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Understanding the mechanical behavior of nanotwinned materials in alloys is essential, particularly in relation to solute-influenced twin boundary (TB) migration. This research employs atomistic simulations and theoretical analysis to explore the influence of solute atoms on TB migration in CuAg alloys. Contrary to conventional beliefs, simulations reveal that solute Ag atoms enhance TB migration, challenging established perceptions. Nudged elastic band calculations confirm that Ag solutes substantially reduce energy barriers, shedding light on the mechanism driving solute-enhanced TB migration. This work opens novel avenues for investigating point defect impacts on TB mobility, offering insights into alloy element roles in grain boundary migration and polycrystalline material properties. [ABSTRACT FROM AUTHOR]

In minimally invasive surgery, the tendency for human tissue to adhere to the electrosurgical scalpel can complicate procedures and elevate the risk of medical accidents. Consequently, the development of an electrosurgical scalpel with an anti-sticking coating is critically important. Drawing inspiration from nature, we identified that the leaves of Setaria Virids exhibit exceptional non-stick properties. Utilizing this natural surface texture as a model, we designed and fabricated a specialized anti-sticking surface for electrosurgical scalpels. Employing nanosecond laser direct writing ablation technology, we created a micro-nano textured surface on the high-frequency electrosurgical scalpel that mimics the structure found on Setaria Virids leaves. Subsequently, a TiO2 coating was deposited onto the ablated scalpel surface via magnetron sputtering, followed by plasma-induced hydrophobic modification and treatment with octadecyltrichlorosilane (OTS) to enhance the surface's affinity for silicone oil, thereby constructing a self-lubricating and anti-sticking surface. The spreading behavior of deionized water, absolute ethanol, and dimethyl silicone oil on this textured surface is investigated to confirm the effectiveness of the self-lubrication mechanism. Furthermore, the sticking force and quality are compared between the anti-sticking electrosurgical scalpel and a standard high-frequency electrosurgical scalpel to demonstrate the efficacy of the nanosecond laser-ablated micro-nano texture in preventing sticking. The findings indicate that the self-lubricating anti-sticking surface fabricated using this texture exhibits superior anti-sticking properties. [ABSTRACT FROM AUTHOR]

Improving energy efficiency and cost reduction is a perennial challenge in engineering. Natural biological systems have evolved unique functional surfaces or special physiological functions over centuries to adapt to their complex environments. Among these biological wonders, fish, one of the oldest vertebrate groups, has garnered significant attention due to its exceptional fluid dynamics capabilities. Researchers are actively exploring the potential of fish skin's distinctive structural and material characteristics in reducing resistance. In this study, models of biomimetic imbricated fish scale are established, and the evolution characteristics of the flow field and drag reduction performance on these bionic surfaces are investigated. The results showed a close relationship between the high–low velocity stripes generated and the fluid motion by the imbricated fish scale surface. The stripes' prominence increases with the spacing of the adjacent scales and tilt angle of the fish scale, and the velocity amplitude of the stripes decreases as the exposed length of the imbricated fish scale surface increases. Moreover, the biomimetic imbricated fish scale surface can decrease the velocity gradient and thereby reduce the wall shear stress. The insights gained from the fish skin‐inspired imbricated fish surface provide valuable perspectives for an in‐depth analysis of fish hydrodynamics and offer fresh inspiration for drag reduction and antifouling strategies in engineering applications. [ABSTRACT FROM AUTHOR]

