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The nickel-based casting superalloy K4169 is extensively utilized in aerospace engines for its extraordinary mechanical and thermal properties. However, achieving high surface integrity of the superalloy remains challenging. Ultrasonic-assisted machining (UAM) is an advantageous technology, while the influence on cast superalloy is imperative to be revealed. The study on surface morphology and integrity of K4169 was carried out using ultrasonic-assisted end milling. The results showed that the ultrasonic vibration effectively suppresses surface defects and facilitates a regular surface texture. A more significant deformed layer of 7.3 μm was induced in UAM, representing a 97% enhancement relative to CM. Additionally, surface microhardness and compressive residual stress show a tendency to increase with ultrasonic amplitude. Specifically, the surface compressive residual stress in UAM reached 822 MPa, signifying a 69.6% increase over CM.

The densification of fused glass during processing has a significant impact on the performance and application of fused glass components. However, the precise atomic mechanisms underlying densification remain elusive. In this study, we explore the atomic mechanisms responsible for densification in fused glass during single particle scratching, with a focus on the scratching depths and environmental humidity. We employ reactive force field molecular dynamics (ReaxFF MD) simulations for our investigation. We subjected models to scratching under various humidity conditions using a spherical virtual indenter with a 20 Å radius. The scratching depths were set at 10 Å and 15 Å, respectively, with a constant scraping speed of 40 m/s. Our findings indicate that water molecules impede lateral atom movement on the fused glass surface while enhancing vertical flow. Furthermore, water molecules facilitate the volume recovery of fused glass following scratching. The transfer of hydrogen (H) atoms within the fused glass, facilitated by Si–O–H⋯O–Si structures, plays a crucial role in promoting volume recovery. The ultimate density distribution of fused glass results from a combination of atomic displacement during scratching and subsequent volume recovery. This study enhances our atomic-level understanding of densification generation in fused glass.

Carbon fiber reinforced silicon carbide ceramic matrix (Cf/SiC) composites have the advantages of high temperature resistance, wear resistance, low density, high hardness as well as specific strength. They have been applied extensively in hot-end components of aerospace and braking systems of trains. Nevertheless, grappling with the anisotropy, non-homogeneity, and weak interlayer bonding of Cf/SiC composites presents a major challenge for achieving efficient and low-damage processing. This paper is primarily intended to investigate comprehensively the mechanical properties and damage behavior of Cf/SiC composites by nanoindentation and Vickers indentation tests. The behaviors of indentation damage on the longitudinal section of fiber (LSF), the cross-section of fiber (CSF) and matrix under different loads and the deflection mechanism of matrix crack were analyzed. The findings reveal a pronounced anisotropy between the radial and axial orientations of the fiber, and plastic deformation exists in the matrix. Furthermore, the matrix has the largest hardness and elastic modulus, while the LSF displays the lowest values among the composites. The main forms of indentation damage on the LSF are fiber crack, fiber peel off, fiber cocked up and squamous crack. The main manifestations of indentation damage on CSF are fiber crushing and fiber debonding, with the total surface damage area being comparatively limited. The fiber orientation and interface are influential factors in the crack propagation path of matrix. Notably, the fibers effectively inhibit the crack propagation of the matrix. This investigation provides valuable theoretical guidance for the formation mechanism and suppression strategy of machining damage in Cf/SiC composites.

The visual measurement of deep holes in composite material workpieces constitutes a critical step in the robotic assembly of aerospace components. The positioning accuracy of assembly holes significantly impacts the assembly quality of components. However, the complex texture of the composite material surface and mutual interference between the imaging of the inlet and outlet edges of deep holes significantly challenge hole detection. A visual measurement method for deep holes in composite materials based on the radial penalty Laplacian operator is proposed to address the issues by suppressing visual noise and enhancing the features of hole edges. Coupled with a novel inflection-point-removal algorithm, this approach enables the accurate detection of holes with a diameter of 10 mm and a depth of 50 mm in composite material components, achieving a measurement precision of 0.03 mm.

Abstract The roughness of the contact surface exerts a vital role in rubbing. It is still a significant challenge to understand the microscopic contact of the rough surface at the atomic level. Herein, the rough surface with a special root mean square (RMS) value is constructed by multivariate Weierstrass–Mandelbrot (W–M) function and the rubbing process during that the chemical mechanical polishing (CMP) process of diamond is mimicked utilizing the reactive force field molecular dynamics (ReaxFF MD) simulation. It is found that the contact area A/A 0 is positively related with the load, and the friction force F depends on the number of interfacial bridge bonds. Increasing the surface roughness will increase the friction force and friction coefficient. The model with low roughness and high lubrication has less friction force, and the presence of polishing liquid molecules can decrease the friction force and friction coefficient. The RMS value and the degree of damage show a functional relationship with the applied load and lubrication, i.e., the RMS value decreases more under larger load and higher lubrication, and the diamond substrate occurs severer damage under larger load and lower lubrication. This work will generate fresh insight into the understanding of the microscopic contact of the rough surface at the atomic level.

