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Wrinkle topographies have been studied as simple, versatile, and in some cases biomimetic surface functionalization strategies. To fabricate surface wrinkles, one material phenomenon employed is the mechanical-instability-driven wrinkling of thin films, which occurs when a deforming substrate produces sufficient compressive strain to buckle a surface thin film. Although thin-film wrinkling has been studied on shape-changing functional materials, including shape-memory polymers (SMPs), work to date has been primarily limited to simple geometries, such as flat, uniaxially-contracting substrates. Thus, there is a need for a strategy that would allow deformation of complex substrates or 3D parts to generate wrinkles on surfaces throughout that complex substrate or part. Here, 4D printing of SMPs is combined with polymeric and metallic thin films to develop and study an approach for fiber-level topographic functionalization suitable for use in printing of arbitrarily complex shape-changing substrates or parts. The effect of nozzle temperature, substrate architecture, and film thickness on wrinkles has been characterized, as well as wrinkle topography on nuclear alignment using scanning electron microscopy, atomic force microscopy, and fluorescent imaging. As nozzle temperature increased, wrinkle wavelength increased while strain trapping and nuclear alignment decreased. Moreover, with increasing film thickness, the wavelength increased as well. [ABSTRACT FROM AUTHOR]

Defects such as cracks and high surface roughness are likely to occur in the additive manufacturing of Ti-6Al-4V titanium alloy parts. In order to solve this problem， the ultrasonic rolling micro-forging technology， which is applied in surface strengthening， is combined with the additive manufacturing process. The process of laser fuse additive manufacturing and cooling is simulated by the finite element software， and the effect of ultrasonic rolling micro-forging on the mechanical properties of the additive part surface is analyzed. The results show that the residual stress changes from tensile stress to compressive stress after ultrasonic rolling micro-forging， which effectively reduces the risk of defects such as cracks in additive parts. Meanwhile， the surface equivalent plastic strain and surface micro-hardness of the processed additive increase. In addition， ultrasonic rolling micro-forging has the greatest influence on the contact area of the rolling head. [ABSTRACT FROM AUTHOR]

Heterogeneous photosynthesis is a promising route for sustainable ammonia production, which can utilize renewable energy and water as the hydrogen source under ambient condition. In this study, a series of Bi5O7I (BOI) nanosheets and nanotubes are synthesized, and the surface tensile strain is formed by curling the nanosheets into nanotubes to tune the concentration and location of dynamic vacancies. Scanning transmission electron microscopy (STEM) with spherical aberration correction confirms the presence of intrinsic areal defects on the surface of the BOI nanotube resulted from surface tensile strain. The presence of areal defects lowers the formation energy of I vacancies (IV) at step edge site, thus the IV with higher concentration would be favorably generated under visible light. Rapid scan in situ Fourier transform infrared (FT-IR) analysis in the aqueous media reveals that the IV promotes photocatalytic N2 activation and reduction, and proceeds through an associative alternating mechanism. Specially, after turning off the light, the surface vacancy sites can be reoccupied by I− ions, which enables the protection and regeneration of photocatalyst surface in an aerobic and dark environment. This work provides an innovative strategy to tune concentration and location of dynamic surface vacancies on photocatalysts by building surface tensile strain for advancing sustainable ammonia production. [ABSTRACT FROM AUTHOR]

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mechanical properties of Al alloys make them an ideal candidate for different sections of marine, aerospace, automotive, etc. industries. Recently taking the advantages of additive manufacturing (AM), many complex infrastructures/components can be fabricated with very high design freedom via Al alloys. Although Al alloys have good natural corrosion resistance, however improving this property attracts lots of attention in the past few years. Post-processing methods can play a key role for addressing the issues related to internal and surface anomalies associated with as-built AM parts. Generally, these anomalies have detrimental effects on mechanical properties. In the present study, the effect of laser shock peening (LSP) treatment with different laser pulse overlaps and energies was investigated comprehensively on microstructure, surface texture, porosity, hardness, residual stresses as well as corrosion resistance of laser powder bed fused (L-PBF) AlSi10Mg samples. LSP provides strain deformation on the surface, and the deformation enhances by laser beam energy. LSP1 (laser energy of 1.5 J and 50% overlap) and LSP3 (laser energy of 4.5 J and 50% overlap) introduce maximum local strain of 7.5 and 10.7, respectively. The surface roughness of as-built state µm in terms of Rv was effectively diminished to 16.33 after LSP6 (laser energy of 4.5 J and 75% overlap). The results indicated that due to the modified surface texture, improved hardness and induced high compressive residual stresses in the surface layer. (surface hardness improvement and inducing high surface compressive residual stresses were obtained after LSP6 up to 26% and −289 MPa, respectively); the LSP treated samples exhibited higher corrosion resistance with the corrosion rate decreasing down to 50% as compared to the as-built state. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The super-speed tube transport (SSTT) system is called the fifth traffic mode internationally. One of the critical technical problems for the design of SSTT system is the sealing reliability in vacuum tube structures. In this paper, an experimental study of the sealing capacity and mechanical behavior of the segmental lining is carried out, and the following conclusions are drawn. To meet the requirements of the SSTT system, the existing sealing of the concrete segment structure needs to be further strengthened. The joint spacing decreases with increasing vacuum and increases with vacuum pressure relief. There is an obvious correlation between the strain change and the vacuum pumping, which can be divided into four stages. The influence of the pressure difference and the local airflow movement on the concrete surface strain is dominant by turns at different stages. The concrete surface is suggested to be reinforce on account of the tensile strain caused by the local airflow movement of vacuum pumping is significant. The relative pressure caused by vacuum has little effect on the stress and deformation of the structure. The results of the study can help to understand the sealing capacity and mechanical behavior of the underground segmental lining in a low vacuum environment and be beneficial in choosing the appropriate structure type for the SSTT system. [ABSTRACT FROM AUTHOR]

Part of deep foundation pit support engineering needs to select connected precast concrete square piles (CPCSPs). Under the premise that the quality of precast concrete square piles (PCSPs) meets engineering requirements, the quality of CPCSPs becomes the key factor to ensure the safety of foundation pit support structures. This paper puts forward a new connection technology of CPCSPs and carries out the flexural behavior experiment of unconnected precast concrete square piles (UPCSPs) and CPCSPs. The distribution of crack and strain on different surfaces of UPCSPs and CPCSPs are measured by carbon fiber composite strain sense optical cables, glass fiber composite strain sense optical cables, and fixed-point polyurethane strain sense optical cables. The anti-crack load, ultimate load, bending moment, and flexural deformation of UPCSPs and CPCSPs are measured. The experimental results of UPCSPs and CPCSPs are compared. The results show that the anti-crack strength of CPCSPs is greatly increased while the flexural deformation of CPCSPs is decreased before the occurrence of crack. With the development of crack (failure stage), the outside areas of hoop steel plate exhibit cracks. At this moment, the strength of CPCSPs is no longer controlled by the strength of middle areas. The ultimate strength of CPCSPs is basically equivalent to that of UPCSPs. The ultimate bending moment of CPCSPs is higher than its design value (about 66%∼76%). The selection of CPCSPs in the design of foundation pit support has good reliability. [ABSTRACT FROM AUTHOR]

