Optimization of Fixture Number in Large Thin-Walled Parts Assembly Based on IPSO

There are lots of researches on fixture layout optimization for large thin-walled parts.Current researches focus on the positioning problem,i.e.,optimizing the positions of a constant number of fixtures.However,how to determine the number of fixtures is ignored.In most cases,the number of fixtures located on large thin-walled parts is determined based on engineering experience,which leads to huge fixture number and extra waste.Therefore,this paper constructs an optimization model to minimize the number of fixtures.The constraints are set in the optimization model to ensure that the part deformation is within the surface profile tolerance.In addition,the assembly gap between two parts is also controlled.To conduct the optimization,this paper develops an improved particle swarm optimization(IPSO)algorithm by integrating the shrinkage factor and adaptive inertia weight.In the algorithm,particles are encoded according to the fixture position.Each dimension of the particle is assigned to a sub-region by constraining the optional position range of each fixture to improve the optimization efficiency.Finally,a case study on ship curved panel assembly is provided to prove that our method can optimize the number of fixtures while meeting the assembly quality requirements.This research proposes a method to optimize the number of fixtures,which can reduce the number of fixtures and achieve deformation control at the same time.

Development of Fixture Layout Optimization for Thin-Walled Parts:A Review

An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing literature,this paper summarizes the process of fixture layout optimization and the methods applied.The process of optimization is made up of optimization objective setting,assembly variation/deformation modeling,and fixture layout optimization.This paper makes a review of the fixture layout for thin-walled parts according to these three steps.First,two different kinds of optimization objectives are introduced.Researchers usually consider in-plane variations or out-of-plane deformations when designing objectives.Then,modeling methods for assembly variation and deformation are divided into two categories:Mechanism-based and data-based methods.Several common methods are discussed respectively.After that,optimization algorithms are reviewed systematically.There are two kinds of optimization algorithms:Traditional nonlinear programming and heuristic algorithms.Finally,discussions on the current situation are provided.The research direction of fixture layout optimization in the future is discussed from three aspects:Objective setting,improving modeling accuracy and optimization algorithms.Also,a new research point for fixture layout optimization is discussed.This paper systematically reviews the research on fixture layout optimization for thin-walled parts,and provides a reference for future research in this field.

Optimization of material removal strategy in milling of thin-walled parts

The optimal material removal strategy can improve a geometric accuracy and surface quality of thin-walled parts such as turbine blades and blisks in high-speed ball end milling.The dominant conception in the material removal represents the persistence of the workpiece cutting stiffness in operation to advance the machining accuracy and machining efficiency.On the basis of theoretical models of cutting stiffness and deformation,finite element method (FEM) is applied to calculate the virtual displacements of the thin-walled part under given virtual loads at the nodes of the discrete surface.With the reference of deformation distribution of the thin-walled part,the milling material removal strategy is optimized to make the best of bracing ability of still uncut material.This material removal method is summarized as the lower stiffness region removed firstly and the higher stiffness region removed next.Analytical and experimental results show the availability,which has been verified by the blade machining test in this work,for thin-walled parts to reduce cutting deformation and meliorate machining quality.

Initial residual stress experiment and simulation of thin-walled parts for layer removal method

Thin-walled parts have low stiffness characteristic. Initial residual stress of thin-walled blanks is an important influence factor on machining stability. The present work is to verify the feasibility of an initial residual stress measurement of layer removal method. According to initial residual stress experiment for casting ZL205 A aluminum alloy tapered thin-walled blank by a common method,namely hole-drilling method,three finite element models with initial residual stress are established to simulate the layer removal method in ABAQUS and ANSYS software. By analyzing the results of simulation and experiments,the cutting residual stress inlayer removal process has a significant effect on measurement results. Reducing cutting residual stress is helpful to improve accuracy of layer removal method.

Mapping relationship analysis of welding assembly properties for thin-walled parts with finite element and machine learning algorithm

The finite element(FE)-based simulation of welding characteristics was carried out to explore the relationship among welding assembly properties for the parallel T-shaped thin-walled parts of an antenna structure.The effects of welding direction,clamping,fixture release time,fixed constraints,and welding sequences on these properties were analyzed,and the mapping relationship among welding characteristics was thoroughly examined.Different machine learning algorithms,including the generalized regression neural network(GRNN),wavelet neural network(WNN),and fuzzy neural network(FNN),are used to predict the multiple welding properties of thin-walled parts to mirror their variation trend and verify the correctness of the mapping relationship.Compared with those from GRNN and WNN,the maximum mean relative errors for the predicted values of deformation,temperature,and residual stress with FNN were less than 4.8%,1.4%,and 4.4%,respectively.These results indicate that FNN generated the best predicted welding characteristics.Analysis under various welding conditions also shows a mapping relationship among welding deformation,temperature,and residual stress over a period of time.This finding further provides a paramount basis for the control of welding assembly errors of an antenna structure in the future.

