Hydrostatic Expansion Research Articles

Evaluation of microstructure and mechanical characteristics of 2024 aluminum alloys with μ-Al2O3 additives produced via hydrostatic cyclic expansion extrusion with back-pressure

Grain refinement techniques are commonly used to produce enhanced materials with micro- and nanoscale grain sizes. This study investigates the severe plastic deformation of 2024 aluminum alloys reinforced with microparticles of alumina (Al2O3) using a new method based on hydrostatic cyclic expansion extrusion. Cuboid samples of aluminum 2024 were subjected to severe deformation at 20 °C through the pressing of a steel punch from the top and the application of back-pressure to the bottom part of the workpiece after the addition of the reinforcing powder. The mold design was created to facilitate both modes of operation. The experimental results were used to examine deformation behavior and flow patterns in the samples. Furthermore, the mechanical properties and microstructure of the processed samples were analyzed to determine the effects of the applied strain.

Pelayanan pengujian kekuatan pipa HDPE di Laboratorium Kimia Material Departemen Teknik Material dan Metalurgi FTIRS-ITS

HDPE pipes are widely used in various industries, such as drinking water and sewage infrastructure, petroleum, agriculture, and construction. The advantages of HDPE pipes include corrosion resistance, light weight, easy installation, and low maintenance costs. Checking the quality of HDPE pipes, spesifically from industry that we tested, is important to ensure infrastructure safety, prevent system failure, improve operational efficiency, obtain user satisfaction, and conserve resources. We evaluated HDPE pipes with type PN 12.5 SDR 13.6 from industry in terms of resistance to hydrostatic pressure, tensile strength, and expansion capability. The evaluation was carried out at the Material Chemistry Laboratory of the Department of Material Engineering and Metallurgy FTIRS-ITS ITS in accordance with the standards of SNI 4829.2: 2015, ASTM D 638 M, and SNI 2553: 1999. The results show that HDPE pipes can withstand hydrostatic pressure up to 12 bar without leakage. The average tensile strength is 43.34 MPa with an average elongation of 354%, indicating ductile pipe properties with necking. Pipe expansion was observed to be 0.195%, indicating a good ability of the pipe to undergo expansion.

A new material model for concrete subjected to high rate of loading

This study presents a modified HJC model for simulating the constitutive behaviour of concrete under large strains, high strain rate and high pressure. The original HJC model has been modified by introducing the shear cracking, pore crushing, tensile cracking, and hydrostatic expansion damage models to the yield surface for reproducing the crushing, spalling (crater formed at the front surface), scabbing (crater formed at the rear surface), and radial cracking in the concrete target. The Lode-Angle model has been introduced to describe the yield surface to account for the substantial difference in the shear strength between the tensile and compressive meridians. The strain rate effect has been considered to suitably model the dynamic compressive and tensile strengths. Single element simulations have been performed to substantiate the effect of modifications introduced in the constitutive model. The results of the single element simulation obtained by using the proposed model (MHJC_K&I) have been compared with the results of the two latest modified (MHJC_Kong [1] and MHJC_Liu [2]) models available in the literature. The MHJC_K&I model has described more realistic strength softening under uniaxial compression when compared with the experiment results. Further, the MHJC_K&I model has described accurately the magnitude of tensile strength under uniaxial tension in comparison to the other two models. Under hydrostatic tension, the MHJC_K&I model described the exponential strength softening and the MHJC_Kong model described the linear softening while the MHJC_Liu model had limitation in describing the softening behaviour. The ballistic experiments have also been performed on 100 and 60 mm thick plain concrete targets against 0.4 kg steel projectile at incidence velocities in the range 103–220 m/s. The damage induced in the concrete targets as well as the residual projectile velocities have been obtained. The MHJC_K&I model has been found to effectively reproduce the damage with respect to the size and depth of the crater as well as the radial cracking at the front and rear surfaces of the plain concrete target. The MHJC_Kong and MHJC_Liu models underestimated the size and depth of the crater and described limitations in reproducing the radial cracking. The residual velocities obtained by using the proposed model (MHJC_K&I) have been found to have a good agreement with the actual results.

