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The paper partially covered Active Constrained Layer Damping (ACLD) cantilever beams' dynamic modeling, active vibration control, and parameter optimization techniques as the main topic of this research. The dynamic model of the viscoelastic sandwich beam is created by merging the finite element approach with the Golla Hughes McTavish (GHM) model. The governing equation is constructed based on Hamilton's principle. After the joint reduction of physical space and state space, the model is modified to comply with the demands of active control. The control parameters are optimized based on the Kalman filter and genetic algorithm. The effect of various ACLD coverage architectures and excitation signals on the system's vibration is investigated. According to the research, the genetic algorithm's optimization iteration can quickly find the best solution while achieving accurate model tracking, increasing the effectiveness and precision of active control. The Kalman filter can effectively suppress the impact of vibration and noise exposure to random excitation on the system. [ABSTRACT FROM AUTHOR]

To investigate the effect of drilling speed on the molecular dynamics and subsurface defect evolution mechanism of 3C-SiC single crystals, a coupled molecular dynamic model for drilling is established. A multi-scale molecular dynamic potential energy function is established by combining the variational potential energy between C–Si bonds, based on this, the mechanical response coupling model is developed. By analyzing factors such as molecular dynamics temperature and periodic boundaries, a molecular dynamic differential ensemble environment drilling is constructed to achieve a constant temperature and pressure simulation environment for the evolution of sub-surface defects in single crystal 3C-SiC molecular dynamics. At drilling velocities of 30 m/s, 60 m/s, and 90 m/s, dislocation exchange occurs that the load stability is affected. When the drilling reaches a certain depth, the load tends to be constant, with values of 5.22 × 104 eV/Å, 3.36 × 104 eV/Å, and 0.58 × 104 eV/Å. Load changes during differential drilling impact single crystal 3C-SiC irreversibly. By comparing and analyzing the simulation results at different drilling speeds, it offers ideas for understanding the material response of single crystal 3C-SiC during high-speed machining from the point of view of dislocation energy changes. [ABSTRACT FROM AUTHOR]

The semantic segmentation network based on U-Net (U-shaped network structure) in Si3N4 ceramic bearing cylindrical roller surface defect segmentation has the problems that low accuracy of defect feature extraction and large number of model parameters. It cannot meet the segmentation accuracy requirements of different size defects. The semantic segmentation network (D-A-IU-Net-Semantic segmentation network model with embedded multi-scale defective features) with embedded multi-scale defective feature fusion module is proposed. D-A-IU-Net inherits the encoding–decoding features of U-Net semantic segmentation network in structure and has the ability to sense multi-layer defective features. To reduce the number of model parameters and the network model training time, the D-A-IU-Net network model is downsampled only three times. To address the loss of detailed semantic information during downsampling, the network adopts a depthwise separable convolution layer with stride = 2 instead of the maximum pooling layer in the coding module. The segmentation accuracy is further improved. For overcoming the low segmentation accuracy of tiny defects on Si3N4 ceramic bearing cylindrical roller surface, the Atrous Spatial Pyramid Pooling Module (ASSP module-Hollow space convolution pool pyramid) is added to the bottom of the D-A-IU-Net network model to replace the model structure at the bottom of the U-net network model. To avoid the performance degradation caused by the increasing depth of the network model, two identity blocks are added at the bottom. A dataset of Si3N4 ceramic bearing cylindrical roller surface defects is prepared for validation. The experimental results show that the mIoU (mean Intersection over Union) of the D-A-IU-Net network model reaches 90.70%, the mPA (mean Pixel Accuracy) is improved to 95.13%, and the single image prediction time is 46.53 ms. The region segmentation efficiency of Si3N4 ceramic bearing cylindrical roller surface defects is improved. [ABSTRACT FROM AUTHOR]

To solve the problems of noise coverage defect and low contrast between the defect and the background of ZrO2 ceramic bearing balls, a surface defect extraction algorithm based on shearlet transform image enhancement for ZrO2 ceramic bearing balls is proposed. According to the shape characteristics of ceramic bearing balls, the surface defect image acquisition platform is built to collect and analyze surface defect images. Gaussian filtering weakens the scatter-particle noise in the image, and the threshold corrects the coefficient generated by the shearlet transform. After shearlet transform, the relatively low-frequency and high-frequency parts appear. The low-frequency part reflects the edge information of defects, and the high-frequency part reflects the edge and texture information of defects. Thus, the integrity of the defect is ensured, and an enhanced surface defect image is obtained. The gray histogram of the enhanced image is observed. The optimal threshold is selected by the histogram threshold segmentation method, and the process of defects being completely extracted from the background is realized. Experimental results showed that the extraction rates of pits, scratches, and cracks in ZrO2 ceramic bearing balls' surface images are 95.00%, 92.50%, and 92.50%, respectively. [ABSTRACT FROM AUTHOR]