A model of deformation of thin-wall surface parts during milling machining process

A three-dimensional finite element model was established for the milling of thin-walled parts. The physical model of the milling of the part was established using the AdvantEdge FEM software as the platform. The aluminum alloy impeller was designated as the object to be processed and the boundary conditions which met the actual machining were set. Through the solution, the physical quantities such as the three-way cutting force, the tool temperature, and the tool stress were obtained, and the calculation of the elastic deformation of the thin-walled blade of the free-form surface at the contact points between the tool and the workpiece was realized. The elastic deformation law of the thin-walled blade was then predicted. The results show that the maximum deviation between the predicted value and the actual measured machining value of the elastic deformation was 26.055 μm; the minimum deviation was 2.011 μm, with the average deviation being 10.154 μm. This shows that the prediction is in close agreement with the actual result.

Numerical simulation analysis for deformation deviation and experimental verification for an antenna thin-wall parts considering riveting assembly with finite element method

In the process of thin-wall parts assembly for an antenna,the parts assembly deformation deviation is occurring due to the riveting assembly.In view of the riveting assembly deformation problems,it can be analyzed through transient and static simulation.In this work,the theoretical deformation model for riveting assembly is established with round head rivet.The simulation analysis for riveting deformation is carried out with the riveting assembly piece including four rivets,which comparing with the measuring points experiment results of riveting test piece through dealing with the experimental data using the point coordinate transform method and the space line fitting method.Simultaneously,the deformation deviation of the overall thin-wall parts assembly structure is analyzed through finite element simulation;and its results are verified by the measuring experiment for riveting assembly with the deformation deviation of some key points on the thin-wall parts.Through the comparison analysis,it is shown that the simulation results agree well with the experimental results,which proves the correctness and effectiveness of the theoretical analysis,simulation results and the given experiment data processing method.Through the study on the riveting assembly for thin-wall parts,it will provide a theoretical foundation for improving thin-wall parts assembly quality of large antenna in future.

Welding thermal characteristics analysis with numerical simulation for thin-wall parts assembly under different conditions

In order to analyze the welding thermal characteristics problem,the multiscale finite element(FE)model of T-shape thin-wall assembly structure for different thicknesses and the heat source model are established to emphatically study their welding temperature distributions under different conditions.Simultaneously,different welding technology parameters and welding directions are taken into account,and the fillet weld for different welding parameters is employed on the thin-wall parts.Through comparison analysis,the results show that different welding directions,welding thicknesses and welding heat source parameters have a certain impact on the temperature distribution.Meanwhile,for the thin-wall assembly structure of the same thickness,when the heat source is moving,the greater the moving speed,the smaller the heating area,and the highest temperature will decrease.Therefore,the welding temperature field distribution can be altered by adjusting welding parameters,heat source parameters,welding thickness and welding direction,which is conducive to reducing welding deformation and choosing an appropriate and optimal welding thickness of thin-wall parts and relative welding process parameters,thus improving thin-wall welding structure assembly precision in the actual large-size welding structure assembly process in future.

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.

Relative Varying Dynamics Based Whole Cutting Process Optimization for Thin‑walled Parts

Thin-walled parts are typically difficult-to-cut components due to the complex dynamics in cutting process.The dynamics is variant for part during machining,but invariant for machine tool.The variation of the relative dynamics results in the difference of cutting stage division and cutting parameter selection.This paper develops a novel method for whole cutting process optimization based on the relative varying dynamic characteristic of machining system.A new strategy to distinguish cutting stages depending on the dominated dynamics during machining process is proposed,and a thickness-dependent model to predict the dynamics of part is developed.Optimal cutting parameters change with stages,which can be divided by the critical thickness of part.Based on the dynamics comparison between machine tool and thickness-varying part,the critical thicknesses are predicted by an iterative algorithm.The proposed method is validated by the machining of three benchmarks.Good agreements have been obtained between prediction and experimental results in terms of stages identification,meanwhile,the optimized parameters perform well during the whole cutting process.

Elliptical vibration cutting of large-size thin-walled curved surface parts of pure iron by using diamond tool with active cutting edge shift

Large-size thin-walled curved surface parts of pure iron are crucial in aerospace,national defense,energy and precision physical experiments.However,the high machining accuracy and surface quality are difficult to achieve due to the serious tool wear and deformation when machining the parts with conventional cutting tools.In this paper,an elliptical vibration cutting(EVC)with active cutting edge shift(ACES)based on a long arbor vibration device is proposed for ultraprecision machining the pure iron parts by using diamond tool.Compared with cutting at a fixed cutting edge,the influence of ACES on the EVC was analyzed.Experiments in EVC of pure iron with ACES were conducted.The evolutions of the surface roughness,surface topography,and chip morphology with tool wear in EVC with ACES are revealed.The reasonable parameters of ultraprecision machining the pure iron parts by EVC with ACES were determined.It shows that the ACES has a slight influence on the machined surface roughness and surface topography.The diamond tool life can be significantly prolonged in EVC of pure iron with ACES than that with a fixed cutting edge,so that high profile accuracy and surface quality could be obtained even at higher nominal cutting speed.A typical thin-walled curved surface pure iron part with diameter φ240 mm,height 122 mm,and wall thickness 2 mm was fabricated by the presented method,and its profile error and surface roughness achieved PV 2.2μm and Ra less than 50 nm,respectively.