The off-axis embedment behaviors of unidirectional and multidirectional laminated engineered bamboo panels used for glued-laminated bamboo (glubam) structures under dowel-type bolts with three different diameters, 12, 14, and 16 mm, were experimentally studied in this research. The half-hole loading method given by current standards was adopted to perform the embedment tests. Seven different off-axis loading directions from 0° to 90° related to the main bamboo fiber direction at an interval of 15° in the panel plane were considered. The different failure patterns, stress-displacement curves, and the corresponding full-field surface strain measured through the digital image correlation (DIC) method are reported. The loading angles significantly influenced the embedment performance of unidirectional bamboo panel specimens, and the strength values decreased with the increasing off-axis loading angles. A difference of 35% in the strength values between 0° and 90° loading specimens was observed. However, quasi-isotropic embedment properties were noticed for the multidirectional laminated engineered bamboo panels. The capacity functions were provided to predict the mean off-axis embedment strength and characteristic strength values by inputting the characteristic density values into the functions. Compared with the characteristic strength values estimated through the statistical method, with a 95% probability of exceedance and 75% significant level, the conventional capacity-function method underestimated the off-axis embedment strength values, and thus may leading to an overconservative design. The statistical characteristic embedment strength values are suggested to be used to calibrate the safety factor of capacity equations given by wood standards. Results from this research can be used to predict the ultimate strength of glubam joints under complex loading conditions and obtain reliable design values for engineering applications. [ABSTRACT FROM AUTHOR]

A model of the strain accumulation in nitrogen implanted polycrystalline tungsten films deposited on 110 single-crystalline silicon substrates is presented. The films, with the nominal thickness of 500 nm, were implanted at room temperature, in a direction perpendicular to the sample surface with an energy of 60 keV N 2 + ions and concentrations between 0.5 × 1017/cm2 and 5 × 1017/cm2. The proposed model is based on the simulations of the X-ray diffraction 2θ-ω scans in the vicinities of the 110 W most intense Bragg peak. Up to a fluence of 2 × 1017/cm2, the increase of asymmetry towards lower angles of the 110 W peak is interpreted as a linear increase in strain affecting the entire implanted region. Then, the solubility of N in W saturates and phase transition to fcc β-W 2 N is observed. The phase transition occurs at the surface strain regions of the implanted crystal volume while the lowest strained regions are masked by the β-W 2 N barrier and even evidence some relaxation. After 3 × 1017/cm2, the strain deduced for the 111 and 200 planes of the fcc β-W 2 N formed pseudo-layer increases at different rates. While the former comprises a maximum tensile deformation of 3.8 %, the latter is more resilient to nitrogen irradiation developing less than half of the strain magnitude (1.5 %). After 4 × 1017/cm2, Rutherford backscattering spectrometry measurements suggest partial sputtered N while X-ray diffraction indicates no strain-relief at the remaining surface fcc β-W 2 N. The N concentration derived by the ion beam technique and the combined 110 W/ (111, 200) β-W 2 N strain profiles as functions of depth agree with the Simulations of Ions and Radiation in Matter theoretical predictions. [ABSTRACT FROM AUTHOR]

Low cycle fatigue (LCF) tests were carried out on Ti6Al4V alloy at room temperature for different strain amplitudes ranging from 0.5% to 2%. The microstructure and texture evolutions as a function of strain amplitude have been investigated in the present study. Cyclic softening behaviour was observed at all strain amplitudes, and it was found to increase with increasing the strain amplitude. The fatigue transition life was observed to be at 1.25% strain amplitude. Only (10 1 ¯ 2) type tensile twins were formed during the deformation, and this was found to be significant at higher strain amplitude of 2%. The grains along [ 10 1 ¯ 0 ] were appeared to be the twinning parent, and the twinned products were appeared along [0001]. The [ 10 1 ¯ 0 ] grains were further found to have substantial cyclic deformation than the other grains, such as [ 2 1 ¯ 1 ¯ 0 ] and [0001]. The dominant texture was found along [ 10 1 ¯ 0 ] during the LCF tests. However, the sample at higher strain amplitude of 2% had also prominent [0001] texture along with [ 10 1 ¯ 0 ] texture. Fractographic examination revealed a dimple fracture surface at lower strain amplitude (0.5%), whereas a quasi-cleavage type fracture was observed at higher strain amplitudes (1% & 2%). [ABSTRACT FROM AUTHOR]

This paper reports a study of the reflectance of the optical sensors based on graphene under uniform strain. Assuming the graphene layer is surrounded by two different semi-infinite dielectric media, the generalized Fresnel coefficients are derived as a function of usual quantities (e.g., dielectric constants, incident angles, and strain) and anisotropic optical conductivity. The strain not only changes the electronic band structure but also can be employed to tune the electronic collective excitations (plasmons) and thus the optical reflectance of graphene monolayers. One of the most common techniques for plasmon excitation is the Kretschmann configuration. It is based on the observation of a sharp minimum in the reflection coefficient versus the angle (or wavelength) curve. Because strain induces anisotropy in graphene optical conductivity the strain-dependent orientation plays an important role to manipulate the variation of graphene plasmon energy, which may be useful to synchronize graphene properties in plasmonic devices to enhance light-matter interactions. [ABSTRACT FROM AUTHOR]

