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Carbon-fiber-reinforced polyetheretherketone (CF/PEEK) composites are being increasingly used in aerospace, biomedical, and other industries due to their superior mechanical properties. However, CF/PEEK structural components require secondary processing after curing and molding to meet connection and assembly precision requirements. This process, however, often results in defects such as burrs and pits, which significantly compromise the mechanical performance and assembly quality of the structural components. This study first employed finite element simulations to analyze the laser-assisted milling of CF/PEEK composites, investigating the material removal mechanism under thermal coupling, which was then experimentally validated. Variations in the cutting force, cutting heat, surface damage, and fiber fracture mechanisms during milling were investigated. During laser-assisted milling, the fibers fractured mainly in bending at a cutting angle of 0°, in bending shear at a cutting angle of 45°, in compression at a cutting angle of 90°, and in compression shear at a cutting angle of 135°. The experimental findings were generally consistent with the simulation results. In addition, laser-assisted milling effectively reduced the cutting forces, cutting temperatures, and surface damage compared to conventional milling; laser-assisted milling reduced the cutting forces in the 90° fiber direction by 24.8% (total cutting forces) and 16.3% (feed-cutting forces). The fiber integrity was further increased with increasing spindle speed. [ABSTRACT FROM AUTHOR]

Shearing stimulation with proppant is widely used in geothermal and hydrocarbon reservoirs. However, the shear behavior associated with proppant-proppant and proppant-fracture interactions has not been clearly elaborated. This paper investigates surface damage and the interactions between proppant and surface roughness through direct shear tests with acoustic emission (AE) monitoring. The AE events show distinct spatial and temporal distribution patterns under the influence of proppant. The small magnitude AE events, representing proppant slipping and crushing, start to occur in large areas from the beginning of the shear deformation, and the large magnitude AE events occur mostly at the peak and during the residual phase and are concentrated on asperities. Crushed proppant grains and asperities form a gouge layer that prevents further damage to the fracture surface, reduces shear dilation and promotes aseismic creep. Fine proppant grains tend to remain intact, while the coarse proppant grains tend to be crushed. Our results suggest that acoustic emission characteristics can be used to infer different stages of shear behavior of propped fractures. These findings enhance our understanding of the shear behavior of propped fractures and provide evidence for monitoring their conditions using seismic signals. Highlights: Acoustic emission characteristics can be used to infer different stages of shear behavior of propped fractures. Proppant lubricates the fracture surface and promotes aseismic creep characterized by the abnormally low acoustic emission rate. Proppant-proppant and proppant-fracture interactions generate lower magnitude acoustic emission events than asperity breakage. Large proppant grains tend to be crushed and fine proppant grains tend to fill in the troughs and stay intact. [ABSTRACT FROM AUTHOR]

The environment continues to erode the roofs of ancient buildings in Longmen Ancient Town, posing a threat to the safety of villagers. Scientific detection and diagnosis are important steps in the repair and protection of historical buildings. In order to effectively protect cultural heritage, this study uses the YOLOv8 deep learning model to automatically detect damage on images of traditional residential roofs. The researchers constructed image data sets for the four categories of green vegetation, dry vegetation, missing tiles, and repaired tiles and then perform model training. The results show that the model is generally accurate for missing tiles (0.94 for missing tiles and 0.93 for repaired tiles), and it has a low false detection rate and a low missed detection rate. It does make some mistakes when it comes to green and dry vegetation in complex backgrounds, but the overall detection coverage and F1 score are better. This practical application shows that the model can accurately mark most target areas, especially for the recognition of high-contrast damage types. This study provides efficient and accurate technical support for the diagnosis of traditional roof structures and protection of cultural heritage. [ABSTRACT FROM AUTHOR]

In many steel mills, the working life of continuous casting machine rollers is relatively short, requiring frequent replacement and negatively impacting production efficiency. To effectively extend the service life of these rollers, this study focuses on a continuous casting machine at a steel mill in China. A numerical simulation was conducted, revealing that the rollers in contact with the high-temperature casting billet experience significant thermal and stress impacts. The traditional cooling channel struggles to sufficiently reduce both the surface temperature and stress, resulting in severe thermal fatigue damage to the roller surfaces. Observations of roller surface wear showed signs of adhesive wear, fatigue cracks, and spalling occurring in various regions of the roller, which aligned with the stress distribution predicted by the simulation. In response, the cooling channel structure was modified to enhance the cooling effect of the water. Optimization of both the cooling channel structure and its parameters was carried out using a coupled flow-heat-force numerical simulation method. The optimized cooling channel effectively improved the working condition of the continuous casting roll, as the maximum temperature of the roll surface was reduced from 810 K to 591 K, the circumferential temperature difference was reduced by 38%, and the maximum equivalent stress decreased from 791 MPa to 558 MPa. This adjustment also resulted in a more uniform surface temperature distribution, mitigating the sudden fluctuations in normal stress that are typical of conventional rollers. [ABSTRACT FROM AUTHOR]

Micro-pitting and wear phenomena were studied both experimentally and through simulation, focusing on the relationship between ball roughness and the lambda, Λ, value. The degree of damage due to micro-pitting and wear was investigated under different ball roughness conditions. Cross-sections of micro-pitting and wear were evaluated using optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Morphological observations revealed structures indicative of micro-pitting and wear fatigue, such as plastic flow and crack. In this study, plastic flow thickness, crack angle, and crack depth were used as indicators of the damage degree for micro-pitting and wear. The results from both experiments and simulations indicate that surface roughness contributes significantly to the maximum tangential stress that can initiate the plastic flow and cracks, particularly in micro-pitting. Additionally, the internal stress is expected to have a greater influence on crack propagation.

