Sheet Surface Research Articles

A defect detection method for industrial aluminum sheet surface based on improved YOLOv8 algorithm

In industrial aluminum sheet surface defect detection, false detection, missed detection, and low efficiency are prevalent challenges. Therefore, this paper introduces an improved YOLOv8 algorithm to address these issues. Specifically, the C2f-DSConv module incorporated enhances the network’s feature extraction capabilities, and a small target detection layer (160 × 160) improves the recognition of small targets. Besides, the DyHead dynamic detection head augments target representation, and MPDIoU replaces the regression loss function to refine detection accuracy. The improved algorithm is named YOLOv8n-DSDM, with experimental evaluations on an industrial aluminum sheet surface defect dataset demonstrating its effectiveness. YOLOv8n-DSDM achieves an average mean average precision (mAP50%) of 94.7%, demonstrating a 3.5% improvement over the original YOLOv8n. With a single-frame detection time of 2.5 ms and a parameter count of 3.77 M, YOLOv8n-DSDM meets the real-time detection requirements for industrial applications.

Sonochemical synthesis of graphene oxide-Ag2O nanozyme as an oxidize-like mimic for the highly sensitive detection of lithium in blood serum

Bipolar disorder is commonly treated with lithium carbonate. The concentration of lithium in the blood serum should be closely monitored in patients who require long-term lithium therapy. To date, no colorimetric method of detecting lithium ions has been reported using nanosensors. We have developed a novel chemosensor based on nanozyme (NZ) to address this clinical need. The GO-Ag2O NZs were synthesized by a sonochemical method and used as a colorimetric nanosensor to detect lithium ions in human blood serum (Li (I)). To characterize NZs, various techniques were employed, including XRD, FTIR, TEM, FESEM, EDX, Raman spectroscopy, BET, DLS, Zeta potential, and ICP-OES. According to TEM and FESEM images of GO-Ag2O, the nanoparticles (NPs) of Ag2O are uniformly distributed on the surface of 2D graphene oxide sheets. In addition, silver oxide nanoparticles exhibited a cubic morphology with an average size of 3.5 nm. We have examined the performance of the NZs in an aqueous medium and in human blood serum that contains Li (I). A colorimetric test revealed that NZs synthesized in the presence of ultrasound were more sensitive to Li (I). According to the linearity of the calibration curves’ ranges, Li (I) has a limit of detection (LOD) of 0.01 µg/mL. Furthermore, it displayed a linear range between 0 and 12 µg/mL. GO-Ag2O NZs showed noticeable color changes from green to orange after exposure to Li (I). An incubation time of two minutes was found to be the most effective for sensing. This innovative approach provides a reliable method for monitoring lithium levels and ensuring patient safety during long-term lithium therapy for bipolar disorder.

Numerical Simulation of Forming a 3D Shape by a Multi-Point Die

Multi-point forming (MPF) is considered one of the flexible and creative three-dimensional sheet metal forming processes. Such a technique replaces traditional rigid punches with a set of adjustable-height discrete pins. By altering the relative height of each pin, a variety of three-dimensional curved surfaces can be formed. In order to avoid changing the height of the pins manually, they are attached to springs. Hence, when a load applies at the pins holder, these will take the shape of the die due to the spring properties quickly and easily. However, wrinkles and dimples are inevitable issues that appear when using MPF. In order to investigate and minimize these defects, a finite element approach using ANSYS 15.0 software has been applied to perform numerical simulations for this MPF operation. Two cases have been examined in this study. Whilst the first one includes direct forming between the pins and the metal, a sheet of rubber has been added among them in the second case. The simulation has been conducted on brass (Cu Zn 65-35) with a thickness of (0.71 mm) and rubber with a thickness of (2 mm). The boundary conditions, which are attached to the blank, enable the motion in the y-direction only with respect to the lower profile at a depth of (30) mm, and was immobilized by constraints in the x and z direction. The study has shown remarkable results since the dimples were visible on the sheet surface in the first case, whereas these defects were significantly reduced during the second one. Moreover, the blank profile’s maximum stress and strain have been studied. Due to force distribution, rubber reduces maximum stress and strain to approximately 27% and 49%, respectively, in the second case

Biophysical studies of modified PVC sheet based on sunflower oil for antistatic and blood bags applications