Background: X-ray imaging offers unique possibilities for Digital Image Correlation (DIC), opening the door for full-field deformation measurements of a test article in complex environments where optical DIC suffers severe biases or is impossible. While X-ray DIC has been performed in the past with standard DIC codes designed for optical images, the path-integrated nature of X-ray images places constraints on the experimental setup, predominantly that only a single surface of interest moves/deforms. These requirements are difficult to realize for many practical situations and limit the amount of information that can be garnered in a single test. Other X-ray based diagnostics such as Digital Volume Correlation (DVC) and Projection DVC (P-DVC) overcome these obstacles, but DVC is limited to quasi-static tests, and both DVC and P-DVC necessitate high-resolution computed tomography (CT) scan(s) and often require a potentially invasive pattern throughout the volume of the specimen. Objective: This work presents a novel approach to measure time-resolved displacements and strains on multiple surfaces from a single series of 2D, path-integrated (PI) X-ray images, called PI-DIC. Methods: The principle of optical flow or conservation of intensity—the foundation of DIC—was reframed for path-integrated images, for an exemplar setup comprised of two plates moving and deforming independently. Synthetic images were generated for rigid translations, rigid rotations, and uniform stretches, where each plate underwent a unique motion/deformation. Experimental specimens were fabricated (either an aluminum plate with tantalum features or a plastic plate with steel features) and the two specimens were independently translated. Results: PI-DIC was successfully demonstrated with the synthetic images and validated with the experimental images. Prescribed displacements were recovered for each plate from the single set of path-integrated, deformed images. Errors were approximately 0.02 px for the synthetic images with 1.5% image noise, and 0.05 px for the experimental images. Conclusions: These results provide the foundation for PI-DIC to measure motion and deformation of multiple, independent surfaces with subpixel accuracy from a single series of path-integrated X-ray images. [ABSTRACT FROM AUTHOR]

Background: Damage index parameters that have been formulated to identify damage localization in plastically deformed materials typically require all six stress or strain components. Recently, simulations through Crystal Plasticity Finite Element Method (CPFEM) have been widely used to extract damage initiation parameters. However, these models are rarely verified due to the challenges in measuring the out of plane deformation/strains experimentally. Objective: A damage index combining the effective plastic strain and surface roughness change is investigated for identifying damage accumulation sites in a tensile sample. Method: A point-wise Digital Image Correlation (DIC) technique is developed to measure large deformations from surface topography images, based on which the effective plastic strains and the surface roughness changes are determined at different load levels. A simple technique that creates random, micro size reflective speckles for sub-grain strain calculation is demonstrated. Results: Damage accumulation sites detected by the effective strain, surface roughness change, and the combined damage index are assessed in terms of damage localization and localization consistency. The combined damage index identified the localized damage accumulation sites consistently after the yielding load. In contrast, the effective strain damage index showed a low degree of localization and consistency while the surface roughness damage index detected only half of the damage accumulation sites identified by the combined damage index. The detected damage accumulation sites were found to be associated with grain orientations that favor "sunken" out-of-plane deformations and large misorientations among neighboring grains. Conclusions: Considering both effective plastic strain and out of plane surface deformation, the combined damage index provides an enhanced damage localization and localization consistency. [ABSTRACT FROM AUTHOR]

In recent years, the use of digital image correlation (DIC) in fatigue experiments has become widespread. It is estimated that ~1000 published works exist that outline fatigue experiments in which DIC is employed for displacement and strain measurement. Of these, ~900 were published in the last 10 years. DIC is a noncontact method that uses a series of digital images to calculate full‐field strains on the surface of an object, planer or curved. Typical commercial DIC systems compute strains at resolutions high enough to trace hysteresis loops in metals. Properly operated open‐source systems can do the same. The DIC method is applied not only on optically based digital images but also on digital images from ultra‐high resolution (ultra‐HR) microscopes like a scanning electron microscope (SEM) or on volumetric images from computed tomography (CT) scans. In fatigue analysis, DIC provides much more information than that of an extensometer. Full‐field strains from DIC can be acquired at different scales (i.e., microscale, macroscale, and nanoscale) and can be related to items such as microstructural features, interacting surfaces (e.g., fretting), fatigue crack growth phenomenon, and distinct forms of energy. Because fatigue is a highly complex, strain‐induced process, the DIC method is and will be an important tool for current and future research in fatigue. This review begins with an overview of the history and fundamentals of DIC including an evaluation of the overall performance and accuracy of the method. Publications selected for review are then presented and discussed. Remarks about the present state‐of‐the‐art and an outlook for future work to be done are then provided. Highlights: Survey of digital image correlation (DIC) methods covering configurations, algorithms, performance, and accuracy is presented.Overview of how DIC is applied in dynamic applications is presented.Detailed discussion of DIC relevant to fatigue is presented. [ABSTRACT FROM AUTHOR]

The design of Pt-based nanoarchitectures with controllable compositions and morphologies is necessary to enhance their electrocatalytic activity. Herein, we report a rational design and synthesis of anisotropic mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires for high-efficient electrocatalysis. The catalyst has a uniform core-shell structure with an ultrathin atomic-jagged Pt nanowire core and a mesoporous Pt-skin Pt3Ni framework shell, possessing high electrocatalytic activity, stability and Pt utilisation efficiency. For the oxygen reduction reaction, the anisotropic mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires demonstrated exceptional mass and specific activities of 6.69 A/mgpt and 8.42 mA/cm2 (at 0.9 V versus reversible hydrogen electrode), and the catalyst exhibited high stability with negligible activity decay after 50,000 cycles. The mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowire configuration combines the advantages of three-dimensional open mesopore molecular accessibility and compressive Pt-skin surface strains, which results in more catalytically active sites and weakened chemisorption of oxygenated species, thus boosting its catalytic activity and stability towards electrocatalysis. Controlling the morphology of Pt-based nanostructures can provide a great opportunity to boost their catalytic activity and durability. Here the authors report anisotropic mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires for oxygen reduction reaction with enhanced mass activity and stability. [ABSTRACT FROM AUTHOR]

The application of a semi-flexible pavement (SFP) is an effective solution to solve the rutting problems of the autonomous rail rapid transit (ART) system. The service environment of an ART pavement is significantly different from that of the conventional pavement due to the large axle load and high tire pressure of ART vehicles. A test section was constructed in the Zhuzhou ART system and a tire–pavement coupling FE model was built to explore the distribution features of the dynamic responses as well as to optimize the material and structural design. The tire–pavement coupling model was firstly verified by the field test data and then, utilizing the validated model, the parameter study was performed to analyze the influence of the vehicle operating state and pavement conditions. The simulation results show that the transverse tensile strain at the bottom of the SFP layer is dominant for the fatigue cracking of the pavement. Properly reducing the tire pressure can effectively improve the tensile environment at the bottom of the SFP layer. The action of the braking force may cause significant longitudinal tensile strains at the surface of the SFP layer and lead to transverse cracking of the semi-flexible ART pavement. The interlayer bonding between the SFP layer and the asphalt layer has significant influence on the amplitude and distribution of tensile stress at the bottom of the SFP layer. Moreover, to optimize the tensile environment of the semi-flexible ART pavement, the thickness of the SFP layer and the asphalt concrete layer cannot differ too much under the premise of meeting the requirements of rutting resistance performance. [ABSTRACT FROM AUTHOR]