This investigation centers on exploring the plastic deformation removal mechanism and dislocation dynamics in the nanogrinding of single‐crystal silicon carbide featuring a randomly rough surface. To simulate this, an approach combining the Weierstrass–Mandelbrot fractal surface function with molecular dynamics is employed. Randomly rough surface contours are generated using the Weierstrass–Mandelbrot fractal surface function. By adjusting the fractal dimension, an ideal representation of single‐crystal silicon carbide with randomly rough surfaces is obtained. By combining plastic deformation detection methods, the process of workpiece sliding, plowing, and chip removal is studied, and the plastic deformation removal mechanism of random rough surface grinding is explored. Combining postprocessing methods such as sheer strain and dislocation trajectory, the morphological changes and transformation mechanisms of dislocations are analyzed. Notably, at grinding depth of 33.18 nm, the activation of slip systems induces dislocation formation, enabling plastic deformation. Furthermore, at depths exceeding 144.00‐nm, the emergence of stacking faults on the random rough surface is observed. Throughout the grinding procedure, plastic deformation of debris occurs, leading to the formation of plastic bulges on both sides of the tool, and the debris generated during processing does not impact the defects encountered during secondary grinding of the rough surface. [ABSTRACT FROM AUTHOR]

Regarding the missing texture details in the texture extraction process of Tenglong Yuan blue and white, illumination is unequal. A meta blue and white texture extraction method based on adaptive gamma correction and K-means clustering segmentation coupling algorithm has been proposed. Combining the characteristics of Tenglong Yuan blue and white texture, using grayscale transformation to adjust the brightness of blue and white images, image contrast has been enhanced. Design Gaussian filter, weighted average multiscale Gaussian convolution, constructing 2D gamma convolutions for adaptive gamma correction, enhance the texture of Tenglong Yuan blue and white, the details in the blue and white texture of Tenglong Yuan are richer and more prominent. K-means clustering segmentation algorithm based on Lab space, implementing color segmentation of blue and white images, helps to segment the blue and white texture of Tenglong Yuan. Verification indicates that this method can effectively improve the contrast of blue and white texture; the accuracy rate of Tenglong Yuan blue and white texture segmentation reaches 95%. Effectively improving the accuracy of texture extraction for blue and white elements, the protection and inheritance of Yuan blue and white cultural relics are promoted. [ABSTRACT FROM AUTHOR]

To extract the fuzzy contour features, tiny depth features of surface microcracks in the Si3N4 ceramic bearings roller. An adaptive nano feature extraction and multiscale deep fusion coupling method is proposed, to sufficiently reconstruct the three‐dimensional morphology characteristics of surface microcracks. Construct an adaptive nano feature extraction method, form the surface microcrack image scale space and the Gaussian difference pyramid function equation, realize the detection and matching of global feature points. The sparse point cloud is obtained. Through polar‐line correction, depth estimation, and fusion of feature points on the surface microcracks image, a multiscale depth fusion matching cost pixel function is established to realize a dense point cloud reconstruction of surface microcracks. The reconstruction results show that the highest value of the local convex surface reconstructed by the dense point cloud reaches 1183 nm, and the lowest local concave surface is accurate to 296 nm. Compared with the measurement results of the confocal platform, the relative error of the reconstruction result is 24.6%. The overall feature‐matching rate of the reconstruction reaches 93.3%. It provides a theoretical basis for the study of surface microcrack propagation mechanism and the prediction of bearing life. [ABSTRACT FROM AUTHOR]

