Deployable parabolic cylindrical antennas with lightweight and high deploy/fold ratio are a research hotspot in aerospace.Most of the deployable structures of parabolic cylindrical antennas are double-layer truss stru...Deployable parabolic cylindrical antennas with lightweight and high deploy/fold ratio are a research hotspot in aerospace.Most of the deployable structures of parabolic cylindrical antennas are double-layer truss structures,which are heavy and oversized in folded volume.The 2D origami-inspired structure is a typical single-layer deployable structure,including multiple origami configurations that provide various strategies for designing single-layer deployable structures.This study proposes a design method for origami-inspired single-layer truss structures applied to deployable parabolic cylindrical mesh reflector antennas.Unlike the widely researched thick-panel origami structure,we adopt the strategy of equating the creases in the origami model as links with constant length,and the vertices are regarded as hinges.The design criteria for an origami-inspired single-layer truss structure are researched and summarized by analyzing the engineering issues during design.Based on this design method,a single-layer deployable truss applied to a parabolic cylindrical antenna is presented.An optimization model of the antenna driving components is established to ensure that the antenna can deploy appropriately on the basis of the co-simulation of MATLAB and finite element software Abaqus.The optimization results are validated through software simulation and prototype test.The work presented in this paper can broaden the application of origami-inspired structures and provide a reference for the design of parabolic cylindrical antennas or curved surface mechanisms.展开更多
Alumina dispersion-strengthened copper (ADSC), as a representative particle-reinforced metal matrix composite (PRMMC), exhibits superior wear resistance and high strength. However, challenges arise in their processabi...Alumina dispersion-strengthened copper (ADSC), as a representative particle-reinforced metal matrix composite (PRMMC), exhibits superior wear resistance and high strength. However, challenges arise in their processability because of the non-uniform material properties of biphasic materials. In particular, limited research has been conducted on the reinforcement mechanism and behavior of particles during material cutting deformation of PRMMC with nanoscale particles. In this study, a cutting simulation model for ADSC was established, separating the nanoscale reinforcement particles from the matrix. This model was utilized to analyze the interactions among particles, matrix, and tool during the cutting process, providing insights into chip formation and fracture. Particles with high strength and hardness are more prone to storing stress concentrations, anchoring themselves at grain boundaries to resist grain fibration, thereby influencing the stress distribution in the cutting deformation zone. Stress concentration around the particles leads to the formation of discontinuous chips, indicating that ADSC with high-volume fractions of particle (VFP) exhibits low cutting continuity, which is consistent with the results of cutting experiments. The tool tip that is in contact with particles experiences stress concentration, thereby accelerating tool wear. Cutting ADSC with 1.1% VFP results in tool blunting, which increases the radius of cutting edge from 0.5 to 1.9 μm, accompanied with remarkable coating delamination and wear. Simulation results indicate that the minimum uncut chip thickness increases from 0.04 to 0.07 μm as VFP increases from 0.3% to 1.1%. In conjunction with scratch experiments, MUCT increases with the augmentation of VFP. Computational analysis of the specific cutting force indicates that particles contribute to the material’s size effect. The results of this study provide theoretical guidance for practical engineering machining of ADSC, indicating its great importance for the process design of components made from ADSC.展开更多
The surging interest in planetary exploration underscores the need for deployable aerodynamic decelerators with a low ballistic coefficient.This study introduces a novel approach to designing and constructing mechanic...The surging interest in planetary exploration underscores the need for deployable aerodynamic decelerators with a low ballistic coefficient.This study introduces a novel approach to designing and constructing mechanically deployable aerodynamic decelerators(MDADs)that utilize an umbrella-like mechanism and proposes a new mechanism of MDADs through this method.The proposed method utilizes plane-symmetric 7R(R:revolute joint)linkages,and the kinematics of these linkages are systematically analyzed using the product of exponentials method.The 7R linkage kinematics are equated to an equivalent joint,the foundation for constructing umbrella-like deployable mechanisms.Three distinct types of mechanisms are synthesized using this methodology.Subsequently,their kinematics are analyzed based on the equivalent joint,and the configurations are experimentally validated through 3D-printed models and kinematic simulations.Trajectory simulations and structural analyses are conducted to assess the performance of the deployable mechanisms and provide valuable insights into their capabilities.This research contributes to advancing deployable aerodynamic decelerator technology and offers a promising avenue for future planetary entry,descent,and landing applications.展开更多
Recently,intelligent fault diagnosis methods have been employed in the condition monitoring of rotating machinery.Among them,graph neural networks are emerging as a new feature extraction tool that can mine the relati...Recently,intelligent fault diagnosis methods have been employed in the condition monitoring of rotating machinery.Among them,graph neural networks are emerging as a new feature extraction tool that can mine the relationship characteristics between samples.However,many existing graph construction methods suffer from structural redundancy or missing node relationships,thus limiting the diagnosis accuracy of the models in practice.In this paper,an adaptive adjustment k-nearest neighbor graph-driven dynamic-weighted graph attention network(AAKNN-DWGAT)is proposed to address this problem.First,time-domain signals are transformed into frequency-domain features by using fast Fourier transformation.Subsequently,a frequency similarity evaluation method based on dynamic frequency warping is proposed,which enables the conversion of distance measurements into a frequency similarity matrix(FSM).Then,an adaptive edge construction operation is conducted on the basis of FSM,whereby the effective domain is captured for each node using an adaptive edge adjustment method,generating an AAKNN graph(AAKNNG).Next,the constructed AAKNNG is fed into a dynamic-weighted graph attention network(DWGAT)to extract the fault features of nodes layer by layer.In particular,the proposed DWGAT employs a dynamic-weighted strategy that can update the edge weight periodically using high-level output features,thereby eliminating the adverse impacts caused by noisy signals.Finally,the model outputs fault diagnosis results through a softmax classifier.Two case studies verified the effectiveness and the superiority of the proposed method compared with other graph neural networks and graph construction methods.展开更多
As semiconductor manufacturing moves toward fine feature sizes,precise and efficient resist model calibration has become crucial for optical proximity correction to ensure pattern fidelity.However,traditional calibrat...As semiconductor manufacturing moves toward fine feature sizes,precise and efficient resist model calibration has become crucial for optical proximity correction to ensure pattern fidelity.However,traditional calibration methods struggle with efficiency and scalability and are prone to becoming trapped in local optima.Herein,we propose a surrogate-assisted genetic algorithm(SAGA)that integrates Kriging interpolation-based surrogate models and dynamic adaptive mechanisms to optimize resist model coefficients,convolution kernel parameters,and aerial image settings jointly.By leveraging surrogate models to predict high-performance solutions and adaptively adjusting crossover/mutation rates,SAGA balances global exploration and local exploitation,achieving rapid convergence and superior model accuracy compared with other algorithms.Experimental validation across three resist cases demonstrates that SAGA outperforms conventional genetic algorithms and grid search.Compared with other algorithms,SAGA not only achieves higher accuracy but also converges faster,with its optimization trajectories stabilizing earlier in the iterative process.These results highlight SAGA’s potential for efficient and high-precision resist calibration in computational lithography.展开更多