This study aims to clarify the notch factor effect on the mechanical properties of carbon steel plates and the strain field distribution at the notch during the tensile process. To this end, tensile tests were conducted on 20, 45, and 60 steel notched plates of different sizes at 4 mm/min tensile speed, and the Johnson–Cook intrinsic structure model was used to calibrate the true stress–true strain relationship. The nodal strain and surface strain field distribution at notches were determined based on the digital image correlation (DIC) method, and the tensile process of 45 steel plates was simulated by Abaqus finite element method based on Johnson–Cook model to verify its accuracy. The deformation results of the three materials conformed to the Johnson–Cook model stress-strain law; the notch sensitivity of the materials increased and then decreased with the notch size, reaching the maximum at ρ = 0.2 mm. The DIC method results agreed well with the simulated strains, mainly concentrated near the root of the notch in the x - and y -axis directions. The strains in the xy -plane direction are roughly symmetrically distributed in a 45° shear shape and mainly concentrated at the edge of the notch. [ABSTRACT FROM AUTHOR]

The influence of elongation on the strain inhomogeneity and shape change in twinning-induced plasticity steel rod is systematically investigated to understand the macroscopic shear band (MSB) formation mechanism and to decrease the strain inhomogeneity during the compression-type forming processes. Specimens fabricated by rod flat rolling with elongation (3D rod) and by plane compression without elongation (2D rod) are compared using both finite element analysis and experiment. Despite the similar final product shape, the 2D rod presents a lower effective strain at the surface region than the 3D rod, leading to a high strain inhomogeneity. The higher effective strain at the surface region of the 3D rod is mainly attributed to the elongation of the 3D rod during the rolling. In contrast, the 2D rod exhibits strong dead metal zones owing to the lack of elongation of the specimen. Therefore, the formation of MSBs or strain inhomogeneity of a specimen can be reduced by increasing the elongation of the specimens during the forming process. Both the contact width and lateral spread of the 3D rod are lower than those of the 2D rod because of the elongation of the 3D rod originating from the slip effect at the rod-roll interface during the rolling process. The small frictional effect at the rod and roll interface increased the elongation of the rod, leading to a decrease in the strain inhomogeneity and lateral spreading in the 3D rod. [ABSTRACT FROM AUTHOR]

The present paper studies the critical condition for negative surface tension-driven circumferential wrinkling of soft cylinders based on the linearized Steigmann-Ogden model of surface elasticity. A simple negative surface tension-mode number relation is derived explicitly for arbitrary Poisson ratios of the cylinder and its surface layer and their shear modulus ratio, on which the critical surface residual strain and the associated mode number can be determined easily. For an incompressible solid cylinder with an incompressible thin surface layer, the critical values of surface residual strain and the mode number predicted by the present model are in good agreement with available numerical results based on the popular neo-Hooken nonlinear model for a wide range of material and geometrical parameters. In addition, the critical condition for circumferential wrinkling of the inner surface of a cylindrical hole within an infinite body is also derived. The present work addresses the key role of negative surface tension in circumferential wrinkling of soft cylinders and offers supporting evidence for the efficiency and accuracy of the linear Steigmann-Ogden model for the determination of the critical values for circumferential wrinkling. [ABSTRACT FROM AUTHOR]

To achieve real-time sensing and deformation reconstruction of flexible plate structure, a 3D reconstruction technique based on a quasi-distributed fiber grating sensor network and order-optimized modal superposition method is proposed. Graphic visualization is introduced to the field of deformation monitoring, then the displacement field reconstruction of the typical structure of spacecraft is realized. Firstly, a finite element model of the four-sided fixed-supported plate structure is constructed, and the conversion matrix of surface strain and displacement are obtained based on modal analysis, and then the modal parameters are optimized through static simulation experiments; Secondly, the influence of the number and position of sensors on the reconstruction accuracy is studied, then a high-density distributed fiber grating sensor network is attached to the surface of the plate to construct an experimental FBG model of the spacecraft; Finally, concentrated loads are applied to the structure at different positions, and structure's surface strain information is collected by FBG network, then the morphological reconstruction of the deformed structure is realized based on the improved model superposition method, which proves the feasibility of the algorithm. The results show that the reconstruction method's average absolute error is less than 0.13 mm, so this method can be used to displace field reconstruction problems of flexible structures. [ABSTRACT FROM AUTHOR]

The aim of this manuscript is the experimental and numerical study regarding the influence of friction conditions on plastic deformation behavior by upsetting the A6082 aluminum alloy. The upsetting operation is characteristic of a significant number of metal forming processes: close die forging, open die forging, extrusion, and rolling. The purpose of the experimental tests was to determine: by the ring compression method, the friction coefficient for 3 surface lubrication conditions (dry, mineral oil, graphite in oil) by using the Coulomb friction model; the influence of strains on the friction coefficient; the influence of friction conditions on the formability of the A6082 aluminum alloy upsetted on hammer; study of non-uniformity of strains in upsetting by measuring hardness; change of the tool-sample contact surface and non-uniformity of strains distribution in a material by numerical simulation. Regarding the tribological studies involving numerical simulations on the deformation of metals, they mainly focused on the development of friction models that characterize the friction at the tool-sample interface. The software used for the numerical analysis was Forge@ from Transvalor. [ABSTRACT FROM AUTHOR]

In order to better describe the uniaxial ratcheting behavior of Z2CDN18.12N austenitic stainless steel, the Abdel-Karim-Ohno model was improved under the framework of the unified viscoplastic cyclic constitutive theory. By introducing a plastic strain memory surface into the isotropic hardening rule, the model parameters were determined. Further, the Abdel-Karim-Ohno model and the improved Abdel-Karim-Ohno model were used to predict the uniaxial ratcheting effect behavior of Z2CDN18.12N austenitic stainless steel at the room temperature. The influences of mean stress, stress amplitude, stress rate and loading history on the uniaxial ratcheting strain of Z2CDN18.12N austenitic stainless steel were studied by the two models, respectively. The uniaxial ratcheting strain level increased with the increasing mean stress and stress amplitude, decreased with the increasing stress rate, being more sensitive to the lower stress rate, and the loading history had great influence on the ratcheting behavior. Comparison of the prediction results of the two models with the experimental data proved the effectiveness of the improved model. [ABSTRACT FROM AUTHOR]

