Effect Of Mechanical Deformation Research Articles

A Unique Time-Reversal Algorithm-Enabled Flexible Ultrasound Transducer with a Controllable Acoustic Field.

Flexible ultrasonic devices represent a feasible technology for providing timely signal detection and even a non-invasive disease treatment for the human brain. However, the deformation of the devices is always accompanied by a change in the acoustic field, making it hard for accurate focusing. Herein, we report a stable and flexible transducer. This device can generate a high-intensity acoustic signal with a controllable acoustic field even when the device is bent. The key is to use a low-impedance piezoelectric material and an island-bridge device structure, as well as to design a unique time-reversal algorithm to correct the deviation of signals after transcranial propagation. To provide an in-depth study of the acoustic field of flexible devices, we also analyze the effects of mechanical deformation and structural parameters on the corresponding acoustic response.

Microstructurally resolved electrochemical evolution of mechanical- and irradiation-induced damage in nuclear alloys

There is a need for high-throughput, scale-relevant, and direct electrochemical analysis to understand the corrosion behavior and sensitivity of nuclear materials that are exposed to extreme (high pressure, temperature, and radiation exposure) environments. We demonstrate the multi-scale, multi-modal application of scanning electrochemical cell microscopy (SECCM) to electrochemically profile corrosion alterations in nuclear alloys in a microstructurally resolved manner. Particularly, we identify that both mechanically deformed and irradiated microstructures show reduced charge-transfer resistance that leads to accelerated oxidation. We highlight that the effects of mechanical deformation and irradiation are synergistic, and may in fact, superimpose each other, with implications including general-, galvanic-, and/or irradiation-activated stress-corrosion cracking. Taken together, we highlight the ability of non-destructive, electrochemical interrogations to ascertain how microstructural alterations result in changes in the corrosion tendency of a nuclear alloy: knowledge which has implications to rank, qualify and examine alloys for use in nuclear construction applications.

Effect of strain on the hysteresis loop of PbTiO3 nanoporous

Spontaneous polarisation of ferroelectric materials has been widely applied in electronic components such as random access memory, sensor, and transducer. Among ferroelectric materials, PbTiO3 (PTO) is one of the dominant materials because it has a large spontaneous polarisation value and can operate stably at high temperatures. PTO has been studied in many different structures such as thin film, nanowire, nanodot, nanodisk, and nanotube. In order to clarify the strain effect on the hysteresis loop of PTO nanoporous, the author investigated the effect of mechanical deformation on porous structure PTO materials using calculations based on the core-shell model. The obtained results show that the hysteresis loop is expanded under the compression of the biaxial strain (x, y) and the tensile of the uniaxial strain (z). On the contrary, the loop is shrunk under the tensile of biaxial strain (x, y) and the compression of uniaxial strain (z). Besides, in the study, spontaneous polarisation distribution and regression function of hysteresis loop area - strain of PbTiO3 nanoporous is discussed as well.

Spintronic performance of bent zigzag phosphorene nanoribbons: effects of mechanical deformation and gate voltage.

This study explores the spintronic properties of an innovative device incorporating in-plane bent zigzag phosphorene nanoribbons (ZPNRs). The device features ZPNRs with a channel length of 23.4 nm, bent into circular arcs with varying curvatures. We investigate the impact of mechanical deformation and gate voltage on the spin-dependent properties, including the density of states, transmission coefficients, and spin Seebeck coefficient (SSC). Our results demonstrate that the device exhibits a spin-semiconducting phase with tunable spin-splitting characteristics and spin-dependent transport properties, both of which are influenced by the curvature. An increase in the bending parameter markedly enhances spin splitting, leading to the SSC attaining values as high as 1.35 mV K-1. Moreover, the application of gate voltage further enhances both spin polarization and spin current. The significant impact of mechanical deformation and gate voltage on spintronic performance showcases the potential of bent ZPNRs for advanced applications.

