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This paper explores a new structural design of armature splicing to reduce the machining requirements of maglev guideways. The paper presents the magnetically supported structure and working principle of magnetic levitation worktable machine tools. Rectangular tooth splicing structures for extended long-stroke maglev guideways are designed, and corresponding finite element analysis models are established. After calculating the static three-dimensional magnetic field with the help of ANSYS software, the electromagnetic force produced by the magnetic levitation electromagnet group decreases linearly with increasing splice clearance of the armature and increases linearly with the increasing number of splice teeth. The smaller the number of teeth is or the larger the clearance value is, the more pronounced the change is. When the number of teeth, the width of the teeth and the clearance of the splice are kept constant, the electromagnetic force increases with increasing tooth depth, and a change in the tooth width has little effect on the electromagnetic force. [ABSTRACT FROM AUTHOR]

Cutting toolholders, with designed in-built compliant mechanisms, are frequently used for machining microfeatures. In this paper, compliant structures are designed using trusses as they exhibit a superior strength-to-weight ratio. Systematically stacked two-stage truss structures along with flexure hinges are designed to yield the desired precise cutting motion. The materially reduced efficient design amplifies the output force and greatly assists in overcoming cutting resistance during machining. The characteristics of the designed compliant tool holder are analysed by considering the output force and displacement for a given input. Both mathematical modelling to determine the force and finite element analysis to identify the critical stress regions when subjected to a prescribed input displacement are presented. As part of dynamic analysis, modal analysis and harmonic response studies were performed to determine how the trussed compliant structure deforms when subjected to dynamic loadings. The designed tool holder was additively manufactured using functionally rigid polyamide-12-glass-bead (PA12-GB) material. The performance of the developed cutting tool holder is then verified by machining radially graded surfaces following which, the machining results are presented in this paper. [ABSTRACT FROM AUTHOR]

In order to reduce the machining deformation of thin-walled parts during milling, a non-uniform allowance planning method for thin-walled parts based on the workpiece deformation constraint with the idea of adding materials in reverse material removal sequence is proposed in this paper. This method does not require accurate deformation prediction and extensive experiments compared to traditional error compensation methods. It strives to maximize the allowance to enhance the stiffness of the in-process workpiece. First, a cutting force threshold calculation method is proposed according to the finite element method. The cutting force threshold at different positions is calculated by obtaining the local stiffness characteristics at the cutter-contact point under the constraint of allowable deformation. And then, the maximum machining allowance at the cutter-contact point is calculated depending on the cutting force model. Considering that the stiffness of the workpiece is position-dependent and affected by material removal, the stiffness of the workpiece is updated by adding elements in the reverse cutting direction, and the finishing stock is obtained by surface fitting. Experimental results show that compared with the traditional uniform allowance method, the error of the proposed method is reduced by about 83%, which can effectively reduce the deformation and improve the machining accuracy. [ABSTRACT FROM AUTHOR]

Large thin-walled structural parts have been widely used in aircrafts for the purpose of weight reduction. These parts usually contain various thin-walled complex structures with weak local stiffness, which are easy to deform during machining if improper machining parameters are selected. Thus, local stiffness has to be seriously considered during machining parameter planning. Existing stiffness calculation methods including mechanical methods, empirical formula methods, finite element methods, and surrogate-based methods are either inaccurate or time consuming for complex structures. To address this issue, this paper proposes a data-driven method for predicting local stiffness of aircraft structural parts. First, machining regions of aircraft structural part finishing are classified into bottom, sidewall, rib, and corner to further define the minimum stiffness of machining regions. By representing the part geometry with attribute graph as the input feature, while computing the minimum stiffness using FEM as the output label, stiffness prediction is turned to a graph learning task. Then, graph neural network (GNN) is designed and trained to map the attribute graph of a machining region to its minimum stiffness. In the case study, a dataset of aircraft structural parts is used to train four GNN models to predict the minimum stiffness of the defined four types of machining regions. Compared with FEM results, the average errors on the test set are 6.717%, 7.367%, 7.432%, and 5.962% respectively. In addition, the data driven model once trained, can greatly reduce the time in predicting the stiffness of a new part compared with FEM, which indicates that the proposed method can meet the engineering requirements in both accuracy and computational efficiency. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) is an increasingly concerned trend in Ti-6Al-4V blade manufacturing, while the SLMed Ti-6Al-4V blade cannot be used directly because of poor surface integrity and high residual stresses. Precise machining after SLM is a feasible solution but also a challenge. The low rigidity of the blade will lead to deformation when machining. The deformation can lead to surface error and may make defect parts. Two-step machining processes to address the problems were proposed in this paper. First, a non-uniform allowances distribution was allocated and optimized in semi-finishing based on Ritz solution to elastic deformation. The blade was simplified as a cantilever thin plate with various thicknesses, and the thicknesses of finishing allowances were designed and optimized on the premise of ensuring the thin-wall stiffness of the blade, so as to realize the design of Ritz non-uniform allowances. Then, finishing machining was conducted to achieve precise parts. A blade deformation model was established to evaluate part distortions with cutting force moving and changing. Finite element analysis (FEA) and experimental validation in ball-end milling of a blade were conducted. FEA results and experimental results showed dimensional errors have been reduced up to 50%. Further surface tests demonstrated that the mean surface roughness reduced from 7.88 to 0.815 μm. And the residual surface stresses of the SLM samples changed after semi-finishing machining due to the residual stresses relaxation and redistribution. The results demonstrated that the proposed method enhanced the surface quality of the blade fabricated by SLM. [ABSTRACT FROM AUTHOR]