The metal magnetic memory (MMM) technique is a promising non-destructive inspection method that is sensitive to early damage due to stress concentration in ferromagnetic components. However, quantitative analysis methods for evaluating the stress concentration induced by local plastic deformation have not yet been sufficiently studied due to the lack of a reasonable numerical simulation method. Based on the Jiles-Atherton (J-A) magneto-plastic model, which considers the combined effects of residual stress and strain, the change in the behaviour of residual magnetic field (RMF) signals in an X80 pipeline steel specimen with an indentation is calculated in this paper using finite element (FE) simulations, while systematic experimental research is also carried out. The results show that the model-predicted RMF signals are consistent with the experimental data, which demonstrates the validity of the numerical simulation method. Moreover, the comparison indicates that the RMF FE simulations can provide an effective and reliable way to determine the location and the degree of deformation-induced stress concentration. In addition, the effect of the residual stress and strain on the surface magnetic field and the model is discussed. The results of this study help to improve the accuracy of the MMM technique for evaluating the stress concentration caused by local plastic deformation. [ABSTRACT FROM AUTHOR]

This paper reports soft and stretchable films of liquid metal particles (LMPs) that offer high surface area and high conductivity. Liquid metals (LM) based on gallium are compelling conductors for soft and stretchable devices, yet it is difficult to make electrodes of LM with high surface area due to the tendency of liquids to minimize their surface area. To form films of percolated particles with high surface area, LMPs are first created by sonicating LM in isopropanol with trace amounts of hydrochloric acid and 1,6‐hexane dithiol to decrease the amount of surface oxide on the LMPs. A film of these particles placed on a tacky substrate is initially insulating but percolate into conductive paths by straining the substrate. The resulting electrode has high conductivity (1.64 × 105 S m−1) and high surface area (1257% greater than a bulk LM film with the same areal footprint). Interestingly, these electrodes have nearly strain‐invariant resistance (R/R0 = 1.23 at 600% strain). The ability to create high surface area electrodes in such a simple manner may find use in sensing, capacitive storage, batteries, and energy‐harvesting devices. [ABSTRACT FROM AUTHOR]

Shape sensing is an emerging technique for the reconstruction of deformed shapes using data from a discrete network of strain sensors. The prominence is due to its suitability in promising applications such as structural health monitoring in multiple engineering fields and shape capturing in the medical field. In this work, a physics-informed deep learning model, named SenseNet, was developed for shape sensing applications. Unlike existing neural network approaches for shape sensing, SenseNet incorporates the knowledge of the physics of the problem, so its performance does not rely on the choices of the training data. Compared with numerical physics-based approaches, SenseNet is a mesh-free method, and therefore it offers convenience to problems with complex geometries. SenseNet is composed of two parts: a neural network to predict displacements at the given input coordinates, and a physics part to compute the loss using a function incorporated with physics information. The prior knowledge considered in the loss function includes the boundary conditions and physics relations such as the strain–displacement relation, material constitutive equation, and the governing equation obtained from the law of balance of linear momentum. SenseNet was validated with finite-element solutions for cases with nonlinear displacement fields and stress fields using bending and fixed tension tests, respectively, in both two and three dimensions. A study of the sensor density effects illustrated the fact that the accuracy of the model can be improved using a larger amount of strain data. Because general three dimensional governing equations are incorporated in the model, it was found that SenseNet is capable of reconstructing deformations in volumes with reasonable accuracy using just the surface strain data. Hence, unlike most existing models, SenseNet is not specialized for certain types of elements, and can be extended universally for even thick-body applications. [ABSTRACT FROM AUTHOR]

The Liwa area is near the active shear fault of the Sumatra Fault Zone (SFZ), with a right lateral mechanism where the Kumering segment crosses this area. The geodynamic simulation results based on the pre-seismic modeling using the slip rate input of a recent study, Liwa, and its surroundings show a comparatively high compression level. The seismic moment rate estimation based on the present-day surface strain data shows alignment and consistency with the pre-seismic modeling result and the previous correlation dimension (DC) analysis. The high DC indicated that the Kumering segment indicates a relatively high-stress level. The finding also aligns with the suggestion based on the previous result that more frequent large strike-slip earthquakes occur since the recent study found that the slip is faster than the previous one. And it is consistent with the historical records; Liwa has a minimum of 3 times experienced destructive earthquakes, which occurred in 1908, 1933, and 1994. Although based on a deterministic hazard analysis point of view, the zone around the SFZ will experience the most significant ground shaking since it is close to the source. However, the Probabilistic Seismic Hazard Analysis (PSHA) studied around the southern part of Sumatra Island, especially in areas close to the coast boundary, shows that the shaking caused by the source of the subduction and intermediate depth is more frequent than that of the SFZ source. As the city of Liwa is located near the Kumering Segment and relatively close to the shoreline, evaluating the Seismic Hazard Function (SHF) by integrating megathrust, SFZ, and medium depth sources is necessary. The amplification analysis in the previous study using Liwa's HVSR method showed the most considerable amplification value. Thus, this study intends to evaluate the potential for earthquake hazards based on the probability of integrated sources of megathrust, SFZ, and intermediate depth to deep and deterministic based on SFZ sources around the city of Liwa. The earthquake intensity (MMI) estimation at the surface based on the probabilistic to deterministic point of view is in the range of VI to XI. Therefore, it has the potential to reach the maximum MMI scale. The result of this study might be very beneficial in better understanding the future seismic hazard study and mitigation analysis. [ABSTRACT FROM AUTHOR]

Zagros Orogeny System resulted due to collision of the Arabian with Eurasia. The region has the ocean-continent subduction and continent-continent collision; and convergence velocity shows variation from east to west. Therefore, this region shows the complex tectonic stress and a wide range of diffuse or localized deformation between both plates. The in-situ stress and GPS data are very limited in this region, therefore, we performed a numerical simulation of the stresses causing deformation in the Zagros-Iran region. The deviatoric stresses resulting from the variations in lithospheric density and thickness; and those from shear tractions at the base of lithosphere due to mantle convection were computed using thin-sheet approximation. Surface observations of strain rates, SHmax, plate velocities etc. are explained using the joint models of lithosphere and mantle, suggesting a good coupling between lithosphere and mantle in most parts of Zagros and Iran. However, the deformation in east of Iran is caused primarily by lithospheric stresses. Plate motion of Arabian plate is found to vary along the Zagros belt from north-northeast in south-east of Zagros, north in central Zagros to slight northwest in northwestern Zagros. The output of this study can be used in seismic hazards estimations. [ABSTRACT FROM AUTHOR]