The continuous pursuit of extremely lightweight and multi-functional integrated designs in modern industries requires that structural materials are not limited to ensuring the structural load-bearing function of light...The continuous pursuit of extremely lightweight and multi-functional integrated designs in modern industries requires that structural materials are not limited to ensuring the structural load-bearing function of lightweight designs;rather,they must have high mechanical properties and high damping capabilities.Self-healing materials are becoming popular because of their attractive repairability and reprocessability.Dynamic reversible bonds,which are included in self-healing polymer networks,have been extensively studied with respect to different chemical mechanisms.Nevertheless,the ability to reach high stiffness and high damping performance is crucial.In this review,different types of self-healing materials are introduced,and their complex and contradictory relationships with stiffness,damping,and self-healing properties are explained.This review combines intrinsic damping sources and extrinsic deformation driving modes as a holistic concept of material–structure–performance integrated design methodology to address the extensive challenges of increasing specific damping performance.Specifically,the sources of damping at the nanolevel and the deformation-driving modes at different levels of structural hierarchy are explained in depth to reveal the cross-scale coordination between intrinsic damping sources and extrinsic deformation-driven modes originating from extremely different length scales in the microstructural architecture of a material.The material–structure–performance integrated design methodology is expected to become a key strategy for the sustainable development of breakthrough and transformative damping composite structures for aerospace,terrestrial,and marine transportation.展开更多
A method is proposed to control the minimum width of lattice structure in the topology optimization by using a Multiple Variable Cutting(M-VCUT)based substructure.The geometry of substructure is described by using the...A method is proposed to control the minimum width of lattice structure in the topology optimization by using a Multiple Variable Cutting(M-VCUT)based substructure.The geometry of substructure is described by using the M-VCUT level set approach,and the substructures are condensed to superelements.A data-driven model of substructure is constructed,and it is used for the finite element analysis and sensitivity analysis during the optimization,so that computational costs are reduced.More importantly,only the substructures whose minimum width are larger than an admissible value are considered in the data-driven model,thus inherently enforcing the constraint of minimum width and making the optimization much easier.The effectiveness of the proposed method is demonstrated through several numerical examples.展开更多
The design of single-degree-of-freedom spatial mechanisms tracing a given path is challenging due to the highly non-linear relationships between coupler curves and mechanism parameters.This work introduces an innovati...The design of single-degree-of-freedom spatial mechanisms tracing a given path is challenging due to the highly non-linear relationships between coupler curves and mechanism parameters.This work introduces an innovative application of deep learning to the spatial path synthesis of one-degree-of-freedom spatial revolute–spherical–cylindrical–revolute(RSCR)mechanisms,aiming to find the non-linear mapping between coupler curve and mechanism parameters and generate diverse solutions to the path synthesis problem.Several deep learning models are explored,including multi-layer perceptron(MLP),variational autoencoder(VAE)plus MLP,and a novel model using conditional-β-VAE(c-β-VAE).We found that the c-β-VAE model withβ=10 achieves superior performance by predicting multiple mechanisms capable of generating paths that closely approximate the desired input path.This study also builds a publicly available database of over 5 million paths and their corresponding RSCR mechanisms.The database provides a solid foundation for training deep learning models.An application in the design of human upper-limb rehabilitation mechanism is presented.Several RSCR mechanisms closely matching the wrist and elbow path collected from human movements are found using our deep learning models.This application underscores the potential of RSCR mechanisms and the effectiveness of our model in addressing complex,real-world spatial mechanism design problems.展开更多
Machining-induced damages encountered during the grinding of titanium alloys are a major setback for processing different components from these materials. Recent studies have shown that nanofluid (NF)-based minimum qu...Machining-induced damages encountered during the grinding of titanium alloys are a major setback for processing different components from these materials. Recent studies have shown that nanofluid (NF)-based minimum quantity lubrication (MQL) systems improved the machining lubrication and the titanium alloys’ machinability. In this work, the tribological characteristics of a palm oil-based tripartite hybrid NF (ZnO/Al_(2)O_(3)/Graphene Oxide, GO) are studied. The novel usage of the developed lubricants in MQL systems was examined during the grinding of Ti6-Al-4V (TC4) alloy. The NF was produced by mixing three weight percent mixtures (i.e., 0.1, 0.5, and 1 wt.%) of the nanoparticles in palm oil. A comprehensive tribological and physical investigation was conducted on different percentage compositions of the developed NF to determine the optimum mix ratio of the lubricant. The findings indicate that increasing the NF concentration caused an increment in the dynamic viscosity and frictional coefficient of the NFs. The tripartite hybrid NF exhibited superior tribological and physicochemical properties compared with the pure palm and monotype-based NFs. Moreover, the dynamic viscosity of the tripartite-hybrid-based NFs increased by 12%, 5%, and 11.5% for the Al_(2)O_(3), GO, and ZnO hybrid NFs, respectively. In addition, the machining results indicate that the tripartite hybrid NF lowered the surface roughness, specific grinding, grinding force ratio, tangential, and normal grinding forces by 42%, 40%, 16.5%, 41.5%, and 30%, respectively. Hence, the tripartite hybrid NFs remarkably enhanced the tribology and machining performance of the eco-friendly lubricant.展开更多
The harsh working environment of unmanned mining electric shovels(UMESs)and the considerable inertia changes during the excavation process in the front-end mechanism pose major challenges to excavation trajectory trac...The harsh working environment of unmanned mining electric shovels(UMESs)and the considerable inertia changes during the excavation process in the front-end mechanism pose major challenges to excavation trajectory tracking.In this study,an adaptive Hamilton-Jacobi inequality(HJI)-based robust control method for UMES excavation systems with uncertainty was proposed for trajectory tracking control in intelligent mining.First,the excavation system dynamic model was analyzed using the Lagrangian method,and an excavation resistance prediction model and a material quality prediction model were constructed.The optimal excavation trajectory was described.Then,the HJI theorem was used to design an adaptive controller based on the dynamic model of the UMES,and a generalized regression neural network was introduced to fit the interference term in the control object to ensure the convergence of the control system.Subsequently,a Lyapunov function was constructed to demonstrate the stability of the control system to ensure the reliability of the excavation system.Finally,the method proposed in this study was verified under two different working conditions involving a typical material surface and a real material surface.The numerical simulation results demonstrated that the planned position and velocity were effectively tracked in both working conditions.Furthermore,it maintains an improved tracking effect under different uncertain disturbances,thus verifying the feasibility and robustness of the control system designed in this study.展开更多