Reactivity of Stone-Wales defect in graphene lattice – DFT study

Understanding the reactivity of carbon surfaces is crucial for the development of advanced functional materials. The SW defect is commonly present in carbon materials, but a comprehensive understanding of its effects on the reactivity of carbons is missing. In this study, we systematically investigate the reactivity of graphene surfaces with the Stone-Wales (SW) defect using Density Functional Theory calculations. We explore the atomic adsorption of various elements, including rows 1–3 of the Periodic Table, potassium, calcium, and selected transition metals. Our results demonstrate that the SW defect enhances binding with the studied adsorbates when compared to pristine graphene, with carbon and silicon showing the most significant differences. Additionally, we examine the effects of mechanical deformation on the lattice by constraining the system with the SW defect to the pristine graphene cell. Interestingly, these constraints lead to even stronger binding interactions. Furthermore, for carbon, nitrogen, and oxygen adsorbates, we observe that mechanical deformation triggers the incorporation of adatoms into the carbon bond network, leading to the reorganization of the SW defect structure. This work establishes a foundation for future studies in the defect and strain engineering of graphene, opening avenues for developing advanced materials and catalysts with enhanced reactivity and performance.

Performance assessment of a generic repository in salt host rock based on Task F of DECOVALEX-2023 – BASE's lessons learnt and future work

Abstract. The evaluation of coupled effects of mechanical deformation, fluid and gas flow, thermal loading, and chemical reactions is an important element of the performance and safety assessment of disposal systems for high-level radioactive waste and spent nuclear fuel in deep geological formations. Early investigations showed that to be able to conduct such an evaluation there was a need to enhance process understanding and to develop models capable of simulating coupled thermal–hydro–chemical–mechanical processes over relevant timescales and spatial scales. Recognising these challenges and needs, the DECOVALEX (DEvelopment of COupled models and their VALidation against Experiments) (https://decovalex.org, last access: 24 July 2023) was initiated in 1992 as an international cooperative project of nuclear waste organisations. BASE is one of the funding organisations for the current phase of DECOVALEX-2023 (running from 2020 to 2023) and actively contributes to Task F of the project (https://www.base.bund.de/DE/themen/fa/soa/projekte-aktuell/projekte-aktuell_node.html, last access: 24 July 2023, – “Beteiligung an der internationalen Forschungskooperation DECOVALEX”). Task F (https://www.decovalex.org/D-2023/task-f.html, last access: 24 July 2023) of DECOVALEX seeks to build confidence in the models, methods, and software used for performance assessment of deep geologic repositories and to highlight additional research and development needed to improve performance assessment methodologies. The task focuses on two illustrative disposal concepts for spent nuclear fuel: a generic repository in a fractured crystalline host rock and a generic repository in a salt formation. For each of the disposal concepts a reference case is defined that includes a set of conceptual models and parameters describing features, events, and processes that impact repository performance. Modelling teams work independently and are responsible for determining how best to implement and couple the models. Each team develops its own model(s), calculates agreed performance indicator values, and performs uncertainty and sensitivity analysis. The comparison of model results is conducted in stages, commencing with a comparison of key outputs of individual process models, followed by a comparison of a single deterministic simulation of the full reference case, and proceeding to uncertainty and sensitivity analysis. The present contribution describes recent BASE activities within Task F Salt of DECOVALEX-2023. Lessons learnt are discussed and possible future steps are presented.

Effects of mechanical deformation on dislocation density and phase partitioning in 4130 steel

Interrupted tensile tests were performed on an AISI 4130 pressure vessel steel and investigated by neutron diffraction and scanning microscopy techniques. Analysis of the neutron diffraction patterns reveal a partitioning of ferrite and martensite phases resulting from deformation. A modified Williamson-Hall approach was used to model the broadening of Bragg peaks associated with the two phases as a function of applied strain, revealing an order of magnitude increase in their dislocation densities when the material was strained beyond the ultimate tensile strength (UTS). Lattice strains measured in the ferrite phase were consistently larger than those measured in the martensite phase for all the applied strain levels investigated. Moreover, a strain-induced phase transformation from a predominately martensitic steel to a ferritic steel was observed, with the average martensite phase fraction of an as-received specimen going from 78% to 22% when pulled to failure. Electron Backscatter Diffraction (EBSD) and Scanning Kelvin Probe Force Microscopy (SKPFM) were used to characterize the microstructure and phase fractions of ferrite and martensite associated with the various strain levels. These results agree well with those obtained from neutron diffraction and demonstrate the utility of SKPFM to distinguish between metallic phases with similar crystal structures that may be difficult to detect using conventional methods such as EBSD.