Abstract Severe friction on wheel/rail contact interface in the process of a train emergency braking can cause significant thermal and mechanical phenomena. Obvious friction heat and serious material damage will appear on the contact surface. In this article, the variation law of temperature and surface damage during a wheel sliding contact process are investigated. To achieve the research objective, a three-dimensional (3D) thermo-mechanical coupling contact finite element model (FEM) is established, and the temperature-dependent material parameters are used. The FEM is adopted to analyze the temperature distribution law on the contact surface. At the same time, a sliding contact testing machine is used to study the damage of materials in the contact area during the sliding contact. The study results indicate, the highest temperature of wheel and rail material is respectively 1014 ℃ and 461.8 ℃ during sliding contact. High temperatures are located at the subsurface and surface areas of contact region. When the distance to contact surface exceeds 1.4 mm, the temperature changes slightly. The types of damage on wheel surface are grooves and material peeling, while the flaky spalling, corrosive pitting, adhesion and grooves appear on the rail surface. Meanwhile, many cracks can be found on the contact surface, which is a major factor leading to material damage. The research results of this article are of great significance for understanding the thermal and mechanical damage of wheel/rail materials.

Background Miniplates are frequently used in oral and maxillofacial surgery to address malocclusion issues. However, surface damage to miniplates is a significant concern that can affect surgical outcomes and patient quality of life. This study aims to evaluate the influence of miniplate surface damage on bacterial attachment, which may lead to postoperative infections. Methods Miniplates with varying degrees of surface damage were used in this study. The damaged surfaces were subjected to special treatments to simulate postoperative conditions. Various bacterial strains, including Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus mutans, were tested. Each type of bacteria was cultured on different miniplates for specific durations, and bacterial attachment was subsequently measured and analyzed. Results Surface damage to miniplates significantly influenced bacterial attachment. Miniplates with more severe surface damage exhibited higher levels of bacterial attachment compared to undamaged miniplates. Furthermore, the type of bacteria impacted attachment levels, with certain strains demonstrating higher adhesion than others. Conclusion Surface damage to miniplates increases the risk of postoperative infections due to enhanced bacterial attachment. Therefore, maintaining the integrity of miniplates during and after orthognathic surgery is crucial. Further research is necessary to develop prevention and management strategies for postoperative infections related to miniplate surface damage.

High volume fraction (45 %) silicon carbide particle-reinforced aluminum matrix composites (SiC p /Al-MMCs) play a significant role in various engineering fields due to their outstanding performance. However, damages characterized by SiC particle fracture during machining lead to poor surface integrity, which severely affects the fatigue performance of SiC p /Al composite structural components. Ultrasonic-assisted grinding (UAG) is acknowledged as beneficial for promoting ductile grinding in hard and brittle materials. This study focuses on the critical conditions for ductile-brittle transition in ultrasonic-assisted grinding of SiC p /Al composites and develops a mechanism and data driven model of critical undeformed chip thickness (UCT) for ductile grinding to accurately predict the material removal mode. The model thoroughly integrates considerations of chip morphology, removal mode transition mechanism, and grinding surface damage characteristics. Response surface methodology (RSM) and genetic algorithms (GA) were utilized to correct the impact of processing parameters on the removal regime. Experiments on ultrasonic-assisted side and end grinding were conducted to thoroughly discuss the effects of different undeformed chip thicknesses, grinding speeds and ultrasonic vibration amplitude on surface damage and the critical conditions for the ductile-brittle transition. The findings corroborate the experimental data with the predicted values. Ultrasonic vibration can effectively reduce the brittle fracture of SiC particles in SiC p /Al composites. Appropriately increasing the grinding speed and reducing the chip thickness can enhance the critical chip thickness for ductile grinding and decrease the proportion of brittle surfaces, thereby achieving a balance between surface integrity and grinding efficiency. This research provides guidance for high-performance machining of SiC p /Al composites. [ABSTRACT FROM AUTHOR]

Ambient hydrocarbons adsorbed on the contact surface of nanoelectromechanical (NEM) switches would impact its performance. In this study, we utilized reactive molecular dynamics simulations to investigate the cyclic contact/separation process of Pt(111)/C2H2/Pt(111) systems. Our results demonstrate that substrate damage decreases as acetylene coverage increases from sub-monolayer to multilayer. This suppression occurs due to the presence of acetylene molecules, which can suppress direct (Pt–Pt connection) and indirect (Pt–(Cx)–Pt-like connection) interfacial bonding between the two substrates, depending on their coverage. Moreover, we observed the formation of chain-like oligomers after multiple contact/separation simulations in the monolayer model, much more significantly compared with the sub-monolayer and multilayer models. These oligomers arise from polymerization reactions among fragmented acetylene molecules, primarily formed through acetylene dehydrogenation. In the sub-monolayer model, numerous transferred Pt atoms at the interface hinder bonding between acetylene fragments, whereas in the multilayer model, only a few acetylene fragments form during the contact process, due to the well-organized and dense acetylene layer adsorbed on the substrate surfaces. These insights shed light on the atomic-scale mechanisms underlying substrate damage and chain-like oligomers formation in metal NEM switches. [ABSTRACT FROM AUTHOR]