Interactive operation of physically-based slender flexible parts in an augmented reality environment

In order to deal with the problems of laying and assembly planning of slender flexible parts in electromechanical products,a novel approach to operate the physically-based slender flexible parts in an augmented reality environment is presented in this paper.A discrete dynamic method is used to efficiently build the physical model of slender flexible parts,which is very well suited for interactive operation in the augmented reality environment.In this model,bending penalty force can be calculated by the bending energy function to improve dynamic bending behavior,and a penalty method is used to simplify the calculation of geometric torsion.With a reasonable construction of augmented reality environment,a real-time interactive algorithm based on the operating panel is proposed to enable users to interact with the virtual slender flexible parts in the mixed reality-based scene.A case study in the augmented reality environment shows that the proposed approach is efficient and feasible.

细长轴类零件车削加工质量分析与研究

细长轴类零件应用十分广泛,在实际生产中以车削加工为主,因其刚性较差,在加工时容易造成弯曲变形,影响产品的加工质量,避免此类问题发生显得尤为重要。该文通过对细长轴类零件特点、现存问题、受力情况等进行分析和研究,结合细长轴类零件自身特点,分别从装夹方式、车削方法、刀具几何参数与切削用量的选择,以及利用辅助装置等角度出发,给出了优化细长轴类零件车削加工质量的办法,能够有效保证零件加工质量要求。

细长轴加工技术在复杂零件加工中的应用

细长轴加工技术在提高加工效率和复杂零件质量、降低成本等方面具有显著优势。基于此,详细探讨此项技术的应用实践,包括切削力控制、表面质量优化以及复杂零件加工精度提高,并展示其卓越的性能,以提升整体加工过程的稳定性和可控性。同时,深入剖析该技术在不同材料和结构零件中的实际应用案例,证明其能够为促进制造业高效发展提供有力支撑,在复杂零件加工方面具有广阔的应用前景。

海洋环境纤腰独柱式异形混凝土索塔施工技术

黄茅海跨海通道2座斜拉桥的5座主塔均采用纤腰独柱式异形混凝土索塔,造型优美、结构简洁。结构及施工环境复杂,面临着截面变化剧烈,模板及爬架设计困难;钢筋数量多,高空绑扎效率低安全风险高,保护层厚度控制难度大,影响海洋环境下混凝土耐久性;C55混凝土水泥用量多、水化热大,8cm保护层素混凝土开裂风险高等一系列施工难题。通过采用参数化模板设计、数控机床雕刻加工造型箱模板;钢筋分块部品施工工艺;优化配合比,掺加粘度改性剂,在保护层范围内增设玄武岩纤维等一系列施工措施,解决了相关技术难题,确保了施工质量,提高了施工效率,降低了安全风险,快速优质地完成了异形混凝土索塔的建造,为类似项目的施工提供了借鉴。

细长轴楔横轧模具设计及仿真实验

细长、锥形阶梯轴类大断面收缩率零件(断面收缩率>75%)成形,是楔横轧新技术较特殊的一种成形形式,具有广阔的应用前景,其在成形建筑用材、汽车关键轴类零件等起着不可替代的作用。基于目前对细长、锥形阶梯轴的研究尚不多见,对其成形规律、缺陷的产生机理也缺少了解,该文根据细长轴的几何特殊性,进行了相应的模具设计和布楔设计;基于DEFORM有限元平台,对轧制全过程进行模拟,得到了各模具参数对应力应变的影响变化规律,并利用遗传算法对模具进行了多目标优化设计。

细长轴工件切削颤振的研究

对细长轴工件切削加工中的颤振效应进行分析,通过激振实验,对细长轴工件切削系统的主切削抗力方向的动态特性进行实验研究,得出结论:细长轴工件使得整个切削系统的一阶固有频率降低,二阶固有频率提高。综合考虑,整个切削系统建立了两自由度模型,分析了细长轴工件切削系统的切削颤振以及稳定性条件。

加工超细长轴的切削刀盘设计

根据超细长轴的加工特点,以车刀旋转,工件进给为构思,成功设计了加工超细长轴的旋风刀盘及定心夹头,并分析了该刀盘的工装结构及工作原理,为所需加工超细长轴的企业提供一定的参考。

细长轴零件激光熔覆修复过程温度场数值模拟及变形研究

以细长阶梯轴为研究对象,提出了一种全新的轴类零件建模和网格划分方法。通过数值模拟研究了阶梯轴的温度场分布、应力场分布及轴的变形结果。根据关键节点的温度变化规律,验证了激光熔覆加工能量密度集中,热影响区域小的特点。分析了细长轴在激光熔覆过程中变形的原因,结果表明约束对热变形的抑制有很好的作用。对实际工程应用有重要的指导意义。

热流道注塑中大尺寸细长薄壁塑件成型周期及翘曲变形控制研究

以某型汽车防擦条为例,对原有注塑方案的流道系统及工艺参数进行改进,利用计算机辅助工程(CAE)手段分析改进对于注塑周期及翘曲变形的影响,从而得出控制此类零件注塑周期及翘曲变形的趋势,将改进方案用于指导实际注塑,结果与模拟基本吻合。