Interface Deformation Research Articles

Enhanced interface adhesion in shape memory alloy hybrid composites via an elastomeric interface: An experimental and numerical investigation

Shape Memory Alloy Hybrid Composites (SMAHCs) hold great promise for different applications. However, the interface between SMAs and the matrix presents challenges due to large strains associated with the martensitic transformations (MTs). Although different strategies have been proven effective in increasing interfacial strength, debonding and its prevention remain unresolved. Therefore, to enable MTs in SMAHCs, this paper proposes a novel solution using a rubber-like elastomeric interface. Pull-out SMAHC specimens were tested at different embedding lengths with and without the elastomeric interface. Specimens with the elastomeric interface showed better performance and stress-strain transfer during MT up to SMA wire breakage. The behaviour of the interface was studied using finite element analysis. A fine-tuning method was proposed for the cohesive zone model parameters. Simulated pull-out tests matched experimental data, revealing the debonding mechanisms. However, results with the elastomer underscored the need to fully represent the underlying physics of the highly deformable interface.

The effect of Fe solute atom on interface structure and deformation behavior of Cu/FexNi1-x layered composites by molecular dynamics

Molecular dynamics investigated the effect of Fe solute atom on interface structure and deformation behavior of Cu/FexNi1-x layered composites. Ultimate stress first increases, then decreases, and then increases again with the increase of Fe content. When Fe content is between 20 % and 30 %, ultimate stress reaches the maximum value, which is 15.2 % higher than that of Cu/Ni. As the Fe content increases, stress concentration region on interface shifts from Cu layer to FexNi1-x layer, then to Cu layer, initial dislocation nucleation source on interface transfers from triangular node on Cu side to misfit dislocation line on FexNi1-x side, then to strip region on Cu side, and plastic deformation mechanism of FexNi1-x layer changes from slip of leading and trailing dislocations to slip of partial dislocations, then to slip of perfect dislocations. When Fe content is low, dislocation density rapidly increases to its peak, then decreases, and finally fluctuates around certain value, especially in the Fe30Ni70 layer where the dislocation density decreases to very low value, and interface morphology presents wavy. However, when Fe content is high, dislocation density slowly increases to its peak and then fluctuates around the peak, and interface morphology presents flat. Shear strain width of interface region decreases as Fe content increases, which indicates the interface of Cu/FexNi1-x with low Fe content has good plastic harmonized deformation ability.

Flow structure around a microswimmer at fluid–fluid interface

Living organisms such as bacteria and algae often form biofilms at air–liquid and/or liquid–liquid interfaces. Therefore, it is important to understand the hydrodynamic interaction between the fluid–fluid interface and microorganisms. In the present study, a squirmer model is employed to study the flow field structures around a symmetrically trapped spherical microswimmer at an interface separating two fluids with viscosity contrast. In these simulations, Reynolds ( Re ) and Capillary ( Ca ) numbers are very small, and hence the contribution of inertia and interface deformations are neglected. The squirmer model is validated against the analytical solution obtained by considering a source dipole. It is observed that the flow structure and vorticity distribution around the microswimmers are strongly influenced by the squirmer parameter (β) and viscosity contrast (λ). Furthermore, the interplay between force-dipole and source-dipole along with viscosity contrast leads to a range of flow structures such as symmetric four-lobe and asymmetric quadrupolar flow fields. This flow structure asymmetry around the swimmer is quantified with different steady state orientations (φ). The effect of flow profile on the passive tracer particle transport is explored in terms of trajectories. Specifically, larger values of φ result in more profound curly trajectories.

Improved discrete unified gas-kinetic scheme for interface capturing.