After clinical introduction in 2005, sequentially annealed, highly cross-linked polyethylene (SA HXLPE) was studied for retrievals with short implantation times; however, long-term follow-ups are lacking. The objective of this study was to examine and compare the revision reasons, damage mechanisms, and oxidation indices of SA HXLPE and conventional gamma inert–sterilized (Gamma Inert) ultra-high-molecular-weight polyethylene tibial inserts implanted for >5 years. There were 74 total knee arthroplasty tibial inserts (46 SA HXLPEs, 28 Gamma Inerts) implanted for >5 years (mean 7 ± 2 years) retrieved as part of a multicenter retrieval program. Cruciate-retaining implants comprised 44% of the SA HXLPEs and 14% of the Gamma Inerts. Patient factors and revision reasons were collected from revision operating notes. A semiquantitative scoring method was used to assess surface damage mechanisms. Oxidation was measured using Fourier transform infrared microscopy according to American Society for Testing and Materials 2102. Differences between cohorts were assessed with Mann–Whitney U -tests. Loosening (Gamma Inert: 17 of 28, SA HXLPE: 15 of 46) and instability (Gamma Inert: 6 of 28, SA HXLPE: 15 of 46) were the most common revision reasons for both cohorts. The most prevalent surface damage mechanisms were burnishing, pitting, and scratching, with burnishing of the condyles being higher in Gamma Inert components (P =.022). Mean oxidation was higher in the SA HXLPE inserts at the articulating surface (P =.002) and anterior-posterior faces (P =.023). No difference was observed at the backside surface (P =.060). Revision reasons and surface damage mechanisms were comparable in the Gamma Inert and SA cohorts. Further studies are needed to continue to assess the in vivo damage and clinical relevance, if any, of oxidation in SA HXLPE over longer implantation times, particularly for implants implanted for more than 10 years. [ABSTRACT FROM AUTHOR]

Multi-tooth milling cutters have the advantages of minimal surface damages and low cutting forces and are widely used in composite materials milling such as carbon fiber and wood. Cortical bone is a composite biomaterial similar to carbon fiber and wood; however, the cutting performance of multi-tooth milling cutters on bone cutting is unclear. Here, this paper proposes a multi-tooth milling cutter longitudinal torsional ultrasonic vibration assisted milling (LTVUM) method for cortical bone low damage cutting. The cutting performance of sinusoidal and corn edge cutters for cortical bone LTVUM was studied, and its material removal mechanisms were also established. The results indicated that the multi-tooth milling cutter has a smaller average cutting force, and suppressing the chip burrs and tearing damages. Compared to straight edge cutter, the resultant cutting forces of sinusoidal and corn edge cutters are decreased by 52.58%–61.01% and 45.60%−65.96%. The reason is that the secondary cutting edge of multi-tooth cutter can participate in cutting, reducing the tool squeeze interference. This work provides experimental guidance for the application of multi-tooth milling cutters LTVUM in bone cutting. [ABSTRACT FROM AUTHOR]

This study aimed to examine corrosion-resistance performance of epoxy-coated reinforcements and galvanized reinforcements, among the most widely used anti-corrosion reinforcements. Five types of specimens were used, as follows: (a) Black bar, (b) Black bar coated with epoxy, (c) Black bar galvanized, (d) Black bar coated with epoxy with surface damage, and (e) Black bar galvanized with surface damage. Epoxy-coated bar specimen showed excellent corrosion resistance performance. In the presence of a surface damage, however, corrosion was intensively concentrated near the damage. In the galvanized bar specimen, a trace of light corrosion was observed throughout the surface. This meant that its corrosion resistance performance was rather inferior compared to the epoxy-coated bar specimen. However, the performance remained almost the same with or without a surface damage due to the sacrificial anode effect of zinc. The relative corrosion current density of the galvanized bar specimen was about 1/7 that of the epoxy-coated bar specimen on average. Galvanized reinforcements were capable of continuously providing excellent anti-corrosion performance even in the presence of surface damage formed at the construction field. The suspension concentration density of corrosion products in the cell solution showed a high correlation with other corrosion data. [ABSTRACT FROM AUTHOR]

Spur gears endure contact fatigue loads that can lead to surface damage on the gear teeth. Contact fatigue typically arises from dedendum during engineering and experiments, primarily caused by maximum sub-surface shear stress. This study presents a contact model incorporating profile-shift to examine sub-surface shear stress in relation to the occurrence of tooth root pits. Accurate calculations are performed to determine the distribution of sub-surface stress and meshing duration, considering various modification coefficients. The geometric cause affecting the shear stress near the tooth root is found. A deviation coefficient from base circle is proposed to analyze the influence of modification coefficient and pressure angle, which can be used in design reference. The investigation comprehensively explores the effects of profile-shift and pressure angle of spur gears on stress distribution. [ABSTRACT FROM AUTHOR]

As an important part of traditional Chinese architecture, Fuzhou's ancient houses have unique cultural and historical value. However, over time, environmental factors such as efflorescence and plant growth have caused surface damage to their gray brick walls, leading to a decline in the quality of the buildings' structure and even posing a threat to the buildings' safety. Traditional damage detection methods mainly rely on manual labor, which is inefficient and consumes a lot of human resources. In addition, traditional non-destructive detection methods, such as infrared imaging and laser scanning, often face difficulty in accurately identifying specific types of damage, such as efflorescence and plant growth, on the surface of gray bricks and are easily hampered by diverse surface features. This study uses the YOLOv8 machine learning model for the automated detection of two common types of damage to the gray brick walls of Fuzhou's ancient houses: efflorescence and plant growth. We establish an efficient gray brick surface damage detection model through dataset collection and annotation, experimental parameter optimization, model evaluation, and analysis. The research results reveal the following. (1) Reasonable hyperparameter settings and model-assisted annotation significantly improve the detection accuracy and stability. (2) The model's average precision (AP) is improved from 0.30 to 0.90, demonstrating good robustness in detecting complex backgrounds and high-resolution real-life images. The F1 value of the model's gray brick detection efficiency is improved (classification model performance index) from 0.22 to 0.77. (3) The model's ability to recognize the damage details of gray bricks under high-resolution conditions is significantly enhanced, demonstrating its ability to cope with complex environments. (4) The simplified data enhancement strategy effectively reduces the feature extraction interference and enhances the model's adaptability in different environments. [ABSTRACT FROM AUTHOR]

