Measurement Uncertainty Analysis of the Rotary-scan Method for the Measurable Dimension of Cylindrical Workpieces

The measurement uncertainty analysis is carried out to investigate the measurable dimensions of cylindrical workpieces by the rotary-scan method in this paper.Due to the difficult alignment of the workpiece with a diameter of less than 3 mm by the rotary scan method,the measurement uncertainty of the cylindrical workpiece with a diameter of 3 mm and length of 50 mm which is measured by a roundness measuring machine,is evaluated according to GUM(Guide to the Expression of Uncertainty in Measurement)as an example.Since the uncertainty caused by the eccentricity of the measured workpiece is different with the dimension changing,the measurement uncertainty of cylindrical workpieces with other dimensions can be evaluated the same as the diameter of 3 mm but with different eccentricity.Measurement uncertainty caused by different eccentricities concerning the dimension of the measured cylindrical workpiece is set to simulate the evaluations.Compared to the target value of the measurement uncertainty of 0.1μm,the measurable dimensions of the cylindrical workpiece can be obtained.Experiments and analysis are presented to quantitatively evaluate the reliability of the rotary-scan method for the roundness measurement of cylindrical workpieces.

An electromagnetic semi-active dynamic vibration absorber for thin-walled workpiece vibration suppression in mirror milling

As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness.To address these challenges,we propose a novel tunable electromagnetic semi-active dynamic vibration absorber(ESADVA),which integrates with a magnetic suction follower to form a followed ESADVA(follow-ESADVA)for mirror milling.This system combines a tunable magnet oscillator with a follower,enabling real-time vibration absorption and condition feedback throughout the milling process.Additionally,the device supports self-sensing and frequency adjustment by providing feedback to a linear actuator,which alters the distance between magnets.This resolves the traditional issue of being unable to directly monitor vibration at the machining point due to space constraints and tool interference.The frequency shift characteristics and vibration absorption performance are comprehensively investigated.Theoretical and experimental results demonstrate that the prototyped follow-ESADVA achieves frequency synchronization with the milling tool,resulting in a vibration suppression rate of approximately 47.57%.Moreover,the roughness of the machined surface decreases by18.95%,significantly enhancing the surface quality.The results of this work pave the way for higher-quality machined surfaces and a more stable mirror milling process.

Hot spinning of cylindrical workpieces of TA15 titanium alloy

In order to form large-diameter thin-wall cylindrical workpieces of TA15 titanium alloy,tube hot spinning experiments of the alloy were conducted on a CNC hot spinning machine.The causes of some forming defects occuring in hot spinning,such as crack,pileup,bulge and corrugation,were analyzed and the corresponding measures were put forward to avoid spinning defects,based on which a proper process scheme of hot spinning of TA15 alloy was obtained and the large-diameter and thin-walled cylindrical workpieces were formed with good quality.The results show that spinning temperature has distinct influence on forming quality of spun workpieces.The range of spinning temperature determines the spinnability of titanium alloy and the ununiformity of temperature distribution near the deformation zone leads to the formation of bulge.The reasonable heating method is that the deforming region is heated to the optimum temperature range of 600-700 ℃,the deformed region is heated continuously and a certain length of undeformed region is preheated.With the thickness-to-diameter ratio(t/D) of spun workpiece reducing to certain value(t/D<1%),surface bulge and corrugation is rather easier to come into being,which could be controlled through restraining diameter growth and employing smaller reduction rate and lower temperature in the optimum spinning temperature range.

Modifying the Traditional Analyzing Method of Cylindrical Workpieces’ Deep Drawing Process by Using a Novel Loop Material Theory Method

In this paper, the traditional empirical coefficient method and a novel loop material analytical method presented by the authors have been compared and discussed by analyzing several practical cylindrical workpieces’ deep drawing projects. Also, some conclusions about how to modify the traditional analyzing method of cylindrical workpieces’ deep drawing process could be concluded and the necessity of this modification could be proved.

