Search

This paper utilizes a coupled chemomechanical model that integrates chemical reactions, diffusion, and mechanical deformation to describe the high-temperature interfacial reactions and stress evolution within an enamel coating/Ni-based super-alloy system. Through finite element simulation, we conduct a comprehensive analysis of multiple reactions and processes at the interface. Experimental characterization of the concentration distribution of various elements is employed to verify the accuracy of the proposed chemomechanical model. Additionally, the simulation reveals that the interface region experiences compressive circumferential stress, which can potentially lead to interfacial failure due to buckling. On the other hand, the enamel coating undergoes tensile circumferential stress, resulting in the formation of vertical surface cracks. These findings hold practical implications for the development of advanced coatings with enhanced durability and performance. Future research can further optimize coating design and enhance the reliability of high-temperature applications based on these results. [ABSTRACT FROM AUTHOR]

Highlights In this work, the behavior of carbon fiber reinforced polymer composites (CFRPs) interleaved with electrospun veils under low velocity impact (LVI) conditions and extreme environmental temperatures was investigated. 2/2 twill carbon fiber/epoxy laminates were subjected to LVI at three energy levels (10, 20, and 30 J), and three temperatures (−50°C, room temperature, and 100°C). Two interleaved configurations were explored (six veils placed symmetrically with respect to the middle plane of the laminate and with respect to the external layers of the laminate). Particularly at room temperature and up to 20 J, nanofibrous interlayers effectively reduced localized deformation (by about 13.0%) and delamination (by about 12.2%) when positioned in the outer ply interleaved configuration compared to the reference laminate. At 100°C, this effect is maintained at 10 J, preventing an increase in the delaminated area. At −50°C and 10 J, the promotion of delamination prevented back surface fiber failure. Regarding post‐impact flexural properties, the presence of nanoveils ensured superior mechanical properties compared to the corresponding reference laminate impacted at the same conditions, demonstrating their efficacy in enhancing the damage tolerance of the overall laminate. Electrospun veils were interleaved in 20 layers of 2/2 twill carbon/epoxy laminate. Three configurations were tested under LVI at 10 J, 20 J, 30 J, and −50°C, RT, and 100°C. Observed damage modes include delamination, indentation, and back surface fiber cracks. Veils symmetrically placed in external layers limit delamination at 20 J (RT) and 10 J (100°C). Electrospun veils enhanced CFRP bending and residual post‐impact properties at RT and 100°C. [ABSTRACT FROM AUTHOR]

Purpose: Modifying soil surface conditions is essential in managing water and soil resources. Although the use of soil microorganisms in the bioengineering management in soil and water conservation has been confirmed, the controllability of the surface cracks morphometry on petroleum-contaminated soils using microorganisms has yet to be studied. Therefore, this study aimed to investigate the effect of inoculating soil microorganisms on changing the surface cracks' pattern of soil contaminated with petroleum. Materials and methods: In 2022, the studied soil was taken from Iran's Tehran Oil Refinery area from the top 30 cm of the earth's surface and transferred to the Rain and Erosion Simulation Laboratory of Tarbiat Modares University at the Faculty of Natural Resources. The predominant cyanobacteria of Microcoleus sp. Oscillatoria sp. Lyngbya sp. Nostoc sp, and Phormidium sp. bacteria of Bacillus sp. and Azetobacter sp. fungus of Penicillium oxalicum were identified, purified and proliferated. The study was conducted at a 0.5 × 0.5-m plot scale in two replications for four treatments. Uncontaminated and gasoil-contaminated soils, during one month, were inoculated by bacteria, cyanobacteria, and fungus. The soil was contaminated using 720 mL of gasoil evenly sprayed. The morphometric characteristics of soil surface cracks were investigated using the PCAS software. Results and discussion: Results indicated that soil microorganisms influence the soil cracking patterns. So, the mean area, length, and width of cracks increased by 99.55%, 50.90%, and 29.60% in uncontaminated plots inoculated with cyanobacteria compared to the control treatment. In gasoil treatment, fungus-inoculated soils performed better than control plots, and the mean area and length increased by 19.51% and 29.58%, respectively, while width decreased by 17.29%. Microorganisms caused the agglutination of aggregates by secreting enzymes and exopolysaccharides, stabilizing soil particles, generating cracks, covering the soil surface, and improving the soil's rheological properties. Conclusion: Finally, the results of the present study showed that modifying the surface of the petroleum-contaminated soil by inoculating soil microorganisms is a way to improve the hydrologic and rheologic characteristics of the soil. [ABSTRACT FROM AUTHOR]

Highlights: Most of the studies on oil tanks have focused on the analysis of deformation and settlement, and more research needs to be done on crack extraction from external LNG tanks. Oil tanks are more sensitive to temperature due to the lower temperature inside the tank. Using infrared images as a dataset for crack recognition can identify cracks that the naked eye cannot see, and a convolutional neural network that introduces a channel attention mechanism is used for crack recognition with a recognition accuracy of 85.9%. The automatic extraction of three-dimensional (3D) crack point clouds using depth images is novel and accurate, with an accuracy of about 97.6%. The precise detection and ongoing surveillance of surface fractures on exterior LNG storage tanks are crucial in guaranteeing the secure transit and storage of natural gas. Undetected fractures have the potential to result in the release of liquefied natural gas (LNG), hence presenting a significant risk to both public health and the environment. This paper presents a novel approach for crack identification, which involves the integration of thermal infrared images and point clouds derived from close-range images captured by unmanned aerial vehicles (UAVs). The aim of this approach is to overcome the limitations of conventional manual detection methods, namely in terms of efficiency and safety concerns. The primary approach for acquiring two-dimensional photographs of the tank surface is the utilization of infrared technology to generate an infrared dataset capturing the presence of fractures on the storage tanks' exterior. The utilization of the attention mechanism convolutional neural network is employed during the process of model training. The UAV close-range photos were utilized in close-range photogrammetry to generate an accurate point cloud model. This was achieved by incorporating control point coordinates and matching feature points. The infrared photos that were discovered were subsequently matched with this particular model. The 3D model that was officially was employed as a point of reference on the unfolded two-dimensional (2D) plane. To construct the depth image, a least-squares approach of least-column fitting was utilized. In order to validate the accuracy of the automated extraction process, a manual crack extraction was conducted on the original close-range image point cloud of the tank exterior. The results indicated that the extracted cracks exhibited an accuracy level of around 97.6%. The experimental findings demonstrate that the process of crack extraction exhibits a high level of accuracy, hence presenting numerous possible applications in the realms of maintenance management and intelligent monitoring. The utilization of this technology is appropriate for the purpose of monitoring the thermal conditions and structural soundness of LNG storage tanks. [ABSTRACT FROM AUTHOR]

This study identifies optimal cooling rates and critical strain thresholds to prevent cracking in Cr12MoV billets during continuous casting through thermoplastic experiments, high‐temperature tensile tests, and a thermal–mechanical coupled simulation model. The result shows that the critical strain (dimensionless) for corner crack propagation at temperatures of 750, 800, and 850 °C are determined to be 0.125, 0.132, and 0.147, respectively. The critical strain for internal crack formation is found to be 0.03. The simulation results indicate that as the billet enters the first straightening roll, the corner strain is 0.035 and the central strain is 0.025. Upon exiting the fourth straightening roll, the corner strain increases to 0.038, while the central strain decreases to 0.021. Through simulation and high‐temperature confocal in situ observation, it can be concluded that a surface cooling rate of ≥5 °C s−1 effectively prevents cracks during the bending and straightening stage of continuous casting. [ABSTRACT FROM AUTHOR]