In this work, the surface of polyvinyl chloride PVC sheet was modified by blending it with sunflower seed oil SSO to obtain PVC sheet/SSO films of ratios 100/0, 90/10, 80/20, 70/30, 60/40, and 50/50 (v/v)% using the solution casting method. Various techniques were used to characterize the prepared films, besides the use of hemolysis assays and blood clot formation tests. FTIR spectra revealed that there was a good interaction between the PVC sheet and the oil. The dielectric measurement indicated that SSO addition enhanced the dielectric properties of the sheet. The study of dielectric relaxation times confirmed the interaction between SSO and the sheet. DC conductivity increased to 6 × 10–6 S/m, so it could be applied in antistatic applications. Also, SSO addition increased the value of the thermal stability. According to SEM micrographs, the film was roughened at a ratio of 60/40 and smoothed out at 50/50. This behavior was confirmed with roughness and contact angle measurement results, in which the film of ratio 60/40 had the highest value equal to (72.03°) and then decreased at 50/50 to (59.62°). These results were confirmed by XRD measurement as the crystallinity increased at the film ratio of 60/40 and decreased again at 50/50. Also, the ratio of 60/40 demonstrated a large decrease in thrombus weights along with a slight increase in hemolysis, which is within the acceptable range and has a high degree of biocompatibility, so this concentration is recommended to be used in blood bags applications.

Simulation and Experimental Approach for Metal Forming with a Multi-Point Die

Multi-point forming (MPF) is considered a flexible and innovative sheet metal forming process that allows for the creation of three-dimensional curved surfaces. This study investigates the effects of various parameters on the final product in metal forming using a multi-point die. The research employs a combination of numerical simulations and experimental work to analyze and minimize defects in the forming process. The concentration is on brass (Cu Zn 65-35) and rubber materials, with specific thicknesses of 0.71 mm and 2 mm, respectively. Although ANSYS 15.0 is used to study the stresses and strains resulting from the formation process with the multi-point die (MPD), the experimental work was conducted to study the effect of two parameters: forming speeds (5 and 15 mm/min) and holding times (1, 3, and 5 minutes were used in this process). The simulation results reveal that the use of rubber significantly reduces defects such as dimples on the sheet surface. Additionally, the presence of rubber helps distribute the force, leading to a reduction in maximum stress and strain in the blank profile to approximately 27% and 49%, respectively, in the second case. The study also explores the impact of forming speed and holding time on spring back. BY measuring the dimensional accuracy of the final products. A forming speed of 5 mm/min and a holding time of 5 minutes resulted in the best outcomes, with a minimum average spring back (0.997). Moreover, the ANOVA algorithm was used to discuss the results which indicated that the forming speed and holding time significantly affect the dimensional accuracy. The research shows that altering settings and adding rubber to multi-point forming improves product quality and accuracy. This study enhances metal forming knowledge and improves industrial processes.

Observation of the early stages of environmental contamination in graphene by friction force.

Exposure to ambient air contaminates the surface of graphene sheets. Contamination may arise from different sources, and its nature alters the frictional behavior of the material. These changes in friction enable the observation of the early stages of contaminants' adsorption in graphene. Using a friction force microscope, we show that molecular adsorption initiates at the edges and mechanical defects in the monolayer. Once the monolayer is covered, the contaminants spread over the additional graphene layers. With this method, we estimate the contamination kinetics. In monolayer graphene, the surface area covered with adsorbed molecules increases with time of air exposure at a rate of 10-14m2/s, while in bilayer graphene, it is one order of magnitude smaller. Finally, as the contaminants cover the additional graphene layers, friction no longer has a difference concerning the number of graphene layers.