Surface thermal damage in a difficult-to-process metal precision grinding workpiece has emerged as a technical bottleneck restricting machining quality.As an alternative to traditional pouring cooling,a green clean mi...Surface thermal damage in a difficult-to-process metal precision grinding workpiece has emerged as a technical bottleneck restricting machining quality.As an alternative to traditional pouring cooling,a green clean minimum-quantity lubrication technology still has defects,such as insufficient heat dissipation.The use of cryogenic air instead of normal temperature air,that is,the supply of low-temperature energized lubricant,can effectively improve oil film heat transfer and lubrication performance in a grinding area.Under the premise of ensuring the effective flow of lubricating oil in a grinding zone,the thickness of a liquid film in the wedge zone of a grinding wheel or workpiece is the key factor for determining its performance.However,the dynamic mechanism of droplet formation and distribution of liquid film thickness are still unclear.Hence,the mechanism by which nozzle orientation influences the effective region of a liquid film was analyzed,and the range of nozzle inclination that helps to atomize droplets and enables them to enter the grinding zone was revealed.Then,the dynamic mechanism of atomized droplet film formation was analyzed,and the influence of normal and tangential momentum sources generated by gas impingement perturbation flow and droplet impingement steady flow on the driving effect of liquid film flow was revealed.The thickness distribution model of a liquid film in the impact zone of gas–liquid two-phase flow under different cryogenic air temperatures was established.The model results under different working conditions were obtained by numerical analysis,and validation experiments were carried out.Results show that the measured values agree with the theoretical values.At 0.4 MPa air pressure,the thickness of the liquid film in the impact zone of the atomized droplets increases with decreasing cryogenic air temperature.At−10 and−50°C,the thickness of the liquid film is 0.92 and 1.26 mm,respectively.Further,on the basis of the surface topography model of cubic boron nitride grinding wheel,the pose relationship of any three adjacent abrasive particles was analyzed,and the theoretical model of abrasive clearance volume was established.The dynamic variation of abrasive clearance volume distribution domain is[70.46,78.72]mm3,and the total volume distribution domain is[140.84,155.67]mm3.The research will provide a theoretical basis for the application of cryogenic air minimum quantity lubrication technology to hard metal grinding.展开更多
In confined spaces,conventional ground mobile robots may be unable to reach the target location because of limited maneuvering space or the inability to overcome obstacles.This study presents a ground mobile mechanism...In confined spaces,conventional ground mobile robots may be unable to reach the target location because of limited maneuvering space or the inability to overcome obstacles.This study presents a ground mobile mechanism with a multi-loop reconfigurable trunk(GMMRT)designed to enhance mobility in constrained spaces,such as narrow gaps,ditches,and cross-shaped channels.GMMRT can effectively overcome obstacles in confined spaces through the coordinated motion of its wheels and reconfigurable trunk.Its reconfigurable trunk comprises six limbs and four vertex platforms,forming a versatile,adaptable structure.GMMRT supports two topological structures:wheeled mobility and overall rolling.It features three distinct motion modes:(i)adjusting external dimensions,(ii)performing zero-radius steering,and(iii)overall deformation rolling motion.The kinematic model of GMMRT is established,and its parameters are described using Denavit–Hartenberg parameters.The degrees of freedom under the two topological structures are analyzed on the basis of screw theory.Torque analysis of servo motors is conducted through dynamic analysis.An experimental prototype is designed to validate the three motion modes and servo motor selection,and relevant experiments are performed.Through the development and experimental validation of GMMRT,this work advances mobile robot design for confined spaces and provides a promising approach to overcome the limitations of conventional ground robots.展开更多
Real-time slip detection and state estimation are crucial for locomotion control,facilitating posture adjustment and stability recovery of multi-legged robots moving on slippery terrain.However,existing proprioceptive...Real-time slip detection and state estimation are crucial for locomotion control,facilitating posture adjustment and stability recovery of multi-legged robots moving on slippery terrain.However,existing proprioceptive methods rely on the fixed-contact assumption with fixed noise and suffer from low accuracy when multiple legs slip simultaneously.This paper proposes a novel proprioceptive approach for multi-legged robots moving in slippery scenarios to cope with slippage of multiple legs.In slip detection,the proprioceptive states of the robot are fed into a convolutional neural network to detect slip event(s)of the robot,enabling accurate identification of slipping legs even under simultaneous multi-leg slippage.For state estimation,an invariant extended Kalman filter is employed to fuse the motion information with the detected slip event(s)to obtain the robot state.By incorporating slip event(s)and foot velocity into the system motion equation of the filter,the proposed method better leverages leg odometry information and achieves more precise state estimation compared with existing methods.Simulations on a quadruped and a hexapod demonstrate the effectiveness and increased accuracy during multi-leg slippage.Experimental results for the quadruped robot show that the proposed approach achieves a 48% reduction in the root mean square error and a 47%reduction in the maximum error in velocity estimation under severe multi-leg slippage compared with the existing methods.展开更多
Micro/nano functional structures (MNFSs) have attracted substantial attention because of theiroutstanding performance in optical, tribological, thermal, electronic, and biomedical applications. Despite thedevelopment ...Micro/nano functional structures (MNFSs) have attracted substantial attention because of theiroutstanding performance in optical, tribological, thermal, electronic, and biomedical applications. Despite thedevelopment of various mechanical and non-mechanical machining methods, achieving the high-efficiency, high-precision fabrication of MNFS from difficult-to-cut materials remains a significant technical challenge. This reviewbegins with an introduction to typical artificial MNFSs and their stringent requirements and then provides acomprehensive survey of MNFSs, focusing on etching methods. In particular, plasma etching demonstrates notableadvantages in MNFS fabrication. However, two critical challenges persist: accurately controlling topographicalinformation during pattern transfer in plasma etching and achieving high-quality, uniform patterning masks overlarge areas. These issues are addressed by thoroughly analyzing and summarizing the modeling of plasma etchingand the simulation of feature profiles. Various hybrid etching machining (HEM) strategies, including laser andetching combined machining, cutting and etching combined machining, molding and etching combined machining,and self-assembly and etching combined machining, are categorized and compared in detail to facilitate themanufacturing of complex MNFSs. Finally, this review summarizes current deficiencies and future challenges ofHEM, laying the groundwork for further advancements in MNFS fabrication and intelligent HEM technologies.展开更多
Tool anomalies in computer numerical control(CNC)milling processes are unpredictable,hindering the promotion of fully automated machining.Traditional detection systems often struggle with stability due to the irregula...Tool anomalies in computer numerical control(CNC)milling processes are unpredictable,hindering the promotion of fully automated machining.Traditional detection systems often struggle with stability due to the irregular and non-parametric nature of signals generated during dynamic milling.This study proposes an improved probability and statistics-based model for constructing tool anomaly thresholds in the time domain,with the decision-making strategy seamlessly integrated into CNC milling systems.A robust data acquisition and preprocessing framework was developed to improve the accuracy and reliability of real-time monitoring data.A Gaussian process model was employed to construct an anomaly detection threshold data set from irregular signals.Anomalies were identified when monitoring indicators surpassed the established threshold.The proposed method was validated through milling experiments of a turbine blisk,demonstrating an overall anomaly detection accuracy of 91.45%,which exceeds those of four other typical anomaly detection methods.These results confirm the effectiveness of the proposed method and its potential applicability in industry.展开更多