A Predictive Modeling Based on Regression and Artificial Neural Network Analysis of Laser Transformation Hardening for Cylindrical Steel Workpieces

Laser surface hardening is a very promising hardening process for ferrous alloys where transformations occur during cooling after laser heating in the solid state. The characteristics of the hardened surface depend on the physicochemical properties of the material as well as the heating system parameters. To exploit the benefits presented by the laser hardening process, it is necessary to develop an integrated strategy to control the process parameters in order to produce desired hardened surface attributes without being forced to use the traditional and fastidious trial and error procedures. This study presents a comprehensive modelling approach for predicting the hardened surface physical and geometrical attributes. The laser surface transformation hardening of cylindrical AISI 4340 steel workpieces is modeled using the conventional regression equation method as well as artificial neural network method. The process parameters included in the study are laser power, beam scanning speed, and the workpiece rotational speed. The upper and the lower limits for each parameter are chosen considering the start of the transformation hardening and the maximum hardened zone without surface melting. The resulting models are able to predict the depths representing the maximum hardness zone, the hardness drop zone, and the overheated zone without martensite transformation. Because of its ability to model highly nonlinear problems, the ANN based model presents the best modelling results and can predict the hardness profile with good accuracy.

Milling Parameters Optimization of Al-Li Alloy Thin-Wall Workpieces Using Response Surface Methodology and Particle Swarm Optimization

To improve the milling surface quality of the Al-Li alloy thin-wall workpieces and reduce the cutting energy consumption.Experimental research on the milling processing of AA2195 Al-Li alloy thin-wall workpieces based on Response Surface Methodology was carried out.The single factor and interaction of milling parameters on surface roughness and specific cutting energy were analyzed,and the multi-objective optimization model was constructed.The Multiobjective Particle Swarm Optimization algorithm introducing the Chaos Local Search algorithm and the adaptive inertial weight was applied to determine the optimal combination of milling parameters.It was observed that surface roughness was mainly influenced by feed per tooth,and specific cutting energy was negatively correlated with feed per tooth,radial cutting depth and axial cutting depth,while cutting speed has a non-significant influence on specific cutting energy.The optimal combination of milling parameters with different priorities was obtained.The experimental results showed that the maximum relative error of measured and predicted values was 8.05%,and the model had high reliability,which ensured the low surface roughness and cutting energy consumption.It was of great guiding significance for the success of Al-Li alloy thin-wall milling with a high precision and energy efficiency.

Research on embedded locally resonant metamaterials used for vibration attenuation of thin-walled workpieces in mirror milling

The shell composed of large-scale parts is the essential component of mechanical structures in the aerospace,shipping,and railway industries.These workpieces are characterized by thin walls and weak rigidity,thus requiring an effective technology for high-performance machining.Accordingly,an embedded locally resonant metamaterial with double resonators is proposed and combined with the magnetic follow-up support technology to attenuate the vibration of thin-walled parts for the first time.The band structures and parametric adjustment laws are systematically investigated and validated by analytical calculation and finite element method,which proves the proposed model is broadband,lightweight,and flexible in low frequencies.Its characteristics,as well as the relatively simple structure,are unique advantages for thin-walled structure milling.Finally,mirror milling experiments have been performed to assess the slave module with the proposed substructure.From the results,the root mean square amplitude of the thin-walled workpiece with the combined device decreases by nearly 9%,which means that the performance has been improved by the combined device.Furthermore,this work provides an integrated and efficient solution for vibration suppression in thin-walled parts milling,which extends locally resonant metamaterials to practical engineering fields and helps to improve the status quo of mirror milling from the perspective of metamaterials.

Arc Extraction Analysis for Circularity Measurement of Small Cylindrical Parts by the Segmenting-stitching Method

To reduce the stitching error of circularity measurement of small cylindrical workpieces(Diameter less than 3 mm)by the segmenting-stitching method,arc contour extraction is analyzed in this paper.The coordinates of cross-sectional circle of a small cylindrical part are segmented into several equal arcs to be obtained by a two-dimensional coordinate measuring machine.The circularity contour of the small cylindrical part can be formed by stitching a series of arc contours which are calculated by the obtained arc coordinate data.Due to the different measuring pressure angles of different measuring positions,the accuracy of obtained arc coordinate points is different.The bigger the pressure angle is,the accurate the obtained arc coordinate data are.The experiments show that the accuracy of two ends of the arc data is not as good as the central part.Therefore,the two ends of the obtained arc data are appropriately to be cut off,namely,only the central part of the arc data are extracted to be used for the stitching.As a result,the mean value of the matching coefficient is enhanced by 12%,the deviation between the overlap part of the neighbouring arc contour is reduced by 26%,and the average curvature of the arc contours is improved with the extraction method.Thus,the accuracy of the stitched circularity contour can be improved by this extraction procedure in the segmenting-stitching method for the circularity measurement of the small cylindrical parts.