To investigate the effect of nano-indentation depth on the elastic–plastic transition mechanism of 6H-SiC, the loading process of nano-indentation on a 6H-SiC⟨0001⟩ crystal surface is analyzed by using the molecular dynamics method. Diamond indenters and 6H-SiC amorphous nanolayers are constructed; Tersoff and Vashishta potential functions are established to describe the interactions between atoms; and simulated environmental factors, such as relaxation conditions, ensemble, and loading speed, are optimized. The stress distribution and internal deformation characteristics are analyzed by combining load–displacement curves, radial distribution curves, dislocation nucleation, and their evolutive processes. The load–displacement curve deviates from the theoretical value at a depth of 3.8 nm and enters the elastic to plastic transition phase, where the shear stresses generated by friction on the contact surfaces cause the atoms on the stacked layers in the elastic phase to move in a directional manner and form dislocations: edge-type dislocations connecting the two layer dislocations and horizontal spiral dislocations. The plastic deformation phase starts at a depth of 5.9 nm, the atoms keep migrating and reorganizing, the original dislocation rings break to form incomplete dislocations, and the new dislocations formed by the combination of partial edge-type dislocation rings expand internally until fracture. The formation and expansion of dislocations contribute to the elasto-plastic transformation of 6H-SiC, and amorphous states are found to be involved in the deformation process at both the indentation contact surface and the deformation layer. Moreover, there are differences in the direction of dislocation expansion due to the inhomogeneous stress distribution at the contact surface. [ABSTRACT FROM AUTHOR]

The molecular dynamics method was used to analyze the influence of simulated temperature on the damage expansion process of the 3C-SiC sample under nano-indentation loading in order to study the influence of temperature on the internal damage and expansion mechanism of the 3C-SiC single crystal sample further during the nano-indentation loading process. A simulation test platform for diamond indenter indentation was established. The process of stress and strain distribution, dislocation evolution, dislocation expansion and potential energy change were analyzed, combined with the radial distribution function and load displacement curve. The influence of temperature on the 3C-SiC material was discussed. The variation trend of the potential energy-step curve is basically the same at the temperatures of 0 K, 300 K, 600 K and 900 K. The difference in strain distribution was characterized by the influence of temperature on stress intensity, expansion direction and type. The microcosmic manifestation is the significant difference in the dislocation slip at low temperature. In the process of dislocation evolution and expansion, dislocation climbs at room temperature and increases at high temperature, which is closely related to energy release. This study has certain guiding significance for investigating the internal damage difference and temperature effect of the 3C-SiC sample. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate whether the grain size of ceramic materials follows the classical Hall–Petch effect and the effect of grain boundaries and grains on the subsurface crack propagation of nano-polycrystalline 6H-SiC by molecular dynamics. We established an initial friction model of diamond on nano-polycrystalline 6H-SiC based on the Voronoi's polycrystalline construction method. Construct Tersoff and Vashishta potential functions. Molecular dynamics parameters were optimized according to 6H-SiC relaxation equilibrium state model, and initial friction model was modified by integrating potential function, boundary conditions, relaxation equilibrium, temperature control, time step and other parameters. Combined with the molecular defect analysis method, radial distribution function, and the influence of stress, strain, and dislocation on the surface crack theory, the shear strain and shear stress distribution trend and sub-surface damage rate of grain boundaries were calculated. It was found that the potential energy increases with the increase in the grain size. The atoms between grain boundaries show a "stress concentration" phenomenon and transfer between the grain boundaries. Under the action of friction, the crystal breaks, and the HP phenomenon is obvious. The degree of damage to the grain boundary is smaller than that of the grain. The larger the grain size, the smaller is the hardness of the crystal and higher is the possibility of the crystal fracture, which is obvious in crystals with larger grain size. The IHP effect was observed in the crystal with an average grain size of 16.0 nm. The results show that the HP and IHP effects also exist in ceramic materials, and the crossover mechanism between the grain boundaries and grains is another driving force for the change in the crystal structure. [ABSTRACT FROM AUTHOR]

In order to explore the deformation law of nanoindentation dislocation on different crystal planes of 6H-SiC by cube indenter at high temperature, the (0001), (1 1 ¯ 00) and (2 1 ¯ 1 ¯ 0) crystal planes were simulated by molecular dynamics, and changes of dislocation and shear stress under different crystal planes were analyzed. With the deepening of indentation depth, the formation of dislocations on different indentation surfaces has a certain repeatability. The crystal plane (0001) continuously generates horizontal dislocations around the indentation, (1 1 ¯ 00) the crystal plane generates two square dislocation rings moving downward at a time, and (2 1 ¯ 1 ¯ 0) the crystal plane generates one square dislocation ring moving downward at a time. [ABSTRACT FROM AUTHOR]