Ion-beam radiation-induced Eshelby transformations: The mean and variance in hydrostatic and shear residual stresses

Ion beam plays a pivotal role in ion implantations and the fabrication of nanostructures. However, there lacks a quantitative model to describe the residual stresses associated with the ion-beam radiation. Radiation-induced residual stress/transformation strain have been mostly recognized in the hydrostatic sub strain space. Here, we use molecular dynamics (MD) simulations to show that the response of a material to irradiation is generally anisotropic that depends on the ion-beam direction, and should be described using tensorial quantities. We demonstrate that accelerator-based ion beam irradiation, combined with the intrinsic lattice anisotropy and externally induced anisotropy (such as anisotropic mechanical loadings), causes radiation-actuated shear transformation strains in addition to hydrostatic expansion. We map out these complex correlations for several materials. Radiation-induced defects are shown to be responsible for residual shear stresses in the manner of Eshelby inclusion transformation. We propose such tensorial response model should be considered for accurate nanoscale fabrication using ion-beam irradiation.

Recent Trends in Transport of Surface Carbonaceous Aerosols to the Upper‐Troposphere‐Lower‐Stratosphere Linked to Expansion of the Asian Summer Monsoon Anticyclone

AbstractUsing Modern‐Era Retrospective analysis for Research and Applications Version‐2 (MERRA‐2) re‐analyses, we have examined recent trends (2000–2019) in transport of surface carbonaceous aerosols (CAs), that is, organic carbon and black carbon, to the upper troposphere and lower stratosphere (UTLS) during the Asian summer monsoon (ASM). We find a significant increased concentration of UTLS CA, linked to a linear trend in an expansion of the Asian Summer Monsoon Anticyclone (ASMA). Over core monsoon latitudes (25°–35°N), the trends in UTLS CA are enabled by increased upward transport from surface sources via an intensified monsoon meridional circulation, with increased latent heating over the southern Tibetan Plateau and foothill regions, enhanced by feedback processes associated with radiative heating by UTLS CA. In the extra‐tropics, increased UTLS CA stems primarily from an extended source of increased wildfire emissions over eastern Siberia and northern Asia, coincident with a large‐scale anomalous anticyclone with enhanced surface warming and drying near (80°–120°E, 55°–70°N). Here, CAs are transported upward from the surface to the ULS, likely by increased pyro‐convection associated with enhanced wildfires, and enter the tropical UTLS via increased equatorward transport on the eastern flanks of anomalous upper‐level anticyclones, coupled to the expanded ASMA. Overall, the increasing UTLS CA trends associated with expansion of the ASMA are consistent with a hydrostatic expansion of a warming troposphere, reflected in a rise in the tropical tropopause and consequential dynamical adjustments of the ASM subtropical jetstream, modulating the climate of the greater ASM region.

Optical properties of InAs, InSb and InAs[formula omitted]Sb[formula omitted] (x=0.25, 0.5, 0.75) alloys under strain

Applying hydrostatic and biaxial lattice expansion, the optical properties of InAs, InSb and their ternary alloys InAsxSb1−x have been investigated using density functional theory by employing the WIEN2k package. Under hydrostatic lattice expansion, we observe a conversion to narrow or zero band gap semiconductors, while under biaxial lattice expansion a conversion to topological semiconductors occurs. We further investigate how the optical properties, investigated within the random phase approximation, changes upon the transformation to topological semiconductors, narrow or zero gap semiconductors. Under hydrostatic lattice expansion, for all compounds except for InAs, the static dielectric constant increases linearly. According to our results, moderate biaxial lattice expansions between 1% to 4% cause a conversion to topological semiconducting state while the static dielectric constant of these compounds is found to increase smoothly during the transformation. With the strain increasing, the optical absorption spectra can be red-shifted significantly , and the optical absorption can be enhanced in some regions of electromagnetism spectrum.

Does the Sastry transition control cavitation in simple liquids?

We examine the Sastry (athermal cavitation) transitions for model monatomic liquids interacting via Lennard-Jones as well as shorter- and longer-ranged pair potentials. Low-temperature thermodynamically stable liquids have ρ < ρS except when the attractive forces are long-ranged. For moderate- and short-ranged attractions, stable liquids with ρ > ρS exist at higher temperatures; the pressures in these liquids are high, but the Sastry transition may strongly influence their cavitation under dynamic hydrostatic expansion. The temperature T* at which stable ρ > ρS liquids emerge is ∼0.84ϵ/kB for Lennard-Jones liquids; T* decreases (increases) rapidly with increasing (decreasing) pair-interaction range. In particular, for short-ranged potentials, T* is above the critical temperature. All liquids' inherent structures are isostructural (isomorphic) for densities below (above) the Sastry density ρS. Overall, our results suggest that the barriers to cavitation in most simple liquids under ambient conditions for which significant cavitation is likely to occur are primarily vibrational-energetic and entropic rather than configurational-energetic. The most likely exceptions to this rule are liquids with long-ranged pair interactions, such as alkali metals.

