With the rapid development of the offshore wind power industry, the construction process of offshore wind power jackets faces numerous quality risks, particularly in welding, coating, and assembly operations. This paper aims to investigate the identification, assessment, and management of quality risks during the construction of offshore wind turbine foundation structures. By establishing a multidimensional quality risk assessment framework, key risk factors affecting quality were identified through expert interviews and brainstorming sessions. Comprehensive evaluations of these risk factors were conducted using the Entropy Weight Method (EWM), the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), and Grey Relational Analysis (GRA). The findings indicate that welding and coating processes pose the highest risks during construction. Based on these assessments, corresponding risk mitigation measures are proposed, including process optimization, automation enhancement, environmental control, and management system refinement. This study provides theoretical foundations and practical guidance for improving construction quality and reducing costs in offshore wind turbine foundation manufacturing. It advances quality risk management by introducing an integrated evaluation model that addresses the limitations of single-method approaches in complex construction scenarios.

4H-SiC substrate is widely employed in semiconductor device fabrication owing to its unique crystal structure and excellent physicochemical properties. However, its deformation behavior during substrate processing remains complex and not fully understood. In this study, molecular dynamics (MD) simulations were performed to systematically investigate the deformation mechanism of single-crystal 4H-SiC during nanoindentation, serving as an atomic-scale analogue of the workpiece-abrasive interaction during substrate processing. Specifically, the relationship between the fluctuations of the load-depth curve and slip were revealed, with particular emphasis on the basal slip (BS) and prismatic slip (PS) behaviors. The results indicate that the fluctuations in the load-depth curve are primarily associated with the nucleation and propagation of dislocations. The initiation of BS is predominantly influenced by the atomic arrangement and stress distribution, while PS initiates at the terminus of BS as the indentation depth increases. Finally, nanoindentation experiments were conducted to validate the reliability of the MD simulations. These findings provide valuable insights into the deformation mechanism and mechanical behavior of 4H-SiC during practical substrate processing.

Sapphire substrates are essential for advanced optoelectronic and power devices, but their extreme hardness and strong elastic-plastic anisotropy readily induce severe subsurface damage (SSD) during conventional machining, limiting wafer-scale yield and device reliability. Although ultrasonic vibration-assisted scratching (UVAS) can reduce forces and damage, the defect-suppression mechanisms on the A-plane and their dependence on vibration parameters and scratching direction remain insufficiently resolved. This paper used molecular dynamics simulations of UVAS to elucidate the coupled roles of vibrational parameters and crystal orientation on dislocation/ twinning activity, amorphization, and SSD depth. Results show that UVAS significantly suppresses the formation of dislocation networks and twinning through cyclic unloading, thereby reducing damage depth. However, extremely high frequencies and strain rates promote atomic amorphization and thicken the damage layer. A strong anisotropic response is observed: scratching along the [0001] orientation produces a denser but shallower defect zone along the [1100] orientation. Building on Schmid-type criteria, an ultrasonically modulated damage activation model is developed to reproduce the within-cycle activation/suppression of slip and twinning systems and to provide a predictive framework for parameter selection. By integrating atomistic insights with continuum-scale modeling, the present study provides the first mechanistic guidelines for ultrasonic vibration-assisted processes of anisotropic sapphire.

The significant anisotropy of single-crystal diamond (SCD) leads to complex plastic deformation and subsurface damage during machining, which has become a key bottleneck in achieving high-efficiency and low-damage processing. In this study, nanoindentation molecular dynamics simulations were employed to systematically reveal the influence of anisotropy on the plastic deformation behavior and subsurface damage (SSD) of SCD. The results indicate that the pop-in events in the load–depth curves are closely associated with the activation of crystal slip. The spatial distribution of dislocations is highly consistent with the crystallographic symmetry of the corresponding crystal planes, and a transition in the plastic mechanism from phase transformation (PT)-dominated to dislocation-dominated occurs on all crystal planes. The (001) plane exhibits the largest critical transition depth, while the (110) plane shows the smallest. Further analysis reveals that the activation sequence of different slip systems significantly affects the evolution path of SSD. Accordingly, a SSD evolution model based on crystal slip was established. The model achieves an average prediction error of less than 3.7% for the slip factor, validating the evolution mechanism of SSD dominated by crystal slip. This study provides a theoretical foundation and atomic-scale mechanistic understanding of the anisotropic machining damage in single-crystal diamond.