Severe friction on wheel/rail contact interface in the process of a train emergency braking can cause significant thermal and mechanical phenomena. Obvious friction heat and serious material damage will appear on the contact surface. In this article, the variation law of temperature and surface damage during a wheel sliding contact process are investigated. To achieve the research objective, a three-dimensional (3D) thermo-mechanical coupling contact finite element model (FEM) is established, and the temperature-dependent material parameters are used. The FEM is adopted to analyze the temperature distribution law on the contact surface. At the same time, a sliding contact testing machine is used to study the damage of materials in the contact area during the sliding contact. The study results indicate, the highest temperature of wheel and rail material is respectively 1014 ℃ and 461.8 ℃ during sliding contact. High temperatures are located at the subsurface and surface areas of contact region. When the distance to contact surface exceeds 1.4 mm, the temperature changes slightly. The types of damage on wheel surface are grooves and material peeling, while the flaky spalling, corrosive pitting, adhesion and grooves appear on the rail surface. Meanwhile, many cracks can be found on the contact surface, which is a major factor leading to material damage. The research results of this article are of great significance for understanding the thermal and mechanical damage of wheel/rail materials. [ABSTRACT FROM AUTHOR]

To investigate the effect of polypropylene fibers on the mechanical properties of concrete structures in cold regions, obtain an appropriate amount of polypropylene fiber content, and improve the frost resistance of the structure, freeze-thaw cycle tests were conducted on three groups of reinforced concrete short column specimens with different polypropylene fiber contents. The depth of surface damage of the specimen was detected using ultrasonic method. The stress process and failure of the specimen were analyzed through axial compression test, and the corresponding changes in compressive toughness were discussed. A formula for calculating the axial compressive bearing capacity of polypropylene fiber reinforced concrete short columns after freeze-thaw cycles was established. The test results indicate that the addition of polypropylene fibers can reduce the compressive bearing capacity of reinforced concrete short columns. An appropriate amount of polypropylene fiber can enhance the frost resistance, ductility and toughness of concrete components, and the recommended volume fraction of polypropylene fiber is 0.08-0.12%. [ABSTRACT FROM AUTHOR]

As a typical optical hard and brittle material, the efficient machining methods of glass-ceramic have always been a research hotspot. Based on previous research, this article conducted surface damage analysis on glass-ceramic using in-situ laser-assisted machining (LAM) orthogonal experimental results, and summarized that the surface damage of glass-ceramic mainly includes scratches, pits, and brittle fracture. Surface analysis confirmed that in-situ LAM can effectively reduce cutting forces and improve surface quality compared to conventional cutting. The artificial neural network (ANN) and genetic algorithm (GA) were used to fit and train and conduct multi-objective optimization for the data from in-situ LAM orthogonal experiments with resultant cutting force and surface roughness as eigenvalues. The Pareto optimal front curve with multiple groups of optimal solutions was obtained through multi-objective optimization using GA. The actual in-situ LAM experimental values were compared with the predicted values in the Pareto front, the relative error of the resultant force and the relative error of the surface roughness are both very small. In-situ LAM experiments based on response surface methodology (RSM) with surface roughness as the characteristic value were conducted. The optimal machining parameters for RSM optimization, as well as the minimum values for resultant force and surface roughness were obtained. Through comparative analysis, it was found that RSM has better multi-objective optimization performance than GA. Research content of this article provides reference and guidance for the multi-objective optimization analysis method of hard and brittle materials such as glass-ceramic after LAM. [ABSTRACT FROM AUTHOR]

This study presents a comparative investigation of the tribological behaviour and microstructural characteristics of two different alloys, namely, 77.3% Al--1.8% Fe--16.7% Si (Al--Si-based alloy) and 62.9% Al--14.4% Fe-- 16.9% Si (Al--Fe--Si-based alloy). High temperature alloys are fabricated by stir-casting technique. Tribology analysis is conducted to assess wear, crack formation, and cavity zones for both alloys using scanning electron microscopy. In addition, optical micrography is used to examine their microstructures. The results reveal significant differences between the two alloys: with the high concentration, Si-alloy specimen exhibits higher Vickers hardness and superior wear resistance compared to the low-concentration Si-alloy specimen. Optical micrographs confirm a well-defined grain distribution for the former alloy and a similar homogeneous microstructure for the latter. [ABSTRACT FROM AUTHOR]

In order to achieve the goal of reducing surface damage during coordinated mining of large dip (inclined) coal seams, taking the occurrence conditions of coal seams in a certain mine in Gansu Province as the background, UDEC numerical simulation software was used to explore the problem of controlling surface movement and deformation during coordinated mining of large dip (inclined) coal seams. The results indicate that during the mining of large dip (inclined) coal seams, the surface damage is more severe when the working face is buried at a shallow depth. As the burial depth of the working face increases, the impact on the surface gradually weakens; in the mining of multiple coal seams, the core problem of surface loss reduction in coordinated mining between coal seams is to make the surface of the working face with shallow buried depth not move or move less, make the surface further sink within the influence range of coal pillar, reduce the uneven deformation degree of surface subsidence and movement deformation, and prevent large mining cracks on the surface; the uniformity of surface movement, the degree of surface tension and the degree of surface deformation can be characterized by the coefficient of variation, the slope of horizontal movement in the tension region, the surface level, inclination and curvature deformation; the optimal fault distance of the working face controlled by surface movement and deformation under this geological mining condition is 80 m, the horizontal distance of the remaining coal pillar of 1# coal from the uphill boundary of 4# coal working face is about 71.9 m, and the distance from the downhill boundary is 39.9 m.