In order to explore the elastic-plastic deformation law of 3C-SiC ceramic parts using hemispherical and regular pyramid indenters under ultimate load, the evolution of dislocations in nanoindentation simulation was analyzed and compared with the elastic-plastic deformation process in load displacement curves. In the dislocation analyses, we found the generation, combination, and separation of "petal shaped" horizontal dislocations and "gliding umbrella" crossing, horizontal and vertical dislocations, and special slip phenomena. In the load displacement curve, the elastic and elastic-plastic deformation show similar linear changes, and the plastic deformation presents a fluctuation state below the limit load and a rising state derived from the limit load, respectively. The simulation limit load value and the occurrence period of limit load are different with the two indenters. There is a strong correlation between evolution of dislocations and elastic-to-plastic deformation process, reflected in the load displacement curve. [ABSTRACT FROM AUTHOR]

In this paper, the atomization characteristics of Si3N4 ceramic dry granulation affect the performance of Si3N4 ceramic bearing balls. In order to improve the dry granulation characteristics and the comprehensive performance of Si3N4 ceramic bearing balls, the atomization mechanism of the spinning nozzle used for Si3N4 dry granulation was studied in detail. The interaction between air and binder in the pressure-swirl nozzle is analyzed based on VOF method, the modified realizable k − turbulence model is used to simulate the flow field inside and outside the pressure-swirl nozzle, the effects of nozzle inlet parameters including the number of tangential inlets and the deflection angle of tangential inlets on the binder volume fraction, velocity distribution and pressure distribution are analyzed. The results show that when the number of tangential inlets increases from 1 to 4, the swirl strength of gas–liquid two-phase in the nozzle increases, the mean diameter of air core increases from 1.51 mm to 2.01 mm, and the spray cone angle increases from 18.5 ∘ to 26.4 ∘ . Besides, when the deflection angle of tangential inlet increases from 0 ∘ to 15 ∘ , the swirl strength of gas–liquid two-phase in the nozzle with the deflection angle of tangential inlet of 10 ∘ is the largest, and the mean diameter of air core and spray cone angle is 3.04 mm and 30.7 ∘ , respectively. Based on the atomization experiment platform of the electric control fuel system, the mean diameter of air core and spray cone angle are measured, the micromorphology of Si3N4 particles is observed, which verifies the correctness of numerical simulation. When the Si3N4 particles are prepared by dry granulation, taking the atomization performance of nozzle into consideration, the pressure-swirl nozzle with 4 tangential inlets and 10 ∘ deflection angle should be selected. [ABSTRACT FROM AUTHOR]

To improve the uniformity of the flow field and the poor axial velocity in the chamber of Si3N4 dry granulation, the influence of geometric parameters at open turbine combined structure on the flow field distribution is studied. The Euler–Euler gas-solid two-phase flow model is established and the physical model of dry granulation chamber under the combined structure is simplified. Under the same radial structure, the volume distribution and velocity field of Si3N4 particles in the granulation chamber with a different number and angle of the axial structure at the open turbine are analyzed by the CFD method. The influence of the axial structure at the open turbine on the flow field distribution of Si3N4 particles under different geometric parameters is compared. The results show that the axial structure of the open turbine in the granulation chamber is the most uniform when the number of blades is 6 and the inclination angle is 4 5 ∘ , and the circulating flow of the upper and lower parts of Si3N4 powder is strong. [ABSTRACT FROM AUTHOR]

In order to improve the whirling phenomenon of Si 3 N 4 particles in the granulation chamber, the influence of the structure of the granulation chamber on the internal distribution is explored. Euler Euler's two-phase flow model is established. The flow field in the combined structure granulation chamber with different layout is simulated. The volume distribution and velocity field change of Si 3 N 4 particles in the combined structure granulation chamber with different layout are analyzed. The results show that the angle between two adjacent composite structures is 20 ∘ , 60 ∘ , 80 ∘ and completely standard the Si 3 N 4 particles with volume fraction index greater than 0.8 account for 10.2%, 11.5%, 12.5% and 6.7% of the total volume respectively. When the combined structure is completely standard, several small convolutions are found. The whirling phenomenon in the granulation chamber is improved. When the angle between two adjacent composite structures is 20 ∘ , 60 ∘ , 80 ∘ and complete standard, the proportion of qualified particles is 59%, 64%, 66% and 68%. The fluidity index is 84, 85, 87 and 88, respectively. To sum up, the combination structure of the granulation chamber is a complete standard, it is beneficial to improve the spin phenomenon of Si 3 N 4 particles in the granulation chamber. [ABSTRACT FROM AUTHOR]