The robotic drilling of assembly holes is a crucial process in aerospace manufacturing, in which measuring the normal of the workpiece surface is a key step to guide the robot to the correct pose and guarantee the perpendicularity of the hole axis. Multiple laser displacement sensors can be used to satisfy the portable and in-site measurement requirements, but there is still a lack of accurate analysis and layout design. In this paper, a simplified parametric method is proposed for multi-sensor normal measurement devices with a symmetrical layout, using three parameters: the sensor number, the laser beam slant angle, and the laser spot distribution radius. A normal measurement error distribution simulation method considering the random sensor errors is proposed. The measurement error distribution laws at different sensor numbers, the laser beam slant angle, and the laser spot distribution radius are revealed as a pyramid-like region. The influential factors on normal measurement accuracy, such as sensor accuracy, quantity and installation position, are analyzed by a simulation and verified experimentally on a five-axis precision machine tool. The results show that increasing the laser beam slant angle and laser spot distribution radius significantly reduces the normal measurement errors. With the laser beam slant angle ≥15° and the laser spot distribution radius ≥19 mm, the normal measurement error falls below 0.05°, ensuring normal accuracy in robotic drilling.

The new generation antenna has high-quality processing requirements on the resin-rich layer of the reflecting surface. A polishing experiment on the resin-rich layer was carried out to study the parameters affecting the surface roughness of the layer, namely polishing time, abrasive particle size, abrasive particle mass fraction, loading pressure and polishing speed. The results show that under the current conditions, the surface roughness first decreases and then tends to be stable with the increase of polishing time. It increases with the increase of the abrasive particle size or the loading pressure, and first decreases and then increases with the increase of the abrasive particle mass fraction or the polishing speed. On this basis, an optimized process parameter combination is formed, which includes an abrasive size of 25 nm, an abrasive particle mass fraction of 20%, a loading pressure of 14.1 kPa, a polishing speed of 50 r/min, a polishing time of 1.0 hours, and a slurry flow rate of 10 mL/min. A high-quality resin rich layer polished surface with a surface roughness Sa of 4.73 nm can be obtained by machining with this parameter combination.

Abstract Double-sided lapping is an precision machining method capable of obtaining high-precision surface. However, during the lapping process of thin pure copper substrate, the workpiece will be warped due to the influence of residual stress, including the machining stress and initial residual stress, which will deteriorate the flatness of the workpiece and ultimately affect the performance of components. In this study, finite element method (FEM) was adopted to study the effect of residual stress-related on the deformation of pure copper substrate during double-sided lapping. Considering the initial residual stress of the workpiece, the stress caused by the lapping and their distribution characteristics, a prediction model was proposed for simulating workpiece machining deformation in lapping process by measuring the material removal rate of the upper and lower surfaces of the workpiece under the corresponding parameters. The results showed that the primary cause of the warping deformation of the workpiece in the double-sided lapping is the redistribution of initial residual stress caused by uneven material removal on the both surfaces. The finite element simulation results were in good agreement with the experimental results.

Fatigue properties are crucial for critical aero-engine components in extreme service environments, which are significantly affected by surface integrity (SI) indexes (especially surface topography, residual stress σ _res , and microhardness) after machining processes. Normal-direction ultrasonic vibration-assisted face grinding (ND-UVAFG) has advantages in improving the machinability of Inconel 718, but there is a competitive relationship between higher compressive σ _res and higher surface roughness R _a in affecting fatigue strength. The lack of a quantitative relationship between multiple SI indexes and fatigue strength makes the indeterminacy of a regulatory strategy for improving fatigue properties. In this work, a model of fatigue strength ( σ _f ) _sur considering multiple SI indexes was developed. Then, high-cycle fatigue tests were carried out on Inconel 718 samples with different SI characteristics, and the influence of ND-UVAFG process parameters on SI was analyzed. Based on SI indexes data, the ( σ _f ) _sur distribution in the grinding surface layer for ND-UVAFG Inconel 718 samples was determined using the developed model, and then the fatigue crack initiation (FCI) sites were further predicted. The predicted FCI sites corresponded well with the experimental results, thereby verifying this model. A strategy for improving the fatigue life was proposed in this work, which was to transfer the fatigue source from the machined surface to the bulk material by controlling the SI indexes. Finally, a critical condition of SI indexes that FCI sites appeared on the surface or in bulk material was given by fitting the predicted results. According to the critical condition, an SI field where FCI sites appeared in the bulk material could be obtained. In this field, the fatigue life of Inconel 718 samples could be improved by approximately 140%.

