查看更多>>摘要：Atomic and close-to-atomic scale manufactur-ing(ACSM)is the core competence of Manufacturing Ⅲ.Unlike other conceptions or terminologies that only focus on the atomic level precision,ACSM defines a new realm of manufacturing where quantum mechanics plays the dominant role in the atom/molecule addition,migration and removal,considering the uncertainty principle and the discrete nature of particles.As ACSM is still in its infant stage,only little has been systematically elaborated at the core proposition of ACSM by now,hence there is a need to understand its concept and vision.This article elucidates the development of ACSM and clarifies its proposition,which aims to achieve a clearer understanding on ACSM and direct more effective efforts toward this promising area.
查看更多>>摘要：An effective and reliable prediction of the remaining useful life(RUL)of a tool is important to a metal forming process because it can significantly reduce unexpected maintenance,avoid machine shutdowns and increase system stability.This study proposes a new data-driven approach to the RUL prediction for metal forming processes under multiple contact sliding conditions.The data-driven approach took advantage of bidirectional long short-term memory(BLSTM)and convolutional neural net-works(CNN).A pre-trained lightweight CNN-based net-work,WearNet,was re-trained to classify the wear states of workpiece surfaces with a high accuracy,then the clas-sification results were passed into a BLSTM-based regres-sion model as inputs for RUL estimation.The experimental results demonstrated that this approach was able to predict the RUL values with a small error(below 5％)and a low root mean square error(RMSE)(around 1.5),which was more superior and robust than the other state-of-the-art methods.
查看更多>>摘要：In this research,a method employing micro-extrusion was designed to produce the micro-scaled barrel-shaped parts with complex geometrical features to study the feasibility of the proposed microforming method and its grain size effect on the formability of the complicated internal features in terms of deformation behavior,mate-rial evolution,accuracy of dimensions and final components quality.The results reveal that the deformation behavior is highly affected by grain size and becomes unpredictable with increased grain size.In addition,assembly parameters including feature dimension,tolerance and coaxiality also vary with grain size,and the variation of grain size needs to be accommodated by different assembly types,viz.,clear-ance fit or transition fit.From the microstructural evolution aspect,it was identified there were two dead zones and four shear bands,and the formation of these deformation zones was barely affected by the variation in grain size.Though bulges,cracks,and fracture induced voids were observed on the surface of the final components,tailoring the microstruc-ture of the working material with finer grains could signifi-cantly avoid these defects.This study advances the under-standing of forming microparts by extrusion processes and provides guidance for microforming of similar microparts.
查看更多>>摘要：The vibration disturbance from an external environment affects the machining accuracy of ultra-pre-cision machining equipment.Most active vibration-isola-tion systems(AVIS)have been developed based on static loads.When a vibration-isolation load changes dynami-cally during ultra-precision turning lathe machining,the system parameters change,and the efficiency of the active vibration-isolation system based on the traditional control strategy deteriorates.To solve this problem,this paper proposes a vibration-isolation control strategy based on a genetic algorithm-back propagation neural network-PID(GA-BP-PID)control,which can automatically adjust the control parameters according to the machining conditions.Vibration-isolation simulations and experiments based on passive vibration isolation,a PID algorithm,and the GA-BP-PID algorithm under dynamic load machining conditions were conducted.The experimental results demonstrated that the active vibration-isolation control strategy designed in this study could effectively attenuate vibration disturbances in the external environment under dynamic load conditions.This design is reasonable and feasible.
查看更多>>摘要：An online detection technology must be devel-oped for realizing the real-time control of friction stir weld-ing.In this study,the three-dimensional force exerted on a material during friction stir welding was collected synchro-nously and the relationship between the forces and weld-ing quality was investigated.The results indicated that the fluctuation period of the traverse force was equal to that of the lateral force during the stable welding stage.The phase difference between two horizontal forces was n/2.The val-ues of the horizontal forces increased with welding speed,whereas their amplitudes remained the same.The proposed force model showed that the traverse and lateral forces con-formed to an elliptical curve,and this result was consist-ent with the behavior of the measured data.The variational mode decomposition was used to process the plunge force.The intrinsic mode function that represented the real fluc-tuation in the plunge force varied at the same frequency as the spindle rotational speed.When tunnel defects occurred,the fluctuation period features were consistent with those obtained during normal welding,whereas the ratio param-eter defined in this study increased significantly.
查看更多>>摘要：Accurate intelligent reasoning systems are vital for intelligent manufacturing.In this study,a new intelli-gent reasoning system was developed for milling processes to accurately predict tool wear and dynamically optimize machining parameters.The developed system consists of a self-learning algorithm with an improved particle swarm optimization(IPSO)learning algorithm,prediction model determined by an improved case-based reasoning(ICBR)method,and optimization model containing an improved adaptive neural fuzzy inference system(IANFIS)and IPSO.Experimental results showed that the IPSO algorithm exhib-ited the best global convergence performance.The ICBR method was observed to have a better performance in pre-dicting tool wear than standard CBR methods.The IANFIS model,in combination with IPSO,enabled the optimiza-tion of multiple objectives,thus generating optimal milling parameters.This paper offers a practical approach to devel-oping accurate intelligent reasoning systems for sustainable and intelligent manufacturing.