Reducing resistance to surface friction is challenging in the field of engineering. Natural biological systems have evolved unique functional surfaces or special physiological functions to adapt to their complex environments over centuries. Among these biological wonders, fish, one of the oldest in the vertebrate group, have garnered attention due to their exceptional fluid dynamics capabilities. Fish skin has inspired innovation in reducing surface friction due to its unique structures and material properties. Herein, drawing inspiration from the unique properties of fish scales, a periodic array of fish scales was fabricated by laser ablation on a polished aluminum template. The morphology of the biomimetic fish scale surface was characterized using scanning electron microscopy and a white-light interfering profilometer. Drag reduction performance was measured in a closed circulating water tunnel. The maximum drag reduction was 10.26% at a Reynolds number of 39,532, and the drag reduction performance gradually decreased with an increase in the distance between fish scales. The mechanism of the biomimetic drag reduction surface was analyzed using computational fluid dynamics. Streamwise vortices were generated at the valley of the biomimetic fish scale, replacing sliding friction with rolling friction. These results are expected to provide a foundation for in-depth analysis of the hydrodynamic performance of fish and serve as new inspiration for drag reduction and antifouling. [ABSTRACT FROM AUTHOR]

Using hybrid molecular dynamics and Monte Carlo simulations, we examine the role of lattice distortion (LD) and chemical short-range ordering (CSRO) on the development of defects ahead of a mode I crack in medium entropy alloy CoCrNi. We show that CSRO noticeably increases fracture toughness. The result can be explained by the effect of CSRO on lowering LD and increasing intrinsic stacking fault energy and the direct impact CSRO has on the energetic barriers for emitting partial dislocations and forming nanotwins from CoCr clusters on the crack tip. CSRO allows the nanotwin domains to further support inelastic deformation, such as dislocation glide and amorphization, leading to stable crack-tip plasticity and postponement of softening. These findings imply that the superior fracture toughness in CoCrNi can be attributed to the non-negligible CSRO that naturally exists. [ABSTRACT FROM AUTHOR]

For high‐speed moving objects, drag reduction has been a prolonged major challenge. To address this problem, passive and negative strategies have been proposed in the preceding decades. The integration of creatures and nature has been continuously perfected during biological evolution. Unique structure characteristics, material properties, and special functions of marine organisms can provide inexhaustible inspirations to solve this intractable problem of drag reduction. Therefore, a simple and low‐cost laser ablation method was proposed. A multi‐scale and multi‐level riblet (MSLR) surface inspired by the denticles of the sharkskin was fabricated by controlling the density of the laser path and ablation times. The morphology and topographic features were characterised using an electron microscope and a scanning white‐light interfering profilometer. Then, the drag reduction capacity of the bionic riblet surface was measured in a circulating water tunnel. Finally, the mechanism of drag reduction was analysed by the computational fluid dynamics (CFD) method. The results show that the MSLR surface has a stable drag reduction capacity with an increase in Reynold (Re) number which was contributed by high‐low velocity stripes formed on the MSLR surface. This study can provide a reference for fabricating spatial riblets with efficient drag reduction at different values of Re and improving marine antifouling. [ABSTRACT FROM AUTHOR]

High-entropy alloys are a class of materials that contain five or more elements in near-equiatomic proportions.sup.1,2. Their unconventional compositions and chemical structures hold promise for achieving unprecedented combinations of mechanical properties.sup.3-8. Rational design of such alloys hinges on an understanding of the composition-structure-property relationships in a near-infinite compositional space.sup.9,10. Here we use atomic-resolution chemical mapping to reveal the element distribution of the widely studied face-centred cubic CrMnFeCoNi Cantor alloy.sup.2 and of a new face-centred cubic alloy, CrFeCoNiPd. In the Cantor alloy, the distribution of the five constituent elements is relatively random and uniform. By contrast, in the CrFeCoNiPd alloy, in which the palladium atoms have a markedly different atomic size and electronegativity from the other elements, the homogeneity decreases considerably; all five elements tend to show greater aggregation, with a wavelength of incipient concentration waves.sup.11,12 as small as 1 to 3 nanometres. The resulting nanoscale alternating tensile and compressive strain fields lead to considerable resistance to dislocation glide. In situ transmission electron microscopy during straining experiments reveals massive dislocation cross-slip from the early stage of plastic deformation, resulting in strong dislocation interactions between multiple slip systems. These deformation mechanisms in the CrFeCoNiPd alloy, which differ markedly from those in the Cantor alloy and other face-centred cubic high-entropy alloys, are promoted by pronounced fluctuations in composition and an increase in stacking-fault energy, leading to higher yield strength without compromising strain hardening and tensile ductility. Mapping atomic-scale element distributions opens opportunities for understanding chemical structures and thus providing a basis for tuning composition and atomic configurations to obtain outstanding mechanical properties. In high-entropy alloys, atomic-resolution chemical mapping shows that swapping some of the atoms for larger, more electronegative elements results in atomic-scale modulations that produce higher yield strength, excellent strain hardening and ductility., Author(s): Qingqing Ding [sup.1] , Yin Zhang [sup.2] , Xiao Chen [sup.3] , Xiaoqian Fu [sup.1] , Dengke Chen [sup.2] , Sijing Chen [sup.1] , Lin Gu [sup.4] , Fei [...]