Sintered NdFeB, owing to its outstanding magnetic properties, finds widespread applications in diverse fields. However, its susceptibility to corrosion limits its utility. To enhance its corrosion resistance, a rotating transverse magnetic field is incorporated into the electrical discharge machining milling (EDM-M) process. Comparative experiments are conducted on sintered NdFeB by EDM-M, fixed transverse magnetic field assisted EDM-M(FTMEDM-M), and rotating transverse magnetic field assisted EDM-M(RTMEDM-M). Results indicate that the RTMEDM-M process yields the least surface cracks, the least "caves", and the recast layer which is the most uniform and the most continuous. Its impedance value is the highest, self-corrosion potential is the largest, and self-corrosion current density is the lowest according to its electrochemical impedance spectroscopy (EIS). In addition, its mass loss per unit area is the least, with the latest and the weakest reaction of chemical corrosion of the workpiece surface. [ABSTRACT FROM AUTHOR]

In underground engineering, the detection of structural cracks on tunnel surfaces stands as a pivotal task in ensuring the health and reliability of tunnel structures. However, the dim and dusty environment inherent to underground engineering poses considerable challenges to crack segmentation. This paper proposes a crack segmentation algorithm termed as Focused Detection for Subsurface Cracks YOLOv8 (FDSC-YOLOv8) specifically designed for underground engineering structural surfaces. Firstly, to improve the extraction of multi-layer convolutional features, the fixed convolutional module is replaced with a deformable convolutional module. Secondly, the model's receptive field is enhanced by introducing a multi-branch convolutional module, improving the extraction of shallow features for small targets. Next, the Dynamic Snake Convolution module is incorporated to enhance the extraction capability for slender and weak cracks. Finally, the Convolutional Block Attention Module (CBAM) module is employed to achieve better target determination. The FDSC-YOLOv8s algorithm's mAP50 and mAP50-95 reach 96.5% and 66.4%, according to the testing data. [ABSTRACT FROM AUTHOR]

Hydrogen‐induced cracking (HIC) in high‐strength 45CrNiMoVA steel is investigated using smooth and notched cylindrical specimens by performing uniaxial tensile tests. Specimens with different notch geometries are used to analyze the interacting effects of the stress concentration factor and HIC micromechanism. The results show that hydrogen charging reduces the elongation at fracture and the ultimate tensile strength of smooth tensile specimens. The microscopic fracture mode changes from ductile dimples with some quasicleavage fracture without hydrogen to a mixture of brittle quasicleavage and intergranular cracking with hydrogen. For notched specimens with a lower notch root radius, significant stress concentration occurs at the notch root, which enriches hydrogen in these highly stressed regions. This causes a lower notch tensile strength and greater susceptibility to hydrogen embrittlement. Microfracture observations show that the area fraction of the intergranular cracking surface increases gradually, and the brittle zone moves farther away from the notch root upon decreasing the notch root radius, causing the embrittlement index to remain high. These results will help determine the applicability of existing steel for hydrogen service and also provide guidance for developing new high‐strength martensitic steels that can resist hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

The study investigated the reinforcing effect of vetiver root on soil by conducting outdoor planting tests and indoor root tests. The cracking indexes of soil specimens with varying root contents were analyzed, and a statistical model was established to determine the relationship between the cracking indexes, the number of dry and wet cycles, and the root content. The study revealed the crack evolution law of vetiver-reinforced expansive soil. The study explored the mechanism of the vegetation root in inhibiting the cracking of expansive soil and determined the optimal planting density of vetiver grass through outdoor planting tests. The results indicate that: The surface crack rate (CR), total crack length (CL), and crack number (CN) in the root-soil specimen exhibited exponential growth with an increase in the number of wet and dry cycles. This growth was more pronounced during the first and second cycles. The vetiver root could effectively reduce soil crack formation, and the specimen's cracking resistance is positively correlated with the root content. With the root content increased, the CR, CN, and CL decreased. The logistic model is suited to the CL of added root soil. The logistic model is more suitable for the growth model of the CR of the expansive soil with low root content, while the Boltzmann model is more suitable for the growth model of the CR of the expansive soil with high root content. Width of crack (CW) is better suited to the DoseResp growth model. The Boltzmann model is more applicable to the CN in expansive soils with low reinforcement, while the logistic growth model is more suitable for the development of CN above 0.21% root content. The development of the crack network was influenced by two key factors: the root content and the number of wet and dry cycles. Under the condition of planting roots, the development of crack networks in expansive soil differs from that of expansive soil with added roots, and there is no clear pattern to follow. The inhibitory effect of the vetiver root on cracking of expansive soil is related to the planting density of vetiver. [ABSTRACT FROM AUTHOR]

The main purpose of this study was to produce biodegradable film based on kombucha mushroom (KM), so kombucha mushroom was grown and used to prepare biodegradable film. Glycerol (Gl), corn starch (St), and parsley extract (PE) were used to improve the characteristics of the kombucha mushroom‐based film. The physicochemical, thermal, and antibacterial properties of the films were investigated using different techniques. The obtained results showed that starch significantly increased the tensile strength of the film (3 Mpa) and glycerol improved the flexibility of the film (70%). Starch increased the film's resistance to dissolution in water, and parsley extract and starch improved water vapor permeability. The pure film of kombucha mushroom had good antioxidant (40% ± 2%) and antibacterial properties, and parsley extract significantly increased these properties of the film, so that the prepared film can be considered as an active film. Starch had no significant effect on antioxidant and antibacterial properties. The pure kombucha mushroom film had cracks on the surface, and the addition of starch removed these cracks and made the structure of the film more homogeneous. Electrostatic interactions between kombucha mushroom, glycerol, starch, and parsley extract were confirmed by Fourier transform infrared spectroscopy (FTIR) results. The pure film of kombucha mushroom was a completely amorphous film, which glycerol, parsley extract, and starch improved the crystallinity of the film. Glycerol and parsley extract decreased the thermal resistance of the film, but starch increased this property significantly (about 40°C), so that the kombucha mushroom/glycerol/starch/parsley extract composite film had the highest thermal resistance. In addition to having acceptable mechanical, thermal, and structural properties, the film based on kombucha mushroom can be used as an active film in the packaging of food products sensitive to microbial and oxidative spoilage due to having suitable antioxidant and antimicrobial properties. [ABSTRACT FROM AUTHOR]

Pore and crack formation in parts produced by additive manufacturing (AM) processes, such as laser powder bed fusion, is one of the issues associated with AM technology. Surface and subsurface cracks and pores are induced during the printing process, undermining the printed part durability. In-situ detection of defects will enable the real-time or intermittent control of the process, resulting in higher product quality. In this paper, a new eddy current-based probe design is proposed to detect these defects in parts with various defects that mimic pores and cracks in additively manufactured parts. Electromagnetic finite element analyses were carried out to optimize the probe geometry, followed by fabricating a prototype. Artificial defects were seeded in stainless steel plates to assess the feasibility of detecting various flaws with different widths and lengths. The smallest defect detected had a 0.17 mm radius for blind holes and a 0.43 mm notch with a 5 mm length. All the defects were 0.5 mm from the surface, and the probe was placed on the back surface of the defects. The surface roughness of the tested samples was less than 2 µm. The results show promise for detecting defects, indicating a potential application in AM. [ABSTRACT FROM AUTHOR]