CFRP/Ti stacks composed of carbon fiber-reinforced plastic composites (CFRP) and titanium alloys (Ti) are widely used in aerospace fields. However, in the integrated hole-making process of CFRP/Ti stacks, the machining characteristics of various materials are significantly different, and constant machining parameters cannot simultaneously meet the high-quality machining requirements of two materials. In addition, errors exist between the actual thickness of each material layer and the theoretical value, which causes an impediment to the monitoring of the machining interface and the corresponding adjustment of parameters. An adaptive machining method for the helical milling of CFRP/Ti stacks based on interface identification is proposed in this paper. The machining characteristics of the pneumatic spindle and the interface state in the helical milling of CFRP/Ti stacks are analyzed using self-developed portable helical milling equipment, and a new algorithm for the real-time monitoring of the machining interface position and adaptive adjustment of the machining parameters according to the interface identification result is proposed. Helical milling experiments were carried out, the results show that the proposed method can effectively identify the position of the machining interface with good identification accuracy. Moreover, the proposed parameter-adaptive optimized machining method for CFRP/Ti stacks can significantly improve hole diameter accuracy and machining quality.

The improvement of the surface quality of complex structural parts is a major challenge. Electrochemical mechanical polishing (ECMP) plays an important role in the polishing of wafers due to its high material removal rate. However, electrochemical mechanical polishing of the surface of complex structures, such as the bevels of turbine blades, has been little investigated. This paper proposes a new method, moist particle electrolyte electrochemical mechanical polishing (MPE-ECMP), for polishing the surfaces of complex structural parts. Using a sulfonated cation exchange resin as a moist particle electrolyte (MPE), polarization curves are measured using linear scanning voltammetry (LSV) and a selected potential of 1.0 V vs. Hg|Hg2SO4 over a 1 h polishing period. The elemental changes on the copper surface are examined by energy dispersive spectroscopy (EDS) and those on the MPE surface are studied using X-ray photoelectron spectrometry (XPS) to explain the material removal mechanism. The results show that the surface roughness of copper is reduced from the initial Sa = 433.48 nm to Sa = 21.83 nm, a reduction of 95.0%, that no copper oxides are generated during the MPE-ECMP process and that the MPE adsorbs released Cu2+. It is demonstrated that MPE-ECMP has good surface finishing properties for beveled surfaces, and provides an effective approach for surface polishing of complex structural parts.

There is a large demand for aluminum alloy assembly hole machining in aerospace manufacturing industry. The assembly hole is mainly realized by drilling, and there is a problem that the aluminum alloy exit burr is too large in the processing. The exit burr directly affects the accuracy, fatigue strength and assembly performance of the workpiece. The deburring process will greatly increase the man hour and cost. Therefore, it is necessary to study the exit burr of aluminum alloy assembly hole drilling to realize the control of exit burr. This paper systematically discusses the types, measurement methods, formation mechanism, height prediction and gross control methods of exit burr in aluminum alloy drilling, in order to provide help for the research of exit burr in aluminum alloy drilling.

Off-axis parabolic mirrors have extensive applications in X-ray optics, with the precision of their curvature directly impacting grazing-incidence focusing performance. Notably, the off-axis parabolic surface has non-rotating and non-symmetrical characteristics. Ultra-precision raster grinding utilizing a diamond wheel is a common method. Crucially, establishing an optimal wheel path stands as the key to ensuring surface accuracy during off-axis paraboloid grinding. In this study, according to the double curvature property of an off-axis parabolic surface, two different wheel paths were compared: one tracing the meridian direction (parabolic generatrix) and the other following the arc vector direction (arc). The results showed that the wheel path in raster grinding stepping along the arc vector direction can obtain a smaller scallop height and higher surface accuracy. The surface accuracy of one step along the arc vector direction is 9.6 μm, and that of the other step along the meridian direction is 32.6 μm. A model of the scallop height was established based on the relative relationship between adjacent wheel paths, and the error is within 5%. According to the correlation between scallop height and shape error, we conducted an analysis of the spatial distribution of shape errors under varying wheel paths. The wheel path that steps along the arc vector is more suitable for raster grinding of the off-axis paraboloid. The above study can provide theoretical guidance for the wheel path planning of off-axis parabolic mirrors with high surface accuracy.

Seasonal–trend-decomposed transformer has empowered long-term time series forecasting via capturing global temporal dependencies (e.g., period-based dependencies) in disentangled temporal patterns. However, existing methods design various auto-correlation or attention mechanisms in the seasonal view while ignoring the fine-grained temporal patterns in the trend view in the series decomposition component, which causes an information utilization bottleneck. To this end, a Transformer-based seasonal–trend decomposition methodology with a multi-scale attention mechanism in the trend view and a multi-view attention mechanism in the seasonal view is proposed, called DESTformer. Specifically, rather than utilizing the moving average operation in obtaining trend data, a frequency domain transform is first applied to extract seasonal (high-frequency) and trend (low-frequency) components, explicitly capturing different temporal patterns in both seasonal and trend views. For the trend component, a multi-scale attention mechanism is designed to capture fine-grained sub-trends under different receptive fields. For the seasonal component, instead of the frequency-only attention mechanism, a multi-view frequency domain (i.e., frequency, amplitude, and phase) attention mechanism is designed to enhance the ability to capture the complex periodic changes. Extensive experiments are conducted on six benchmark datasets covering five practical applications: energy, transportation, economics, weather, and disease. Compared to the state-of-the-art FEDformer, our model shows reduced MSE and MAE by averages of 6.5% and 3.7%, respectively. Such experimental results verify the effectiveness of our method and point out a new way towards handling trends and seasonal patterns in long-term time series forecasting tasks.