Experimental and model investigation of spreading characteristics of the liquid sheet formed by jet impinging on a circular plane

The focus of this paper is on the spreading characteristics of the liquid sheet formed by jet impinging on a circular plane. The liquid sheet is studied in two parts: the liquid film that spreads radially on the circular plane, and the free liquid sheet after leaving the circular plane, the former determines the initial thickness and velocity of the latter. Experimental results show that, for the liquid film on the circular plane part, as the jet velocity increases, the liquid film thickness increases due to the film velocity loss caused by the inelastic collision. The liquid film thickness is positively correlated with the jet radius and negatively correlated with the circular plane radius. Liquid viscosity slows the spreading of liquid film, forms the boundary layer, and thickens the liquid film. The surface tension inhibits the velocity loss due to the inelastic collision. For the free liquid sheet part, surface tension and gravity promote the bending of the liquid sheet. The larger the initial momentum of the liquid sheet leaving the circular plane, the larger the maximum spreading range of free liquid sheet reaching the equator. As for the theoretical model, a film velocity correction coefficient reflecting collision loss is introduced to improve the radial spreading theory of the liquid film on a solid surface, and a streamline function is assumed to solve the momentum integral equation of free liquid sheet. The predicted streamline agrees well with the experimental data.

Improved near-resonant two photon absorption of α-MnO2 nanowires surface functionalized reduced graphene oxide sheets

The versatile study of graphene derivatives has resurgence of interest on understanding its nonlinear optical response at different nanoscales. Nanostructured manganese dioxide: reduced graphene oxide (MnO2: rGO) hybrids were synthesized by reduction method by varying the content of rGO (5, 10, 15 & 20 wt%). X-ray Photoelectron Spectroscopy studies confirmed the surface functionalization of MnO2 on rGO. Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Tunnelling Electron Microscopy (HRTEM) witness that with respect to the content of rGO, the morphology of MnO2 varies radically from clusters to nanorods to nanowires over the surface of rGO sheets. Ground state absorption spectra of the hybrids have absorption edge at 268 nm corresponding to combined metal oxide charge transfer between rGO (π-π* transition of CC and n-π transition of C-O bonds) and MnO2 (d-d transition). Moreover, hierarchical MnO2 nanowire network resided on 2D rGO sheets involves broad absorption at the visible spectral domain due to polaron transition as well the localization of π- π* transited electrons that facilitates the probability of occurrence of excited state absorption. Intensity dependent open aperture Z-scan technique of the prepared hybrids using Q-switched Nd: YAG 532 nm nanopulsed laser reveals unusual transitions and enhanced nonlinear absorption. MnO2:(5 wt%) rGO shows saturable absorption (SA) at low intensity and changeover dynamically to reverse saturable absorption (RSA) at higher intensity. MnO2:(10 & 15 wt%) rGO exposes coupled nonlinear absorption (SA + RSA) owing to the combined effect of graphene (π-states) and MnO2 (σ-states). MnO2:(20 wt%) rGO exhibits a stronger RSA ascribed to sequential two photon absorption. The third-order nonlinear absorption coefficient and limiting threshold of MnO2: rGO (20 wt%) are 4.04 ×10-10 m/W and 0.84 ×1012 W/m2, which shows five-fold increase compared to bare rGO and MnO2. The obtained results propose that the optical nonlinearity of MnO2 nanowires surface functionalized rGO sheets can significantly be tuned to meet the requirements for fabricating laser safety devices.

Effects of stress relief annealing in NGO steels

The effect of stress relief annealing (SRA) has been investigated on two classes of non-grain oriented (NGO) steels and with different sheet thickness. Magnetic properties were measured on mechanically sheared and water jet cut Epstein strips before and after SRA treatment at 800 °C in a nitrogen gas atmosphere. Significant improvement in power loss was achieved for the steel with lower aluminium content after SRA but the effect was much smaller for steel with the higher aluminium level, especially for thinner sheets where the SRA treatment was actually deleterious. No change in steel chemistry after SRA was found that could explain these differences. Microstructural examination showed residual dislocation substructures due to shearing before SRA and recrystallisation along the sheared edges together with recovery of the dislocation structures afterwards.A completely new finding was the presence of dislocation loops after SRA in the steel with higher aluminium content. These were not present previously but were created during the heat treatment. The presence of these dislocation loops is proposed as the reason for the weak or adverse effect of SRA on power loss. Detailed electron microscopy revealed that there are two families of dislocation loops having either Burgers’ vectors of a 〈100〉 lying on {100} planes or a√3/2 〈111〉 on {111 planes}. A model is presented whereby oxidation which occurs at the sheet surfaces causes a concentration gradient within which the Al atoms diffuse. This process necessitates a balancing flux of vacancies diffusing into the interior. When the content of vacancies exceeds the equilibrium content they agglomerate and ‘precipitate’ out as vacancy dislocation loops.