Concrete surface crack detection is a critical research area for ensuring the safety of infrastructure, such as bridges, tunnels and nuclear power plants, and facilitating timely structural damage repair. Addressing issues in existing methods, such as high cost, lengthy processing times, low efficiency, poor effectiveness and difficulty in application on mobile terminals, this paper proposes an improved lightweight concrete surface crack detection algorithm, YOLOv8-Crack Detection (YOLOv8-CD), based on an improved YOLOv8. The algorithm integrates the strengths of visual attention networks (VANs) and Large Convolutional Attention (LCA) modules, introducing a Large Separable Kernel Attention (LSKA) module for extracting concrete surface crack and local feature information, adapted for features such as fracture susceptibility, large spans and slender shapes, thereby effectively emphasizing crack shapes. The Ghost module in the YOLOv8 backbone efficiently extracts essential information from original features at a minimal cost, enhancing feature extraction capability. Moreover, replacing the original convolution structure with GSConv in the neck network and employing the VoV-GSCSP module adapted for the YOLOv8 framework reduces floating-point operations during feature channel fusion, thereby lowering computational complexity whilst maintaining model accuracy. Experimental results on the RDD2022 and Wall Crack datasets demonstrate the improved algorithm increases in mAP50 by 15.2% and 12.3%, respectively, and in mAP50-95 by 22.7% and 17.2%, respectively, whilst achieving a reduced model computational load of only 7.9 × 109, a decrease of 3.6%. The algorithm achieves a detection speed of 88 FPS, enabling real-time and accurate detection of concrete surface crack targets. Comparison with other mainstream object detection algorithms validates the effectiveness and superiority of the proposed approach. [ABSTRACT FROM AUTHOR]

This study proposed a strategy to prepare metalized pellets for direct steelmaking by hydrogen cooling reduction (HCR) of iron ore pellets with a focus on the effect of H2 flow rate on the process. It was demonstrated that increasing H2 flow rate could effectively enhance the reduction performance of iron ore pellets. However, due to the influence of the countercurrent diffusion resistance of gas molecules, too high H2 flow rate no longer promoted the reduction of the pellets when the maximum reduction rate was reached. The reduction swelling index (RSI) of the pellets initially increased and then decreased with increasing H2 flow rate. This change was associated with the decreased content of Fe2SiO4 in the metalized pellets and the changes in porosity and iron particle size. The compressive strength (CS) decreased continuously, showing a sharp decline when the H2 flow rate reached 0.6 L/min. It was attributed to the significant increases in porosity and average pore size of the metalized pellets, with the presence of surface cracks. When the H2 flow rate was 0.8 L/min, the metalized pellets had the optimal performance, namely, reduction degree of 91.45%, metallization degree of 84.07%, total iron content of 80.67 wt%, RSI of 4.66%, and CS of 1265 N/p. The findings demonstrated the importance of controlling the H2 flow rate in the preparation of metallized pellets by HCR. [ABSTRACT FROM AUTHOR]

Electrocatalytic alcohol oxidation (EAO) is an attractive alternative to the sluggish oxygen evolution reaction in electrochemical hydrogen evolution cells. However, the development of high-performance bifunctional electrocatalysts is a major challenge. Herein, we developed a nitrogen-doped bimetallic oxide electrocatalyst (WO-N/NF) by a one-step hydrothermal method for the selective electrooxidation of benzyl alcohol to benzoic acid in alkaline electrolytes. The WO-N/NF electrode features block-shaped particles on a rough, inhomogeneous surface with cracks and lumpy nodules, increasing active sites and enhancing electrolyte diffusion. The electrode demonstrates exceptional activity, stability, and selectivity, achieving efficient benzoic acid production while reducing the electrolysis voltage. A low onset potential of 1.38 V (vs. RHE) is achieved to reach a current density of 100 mA cm−2 in 1.0 M KOH electrolyte with only 0.2 mmol of metal precursors, which is 396 mV lower than that of water oxidation. The analysis reveals a yield, conversion, and selectivity of 98.41%, 99.66%, and 99.74%, respectively, with a Faradaic efficiency of 98.77%. This work provides insight into the rational design of a highly active and selective catalyst for electrocatalytic alcohol oxidation. [ABSTRACT FROM AUTHOR]

The effect of shot peening (SP) on pre‐fatigue tested carburized steel was investigated. Plane‐bending fatigue tests were conducted on carburized CrMo steel that was pre‐fatigue tested and treated with SP. Fatigue cracks were induced by pre‐fatigue tests with a stress amplitude of σa = 1000 MPa, and the number of the pre‐fatigue test cycles was 2.0 × 104 (L5 test) and 4.0 × 104 (L15 test). We compared the fatigue lives of the fatigue‐damaged and smooth specimens without fatigue damage treated with the same SP. The fatigue life of the L5 tested specimens with SP was longer than that of the non‐fatigue damaged smooth specimens after SP. Therefore, the fatigue cracks introduced by the L5 test can be rendered harmless by SP. Furthermore, near‐surface material properties were evaluated and the mechanisms of rendering surface cracks harmless were investigated. [ABSTRACT FROM AUTHOR]

Featured Application: The findings of this study can inform the selection of the most appropriate post-printing process for achieving the desired final physical characteristics of 3D-printed foods. Extrusion-based three-dimensional (3D) food printing (3DFP) enhances the customization of 3D-printed foods by using multiple food pastes. Post-printing processes like baking are usually necessary and significantly impact the stability of the 3D-printed foods. This study aimed to produce multi-material 3D-printed foods using nixtamalized corn dough and chickpea paste (CP) in extrusion-based 3DFP and to study the effect of post-printing processes (water oven cooking and steam cooking) and the type of material used (single- or multi-material) on the final appearance, weight, size, and texture of the 3D-printed foods. Multi-material 3D-printed foods were successfully produced using extrusion-based 3DFP. Steam-cooked 3D-printed foods cooked uniformly and had a better appearance, as they did not develop surface cracks compared to water oven-cooked foods. Water-oven cooked foods experienced a greater weight loss of 35.6%, and higher height and length reduction of 1.5% and 8.4%, respectively. Steam-cooked multi-material 3D-printed foods were harder at 40% of strain, with force values of 66.9 and 46.3 N for water-oven cooked foods. Post-printing processes, as well as the presence of CP in the middle of the 3D-printed foods, influenced their final appearance, weight, size, and texture. This study offers interesting findings for the innovative design of chickpea- and corn-based multi-material 3D-printed foods. [ABSTRACT FROM AUTHOR]

BACKGROUND RESULTS CONCLUSION The objective of this experiment was to investigate the role of endogenous proteins and lipids in the structural and physicochemical properties of starch in heat‐moisture treatment (HMT) rice flour and to reveal their effect on starch digestibility under heat.The findings indicate that, in the absence of endogenous proteins and lipids acting as a physical barrier, especially proteins, the interaction between rice flour and endogenous proteins and lipids diminished. This reduction led to fewer starch–protein inclusion complexes and starch–lipid complexes, altering the granule aggregation structure of rice flour. It resulted in a decrease in particle size, an increase in agglomeration between starch granules, and more surface cracking on rice granules. Under HMT conditions with a moisture content of 30%, slight gelatinization of the starch granules occurred, contributing to an increased starch hydrolysis rate. In addition, the elevated thermal energy effect of HMT enhanced interactions between starch molecular chains. These resulted in a decrease in crystallinity, short‐range ordering, and the content of double‐helix structure within starch granules. These structural transformations led to higher pasting temperatures, improved hot and cold paste stability, and a decrease in peak viscosity, breakdown, setback, and enthalpy of pasting of the starch granules.The combined analysis of microstructure, physicochemical properties, and in vitro digestion characteristics has enabled us to further enhance our understanding of the interaction mechanisms between endogenous proteins, lipids, and starches during HMT. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Stratified rock masses comprise various rocks with different thicknesses, lithologies, and compositions. They exhibit unique cracking morphology and failure modes when subjected to external loads. Understanding and mastering the fracture morphology and failure laws of stratified rock masses under three-dimensional mechanical conditions is crucial for researching disasters in underground engineering geology. This paper presents a three-dimensional double-layer rock mass model established using the numerical calculation method based on mesoscopic statistical damage mechanics. The model simulates the cracking mode of the rock surface under biaxial tensile conditions. The simulation results are quantified using PCAS software. Crack indexes, such as the number of cracked blocks, average cracked block area, and surface crack rate, are used to evaluate the degree of influence of different factors on the cracking of the rock surface layer. The results indicate that the degree of surface crack development varies linearly with the degree of homogeneity (m). Additionally, the layer thickness ratio (η) is positively correlated with the average fragmentation area, and the two are logarithmic. Regardless of the model scale, the average circumference of each block is approximately equal to the model side length. The model exhibits the highest degree of crack development when the loads in the x and y directions are equal. Moreover, the degree of crack development in the model is also influenced by the loading per step, and the two are proportional. [ABSTRACT FROM AUTHOR]