In the rotor system of aero-engines,the main purpose of a bolted flange connection structure is to transfer torque and speed,and the rotor system may exhibit bolt loosening and connection structure failure under compl...In the rotor system of aero-engines,the main purpose of a bolted flange connection structure is to transfer torque and speed,and the rotor system may exhibit bolt loosening and connection structure failure under complex working conditions,high speed rotation,and external excitation unbalanced force.In addition,the bolted connection structure in the rotor system is mainly subjected to torsional vibration excitation,and using experimental methods to analyze the dynamic response law of different structural parameters of a bolted connection structure under torsional vibration excitation is complicated.Therefore,on the basis of the concentrated mass method and the elastic interaction characteristics within the bolted system,this study establishes dynamic models of one-bolted and multi-bolted connection structural systems under torsional excitation.On the basis of this dynamic model,the dynamic response characteristics of different thread parameters,external excitation,bolt stiffness,and compression stiffness of the connected parts in a one-bolted connection system and the influence laws of different elastic modulus,bolt numbers,and the thickness of the connected parts on the loosening of the multi-bolted connection system are analyzed.Results show that small thread pitch,external excitation amplitude and frequency,compressive stiffness,bolt stiffness,and elastic modulus and large tooth angle,number of bolts,and thickness of connected parts can appropriately improve the anti-loosening performance of the bolted connection system.This study also uses a comparative verification method combining finite element simulation and experiment to verify the correctness of the established dynamic model effectively.展开更多
Ultra-high-strength steels have been widely utilized in the aviation industry due to their superior mechanical and physical properties.However,the intense friction occurring at the tool–workpiece interface can result...Ultra-high-strength steels have been widely utilized in the aviation industry due to their superior mechanical and physical properties.However,the intense friction occurring at the tool–workpiece interface can result in significant tool wear,impacting both the machining efficiency and surface quality.Therefore,a deep understanding of the tribological behavior at the tool–workpiece interface is crucial for extending tool life.The current study proposed a novel open tribo-system to simulate the intermittent contact conditions between the tool and the workpiece during the milling process.An improved friction model was established to calculate the real friction coefficient under intermittent contact conditions.Tribological comparative experiments on ultra-highstrength steel and cemented carbide were conducted under various cooling conditions:dry,high-pressure air cooling(HPAC),air atomization of cutting fluid(AACF),and ultrasonic atomization of cutting fluid(UACF).The influences of various cooling conditions on the tribological characteristics were investigated,with a focus on the depth of the wear mark,height of the pile-up,measured force,adhesion friction coefficient,and wear morphology.The results reveal that the depth of the wear mark,height of the pile-up,and measured forces play pivotal roles in determining the adhesion friction coefficient.The synergistic action of airflow and droplets results in the formation of a liquid film,improving the friction at the interface between the ball and the workpiece.Compared with the AACF condition,the UACF condition results in a 7.7% reduction in the adhesion friction coefficient due to its excellent film-forming ability stemming from its small droplet size and uniform droplet size distribution.Abrasive wear,adhesive wear,and oxidative wear are the primary wear types for cemented carbide,regardless of the cooling conditions.The effective cooling and lubrication capability provided by the uniform liquid film in UACF contributes to improving the wear resistance of cemented carbide,offering valuable insights for mitigating tool wear.展开更多
Plunge milling,which is recognized for its efficiency,has gradually been adopted for the roughing of integral impellers in recent years.However,several challenges persist,such as redundant tool paths,difficulties in m...Plunge milling,which is recognized for its efficiency,has gradually been adopted for the roughing of integral impellers in recent years.However,several challenges persist,such as redundant tool paths,difficulties in managing the Sudden Increase of Radial Depth(SIRD),and excessive residual material in the adjusted tool path by plunge milling,which collectively constrain the efficiency of the plunge milling process.To address these challenges,this study proposes a five-axis plunge milling method with double-row slotting tailored for integral impellers.This method segments the machining area based on the width of the impeller runner and utilizes various tools with different diameters to enhance machining efficiency.The plunge milling path is optimized to facilitate efficient material removal while maintaining cutting stability,which addresses issues related to cutting overload and chip accumulation.In addition,an efficient method for SIRD identification and exclusion is proposed to minimize residual material.Simulation and practical machining results confirm that the proposed plunge milling method with double-row slotting significantly improves machining efficiency,which achieves enhancements of over 1.5 times compared with traditional methods.展开更多
A material removal mechanism is a prerequisite to maintaining high-quality surfaces for high-shear and low-pressure grinding using body-armor-like grinding wheels(BAGWs).However,the pressure distribution and material ...A material removal mechanism is a prerequisite to maintaining high-quality surfaces for high-shear and low-pressure grinding using body-armor-like grinding wheels(BAGWs).However,the pressure distribution and material removal efficiency for machining brittle materials using BAGWs remain unclear.This research investigated two types of elastic deformations during grinding by analyzing the contact mechanism between BAGWs and the workpiece.Additionally,the model of elastohydrodynamic pressure distribution was refined,and the material removal mechanism for machining brittle materials,incorporating the maximum undeformed chip thickness,was revealed.A material removal rate(MRR)model was established based on Hertzian contact,ductile-brittle transition,and spherical indentation theory.The theoretical model was validated through single-factor experiments utilizing a high-shear and low-pressure grinding experimental platform.At a normal grinding force of 15 N and a grinding speed of 10 m/s,the MRR could reach up to 0.276 mm3/s.The experimental results revealed that the model could accurately predict the MRR under various grinding parameters,with an average prediction error of 8.5%.展开更多
Multiscale structures require excellent multiphysical properties to withstand the loads in various complex engineering fields.In this study,a concurrent isogeometric topology optimization method is proposed to design ...Multiscale structures require excellent multiphysical properties to withstand the loads in various complex engineering fields.In this study,a concurrent isogeometric topology optimization method is proposed to design multiscale structures with high thermal conductivity and low mechanical compliance.First,the mathematical description model of multi-objective topology optimization for multiscale structures is constructed,and a single-objective concurrent isogeometric topology optimization formulation for mechanical and thermal compliance is proposed.Then,by combining the isogeometric analysis method,the material interpolation model and decoupled sensitivity analysis scheme of the objective function are established on macro and micro scales.The solid isotropic material with penalization method is employed to update iteratively the macro and microstructure topologies simultaneously.Finally,the feasibility and advantages of the proposed approach are illustrated by several 2D and 3D numerical examples with different volume fractions,while the effects of volume fraction and different boundary conditions on the final configuration and multi-objective performance of the multiscale structure are explored.Results show that the isogeometric concurrent design of multiscale structures through multi-objective optimization can produce better multi-objective performance compared with a single-scale one.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52475280).