Phase-field modeling of pitting and mechanically-assisted corrosion of Mg alloys for biomedical applications.

A phase-field model is developed to simulate the corrosion of Mg alloys in body fluids. The model incorporates both Mg dissolution and the transport of Mg ions in solution, naturally predicting the transition from activation-controlled to diffusion-controlled bio-corrosion. In addition to uniform corrosion, the presented framework captures pitting corrosion and accounts for the synergistic effect of aggressive environments and mechanical loading in accelerating corrosion kinetics. The model applies to arbitrary 2D and 3D geometries with no special treatment for the evolution of the corrosion front, which is described using a diffuse interface approach. Experiments are conducted to validate the model and a good agreement is attained against in vitro measurements on Mg wires. The potential of the model to capture mechano-chemical effects during corrosion is demonstrated in case studies considering Mg wires in tension and bioabsorbable coronary Mg stents subjected to mechanical loading. The proposed methodology can be used to assess the in vitro and in vivo service life of Mg-based biomedical devices and optimize the design taking into account the effect of mechanical deformation on the corrosion rate. The model has the potential to advocate further development of Mg alloys as a biodegradable implant material for biomedical applications. STATEMENT OF SIGNIFICANCE: A physically-based model is developed to simulate the corrosion of bioabsorbable metals in environments that resemble biological fluids. The model captures pitting corrosion and incorporates the role of mechanical fields in enhancing the corrosion of bioabsorbable metals. Model predictions are validated against dedicated in vitro corrosion experiments on Mg wires. The potential of the model to capture mechano-chemical effects is demonstrated in representative examples. The simulations show that the presence of mechanical fields leads to the formation of cracks accelerating the failure of Mg wires, whereas pitting severely compromises the structural integrity of coronary Mg stents. This work extends phase-field modeling to bioengineering and provides a mechanistic tool for assessing the service life of bioabsorbable metallic biomedical devices.

Fabric-Based Electrochemical Glucose Sensor with Integrated Millifluidic Path from a Hydrophobic Batik Wax

In recent years, measuring and monitoring analyte concentrations continuously, frequently, and periodically has been a vital necessity for certain individuals. We developed a cotton-based millifluidic fabric-based electrochemical device (mFED) to monitor glucose continuously and evaluate the effects of mechanical deformation on the device’s electrochemical performance. The mFED was fabricated using stencil printing (thick film method) for patterning the electrodes and wax-patterning to make the reaction zone. The analytical performance of the device was carried out using the chronoamperometry method at a detection potential of −0.2 V. The mFED has a linear working range of 0–20 mM of glucose, with LOD and LOQ of 0.98 mM and 3.26 mM. The 3D mFED shows the potential to be integrated as a wearable sensor that can continuously measure glucose under mechanical deformation.

Optical solitons in curved spacetime

Light propagation in curved spacetime is at the basis of some of the most stringent tests of Einstein’s general relativity. At the same time, light propagation in media is at the basis of several communication systems. Given the ubiquity of the gravitational field, and the exquisite level of sensitivity of optical measurements, the time is ripe for investigations combining these two aspects and studying light propagation in media located in curved spacetime. In this work, we focus on the effect of a weak gravitational field on the propagation of optical solitons in non-linear optical media. We derive a non-linear Schrödinger equation describing the propagation of an optical pulse in an effective, gradient-index medium in flat spacetime, encoding both the material properties and curved spacetime effects. In analyzing the special case of propagation in a 1D optical fiber, we also include the effect of mechanical deformations and show it to be the dominant effect for a fiber oriented in the radial direction in Schwarzschild spacetime.