Damage to the substrate hinders the application of laser paint stripping (LPS) on carbon fiber reinforced polymers (CFRP), but the damage mechanism is currently unknown. In this paper, the LPS characteristics of CFRP, such as paint stripping depth, surface morphology and dynamic behavior, are firstly obtained. Subsequently, the surface damage mechanism of CFRP is discussed in detail by theoretical analysis and finite element method, and the effect of substrate damage on adhesive properties is investigated. The results show that it is difficult for LPS to obtain a complete surface free of paint residue. The strong laser plasma impact and resin pyrolysis pressure cause the resin to crack and flake before the paint is fully ablated. The carbon fiber then breaks and are thrown outward by heat and forces, and the surface with slightly fracture of the fiber will facilitate bonding with the paint.

The present paper is concerned with the Rayleigh wave propagation in the machined surface with a thin damaged layer with residual stress. We assume that the layer and the half-space are bonded perfectly to each other. Biot's theory of small deformations influenced by initial stress forms the basis for this study. With the help of the effective boundary condition method, a third-order approximate secular equation of Rayleigh waves is established for the case that the layer and half-space are both orthotropic. In addition, an explicit third-order approximate formula for the Rayleigh wave velocity is derived from the secular equation. By considering a sample of silicon wafer by fine grinding with fine abrasive grains, the accuracy of the approximate formula has been verified. This study is meant to serve as the mathematical foundation for non-destructive testing of residual stress in the practical applications. [ABSTRACT FROM AUTHOR]

The effects of laser shock peening (LSP) on the surface state and wear resistance of M50 steel are studied by microstructure observation, hardness, and residual stress detection. Results show that after LSP, the carbides on the surface of steel are broken and micro-pits appear. After removing the surface carbide damage by electrolytic polishing, the number of sub-surface carbides increases, and the maximum content is 26.1%. After LSP, the wear resistance of the steel is improved because LSP causes a large residual compressive stress on the surface. The wear performance of the sample after removing the surface damage becomes better, which is related to the elimination of many crack sources and the larger residual compressive stress. [ABSTRACT FROM AUTHOR]

Glycinium oxalate (GO) and Bis(glycinium) oxalate (BGO) crystals are successfully grown using the slow evaporation solution growth technique. Following their growth, the crystals are subjected to a series of acoustic shock pulses. The effects of these shock pulses on the structural, optical, dielectric, and morphological properties of the crystals are comprehensively analyzed using various characterization techniques, including powder X‐ray diffraction (XRD), UV‐Visible spectroscopy, dielectric spectroscopy, and optical microscopy. Structural analysis through XRD reveals shifts in diffraction peak positions, indicating structural deformations. Fourier transform infrared spectroscopy analysis assesses the chemical stability of GO and BGO under shocked conditions. UV‐Visible spectroscopy shows alterations in optical transmission with successive shock pulses, attributed to structural and surface defects. Dielectric properties are investigated over a frequency range from 1 Hz to 1 MHz, revealing variations in dielectric constant and loss tangent, which provide insights into the electrical behavior of the materials under normal and shocked conditions. Optical and scanning electron microscopy examine surface morphology, visualizing defects induced by the shock pulses. This study highlights the significant impact of shock pulses on the structural properties, optical transmission, dielectric properties, and surface morphology of GO and BGO crystals, offering valuable information on their resilience under dynamic conditions and potential applications. [ABSTRACT FROM AUTHOR]

Mechanical contacts in dry conditions are often characterized by an interfacial layer called “third body”, which generally originates from the degradations of the surfaces, but which can exhibit strongly different material properties. This layer is a direct consequence of past wear, but also exerts a control on the rate at which surfaces in contact will keep getting worn. A comprehensive understanding of mechanical contacts therefore relies on a theory describing the interplay between this sheared layer and the moving surfaces which confine it. In this paper, we make a step towards such a theory by quantitatively investigating the link between the flow regime of the third body and the mechanical loading it applies to the surfaces. For that purpose, a previously developed local model of solid flow based on the Multibody Meshfree Approach is employed, in order to simulate characteristic flow regimes identified in experiments. Typical stress concentration patterns endured by the surfaces are then described and quantified, and a simple damage model is used to demonstrate how such a model could lead to wear prediction. We demonstrate that agglomerated flow regimes are prone to enhance large and deep damaging of surfaces, while granular third body flows have a more limited and shallow damaging effect. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced silicon carbide ceramic matrix composites (C f /SiC composites) have a wide range of applications in aerospace, nuclear energy, braking systems owing to its excellent mechanical performance. Nevertheless, the hardness, brittleness, heterogeneity, and anisotropy of C f /SiC composites give rise to difficulties in machining them. In addition, the characterization and formation mechanism of surface damage in the grinding of C f /SiC composites have not been fully elucidated. The purpose of this paper is to provide a characterization method for surface damage of C f /SiC composites and an evaluation index for surface edge chipping damage (SECD) through conventional scratching (CS) / ultrasonic vibration assisted scratching (UVAS) tests with single abrasive. Towards revealing the surface damage behavior of C f /SiC composites during scratching, as well as the impact of fiber orientation on surface damage. The findings indicate that main forms of surface damage of C f /SiC composites in single abrasive scratching are fiber breakage, fiber fracture-shedding, fiber fracture, fiber-matrix interface debonding, interface fragmentation, matrix cracking, and matrix microcracks. Further, ultrasonic vibration could help to suppress the SECD, and the SECD factor was smallest when scratching along the perpendicular fiber. Furthermore, the fiber orientation can significantly affect the scratching force and cross-sectional area of scratches on C f /SiC composites via single abrasive scratching. The tangential scratching force was usually smaller as compared to the normal scratching force, and the cross-sectional area of scratches in UVAS is smaller than that in CS. Based on the above findings, this study elucidates the formation and evolution of surface damage after scratching under different fiber orientations, filling the research gap in surface damage under ultrasonic assisted machining of C f /SiC composites and providing technical guidance for the machining. [Display omitted] [ABSTRACT FROM AUTHOR]