Microstructural, Mechanical and Corrosion Properties of AZ91 Magnesium Alloy Processed by a Severe Plastic Deformation Method of Hydrostatic Cyclic Expansion Extrusion

This research investigates the microstructural evolution, mechanical properties, and corrosion behavior of AZ91 magnesium alloy after the process of hydrostatic cyclic expansion extrusion (HCEE) at elevated temperature. The HCEE process is able to produce long length ultrafine-grained rods by applying high hydrostatic pressure. The results showed that ultrafine-grained microstructure appears after the consecutive passes of the process, which led to the higher hardness and strength with an increased elongation to failure in the processed rods at room temperature. The ultimate tensile strength and elongation to failure of the processed rod after two cycles of the HCEE increased more than 2 and 2.6 times, respectively. Moreover, an increase in hardness was more than 100% after the second cycle of the process and its distribution was more uniform. Furthermore, the ultrafine-grained microstructure after the HCEE resulted in the movement of potentiodynamic polarization derived curves to higher values of corrosion potential (Ecorr) and lower current density (Icorr), which shows the capability of the HCEE process in improving the corrosion resistance of AZ91 magnesium alloy rods. These increases in corrosion resistance were further indicated by the Nyquist diagram derived from the electrochemical impedance spectroscopy scanning and evolved hydrogen amount after 208 h of immersion in 3.5% NaCl solution. The novel HCEE process shows further its capability in producing long length ultrafine-grained rods with superior mechanical and corrosion properties rather than other severe plastic deformation techniques.

Processing of AM60 magnesium alloy by hydrostatic cyclic expansion extrusion at elevated temperature as a new severe plastic deformation method

Hydrostatic cyclic expansion extrusion (HCEE) process at elevated temperatures is proposed as a method for processing less deformable materials such as magnesium and for producing long ultrafine-grained rods. In the HCEE process at elevated temperatures, high-pressure molten linear low-density polyethylene (LLDPE) was used as a fluid to eliminate frictional forces. To study the capability of the process, AM60 magnesium rods were processed and the properties were investigated. The mechanical properties were found to improve significantly after the HCEE process. The yield and ultimate strengths increased from initial values of 138 and 221 MPa to 212 and 317 MPa, respectively. Moreover, the elongation was enhanced due to the refined grains and the existence of high hydrostatic pressure. Furthermore, the microhardness was increased from HV 55.0 to HV 72.5. The microstructural analysis revealed that ultrafine-grained structure could be produced by the HCEE process. Moreover, the size of the particles decreased, and these particles thoroughly scattered between the grains. Finite element analysis showed that the HCEE was independent of the length of the sample, which makes the process suitable for industrial applications.

The influence of pH on the interfacial behaviour of Quillaja bark saponin at the air-solution interface

The interfacial behavior of surfactants present in a natural extract from Quillaja saponaria Molina bark at the air-solution interface is studied by measurements of interfacial tension, interfacial elasticity, and interfacial reflectance FTIR spectroscopy. The active molecule, saponin, is observed directly at the air-solution interface (via reflectance FTIR spectroscopy) above and below the pKa of the molecule, and spectra confirm the altered charge of the interfacial layer at the two solution conditions. For all concentrations of saponin studied, and at pH values below and above pKa (i.e. pH 3 and 7), a reduction in interfacial tension as a function of time is observed, with some differences in early time-scale adsorption and with lower values of quasi-equilibrium interfacial tension for pH 3. The interfacial layer is seen to be elastic, as determined from measurements of hydrostatic expansion, with some variation at the two pH values, and as a function of concentration. In addition to interfacial layer characterisation, the interaction between two air-solution interfaces is probed using bubble collisions with an air-solution interface. This experiment allows for observation of thin film drainage kinetics and determination of the final foam film thickness for the case when one of the interfaces is at equilibrium while the dynamic adsorption layer is being established at the other. This is the first time when the interactions between such interfaces (i.e. only one being at equilibrium) have been studied. This is of particular importance for the formation stage of foams, during which time many of the interfaces are not at equilibrium. When two interfaces interact across a thin liquid film, pH is seen to significantly influence foam film thickness.