3D RIGID－PLASTIC FINTEELEMENT ANALYSIS OF BACKWARD SPINNING OF CYLINDRICAL WORKPIECE

Backward spinning is analyzed by 3D rigid-plastic FEM.A 3D mechanical model for backward spinning is presented. The distributions are obtained of strain一rate and stress in the con- tact area of the roller and its adjacent area.The results can well intemret the principle of defonnation of backward spinning. The relationship between the roller angle and three components ofspinning force is found out, and the optimum roller angle, when the general spinning foree gets to the minimum value, is calculated. The distributions of defonnation area obtained by FEM agree with the experimental result well.

Elastic Buckling of Bionic Cylindrical Shells Based on Bamboo

High load-bearing efficiency is one of the advantages of biological structures after the evolution of billions of years. Biomimicking from nature may offer the potential for lightweight design. In the viewpoint ofrnechanics properties, the culm of bamboo comprises of two types of cells and the number of the vascular bundles takes a gradient of distribution. A three-point bending test was carried out to measure the elastic modulus. Results show that the elastic modulus of bamboo decreases gradually from the periphery towards the centre. Based on the structural characteristics of bamboo, a bionic cylindrical structure was designed to mimic the gradient distribution of vascular bundles and parenchyma cells. The buckling resistance of the bionic structure was compared with that of a traditional shell of equal mass under axial pressure by finite element simulations. Results show that the load-bearing capacity of bionic shell is increased by 124.8%. The buckling mode of bionic structure is global buckling while that of the conventional shell is local buckling.

Modeling and analysis for time-varying dynamics of thin-walled workpieces in mirror milling considering material removal

To reduce the vibration and deformation of large thin-walled workpieces during the milling process,mirror milling is widely used due to its point-to-point support and strong applicability.The influence of the support head on the workpiece’s dynamic characteristics is crucial in determining whether the mirror milling process is reliable and effective.Therefore,this study establishes a time-varying dynamic model for mirror milling of thin-walled workpieces with various boundary conditions to accurately analyze and predict the dynamic characteristics and response of the workpiece.First,a new analytical method for material removal with extensive applicability and high precision is proposed.In this method,the Ritz mode shape is used to approximate the workpiece’s mode shape as it changes during material removal.Next,the Hertz contact theory is adopted to establish a tool-workpiece-support head coupling model,which considers the jump-off phenomenon between them.Subsequently,the dynamic model is solved using the Newmark-β numerical integration method to obtain the workpiece’s time-domain acceleration and displacement responses under the forced vibration.Finally,the measured frequency response function(FRF)and vibration signals of workpieces verify the correctness of the proposed mirror milling model for thin-walled workpieces considering material removal.In addition,this paper analyzes the dynamic characteristics and forced vibration law of workpieces in mirror milling,which lays the foundation for high precision mirror milling.

Deformation Analysis and Fixture Design of Thin-walled Cylinder in Drilling Process Based on TRIZ Theory

Thin-walled cylindrical workpiece is easy to deform during machining and clamping processes due to the insufficient rigidi.Moreover,it’s also difficult to ensure the perpendicularity of flange holes during drilling process.In this paper,the element birth and death technique is used to obtain the axial deformation of the hole through finite element simulation.The measured value of the perpendicularity of the hole was compared with the simulated value to verify then the rationality of the simulation model.To reduce the perpendicularity error of the hole in the drilling process,the theory of inventive principle solution(TRIZ)was used to analyze the drilling process of thin-walled cylinder,and the corresponding fixture was developed to adjust the supporting surface height adaptively.Three different fixture supporting layout schemes were used for numerical simulation of drilling process,and the maximum,average and standard deviation of the axial deformation of the flange holes and their maximum hole perpendicularity errors were comparatively analyzed,and the optimal arrangement was optimized.The results show that the proposed deformation control strategy can effectively improve the drilling deformation of thin-walled cylindrical workpiece,thereby significantly improving the machining quality of the parts.