Gravimetric characteristics and friction parameters of common bean (Phaseolus vulgaris L.)

When designing appropriate machinery systems, equipment, and infrastructures for interacting with, cultivating, gathering, and agriculture-related processing, it is required to have an understanding of the engineering characteristics of agricultural products. This unpredictability makes it difficult to design or develop machines that can efficiently and effectively manage a wide range of product characteristics. Experimental analysis was used to accomplish the study's objective, which was to investigate the implications of variation on the gravimetric characteristics and frictional parameters of common bean (Phaseolus vulgaris L.) concerning the design of the threshing machine. The mean average values of gravimetric parameters were determined by analysing the experimental data: arithmetic mean diameter (7.042 ± 0.473 mm), geometric diameter (6.737 ± 0.463 mm), bulk density (781.20 ± 25.34 kg m-3), true density (1347.03 ± 143.0 kg m-3), porosity (41.385 ± 7.05%), width (6.316 ± 0.502 mm), thickness (4.962 ± 0.50 mm), projected area (49.194 ± 6.715 mm2), and volume of the seed (161.689 ± 3.778 mm3). The average moisture content values were found to be 11.214±1.185% on a dry basis, the static coefficient of friction varied between 0.276 and 0.386 on the surface of iron sheets, 0.294 to 0.435 on stainless steel, 0.317 to 0.434 on galvanized iron, 0.321 to 0.451 on medium density fiberboard, 0.319 to 0.480 on aluminum, 0.310 to 0.470 on painted sheets, 0.320 to 0.440 on glass, 0.333 to 0.447 on plastic, and 0.374 to 0.575 on rubber. Perforated sheet surfaces showed the highest static coefficients of friction, followed by rubber, plastic, plywood, glass, aluminum, galvanized iron, painted sheet, stainless steel, and iron sheet surfaces. These data are not only required for predicting loads in agricultural storage structures but are also needed to establish useful sources for the development of machinery for handling, cleaning, storing, transporting and drying, among other things.

Identification of structural defects and their impact on the magnetic memory, static and cyclic strength of VNS9-SH thin sheet trip-steel

Identification of microstructure defects, which are stress concentrators (SC) during the operation of mechanical engineering products, is an important scientific and practical task relevant for manufacturing enterprises. This problem becomes especially urgent and difficult for critical helicopter parts made of sheet TRIP steel VNS9-Sh (23Kh15N5AM3-Sh) and operating under cyclic loads due to the complex microstructure of the steel and small thickness of strips and sheets. To assess the impact of structural defects on the cyclic strength of products made of the steel under study, the specimens were preliminary sorted proceeding from the results of their testing using the method of metal magnetic memory (MMM) and metallographic studies. The MMM method is a structure-sensitive procedure which provides information about the presence of structural defects that arise during the manufacture. Magnetic anomalies in the form of sharp local changes in the intrinsic stray magnetic field (SSMF) (H) and its gradient |ΔH| along the length of the controlled section Δx, were identified on the surface of sheets cut from five different batches. A conventional classification of the identified anomalies was made according to the magnitude of the magnetic field gradient. The specimens of two types were cut in zones of magnetic anomalies and outside them: type 1 — for cyclic tests and type 2 — for metallographic studies. The geometric parameters and field gradient values of magnetic anomalies on specimens of type 1 and type 2 were the same. Metallographic studies in zones of maximum magnetic field gradient on type 2 specimens revealed defects in the form of a strip at the boundary of different structures, which is a structural stress concentrator (SSC) and a source of the inhomogeneity and changes in the magnetic properties. Type 1 specimens with similar magnetic anomalies and Type 1 specimens cut from sheets outside zones of magnetic anomalies were then selected for cyclic testing. Comparative tests for cyclic strength of the specimens with and without specified SSC were carried out. It is shown that the presence of SSC zones in the specimens reduces the number of cycles to failure during cyclic tests by 1 – 2 orders of magnitude compared to the specimens free of SSC. Based on cyclic tensile tests of specimens, a limiting value of the magnetic field gradient was determined that corresponds to the acceptable level of stress concentration on structural defects. This value is recommended for use as a rejection criterion when examining a new tape by the MMM method.