In this paper, we extend the improved discrete unified gas-kinetic scheme (DUGKS) from solving the hydrodynamic equationsto addressing the phase field equations, building upon our prior work [Wang et al., Phys. Fluids 35, 017106 (2023)10.1063/5.0128912]. The conservative Allen-Cahn equationand its modified form are presented first, followed by the construction of two improved DUGKS methods for interface capturing, based on the corresponding kinetic equations. The improved DUGKS for interface capturing utilizes the node distribution function instead of the interface center distribution function for evaluating the interface flux. The improved DUGKS enhances the numerical stability of the original DUGKS, and the good stability allows the calculations to be performed using large time steps, reducing the cumulative error from which more accurate predictions can be obtained. To verify the validity of the scheme, a series of numerical experiments were further carried out, including the diagonal translation, Zalesak's disk rotation, reversed single vortex, and deformation field. The comparison with the benchmark data shows that the improved DUGKS can simply and effectively capture the sharp interface and complex deformation interface of the two-phase flow interface.

High-pressure homogenization to improve the stability of liquid diabetes formula food for special medical purposes: Structural characteristics of casein–polysaccharide complexes

The stability of diabetes formula food for special medical purposes (D-FSMP) was improved by high-pressure homogenization (HPH) at different homogenization pressures (up to 70 MPa) and number of passes (up to 6 times). The process at 60 MPa/4 times was the best. Casein had the highest surface hydrophobicity in this condition. The casein–polysaccharide complexes were endowed with the smallest size (transmission electron microscopy images). The complex particles exhibited nearly neutral wettability (the three-phase contact angle was 90.89°), lower interfacial tension, and the highest emulsifying activity index (EAI) and emulsifying stability index (ESI). The prepared D-FSMP system exhibited the narrowest particle size distribution range, the strongest interfacial deformation resistance and the best storage stability. Therefore, an appropriate intensity of HPH could enhance the stability of D-FSMP by improving the interfacial and emulsifying properties of casein–polysaccharide complexes. This study provides practical guidance on the productions of stable D-FSMP.

The velocity studies in the pure viscoelastic liquid core in displacement flow with interfacial instabilities

The velocity profiles in the core of a pure viscoelastic liquid displacing a Newtonian oil in a 500 µm microchannel were measured with micro-particle image velocimetry (µPIV) to investigate the onset of elastic turbulence. During displacement, a film of the displaced phase remains on the channel wall while interfacial instabilities develop upstream of the displacing core. Two displacing phase flow rates were investigated at 0.1 ml/min and 0.2 ml/min, corresponding to elastic Mach numbers, Ma, of 0.43 and 0.86 respectively. It was found that the velocity profiles in the streamwise and wall-normal directions are almost symmetric with respect to the centre of the core phase, apart from the case at high Ma and at the position of maximum interface deformation. Velocity fluctuations are present for the 0.2 ml/min while they are almost zero for the 0.1 ml/min, indicating the presence of elastic turbulence at large flow rate. Similarly, the calculated turbulence strengths at different directions (which make up the turbulent kinetic energy) and the Reynolds stresses have significant values at 0.2 ml/min but are almost zero at the low flow rate. In both flow rates, a circulation pattern is formed below the interfacial instability.

Flow‐induced interfacial deformation structures (FIDS): Implications for the interpretation of palaeocurrents, flow dynamics and substrate rheology

ABSTRACTSole structures on the base of turbidites, and other bed types, are typically classified into scour marks and tool marks, such as flutes, grooves, skim marks and prod marks. Yet, there are a range of other common sole marks that are unrelated to scouring or tools, and whose origin is poorly understood. Prominent among these sole structures are longitudinal ridges and furrows, and ‘dinosaur leather’ structures associated with mud ripples. Herein, these features are described and it is argued that they are the product of deformation of the substrate during a sediment gravity flow event. In these flow‐induced interfacial deformation structures (FIDS), a soft cohesive substrate undergoes deformation in response to a buoyant force induced by the denser basal component of an overriding flow, and the flow interacts with this buoyant deformation through shear to remould the substrate. Variations in the relative strength of these buoyant and shear‐induced forces explain the wide range of FIDS that can form. This FIDS model reinterprets the formation of longitudinal ridges and furrows, which have previously been classified as scour marks, and explains their distinctive spatial patterns. Furthermore, the new model builds on the seminal work of Dżułyński and colleagues in the 1960s and 1970s, who identified that these structures contain key palaeocurrent information, and it is argued that such information is largely under‐utilized. Importantly, alongside their utility as palaeocurrent indicators, FIDS provide insights into the rheology of the substrate at the time of their formation, and thus the nature of basal flow conditions in the formative flows.