The mechanical behavior and cracking patterns of thermally‐shocked additively manufactured alumina were investigated. The flexural strength of test specimens that had been heated to temperatures ranging from 200°C to 1000°C and then rapidly quenched in water was determined at ambient temperature by four‐point bending. Results indicated that the surface cracking patterns had a multifractal structure and that an increase in the thermal shock temperature led to an increase in the density and uniformity of the crack network. The flexural strength results were analyzed with Weibull statistics, where the Weibull moduli for most of the thermal shock conditions tested were found to be statistically indistinguishable. It was also found that a significant decrease (∼50%) in flexural strength occurred for heating temperatures ≥300°C. The effect of the manufacturing method on cracking patterns is discussed, as well as the implication of the material behavior for practical applications of these materials. [ABSTRACT FROM AUTHOR]

AbstractIn this study, the progress of surface crack and high cycle fatigue of the surface piercing propellers (SPPs) are investigated numerically using the finite element method. The cyclic load is calculated from the hydrodynamic pressure on the blade by simulating the fluid around the blade using the computational fluid dynamics software STAR-CCM+. The initial cracks are assumed to be created near the blade root. The fatigue life is calculated from the Paris-Erdogan equation. The results show that the crack close to the root has a shorter life and the stresses at the crack front depend on the blade-water interaction duration. [ABSTRACT FROM AUTHOR]

Steel hollow structure section (HSS) chord-to-branch joints in Vierendeel trusses are concerned for their proneness to fracture due to imperfection in fabrication. In this paper, the stress intensity factors (SIFs) for HSS chord-to-branch joints are examined based on fracture mechanics and finite element modelling. Through a well-prepared sub-modelling strategy, the influences of geometric parameters related to the crack propagation behaviour are analysed and discussed. The crack front of the HSS chord-to-branch joint without the axial stress of the branch is shown to have notably high SIFs at the deepest point and the surface point. Alternatively, the concentration of highest SIFs at the deepest point of the elliptical arc of the crack becomes significant with the increase of the axial stress of the branch. The increase of the chord wall thickness is shown to be beneficial in the reduction of the SIFs for HSS chord-to-branch joints, especially for lower chord width ratio normalized by thickness. Conversely, the influence of the crack shape indicated by larger aspect ratio on the reduced SIFs becomes obvious and consistent for greater chord width ratio normalized by thickness. The SIFs for HSS chord-to-branch joints are decreased with the increase of the normalized crack depth with respect to the chord wall thickness, particular for shallow surface cracks. Such a trend becomes obvious for the joints with lower fillet weld leg length of equal leg fillet welds with respect to the chord wall thickness or with lower weld leg length along the HSS branch with respect to that along the chord. [ABSTRACT FROM AUTHOR]

In this work, a two-parameter inversion problem is analyzed, related to surface crack widths for measuring depths of normal surface notches, based on a laser-based ultrasonic measurement method in the time domain. In determining the depth measurement formulas, the main technique is the time delay between reflected and scattered waves. Scattered waves are generated by two reflections along the bottom and three mode transformations at the surface of the crack tips. Moreover, the scattering angle of the mode-conversion waves is 30°. These two key factors lead to corrected item "2wβ" in the depth measurement formula. A laser-based ultrasonic experimental platform is built to generate and receive surface waves in a non-contact manner on aluminum and steel specimens with surface cracks. The depth measurement method proposed in this paper has been validated through theoretical, simulation, and experimental methods. Finally, in this paper, an effective approach for quantitatively measuring crack depths, based on laser ultrasound, using the time-domain properties of surface wave propagation is provided. [ABSTRACT FROM AUTHOR]

One of the key tasks to ensure infrastructure safety is the periodic detection of bridge cracks. Since manual crack detection is subjective and inefficient, it is very important to develop an automatic crack recognition system by using machine vision. Inspired by the pyramid vision transformer (PVT) and the feature pyramid network (FPN) variants, a method combining PVT, residual transformer (REST), holistically nested edge detection (HED), and downstream detection tasks is proposed in this paper, which is named EVPTMFF (efficient visual pyramid transformer and multiple-feature fusion). Based on the PVT, the multiheaded attention module was replaced and the efficient attention module was adopted, which could process the data efficiently and flexibly. To improve the performance of EVPTMFF, the original perceptual field windows were changed. The adjacent windows were partially overlapped, which was more conducive to feature interaction and improves detection performance. To prove the generalization ability of the model, three different data sets related to bridges were collected and formed. We carried out experiments on these three data sets, and EVPTMFF showed good results. Especially for larger data sets, the performance advantage was more significant. Practical Applications: The crack detection model proposed in this paper presents a good detection effect under different illumination and interference. And the detection results, collected data, time, and other information are saved to the bridge crack detection software. This can help engineers quickly and accurately detect cracks on the bridge surface, as well as predict the development trend of cracks and possible safety issues. In practical application, the bridge crack detection system can help engineers find and solve the bridge crack problem in time and avoid the security risks and economic losses caused by cracks. At the same time, the efficiency and accuracy of bridge maintenance can be improved, and the maintenance cost and time can be reduced. The bridge crack detection system can be integrated with other hardware equipment and management systems to form a complete bridge management platform, which contributes to the traffic construction and social and economic development of the city. [ABSTRACT FROM AUTHOR]

Concrete cracking is one of the most significant damage types in reinforced concrete structures due to its potential to adversely affect durability, safety, and serviceability and even reduce the bearing capacity during operation. Thus, damage inspection of damage caused by concrete cracking is important for management, maintenance, and structural assessment for both damaged and undamaged existing buildings but with concrete cracking after a long time of use that needs reconstruction or renovation. This study provides an improved building damage inspection approach by applying Unmanned Aerial Vehicles (UAVs) and state‐of‐the‐art deep learning algorithms to detect concrete cracks on building surfaces. Two distinct architectures for Convolutional Neural Networks (CNNs), namely ResNet50 and YOLOv8 based on classification, and object detection approaches to create a total of 11 models are established, trained, and compared. The classification models attained accuracy levels exceeding 99%, whereas the object detection models achieved approximately 85%. All models effectively identified and accurately located concrete cracks on building surfaces. Besides, the CNN models' capacity to detect cracks is influenced by a variety of model hyperparameters, encompassing factors such as model architecture, the number of network layers, different training dataset sizes, and the quantity of trainable parameters necessary to learn the specific features of detection targets during the training process. The results of this study ultimately demonstrate that the proposed approach can yield accurate detection results and holds high potential for application in crack inspection to advance automatic damage inspection in building structures to a greater extent. In addition, it is important to note that a universal rule cannot be established rule as a larger and more complex model, or an increased number of trainable parameters, necessarily leads to improved detection performance. Models that are trained from scratch using local datasets might not necessarily result in enhanced performance in comparison to the improvements gained through fine‐tuning via transfer learning. Therefore, an appropriate training type, dataset size, task complexity, computational resources, and time demands to achieve a balance between accuracy and efficiency should be considered for specific application scenarios. [ABSTRACT FROM AUTHOR]