A dual-purpose photocatalytic reaction for hydrogen evolution and simultaneous organic pollutant degradation of V2O5/Ppy based composite photocatalyst

The present work reports for the facile synthesis of novel vanadium oxide/polypyrrole (V2O5/Ppy) nanohybrids using various loadings of the V2O5. This novel hybrid photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, UV–Visible absorption spectra (UV–Vis), photoluminescence spectra (PLS) and N2 adsorption-desorption analysis. XRD and TEM results suggest that V2O5 with individual spherical shaped nanoparticles of around 20–25 nm, which is uniformly wrapped on the surface of the Ppy sheets. A significant reduction in the bad gap energy (3.06–2.13 eV) and prevent the electron-hole recombination process was examined by UV and PL studies. The photocatalytic degradation efficiency was carried out for Reactive Black 31 (RB 31) and 4-chlorophenol (4-CP) dyes under visible light. The results illustrate that the optimal hybrid catalyst could reach 99 % of removal efficiency towards RB31 with visible light irradiation for 60 min. Moreover, the catalyst show high TOC efficiency (88%) high apparent constant (0.9189 min−1), and good stability with multiple cycle experiments. The improved photocatalytic mechanism was also discussed in detail. In comparison to V2O5 (425 μmol−1h−1 of H2) and PPy (151 μmol−1h−1 of H2), the optimised composite, 15 wt% V2O5 incorporated PPy showed a remarkable production rate under visible light (2255 μmol−1h−1 of H2).

Investigation on damage evolution mechanism of various FRP strengthened concrete subjected to chemical-freeze-thaw coupling erosion.

The corrosion resistance of FRP-reinforced ordinary concrete members under the combined action of harsh environments (i.e., alkaline or acidic solutions, salt solutions) and freeze-thaw cycles is still unclear. To study the mechanical and apparent deterioration of carbon/basalt/glass/aramid fiber cloth reinforced concrete under chemical and freeze-thaw coupling. Plain concrete blocks and FRP-bonded concrete blocks were fabricated. The tensile properties of the FRP sheet and epoxy resin sheet before and after chemical freezing, the compressive strength of the FRP reinforced test block, and the bending capacity of the prismatic test block pasted with FRP on the prefabricated crack side were tested. The deterioration mechanism of the test block was analyzed through the change of surface photos. Based on the experimental data, the Lam-Teng constitutive model of concrete reinforced by alkali-freeze coupling FRP is modified. The results indicate that, in terms of apparent properties, with the increase in the duration of chemical freeze-thaw erosion, the surface of epoxy resin sheets exhibits an increase in pores, along with the emergence of small cracks and wrinkles. The texture of FRP sheets becomes blurred, and cracks and wrinkles appear on the surface. In terms of failure modes, as the number of chemical coupling erosion cycles increases, the location of failure in epoxy resin sheets becomes uncertain, and the failure plane tilts towards the direction of the applied load. The failure mode of FRP sheets remains unchanged. However, the bonding strength between FRP sheets and concrete decreases, resulting in a weakened reinforcement effect. In terms of mechanical properties, FRP sheets undergo the most severe degradation in the coupled environment of acid freeze-thaw cycles. Among them, GFRP experiences the largest degradation in tensile strength, reaching up to 30.17%. In terms of tensile performance, the sheets rank from highest to lowest as follows: CFRP, BFRP, AFRP, and GFRP.As the duration of chemical freeze-coupled erosion increases, the loss rate of compressive strength for specimens bonded with CFRP is the smallest (9.62% in salt freeze-thaw environment), while the loss rate of bearing capacity is higher for specimens reinforced with GFRP (33.8% in acid freeze-thaw environment). In contrast, the loss rate of bearing capacity is lower for specimens reinforced with CFRP (13.6% in salt freeze-thaw environment), but still higher for specimens reinforced with GFRP (25.8% in acid freeze-thaw environment).

Experimental investigation of the polymer-metal hybrids interfacial bonding fabricated by fused deposition modeling

In this paper, the fabrication of polymer-metal hybrids by fused deposition modeling was evaluated. 6061 aluminum alloy and polylactic acid were used in the manufacturing process. Also, to strengthen the bonding between the metal and polymer components, a two-component epoxy adhesive was used. The pull-off adhesion test was performed to evaluate the interfacial bonding strength of the specimens. In this study, the effect of bed temperature, print speed, printer nozzle diameter, and aluminum sheet surface roughness on the bond strength of polymer-metal hybrids has been investigated. The results showed that increasing the bed temperature, and aluminum sheet surface roughness, and also decreasing the print speed led to increase the bond strength of polymer-metal hybrids. Finally, by using the experimental data, an optimal specimen was produced. The interfacial bonding strength of the optimal specimen is about 64% stronger than the initial specimen.