This paper presents a physics-based model able to simulate the flow stress behavior of the Ti6Al4V alloy during subsequent severe plastic deformation processes, namely turning and burnishing. All the physical and metallurgical mechanisms that accommodate the deformation were considered to describe the material strengthening and they were implemented via user subroutine in a commercial finite element software. Then, the proposed numerical model was used to investigate the effect of combined turning/burnishing processes on the surface integrity of manufactured Ti6Al4V components. Turning and roller burnishing experiments were conducted to validate the proposed finite element model and to analyze the microstructural phenomena and the output variables. The implemented model well fits experimental results, precisely predicting the evolution of grain size, dislocations, hardness, and residual stresses. Different process combinations can lead to similar microstructures and information on different contributions can be highlighted through physics-based modelling and simulated process combinations. [ABSTRACT FROM AUTHOR]

It is very prone to cause large-amplitude cutting vibrations, or even regenerative chatter, when milling thin-walled workpiece due to its low dynamic stiffness. The utilization of fixture support is one of the most effective measures to mitigate vibrations and improve stability limits, which has gained more and more attention. However, the dynamics model of the tool-workpiece-fixture system and the influence of fixture support force have not been fully developed. In this paper, a pneumatic fixture is designed and used to exert controllable support force on the thin-walled workpiece by precisely tunning the air pressure. The position-dependent modal parameters of the thin-walled workpiece under different fixture support forces are identified by combining experimental modal test and finite element analysis. The milling dynamics is then modeled into a delay differential equation with position-dependent coefficients. On this basis, the three-dimensional stability lobe diagrams (SLDs) are obtained in the parameter space of tool path, spindle speed, and axial depth of cut. Both stable and chatter cutting tests are performed to verify the predicted SLDs, and the cutting signals under different fixture support forces are compared in detail. Experimental results reveal that the proposed model can accurately predict the chatter stability of thin-walled workpiece with fixture support, and the stability limit can be successfully improved by tunning the support force. Some important conclusions on the influence of fixture support forces are also drawn based on detailed simulation and experimental analyses. [ABSTRACT FROM AUTHOR]

Fiber-reinforced composites/fiber-reinforced polymer is excellent material owning the performance of high strength, high toughness, light weight, good fatigue resistance and shock absorption, and strong designability. It has a wide range of application prospects. The reinforcing fiber makes the cutting of the composites far from easy. When machining of FRP, the high tool wear, defects on machined surface, and poor processing efficiency severely restrict its wide application. Exploring the cutting mechanism of FRP has very important practical significance. In recent years, simulation technology based on discrete element and finite element methods has gradually been applied to the research field of material cutting. This paper summarizes the methods, theories, and conclusions in cutting simulation of fiber-reinforced composites in recent years, and finally puts forward the future focus and development direction of fiber reinforced composite cutting simulation research. [ABSTRACT FROM AUTHOR]

Aluminum alloys are widely used in aerospace products because of their high specific stiffness and high specific strength. In the machining process of thin-walled aluminum ring workpieces, with the removal of materials, the stiffness of the parts decreases and the residual stress (RS) is released, resulting in obvious machining deformation (MD) of workpieces. Taking the typical 2219 aluminum alloy rolled ring as the research object, a new theoretical analysis model and a finite element model coupled with multi-physics and multi-processing are established to analyze the initial residual stress (IRS) distribution and the MD law. The accuracy of simulation prediction results regarding IRS and MD is verified by experiments, while the equivalent theoretical analytical model qualitatively explains the MD of the ring due to IRS. The IRS of the rolled ring is about 40 ~ 80 MPa, which induces a maximum MD of 0.4016 mm (from 89.9985 to 90.4001 mm) and an elliptical cross-section. The relative error of the MD result is 23.92%, while the ellipticity is only 11.30%. [ABSTRACT FROM AUTHOR]