The evaluation of strain in rock masses is crucial information for slope stability studies. For this purpose, a monitoring system for analyzing surface strain using resistivity strain gauges has been tested. Strain is a function of stress, and it is known that stress affects the mechanical properties of geomaterials and can lead to the destabilization of rock slopes. However, stress is difficult to measure in situ. In industrial practice, resistivity strain gauges are used for strain measurement, allowing even small strain changes to be recorded. This setting of dataloggers is usually expensive and there is no accounting for the influence of exogenous factors. Here, the aim of applying resistivity strain gauges in different configurations to measure surface strain in natural conditions, and to determine how the results are affected by factors such as temperature and incoming solar radiation, has been pursued. Subsequently, these factors were mathematically estimated, and a data processing system was created to process the results of each configuration. Finally, the new strategy was evaluated to measure in situ strain by estimating the effect of temperature. The approach highlighted high theoretical accuracy, hence the ability to detect strain variations in field conditions. Therefore, by adjusting for the influence of temperature, it is potentially possible to measure the deformation trend more accurately, while maintaining a lower cost for the sensors. [ABSTRACT FROM AUTHOR]

Fe2Ni2CrAl multi-principal elements alloy (MPEA) has been regarded as promising candidate for engineering application due to its desirable combination of strength and plasticity. In this work, the microstructure, hardness and wear resistance of Fe2Ni2CrAl MPEA were systematically investigated. This alloy has a dual-phase structure, comprised of the FCC and BCC/+B2 phase. The average nanohardness is 4.59 GPa, and the average elastic modulus is 199.4 GPa. By performing reciprocating ball-on-flat friction tests, the Fe2Ni2CrAl MPEA shows good wear resistance, with a wear rate of 8.72 × 10−5 mm3/(Nm) and average friction coefficient of ~ 0.54. The wear mechanisms are a mixture of adhesive, abrasive and oxidation wear, accompanied by cracks and delamination. Molecular dynamics (MD) was utilized to study the wear behavior at nanoscale. The surface suffers severer deformation during the first slide. Then, the reciprocating friction contributes to the surface strain hardening in the later slide. The large displacement and shear strain region were concentrated below the rigid ball, and the atomic damage was identified. Fewer dislocations are produced during reciprocating friction, accompanied with the reduced atomic shear strain and lattice deterioration. The Shockley-type dislocation plays a dominant role in the whole nano-wear process. This work explored the friction behavior in depth and provided a deep insight into wear mechanisms for Fe2Ni2CrAl MPEAs. [ABSTRACT FROM AUTHOR]

2D metallene nanomaterials have spurred considerable attention in heterogeneous catalysis by virtue of sufficient unsaturated metal atoms, high specific surface area and surface strain. Nevertheless, the strong metallic bonding in nanoparticles aggravates the difficulty in the controllable regulation of the geometry of metallenes. Here we propose an efficient galvanic replacement strategy to construct Pd metallenes loaded on Nb2C MXenes at room temperature, which is triggered by strong metal-support interaction based on MD simulations. The Pd metallenes feature a chair structure of six-membered ring with the coordination number of Pd as low as 3. Coverage-dependent kinetic analysis based on first-principles calculations reveals that the tripodal Pd metallenes promote the diffusion of alkene and inhibit its overhydrogenation. As a consequence, Pd/Nb2C delivers an outstanding turnover frequency of 10372 h−1 and a high selectivity of 96% at 25 oC in the semihydrogenation of alkynes without compromising the stability. This strategy is general and scalable considering the plentiful members of the MXene family, which can set a foundation for the design of novel supported-metallene catalysts for demanding transformations. 2D metallenes have spurred considerable interests in heterogeneous catalytic reactions. Here the authors report an efficient galvanic replacement strategy to construct Pd metallenes mediated by Nb2C MXenes for boosting alkynes semihydrogenation. [ABSTRACT FROM AUTHOR]

A new general method is presented to calculate local strains in geomembranes from the deformed shape imposed by overlying coarse gravel particles under vertical pressure. Past methods assume that the geomembrane attains its deformed shape by only deforming vertically and hence neglect the effect of lateral displacements on strain. The new method treats the geomembrane as a thin plate with mid surface components of displacements in three directions (x, y and z). Lateral components of displacements (those in the x and y directions) are related to vertical displacements (z direction) by large-strain-displacement relationships and compatibility of strains. Normal and shear strains in the lateral directions are calculated using Airy's stress function and a linear elastic constitutive law. Bending and torsional strains calculated from curvature and are added to the mid surface strains to find strains on the top and bottom surfaces. The method was validated against data sets with known three-dimensional displacements and strain generated by finite element analysis. The application of the new method to calculate local strains in a geomembrane from the deformed shape obtained from a protection-layer-assessment physical test is illustrated. • A new general method for calculating local geomembrane strain from gravel particle indentations is presented. • The new thin plate method considers both vertical and lateral displacements. • Only vertical displacements from the deformed shape of the geomembrane are required as input. • Lateral displacements are considered via large-strain-displacement relationships and compatibility of strains. • The method was validated by comparison with geometrically-nonlinear finite element analysis. • Past methods were found to under predict the maximum strain by 60 to 70%. [ABSTRACT FROM AUTHOR]

Multi-field information monitoring is useful to better understand the deformation and failure behaviour of landslides. Therefore, in this study, a physical slope model under excavation was analysed through multi-field monitoring to ascertain the failure mechanism of the slope. During the process of physical model tests, ① area information including 2D surface displacement, 2D surface strain, velocity, 2D surface temperature, and 3D surface deformation, ② line information including deep displacement and deep strain, and ③ point information of the earth pressure of the model were acquired via multi-field monitoring. The pre-failure, failure, and post-failure stages of the slope model are analysed through multi-field monitoring. The results indicate that the relative displacement between the yielding and stationary parts and a triangular shear plane reflect the deformation behaviour of the slope related to the arching effect. The arch ring expands and becomes elongated during the excavation process. The slope failure time can be effectively predicted via the inverse velocity method. Multi-field monitoring can reveal the behaviour of the slope model from different perspectives and offer new insights into the failure mechanism of the slope. [ABSTRACT FROM AUTHOR]