In order to explore the effect of dry granulation time on the compactness of silicon nitride ceramic particles, the water content, micro-morphology and particles strength of the particles under different granulation time were compared and analyzed base on the self-design granulation time-particle compactness experimental platform. The results show that with the increase of granulation time, the moisture content of silicon nitride particles decreased linearly, and the micro-morphology of silicon nitride particles showed three states; rough, smooth and cracky. When the granulation time was 5 min, the water content of the form silicon nitride particles was about 9%, which reached the optimal production value. SEM images show that the surface of the silicon nitride particles was smooth and crackless. and the particles strength reached the maximum value of 2.5 N measured by experiment. [ABSTRACT FROM AUTHOR]

During superheated steam fluidized bed drying process, the operating pressure has an important influence on heat and mass transfer characteristics and the vapor-solid two-phase flow characteristics. Based on the two-dimensional unsteady model of rapeseeds drying process, the influence of operating pressure on the superheated steam fluidized bed drying kinetics was revealed by computer numerical simulation. The quantitative analysis of relationship between operating pressure and maximum drying rate was conducted under negative pressure, near atmospheric pressure and high pressure environment, respectively. The optimum operating pressure values for superheated steam fluidized bed drying were obtained with the imported superheated steam temperature and superficial velocity. The simulation results provide a theoretical reference for superheated steam fluidized bed drying technology applying to agro-processing projects. [ABSTRACT FROM AUTHOR]

Silicon nitride ceramics were prepared using different amounts of MgO or Y2O3 powder as sintering aids (2%,4%,6%,8%, and 10%), ball milling, granulating, shaping and sintering at 1 750 °C under 6 MPa nitrogen. The relative density of the specimens was determined, the phase composition and microstructure were explored. The results show that (1)the maximum relative density reached 96.5% or 98% with 6% MgO or 8% Y2O3, respectively;(2)with the same addition, the relative density of the sample with Y2O3 powder is higher than that with MgO powder, indicating that Y2O3 preforms better than MgO in promoting sintering densification;(3)MgO and Y2O3 powder both can promote the transition from α-Si3N4 to β-Si3N4. [ABSTRACT FROM AUTHOR]

Athree-layer composite plate element is developed for finite element modeling and vibration analysis of sandwich plate with frequency-dependent viscoelastic material core. The plate element is quadrilateral element bounded by four-node with 7-degree-of-freedom per node. The frequency-dependent characteristics of viscoelastic material parameters are described using the Biot model. The method of identifying the parameters of the Biot model is given. By introducing auxiliary coordinates, the Biot model is combined with the finite element equation of the viscoelastic sandwich plate. Through a series of mathematical transformations, the equation is transformed into a standard second-order steady linear system equation form to simplify the solution process. Finally, the vibration characteristics of the viscoelastic sandwich plate are analyzed and experimentally studied. The results show that the method in this paper is correct and reliable, and it has certain reference and application value for solving similar engineering vibration problems. [ABSTRACT FROM AUTHOR]

In this work, a finite element model was developed for vibration analysis of sandwich beam with a viscoelastic material core sandwiched between two elastic layers. The frequency-dependent viscoelastic dynamics of the sandwich beam were investigated by using finite element analysis and experimental validation. The stiffness and damping of the viscoelastic material core is frequency-dependent, which results in complex vibration modes of the sandwich beam system. A third order seven parameter Biot model was used to describe the frequency-dependent viscoelastic behavior, which was then incorporated with the finite elements of the sandwich beam. Considering the parameters identification, a strategy to determine the parameters of the Biot model has been outlined, and the curve fitting results closely follow the experiment. With identified model parameters, numerical simulations were carried out to predict the vibration and damping behavior in the first three vibration modes, and the results showed that the finite model presented here had good accuracy and efficiency in the specific frequency range of interest. The experimental testing on the viscoelastic sandwich beam validated the numerical predication. The experimental results also showed that the finite element modeling method of sandwich beams that was proposed was correct, simple and effective. [ABSTRACT FROM AUTHOR]