Micro-milling is a significant application in manufacturing components for various crucial fields such that inertial navigation. Strict requirements for machining quality, such as surface finish and dimensional accuracy, are proposed to ensure adequate functionality of inertial navigation components. However, it is severely limited by burr formation, especially at the work position of the component. To this end, this paper first presents an improved Canny-based algorithm for extracting continuous edges of exit burrs. The characterizations of the extracted burrs are then carried out for various machining processes. Based on orthogonal experiments of the machining process, the influence and the interaction influence of the feed per tooth and depth of cut on crucial burrs, including exit-burrs and exit side burrs, are revealed by analysis of mean. It is observed that the depth of cut has more significant impacts on formations of exit-burrs and exit side burrs. An analytical model, considering tool runout, is then established to predict the burr height of exit side burrs, and the applicability of the model is comparatively analyzed, showing that tool runout should not be ignored in predicting burr characters. The mean height of exit-burrs is predicted by modeling an analytical model based on the experimental results. The rootmean-square error (RMSE) of the predicted exit-burrs is 4.363 mu m, noting that the prediction of burr characters in micro-milling is extremely challenging due to the complex process of material removal and microstructural effects encountered during the micro-scaled machining process.

In Selective Laser Melting (SLM), the formability challenges posed by the high laser reflectivity and thermal conductivity of Cu10Sn alloy have become a significant bottleneck, limiting its potential for advanced applications. Current research predominantly focuses on optimizing laser processing parameters. However, the powder parameters are equally crucial to the forming quality and mechanical properties of the parts. Therefore, this study investigated the effect of powder parameters (average particle size, particle size distribution, and powder layer thickness) on the relative density and hardness of the sample. The results show that the variation in sample properties is mainly dominated by the effect of powder parameters on particle stacking characteristics. Specifically, the average particle size (D-50) and particle size distribution Span can significantly increase the packing density of the powder layer. Reducing the powder layer thickness helps to exclude large-sized particles from the layer. Under specific powder parameter combinations, the laser absorption ability and melting properties of the powder layer are improved. The optimum relative density of the sample can reach 99.97 %, with a maximum microhardness of 181.10 HV in the X-Z plane (vertical section) and 168.04 HV in the X-Y plane (horizontal section). Additionally, effects of surface porosity and hardness on tribological properties of samples were investigated. The results show that higher surface porosity and lower hardness contribute to the wear resistance of Cu10Sn alloy samples.

Electrostatic atomization minimum quantity lubrication (EMQL) technology has been developed to address the need for environmentally friendly, efficient, and low-damage grinding of challenging titanium alloy materials. EMQL leverages multiple physical fields to achieve precise atomization of micro-lubricants, enabling effective lubrication in high temperature, high pressure, and high-speed grinding environments through the use of electric traction. Notably, the applied electric field not only enhances atomization and lubrication capabilities of micro-lubricants but also significantly impacts heat transfer within the grinding zone. In order to explore the influence mechanism of external electric field on spatial heat transfer, this paper first comparatively analyzes the grinding heat under dry grinding, MQL, and EMQL conditions and explores the intensity of the effect of external electric field on the heat transfer behavior in the grinding zone. Furthermore, the COMSOL numerical calculation platform was used to establish an electric field-enhanced (EHD) heat transfer model, clarifying charged particles' migration rules between poles. By considering the electroviscous effect, the study reveals the evolution of heat transfer structures in the presence of an electric field and its impact on heat transfer mechanisms.

Inadequate control of surface defects generated in traditional grinding SiCp/Al composites limits service performances of SiCp/Al components. Aiming at decreasing machining surface defects, ultrasonic vibration (UV) technique was imported. This paper first studied surface formation mechanism by a finite element method (FEM) considering the particle-matrix interface for traditional scratching SiCp/Al components processes instead of grinding processes and contrastively analyzed the advantages of employing UV assisted technique. Based on the machined surface features, some quantitative surface characterizations were analyzed based on the analysis of mean (AOM) to explore the significant degree of impacts from the UV-assisted grinding parameters on machined surfaces, and a comprehensive surface characterization that can present surface roughness and surficial structures was then proposed as an optimization objective in an established multi-objective process optimization model by NSGA-II. The calculated optimal UV-assisted grinding processing was then verified as effective for achieving exquisite surface qualities of grinding SiCp/Al Composites.