Creating a smooth surface finish with nanometer-scale roughness on SiC is extremely difficult due to its hard, brittle properties and crystal anisotropy. In this study, nanoscratching tests were performed on single-crystal 4H-SiC along various crystal directions by using a sharp Berkovich tip (radius ~150 nm) and a blunt spherical tip (radius ~1 μm), respectively, to reveal the effects of tool geometry on its surface integrity. Results indicate that, under the same load conditions, the Berkovich face-forward tip produced the greatest penetration depth, followed by the Berkovich edge-forward tip and the spherical tip. The extent of surface and subsurface damage caused by the three tips follows the same trend as the penetration depth. Phase transformation did not occur in the scratched surface with the three tips, while it was occurred in the chips generated with Berkovich face-forward tip. The critical load for surface crack formation was larger when scratching along <01−10> directions compared to scratching along <11−20> directions, independent of tool geometry. Microcrack-like defects may form in the subsurface even the surface is free of damage. The microcracks were caused by {01−11} pyramidal and slip and by {11−22} pyramidal slip when scratching along <11−20> and <01−10> directions, respectively. [ABSTRACT FROM AUTHOR]

Two-dimensional ultrasonic-assisted grinding (2D-UAG) has exhibited advantages in improving the machining quality of hard and brittle materials. However, the grinding mechanism in this process has not been thoroughly revealed due to the complicated material removal behaviors. In this study, multi-step 2D-UAG experiments of silicon carbide are conducted to investigate the effects of machining parameters on surface quality. The experimental results demonstrate that the tool amplitude and the workpiece amplitude have similar effects on surface roughness. In the rough grinding stage, the surface roughness decreases continuously with increasing ultrasonic amplitudes and the material is mainly removed by brittle fracture with different surface defects. Under semi-finishing and finishing grinding steps, the surface roughness first declines and then increases as the tool amplitude or workpiece amplitude grows from 0 μm to 8 μm and the inflection point appears around 4 μm. The surface damage contains small-sized pits with band-like distribution and localized grooves. Furthermore, the influences of cutting parameters on surface quality are similar to those in conventional grinding. Discussions of the underlying mechanisms for the experimental phenomena are also provided based on kinematic analysis. The conclusions gained in this study can provide references for the optimization of machining parameters in 2D-UAG of hard and brittle materials. [ABSTRACT FROM AUTHOR]

Yttria particle reinforced tungsten plates with different thickness reduction were prepared by powder metallurgy technology combined with rolling process. The prepared samples with different recrystallization volume fractions were subjected to transient laser thermal shock experiments to study the surface damage and microstructure evolution under the synergistic effect of recrystallization caused by long-term steady-state heat load and transient thermal shock. In the results, the cracks, melting, and other damages occur on the sample surface because of the thermal shock loading. Moreover, the recrystallization process would accelerate the widening of cracks and the enlargement of melting area, which greatly reduces the ability of the materials to resist transient heat loading. Under the same power density, the damage level of the samples with 67% thickness reduction is obviously lower than that with 50% thickness reduction, and the former has better thermal shock resistance; the molten zones of these two samples are composed by the columnar grains, which are associated with the grain size of the initial matrix below, and the columnar grains formed in rolled samples are finer and numerous, while those of the fully recrystallized samples are coarser.

ABSTRACTLaser surface texturing (LST) with different patterns was performed on silicon nitride (Si3N4) ceramic. Effect of patterns created by LST on coefficient of friction (COF) and surface damage under dry friction was investigated. Results indicated that fluctuation of COF decreased with the increasing loading force for both un-textured and textured samples. Under the same loading force, COF of Si3N4 ceramic with textured patterns was more stable than the samples with smoothly finished surface. The COF of textured samples was not always lower than that of un-textured samples. This may be caused by differences in the distribution of debris and the continuity of surface contact. The worn surface existed damages of plow and crack. However, peeling was observed on un-textured samples only. The surface damage of textured samples was slighter than un-textured samples. Especially under the high loading force, catastrophic damage appeared on the smooth surface. The worn surface of textured samples still maintained the similar state. This could be mainly due to the more complex friction process on the surface of textured sample. The wear rate of the frictional pair was also studied. The mechanisms of friction process for smooth and textured surface were analyzed.