The selection mechanism of mineral bridges at the interface of stacked biological materials for a strength-toughness tradeoff

The strength-toughness tradeoff in biological materials such as nacre and bone is essentially due to their stacked microstructures formed by hard and soft phases. In some of these materials, purely soft phase acts as interface layers linking hard phases (platelets), while in some others, hard-phase bridges exist in the soft phase to form a hybrid interface. In order to disclose the selection mechanism of such different interface structures in biological materials, a novel shear-lag model with an interface consisting of alternatively distributed elasto-plastic (soft) and brittle-elastic (hard) segments is proposed. Using this model, solutions of tensile stress and tensile displacement in hard platelets and shear stresses in soft and hard interfacial segments are analytically achieved. Effects of the hybrid interface on the effective mechanical performances of the composite are analyzed, the results of which are well consistent with the existing experimental observations in biocomposites and bio-inspired composites. The most important finding is that the fracture strain of the soft phase has a decisive effect on the selection of a purely soft-phase interface or a hybrid interface of hard and soft phases in stacked biological materials in order to realize a tradeoff between strength and toughness. When the failure strain of the soft phase is relatively small, such as nacre, the purely soft-phase interface is too weak to transfer enough load to the platelet, and hard bridges are necessarily required to reinforce the interface and guarantee an efficient load transfer. When the soft phase has a sufficiently large failure strain, such as bone, the purely soft-phase interface is tough enough to sustain a large shear deformation, realizing an efficient load transfer and adequate utilization of all constituents, while an additional hard bridge is not conducive to the composite toughness due to its reducing effect on the interfacial shear deformation. The results not only help people gain a deeper understanding of the secrets behind the construction of different interfaces in biological materials, but also provide useful guidance for interface optimization design in strong and tough artificial materials.

Simultaneous PIV/LIF Measurements Of Velocity And Oxygen In An Advecting Air-Water Channel Flow

We investigate oxygen transfer across an air-water interface using an integrated Particle Image Velocimetry (PIV) and Laser-Induced Fluorescence (LIF) system. This setup allows for the simultaneous measurement of velocity and dissolved oxygen (DO) concentration fields, alongside the visualization of the air-water interface. The imaging process begins with zero DO concentration and continues until oxygen saturation in the water is achieved. Calibration of the oxygen LIF intensity field is performed using these images, benchmarked against measurements from an optical oxygen point probe, to ensure accurate conversion to a physically relevant unit. The air channel generates an air flow with a center-line mean velocity of 8.84 m/s, corresponding to a Taylor Reynolds number of 100. This high-velocity air flow results in the formation of wavy structures on the water interface creating situations similar to those found in nature (such as rivers and oceans). The wavy structures create reflections from the air-water interface; these reflections are mitigated during post-processing using a Wavelet-Fast Fourier Transform (W-FFT) method to remove high intensity noise. Additionally, the wind shear generated by the air flow induces high turbulence intensity and vortices near the air-water interface, significantly enhancing the dissolution of oxygen into the water. This turbulence and the associated vortical structures play a crucial role in the mixing process and the overall oxygen transfer efficiency. The study presents instantaneous dissolved oxygen structures overlapped with velocity structures in a flow with deformable interface, providing some insights into the oxygen transfer and mixing processes.