To address the critical challenges of poor form accuracy control and limited lapping efficiency associated with semi-fixed gel abrasive pads in sapphire substrate processing, this study proposes a novel grid pattern-structured composite lapping pad based on the "rigidity-flexibility coupling" concept. The design features a continuous grid pattern support skeleton fabricated from high-modulus resin, with soft gel containing diamond abrasives filled into the grid pattern cells as lapping units. The rigid resin skeleton ensures macroscopic form retention, while the lateral confinement imposed by the grid pattern cell walls on the gel induces a "local pressure amplification" effect, thereby enhancing the effective cutting load of individual abrasive grits. First, an analytical mechanical model describing the compressive deformation of the composite pad is established, quantitatively revealing the intrinsic relationships between the gel area ratio gamma and both the overall pad compression and the stress distribution between the gel and resin phases. Subsequently, finite element simulation is employed to validate the model accuracy and elucidate the microscopic mechanisms underlying non-uniform stress distribution and constraint-induced stress enhancement within the grid pattern unit. Finally, two typical grid pattern-structured pads with gamma = 44% and 69% are designed, fabricated, and subjected to comparative lapping experiments on sapphire substrates. The results demonstrate that the pad with gamma = 69% achieves a material removal rate (MRR) of 1.027nm/min, representing an approximately 29.7% improvement over the gamma = 44% pad. Furthermore, it yields smaller standard deviation in surface roughness and lower total thickness variation (TTV) of the processed substrate, exhibiting superior processing efficiency and uniformity. This study offer a valuable reference for the design of composite polishing pads applied to high-efficiency and low-damage planarization of sapphire substrates, offering both theoretical guidance and engineering feasibility.

Ultrasonic vibration-assisted grinding (UVAG) is a promising, low-damage, high-efficiency and environmentally friendly technique for machining sapphire, yet its atomistic mechanisms and orientation dependence remain poorly understood. In this work, we employ molecular dynamics (MD) simulations to compare ultrasonic vibration-assisted scratching (UVAS) with conventional scratching (CS) on the A/C/M/R-planes of sapphire. Applying ultrasonic vibration dramatically reduces the scratching force by redistributing the stress field and activating cyclic deformation mechanisms, with the force-reduction sequence A approximate to M > C > R. Surface-topography analysis shows that chip pile-up modes depend on crystal orientation; ultrasonic vibration not only lowers the pile-up height but also makes it more uniform. Moreover, ultrasonic vibration mitigates subsurface damage by suppressing tangled dislocation networks on the A- and M-planes and by promoting the nucleation of dislocations and twinning on the C- and R-planes, with the C-plane experiencing the least damage. These results systematically clarify the coupled effects of ultrasonic vibration and sapphire anisotropy, providing valuable guidance for selecting crystal orientations and vibration parameters during ultra-precision grinding of electronic devices, such as sustainable clean-energy LEDs.

In order to explore the effect of stress on the damage of 4H-SiC materials, this paper employed single abrasive grain indentation simulation based on the Smoothed-Particle Hydrodynamics (SPH) method, and verified the accuracy of the indentation model through an indentation experiment on a single abrasive grain. The research examined the consequences of varying pressures on the processing of 4H-SiC, including parameters such as the depth of abrasive grain penetration, the stress-affected region, and the initiation and propagation of cracks. Subsequently, mathematical models were developed to characterize stress variations under different pressure conditions. The findings reveal several vital insights: First, a discernible linear relationship exists between the depth of abrasive grain penetration into 4H-SiC and the applied pressure. Second, within a specific pressure range, the stress-affected zone within the workpiece enlarges as the applied pressure increases. However, when cracks form within the workpiece, the dimensions of the stress-affected zone exhibit fluctuations. During the abrasive grain indentation phase, a discernible pattern emerges in the stress distribution within the workpiece.