Assessing the effect of mechanical deformation of the panasonic NCR18650B lithium-ion power cell housing on its fire safety

This paper considers the deformation properties of the body of the lithium-ion power cell (LIPC) Panasonic NCR18650B (LiNi0.8Co0.15Al0.05O2) exposed to the action of static load at various techniques of fixing the cell. Determining the properties of LIPCs under appropriate conditions makes it possible to fill the gap in existing studies, which will further ensure the safety of their use. Based on the results of experimental studies, the LIPC rigidity and temperature indicators were determined in accordance with the applied load. The most dangerous variant, from the point of view of fire danger, of applying a static load on the cell has been established. It was experimentally established that, on average, the Panasonic NCR18650B LIPC housing can withstand a load of about 80 kg·s/cm2 (or 7.84 MPa) without further ignition. An increase in pressure force in the range exceeding 85–90 kg·s/cm2 leads to an irreversible chain thermochemical reaction, which, within 2–3 seconds, leads to LIPC ignition. Compressing the LIPC evenly along its lateral surface showed the occurrence of combustion at the load on the cell equal to 150 kg·s/cm2. The average temperature of the cell during combustion caused by the deformation of the housing is 350–450 °C, and the maximum value is registered in the range of 580–680 °C. The mathematical model built on the basis of the mathematical theory of thin shells adequately describes the stressed-strained state of the cylindrical body of cells under the action of a force concentrated and distributed load. The estimation model is satisfactorily verified by experimental results, making it possible to improve the strength and rigidity of LIPC housing by choosing the appropriate steel grade for its body, the geometric dimensions, and the structural technique of its fastening.

Effects of Mechanical Deformation on Dislocation Density, Phase Separation and Hydrogen Diffusion in 4130 Steel

Effects of Mechanical Deformation on Dislocation Density, Phase Separation and Hydrogen Diffusion in 4130 Steel

Understanding thermal and mechanical effects on lithium plating in lithium-ion batteries

Lithium plating is one of the main concerns for cell durability, as cyclable lithium and cell capacity are decreased during the process. Thermal and mechanical loads can influence cell behavior, including lithium plating driving forces, as suggested by the Arrhenius equation and the Bruggeman relation, respectively. Hence, a 1D and a 3D model are employed to study the thermal and mechanical effects on lithium plating in a lithium-ion battery with a high areal capacity (4 mAh/cm2). The 1D model assumes uniform mechanical and temperature profile, while the 3D model is capable of capturing the nonuniformity of stress and temperature in the cell. The effects of mechanical deformation and different temperatures on the process of lithium plating are investigated in this study. With the help of the 1D charging simulations, it is observed that lower temperatures increase the risk of lithium plating and the presence of mechanical deformations can accelerate its initiation. Furthermore, 3D charging simulations indicated that folds and boundaries of jellyrolls are more susceptible to lithium plating due to the higher stress concentration and lower temperature, respectively.

Mechanical, Elastic, and Adhesive Properties of Two‐Dimensional Materials: From Straining Techniques to State‐of‐the‐Art Local Probe Measurements

Abstract2D materials, such as graphene, hexagonal boron nitride (hBN), and transition‐metal dichalcogenides (TMDs), are intrinsically flexible, can withstand very large strains (>10% lattice deformations), and their optoelectronic properties display a clear and distinctive response to an applied stress. As such, they are uniquely positioned both for the investigation of the effects of mechanical deformations on solid‐state systems and for the exploitation of these effects in innovative devices. For example, 2D materials can be easily employed to transduce nanometric mechanical deformations into, e.g., clearly detectable electrical signals, thus enabling the fabrication of high‐performance sensors; just as easily, however, external stresses can be used as a “knob” to dynamically control the properties of 2D materials, thereby leading to the realization of strain‐tuneable, fully reconfigurable devices. Here, the main methods are reviewed to induce and characterize, at the nm level, mechanical deformations in 2D materials. After presenting the latest results concerning the mechanical, elastic, and adhesive properties of these unique systems, one of their most promising applications is briefly discussed: the realization of nano‐electromechanical systems based on vibrating 2D membranes, potentially capable of operating at high frequencies (>100 MHz) and over a large dynamic range.