Missing and broken states of railway fasteners are directly related to driving safety. A deep network image detection method for railway fasteners based on residual network-single shot multibox detector (ResNet-SSD) is proposed to improve detection performance. Firstly, virtual image technology is used to simulate the defect states of fasteners, so as to expand feature information and overcome the imbalance problem of various fastener images. Secondly, ResNet is used to construct feature extraction network, and SSD is used for target detection to form ResNet-SSD network to detect the defect states of fasteners. Experimental results show that the ResNet-SSD has faster convergence speed and mean average precision (mAP) is increased by 3.06% from 95.47% to 98.53% after using the virtual image to expand the field collected fastener set; The detection accuracy of ResNet-SSD can reach 98.5% when the recall is 98.8%, which is higher than that of VGG16-SSD and the same as that of Faster-RCNN when intersection over union(IoU) is 0.5; The detection speed of this method is 6 times that of Faster RCNN and 1.5 times that of VGG16-SSD. Therefore, this method can meet the needs of real-time detection of railway fasteners. [ABSTRACT FROM AUTHOR]

Reduction of energy consumption and improvement of cruising speed are greatly necessary for underwater vehicles. Previously, regular riblets have been machined and the drag reduction has been verified; however, the riblet parameters are not adjusted like the denticles of sharkskin, which adapt quickly to the complex changing fluid flow. To achieve an improved drag reduction effect on the complicated shape surface, a simple, low‐cost, and timesaving stretching approach was proposed to adjust the riblet parameters on the underwater vehicle surface by controllable deformation. Nature latex rubber membrane with regular micro‐riblets was prepared as a stretching flexible film, and the spacing and height of the micro‐riblets were adjusted by adaptive control of the stretching ratio. The circulating water channel experiment verified the effectiveness and feasibility of the self‐adaptive drag reduction by the controllable deformation method. The results demonstrated that the drag reduction rate of the controllable deformation bionic fish skin was 4.26% compared with a smooth surface at 0.25 m/s with an angle of attack of 0°, which is better than any other angle. The controllable deformation bionic fish skin provides a feasible method for the drag reduction of complex surface adaptive underwater vehicles. [ABSTRACT FROM AUTHOR]

This paper uses numerical simulation to investigate the effects of diluents on the flame structure and NO generation of H2/CO micromixing flames. The results show that under the same thermal power condition, the diluents reduce the flame temperature and decrease the combustion reaction rate and flame propagation velocity. In addition, the diluents downsize the flame and force it downstream. With an increase in the diluent fraction, these trends are amplified. The NO production decreases due to the diluents, and the NO is lowest when H2O is added. When the diluents are CO2 and H2O, the NO generation is dominated by the reactants' concentration. This results in the lowest temperature not corresponding to the lowest NO production. The diluents also reduce the sensitivity of the NO production to the temperature, and the CO2 diluent highly weakens the sensitivity. [ABSTRACT FROM AUTHOR]