Local Stress Research Articles

Nonlinear behavior simulation of ceramic-matrix composites using constituent-volume homogenization method

The nonlinear behavior of ceramic-matrix composites is affected by interface debonding and fiber pull-out. In this paper, we propose the constituent-volume homogenization method (CVHM) to replace the conventional bundle homogenization method, in order to model the behavior of trans-element debonding in woven structures using finite element method. Based on the CVHM, we establish the elastic relation of the relative motion between the fiber and the matrix, and the elastic constitutive relations for the constituents. Methods have also been developed to calculate the microscopic local stress of bundle under pull-out and multiaxial loads. Based on the above studies, we develop a procedure to analyze the stress-strain relation of braided composites using the CVHM. To validate the proposed method, we estimate the nonlinear behavior of the 2D plain-weave ceramic-matrix composites and compare the results with experimental data. The influence of interface shear strength (ISS) and the fiber ultimate tensile strength (UTS) on the nonlinear behavior is investigated.

Characteristics of stitching holes in plain-woven SiCf/SiC and its influence on tensile behavior

A certain number of stitching holes are randomly distributed in SiCf/SiC composites prepared by CVI method. The existence of these stitching holes disrupts the continuity of the internal fiber bundles and has a certain influence on the mechanical properties of the materials. In order to study the influence of stitching holes on the tensile behavior of plain-woven SiCf/SiC, this paper uses CT technology to scan the interior of plain-woven SiCf/SiC to obtain the morphology and distribution of the internal stitching holes. Then, cells containing stitching holes were modeled to study the influence of different characteristics of stitching holes on the tensile behavior of SiCf/SiC. Finally, the tensile behavior and damage process of the cell with stitching hole at the fracture location of the specimen and the cell with stitching hole near the fracture location were studied by modeling the specimen level cell with the thickness of the specimen. The conclusions are as follows: (1) A certain number of stitching holes were randomly distributed inside the specimen. The inclination angles of the stitching holes are mostly 70°–80°, and the radius of the stitching holes is mostly 0.25 mm–0.28 mm (2) The influence of stitching hole characteristics on the tensile behavior of plain-woven SiCf/SiC is as follows: Position > Hole radius > Inclination angle. Among the positional characteristics, the Type-Ⅱ model has the greatest influence on the weakening of the tensile behavior due to more pronounced stress concentration phenomenon. (3) The stitching hole at the edge of the specimen has the greatest influence on the weakening of the specimen strength and is accompanied by obvious stress concentration. In the section containing the stitching holes, the maximum local stresses in the fiber bundle and matrix are about 1.5 times that of the other two models, resulting in earlier damage initiation and faster accumulation.

Oxidation behavior and failure mechanisms of enamel coatings at different temperature

This work studies the prolonged high-temperature oxidation behavior and failure mechanisms of enamel coatings at three distinct temperatures: 600°C, 800°C, and 1000°C. The evolution of the coating’s microstructural morphology was characterized, and the kinematics of porosity, crystal precipitation, and oxide layer thickness were measured. The results indicated that at 600°C and 800°C, the coatings exhibit strong oxidation resistance and retain their mechanical integrity. However, at 1000°C, the coatings rapidly deteriorate due to formation of Cr microcrystalline bands and the diffusion of oxidation layer, leading to volume expansion and element segregation. These factors result in the formation of voids and stress concentrations. The precipitation of crystals further exacerbates localized stress and microcracks, increasing the brittleness and enlarging the stress concentration areas, ultimately causing coating spallation. The effects of cooling rate on the long-term oxidation lifetime of the coatings were also examined. The findings of this work suggest that the temperatures below 800°C are suitable for long-term application of the enamel coatings, while exposure to 1000°C results in their rapid failure.

Topological DNA blends exhibit resonant deformation fields and strain propagation dynamics tuned by steric constraints.