Effects of Mechanical Deformation on the Opto-Electronic Responses, Reactivity, and Performance of Conjugated Polymers: A DFT Study.

The development of polymers for optoelectronic applications is an important research area; however, a deeper understanding of the effects induced by mechanical deformations on their intrinsic properties is needed to expand their applicability and improve their durability. Despite the number of recent studies on the mechanochemistry of organic materials, the basic knowledge and applicability of such concepts in these materials are far from those for their inorganic counterparts. To bring light to this, here we employ molecular modeling techniques to evaluate the effects of mechanical deformations on the structural, optoelectronic, and reactivity properties of traditional semiconducting polymers, such as polyaniline (PANI), polythiophene (PT), poly (p-phenylene vinylene) (PPV), and polypyrrole (PPy). For this purpose, density functional theory (DFT)-based calculations were conducted for the distinct systems at varied stretching levels in order to identify the influence of structural deformations on the electronic structure of the systems. In general, it is noticed that the elongation process leads to an increase in electronic gaps, hypsochromic effects in the optical absorption spectrum, and small changes in local reactivities. Such changes can influence the performance of polymer-based devices, allowing us to establish significant structure deformation response relationships.

Tuning of circular photogalvanic effect of surface states in the topological insulator Sb2Te3 via structural deformation

Strain is a useful method to manipulate properties of three-dimensional (3D) topological insulators (TIs). In this study, we demonstrate the possibility to tune the circular photogalvanic effect (CPGE) of surface states of 3D TI Sb2Te3 films by applying external strain. The CPGE of 3D TI Sb2Te3 grown on SrTiO3 (STO) with different thicknesses has been systematically investigated. It is found that as the thickness of Sb2Te3 films increases from 7-quintuple layer (QL) to 27-QL, the CPGE current first increases and then decreases. Additionally, the CPGE currents demonstrate remarkable temperature dependence, which even reverse sign when the temperature is increased from 77 to 300 K. This phenomenon is due to the vertical thermoelectric effect and inverse spin Hall effect. Finally, the CPGE measurements of Sb2Te3 films under different mechanical strains are performed, and it is found that the CPGE current linearly decreases with the increase in the external strain. The variation in the CPGE current can be tuned up to 11% and 44% in the 18- and 12-QL Sb2Te3 grown on STO substrates under a tensile strain of 0.0225 and 0.0066, respectively. In particular, it can even reach 100% in the 30-QL Sb2Te3 film grown on an InP substrate under a tensile strain of 0.0033, which is due to the combined effect of mechanical deformation and spin injection from substrates. Our work provides a method to effectively manipulate the CPGE in 3D TIs by the combined effect of mechanical strain and spin injection from substrates, which paves the way for novel opto-spintronic devices.

Effects of Mechanical Deformation on Dislocation Density and Phase Partitioning in 4130 Steel

Effects of Mechanical Deformation on Dislocation Density and Phase Partitioning in 4130 Steel

Universal Strain Energy-Mediated Dynamic Porosity in Physically Networked Elastomers and Their Applications.

Mechanical and physical properties of porous polymers are highly dependent on the arrangement of their internal pores, which once synthesized are widely considered static. However, here we introduce an unconventional dynamic porosity strategy in physically networked elastomer polymers, irrespective of their chemistry. This strategy allows for an omnidirectional and reversible reconfiguration of porosity in response to applied mechanical deformations, even at ambient conditions. In particular, the normal contact pressure between human fingers (just 0.62 MPa) applied on thin elastomer films results in a permanent reversion of the pores to a denser and more solid state. The porous-to-solid transition leads to a 3 order of magnitude reduction in pore density and up to a 22% relative volumetric shrinkage of the films, resulting in an opaque-to-transparent transition (OTT) that acts as a visual indication of porosity state (porous vs nonporous). It is shown that the pore reversion pressure onset is dependent on the average pore-to-pore distance that is controllable through process-specific parameters. Furthermore, the porosity transition is reversible for multiple cycles when the through-plane compression activation is coupled with an in-plane stretch (ε = 700%). A strain energy-mediated thermodynamic model is successfully implemented to confirm the effects of mechanical deformations on pore reversion and generation. Finally, applications of the newfound dynamic porosity concept are exploited for pressure indication, on-demand modulation of materials' mechanical and thermal characteristics, and flexible photomasks.