The stability of the roof in coal mining plays a crucial role in ensuring safe excavation. After coal extraction, the roof experiences complex and unbalanced stress conditions, leading to diverse roof failure behaviors, particularly in the case of thick roofs. This study examines the failure behaviors of roofs with different thicknesses through a combination of on-site measurements, physical modeling, and numerical modeling. The on-site results indicate that the failure of thick roof leads to larger magnitudes, increased magnitude variance, and energy compared to thin roof. A self-developed three-dimensional roof fracture experimental platform was utilized to conduct loading experiments on roofs with different thicknesses. The experimental results reveal that roof thickness significantly impacts peak load, deformation characteristics, crack patterns, and acoustic emission (AE) signals. Thin roof failure only generates tensile cracks, while thick roof failure produces both tensile and shear cracks. This suggests that an increase in roof thickness leads to a transition in the roof's failure mode from pure tensile failure to tensile-shear mixed failure or shear failure. The energy of AE events has a threshold. When below this threshold, more AE events occur for thin roofs, and when above it, thick roofs exhibit more AE events. The digital image correlation (DIC) results and AE location indicate roof failure initiates from the upper surface of the roof, where "O" shaped cracks form around the periphery, followed by gradual development of cracks on the lower surface. Thin roofs exhibit regular "X" shaped crack on lower surface, while thick roofs display additional branching and inflection points based on "X" shaped crack on lower surface. Numerical modeling using four polygonal particle roof models confirms the influence of roof thicknesses on peak load, deformation, and crack distribution, aligning with experimental and on-site results. These findings offer valuable theoretical support for controlling the stability of surrounding rock conditions in the presence of different roof thicknesses. Highlights: Roof thickness significantly affects coal mine safety, leading to diverse roof failure behaviors. On-site measurements, physical experiments, and numerical simulations reveal insights into roof behaviors. An experimental platform was established to explore the correlation between roof thickness and failure behavior. Thicker roofs exhibit higher peak loads, reduced deflection, complex crack propagation, and a tensile-shear mixed failure or shear failure. Numerical models of polygonal particle roofs further corroborate the impact of roof thickness on failure behavior, offering practical support for coal mine stability. [ABSTRACT FROM AUTHOR]

In cold regions, rock fractures can expand under the force of frost heave pressure, potentially triggering severe geological catastrophes such as collapses and landslides on rock slopes. Nevertheless, a comprehensive study of the evolution patterns and causes of frost heave pressure within rock fractures is currently lacking. To address this gap, this paper focuses on single-cracked sandstone and identifies four distinct types of frost heave pressure curves by conducting monitoring tests under various conditions. Each type of curve was thoroughly analyzed to understand its evolution and the underlying causes. It was found that the rupture and drop type curve can be segmented into five stages: incubation, eruption, drop, equilibrium, and dissipation. The drop stage is predominantly attributed to the fracturing of the crack influenced by frost heave pressure. Compared with the rupture and drop type curve, the stable type curve, where the crack does not expand during the freeze–thaw cycle, lacks a drop stage. Furthermore, samples displaying a stable descent type curve possess a higher freezing temperature, causing a noticeable delay in the emergence of their frost heave pressure. This curve, when compared with the stable type, shows a faster reduction in frost heave pressure during the equilibrium stage. For the secondary frost heave type curve, secondary frost heave emerges within the rock fracture at the onset of thawing, with the rupture of ice proving critical to this phenomenon. The frost heave pressure distributed along the crack surfaces of the four types of curves displays a lack of uniformity. This unevenness is observed to correlate with the inconsistent growth of ice according to its self-purification principle. Finally, based on the experimental results, a novel criterion for frost heave pressure and rock fracture cracking is proposed. Highlights: Four distinct frost heave pressure curves are obtained, and the underlying causes of each are examined. The uneven growth of ice causes non-uniform frost heave pressure distribution within the fracture. Ice rupture is pivotal to the formation of secondary frost heave. A novel criterion for frost heave pressure and rock fracture cracking is proposed. [ABSTRACT FROM AUTHOR]

In order to enhance the corrosion resistance of calcium-based phosphate coating, the molybdenum-modified coating was successfully prepared by adding Na2MoO4 in a phosphate bath. The prepared composite film layers were studied by EDS, XRD and SEM. The corrosion resistance performances of the films were investigated by electrochemical measurements. The results showed the main composition of molybdenum-modified film was MoO2, MoP2, and MoP4, the diameter of cracks on the surface of the coating was significantly reduced, which provided better protection to the substrate. In addition, the potentiodynamic polarization curves of the molybdenum-modified film show that the corrosion potential was positively shifted by 0.068 V compared to the calcium-based phosphate coating and the corrosion current was reduced to 2.556 × 10 − 5 A · cm − 2 , indicating improved corrosion resistance. [ABSTRACT FROM AUTHOR]

In this study, the response of soft clay was assessed during electrokinetic consolidation. The laboratory-based experimental study was conducted in a custom-designed test set-up focusing on soft clay's engineering and physicochemical response during and at the end of the electrokinetic consolidation. Six electrokinetic consolidation tests were performed under self-weight for 24 h with different voltage gradients. The operational response was investigated by monitoring the electric current and the power consumed during the test. Further, the variation of ohmic heating, volumetric water content, and water potential was continuously measured. The efficacy in enhancing the engineering response is analysed by investigating cumulative discharge, surface settlement, water content, and undrained shear strength of the soft soil. At the end of the test, the effect of electrochemical reactions in altering the soft clay's pH, microfabric, and mineral phases was investigated. Finally, the quantification of the surface crack was investigated, and their dependence on the applied voltage gradient was established. The study results show substantial enhancement in the engineering characteristics of soft clay. It significantly accelerates the dewatering efficacy, increases the undrained shear strength and surface settlement, and reduces the water content of the soft clay irrespective of the applied voltage gradient. The electrokinetic consolidation increases the temperature of the soft clay. The measured surface cracks give the crack intensity factor of 1.95, 2.10, and 2.15% for the applied voltage gradient of 0.05, 0.10, and 0.15 V/mm, respectively. [ABSTRACT FROM AUTHOR]

Corrosion of steel rebar in reinforced concrete (RC) constructions is an issue of great concern toward ensuring the integrity of civil structures, and thus, detection of the on-set of corrosion process, if any, will tremendously help in taking timely and effective measures. To address this issue, the current work aims to evaluate the potential of using different nonlinear ultrasonic (NLU) methods to detect corrosion through analysis of the signal characteristics from both time and frequency domain. Three NLU parameters (from time and frequency domain response) are studied by using an indirect type of measurement obtained from RC specimens undergoing accelerated corrosion process. Signal subtraction method (SSM)-based time domain nonlinear parameter and sideband peak count (SPC)-based frequency domain nonlinear parameter are found to be effective in detecting the specific damage stages during the corrosion process. There exists a significant shift in the cumulative nonlinear parameter curve arrived based on SSM when the mass loss is around 14 g, corresponding to the time at which the first surface crack of about 0.2 mm width appeared. Cumulative nonlinear parameter curve arrived based on SPC, shows a drastic shift when the mass loss is only 2 g, i.e., at the time when microcrack initiates inside concrete. To provide a complete monitoring solution, the complementary abilities of both time and frequency domain NLUs are used for the first time to formulate a damage index that can effectively monitor the progression of damage caused by corrosion from the beginning of the process until the point of failure. [ABSTRACT FROM AUTHOR]

Understanding the cracking behaviors and failure mechanisms of soft rocks with existing cracks is crucial in designing rock engineering structures. Hence, we studied the influence of crack parameters, including crack inclination angle, crack number, and crack form, on the strength characteristics and cracking behaviors of silty mudstone using uniaxial compression tests and numerical simulation. The mechanisms of crack initiation, propagation, and coalescence in silty mudstone with preexisting cracks are discussed in this paper. The results showed that the stress-strain curves of silty mudstone with preexisting cracks can be divided into three stages: the load compaction, crack extension, and postpeak damage stages. Preexisting cracks had a weakening effect on the mechanical properties of silty mudstone, and the main order of influence of the various factors was crack inclination angle, crack number, and crack form. The failure mode of silty mudstone with preexisting vertical cracks was mainly composite tensile-shear failure; the failure modes of rocks with single and double cracks were tensile failure, shear failure, and composite tensile-shear failure. The damage process of silty mudstone with preexisting cracks under stress was as follows. The propagation and coalescence of cracks caused cracking of weak surfaces within the rock mass. The cracks propagated along the axial stress direction or preexisting crack direction under different stress states to form macroscopic crack surfaces, which ultimately led to rock mass failure. In addition, the strength characteristics and cracking behaviors of silty mudstone simulated using FLAC3D version 6.0 were consistent with the experimental results. [ABSTRACT FROM AUTHOR]