SiC fiber reinforced SiC ceramic matrix composites (SiCf/SiC) have problems such as poor machining quality and difficult material removal. To study these problems, SiCf/SiC composites were processed by ultrasonic-assisted helical grinding. The exit quality of hole, hole wall morphology and three-dimensional surface roughness of hole wall were explored. The results show that compared with traditional hole making, the material at the exit of the hole made by ultrasonic-assisted helical grinding has no large area chipping. The periodic change of the angle θ between the direction of the cutting speed of the grinding wheel and the fiber direction leads to regular changes in the surface morphology of the hole wall. When θ is 0°/180°, the fiber and the matrix are debonded. When θ is 45°, the fiber is sheared and fractured. When θ is 90°, the fiber is crushed and fractured. When θ is 135°, the fiber has both shear fracture and extrusion fracture. The hole wall surface roughness Sa is the lowest value when θ is 90°, and Sa is the highest value when θ is 135°. Within a certain range, the surface roughness value Sa decreases with the increase of the ultrasonic amplitude, with a maximum decrease of 38.7%, and increases with the increase of the feed rate, with a maximum increase of 39.3%.

Ultrasonic cutting is an advanced technology for processing Nomex honeycomb materials. The disc cutter is one of the most commonly used tools, whose wear and breakage state have an important impact on the honeycomb material machining process. Currently, the disc cutter lacks systematic characterization methods, and its tool wear laws are not yet clear. This paper conducts a wear experiment of the disc cutter in an ultrasonic cutting Nomex honeycomb core and proposes the attributes of cutting edge rounding (CER), flank wear VB, diameter reduction, and cutting edge breakage width to characterize the tool wear and breakage forms quantitatively. Moreover, the tool wear and breakage forms of the disc cutter are categorized, and the variation laws of the disc cutter wear and breakage characteristics are studied. The experimental study reveals that the wear forms of the disc cutter are mainly cutting edge dulling and flank wear. The CER and flank wear VB increase with increasing cutting length, and the wear mechanism is mainly abrasive wear. The breakage forms are mainly chipping and cracking breakage. The diameter reduction changed slowly, and the cutting edge breakage width tended to increase. The surface quality of the honeycomb gradually deteriorates with the increase of tool wear and breakage. The experimental results are important to study the tool wear mechanism of ultrasonic cutting of the Nomex honeycomb core with the disc cutter as well as tool design and manufacture.

Ultrasonic elliptical vibration cutting has a wide range of applications in the field of precision cutting of difficult-to-machine metal materials. However, due to its intermittent cutting characteristics and the weak rigidity of the horn, cutting chatter is prone to occur during its cutting process, which has an important impact on cutting surface quality and tool wear. In this paper, the rigid/viscoplastic rod model is used to simulate the horn in the ultrasonic elliptical vibration cutting device, and the influence factors of the amplitude-frequency response of the horn are analyzed. The influence of cutting speed and cutting depth on cutting chatter was studied by ultrasonic elliptical vibration cutting experiment of tungsten heavy alloy, and the influence of cutting chatter on cutting surface morphology and diamond tool wear was studied. The research shows that cutting speed will change the excitation frequency of the horn, and reasonable cutting speed can inhibit the occurrence of cutting chatter and avoid resonance of the horn. The cutting depth will affect the excitation amplitude and amplify the vibration amplitude when chatter or resonance occurs. The experimental results show that in ultrasonic elliptical vibration cutting of heavy tungsten alloy, chatter suppression can significantly improve the quality of the cutting surface and reduce the wear of diamond tools.

GH4068 superalloy is a new type of nickel-based superalloy in the aerospace field. It is an important alloy material for the manufacture of aircraft tubular components and aero-engine hot-end components. These components need to be machined with good surface quality to meet their use requirements. New hybrid machining processes can improve the quality of surface finish compared to conventional machines. In this paper, ultrasonic assisted turning (UAT) technology was applied to the machining of GH4068 superalloy. The experimental system of UAT was established. Experiments of UAT and conventional turning (CT) of GH4068 superalloy were carried out to study the effects of cutting speed, feed speed, cutting depth and vibration amplitude on cutting force and surface roughness. The surface morphology of the workpiece and chip were observed. The experimental results show that Fx and Fy can be reduced by a maximum of 44% and 63%, respectively, and the surface roughness can be reduced by a maximum of 31% after adding ultrasonic vibration. Compared with CT, the UAT has a better machining quality, a more obvious chip-breaking effect, and a smaller chip bending radius, which guides the high-quality processing of the GH4068 superalloy.