封头接管移栽夹持机构设计与实验

在工业机器人自动焊接领域中,实现对焊接工件夹持与焊枪协同焊接的移栽夹持机构在焊接过程中发挥着重要的作用。通常在工业领域中,焊接工件的形状与焊接情况不同,因此需要设计专用夹具。针对一种圆柱形工件夹持问题,设计一个内壁柔性夹持移栽机构,应用于视觉辅助多机械臂焊接工况中,将焊接零件准确移栽到指定焊接位置上,与焊接机器人协同实现自动焊接。设计移栽夹持机构,展开静力学仿真验证模型正确性,最后搭建实物验证环境进行夹持实验。结果表明:第一阶段实验放置成功率达到100%,第二阶段实验移栽机构满足焊接距离2 mm精度要求,为封头接管的移栽提供良好的条件,有利于封头接管自动焊接。

Axisymmetric 3:1 internal resonance of thin-walled hyperelastic cylindrical shells under both axial and radial excitations

Nonlinear vibration with axisymmetric 3:1 internal resonance is investigated for an incompressible neo-Hookean hyperelastic cylindrical shell under both axial and radial harmonic excitations.A full nonlinear strain-displacement relation is derived from the large deflection theory of thin-walled shells.A set of nonlinear differential equations describing the large deflection vibration are formulated by the Lagrange equation and the assumption of small strains.Steady-state responses of the system are predicted via the harmonic balance method with the arc length continuation,and their stabilities are determined via the modified sorting method.The effects of excitations on the steady-state responses are analyzed.The results reveal a crucial role played by the phase difference in the structural response,and the phase difference can effectively control the amplitude of vibration.

大工件高精度内孔圆柱度的自动测量方法研究

针对非回转体类大尺寸工件的高精度内孔圆柱度测量难题,提出一种新的测量方法。通过对圆柱度误差的评定方法和采点方式的分析对比,确定比对式接触测量方式。以卫星观测跟踪支架为例,确定测量点提取方案采用鸟笼法,评价方法采用最大内接圆柱法,圆柱度测头采用高精度传感器3个截面布置,每个截面圆周均布8个传感器方式,高精度驱动机构带动测头进入内孔自动完成测量,通过圆柱度的软件算法自动计算出圆柱度,并分析测量结果,其测量误差符合测量仪器的最大允许误差为工件公差的1/10原则,测量结果完全符合工件的精度要求。整体测量方案集成三坐标测量机和圆柱度测量专机,实现整个工件的自动化智能检测。

一种基于激光测量的自动钻孔系统研究

针对弹药壳体等圆柱体工件表面的自动钻孔需求,基于激光测量技术提出一种龙门式机器人自动钻孔系统设计方法。采用激光位移测量技术实现了工件轴向基准接合面、预制孔中心轴向位置、预制孔中心圆周位置等参数的在线监测和计算,自动识别钻孔目标位置。通过伺服电机驱动三坐标桁架机械手实现钻孔机构在工件长度方向和圆周方向钻孔位置全覆盖,并利用PID控制算法实现钻孔深度的精确控制。经过试验证明:该钻孔系统运行稳定,预制孔中心位置测量标准差为0.02 mm,钻孔深度精度达到0.15 mm,提高了钻孔质量,实现了弹药壳体钻孔工序的人机隔离,能够满足实际生产需求。

基于激光投影法的圆柱工件直径测量误差分析

针对激光光束投影法直径测量精度受多种因素影响而下降的问题,提出了一种计算圆柱体直径的解析几何方法。分别用解析几何方法和近似等腰三角形方法推导出圆柱工件直径计算公式,并进行了圆柱工件直径测量仿真,分析了激光源位置、被测工件位置、线阵CCD分辨率和被测工件直径等参数对直径测量结果的影响。结果表明,在激光源位置、工件位置和工件直径变化时,提出的解析几何方法仍能够保证直径测量的准确性,其测量误差只与线阵CCD传感器的分辨率有关;提高CCD传感器的分辨率,可以提升圆柱工件直径的测量精度。采用解析几何方法和高分辨率的线阵CCD可满足激光直径测量系统高精度的应用要求。