Abstract P127: Pericyte Detachment is Involved in Renal Congestion in a Novel Rat Model

Increased central venous pressure in congestive heart failure is responsible for renal dysfunction; however, the underlying mechanisms are unclear. We hypothesized that renal interstitial hydrostatic pressure (RIHP) and expansion pressures of the vasa recta are responsible for pericyte detachment resulting renal congestion-mediated fibrosis. We created a novel rat renal congestion model and investigated the effect of renal congestion on hemodynamics and its molecular mechanisms. The inferior vena cava (IVC) between the renal veins was ligated by suture in male Sprague-Dawley rats to increase upstream IVC pressure and induce congestion in the left kidney only. Left kidney congestion reduced renal blood flow in cortex (33.6%, 28.3 to 16.0 mL/min) and in medulla (41.8%, 11.9 to 6.9 mL/min) and glomerular filtration rate (1.16 to 0.20 mL/min/kg BW), and increased RIHP (12.6 to 17.6 mm Hg). Hypoxia was observed in the medullary thick ascending limb of Henle, only in the congestive kidneys. Tubulointerstitial injury, podocyte injury, albuminuria, and reduced creatinine clearance were observed in the congestive kidneys. Molecules related to extracellular matrix expansion, tubular injury, and focal adhesion were upregulated in microarray analysis. Renal decapsulation ameliorated the tubulointerstitial injury (mRNA expression of Kim1 15.3 to 4.3 A.U., αSma 5.3 to 2.8 A.U.). Electron microscopy captured pericyte detachment in the congestive kidneys. Transgelin and platelet-derived growth factor receptors (PDGFRs), as indicators of pericyte-myofibroblast transition, were upregulated in the pericytes and the adjacent interstitium. Imatinib, a PDGFR inhibitor, ameliorated the interstitial injury. Our results reveal a novel mechanism of worsening renal function associated with congestive heart failure, and provide a new therapeutic strategy based on a better understanding of the pericyte-myofibroblast transition.

Damage and Failure of Axonal Microtubule under Extreme High Strain Rate: An In-Silico Molecular Dynamics Study

As a major cytoskeleton element of the axon, the breaking of microtubules (MTs) has been considered as a major cause of the axon degeneration. High strain rate loading is considered as one of the key factors in microtubule breaking. Due to the small size of microtubule, the real-time behavior of microtubule breaking is hard to capture. This study employs fully-atomistic molecular dynamics (MD) simulation to determine the failure modes of microtubule under different loadings conditions such as, unidirectional stretching, bending and hydrostatic expansion. For each loading conditions, MT is subjected to extreme high strain rate (108–109 s−1) loading. We argue that such level of high strain rate may be realized during cavitation bubble implosion. For each loading type, we have determined the critical energy for MT rupture. The associated rupture mechanisms are also discussed. We observed that the stretching has the lowest energy barrier to break the MT at the nanosecond time scale. Moreover, the breakage between the dimers starts at ~16% of total strain when stretched, which is much smaller compared to the reported strain-at-failure (50%) for lower strain rate loading. It suggests that MT fails at a significantly smaller strain states when loaded at higher strain rates.

Hydrostatic cyclic expansion extrusion (HCEE) as a novel severe plastic deformation process for producing long nanostructured metals

In this paper, hydrostatic cyclic expansion extrusion (HCEE) is developed as a new severe plastic deformation technique for processing of the relatively longer ultrafine grained samples. Increasing the length of the processed sample, decreasing the processing load astonishingly, and increasing the hydrostatic stresses are the main advantages of HCEE. In this process, pressurized hydraulic fluid surrounded workplace played the primary role in reducing the friction load and in reducing consequently total load. The HCEE process was applied to commercial pure aluminum 1050 samples at room temperature, and then microstructural evolution and mechanical properties were examined. Microstructure analysis using back-scatter diffraction (EBSD) revealed that a significant grain refinement is achieved after the HCEE process. The average size of grains and subgrains decreased to ~700 nm after two passes of the HCEE process from the initial value of 50 µm in the unprocessed sample. Yield and ultimate strength were increased from 40 MPa and 52MPa to 125 and 137 MPa after two passes of HCEE process. Also, microhardness was increased from 36 HV to 45 HV after the first pass. The process seems to be very promising for industrial application of SPD processing which suffer from the main challenge of limited sample size.

Alignment and nonlinear elasticity in biopolymer gels.

We present a Landau-type theory for the nonlinear elasticity of biopolymer gels with a part of the order parameter describing induced nematic order of fibers in the gel. We attribute the nonlinear elastic behavior of these materials to fiber alignment induced by strain. We suggest an application to contact guidance of cell motility in tissue. We compare our theory to simulation of a disordered lattice model for biopolymers. We treat homogeneous deformations such as simple shear, hydrostatic expansion, and simple extension, and obtain good agreement between theory and simulation. We also consider a localized perturbation which is a simple model for a contracting cell in a medium.