The high-speed-dry (HSD) machining is now recognized as a strong potential dry-cutting technique to tackle the rapidly growing productivity demand of carbon-fiber-reinforced-polyetheretherketone (CF/PEEK). The thermal-field is an essential breakthrough for eliminating the severe thermal effect of cutting temperature beyond CF/PEEK glass transition temperature Tg. However, the anisotropy and temperature-sensitive thermal conductivity of CF/PEEK lead to great challenges in thermal analytical modeling. Addressing this issue, a novel thermal-field analytical model that incorporates fiber orientation-dominated thermal anisotropy is developed to investigate the thermal field of machined surface layer for unidirectional (UD) CF/PEEK HSD milling, where the nonlinear thermal conductivity of CF/PEEK are imported into this model. With experiment verification, the thermal-field model can forecast the spatio-temporal distribution of workpiece temperature. Then, the thermal mechanisms of fiber orientations and milling parameters are clarified to restrict workpiece temperature within the Tg for limited thermal damage and reveal the feasibility essence of CF/PEEK HSD milling.

As an emerging composite material with high specific strength, CF/PEEK which is widely used in the aerospace field has not only high specific modulus, strong impact resistance and high temperature resistance, but also weldability and recoverability compared with the traditional thermosetting composite material. However, due to strong anisotropy and thermal flow characteristics of matrix, CF/PEEK has surface machining defects that are difficult to be controlled during dry cutting, so it’s difficult to be applied for structural/functional components at micro scale. In this paper, the damage characteristics of CF/PEEK machining surface under the conditions of micro-milling were investigated. Initially, a quantitative characterization system for surface damage characteristics in CF/PEEK micro-milling was established. The surface roughness, surface character, surface structure and surface complexity were studied respectively. Based on the designed orthogonal experiments of micro milling and the established quantitative characterization system of machining surface damage characteristics, a multi-objective optimization model of CF/PEEK micro milling process based on grey relational analysis and response surface method was established in this paper, and the damage characteristics of CF/PEEK micro milling process under different micro-milling process parameters were studied. It is found that the partially removal of carbon fiber reinforcement can be achieved by the micro-milling process, and the effective regulation of the surface damage characteristics of CF/PEEK micro-milling can be achieved by the correlation between the microscopic surface damage characteristics and the quantitative characterization system.

SiC/Al composites are widely used in aerospace and other fields due to their excellent mechanical properties. For large-concentration composites, due to the extremely high proportion of SiC and the unstable interface between the two phases, the SiC particles are broken and detached during the processing, which makes the surface quality of the workpiece insufficient to meet the service requirements. Electrically assisted cutting technology is expected to break through this technical bottleneck. This paper investigates the surface quality of high-concentration SiC/Al grinding with electroassisted biolubricant MQL. The surface morphology after processing is observed. Firstly, by comparing the traditional grinding and electrically assisted grinding conditions, it is found that the fundamental reason for the improvement in the grinding surface quality using a pulse current is the improvement in the Al plasticity. Secondly, based on the thermal effect and non-thermal effect of the pulse current, the influence of the electrical parameters (current, duty cycle and frequency) on the machining indication quality is discussed. It is found that when the current and duty cycle increase, the machining surface quality will also increase, while the frequency change has little effect on the surface quality. Finally, friction and wear experiments are carried out on the grinding surface under different working conditions to explore the friction and wear characteristics of the surface of the workpiece. The results show that the pulse current can significantly improve the wear resistance of the grinding surface.

High-performance carbon fiber-reinforced polyether-ether-ketone (CF/PEEK) has been gradually applied in aerospace and automobile applications because of its high strength-to-weight ratio and impact resistance. The dry-machining requirement tends to cause the cutting temperature to surpass the glass transition temperature (Tg), leading to poor surface quality, which is the bottleneck for dry milling of CF/PEEK. Temperature suppression has become an important breakthrough in the feasibility of high-speed dry (HSD) milling of CF/PEEK. However, heat partitioning and jet heat transfer mechanisms pose strong challenges for temperature suppression analytical modeling. To address this gap, an innovative temperature suppression analytical model based on heat partitioning and jet heat transfer mechanisms is first developed for suppressing workpiece temperature via the first-time implementation of an air jet cooling process in the HSD milling of UD-CF/PEEK. Then, verification experiments of the HSD milling of UD-CF/PEEK with four fiber orientations are performed for dry and air jet cooling conditions. The chip morphologies are characterized to reveal the formation mechanism and heat-carrying capacity of the chip. The milling force model can obtain the force coefficients and the total cutting heat. The workpiece temperature increase model is validated to elucidate the machined surface temperature evolution and heat partition characteristics. On this basis, an analytical model is verified to predict the workpiece temperature of air jet cooling HSD milled with UD-CF/PEEK with a prediction accuracy greater than 90%. Compared with those under dry conditions, the machined surface temperatures for the four fiber orientations decreased by 30%-50% and were suppressed within the Tg range under air jet cooling conditions, resulting in better surface quality. This work describes a feasible process for the HSD milling of CF/PEEK.