文摘Deployable parabolic cylindrical antennas with lightweight and high deploy/fold ratio are a research hotspot in aerospace.Most of the deployable structures of parabolic cylindrical antennas are double-layer truss structures,which are heavy and oversized in folded volume.The 2D origami-inspired structure is a typical single-layer deployable structure,including multiple origami configurations that provide various strategies for designing single-layer deployable structures.This study proposes a design method for origami-inspired single-layer truss structures applied to deployable parabolic cylindrical mesh reflector antennas.Unlike the widely researched thick-panel origami structure,we adopt the strategy of equating the creases in the origami model as links with constant length,and the vertices are regarded as hinges.The design criteria for an origami-inspired single-layer truss structure are researched and summarized by analyzing the engineering issues during design.Based on this design method,a single-layer deployable truss applied to a parabolic cylindrical antenna is presented.An optimization model of the antenna driving components is established to ensure that the antenna can deploy appropriately on the basis of the co-simulation of MATLAB and finite element software Abaqus.The optimization results are validated through software simulation and prototype test.The work presented in this paper can broaden the application of origami-inspired structures and provide a reference for the design of parabolic cylindrical antennas or curved surface mechanisms.
基金supported by the National Key R&D Program of China(Grant No.2023YFC2413303)the National Natural Science Foundation of China(Grant No.52075128)the Natural Science Foundation of Heilongjiang Province,China(Grant No.YQ2020E013).
文摘Alumina dispersion-strengthened copper (ADSC), as a representative particle-reinforced metal matrix composite (PRMMC), exhibits superior wear resistance and high strength. However, challenges arise in their processability because of the non-uniform material properties of biphasic materials. In particular, limited research has been conducted on the reinforcement mechanism and behavior of particles during material cutting deformation of PRMMC with nanoscale particles. In this study, a cutting simulation model for ADSC was established, separating the nanoscale reinforcement particles from the matrix. This model was utilized to analyze the interactions among particles, matrix, and tool during the cutting process, providing insights into chip formation and fracture. Particles with high strength and hardness are more prone to storing stress concentrations, anchoring themselves at grain boundaries to resist grain fibration, thereby influencing the stress distribution in the cutting deformation zone. Stress concentration around the particles leads to the formation of discontinuous chips, indicating that ADSC with high-volume fractions of particle (VFP) exhibits low cutting continuity, which is consistent with the results of cutting experiments. The tool tip that is in contact with particles experiences stress concentration, thereby accelerating tool wear. Cutting ADSC with 1.1% VFP results in tool blunting, which increases the radius of cutting edge from 0.5 to 1.9 μm, accompanied with remarkable coating delamination and wear. Simulation results indicate that the minimum uncut chip thickness increases from 0.04 to 0.07 μm as VFP increases from 0.3% to 1.1%. In conjunction with scratch experiments, MUCT increases with the augmentation of VFP. Computational analysis of the specific cutting force indicates that particles contribute to the material’s size effect. The results of this study provide theoretical guidance for practical engineering machining of ADSC, indicating its great importance for the process design of components made from ADSC.
基金supported by the National Natural Science Foundation of China(Grant No.52175010)the Self-Planned Task of the State Key Laboratory of Robotics and Systems,Harbin Institute of Technology,China(Grant No.SKLRS202202B).
文摘The surging interest in planetary exploration underscores the need for deployable aerodynamic decelerators with a low ballistic coefficient.This study introduces a novel approach to designing and constructing mechanically deployable aerodynamic decelerators(MDADs)that utilize an umbrella-like mechanism and proposes a new mechanism of MDADs through this method.The proposed method utilizes plane-symmetric 7R(R:revolute joint)linkages,and the kinematics of these linkages are systematically analyzed using the product of exponentials method.The 7R linkage kinematics are equated to an equivalent joint,the foundation for constructing umbrella-like deployable mechanisms.Three distinct types of mechanisms are synthesized using this methodology.Subsequently,their kinematics are analyzed based on the equivalent joint,and the configurations are experimentally validated through 3D-printed models and kinematic simulations.Trajectory simulations and structural analyses are conducted to assess the performance of the deployable mechanisms and provide valuable insights into their capabilities.This research contributes to advancing deployable aerodynamic decelerator technology and offers a promising avenue for future planetary entry,descent,and landing applications.
基金financially supported by the National Natural Science Foundation of China(Grant No.51905396).
文摘Recently,intelligent fault diagnosis methods have been employed in the condition monitoring of rotating machinery.Among them,graph neural networks are emerging as a new feature extraction tool that can mine the relationship characteristics between samples.However,many existing graph construction methods suffer from structural redundancy or missing node relationships,thus limiting the diagnosis accuracy of the models in practice.In this paper,an adaptive adjustment k-nearest neighbor graph-driven dynamic-weighted graph attention network(AAKNN-DWGAT)is proposed to address this problem.First,time-domain signals are transformed into frequency-domain features by using fast Fourier transformation.Subsequently,a frequency similarity evaluation method based on dynamic frequency warping is proposed,which enables the conversion of distance measurements into a frequency similarity matrix(FSM).Then,an adaptive edge construction operation is conducted on the basis of FSM,whereby the effective domain is captured for each node using an adaptive edge adjustment method,generating an AAKNN graph(AAKNNG).Next,the constructed AAKNNG is fed into a dynamic-weighted graph attention network(DWGAT)to extract the fault features of nodes layer by layer.In particular,the proposed DWGAT employs a dynamic-weighted strategy that can update the edge weight periodically using high-level output features,thereby eliminating the adverse impacts caused by noisy signals.Finally,the model outputs fault diagnosis results through a softmax classifier.Two case studies verified the effectiveness and the superiority of the proposed method compared with other graph neural networks and graph construction methods.
基金funded by the National Natural Science Foundation of China(Grant Nos.52205592 and 52130504)Key Research and Development Plan of Hubei Province,China(Grant No.2022BAA013)+1 种基金Major Program(JD)of Hubei Province,China(Grant No.2023BAA008-2)Innovation Project of Optics Valley Laboratory,China(Grant No.OVL2023PY003)。
文摘As semiconductor manufacturing moves toward fine feature sizes,precise and efficient resist model calibration has become crucial for optical proximity correction to ensure pattern fidelity.However,traditional calibration methods struggle with efficiency and scalability and are prone to becoming trapped in local optima.Herein,we propose a surrogate-assisted genetic algorithm(SAGA)that integrates Kriging interpolation-based surrogate models and dynamic adaptive mechanisms to optimize resist model coefficients,convolution kernel parameters,and aerial image settings jointly.By leveraging surrogate models to predict high-performance solutions and adaptively adjusting crossover/mutation rates,SAGA balances global exploration and local exploitation,achieving rapid convergence and superior model accuracy compared with other algorithms.Experimental validation across three resist cases demonstrates that SAGA outperforms conventional genetic algorithms and grid search.Compared with other algorithms,SAGA not only achieves higher accuracy but also converges faster,with its optimization trajectories stabilizing earlier in the iterative process.These results highlight SAGA’s potential for efficient and high-precision resist calibration in computational lithography.
基金supported by the National Natural Science Foundation of China(Grant No.52175095)the Young Top-notch Talent Cultivation Program of Hubei Province of China.