Understanding how polymers deform in response to local stresses and strains, and how strains propagate from a local disturbance, are grand challenges in wide-ranging fields from materials manufacturing to cell mechanics. These dynamics are particularly complex for blends of polymers of distinct topologies, for which several different species-dependent mechanisms may contribute. Here, we use OpTiDDM (Optical-Tweezers-integrating-Differential-Dynamic-Microscopy) to elucidate deformation fields and propagation dynamics of binary blends of linear, ring and supercoiled DNA of varying sizes. We reveal robust non-monotonic dependence of strain alignment and superdiffusive transport with strain rate. However, peak alignment and superdiffusivity are surprisingly decoupled, occurring at different strain rates resonant with the distinct relaxation rates of the different topologies. Despite this universal resonance, we find that strain propagation of ring-linear blends is dictated by entanglements while supercoiled-ring blends are governed by Rouse dynamics. Our results capture critical subtleties in propagation and deformation dynamics of topological blends, shedding new light on the governing physics and offering a route towards decoupled tuning of response features. We anticipate our approach to be broadly generalizable to mapping the deformation dynamics of polymer blends, with an eye towards bottom-up bespoke materials design. STATEMENT OF SIGNIFICANCE: In biology and in manufacturing, biomaterials are often subject to localized and spatially nonuniform strains and stresses. Yet, understanding the extent to which strains are absorbed, distributed, or propagated across different spatiotemporal scales remains a grand challenge. Here, we combine optical tweezers with differential dynamic microscopy to elucidate deformation fields and propagation dynamics of blends of linear, ring and supercoiled DNA, revealing robust non-monotonic trends and decoupling of strain alignment and superdiffusivity, and capturing critical subtleties in propagation and deformation dynamics. Our results, shedding important new physical insight to guide decoupled tuning of response features, may be leveraged to map the deformation dynamics of wide-ranging systems of biopolymers and other macromolecules, with an eye towards bottom-up bespoke biomaterials design.

The role of irradiation-enhanced interstitial diffusion in over-pressurizing fission gas bubbles in UO2

Fission gas bubbles in UO2 nuclear fuel have been observed to exhibit pressures in excess of the equilibrium bubble pressure; however, the cause of bubble over-pressurization has not yet been demonstrated. The mechanical interaction between a bubble and the surrounding matrix or grain boundary depends on the internal pressure of the bubble and local stress state, such that over-pressurized bubbles are thought to be responsible for fragmentation and pulverization, when exposed to a temperature ramp. Here, we investigate the role of U interstitials, produced through irradiation, in over-pressurizing bubbles by using a combined molecular dynamics (MD) and cluster dynamics approach. Firstly, the energies for the capture of interstitials and vacancies by bubbles have been determined from MD as a function of the ratio of gas atoms to vacancies that make up the bubble. Secondly, these reaction energies have been implemented in the cluster dynamics code Centipede to predict bubble over-pressurization as a function of temperature for typical fission rates. It was found that there is a transition from low pressure bubbles (at high temperatures) to high pressure bubbles (at lower temperatures). The cause of this behavior was shown to be the creation of irradiation-induced interstitials that are highly mobile relative to vacancies at low temperature; whereas, vacancies are sufficiently mobile at high temperatures to limit bubble pressures. This result supports the hypothesis that over-pressurized bubbles form during steady-state operation and that this behavior is highly sensitive to the local pellet temperature.

A nonequilibrium statistical mechanics derivation of the hydrodynamic equations of simple fluids using a noncanonical form of the Poisson bracket

The continuum level hydrodynamic equations of a simple fluid were derived by Irving and Kirkwood directly from discrete particle dynamics using statistical mechanics almost 75 years ago. Their elegant derivation demonstrated the fundamental molecular basis of macroscopic fluid flow and culminated in molecular expressions for the stress tensor and heat current density that have since been employed in countless molecular simulations to date. In this article, an alternative derivation is presented, which leads to more general expressions for the fundamental transport relationships and which arrives at them in a more straightforward chain of consistency that ensues directly from the Principle of Least Action. The main point of departure from the Irving–Kirkwood derivation is the application of a transformation mapping of the total momentum of each individual particle onto the sum of its peculiar momentum and its momentum relative to the local velocity field. This mapping provides a phase-space distribution function applicable in the space of particle positions and peculiar momentum, from which a noncanonical Poisson bracket can be derived in terms of the same set of microscopic variables. For a given dynamic variable, expressed in terms of particle positions and peculiar momenta, the expectation value of the noncanonical Poisson bracket of the dynamic variable is shown to correspond to the evolution equation of the expectation value of the dynamic variable. This allows for a direct derivation of all macroscopic density evolution equations (mass, momentum, and energy density fields) using a systematic procedure free of assumptions concerning the macroscopic state of the system. Furthermore, an explicit expression of the time evolution of the entropy density at the hydrodynamic level is derived following the same procedure. Finally, in the limit of short-range interparticle interactions, a molecular-based expression for the local stress tensor as properly defined from continuum mechanics is developed at the hydrodynamic level that elucidates the continuum mechanics connection of the general stress expression of Irving and Kirkwood.