Silicon carbide(SiC) is a hot topic in current semiconductor material research and is widely used but typically difficult to process. It was found that the interface reaction between the metal Fe and single crystal SiC contributes to the removal of single crystal SiC materials. The diffusion between the atoms of Fe and SiC is the basis of solid state mass transfer and reaction. In this paper, a series of static diffusion simulations of metal iron and SiC at different temperatures by molecular dynamics (MD) method are conducted to elucidate the mechanism of static diffusion in Fe/4H-SiC. It was found that the diffusion temperature range of iron (Fe) on the carbon face of 4H-SiC is similar to experimental results, and the thickness of the diffusion layer increases with temperature, consistent with experimental observations, verifying the accuracy of the simulation model. Based on that, a series of frictional diffusion simulations of metal iron and SiC at different speeds are carried out to elucidate the mechanism of frictional diffusion in Fe/4H-SiC. The study also indicated that frictional diffusion can occur at temperatures much lower than free interface diffusion. The friction speed has a significant impact on diffusion behavior, mainly manifested in the significantly different diffusion characteristics of carbon surfaces at different speeds. In addition, the increase in friction speed makes the diffusion zone more pronounced.

Carbon fiber reinforced polymer (CFRP) is an ideal lightweight material for a wide range of applications, including aerospace, due to its superior mechanical properties. In this study, a microscopic finite element model of CFRP is developed using the Finite Element Method to simulate the scratching process with a single grain. The fiber damage mechanism is investigated, and the effects of grain scratching speed, the depth of the surface fibers embedded in the matrix, and the depth of the grain cutting into subsurface fibers on the damage and removal of surface and subsurface fibers in CFRP are discussed. The results indicate that the formation of slanted fractures in fibers is closely associated with the initiation and propagation of central cracks, transverse cracks at both ends, and longitudinal cracks. With increasing scratching velocity, fiber damage exhibits a decreasing trend. No transverse cracks are observed in surface layer fibers at a scratching velocity of V = 120 m/s and in sub-surface fibers at V >= 90 m/s. Under scratching conditions of V >= 90 m/s, the damage in both surface and sub-surface fibers tends to be mitigated. This study provides new insights into the fiber damage mechanism of CFRP during grinding processes and offers a theoretical basis for optimizing grinding parameters and improving processing quality.

Sapphire has extensive applications in advanced manufacturing fields, including electronics and semiconductors. However, its pronounced anisotropy poses significant challenges for ultra-precision machining and effective damage control. This study systematically investigates the anisotropic mechanisms of plastic deformation and subsurface damage (SSD) evolution across different sapphire crystal planes. This is achieved using molecular dynamics simulations, nanoindentation experiments, and transmission electron microscopy characterization. The results definitively show that distinct slip system behaviors depend on crystal orientation: the basal plane acts as the primary slip plane for the A/M/R-planes, whereas the rhombohedral slip is dominant for the C-plane. Subsurface damage of the A/M-planes is dominated by the formation of dislocation loops, whereas the C/Rplanes primarily exhibit cross-slips. It was also identified that crack initiation and propagation mechanisms are closely linked to twinning behaviors. Cracks preferentially nucleate and propagate along the twinning planes, with basal and rhombohedral twinning playing key roles. The formation and evolution of SSD are significantly influenced by the activation and interaction of slip systems, leading to variations in damage depth, with a clear trend of M-plane >A-plane >R-plane. On the C-plane, basal slip initially minimizes damage; however, increased indentation depth activates rhombohedral slip, exacerbating SSD. Furthermore, a theoretical slip system activation model was successfully developed and validated, accurately predicting SSD evolution. These findings provide a robust theoretical basis for optimizing low-damage ultra-precision machining processes for sapphire and other anisotropic crystalline materials.

To investigate the influence of defects on the damage mechanism of 4H–SiC, this study primarily conducted molecular dynamics simulations of a single diamond abrasive indentation process and carried out subsequent nanoindentation experiments on 4H–SiC samples. The simulation and experimental results were compared, and the force–displacement curves showed consistent trends. On this basis, the scratching simulation of an ideal material and a single diamond abrasive particle containing 4H–SiC with dislocation defects was carried out to study the influence of internal dislocation (screw dislocation and edge dislocation) in 4H–SiC and its position on the material damage mechanism during scratching, and the development and evolution of internal dislocation were further analyzed. The results reveal that the presence of internal dislocations in the material is one of the causes of the formation of dislocation loops.