In recent years, computer vision technology has been extensively applied in the field of defect detection for transportation infrastructure, particularly in the detection of road surface cracks. Given the variations in performance and parameters across different models, this paper proposes an improved Faster R-CNN crack recognition model that incorporates attention mechanisms. The main content of this study includes the use of the residual network ResNet50 as the basic backbone network for feature extraction in Faster R-CNN, integrated with the Squeeze-and-Excitation Network (SENet) to enhance the model's attention mechanisms. We thoroughly explored the effects of integrating SENet at different layers within each bottleneck of the Faster R-CNN and its specific impact on model performance. Particularly, SENet was added to the third convolutional layer, and its performance enhancement was investigated through 20 iterations. Experimental results demonstrate that the inclusion of SENet in the third convolutional layer significantly improves the model's accuracy in detecting road surface cracks and optimizes resource utilization after 20 iterations, thereby proving that the addition of SENet substantially enhances the model's performance. [ABSTRACT FROM AUTHOR]

BACKGROUND: The study aimed to determine the effects of instant controlled decompression of steam pressure, termed as ICPD (instant controlled pressure drop) on fresh tea leaves, when combined with refractance window drying (RWD) of rolled green teas during green tea manufacturing. The ICPD steam treatment pressure (TP; 0.1–0.3 MPa), treatment time (TT; 10–20 s) and refractance window drying temperature (RWDT; 70–90 °C) were used as the processing parameters for manufacturing of green tea. RESULT: Response surface methodology was employed to enumerate the effects of ICPD process conditions and temperature of RWD on total phenolic content (TPC), total flavonoid content (TFC) and DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) radical scavenging activity of the green tea infusion. An optimum condition for green tea processing was found at TP 0.2 MPa, TT 20 s with RWDT at 70 °C. In comparison to made green tea manufactured without ICPD treatment, the ICPD treated green tea showed enhanced TPC, TFC and DPPH radical scavenging activity along with better colour and sensory attributes. The microstructural study of ICPD treated green tea samples showed more deformed cell surface integrity, larger stomatal pore size and cracks at the leaf surface in comparison with non‐treated green tea sample. CONCLUSION: Present study reveals that an ICPD treatment at 0.2 MPa for 20 s can be used as an alternative to the traditional enzyme inactivation step of hot water treatment, for green tea leaves to improve the infusion quality in terms of increased levels of TPC and TFC and DPPH radical scavenging activity. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Contrary to the second-order Phase field model (PFM) of fracture, fourth-order PFM provides a more precise representation of the crack surface by incorporating higher-order derivatives (curvature) of the phase-field order parameter in the so-called crack density functional. As a result, in a finite element setting, the weak form of the phase-field governing differential equation requires C 1 continuity in the basis function. C 0 Sibson interpolants or Natural element interpolants are obtained by the ratio of area traced by the second-order Voronoi cell over the first-order Voronoi cells, which is based on the natural neighbor of a nodal point set. C 1 Sibson interpolants are obtained by degree elevating the evaluated C 0 interpolants in the Bernstein-Bezier patch of a cubic simplex. For better computational efficiency while accounting only for the tensile part for driving fracture, a hybrid PFM is adopted. In this work, the numerical implementation of higher-order PFM with C 1 Sibson interpolants along with some benchmark examples are presented to showcase the performance of this method for simulating fracture in brittle materials. [ABSTRACT FROM AUTHOR]

The present article investigates the performance of powder-mixed die sink electrical discharge machining (PMEDM) under the influence of micro-flakes graphite (Gr) powder additive in dielectric (1.25 and 2.5 g/l of concentrations) during machining two workpiece materials of D2 steel and mild steel that are extensively employed alloys in the die and mold industry. Micro-flakes are chosen due to the necessity for fewer particles to fill the gap in the machining process, resulting in reduced pollution within the gap. The assessment of the PMEDM procedure's results is conducted based on several parameters, including the material removal rate (MRR), electrode wear ratio (EWR), average surface roughness (Ra), morphology, machined surface elemental content and recast layer. The results indicated that Gr PMEDM process offers higher machining performance in terms of MRR, EWR and the machined surface quality compared to die sink EDM process in pure dielectric. The optimum concentration was found to be 2.5 g/l Gr powder mixed dielectric for both workpiece materials. Furthermore, it was specified that the chemical composition and mechanical properties of the workpiece considerably affect the performance of die sink EDM and PMEDM. Unlike what has been discussed previously in the literature, present study revealed that formation of micro-crack and its density as well as micro-defects on the machined surface is highly dependent on workpiece elemental composition and mechanical properties. The concentration of cracks was particularly higher in areas with higher Cr atomic concentration, which increased the crack density in D2 steel. [ABSTRACT FROM AUTHOR]

Damages induced on the tungsten surface at two different operating conditions of a kilojoule plasma focus device are studied. In one condition, the tungsten samples were exposed to axial plasma shocks that are formed after pinch disruption, and in the other condition, the pinch phenomenon was absent or weak. Melting, craters, and cracking on the surfaces were observed in both cases. In the former case, the charged particle beams and post-pinch material ejection will play a role in impacting the surface; however, in the latter case those phenomena will have small contributions because of the absence or weak formation of the pinch. A damage factor of ∼ 10 9 W m−2 s0.5 was estimated at a distance of 3 cm from the pinch exit using the method given in Akel et al. [J. Fusion Energy 35, 694–701 (2016)] and Klimov et al. [J. Nucl. Mater. 390, 721–726 (2009)] for the former case. The present work suggests that at pressures lower than the pinch-occurring pressure, only axial plasma shock effects on the targeted surface can be studied and that they can be separated from the effects produced by the charged particle beams mixed with axial plasma shocks in the case of pinch occurrence. [ABSTRACT FROM AUTHOR]

Longitudinal crack defects are a frequent occurrence on the surface of thin slabs during the high-speed continuous casting process. Therefore, this study undertakes a detailed analysis of the solidification characteristics of hyper-peritectic steel thin slabs. By establishing a three-dimensional heat transfer numerical model of the thin slab, the formation mechanism of longitudinal cracks caused by uneven growth of the initial shell is determined. Based on the mechanism of longitudinal crack formation, by adjusting the performance parameters of the mold flux, the contradiction between the heat transfer control and lubrication improvement of the mold flux is fully coordinated, further reducing the incidence of longitudinal cracks on the surface of the casting thin slab. The results show that, using the optimized mold flux, the basicity increases from 1.60 to 1.68, the F- mass fraction increases from 10.67% to 11.22%, the Na2O mass fraction increases from 4.35% to 5.28%, the Li2O mass fraction increases from 0.68% to 0.75%, and the carbon mass fraction reduces from 10.86% to 10.47%. The crystallization performance and rheological properties of the mold flux significantly improve, reducing the heat transfer performance while ensuring the lubrication ability of the molten slag. After optimizing the mold flux, a surface detection system was used to statistically analyze the longitudinal cracks on the surface of the casting thin slab. The proportion of longitudinal cracks (crack length/steel coil length, where each coil produced is about 32 m long) on the surface of the thin slab decreases from 0.056% to 0.031%, and the surface quality of the thin slab significantly improves. [ABSTRACT FROM AUTHOR]