Artificial Intelligence Techniques for the Hydrodynamic Characterization of Two-Phase Liquid–Gas Flows: An Overview and Bibliometric Analysis

Accurately and instantly estimating the hydrodynamic characteristics in two-phase liquid–gas flow is crucial for industries like oil, gas, and other multiphase flow sectors to reduce costs and emissions, boost efficiency, and enhance operational safety. This type of flow involves constant slippage between gas and liquid phases caused by a deformable interface, resulting in changes in gas volumetric fraction and the creation of structures known as flow patterns. Empirical and numerical methods used for prediction often result in significant inaccuracies during scale-up processes. Different methodologies based on artificial intelligence (AI) are currently being applied to predict hydrodynamic characteristics in two-phase liquid–gas flow, which was corroborated with the bibliometric analysis where AI techniques were found to have been applied in flow pattern recognition, volumetric fraction determination for each fluid, and pressure gradient estimation. The results revealed that a total of 178 keywords in 70 articles, 29 of which reached the threshold (machine learning, flow pattern, two-phase flow, artificial intelligence, and neural networks as the high predominance), were published mainly in Flow Measurement and Instrumentation. This journal has the highest number of published articles related to the studied topic, with nine articles. The most relevant author is Efteknari-Zadeh, E, from the Institute of Optics and Quantum Electronics.

Three-Dimensional Measurements Of Deformable Oil Droplets In Turbulence

This work introduces an experimental facility designed to generate turbulence with a high energy dissipation rate of up to 0.3 m^2/s^3 , sufficient to induce deformation and fragmentation of oil droplets. The turbulence is produced by opposing arrays consisting of 24 jet streams in total, each with Reynolds numbers ranging from 12,000 to 50,000. Flow regimes are determined using 3D Particle Tracking Velocimetry (PTV) conducted in the center of the octagonal test section. The statistical analysis of the turbulence reveals a nearly homogeneous and isotropic nature. A 3D imaging system, equipped with six high-speed cameras, allows for the reconstruction of droplets using the multiple algebraic reconstruction technique algorithm, fostering both visualization and quantification of interface deformation. Additionally, the system enables the tracking of the breakup process. The presented setup is able to couple the measurements of the droplet shapes with surrounding turbulence in 3D dproplet topology reconstruction coupled with surrounding flow measurements. We demonstrate the capability of our imaging system and reconstruction methods for multiphase flow studies with an example of full 3D droplet topology reconstruction coupled with surrounding flow measurements.

Droplet boiling on two-tier hierarchical micro-pillar array surface – Nucleate boiling regime

Although hierarchical structured surfaces have shown great potential in improving heat transfer performance of boiling, the mechanisms associated with structure configuration and structure size remain elusive. In this work, the nucleate boiling regime of droplet on single-tier micro-pillar array (SM) surfaces and three types of two-tier hierarchical micro-pillar array (THM) surfaces is investigated comprehensively using the lattice Boltzmann model. Effects brought by the primary pillar size and the secondary pillar configuration on the development of vapor confined in pillar gaps are emphatically discussed from bubble nucleation through vapor coalescence to vapor expansion. Boiling dynamic characteristics concerning droplet morphological evolution, liquid-vapor interfacial deformation and triple-phase contact line (TPCL) motion are elucidated by the distributions of vapor pressure, fluid temperature and substrate heat flux. It is most efficient for the secondary pillar to enhance boiling heat transfer performance when configured on the side of primary pillar and least efficient when configured on the top of primary pillar.

Failure Mechanisms in Stainless Steel/Carbon Steel Clad Plate Under Shear Tensile Loading: Experimental and Modeling Methods

The deformation behavior of a stainless steel/carbon steel (SS/CS) clad plate under interface shear loading is characterized in this work. A 2D digital image correlation method is applied to track the strain field variation near the interface during shear tensile tests. Then, a cohesive zone model (CZM) finite‐element method is developed to clarify the delamination behavior of the tested clad plate. Finally, the interfacial failure characteristics of the SS/CS clad plate are further presented through the comparison between the finite‐element method and fractography analysis at the interface. In the experimental and simulation results, it is shown that the mixed‐mode CZM, which couples the constitutive equations of three fracture modes, demonstrates excellent capabilities in capturing SS/CS interfacial deformation behavior. The main deformation mode in shear tensile tests is variable according to locations. The central region at the bonded surface is dominated by the shear delamination mode, and the region near the notches shows shifted crack propagation toward normal mode. These abrupt interfacial failures can be clarified via stress state and local damage analysis of the well‐reproduced finite‐element model of cladding material.