Carbon fiber-reinforced plastic/titanium alloy (CFRP/Ti) stacks are widely used in the aerospace field based on their high strength to weight ratio and heat resistance. High-quality bolt hole assembly is critical for the safety of the aerospace industry. Reaming is a crucial process in precision machining and is extensively used to improve the quality of bolt holes. Due to the different properties of the material, machining with conventional reaming (CR) presents some challenges, such as tolerance variations across the hole group and difficulty in controlling thrust. In this paper, ultrasonic vibration is applied to the reaming process. A geometrical model of ultrasonic vibration reaming (UVR) was established to analyze its kinematic law. UVR experiments on CFRP/Ti stacks were carried out to study the influence of different ultrasonic amplitudes on reaming thrust and the influence of tool speed on thrust, dimensional accuracy, and surface roughness under optimal ultrasonic amplitude. The average thrust forces in UVR decreased by over 57% (Ti) and 40% (CFRP), respectively, compared to CR. The roughness of CFRP is reduced by 20% with UVR and 28% for titanium alloys. The surface topography of the holes is significantly improved by UVR. This work guides the manufacture of high-quality bolt holes for CFRP/Ti stacks.

Because of the high hardness, brittleness, and anisotropy of reaction-bonded silicon carbide composites (RB-SiC), it is challenging to process high-quality textures on their surfaces. With the advantages of high processing accuracy and low processing damage, femtosecond laser processing is the preferred technology for the precision processing of difficult-to-process materials. The present work used a femtosecond laser with a linear scanning path and a spot diameter of 18 µm to process microgrooves on RB-SiC. The influence of different processing parameters on the microgroove profile, dimensions, and ablation rate (AR) was investigated. The ablation width Wa and average ablation depth Da of microgrooves were evaluated, and the various patterns of varying processing parameters were obtained. A model for Wa prediction was developed based on the laser fluence within the finite length (FL). As a result, the experimental values were distributed near the prediction curve with a maximum error of 20.4%, showing an upward trend of gradually decreasing increments. For a single pass, the AR value was mainly determined by the laser energy, which could reach the scale of 106 μm3/s when the laser energy was greater than 50 μJ. For multiple passes, the AR value decreased as the number of passes increased and it finally stabilized. The above research will provide theoretical and experimental support for the high-quality and efficient processing of RB-SiC surface textures.

Additive forging is a newly developed method to manufacture heavy forgings by using multilayer hot-compression bonding. However, the relationship between surface cleaning and bonding performance of bonded samples in the additive forging process is unclear. This paper studies the effect of surface cleaning on interface bonding performance for the first time. A new characterization method of surface cleanliness consisting of water contact angles, relative fluorescence units, and optical observation was proposed to characterize the cleaning effect. The micromorphologies and tensile properties were used to evaluate interface bonding performance. Elemental analysis and morphological analysis were used to infer the hindrance mechanism of contaminants. The results show that the new characterization method can effectively characterize the surface cleanliness of substrates. Moreover, the interfacial bonding performance results indicate that surface cleaning had a great influence on the bonding performance for 316H stainless steel joints manufactured by additive forging. Finally, the hindrance mechanisms of particles, chips, and oil contaminants were attributed to the hindrance effect in a radial direction, along the interface direction, and perpendicular to the interface direction respectively. This research builds a relationship between surface cleaning and bonding performance, which helps achieve high-performance manufacturing of heavy forgings.

Machining surface topography is a key factor affecting the properties of optical materials. It is generally accepted that the fracture mode tends to dominate practical concerns on machined parts and the elastic recovery area decreases with the increase of normal load. However, material removal rate is low for ductile zone processing of brittle materials. In this case, pile-up and elastic recovery are key factors for surface quality. In this study, an accurate scratching and ploughing hardness model with consideration of both pile-up and elastic recovery was established based on a series of continuous and constant nanoscratch tests. The hardness evolution mechanism under different nanoscratch deformation modes was then investigated. It was found that, in different modes, hardness values exhibited different characteristics due to the change of elastic recovery rate and the intersection of elastic and plastic states. Further, the mapping relationship between hardness dispersion and surface morphology characteristics was also investigated. The results indicated that high degree of hardness dispersion usually corresponded to modes Ⅰ and Ⅱ while stable hardness value represented a steady plastic stage. Based on the intrinsic relationship between evolution of hardness and deformation modes, predicting hardness distribution by in-situ testing data and then adjusting deformation mode in real time would be helpful in optimizing surface quality.