Stress-constrained concurrent multiscale topological design of porous composites based on discrete material optimisation

Porous composites have attracted increasing attention in recent decades. This study develops a concurrent multiscale topology optimisation (CMTO) method under a prescribed stress constraint for designing porous composites with multi-domain microstructures. First, to address the difficulty of predicting local stress due to varying of microstructural type throughout the optimisation process, a continuous and differentiable stress measure is proposed to effectively approximate the local stress. Second, an inverse homogenisation method based on isogeometric analysis (IGA) is developed to improve the accuracy of stress prediction, and then it is integrated into a CMTO which is developed based on the discrete material optimisation (DMO) interpolation scheme. Third, a stress constraint which is differentiable with respect to both macro and micro design variables is proposed to enable the stress-constrained concurrent optimisation of the macrostructural configuration, microstructural configuration and distribution. Fourth, a novel post-processing approach is established to achieve smooth while volume preserving contour of unit cells with layouts. Finally, two benchmark design examples, namely l-bracket and Crack problems, are implemented using the presented CMTO under a global stress constraint to demonstrate the effectiveness of the proposed method. The result indicates that the proposed method can effectively decrease the stress concentration via three design manners, i.e., the macrostructural configuration, microstructural configuration and distribution. Also, an “interface-enlarging” phenomenon was interestingly but reasonably found in those cases when subjected to stress-constraint considerations.

Recent advances in understanding the roles of T cells in atrial fibrillation

Atrial fibrillation (AF) is a common arrhythmia associated with severe outcomes like heart failure and stroke. Recent studies highlight the crucial role of T in AF. Clinical studies have observed elevated levels of CD4+CD28null T cells, Th17/Treg cells, CD8+ cells, and related markers in the peripheral blood or atrial tissue of AF patients, correlating with disease severity and cardiovascular events. These T cell subsets contribute to AF through: (1) releasing inflammatory factors like TNF-α and IL-17 which affect calcium homeostasis and electrical activity in atrial myocytes and/or promote atrial fibrosis; (2) recruiting inflammatory cells such as macrophages, causing local inflammation, oxidative stress, and atrial remodeling; (3) secreting cytotoxic proteins like perforin and granzymes, inducing apoptosis in atrial myocytes and affecting their action potentials; (4) direct contact, influencing atrial myocyte electrophysiology. Understanding these T cell-mediated mechanisms may uncover new therapeutic targets for AF.

Drug-Loaded Mesoporous Polydopamine Nanoparticles in Chitosan Hydrogels Enable Myocardial Infarction Repair through ROS Scavenging and Inhibition of Apoptosis.

In this study, we synthesized mesoporous polydopamine nanoparticles (MPDA NPs) using an emulsion-induced interface assembly strategy and loaded epigallocatechin gallate (EGCG) into MPDA NPs via electrostatic attraction to form EGCG@MPDA NPs. In the post myocardial infarction (MI) environment, these interventions specifically aimed to eliminate reactive oxygen species (ROS) and facilitate the repair of MI. We further combined them with a thermosensitive chitosan (CS) hydrogel to construct an injectable composite hydrogel (EGCG@MPDA/CS hydrogel). Utilizing in vitro experiments, the EGCG@MPDA/CS hydrogel exhibited excellent ROS-scavenging ability of H9C2 cells under the oxidative stress environment and also could inhibit their apoptosis. The EGCG@MPDA/CS hydrogel significantly promoted left ventricular ejection fraction (LVEF) in infarcted rat models post injection for 28 days compared to the PBS group (51.25 ± 1.73% vs 29.31 ± 0.78%, P < 0.05). In comparison to the PBS group, histological analysis revealed a substantial increase in left ventricular (LV) wall thickness in the EGCG@MPDA/CS hydrogel group (from 0.58 ± 0.03 to 1.39 ± 1.11 mm, P < 0.05). This work presents a novel approach to enhance MI repair by employing the EGCG@MPDA/CS hydrogel. This hydrogel effectively reduces local oxidative stress by ROS and stimulates the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway.