Ultrasonic vibration-assisted grinding (UVG) has several advantages, such as small grinding force, good surface quality, and high grinding efficiency, outperforming conventional grinding (CG). However, it is sensitive to process parameters, making optimal processing parameters crucial and a major challenge. Therefore, in this study, we introduce a model based on the AAC theory, which uses only three quantities (vibration Angle, contact Area, and influence Coefficient of adjacent abrasive particles) to assess the forces during UVG. These three quantities depend on the movement trajectory, mutual contact relationship between the workpiece and abrasive particles, and spacing between abrasive particles. The effects of these three quantities on the scratch force were examined using molecular dynamics (MD) simulations. The reduction ratios of forces (tangential and normal directions) gradually increased with increasing angle, while the differences in the force reduction ratios for the different contact areas were not significant. As the influence coefficient increased, the reduction ratio of the tangential force increased and then flattened, and the reduction of the normal force increased and then slightly decreased. Spearman’s correlation analysis shows that the vibration angle has the most effect on the reduction ratio of the scratch force. And the AAC theory was verified by UVG experiments.

Ultrasonic vibration-assisted grinding is typically used for ultra-precision machining of hard and brittle materials in aerospace, medical and semiconductor industry. Single grain scratching force is a key to understand its mechanism. Herein, a scratching force model of axial ultrasonic vibration-assisted single-grain scratching was proposed, based on the deformation of chips, friction, and material pile-up forces of a single grain during scratching. The single-crystal silicon carbide was selected as the model material. The molecular dynamics method was employed to simulate single-grain scratching. The scratching forces obtained from the simulations were consistent with the theoretical model with a difference of 4.13 %. The period of the normal force and tangential force is half of that of the vibration and the axial force. The discrepancies are 11.26 % and 4.05 % in tangential and normal directions, respectively, referring to experiment. Axial ultrasonic vibration-assisted scratching facilitates the cyclical removal of brittle and ductile phases, which corroborates the conclusion about the periodicity of the force. Our insights might be helpful in the arrangement of grains on the surface of the grinding wheel and advanced machining design.

Coupling of multiple abrasive grains is crucial for the efficiency in the grinding process and grinder design. Here the coupling effect in a double-grain model in vibration-assisted scratch of single-crystal silicon carbide (SiC) have been investigated using the molecular dynamics simulations for both simultaneous and sequential scratch processes. The coupling between the double abrasive grains affect the scratch force, stress, amorphous layer and surface morphology. The reduction ratios of tangential and normal force and the influenced material volume show that the critical distance for the inhibition of the coupling of vibration-assisted scratch is significantly greater than that in conventional scratch. The change of overlap ratio can reflect the change trend of the scratch force reduction ratio. In the vibration-assisted grinding, the increase of overlap ratio also intensifies the coupling of the abrasive grains, resulting in faster material removal, smaller scratch force and better surface finish. In-sights obtained through the molecular dynamics analysis in this work into the coupling effects of abrasive grains in the vibration-assisted grinding process is believed to be beneficial in the development of grinding wheels and the optimization of machining processes.

An investigation was conducted to explore the mechanisms of the scratching of monocrystalline silicon carbide with a single diamond grit. The scratching was repeated on a silicon carbide workpiece to generate different wear shapes of the diamond grit. The forces were recorded during each scratching and the wear of the diamond grit together with the silicon carbide morphologies was monitored at a fixed interval. Based on the different diamond wear shapes determined through scratching experiments, a smoothed particle hydrodynamics method was used to simulate the scratching process. In addition to the items monitored in the experiments, the simulation was also used to analyze the change of subsurface damages on silicon carbide and to predict the mechanisms of diamond damage. It is shown that double-edged abrasive grits might lead to a better silicon carbide surface quality in scratching. The simulation results indicate that the maximum equivalent stress distribution might be used to predict the damage of the diamond grits during scratching. The findings of this article will be of benefit to the optimal selection of machining parameters and the optimal design of diamond tools for abrasive machining of monocrystalline silicon carbide.