Due to the direct contact between the probe and sample, the contact of the four-probe method is important for the structural integrity of the sample and the accuracy of electrical resistivity measurements, especially for surface-coated metal foils with multilayered structures. Here, we analyzed the accuracy and stability of four-probe method probing on different sides of copper (Cu) foils covered with graphene (Gr). Theoretical simulations showed similar potential distributions on the probe tip when probing on the Cu and Gr sides. The resistivity of the Gr/Cu foil was 2.31 ± 0.02 μΩ·cm when measured by probing on the Cu side, and 2.30 ± 0.10 μΩ·cm when measured by probing on the Gr side. The major difference in the mean deviation is attributed to surface damage. In addition, the method of probing on the Cu side was sensitive to the resistivity changes of Gr induced by polymers with a dielectric constant range of 2~12, which is consistent with the calculations based on the random phase approximation theory. Our results demonstrated that the probing position on the metal side in the four-probe method can effectively protect the structural integrity of the functional surface-coated layer and maintain the high sensitivity of the measurement, providing guidance for the resistivity measurements of other similarly heterogeneous materials. [ABSTRACT FROM AUTHOR]

Surface damage of concrete induced by freezing and thawing (F-T) cycles in cold regions is characterised by peeling and pits as features of the damaged concrete surface, which needs characterising before repairing. A spot laser ranging system was established with high accuracy, and its ability to detect concrete surface features was evaluated. A 50 mm × 50 mm zone on a surface of C30 concrete specimen, with 2550 measurement points in it, was defined to obtain vertical displacements and other parameters. Mean vertical displacement of measurement points increase with F-T cycles. Effectiveness of the proposed method to characterise concrete surface damage is verified by significant regression relationship between mean vertical displacement and mass of scaling substances per unit area. Analysis of other parameters reveals that frost pit's depth increases within initial 8 F-T cycles, while its cross-sectional area increases in the subsequent 12 F-T cycles. However, in the final 8 F-T cycles, frost pit's cross-sectional area increases more significantly. Thus, the system is well performed in detecting frost pits on concrete surface non-destructively. The insights prolongate application of laser technology, which provides a new perspective to study the evolution of surface damage of concrete subjected to F-T cycles. [ABSTRACT FROM AUTHOR]

With the rapid development of silicon carbide (SiC) power devices and chip technology, the demand for grinding process of SiC wafers has become increasingly crucial due to the escalating requirements for physical strength, heat dissipation and size. Therefore, grinding process of SiC wafers has gradually become an important issue in manuscription processing. Due to its low fracture toughness, the SiC wafers are prone to cracking during grinding processes. It's a big challenge in achieving an efficient and high-quality grinding process for SiC wafers. Based on the process and principle analysis of SiC wafer grinding, the influence of four key parameters in the grinding process, i. e., grinding wheel size, feed rate, grinding wheel speed and chuck table speed on wafer surface edge breakage, were studied in this paper. The process of improving the processability of wafer by annealing is presented, and the surface integrity improving process of wafer is proposed. The study reveals the control method of wafer grinding processing surface quality, offered an efficient process route for reducing surface damage and improving the surface layer quality of chips, and verified the machining effect through experiments. The relevant results have important guiding significance for the wafer grinding process of hard and brittle materials. [ABSTRACT FROM AUTHOR]

Laser surface texturing (LST) with different patterns was performed on silicon nitride (Si3N4) ceramic. Effect of patterns created by LST on coefficient of friction (COF) and surface damage under dry friction was investigated. Results indicated that fluctuation of COF decreased with the increasing loading force for both un-textured and textured samples. Under the same loading force, COF of Si3N4 ceramic with textured patterns was more stable than the samples with smoothly finished surface. The COF of textured samples was not always lower than that of un-textured samples. This may be caused by differences in the distribution of debris and the continuity of surface contact. The worn surface existed damages of plow and crack. However, peeling was observed on un-textured samples only. The surface damage of textured samples was slighter than un-textured samples. Especially under the high loading force, catastrophic damage appeared on the smooth surface. The worn surface of textured samples still maintained the similar state. This could be mainly due to the more complex friction process on the surface of textured sample. The wear rate of the frictional pair was also studied. The mechanisms of friction process for smooth and textured surface were analyzed. [ABSTRACT FROM AUTHOR]

Traditional surface damage detection algorithms for agricultural products cannot be applied to large-scale instances due to the difficulty of their implementation. Thus, research on automatic identification and classification algorithms for agricultural products surface damage based on deep learning has emerged. This study proposed a deep learning-based algorithm for automatic identification and classification of surface damage of agricultural products and compared it with six mainstream classification models in plantvillage in terms of generalization ability, training time, and amount of pre-training data. The results proved that the model proposed in this study was the best in all aspects and had the highest accuracy when the pre-training data reached 40,000. This study verified the superiority and generalization ability of the proposed model and provided a new solution and reference standard in the field of agricultural product surface damage detection. Further, the results provided valuable reference and inspiration for related research and practice. [ABSTRACT FROM AUTHOR]