Modeling, validation, and optimization of a rotating advanced oxidation contactor equipped with TiO2-zeolite composite sheets for sulfamethazine removal

The necessity to remove antibiotic residues such as sulfamethazine from veterinary/hospital wastewater is evident due to their widespread existence, challenges in treatment, and potential harm in aquatic ecosystems. This study focused on modeling, validating, and optimizing the removal of sulfamethazine (SMT) using two lab-scale rotating advanced oxidation contactor (RAOC) systems equipped with TiO2-zeolite composite sheets. Four key parameters—temperature, UV intensity, rotation speed, and sheet area by tank volume (A/V)—were investigated to understand their individual effects and interactions using the drum-RAOC system. The adsorption and decomposition processes of the RAOC systems were separately studied. In terms of the adsorption process, A/V was found to be the primary parameter influencing RAOC performance, with significant interaction observed between temperature and A/V. For the decomposition process, A/V and UV intensity were identified as the dominant parameters, with interactions affecting photocatalysis performance. Kinetic fitting was used to explore the underlying mechanisms, and liquid film thickness on the sheet surface was employed to support the explanations. Furthermore, validation experiments conducted using the disk-RAOC system confirmed the accuracy and applicability of these models. Through comprehensive optimization, the optimal parameter set was determined: temperature of 20°C, rotation speed of 5 rpm, UV intensity of 1.5 mW/cm2, and A/V of 200 cm2/L. Additionally, the current findings were compared with previous studies to illustrate the efficiency of RAOC systems. These results provide valuable guidelines for designing and operating RAOC systems and serve as a reference for balancing performance and consumption in immobilized photocatalysis systems.

A comparative study of mass balance in the Lambert Glacier and Amery Ice Shelf along the Chinese inland traverse during 2019–2023 using altimetry, gravity, and in-situ observations

Abstract. The new photon-counting laser altimetry satellite ICESat-2 was successfully launched on September 15, 2018 with an unprecedented ice surface elevation measurement accuracy of 2–4 cm. It is meaningful for accurately estimating volumetric changes in the Antarctic Ice Sheet. Cross-validation of different types of data, especially comparison with in-situ data, is important for the ice sheet mass balance results of a new satellite. This paper proposes an elevation-difference method of grid elevation change rate model, based on ICESat-2 ATL11 elevation time series data, to distinguish the linear change trend of ice sheet surface elevation from the elevation change resulting from periodic precipitation. In order to compare the estimated elevation-change rate with the flux computed from in-situ snow stake velocity measurements and GRACE-FO gravity survey data, we made corrections for firn air content, elastic, and glacier isostatic adjustment. Based on the ATL11 data from 2019 to 2023, our results show that the ice sheet change in Basin 11 along the CHINARE traverse is from ~0.019 m yr−1 to ~0.121 m yr−1, and the mass balance in the upstream of the traverse in Basin 11 is ~1.9±0.2 Gt yr−1. It is comparable to ~2.4±1.2 Gt yr−1 from GRACE-FO during the same time period. Furthermore, the flux across traverse-11.9±1.1 Gt yr−1 is comparable to that of ~-9.7±0.9 Gt yr−1 across the same flux gate during 1997–2009 which is calculated based on GNSS-derived ice velocity observations, considering the time period difference and uncertainties.