查看更多>>摘要：The automatic cutting of intersecting pipes is a challenging task in manufacturing.For improved automa-tion and accuracy,this paper proposes a model-driven path planning approach for the robotic plasma cutting of a branch pipe with a single Y-groove.Firstly,it summarizes the inter-section forms and introduces a dual-pipe intersection model.Based on this model,the moving three-plane structure(a description unit of the geometric characteristics of the inter-secting curve)is constructed,and a geometric model of the branch pipe with a single Y-groove is defined.Secondly,a novel mathematical model for plasma radius and taper com-pensation is established.Then,the compensation model and groove model are integrated by establishing movable frames.Thirdly,to prevent collisions between the plasma torch and workpiece,the torch height is planned and a branch pipe-rotating scheme is proposed.Through the established models and moving frames,the planned path description of cutting robot is provided in this novel scheme.The accuracy of the proposed method is verified by simulations and robotic cut-ting experiments.
查看更多>>摘要：Miniature scalpels are mainly used in microsur-geries such as ophthalmic and cardiovascular surgeries.The size of a miniature scalpel is only a few millimeters,and the precision of the blade shape is high,which makes pro-duction of miniature scalpels extremely difficult.This study proposes a new sharpening process for grinding miniature scalpels on a four-axis machine tool.A post-processing algo-rithm for a four-axis grinding machine based on a kinemat-ics model is established.We then propose a corresponding parameter calibration method for the parameters used in the kinematics model.Because of possible errors in the param-eter calibration,a contour-based error compensation method is proposed for accurate adjustments to the edge shape fol-lowing grinding.This can solve the problem of large devia-tions between the actual edge shape after grinding and the ideal edge shape.The effectiveness of the proposed process planning and error compensation method is verified experi-mentally,and the grinding process parameters of the minia-ture scalpel are optimized to improve its surface processing quality.The sharpness of the optimized miniature scalpel is less than 0.75 N,and the blade shape is symmetrical,which meets the technical requirements of miniature scalpels.
查看更多>>摘要：This work aims to present and explore thermal management techniques for the wire arc additive manufac-turing(WAAM)of IN718 components.Excessive heat can be mitigated via air or water cooling.In this study,the mate-rial was deposited under four different heat-input conditions with air or water cooling.In air cooling,the layer is depos-ited in a normal atmospheric air environment,whereas with water cooling,the material is deposited inside a water tank by varying the water level.To validate the air and water cooling thermal management techniques,IN718 single-pass and multilayer linear walls were deposited using the bidi-rectional gas metal arc welding based WAAM setup under four different heat input conditions.During the deposition of single layers,the temperature profiles were recorded,and the geometric and microstructural features were explored.For multilayer wall structures,the mechanical properties(hard-ness,tensile strength,and elongation)were determined and assessed using the corresponding microstructural features explored through scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and electron back-scatter diffraction(EBSD)analyses.The microstructure observed through SEM analysis in the building direction was found to be nonhomogenous compared with that in the deposition direction.Moreover,water cooling was found to govern bead characteristics,such as wall width and height.The grain size and anisotropy of the mechanical proper-ties also decreased in the water-cooled case.Hence,water cooling is an economical and efficient method to mitigate excessive heat accumulation in WAAM-deposited IN718.
查看更多>>摘要：The mixing of powders is a highly relevant field under additive manufacturing,however,it has attracted limited interest to date.The in-situ mixing of various pow-ders remains a significant challenge.This paper proposes a new method utilizing a static mixer for the in-situ mixing of multiple powders through the laser-based directed energy deposition(DED)of functionally graded materials.Firstly,a powder-mixing experimental platform was established;WC and 316L powders were selected for the mixing experiments.Secondly,scanning electron microscopy,energy dispersive spectroscopy,and image processing were used to visually evaluate the homogeneity and proportion of the in-situ mixed powder.Furthermore,powder-mixing simulations were conducted to determine the powder-mixing mecha-nism.In the simulations,a powder carrier gas flow field and particle mixing were employed.Finally,a WC/316L metal matrix composite sample was produced using laser-based DED to verify the application potential of the static mixer.It was found that the static mixer could adjust the powder ratio online,and a response time of 1-2 s should be con-sidered when adjusting the ratio of the mixed powder.A feasible approach for in-situ powder mixing for laser-based DED was demonstrated and investigated,creating the basis for functionally graded materials.
NETL
NSTL
万方数据