The phenomenon of mesoscale deformation-induced surface roughening in titanium polycrystals is examined experimentally and numerically. The evolution of the surface morphology under uniaxial tension is analyzed in terms of the standard and ad hoc roughness parameters and the fractal dimension. The statistical estimates are compared to the grain-scale stress-strain fields in order to reveal an interrelation between the in-plane plastic strains and out-of-plane surface displacements. A strong correlation with a determination coefficient of 0.99 is revealed between the dimensionless roughness parameter Rd and the corresponding in-plane plastic strain. The standard roughness parameters Ra and RRMS are shown to correlate linearly with the in-plane strains, but only for moderate tensile deformation, which is due to filtering out low-frequency components in the surface profiles. The fractal dimension DF changes with the subsection strains in a sawtooth fashion, with an abrupt drop in the neck region. The descent portions of the DF dependences are supposedly related to the appearance of low-frequency components in the structure of the surface profiles. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We report on the thickness scaling behavior of ferroelectric Sc0.3Al0.7N (ScAlN) films grown on Mo substrates by molecular beam epitaxy. Switchable ferroelectricity is confirmed in ScAlN films with thicknesses ranging from 100 to 5 nm. An increase in coercive field and a significant diminution of remnant polarization are found when the ferroelectric layer is scaled down to below 20 nm. Notably, a switching voltage of 2–3.8 V and saturated remnant polarization of ∼23 μC/cm2 are measured in 5 nm thick ScAlN. X-ray diffractions and transmission electron microscopy studies indicate that the increase in coercive field and diminishment in switchable polarization can be closely linked to the surface oxidation and strain state in ultrathin ScAlN films. This work sheds light on the fundamental thickness scaling fingerprints of ScAlN thin films and represents an important step for next-generation compact and power-efficient devices and applications based on nitride ferroelectrics. [ABSTRACT FROM AUTHOR]

Rotationally accelerated shot peening imposes high strain rates and strain accumulation on the surface of a pure nickel. As a result, a gradient structure is developed from the surface to the interior of the bulk sample. In addition to dislocation activities and deformation twinning, shear band is activated to accommodate localized shear strains at the outmost surface. A high density of defects accumulated during the strain hardening process is a prerequisite for the shear banding deformation. The orientation relationship between the deformed matrix and the shear bands, and thermally assisted mechanical rotation of nanograins occurred during partial dynamic recrystallization, together reveal the adiabatic nature of shear localization. [ABSTRACT FROM AUTHOR]

Lightweight sheet metals are attractive for aerospace and automotive applications due to their exceptional properties, such as low density and high strength. Sheet metal forming (SMF) is a key technology to manufacturing lightweight thin-walled complex-shaped components. With the development of SMF, numerical simulation and theoretical modelling are promoted to enhance the performance of new SMF technologies. Thus, it is extraordinarily valuable to present a comprehensive review of historical development in SMF followed by state-of-the-art advanced characterization and modelling approaches for lightweight metallic materials. First, the importance of lightweight materials and their relationship with SMF followed by the historical development of SMF are reviewed. Then, the progress of advanced finite element technologies for simulating metal forming with lightweight alloys is covered. The constitutive modelling of lightweight alloys with an explanation of state-of-the-art advanced characterization to identify the constitutive parameters are presented. Then, the formability of sheet metals with major influencing factors, the techniques for measuring surface strains in SMF and the experimental and modelling approaches for determining the formability limits are clarified. Finally, the review is concluded by affording discussion of the present and future trends which may be used in SMF for lightweight metallic materials. [ABSTRACT FROM AUTHOR]

Aluminum alloys are one of the most common structural materials. To improve the mechanical properties, an alloy of the Al–Zn–Mg–Ca–Fe system was proposed. In this alloy, when Fe and Ca are added, compact particles of the Al10CaFe2 compound are formed, which significantly reduces the negative effect of Fe on the mechanical properties. Because of the high solidification rate (about 600 K/s) during cylindrical ingot (~33 mm) production, the electromagnetic casting method (ECM) makes it possible to obtain a highly dispersed structure in the cast state. The size of the dendritic cell is ~7 μm, while the entire amount of Fe is bound into eutectic inclusions of the Al10CaFe2 phase with an average size of less than 3 μm. In this study, the effect of radial shear rolling (RSR) on the formation of the structure and hardening of the Al–8%Zn–3.3%Mg–0.8%Ca–1.1%Fe alloy obtained by EMC was studied. Computer simulation of the RSR process made it possible to analyze the temperature and stress–strain state of the alloy and to select the optimal rolling modes. It was shown that the flow features during RSR and the severe shear strains near the surface of the rod (10 mm) provided a refining and decrease in the size of the initial Fe-containing particles. [ABSTRACT FROM AUTHOR]

To examine the effect of inorganic phosphate-solubilizing bacteria (IPB) on phosphorus release from sediment in the Swan Lagoon in Rongcheng, an indoor simulation test was performed with three IPB strains and surface sediments. Changes in total phosphorus (TP) concentration, pH, and oxidation/reduction potential in the overlying water under different IPB inoculation conditions were analyzed. In addition, the concentrations of different forms of inorganic phosphorus in the sediments were determined after the experiment. During the early stage of the experiment, the pH value of the water decreased following inoculation with IPB; The pH of the sterilized sediment and non-sterilized sediment groups decreased to 6.46-6.88 and 6.66-6.78, respectively. The water oxidation/reduction potential in the different treatments decreased continuously over time, and the sediment–water interface became anaerobic. In the sterilized group, inoculation with IPB significantly promoted the release of phosphorus from the sediments. At the later stage, the water total phosphorous concentrations in the inoculation treatments were much higher than that of the control. In the non-sterilized group, TP concentrations increased slowly over time with a small difference observed among the different IPB treatments. At the end of the experiment, the concentrations of HCl-P in most sediments inoculated with IPB had clearly decreased by 19.92-50.08 mg·kg-1, and the BD-P concentrations decreased by 1.81-4.19 mg·kg-1. However, the NaOH-P concentration did not decrease. The results indicate that inoculation of IPB can greatly reduce the pH of water, leading to the dissolution and release of HCl-P from sediment. In Swan Lagoon, HCl-P is the main form of phosphorus in the sediment as produced via the action of IPB, indicating its strong effects on the phosphorus level in the overlying water. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to evaluate the surface strain at the cervical area of endodontically treated molars with a large pulp chamber restored using a composite resin core with three different types of core build-up systems. Methods: Reproduction models of human mandibular molars with prepared post spaces were used in this study. Roots duplicated with a composite resin were used as the experimental teeth. Three types of core build-up systems were used: composite resin core(RC), composite resin core with fiber posts (FC), and composite resin core with a prefabricated zirconia tube (ZC). Each group comprised eight specimens. Crowns made of yttria partially stabilized zirconia were cemented with dual-cure resin cement. Four strain gauges were attached to the surfaces of each specimen: the cervical area of the root and crown, on the buccal and lingual sides. The surface strain at each cervical area was measured using a static loading test and statistically analyzed. Results: In the case of static loading to the buccal cusp inner slope, ZC showed a significantly lower strain than RC in the crown on the buccal side and in the root and FC in the root. In the central fossa, ZC showed a significantly lower strain than FC in the root on the lingual side. Conclusions: The prefabricated zirconia tube reduced the surface strain at the cervical area of the buccal/lingual root in molars; however, the effect was small in the cervical area of the crown. [ABSTRACT FROM AUTHOR]