Influence of Supraglacial Lakes on Accuracy of Inversion of Greenland Ice Sheet Surface Melt Data in Different Passive Microwave Bands

The occurrence of Supraglacial Lakes (SGLs) may influence the signals acquired with microwave radiometers, which may result in a degree of uncertainty when employing microwave radiometer data for the detection of surface melt. Accurate monitoring of surface melting requires a reasonable assessment of this uncertainty. However, there is a scarcity of research in this field. Therefore, in this study, we computed surface melt in the vicinity of Automatic Weather Stations (AWSs) by employing Defense Meteorological Satellite Program (DMSP) Ka-band data and Soil Moisture and Ocean Salinity (SMOS) satellite L-band data and extracted SGL pixels by utilizing Sentinel-2 data. A comparison between surface melt results derived from AWS air temperature estimates and those obtained with remote sensing inversion in the two different bands was conducted for sites below the mean snowline elevation during the summers of 2016 to 2020. Compared with sites with no SGLs, the commission error (CO) of DMSP morning and evening data at sites where these water bodies were present increased by 36% and 30%, respectively, and the number of days with CO increased by 12 and 3 days, respectively. The omission error (OM) of SMOS morning and evening data increased by 33% and 32%, respectively, and the number of days with OM increased by 17 and 21 days, respectively. Identifying the source of error is a prerequisite for the improvement of surface melt algorithms, for which this study provides a basis.

Comparison of the hydrogen damage of different rolling surfaces of TC4 Ti alloy sheet

Abstract The microstructure of three rolling surfaces of TC4 sheet is different, and their resistance ability to hydrogen damage lacks systematic research. Thus, the hydrogen damage behavior of TC4 rolling sheet was investigated in this paper. The hydrogen diffusion law along different rolling directions and the precipitation of hydrides on different rolling surfaces were compared. It is found that the shape and distribution of α and β phases are changed under the action of extrusion force during the rolling process, and they are arranged in striped shape on the R-N surface along the R direction, and the diffusion of hydrogen along the R direction is faster due to the existence of continuous β phases as hydrogen diffusion channels, resulting in the more serious hydrogen damage. Besides the hydrides mainly deposited at the α and β phase boundaries, the hydrides precipitated in the interior of α phases on the R-N surface are more than that on the R-T surface due to the different distribution state of β phases.

Flutter characteristics of a sheet with an elastic support in three-dimensional uniform flow

In the manufacturing processes of thin flexible plates (sheets) such as polarizing films, the flutter can be caused to the sheets due to the interaction between the motion of the sheets and fluid flow. Then, the flutter can cause serious damage to the sheets, leading to the wrinkles and scratches. Thus, it is crucial to investigate a detailed characteristics and excitation mechanism of the flutter. In the present study, a detailed flutter characteristics and excitation mechanism of a rectangular sheet with an elastic support is investigated. The elastic support is implemented using a fine flexible wire. The influence of bending stiffness of the support section on the flutter velocity and frequency is clarified through wind-tunnel experiments and numerical analysis. Moreover, the work done by the fluid force on the sheet surface was determined.The flutter velocity and frequency drastically decrease owing to decrease in bending stiffness of the support section regardless of the aspect and mass ratio. Then, the positive work region around the leading edge of the sheet expands owing to the large-amplitude oscillation around the leading edge. The expansion of positive work region owing to a large-amplitude oscillation around the leading edge of the sheet destabilizes the system.

Fatigue behaviour and life prediction of self-piercing riveted joints in DP590/AA5754 dissimilar sheets

This paper investigates the fatigue properties of self-piercing riveted joints made by DP590 steel and AA5754 aluminium alloy. The fatigue failure mechanism and fatigue fretting mechanism of the joint were well revealed by analysing the microstructure features of fracture surfaces of sheets and rivets as well as viewing and measuring the distribution and chemical composition of fretting debris. The fatigue life of the joint was also predicted based on the stress intensity factor of the kinked crack of the lower sheet. The results confirmed that two failure modes occurred during fatigue: lower sheet fracture and rivet fracture. During the fatigue failure, cracks appeared in both the lower sheet and the rivets, indicating a competitive relationship between the propagation of cracks in the lower sheet and the rivets. In the range of 40 % and 50 % load level, fatigue crack propagation of the lower sheet is dominant and fracture failure of the lower sheet occurs. Rivet fatigue crack propagation has a significant advantage in the 60 % load range and rivet fracture failure often occurs. It was found that the fatigue failure of the lower sheet is mainly influenced by the main crack, which produces two different morphological sections. Fretting wear of the contact surface was the source of crack initiation, and the fretting debris promoted crack initiation and propagation. Cracks propagate along the width and thickness of the plate, as well as the thickness of the rivet neck. The stress intensity factor range can properly predict the fatigue life of joints.