Exploring the Atwood number impact on shock-driven hydrodynamic instability at pentagonal interface using discontinuous Galerkin simulations

Investigation of Atwood number impact is crucial for comprehending the flow dynamics of the evolving hydrodynamic instability. In this paper, the Atwood number impacts on the shock-driven hydrodynamic instability at a backward-facing pentagonal interface in its early stages are explored numerically. The shock-driven pentagonal interface has a unique property in which the incident angle of the shock wave is constant along the interface edge. This property provides the ideal environment for the shock-refraction process. To examine the Atwood number impact, we consider five distinct gases, including sulfur hexafluoride, krypton, argon, neon, and helium, which are filled inside the pentagonal interface and surrounded by nitrogen gas. A mixed modal discontinuous Galerkin method is used to solve the two-dimensional Navier–Stokes–Fourier equations for two-component gas flows for numerical simulations. The simulation results illustrate that the Atwood number plays a crucial role in the flow fields of the shocked-pentagonal gas interface, which have not been reported in the literature. The flow fields are greatly impacted by the Atwood number, leading to complex wave patterns, shock focusing, jet formation, interface deformation, and vorticity generation. Further, the Atwood number effects on the flow fields are also thoroughly examined by a quantitative study based on the integral quantities and the interface features. Finally, a quantitative analysis is performed to examine the intrinsic differences between the evolution of the flow fields at the square and pentagonal interfaces.

The Paradoxical Behavior of Rough Colloids at Fluid Interfaces.

Colloidal particles adsorb and remain trapped at immiscible fluid interfaces due to strong interfacial adsorption energy with a contact angle defined by the chemistry of the particle and fluid phases. An undulated contact line may appear due to either particle surface roughness or shape anisotropy, which results in a quadrupolar interfacial deformation and strong long-range capillary interaction between neighboring particles. While each effect has been observed separately, here we report the paradoxical impact of surface roughness on spherical and anisotropic ellipsoidal polymer colloids. Using a seeded emulsion polymerization technique, we synthesize spherical and ellipsoidal particles with controlled roughness magnitudes and topography (convex/concave). Via in situ measurement of the interfacial deformation around colloids at an air-water interface, we find that while surface roughness strengthens the quadrupolar deformation in spheres as expected by theory, in stark contrast, it weakens the same in ellipsoids. As roughness increases, particles of both shapes become more hydrophilic, and their apparent contact angle decreases. Using numerical predictions, we show that this partially explains the decreased interfacial deformation and capillary interactions between the ellipsoids. Therefore, particle surface engineering has the potential to decrease the capillary deformation by asymmetric particles via changing their capillary pinning, as well as wetting behavior at fluid interfaces.

Investigation on the cyclic shear properties of steel-crushed red mudstone particles interface

The cyclic shear characteristics between the structure and soil are critical to the bearing capacity of an infrastructure. In this study, the cyclic shear behavior of the interface between rough steel and crushed red mudstone particles under constant normal load (CNL) and constant normal stiffness (CNS) boundary conditions are investigated using an improved large-scale cyclic shear apparatus. Under the two normal boundary conditions, the variation rule of the interface shear stress with shear displacement is similar, and the interface generally exhibits softening behavior during cyclic shear. Nevertheless, the interface shear strength and deformation values are not equal for the two boundary conditions, i.e., under the CNL boundary condition, higher interface shear strengths are usually obtained, and more significant normal densification behavior is exhibited compared to the CNS boundary condition. The peak shear strength of the interface has a linear relationship with the normal stress, which conforms to the Mohr-Coulomb failure criterion. Additionally, the influence of water content on the interface deformation and cyclic shear strength under the above boundary conditions are explored. The water content does not change the interface volumetric response pattern but is reflected in the magnitude. Regarding interface shear strength, the interface softening phenomenon is more significant with increased water content. The interface shear strength of the initial and residual states is analyzed, while the relationship between the interface shear strength parameters and water content is established.