Since droplet collision with walls has become a research hotspot, scholars have conducted a large number of studies on the dynamic behavior of electrically neutral droplets colliding with dry walls. However, with the rapid development of electrostatic spray technology, there is an increasingly urgent need to study the dynamic process of collision between charged droplets and walls. In this paper, considering the actual working conditions of electrostatic spray, an electric field model is introduced based on the two-phase flow field. Through the coupling of a multiphase flow field and electric field and a multiphysics field, the dynamic numerical calculation method is used to explore the collision electrodynamic behavior of charged droplets and liquid film. The dynamic evolution process of the formation and development of the liquid crown in the collision zone was clarified, and the critical velocity and critical Weber number of the rebound, spreading, and splashing of charged droplets were tracked. The distribution characteristics of electrostatic field, pressure field, and velocity field under different working conditions are analyzed, and the dynamic mechanism of the charged droplet collision liquid film under multi-physics coupling is revealed based on the electro-viscous effect. It is confirmed that the external electric field can increase the critical velocity of droplet splashing and fragmentation and promote the spreading and fusion behavior of droplets and liquid films. The influence of the impact angle of charged droplets on the collision behavior was further explored. It was found that the charged droplets not only have a smaller critical angle for fragmentation and splashing, but also have a faster settling and fusion speed.

As an emerging material, Carbon fiber reinforced polyetheretherketone (CF/PEEK) is widely used in aviation, automotive, sports products, medical equipment and other high-end manufacturing industries due to its high shock resistance, thermostability, and recyclability. However, its dry-machining is an unclear dynamic material removal process which limits the machining efficiency and surface quality. To this end, we first presented composite light ropes model in machining composites considering size effect. Based on composite light ropes model, cutting region is affected by bending, stretching, pressing, bouncing and delamination, as the cutting mechanisms of carbon fiber and matrix are different. The carbon fibers distribution in chip is first introduced into the model to confirm the fiber deformation at different position. Based on composite light ropes model and elastic-plastic theory, the cutting force prediction model is obtained. To complete the model, the free-damped vibration force prediction model is established in empty cutting stage. The dynamics force prediction model is proofed with high prediction accuracy. Besides, the influences of cutting parameters on cutting and vibration force are analyzed by nonlinear regression analysis. It demonstrated that size effect is of great importance in establishing cutting force prediction model and revealing cutting mechanisms of CF/PEEK.

To show the effect of surface texture on transfer film growth of continuous carbon fiber-reinforced thermoplastic poly(ether ether ketone) (CCF-PEEK), tribological behaviors of untextured and laser-engraved-dimple-textured WC–Co, TiN and DLC surfaces dry-sliding against CCF-PEEK pin were studied in ambient atmosphere ( pv  = 0.46 MPa•m/s). Little tribo-film formed on untextured WC–Co, TiN and DLC, but continuous, relatively uniform CCF-PEEK transfer films with micron-level thickness grew from the majority of dimples along the sliding direction on textured WC–Co, TiN and DLC. A stable reduction in coefficient of friction by nearly 38.3% was achieved by textured WC–Co compared to the untextured. Texturing also yielded significant friction reduction to TiN, but almost did not lower the friction of DLC. Micro-cutting effect from the dimple texture edges probably caused considerable material removal of the counterpart CCF-PEEK pin and the repetitive friction cycles shaped the CCF-PEEK wear debris into the tribo-films. The friction reduction could be primarily attributed to the substantial mediation of tribological CCF-PEEK transfer films on the sliding interface. This study indicates that surface texture can facilitate the growth of polymeric transfer films with tribological application potentials in dry-sliding conditions.

Carbon fiber reinforced polymer (CFRP) composites have been widely used in high-tech industries due to excellent performances. Because subsequent machining operations, including drilling and trimming, et al., are necessary to meet dimensional or assembly-related requirement, accurate prediction of cutting forces is of great importance to improve tool life and machining quality, which is good for planning and improving machining process of CFRP composites. To explore this issue, the paper gives a detailed review and discussion of the cutting force models, including, mechanistic models; macro-mechanical models; micro-mechanical models and numerical models. Among them, macro-mechanical models are the earliest proposed cutting force models, while mechanistic models are the most studied. This paper predicts and analyzes the future development trend of cutting force models, including variable diversification development for semi-empirical models, study on process-oriented cutting force models, research on cutting mechanisms and study on intelligent manufacturing-oriented cutting force models based on modular development of numerical models.