Perspectives on Adhesive–Bolted Hybrid Connection between Fe Shape Memory Alloys and Concrete Structures for Active Reinforcements

The prestressed active reinforcement of concrete structures using iron-based shape memory alloys (Fe-SMAs) is investigated in this experimental study through three connecting methods: adhesive–bolted hybrid connection, bolted connection, and adhesively bonded connection by activating at elevated temperatures (heating and cooling) and constraining deformation to generate prestress inside Fe-SMAs, through which compressive stress is generated in the parent concrete structures. In tests, the Fe-SMA is activated at 250 °C using a hot air gun, generating a prestress of 184.6–246 MPa. The experimental results show that local stress concentration in the concrete specimen and Fe-SMA plate around the hole is caused by the bolted connection. The adhesively bonded connection is prone to softening and slip of the structural adhesive during the activation process, thereby reducing the overall recovery force of Fe-SMAs. The adhesive–bolted hybrid connection effectively mitigates the local stress concentration problem of concrete and Fe-SMAs at anchor holes, while avoiding the prestress loss caused by the softening and slip of structural adhesive during elevated-temperature activation, achieving good reinforcement effect. This study on the connection methods of an Fe-SMA for reinforcing concrete structures provides both experimental support and practical guidance for its engineering application, offering new perspectives for future research.

Cracking resistance behavior of HVAF-sprayed monolayer and hierarchical Fe-based amorphous coatings under bending stress

The bending strength and fracture toughness are two key indicators that determine the service performance of thermally sprayed Fe-based amorphous coatings (AMCs) in harsh environments. Unfortunately, due to the inherent heterogeneous porosity and limited thickness (typically <1 mm) of the coatings, obtaining these properties is constrained by traditional fracture analysis methods. To address this, a three-point bending combined with the digital image correlation (DIC) method, without prefabricating notch or removing substrate, was proposed in the current work, and the effect of hierarchical structures on the fracture performance of the coatings was successfully revealed. Excitingly, the results show that compared to monolayer coating, hierarchical structures comprising two layers with different porosities can realize the synergistic improvement in the fracture strength and fracture strain of the coatings by alleviating local stress concentration and inducing crack deflection. Further, a finite element method (FEM) was employed to gain insight into the intrinsic relationship between the coating microstructures and the crack evolution behavior. This work not only proposes a simple method for evaluating the fracture performance of Fe-based AMCs sprayed with high velocity air fuel (HVAF), but also presents an innovative idea for optimizing the coating's properties.

In-Situ EBSD investigation of how annealed twins produce excellent strength-ductility synergy in Al0.25FeCoNiV duplex high-entropy alloy

The development of high-entropy alloys (HEAs) has been historically constrained by trade-off between strength and ductility. In this study, the Al0.25FeCoNiV duplex HEA showed a yield strength of 625 ± 35.2 MPa and a fracture elongation of 48 ± 1.5 % after rolling and annealing. These values are 43 % and 60 % higher, respectively, than the as-cast specimens, demonstrating an excellent synergy between strength and ductility. Through in-situ electron backscatter diffraction (EBSD) tensile experiments and transmission electron microscopy characterization of the as-cast and annealed specimens, respectively, it is found that the superior mechanical properties of the annealed specimens are primarily attributable to the multilevel strengthening and strain-hardening coupling mechanism established by the synergistic action of phase boundaries (PBs), twin boundaries (TBs), and high-angle grain boundaries. This mechanism effectively suppresses strain localization and prevents premature fracture caused by local stress concentration at PBs. The strengthening mechanism of TBs on the mechanical properties of HEAs was investigated by examining the interaction mechanisms between annealed TBs and dislocations, as well as the coordinated plastic deformation mechanism of twins. This study provides novel insights into the development of innovative HEAs with enhanced properties and advances the understanding of the role of TBs in the strengthening mechanisms of materials.

Hoop tensile properties and crack propagation investigation of 2D braided SiCf/SiC composite tubes: Experiments and simulations

SiCf/SiC composites are promising candidates for advanced pressurized water reactors (PWRs) fuel cladding materials due to their enhanced accident tolerance. Their mechanical properties are strongly influenced by the braided structure of continuous SiC fibers. This study fabricated SiCf/SiC composite tubes with braid angles ranging from 30° to 50°, evaluating their hoop tensile properties through expansion-due-to-compression (EDC) experiments and analyzing the damage process using finite element method simulation. Results indicate that variations in braid angles significantly affect structural density, thereby impacting mechanical strength under hoop tensile stress. Increased braid angles result in smaller pore units and higher pore density, leading to local stress concentrations and varied deflections at overlapping regions. The dynamic propagation behavior of cracks was investigated through acoustic and structural nondestructive testing methods. Finite element analysis of different braid configurations highlights the pivotal role of pore units in the initiation and propagation of hoop tensile cracks. This study enhances the understanding of toughening structures in 2D braided composites and provides a theoretical basis for future accident-tolerant fuel cladding design.