In the agricultural field, concrete headworks is the most important structure for the irrigation system. In recent years, a number of agricultural concrete infrastructures aging for a long-term period have been increasing. For maintenance and management, conventional inspection methods are time-consuming and costly, such as the electromagnetic wave method and elastic wave method. The detection of surface damage is more effective, safe and reliable than before since the laser scanning method provides detailed geometric information about the structure. The fundamental studies on point cloud data have been conducted in the civil engineering fields; nevertheless, the characteristics of point cloud in agricultural infrastructures, such as dam, headworks and canal, have not been discussed. In this study, 3D point clouds are generated for a concrete irrigation structure using the laser scanning method. The characteristics of surface damage which are quantitatively evaluated using point cloud information, geometric information and intensity parameter are investigated. The types of detected damage are efflorescence and cracks. It is investigated whether point clouds generated from a single scan or multiple scans are more effective for highly accurate detection. The characteristics of surface damage are evaluated by geometric features. The distance between the fitted plane and points is calculated by RANSAC algorithm and roughness parameter. The amount of efflorescence is detected by the distance between the fitted plane from RANSAC algorithm and points. The crack is detected by the local plane fitting method. The types of damage are characterized by the intensity parameter which is related to the color, roughness and moisture of the object. The surface damage and condition are evaluated by both geometric information and intensity parameter. These results show the unique parameters of point clouds from laser scanning methods, such as geometric features and intensity parameter, are useful to evaluate the characteristics of surface damage. [ABSTRACT FROM AUTHOR]

Abstract The surfaces of lotus leaves with micro- and nano-waxy cuticle structures are superhydrophobic and possess a self-healing ability to regain hydrophobicity after damage. Inspired by this phenomenon, the problem of water-repellent coatings used in natural environments failing to perform after damage can be solved if these coatings are endowed with rapid self-repair and self-growth functions. However, there has been almost no exploration into the hydrophobicity self-repair process in lotus leaves. The changes in surface morphology during the hydrophobicity recovery process are not understood. There is a lack of research on the hydrophobicity recovery in lotus leaves. In this study, the damage and recovery experiments on lotus leaf surfaces were carried out in an artificial climate chamber, and the water repellency recovery process and typical water repellency roughness parameters regained time were obtained. Upon analyzing the differences in the recovery process of different damage types, the recovery mechanism after lotus leaf surface damage was obtained. Finally, it was found that the microscopic roughness determined the static contact angle (WCA) of the lotus leaf surface, and the nanoscopic roughness determined the rolling angle (SA). The dual factors of the recovery of the extruded epidermal tissue and the regeneration of the epidermal wax crystals determined the hydrophobicity recovery process in damaged lotus leaves.

The azimuth wheel-rail of large reflector antennas is one of the key components, it not only supports the whole weight of the antenna, but also directly affects the antennas’ pointing performance by its surface accuracy. Usually, the whole weight of the large reflector antenna is thousands of tons, its azimuth frame rollers have great contact stress with the wheel-rail surface, repeated rolling can cause rolling contact fatigue on the wheel-rail surface, resulting in wear, cracks and other damage to the wheel-rail, and even lead to failure or fracture of the wheel-rail in serious cases, so it is very important to monitor the damage of the antenna wheel-rail. Current studies are based on Hertzian theory for stress analysis of rollers and wheel-rails, it cannot visually determine the damage. In order to visually detect the usage of antenna wheel-rail surfaces, this paper, for the first time, proposed the method using electromagnetic ultrasonic detection to detect the damage of antenna wheel-rail surface. Based on the principle of electromagnetic ultrasonic nondestructive testing, the simplified wheel-rail model containing wear, corrosion and crack damages are simulated. The results show that this method can effectively detect the surface damage of the antenna wheel-rail surface, and it can provide an important reference for the research of wheel-rail damage detection of large reflector antennas.

In many steel mills, the working life of continuous casting machine rollers is relatively short, requiring frequent replacement and negatively impacting production efficiency. To effectively extend the service life of these rollers, this study focuses on a continuous casting machine at a steel mill in China. A numerical simulation was conducted, revealing that the rollers in contact with the high-temperature casting billet experience significant thermal and stress impacts. The traditional cooling channel struggles to sufficiently reduce both the surface temperature and stress, resulting in severe thermal fatigue damage to the roller surfaces. Observations of roller surface wear showed signs of adhesive wear, fatigue cracks, and spalling occurring in various regions of the roller, which aligned with the stress distribution predicted by the simulation. In response, the cooling channel structure was modified to enhance the cooling effect of the water. Optimization of both the cooling channel structure and its parameters was carried out using a coupled flow-heat-force numerical simulation method. The optimized cooling channel effectively improved the working condition of the continuous casting roll, as the maximum temperature of the roll surface was reduced from 810 K to 591 K, the circumferential temperature difference was reduced by 38%, and the maximum equivalent stress decreased from 791 MPa to 558 MPa. This adjustment also resulted in a more uniform surface temperature distribution, mitigating the sudden fluctuations in normal stress that are typical of conventional rollers.

The surfaces of lotus leaves with micro- and nano-waxy cuticle structures are superhydrophobic and possess a self-healing ability to regain hydrophobicity after damage. Inspired by this phenomenon, the problem of water-repellent coatings used in natural environments failing to perform after damage can be solved if these coatings are endowed with rapid self-repair and self-growth functions. However, there has been almost no exploration into the hydrophobicity self-repair process in lotus leaves. The changes in surface morphology during the hydrophobicity recovery process are not understood. There is a lack of research on the hydrophobicity recovery in lotus leaves. In this study, the damage and recovery experiments on lotus leaf surfaces were carried out in an artificial climate chamber, and the water repellency recovery process and typical water repellency roughness parameters regained time were obtained. Upon analyzing the differences in the recovery process of different damage types, the recovery mechanism after lotus leaf surface damage was obtained. Finally, it was found that the microscopic roughness determined the static contact angle (WCA) of the lotus leaf surface, and the nanoscopic roughness determined the rolling angle (SA). The dual factors of the recovery of the extruded epidermal tissue and the regeneration of the epidermal wax crystals determined the hydrophobicity recovery process in damaged lotus leaves. [ABSTRACT FROM AUTHOR]