Back Grinding of Wafer with Outer Rim (BGWOR) is a novel method for carrier-less thinning of silicon wafers. Silicon wafers are widely used in integrated circuits (ICs). The topography of the wafer will not only directly affect the efficiency of subsequent processing of semiconductor devices, but correspondingly affect the performance and life of these devices. However, there are few studies on the shape of the ground wafer in BGWOR. In this paper, the mathematical model of the wafer topography in BGWOR was developed. With this model, the radial thickness and total thickness variation (TTV) of a wafer under different parameters, including inclination angles and radii of grinding wheel for dressing chuck, were simulated by MATLAB. Inclination angles and radii of grinding wheels for the dressing chuck had a great influence on the radial thickness and TTV of a wafer in the BGWOR. Lastly, the pilot experiments were conducted to validate the theoretical model of grinding topography and TTV of the wafer in BGWOR. To enhance the flatness of the ground wafer, it is essential to control the shape of the dressing chuck. The research results are helpful to the optimization of the dressing process of the chuck in the BGWOR.

Polyetheretherketone (PEEK) is a promising thermo-plastic polymer material due to its excellent mechanical properties. To further improve the mechanical properties of PEEK, different kinds of short fibers are added into the PEEK matrix. The grinding machinability of short-fiber-reinforced PEEK varies with the effect of fiber type and content. Therefore, it is crucial to investigate the surface quality and removal mechanism of fiber-reinforced PEEK in ultra-precision grinding. In this paper, different fiber types and mass fractions of short-fiber-reinforced PEEK, including carbon-fiber-reinforced PEEK (CF/PEEK) and glass-fiber-reinforced PEEK (GF/PEEK), are employed. The grinding machinability of short-fiber-reinforced PEEK was investigated using grinding experiments with grinding wheels of different grit sizes. The effects of the fiber type and mass fraction on the surface quality and removal mechanism during grinding were discussed. The results showed that the brittle–ductile transition depth of carbon fiber was much larger than that of glass fiber, so it was easier to achieve ductile removal in grinding with the carbon fiber. Therefore, the ground surface roughness of CF/PEEK was smaller than that of GF/PEEK under the same grinding conditions. With the increase in carbon fiber mass fraction, the ground surface roughness of CF/PEEK decreased due to the higher hardness. The brittle–ductile transition depth of glass fiber was small, and it was easy to achieve brittle removal when grinding. When the glass fiber removal mode was brittle removal, the GF/PEEK surface roughness increased with the increase in glass fiber content.

Silicon carbide (SiC) is a promising semiconductor material for making high-performance power electronics with higher withstand voltage and lower loss. The development of cost-effective machining technology for fabricating SiC wafers requires a complete understanding of the deformation and removal mechanism. In this study, molecular dynamics (MD) simulations were carried out to investigate the origins of the differences in elastic–plastic deformation characteristics of the SiC polytypes, including 3C-SiC, 4H-SiC and 6H-SiC, during nanoindentation. The atomic structures, pair correlation function and dislocation distribution during nanoindentation were extracted and analyzed. The main factors that cause elastic–plastic deformation have been revealed. The simulation results show that the deformation mechanisms of SiC polytypes are all dominated by amorphous phase transformation and dislocation behaviors. Most of the amorphous atoms recovered after completed unload. Dislocation analysis shows that the dislocations of 3C-SiC are mainly perfect dislocations during loading, while the perfect dislocations in 4H-SiC and 6H-SiC are relatively few. In addition, 4H-SiC also formed two types of stacking faults.

In the electrochemical mechanical polishing (ECMP) of copper, hydroxyethylidene diphosphonic acid (HEDP) can work with other water treatment agents to suppress electrolysis and smooth the metal surface. According to Faraday's law, a conventional operating potential lower than 4 V vs. SCE limits the material removal rate (MRR). To solve this problem, potentiodynamic corrosion, potentiostatic corrosion and ECMP experiments were conducted at higher potentials to study the feasibility of the process. The results show that at 6 V vs. SCE, the roughness of a copper wafer was improved, with a MRR of about 0.9 μm·min−1, higher than that obtained at the conventional potential. A sample of the barrier film on the copper surface was collected and analyzed by energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and mass spectrometry to investigate the reaction mechanism. It is shown that the copper ions ionized from the working electrode (WE) react with two HEDP molecules to form the coordination compound [CuL2]6−, then K+ combines with [CuL2]6− to produce the coordination compound [KCuL2]5−. Keywords: Hydroxyethylidene diphosphonic acid, Electrochemical mechanical polishing, Copper, Reaction mechanism