文摘The continuous pursuit of extremely lightweight and multi-functional integrated designs in modern industries requires that structural materials are not limited to ensuring the structural load-bearing function of lightweight designs;rather,they must have high mechanical properties and high damping capabilities.Self-healing materials are becoming popular because of their attractive repairability and reprocessability.Dynamic reversible bonds,which are included in self-healing polymer networks,have been extensively studied with respect to different chemical mechanisms.Nevertheless,the ability to reach high stiffness and high damping performance is crucial.In this review,different types of self-healing materials are introduced,and their complex and contradictory relationships with stiffness,damping,and self-healing properties are explained.This review combines intrinsic damping sources and extrinsic deformation driving modes as a holistic concept of material–structure–performance integrated design methodology to address the extensive challenges of increasing specific damping performance.Specifically,the sources of damping at the nanolevel and the deformation-driving modes at different levels of structural hierarchy are explained in depth to reveal the cross-scale coordination between intrinsic damping sources and extrinsic deformation-driven modes originating from extremely different length scales in the microstructural architecture of a material.The material–structure–performance integrated design methodology is expected to become a key strategy for the sustainable development of breakthrough and transformative damping composite structures for aerospace,terrestrial,and marine transportation.
基金supported by the National Natural Science Foundation of China(Grant No.12272144).
文摘A method is proposed to control the minimum width of lattice structure in the topology optimization by using a Multiple Variable Cutting(M-VCUT)based substructure.The geometry of substructure is described by using the M-VCUT level set approach,and the substructures are condensed to superelements.A data-driven model of substructure is constructed,and it is used for the finite element analysis and sensitivity analysis during the optimization,so that computational costs are reduced.More importantly,only the substructures whose minimum width are larger than an admissible value are considered in the data-driven model,thus inherently enforcing the constraint of minimum width and making the optimization much easier.The effectiveness of the proposed method is demonstrated through several numerical examples.
基金supported by the National Science Foundation of USA(under Grant No.STTR phase II\#2126882)the co-author/co-PI Dr.Purwar,who also holds stocks in Mechanismic Inc.,USA.
文摘The design of single-degree-of-freedom spatial mechanisms tracing a given path is challenging due to the highly non-linear relationships between coupler curves and mechanism parameters.This work introduces an innovative application of deep learning to the spatial path synthesis of one-degree-of-freedom spatial revolute–spherical–cylindrical–revolute(RSCR)mechanisms,aiming to find the non-linear mapping between coupler curve and mechanism parameters and generate diverse solutions to the path synthesis problem.Several deep learning models are explored,including multi-layer perceptron(MLP),variational autoencoder(VAE)plus MLP,and a novel model using conditional-β-VAE(c-β-VAE).We found that the c-β-VAE model withβ=10 achieves superior performance by predicting multiple mechanisms capable of generating paths that closely approximate the desired input path.This study also builds a publicly available database of over 5 million paths and their corresponding RSCR mechanisms.The database provides a solid foundation for training deep learning models.An application in the design of human upper-limb rehabilitation mechanism is presented.Several RSCR mechanisms closely matching the wrist and elbow path collected from human movements are found using our deep learning models.This application underscores the potential of RSCR mechanisms and the effectiveness of our model in addressing complex,real-world spatial mechanism design problems.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52305477,52375447,52305474,and 52205481)the Major Special Projects of Aero-engine and Gas Turbine,China(Grant No.2017-VII-0002-0095)+5 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20210407)the Special Fund of Taishan Scholars Project,China(Grant No.tsqn202211179)the Youth Talent Promotion Project in Shandong,China(Grant No.SDAST2021qt12)Qingdao Postdoctoral Researchers Applied Research Project,China(Grant No.QDBSH20230102050)the Support plan for Outstanding Youth Innovation Team in Universities of Shandong Province,China(Grant No.2023KJ114)Qingdao Science and Technology Planning Park Cultivation Plan(Grant No.23-1-5-yqpy-17-qy).
文摘Machining-induced damages encountered during the grinding of titanium alloys are a major setback for processing different components from these materials. Recent studies have shown that nanofluid (NF)-based minimum quantity lubrication (MQL) systems improved the machining lubrication and the titanium alloys’ machinability. In this work, the tribological characteristics of a palm oil-based tripartite hybrid NF (ZnO/Al_(2)O_(3)/Graphene Oxide, GO) are studied. The novel usage of the developed lubricants in MQL systems was examined during the grinding of Ti6-Al-4V (TC4) alloy. The NF was produced by mixing three weight percent mixtures (i.e., 0.1, 0.5, and 1 wt.%) of the nanoparticles in palm oil. A comprehensive tribological and physical investigation was conducted on different percentage compositions of the developed NF to determine the optimum mix ratio of the lubricant. The findings indicate that increasing the NF concentration caused an increment in the dynamic viscosity and frictional coefficient of the NFs. The tripartite hybrid NF exhibited superior tribological and physicochemical properties compared with the pure palm and monotype-based NFs. Moreover, the dynamic viscosity of the tripartite-hybrid-based NFs increased by 12%, 5%, and 11.5% for the Al_(2)O_(3), GO, and ZnO hybrid NFs, respectively. In addition, the machining results indicate that the tripartite hybrid NF lowered the surface roughness, specific grinding, grinding force ratio, tangential, and normal grinding forces by 42%, 40%, 16.5%, 41.5%, and 30%, respectively. Hence, the tripartite hybrid NFs remarkably enhanced the tribology and machining performance of the eco-friendly lubricant.
基金supported by the Major Science and Technology Project of Shanxi Province,China(Grant No.20191101014)the National Natural Science Foundation of China(Grant No.52075068).
文摘The harsh working environment of unmanned mining electric shovels(UMESs)and the considerable inertia changes during the excavation process in the front-end mechanism pose major challenges to excavation trajectory tracking.In this study,an adaptive Hamilton-Jacobi inequality(HJI)-based robust control method for UMES excavation systems with uncertainty was proposed for trajectory tracking control in intelligent mining.First,the excavation system dynamic model was analyzed using the Lagrangian method,and an excavation resistance prediction model and a material quality prediction model were constructed.The optimal excavation trajectory was described.Then,the HJI theorem was used to design an adaptive controller based on the dynamic model of the UMES,and a generalized regression neural network was introduced to fit the interference term in the control object to ensure the convergence of the control system.Subsequently,a Lyapunov function was constructed to demonstrate the stability of the control system to ensure the reliability of the excavation system.Finally,the method proposed in this study was verified under two different working conditions involving a typical material surface and a real material surface.The numerical simulation results demonstrated that the planned position and velocity were effectively tracked in both working conditions.Furthermore,it maintains an improved tracking effect under different uncertain disturbances,thus verifying the feasibility and robustness of the control system designed in this study.
基金financially supported by the National Natural Science Foundation of China(Grant No.52375447)Shandong Provincial Natural Science Foundation of General Program,China(Grant No.ZR2024ME205)+1 种基金the Special Fund of Taishan Scholars Project,China(Grant No.tsqn202408220)Shandong Provincial Natural Science Foundation of Youth Fund,China(Grant No.ZR2021QE116).