Quaternary ammonium salts (QAS) commonly occur as active substances in disinfectants. QAS have the important property of coating abiotic surfaces, which prevents adhesion of microorganisms, thus inhibiting biofilm formation. In this study, a group of nine monomeric QAS, differing in the structure and length of the aliphatic chain (C12, C14, C16) and the counterion (methylcarbonate, acetate, bromide), were investigated. The study included an analysis of their action against planktonic forms as well as bacterial biofilms. The compounds were tested for their anti-adhesion properties on stainless steel, polystyrene, silicone and glass surfaces. Moreover, mutagenicity analysis and evaluation of hemolytic properties were performed. It was found that compounds with 16-carbon hydrophobic chains were the most promising against both planktonic forms and biofilms. Tested surfactants (C12, C14, C16) showed anti-adhesion activity but it was dependent on the type of the surface and strain used. The tested compounds at MIC concentrations did not cause hemolysis of sheep blood cells. The type of counterion was not as significant for the activity of the compound as the length of the hydrophobic aliphatic chain. [ABSTRACT FROM AUTHOR]

Laminated plates are often modeled with infinite dimensions in terms of the so-called Whitney–Nuismer (WN) stress criteria, which form a theoretical basis for predicting the residual properties of open-hole structures. Based upon the WN stress criteria, this study derived a new formulation involving finite width; the effects of notch shape and size on the applicability of new formulae and the tensile properties of carbon-fiber-reinforced plastic (CFRP) laminates were investigated via experimental and theoretical analyses. The specimens were prepared by using laminates reinforced by plain woven carbon fiber fabrics and machined with or without an open circular hole or a straight notch. Standard tensile tests were performed and measured using the digital image correlation (DIC) technique, aiming to characterize the full-field surface strain. Continuum damage mechanics (CDMs)-based finite element models were developed to predict the stress concentration factors and failure processes of notched specimens. The characteristic distances in the stress criterion models were calibrated using the experimental results of un-notched and notched specimens, such that the failure of carbon fiber laminates with or without straight notches could be analytically predicted. The experimental results demonstrated well the effectiveness of the present formulations. The new formula provides an effective approach to implementing a finite-width stress criterion for evaluating the tensile properties of notched fiber-reinforced laminates. In addition, the notch size has a great effect on strength prediction while the fiber direction has a great influence on the fracture mode. [ABSTRACT FROM AUTHOR]

A facile and general strategy for the preparation of highly dispersed PtCo/C catalysts with a Pt-enriched surface is reported. The thermal treatment of the PtCo/C catalyst changes the structure orientation from disordered to ordered phase. Ordered PtCo/C intermetallic catalyst exhibits significantly enhanced electrocatalytic activity and durability toward oxygen reduction reaction (ORR) compared with its disordered counterpart and commercially available PtCo/C, with a mass activity and specific activity of 0.68 A mg Pt −1@0.90 V and 1.15 mA cm−2, respectively. In addition, the mass activity only decreased by 25.1% after 30,000 potential cycles from 0.60 to 1.00 V at a scan rate of 100 mV s−1. Therefore, the improved ORR activity and stability can be ascribed to the atomic ordered surface arrangement and reasonable surface compress strain originated from Pt-enriched surface. • A widely applicable strategy to synthesize ordered intermetallic PtCo/C. • Ordered surface arrangement and reasonable surface compress strain contributed to high activity. • Ordered PtCo/C shows ORR mass activity of 0.68 A mg−1 Pt @ 0.90 V. • Ordered PtCo/C exhibits a mass activity loss of only 25.1% after ADT. [ABSTRACT FROM AUTHOR]

Distributed acoustic sensing (DAS) strain rate and particle velocity can be compared through approximate scaling with medium velocity. We instead performed a direct comparison between array derived dynamic strain (ADDS) rate and DAS strain rate for six frequency bands. The PoroTomo project at Brady's Hot Springs, Nevada, deployed a 240‐geophone 3C array co‐located with fiber‐optic DAS system and 8.7 km of buried cable. We selected subsets of the geophone array to create four smaller arrays and computed ADDS. The horizontal components of the ADDS were rotated into the direction of the fiber‐optic cable and then compared with the observed DAS strain rates. From three example regional earthquakes of local magnitudes 2.9, 4.1, and 4.3, the ADDS are found to be coherent with DAS for frequencies ≤1 Hz. For frequencies >1‐Hz, this correlation decays quickly. Small differences between linear and areal dynamic strains at 1‐Hz suggest poor signal‐to‐noise or localized strain that is perturbed by shallow heterogeneities compare to the average strain propagating across the geophone array. The implication is that around 1‐Hz, straight fiber DAS is measuring axial strain along the fiber and can provide good approximations to translational particle motions. However, above 1‐Hz, DAS becomes more sensitive to shallow velocity gradients that can be beneficial for geophysical imaging yet becomes a limitation for traditional seismic analysis methods depending on absolute amplitude and phase from translational particle motions. Plain Language Summary: Seismological measurements including ground displacement are based on the motion at a point in 3‐dimensional space through time. Fiber‐optic distributed acoustic sensing (DAS) instead measures strain, a component of deformation that is the difference in motion between two points in space through time. We know that strain is much more sensitive to shallow Earth structure beneath the receiver and surrounding topography than traditionally measured particle motions. We examine the variability of surface strain along a line versus the average strain over an area and also how these variabilities change over both frequency and spatially across the extent of an array. We show that the strain over an area versus axial strain measured from DAS varies in amplitude and phase for several frequency bands. These results have implications on how methods developed in seismology based on traditional seismometers can be used with fiber‐optic DAS data analysis. Key Points: Array derived dynamic strains (ADDSs) are in agreement (correlation coefficients ∼0.9) with distributed acoustic sensing (DAS) strain rate for f ≤ 1 HzFor f > 1 Hz, the correlation between DAS and array derived strains decays quicklyThe root‐mean‐square amplitude ratios between ADDS rate and DAS strain rate is ∼1 below f ∼ 2 Hz but increases with frequency [ABSTRACT FROM AUTHOR]