Polyetheretherketone (PEEK) is a novel polymer material with excellent material properties. The hardness and strength of PEEK can be further improved by introducing fiber reinforcements to meet the high-performance index of the aerospace industry. The machinability will be influenced when the material properties change. Therefore, it is crucial to investigate the influence of material properties of the fiber-reinforced PEEK on machinability. In this paper, the main materials include pure PEEK, short carbon-fiber-reinforced PEEK (CF/PEEK), and short glass-fiber-reinforced PEEK (GF/PEEK). The effects of the fiber type and mass fraction on the tensile strength, hardness, and elastic modulus of materials were discussed using the tensile test and nanoindentation experiments. Furthermore, the fiber-reinforced PEEK lapping machinability was investigated using lapping experiments with abrasive papers of different mesh sizes. The results showed that the hardness and elastic modulus of PEEK could be improved with fiber mass fraction, and the tensile strength of CF/PEEK can be improved compared with that of GF/PEEK. In terms of lapping ability, the material removal rates of the fiber-reinforced materials were found to be lower than the pure PEEK due to the higher hardness of the fiber. During the lapping process, the material removal methods mainly included the ductile deformation or desquamation of reinforcing fiber and ductile removal of the PEEK matrix. The lapped surface roughness of PEEK material can be improved by fiber reinforcement.

Removing carbon deposition (CD) has always been a challenging problem. On the inner surface of a turbo shaft, CD is observed by scanning electron microscopy (SEM) to analyze its microstructure and composition, and its formation mechanism is analyzed by X-ray diffraction (XRD), infrared spectroscopy, and Raman spectroscopy. Considering the physical and chemical properties of deposited carbon, chemically assisted magnetic grinding (CAMG) is proposed and tested by a translational permanent magnet grinding device. By analyzing the removing mechanism of CAMG, response surface analysis is adopted to analyze the influence law of surface roughness based on the interactions between pairs of the three following parameters: the rotational speed of the rotating magnetic field, needle type, and grinding time. The optimal process parameters can be obtained with a rotational speed of the rotating magnetic field of 600 r/min, a needle type of Φ 1.0 × 5 mm, and a grinding time of 60 min. The surface quality of the workpiece processed by CAMG can be comprehensively appraised by observing the microstructure, calculating the carbon deposit removal ratio and testing the surface stress. Compared to single magnetic grinding, CAMG is more environmentally friendly and has a higher removal ratio and better surface quality with an obvious decrease in residual stress. By professional tests, the remaining deposited carbon is less than the specified value required by the technology, which satisfies the requirements of enterprises.

Mechanical drilling can change the microstructure of the regions near the hole wall, remarkably affecting the working performance of precision parts. The present work investigated the microstructural evolution in the regions from the drilled hole wall to the inner matrix of the soft magnetic 49Fe-49Co-2V alloy after the common drilling experiments were carried out. The microstructures and microhardness in different regions near the hole wall along the radial direction were characterized with OM, SEM, TEM, EBSD and Vickers Microhardness tester. The experimental results show that the nearest region to the hole wall is constituted of nano-sized refined grains. It exhibits a disordered BCC phase due to the rapid cooling from the high temperature during the drilling, different from the dual-phase of BCC and B2 of the matrix. The second-nearest region to the hole wall is distributed by a huge number of dislocations, leading to a maximum in microhardness. The microstructural evolution contributes to the variation of the microhardness, which increases firstly, reaches a maximum, and then decreases to the level of the matrix with the distance increasing from the hole wall. This variation tendency is discussed in light of both refined grain-boundary strengthening and dislocation strengthening mechanisms. Keywords: 49Fe-49Co-2V alloy, Drilling, Microstructural evolution, Microhardness, Strengthening mechanisms

Thin-walled parts are widely used in shock wave and detonation physics experiments, which require high surface accuracy and equal thickness. In order to obtain the wall thickness of thin-walled spherical shell parts accurately, a new measurement method is proposed. The trajectories, including meridian and concentric trajectories, are employed to measure the thickness of thin-walled spherical shell parts. The measurement data of the inner and outer surfaces are unified in the same coordinate system, and the thickness is obtained based on a reconstruction model. The meridian and concentric circles’ trajectories are used for measuring a spherical shell with an outer diameter of Φ210.6 mm and an inner diameter of Φ206.4 mm. Without the data in the top area, the surface errors of the outer and inner surfaces are about 5 μm and 6 μm, respectively, and the wall-thickness error is about 8 μm with the meridian trajectory.

The dwell time algorithm is one of the key technologies that determines the accuracy of a workpiece in the field of ultra-precision computer-controlled optical surfacing. Existing algorithms mainly consider meticulous mathematics theory and high convergence rates, making the computation process more uneven, and the flatness cannot be further improved. In this paper, a reasonable elementary approximation algorithm of dwell time is proposed on the basis of the theoretical requirement of a removal function in the subaperture polishing and single-peak rotational symmetry character of its practical distribution. Then, the algorithm is well discussed with theoretical analysis and numerical simulation in cases of one-dimension and two-dimensions. In contrast to conventional dwell time algorithms, this proposed algorithm transforms superposition and coupling features of the deconvolution problem into an elementary approximation issue of function value. Compared with the conventional methods, it has obvious advantages for improving calculation efficiency and flatness, and is of great significance for the efficient computation of large-aperture optical polishing. The flatness of φ150 mm and φ100 mm workpieces have achieved PVr150 = 0.028 λ and PVcr100 = 0.014 λ respectively.