Carbon fiber-reinforced polymer (CFRP) composites have been widely used in the aerospace industry due to their excellent mechanical properties. Cutting mechanisms of machining CFRP and its effect on machined surface integrity are still unclear due to inhomogeneity and anisotropy. To this end, this paper studied the cutting mechanisms of CFRP by establishing an impact-based Specific Cutting Energy (SCE) distribution prediction model of high speed dry (HSD) milling CFRP which is be an effective and eco-friendly cutting method. SCE is divided into five sub-SCEs affected by shearing, pressing, impacting, bouncing and delamination, respectively. Among them, sub-SCEs generated by pressing and impacting are influenced by carbon fiber distribution due to size effect and material properties, carbon fiber distribution model was introduced into the SCE prediction model. The proposed model was verified with maximum relative error 7.6%, demonstrating that impact and size effect are of great significance in revealing the cutting mechanism of CFRP. To clarify the effect of SCE distribution on surface integrity, three-dimensional (3D) arithmetic mean height and 3D fractal dimension were used to quantitative characterization of the surface integrity and sub-SCEs are diagnosed for obtaining the way of sub-SCE distribution effecting surface integrity by correlation analysis. According to SCE diagnosis, the milling parameters are optimized by removing sub-SCEs unrelated to surface integrity, founding that HSD milling can reduce machining defects.

As the radius of carbon fibers and cutting edge are in the same order of magnitude, workpiece self-action, which could not be neglected in machining Carbon Fiber Reinforced Polymer (CFRP) considering size effect, has become a new perspective. Specific Cutting Energy (SCE) is a significant indicator for chip formation, cutting forces, tool wear, and machined surface integrity. Based on this, we presented a light springs model to clarify workpiece self-action to establish a specific cutting energy (SCE) prediction model of high speed dry (HSD) milling CFRP. The light springs model, which was also a direct reflection of the size effect, reflected the interaction of carbon fibers, interfaces and the matrix. The carbon fibers distribution in the chip was counted to confirm the light springs deformation at different position as carbon fiber and interface are consisted of the light spring. First of all, based on workpiece self-action and elastic-plastic theory, the cutting mechanisms were clarified to calculate SCE with high prediction accuracy (maximum relative error 7.7%). Furthermore, SCE distribution was obtained based on different cutting mechanisms, including bending, stretching, delamination and pressing bouncing. To improve machined surface integrity, three-dimensional (3D) arithmetic mean height and 3D fractal dimension were used for quantitative characterization of the surface integrity. The paper defined integrated evaluation indexes SCEDS and SCESa to reflect effective SCE to optimize milling parameters based on correlation analysis of SCE distribution and surface quality, founding that HSD milling operation could reduce machining defects.

Carbon fiber reinforced polyetheretherketone (CF/PEEK) is widely applied in aerospace and medical fields due to its excellent strength-to-weight ratio, fatigue resistance and biocompatibility. However, traditional dry machining significantly limits the improvement of machining efficiency and surface quality. Addressing this issue, this paper proposes a process optimization method of high machining efficiency and low surface defects for high-speed dry (HSD) milling UD-CF/PEEK, based on analyzing the thermal effect of cutting temperature. Mixed level orthogonal experiments are designed for dry milling unidirectional (UD) CF/PEEK laminates with the fiber orientation of 0 degrees and 90 degrees. Three-dimensional surface roughness S-q, cutting temperature T-c and material removal rate MRR are extracted to characterize experiment results. The results show that the cutting temperature is mainly affected by cutting speed and fiber orientation, and machined surface defect is mainly caused by the thermal effect of high cutting temperature. Then, a process optimization model of high machining efficiency and low surface defects is established based on the genetic algorithm optimized BP (GA-BP) neural network, non dominated sorting genetic algorithm (NSGA-II) and technique for order preference by similarity to an ideal solution (TOPSIS). The optimization objectives are S-q, MRR and T-c, and T-c also serves as a constraint of the thermal effect. Verification experiments are carried out, and results reveal that the surface defects are significantly reduced by limited thermal effect, and the model can be used to effectively improve machining efficiency and surface quality for HSD milling UD-CF/PEEK. Besides, the material removal rate generated by the HSD milling operation can easily reach 2-3 times higher than the traditional low-speed dry milling operation. The optimized cutting speed in HSD milling UD-CF/PEEK is recommended as 1300-1600 m/min. This study provides significant technical guidance for the machinability improvement of HSD milling UD-CF/PEEK in practice.

