TEM.     

Generation of a pressure–impulse diagram for a temporary soil wall using an analytical rigid-body rotation model

This study aimed to provide a simple and efficient model to calculate a time history of response and construct a pressure–impulse (P–I) iso-damage curve for a free-standing soil-filled HESCO Bastion (HB) concertainer^® wall subjected to blast loading based on the maximum rotation of the wall. An analytical model is formulated for a free-standing HB simple straight wall based on rigid-body rotation. The maximum rotations observed in a full-scale blast testing of free-standing simple straight walls were compared with the maximum rotations calculated using the proposed analytical model and are in good agreement. The model is subsequently used to calculate a P–I curve for the wall, which is a common iso-damage curve used in a blast-resistant design, and represents various combinations of blast pressures and impulses required to damage the wall to a selected failure criterion. The failure criterion was selected as the critical amount of rotation required to completely overturn the wall. The resulting P–I curve was plotted along with the different charge performance curves or the pressures and impulses of different charge sizes. The curves show that the overturning of the HB walls, except for extremely large charge sizes, is governed by the amount of blast impulse and not the blast peak pressures. This indicates that the response of HB walls is impulse dominated. The effect that material density has on P–I curves was studied and found to be relatively insignificant. The P–I curves calculated based on different degrees of rotation as failure criteria were also plotted and compared. The curves showed that the required blast impulse to rotate the wall to 75% of the complete overturning angle and the required blast impulse to completely overturn the wall were very close. This illustrates that the magnitude of rotation becomes increasingly sensitive to blast impulse as blast impulse approaches the critical blast impulse required to completely overturn the wall.     

An analytical investigation of elastic–plastic behaviors of 3D warp and woof auxetic structures

International Journal of Mechanics and Materials in Design - The present paper was conducted to calculate Young's modulus and Negative Poisson's ratio (NPR) of a warp and woof (WAW) 3D...     

Journal of the Academy of Marketing Science 1973–2018: an analytical retrospective

Scientometrics - This paper analyses the entire publication history of the Journal of the Academy of Marketing Science (JAMS) by analyzing 1747 documents from 1973 to June 2018. Citation networks...     

Refinement of the V-O phase diagram in the range 25–50 at % oxygen

The boundaries of the V₁₄O₆ + V _x O _z two-phase region in the V-O system at temperatures from ? 1050 to ? 1650 K have been determined experimentally. The V-O phase diagram has been refined in the range 25–50 at % oxygen using structural and microstructural data for vanadium oxides containing less than 50 at % oxygen in conjunction with earlier results. The possibility of ordering of cubic vanadium monoxide has been examined.     

Thermodynamic calculation of the phase diagram for the Al–B–C system at pressure 7.7 GPa

The phase diagram of the Al–B–C system has been calculated at pressure 7.7 GPa using models of the phenomenological thermodynamics with the interaction parameters derived from the experimental data on the phase equilibria at high pressures and temperatures.     

The Tl–I phase diagram revisited and the thermodynamic properties of thallium iodides

The Tl–I system has been studied using differential thermal analysis, X-ray diffraction, and emf measurements on TlI concentration cells. A more accurate Tl–I phase diagram is presented, according to which the compounds existing in the Tl–I system are TlI, Tl₂I₃, and TlI₃. Thallium monoiodide melts congruently at 715 K and undergoes a polymorphic transformation at 440 K. The other iodides melt peritectically at 535 and 404 K, respectively. In contrast to what was reported previously, no compound of composition Tl₃I₄ has been obtained. Using experimental emf data, we evaluated relative partial molar thermodynamic functions of the TlI in alloys of the TlI–I system and the standard Gibbs free energy, enthalpy of formation, and standard entropies of TlI₃ (?ΔG ₂₉₈ ⁰ = 142.79 ± 0.73 kJ/mol, ?ΔH ₂₉₈ ⁰ = 135.37 ± 2.85 kJ/mol, and S ₂₉₈ ⁰ = 263.3 ± 7.4 J/(mol K)) and Tl₂I₃ (271.39 ± 1.47, 262.40 ± 5.34, and 322.8 ± 13.2).     

Statistical description of the effect of Zr addition on the behavior of microcracks in Cu–6Ni–2Mn–2Sn–2Al Alloy

As possible substitutes for high-strength Cu–Be alloys, Cu–6Ni–2Mn–2Sn–2Al alloys have been developed. To clarify the physical background of the effect of trace Zr on the fatigue strength of such alloys, the initiation and propagation behavior of a major crack that led to the fracture of the tested specimens was monitored. When the stress amplitude was less than σ _a = 350 MPa, the fatigue life of the alloys with Zr was about 2–2.5 times larger than that of the alloy without Zr. When σ _a > 350 MPa, the effect of Zr addition on the fatigue life dramatically decreases as the stress amplitude increases. The increased fatigue life due to Zr addition resulted from an enhancement of the crack initiation life and microcrack growth life. The enhanced crack initiation life was mainly attributed to the strengthening of grain boundaries due to the precipitation of SnZr compounds. A statistical analysis of the behavior of multiple cracks was made to quantitatively evaluate the scatter in fatigue behavior. The statistical analysis supported the conclusions obtained from the behavior of a major crack.     

A new analytical model of normal penetration of projectiles into the light-weight ceramic–metal targets

In this paper based on Zaera and Sanchez-Galvez [4] model, a new analytical model has been presented for penetration of deformable projectiles into ceramic–metal targets. By considering erosion and flattening of projectile tip, the one-dimensional equation of motion has been established. The momentum equation has been employed to describe the fragmented ceramic conoid. Considering work hardening material behavior, energy conservation equation has also been used for modeling the deformation of back-up metallic plate. Semi-angle of ceramic conoid is modified based on Wilson and Hetherington [8] experiments. The ballistic limit and residual velocity of projectile predicted by new analytical model have a good agreement with the experimental results.