Cutting force is one of the most important factors in the ultrasonically assisted grinding (UAG) of hard and brittle materials. Many theoretical and experimental studies show that UAG can effectively reduce cutting forces. The existing models for UAG mostly assume an ideal grinding wheel with abrasives in both the end and lateral faces to accomplish material removal, whereas the important role of the transition fillet surface is ignored. In this study, a theoretical cutting force model is presented to predict cutting forces with the consideration of the diamond abrasives in the end face, the lateral face, and the transition fillet surface of the grinding tool. This study analyzed and calculated the vibration amplitudes and the cutting forces in both the normal and tangential directions. It discusses the influences of the input parameters (rotation speed, feed rate, amplitude, depth and radius of transition fillet) on cutting forces. The study demonstrates that the fillet radius is an important factor affecting the grinding force. With an increase in fillet radius from 0.2 to 1.2 mm, the grinding force increases by 139.6% in the axial direction and decreases by 70% in the feed direction. The error of the proposed cutting force model is 10.3%, and the experimental results verify the correctness of the force model.

The technology of magnetic abrasive finishing is one of the important finishing technologies. Combining with low-frequency vibration and ultrasonic vibration, it can attain higher precision, quality and efficiency. The characteristics and the related current research of magnetic abrasive finishing, vibration assisted magnetic abrasive finishing and ultrasonic assisted magnetic abrasive finishing are introduced. According to the characteristics of the difficult-to-machine alloy's complex surface, the important problems for further study are presented to realize the finishing of complex surface with the technology of magnetic abrasive finishing, such as increasing the machining efficiency by enhancing the magnetic flux density of machining gap and compounding of magnetic energy and others, establishing of the control function during machining and the process planning method for magnetic abrasive finishing of complex surface under the space geometry restraint of complex surface on magnetic pole, etc.

To clarify the influence mechanism of strain rate effect on deformation characteristics of aluminum nitride (AlN) ceramics, some varied-velocity nanoscratching tests were carried out using a Berkovich indenter in this paper. The deformation characteristics of the scratched grooves were observed using the scanning electron microscope. The experimental results showed higher scratch speed would lead to shallower penetration depth, fewer cracks, and indenter fewer slipping, which was more conducive to the plastic deformation of AlN ceramics. Considering the strain rate effect and the elastic recovery of material, a model for predicting the Berkovich indenter penetration depth under edge-forward mode was established. The prediction results were consistent with the experimental data, and the error was less than 5%, indicating that the model is effective. Based on the Boussinesq field, the Cerruti field, and the Sliding bubble field, a strain rate dependent scratch stress field model was established. The stress field revealed higher scratch speed may significantly reduce the maximum principal stress in the stress field under the indenter, which is the fundamental reason for reducing the crack damage and promoting the plastic deformation. The above study can provide theoretical guidance for reducing the processing damage of AlN ceramics.

The vertical surface is a common and typical characteristic structure among Nomex honeycomb core components. However, the conventional high-speed milling and ultrasonic cutting struggle to meet the high-quality machining requirements of a vertical surface. In this study, an ultrasonic trepanning method is proposed and a special ultrasonic trepanning tool is developed, aiming to improve the machining quality of the vertical surface. The trepanning quality of the vertical surface is further studied from the aspects of dimensional error and trepanning incision quality. Based on the kinematic characteristics of ultrasonic trepanning, a theoretical model of dimensional error in trepanning is established. Meanwhile, the influence of ultrasonic vibration on the trepanning process is analyzed, and the result shows that ultrasonic vibration significantly improves the equivalent elastic constant of the honeycomb core material. The theoretical model is proposed to predict the trepanning dimensional error, which is verified by experiment. The effectiveness of the ultrasonic vibration on the incision quality is verified by several experiments, and the quantitative analysis results demonstrate that ultrasonic vibration significantly improves the trepanning quality of the vertical surface.

Ultrasonic assisted grinding (UAG) has been considered as a prominent processing method of the reaction bonded silicon carbide (RBSiC). To improve the knowledge of UAG process, both conventional grinding (CG) and UAG were used to process the RBSiC for in-depth investigation. Grinding forces, surface topographies, and subsurface damages during CG and UAG were compared. Furtherly, the ground surface was analyzed on aspects of both topographical characteristics and material removal mechanism. The results indicated that the removal of material is mainly achieved by the intersections of cracks initiated from both big SiC particles and mixture area of silicon matrix and small SiC grains. The crack propagation during UAG was more intensified due to the ultrasonic impact, which results in higher efficiency of machining RBSiC.