To reveal the effect of salt solution condition on adsorption behaviors of boundary lubrication additive poly(carboxylate ether) (PCE), normal interaction forces are directly measured between charged mica surfaces in multiple aqueous solutions of a commercial PCE by a surface forces apparatus. Force—distance measurements indicate that the PCE weakly adsorbs onto mica from 0.1 mol/L K2SO4 and its boundary adsorption layers (about 50 Å thick) are totally squeezed out from the surface gap under an equivalent load level of three to four atmosphere pressures. The PCE is able to immediately accomplish the same adsorption after desorption. In the same ionic strength condition of 0.1 mol/L Ca(NO3)2, the PCE does not adsorb onto mica. However, the PCE builds up a 40-angstrom-thick robust adsorption layer on mica in the low calcium solution of 5 mmol/L Ca(NO3)2. Divalent Ca ions are able to bridge adsorbed PCE layers while monovalent K ions unable. The divalent cation bridging adsorption mechanism only functions in a finite ion concentration range.

Micro-milling is widely used in various crucial fields with the ability of machining micro- and meso-scaled functional structures on various materials efficiently. However, the micro-milling force model is not comprehensively developed yet when tool feature sizes continually decrease to under 200 µm in a low-stiffness system. This paper proposes an analytical force model considering the influence of tool radius, size effect, tool runout, tool deflection, and the actual trochoidal trajectories and the interaction of historical tool teeth trajectories (IHTTT). Different micro-milling status are recognized by analyzing the cutting process of different tool teeth. Conditions of single-tooth cutting status are determined by a proposed numerical algorithm, and entry angle and exit angle are analyzed under various cutting conditions for the low-stiffness system. Three micro-milling status, including single-tooth cutting status, are distinguished based on the instantaneous undeformed chip thickness resulting in three types of material removal mechanisms in predicting micro-milling force components. Discontinuous change rates of undeformed chip thickness are found in the low-stiffness micro-milling system. The proposed micro-milling force model is then verified through experiments of micro slot milling Elgiloy alloy with a 150-μm-diametrical two-teeth micro-end mill. The experimental results show a root-mean-square error (RSME) of 0.092 N in the predicted resultant force, accounting for approximately 5.12% of the measured force, by which the proposed theoretical model is verified to be of good prediction accuracy.

Carbon fiber reinforced polyetheretherketone (CF/PEEK) is an emerging material that is widely used in the automotive and aviation industry due to its high shock resistance, thermostability, and recyclability. However, its dry-machining requirement with an unclear dynamic material removal process limits the machining efficiency and surface quality. To this end, we firstly established a two-dimensional joint probability distribution model of cutting carbon fibers based on the microstructure of CF/PEEK. Compared with previous brittle models, the plastic model is verified to be more consistent with experimental results. A high-speed dry (HSD) milling force model considering carbon fiber distribution is then developed and is proofed with a high prediction accuracy of about 92.6%. With the proposed model, the milling force can be separated into forces of cutting carbon fibers and PEEK matrix, by which the influences of high-speed dry milling process on carbon fibers and PEEK matrix can be analyzed. The results show that carbon fiber distribution exhibits a significant impact on milling force and is more easily affected by milling parameters compared with the PEEK matrix. It is also verified feasible to HSD milling CF/PEEK, and the work gives the guidance of breaking the low-speed machining limits by improving the machining process.

A micromechanics model based on multi-phase modeling was established by using ABAQUS software. The material removal mechanism of SiC particle and the interactions among the cutting tool, SiC particle, Al matrix, and interface were studied, and the simulation results were compared to the experimental results. Different relative positions between the cutting tool and SiC particles can lead to different removal modes of SiC particles, including rolled or penetrated in Al matrix mode, fractured mode, and pulled out mode. Among them, fractured mode can be further divided into partial fractured mode and complete fractured mode. In complete fractured mode and pulled out mode, the SiC particle and its surrounding interface are seriously destroyed. Therefore, in the actual machining process, a small value of cutting depth should be chosen to make the SiC particle removed in rolled or penetrated in Al matrix mode or partial fractured mode for a better structural integrity of SiCp/Al composites. The pit as a result of SiC particle fractured and pulled out from Al matrix is the main defect on the machined surface. With the assistance of ultrasonic vibration, friction coefficient between the cutting tool and workpiece can be decreased. Thus, a better surface integrity of SiCp/Al composites can be obtained. The simulation results agree well with the experimental results.