Mechanical Stretching of the Airways Provokes Respiratory Oxidative Stress in a Subset of Asthma and COPD Patients

Respiration is normally accompanied by repetitive stretching and relaxation of the bronchial walls. However, bronchial obstruction typically emerging in asthma and COPD significantly increases the effect of mechanical deformation on the airway epithelial lining causing mechanical stress. Obstructive lung pathology is also usually characterized by chronic airway inflammation and ROS production. Oxidative stress arising during the natural course of asthma and COPD has multiple effects on the progression of these diseases due to aggravated synthesis of pro-inflammatory mediators, mucus hypersecretion, increased permeability of the epithelial barrier and fibrosis. The aim of this study was to investigate the effect of experimentally induced mechanical stress in the airways on the production of 8-isoprostane, a marker of oxidative stress, in asthma and COPD patients. The study included 75 asthma patients and 42 COPD patients with mean age of 47.0±1.47 years. Mechanical stress was induced during the test with 5-min isocapnic (5% CO2) inspiratory resistive breathing with load at 45% of maximum inspiratory pressure. Lung function was measured by standard spirometry and body plethysmography just before and after the test. We accepted the changes (Δ) of FEV1 ≥ 10% and sGaw ≥ 20% as indicative for significant airway response. 8-isoprostane level was quantified by ELISA in exhaled breath condensate collected during 15 min before and after the experimental mechanical stress. The airway responses measured by spirometry and body plethysmography were not concordant: 14% were considered significant only by ΔFEV1 while 36% were significant solely according to ΔsGaw. Besides, there was no correlation between ΔFEV1 and ΔsGaw. The studied patients with ΔsGaw ≥20% or ≤-20% did not differ in baseline (18.0 (13.2-26.4) pg/ml vs. 18.8 (11.9-24.2) pg/ml, respectively, p=0.87) and post-test (18.2 (11.4-22.4) pg/ml vs. 19.6 (15.1-26.7) pg/ml, respectively, p=0.31) concentrations of 8-isoprostane. However, the difference in the relative change of 8-isoprostane level (Δ8-iso) was significant between the groups (-18.7 (-31.7-3.64)% vs. 8.5 (-11.6-30.0)%, p=0.02). In general, the patients with increase in sGaw ≥20% had decrease in 8-isoprostane level. On the contrary, in the patients with significant reduction of sGaw the production of 8-isoprostane was rather elevated in response to the mechanical stress. Increase in 8-isoprostane by ≥20% was observed in 45.5% of patients with ΔsGaw ≤-20%, in 32.8% of patients with low amplitude response (-20%≤ΔsGaw≤20%) and only in 13.8% of patients with ΔsGaw ≥20% (p=0.04). In addition, Δ8-iso was negatively correlated with ΔsGaw (R=-0.18, p=0.05). No significant associations were observed between 8-isoprostane levels and ΔFEV1. In summary, we established that about 30% of asthma and COPD patients respond to inspiratory resisting breathing with significant increase of 8-isoprostane level. This reaction is most common in patients with reduction of airway conductance (sGaw) after the test but not dependent on ΔFEV1.

High performance thermal link with small spring constant for cryogenic applications

We developed a soft and high thermal conductive thermal link for cryogenic applications. The measured maximum thermal conductivity was approximately 18500 W/m/K at 10 K. This spring constant was 1/43 of that of a single thick wire with the same cross-sectional area at room temperature. We reached these performances by utilizing high purity aluminum (99.9999%, 6 N) and by stranding many thin wires that are 0.15 mm in diameter. The electrical Residual Resistivity Ratio was also measured and used to estimate the thermal conductivity by the Wiedemann–Franz law. We observed the size effect on the electrical conductivity, and evaluated the effect of mechanical deformation to the RRR. These evaluations allow us to design a pragmatic thermal link for cryogenic application.