Mass minimization using the reaction-diffusion level set method by considering local stress constraints in an integral form

Research in topology optimization with stress constraints has shown that defining the stress constraint locally yields better performance compared to global methods. However, an examination of the formulas for local stress constraints reveals a limitation - the constraint is only satisfied at points where it is explicitly defined, failing to guarantee satisfaction across the entire design domain. To address this shortcoming, this paper proposes utilizing an integral form of the stress constraint. The integral formulation theoretically ensures that the stress constraint is satisfied over whole design domain. The objective is to minimize the mass of plane stress structures using reaction-diffusion level set method while incorporating local stress constraints in this integral form. The methodology utilizes finite element approximations for geometry and displacements, defining local stress constraints through an integral formulation. A Lagrangian function combines objective and constraint functions, with sensitivity analysis performed during optimization based on level set function changes. Structural boundaries are updated using the Hamilton-Jacobi equation. The paper presents numerical examples with varying loads and support conditions to demonstrate the effectiveness of this integral stress constraint approach. Results illustrate the capability of the proposed method to generate optimal topologies while satisfying stress constraints across the entire design space.

Polydopamine-coated chondroitin sulfate methacryloyl multifunctional microspheres for wound treatment

The disappearance of the protective barrier after skin injury leads to the overproduction of reactive oxygen species (ROS) in response to various stimuli. Oxidative stress is one of the most important causes of delayed wound healing, leading to negative outcomes, such as excessive inflammatory response and impaired angiogenesis. In this study, we used microfluidic technology to integrate Prussian blue nanozymes and vascular endothelial growth factor and constructed multifunctional microspheres that improved local oxidative stress. In order to enhance the adhesion of the microspheres on the wound surface and prolong the release of the drug, we coated them with dopamine, ensuring uniform encapsulation on their surface. The microspheres adhered well to the wound surface and promoted wound healing by scavenging ROS, reducing the inflammatory response, and promoting angiogenesis. This strategy of integrating nanozymes and growth factors can have a synergistic effect, which is significant for wound healing.

A novel method for shape pre-optimization of fir-tree couplings in blade-disk connections

This paper presents an innovative approach to the pre-optimization of the blade-disk fir-tree coupling, with the intent of advancing the design and analysis of such connections in turbomachinery. These couplings are subjected to extreme mechanical loads, primarily from centrifugal forces during turbine operation, compounded by aerodynamic and vibrational forces. These conditions pose substantial challenges to ensuring the structural integrity and long-term reliability of the connections. Failure of the blade-disk attachment can lead to catastrophic consequences, making the optimization of these joints crucial.The proposed pre-optimization method addresses this by optimizing the distribution of material between the blade-root, disk-post, and engaging teeth, ensuring uniform load distribution across all teeth. A novel one-dimensional radial spring model is introduced, which simplifies the representation of the joint. The method achieves accurate load-sharing without requiring knowledge of the spring stiffness values, instead relying on stiffness ratios, which in turn are approximated equal to ratios between the areas of throat cross-sections. This approach effectively balances tensile stresses, contact pressures, and, proportionally, local stress peaks, all while streamlining the design process.Validation against finite element models demonstrates the model’s accuracy across different joint configurations with varying numbers of teeth. This method serves as a foundation for more detailed analysis and future optimization efforts, including those targeting specific failure mechanisms such as fretting fatigue and peak stress mitigation. Overall, this work offers a practical and efficient approach to enhancing the performance and reliability of blade-disk connections in turbomachinery.