Single-crystal silicon carbide (SiC) is widely used because of its excellent properties. However, SiC is a typical hard and brittle material, and there are many challenges in realizing its high efficiency and high-precision machining. Grinding is the main method used to achieve the high-efficiency processing of SiC, but the contradiction between processing quality and processing efficiency is prominent. Vibration-assisted grinding is an effective method to realize high-efficiency and precision machining of SiC. To reveal the vibration-assisted grinding mechanism of SiC, the vibration-assisted nano-scratch process is studied using the molecular dynamics method, and the material removal process and damage formation mechanism in the vibration-assisted scratch are analyzed. Aiming at the three main structural crystal types, 3C-, 4H- and 6H-SiC, scratch simulations were carried out. The vibration-assisted scratch characteristics of SiC polytypes were evaluated from the perspectives of scratch force and the amorphous layer. It was found that the effects of vibration-assisted scratch on different crystal structures of SiC differ, and 3C-SiC is quite different from 4H- and 6H-SiC. Through vibration-assisted scratch simulations under different scratch conditions and vibration characteristics, the influence laws for machining parameters and vibration characteristic parameters were explored. It was found that increasing the frequency and amplitude was beneficial for improving the machining effect. This provides a basis for vibration-assisted grinding technology to be used in the high-efficiency precision machining of SiC.

Silicon carbide is an ideal material for advanced electronics, military, and aerospace applications due to its superior physical and chemical properties. In order to understand the effect of crystal anisotropy of 4H-SiC on its processability, nanoindentation and nanoscratch tests on various crystallographic planes and orientations were performed and the results outlined in this paper. The results show that the C-plane of 4H-SiC is more rigid, while the Si-plane is more elastic and ductile. Better surface quality may be obtained on the Si-plane in nanoscale abrasive machining. The maximum lateral force, maximum residual depth of the scratch, and maximum crack width on the C- and Si-planes of 4H-SiC are significantly periodic in crystallographic orientations at 30° intervals. The scratch along the <112¯0> direction is more prone to crack expansion, and better machined surface quality is easy to obtain along the <101¯0> directions of C- and Si-planes.

Owing to outstanding mechanical, optical, thermal stability and chemical stability properties, sapphire has widespread use in semiconductors, aerospace and other fields. However, it is difficult to machine it efficiently and precisely because of its brittleness and hardness. In this work, the processing and mechanism of machining sapphire using ultrasonic vibration-assisted grinding technology have been investigated via experiment. The machining factors have been analyzed, including the condition of machined surface, specific grinding energy, force and force ratio. Referring to conventional grinding, the application of ultrasonic vibration reduces the force, force ratio, specific energy, and the reduction ratio is direction dependent. The effect on surface roughness and morphology is also anisotropic. Regarding the smoothness of the surface, the suitable directions were axial and tangential, while there was no noticeable improvement in the radial direction. Our results and insights could be beneficial for the precise machining of brittle materials and quality management.

To ensure the reliable bonding and low thermal damage of brazed diamond grits, a Ni-free Cu-Sn-Cr filler alloy was developed based on our previous study. Interfacial microstructure of diamond grits brazing used by Cu-22Sn-3Cr (in wt. %) filler alloy at 950 °C for 5, 10, 20, and 40 min were systematically investigated. Only Cr7C3 was generated at the interface between diamond and Cu-22Sn-3Cr alloy, and the thickness of Cr7C3 was increased after extended brazing time. The grinding performance of diamond tools brazed using Cu-22Sn-3Cr alloy has fewer ratios of diamond grits with breakage and fall-off failures and thus was found to be superior to that brazed by Ni-14Cr-10P filler alloy. In addition, alloy composition has a more significant influence than brazing time on the interfacial microstructure and mechanical behavior of brazed diamond grits; and the higher mechanical behavior of diamond grits brazed using Cu-Sn-Cr filler alloy is proved to be closely related to the low solubility of C in Cu-Sn-based alloy. Results obtained in this work are also crucial for developing a diamond brazing technique to fabricate diamond-related materials and devices.

Through a series of single-scratch experiments, the damaged process of diamond grit and the material removal mechanism of single crystal silicon carbide (SiC) were investigated. The <111> and <110> planes of single diamond grits were used to scratch the carbon (C) face and silicon (Si) face of single crystal SiC, respectively. The damaged process and corresponding typical damaged morphology of diamond grits on different planes were analyzed. The material removal mechanism of single crystal SiC (C face and Si face) is analyzed. The results show that the contact width and the breaking angle were determined as the key damaged parameters of diamond grit by the analysis of the damaged process. However, the key factor to reduce surface damage is the state of the micro-edges that appear on the crystal plane of the diamond grit in contact with the workpiece during the scratching process.