Longitudinal surface cracks are prevalent in the continuous casting of hypo-peritectic beam blanks, primarily related to multiphysics non-uniformity (multi-phase field, flow field, temperature field) within the mold. Therefore, multi-phase and coupled flow-thermal models were constructed to investigate the non-uniform multiphysics characteristics in the beam blank mold with a single nozzle and its effect on the formation of longitudinal cracks. First, the three-phase flow model reveals significant unevenness slag distribution along the web width, positively correlated to surface velocity of the molten steel. Subsequently, considering the impact of the solidification shell, surface velocity decreases nonlinearly with increasing immersion depth, influenced by web vortex position in the X-direction, which is also influenced by mold curvature, and interaction between web and side vortexes. Furthermore, the temperature field distribution inside the mold is non-uniform. Under the effect of the single-web recirculation flow, the temperature near the meniscus at the NN (position near the nozzle) side of the web is lower than that at the FN (position far away from the nozzle) side, resulting in more intensive initial cooling at this position. Meanwhile, a reheating zone exists at the mold exit of the NN side. Statistical analysis revealed that the absolute values of Spearman coefficient between the non-uniformity of shell thickness and the temperature and flow velocity of the molten steel exceed 0.6, which is related to the depth of the web vortex. Finally, from the perspective of the influence of SEN's immersion depth on multiphysics, the high surface velocity of the steel, strong cooling near the meniscus, and non-uniform shell thickness at the mold exit can be relieved with an immersion depth of 75 mm. The plant experiment confirmed that increasing the immersion depth from 65 to 75 mm leads to a relative reduction of 39 and 43 pct in the longitudinal cracks ratio for strands and rolled products, respectively. [ABSTRACT FROM AUTHOR]

The present article addresses the influence of surface mechanical attrition treatment (SMAT) parameters such as a size of the balls (2, 5 and 8 mm ∅ 316L stainless steel (SS) balls) and treatment time (15, 30, 45 and 60 min) on the microstructural features, deformation characteristics, surface roughness and compressive residual stress induced on EN 8 steel. The effective deformation is ~ 25 μm from the top surface along with elongated grains in the near subsurface region. The decrease in crystallite size and an increase in micro-strain become more pronounced during SMAT using balls with a larger diameter and for a longer treatment time. A similar trend is observed in surface roughness. This is mainly attributed to the involvement of higher kinetic energy imposed by SMAT on EN 8 steel. The residual stress induced during SMAT of EN 8 steel measured by x-ray diffraction (XRD) measurements is higher when treated using 2 mm ∅ SS balls when compared to those treated using 5 and 8 mm ∅ SS balls for a similar time duration. Irrespective of the size of the balls, an increase in treatment time has led to a decrease in the residual stress of EN8 steel. Over working of EN8 steel that creates surface cracking has been considered responsible for the decrease in residual stress of EN8 steel treated using 5 and 8 mm ∅ SS balls for any given time duration as well as with an increase in treatment time for a given size of the balls. The development surface cone cracks and material removal from the surface evidenced from the microstructure validates such as an occurrence. When the duration of SMAT is limited to 15 min, a large difference in residual stress values is observed for the EN8 steel treated using 2, 5 and 8 mm ∅ balls, whereas with a further increase in treatment time, the difference between them becomes marginal. Hence, in order to achieve better mechanical properties, the treatment time employed for SMAT of carbon steels should be carefully optimized. The other option available is to choose lower size balls for SMAT. The change in residual stress of EN8 steel as a function of process parameters employed for SMAT and the correlation between the ball size and treatment time with the residual stress are discussed. [ABSTRACT FROM AUTHOR]

This work demonstrates the potentials of a commercially available few-layer graphene (FLG) in enhancing the electro-dissipative properties, mechanical strength, and UV protection of polyolefin blend composites; interesting features of electronic packaging materials. Polyethylene (PE)/ polypropylene (PP)/ FLG blend composites were prepared following two steps. Firstly, different concentrations of FLG were mixed with either the PE or PP phases. Subsequently, in the second step, this pre-mixture was melt-blended with the other phase of the blend. FLG-filled composites were characterized in terms of electrical conductivity, morphological evolution upon shear-induced deformation, mechanical properties, and UV stability of polyolefin blend composites. Premixing of FLG with the PP phase has been observed to be a better mixing strategy to attain higher electrical conductivity in PE/PP/FLG blend composite. This observation is attributed to the influential effect of FLG migration from a thermodynamically less favourable PP phase to a favourable PE phase via the PE/PP interface. Interestingly, the addition of 4 wt.% (~2 vol.%) and 5 wt.% (~2.5 vol.%) of FLG increased an electrical conductivity of ~10 orders of magnitude in PE/PP—60/40 (1.87 × 10−5 S/cm) and PE/PP—20/80 (1.25 × 10−5 S/cm) blends, respectively. Furthermore, shear-induced deformation did not alter the electrical conductivity of the FLG-filled composite, indicating that the conductive FLG network within the composite is resilient to such deformation. In addition, 1 wt.% FLG was observed to be sufficient to retain the original mechanical properties in UV-exposed polyolefin composites. FLG exhibited pronounced UV stabilizing effects, particularly in PE-rich blends, mitigating surface cracking and preserving ductility. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology 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.)

In this paper, the effects of equivalence ratio (0.8-2.0) and temperature (30°C-120°C) on ethanol, acetone, and, ethyl acetate vapors explosion characteristics through experimental and numerical studies were investigated. The explosion overpressure and flame propagation velocity were recorded through the pressure transducer and high-speed camera. The results showed that the flame propagation velocity, peak explosion overpressure, and peak growth rate of explosion overpressure increased first and then decreased with the increase of equivalence ratio. The cracks on the flame surface enhanced with the increase of the equivalence ratio. As the initial temperature increased, peak explosion overpressure, the flame propagation velocity, and peak growth rate of explosion overpressure gradually increased. The sensitivity analysis of laminar burning velocity indicated that with the change of equivalence ratio and initial temperature, the shared elementary reactions that increased the reactivity were H + O2 < = > O + OH, HCO + M < = > H + CO + M, and CO + OH < = > CO2 + H, and the shared elementary reaction that reduced the reactivity was H + OH + M < = > H2O + M. The main factor affecting laminar burning velocity was the mole fraction of H and OH radicals. [ABSTRACT FROM AUTHOR]

Hydraulic concrete structures often suffer from cracking that could lead to engineering accidents. Thus, it is important to identify emerging concrete cracks so that the premonitory danger of the components can be comprehensively evaluated, and the disaster management level can be advanced to the initial stage of the hazard. This study investigated the use of ultrasound-excited thermography to detect surface microcracks in concrete engineering components. A detection system and method for the synergistic excitation of multiple excitation sources were developed, and self-adaptive pressure-loading sleeves containing back shafts made of glass fibre-reinforced nylon were developed to exert pressure on the transducers. Eighteen groups of in-situ experiments were conducted on important parts of the key component using a combination of 28-kHz and 40-kHz-transducers with a power of 100 W. The results demonstrate that ultrasound-excited thermography with the synergistic excitation of multiple excitation sources can be applied to detect surface cracks in approximately semi-infinite reinforced concrete members in-situ. The radius of the current investigation of cracks stimulated by one 100-W transducer pressed by the self-adaptive sleeve in reinforced concrete members is as far as 300 mm. The minimum widths of the detected cracks are 0.03 mm. [ABSTRACT FROM AUTHOR]

AbstractThe effects of crack width, crack depth and water-cement ratio (w/c) on calcium dissolution resistance of cracked concrete were evaluated. Results show that the degradation in physical properties and mechanical properties of concrete after dissolution increase with the increasing crack width, crack depth and w/c. In the case of concrete with w/c of 0.40 and dissolution age of 100 d, the degradation of splitting tensile strength of specimens with crack widths of 0.1, 0.2 and 0.3 mm was 1.27 times, 1.39 times and 1.54 times that of uncracked specimens. Dissolution resistance of cracked concrete is obviously lower than that of uncracked concrete, and the effect of crack width on it is more significant than that of crack depth, and the higher the w/c of concrete, the more significant the effect of crack width. Dissolution damage increasing coefficient of cracked concrete can be used to quantitatively characterise the effect of cracks on the dissolution damage of concrete, and its maximum value is approximately 1.08 corresponding to the crack width of 0.3 mm. The results of this study can be used as a reference for the accurate evaluation of calcium dissolution resistance and service life of the water-related concrete structures. [ABSTRACT FROM AUTHOR]