Transverse instability of traveling wave created by longwave Marangoni convection in the liquid layer covered by insoluble surfactant

We consider the Marangoni convection in a liquid layer heated from below. The liquid interface is covered by insoluble surfactant that plays an active role in the pattern formation together with inhomogeneity of temperature along the interface and surface deformability. In the vicinity of the onset of Marangoni convection, besides different kinds of stationary patterns (hexagons, rolls, squares), the appearance of wave patterns is possible. We analyze the transverse instability of the single traveling wave (TW) using generalizations of the complex Ginzburg–Landau equation (CGLE).

The Laminated/Network Interface Design and Deformation Behavior of Multilayer Steel

The Laminated/Network Interface Design and Deformation Behavior of Multilayer Steel

Mechanical properties and bonding mechanism on interfaces containing work-hardening surface layer of roll-bonded 6061 Al/Q235 steel composite plates

The film theory is widely accepted as a bonding mechanism of metallic laminate composites (MLCs). It states that the fresh metal contact after the rupture of the surface film is an important condition for the bonding of MLCs. However, the bonding performance and mechanisms at the interfaces containing surface films have not been sufficiently investigated. In this study, steel–aluminium composite plates were used to study the bonding state, elemental diffusion behaviour, and mechanical properties of the bonding interface between the steel-side work-hardened surface layer (WHSL) and the aluminium matrix. The results indicate that the Al and Mg atoms inside the Al matrix can diffuse to about 100–150 nm into the WHSL (Fe3O4) and undergo selective oxidation, thus generating Fe0.1MgAl2O4 particles during annealing. However, the Fe atoms in the WHSL cannot diffuse into the aluminium matrix, thereby preventing the WHSL–Al interface from generating intermetallic compounds and maintaining beneficial bonding properties after long-term annealing. Additionally, compared to the steel–aluminium composite plate without a WHSL, the steel–aluminium composite plate with a WHSL exhibited a superior bonding performance. It also demonstrated an elongation increase of 28.67%, the mechanism of this increased elongation was also studied. Under the same degree of bending, the composite plates with WHSL maintained a stable bonding state and formed a unique interface deformation mode around the WHSL–Al interface after bending, which are highly desirable bending properties.

Unfolding of shocked hydrodynamic instability at SF[formula omitted] elliptical interface: Physical insights from numerical simulations

The Richtmyer–Meshkov (RM) instability widely exists in variety of industrial and scientific applications, such as in inertial confinement fusion, astrophysics explosions, supersonic combustion, bubble dynamics and cavitation. This study investigates the unfolding physical phenomena of RM instability at SF6 elliptical bubbles using numerical simulations. In contrast to cylindrical bubble, both shocked horizontal/vertical-aligned elliptical bubbles with different aspect ratios are considered, emphasizing the aspect ratio effects on flow morphology, complex wave patterns, interface deformation, vorticity generation, and interface features. For this purpose, a two-dimensional system of compressible Navier–Stokes-Fourier equations for multicomponent flows are solved using by a mixed modal discontinuous Galerkin method. Numerical simulations illustrate that the aspect ratio of elliptical bubbles have a significant influence on the vortex dynamics and the associated RM instability flows in contrast to the cylindrical bubble. In horizontal-aligned elliptical bubbles, some additional complex waves pattern, including inward jet and secondary vortex rings are observed. While, in vertical-aligned elliptical bubbles, the interface between two primary vortex rings is always vertical and has a “hippocampus” appearance due to the enhancement of downstream velocity. The baroclinic vorticity due to misalignment of density and pressure gradients at interface affects the bubble deformation and induces the Kelvin–Helmholtz instability, which leads to turbulent mixing. It is observed that the complexity of the vorticity fields is enhanced with increasing aspect ratios. Further, these aspect ratio effects result in integral diagnostic of important spatially integrated fields, and various interface features.