Influence of lattice expansion on the topological band order of InAsxSb1−x (x = 0, 0.25, 0.5, 0.75, 1) alloys

The topological band structures of InAsxSb1−x (x=0, 0.25, 0.5, 0.75, 1) alloys have been investigated using density functional theory by utilizing the Wien2k package. These alloys are in a topologically trivial phase in their unstrained states and exhibit a small band gap. Since in small band-gap cubic semiconductors the nontrivial topological phase can be achieved by lattice expansion, we investigate the effect of hydrostatic and biaxial lattice expansion on band inversion strength and band order of these alloys. It is found that under reasonable hydrostatic lattice expansion, InAsxSb1−x (x=0, 0.25, 0.75, 1) alloys with cubic symmetry and InAs0.5Sb0.5 alloy with tetragonal symmetry, are converted to nontrivial topological semiconductors with zero band gap and non-zero band gap, respectively. In order to convert InAsxSb1−x (x=0, 0.25, 0.75, 1) alloys into topological semiconductors with non-zero band gap, we let the systems of InAsxSb1−x (x=0, 0.25, 0.75, 1) alloys undergo a biaxial lattice expansion. Thus by breaking the cubic symmetry in these alloys, not only they are converted to topologically nontrivial phase but also a small band gap is opened at Γ point.

Elimination of defects in In–Mg codoped GaN layers probed by strain analysis

The effect of In codoping effect in GaN:Mg layers were investigated through strain analysis. A hydrostatic lattice expansion is induced by In doping which cannot be simply explained by the size effect of In and Mg dopants. Together with the photoluminescence spectrums, this lattice expansion is a strong evidence for the elimination of nitrogen vacancies. The biaxial strain and edge dislocations are reduced with In doping. A theoretic model of interaction between In atoms and edge dislocations are established to explain this phenomenon.

Constitutive modeling of void-growth-based tensile ductile failures with stress triaxiality effects

In most metals and alloys, the evolution of voids has been generally recognized as the basic failure mechanism. Furthermore, stress triaxiality has been found to influence void growth dramatically. Besides strain intensity, it is understood to be the most important factor that controls the initiation of ductile fracture. We include sensitivity of stress triaxiality in a variational porous plasticity model, which was originally derived from hydrostatic expansion. Under loading conditions rather than hydrostatic deformation, we allow the critical pressure for voids to be exceeded so that the growth due to plasticity becomes dependent on the stress triaxiality. The limitations of the spherical void growth assumption are investigated. Our improved constitutive model is validated through good agreements with experimental data. Its capacity for reproducing realistic failure patterns is also indicated by a numerical simulation of a compact tensile (CT) test.

Prediction of topological insulating behavior in inverse Heusler compounds from first principles

The topological band structures of the X2YZ inverse Heusler compounds have been investigated by the first-principle calculations. The results of this study clearly indicate that a large number of inverse Heusler compounds naturally exhibit an inverted band structure. We found that, similar to the half-Heusler family, these inverse Heusler compounds can realize the topological insulating state under hydrostatic or uniaxial lattice expansion. Importantly, most of these compounds possess a negative formation energy, which makes them more suitable in material growth and could easily achieve the topological insulating behavior by alloying or proper strain.

Strain tuning of topological band order in cubic semiconductors

We theoretically explore the possibility of tuning the topological order of cubic diamond/zinc-blende semiconductors with external strain. Based on the tight-binding model, we analyze the evolution of the cubic semiconductor band structure under hydrostatic or biaxial lattice expansion, by which a generic guiding principle is established that lattice expansion can induce a topological phase transition of small band-gap cubic semiconductors via a band inversion, and further breaking of the cubic symmetry leads to a topological insulating phase. Using density functional theory calculations, we demonstrate that a prototype topological trivial semiconductor, InSb, is converted to a nontrivial topological semiconductor with a 2$%$--3$%$ biaxial lattice expansion.

Atomistic Characterization of Stochastic Cavitation of a Binary Metallic Liquid under Negative Pressure.

We demonstrate the stochastic nature of cavitation in a binary metallic liquid Cu46Zr54 during hydrostatic expansion by employing molecular dynamics (MD) simulations using a quantum mechanics (QM)-derived potential. The activation volume is obtained from MD simulations and transition-state theory. Extrapolation of the pressure dependence of the activation volume from our MD simulations to low tensile pressure agrees remarkably with macroscale cavitation experiments. We find that classical nucleation theory can predict the cavitation rate if we incorporate the Tolman length derived from the MD simulations.