Coupling stress and transmissivity to define equivalent directional hydraulic conductivity of fractured rocks

A DFN (Discrete Fracture Network) modelling approach is developed to couple stresses with fracture transmissivities and to evaluate large scale rock mass hydraulic conductivity. The transmissivity-stress coupling relies on a negative exponential correlation between normal stress acting on a fracture and fracture transmissivity, bounded by residual and maximal apertures. The remote stresses and the local stress fluctuations induced by the fractures themselves are combined in a semi-analytical approach to compute the normal stress acting on each fracture of a DFN. Directional equivalent hydraulic conductivities are numerically computed in all directions from a spherical permeameter setup. The resulting properties are first a cloud of points, where each point defines a direction and an equivalent hydraulic conductivity. The distribution of equivalent hydraulic conductivities is analyzed to define mean values, preferential directions and anisotropy ratio. The entire workflow is developed in the numerical platform DFN.lab. The capacity of the method to investigate the impact of the in-situ stresses on the rock mass hydraulic conductivity is illustrated for fracturing and in-situ stress conditions similar to the conditions at the Forsmark site in Sweden. We find that the stress fluctuations induced by the fractures have a significant impact on the resulting hydraulic conductivity field. They limit the anisotropy ratio to values close to a factor of 3 while the transmissivity distribution is correlated to orientations and spans several orders of magnitude. Sensitivity analyses, performed by changing the parameters of the transmissivity-stress law, show quantitatively how the directional hydraulic conductivities are rather controlled by the orientations of the in-situ stresses or by the underlying connectivity structure of the DFN.

Monoamine Oxidase Contributes to Valvular Oxidative Stress: A Prospective Observational Pilot Study in Patients with Severe Mitral Regurgitation.

Monoamine oxidases (MAOs), mitochondrial enzymes that constantly produce hydrogen peroxide (H2O2) as a byproduct of their activity, have been recently acknowledged as contributors to oxidative stress in cardiometabolic pathologies. The present study aimed to assess whether MAOs are mediators of valvular oxidative stress and interact in vitro with angiotensin 2 (ANG2) to mimic the activation of the renin-angiotensin system. To this aim, valvular tissue samples were harvested from 30 patients diagnosed with severe primary mitral regurgitation and indication for surgical repair. Their reactive oxygen species (ROS) levels were assessed by means of a ferrous oxidation xylenol orange (FOX) assay, while MAO expression was assessed by immune fluorescence (protein) and qRT-PCR (mRNA). The experiments were performed using native valvular tissue acutely incubated or not with angiotensin 2 (ANG2), MAO inhibitors (MAOI) and the angiotensin receptor blocker, irbesartan (Irb). Correlations between oxidative stress and echocardiographic parameters were also analyzed. Ex vivo incubation with ANG2 increased MAO-A and -B expression and ROS generation. The level of valvular oxidative stress was negatively correlated with the left ventricular ejection fraction. MAOI and Irb reduced valvular H2O2. production. In conclusion, both MAO isoforms are expressed in pathological human mitral valves and contribute to local oxidative stress and ventricular functional impairment and can be modulated by the local renin-angiotensin system.

Effect of macro- and micro-morphology on fluid film properties based on plasto-elastohydrodynamic lubrication

Purpose The developed plasto-elastohydrodynamic lubrication (PEHL) model is used to demonstrate the permanent change of macro morphology by critical high local stress at micro asperities in contact, which may further affect the fluid-film characteristics. Design/methodology/approach Geometric morphology is integrated into the PEHL model to elucidate the fluid-film properties governed by both macro- and micromorphologies. Findings Results show the model, accounting for combination of elastic and plastic deformations, realistically reveals fluid film distribution affected by the significant pressure highly concentrated within surface micro roughness interaction. The designed macroscopic textured surface mitigates the fluid film rupture phenomenon and prevents accumulated wear degradation from plastic deformation. Originality/value The PEHL model takes into account both elastic and plastic deformations and realistically reveals the fluid film distribution affected by large pressures that are highly concentrated in surface micro-roughness interactions. The macro-textured surfaces are designed to mitigate fluid film rupture phenomena and prevent cumulative wear caused by plastic deformation. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2024-0170/

Ultrasonic vibration-induced amorphization in the Cu-Al interface

A ∼ 40 nm thick nanocrystal-amorphous mixed zone was found at the Cu/Al interface induced by ultrasonic welding. It is believed that the formation of amorphous Cu/Al alloys is attributed to the local free energy increase and shear stresses during ultrasonic vibration. The lowering of the amorphization barrier is a prerequisite for ultrasonic vibration-induced interfacial amorphization, which is in intrinsic contrast to previously reported dislocation-mediated amorphization.