文摘Surface thermal damage in a difficult-to-process metal precision grinding workpiece has emerged as a technical bottleneck restricting machining quality.As an alternative to traditional pouring cooling,a green clean minimum-quantity lubrication technology still has defects,such as insufficient heat dissipation.The use of cryogenic air instead of normal temperature air,that is,the supply of low-temperature energized lubricant,can effectively improve oil film heat transfer and lubrication performance in a grinding area.Under the premise of ensuring the effective flow of lubricating oil in a grinding zone,the thickness of a liquid film in the wedge zone of a grinding wheel or workpiece is the key factor for determining its performance.However,the dynamic mechanism of droplet formation and distribution of liquid film thickness are still unclear.Hence,the mechanism by which nozzle orientation influences the effective region of a liquid film was analyzed,and the range of nozzle inclination that helps to atomize droplets and enables them to enter the grinding zone was revealed.Then,the dynamic mechanism of atomized droplet film formation was analyzed,and the influence of normal and tangential momentum sources generated by gas impingement perturbation flow and droplet impingement steady flow on the driving effect of liquid film flow was revealed.The thickness distribution model of a liquid film in the impact zone of gas–liquid two-phase flow under different cryogenic air temperatures was established.The model results under different working conditions were obtained by numerical analysis,and validation experiments were carried out.Results show that the measured values agree with the theoretical values.At 0.4 MPa air pressure,the thickness of the liquid film in the impact zone of the atomized droplets increases with decreasing cryogenic air temperature.At−10 and−50°C,the thickness of the liquid film is 0.92 and 1.26 mm,respectively.Further,on the basis of the surface topography model of cubic boron nitride grinding wheel,the pose relationship of any three adjacent abrasive particles was analyzed,and the theoretical model of abrasive clearance volume was established.The dynamic variation of abrasive clearance volume distribution domain is[70.46,78.72]mm3,and the total volume distribution domain is[140.84,155.67]mm3.The research will provide a theoretical basis for the application of cryogenic air minimum quantity lubrication technology to hard metal grinding.
基金supported by the Fundamental Research Funds for the Central Universities,China(Grant No.2024JBZX012).
文摘In confined spaces,conventional ground mobile robots may be unable to reach the target location because of limited maneuvering space or the inability to overcome obstacles.This study presents a ground mobile mechanism with a multi-loop reconfigurable trunk(GMMRT)designed to enhance mobility in constrained spaces,such as narrow gaps,ditches,and cross-shaped channels.GMMRT can effectively overcome obstacles in confined spaces through the coordinated motion of its wheels and reconfigurable trunk.Its reconfigurable trunk comprises six limbs and four vertex platforms,forming a versatile,adaptable structure.GMMRT supports two topological structures:wheeled mobility and overall rolling.It features three distinct motion modes:(i)adjusting external dimensions,(ii)performing zero-radius steering,and(iii)overall deformation rolling motion.The kinematic model of GMMRT is established,and its parameters are described using Denavit–Hartenberg parameters.The degrees of freedom under the two topological structures are analyzed on the basis of screw theory.Torque analysis of servo motors is conducted through dynamic analysis.An experimental prototype is designed to validate the three motion modes and servo motor selection,and relevant experiments are performed.Through the development and experimental validation of GMMRT,this work advances mobile robot design for confined spaces and provides a promising approach to overcome the limitations of conventional ground robots.
基金supported by the National Natural Science Foundation of China(Grant No.52375014)Guangdong Innovative and Entrepreneurial Research Team Program,China(Grant No.2019ZT08Z780)Dongguan Introduction Program of Leading Innovative and Entrepreneurial Talents,China(Grant No.20181220).
文摘Real-time slip detection and state estimation are crucial for locomotion control,facilitating posture adjustment and stability recovery of multi-legged robots moving on slippery terrain.However,existing proprioceptive methods rely on the fixed-contact assumption with fixed noise and suffer from low accuracy when multiple legs slip simultaneously.This paper proposes a novel proprioceptive approach for multi-legged robots moving in slippery scenarios to cope with slippage of multiple legs.In slip detection,the proprioceptive states of the robot are fed into a convolutional neural network to detect slip event(s)of the robot,enabling accurate identification of slipping legs even under simultaneous multi-leg slippage.For state estimation,an invariant extended Kalman filter is employed to fuse the motion information with the detected slip event(s)to obtain the robot state.By incorporating slip event(s)and foot velocity into the system motion equation of the filter,the proposed method better leverages leg odometry information and achieves more precise state estimation compared with existing methods.Simulations on a quadruped and a hexapod demonstrate the effectiveness and increased accuracy during multi-leg slippage.Experimental results for the quadruped robot show that the proposed approach achieves a 48% reduction in the root mean square error and a 47%reduction in the maximum error in velocity estimation under severe multi-leg slippage compared with the existing methods.
基金supports by the National Natural Science Foundation of China(Grant Nos.52435008,52205440,and 52205441).
文摘Micro/nano functional structures (MNFSs) have attracted substantial attention because of theiroutstanding performance in optical, tribological, thermal, electronic, and biomedical applications. Despite thedevelopment of various mechanical and non-mechanical machining methods, achieving the high-efficiency, high-precision fabrication of MNFS from difficult-to-cut materials remains a significant technical challenge. This reviewbegins with an introduction to typical artificial MNFSs and their stringent requirements and then provides acomprehensive survey of MNFSs, focusing on etching methods. In particular, plasma etching demonstrates notableadvantages in MNFS fabrication. However, two critical challenges persist: accurately controlling topographicalinformation during pattern transfer in plasma etching and achieving high-quality, uniform patterning masks overlarge areas. These issues are addressed by thoroughly analyzing and summarizing the modeling of plasma etchingand the simulation of feature profiles. Various hybrid etching machining (HEM) strategies, including laser andetching combined machining, cutting and etching combined machining, molding and etching combined machining,and self-assembly and etching combined machining, are categorized and compared in detail to facilitate themanufacturing of complex MNFSs. Finally, this review summarizes current deficiencies and future challenges ofHEM, laying the groundwork for further advancements in MNFS fabrication and intelligent HEM technologies.
基金supported by the National Science and Technology Major Project of China(Grant No.J2019-VII-0001-0141).
文摘Tool anomalies in computer numerical control(CNC)milling processes are unpredictable,hindering the promotion of fully automated machining.Traditional detection systems often struggle with stability due to the irregular and non-parametric nature of signals generated during dynamic milling.This study proposes an improved probability and statistics-based model for constructing tool anomaly thresholds in the time domain,with the decision-making strategy seamlessly integrated into CNC milling systems.A robust data acquisition and preprocessing framework was developed to improve the accuracy and reliability of real-time monitoring data.A Gaussian process model was employed to construct an anomaly detection threshold data set from irregular signals.Anomalies were identified when monitoring indicators surpassed the established threshold.The proposed method was validated through milling experiments of a turbine blisk,demonstrating an overall anomaly detection accuracy of 91.45%,which exceeds those of four other typical anomaly detection methods.These results confirm the effectiveness of the proposed method and its potential applicability in industry.
基金the financial support of the National Natural Science Foundation of China(NSFC)(Grant No.52375113)the Natural Science Foundation of Liaoning Province of China(Grant No.2022-MS-298)+1 种基金Shenyang Youth Science and Technology Innovation Talent Fund,China(Grant No.RC230309)the Scientific Research Fund of Liaoning Education Department,China(Grant No.LJKMZ20220531).