Incorporating strengthening phase with a higher thermal stability than traditional L12-ordered Ni3Al phase offers a promising avenue for developing the next-generation Ni-based superalloys. In this study, a powder metallurgy superalloy featuring addition of high-melting-point δ-Nb3Al was fabricated to investigate the high-temperature oxidation behavior at 900 °C. Heterogeneous and accelerated oxidation resulting from the various phase transition products in the alloy were observed. Notably, the preferential oxidation of δ-Nb3Al to Nb2O5 causes obvious surface bulges and cracks. The matrix and Laves phase form oxide layers containing a discontinuous Al2O3. The oxidation mechanism was elucidated through the formation oxidation diagrams based on Gibbs formation energy and total valence of Al2O3. The low Al content in matrix and the high Nb content in Laves phase were identified to cause the discontinuity of surface Al2O3 layer. Additionally, Nb could impede oxygen diffusion within Al2O3 by reducing oxygen vacancy concentration. The findings will provide optimization guidance for the composition design and oxidation protection of novel δ-Nb3Al-strengthened Ni-based superalloys. [ABSTRACT FROM AUTHOR]

One advantage of twin-roll casting for aluminum alloys is that hot rolling can be omitted, thus shortening the process. The effect of inline hot rolling on the anisotropy of the mechanical properties, especially the elongation, of the roll-cast strip has not been investigated. In a high-speed twin-roll caster, inline hot rolling forms the metal shape before the temperature of the cast strip decreases below the temperature needed for hot rolling. In this study, inline hot rolling of Al-5%Mg strips cast using an unequal diameter twin-roll caster was performed to validate the technique and evaluate its ability to reduce surface cracking and improve the elongation anisotropy. A rolling speed of 30 m/min was used, and the effects of temperature and thickness reduction during inline hot rolling on the surface and mechanical properties were investigated. Inline hot rolling was found to effectively reduce the formation of surface cracks and the anisotropy of the mechanical properties. [ABSTRACT FROM AUTHOR]

High-strength concrete (HSC) has a high compressive strength, high density, excellent durability, and seepage resistance, but its deformation ability is weak. Adding fibers can improve the physical and mechanical properties of HSC. Additionally, the HSC structure may face the threat of fire. In the process of fire extinguishing, the damage mechanism of high-temperature-resistant concrete is complicated due to the different contact conditions with water at different locations. Hence, it is essential to conduct pertinent research on the behavior of fiber-reinforced HSC with different cooling methods after high-temperature action. In this paper, polyvinyl alcohol fiber (PVA fiber) was selected to be added into the HSC to carry out high-temperature experimental research, so as to explore the apparent changes, failure pattern, and mass loss rate of the fiber-reinforced HSC using different cooling methods and analyze the influence of its residual compressive strength and flexural strength. The test results suggest that, with the increase in heating temperature, the color of the specimen's surface transitions from dark blue-gray to white, and the quantity of surface cracks on the specimen gradually rises. The mechanical strength gradually decreases as the heating temperature increases. At a consistent heating temperature, the mechanical strength initially rises, and then falls with an increase in fiber content. The maximum compressive strength and flexural strength were achieved at PVA fiber contents of 0.2% and 0.3%, respectively. For different temperatures and fiber contents, the mechanical strength after natural cooling is generally higher than that after immersion cooling. In addition, X-ray polycrystalline diffractometry (XRD) and scanning electron microscopy (SEM) tests were conducted to analyze the compositional alterations and microstructure of the fiber-reinforced HSC following high-temperature exposure, accompanied by an explanation of the factors influencing the alterations in the physical and mechanical properties. Therefore, the findings of this study can serve as a valuable reference for the utilization of HSC in engineering structures and contribute to the advancement of HSC technology. [ABSTRACT FROM AUTHOR]

This study aimed to investigate drying times mathematical models and assess the color, rehydration capacity, and microstructure of dried peach using electrohydrodynamic (EHD), hot air, and electrohydrodynamic-hot air (EHD-hot air) drying methods. Peach samples were subjected to drying with two different air temperatures (50 and 55 °C) and electric field (EF, 6.67 and 10 kV cm−1) under constant air velocity (1.5 m s−1). The longest drying durations were obtained in the EHD method (720 and 600 min), followed by hot air (290 and 260 min) and EHD-hot air method (120, 140, 170, and 200 min), respectively. The drying curves were best described by the Midilli et al. and Logarithmic models. The L* values of the samples subjected to hot air drying were found to be lower than those obtained through other methods. No significant effect of the electric field on rehydration capacity was observed. The study revealed that increased temperature and electric field led to surface cracks on the peach. The study highlights the compatibility of the EHD method with the hot air method, suggesting its potential application within the drying industry. From these findings, it was seen that the EHD-hot air combination method could be an alternative to the hot air method in the food industry by reducing the drying time of peaches and considering that the color parameters are generally better than the hot air method. [ABSTRACT FROM AUTHOR]

The structure and physico-mechanical properties of Canabinus sativa L. fibre from a specific agro-climatic region of India were thoroughly studied. The fine structure of the fibre was examined by FTIR, TGA, XRD, component analysis, and SEM. SEM shows heterogeneous morphology with prominent longitudinal ridges having cracks and surface impurities. XRD shows a moderate degree of crystallinity (49%) but sharp peaks indicating the presence of an appreciable amount of cellulose matter. FTIR reveals the presence of large quantities of hydroxyl and aldehyde along with phenolic groups. The fine structure of European hemp fibre was compared with the Indian hemp fibres. Component and thermal analyses indicate the presence of hemicellulose and cellulose as major constituents along with lignin. The breaker carded fibre shows that hemp is longer, finer, lighter, stronger, more extensible, more flexible, and has lower crystalline fibre than jute. Its colour value is also better than that of jute. Hemp yarn is better than jute yarn, especially in bulk, flexibility, elongation, and modulus. Blended yarn is better in strength and work of rupture but inferior in hairiness. Studies show that hemp fabric has better properties than jute fabric, especially in terms of flexibility, bulk, and strength. A jute processing system may be a very good option for hemp fibre and can be used to make jute blended yarn and 100% hemp yarn for apparel and furnishing grade fabric with better functional properties. [ABSTRACT FROM AUTHOR]

The present work investigates the surface modification of a second-generation, SX nickel-based superalloy by using a continuous wave laser with various laser powers under the conductive mode of heat penetration. The aim was to reduce the surface strength to improve the machinability. The results show that the laser surface modified (LSM) geometry and their surface irregularities increase with an increase in laser power. The cross section of the LSM geometry under lower powers is semi-elliptical in shape, whereas it becomes a top-hat shape under higher laser powers. Fine dendrites of around 10 µm with various morphologies are formed in the LSM geometry. The dendrite size increases with an increase in laser power except at the highest laser power. The LSM geometry consists of longitudinal and transverse cracks along the scanning direction. The longitudinal cracks are formed near the centerline at lower laser powers, whereas the transverse cracks are formed at a faraway distance from the centerline at higher laser powers. The longitudinal cracks have vertical cracking and transverse cracks have zig-zagged cracking beneath the surface. The total crack length increases with an increase in laser power. The LSM interface consists of dense micropores and microcracks at the inter-dendric region. However, the LSM region consists of lesser microsegregation and fine dendrites than the base metal, its microhardness is lower than the base metal due to the formation of laser-induced defects. [ABSTRACT FROM AUTHOR]