The dynamic reliability of the heavy-duty CNC machine tool beam is directly related to the machining accuracy which is challenging to maintain because of the gantry machine structure. It is important to evaluate the reliability and accuracy of gantry machine components, especially the tool beam. This research investigated the dynamic accuracy of a segmented beam of gantry heavy machine tool by studying the surface morphology of the joint surface. The mechanical model of a single asperity is established based on the finite element method. The elastic and the plastic stage deformation boundary values are obtained, and the contact model of the full joint surface is established by using the Gaussian distribution characteristics. The finite element model of the sectional beam is developed by transforming the contact parameters of the joint surface. The accuracy of the model is verified by the field modal experiment. Additionally, the proposed model is used to analyze the impact of vibration on machining accuracy. The results revealed that the proposed model is highly reliable. [ABSTRACT FROM AUTHOR]

Laser-assisted machining (LAM) is a new manufacturing technology to improve the productivity of metal matrix composites (MMCs). However, there are many arguments about whether LAM is good for improving chip deformation, and there is also a lot of debate about surface integrity. The quality of surface integrity is closely correlated with the chip formation in LAM of MMCs depending on the processing conditions and constituents in composites. In this study, interaction process between 1064-nm diode laser and 45%SiCp/Al composites is theoretically described. The chip formation mechanism in LAM of 45%SiC/Al composites at different temperatures is revealed by analyzing the chip root morphology and chip chip-breaking process with an assistance of finite element model. The thermal mismatch stress of particles and matrix in the shear deformation zone are derived applying the Eshelby equivalent strain equations and thermal expansion coefficient and elastic modulus. Based on these, mechanisms of chip deformation and fracture in LAM are elucidated further. The various surface morphology (plastic side stream, surface scratches, particle pull-out, particles broken) dependent on the coupling of the force loads, thermal loads, and removal model of reinforcement particles are deeply investigated through LAM experiments. The surface morphology experiment results show that particle aggregation occurs between two or more adjacent SiC particles because the multiple SiC particles appear simultaneously at cutting path of tools. An analysis model was established to evaluate particle agglomeration in LAM according to the influence rules of tool geometry and particle size. Moreover, technological experiments focus on the effect of LAM variables, like laser power and scanning velocity on the microhardness and surface roughness of cross-section layer, mechanisms of which are analyzed from multiple perspectives. [ABSTRACT FROM AUTHOR]

Brazed superabrasive tool has been widely used in machining of difficult-to-cut materials to improve the machining efficiency and quality. However, the severe wear and associated short service life have to be faced for conventional induction brazed (CIB) abrasive tools during machining processes, owing to its weak bonding strength between abrasive grains and metal-bonded phases. In this case, the method of ultrasonic vibration–assisted induction brazing (UVAIB) was proposed to fabricate tools, through introducing ultrasonic vibration into brazing process to improve the abrasive bonding strength. Here, a novel UVAIB device was developed, and the geometric designation parameters were optimized using a finite element simulating method. In addition, the performance of UVAIB device was tested in terms of the impedance and amplitude. Subsequently, the comparative experiment trials were performed with the brazed abrasive tools under the CIB and UVAIB method. Results show that the ultrasonic energy loss of UVAIB device can be reduced, and then, the amplification value and vibration uniformity reach 8 and 92%, respectively. In addition, a large number of pores and macro-cracks inside tool's metallic matrix for CIB can be observed, whereas the number of pores is reduced by 75%, and only fewer and smaller micro-cracks are found for UVAIB. Furthermore, compared with the grains' intergranular fracture for CIB, UVAIB exhibits the transgranular fracture mode due to its higher bonding strength after adopting the ultrasonic vibrating method. [ABSTRACT FROM AUTHOR]

Thin-walled structural parts, such as aeroengine casings, impellers, blades, and disks, are widely used in the aerospace industry due to their outstanding performance. A more efficient and accurate prediction approach for machining distortion has also been widely considered. The traditional finite element analysis approach, which is commonly used in the industry, has some limitations in both efficiency and accuracy. To resolve the above problems, a hybrid surrogate model considering uncertainties is proposed to estimate the machining distortion of thin-walled parts. In terms of efficiency improvement, a hybrid three-layer gradient surrogate model to integrate the response surface regression model and the Gaussian process regression model is introduced to replace the multi-physical finite element analysis model. In terms of accuracy improvement, the calibration and quantification of uncertainties within the model are carried out. The uncertainties are divided into four parts, including cutting contact area uncertainty, tool wear uncertainty, mechanism modelling uncertainty, and unquantified uncertainty, which are determined through an iterative solving algorithm, an experimental calibration approach, and Bayesian inference simultaneously. An aeroengine combustor casing is selected as a case study to validate the effectiveness of the proposed estimation model. The predicted results indicate that the estimation time is less than 24 ms , and the average estimation deviation is 3.1400 μ m . Compared with the traditional finite element analysis model, the proposed methodology can significantly reduce the estimation time with higher accuracy. [ABSTRACT FROM AUTHOR]