文摘In the rotor system of aero-engines,the main purpose of a bolted flange connection structure is to transfer torque and speed,and the rotor system may exhibit bolt loosening and connection structure failure under complex working conditions,high speed rotation,and external excitation unbalanced force.In addition,the bolted connection structure in the rotor system is mainly subjected to torsional vibration excitation,and using experimental methods to analyze the dynamic response law of different structural parameters of a bolted connection structure under torsional vibration excitation is complicated.Therefore,on the basis of the concentrated mass method and the elastic interaction characteristics within the bolted system,this study establishes dynamic models of one-bolted and multi-bolted connection structural systems under torsional excitation.On the basis of this dynamic model,the dynamic response characteristics of different thread parameters,external excitation,bolt stiffness,and compression stiffness of the connected parts in a one-bolted connection system and the influence laws of different elastic modulus,bolt numbers,and the thickness of the connected parts on the loosening of the multi-bolted connection system are analyzed.Results show that small thread pitch,external excitation amplitude and frequency,compressive stiffness,bolt stiffness,and elastic modulus and large tooth angle,number of bolts,and thickness of connected parts can appropriately improve the anti-loosening performance of the bolted connection system.This study also uses a comparative verification method combining finite element simulation and experiment to verify the correctness of the established dynamic model effectively.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.92160301,92060203,52175415,and 52205475)the Science Center for Gas Turbine Project,China(Grant No.P2023-B-Ⅳ-003-001)+3 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20210295)the National Key Laboratory of Science and Technology on Helicopter Transmission(Nanjing University of Aeronautics and Astronautics,NUAA,China)(Grant No.HTL-A-22G12)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX21_0189)the Funding for Outstanding Doctoral Dissertation in NUAA,China(Grant No.BCXJ22-07).
文摘Ultra-high-strength steels have been widely utilized in the aviation industry due to their superior mechanical and physical properties.However,the intense friction occurring at the tool–workpiece interface can result in significant tool wear,impacting both the machining efficiency and surface quality.Therefore,a deep understanding of the tribological behavior at the tool–workpiece interface is crucial for extending tool life.The current study proposed a novel open tribo-system to simulate the intermittent contact conditions between the tool and the workpiece during the milling process.An improved friction model was established to calculate the real friction coefficient under intermittent contact conditions.Tribological comparative experiments on ultra-highstrength steel and cemented carbide were conducted under various cooling conditions:dry,high-pressure air cooling(HPAC),air atomization of cutting fluid(AACF),and ultrasonic atomization of cutting fluid(UACF).The influences of various cooling conditions on the tribological characteristics were investigated,with a focus on the depth of the wear mark,height of the pile-up,measured force,adhesion friction coefficient,and wear morphology.The results reveal that the depth of the wear mark,height of the pile-up,and measured forces play pivotal roles in determining the adhesion friction coefficient.The synergistic action of airflow and droplets results in the formation of a liquid film,improving the friction at the interface between the ball and the workpiece.Compared with the AACF condition,the UACF condition results in a 7.7% reduction in the adhesion friction coefficient due to its excellent film-forming ability stemming from its small droplet size and uniform droplet size distribution.Abrasive wear,adhesive wear,and oxidative wear are the primary wear types for cemented carbide,regardless of the cooling conditions.The effective cooling and lubrication capability provided by the uniform liquid film in UACF contributes to improving the wear resistance of cemented carbide,offering valuable insights for mitigating tool wear.
基金supported by the National Natural Science Foundation of China(Grant No.52075076).
文摘Plunge milling,which is recognized for its efficiency,has gradually been adopted for the roughing of integral impellers in recent years.However,several challenges persist,such as redundant tool paths,difficulties in managing the Sudden Increase of Radial Depth(SIRD),and excessive residual material in the adjusted tool path by plunge milling,which collectively constrain the efficiency of the plunge milling process.To address these challenges,this study proposes a five-axis plunge milling method with double-row slotting tailored for integral impellers.This method segments the machining area based on the width of the impeller runner and utilizes various tools with different diameters to enhance machining efficiency.The plunge milling path is optimized to facilitate efficient material removal while maintaining cutting stability,which addresses issues related to cutting overload and chip accumulation.In addition,an efficient method for SIRD identification and exclusion is proposed to minimize residual material.Simulation and practical machining results confirm that the proposed plunge milling method with double-row slotting significantly improves machining efficiency,which achieves enhancements of over 1.5 times compared with traditional methods.
基金supported by the National Natural Science Foundation of China(Grant No.51875329)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2023ME112)+2 种基金the Taishan Scholar Special Foundation of Shandong Province,China(Grant Nos.tstp20240826 and tsqn201812064)the Key Research and Development Project of the Ningxia Hui Autonomous Region,China(Grant No.2024BEE02019)the Shandong Science and Technology Small and Medium-sized Enterprises Innovation Capacity Enhancement Project,China(Grant Nos.2022TSGC1261 and 2022TSGC1333).
文摘A material removal mechanism is a prerequisite to maintaining high-quality surfaces for high-shear and low-pressure grinding using body-armor-like grinding wheels(BAGWs).However,the pressure distribution and material removal efficiency for machining brittle materials using BAGWs remain unclear.This research investigated two types of elastic deformations during grinding by analyzing the contact mechanism between BAGWs and the workpiece.Additionally,the model of elastohydrodynamic pressure distribution was refined,and the material removal mechanism for machining brittle materials,incorporating the maximum undeformed chip thickness,was revealed.A material removal rate(MRR)model was established based on Hertzian contact,ductile-brittle transition,and spherical indentation theory.The theoretical model was validated through single-factor experiments utilizing a high-shear and low-pressure grinding experimental platform.At a normal grinding force of 15 N and a grinding speed of 10 m/s,the MRR could reach up to 0.276 mm3/s.The experimental results revealed that the model could accurately predict the MRR under various grinding parameters,with an average prediction error of 8.5%.
基金supported by the National Key R&D Program of China(Grant No.2022YFB3302900)the National Natural Science Foundation of China(Grant No.52475261).
文摘Multiscale structures require excellent multiphysical properties to withstand the loads in various complex engineering fields.In this study,a concurrent isogeometric topology optimization method is proposed to design multiscale structures with high thermal conductivity and low mechanical compliance.First,the mathematical description model of multi-objective topology optimization for multiscale structures is constructed,and a single-objective concurrent isogeometric topology optimization formulation for mechanical and thermal compliance is proposed.Then,by combining the isogeometric analysis method,the material interpolation model and decoupled sensitivity analysis scheme of the objective function are established on macro and micro scales.The solid isotropic material with penalization method is employed to update iteratively the macro and microstructure topologies simultaneously.Finally,the feasibility and advantages of the proposed approach are illustrated by several 2D and 3D numerical examples with different volume fractions,while the effects of volume fraction and different boundary conditions on the final configuration and multi-objective performance of the multiscale structure are explored.Results show that the isogeometric concurrent design of multiscale structures through multi-objective optimization can produce better multi-objective performance compared with a single-scale one.