Vibration suppression of thin-walled workpiece machining considering external damping properties based on magnetorheological fluids flexible fixture

Milling of the thin-walled workpiece in the aerospace industry is a critical process due to the high flexibility of the workpiece. In this paper, a flexible fixture based on the magnetorheological (MR) fluids is designed to investigate the regenerative chatter suppression during the machining. Based on the analysis of typical structural components in the aerospace industry, a general complex thin-walled workpiece with fixture and damping constraint can be equivalent as a rectangular cantilever beam. On the basis of the equivalent models, natural frequency and mode shape function of the thin-walled workpiece is obtained according to the Euler-Bernoulli beam assumptions. Then, the displacement response function of the bending vibration of the beam is represented by the product of all the mode shape function and the generalized coordinate. Furthermore, a dynamic equation of the workpiece-fixture system considering the external damping factor is proposed using the Lagrangian method in terms of all the mode shape function and the generalized coordinate, and the response of system under the dynamic cutting force is calculated to evaluate the stability of the milling process under damping control. Finally, the feasibility and effectiveness of the proposed approach are validated by the impact hammer experiments and several machining tests. (C) 2016 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.

Position-varying surface roughness prediction method considering compensated acceleration in milling of thin-walled workpiece

Machined surface roughness will affect parts?service performance.Thus,predicting it in the machining is important to avoid rejects.Surface roughness will be affected by system position dependent vibration even under constant parameter with certain toolpath processing in the finishing.Aiming at surface roughness prediction in the machining process,this paper proposes a position-varying surface roughness prediction method based on compensated acceleration by using regression analysis.To reduce the stochastic error of measuring the machined surface profile height,the surface area is repeatedly measured three times,and Pauta criterion is adopted to eliminate abnormal points.The actual vibration state at any processing position is obtained through the single-point monitoring acceleration compensation model.Seven acceleration features are extracted,and valley,which has the highest/^-square proving the effectiveness of the filtering features,is selected as the input of the prediction model by mutual information coefficients.Finally,by comparing the measured and predicted surface roughness curves,they have the same trends,with the average error of 16.28%and the minimum error of 0.16%.Moreover,the prediction curve matches and agrees well with the actual surface state,which verifies the accuracy and reliability of the model.

Variation characteristic of drilling force and influence of cutting parameter of SiCp/Al composite thin-walled workpiece

In this paper,the variation characteristic of the drilling force,and the influences of cutting speed,feed rate,and workpiece thickness on the drilling force,were eval・uated when drilling a silicon carbide particle reinforced aluminum matrix(SiCp/Al)composite thin-walled workpiece with a high volume fraction.Under the condition that the workpiece thickness was less than the drill tip height,three characteristic stages of drilling force variation were proposed.The results indicate that there is a sign币cant difference between the variations in the drilling force when drilling a thin-walled workpiece compared to thick-walled workpiece.When the chisel edge drills out the lower surface of the workpiece,there is an abrupt decrease in the thrust forces of the thin-walled and thick-walled workpieces.In addition,there is an abrupt decrease in the torque of the thick-walled workpiece,whereas that of the thinwalled workpiece increases.According to the thickness of the thin-walled workpiece,the instant of the abrupt decrease in the thrust force may lead or lag behind the theoretical instant at which the chisel edge reaches the lower surface of the workpiece without deformation.When drilling a thin-walled hole,the cutting speed has a slight influence on the thrust force,and there is a slight increase in the torque in accordance with an increase in the cutting speed.The thrust force and torque increase in accordance with an increase in the feed rate.When drilling a thinwalled workpiece with a thickness of 1 mm,the critical thickness of workpiece cracking decreases in accordance with an increase in the cutting speed,and increases in accordance with an increase in the feed rate.When drilling a thin-walled workpiece with a thickness of 0.5 mm,the concave deformation of the workpiece and the critical thickness of the workpiece cracking increase in accordance with an increase in the feed rate.However,the increment in the critical thickness of the workpiece cracking is less than that in the concave deformation of the workpiece.